GB1463378A - Process for preparing self-extinguishing expandable polymer - Google Patents

Abstract

1463378 Self-extinguishing expandable polymer particles ARCO POLYMERS Inc 28 June 1974 [9 July 1973] 28947/74 Headings C3P and C3C Self-extinguishing expandable alkenyl aromatic polymer particles (e.g. polystyrene) are prepared by: (a) polymerizing an alkenyl aromatic monomer (e.g. styrene) in aqueous suspension, in the presence of a catalytic amount of a free-radical initiator, until the polymerization has progressed to a degree of conversion of monomer to polymer of 92-98%; (b) adding pentabromochlorocyclohexane in an amount of at least 0À5% by weight, based on the weight of monomer, a blowing agent and a free-radical initiator; and (c) completing the polymerization in aqueous suspension. The polymerization may be at 70-120‹ C. and the materials added in step (b) may be added in admixture. Preferably, 0À5-5% of pentabromochlorocyclohexane, 5- 15% of blowing agent and 0À3-0À5% of freeradical initiator are added, the percentages being based on the weight of monomer. The blowing agent may be a compound which is a gas, or which normally is a liquid but vaporizes on heating (preferably a C 1-7 aliphatic hydrocarbon or a halogenated derivative thereof, e.g. n-pentane). The free-radical initiator may be benzoyl peroxide, lauroyl peroxide, tbutyl perbenzoate or 2,5-dimethyl-2,5-di(tbutylperoxy)hexane. The aqueous suspension may comprise a suspending agent, which may be polyvinyl alcohol, hydroxyethyl cellulose, or a mixture of tricalcium phosphate and an anionic surfactant (e.g. sodium dodecylbenzene sulphonate). In the examples the expandable beads of polystyrene were moulded into foam strips.