| CPC C08G 63/672 (2013.01) [C07C 67/56 (2013.01); C08G 63/78 (2013.01)] | 14 Claims |
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1. A method for preparation of a polyester copolymer comprising the steps of:
1) Mixing bis-2-hydroxyethyl terephthalate and water (step 1);
2) Adding activated carbon to the mixture of step 1 (step 2);
3) Recovering bis-2-hydroxyethyl terephthalate from the mixture of step 2 (step 3);
4) Preparing an oligomer by an esterification reaction of an aqueous solution containing bis-2-hydroxyethyl terephthalate purified by step 3, a dicarboxylic acid or its derivative, and a diol containing ethylene glycol and a comonomer (step 4); and
5) preparing a polyester copolymer by a polycondensation reaction of the oligomer (step 5),
wherein a concentration of the aqueous solution containing bis-2-hydroxyethyl terephthalate is 25 to 99 wt %,
wherein the dicarboxylic acid or its derivative is terephthalic acid, dimethyl terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl dicarboxylic acid, 4,4′-stilbenedicarboxylic acid, 2,5-furandicarboxylic acid, or 2,5-thiophenedicarboxylic acid,
wherein the step 4 is performed at a pressure of 0.1 to 3.0 kg/cm2 and a temperature of 200 to 300° C., and
wherein a haze measured with respect to a 6 mm-thick specimen of the prepared polyester copolymer is 3 or less.
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