METHOD OF MANUFACTURING POLYMER PARTICLES HAVING UNIFORM CROSSLIN KING AND EXPANDED SHAPED ARTICLES FORMED THEREFROM

摘要

1383924 Cross linked polyolefins and foamable particles thereof KANEGAFUCHI KAGAKU KOGYO KK 21 March 1972 [25 March 1971(3)] 13277/72 Headings C3C and C3P Cross linked polyolefin resin particles are prepared by a method which comprises forming a suspension in water of polyolefin resin particles, by adding an aqueous solution of a surface active agent, containing a soluble or finely dispersed cross linking agent and a suspension stabilizer compatible with the cross linking agent, preferably a water-insoluble inorganic metal compound, and heating to a temperature sufficient to cause penetration of the cross linking agent into the particles and subsequently to a temperature sufficient to initiate a cross linking reaction. Where the particles produced have a gel content of 10 to 70% foamable cross linked particles may be prepared by adding a foaming agent thereto, and the foamable material may be prefoamed, stored and subsequently foamed by heating in an open mould. The resin may be polyethylene, polypropylene, an ethylene/vinyl acetate copolymer, or a polymer or copolymer of butadiene, styrene or vinyl chloride. The surface active agent may be a polyoxyethylene octylphenol ether, sodium dodecylbenzene sulphonate or sodium dialkyl sulphosuccinate. The cross linking agent may be dicumyl peroxide, 2,5-dimethyl-2,5-di-t.-butylperoxyhexane, di-t.-butyl perphthalate or t.- butyl hydroperoxide, optionally with a cross linking assistant such as divinyl benzene or acetylene. The inorganic metal salt may be a phosphate, oxide or hydroxide, e.g. calcium phosphate, zinc phosphate and aluminium hydroxide. The foaming agent may be a volatile hydrocarbon or halogenated hydrocarbon, and foaming may be effected by exposure to steam, hot air or liquid, infra-red radiation or high frequency magnetic field. In examples polyethylene resin particles are cross linked with dicumyl peroxide in aqueous suspension in the presence of surface active agents and (1, 4 and 6 to 9) calcium phosphate, (2 and 5) zinc phosphate and (3) aluminium hydroxide, and the products foamed with (1 to 4, 6, 7 and 9) difluorodichloromethane and (5 and 8) dichlorotetrafluoroethane.