Hydrophobic Thermal Insulation

Abstract

Thermal insulation materials which have no binders in the form of liquids, which adhesively bond particles, and which are treated with low-volatility organosilanes or organosiloxanes whose boiling points are greater than 130° C. under atmospheric pressure, the k thermal conductivity being between 0.014 and 0.040 W/mK and the density being in the range from 50 to 300 kg/m3.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the national phase filing of international patent application No. PCT/EP2010/068876, filed 3 Dec. 2010, and claims priority of German patent application number 10 2009 054 566.2, filed 11 Dec. 2009, the entireties of which applications are incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to porous thermal insulation and moldings made therefrom.

BACKGROUND OF THE INVENTION

Thermal insulation for saving energy has attained great prominence in the context of desire for sustainable development and the increasing cost of energy. Thermal insulation is gaining ever greater importance in the light of increasing energy prices, increasingly scarce resources, the desire for reducing CO₂ emissions, the necessity of a sustainable reduction in energy demand and also the increasingly demanding requirements which protection against heat and cold will have to meet in the future. These increasingly demanding requirements for optimizing thermal insulation apply equally in buildings, e.g. new buildings or existing buildings, and to thermal insulation in the mobile, logistics and stationary sectors.

Building materials such as steel, concrete, masonry and glass and also natural rock are relatively good thermal conductors so that the exterior walls of buildings made thereof very quickly give off heat from the inside to the outside in cold weather.

Development is therefore aimed, firstly, at improving the insulation properties by increasing the porosity of these building materials as in the case of, for example, concrete and masonry, and secondly at cladding the outer walls with thermal insulation materials.

The thermal insulation materials which are mostly used at present are materials having a low thermal conductivity.

Materials used are:

organic insulation materials

foamed plastics such as polystyrene, Neopor, polyurethane wood fiber materials such as wood wool and cork

vegetable or animal fibers such as hemp, flax, wool

inorganic thermal insulation materials

mineral and glass wool, foamed glass in plate form

calcium silicate boards and gypsum plasterboards

mineral foams such as porous concrete, pumice, perlite and vermiculite

The abovementioned conventional thermal insulation materials are mostly used in the form of foamed or pressed boards and moldings, alone or in combination with others. Thus, it is possible, for example, to introduce the polyurethanes and polystyrenes as foams directly into the hollow spaces of the building blocks (DE 8 504 737/U1) or, as described in DE 102 29 856 B4, introduce them as solid boards. According to DE 102 17548 A1, this technology is also possible using mineral wool cut to size. However, all these insulation embodiments have the following weaknesses, in detail:

all these materials have a thermal insulation effectiveness which is too low for the demanding requirements needed today. The thermal conductivities are all above 0.030 W/mK, and the materials therefore have a high space requirement and are, inter alia, not lastingly stable in terms of the thermal insulation.

Further disadvantages are:

excessively high moisture absorption and sensitivity to water

time-consuming and costly application to the exterior wall (e.g. adhesive bonding, pegging, screwing, installation of support systems, etc.; heat bridges are partly preprogrammed here)

additional bonding layers, e.g. to aid adhesion of renders

in the case of organic insulation materials, the combustibility is also an issue

Very good insulation action is displayed by vacuum insulation panels, known as VIPs for short. The vacuum insulation panels have a thermal conductivity of from about 0.004 to 0.008 W/mK (depending on the core material and reduced pressure) and therefore have an 8- to 25-fold better thermal insulation action than conventional thermal insulation systems. They therefore allow slim constructions with optimal thermal insulation which can be used both in the building sector and in the household appliance, cooling and logistics sectors.

Vacuum insulation panels based on porous thermal insulation materials, polyurethane foam boards and pressed fibers as core material together with composite films (e.g. aluminum composite films or metalized films) are generally known and have been adequately described (cf. VIP-Bau.de)

However, this VIP technology has the following serious disadvantages:

when air gets into these evacuated panels due to damage, this means the end of the very good thermal insulation.

The insulating action then corresponds only to that of the core materials used.

The life is limited in terms of time by the diffusion of gases through the barrier or sheath into the vacuum panels.

In the case of small units, the good thermal insulation properties are again largely negated by the formation of heat bridges.

In the building sector, the following disadvantages, in particular, also apply:

due to the virtually gas-impermeable barriers which are necessary, the panels do not breathe.

Handling and processability on site, especially on building sites, is difficult or impossible.

Owing to the structure of the films, diffusion of surrounding gases (mainly nitrogen, oxygen, CO₂ and water vapor) always occurs. A long life is therefore not ensured and the life is finite.

Porous thermal insulation materials, e.g. those based on pyrogenic silica, have lower thermal conductivities (0.018-0.024 W/mK).

Pyrogenic silicas are produced by flame hydrolysis of volatile silicon compounds such as organic and inorganic chlorosilanes. These pyrogenic silicas produced in this way have a highly porous structure and are hydrophilic.

The disadvantages of these porous thermal insulation materials based on pyrogenic silicas are therefore:

high moisture absorption and therefore increasing thermal conductivities and thus a decrease in the thermal insulation properties.

In the building sector, this can additionally lead to the growth of mold.

When used in vacuum panels, energy transport can take place via water molecules as a result of moisture absorption, and this can have an adverse effect on the thermal conductivity of the system.

SUMMARY OF THE INVENTION

It is an object of the invention to solve the problems of the prior art, in particular to achieve a substantial improvement in the thermal insulation properties of thermal insulation materials based on porous insulation materials, keep them at a high level over the long term and, by compaction or pressing, bring the insulation materials into shapes which are practicable in use.

The object is achieved by the features of claim 1.

The invention provides thermal insulation materials as claimed in claim 1.

Advantageous embodiments are defined in the dependent claims.

The invention is based on the idea that porous thermal insulation materials consist essentially of finely divided, nanosize silicas, preferably pyrogenic silicas, infrared opacifiers and fibers.

DETAILED DESCRIPTION OF THE INVENTION

The thermal insulation materials of the invention do not contain any binders in the form of liquids which adhesively bond particles.

However, it has now been found that the above objectives are achieved by addition of relatively nonvolatile organosilanes or relatively nonvolatile organosiloxanes during the mixing process for producing porous thermal insulation materials.

This mixture is moldable and pressable immediately after the addition. The addition of the relatively nonvolatile organosilanes or relatively nonvolatile organosiloxanes occurs in the liquid or gaseous state. Intensive, homogeneous mixing of the components is important so that the reaction (hydrophobicization) from “the inside out” is ensured. It is in principle also possible to add the relatively nonvolatile organosilanes or relatively nonvolatile organosiloxanes to the individual components such as silicas, infrared opacifiers and substitute materials.

The reaction of the relatively nonvolatile organosilanes or relatively nonvolatile organosiloxanes with the silanol groups of the silica preferably takes place during the pressing process or immediately afterward. The reaction can, depending on requirements, be accelerated or retarded, i.e. controlled, by supply of heat or removal of heat (cooling) or by means of accelerators, i.e. polar substances such as water, alcohols or hydrogen chloride, optionally under slightly superatmospheric pressure. Excess materials or dissociation products from the hydrophobicization process are subsequently driven off by heating at temperatures of preferably from 70° C. to 130° C.

In a further preferred embodiment, the thermal insulation materials are physically impregnated with the relatively nonvolatile organosilanes or relatively nonvolatile organosiloxanes, i.e. the relatively nonvolatile organosilanes or relatively nonvolatile organosiloxanes are adsorbed on the pulverulent individual constituents of the thermal insulation mixture without a subsequent chemical reaction during or after the pressing process.

The resulting boards or moldings are lastingly hydrophobic throughout the material.

These thermal insulation materials produced according to the invention have a low, constant thermal conductivity X in the range of preferably 0.014-0.045 W/mK, preferably 0.015-0.040 W/mK, particularly preferably 0.018-0.035 W/mK, and their density is in the range of preferably from 20 to 500 kg/m³, preferably from 20 to 250 kg/m³, particularly preferably from 20 to 200 kg/m³.

A preferred embodiment according to the invention is the following composition: pyrogenic silica or silicon dioxide aerogels preferably 5-98% by weight, more preferably 10-80% by weight, particularly preferably 20-70% by weight, opacifiers preferably 3-50% by weight, more preferably 5-45% by weight, particularly preferably 5-40% by weight, finely divided inorganic further additives preferably 0-65% by weight, preferably 0-60% by weight, particularly preferably 0-50% by weight.

Furthermore, the thermal insulation materials of the invention have a high hydrophobicity all through. That is to say, they are water-repellent, with the moisture absorption preferably being less than 20% by weight, more preferably less than 10% by weight, particularly preferably less than 5% by weight and in a special embodiment less than 1% by weight.

The thermal insulation materials are preferably porous thermal insulation materials, characterized in that the porosity s of the thermal insulation material is in the range of preferably from 77% to 99%, more preferably in the range from 89% to 99% and particularly preferably in the range from 91% to 99%, with the pore diameter being in the range from 20 nm to 500 nm, preferably from 20 nm to 200 nm and particularly preferably from 20 nm to 100 nm. The porosity c is defined as ε=(1−ρ/ρ₀)×100, where ρ is the apparent density of the thermal insulation material and ρ₀ is the pure density. The pore diameter can be obtained by means of mercury porosimetry or gas adsorption isotherms.

Furthermore, the thermal insulation materials of the invention are permeable to water vapor.

Furthermore, the thermal insulation materials of the invention are not combustible (burning class A).

Furthermore, the thermal insulation materials of the invention are preferably chemically neutral and physiologically acceptable in the construction sector.

The relatively nonvolatile organosilanes or relatively nonvolatile organosiloxanes used according to the invention have the decisive advantage over the conventional hydrophobicizing agents such as stearates, siliconates, waxes and fats, etc., that they can easily be atomized as an aerosol, e.g. by means of commercial 1-fluid nozzles or 2-fluid nozzles or 3-fluid nozzles or atomizers, and therefore are optimally distributed on the silica surface and undergo a chemical reaction with the silanol groups present on the silica. Thus, the hydrophilic silanol groups are replaced completely, lastingly and all through by organophilic hydrophobic groups. The vapor pressures of the relatively nonvolatile organosilanes or relatively nonvolatile organosiloxanes used are above 250 mbar at 20 degrees Celsius, preferably above 500 mbar at 20 degrees Celsius, particularly preferably above 1000 mbar at 20 degrees Celsius.

The boiling points of the relatively nonvolatile organosilanes or organosiloxanes used are preferably greater than 130° C. at atmospheric pressure, more preferably greater than 200° C. at atmospheric pressure, particularly preferably greater than 500° C. at atmospheric pressure, and the relatively nonvolatile organosilanes or organosiloxanes used can very particularly preferably not be vaporized without decomposition at atmospheric pressure.

The relatively nonvolatile organosilanes or organosiloxanes are preferably added as finely divided aerosol. This ensures optimal distribution of the relatively nonvolatile organosilanes or organosiloxanes on the porous thermal insulation material mixture without destruction of the silica structure.

The relatively nonvolatile organosilanes or relatively nonvolatile organosiloxanes used according to the invention have the advantage over volatile organosilanes or organosiloxanes that they do not desorb during the production process for the thermal insulation material and escape via the offgas into the environment.

According to the invention, the use of binders with the negative properties described below (hollow building blocks) can be completely dispensed with.

The core material according to the invention comprises porous thermal insulation materials which preferably contain pyrogenic silicas and silicon dioxide aerogel as base material. Opacifiers, fibers and/or other fillers are preferably added thereto.

Pyrogenic silicas are produced by flame hydrolysis of volatile silicon compounds such as organic and inorganic chlorosilanes. These pyrogenic silicas have a highly porous structure. Silicon dioxide aerogels are produced by specific drying processes from aqueous silicon dioxide gels and have a very highly porous structure and are therefore highly effective insulation materials.

Further components of these thermal insulation materials are compounds which can absorb, scatter and reflect thermal radiation in the infrared range. They are generally referred to as infrared opacifiers. These opacifiers preferably have a maximum in the range of preferably from 1.5 to 10 m in the infrared spectral range. The particle size of these particles is preferably in the range 0.5-15 μm. Examples of such substances are preferably titanium oxides, zirconium oxides, ilmenites, iron titanates, iron oxides, zirconium silicates, silicon carbide, manganese oxides and carbon black.

The thermal insulation materials of the invention preferably have the following additives: precipitated silicas, pyrogenic silicas, SiO₂-containing fly dusts from electrochemical silicon production and the thermal utilization of residues of volatile silicon compounds and also naturally occurring SiO₂-containing compounds, thermally expanded minerals.

For reinforcement or strengthening, i.e. mechanical reinforcement, fibers are concomitantly used. These fibers can be of inorganic or organic origin.

Examples of inorganic fibers are preferably glass wool, rock wool, basalt fibers, slag wool and ceramic fibers composed of melts of aluminum and/or silicon dioxide and also further inorganic metal oxides. Pure silicon dioxide fibers are, for example, silica fibers.

Organic fibers are preferably, for example, cellulose fibers, textile fibers or synthetic polymer fibers.

The following dimensions are used:

diameter preferably 1-12 μm, more preferably 6-9 μm; length preferably 1-25 mm, preferably 3-10 mm.

For technical and economic reasons, inorganic filler materials can be added to the mixture.

Use is preferably made of various, synthetically produced modifications of silicon dioxide, e.g. precipitated silicas, electric arc silicas, SiO₂-containing fly dusts formed by oxidation of volatile silicon monoxide in the electrochemical production of silicon or ferrosilicon. Silicas produced by leaching of silicates such as calcium silicate, magnesium silicate and mixed silicates such as olivine (magnesium iron silicate) by means of acids can likewise be used. Furthermore, naturally occurring SiO₂-containing compounds such as diatomaceous earths and kieselguhrs are used. It is likewise possible to employ: thermally expanded minerals such as preferably perlites and vermiculites. Depending on requirements, preferably finely divided metal oxides such as preferably aluminum oxide, titanium dioxide, iron oxide can be added.

The core material not only has to repel water but also has to prevent adduct formation with an absorption of moisture. This moisture absorption is caused by silanol groups present on the silica, to which the water becomes attached. Making core materials consisting of foamed perlites water-repellent by means of preferably alkali metal and/or alkaline earth metal stearates, siliconates, waxes and fats is known (DE3037409 A1). When these substances are used, formation of, in particular, a surface layer, customarily referred to as “coating”, takes place. Although the core materials which have been treated in this way repel liquid water, they absorb water vapor in the form of atmospheric moisture and thus lead to a deterioration in the insulating properties. Reacting pyrogenic silicas with organosilanes and thus making them hydrophobic, i.e. water-repellent, is known, for example, from DE 4221716 A1.

However, such hydrophobic silicas cannot be compacted sufficiently and cannot be pressed since intermeshing of the silica particles of the silanol groups is no longer ensured due to capping with organic groups. Pressing of a mixture provided with hydrophobic silica is likewise not possible. However, pressing is absolutely necessary for consolidation and thus for anchoring in the hollow spaces of the hollow building blocks.

Chemical after-treatment of the insulation material with organosilanes in the hollow spaces after pressing is very difficult since penetration of the core material can occur only very slowly under high pressure (autoclaves).

In addition, the structure of the core material is partly destroyed in this process.

As relatively nonvolatile organosilanes, preference is given to using organosilanes of the general formula

R¹_nR²_mSiX_4−(n+m)   (I)

where n and m can be 0, 1, 2 or 3 and the sum n+m is less than or equal to 3 and

R¹ is a saturated or singly or multiply unsaturated, monovalent, Si—C-bonded C₁-C₂₀-hydrocarbon radical optionally substituted by —CN, —NCO, —NR³, —COOH, —COOR³, -halogen, -acryl, -epoxy, —SH, —OH or —CONR³₂, preferably a C₁-C₁₈-hydrocarbon radical, or an aryl radical or C₁-C₁₅-hydrocarbonoxy radical, preferably a C₁-C₈-hydrocarbonoxy radical, particularly preferably a C₁-C₄-hydrocarbonoxy radical, in which one or more, nonadjacent methylene units can in each case be replaced by —O—, —CO—, —COO—, —OCO— or —OCOO—, —S— or —NR³-groups and in which one or more, nonadjacent methine units can be replaced by —N═, —N═N— or —P═ groups, where

R² is hydrogen or a saturated or singly or multiply unsaturated, monovalent, Si—C-bonded C₁-C₂₀-hydrocarbon radical optionally substituted by —CN, —NCO, —NR³₂, —COOH, —COOR³, -halogen, -acryl, -epoxy, —SH, —OH or —CONR³₂, preferably a C₁-C₁₈-hydrocarbon radical, or an aryl radical or C₁-C₁₅-hydrocarbonoxy radical, preferably a C₁-C₈-hydrocarbonoxy radical, particularly preferably a C₁-C₄-hydrocarbonoxy radical, in which one or more, nonadjacent methylene units can in each case be replaced by —O—, —CO—, —COO—, —OCO— or —OCOO—, —S— or —NR³- groups and in which one or more, nonadjacent methine units can be replaced by —N═, —N═N— or —P═ groups, where

R³ is as defined for R² and R² and R³ can be identical or different,

X is a C—O-bonded C₁-C₁₅-hydrocarbon radical, preferably a C₁-C₈-hydrocarbon radical, particularly preferably a C₁-C₃-hydrocarbon radical, or an acetyl radical or a halogen radical, preferably chlorine, or an OH radical,

or

R¹_iR²_jSi—Y—SiR¹_iR²_j   (II)

R¹ and R² are as defined above, i and j can be 0, 2 or 3 and the sum i+j is equal to 3 and

Y can be the group NH or —O—,

with the proviso that the boiling points of the relatively nonvolatile organosilanes used are greater than 130° C. at atmospheric pressure, preferably greater than 200° C. at atmospheric pressure, particularly preferably greater than 500° C. at atmospheric pressure, or the relatively nonvolatile organosilanes used very particularly preferably cannot be vaporized without decomposition at atmospheric pressure.

As relatively nonvolatile organosiloxanes, preference is given to using organosiloxanes consisting of building blocks of the general formulae

(R¹_aX_bSiO_1/2)   (III-a)

(R¹₂SiO_2/2)   (III-b)

(R¹SiO_3/2)   (III-c)

(R¹R²SiO_2/2)   (III-d)

(SiO_4/2)   (III-e)

where the building blocks can be present in any mixtures, with the proviso that the boiling points of the relatively nonvolatile organosiloxanes used are greater than 130° C. at atmospheric pressure, preferably greater than 200° C. at atmospheric pressure, particularly preferably greater than 500° C. at atmospheric pressure, or the relatively nonvolatile organosiloxanes used very particularly preferably cannot be vaporized without decomposition at atmospheric pressure,

where

R¹, R², R³ and X are as defined above and can in each case be identical or different, and

a and b can be 0, 1, 2 or 3, with the proviso that the sum a +b is equal to 3.

Preference is given to using chain-like organopolysiloxanes which preferably consist of two building blocks of the general formula III-a and preferably from 1 to 100 000 building blocks of the general formula III-b, preferably from 1 to 50 000 building blocks of the general formula III-b, particularly preferably from 1 to 10 000 building blocks of the general formula III-b and particularly preferably from 1 to 5000 building blocks of the general formula III-b, where R¹ is preferably methyl and X is preferably —OCH₃ or —OH.

The kinematic viscosity of the chain-like organosiloxanes measured at 25° C. is preferably from 1 mm²/s to 100 000 mm²/s, more preferably from 2 mm²/s to 50 000 mm²/s and particularly preferably from 5 mm²/s to 10 000 mm²/s.

Preference is given to using chain-like organofunctional organopolysiloxanes consisting of preferably 2 building blocks of the general formula III-a and preferably from 1 to 100 000 building blocks of the general formula III-b and preferably from 1 to 500 building blocks of the general formula III-d, preferably from 1 to 50 000 building blocks of the general formula III-b and preferably from 1 to 250 building blocks of the general formula III-d, particularly preferably from 1 to 10 000 building blocks of the general formula III-b and preferably from 1 to 200 building blocks of the general formula III-d, and very particularly preferably from 1 to 5000 building blocks of the general formula III-b and from 1 to 100 building blocks of the general formula III-d, where R1 is preferably methyl and R2 is preferably —CH₂—CH₂—CH₂—NH₂ or —CH₂—CH₂—CH₂—NH—CH₂—CH₂—NH₂.

Preference is given to using crosslinked or partially crosslinked organopolysiloxanes, known as silicone resins, preferably ones which contain building blocks of the general formula III-a and building blocks of the general formula III-e, particularly preferably with R1=methyl, a=3 and b=0, or ones which preferably contain building blocks of the general formula III-c and building blocks of the general formula III-b, particularly preferably with R1 =methyl.

The relatively nonvolatile organosilanes or organosiloxanes can be used in pure form or in any mixtures.

The amounts of the relatively nonvolatile silanes or relatively nonvolatile organosiloxanes added depend on the specific surface area (BET surface area) of the silicas, the proportion of these in the mixture and also on the type of the silanes. The amount added is preferably 0.5-20 percent by weight, preferably in the range from 1 to 10 percent by weight. The silanes are added during production of the mixture, preferably in liquid form, and it is necessary for intimate mixing of the individual components to take place.

The production of the porous thermal insulation materials can generally take place in various mixing apparatuses.

However, planetary mixers are preferably employed. Here, it is advantageous firstly to premix the fibers with part of the second mixing components to give a type of masterbatch in order to ensure complete dispersion of the fibers. After dispersion of the fibers, the major part of the mixing components is added. As last step of the mixing sequence, the relatively nonvolatile silanes or relatively nonvolatile organosiloxanes are added.

After the mixing process is complete, the bulk density of the mixture can, depending on the type and amount of the components, be in the range of preferably 40-180 g/l, more preferably 40-90 g/l. The powder flow of the resulting porous mixture is very good, and it can therefore be pressed without problems and homogeneously to form boards or, for example, be introduced and pressed into the hollow spaces of hollow building blocks. In the case of pressing to form boards, significant influence can be exercised over the weight, the density and as a result also the thermal conductivity of the insulation material by fixing particular board thicknesses. The lower the density of the boards, the lower the thermal conductivity and the better the thermal insulation properties. Realistic densities are in the range of preferably 80-300 kg/m³, more preferably 100-200 kg/m³.

The porous, hydrophobic thermal insulation materials produced in the manner described are used according to the invention:

as insulation in hollow building blocks

as core insulation in multishell building blocks

as core insulation for vacuum insulation panels (VIPs)

as core insulation for thermal insulation composite systems (TICSs)

as insulation in cavity walls made of masonry

The invention further provides moldings, building blocks, building systems and composite building systems comprising the thermal insulation materials of the invention, with these moldings, building blocks, building systems and composite building systems consisting partly or completely of the thermal insulation materials.

One use of the hydrophobic, porous thermal insulation materials described above in the context of the invention is, according to the invention, in hollow building blocks.

Hollow building blocks are building elements which have one or more hollow spaces. They can consist of inorganic, ceramic materials such as fired clay (bricks), concrete, glass, gypsum plaster and natural products such as natural stone, e.g. calcareous sandstone. Preference is given to using hollow building blocks composed of brick, concrete and lightweight concrete.

Embodiments are wall building blocks, floor slabs, ceiling elements and building entrance elements.

It is also known that the hollow spaces of these building elements can be filled with porous hollow space-structured insulation materials such as Styropor foam or perlite foam (DE 3037409 A1 and DE-A 2825508). These building elements are referred to as hollow building blocks with integrated thermal insulation.

Hollow building blocks having integrated thermal insulation have the advantage that the masonry character of the construction is retained.

The use of these hollow building blocks with integrated thermal insulation should ensure particularly good thermal insulation and a favorable water vapor permeability and also hardly any water absorption in the masonry, and the storage of heat should also be improved.

The insulation materials in these hollow building blocks with integrated thermal insulation can be of either organic or inorganic origin.

As organic materials, preference is given to using foamed polystyrene particles as insulation material. Here, the foamed polymer particles are joined and anchored to one another at the surface, leaving gas-permeable interstices free.

Production is carried out by filling the hollow spaces with loose polystyrene pellets and subsequently foaming the latter by means of hot gases, usually steam. Such insulating building blocks have an improved thermal insulation capability. A disadvantage is the combustibility of the organic constituents of these building elements. Likewise, the thermal insulation capability decreases greatly over time due to the absorption of water/moisture.

As inorganic materials for hollow building blocks with integrated thermal insulation, preference is given to using foamed perlites and vermiculites. Preference is given to using foamed perlites which are bonded and strengthened by means of binders such as aqueous dispersions based on vinyl acetate and acrylic-vinyl acetate copolymers. These fillings with the necessary binders have a high proportion of combustible components, and the resulting thermal insulation is also not optimal.

Bonding and strengthening of the perlites can likewise be achieved using alkali metal water glasses as binders. This process leads to core materials which are strongly alkaline, hygroscopic and lead to efflorescence. In addition, the already unsatisfactory thermal insulation properties are decreased further. The use of silica sol as binder leads to a poorly consolidated insulation material having a high water absorption and poor thermal insulation properties.

The use according to the invention of the hydrophobic porous thermal insulation materials described in hollow building blocks improves the thermal insulation properties of these blocks and keeps them lastingly at a high level.

According to the invention, the appropriate thermal insulation materials can be pressed to give precisely dimensioned boards and integrated into the chambers of the hollow building blocks, but it is also possible to introduce the mixture admixed with relatively nonvolatile silanes or relatively nonvolatile organosiloxanes into the chambers of the building blocks and press them directly in the chambers by means of pressing aids. As an alternative, precisely dimensioned boards can be cut from previously produced large boards and integrated into the building blocks.

It is likewise possible to fix the boards in the hollow spaces by means of, preferably, PUR foam or other adhesive foams, or adhesives.

Likewise, envelopment with nonwovens, for example to prevent mechanical influences and thus emission of dust from the thermal insulation, can be carried out.

To utilize the effectiveness of the achievable thermal insulations in relation to costs, combinations which are effective according to the invention of highly efficient hydrophobic porous thermal insulation with conventional thermal insulation systems having lesser thermal insulation effects are possible. Likewise, depending on the use and insulating capability, single or multiple hollow chambers without thermal insulation materials can also be provided.

Examples

An example of the separate core material (A) according to the invention for hollow building blocks and a comparative example of conventional core material (B) are described below.

Mixing was carried out in a cyclone mixer at 3000 rpm.

To measure the thermal conductivity (λ), a molding having the dimensions 250×250×25 mm was pressed from the mixed material on a hydraulic press at a pressure of about 50 kg/cm2.

Mixture A:

Formulation:

Pyrogenic silica (BET surface area 200 m²/g; obtainable under the designation HDK® N20 from Wacker Chemie AG) 80% by weight

Glass fibers (length 6 mm; thickness 7 μm) 3% by weight

Rutile (particle size about 10 μm) 15% by weight

Aminopolydimethylsiloxane (amine number 3; kin. viscosity at 25° C. 30 mm²/s) 2% by weight

Weight of the total mixture: 1025 g 30 g of fibers, 75 g of rutile and 200 g of silica were firstly premixed for 3 minutes to disperse the fibers. The remainder of the solid components (625 g of silica, 75 g of rutile) was subsequently added and the mixture was mixed for a further 2 minutes. 20 g of aminopoly-dimethylsiloxane were then added to this mixture and the mixture was stirred for a further one minute.

312 g were taken from the finished mixture and pressed to form a solid body having external dimensions of 250×250×25 mm.

This molding was subsequently heated at 150° C. for 60 minutes.

Mixture B:

Formulation:

Foamed perlite 68% by weight

Potassium water glass 32% by weight

Weight of the total mixture: 1000 g

The components were mixed for 5 minutes in the same mixing apparatus as in (A). 344 g of the mixture were pressed to give a molding having the same external dimensions as in (A) and subsequently heated at 150° C. for 20 minutes.

Mixture C:

Formulation:

Pyrogenic silica (BET surface area 300 m²/g; obtainable under the designation HDK® T30 from Wacker Chemie AG) 84.5% by weight

Cellulose wool 3% by weight

Carbon black (Evonik, flame black 101) 10% by weight

OH-terminated polydimethylsiloxane (viscosity 30 mm²/s) 3% by weight

Weight of the total mixture: 1030 g

30 g of fibers, 100 g of carbon black and 200 g of silica were firstly premixed for 3 minutes to disperse the fibers. The remainder of the solid components (670 g of silica) was subsequently added and the mixture was mixed for a further 2 minutes. 30 g of OH-terminated polydimethylsiloxane were then added to this mixture and the mixture was stirred for a further one minute.

187.5 g were taken from the finished mixture and pressed to give a molding having external dimensions of 250×250×25 mm. This molding was subsequently heated at 125° C. for 60 minutes.

Results:

			Apparent
	Dimensions	Weight	density	λ	Hydro-
Mixture	(mm)	(g)	g/l	mW/mK	phobicity
A	250 × 250 × 25	312.0	200	18	yes
B	250 × 250 × 25	344.0	220	24	no
C	250 × 250 × 25	187.5	120	22	yes

Determination of the thermal conductivity: Poensgen plate apparatus using the two-plate method in accordance with DIN EN 12667 in horizontal position.

Determination of the hydrophobicity: Application of a drop of water to a board. If the drop soaks in within a period of 1 hour: hydrophobicity no, if the drop does not soak in over a period of 1 hour: hydrophobicity yes.

Claims

1-7. (canceled)

8. A thermal insulation material which does not contain any binders in the form of liquids which adhesively bond particles and has been treated with relatively nonvolatile organosilanes or organosiloxanes composed of building blocks of the general formulae

(R1aXbSiO1/2)   (III-a)

(R12SiO2/2)   (III-b)

(R1SiO3/2)   (III-c)

(R1R2SiO2/2)   (III-d)

(SiO4/2)   (III-e)

where the building blocks can be present in any mixtures, with the proviso that the boiling points of the relatively nonvolatile organosiloxanes used are greater than 130° C. at atmospheric pressure, where

R1, R2, R3 and X are as defined above and can in each case be identical or different, and

a and b can be 0, 1, 2 or 3, with the proviso that the sum a+b is equal to 3, whose boiling points are greater than 130° C. at atmospheric pressure, where the thermal conductivity λ is in the range from 0.014 to 0.040 W/mK and the density is in the range from to 300 kg/m3, where the thermal insulation material has the following composition:

pyrogenic silica or silicon dioxide aerogels 5-98% by weight, opacifiers 3-50% by weight, further additives 0-65% by weight.

9. The thermal insulation material as claimed in claim 8, characterized in that the relatively nonvolatile organosilanes used have the general formula

R1nR2mSiX4−(n+m)   (I)

where n and m can be 0, 1, 2 or 3 and the sum n +m is less than or equal to 3 and

R1 is a saturated or singly or multiply unsaturated, monovalent, Si—C-bonded C1-C20-hydrocarbon radical optionally substituted by —CN, —NCO, —NR1R3, —COOH, —COOR2, -halogen, -acryl, -epoxy, —SH, —OH or —CONR22, or an aryl radical or C1-C15-hydrocarbonoxy radical, in which one or more, nonadjacent methylene units can in each case be replaced by —O—, —CO—, —COO—, —OCO— or —OCOO—, —S— or —NR1- groups and in which one or more, nonadjacent methine units can be replaced by —N═, —N═N— or —P═ groups, and X=halogen, nitrogen radical, OR3, OCOR3, O(CH2)1OR3, where

R2 is hydrogen or a saturated or singly or multiply unsaturated, monovalent, Si—C-bonded C1-C20-hydrocarbon radical optionally substituted by —CN, —NCO, —NR12, —COOH, —COOR1, -halogen, -acryl, -epoxy, —SH, —OH or —CONR32, or an aryl radical or C1-C15-hydrocarbonoxy radical, in which one or more, nonadjacent methylene units can in each case be replaced by —O—, —CO—, —COO—, —OCO— or —OCOO—, —S— or —NR1- groups and in which one or more, nonadjacent methine units can be replaced by —N═, —N⊚N— or —P═ groups, and X=halogen, nitrogen radical, OR3, OCOR3, O(CH2)1OR3, where

R3 is as defined for R2 and R2 and R3 can be identical or different,

X is a C—O-bonded C1-C15-hydrocarbon radical or an acetyl radical or a halogen radical or an OH radical,

and 1 =1, 2, 3,

or R1iR2jSi—Y—SiR1iR2j   (II)

where

R1 and R2 are as defined above, i and j can be 0, 1, 2 or 3 and the sum i+j is equal to 3 and

Y can be the group NH or —O—,

with the proviso that the boiling points of the relatively nonvolatile organosilanes used are greater than 130° C. at atmospheric pressure.

10. The thermal insulation material as claimed in claim 8, wherein the following infrared opacifiers are used: titanium oxides, zirconium oxides, ilmenites, iron titanates, iron oxides, zirconium silicates, silicon carbide, manganese oxides and carbon black.

11. The thermal insulation material as claimed in claim 9, wherein the following infrared opacifiers are used: titanium oxides, zirconium oxides, ilmenites, iron titanates, iron oxides, zirconium silicates, silicon carbide, manganese oxides and carbon black.

12. The thermal insulation material as claimed in claim 8, comprising the following additives: precipitated silicas, pyrogenic silicas, SiO2-containing fly dusts from electrochemical silicon production and the thermal utilization of residues of volatile silicon compounds and also naturally occurring SiO2-containing compounds, thermally expanded minerals.

13. A molding, building block, building system or composite building system, characterized in that it comprises or consists partially or completely of thermal insulation material as claimed in claim 8.