Patent GB-806298-A (GB)
Title: Method of making latent foaming thermoplastic resin compositions
IPC: C08J9/18
Filed: 1956-09-14
Abstract: Thermoplastic resins selected from (a) polymers and copolymers of monovinyl aromatic hydrocarbons of the benzene series and their nuclear halogenated derivatives; (b) copolymers of 99.75 to 99.99 per cent of at least one monovinyl aromatic hydrocarbon of the benzene series or their nuclear halogenated derivatives with 0.25 to 0.01 per cent of a polyvinyl aromatic hydrocarbon; and (c) copolymers of 2 to 15 per cent of natural rubber or a rubbery copolymer of 40 to 80 per cent butadiene and 60 to 20 per cent styrene with such monovinyl compounds are impregnated by heating at 70 DEG  to 125 DEG  C., under at least the autogenous pressure of the mixture, with at least 10 per cent of dichlorodifluoromethane, whereby at least 4 per cent thereof is absorbed, cooling to not greater than 40 DEG  C., releasing the pressure and separating the impregnated resin.  Specified monovinyl compounds are styrene, vinyltoluene, vinylxylene, isopropylstyrene, ethylvinylbenzene, ethylvinyltoluene, chlorostyrene, bromostyrene, fluorostyrene, dichlorostyrene and archlorovinyltoluene.  Specified polyvinyl hydrocarbons are divinylbenzene, divinyltoluene and divinylxylene.  The resins may contain plasticisers, stabilizers, pigments, dyes, fillers, lubricants, flow agents and fire retardants and may be in the form of granules, spheres, beads, bars, strips, sheets or films.  The impregnation may be conducted in the presence of an inert medium, e.g. water or brine, which may contain suspending agents, e.g. methylcellulose, antifoaming agents, e.g. a mixture of dimethylpolysiloxane and finely-divided silica, and sodium dichromate.  The product may be washed and dried and, preferably after ageing, expanded to form porous products, e.g. by heating in an oil bath or an enclosed mould. Specification 614,458 is referred to.ALSO:Foamed thermoplastic resins are prepared by heating compositions comprising (a) polymers and copolymers of monovinyl aromatic hydrocarbons of the benzene series and their nuclear halogenated derivatives, (b) copolymers of 99,75 to 99,99 per cent. of at least one monovinyl aromatic hydrocarbon of the benzene series or their nuclear halogenated derivatives with 0,25 to 0,01 per cent. of a polyvinyl aromatic hydrocarbon or (c) copolymers of 2 to 15 per cent. of natural rubber or a rubbery copolymer of 40 to 80 per cent. of butadiene and 60 to 20 per cent. of styrene with such monovinyl compounds, which have been impregnated by heating at 70 DEG  to 125 DEG C., under at least the autogenous pressure of the mixture, with at least 10 per cent. of dichlorodifluoromethane until at least 4 per cent. thereof has been absorbed, cooling to not greater than 40 DEG C. releasing the pressure and separating the impregnated resin. Specified monovinyl compounds are styrene, vinyltoluene, vinylxylene, isopropylstyrene, ethylvinylbenzene, ethylvinyltoluene, chlorostyrene, bromostyrene, fluorostyrene, dichlorostyrene and ar-chlorovinyltoluene.  Specified polyvinyl hydrocarbons are divinyl benzene, divinyltoluene and divinylxylene.  The resins may be in the form of granules, spheres, beads, bars, strips, sheets or films and may contain plasticizers, stabilizers, pigments, dyes, fillers, lubricants, flow agents and fire retardants. Impregnation may be effected in the presence of an inert medium, e.g. water or brine, which may contain suspending agents, e.g. methyl cellulose, antifoaming agents, e.g. a mixture of liquid dimethylpolysiloxane and finely divided silica, and sodium dichromate.  The impregnated resins may be expanded, preferably after ageing by heating in an oil bath or an enclosed mould. Specification 614,458 is referred to.