PURPOSE: A halogen-containing diol is added to a polybutylene terephthalate of specific intrinsic viscosity and the polycondensation reaction is effected to produce flame-retardant polyester with high polymerization degree, impact strength and toughness with industrial advantage.
CONSTITUTION: (A) Bishydroxybutyl terephthalate or its oligomer of less than 0.15 intrinsic viscosity is combined with (B) polyethylene terephthalate of 0.2 or higher, preferably 0.5W1.5 intrinsic viscosity and (C) a diol having the aromatic ring substituted with halogen atoms, preferably 2,2-bis[3,5-dibromo-4-(2-hydroxyethoxy) phenyl]propane and they are subjected to polycondensation reaction. The component C is added so as to adjust the halogen content to preferably 3W15wt% in the resulting polyester.
MORITA SHIYOUHACHI
YOSHII TOORU
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