Method for producing polyester resin by using regenerated bis(2-hydroxyethyl) terephthalate aqueous solution
AssigneeSK Chemicals Co., Ltd.
InventorsDa-Young Hwang, Ha-Neul Kim, Yoo Jin Lee
Life of this patent
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Abstract
A regenerated bis(2-hydroxyethyl) terephthalate obtained by the depolymerization of waste polyester is mixed with water to prepare an aqueous solution under specific temperature and concentration conditions, thereby ensuring storage stability. By introducing such a regenerated bis(2-hydroxyethyl) terephthalate aqueous solution into the polymerization of a polyester resin, the uniformity of raw materials and reaction efficiency can be increased, thereby improving the quality of the final polyester resin.
Claims13
A process for preparing a polyester resin, which comprises:
- (1) depolymerizing waste polyester to prepare recycled bis(2-hydroxyethyl) terephthalate;
- (2) mixing the recycled bis(2-hydroxyethyl) terephthalate with water at 60° C. to 110° C. to prepare an aqueous solution of recycled bis(2-hydroxyethyl) terephthalate having a concentration of 50% by weight to 95% by weight, wherein the concentration is the weight of the recycled bis(2-hydroxyethyl) terephthalate based on the total weight of the aqueous solution of recycled bis(2-hydroxyethyl) terephthalate;
- and
- (3) preparing a polyester resin through an esterification reaction and a polycondensation reaction using the aqueous solution of recycled bis(2-hydroxyethyl) terephthalate,
- wherein a change in yellow index (ΔYID) calculated by following equation is 6 or less:
- ΔYID=YID (day 5)−YID (day 0)
- wherein:
- YID (day 5) is a yellow index (YID) value measured when recycled bis(2-hydroxyethyl) terephthalate obtained by storing the aqueous solution of recycled bis(2-hydroxyethyl) terephthalate prepared in step (2) at 60° C. to 110° C. for 5 days and then evaporating water is dissolved in ethylene glycol at a concentration of 25% by weight at 120° C. for 1 hour,
- YID (day 0) is a yellow index (YID) value measured when recycled bis(2-hydroxyethyl) terephthalate prepared in step (1) is dissolved in ethylene glycol at a concentration of 25% by weight at 120° C. for 1 hour, and
- the yellow index (YID) value is calculated using a color analyzer based on transmission data for a solution obtained with Illuminant D65 using Color Flex EZ of Hunterlab at an observer's angle of 2°.
A process for preparing an aqueous solution of recycled bis(2-hydroxyethyl) terephthalate, which comprises:
- (1) depolymerizing waste polyester to prepare recycled bis(2-hydroxyethyl) terephthalate;
- and
- (2) mixing the recycled bis(2-hydroxyethyl) terephthalate with water at 60° C. to 110° C. to prepare an aqueous solution thereof having a concentration of 50% by weight to 95% by weight, wherein the concentration is the weight of the recycled bis(2-hydroxyethyl) terephthalate based on the total weight of the aqueous solution of recycled bis(2-hydroxyethyl) terephthalate,
- wherein a change in yellow index (ΔYID) calculated by following equation is 6 or less:
- ΔYID=YID (day 5)−YID (day 0)
- wherein:
- YID (day 5) is a yellow index (YID) value measured when recycled bis(2-hydroxyethyl) terephthalate obtained by storing the aqueous solution of recycled bis(2-hydroxyethyl) terephthalate prepared in step (2) at 60° C. to 110° C. for 5 days and then evaporating water is dissolved in ethylene glycol at a concentration of 25% by weight at 120° C. for 1 hour,
- YID (day 0) is a yellow index (YID) value measured when recycled bis(2-hydroxyethyl) terephthalate prepared in step (1) is dissolved in ethylene glycol at a concentration of 25% by weight at 120° C. for 1 hour, and
- the yellow index (YID) value is calculated using a color analyzer based on transmission data for a solution obtained with Illuminant D65 using Color Flex EZ of Hunterlab at an observer's angle of 2°.
Dependencies are inferred from the claim text.