Verfahren zur Herstellung von Mischpolymeren

摘要

Copolymers are prepared containing recurring units of the formula wherein R, R1 and R2 are the same or different and are each a hydrogen atom, an alkyl group of 1 to 3 carbon atoms, a phenyl or a cyclohexyl group, R1 and R11 are the same or different and are each a hydrogen atom or an alkyl group of 1 to 3 carbon atoms, m is 0, 1, 2, 3 or 4 and n is 0 or 1, and n and m total at least 1. The copolymers are prepared by copolymerizing a compound of the general formula or a hydrolysable acetal derivative thereof, and a compound of the general formula where the symbols have the meanings assigned to them above, and, where an acetal compound is employed, hydrolysing the acetal group to form a dihydroxyalkyl group. Compounds of type I specified are N-2 : 3-dihydroxypropyl acrylamide and methacrylamide, and N-1 : 3-dihydroxy - 2 - methylisopropyl acrylamide and methacrylamide; as hydrolysable acetal derivatives thereof there are specified 2 : 2-dimethyl-4 - N - acrylamidomethyl - 1 : 3 - dioxolan and the corresponding methacrylamide derivative, and 2 : 2 : 5 - trimethyl - 5 - N - acrylamido-1 : 3-dioxan and the corresponding methacrylamide derivative. Compounds of type II specified are acrylamide, methacrylamide, ethacrylamide, propacrylamide, cyclohexacrylamide, N-methylmethacrylamide, N - isopropylmethacrylamide, N - phenylacrylamide, N - phenylmethacrylamide, N-isopropylacrylamide, N : N-dimethylacrylamide, N : N - diethylacrylamide and N-methy-N-ethylacrylamide. If desired more than one compound of the above types may be used in preparing the copolymer. Polymerization is preferably effected in a solvent or diluent, e.g. water or mixtures thereof with miscible solvents such as methanol, ethanol, propanol, isopropyl alcohol and tert.-butyl alcohol, and may be accelerated by heat, light and/or an initiator such as benzoyl, acetyl and tert.-butyl peroxides, tert.-butyl and cumene hydroperoxides, hydrogen peroxide, sodium perborate and persulphate, ammonium persulphatesodium bisulphite, hydrogen peroxide-thiourea, potassium persulphate-ferrous sulphate, azobis - (isobutyronitrile), azobis - (alpha; gamma - dimethylvaleronitrile), azobis - (alpha: gamma:gamma - trimethylvaleronitrile), azobis - (alpha - methylbutyronitrile) and azobis-(isobutyramidine hydrochloride). The copolymers are soluble in water and with alkaline solutions containing borate ions form cross-linked gels which de-gel when acidified. Suitable gelling agents are sodium and potassium tetraborates, metaborates and orthoborates, glyceryl borate, the sorbitol, mannitol and dulcitol monoborates and diborates and the compounds described in U.S.A. Specifications 2,223,349 and 2,223,948. The copolymers are used in the preparation of photographic films and layers. Specification 784,225 also is referred to.