Abstract: A method of dispersing a solid particulate material in an aqueous medium by addition to the aqueous medium of a dispersing agent wherein the solid particulate material is to be used as a filler or pigment in a sheet material which is required to come into contact with foodstuffs, wherein the dispersing agent is a composition comprising:

Abstract: A method of treating solid-containing material contained in or produced from an effluent or waste from a process for the treating of waste paper. The solid-containing material includes constituents of the waste paper and organic material including cellulose fibers and inorganic particulate material including calcium carbonate and other inorganic particulate material included in the waste paper. The solid-containing material is subjected to a heat treatment that incinerates the organic material present and forms from the inorganic particulate material present a calcined product including calcium oxide from thermal decomposition of calcium carbonate. The calcined product is formed into an aqueous suspension wherein calcium oxide is converted to calcium hydroxide.

Abstract: A granular material for the sorption of organic material comprises granules of an inorganic silicon-containing material having negatively charged sites and having an average granule size of at least 50 microns, the granules being porous and coated on their outer and inner surfaces with a film of an organic polymeric material having polar and non-polar moieties. The organic polymeric material may form from 0.25% to 10% by weight of the weight of the inorganic material.The granular material may be prepared by treating an aqueous suspension of the inorganic material with a material comprising the organic polymeric material. The inorganic silicon-containing material may comprise a silicate, eg. an aluminosilicate, eg. a kandite and/or smectite clay which may be a foamed material which has been calcined. The polymeric material may comprise a nitrogen-containing polymer which can be employed in the form of an acid colloidal medium, eg. a melamine-aldehyde polymer.

Abstract: There is disclosed a method of preparing a concentrated aqueous suspension of a finely ground particulate material by a multistage grinding process in which an aqueous suspension of the particulate material is passed to and treated by grinding in each of a series of grinding stages, wherein a water soluble polycarboxylate dispersing agent for the particulate material is added to the suspension at each of a plurality of dispersion agent addition sites or stages. The invention is characterised in that the aqueous suspension when treated by grinding in at least one of the grinding stages has a pH on the inclusive range 8.5 to 9.8. Using the method described, suspensions can be prepared which are rheologically stable with time, and which contain a relatively high proportion by weight of a finely divided pigment.

Abstract: There is disclosed a process for improving one or more properties of kaolin comprising:(a) providing an aqueous suspension of particulate kaolin clay;(b) introducing into the aqueous suspension a first reagent comprising a source of alkaline earth metal ions and a second reagent comprising a source of carbonate ions to precipitate an alkaline earth metal carbonate in the said aqueous suspension of the said particulate kaolin clay whereby the said particulate kaolin clay present at the start of the process becomes entrained by and bonded to the alkaline earth metal carbonate to form a composite particulate product which may be used in paper making or paper coating or as a filler or extender in compositions for other applications. The alkaline earth metal ions may be calcium ions provided by calcium hydroxide obtained by slaking lime either in the aqueous suspension or separately. The carbonate ions may be provided by carbon dioxide.

Abstract: A ceramic particulate material which comprises particles having an irregular three dimensional surface profile having jagged projections and a median particle diameter of 200 micrometers or less, the particles being fractals produced by comminution of foamed ceramic material. The material may be such that in a sphere of rotation of the particle, from 30% to 80% of the volume of the sphere is void, the remainder being continuous solid material. The material may be produced by a process which includes providing a suspension of ceramic forming particles e.g., of an aluminosilicate such as clay, in a liquid medium; incorporating a gas in the liquid medium before or after formation of the suspension therein to produce a foamed suspension; extruding the foamed suspension; optionally drying the extrudate formed thereby; calcining the extrudate; and comminuting the calcined material, e.g. by crushing. The material may be used as a substitute for diatomite.

Abstract: A method of improving the strength and/or plasticity of a clay composition comprising a kandite clay and an organic additive comprising at least one water soluble compound having a plurality of basic groups wherein the organic additive is present in an amount of from about 0.05% by weight to about 0.5% by weight based on the dry weight of the kandite clay present, which method comprises treating the kandite clay by adding thereto a monovalent ion activated smectite clay or a monovalent ion activating agent for a smectite clay or both whereby the amount of monovalent ion activated non-calcined smectite clay present in the clay composition is adjusted to be in the range from about 1% by weight to about 5% by weight based upon the dry weight of the kandite clay present.

Abstract: A method of producing an aqueous suspension of calcium hydroxide which comprises passing a gaseous flow incorporating particles of calcium carbonate through a calcining furnace thermally to decompose the calcium carbonate, delivering a flow of the decomposition products formed in the furnace comprising calcium oxide particles suspended in gas comprising carbon dioxide to a vessel wherein the calcium oxide particles are contacted with water to produce an aqueous suspension of calcium hydroxide and separating the aqueous suspension from the said gas.

Abstract: A composition suitable for adding to water to produce a water-resistant hydraulic solid which composition comprises components (a), (b) and (c) as follows:(a) calcium sulphate hemihydrate;(b) portland cement;(c) calcined clay having a pozzolanic activity;wherein the percentages by weight of components (a), (b) and (c) in the said composition are in the respective ranges:(a) from 20% to 98%;(b) from 1% to 50%;(c) from 1% to 30%;the percentages of components (a), (b) and (c) adding to 100% in the three component composition.

Abstract: A method of producing a multiple coated cellulosic sheet product having a surface which is smooth, bright and capable of being printed upon, includes the steps of coating a substrate comprising a cellulosic sheet with a first layer of an inorganic pigment-containing aqueous coating composition, and coating the first layer with a second layer of an inorganic pigment-containing aqueous coating composition to form a product in which the first layer is bonded to the cellulosic sheet and the second layer is bonded to and inseparable from the first layer, wherein there is incorporated into the first layer a sizing agent in an amount of up to 0.6% by weight based on the dry weight of the pigment present in the first layer. The sizing agent is selected from alkene ketene dimers, alkenyl succinic anhydrides, and anionic polyurethane sizes.

Abstract: An inorganic particulate material suitable for use as a pigment material in a paper coating composition has a particle size distribution which when represented as a graph of percentage of weight of particles having an equivalent spherical diameter (esd) of given size versus particle esd expressed in microns and plotted on a logarithmic base 10 scale has the following features: (a) a first peak at the coarse particle size and a second peak at a finer particle size and a dip or trough between the first and second peaks; (b) the mean particle size x.sub.1 of the particles making up the first peak being 2 to 4 microns; (c) the relationship between the first and second peaks being such that the value of the mean particle size x.sub.2 of the particles making up the second peak is separated in the particle size distribution graph from the value of x.sub.1 by at least 0.5; and (d) the minimum of the dip or trough is at a given particle esd dimension of between 0.5 and 5 microns.

Abstract: A method of preparing an inorganic particulate material suitable for incorporation in a composition comprising a hydrophobic polymeric material includes the steps of (a) processing an aqueous suspension of an inorganic particulate material in the presence of a water soluble dispersing agent; (b) adding a surfactant to the particulate material; and (c) drying the particulate material. The inorganic particulate material to which the surfactant has been added may be further treated by addition thereto of a further surface treatment agent which is a hydrophobising surface treatment agent, eg. a carboxylic acid or salt thereof. The surfactant may be a non-ionic surfactant and may be added to the particulate material whilst in the form of a dispersed aqueous suspension. The further surface treatment agent may be added to the particulate material during or after the drying step (c).

Abstract: A method of treating a dilute aqueous suspension of solid particulate material comprising waste material from a process for recovering petroleum from oil sand includes diluting the suspension with at least 75% of its own volume of water thereby to increase the settling rate of the particulate material and allowing the particulate material to settle to form a concentrated solid sediment. The treated suspension may have been obtained from a process in which an alkaline solution is used to treat the oil sand. The water from which the concentrated solid sediment is separated may be returned to the process for recovering petroleum from oil sand. The solid sediment may be transferred to a separation vessel in which it is fractionated into a coarse particle fraction and a fine particle fraction. The fine particle fraction may comprise essentially particles having an equivalent spherical diameter not greater than 3 .mu.m. The concentrated solid material recovered may be calcined to form a pozzolanic material.

Abstract: A method is described for the treatment of a solid containing material obtained from effluent from an industrial plant or process, eg. a plant for the de-inking of waste paper. Such effluent comprises an aqueous suspension of solids comprising organic material and inorganic particulate material. The inorganic particulate material contains a substantial amount of calcium carbonate and is likely also to contain kaolin or metakaolin. The solids may also contain carbon particles. The method includes subjecting the solid containing material to a heat treatment process such that the temperature is controlled to be maintained in the range 600.degree. C. to 800.degree. C. preferably 600.degree. C. to 750.degree. C., to cause burning of the organic material without decomposition of more than about 50% by weight, preferably not more than about 10% by weight, of the calcium carbonate present to produce a particulate calcium carbonate-containing inorganic material substantially free of organic material.

Abstract: There is disclosed a method for the preparation of a precipitated calcium carbonate (PCC) for use as a pigment in paper coating compositions, the method comprising the steps of (a) carbonating an aqueous lime-containing medium to produce an aqueous suspension of a PCC predominantly in a selected crystal form, (b) at least partially dewatering the PCC-containing suspension; and (c) subjecting the PCC-containing suspension to comminution by high shear attrition grinding with an attrition grinding medium. Steps (b) and (c) may be applied in either order, ie. (b) followed by (c) or alternatively (c) followed by (b). The dewatering step (b) is preferably carried out using a pressure filter device operating at a pressure of at least 5 MPa, preferably at least 10 MPa. A pH reduction step may be applied after steps (b) and (c). Also disclosed are pigments produced by the method and pigment and paper coating compositions including such pigments.

Abstract: A process is described for preparing .beta.'-sialon comprising heating a mixture of particles comprising from 70% to 90% by weight of particles of an aluminosilicate material and from 30% to 10% by weight of particles of a carbonaceous material at a temperature in the range of from 1300.degree. C. to 1600.degree. C. in nitrogen in a vessel in a manner such that the particles are in substantially continuous motion relative to each other and relative to the nitrogen. The residence time of the particles in the vessel does not exceed 3 hours.

Abstract: A decanter centrifuge for separating a feed suspension of a particular solid material in a liquid into two fractions, i.e. a heavy fraction containing heavy particles and a light fraction containing light particles, or no particles at all, is described. The centrifuge has a rotatably mounted elongated bowl having closed ends with a side wall extending therebetween. A helical scroll is rotatably mounted coaxially within the bowl, and the bowl and the scroll may be rotated at different rotational speeds. A pipe coaxially mounted in a tubular shaft and rotatably supporting the scroll, feeds the suspension into the bowl. Several outlets in the wall of the bowl discharge the heavy fraction from the bowl. The light fraction travels through the length of the bowl by the helical scroll and is discharged from outlets located downstream from those that discharge the heavy fraction. The delivery region is also nearer to the outlets for the heavy fraction than to the outlets for the light fraction.

Abstract: A process for improving the rheological properties of an aqueous suspension of a particulate inorganic material which comprises the steps of: (a) forming an aqueous suspension of the particulate inorganic material and an effective amount of an anionic polyelectrolyte dispersing agent; (b) diluting the suspension formed in step (a) with water while maintaining the particulate in the dispersed state of step (a) to give a solids concentration of not less than 20% by weight of the particulate inorganic material; and (c) reconcentrating the diluted suspension formed in step (b) to give a solids concentration of at least 50% by weight of the particulate inorganic material.

Abstract: A granular filler comprising a particulate inorganic material; from 0.1% to 10% by weight, based on the weight of the organic material, of fine carbon black; and sufficient amount of a natural or synthetic latex composition to provide from 1% to 10% by weight of elastomer solids, based on the weight of the inorganic material, wherein the granules have diameters within the range of from 0.01 mm to 0.1 mm.

Abstract: Apparatus for continuously separating relatively coarse particles from a suspension of a mixture of particles in a liquid, wherein the suspension is caused to pass through a screening medium which is rotating in its own plane and wherein the screening medium extends over and across the upper end of a rotary drum having generally downwardly depending side walls and wherein the side walls diverge outwardly in a downward direction.