Patent GB-601896-A (GB)
Title: Improvements in cellulose ester products
IPC: C08J7/06
Filed: 1945-10-10
Abstract: The light-proofing (especially against ultraviolet light) of sheets, moulded articles, and other shaped articles of substantial p thickness composed essentially of an organic ester of cellulose comprises the application to the article &c. of a composition comprising an ester of a hydroxy-aryl carboxylic acid with a phenol or an aromatic alcohol under conditions which limit the penetration to the surface layers.  The cellulose ester comprising the basis of the article may be cellulose acetate, propionate, butyrate or a mixed ester such as cellulose acetate propionate or cellulose acetate butyrate, and the article &c. may be made by any known method.  The solvent in which the aromatic hydroxy-aryl ester is dissolved should be a swelling agent for the cellulose ester, such as ethyl acetate, acetone, ethyl lactate, tetrachloroethane, ethylene glycol monomethyl ether, benzyl alcohol, diacetone alcohol, dioxane, methyl alcohol or benzene or a mixture of two or more of these.  The acid component of the ester which acts as a protecting agent is preferably an o-hydroxy carboxylic acid such as salicylic acid; the actual protecting agent may be therefore phenyl salicylate.  In one method the article is immersed for a suitable period in a solution of the ester in any of the above-named solvents or in a mixture of them. An alternative method comprises coating the article with a composition of a solution in a volatile solvent of a film-forming material and the protecting agent, plasticizers and synthetic resins (to give toughness to the coating) being present if desired.  The film-forming material may be a film-forming derivative of cellulose of approximately the same constitution as the article to be coated, or may be any substance compatible with the ester comprising the article such as polyvinyl acetate, copolymers of polyvinyl acetate and polyvinyl chloride, polymerized acrylic acid derivatives, polystyrene or derivatives thereof.  Suitable plasticizers are dimethyl and diethyl phthalate, tricresyl phosphate &c.  Examples of synthetic resins which may be present are the di-ethylene glycol-phthalic anhydride resins, toluene sulphonamide-formaldehyde resins and polyvinyl and polyacrylic resins.  In an example a cellulose acetate sheet 0.125 inches thick containing by weight 20 per cent of diethyl phthalate and 10 per cent triphenyl phosphate is immersed for 20 seconds at room temperature in a bath containing 15 parts by weight of phenyl salicylate and 85 parts by weight of acetone. The sheet is removed, drained and the acetone allowed to evaporate.  After exposure for a few seconds to acetone vapour to prevent any tendency on the part of the protecting agent to crystallize on the surface the sheet is plate polished and given a weathering test for 240 hours.  This test consists in exposure according to the following cycle 2 hours in a fog chamber, 2 hours ultra-violet irradiation, 2 hours in a fog chamber, 18 hours irradiation.  After the test the sheet shows no crazing, discoloration, viscosity breakdown or surface exudation unlike an untreated sheet.  Specification 563,287 is referred to.  The Specification as open to inspection under Sect. 91 refers also to the treatment of filaments, films, fabrics and foils made from thermoplastic materials having a basis of an organic ester of cellulose.  In an additional example a cellulose acetate fabric is partly immersed in a 10 per cent ethyl alcohol solution of phenyl salicylate for 2 minutes, dried and exposed to the weathering test for 240 hours.  The untreated part is discoloured and breaks on creasing, the treated part showing neither discoloration nor brittleness.  This subject-matter does not appear in the Specification as accepted.ALSO:The light-proofing (especially against ultraviolet light) of sheets, moulded articles and other shaped articles of substantial thickness composed essentially of an organic ester of cellulose, comprises the application to the article &c. of a composition comprising an ester of a hydroxy-aryl carboxylic acid with a phenol or an aromatic alcohol under conditions which limit the penetration to the surface layers.  The cellulose ester comprising the basis of the article may be cellulose acetate, propionate, butyrate or a mixed ester such as cellulose acetate propionate or cellulose acetate butyrate, and the article &c. may be made by any known method.  The solvent in which the aromatic hydroxy-aryl ester is dissolved should be a swelling agent for the cellulose ester, such as ethylacetate, acetone, ethyl lactate, tetrachloroethane, ethylene glycol monomethyl ether, benzyl alcohol, diacetone alcohol, dioxane, methyl alcohol or benzene, or a mixture of two or more of these.  The acid component of the ester which acts as a protecting agent is preferably an o-hydroxy carboxylic acid such as salicylic acid: the actual protecting agent may be therefore phenyl salicylate.  In one method, the article is immersed for a suitable period in a solution of the ester in any of the above-named solvents or in a mixture of them. An alternative method comprises coating the article with a composition of a solution in a volatile solvent of a film-forming material and the protecting agent, plasticizers and synthetic resins (to give toughness to the coating) being present if desired.  The film-forming material may be a film-forming derivative of cellulose of approximately the same constitution as the article to be coated, or may be any substance compatible with the ester comprising the article such as polyvinyl acetate, copolymers of polyvinyl acetate and polyvinyl chloride, polymerized acrylic acid derivatives, polystyrene or derivatives thereof.  Suitable plasticizers are dimethyl and diethyl phthalate, tricresyl phosphate, &c.  Examples of synthetic resins which may be present are the di-ethylene glycolphthalic anhydride resins, toluene sulphonamide-formaldehyde resins and polyvinyl and polyacrylic resins.  In an example, a cellulose acetate sheet 0.125 inches thick containing by weight 20 per cent of diethyl phthalate and 10 per cent triphenyl phosphate is immersed for 20 seconds at room temperature in a bath containing 15 parts by weight of phenyl salicylate and 85 parts by weight of acetone. The sheet is removed, drained and the acetone allowed to evaporate.  After exposure for a few seconds to acetone vapour to prevent any tendency on the part of the protecting agent to crystallize on the surface, the sheet is plate polished and given a weathering test for 240 hours.  This test consists in exposure according to the following cycle: 2 hours in a fog chamber, 2 hours ultra-violet irradiation, 2 hours in a fog chamber, 18 hours irradiation.  After the test, the sheet shows no crazing discolouration, viscosity breakdown or surface exudation unlike an untreated sheet.  Specification 563,287 is referred to.  The Specification as open to inspection under Sect. 91 refers also to the treatment of filaments, films, fabrics and foils made from thermoplastic materials having a basis of an organic ester of cellulose.  In an additional example, a cellulose acetate fabric is partly immersed in a 10 per cent ethyl alcohol solution of phenyl salicylate for 2 minutes, dried and exposed to the weathering test for 240 hours.  The untreated part is discoloured and breaks on creasing, the treated part showing neither discolouration nor brittleness.  This subject-matter does not appear in the Specification as accepted.