Improvements in plasticizing of vulcanized rubber

摘要

Vulcanized rubber scrap is plasticized by working mechanically under oxidizing conditions and at a low temperature with an acid and a compound, such as a mercaptan or a thiophenol, having the composition RSH, where R represents an alkyl, alicyclic, or heterocyclic radical which may be substituted with a functional group other than one which confers accelerating properties. The acids are preferably the saturated or unsaturated higher fatty acids such as stearic or oleic acid, or rosin acids may be used provided an antioxidant be present; small amounts of acid only are required, depending on the amount of zinc oxide and similar materials present in the scrap rubber. The following sulphur compounds are stated to be suitable: benzyl mercaptan, 2-ethyl hexyl mercaptan, 2-mercapto octane, lauryl mercaptan, thioglycollic acid, a -mercapto-stearic acid, b ,b 1-dimercaptodiethyl ether, tetrahydrofurfuryl mercaptan, 4-morpholin methyl mercaptan, 2,5-dimercapto-1,3,4-thiodiazole, dimethyl thiophenol, bornyl mercaptan, octyl mercaptan, dodecyl mercaptan, xylyl mercaptan, p-thiocresol, thiophenol, and a - or b -thionaphthol. The oxidizing conditions may be produced by working in the presence of atmospheric air or by the addition of a small quantity of an oxidizing-agent such as benzoyl peroxide, hydrogen peroxide, or ammonium persulphate. The temperature should not exceed 65 DEG C.