Chemical modification of gelatin for silver halide colour emulsion - with 1,1-di:methyl- 3-allyl-sulphonyl- methyl-4-sulpho- methyl- pyrrolidinium betaine, limiting viscosity increase on adding colour coupler

摘要

Prodn. of chemically modified gelatin (I) for gelatino-Ag halide colour emulsions involves alkaline decomposition of defatted and macerated crushed bone or split cowhide with lime in the usual way, deliming, extn. with hot water, filtration and concn.. The novel features are that, after filtration and before or during concn., the aq. gelatin soln. is adjusted to pH 9.5-10.5; 1,1- dimethyl- 3-allyl-sulphonyl-methyl- 4-sulpho-methyl pyrrolidinium betaine (II) is stirred into this and dissolved at 60-80 deg. C; the pH is re-adjusted after 30-60 min reaction; and the (I) soln. is worked up in the usual way, i.e. conc., set, crumbled and dried. ADVANTAGE - In emulsions contg. (I), the increase in viscosity on adding the colour coupler is very limited, whilst the sensitometric properties of the emulsion and physico-mechanical properties of the film are retained and the brittleness is reduced.