METHOD FOR PRODUCING AN ARTICLE FOR USE IN THE FOUNDRY INDUSTRY, CORRESPONDING GRANULAR MATERIAL AND KIT, APPARATUSES, AND USES

Abstract

The invention relates to a method for producing an article for use in the foundry industry, selected from a group consisting of granular material for producing a pourable additive, a solid pourable additive, an inorganic binder, and a molding material mixture. The invention also relates to a corresponding granular material comprising particulate amorphous silica and to a kit for producing an inorganic binder. The invention also relates to an apparatus for carrying out the method according to the invention and to a corresponding use of particulate amorphous silica and to the corresponding use of a granular material.

Description

The present invention relates to a process for producing an article for use in the foundry industry, selected from the group consisting of granular material for production of a pourable additive, solid pourable additive, inorganic binder and molding material mixture. Further details of the process of the invention will be apparent from the appended claims and from the description that follows. The present invention additionally relates to a corresponding granular material comprising particulate amorphous silicon dioxide. The present invention further relates to a kit for production of an inorganic binder. The present invention also relates to an apparatus for performance of the process of the invention. The present invention further relates to a corresponding use of particulate amorphous silicon dioxide. The present invention additionally relates to the corresponding use of a granular material. Details of each will be apparent from the appended claims and the description that follows.

Casting in a lost mold is a widely used process for producing near-net-shape components. After the casting, the mold is destroyed, and the cast part is removed. Lost molds are casting molds and hence negatives; they contain the cavity to be cast that results in the finished cast part. The inner contours of the future cast part are formed by cores. In the production of the casting mold, a model of the cast part to be manufactured forms the cavity in the molding material.

By contrast with sand casting methods in which the casting molds (lost molds) are destroyed after casting to remove the cast part, metallic permanent molds, manufactured from cast iron or steel for example, can be reutilized for the next casting after the cast part has been removed. It is also possible to work by diecasting, in which case the liquid metal melt is injected into a diecasting mold under high pressure at a high mold filling rate. The aforementioned casting methods are also preferred in the context of the present invention. Mold base materials used for casting molds (in sand casting methods with lost molds) and cores are predominantly refractory grainy substances, for example washed classified quartz sand. For production of the casting molds, the mold base materials are bound with inorganic or organic binders. The binder creates fixed coherence between the particles of the mold base material, such that the casting mold or core gains the requisite mechanical stability. The refractory mold base material premixed with the binder is preferably in a free-flowing form, such that it can be introduced into a suitable cavity and compacted therein. The molding materials are compacted in order to increase strength.

Casting molds and cores must fulfill various demands. During the actual casting operation, they must first have sufficient strength and thermal stability to be able to accommodate the liquid metal in the cavity formed from one or more (partial) casting molds. After the solidifying operation has commenced, the mechanical stability of the cast part is assured by a solidified metal layer that forms along the walls of the casting mold.

The material of the casting mold is then supposed to change under the influence of the heat released by the metal such that it loses its mechanical strength, i.e. the coherence between individual particles of refractory material is lost. In the ideal case, casting molds and cores break down again to form a fine sand that can be removed easily from the cast part and have correspondingly favorable breakdown properties.

Inorganic binders have long been known, especially those based on waterglasses. Three different methods in particular are available for curing of the waterglasses, which may also be combined: (i) passage of a gas, e.g. CO₂, air or a combination of the two; (ii) addition of liquid or solid curing agents, e.g. particular esters, and (iii) thermal curing, for example in what is called a hotbox method or by microwave treatment.

However, the use of inorganic binder systems is frequently associated with other typical disadvantages:

For instance, it is relatively common for foundry moldings produced from inorganic binders to have low strengths unless suitable special measures are taken. This becomes particularly clearly apparent immediately after the removal of the core or casting mold or of the molding from the mold. The strengths at this time (“hot strength” or “immediate strength”) are particularly important for the safe handling of the cores or forms on removal from the mold. Also important is a high “cold strength” (i.e. the strength after complete curing of the core or of the casting mold), in order that the desired cast part can be produced with a minimum level of casting defects.

Document EP 1 802 409 B1 discloses a molding material mixture for producing casting molds for metal processing, at least comprising: a refractory mold base material, a waterglass-based binder, characterized in that a proportion of a particulate synthetic amorphous silicon dioxide has been added to the molding material mixture.

Document DE 10 2013 111 626 A1 discloses a molding material mixture for production of molds or cores, at least comprising: a refractory mold base material, waterglass as binder, particulate amorphous silicon dioxide and one or more pulverulent oxidic boron compounds. The document additionally discloses that the addition of boron compounds to the molding material mixture improves the moisture stability of the cores and molds produced therewith.

Document WO2014/202042A1 discloses a molding material mixture for production of casting molds and cores for metal processing, comprising at least one refractory mold base material, particulate amorphous SiO₂, waterglass and lithium compounds. The document additionally discloses that the addition of lithium compounds to the molding material mixture improves the moisture stability of the moldings produced therewith.

Document DE 10 2012 104 934 A1 discloses a molding material mixture for production of casting molds for metal processing, at least comprising: a refractory mold base material, a waterglass-based binder and barium sulfate.

Document DE 10 2012 113 073 A1 discloses a molding material mixture for production of forms and cores for metal processing, comprising at least a) a refractory mold base material, b) an inorganic binder and c) at least one particulate metal oxide, wherein the particulate metal oxide comprises or consists of at least one aluminum oxide in the alpha phase and/or at least one mixed aluminum/silicon oxide, excluding mixed aluminum/silicon oxides having sheet silicate structure.

Document DE 10 2012 113 074 A1 discloses a molding material mixture for production of forms and cores for metal processing, comprising at least one refractory mold base material, an organic binder and at least one particulate mixed metal oxide. Oxides of aluminum and of zirconium are used in a specific manner.

Document DE 10 2017 107 531 A1 discloses a process for producing casting molds, cores, and mold base materials regenerated therefrom. Particulate sheet silicates are used in a specific manner.

Document EP 2 104 580 B1 discloses a molding material mixture for production of casting molds for metal processing, at least comprising: a refractory mold base material; a waterglass-based binder; a proportion of a particulate metal oxide selected from the group of silicon dioxide, aluminum oxide, titanium oxide and zinc oxide. A carbohydrate has been added to the molding material mixture.

Document EP 2 097 192 B1 discloses a molding material mixture for production of casting molds for metal processing, at least comprising: a refractory mold base material; a waterglass-based binder; a proportion of a particulate metal oxide selected from the group of silicon dioxide, aluminum oxide, titanium oxide and zinc oxide. A proportion of a phosphorus compound has been added to the molding material mixture.

Document DE 10 2012 020 509 A1 discloses a molding material mixture for production of casting molds and cores for metal processing, comprising at least: a refractory mold base material, an inorganic binder and particulate amorphous SiO₂, producible by the thermal breakdown of ZrSiO₄ to give ZrO₂ and SiO₂.

Document DE 10 2012 020 510 A1 discloses a molding material mixture for production of casting molds and cores for metal processing, comprising at least: a refractory mold base material, an inorganic binder and particulate amorphous SiO₂, producible by the oxidation of metallic silicon by means of an oxygenous gas.

Document DE 10 2012 020 511 A1 discloses a molding material mixture for production of casting molds and cores for metal processing, comprising at least: a refractory mold base material, an inorganic binder and particulate amorphous SiO₂, producible by melting crystalline quartz and rapid recooling.

Document DE 10 2012 020 073 A1 discloses a molding material mixture for production of casting molds and cores for metal processing, comprising at least: a refractory mold base material, an inorganic binder and particulate amorphous SiO₂, producible by the oxidation of metallic silicon by means of an oxygenous gas.

Document WO 2009/056320 discloses a molding material mixture for production of casting molds for metal processing, at least comprising: a refractory mold base material; a waterglass-based binder; a proportion of a particulate metal oxide selected from the group of silicon dioxide, aluminum oxide, titanium oxide and zinc oxide. A proportion of at least one surface-active substance has been added to the molding material mixture.

The patent documents acknowledged above already disclose molding material mixtures comprising particulate amorphous SiO₂. It is also known therefrom that, proceeding from particular base formulations, the addition of selected additives influences the properties of molding material mixtures and moldings resulting therefrom.

In the foundry industry, there is a need to use binders and molding material mixtures comprising particulate amorphous silicon dioxide and optionally further solid additives, but at the same time to minimize the inconvenience involved in individual dosage and mixing, which has to date additionally been associated in practice with health risks resulting from contamination of breathable air. At the same time, it is to be ensured that repeatedly produced binders and molding material mixtures always have the same composition and always have the same product properties.

In addition, there is a need to use substances even in gel or liquid form that do not have prolonged stability in waterglass as constituents of corresponding binders and molding material mixtures without any need for additional metering steps.

There is additionally a need to use various particulate substances each having very different particle size distributions as additives for molding material mixtures without any need for additional metering steps and without any resultant differences, for example, in the compositions of the molding material mixtures formed depending on the fill levels in the reservoir vessels for the particulate substances.

There is additionally a need to add solid and liquid additives for molding material mixtures to molding material mixtures in a fixedly defined relative ratio to one another and by means of a single common metering step.

Very particularly, there is a need to be able to combine the known positive properties of additives for molding material mixtures without needing additional metering steps for every component added and without having to deal with additional problems with the storage of the additives.

The present invention is defined in the claims and described in detail hereinafter.

The present invention relates, in its categories, to a process for producing an article for use in the foundry industry, to a granular material, to an apparatus for performance of a process, to a use of particulate amorphous silicon dioxide, and to a use of a granular material. Embodiments, aspects or properties that are described in connection with one of these categories or described as preferred are each correspondingly or analogously applicable to the respective other categories, and vice versa.

Unless stated otherwise, preferred aspects or embodiments of the invention and their various categories can be combined with other aspects or embodiments of the invention and their various categories, especially with other preferred aspects or embodiments. The combination of respectively preferred aspects or embodiments with one another again results in preferred aspects or embodiments of the invention.

In a primary aspect of the present invention, the above-specified objects are achieved and problems are solved in whole or in part by a process for producing an article for use in the foundry industry

• • selected from the group consisting of
    • granular material for production of a pourable additive for use as a constituent of an inorganic binder in the foundry industry,
    • solid pourable additive for use as a constituent of an inorganic binder in the foundry industry,
    • inorganic binder for use in the foundry industry,
    • molding material mixture comprising an inorganic binder for use in the foundry industry,
  • and
    • moldings (especially cores, casting molds and feeders) for use in the casting of metallic cast parts in the foundry industry,
  • comprising the following steps for production of the article:
    • producing or providing particulate amorphous silicon dioxide comprising silicon dioxide in a proportion of at least 80% by weight, preferably in a proportion of at least 90% by weight, based on the total mass of the particulate amorphous silicon dioxide,
    • combining the particles of the particulate amorphous silicon dioxide in an enlargement step to give grains, so as to result in a granular material comprising a multitude of individual grains each comprising combined particles and each comprising a proportion of at least 30% by weight, preferably at least 40% by weight, more preferably at least 50% by weight, of particulate amorphous silicon dioxide, based on the mass of the respective grain, where the average grain diameter of the granular material is greater than 0.2 mm, determined by sieving.

The granular material, the solid pourable additive, the inorganic binder and the molding material mixture are each intermediates as produced successively (in the specified sequence) in the production of a casting mold or core. Each of these intermediates may be individually stored or else transported.

The term “granular material” is thus understood in the context of the above definition to mean the entirety of a multitude of grains as defined above.

The grains here are the product of an enlargement step performed as planned, and contain particulate amorphous silicon dioxide (and optionally further substances). The grains are thus in each case a composite, for example an agglomerate or aggregate.

The term “particulate” preferably refers to the particles of a solid powder (including dusts) that is preferably pourable and hence also sievable.

Particulate amorphous silicon dioxide used may be either synthetically produced types (for example as defined in the prior art acknowledged at the outset) or naturally occurring types. The latter are known, for example, from DE 10 2007 045 649, but they are not preferred since they frequently contain not inconsiderable crystalline components and are therefore classified as carcinogenic.

The “particulate amorphous silicon dioxide comprising silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate amorphous silicon dioxide” is preferably a particulate synthetic amorphous silicon dioxide. According to the origin or preparation process, natural and/or synthetic amorphous silicon dioxide contains up to 50% by weight of secondary constituents, i.e. crystalline silicon dioxide and/or non-silicon dioxide substances. Thus, commercially available (synthetic or natural) “particulate amorphous silicon dioxide”, aside from silicon dioxide, typically contains proportions of one or more further inorganic oxides and of unavoidable impurities. In the context of the present invention, preference is given to synthetic amorphous silicon dioxide containing secondary constituents in a proportion of less than 30% by weight and/or silicon dioxide in a proportion of at least 80% by weight, very particular preference to particulate synthetic amorphous silicon dioxide containing secondary constituents in a proportion of less than 20% by weight and/or silicon dioxide in a proportion of at least 90% by weight, based in each case on the total mass of the particulate amorphous silicon dioxide.

Typically, and preferably in some cases, the particulate amorphous silicon dioxide produced or provided comprises particles in the form of dust.

The proportion of particulate amorphous silicon dioxide in the grains of the granular material may (after appropriate sample processing, especially after sieving according to VDG-Merkblatt P 27, see below) be determined or confirmed, for example, by means of x-ray fluorescence analysis to DIN EN ISO 12677, DIN 51001, optionally in combination with optical and/or spectroscopic methods and/or wet-chemical methods; the person skilled in the art will preferably choose a suitable method of determination with knowledge of the materials used in the process.

The particulate amorphous silicon dioxide produced or provided preferably comprises particles having a size of less than 20 μm, more preferably particles having a size of 0.1 μm to 5 μm, most preferably particles having a size of 0.1 μm to 1.5 μm, determined by scanning electron microscopy (SEM) or laser diffraction.

Preference is given in many cases to a process wherein, for the resulting granular material, the index for the evolution of dust by the rotation method is lower than that of the particulate amorphous silicon dioxide produced or provided, preferably at least 15% lower, more preferably at least 25% lower, most preferably at least 40% lower, in each case preferably determined to DIN 55992-1 (date: June 2006), Type I, Rotating drum principle (for example using a Heubach dustmeter).

What is meant by “synthetically produced” particulate amorphous silicon dioxide in the context of the present text is that the amorphous silicon dioxide is

• • the target product of a planned chemical reaction process for industrial synthesis of amorphous silicon dioxide
    or
  • a by-product of a planned chemical reaction process for industrial synthesis of a target product that is not amorphous silicon dioxide.

One example of a reaction process with amorphous silicon dioxide as its target product is the flame hydrolysis of silicon tetrachloride. The amorphous SiO₂ (“silicon dioxide”) produced by this process is also referred to as “pyrogenic SiO₂” (“pyrogenic silicon dioxide”) or as pyrogenic silica or as fumed silica (CAS RN 112945-52-5).

One example of a reaction process in which amorphous silicon dioxide is formed as a by-product is the reduction of quartz with coke, for example, in an arc furnace for production of silicon or ferrosilicon as target product. The amorphous SiO₂ (“silicon dioxide”) thus produced is also referred to as silica dust, silicon dioxide dust or SiO₂ fume condensate or as “silica fume” or microsilica (CAS RN 69012-64-2).

A further reaction process in which amorphous silicon dioxide is synthetically produced is the thermal breakdown of ZrSiO₄ in an arc furnace to give ZrO₂ and SiO₂.

The literature frequently refers to amorphous silicon dioxide formed by flame hydrolysis of silicon tetrachloride, to amorphous silicon dioxide formed as a by-product in the reduction of quartz with coke, for example, in the arc furnace and to amorphous silicon dioxide formed by thermal breakdown of ZrSiO₄ as “pyrogenic SiO₂” (“pyrogenic silicon dioxide”) or as pyrogenic silica. This terminology is also employed in the context of the present application.

In the context of the present invention, pyrogenic particulate amorphous silicon dioxide to be used with particular preference in the context of the present invention includes those types of particulate amorphous silicon dioxide that are identified by CAS RN 69012-64-2 and CAS RN 112945-52-5. These types of pyrogenic particulate amorphous silicon dioxide that are to be used with particular preference in accordance with the invention can be produced in a manner known per se, especially by reduction of quartz with carbon (e.g. coke) in an arc furnace with subsequent oxidation to silicon dioxide (preferably in the production of ferrosilicon and silicon). Likewise particularly preferred is SiO₂ prepared by thermal breakdown of ZrSiO₄ to give ZrO₂ from ZrSiO₄, and SiO₂ obtained by flame hydrolysis of silicon tetrachloride.

Particulate amorphous silicon dioxide of the type produced by reduction of quartz with carbon (e.g. coke) in an arc (in the production of ferrosilicon and silicon) contains carbon. Particulate amorphous silicon dioxide of the type produced by thermal breakdown of ZrSiO₄ contains oxidic zirconium compounds.

Particulate synthetic amorphous silicon dioxide producible by oxidation of metallic silicon by means of an oxygenous gas and particulate synthetic amorphous silicon dioxide producible by quenching a silicon dioxide melt are very pure SiO₂ having only a very small number of unavoidable impurities.

Most preferably, the pyrogenic particulate amorphous silicon dioxide to be used with preference in accordance with the invention comprises particulate amorphous silicon dioxide of the type identified by CAS RN 69012-64-2. This is preferably produced by the reduction of quartz with carbon (e.g. coke) in an arc (for example in the production of ferrosilicon and silicon), or is obtained as a by-product (silica fume) in the production of ferrosilicon and silicon. Likewise very particularly preferred is SiO₂ prepared by thermal breakdown of ZrSiO₄ to give ZrO₂ from ZrSiO₄. Particulate amorphous silicon dioxide of these types is also referred to as “microsilica” in the specialist field.

The “CAS RN” stands here for the CAS registry number and CAS register number (CAS=Chemical Abstracts Service).

Various methods are suitable for combining of the particles of the particulate amorphous silicon dioxide (and optionally further substances) in an enlargement step to give grains, so as to result in a granular material comprising a multitude of individual grains. Examples of suitable methods include pelletizing, briqueting, tableting, granulating, agglomerating, extruding and others.

The “Handbuch derAgglomerationstechnik” [Handbook of Agglomeration Technology] by the author Gerald Heinze (WILEY-VCH Verlag GmbH, 2000, ISBN: 3-527-29788-X) discloses processes and products from the field of agglomeration technology.

EP 1 602 425 A1 discloses granular materials obtainable from silicon dioxide powder having a content of at least 90% amorphous SiO₂ by granulation, especially by pelletization with addition of water and subsequent drying.

A “molding material mixture” in the context of the invention defined above comprises a mold base material as one of multiple constituents. The mold base material here is preferably a refractory mold base material.

In the present text, in accordance with the customary understanding of the person skilled in the art, “refractory” masses, materials and minerals refer to those that can at least briefly withstand the thermal stress in the course of casting or solidifying of an iron melt, usually cast iron. Suitable (refractory) mold base materials are natural and synthetic mold base materials, for example quartz sand, zircon sand or chrome ore sand, olivine, vermiculite, bauxite or fireclay, and mixtures thereof.

The juncture of addition of the additive to the further constituents in the production of the molding material mixture or of the molding material mixture provided with the additive is arbitrary and can be chosen freely. For example, the additive can be added last to the otherwise finished molding material mixture or can first be premixed with one or more of the constituents mentioned before one or more further constituents are finally mixed into the molding material mixture.

A solid pourable additive is understood to mean an additive for molding material mixtures in the form of a bitty aggregate in a pourable form and amount, with the individual piece of this aggregate having a size of less than 0.2 mm, determined by sieving.

An “inorganic binder” in the context of the above definition of the invention is typically a multicomponent binder system comprising additives comprising at least particulate amorphous silicon dioxide, and a solution or dispersion comprising waterglass. Said constituents are present here as two or more spatially separate components or as a mixture. “Inorganic binders” may, as well as particulate amorphous silicon dioxide, also contain further particulate materials and/or further materials in liquid or gel form, each as part of a mixture and/or as spatially separate components.

Mixture constituents that would be unacceptable as an individual component in a foundry process (for example respirable crystalline SiO₂, classified as carcinogenic), in some cases, albeit not preferably, are used in accordance with the invention in the granular material since release in dust form can be effectively prevented or reduced to a considerable degree.

What is meant by the term “combining” is the combining of the particles of the particulate amorphous silicon dioxide with one another and optionally also with further constituents (see below).

The process of the invention is suitable for the production of all moldings customary for metal casting, i.e., for example, of cores, casting molds and feeders. It is also particularly advantageously possible to produce moldings having sections with very thin walls. It is likewise particularly advantageously possible to produce moldings that combine a maximum relative molding weight (weight based on the volume of a given body of predetermined geometry; in the case of cores, this is referred to as core weight) with a particularly high one-hour strength.

The present invention, with its various aspects, especially and preferably relates to a process (as described above, preferably as identified above as preferred) for producing an article for use in the foundry industry, selected from the group consisting of

• • solid pourable additive for use as a constituent of an inorganic binder in the foundry industry,
  • inorganic binder for use in the foundry industry,
  • molding material mixture comprising an inorganic binder for use in the foundry industry,
  •  and
  • moldings for use in the casting of metallic cast parts in the foundry industry,
  •  comprising the steps of:
  • producing a granular material by a process as described above, preferably as identified above as preferred,
  • comminuting the grains of the granular material, so as to result in a solid pourable additive.

The person skilled in the art is able to select from a multitude of methods for the comminution of the grains of the granular material, so as to result in a solid pourable additive. The comminuting preferably comprises grinding or crushing. But the granular material can also be comminuted in other ways.

In a preferred embodiment, the comminuting, preferably the grinding or crushing, takes place in a closed apparatus, such that no significant amounts of dust and/or fine dust are released outside the apparatus and contaminate the breathable air. In that case, preference is given to metering the resulting solid pourable additive into the further constituents of the inorganic binder or molding material mixtures such that this also does not release any dust and/or fine dust.

The invention especially and preferably relates to a process (as described above, preferably as identified above as preferred) for producing an article for use in the foundry industry,

• • selected from the group consisting of
    • inorganic binder for use in the foundry industry,
    • molding material mixture comprising an inorganic binder for use in the foundry industry,
  • and
    • moldings for use in the casting of metallic cast parts in the foundry industry,
  • (i) comprising the steps of:
    • producing the solid pourable additive by an above-defined process of the invention (preferably in a configuration identified as preferred),
    • contacting the solid pourable additive produced with waterglass or suspending the solid pourable additive produced in waterglass,
  • or
  • (ii) comprising the steps of:
    • producing a granular material by an above-defined process of the invention
    • contacting the granular material produced with waterglass, in the presence or absence of refractory mold base material, and comminuting the grains of the granular material at the same time or thereafter.

Waterglass may be produced, for example, by dissolving vitreous sodium and potassium silicates in water in an autoclave at elevated temperature or from lithium silicates in a hydrothermal process. According to the invention, it is possible to use waterglass containing one, two or more of the alkali metal ions mentioned. The proportion of waterglass in a molding material mixture in the context of the present invention is preferably in the range from 0.6% to 3% by weight.

The contacting of the solid pourable additive produced with waterglass or suspending of the solid pourable additive produced in waterglass that takes place in variant (i) requires the granular material produced beforehand first to have been processed by comminution, preferably by grinding or crushing, to give a solid pourable additive. Thus, solid pourable additive produced from the granular material comes into contact with the waterglass, or is suspended therein. More preferably, the contacting of the solid pourable additive produced with waterglass takes place in such a way that refractory mold base material is initially charged, then the solid pourable additive is added and, finally, waterglass is added, and, at the same time or thereafter, mixing all components used until they have preferably been blended homogeneously with one another. In less preferred embodiments, the sequence can also be altered, such that, for example, the refractory mold base material is initially charged, then the waterglass is added and only then is the solid pourable additive added, and, at the same time and/or thereafter, all the components used are mixed until they have been blended homogeneously with one another. In a further embodiment, the solid pourable additive is blended with the waterglass to give a suspension and then this suspension is added to the initial charge of refractory mold base material, and, at the same time and thereafter, all components used are mixed until they have been blended homogeneously with one another.

The contacting of the granular material produced with waterglass in the presence or absence of refractory mold base material that takes place in variant (ii) and, at the same time or thereafter, comminuting of the grains of the granular material means that (initially uncomminuted) grains of the granular material are contacted with the waterglass. The person skilled in the art, according to the circumstances of the individual case, will be able to achieve comminution of the grains by adjusting the studding conditions to the demands of the individual case in the contacting and blending of the granular material produced with waterglass. The person skilled in the art will likewise be able, according to the circumstances of the individual case, by appropriate adjustment of the stirring conditions, to blend the granular material with the waterglass in such a way that there is essentially no comminution of the individual grains of the granular material. In both cases, the contacting and blending of the granular material produced with waterglass can take place in the presence or absence of refractory mold base material. If the contacting of the granular material produced with waterglass takes place in the presence of refractory mold base material, it is preferable that blending takes place on contacting (or immediately thereafter) and this blending comminutes the grains of the granular material.

In each of variants (i) and (ii), it is possible to use waterglass in the form of a mixture with one or more additives, for example a mixture comprising waterglass and one or more surfactants.

In a departure from the prior art, in the process of the invention, there is no direct use of particulate amorphous SiO₂ for production of the inorganic binder or of the molding material mixture, but rather exclusively of the granular material produced or the solid pourable additive produced therefrom.

The effects and advantages set out above in connection with the process of the invention are achieved here to a particular degree.

The invention relates especially and preferably to a process of the invention (as described above, preferably as identified above as preferred) for producing a molding material mixture comprising refractory mold base material and an inorganic binder comprising waterglass and particulate amorphous silicon dioxide for use in the foundry industry,

• • comprising the steps of:
    • producing an inorganic binder by an above-defined process of the invention (preferably in a configuration identified as preferred),
  • and
    • (i) at the same time mixing the constituents used for production of the inorganic binder with a refractory mold base material
  • and/or
    • (ii) thereafter mixing the inorganic binder produced with a refractory mold base material.

The molding material mixture can be produced by mixing the individual constituents used for production of the inorganic binder with one another in the presence of a refractory mold base material to give the molding material mixture. The molding material mixture can likewise be produced by first producing the inorganic binder by mixing the constituents of the inorganic binder and mixing the ready-produced inorganic binder with a refractory mold base material to give the molding material mixture. According to the requirements of the individual case, one or both variants in each case or a combination of the two variants may be preferred.

The refractory mold base material preferably accounts for more than 80% by weight, preferably more than 90% by weight, more preferably more than 95% by weight, of the total mass of the molding material mixture. The refractory mold base material to be used in accordance with the invention is preferably in particulate form. It is preferably free-flowing.

The refractory mold base material preferably has an AFS grain fineness number in the range from 30 to 100. The AFS grain fineness number is determined here according to VDG-Merkblatt (information sheet from the “Verein deutscher GieBereifachleute” [Society of German Foundry Experts]) P 34 of October 1999, point 5.2. The AFS grain fineness number is specified therein by the formula

$\mathrm{AFS}\mathrm{grain}\mathrm{fineness}\mathrm{number}=\frac{\sum g_i\times M{3}_i}{g}$

Preference is given to a process of the invention (as described above, preferably as identified above as preferred), wherein, in the step of combining the particles of the particulate amorphous silicon dioxide in an enlargement step to give grains, so as to result in a granular material comprising a multitude of individual grains each comprising combined particles and each comprising a proportion of at least 30% by weight, preferably at least 40% by weight, more preferably at least 50% by weight, of particulate amorphous silicon dioxide, based on the mass of the respective grain, the average grain diameter of the (resulting) granular material is greater than 0.5 mm, preferably greater than 1 mm, determined by sieving.

This preferred process of the invention thus leads to granular materials in which the grains have an average grain diameter of greater than 0.5 mm, preferably an average grain diameter of greater than 1 mm (determined by sieving), and each comprise a proportion of at least 30% by weight, preferably at least 40% by weight, more preferably at least 50% by weight, of particulate amorphous silicon dioxide (as stated above). The granular materials produced by this method have particularly advantageous combinations of the following properties: homogeneous composition, high bulk density, good flowability, good conveyability, good meterability, low dust level, avoidance of separation phenomena, comminutability, high molding weight of the moldings producible with use thereof, elevated moisture stability (moisture resistance) of the moldings producible with use thereof.

Preference is given to a process of the invention (as described above, preferably as identified above as preferred), wherein the particulate amorphous silicon dioxide comprising silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate amorphous silicon dioxide, consists wholly or partly of particulate synthetic amorphous silicon dioxide.

According to the requirements of the individual case, it is particularly advantageous when the particulate amorphous silicon dioxide (comprising silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate amorphous silicon dioxide) consists wholly or only partly of particulate synthetic amorphous silicon dioxide. With the regularly preferred use of synthetic amorphous silicon dioxide, it is possible to achieve particularly advantageous combinations of properties of moldings obtainable therefrom in uniform, predictable quality.

Preference is given to a process of the invention (as described above, preferably as identified above as preferred) wherein the proportion of silicon dioxide in the granular material as a whole, determined by means of x-ray fluorescence analysis, and the proportion of silicon dioxide in at least 90% of the grains of the granular material having a grain diameter greater than 1 mm, preferably greater than 0.5 mm, more preferably greater than 0.2 mm, in each case determined by means of sieving and subsequent x-ray fluorescence analysis, differs by not more than 30%, preferably differs by not more than 20%, more preferably differs by not more than 10%, based on the proportion of silicon dioxide in the granular material as a whole.

The proportion of silicon dioxide both in the granular material as a whole and in the individual grains of the granular material is ascertained by means of x-ray fluorescence analysis to DIN EN ISO 12677, DIN 51001. The (average) grain diameter is determined by sieving according to VDG-Merkblatt (i.e. information sheet from the “Vereins deutscher GieBereifachleute”) P 27 of October 1999, point 4.3, which specifies the use of test sieves according to DIN ISO 3310. What is meant by the fact that the proportion of silicon dioxide in the granular material as a whole (determined by x-ray fluorescence analysis) and the proportion of silicon dioxide (determined by x-ray fluorescence analysis) in at least 90% of the individual grains of the granular material having a grain diameter greater than 1 mm (determined by sieving), preferably greater than 0.5 mm (determined by sieving), more preferably greater than 0.2 mm (determined by sieving), differ by not more than 30%, preferably by not more than 20%, more preferably by not more than 10% (based on the proportion of silicon dioxide in the granular material as a whole), is that these granule grains of this (minimum) size in their composition are good representatives of the overall composition of the granular material and hence of the entirety of the material used. For each of the sizes mentioned (1 mm, 0.5 mm, 0.2 mm), according to the individual case, it is also possible for any of the maximum differences specified (30%, 20%, 10%) to be relevant and advantageous. Thus, according to the requirements of the individual case, any resultant combination of size and maximum difference is preferred.

Preference is given to a process of the invention (as described above, preferably as identified above as preferred), wherein, in the enlargement step, the particles of the particulate amorphous silicon dioxide are mixed and/or contacted with one, two or more further materials independently selected from the group consisting of:

• • liquids, including substances in gel form, preferably liquid wetting agents and/or suspension media, preferably water,
  • particulate materials, preferably particulate inorganic materials, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably pulverulent oxidic boron compounds, and mixtures thereof,
  • water-soluble materials,
  • alkali metal hydroxides,
  • surfactants,
  • film formers,
  • rheological additives (thickeners, suspension aids),
  • hydrophobizing agents, preferably organosilicon compounds, silanes, silicones and siloxanes, waxes, paraffins, metal soaps,
  •  and
  • carbohydrates.

The particulate amorphous silicon dioxide is preferably mixed and/or contacted in the enlargement step with one, two or more further materials (that are not themselves particulate amorphous silicon dioxide). The selection of the one, two or more further materials with which the particulate amorphous silicon dioxide is mixed and/or contacted in the enlargement step is made independently from the above list, meaning that the selection of a first material has no effect on the selection of any subsequent material(s).

The surfactant(s) is/are preferably independently selected from the group consisting of or comprising: oleyl sulfate, stearyl sulfate, palmityl sulfate, myristyl sulfate, lauryl sulfate, decyl sulfate, octyl sulfate, 2-ethylhexyl sulfate, 2-ethyloctyl sulfate, 2-ethyldecyl sulfate, palmitoleyl sulfate, linolyl sulfate, lauryl sulfonate, 2-ethyldecyl sulfonate, palmityl sulfonate, stearyl sulfonate, 2-ethylstearyl sulfonate, linolyl sulfonate, hexyl phosphate, 2-ethylhexyl phosphate, capryl phosphate, lauryl phosphate, myristyl phosphate, palmityl phosphate, palmitoleyl phosphate, oleyl phosphate, stearyl phosphate, poly(ethane-1,2-diyl)phenol hydroxyphosphate, poly(ethane-1,2-diyl)stearyl phosphate, poly(ethane-1,2-diyl)oleyl phosphate, polycarboxylate ethers in water (e.g. Melpers 0030, from BASF), modified polyacrylate in water (e.g. Melpers VP 4547/240 L, from BASF), 2-ethylhexyl sulfate in water (e.g. Texapon EHS, from Cognis), polyglucoside in water (e.g. Glukopon 225 DK, from Cognis), sodium octylsulfate in water (e.g. Texapon 842, from Lakeland), modified carboxylate ethers (e.g. Castament ES 60, solid-state, from BASF).

The film former(s) is/are preferably independently selected from the group consisting of or comprising: polyvinylalcohol and acrylic acid.

The rheological additive(s) (thickeners, suspension aids) is/are preferably independently selected from the group consisting of or comprising:

• • swellable clays, preferably sodium bentonite or attapulgite/palygorskite,
  • swellable polymers, preferably cellulose derivatives, especially carboxymethyl, methyl, ethyl, hydroxyethyl and hydroxypropyl cellulose, plant mucilages, polyvinylpyrrolidone, pectin, gelatin, agar-agar, polypeptides and/or alginates.

The hydrophobizing agent(s) is/are preferably independently selected from the group consisting of or comprising: preferably organosilicon compounds, silanes, silanols, preferably trimethylsilanol, silicones and siloxanes, preferably polydimethylsiloxane, waxes, paraffins, metal soaps.

The materials listed above are those that are preferred in the context of the present invention. Further materials may likewise be used according to the requirements of the individual case.

The aforementioned materials may thus also be used in the process of the invention without any need for an additional dosage step or additional storage vessels in the foundry. It is also possible to introduce those components, preferably including those liquid components (including those in gel form) that do not have prolonged stability in waterglass, into a molding material mixture produced in accordance with the invention without an additional dosage step, in that they are incorporated into the granules formed in the enlargement step.

The term “carbohydrate” in the context of this text is understood to mean aldoses (polyhydroxyaldehydes) and ketoses (polyhydroxyketones), and also higher molecular weight compounds that can be converted to such compounds by hydrolysis. Carbohydrates that are used in the context of the present invention are oligomers and polymers having a chain length of n>2. The invention also relates to a process of the invention (as described above, preferably as identified above as preferred), wherein grains of the granular material resulting from the enlargement step, preferably at least 90% of the grains of the granular material having a particle diameter greater than 1 mm, preferably greater than 0.5 mm, more preferably greater than 0.2 mm, in each case determined by sieving,

• • (i) comprise particulate amorphous silicon dioxide and one, two, more than two or all of the further solid materials present in the enlargement step
  •  and/or
  • (ii) comprise particulate amorphous silicon dioxide and one, two or more further materials independently selected from the group consisting of:
    • particulate materials, preferably particulate inorganic materials, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably pulverulent oxidic boron compounds, and mixtures thereof,
    • water-soluble materials,
    • alkali metal hydroxides,
    • surfactants,
    • film formers,
    • rheological additives (thickeners, suspension aids),
    • hydrophobizing agents, preferably organosilicon compounds, silanes, silicones and siloxanes, waxes, paraffins, metal soaps,
  • and
    • carbohydrates.

The proportion/presence of silicon dioxide in the individual grains of the granular material is ascertained by means of x-ray fluorescence analysis to DIN EN ISO 12677, DIN 51001. The grain diameter is determined by sieving according to VDG-Merkblatt (i.e. information sheet from the “Vereins deutscher GieBereifachleute”) P 27 of October 1999, point 4.3, which specifies the use of test sieves according to DIN ISO 3310. The presence of the one, two, more than two or all further solid materials present in the enlargement step in the grains of the granular material may (especially after sieving according to VDG-Merkblatt P 27, see above) likewise be determined or confirmed, for example, by means of x-ray fluorescence analysis according to DIN EN ISO 12677, DIN 51001, optionally in combination with optical and/or spectroscopic methods and/or wet-chemical methods. The person skilled in the art will choose a suitable method of determination, preferably with knowledge of the materials used in the process.

The fact that grains of the granular material, preferably at least 90% of the grains of the granular material having a grain diameter greater than 0.2 mm, preferably greater than 0.5 mm, more preferably greater than 1 mm (in each case determined by sieving), comprise particulate amorphous silicon dioxide and one, two or more than two or all of the other solid materials present in the enlargement step means that one, two or more than two or all of the other solid materials present in the enlargement step are part of the resulting granular material, preferably part of at least 90% of the grains of the granular material (having a grain diameter greater than 0.2 mm, preferably greater than 0.5 mm, more preferably greater than 1 mm). Thus, the one, two or more than two or all of the other solid materials present in the enlargement step are preferably part of the granular material; more preferably, they are distributed sufficiently uniformly within the granular material that they are present in at least 90% of the grains of the granular material having a grain diameter of greater than 1 mm, preferably greater than 0.5 mm, more preferably greater than 0.2 mm (in each case determined by sieving).

The one, two, more than two or all of the other materials present in the enlargement step in addition to the particulate amorphous silicon dioxide are selected independently from one another. Each of the possible resultant combinations, according to the requirements of the individual case, leads to particularly advantageous properties or combinations of properties of the molded articles producible therefrom.

Preference is given to a process of the invention (as described above, preferably as identified above as preferred), wherein

• • the producing of particulate amorphous silicon dioxide comprising silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate amorphous silicon dioxide, comprises the step of:
    • mixing two or more different types of particulate amorphous silicon dioxide, where the two or more types differ by their particle size distribution, preferably determined by laser scattering, for example by the median value of their particle size distribution, determined by laser scattering, and/or their chemical composition.

It is possible here for both types of particulate amorphous silicon dioxide to be selected such that they are chemically different and additionally have different particle size distribution. Alternatively, both types may be selected such that they merely have different particle size distributions with identical chemical composition. It is additionally possible for both types of particulate amorphous silicon dioxide to be selected such that they are chemically different but have the same particle size distribution.

The median value of a particle size distribution is understood to mean the value at which half of the particle population examined has a smaller size than that value, while the other half of the particle population examined has a greater size than that value. This value is preferably ascertained as described further down in example 1 for a commercially available material.

What is meant (here and hereinafter) by “determined by means of light scattering” is that a sample of the particulate material to be examined—if required—is pretreated analogously to the method of example 1 (see below) and the particle size distribution of the material thus pretreated is then determined by means of laser scattering as in example 1 (see below).

The invention also relates to a process of the invention (as just described, preferably as identified above as preferred),

• • (i)—wherein a first type of particulate amorphous silicon dioxide has a particle size distribution having a median in the range from 0.1 to 0.4 μm, determined by laser scattering,
    • and
    • wherein a further type of particulate amorphous silicon dioxide has a particle size distribution having a median in the range from 0.7 to 1.5 μm, determined by laser scattering,
  • and/or
  • (ii)—wherein one, two, more than two or all of the different types of particulate amorphous silicon dioxide is selected or are independently selected from the group (of chemically different materials) consisting of
    • particulate synthetic amorphous silicon dioxide containing silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate synthetic amorphous silicon dioxide, and at least carbon as secondary constituent, preferably producible by reducing quartz in an arc furnace;
    • particulate synthetic amorphous silicon dioxide comprising oxidic zirconium as secondary constituent and preferably producible by thermal breakdown of ZrSiO₄
    • particulate synthetic amorphous silicon dioxide producible by oxidizing metallic silicon by means of an oxygenous gas;
    • particulate synthetic amorphous silicon dioxide producible by quenching a silicon dioxide melt.

Preference is given to a process of the invention (as described above, preferably as identified above as preferred) wherein at least 90% of the grains of the granular material having a particle diameter greater than 0.2 mm, preferably greater than 0.5 mm, more preferably greater than 1 mm, in each case determined by sieving, comprise both or at least two of the different types of particulate amorphous silicon dioxide, preferably determined or confirmed (after appropriate sample processing, especially by sieving according to VDG-Merkblatt P 27, see below), for example by means of x-ray fluorescence analysis according to DIN EN ISO 12677, DIN 51001, optionally in combination with optical and/or spectroscopic methods and/or wet-chemical methods; the person skilled in the art will choose a suitable method of determination, preferably with knowledge of the materials used in the process.

Preference is given to a process of the invention (as described above, preferably as identified above as preferred), wherein the enlargement step comprises one or more measures independently selected from the group consisting of:

• • granulating
  • extruding
  •  and
  • agglomerating, preferably press agglomerating.

Further suitable processes for performing the enlargement step are known from the prior art and may likewise be used in accordance with the invention alternatively or additionally, i.e., for example, pelletizing, briquetting, tableting and others. Reference is made to the above remarks.

The invention also relates to a granular material having an average grain diameter greater than 0.2 mm, determined by sieving, for production of a pourable additive for use as a constituent of an inorganic binder in the foundry industry, comprising (preferably synthetic) particulate amorphous silicon dioxide,

• • (a) wherein the granular material additionally comprises
    • one, two or more further materials independently selected from the group consisting of:
      • particulate materials, preferably particulate inorganic materials, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably pulverulent oxidic boron compounds, and mixtures thereof,
      • water-soluble materials,
      • alkali metal hydroxides,
      • surfactants,
      • film formers,
      • hydrophobizing agents, preferably organosilicon compounds, silanes, silicones and siloxanes, waxes, paraffins, metal soaps,
    • and
      • carbohydrates,
    • wherein at least 90% of the grains of the granular material having a grain diameter greater than 0.2 mm, preferably greater than 0.5 mm, more preferably greater than 1 mm, in each case determined by sieving, comprise particulate amorphous silicon dioxide, and one, two or more of said further materials,
  • and/or
  • (b) wherein the particulate amorphous silicon dioxide comprises a proportion of at least 80% by weight of silicon dioxide, based on the total mass of the particulate amorphous silicon dioxide, preferably consisting wholly or partly of particulate synthetic amorphous silicon dioxide,
  • and/or
  • (c) wherein the proportion of silicon dioxide in the granular material as a whole, determined by means of x-ray fluorescence analysis, and the proportion of silicon dioxide in at least 90% of the grains of the granular material having a grain diameter greater than 1 mm, in each case determined by means of sieving and subsequent x-ray fluorescence analysis, differs by not more than 30%, preferably differs by not more than 20%, more preferably differs by not more than 10%, based on the proportion of silicon dioxide in the granular material as a whole,
  • and/or
  • (d) wherein, in the granular material, the particulate amorphous silicon dioxide comprises two or more different types of particulate amorphous silicon dioxide, where the two or more types differ by their chemical composition, preferably determined or confirmed (especially after sieving according to VDG-Merkblatt P 27, see above) by means of x-ray fluorescence analysis according to DIN EN ISO 12677, DIN 51001 (optionally in combination with optical and/or spectroscopic methods and/or wet-chemical methods; the person skilled in the art will choose a suitable method of determination, preferably with knowledge of the materials used in the process),
    • wherein preferably one, two, more than two or all of the different types of particulate amorphous silicon dioxide is selected or are independently selected from the group consisting of
      • particulate synthetic amorphous silicon dioxide containing silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate synthetic amorphous silicon dioxide, and at least carbon as secondary constituent, preferably producible by reducing quartz in an arc furnace;
      • particulate synthetic amorphous silicon dioxide comprising oxidic zirconium as secondary constituent and preferably producible by thermal breakdown of ZrSiO₄
      • particulate synthetic amorphous silicon dioxide producible by oxidizing metallic silicon by means of an oxygenous gas;
      • particulate synthetic amorphous silicon dioxide producible by quenching a silicon dioxide melt
  • and/or
  • (e) wherein the granular material is producible by a process as described above, preferably as identified above as preferred.

The granular material thus defined (i.e. the entirety of specific grains, see above) has particularly advantageous combinations of the following properties: homogeneous composition, high bulk density, low dust level, good flowability, good conveyability, good meterability, low dust level, avoidance of separation phenomena, comminutability, high molding weight of the moldings producible with use thereof, elevated moisture stability (moisture resistance) of the moldings producible with use thereof.

Configurations (a) and (e) are of particularly high economic relevance and therefore preferred in many cases.

The invention also relates to a kit comprising, as spatially separate component, a granular material (as described above, preferably as identified above as preferred).

The invention also relates to a kit for production of an inorganic binder (as described above, preferably as identified above as preferred), more preferably a binder comprising and/or consisting of an inorganic multicomponent binder system, at least comprising, as components in a mutually spatially separate arrangement,

• • a granular material (as described above, preferably as identified above as preferred),
  •  and
  • a solution or dispersion comprising waterglass.

The kit of the invention is particularly suitable for performance of processes of the invention by which the successor products of the granular material are produced (binder; molding material mixture; molding).

The effects and advantages set out above in connection with processes of the invention and granular material of the invention are achieved when the kit of the invention is used.

The invention also relates to an apparatus for performance of a process of the invention (as described above, preferably as identified above as preferred), comprising

• • a reservoir vessel containing particulate amorphous silicon dioxide, comprising silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate amorphous silicon dioxide,
  • a mixing or contacting device for mixing or contacting the particulate amorphous silicon dioxide with one, two or more further materials,
  • a device for granulating, extruding and/or agglomerating the particulate amorphous silicon dioxide that has been mixed or contacted with one, two or more further materials.

The apparatus of the invention is particularly suitable for performance of processes of the invention and for production of granular material of the invention.

The effects and advantages set out above in connection with processes of the invention and granular material of the invention may be achieved when the apparatus of the invention is used and established according to requirements of the individual case.

Preference is given to an apparatus of the invention (as described above, preferably as identified above as preferred), additionally comprising one or more apparatus elements selected from the group consisting of

• • device for transferring particulate amorphous silicon dioxide from the reservoir vessel into the mixing or contacting apparatus,
  • one or more reservoir vessels containing liquid, preferably liquid wetting agent and/or suspension medium, preferably water,
  • one or more reservoir vessels containing particulate material, preferably particulate inorganic material, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably pulverulent oxidic boron compounds, and mixtures thereof,
  • one or more reservoir vessels containing a water-soluble material,
  • one or more reservoir vessels containing one or more surfactants,
  • one or more reservoir vessels containing one or more hydrophobizing agents,
  • one or more reservoir vessels containing one or more carbohydrates.

According to the requirements of the individual case, the preferred apparatus (plant) is particularly advantageously suitable for performance of a process of the invention and for production of a granular material of the invention.

Preference is given to an apparatus of the invention (as described above, preferably as identified above as preferred), additionally comprising a device for dispensing or transporting granular material produced.

The invention also relates to the corresponding use (as described above, preferably as identified above as preferred) of (preferably synthetic) particulate amorphous silicon dioxide for production of or as a constituent of a granular material.

The inventive use of particulate amorphous silicon dioxide for production of or as a constituent of a granular material, depending on the particle size distribution of the particulate amorphous silicon dioxide, with a molding material mixture produced therefrom produces a molding having a specific, preferably particularly high, relative molding weight (in the case of cores: core weight). The inventive use of particulate amorphous silicon dioxide for production of or as a constituent of a granular material, depending on the particle size distribution of the particulate amorphous silicon dioxide, with the molding material mixture produced therefrom produces a molding having a specific, preferably particularly high, moisture stability.

The invention also relates to the use of a granular material (as described above, preferably as identified above as in accordance with the invention or as preferred) for production of a solid pourable additive with homogenized grain composition for use as a constituent of an inorganic binder in the foundry industry.

Preferred aspects of the present invention are specified hereinafter.

• 1. A process for producing a granular material for production of a pourable additive for use as a constituent of an inorganic binder in the foundry industry,
  • comprising the following steps for production of the granular material:
    • producing or providing particulate amorphous silicon dioxide comprising silicon dioxide in a proportion of at least 80% by weight, preferably in a proportion of at least 90% by weight, based on the total mass of the particulate amorphous silicon dioxide,
    • combining the particles of the particulate amorphous silicon dioxide in an enlargement step to give grains, so as to result in a granular material comprising a multitude of individual grains each comprising combined particles and each comprising a proportion of at least 30% by weight, preferably at least 40% by weight, more preferably at least 50% by weight, of particulate amorphous silicon dioxide, based on the mass of the respective grain, where the average grain diameter of the granular material is greater than 0.2 mm, determined by sieving,
  • wherein the particulate amorphous silicon dioxide produced or provided preferably comprises particles having a size of less than 20 μm, more preferably particles having a size of 0.1 μm to 5 μm, most preferably particles having a size of 0.1 μm to 1.5 μm, determined by scanning electron microscopy (SEM) or laser diffraction.

The product of this process is said granular material.

• 2. A process for producing a solid pourable additive for use as a constituent of an inorganic binder in the foundry industry,
  • comprising the following (and further) steps for production of the solid pourable additive:
    • producing or providing particulate amorphous silicon dioxide comprising silicon dioxide in a proportion of at least 80% by weight, preferably in a proportion of at least 90% by weight, based on the total mass of the particulate amorphous silicon dioxide,
    • combining the particles of the particulate amorphous silicon dioxide in an enlargement step to give grains, so as to result in a granular material comprising a multitude of individual grains each comprising combined particles and each comprising a proportion of at least 30% by weight, preferably at least 40% by weight, more preferably at least 50% by weight, of particulate amorphous silicon dioxide, based on the mass of the respective grain, where the average grain diameter of the granular material is greater than 0.2 mm, determined by sieving,
  • wherein the particulate amorphous silicon dioxide produced or provided preferably comprises particles having a size of less than 20 μm, more preferably particles having a size of 0.1 μm to 5 μm, most preferably particles having a size of 0.1 μm to 1.5 μm, determined by scanning electron microscopy (SEM) or laser diffraction.
• 3. A process for producing an inorganic binder for use in the foundry industry
  • comprising the following (and further) steps for production of the inorganic binder:
    • producing or providing particulate amorphous silicon dioxide comprising silicon dioxide in a proportion of at least 80% by weight, preferably in a proportion of at least 90% by weight, based on the total mass of the particulate amorphous silicon dioxide,
    • combining the particles of the particulate amorphous silicon dioxide in an enlargement step to give grains, so as to result in a granular material comprising a multitude of individual grains each comprising combined particles and each comprising a proportion of at least 30% by weight, preferably at least 40% by weight, more preferably at least 50% by weight, of particulate amorphous silicon dioxide, based on the mass of the respective grain, where the average grain diameter of the granular material is greater than 0.2 mm, determined by sieving,
  • wherein the particulate amorphous silicon dioxide produced or provided preferably comprises particles having a size of less than 20 μm, more preferably particles having a size of 0.1 μm to 5 μm, most preferably particles having a size of 0.1 μm to 1.5 μm, determined by scanning electron microscopy (SEM) or laser diffraction.
• 4. A process for producing a molding material mixture comprising an organic binder for use in the foundry industry,
  • comprising the following (and further) steps for production of the molding material mixture:
    • producing or providing particulate amorphous silicon dioxide comprising silicon dioxide in a proportion of at least 80% by weight, preferably in a proportion of at least 90% by weight, based on the total mass of the particulate amorphous silicon dioxide,
    • combining the particles of the particulate amorphous silicon dioxide in an enlargement step to give grains, so as to result in a granular material comprising a multitude of individual grains each comprising combined particles and each comprising a proportion of at least 30% by weight, preferably at least 40% by weight, more preferably at least 50% by weight, of particulate amorphous silicon dioxide, based on the mass of the respective grain, where the average grain diameter of the granular material is greater than 0.2 mm, determined by sieving,
  • wherein the particulate amorphous silicon dioxide produced or provided preferably comprises particles having a size of less than 20 μm, more preferably particles having a size of 0.1 μm to 5 μm, most preferably particles having a size of 0.1 μm to 1.5 μm, determined by scanning electron microscopy (SEM) or laser diffraction.
• 5. A process for producing a molding for use in the casting of metallic cast parts in the foundry industry,
  • comprising the following (and further) steps for production of the molding:
    • producing or providing particulate amorphous silicon dioxide comprising silicon dioxide in a proportion of at least 80% by weight, preferably in a proportion of at least 90% by weight, based on the total mass of the particulate amorphous silicon dioxide,
    • combining the particles of the particulate amorphous silicon dioxide in an enlargement step to give grains, so as to result in a granular material comprising a multitude of individual grains each comprising combined particles and each comprising a proportion of at least 30% by weight, preferably at least 40% by weight, more preferably at least 50% by weight, of particulate amorphous silicon dioxide, based on the mass of the respective grain, where the average grain diameter of the granular material is greater than 0.2 mm, determined by sieving, wherein the particulate amorphous silicon dioxide produced or provided preferably comprises particles having a size of less than 20 μm, more preferably particles having a size of 0.1 μm to 5 μm, most preferably particles having a size of 0.1 μm to 1.5 μm, determined by scanning electron microscopy (SEM) or laser diffraction.
• 6. The process according to aspect 2 for producing a solid pourable additive for use as a constituent of an inorganic binder in the foundry industry,
  • comprising the steps of:
    • producing a granular material by a process according to aspect 1,
    • comminuting the grains of the granular material, so as to result in a solid pourable additive.
• 7. The process according to aspect 3 for producing an inorganic binder for use in the foundry industry
  • comprising the steps of:
    • producing a granular material by a process according to aspect 1,
    • comminuting the grains of the granular material, so as to result in a solid pourable additive.
• 8. The process according to aspect 4 for producing a molding material mixture comprising an organic binder for use in the foundry industry,
  • comprising the steps of:
    • producing a granular material by a process according to aspect 1,
    • comminuting the grains of the granular material, so as to result in a solid pourable additive.
• 9. The process according to aspect 5 for producing a molding for use in the casting of metallic cast parts in the foundry industry,
  • comprising the steps of:
    • producing a granular material by a process according to aspect 1,
    • comminuting the grains of the granular material, so as to result in a solid pourable additive.
• 10. The process according to either of the preceding aspects 3 and 7 for producing an inorganic binder for use in the foundry industry,
  • comprising the steps of:
    • producing the solid pourable additive by a process according to either of aspects 2 and 6,
    • contacting the solid pourable additive produced with waterglass or suspending the solid pourable additive produced in waterglass,
• 11. The process according to any of the preceding aspects 3, 7 and 10 for producing an inorganic binder for use in the foundry industry,
  • comprising the steps of:
    • producing a granular material by a process according to any of aspects 1 to 9,
    • contacting the granular material produced with waterglass, in the presence or absence of refractory mold base material, and comminuting the grains of the granular material at the same time or thereafter.
• 12. The process according to either of the preceding aspects 4 and 8 for producing a molding material mixture comprising an inorganic binder for use in the foundry industry,
  • comprising the steps of:
    • producing the solid pourable additive by a process according to any of aspects 2, 6 and 10,
    • contacting the solid pourable additive produced with waterglass or suspending the solid pourable additive produced in waterglass.
• 13. The process according to any of the preceding aspects 4, 8 and 12 for producing a molding material mixture comprising an inorganic binder for use in the foundry industry,
  • comprising the steps of:
    • producing a granular material by a process according to any of aspects 1 to 9 or 11,
    • contacting the granular material produced with waterglass, in the presence or absence of refractory mold base material, and comminuting the grains of the granular material at the same time or thereafter.
• 14. The process according to either of the preceding aspects 5 and 9 for producing a molding for use in the casting of metallic cast parts in the foundry industry,
  • comprising the steps of:
    • producing the solid pourable additive by a process according to any of aspects 2, 6 and 10,
    • contacting the solid pourable additive produced with waterglass or suspending the solid pourable additive produced in waterglass.
• 15 The process according to any of the preceding aspects 5, 9 and 14 for producing a molding for use in the casting of metallic cast parts in the foundry industry,
  • comprising the steps of:
    • producing a granular material by a process according to any of aspects 1 to 9, 11 and 13,
    • contacting the granular material produced with waterglass, in the presence or absence of refractory mold base material, and comminuting the grains of the granular material at the same time or thereafter.
• 16. The process according to any of the preceding aspects 4, 8, 12 and 13 for producing a molding material mixture comprising refractory mold base material and an inorganic binder comprising waterglass and particulate amorphous silicon dioxide for use in the foundry industry,
  • comprising the steps of:
    • producing an inorganic binder according to any of aspects 3, 7, 10 and 11,
  • and
    • at the same time mixing the constituents used for production of the inorganic binder with a refractory mold base material.
• 17. The process according to any of the preceding aspects 4, 8, 12, 13 and 16 for producing a molding material mixture comprising refractory mold base material and an inorganic binder comprising waterglass and particulate amorphous silicon dioxide for use in the foundry industry,
  • comprising the steps of:
    • producing an inorganic binder according to any of aspects 3, 7, 10, 11, 16,
  • and
    • at the same time mixing the constituents used for production of the inorganic binder with a refractory mold base material
  • and
    • thereafter mixing the inorganic binder produced with a refractory mold base material.
• 18. The process according to any of claims 4, 8, 12, 13, 16 and 17 for producing a molding material mixture comprising refractory mold base material and an inorganic binder comprising waterglass and particulate amorphous silicon dioxide for use in the foundry industry,
  • comprising the steps of:
    • producing an inorganic binder according to any of aspects 3, 7, 10, 11, 16, 17,
  • and
    • thereafter mixing the inorganic binder produced with a refractory mold base material.
• 19. The process according to any of aspects 1 to 5, wherein, in the step of
  • combining the particles of the particulate amorphous silicon dioxide in an enlargement step to give grains, so as to result in a granular material comprising a multitude of individual grains each comprising combined particles and each comprising a proportion of at least 30% by weight, preferably at least 40% by weight, more preferably at least 50% by weight, of particulate amorphous silicon dioxide, based on the mass of the respective grain,
  • the average grain diameter of the granular material is greater than 0.5 mm, preferably greater than 1 mm, determined by sieving.
• 20. The process according to any of the preceding aspects, wherein the particulate amorphous silicon dioxide comprising silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate amorphous silicon dioxide, consists wholly of particulate synthetic amorphous silicon dioxide.
• 21. The process according to any of the preceding aspects, wherein the particulate amorphous silicon dioxide comprising silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate amorphous silicon dioxide, consists partly of particulate synthetic amorphous silicon dioxide.
• 22. The process according to any of the preceding aspects, wherein the proportion of silicon dioxide in the granular material as a whole, determined by means of x-ray fluorescence analysis, and the proportion of silicon dioxide in at least 90% of the grains of the granular material having a grain diameter greater than 1 mm, determined by means of sieving and subsequent x-ray fluorescence analysis, differs by not more than 30%, based on the proportion of silicon dioxide in the granular material as a whole.
• 23. The process according to any of the preceding aspects, wherein the proportion of silicon dioxide in the granular material as a whole, determined by means of x-ray fluorescence analysis, and the proportion of silicon dioxide in at least 90% of the grains of the granular material having a grain diameter greater than 1 mm, determined by means of sieving and subsequent x-ray fluorescence analysis, differs by not more than 20%, based on the proportion of silicon dioxide in the granular material as a whole.
• 24. The process according to any of the preceding aspects, wherein the proportion of silicon dioxide in the granular material as a whole, determined by means of x-ray fluorescence analysis, and the proportion of silicon dioxide in at least 90% of the grains of the granular material having a grain diameter greater than 1 mm, determined by means of sieving and subsequent x-ray fluorescence analysis, differs by not more than 10%, based on the proportion of silicon dioxide in the granular material as a whole.
• 25. The process according to any of the preceding aspects, wherein the proportion of silicon dioxide in the granular material as a whole, determined by means of x-ray fluorescence analysis, and the proportion of silicon dioxide in at least 90% of the grains of the granular material having a grain diameter greater than 0.5 mm, determined by means of sieving and subsequent x-ray fluorescence analysis, differs by not more than 30%, based on the proportion of silicon dioxide in the granular material as a whole.
• 26. The process according to any of the preceding aspects, wherein the proportion of silicon dioxide in the granular material as a whole, determined by means of x-ray fluorescence analysis, and the proportion of silicon dioxide in at least 90% of the grains of the granular material having a grain diameter greater than 0.5 mm, determined by means of sieving and subsequent x-ray fluorescence analysis, differs by not more than 20%, based on the proportion of silicon dioxide in the granular material as a whole.
• 27. The process according to any of the preceding aspects, wherein the proportion of silicon dioxide in the granular material as a whole, determined by means of x-ray fluorescence analysis, and the proportion of silicon dioxide in at least 90% of the grains of the granular material having a grain diameter greater than 0.5 mm, determined by means of sieving and subsequent x-ray fluorescence analysis, differs by not more than 10%, based on the proportion of silicon dioxide in the granular material as a whole.
• 28. The process according to any of the preceding aspects, wherein the proportion of silicon dioxide in the granular material as a whole, determined by means of x-ray fluorescence analysis, and the proportion of silicon dioxide in at least 90% of the grains of the granular material having a grain diameter greater than 0.2 mm, determined by means of sieving and subsequent x-ray fluorescence analysis, differs by not more than 30%, based on the proportion of silicon dioxide in the granular material as a whole.
• 29. The process according to any of the preceding aspects, wherein the proportion of silicon dioxide in the granular material as a whole, determined by means of x-ray fluorescence analysis, and the proportion of silicon dioxide in at least 90% of the grains of the granular material having a grain diameter greater than 0.2 mm, determined by means of sieving and subsequent x-ray fluorescence analysis, differs by not more than 20%, based on the proportion of silicon dioxide in the granular material as a whole.
• 30. The process according to any of the preceding aspects, wherein the proportion of silicon dioxide in the granular material as a whole, determined by means of x-ray fluorescence analysis, and the proportion of silicon dioxide in at least 90% of the grains of the granular material having a grain diameter greater than 0.2 mm, determined by means of sieving and subsequent x-ray fluorescence analysis, differs by not more than 10%, based on the proportion of silicon dioxide in the granular material as a whole.
• 31. The process according to any of the preceding aspects, wherein, in the enlargement step, the particles of the particulate amorphous silicon dioxide are mixed and/or contacted with one, two or more further materials independently selected from the group consisting of:
  • liquids, preferably liquid wetting agents and/or suspension media, preferably water,
  • particulate materials, preferably particulate inorganic materials, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably pulverulent oxidic boron compounds, and mixtures thereof,
  • water-soluble materials,
  • alkali metal hydroxides,
  • surfactants,
  • film formers,
  • hydrophobizing agents, preferably organosilicon compounds, silanes, silicones and siloxanes, waxes, paraffins, metal soaps,
•  and
  • carbohydrates.
• 32. The process according to aspect 31, wherein grains of the granular material that results from the enlargement step, preferably at least 90% of the grains of the granular material having a grain diameter greater than 1 mm, preferably greater than 0.5 mm, more preferably greater than 0.2 mm, in each case determined by means of sieving,
  • (i) comprise particulate amorphous silicon dioxide and one, two, more than two or all of the further solid materials present in the enlargement step
•  and
  • (ii) comprise particulate amorphous silicon dioxide and one, two or more further materials independently selected from the group consisting of:
    • particulate materials, preferably particulate inorganic materials, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably pulverulent oxidic boron compounds, and mixtures thereof,
    • water-soluble materials,
    • alkali metal hydroxides,
    • surfactants,
    • film formers,
    • hydrophobizing agents, preferably organosilicon compounds, silanes, silicones and siloxanes, waxes, paraffins, metal soaps,
  • and
    • carbohydrates.
• 33. The process according to aspect 31, wherein grains of the granular material that results from the enlargement step, preferably at least 90% of the grains of the granular material having a grain diameter greater than 1 mm, preferably greater than 0.5 mm, more preferably greater than 0.2 mm, in each case determined by means of sieving,
  • comprise particulate amorphous silicon dioxide and one, two, more than two or all of the other solid materials present in the enlargement step.
• 34. The process according to aspect 31, wherein grains of the granular material that results from the enlargement step, preferably at least 90% of the grains of the granular material having a grain diameter greater than 1 mm, preferably greater than 0.5 mm, more preferably greater than 0.2 mm, in each case determined by means of sieving,
  • comprise particulate amorphous silicon dioxide and one, two or more further materials independently selected from the group consisting of:
    • particulate materials, preferably particulate inorganic materials, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably pulverulent oxidic boron compounds, and mixtures thereof,
    • water-soluble materials,
    • alkali metal hydroxides,
    • surfactants,
    • film formers,
    • hydrophobizing agents, preferably organosilicon compounds, silanes, silicones and siloxanes, waxes, paraffins, metal soaps,
  • and
    • carbohydrates.
• 35. The process according to any of the preceding aspects, wherein
  • the producing of particulate amorphous silicon dioxide comprising silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate amorphous silicon dioxide, comprises the step of:
    • mixing two or more different types of particulate amorphous silicon dioxide, where the two or more types differ by their particle size distribution and/or their chemical composition.
• 36. The process according to aspect 35, wherein
  • one type of particulate amorphous silicon dioxide has a particle size distribution having a median in the range from 0.1 to 0.4 μm, determined by laser scattering.
• 37. The process according to aspect 35, wherein
  • one type of particulate amorphous silicon dioxide has a particle size distribution having a median in the range from 0.7 to 1.5 μm, determined by laser scattering.
• 38. The process according to aspect 35, wherein
  • one, two, more than two or all of the different types of particulate amorphous silicon dioxide is selected or are independently selected from the group consisting of
    • particulate synthetic amorphous silicon dioxide containing silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate synthetic amorphous silicon dioxide, and at least carbon as secondary constituent, preferably producible by reducing quartz in an arc furnace;
    • particulate synthetic amorphous silicon dioxide comprising oxidic zirconium as secondary constituent and preferably producible by thermal breakdown of ZrSiO₄
    • particulate synthetic amorphous silicon dioxide producible by oxidizing metallic silicon by means of an oxygenous gas;
    • particulate synthetic amorphous silicon dioxide producible by quenching a silicon dioxide melt.
• 39. The process according to aspect 35,
  • wherein a first type of particulate amorphous silicon dioxide has a particle size distribution having a median in the range from 0.1 to 0.4 μm, determined by laser scattering,
•  and
  • wherein a further type of particulate amorphous silicon dioxide has a particle size distribution having a median in the range from 0.7 to 1.5 μm, determined by laser scattering.
• 40. The process according to aspect 35,
  • wherein a first type of particulate amorphous silicon dioxide has a particle size distribution having a median in the range from 0.1 to 0.4 μm, determined by laser scattering,
•  and
  • wherein one, two, more than two or all the different types of particulate amorphous silicon dioxide is selected or are independently selected from the group consisting of
    • particulate synthetic amorphous silicon dioxide containing silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate synthetic amorphous silicon dioxide, and at least carbon as secondary constituent, preferably producible by reducing quartz in an arc furnace;
    • particulate synthetic amorphous silicon dioxide comprising oxidic zirconium as secondary constituent and preferably producible by thermal breakdown of ZrSiO₄
    • particulate synthetic amorphous silicon dioxide producible by oxidizing metallic silicon by means of an oxygenous gas;
    • particulate synthetic amorphous silicon dioxide producible by quenching a silicon dioxide melt.
• 41. The process according to aspect 35,
  • wherein a first type of particulate amorphous silicon dioxide has a particle size distribution having a median in the range from 0.1 to 0.4 μm, determined by laser scattering,
•  and
  • wherein a further type of particulate amorphous silicon dioxide has a particle size distribution having a median in the range from 0.7 to 1.5 μm, determined by laser scattering,
•  and
  • wherein one, two, more than two or all the different types of particulate amorphous silicon dioxide is selected or are independently selected from the group consisting of
    • particulate synthetic amorphous silicon dioxide containing silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate synthetic amorphous silicon dioxide, and at least carbon as secondary constituent, preferably producible by reducing quartz in an arc furnace;
    • particulate synthetic amorphous silicon dioxide comprising oxidic zirconium as secondary constituent and preferably producible by thermal breakdown of ZrSiO₄
    • particulate synthetic amorphous silicon dioxide producible by oxidizing metallic silicon by means of an oxygenous gas;
    • particulate synthetic amorphous silicon dioxide producible by quenching a silicon dioxide melt.
• 42. The process according to aspect 35,
  • wherein a further type of particulate amorphous silicon dioxide has a particle size distribution having a median in the range from 0.7 to 1.5 μm, determined by laser scattering,
•  and
  • wherein one, two, more than two or all the different types of particulate amorphous silicon dioxide is selected or are independently selected from the group consisting of
    • particulate synthetic amorphous silicon dioxide containing silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate synthetic amorphous silicon dioxide, and at least carbon as secondary constituent, preferably producible by reducing quartz in an arc furnace;
    • particulate synthetic amorphous silicon dioxide comprising oxidic zirconium as secondary constituent and preferably producible by thermal breakdown of ZrSiO₄
    • particulate synthetic amorphous silicon dioxide producible by oxidizing metallic silicon by means of an oxygenous gas;
    • particulate synthetic amorphous silicon dioxide producible by quenching a silicon dioxide melt.
• 43. The process according to any of aspects 35 to 42, wherein at least 90% of the grains of the granular material having a particle diameter greater than 0.2 mm, preferably greater than 0.5 mm, more preferably greater than 1 mm, in each case determined by sieving, comprise both or at least two of the different types of particulate amorphous silicon dioxide, preferably determined or confirmed (especially by sieving according to VDG-Merkblatt P 27, see above), for example by means of x-ray fluorescence analysis according to DIN EN ISO 12677, DIN 51001, optionally in combination with optical and/or spectroscopic methods and/or wet-chemical methods; the person skilled in the art will choose a suitable method of determination, preferably with knowledge of the materials used in the process.
• 44. The process according to one of the preceding aspects, wherein the enlargement step comprises one or more measures independently selected from the group consisting of:
  • granulating
  • extruding
•  and
  • agglomerating.
• 45. A granular material having an average grain diameter greater than 0.2 mm, determined by sieving, for production of a pourable additive for use as a constituent of an inorganic binder in the foundry industry, comprising particulate amorphous silicon dioxide,
  • (a) wherein the granular material additionally comprises
    • one, two or more further materials independently selected from the group consisting of:
      • particulate materials, preferably particulate inorganic materials, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably pulverulent oxidic boron compounds, and mixtures thereof,
      • water-soluble materials,
      • alkali metal hydroxides,
      • surfactants,
      • film formers,
      • hydrophobizing agents, preferably organosilicon compounds, silanes, silicones and siloxanes, waxes, paraffins, metal soaps,
    • and
      • carbohydrates,
    • wherein at least 90% of the grains of the granular material having a grain diameter greater than 0.2 mm, preferably greater than 0.5 mm, more preferably greater than 1 mm, in each case determined by sieving, comprise particulate amorphous silicon dioxide, and one, two or more of said further materials,
  • and/or
  • (b) wherein the particulate amorphous silicon dioxide comprises a proportion of at least 80% by weight of silicon dioxide, based on the total mass of the particulate amorphous silicon dioxide, preferably consisting wholly or partly of particulate synthetic amorphous silicon dioxide,
  • and/or
  • (c) wherein the proportion of silicon dioxide in the granular material as a whole, determined by means of x-ray fluorescence analysis, and the proportion of silicon dioxide in at least 90% of the grains of the granular material having a grain diameter greater than 1 mm, in each case determined by means of sieving and subsequent x-ray fluorescence analysis, differs by not more than 30%, preferably differs by not more than 20%, more preferably differs by not more than 10%, based on the proportion of silicon dioxide in the granular material as a whole,
  • and/or
  • (d) wherein, in the granular material, the particulate amorphous silicon dioxide comprises two or more different types of particulate amorphous silicon dioxide, where the two or more types differ by their chemical composition,
    • wherein preferably one, two, more than two or all of the different types of particulate amorphous silicon dioxide is selected or are independently selected from the group consisting of:
      • particulate synthetic amorphous silicon dioxide containing silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate synthetic amorphous silicon dioxide, and at least carbon as secondary constituent, preferably producible by reducing quartz in an arc furnace;
      • particulate synthetic amorphous silicon dioxide comprising oxidic zirconium as secondary constituent and preferably producible by thermal breakdown of ZrSiO₄
      • particulate synthetic amorphous silicon dioxide producible by oxidizing metallic silicon by means of an oxygenous gas;
      • particulate synthetic amorphous silicon dioxide producible by quenching a silicon dioxide melt
  • and/or
  • (e) wherein the granular material is producible by a process according to any of aspects 1 to 9 or any of aspects 20 to 44.
• 46. A granular material having an average grain diameter greater than 0.2 mm, determined by sieving, for production of a pourable additive for use as a constituent of an inorganic binder in the foundry industry, comprising particulate amorphous silicon dioxide,
  • (a) wherein the granular material additionally comprises
    • one, two or more further materials independently selected from the group consisting of
      • particulate materials, preferably particulate inorganic materials, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably pulverulent oxidic boron compounds, and mixtures thereof,
      • water-soluble materials,
      • alkali metal hydroxides,
      • surfactants,
      • film formers,
      • hydrophobizing agents, preferably organosilicon compounds, silanes, silicones and siloxanes, waxes, paraffins, metal soaps,
    • and
      • carbohydrates,
    • wherein at least 90% of the grains of the granular material having a grain diameter greater than 0.2 mm, preferably greater than 0.5 mm, more preferably greater than 1 mm, in each case determined by sieving, comprise particulate amorphous silicon dioxide, and one, two or more of said further materials,
  • and
  • (b) wherein the particulate amorphous silicon dioxide comprises a proportion of at least 80% by weight of silicon dioxide, based on the total mass of the particulate amorphous silicon dioxide, preferably consisting wholly or partly of particulate synthetic amorphous silicon dioxide,
  • and
  • (c) wherein the proportion of silicon dioxide in the granular material as a whole, determined by means of x-ray fluorescence analysis, and the proportion of silicon dioxide in at least 90% of the grains of the granular material having a grain diameter greater than 1 mm, in each case determined by means of sieving and subsequent x-ray fluorescence analysis, differs by not more than 30%, preferably differs by not more than 20%, more preferably differs by not more than 10%, based on the proportion of silicon dioxide in the granular material as a whole,
  • and
  • (d) wherein, in the granular material, the particulate amorphous silicon dioxide comprises two or more different types of particulate amorphous silicon dioxide, where the two or more types differ by their chemical composition,
    • wherein preferably one, two, more than two or all of the different types of particulate amorphous silicon dioxide is selected or are independently selected from the group consisting of
      • particulate synthetic amorphous silicon dioxide containing silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate synthetic amorphous silicon dioxide, and at least carbon as secondary constituent, preferably producible by reducing quartz in an arc furnace;
      • particulate synthetic amorphous silicon dioxide comprising oxidic zirconium as secondary constituent and preferably producible by thermal breakdown of ZrSiO₄
      • particulate synthetic amorphous silicon dioxide producible by oxidizing metallic silicon by means of an oxygenous gas;
      • particulate synthetic amorphous silicon dioxide producible by quenching a silicon dioxide melt
  • and
  • (e) wherein the granular material is producible by a process according to any of aspects 1 to 9 or any of aspects 20 to 44.
• 47. A granular material having an average grain diameter greater than 0.2 mm, determined by sieving, for production of a pourable additive for use as a constituent of an inorganic binder in the foundry industry, comprising particulate amorphous silicon dioxide,
  • wherein the granular material additionally comprises
    • one, two or more further materials independently selected from the group consisting of:
      • particulate materials, preferably particulate inorganic materials, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably pulverulent oxidic boron compounds, and mixtures thereof,
      • water-soluble materials,
      • alkali metal hydroxides,
      • surfactants,
      • film formers,
      • hydrophobizing agents, preferably organosilicon compounds, silanes, silicones and siloxanes, waxes, paraffins, metal soaps,
    • and
      • carbohydrates,
    • wherein at least 90% of the grains of the granular material having a grain diameter greater than 0.2 mm, preferably greater than 0.5 mm, more preferably greater than 1 mm, in each case determined by sieving, comprise particulate amorphous silicon dioxide, and one, two or more of said further materials.
• 48. A granular material having an average grain diameter greater than 0.2 mm, determined by sieving, for production of a pourable additive for use as a constituent of an inorganic binder in the foundry industry, comprising particulate amorphous silicon dioxide,
  • wherein the particulate amorphous silicon dioxide comprises a proportion of at least 80% by weight of silicon dioxide, based on the total mass of the particulate amorphous silicon dioxide, preferably consisting wholly or partly of particulate synthetic amorphous silicon dioxide,
• 49 A granular material having an average grain diameter greater than 0.2 mm, determined by sieving, for production of a pourable additive for use as a constituent of an inorganic binder in the foundry industry, comprising particulate amorphous silicon dioxide,
  • wherein the proportion of silicon dioxide in the granular material as a whole, determined by means of x-ray fluorescence analysis, and the proportion of silicon dioxide in at least 90% of the grains of the granular material having a grain diameter greater than 1 mm, in each case determined by means of sieving and subsequent x-ray fluorescence analysis, differs by not more than 30%, preferably differs by not more than 20%, more preferably differs by not more than 10%, based on the proportion of silicon dioxide in the granular material as a whole.
• 50. A granular material having an average grain diameter greater than 0.2 mm, determined by sieving, for production of a pourable additive for use as a constituent of an inorganic binder in the foundry industry, comprising particulate amorphous silicon dioxide,
  • wherein, in the granular material, the particulate amorphous silicon dioxide comprises two or more different types of particulate amorphous silicon dioxide, where the two or more types differ by their chemical composition,
  • wherein preferably one, two, more than two or all of the different types of particulate amorphous silicon dioxide is selected or are independently selected from the group consisting of
    • particulate synthetic amorphous silicon dioxide containing silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate synthetic amorphous silicon dioxide, and at least carbon as secondary constituent, preferably producible by reducing quartz in an arc furnace;
    • particulate synthetic amorphous silicon dioxide comprising oxidic zirconium as secondary constituent and preferably producible by thermal breakdown of ZrSiO₄
    • particulate synthetic amorphous silicon dioxide producible by oxidizing metallic silicon by means of an oxygenous gas;
    • particulate synthetic amorphous silicon dioxide producible by quenching a silicon dioxide melt.
• 51. A granular material having an average grain diameter greater than 0.2 mm, determined by sieving, for production of a pourable additive for use as a constituent of an inorganic binder in the foundry industry, comprising particulate amorphous silicon dioxide,
  • wherein the granular material is producible by a process according to any of aspects 1 to 9 or any of aspects 20 to 44.
• 52. A kit comprising, as a component in a spatially separate arrangement, a granular material according to any of aspects 45 to 51, preferably
  • kit for production of an inorganic binder, preferably a binder comprising and/or consisting of an inorganic multicomponent binder system, at least comprising, as components in a mutually spatially separate arrangement,
    • a granular material according to any of aspects 45 to 51
  • and
    • a solution or dispersion comprising waterglass.
• 53. An apparatus for performing a process according to any of aspects 1 to 44, comprising
  • a reservoir vessel containing particulate amorphous silicon dioxide, comprising silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate amorphous silicon dioxide,
  • a mixing or contacting device for mixing or contacting the particulate amorphous silicon dioxide with one, two or more further materials,
  • a device for granulating, extruding and/or agglomerating the particulate amorphous silicon dioxide that has been mixed or contacted with one, two or more further materials.
• 54. The apparatus according to aspect 53, additionally comprising one or more apparatus elements selected from the group consisting of
  • device for transferring particulate amorphous silicon dioxide from the reservoir vessel into the mixing or contacting apparatus,
  • one or more reservoir vessels containing liquid, preferably liquid wetting agent and/or suspension medium, preferably water,
  • one or more reservoir vessels containing particulate material, preferably particulate inorganic material, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably pulverulent oxidic boron compounds, and mixtures thereof,
  • one or more reservoir vessels containing a water-soluble material,
  • one or more reservoir vessels containing one or more surfactants,
    • one or more reservoir vessels containing one or more hydrophobizing agents,
    • one or more reservoir vessels containing one or more carbohydrates.
• 55. The apparatus according to aspect 53 or 54, additionally comprising a device for dispensing or transporting granular material produced.
• 56. The use of particulate amorphous silicon dioxide for production of or as a constituent of a granular material according to aspect 45 to 51.
• 57. The use of a granular material according to any of aspects 45 to 51 for production of a solid pourable additive with homogenized grain composition for use as a constituent of an inorganic binder in the foundry industry.

The invention is elucidated in detail hereinafter with reference to figures.

FIG. 1 shows a flow diagram of a first embodiment of an inventive process 100 for producing a molding material mixture 107 for use in the foundry industry.

In a first step 101 of the process 100, a particulate amorphous silicon dioxide is produced or provided, as defined above.

In a second (enlargement) step 102, the particles of the particulate amorphous silicon dioxide are combined to give grains, so as to result in an above-defined granular material 103 comprising a multitude of individual grains.

The granular material produced is already a product of a process of the invention.

In a further step 104, the granular material produced is contacted directly with waterglass, so as to result in an inorganic binder 105. The inorganic binder produced is likewise a product of a process of the invention.

In an additional step 106, the inorganic binder 105 produced is mixed with a refractory mold base material, so as to result in a molding material mixture 107 as product of the process of the invention.

In a further step 108, the molding material mixture 107 produced is molded and (at least partly) cured, so as to result in a molding 109 as product of the process of the invention.

FIG. 2 shows a flow diagram of a second embodiment of an inventive process 200 for producing a molding material mixture 209 for use in the foundry industry.

In a first step 201 of the process 200, a particulate amorphous silicon dioxide is produced or provided, as defined above.

In a second (enlargement) step 202, the particles of the particulate amorphous silicon dioxide are combined to give grains, so as to result in an above-defined granular material 203 comprising a multitude of individual grains. The granular material produced is already a product of a process of the invention.

In a next step 204, the grains of the granular material 203 are comminuted, so as to form a solid pourable additive 205. The additive produced is likewise a product of a process of the invention.

In a further step 206, the granular material produced is contacted with waterglass, so as to result in an inorganic binder 207. The inorganic binder produced is likewise a product of a process of the invention.

In an additional step 208, the inorganic binder 207 produced is mixed with a refractory mold base material, so as to result in a molding material mixture 209 as product of the process of the invention.

In a further step 210, the molding material mixture 209 produced is molded and (at least partly) cured, so as to result in a molding 211 as product of the process of the invention.

FIG. 3 shows a flow diagram of an alternative embodiment of an inventive process 300 for producing a molding material mixture 309 for use in the foundry industry.

In a first step 301 of the process 300, a particulate amorphous silicon dioxide is produced or provided, as defined above.

In a separate step 301a, further materials are produced or provided (as defined in aspect 27 and the description above).

In a next (enlargement) step 302, the particles of the particulate amorphous silicon dioxide are combined to grains, wherein the further materials produced or provided in step 301a are added before or during step 302a, such that the particles of the particulate amorphous silicon dioxide are mixed and/or contacted with these further materials in the enlargement step, such that the enlargement step results in an above-defined granular material 303 comprising a multitude of individual grains. These individual grains comprise the particulate amorphous silicon dioxide and the further materials. The granular material produced is already a product of a process of the invention.

In a subsequent step 304, the grains of the granular material 303 are comminuted, so as to form a solid pourable additive 305. The additive produced is likewise a product of a process of the invention.

In a further step 306, the granular material produced is contacted with waterglass, so as to result in an organic binder 307. The inorganic binder produced is likewise a product of a process of the invention.

In a next step 308, the inorganic binder 307 produced is mixed with a refractory mold base material, so as to result in a molding material mixture 309 as product of the process of the invention.

In a further step 310, the molding material mixture 309 produced is molded and (at least partly) cured, so as to result in a molding 311 as product of the process of the invention.

Steps 102, 202 and 302 shown in FIGS. 1, 2 and 3 represent steps essential to the respective embodiment of the process of the invention. There is no model for such steps in the prior art.

EXAMPLE 1—METHODOLOGY OF DETERMINATION OF PARTICLE SIZE DISTRIBUTION BY MEANS OF LASER SCATTERING

The selection of the substances in this example is merely illustrative, and it is also possible to determine particle size distributions or medians of other particulate species to be used in the context of the present invention by means of laser scattering according to the procedure in this example.

1.1 Sample Preparation:

By way of example, particle size distributions of silica fume particles (CAS number: 65012-64-2; particulate amorphous silicon dioxide) that are commercially available (RW Silicium GmbH) and in particulate powder form from Si production were determined.

In each case, about 1 teaspoon of this particulate amorphous silicon dioxide was admixed with about 100 mL of demineralized water, and the resultant mixture was stirred with a magnetic stirrer (IKAMAG RET) at a stirrer speed of 500 revolutions per minute for 30 seconds. Subsequently, an ultrasound probe (from Hielscher; model: UP200HT) preadjusted to 100% amplitude, equipped with a S26d7 sonotrode (from Hielscher), was immersed into the sample, and the sample was sonicated therewith. The sonication was continuous (not pulsed). For the silica fume particles examined, optimal sonication times of 300 seconds were chosen, which were determined beforehand as described in point 1.3 below of example 1.

1.2 Laser Scattering Measurements:

The measurements were conducted with a Horiba LA-960 instrument (LA-960 hereinafter). For the measurements, circulation speed was set to 6, stirrer speed to 8, data recording for the sample to 30 000, convergence factor to 15, the mode of distribution to volume, and refractive index (R) to 1.50-0.01i (1.33 for demineralized water dispersion medium) and refractive index (B) to 1.50-0.01i (1.33 for demineralized water dispersion medium). Laser scattering measurements were conducted at room temperature (20° C. to 25° C.).

The measurement chamber of the LA-960 was filled to an extent of three quarters with demineralized water (maximum fill level). Then the stirrer was started at the set speed, the circulation was switched on and the water was degassed. Subsequently, a zero measurement was conducted with the parameters specified.

A disposable pipette was then used to take a 0.5-3.0 mL sample centrally from the sample prepared according to point 1.1 of example 1 immediately after the ultrasound treatment. Subsequently, the complete contents of the pipette were introduced into the measurement chamber, such that the transmittance of the red laser was between 80% and 90% and the transmittance of the blue laser was between 70% and 90%. Then the measurement was started. The measurements were evaluated in an automated manner on the basis of the parameters specified.

For the silica fume particles examined from Si production, a particle size distribution was ascertained with a median rounded to the second post-decimal place.

1.3 Determination of Optimal Sonication Time:

The optimal duration of ultrasound sonication, which is dependent on the type of sample, is ascertained by conducting a measurement series with different sonication times for each particulate species. This is done by extending the sonication time, starting from 10 seconds, by 10 seconds each time for every further sample, and determining the respective particle size distribution by means of laser scattering (LA-960) immediately after the end of sonication as described in point 1.2 of example 1. With increasing duration of sonication, the median ascertained in the particle size distribution falls at first, before ultimately rising again at longer sonication times. For the ultrasound sonications described in point 1.1 of example 1, the sonication time chosen was that at which, in these measurements series, the lowest median of the particle size distribution was determined for the particle species; this sonication time is the “optimal” sonication time.

EXAMPLE 2—PRODUCTION METHOD FOR GRANULAR MATERIALS

10 kg of synthetic particulate amorphous silicon dioxide (in powder form, particle size <1.5 μm; e.g. Microsilica POS B-W 90 LD (Possehl Erzkontor GmbH) or silica fume (Doral Fused Materials Pty., Ltd.); production process in each case: production of ZrO₂ and SiO₂ from ZrSiO₄) are introduced into a plowshare mixer (from Gebrüder Lödige Maschinenbau GmbH, model L50), and the plowshare mixer, for mixing, is operated at a speed of rotation of the plowshare shaft of 180 revolutions per minute and of the bladed head of 3000 revolutions per minute. During the mixing, water is fed into the synthetic particulate amorphous silicon dioxide in several steps: 0.25 kg of water followed by a mixing time of 60 seconds, then an additional 0.5 kg of water followed by a mixing time of a further 240 seconds, then an additional 0.5 kg of water followed by a mixing time of a further 120 seconds, and then an additional 1.0 kg of water followed by a mixing time after a further mixing time of 180 seconds.

The suspension thus produced is dripped by means of a pipette in individual droplets onto a commercial aluminum foil (which has optionally been sprayed with separating agent) heated to 250° C. on a hotplate and dried, such that the particles of the powder used combine to form grains and result in a granular material of the invention. The hotplate is preferably protected here from soiling with a further layer of aluminum foil (arranged beneath the layer that comes into contact with the suspension).

The proportion by mass of the particles having a size of less than 20 μm, determined by means of laser scattering, in the granular material is lower than in the particulate amorphous silicon dioxide.

EXAMPLE 3—BULK DENSITY; REDUCED EVOLUTION OF DUST

Bulk density is determined with a laboratory balance (measurement uncertainty ±0.1 g), a metal measuring cylinder having a volume of (100±0.5) mL and an internal diameter of (45±5) mm, and a funnel (according to DIN EN ISO 60) with a closed lower opening.

The funnel is secured centrally above the measuring cylinder at a height of 20 mm to 30 mm, and the sample is mixed well. About 120 mL to 130 mL of the sample is introduced into the funnel. The closure of the funnel is opened quickly, such that the sample material drops into the cylinder. Excess sample material is stripped off the cylinder with the aid of a straight-edged article, and then the contents of the cylinder are weighed; the mass of the contents of the cylinder is m_sample.

The evaluation is made by the following formula:

$\mathrm{Bulk}\mathrm{density}\left[\frac{g}{L}\right]=m_{\mathrm{sample}}\left[g\right]·10\left[\frac{1}{L}\right]$

The result is reported to 1 g/L.

According to example 2, synthetic particulate amorphous silicon dioxide having a bulk density of 550 g/L was used to produce a granular material. After drying, the granular material of the invention thus obtained had an average grain diameter of 6 mm and a bulk density of 950 g/L.

When poured, the granular material showed much lower evolution of (fine) dust than the starting material, the synthetic particulate amorphous silicon dioxide having a bulk density of 550 g/L.

EXAMPLE 4—EXAMINATION OF ONE-HOUR STRENGTH OF DIFFERENT TEST BARS

4.1 Production of a Molding Material Mixture 4-A

0.80 part by weight of synthetic particulate amorphous silicon dioxide having a bulk density of about 550 g/L (pulverulent; non-granulated; e.g. Microsilica POS B-W 90 LD (Possehl Erzkontor GmbH) or silica fume (Doral Fused Materials Pty., Ltd.); production process in each case: production of ZrO₂ and SiO₂ from ZrSiO₄) was mixed manually with 100 parts by weight of H-S 00232 sand (quartz sand, from Quarzwerke GmbH, AFS grain fineness number 47). Then 2.00 parts by weight of a water glass-based liquid binder (commercial material named Cordis 9032; Hüttenes-Albertus Chemische Werke GmbH) was added and all components were mixed with one another for 120 s in a bull mixer (RN 10/20 type, from Morek Multiserw) at 220 revolutions per minute, such that the materials used were distributed homogeneously, and so as to result in a molding material mixture.

4.2 Production of a Molding Material Mixture 4-B

Synthetic particulate amorphous silicon dioxide having a bulk density of 550 g/L (identical to the material used in example 4.1) and water were used according to example 2 to produce a granular material. The granular material thus produced was ground in a mixer (from Bosch, Universal Plus MUM 6N11 food processor) for 10 s so as to result in a solid pourable additive.

0.80 part by weight of this solid pourable additive was mixed manually with 100 parts by weight of H-S 00232 sand (quartz sand, from Quarzwerke GmbH, AFS grain fineness number 47). Then 2.00 parts by weight of a water glass-based liquid binder (commercial material named Cordis 9032; Hüttenes-Albertus Chemische Werke GmbH) was added and all components were mixed with one another for 120 s in a bull mixer (RN 10/20 type, from Morek Multiserw) at 220 revolutions per minute, such that the materials used were distributed homogeneously, and so as to result in a molding material mixture.

4.3 Production of a Molding Material Mixture 4-C

From 20.05 kg of synthetic particulate amorphous silicon dioxide having a bulk density of about 550 g/L (identical to the material used in example 4.1) was introduced into a plowshare mixer (from Gebrüder Lödige Maschinenbau GmbH, model L50). 3 kg of water was fed into the synthetic particulate amorphous silicon dioxide, and the plowshare mixer was operated at a speed of rotation of the plowshare shaft of 180 revolutions per minute and of the bladed head of 3000 revolutions per minute for 120 seconds. Then the bladed head was switched off and mixing was continued at a speed of rotation of the plowshare shaft of 180 revolutions per minute, such that a soft granular material was formed.

A portion of the still-moist soft granular material was then dried to constant weight at 105° C., so as to result in a (dried) granular material. The cooled dried material was then classified by means of a sieving tower in accordance with VDG-Merkblatt P 27, October 1999, and the fractions <125 μm were discarded. The sieving yield was about 85%.

When poured, the classified granular material showed much lower evolution of (fine) dust than the starting material, the particulate amorphous silicon dioxide having a bulk density of about 550 g/L.

The classified granular material thus produced was ground in a mixer (from Bosch, Universal Plus MUM 6N11 food processor) for 10 s so as to form a solid pourable additive.

0.80 part by weight of this solid pourable additive was mixed manually with 100 parts by weight of H-S 00232 sand (quartz sand, from Quarzwerke GmbH, AFS grain fineness number 47). Then 2.00 parts by weight of a water glass-based liquid binder (commercial material named Cordis 9032; Hüttenes-Albertus Chemische Werke GmbH) was added and all components were mixed with one another for 120 s in a bull mixer (RN 10/20 type, from Morek Multiserw) at 220 revolutions per minute, such that the materials used were distributed homogeneously, and so as to result in a molding material mixture.

4.4 Production of Test Bars

Molding material mixtures 4-A, 4-B and 4-C produced according to points 4.1, 4.2 and 4.3 of example 4 were each formed to test bars having dimensions of 22.4 mm×22.4 mm×185 mm. For this purpose, the respective molding material mixtures were introduced with compressed air (4 bar) and a shooting time of 3 seconds into a mold for test bars having a temperature of 160° C. Subsequently, the test bars were subjected to hot curing at 160° C. without gas supply for 30 seconds. Thereafter, the mold was opened, and the cured test bars were removed and stored for cooling.

4.5 Determination of One-Hour Strength

The test bars produced from molding material mixtures 4-A, 4-B and 4-C according to point 4.4 of example 4, after a cooling time of one hour, were introduced into a Georg Fischer strength tester, equipped with a 3-point bending device (from Morek Multiserw), and the force that led to fracture of the test bar was measured. The value read off (in N/cm²) indicated the one-hour strength. Results are shown in table 1, with the respective one-hour strength figure corresponding to a median from 6 individual measurements.

TABLE 1
Molding material One-hour strength
mixture no.      (N/cm2)
4-A              500
4-B              520
4-C              520

The results listed in table 1 show that test bars produced using a granular material (produced by a process of the invention) or a solid pourable additive (produced by a process of the invention) surprisingly have elevated one-hour strength.

EXAMPLE 5—PRODUCTION OF GRANULAR MATERIALS WITH HOMOGENEOUS DISTRIBUTION OF MULTIPLE ADDITIVES

Analogously to the production method from example 2, granular materials were produced in a multitude of in-house experiments, with addition of one or more of the following substances as a further material, in each case in addition to the particulate amorphous silicon dioxide used:

• • liquids, preferably liquid suspension media, preferably water,
  • particulate materials, preferably particulate inorganic materials, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably pulverulent oxidic boron compounds, and mixtures thereof,
  • water-soluble materials,
  • alkali metal hydroxides,
  • surfactants, preferably selected from the group consisting of:
    • oleyl sulfate, stearyl sulfate, palmityl sulfate, myristyl sulfate, lauryl sulfate, decyl sulfate, octyl sulfate, 2-ethylhexyl sulfate, 2-ethyloctyl sulfate, 2-ethyldecyl sulfate, palmitoleyl sulfate, linolyl sulfate, lauryl sulfonate, 2-ethyldecyl sulfonate, palmityl sulfonate, stearyl sulfonate, 2-ethylstearyl sulfonate, linolyl sulfonate, hexyl phosphate, 2-ethylhexyl phosphate, capryl phosphate, lauryl phosphate, myristyl phosphate, palmityl phosphate, palmitoleyl phosphate, oleyl phosphate, stearyl phosphate, poly(ethane-1,2-diyl)phenol hydroxyphosphate, poly(ethane-1,2-diyl)stearyl phosphate, poly(ethane-1,2-diyl)oleyl phosphate, polycarboxylate ethers in water (Melpers 0030, from BASF), modified polyacrylate in water (Melpers VP 4547/240 L, from BASF), 2-ethylhexyl sulfate in water (Texapon EHS, from Cognis), polyglucoside in water (Glukopon 225 DK, from Cognis), sodium octylsulfate in water (Texapon 842, from Lakeland), modified carboxylate ethers (Castament ES 60, solid-state, from BASF).
  • film formers, preferably polyvinylalcohol and/or acrylic acid,
  • rheological additives (thickeners, suspension aids), preferably selected from the group consisting of:
    • swellable clays, preferably sodium bentonite or attapulgite/palygorskite,
    • swellable polymers, preferably cellulose derivatives, especially carboxymethyl, methyl, ethyl, hydroxyethyl and hydroxypropyl cellulose, plant mucilages, polyvinylpyrrolidone, pectin, gelatin, agar-agar, polypeptides and/or alginates,
  • hydrophobizing agents, preferably organosilicon compounds, silanes, silanols, preferably trimethylsilanol, silicones and siloxanes, preferably polydimethylsiloxane, waxes, paraffins, metal soaps,
  •  and
  • carbohydrates.

Granular materials were obtained in an analogous manner in each case. The granular materials obtained can each be processed by grinding to give solid pourable additive. Granular materials or solid pourable additives were each processed successfully to give molding material mixtures, and these were processed further to give test bars.

Claims

1. A process for producing an article for use in the foundry industry selected from the group consisting of and comprising the following steps for production of the article:

granular material for production of a pourable additive for use as a constituent of an inorganic binder in the foundry industry,

solid pourable additive for use as a constituent of an inorganic binder in the foundry industry,

inorganic binder for use in the foundry industry,

molding material mixture comprising an inorganic binder for use in the foundry industry,

moldings for use in the casting of metallic cast parts in the foundry industry,

producing or providing particulate amorphous silicon dioxide comprising silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate amorphous silicon dioxide,

combining the particles of the particulate amorphous silicon dioxide in an enlargement step to give grains, so as to result in a granular material comprising a multitude of individual grains each comprising combined particles and each comprising a proportion of at least 30% by weight of particulate amorphous silicon dioxide, based on the mass of the respective grain, where the average grain diameter of the granular material is greater than 0.2 mm, determined by sieving.

2. The process as claimed in claim 1 for producing an article for use in the foundry industry selected from the group consisting of and comprising the steps of:

solid pourable additive for use as a constituent of an inorganic binder in the foundry industry,

inorganic binder for use in the foundry industry,

molding material mixture comprising an inorganic binder for use in the foundry industry,

moldings for use in the casting of metallic cast parts in the foundry industry,

producing a granular material by a process as claimed in claim 1,

comminuting the grains of the granular material, so as to result in a solid pourable additive.

3. The process as claimed in claim 1 for producing an article for use in the foundry industry selected from the group consisting of and

inorganic binder for use in the foundry industry,

molding material mixture comprising an inorganic binder for use in the foundry industry,

moldings for use in the casting of metallic cast parts in the foundry industry,

(i) comprising the steps of: producing the solid pourable additive by a process as claimed in claim 1, contacting the solid pourable additive produced with waterglass or suspending the solid pourable additive produced in waterglass,

or

(ii) comprising the steps of: producing a granular material by a process as claimed in claim 1, contacting the granular material produced with waterglass, in the presence or absence of refractory mold base material, and comminuting the grains of the granular material at the same time or thereafter.

4. The process as claimed in claim 1 for producing a molding material mixture comprising refractory mold base material and an inorganic binder comprising waterglass and particulate amorphous silicon dioxide for use in the foundry industry,

comprising the steps of: producing an inorganic binder as per claim 1,

and (i) at the same time mixing the constituents used for production of the inorganic binder with a refractory mold base material

and/or (ii) thereafter mixing the inorganic binder produced with a refractory mold base material.

5. The process as claimed in claim 1, wherein, in the step of

combining the particles of the particulate amorphous silicon dioxide in an enlargement step to give grains, so as to result in a granular material comprising a multitude of individual grains each comprising combined particles and each comprising a proportion of at least 30% by weight, preferably at least 40% by weight, more preferably at least 50% by weight, of particulate amorphous silicon dioxide, based on the mass of the respective grain,

the average grain diameter of the granular material is greater than 0.5 mm, preferably greater than 1 mm, determined by sieving.

6. The process as claimed in claim 1, wherein the particulate amorphous silicon dioxide comprising silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate amorphous silicon dioxide, consists wholly or partly of particulate synthetic amorphous silicon dioxide.

7. The process as claimed in claim 1, wherein the proportion of silicon dioxide in the granular material as a whole, determined by means of x-ray fluorescence analysis, and the proportion of silicon dioxide in at least 90% of the grains of the granular material having a grain diameter greater than 1 mm, preferably greater than 0.5 mm, more preferably greater than 0.2 mm, in each case determined by means of sieving and subsequent x-ray fluorescence analysis, differs by not more than 30%, preferably differs by not more than 20%, more preferably differs by not more than 10%, based on the proportion of silicon dioxide in the granular material as a whole.

8. The process as claimed in claim 1, wherein, in the enlargement step, the particles of the particulate amorphous silicon dioxide are mixed and/or contacted with one, two or more further materials independently selected from the group consisting of:

liquids, preferably liquid wetting agents and/or suspension media, preferably water,

particulate materials, preferably particulate inorganic materials, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably pulverulent oxidic boron compounds, and mixtures thereof,

water-soluble materials,

alkali metal hydroxides,

surfactants,

film formers,

hydrophobizing agents, preferably organosilicon compounds, silanes, silicones and siloxanes, waxes, paraffins, metal soaps,

 and

carbohydrates.

9. The process as claimed in claim 8, wherein grains of the granular material that results from the enlargement step, preferably at least 90% of the grains of the granular material having a grain diameter greater than 1 mm, preferably greater than 0.5 mm, more preferably greater than 0.2 mm, in each case determined by means of sieving, and/or

(i) comprise particulate amorphous silicon dioxide and one, two, more than two or all of the further solid materials present in the enlargement step

(ii) comprise particulate amorphous silicon dioxide and one, two or more further materials independently selected from the group consisting of: particulate materials, preferably particulate inorganic materials, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably pulverulent oxidic boron compounds, and mixtures thereof, water-soluble materials, alkali metal hydroxides, surfactants, film formers, hydrophobizing agents, preferably organosilicon compounds, silanes, silicones and siloxanes, waxes, paraffins, metal soaps,

and carbohydrates.

10. The process as claimed in claim 1, wherein

the producing of particulate amorphous silicon dioxide comprising silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate amorphous silicon dioxide, comprises the step of: mixing two or more different types of particulate amorphous silicon dioxide, where the two or more types differ by their particle size distribution and/or their chemical composition.

11. The process as claimed in claim 10,

(i)—wherein a first type of particulate amorphous silicon dioxide has a particle size distribution having a median in the range from 0.1 to 0.4 μm, determined by laser scattering,

and wherein a further type of particulate amorphous silicon dioxide has a particle size distribution having a median in the range from 0.7 to 1.5 μm, determined by laser scattering,

and/or

(ii)—wherein one, two, more than two or all of the different types of particulate amorphous silicon dioxide is selected or are independently selected from the group consisting of particulate synthetic amorphous silicon dioxide containing silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate synthetic amorphous silicon dioxide, and at least carbon as secondary constituent, preferably producible by reducing quartz in an arc furnace; particulate synthetic amorphous silicon dioxide comprising oxidic zirconium as secondary constituent and preferably producible by thermal breakdown of ZrSiO4 particulate synthetic amorphous silicon dioxide producible by oxidizing metallic silicon by means of an oxygenous gas; particulate synthetic amorphous silicon dioxide producible by quenching a silicon dioxide melt.

12. The process as claimed in claim 10, wherein at least 90% of the grains of the granular material having a grain diameter greater than 0.2 mm, preferably greater than 0.5 mm, more preferably greater than 1 mm, in each case determined by sieving, comprise both or at least two of the different types of particulate amorphous silicon dioxide.

13. The process as claimed in claim 1, wherein the enlargement step comprises one or more measures independently selected from the group consisting of: and

granulating

extruding

agglomerating.

14. A granular material having an average grain diameter greater than 0.2 mm, determined by sieving, for production of a pourable additive for use as a constituent of an inorganic binder in the foundry industry, comprising particulate amorphous silicon dioxide,

(a) wherein the granular material additionally comprises one, two or more further materials independently selected from the group consisting of: particulate materials, preferably particulate inorganic materials, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably pulverulent oxidic boron compounds, and mixtures thereof, water-soluble materials, alkali metal hydroxides, surfactants, film formers, hydrophobizing agents, preferably organosilicon compounds, silanes, silicones and siloxanes, waxes, paraffins, metal soaps, and carbohydrates, wherein at least 90% of the grains of the granular material having a grain diameter greater than 0.2 mm, preferably greater than 0.5 mm, more preferably greater than 1 mm, in each case determined by sieving, comprise particulate amorphous silicon dioxide, and one, two or more of said further materials,

and/or

(b) wherein the particulate amorphous silicon dioxide comprises a proportion of at least 80% by weight of silicon dioxide, based on the total mass of the particulate amorphous silicon dioxide, preferably consisting wholly or partly of particulate synthetic amorphous silicon dioxide,

and/or

(c) wherein the proportion of silicon dioxide in the granular material as a whole, determined by means of x-ray fluorescence analysis, and the proportion of silicon dioxide in at least 90% of the grains of the granular material having a grain diameter greater than 1 mm, in each case determined by means of sieving and subsequent x-ray fluorescence analysis, differs by not more than 30%, preferably differs by not more than 20%, more preferably differs by not more than 10%, based on the proportion of silicon dioxide in the granular material as a whole,

and/or

(d) wherein, in the granular material, the particulate amorphous silicon dioxide comprises two or more different types of particulate amorphous silicon dioxide, where the two or more types differ by their chemical composition, wherein preferably one, two, more than two or all of the different types of particulate amorphous silicon dioxide is selected or are independently selected from the group consisting of particulate synthetic amorphous silicon dioxide containing silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate synthetic amorphous silicon dioxide, and at least carbon as secondary constituent, preferably producible by reducing quartz in an arc furnace; particulate synthetic amorphous silicon dioxide comprising oxidic zirconium as secondary constituent and preferably producible by thermal breakdown of ZrSiO4 particulate synthetic amorphous silicon dioxide producible by oxidizing metallic silicon by means of an oxygenous gas; particulate synthetic amorphous silicon dioxide producible by quenching a silicon dioxide melt

and/or

(e) wherein the granular material is producible by a process as claimed in claim 1.

15. A kit for production of an inorganic binder, at least comprising, as components in a mutually spatially separate arrangement, and

a granular material as claimed in claim 14

a solution or dispersion comprising waterglass.

16. An apparatus for performing a process as claimed in claim 1, comprising

a reservoir vessel containing particulate amorphous silicon dioxide, comprising silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate amorphous silicon dioxide,

a mixing or contacting device for mixing or contacting the particulate amorphous silicon dioxide with one, two or more further materials,

a device for granulating, extruding and/or agglomerating the particulate amorphous silicon dioxide that has been mixed or contacted with one, two or more further materials.

17. The apparatus as claimed in claim 16, additionally comprising one or more apparatus elements selected from the group consisting of

device for transferring particulate amorphous silicon dioxide from the reservoir vessel into the mixing or contacting apparatus,

one or more reservoir vessels containing liquid, preferably liquid wetting agent and/or suspension medium, preferably water,

one or more reservoir vessels containing particulate material, preferably particulate inorganic material, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably pulverulent oxidic boron compounds, and mixtures thereof,

one or more reservoir vessels containing a water-soluble material,

one or more reservoir vessels containing one or more surfactants,

one or more reservoir vessels containing one or more hydrophobizing agents,

one or more reservoir vessels containing one or more carbohydrates.

18. The apparatus as claimed in claim 16, additionally comprising a device for dispensing or transporting granular material produced.

19. Method of making a granular material as claimed in claim 14, comprising the use of particulate amorphous silicon dioxide.

20. Method of producing a solid pourable additive with homogenized grain composition comprising a granular material as claimed in claim 14, wherein the homogenized grain composition if for use as a constituent of an inorganic binder in the foundry industry.