Preparation of poly(trimethylene terephthalate) with low level of di(1,3-propylene glycol)

Abstract

A process of preparing poly(trimethylene terephthalate) containing less than 2.0 mole % of DPG comprising: (a) providing a molar amount of 1,3-propanediol:C1 to C4 dialkyl ester of terephthalic acid of 1.2:1 to 1.9:1, (b) reacting the 1,3-propanediol with the C1 to C4 dialkyl ester of terephthalic, acid to form bis(3-hydroxypropyl)terephthalate monomer in the presence of 10-100 ppm (as titanium metal) of an organic titanate catalyst, by weight of the poly(trimethylene terephthalate), and (c) polymerizing the bis(3-hydroxypropyl)terephthalate monomer to obtain the poly(trimethylene terephthalate); and poly(trimethylene terephthalate) produced by the process.

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