Abstract: An apparatus and a process for drying a suspension of a finely divided particulate solid material to produce the solid material in a substantially dry and unagglomerated form. The apparatus consists of a grinding chamber containing a particulate grinding medium such as silica having a diameter of 1-5 mm, a conduit for introducing the suspension into the grinding chamber and an impeller which rotates in the grinding chamber. The grinding chamber has a perforated base through which a heated gas is introduced to provide an upward flow of gas through the grinding chamber and through the grinding medium. As the particulate material is dried, fine particles of the dried material are carried upwards in the upflow of gas through the grinding chamber. A filter such as one or more cyclones and/or a bag filter assembly is located downstream of the grinding chamber in order to separate the particles of dried material from the gas.

Abstract: There is disclosed a method for immobilizing an oily or non-polar substance in a concrete matrix comprising the following steps:(a) absorbing the said oily or non-polar substance into a calcined clay mineral;(b) incorporating the calcined clay mineral and absorbed oily or non-polar substance formed in step (i) in a hardenable concrete mix; and(c) permitting the resultant concrete mix to harden.

Abstract: A method for recovery and use of a particulate waste material, i.e. inorganic and/or organic solid fines, present in an aqueous suspension, comprising the steps of:a) treating the aqueous suspension so as to precipitate, in the presence of the solid fines, crystals of an alkaline earth metal carbonate whereby the solid fines become entrained by and bonded to the crystals, thereby forming in the aqueous suspension a mixed aggregated particulate solid comprising the crystals and the fines; andb) recovering the mixed aggregated particulate solid and supplying such solid for use as a filler or pigment in a filler- or pigment-containing composition.

Abstract: There is disclosed a process for separating fine solids from water in the used water recovery system of a sheet forming mill, wherein the used water recovery system includes at least one stage in which an alkaline earth metal carbonate is precipitated in the aqueous suspension constituting the used water whereby the particulate material present in the used water becomes entrained in the alkaline earth metal carbonate precipitate. By the invention it is possible to recover the water and the fine solid materials which pass through the wire mesh belt of a paper or board forming machine, and optionally recycle those recovered materials.

Abstract: A method of coating paper with a paper coating composition having a solids concentration of at least 45% by weight, consisting essentially of an aqueous cationic dispersion of a particulate calcium carbonate pigment and a nonionic or cationic adhesive, wherein the pigment has a particle size distribution such that no more than 1% by weight of the particles have an equivalent spherical diameter larger than 10 microns, at least 65% by weight of the particles have an equivalent spherical diameter smaller than 2 microns and not more than 10% by weight of the particles have an equivalent spherical diameter smaller than 0.25 micron, and wherein said pigment is dispersed with a combination of a cationic polyelectrolyte and an anionic polyelectrolyte, with the amount of cationic polyelectrolyte being in the range of about 0.01% to about 1.5% by weight, based on the weight of the dry pigment, and with the amount of anionic polyelectrolyte being in the range of about 0.01% to about 0.5% by weight.

Abstract: There is disclosed a thermoplastics composition comprising a thermoplastic polymer having incorporated therein a coated particulate inorganic material. The coating on the particles of the inorganic material comprises a combination of a natural or synthetic polymeric material and a wax having a melting point not higher than the melting point of the thermoplastics polymer, and the polymeric material is present in the coating in an amount of from 1% to 10% by weight, based on the weight of dry inorganic material.The improved thermoplastic composition of the invention may be used in making moulded components for automobiles.

Abstract: There is disclosed a coating composition for the preparation of a CF sheet (i.e. a receiving sheet) of a carbonless paper copying system comprising a CF sheet and a CB sheet (i.e. a donating sheet). The coating composition comprises a color developer and an extender, wherein the extender comprises a particulate inorganic material which has been modified by treatment with a treating agent which has (i) a non-polar hydrophobic portion comprising at least one hydrocarbon group having a chain length of from 8 to 30 carbon atoms and (ii) a polar portion which is capable of binding with sites on the surface of the pigment particles.

Abstract: There is disclosed a coating composition for the preparation of a CF sheet (i.e. a receiving sheet) of a carbonless paper copying system comprising a CF sheet and a CB sheet (i.e. a donating sheet). The coating composition comprises a color developer and an extender, wherein the extender comprises a particulate inorganic material which has been modified by treatment with a treating agent which has (i) a non-polar hydrophobic portion comprising at least one hydrocarbon group having a chain length of from 8 to 30 carbon atoms and (ii) a polar portion which is capable of binding with sites on the surface of the pigment particles.

Abstract: Method and apparatus for obtaining the average aspect ratio of non-spherical particles in suspension. The particles are caused to orient generally in one direction and the conductivity of the particles are measured in such direction while simultaneously measuring the conductivity of the particles in a traverse direction. The difference between the two conductivity measurements is indicative of the average aspect ratio of the particles in suspension.

Abstract: The calcium carbonate is prepared by:(a) slaking quicklime in an aqueous medium;(b) carbonating and neutralising the suspension of slaked lime formed in step (a) using a gas comprising carbon dioxide; and(c) separating the precipitated calcium carbonate formed in step (b) from the aqueous medium in which it is suspended. There is added 0.1% to 2% by weight, based on the weight of dry calcium oxide, of a reagent having one or more active hydrogen atoms (or a salt thereof), to the aqueous medium in which the quicklime is slaked in step (a).

Abstract: There is disclosed a process for separating fine solids from water in the used water recovery system of a sheet forming mill, wherein the used water recovery system includes at least one stage in which an alkaline earth metal carbonate is precipitated in the aqueous suspension constituting the used water whereby the particulate material present in the used water becomes entrained in the alkaline earth metal carbonate precipitate. By the invention it is possible to recover the water and the fine solid materials which pass through the wire mesh belt of a paper or board forming machine, and optionally recycle those recovered materials.

Abstract: There is disclosed a process for producing a finely ground alkaline earth metal pigment. The process comprises the steps of:(a) preparing an aqueous suspension comprising from 40 to 70% by weight of a particulate alkaline earth metal compound, such as calcium carbonate;(b) subjecting the suspension formed in step (a) to attrition grinding with a particulate grinding medium under conditions such as to yield a product having a particle size distribution such that at least 90% by weight of the particles have an equivalent spherical diameter smaller than 2 .mu.m, and preferably at least 80% by weight of the particles have an equivalent spherical diameter smaller than 1 .mu.m; and(c) allowing water to evaporate from the suspension under the action of heat contained in the suspension until the percentage by weight of dry alkaline earth metal compound in the suspension is at least 70% by weight.

Abstract: The present invention relates to apparatus for comminuting a material. The apparatus comprises a support (4) which is rotatable about a primary axis, and a grinding vessel (17), defining a grinding chamber, which is mounted on the support (4) for rotation about a secondary axis which is substantially parallel to the primary axis. The grinding vessel (17) is provided with an inlet (34) for a feed suspension of particulate solid material and an outlet (36) for a suspension for a fine product. In the first embodiment the grinding vessel (17) communicates with the outlet (36 ) through a screen (35 ). In the second embodiment, the inlet (34) comprises means for regulating the flow rate of the feed suspension. The invention also relates to a process for comminuting a material in a planetary mill, in which process the material is either ground autogenously or is ground in the presence of a grinding medium consising of particles not larger than 1mm.

Abstract: There is disclosed a paper coating pigment comprising:(a) from 10% to 100% by weight of a first paper coating pigment having a particle size distribution such that at least 75% by weight of the particles have an equivalent spherical diameter smaller than 2 .mu.m and at least 60% by weight have an equivalent spherical diameter smaller than 1 .mu.m, the average particle aspect ratio of the size fraction having an equivalent spherical diameter predominantly smaller than 1 .mu.m being 25 or greater; and(b) up to 90% by weight of a second paper coating pigment.

Abstract: There is disclosed a paper coating composition for use in preparing a coated paper for gravure printing, which composition comprises a suspension in water of 100 parts by weight, on a dry weight basis, of a pigment or mixture of pigments having a particle size distribution such that at least 75% by weight of the particles have an equivalent spherical diameter smaller than 2 .mu.m, and a latex the particles of which do not swell appreciably in water and which have an average size less than 0.2 .mu.m, the latex being employed in an amount such as to provide from 3 to 15 parts by weight latex solids and the composition being substantially free from any viscosifying, film-forming hydrophilic polymeric material.

Abstract: There is disclosed a process for preparing porous ceramic granules, comprising(a) preparing a foam from an aqueous mixture of a particulate aluminosiliceous material and a fluxing material;(b) dividing the foam into discrete particles to form granules; and(c) calcining the granules at an elevated temperature such that sintering of the aluminosiliceous particles occurs.

Abstract: There is described a process for the isolation of a fine mineral product from a low-grade source of the said mineral, the process comprising the following steps:(i) forming a suspension in water of the said mineral source;(ii) subjecting the suspension to grinding with a grinding medium having a specific gravity not greater than 2.0, the amount of energy dissipated in the suspension during the grinding operation being not greater than 50 kW.hrs per tonne of the dry mineral source; and(iii) isolating from the ground suspension a fine fraction of particles comprising an increased amount of the said mineral when compared with the same fraction isolated from the unground mineral source.

Abstract: There is disclosed a process for preparing a filler composition suitable for incorporation in a polyester film-forming material, which process comprises the following steps:(a) calcining a crude kaolin clay under conditions such that the calcined product comprises particles consisting of aggregates of fine kaolin platelets;(b) suspending the calcined clay product from step (a) in water containing a dispersing agent for the calcined clay, so as to form a suspension containing from 40% to 70% by weight of dry calcined clay;(c) subjecting the suspension formed in step (b) to comminution by attrition grinding with a particulate grinding medium for a time sufficient to reduce the average diameter of the aggregate particles to within the range from 0.3 .mu.m to 0.9 .mu.m, and to ensure that the calcined clay is substantially free of particles having an equivalent spherical diameter larger than 5 .mu.

Abstract: There is disclosed an aqueous paper coating composition which comprises at least 45% by weight of a particulate pigment dispersed with a dispersing agent, and an adhesive; characterized in that said dispersing agent comprises an anionic polyelectrolyte and a cationic polyelectrolyte, the cationic polyelectrolyte being present in an amount sufficient to render the particles cationic, in that said adhesive is a cationic or non-ionic adhesive and in that said particulate pigment is one which is not capable of being dispersed in water at high solids, and following vigorous mixing, in the sole presence of said cationic polyelectrolyte. Also disclosed is a method for making the paper coating composition, a method for coating a paper with a paper coating composition and the resulting coated paper. The coated paper of the invention is particularly suited to recycling.

Abstract: The present invention relates to apparatus for comminuting a material. The apparatus comprises a support (4) which is rotatable about a primary axis, and a grinding vessel (17), defining a grinding chamber, which is mounted on the support (4) for rotation about a secondary axis which is substantially parallel to the primary axis. The grinding vessel (17) is provided with an inlet (34) for a feed suspension of particulate solid material and an outlet (36) for a suspension for a fine product. In the first embodiment the grinding vessel (17) communicates with the outlet (36) through a screen (35). In the second embodiment, the inlet (34) comprises means for regulating the flow rate of the feed suspension. The invention also relates to a process for comminuting a material in a planetary mill, in which process the material is either ground autogenously or is ground in the presence of a grinding medium consisting of particles not larger than 1 mm.