Process for solid phase polymerization of polyester
AssigneeBepex Corporation
InventorDale J. Herron
Life of this patent
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Abstract
A process for the continuous production of high molecular weight polyethylene terephthalate wherein the granular polymer having an intrinsic viscosity of at least 0.4 is crystallized, dried and polymerized in the solid phase by polycondensation. Two methods of crystallization are described which aid the process in overcoming problems associated with sticking in the polymerization stage. The method is characterized by polycondensation at a temperature greater than the crystallization temperature.
Claims8
A process for continuous production of high molecular weight polyethylene terephthalate by polycondensation in the solid phase from a dried granulated polyethylene terephthalate having a beginning intrinsic viscosity of at least 0.4 without occurrence of stickiness of the granulate, which process comprises:
- (A) crystallizing the polymer by heating at a temperature in the range of about 180.degree. to 220.degree. C. under forced motion and under an inert gas atmosphere for a residence time less than about 1.5 hours;
- (B) discharging the crystallized product at a temperature of at least 180.degree. C., a density of at least 1.385 grams per cubic centimeter, and a moisture content of less than 0.02 percent by weight;
- (C) continuously introducing the crystallized granulate to a continuous fixed bed reactor and polycondensing in contact with an inert gas at a temperature in the range of about 210.degree. to 235.degree. C. to achieve a reaction temperature within the range of about 200.degree. to 230.degree. C. and higher than the crystallization temperature, whereby polycondensation takes place and sticking of the granulate is avoided;
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- (D) continuously removing the polycondensed granulate flowing from the reaction zone.
Dependencies are inferred from the claim text.