Polyester fiber, preparaion method thereof and molded article formed therefrom
The present invention relates to a polyester fiber, a preparation method thereof and a molded article prepared therefrom. The polyester fiber comprises a diol moiety derived from isosorbide in a specific amount and is formed into a polyester resin having a specific oligomer content, thereby providing a molded article having excellent saline water resistance, chemical resistance, light resistance and good knot strength, and capable of maintaining high transparency.
1. A method for preparing a polyester fiber comprising the steps of:
(a) carrying out an esterification reaction of a dicarboxylic acid including terephthalic acid thereof and a diol comprising 1 mol to 25 mol of isosorbide and 65 mol to 200 mol of ethylene glycol based on 100 mol of the total dicarboxylic acid;
(b) subjecting the esterification reaction product to a polycondensation reaction to prepare a polyester resin polymerized with a dicarboxylic acid including terephthalic acid and a diol including isosorbide, thereby having an alternating structure of an acid moiety derived from the dicarboxylic acid and a diol moiety derived from the diol, wherein the polyester resin includes 1 to 20 mol % of a diol moiety derived from isosorbide and 2 to 5 mol % of a diol moiety derived from diethylene glycol based on the total diol moieties derived from the diol;
(c) melt-spinning the polyester resin obtained in step (b) at 240° C. to 310° C.; and
(d) drawing the melt-spun undrawn fiber obtained in step (c) at a temperature equal to or higher than the glass transition temperature of the polyester resin,
wherein, in step (a), the initial mixing molar ratio of the dicarboxylic acid to the diol is adjusted to 1:1.01 to 1.05, and
wherein in step (b), the polycondensation is carried out so that an intrinsic viscosity, which is measured at 35° C. after dissolving the product obtained by the polycondensation reaction in orthochlorophenol at a concentration of 1.2 g/dl at 150° C. for 15 minutes, reaches 0.45 dl/g to 0.75 dl/g,
wherein the polyester resin has an alternating structure of an acid moiety derived from the dicarboxylic acid and diol moieties derived from the diol, the dicarboxylic acid includes 90 mol % or more of the terephthalic acid based on the total dicarboxylic acid, and the polyester resin includes 1 to 20 mol % of a diol moiety derived from isosorbide, 2 to 5 mol % of a diol moiety derived from diethylene glycol, and the remainder of a diol moiety derived from ethylene glycol, based on the total diol moieties derived from the diol, and
wherein the polyester resin has a molecular weight distribution of 2.8 to 4.0.
2. The method of preparing a polyester fiber 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.
3. The method of preparing a polyester fiber of claim 1 , wherein the undrawn fiber is drawn at a draw ratio of 3 times or more in step (d).
4. The method of preparing a polyester fiber of claim 1 , wherein the step (d) is carried out at a temperature of 80° C. to 220° C.
5. The method of preparing a polyester fiber of claim 1 , further comprising, after step (b) and before step (c), (b0-1) a step of crystallizing the polymer prepared by polycondensation reaction; and (b0-2) a step of 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, is higher than the intrinsic viscosity of the resin obtained in step (b) by 0.05 to 0.40 dl/g.
6. The method of preparing a polyester fiber of claim 1 , wherein the polyester resin has an oligomer content of 1.3% by weight or less and a haze of less than 3% as measured according to ASTM D1003-97 for a specimen having a thickness of 6 mm obtained from the polyester resin.