Improvements relating to photopolymerization

Unsaturated polymerizable organic compounds are polymerized by contacting them, in the presence of a compound containing a peroxy linkage, with an irradiated ferric compound which, on irradiation with radiation having a wavelength of from 10-1 to 10-10 cm., gives rise to ferrous ions. Polymerizable compounds specified are acrylamide, methacrylamide, N-ethanol acrylamide, acrylic and methacrylic acids, calcium acrylate, acrylonitrile, methyl and ethyl acrylates, methyl methacrylate, vinyl acetate, butyrate and benzoate, vinyl isopropyl and vinyl butyl ethers, vinyl pyrrolidone and mixtures of ethyl acrylate and vinyl acetate and acrylonitrile and styrene. The above compounds may be polymerized in admixture with small amounts of compounds containing at least two terminal vinyl groups, e.g. divinyl benzene, methylene-bisacrylamide, triallyl cyanurate, divinyl ketone and diglycol diacrylate. Ferric compounds specified are the salts, including ferric ammonium salts, of common organic and inorganic acids and ferric hydroxide, preferred being ferric oxalate, ferric ammonium citrate and potassium ferrioxalate. Peroxy compounds specified are aliphatic and aromatic peroxides and hydroperoxides, aliphatic and aromatic per-acids and esters thereof and ammonium persulphate, preferred being cumene hydroperoxide, di-tert-butyl peroxide and hydrogen peroxide. Polymerization may be carried out in bulk, in an aqueous medium which may contain a colloid carrier for the ferric compound, e.g. gelatin, polyvinyl alcohol, casein, glue, carboxymethyl cellulose, starch or saponified cellulose acetate, or in solution in methanol. The monomer, iron compound and peroxy compound may be brought together in any order, for example, all three may be mixed and then irradiated, or the monomer and iron compound may be mixed and irradiated and then treated with a peroxide. The polymerizing radiation may be ultra-violet or visible light, gamma rays or X-rays. The examples describe the polymerization of mixtures of acrylamide and methylene-bis-acrylamide. The process may be used in the production of polymeric photographic images, in which case the photo-polymerizable composition is coated on a suitable support.