DK303674

• Main Authors: THOMPSON M W V, ROSS J E
• Format: Patent
• Language: English
• Published: 03.02.1975
• Edition: 2
• Subjects: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOIDCHEMISTRY; COLOUR PRINTING; LINING MACHINES; PERFORMING OPERATIONS; PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL; PRINTING; PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; STAMPS; THEIR RELEVANT APPARATUS; TRANSPORTING; TYPEWRITERS

1455576 Microcapsules WIGGINS TEAPE Ltd 30 May 1974 [7 June 1973] 27281/73 Heading B8C A method of producing individual mononuclear oil-containing microcapsules comprises emulsifying an oil in a solution of a gellable hydrophilic colloid (e.g. an aqueous solution of gelatin), adding a solution of carboxymethyl cellulose to the emulsion, effecting complex coacervation so as to form mononuclear microcapsules each comprising a droplet of the oil as a nucleus with a wall of the colloid material and carboxymethyl cellulose around the nucleus, and gelling the microcapsule walls, the dry weight ratio of the colloid material to active content of the carboxymethyl cellulose used being between 1 : 0À35 and 1 : 1À2. The use of methyl cellulose and carboxymethyl cellulose in a ratio of 1 : 1, and also the use of gelatin and carboxymethyl cellulose in a ratio of 1 : 0À5, are disclaimed. The oil may be a mineral oil (e.g. kerosene) or a synthetic oil such as alkylated diarylmethanes, di-isopropyl naphthalene, mono-isopropyl biphenyl, dibenzyl benzenes, heptyl undecyl phthalate, alkylated diarylethanes and alkylated benzenes. Kerosene of alkylated benzene may be used as diluents for other synthetic oils and in the examples partially hydrogenated terphenyl diluted with kerosene is employed. Complex coacervation is effected in the examples, after adding carboxymethyl cellulose to the emulsion of oil in aqueous gelatin solution, by lowering the pH of the mixture from 7À5 to 4À4 by addition of acetic acid, followed by cooling of the mixture from 55 to 10‹ C. Glutaroldehyde solution is then added, the mixture stirred overnight, the pH then raised to 10 by addition of sodium carbonate solution and finally forwaldehyde solution is added. The oil employed may contain dissolved dye and the microcapsules produced may be coated on to a paper base for use in a pressure-sensitive copying system.