Polyethylene terephthalate polyester useful for making hollow containers, e.g. bottles, has a low intrinsic viscosity and a low acetaldehyde content

摘要

Polyester (I) comprising at least 92.5% units derived from terephthalic acid and ethylene glycol has an intrinsic viscosity of 0.45-0.70 dl/g and an acetaldehyde content below 3 ppm. Independent claims are included for: (1) a process for producing (I), comprising producing a polyester with an intrinsic viscosity below 0.8 dl/g by melt polymerization, forming granules of the polyester, crystallizing the granules, and heat-treating the granules at 130-200 deg C to reduce the acetaldehyde content below 3 ppm and give an intrinsic viscosity below 0.7 dl/g; (2) a process for producing preforms, comprising injecting molten (I) into a mold and rapidly cooling the resulting preform to avoid any spherulitic crystallization; (3) preforms produced by the process of (2); (4) hollow containers produced by inflating the preforms of (3); (5) hollow containers or bottles in which the polyester forming the wall has an intrinsic viscosity of 0.45-0.70 dl/g and an acetaldehyde content below 6 ppm.