Thermoplastic co-polyester prepd. by solid state polymerisation - contg. units derived from bis:(beta-hydroxyethoxyphenyl) sulphone

摘要

Thermplastic copolyester is made by melt polymerising terephthalic acid or a 1-4C alkyl ester thereof with ethylene glycol and 2-12 mole% bis(4-ketahydroxyethoxy-phenyl)sulphone (I), the total amt. of glycol and (I) being 110-300 mole.%. Melt polymerisation is continued until the polymeric prod. has an intrinsic viscosity of 0.2-0.7 dl/g. The copolymer is then cooled to a solid state, reduced to particles and heat crystallised. Solid state polycondensation is then carried out to produce a copolyester of inherent viscosity at least 0.65 and higher than that of the melt polymerised prod. The copolymer is used to make bottles, melt formed plastic containers, and packaging film for foodstuffs and beverages. It is more resistant to decomposition in the molten state to form acetaldehyde than is the same copolyester of the same or lower inherent viscosity made entirely by melt polymerisation of polyethylene terephthalate PET made by solid state or melt polymerisation.