Improvements in or relating to the treatment of rubber

Natural rubber is obtained in a softened form by heating an acid aqueous dispersion of rubber containing a small proportion of a solid per-compound dissolved or dispersed therein and a substance which renders the dispersion stable to acid conditions. The per-compound may be an alkaline earth metal persulphate such as barium persulphate, an ammonium or alkali metal persulphate or perborate, or succinyl peroxide, or benzoyl peroxide. Preferably 0.05 to 1.5 per cent based on the weight of the rubber is used. After treatment excess per-compound is destroyed with a water-soluble sulphite or hydrosulphite, hydroquinone or phenyl b -naphthylamine. The dispersion may then be coagulated with polyvalent salts, ethyl alcohol, or boiling water, to give a softened rubber which may be dissolved in benzene, toluene, or carbon tetrachloride to give an adhesive. The stabilizer may be of a non-ionic type such as saturated polyethylene glycol ethers of the formula RO(C2H4O)nH, where R is a straight-chain alkyl radical having 8-20 carbon atoms and n is at least 4, a condensation product of oleic acid and ethylene oxide, a polyethylene glycol phenyl mono-ether, an alkylated phenyl mono-ether of polyethylene glycol, or a polyalkylene ether of a partial sorbitol ester of stearic acid; or an aralkyl sulphonate such as the methyl isopropyl or isobutyl naphthalene sulphonates.