GB735892A - Improvements in or relating to the production of cellulose acetate films, sheets andthe like - Google Patents

Abstract

A cellulose acetate composition, capable of being cast to form sheets, films and the like, comprises a cellulose acetate, having an acetyl content of 42.5-44.0 per cent by weight, in solution in a solvent mixture composed of methylene chloride, methyl alcohol and n-butyl alcohol in proportions falling within the range of 82-94 per cent of methylene chloride, 1-6 per cent of methyl alcohol and 4-13 per cent of n-butyl alcohol. The solution may be cast on to a forming-surface which is maintained at 60-95 DEG F. Plasticizers such as triphenyl phosphate, tricresyl phosphate, diethyl phthalate, dibutyl phthalate or tripropionin may be incorporated in the solution. The films obtained may be used as bases or supports for photographic, including motion-picture, films. If desired the solution may first be obtained in a more dilute state than is required for film-forming, and it may then be concentrated by heating it under pressure, filtering, abruptly releasing the pressure so that solvent volatilizes, and then reincorporating a portion of the condensed solvent with the solute to produce the desired concentration of cellulose acetate, e.g. 18 per cent. In preparing the solution, the cellulose acetate may be dissolved in a methylene chloride-methyl alcohol mixture, and the butyl alcohol containing the plasticizer, if any, may be added, mixing being continued until the solution is uniform. The solution may then be concentrated and cast to form a film. Dyes, pigments and fluorescent materials may be incorporated in the solution, e.g. Eastone Red R, Nigrosine, 7-diethylamino-4-methyl coumarin, Sudan Black G, anthracene, rhodamine, fluorene, chrysene, naphthacene, 2,21-dihydroxy benzalazine, methyl umbelliferone, anthranilic acid, ethyl anthranilate, 3-dimethylaminoacridine and 2 - phenyl - 5 - aminobenzoxazole. Specifications 640,730, 640,731 and 687,728 are referred to.