Patent ID: 7829654

Claim:
A process for synthesizing an elastomeric copolyester from polybutylene terephthalate (PBT) and polyoxytetramethylene glycol, which comprises the steps of: (a) obtaining crude tetrahydrofuran (THF) as a by-product in a synthesis of polybutylene terephthalate wherein starting materials in the synthesis include 1,4-butanediol and free or esterified terephthalic acid and separating the crude tetrahydrofuran from the polybutylene terephthalate; (b) rectifying the crude tetrahydrofuran to separate impurities to yield purified tetrahydrofuran; (c) subjecting the purified tetrahydrofuran to a ring-opening polymerization in the presence of a Lewis acid catalyst to synthesize polyoxytetramethylene glycol, and (d) condensing the polyoxytetramethylene glycol with free or esterified carboxy groups of polybutylene terephthalate to form the elastomeric copolyester, with chain termination and catalyst deactivation accomplished by addition of 1,4-butanediol without separating the Lewis acid catalyst.