GB649549A - Improvements in gelatine derivatives - Google Patents

Abstract

A gelatine derivative is prepared by reacting gelatine with isatoic anhydride. A solution of gelatine in water or other solvent, e.g. formamide as described in Specification 649,548, is mixed with the anhydride under alkaline conditions such as a pH of 8-12, preferably 9.5-10.5, obtained by adding a base such as sodium hydroxide, ammonia or tetramethyl ammonium hydroxide. Temperatures from room up to, say, 110 DEG F. may be used. Any type of gelatine including hydrolysed or degraded gelatine or glue is utilizable. The product is recovered by setting, washing and drying. It may be used to prepare diazonium salts, which can be coupled to give azo dye gelatine derivatives, and in the preparation of silver halide dispersions, e.g. as described in Specification 649,545. In an example, a gelatine solution in water at 50 DEG C. is mixed with caustic soda, isatoic anhydride added, and stirring continued for 20 mins. The product is recovered and converted through the diazonium salt to a dye derivative or reacted with ethyl ortho formate to yield a 4 - keto - 3 : 4 - dihydroquinazoline, thought to be a gelatine derivative.ALSO:A gelatine derivative made by reacting gelatine with isotoic anhydride is converted into a diazonium salt which is coupled to give azo dye gelatine derivatives. In an example, the diazonium salt with sodium nitrite and hydrochloric acid is coupled with b -naphthol to give a pinkish yellow dye, and with chromotropic acid (1,8-dihydroxy-3,6-naphthalene disulphonic acid) to give a red dye.