GB972602A - Latex of cis 1,4-polyisoprene and vulcanized foam manufactured therefrom - Google Patents

Abstract

A latex of cis 1, 4-polyisoprene, produced by solution polymerization, has a cis 1, 4 content of at least 85% e.g. up to 97%, an intrinsic viscosity in toluene at 25 DEG C. of 1.0-10.0 and is free of branching and gel prior to emulsification, the latex has a solids content of 60-70%, contains 0.5-2% of emulsifying agent and has a crosslink density of 0.02 x 10-4-0.1 x 10-4 moles/c.c The emulsifying agent may be a soap of a rosin or fatty acid, amine or quaternary ammonium salts, phosphoric esters, esters of oleic acid or pentaerythritol, or sorbiton mono-oleate. The latex may be produced by emulsifying a hydrocarbon e.g. hexane solution of the polyisoprene, e.g. 10-20% in the presence of water and emulsifying agent, separating the hydrocarbon solvent, concentrating the resultant latex by removing water, adjusting the concentration of the emulsifier, adding to the latex 0.25-0.75% of a sulphur containing vulcanizing agent, e.g. sulphur, and 0.5-1.0% of a vulcanizing agent accelerator, e.g. zinc diethyldithiocarbamate, and vulcanizing the latex at above 40 DEG C. A vulcanized foam is prepared from the latex which contains 1.0-5.0% wax, of m.p. below 100 DEG C., by blending the latex with 1.5-2.5% of a sulphur containing vulcanizing agent, 1.5-2.5% vulcanizing accelerator, 0.20-0.60% thickener e.g. methyl cellulose, 0.5-1.0% foam stabilizer, frothing this blend and adding 3.0-7.0% zinc oxide, sufficient gelling agent, e.g. sodium silicofluoride and potassium hydroxide, to effect gelation in less than 10 min. at 20 DEG C. and vulcanizing the froth to a crosslink density of 1.0 x10-4-1.5 x 10-4 moles/c.c. The latex may contain a stabilizer e.g. an alkylated phenol and the foam may contain a mixture of lecithin and triethanolamine. Dipped goods may be made from the latex. Specification 893,066 is referred to.