GB351444A - Improvements in and relating to the preparation of aqueous emulsions of cellulose derivatives - Google Patents

Abstract

Aqueous emulsions of cellulose derivatives, of predetermined particle size, applicable as paints and impregnating compositions for paper, felt, textile materials, leather, wood and composition boards, are prepared by inverting a preformed "water-in-oil" emulsion in the presence of a predetermined quantity of water. Inversion may be effected by (a) sudden vigorous agitation, (b) sudden addition of water, (c) addition of emulsifying agent, or (d) addition of an already inverted emulsion of similar composition. The emulsifying agent employed is preferably in the form of a dispersion with or in an organic solvent. Solvents, softeners, pigments and resins may be incorporated. The emulsions may be applied by flowing, brushing, or spraying and materials may be impregnated by immersion or by application of the medium under pressure. For impregnation the size of the particles is so chosen as to permit them to pass into the interstices between the fibres or other elements of the base treated, and to bind such elements together without completely filling the interstices. Examples of the invention are as follows:--(1) An emulsifying agent comprising an emulsion, containing 0,5 parts of sodium oleate, 15 parts of gasoline and two parts of water, is added to a composition comprising 10 parts of pyroxylin, 2,5 parts of alcohol, 20 parts of blown linseed oil, 20 parts of butyl acetate and 5 parts of butyl lactate; the product is a "water-in-oil" type emulsion; 98 parts of water are then added in the following ways to give "oil-in-water" emulsions of different particle size: (a) 20 parts in small portions, 10 parts with vigorous stirring, producing inversion, 68 parts with moderate stirring, (particle size 1,19 microns); (b) 35 parts in small portions, 10 parts vigorously, producing inversion, 53 parts, (particle size 1,92 microns); 90 parts in small portions, 8 parts vigorously, producing inversion (particle size 2,23 microns); the last emulsion is unsuitable for paper impregnation. (2) One tenth part of a composition, comprising 10 parts of pyroxyline, 7,1 parts of alcohol, 20 parts of blown linseed oil, 30 parts of ethyl acetate, 10 parts of butyl acetate and 5 parts of gasoline, is mixed with one-tenth part of the emulsifying agent (above), and this water-in-oil emulsion is then inverted as in (1)(a) but using water saturated with ethyl acetate. The remainder of the composition and emulsifying agent are then mixed and treated by dilution with ethyl acetate water, sudden addition of the preformed inverted emulsion, (inversion step), and further dilution. (3) An emulsifying agent as in (1) is added to a composition, comprising 10 parts of pyroxylin, 20 parts of blown linseed oil, and 25 parts of butyl acetate, and 25 parts of water added gradually; inversion is then effected by sudden vigorous agitation and the inverted emulsion diluted with 75 parts of water. (4) A composition comprising 15 parts of celluloid scrap, 75 parts of ethyl acetate and 10 parts of butyl lactate is mixed with one half of an emulsifying mixture, prepared by heating 0,45 parts of sodium oleate with 15 parts of gasoline, and 25 parts of ethyl acetate water added gradually; inversion is then effected by adding the other half of the emulsifying mixture, with vigorous stirring, and the inverted emulsion diluted with 75 parts of ethyl acetate water. (5) Inversion of an emulsion comprising a composition substantially as in (1), and an emulsifying agent containing twice as much soap as in (1), is effected by the continuous addition of water with vigorous stirring; the inverted emulsion is diluted. (6) A pigmented emulsion is prepared by vigorously stirring a "water in-oil" emulsion containing chrome orange, sodium oleate, gasoline, and blown linseed oil, with a prepared and inverted aqueous emulsion comprising pyroxylin, solvents, gum damar and dibutyl phthalate; total inversion is thereby effected, the further addition of emulsifying agent as in (1) being made if necessary; the product is diluted. Other examples containing blown castor oil as an ingredient are given.