Patent GB-862114-A (GB)
Title: Improvements in or relating to the treatment of rubber latices
IPC: C08J9/30
Filed: 1959-10-07
Abstract: Rubber latices suitable for making foamed rubber articles comprise added material of pH8-10.5 in quantity sufficient to provide in the latex monovalent cations in concentration 0.05-0.5% of the rubber, the material being exemplified by an aqueous solution of sodium chloride and sodium hydroxide and an aqueous solution of ammonium chloride and ammonium hydroxide. According to Example 1, a butadiene-styrene copolymer latex of 61% solids content was compounded with sulphur and an accelerator mixture of zinc diethyldithiocarbamate and the zinc salt of mercaptobenzthiazole, with styrenated phenol as antioxidant, with the reaction product of ethyl chloride, ammonia and formaldehyde, with carboxymethyl cellulose as thickening agent, and with a sodium chloride-sodium hydroxide solution of pH 8.5 in quantity sufficient to confer 0.15 part of sodium ions per 100 parts of rubber, the latex so compounded was foamed, and the foam was gelled by the addition of sodium silicofluoride.  According to Example 2, a natural rubber latex of solids content 62% was compounded with sulphur, zinc diethyldithiocarbamate and potassium oleate and was mixed with the same quantity of a butadiene-styrene copolymer latex of 61% solids content, in the mixture were incorporated zinc diethyldithiocarbamate, the zinc salt of mercaptobenzthiazole, the reaction product of ethyl chloride, ammonia and formaldehyde, carboxymethyl cellulose and a sodium chloride-sodium hydroxide solution of pH 8.5 in quantity sufficient to confer 0.075 part of sodium ions per 100 parts of rubber, the latex so compounded was foamed, and the foam was gelled by the addition of sodium silicofluoride.  The butadiene-styrene copolymer latex of these examples had been made by reacting components comprising a soap solution, 68.7 parts of butadiene and 31.3 parts of styrene, short stopping, at a solids content of 42.8%, by 0.15 parts of potassium dimethyldithiocarbamate and 0.015 parts of sodium nitrite in 7.20 parts of water, stripping the unreacted monomers, adding more soap solution, and concentrating to 61% solids.  Latices of the following rubbers may be employed: homopolymers of butadiene, isoprene, 2-methylpentadi-1,3-ene, 2-methylpentadi-3,4-ene, piperylene, 2-furylbutadi-1,3-ene, 2-methoxybutadi1,3-ene, 2-cyanobutadi-1,3-ene, 2-chlorobutadi1,3-ene, 2-bromobutadi-1,3-ene, 2,3-dimethylbutadi-1,3-ene, 2-phenylbutadi-1,3-ene; copolymers of dienes with styrene, methylstyrene, chlorostyrene, p-methoxystyrene, vinylnaphthalene, acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, methyl alpha-chloroacrylate, methylmethacrylate, ethylmethacrylate, butyl methacrylate, methyl ethacrylate, acrylonitrile, methacrylonitrile, vinylidene cya-nide, isobutylene, isoamylene, methyl vinyl ketone, methyl isopropenyl ketone, acrolein, methacrolein, methyl vinyl ether, vinyl acetate, vinyl chloride, vinylidene chloride, vinylfurane, vinylpyridine, 2-methyl-5-vinylpyridine, 2 - methyl - 5 - vinylpyridine, vinyl carbazole, vinylacetylene.ALSO:Foamed rubber articles, e.g. cushions, toys, sponges, insulation material, are made from a rubber latex, e.g. a butadiene-styrene copolymer latex or a mixture of butadiene-styrene copolymer latex and natural rubber latex, containing a material of pH 8-10,5 in quantity sufficient to provide monovalent cations in a concentration of 0,05-0,5% of the rubber. The material is exemplified by an aqueous solution of sodium chloride and sodium hydroxide and an aqueous solution of ammonium chloride and ammonium hydroxide.  In preparing the article, the latex may be compounded with sulphur and a vulcanization accelerater, the compounded latex treated with the material and foamed by whipping, a gelling agent such as a soluble silicofluoride added to the foam, the mixture allowed to gel in a mould, and the gel heated to vulcanize the rubber.