| 摘要 |
The resistance to oxidative degradation of polyethylene and the non-rubbery copolymers of styrene or methyl methacrylate with butadiene-1,3 is improved by incorporating a 2-a -alkylcyclo alkyl-4,6-dimethyl phenol in which the alkyl group has not more than 4 carbon atoms, and the cycloalkyl is cyclopentyl or methylcyclopentyl, cyclohexyl or methyl cyclohexyl. From 0.0001 per cent to 10 per cent by weight may be used and the compositions may be shaped as articles and films. Copolymers of 75 to 95 per cent styrene and 25 to 5 per cent butadiene-1,3 and of 50 to 72 per cent methyl methacrylate and 50 to 28 per cent butadiene-1,3 are referred to. The antioxidants may be incorporated on heated rolls, by mixing or by adding an aqueous dispersion or a solution, e.g. in ethylene glycol to a copolymer latex. In examples: (1) polyethylene is heat softened at 140 DEG C. on rollers, the 2-a -methylcyclohexyl-4,6-dimethyl phenol added and the milling continued. (2) A latex of butadiene-1 : 3-methyl methacrylate copolymer is prepared by aqueous emulsion polymerization in an autoclave in two stages with sodium lauryl sulphate and potassium persulphate, chloride and hydroxide present in the first stage and sodium lauryl sulphate and the disodium salt of methylene dinaphthalene sulphonic acid in the second stage. A solution of 2 - a - methylcyclohexyl - 4,6 - dimethylphenol in ethylene glycol is added at a temperature of 50 DEG C., and films are cast from the latex. (3) A latex of butadiene-styrene copolymer was prepared under pressure in an autoclave using sodium lauryl sulphate and n-dodecyl mercaptan, and a dispersion of 2-a -methylcyclohexyl-4,6-dimethylphenol in a 5 per cent aqueous solution of sodium lauryl sulphate added. The latex is coagulated with aluminium sulphate and a composition of the stabilized copolymer, pale crepe rubber, coumarone resin, zinc oxide, stearic acid, dibenzthiazyl and tetramethylthiuram disulphides, paraffin wax and sulphur is prepared on rollers at 50 DEG C. |
