Acrylic acid derivs for hardening photographic gelatine

Acrylic acid derivs. for hardening gelatine, esp. in the form of photographic emulsions, have the formula (I) (H2C=HC-OC-NH-OC-O)2-Y2 (II) (H2C=CH-OC-NH-OC-NH)2-Y3 (III) X and Z = O, S, NH, or NHCO bonded to Y through the C atom; Y = (CH2)m-, -CH2-CH2-(O-CH2-CH2) q-, -(CH2)r-O-(CH2)r-or -(CH2)r-S-(CH2)r-; or can be CO, or a direct bond when both X and Z are NH and N = 1; and m, n, r and q are positive integers, n is not > 2, m is not > 14, q = 2-4, and r = is not > 4. 0.5-5% wt. (I) is added opt. as a soln. in water, ethanol, dimethylformamide, etc. to the gelatine. The gelatine becomes hardened by the crosslinking action of (I). The use of cpds. (I) does not alter the photographic properties of the light sensitive gelatine layers.