Semi-dull polyester drawn yarns and preparing method thereof

Abstract

A type of semi-dull polyester drawn yarns and preparing method thereof are disclosed. The preparing method is to melt spinning a modified polyester with FDY technique, wherein the modified polyester is the product of the esterification and the successive polycondensation reactions of evenly mixed terephthalic acid, ethylene glycol, main chain silicated diol, fluorinated dicarboxylic acid, matting agent and doped Bi.sub.2O.sub.3, in which the main chain silicated diol could be dimethylsiloxane diol, dimethyldiphenyldisiloxane glycol or tetramethyldisiloxane diol, and in which the fluorinated dicarboxylic acids could be 2,2-difluoro-1,3-malonic acid, 2,2-difluoro-1,4-succinic acid, 2,2-difluoro-1,5-glutaric acid or 2,2,3,3-tetrafluoro-1,4-succinic acid. The obtained fiber has a dye uptake of 87.5-91.8% when dyed at 120° C., and has an intrinsic viscosity drop of 18-26% when stored at 25° C. and R.H. 65% for 60 months. This invention features a method with ease of application and a product with good dyeing and degradation performance.

Claims

1. A preparing method for a semi-dull polyester drawn yarn, which is characterized by manufacturing a fully drawn yarn (FDY) with a modified polyester; wherein the modified polyester is a product of an esterification and successive polycondensation reactions of evenly mixed terephthalic acid, ethylene glycol, a main chain silicated diol, a fluorinated dicarboxylic acid, a matting agent and a doped Bi.sub.2O.sub.3; wherein the main chain silicated diol is selected from the group consisting of dimethylsiloxane diol, dimethyldiphenyldisiloxane glycol and tetramethyldisiloxane diol, and the fluorinated dicarboxylic acid is selected from the group consisting of 2,2-difluoro-1,3-malonic acid, 2,2-difluoro-1,4-succinic acid, 2,2-difluoro-1,5-glutaric acid and 2,2,3,3-tetrafluoro-1,4-succinic acid; wherein the modified polyester has a content of the matting agent of 0.20-0.25 wt %, wherein the doped Bi.sub.2O.sub.3 is obtained through a process of evenly mixing Ca.sup.2+ solution and Bi.sup.3+ solution, then adding in a precipitant until a pH value of the mixed solution becomes 9-10, and finally calcining a precipitate product.

2. The preparing method of claim 1, wherein the Ca.sup.2+ solution is an aqueous one with a concentration of 2-3%, wherein an anion of the Ca.sup.2+ solution is NO.sub.3.sup.−; the Bi.sup.3+ solution is a product of dissolving 20-25 wt % of Bi.sub.2O.sub.3 in nitric acid; the precipitant is ammonia water with a concentration of 2 mol/L; wherein the evenly mixed solution has a (5-8):100 molar ratio of Ca.sup.2+ and Bi.sup.3+ before precipitation; wherein the calcining is preceded by a washing process and a drying process, and the drying process is carried out under a temperature of 105-110° C. for 2-3 hrs; wherein the calcining comprises steps of heating at 400° C. for 2-3 hrs, heating at 700° C. for 1-2 hrs and cooling in air to obtain the doped Bi.sub.2O.sub.3; then crushing the doped Bi.sub.2O.sub.3 into powder with an average size of less than 0.5 μm.

3. The preparing method of claim 2, wherein the modified polyester is manufactured through the following steps: (1) Esterification concocting the terephthalic acid, the ethylene glycol, the main chain silicated diol and the fluorinated dicarboxylic acid into a slurry, and adding in the doped Bi.sub.2O.sub.3, a catalyst, the matting agent and a stabilizer, then carrying out the esterification under a nitrogen pressure ranged from atmospheric pressure to 0.3 MPa, finally ending the esterification when a water distillation rate reaches 90% of a theoretical value; (1.3) Polycondensation after smoothly reducing the nitrogen pressure to less than 500 Pa within 30-50 min, conducting a low vacuum polycondensation for products of the esterification at 250-260° C. for 30-50 min, then further reducing the nitrogen pressure to 100 Pa and continuing with a high vacuum polycondensation at 270-282° C. for 50-90 min.

4. The preparing method of claim 3, wherein a molar ratio of the terephthalic acid and the ethylene glycol is 1:(1.2-2.0), and a total addition of the main chain silicated diol and the fluorinated dicarboxylic acid is 3-5 mol % of an amount of the terephthalic acid, and a molar ratio of the main chain silicated diol and the fluorinated dicarboxylic acid is (2-3):(3-5); and an amount of the doped Bi.sub.2O.sub.3, the catalyst, the matting agent and the stabilizer is 0.04-0.07 wt %, 0.03-0.05 wt %, 0.20-0.25 wt % and 0.01-0.05 wt % of the amount of the terephthalic acid, respectively.

5. The preparing method of claim 4, wherein the catalyst is antimony trioxide, ethylene glycol antimony or antimony acetate, wherein the matting agent is titanium dioxide, and wherein the stabilizer is triphenyl phosphate, trimethyl phosphate or trimethyl phosphite.

6. The preparing method for semi-dull polyester drawn yarns of claim 5, wherein the modified polyester has a molecular weight of 25000-30000 Da and a molecular weight distribution index of 1.8-2.2.

7. The preparing method of claim 1, wherein the FDY technique comprises the steps of metering, spinneret extruding, cooling, oiling, stretching, heat setting and winding, wherein a spinning temperature is 285-295° C., a cooling temperature is 17-22° C., an interlacing pressure is 0.20-0.30 MPa, a first godet roller speed is 2300-2700 m/min, a first godet roller temperature is 80-90° C., a second godet roller speed is 4200-4500 m/min, a second godet roller temperature is 125-140° C., and a winding speed is 4130-4420 m/min.

8. A semi-dull polyester drawn yarn manufactured by the preparing method of claim 1, wherein the modified polyester has a molecular chain structure composed of terephthalic acid segments, ethylene glycol segments, main chain silicated diol segments and fluorinated dicarboxylic acid segments; wherein the modified polyester is dispersed with the matting agent and a doped Bi.sub.2O.sub.3 powder, and a content of the matting agent is 0.20-0.25 wt %.

9. The semi-dull polyester drawn yarn of claim 8, wherein the semi-dull polyester drawn yarn is characterized by mechanical performance indices of monofilament fineness 0.7-3.0 dtex, breaking strength ≥3.5 cN/dtex, elongation at break 32.0±4.0%, interlacing degree 13±2/m, linear density deviation rate ≤1.0%, breaking strength CV value ≤5.0%, breaking elongation CV value ≤9.0%, and boiling water shrinkage rate 6.5±0.5%.

10. The semi-dull polyester drawn yarn of claim 8, wherein the semi-dull polyester drawn yarn is characterized by dyeing performance indices of dye uptake 87.5-91.8% at 120° C., K/S value 22.17-25.56, color fastness to soaping level 5, color fastness to dry crocking level 5, and color fastness to wet crocking more than 4; and by an intrinsic viscosity drop of 18-26% after a storage at 25° C. and R.H. 65% for 60 months.

11. The semi-dull polyester drawn yarn of claim 8, wherein the Ca.sup.2+ solution is an aqueous one with a concentration of 2-3%, wherein an anion of the Ca.sup.2+ solution is NO.sub.3.sup.−; the Bi.sup.3+ solution is a product of dissolving 20-25 wt % of Bi.sub.2O.sub.3 in nitric acid; the precipitant is ammonia water with a concentration of 2 mol/L; wherein the evenly mixed solution has a (5-8):100 molar ratio of Ca.sup.2+ and Bi.sup.3+ before precipitation; wherein the calcining is preceded by a washing process and a drying process, and the drying process is carried out under a temperature of 105-110° C. for 2-3 hrs; wherein the calcining comprises steps of heating at 400° C. for 2-3 hrs, heating at 700° C. for 1-2 hrs and cooling in air to obtain the doped Bi.sub.2O.sub.3; then crushing the doped Bi.sub.2O.sub.3 into powder with an average size of less than 0.5 μm.

12. The semi-dull polyester drawn yarn of claim 8, wherein the modified polyester is manufactured through the following steps: (1) Esterification concocting the terephthalic acid, the ethylene glycol, the main chain silicated diol and the fluorinated dicarboxylic acid into a slurry, and adding in the doped Bi.sub.2O.sub.3, a catalyst, the matting agent and a stabilizer, then carrying out the esterification under a nitrogen pressure ranged from atmospheric pressure to 0.3 MPa, finally ending the esterification when a water distillation rate reaches 90% of a theoretical value; (1.3) Polycondensation after smoothly reducing the nitrogen pressure to less than 500 Pa within 30-50 min, conducting a low vacuum polycondensation for products of the esterification at 250-260° C. for 30-50 min, then further reducing the nitrogen pressure to 100 Pa and continuing with a high vacuum polycondensation at 270-282° C. for 50-90 min.

13. The semi-dull polyester drawn yarn of claim 8, wherein a molar ratio of the terephthalic acid and the ethylene glycol is 1:(1.2-2.0), and a total addition of the main chain silicated diol and the fluorinated dicarboxylic acid is 3-5 mol % of an amount of the terephthalic acid, and a molar ratio of the main chain silicated diol and the fluorinated dicarboxylic acid is (2-3):(3-5); and an amount of the doped Bi.sub.2O.sub.3, the catalyst, the matting agent and the stabilizer are 0.04-0.07 wt %, 0.03-0.05 wt %, 0.20-0.25 wt % and 0.01-0.05 wt % of the amount of the terephthalic acid, respectively.

14. The semi-dull polyester drawn yarn of claim 8, wherein the catalyst is antimony trioxide, ethylene glycol antimony or antimony acetate, wherein the matting agent is titanium dioxide, and wherein the stabilizer is triphenyl phosphate, trimethyl phosphate or trimethyl phosphite.

15. The semi-dull polyester drawn yarn of claim 8, wherein the modified polyester has a molecular weight of 25000-30000 Da and a molecular weight distribution index of 1.8-2.2.

16. The semi-dull polyester drawn yarn of claim 8, wherein the FDY technique comprises the steps of metering, spinneret extruding, cooling, oiling, stretching, heat setting and winding, wherein a spinning temperature is 285-295° C., a cooling temperature is 17-22° C., an interlacing pressure is 0.20-0.30 MPa, a first godet roller speed is 2300-2700 m/min, a first godet roller temperature is 80-90° C., a second godet roller speed is 4200-4500 m/min, a second godet roller temperature is 125-140° C., and a winding speed is 4130-4420 m/min.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) Based on above mentioned method, the following embodiments are carried out for further demonstration in the present invention. It is to be understood that these embodiments are only intended to illustrate the invention and are not intended to limit the scope of the invention. In addition, it should be understood that after reading the contents described in the present invention, those technical personnel in this field can make various changes or modifications to the invention, and these equivalent forms also fall within the scope of the claims attached to the application.

Example 1

(2) A method for preparing the semi-dull polyester drawn yarns, comprising the steps:

(3) (1) Preparation of Modified Polyester

(4) (1.1) Doping Modification of Bi.sub.2O.sub.3

(5) (a) evenly mixing a 2.5 wt % of Ca(NO.sub.3).sub.2 aqueous solution and a 22 wt % of Bi.sub.2O.sub.3 nitric acid solution, maintaining a 7:100 of molar ratio of Ca.sup.2+ and Bi.sup.3+;

(6) (b) depositing the mixed solution by adding 2 mol/L of ammonia water until pH value reaches 10, then washing and drying (105° C., 2.5 hr) the precipitate;

(7) (c) after the treatment composed of a heating at 400° C. for 2.5 hr, a heating at 700° C. for 1.5 hr and a cooling in air, crushing the precipitate to doped Bi.sub.2O.sub.3 powder with an average size of 0.45 μm;

(8) (1.2) Esterification

(9) concocting terephthalic acid, ethylene glycol, dimethylsiloxane diol and 2,2-difluoro-1,3-malonic acid into a slurry (in which the molar ration of terephthalic acid and ethylene glycol is 1:1.2, the total addition of dimethylsiloxane diol and 2,2-difluoro-1,3-malonic acid with a molar ratio of 2:3 is 3 mol % relative to the amount of terephthalic acid), and adding in 0.05 wt % of the doped Bi.sub.2O.sub.3, 0.03 wt % of antimony trioxide, 0.22 wt % of titanium dioxide and 0.02 wt % of triphenyl phosphate (all are relative to the amount of terephthalic acid), then carrying out the esterification under a 0.3 MPa of nitrogen pressure at 250° C., finally ending the reaction when the water distillation rate reaches 90% of the theoretical value;

(10) (1.3) Polycondensation

(11) after smoothly reducing the pressure from normal value to 490 Pa within 30 min, conducting the low vacuum polycondensation for the esterification products at 272° C. for 35 min, then further reducing the pressure to 100 Pa and continuing the high vacuum polycondensation at 270° C. for 50 min, finally obtaining the modified polyester with a molecular weight of 30000 Da and a molecular weight distribution index of 2.0;

(12) (2) Spinning of Semi-Dull Polyester Drawn Yarn

(13) through a FDY technological way including stages of metering, spinneret extruding (at 290° C.), cooling (at 22° C.), oiling, stretching as well as heat setting (carried on with the parameters of interlacing pressure 0.26 MPa, godet roller 1 speed 2300 m/min, godet roller 1 temperature 85° C., godet roller 2 speed 4500 m/min, godet roller 2 temperature 140° C.), and winding (4420 m/min), converting the modified polyester into semi-dull polyester drawn yarns

(14) with the mechanical performance indices of monofilament fineness 0.7 dtex, breaking strength 3.6 cN/dtex, elongation at break 32.0%, interlacing degree 13/m, linear density deviation rate 0.95%, breaking strength CV value 4.4%, breaking elongation CV value 8.8%, and boiling water shrinkage rate 6.0%;

(15) with the dyeing performance indices of dye uptake 87.5% (at 120° C.), K/S value 24.22, color fastness to soaping level 5, color fastness to dry crocking level 5, and color fastness to wet crocking level 5;

(16) and with an intrinsic viscosity drop by 26% when stored at 25° C. and R.H. 65% for 60 months.

(17) Comparison 1

(18) A method for preparing the semi-dull polyester drawn yarns involved steps basically the same as those in Example 1, except for no modification for polyester, from which the finally obtained semi-dull polyester drawn yarns possess

(19) the mechanical performance indices of monofilament fineness 0.7 dtex, breaking strength 3.5 cN/dtex, elongation at break 33.0%, interlacing degree 13/m, linear density deviation rate 0.95%, breaking strength CV value 4.50%, breaking elongation CV value 8.8%, and boiling water shrinkage rate 6.2%;

(20) the dyeing performance indices of dye uptake 85.6% (at 130° C.), K/S value 21.28, color fastness to soaping level 4, color fastness to dry crocking level 4-5, and color fastness to wet crocking level 3-4;

(21) and an intrinsic viscosity drop by 4.2% when stored at 25° C. and R.H. 65% for 60 months.

(22) The comparison shows that the modification herein will significantly improve the dyeing and natural degradation performance of polyester fiber without loss of mechanical properties.

(23) Comparison 2

(24) A method for preparing the semi-dull polyester drawn yarns involved steps basically the same as those in Example 1, except for using 1,6-hexanediol instead of dimethylsiloxane glycol in step (1), from which the finally obtained semi-dull polyester drawn yarns possess

(25) the mechanical performance indices of monofilament fineness 0.7 dtex, breaking strength 3.4 cN/dtex, elongation at break 35.0%, interlacing degree 13/m, linear density deviation rate 0.95%, breaking strength CV value 4.30%, breaking elongation CV value 8.8%, and boiling water shrinkage rate 6.5%;

(26) the dyeing performance indices of dye uptake 84.8% (at 130° C.), K/S value 20.56, color fastness to soaping level 4-5, and color fastness to wet crocking level 4, which are all lower than those in Example 1;

(27) and an intrinsic viscosity drop by 16.7% when stored at 25° C. and R.H. 65% for 60 months.

(28) The comparison shows that the introducing of main-chain silicated diol will import —Si—O—Si— bonds into polyester molecular chains so as to reduce the activation energy for internal rotation and to enlarge the free volume of polyester molecules, leading to a more efficient improvement on the dyeing and natural degradation performance than the alkylene substituent.

(29) Comparison 3

(30) A method for preparing the semi-dull polyester drawn yarns involved steps basically the same as those in Example 1, except for no addition of doped Bi.sub.2O.sub.3 in step (2), from which the finally obtained semi-dull polyester drawn yarns possess

(31) the mechanical performance indices of monofilament fineness 0.7 dtex, breaking strength 3.5 cN/dtex, elongation at break 34.0%, interlacing degree 13/m, linear density deviation rate 0.95%, breaking strength CV value 4.20%, breaking elongation CV value 8.8%, and boiling water shrinkage rate 6.4%;

(32) the dyeing performance indices of dye uptake 87.2% (at 130° C.), K/S value 23.98, color fastness to soaping level 4-5, color fastness to dry crocking level 4, and color fastness to wet crocking level 4, which are all lower than those in Example 1;

(33) and an intrinsic viscosity drop by 13.7% when stored at 25° C. and R.H. 65% for 60 months.

(34) The comparison shows that the importing of doped Bi.sub.2O.sub.3 will bring considerable acceleration to the natural degradation of polyester fiber without loss of processiblity and mechanical properties.

(35) Comparison 4

(36) A method for preparing the semi-dull polyester drawn yarns involved steps basically the same as those in Example 1, except for using 3,3-difluoroglutaric acid instead of 2,2-difluoro-1,3-malonic acid in step (1), from which the finally obtained semi-dull polyester drawn yarns possess

(37) the mechanical performance indices of monofilament fineness 0.7 dtex, breaking strength 3.3 cN/dtex, elongation at break 35.0%, interlacing degree 13/m, linear density deviation rate 0.95%, breaking strength CV value 4.00%, breaking elongation CV value 8.8%, and boiling water shrinkage rate 6.5%;

(38) the dyeing performance indices of dye uptake 86.97% (at 130° C.), K/S value 24.05, color fastness to soaping level 4-5, color fastness to dry crocking level 4, and color fastness to wet crocking level 4, which are all lower than those in Example 1;

(39) and an intrinsic viscosity drop by 12.8% when stored at 25° C. and R.H. 65% for 60 months.

(40) The comparison shows that compared with α-C bonded fluorine atom, β-C bonded fluorine atom in the modified polyester can only make rather weak effect upon the natural degradation of the obtained polyester fiber, because its electron-withdrawing effect just pass to the neighbor atoms of β-C so as to give little influence on the nucleophilic addition reaction of ester carbonyl when attacked by OH.sup.−.

Example 2

(41) A method for preparing the semi-dull polyester drawn yarns, comprising the steps:

(42) (1) Preparation of Modified Polyester

(43) (1.1) Doping Modification of Bi.sub.2O.sub.3

(44) (a) evenly mixing a 2 wt % of Ca(NO.sub.3).sub.2 aqueous solution and a 20 wt % of Bi.sub.2O.sub.3 nitric acid solution, maintaining a 5:100 of molar ratio of Ca.sup.2+ and Bi.sup.3+;

(45) (b) depositing the mixed solution by adding 2 mol/L of ammonia water until pH value reaches 9, then washing and drying (105° C., 2.5 hr) the precipitate;

(46) (c) after the treatment composed of a heating at 400° C. for 2 hr, a heating at 700° C. for 1 hr and a cooling in air, crushing the precipitate to doped Bi.sub.2O.sub.3 powder with an average size of 0.4 μm;

(47) (1.2) Esterification

(48) concocting terephthalic acid, ethylene glycol, dimethyldiphenyldisiloxane glycol and 2,2-difluoro-1,4-succinic acid into a slurry (in which the molar ration of terephthalic acid and ethylene glycol is 1:1.5, the total addition of dimethyldiphenyldisiloxane glycol and 2,2-difluoro-1,4-succinic acid with a molar ratio of 2:5 is 3.2 mol % relative to the amount of terephthalic acid), and adding in 0.04 wt % of the doped Bi.sub.2O.sub.3, 0.04 wt % of antimony trioxide, 0.20 wt % of titanium dioxide and 0.04 wt % of trimethyl phosphate (all are relative to the amount of terephthalic acid), then carrying out the esterification under a 0.2 MPa of nitrogen pressure at 252° C., finally ending the reaction when the water distillation rate reaches 90% of the theoretical value;

(49) (1.3) Polycondensation

(50) after smoothly reducing the pressure from normal value to 420 Pa within 35 min, conducting the low vacuum polycondensation for the esterification products at 270° C. for 40 min, then further reducing the pressure to 95 Pa and continuing the high vacuum polycondensation at 271° C. for 55 min, finally obtaining the modified polyester with a molecular weight of 28000 Da and a molecular weight distribution index of 2.0;

(51) (2) Spinning of Semi-Dull Polyester Drawn Yarn

(52) through a FDY technological way including stages of metering, spinneret extruding (at 285° C.), cooling (at 20° C.), oiling, stretching as well as heat setting (carried on with the parameters of interlacing pressure 0.24 MPa, godet roller 1 speed 2700 m/min, godet roller 1 temperature 90° C., godet roller 2 speed 4300 m/min, godet roller 2 temperature 125° C.), and winding (4130 m/min), converting the modified polyester into semi-dull polyester drawn yarns

(53) with the mechanical performance indices of monofilament fineness 1.5 dtex, breaking strength 3.5 cN/dtex, elongation at break 28.0%, interlacing degree 11/m, linear density deviation rate 0.9%, breaking strength CV value 4.9%, breaking elongation CV value 8.8%, and boiling water shrinkage rate 7.0%;

(54) with the dyeing performance indices of dye uptake 91.8% (at 120° C.), K/S value 22.17, color fastness to soaping level 5, color fastness to dry crocking level 5, and color fastness to wet crocking level 6;

(55) and with an intrinsic viscosity drop by 20% when stored at 25° C. and R.H. 65% for 60 months.

Example 3

(56) A method for preparing the semi-dull polyester drawn yarns, comprising the steps:

(57) (1) Preparation of Modified Polyester

(58) (1.1) Doping Modification of Bi.sub.2O.sub.3

(59) (a) evenly mixing a 3 wt % of Ca(NO.sub.3).sub.2 aqueous solution and a 25 wt % of Bi.sub.2O.sub.3 nitric acid solution, maintaining a 8:100 of molar ratio of Ca.sup.2+ and Bi.sup.3+;

(60) (b) depositing the mixed solution by adding 2 mol/L of ammonia water until pH value reaches 9, then washing and drying (110° C., 3 hr) the precipitate;

(61) (c) after the treatment composed of a heating at 400° C. for 3 hr, a heating at 700° C. for 2 hr and a cooling in air, crushing the precipitate to doped Bi.sub.2O.sub.3 powder with an average size of 0.4 μm;

(62) (1.2) Esterification

(63) concocting terephthalic acid, ethylene glycol, tetramethyldisiloxane diol and 2,2-difluoro-1,5-glutaric acid into a slurry (in which the molar ration of terephthalic acid and ethylene glycol is 1:1.3, the total addition of tetramethyldisiloxane diol and 2,2-difluoro-1,5-glutaric acid with a molar ratio of 2.5:3 is 3.5 mol % relative to the amount of terephthalic acid), and adding in 0.04 wt % of the doped Bi.sub.2O.sub.3, 0.05 wt % of antimony trioxide, 0.24 wt % of titanium dioxide and 0.01 wt % of trimethyl phosphite (all are relative to the amount of terephthalic acid), then carrying out the esterification under a 0.1 MPa of nitrogen pressure at 255° C., finally ending the reaction when the water distillation rate reaches 92% of the theoretical value;

(64) (1.3) Polycondensation

(65) after smoothly reducing the pressure from normal value to 500 Pa within 45 min, conducting the low vacuum polycondensation for the esterification products at 280° C. for 30 min, then further reducing the pressure to 96 Pa and continuing the high vacuum polycondensation at 273° C. for 60 min, finally obtaining the modified polyester with a molecular weight of 25000 Da and a molecular weight distribution index of 2.2;

(66) (2) Spinning of Semi-Dull Polyester Drawn Yarn

(67) through a FDY technological way including stages of metering, spinneret extruding (at 285° C.), cooling (at 17° C.), oiling, stretching as well as heat setting (carried on with the parameters of interlacing pressure 0.30 MPa, godet roller 1 speed 2400 m/min, godet roller 1 temperature 83° C., godet roller 2 speed 4500 m/min, godet roller 2 temperature 125° C.), and winding (4130 m/min), converting the modified polyester into semi-dull polyester drawn yarns

(68) with the mechanical performance indices of monofilament fineness 2.0 dtex, breaking strength 3.6 cN/dtex, elongation at break 36.0%, interlacing degree 15/m, linear density deviation rate 0.95%, breaking strength CV value 4.4%, breaking elongation CV value 8.6%, and boiling water shrinkage rate 6.5%;

(69) with the dyeing performance indices of dye uptake 87.5% (at 120° C.), K/S value 22.17, color fastness to soaping level 5, color fastness to dry crocking level 5, and color fastness to wet crocking level 5;

(70) and with an intrinsic viscosity drop by 18% when stored at 25° C. and R.H. 65% for 60 months.

Example 4

(71) A method for preparing the semi-dull polyester drawn yarns, comprising the steps:

(72) (1) Preparation of Modified Polyester

(73) (1.1) Doping Modification of Bi.sub.2O.sub.3

(74) (a) evenly mixing a 2.5 wt % of Ca(NO.sub.3).sub.2 aqueous solution and a 25 wt % of Bi.sub.2O.sub.3 nitric acid solution, maintaining a 8:100 of molar ratio of Ca.sup.2+ and Bi.sup.3+;

(75) (b) depositing the mixed solution by adding 2 mol/L of ammonia water until pH value reaches 10, then washing and drying (110° C., 3 hr) the precipitate;

(76) (c) after the treatment composed of a heating at 400° C. for 2.5 hr, a heating at 700° C. for 2 hr and a cooling in air, crushing the precipitate to doped Bi.sub.2O.sub.3 powder with an average size of 0.4 μm;

(77) (1.2) Esterification

(78) concocting terephthalic acid, ethylene glycol, dimethylsiloxane diol and 2,2,3,3-tetrafluoro-1,4-succinic acid into a slurry (in which the molar ration of terephthalic acid and ethylene glycol is 1:1.6, the total addition of dimethylsiloxane diol and 2,2,3,3-tetrafluoro-1,4-succinic acid with a molar ratio of 2.2:4 is 4 mol % relative to the amount of terephthalic acid), and adding in 0.07 wt % of the doped Bi.sub.2O.sub.3, 0.04 wt % of antimony trioxide, 0.25 wt % of titanium dioxide and 0.03 wt % of triphenyl phosphate (all are relative to the amount of terephthalic acid), then carrying out the esterification under a 0.1 MPa of nitrogen pressure at 250° C., finally ending the reaction when the water distillation rate reaches 95% of the theoretical value;

(79) (1.3) Polycondensation

(80) after smoothly reducing the pressure from normal value to 440 Pa within 40 min, conducting the low vacuum polycondensation for the esterification products at 278° C. for 40 min, then further reducing the pressure to 99 Pa and continuing the high vacuum polycondensation at 273° C. for 75 min, finally obtaining the modified polyester with a molecular weight of 25000 Da and a molecular weight distribution index of 1.8;

(81) (2) Spinning of Semi-Dull Polyester Drawn Yarn

(82) through a FDY technological way including stages of metering, spinneret extruding (at 295° C.), cooling (at 17° C.), oiling, stretching as well as heat setting (carried on with the parameters of interlacing pressure 0.20 MPa, godet roller 1 speed 2600 m/min, godet roller 1 temperature 90° C., godet roller 2 speed 4200 m/min, godet roller 2 temperature 125° C.), and winding (4360 m/min), converting the modified polyester into semi-dull polyester drawn yarns

(83) with the mechanical performance indices of monofilament fineness 3.0 dtex, breaking strength 3.5 cN/dtex, elongation at break 32.0%, interlacing degree 12/m, linear density deviation rate 1.0%, breaking strength CV value 4.9%, breaking elongation CV value 9.0%, and boiling water shrinkage rate 6.8%;

(84) with the dyeing performance indices of dye uptake 89.63% (at 120° C.), K/S value 25.56, color fastness to soaping level 5, color fastness to dry crocking level 5, and color fastness to wet crocking level 5;

(85) and with an intrinsic viscosity drop by 18% when stored at 25° C. and R.H. 65% for 60 months.

Example 5

(86) A method for preparing the semi-dull polyester drawn yarns, comprising the steps:

(87) (1) Preparation of Modified Polyester

(88) (1.1) Doping Modification of Bi.sub.2O.sub.3

(89) (a) evenly mixing a 2.5 wt % of Ca(NO.sub.3).sub.2 aqueous solution and a 24 wt % of Bi.sub.2O.sub.3 nitric acid solution, maintaining a 6:100 of molar ratio of Ca.sup.2+ and Bi.sup.3+;

(90) (b) depositing the mixed solution by adding 2 mol/L of ammonia water until pH value reaches 10, then washing and drying (107° C., 2.5 hr) the precipitate;

(91) (c) after the treatment composed of a heating at 400° C. for 2.5 hr, a heating at 700° C. for 2 hr and a cooling in air, crushing the precipitate to doped Bi.sub.2O.sub.3 powder with an average size of 0.45 μm;

(92) (1.2) Esterification

(93) concocting terephthalic acid, ethylene glycol, dimethyldiphenyldisiloxane glycol and 2,2-difluoro-1,3-malonic acid into a slurry (in which the molar ration of terephthalic acid and ethylene glycol is 1:1.8, the total addition of dimethyldiphenyldisiloxane glycol and 2,2-difluoro-1,3-malonic acid with a molar ratio of 3:4 is 4 mol % relative to the amount of terephthalic acid), and adding in 0.05 wt % of the doped Bi.sub.2O.sub.3, 0.03 wt % of antimony trioxide, 0.25 wt % of titanium dioxide and 0.01 wt % of trimethyl phosphate (all are relative to the amount of terephthalic acid), then carrying out the esterification in nitrogen under a normal pressure at 260° C., finally ending the reaction when the water distillation rate reaches 91% of the theoretical value;

(94) (1.3) Polycondensation

(95) after smoothly reducing the pressure from normal value to 490 Pa within 50 min, conducting the low vacuum polycondensation for the esterification products at 282° C. for 35 min, then further reducing the pressure to 100 Pa and continuing the high vacuum polycondensation at 274° C. for 80 min, finally obtaining the modified polyester with a molecular weight of 30000 Da and a molecular weight distribution index of 1.8;

(96) (2) Spinning of Semi-Dull Polyester Drawn Yarn

(97) through a FDY technological way including stages of metering, spinneret extruding (at 292° C.), cooling (at 22° C.), oiling, stretching as well as heat setting (carried on with the parameters of interlacing pressure 0.20 MPa, godet roller 1 speed 2300 m/min, godet roller 1 temperature 80° C., godet roller 2 speed 4200 m/min, godet roller 2 temperature 125° C.), and winding (4420 m/min), converting the modified polyester into semi-dull polyester drawn yarns

(98) with the mechanical performance indices of monofilament fineness 1.6 dtex, breaking strength 3.7 cN/dtex, elongation at break 31.0%, interlacing degree 15/m, linear density deviation rate 0.92%, breaking strength CV value 5.0%, breaking elongation CV value 8.4%, and boiling water shrinkage rate 7.0%;

(99) with the dyeing performance indices of dye uptake 89.20% (at 120° C.), K/S value 23.44, color fastness to soaping level 5, color fastness to dry crocking level 5, and color fastness to wet crocking level 6;

(100) and with an intrinsic viscosity drop by 21% when stored at 25° C. and R.H. 65% for 60 months.

Example 6

(101) A method for preparing the semi-dull polyester drawn yarns, comprising the steps:

(102) (1) Preparation of Modified Polyester

(103) (1.1) Doping Modification of Bi.sub.2O.sub.3

(104) (a) evenly mixing a 3 wt % of Ca(NO.sub.3).sub.2 aqueous solution and a 24 wt % of Bi.sub.2O.sub.3 nitric acid solution, maintaining a 7:100 of molar ratio of Ca.sup.2+ and Bi.sup.3+;

(105) (b) depositing the mixed solution by adding 2 mol/L of ammonia water until pH value reaches 10, then washing and drying (110° C., 2.5 hr) the precipitate;

(106) (c) after the treatment composed of a heating at 400° C. for 3 hr, a heating at 700° C. for 1.5 hr and a cooling in air, crushing the precipitate to doped Bi.sub.2O.sub.3 powder with an average size of 0.45 μm;

(107) (1.2) Esterification

(108) concocting terephthalic acid, ethylene glycol, tetramethyldisiloxane diol and 2,2-difluoro-1,4-succinic acid into a slurry (in which the molar ration of terephthalic acid and ethylene glycol is 1:2.0, the total addition of tetramethyldisiloxane diol and 2,2-difluoro-1,4-succinic acid with a molar ratio of 3:5 is 4.5 mol % relative to the amount of terephthalic acid), and adding in 0.07 wt % of the doped Bi.sub.2O.sub.3, 0.04 wt % of antimony trioxide, 0.20 wt % of titanium dioxide and 0.05 wt % of trimethyl phosphite (all are relative to the amount of terephthalic acid), then carrying out the esterification in nitrogen under a normal pressure at 260° C., finally ending the reaction when the water distillation rate reaches 91% of the theoretical value;

(109) (1.3) Polycondensation

(110) after smoothly reducing the pressure from normal value to 450 Pa within 35 min, conducting the low vacuum polycondensation for the esterification products at 270° C. for 50 min, then further reducing the pressure to 100 Pa and continuing the high vacuum polycondensation at 275° C. for 85 min, finally obtaining the modified polyester with a molecular weight of 27800 and a molecular weight distribution index of 1.8;

(111) (2) Spinning of Semi-Dull Polyester Drawn Yarn

(112) through a FDY technological way including stages of metering, spinneret extruding (at 295° C.), cooling (at 18° C.), oiling, stretching as well as heat setting (carried on with the parameters of interlacing pressure 0.20 MPa, godet roller 1 speed 2300 m/min, godet roller 1 temperature 80° C., godet roller 2 speed 4400 m/min, godet roller 2 temperature 130° C.), and winding (4420 m/min), converting the modified polyester into semi-dull polyester drawn yarns

(113) with the mechanical performance indices of monofilament fineness 2.5 dtex, breaking strength 3.5 cN/dtex, elongation at break 33.0%, interlacing degree 11/m, linear density deviation rate 1.0%, breaking strength CV value 5.0%, breaking elongation CV value 8.2%, and boiling water shrinkage rate 6.5%;

(114) with the dyeing performance indices of dye uptake 91.8% (at 120° C.), K/S value 25.56, color fastness to soaping level 5, color fastness to dry crocking level 5, and color fastness to wet crocking level 6;

(115) and with an intrinsic viscosity drop by 22% when stored at 25° C. and R.H. 65% for 60 months.

Example 7

(116) A method for preparing the semi-dull polyester drawn yarns, comprising the steps:

(117) (1) Preparation of Modified Polyester

(118) (1.1) Doping Modification of Bi.sub.2O.sub.3

(119) (a) evenly mixing a 2.5 wt % of Ca(NO.sub.3).sub.2 aqueous solution and a 25 wt % of Bi.sub.2O.sub.3 nitric acid solution, maintaining a 8:100 of molar ratio of Ca.sup.2+ and Bi.sup.3+;

(120) (b) depositing the mixed solution by adding 2 mol/L of ammonia water until pH value reaches 10, then washing and drying (110° C., 3 hr) the precipitate;

(121) (c) after the treatment composed of a heating at 400° C. for 3 hr, a heating at 700° C. for 2 hr and a cooling in air, crushing the precipitate to doped Bi.sub.2O.sub.3 powder with an average size of 0.45 μm;

(122) (1.2) Esterification

(123) concocting terephthalic acid, ethylene glycol, tetramethyldisiloxane diol and 2,2-difluoro-1,5-glutaric acid into a slurry (in which the molar ration of terephthalic acid and ethylene glycol is 1:1.3, the total addition of tetramethyldisiloxane diol and 2,2-difluoro-1,5-glutaric acid with a molar ratio of 2.5:3 is 5 mol % relative to the amount of terephthalic acid), and adding in 0.06 wt % of the doped Bi.sub.2O.sub.3, 0.04 wt % of antimony trioxide, 0.21 wt % of titanium dioxide and 0.01 wt % of trimethyl phosphate (all are relative to the amount of terephthalic acid), then carrying out the esterification under a 0.3 MPa of nitrogen pressure at 260° C., finally ending the reaction when the water distillation rate reaches 99% of the theoretical value;

(124) (1.3) Polycondensation

(125) after smoothly reducing the pressure from normal value to 500 Pa within 45 min, conducting the low vacuum polycondensation for the esterification products at 280° C. for 50 min, then further reducing the pressure to 90 Pa and continuing the high vacuum polycondensation at 277° C. for 90 min, finally obtaining the modified polyester with a molecular weight of 30000 Da and a molecular weight distribution index of 2.2;

(126) (2) Spinning of Semi-Dull Polyester Drawn Yarn

(127) through a FDY technological way including stages of metering, spinneret extruding (at 295° C.), cooling (at 22° C.), oiling, stretching as well as heat setting (carried on with the parameters of interlacing pressure 0.30 MPa, godet roller 1 speed 2700 m/min, godet roller 1 temperature 86° C., godet roller 2 speed 4500 m/min, godet roller 2 temperature 135° C.), and winding (4130 m/min), converting the modified polyester into semi-dull polyester drawn yarns

(128) with the mechanical performance indices of monofilament fineness 1.2 dtex, breaking strength 3.5 cN/dtex, elongation at break 32.0%, interlacing degree 13/m, linear density deviation rate 0.88%, breaking strength CV value 4.5%, breaking elongation CV value 9.0%, and boiling water shrinkage rate 7.0%;

(129) with the dyeing performance indices of dye uptake 87.5% (at 120° C.), K/S value 23.55, color fastness to soaping level 5, color fastness to dry crocking level 5, and color fastness to wet crocking level 6;

(130) and with an intrinsic viscosity drop by 26% when stored at 25° C. and R.H. 65% for 60 months.