GB931148A - - Google Patents

Abstract

931,148. Coating particulate material; cleansing materials. UPJOHN CO. Oct. 28, 1959 [Dec. 22, 1958], No. 36634/59. Classes 91 and 95 [Also in Groups IV(a), VI, XX and XXXV] Particulate solids are coated by forming a uniform dispersion thereof in a solution of a liquid phase-forming macromolecular polymer in aqueous or non-aqueous media and adding thereto a non-aqueous liquid which is a non- solvent for both the polymer and the particles, thereby causing the formation of a liquid, polymer-rich phase which coats the particles, and setting the coating, e.g. by chilling alteration of pH, or addition of divalent or multi-valent ions, e.g. Ca<SP>++</SP>, Mg<SP>++</SP>, Fe<SP>++</SP>, Fc<SP>+++</SP> or Al<SP>+++</SP>. Thereafter, the coatings may be hardened, e.g. by treatment with dicarbonyl compounds, alum, tannic acid, tannic acid and ferric chloride, changes in pH, irradiation or removal of occluded liquid by drying and/or heating and the coated material may be separated, washed and dried. Particles may be precoated, e.g with wax or "Ethocel" (Registered Trade Mark) to give them a lipophilic surface which is preferred if the coating is to be applied from an aqueous medium or with gelatin to give them a hydrophilic surface which is preferred for coating from a non-aqueous medium. Polymers which may be used are carbohydrate acetate phthalates, synthetic and natural macromolecular polymers, e.g. polyvinyl polymers, di- and trinitrocellulose, polystyrene, cellulose acetate, polyvinyl acetate, polyvinyl chloride, polyvinyl alcohol, cellulose acetobutyrate, benzyl cellulose, rubber, linear macromolecular synthetic polymers having an average molecular weight of at least 20,000 and a liniar polymeric structure comprising both lipophilic and hydrophilic units, e.g. hydrolysed styrene-malic acid copolymers, styrene-maleic acid amide copolymers, sulphonated polystyrenes, polymethacrylic acid and methyl vinyl ether-maleic acid copolymers, hydrophilic colloids, e.g. gelatin, albumin, sodium alginate, casein, agar-agar, starch, pectins, carboxymethylcellulose, irish moss and gum arabic, and macromolecular polymers containing basic groups, e.g. diacetylated chitin, polyvinyl pyridine, styrene-vinyl pyridine copolymer, polyvinyl pyridine, polymeric quaternary ammonium salts, e.g. polylysine, polyornithine, poly-p-aminophenyl alanine and polyacrylamide. Specific examples include quercetin coated with agar-agar (slow release dye), alizarin cyanine dye pre-coated with ethyl cellulose and coated with cellulose acetobutyrate and tribasic sodium phosphate coated with styrene-maleic acid copolymer (drain cleanser). Other examples relate to coated iron particles, medicaments, fertilizer and hubicides, and a photo-developer pre-coated with white wax.