Continuous manufacture of poly(trimethylene terephthalate)
AssigneeE. I. Du Pont de Nemours and Company
InventorsJohn Eng, Emily Blum, Daniel Green, Carl Giardino, Gene Parrish, Robert Trotter, Gary Wilson
Life of this patent
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Abstract
This invention relates to a continuous process for production of poly(trimethylene terephthalate), wherein gaseous 1,3-propanediol by-product resulting from the process is condensed in a condenser, the total amount of any trimethylene terephthalate cyclic dimer and poly(trimethylene terephthalate) in the condensed by-product 1,3-propanediol is adjusted, and a portion of the condensed by-product is recycled to the condenser while another portion is recycled back into the process.
Claims19
A continuous process for the production of poly(trimethylene terephthalate) comprising the steps of:
- (a) continuously producing poly(trimethylene terephthalate) oligomers comprising 1,3-trimethylene and terephthalate repeating units and having a degree of polymerization of from about 1.9 to about 3.5 by (i) ester exchange reaction of dimethyl terephthalate with excess 1,3-propanediol at an elevated temperature or (ii) direct esterification reaction of terephthalic acid with excess 1,3-propanediol at an elevated temperature;
- (b) continuously precondensing the poly(trimethylene terephthalate) oligomers to form a poly(trimethylene terephthalate) prepolymer having an intrinsic viscosity of at least about 0.23 dl/g and gaseous by-products comprising volatilized by-product 1,3-propanediol;
- and
- (c) continuously polymerizing the poly(trimethylene terephthalate) prepolymer to form higher molecular weight poly(trimethylene terephthalate) having an intrinsic viscosity of at least about 0.55 dl/g and additional gaseous by-products comprising volatilized by-product 1,3-propanediol, wherein:
- (i) the gaseous by-products are condensed in at least one spray condenser to form condensed by-product 1,3-propanediol comprising 1,3-propanediol and by-product solids comprising trimethylene terephthalate cyclic dimer and, optionally, poly(trimethylene terephthalate), which is then collected in at least one hotwell;
- (ii) the total amount of trimethylene terephthalate cyclic dimer and poly(trimethylene terephthalate) in the condensed by-product 1,3-propanediol is raised at least about 0.2 wt % based on the weight of condensed by-product 1,3-propanediol;
- (iii) a portion of the condensed by-product 1,3-propanediol from the hotwell is cooled in at least one heat exchanger and then sprayed in the at least one spray condenser to condense the gaseous by-products;
- and
- (iv) a portion of the condensed by-product 1,3-propanediol from the hotwell, without purification, is fed back into the ester exchange or direct esterification reactions at one or more locations where the temperature is about 150° C., or higher.
Dependencies are inferred from the claim text.