POLYESTER COMPOSITION

1479633 Foamable flame retardant polyester blends GENERAL ELECTRIC CO 21 June 1974 [2 July 1973] 27730/74 Heading C3C A foamable thermoplastic injection mouldable composition comprises (a) a polyester resin or copolyester resin containing 0À5-2 wt. per cent of units derived from an aliphatic or aromatic dicarboxylic acid and/or a polyol and which is a poly(ethylene terephthalate) or a poly( 1,4 - butylene terephthalate) with either the poly(ethylene terephthalate) or 1-40 wt. per cent of a linear aliphatic polyester resin (b) fibrous glass, mineral and/or synthetic silicate as filler, (c) a minor amount by wt. of a foaming agent and (d) a flame retardant additive different from filler (b). In the examples (1-5) poly(ethylene terephthalate) was blended with chopped glass strands and a carbonate copolymer of bisphenol and tetrabromo-bisphenol A, antimony oxide, poly(2,2-bis(3,5- dibromo - 4 - hydroxyphenyl) - propane carbonate), and/or a carbonate homopolymer of bisphenol-A as flame-retardant and formed into pellets which were then mixed with 5-phenyltetrazole as foaming agent; blends of poly(1,4- butylene terephthalate) and poly(ethylene terephthalate) or poly(epsilon-caprolactone) were also used as the resins.