Polyester resin, method for preparing same, and resin molded product formed therefrom
The present invention relates to a polyester resin. The polyester resin contains a particular content of diol moieties, derived from isosorbide and diethylene glycol, and thus can provide a resin molded product exhibiting high transparency in spite of a large wall thickness thereof.
1. A method for preparing a polyester resin comprising the steps of:
(a) carrying out an esterification reaction or a transesterification reaction of (i) a dicarboxylic acid or a derivative thereof including terephthalic acid or a derivative thereof and (ii) a diol including 6.5 mol to 25 mol of isosorbide and 80 mol to 200 mol of ethylene glycol based on 100 mol of the total dicarboxylic acid or a derivative thereof;
(b) subjecting the esterification or transesterification reaction product to a polycondensation reaction so that an intrinsic viscosity, which is measured at 35° C. after dissolving the reaction product in orthochlorophenol at a concentration of 1.2 g/dl at 150° C. for 15 minutes, reaches 0.60 dl/g to 0.75 dl/g;
(c) crystallizing the polymer prepared by the polycondensation reaction; and
(d) subjecting the crystallized polymer to a solid phase polymerization such that the intrinsic viscosity, which is measured at 35° C. after dissolving the polymer in orthochlorophenol at a concentration of 1.2 g/dl at 150° C. for 15 minutes, reaches a value of 0.25 to 0.40 dl/g higher than the intrinsic viscosity of the resin obtained in step (b),
wherein the intrinsic viscosity of the resin obtained in step (d) is 0.85 dl/g to 1.0 dl/g, and
wherein the polyester resin includes 6 mol % to 12 mol % of a diol moiety derived from isosorbide based on the total diol moieties derived from the diol.
2. The method of preparing a polyester resin of claim 1 , wherein the (i) dicarboxylic acid or a derivative thereof is a dicarboxylic acid, and the initial mixing molar ratio of the (i) dicarboxylic acid: the (ii) diol is adjusted to 1: 1.01 to 1.05, or the (i) dicarboxylic acid or a derivative thereof is a dicarboxylic acid alkyl ester or a dicarboxylic acid anhydride, and the initial mixing molar ratio of the (i) dicarboxylic acid derivative: the (ii) diol is adjusted to 1: 2.0 to 1: 2.1.
3. The method of preparing a polyester resin of claim 1 , wherein a part of the (ii) diol is further added during the reaction.
4. The method of preparing a polyester resin of claim 1 , wherein a polycondensation catalyst, a stabilizer, a coloring agent, a crystallizing agent, an antioxidant or a branching agent is added to the slurry before the start of the (a) esterification reaction or the transesterification reaction, or to the product after the completion of the reaction.
5. The method of preparing a polyester resin of claim 1 , further comprising removing unreacted materials including isosorbide by allowing the product obtained by the esterification reaction or the transesterification reaction to stand under a reduced pressure condition of 400 to 1 mmHg for 0.2 to 3 hours, before the (b) polycondensation reaction.
6. The method of preparing a polyester resin of claim 2 , wherein a part of the (ii) diol is further added during the reaction.
7. The method of preparing a polyester resin of claim 1 , wherein the polyester resin further includes 2 mol % to 5 mol % of a diol moiety derived from diethylene glycol, and remainder of a diol moiety derived from ethylene glycol based on the total diol moieties derived from (ii) the diol.