GB1219469A - Cellular foamed products from polymers of proplylene and process for their preparation - Google Patents

Abstract

1,219,469. Foamed cross-linked propylene polymers. TORAY INDUSTRIES Inc. 31 May, 1968 [31 May, 1967; 22 Aug., 1967; 21 Sept., 1967], No. 26371/68. Headings C3C and C3P. A cellular foamed product comprises a propylene polymer crosslinked by 0À1 to 30% by weight of the polymer, of a cross-linking agent, the polymer being a stereospecific homopolymer of propylene, block or graft copolymer containing more than 50% by weight of crystalline propylene and another monomer containing a CH 2 = C < group, or a mixture of thermoplastic polymers containing more than 50% by weight of stereospecific polypropylene, the cross-linking agent being a polyacrylate, polymethacrylate, polyvinyl ether or polyallyl ether of a polyhydric alcohol having 5 to 20 carbon atoms per molecule and at least one aliphatic or aromatic ring, or a polyallyl ester, polyvinyl ester, polyacryloyloxyalkyl ester or polymethacryloyloxyalkyl ester of a polyhydric carboxylic acid having at least 5 carbon atoms in its longest carbon chain and less than 20 carbon atoms per molecule, the propylene polymer having a cross-linking degree (as defined) of 5 to 90, and the foam having an average cell diameter of 10 to 500 microns, an apparent density of 0À01 to 0À5 grams per cubic centimetre and at least 50% of the cells of the foam being closed cells. The cellular foamed product may be made by mixing together the polymer, the cross-linking agent and a normally liquid or solid foaming agent which has a decomposition point higher than the softening point of the polymer, irradiating the mixture with radiation of a wavelength less than visible light, and heating the mixture to a temperature higher than the decomposition point of the foaming agent and higher than the softening point of the propylene polymer. The foaming agents used in the examples are azodicarbonamide or p-toluenesulphonyl semicarbazide.