GB1383924A - Method of manufacturing polymer particles having uniform crosslin king and expanded shaped articles formed therefrom - Google Patents

Abstract

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.