ES337150A1 - Moulding compositions for the production of foamed articles - Google Patents

Abstract

A composition comprises an expandable " styrene polymer " (as hereinafter defined) containing in homogenous distribution an expanding agent and from 0.001 to 0.1% by weight of the " styrene polymer " of a brominated aliphatic and/or cycloaliphatic organic compound other than a brominated polymer of a 1,3-diene, having a molecular weight of from 250 to 500,000 and a bromine content of from 30 to 95% by weight, the number of bromine atoms contained in the molecule being at least 3. The brominated organic compounds may be either liquid or solid, have a B.P. of more than 100 C. at atmospheric pressure and may be bromoform, 1,1,2,2-tetrabromo-ethane, 1,2,3,4,5,6 - hexabromocyclohexane, tris - 2,3- dibromopropylphosphate and N,N1,N11 - tris- (2,3 - dibromopropionyl) - trimethylene triamine. A " styrene polymer " means a normally solid polymer of unsubstituted styrene or a substituted styrene such as vinyl toluene, vinylxylene, ar-isopropenylstyrene, ar-tert-butyl. styrene and a-methylstyrene and mixtures of these monomers with one another and/or with styrene, and also includes well-known addition copolymers of styrene or substituted styrenes with less than 50% by weight of at least one other readily polymerizable olefinically unsaturated compound having a vinyl group, e.g. [alpha]-methylstyrene, nuclear chlorinated styrene, methacrylonitrile, acrylonitrile, esters of acrylic and methacrylic acid and alkanols having 1-8C, vinyl pyridine, N-vinyl carbazole and butadiene. Preferred foaming agents are gaseous or liquid organic compounds which do not dissolve the " styrene polymer " and whose B.P. is lower than the softening point of the polymer. Suitable ones are saturated aliphatic or cycloaliphatic hydrocarbons having 3 to 7C, e.g. propane, butane, pentane, cyclopentane, hexane, cyclohexane or petroleum ether, or halohydrocarbons, preferably chlorohydrocarbons and fluorohydrocarbons having 1-6C such as dichlorodifluoromethane and trifluorochloromethane. The composition may contain impact-resistant styrene polymers and additives such as plasticizers, lubricants, stabilizers, dyes or fillers. The moulding materials are in particulate form, e.g. beads, cylindrical granules or lumps. They may be made either by polymerizing monomeric styrene with or without other monomers in the presence of an expanding agent and the bromine compounds or by polymerizing styrene in aqueous suspension and adding the bromine compounds with or without the expanding agent, during polymerization at a point when the particles no longer divide. They are heated in molds which are not gastight when closed, thus causing the particles to expand and fuse together to form articles whose dimensions correspond to those of the mold's internal cavity.