DEGRADABLE POLYESTER FIBER AND ITS PREPARATION METHOD

Abstract

A degradable polyester fiber and its preparation method are disclosed. The preparation method is to cool a PET melt dispersing with doped ZrO.sub.2 powder by ring-blowing after extruded from a trilobal spinneret hole on a spinneret, and manufacture a fully drawn yarn (FDY) according to an FDY process with the PET melt, then the degradable polyester fiber is prepared after a relaxation heat treatment. The trilobal spinneret hole on the spinneret has three leaves with unequal lengths and angles, and all the trilobal spinneret holes are distributed in concentric circles, with a center line of the leaf opposite to the smallest angle in each trilobal spinneret hole passing through the center of the circle, and pointing away from the center of the circle. The process is simple, and the obtain fiber has good performances in degradation and elasticity.

Claims

1. A method for preparing a degradable polyester fiber, comprising: cooling a polyethylene terephthalate (PET) melt by ring-blowing after extruded from a trilobal spinneret hole on a spinneret; then manufacturing a fully drawn yarn (FDY) according to an FDY process with the PET melt; and performing a relaxation heat treatment to obtain the degradable polyester fiber; wherein the PET melt disperses with a doped ZrO.sub.2 powder, the doped ZrO.sub.2 powder is obtained through a process of evenly mixing a M.sup.x+ solution and a Zr.sup.4+ solution at first, then dripping in a precipitant until a pH value is 9-10 to obtain a precipitate, and finally calcining the precipitate; wherein M.sup.x+ in the M.sup.x+ solution is more than one ion selected from the group consisting of Mg.sup.2+, Li.sup.+, and Zn.sup.2+; wherein a ratio of angles between centre lines of three leaves from a same trilobal spinneret hole is 1.0:(1.5-3.1):(1.5-3.1); wherein a ratio of lengths of two leaves forming a smallest angle to a length of an other leaf from the same trilobal spinneret hole is 3:3:2; wherein a ratio of a length to a width of a shortest leaf is (1.5-2):1, with same widths of other two leaves from the same trilobal spinneret hole; wherein shapes and sizes of three leaves from different trilobal spinneret holes are the same; wherein all the trilobal spinneret holes are distributed in concentric circles, with a center line of a leaf opposite to the smallest angle in each trilobal spinneret hole passing through a center of the concentric circles, and pointing away from the center of the concentric circles; wherein the FDY process involves technological parameters: a cooling temperature of 20-25° C., and a cooling wind speed of 1.80-2.30 m/s.

2. The method of claim 1, wherein the PET melt has an intrinsic viscosity of 0.60-0.66 dL/g.

3. The method of claim 2, wherein the FDY process further involves technological parameters: a spinning temperature of 280-285° C., a first godet roller speed of 1800-2000 m/min, a first godet roller temperature of 85-95° C., a second godet roller speed of 3500-3700 m/min, a second godet roller temperature of 160-180° C., and a winding speed of 3430-3610 m/min.

4. The method of claim 1, wherein a content of the doped ZrO.sub.2 powder in the PET melt is 0.03-0.06 wt %.

5. The method of claim 4, wherein the M.sup.x+ solution is an aqueous solution with a concentration of 1-2 wt % and an anion in the M.sup.x+ solution is NO.sub.3.sup.−; wherein the Zr.sup.4+ solution is a product of dissolving 20-25 wt % of ZrO.sub.2 in nitric acid; wherein the precipitant is ammonia water with a concentration of 2 mol/L; wherein a solution blending before a coprecipitation is to make a mixture containing (5-8):100 (molar ratio) of M.sup.x+ respecting to Zr.sup.4+.

6. The method of claim 5, wherein the calcining is preceded by a washing process and a drying process for the precipitate, and the drying process is carried out at a temperature of 105-110° C. for 2-3 h; wherein the calcining includes steps of a 400° C. heating for 2-3 h, a 700° C. heating for 1-2 h, and a cooling in air.

7. The method of claim 1, wherein the relaxation heat treatment has a temperature of 90-120° C. and a time of 20-30 min.

8. A degradable polyester fiber, wherein the degradable polyester fiber is prepared by the method of claim 1, the degradable polyester fiber has a three-dimensional crimp shape, and comprises a plurality of PET monofilaments containing the doped ZrO.sub.2 powder in a trilobal cross-section.

9. The degradable polyester fiber of claim 8, wherein the degradable polyester fiber comprises mechanical performance indices: a crimp shrinkage of 22-26%, a crimp stability of 77-81%, a shrinkage elongation of 56-62%, and a crimp elastic recovery rate of 75-80%.

10. The degradable polyester fiber of claim 8, wherein the degradable polyester fiber comprises mechanical performance indices: a breaking strength of ≥2.7 cN/dtex, an elongation at break of 45.0±5.0%, a total fineness of 100-150 dtex, and an intrinsic viscosity drop of 10-16% after a storage at 25° C. and a R.H. 65% for 60 months.

11. The degradable polyester fiber of claim 8, wherein during a preparation of the degradable polyester fiber, the PET melt has an intrinsic viscosity of 0.60-0.66 dL/g.

12. The degradable polyester fiber of claim 11, wherein during the preparation of the degradable polyester fiber, the FDY process further involves technological parameters: a spinning temperature of 280-285° C., a first godet roller speed of 1800-2000 m/min, a first godet roller temperature of 85-95° C., a second godet roller speed of 3500-3700 m/min, a second godet roller temperature of 160-180° C., and a winding speed of 3430-3610 m/min.

13. The degradable polyester fiber of claim 8, wherein during a preparation of the degradable polyester fiber, a content of the doped ZrO.sub.2 powder in the PET melt is 0.03-0.06 wt %.

14. The degradable polyester fiber of claim 13, wherein during the preparation of the degradable polyester fiber, the M.sup.x+ solution is an aqueous solution with a concentration of 1-2 wt % and an anion in the M.sup.x+ solution is NO.sub.3.sup.−; wherein the Zr.sup.4+ solution is a product of dissolving 20-25 wt % of ZrO.sub.2 in nitric acid; wherein the precipitant is ammonia water with a concentration of 2 mol/L; wherein a solution blending before a coprecipitation is to make a mixture containing (5-8):100 (molar ratio) of M.sup.x+ respecting to Zr.sup.4+.

15. The degradable polyester fiber of claim 14, wherein during the preparation of the degradable polyester fiber, the calcining is preceded by a washing process and a drying process for the precipitate, and the drying process is carried out at a temperature of 105-110° C. for 2-3 h; wherein the calcining includes steps of a 400° C. heating for 2-3 h, a 700° C. heating for 1-2 h, and a cooling in air.

16. The degradable polyester fiber of claim 8, wherein during a preparation of the degradable polyester fiber, the relaxation heat treatment has a temperature of 90-120° C. and a time of 20-30 min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 is a schematic diagram of the structure of the trilobal spinneret hole in the present invention;

[0031] FIG. 2 is a schematic diagram of the distribution of the trilobal spinneret holes on a spinneret in the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] 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.

[0033] The crimp shrinkage and crimp stability in the present invention are obtained by testing the tow by using GB6506-2001 “Synthetic fiber—Test method for crimp contraction properties of textured filament yarns”;

[0034] The text methods of the shrinkage elongation (reflecting the degree of elasticity and crimp of textured filament yarns, wherein the fibers are subjected to a light load and then to a heavy load, and the ratio of the difference in length to the curl length is calculated for both loads) and the crimp elastic recovery rate are as follows:

[0035] Firstly, cut two fiber samples of about 50 cm in length, put them into 100° C. hot water for 30 minutes, take them out and dry them naturally, next intercept a sample of about 30 cm in length, wherein fix one end and load another end with a load of 0.0018 cN/dtex for 30 seconds, and mark it at 20 cm, that is, the initial length l.sub.1 of the sample; then load another end with a load of 0.09 cN/dtex for 30 seconds, and measure the position of the marked point, which is the length l.sub.2 of the sample under heavier load; finally remove the load and let the sample retract for 2 minutes, next add a load of 0.0018 cN/dtex for 30 seconds and measure the position of the marked point, which is the recovery length l.sub.3; the shrinkage elongation (CE) and the crimp elastic recovery rate (SR) are calculated as follows:

CE=(l.sub.2−l.sub.1)/l.sub.1;

SR=(l.sub.2−l.sub.3)/(l.sub.2−l.sub.1).

[0036] The trilobal spinneret holes and their distribution on a spinneret in the present invention are shown in FIGS. 1-2; wherein a ratio of angles between centre lines of three leaves from the same trilobal spinneret hole is 1.0:(1.5-3.1):(1.5-3.1); wherein the ratio of lengths of two leaves forming the smallest angle to the length of the other leaf from the same trilobal spinneret hole is 3:3:2; wherein the ratio of the length to the width of the shortest leaf is (1.5-2):1, with the same widths of other two leaves from the same trilobal spinneret hole; wherein the shapes and sizes of three leaves from different trilobal spinneret holes are the same; wherein all the trilobal spinneret holes are distributed in concentric circles, with a center line of the leaf opposite to the smallest angle in each trilobal spinneret hole passing through the center of the circle, and pointing away from the center of the circle. The figures are for illustration only and should not be construed as limiting the present invention.

Example 1

[0037] A method for preparing a degradable polyester fiber is to cool a PET melt with an intrinsic viscosity of 0.6 dL/g by ring-blowing after extruded from a trilobal spinneret hole on a spinneret, and manufacture an FDY according to an FDY process with the PET melt, then the degradable polyester fiber is prepared after a relaxation heat treatment;

[0038] wherein the PET melt is dispersed with 0.03 wt % of doped ZrO.sub.2 powder, wherein the process of doping is evenly mixing the 1 wt % of Mg(NO.sub.3).sub.2 aqueous solution and the 20 wt % of ZrO.sub.2 nitric acid solution in a molar ratio 5:100 of Mg.sup.2+ and Zr.sup.4+; then depositing the mixed solution by dripping in 2 mol/L of ammonia water till pH=9, and washing and drying (at 105° C. for 2 h) the precipitate; after the treatments including a heating at 400° C. for 2 h, a heating at 700° C. for 1 h and a cooling in air, finally calcining the precipitate;

[0039] wherein a ratio of angles between centre lines of three leaves from the same trilobal spinneret hole is 1.0:1.5:1.5; wherein the ratio of lengths of two leaves forming the smallest angle to the length of the other leaf from the same trilobal spinneret hole is 3:3:2; wherein the ratio of the length to the width of the shortest leaf is 1.5:1, with the same widths of other two leaves from the same trilobal spinneret hole; wherein the shapes and sizes of three leaves from different trilobal spinneret holes are the same; wherein all the trilobal spinneret holes are distributed in concentric circles, with a center line of the leaf opposite to the smallest angle in each trilobal spinneret hole passing through the center of the circle, and pointing away from the center of the circle;

[0040] wherein the FDY process involves technological parameters: a spinning temperature of 280° C., a cooling temperature of 20° C., a cooling wind speed of 1.8 m/s, a godet roller 1 speed of 1800 m/min, a godet roller 1 temperature of 85° C., a godet roller 2 speed of 3500 m/min, a godet roller 2 temperature of 160° C., and a winding speed of 3430 m/min;

[0041] wherein the relaxation heat treatment has a temperature of 90° C., and a time of 30 minutes.

[0042] The prepared degradable polyester fiber has a three-dimensional crimp shape, and comprises a plurality of PET monofilaments containing doped ZrO.sub.2 powder in a trilobal cross-section; wherein the degradable polyester fiber comprises mechanical performance indices: a crimp shrinkage of 22%, a crimp stability of 77%, a shrinkage elongation of 56%, and a crimp elastic recovery rate of 75%, a breaking strength of 2.7 cN/dtex, an elongation at break of 50%, a total fineness of 100 dtex, and an intrinsic viscosity drop of 10% after a storage at 25° C. and a R.H. 65% for 60 months.

Example 2

[0043] A method for preparing a degradable polyester fiber is to cool a PET melt with an intrinsic viscosity of 0.62 dL/g by ring-blowing after extruded from a trilobal spinneret hole on a spinneret, and manufacture an FDY according to an FDY process with the PET melt, then the degradable polyester fiber is prepared after a relaxation heat treatment;

[0044] wherein the PET melt is dispersed with 0.03 wt % of doped ZrO.sub.2 powder, wherein the process of doping is evenly mixing the 1 wt % of Mg(NO.sub.3).sub.2 aqueous solution and the 21 wt % of ZrO.sub.2 nitric acid solution in a molar ratio 8:100 of Mg.sup.2+ and Zr.sup.4+; then depositing the mixed solution by dripping in 2 mol/L of ammonia water till pH=9, and washing and drying (at 105° C. for 2 h) the precipitate; after the treatments including a heating at 400° C. for 3 h, a heating at 700° C. for 2 h and a cooling in air, finally calcining the precipitate;

[0045] wherein a ratio of angles between centre lines of three leaves from the same trilobal spinneret hole is 1.0:1.5:1.5; wherein the ratio of lengths of two leaves forming the smallest angle to the length of the other leaf from the same trilobal spinneret hole is 3:3:2; wherein the ratio of the length to the width of the shortest leaf is 1.5:1, with the same widths of other two leaves from the same trilobal spinneret hole; wherein the shapes and sizes of three leaves from different trilobal spinneret holes are the same; wherein all the trilobal spinneret holes are distributed in concentric circles, with a center line of the leaf opposite to the smallest angle in each trilobal spinneret hole passing through the center of the circle, and pointing away from the center of the circle;

[0046] wherein the FDY process involves technological parameters: a spinning temperature of 280° C., a cooling temperature of 21° C., a cooling wind speed of 1.8 m/s, a godet roller 1 speed of 1818 m/min, a godet roller 1 temperature of 93° C., a godet roller 2 speed of 3538 m/min, a godet roller 2 temperature of 163° C., and a winding speed of 3434 m/min;

[0047] wherein the relaxation heat treatment has a temperature of 92° C., and a time of 25 minutes.

[0048] The prepared degradable polyester fiber has a three-dimensional crimp shape, and comprises a plurality of PET monofilaments containing doped ZrO.sub.2 powder in a trilobal cross-section; wherein the degradable polyester fiber comprises mechanical performance indices: a crimp shrinkage of 22%, a crimp stability of 77%, a shrinkage elongation of 57%, and a crimp elastic recovery rate of 75%, a breaking strength of 2.8 cN/dtex, an elongation at break of 50%, a total fineness of 146 dtex, and an intrinsic viscosity drop of 11% after a storage at 25° C. and a R.H. 65% for 60 months.

Example 3

[0049] A method for preparing a degradable polyester fiber is to cool a PET melt with an intrinsic viscosity of 0.61 dL/g by ring-blowing after extruded from a trilobal spinneret hole on a spinneret, and manufacture an FDY according to an FDY process with the PET melt, then the degradable polyester fiber is prepared after a relaxation heat treatment;

[0050] wherein the PET melt is dispersed with 0.03 wt % of doped ZrO.sub.2 powder, wherein the process of doping is evenly mixing the 1 wt % of LiNO.sub.3 aqueous solution and the 25 wt % of ZrO.sub.2 nitric acid solution in a molar ratio 5:100 of Li.sup.+ and Zr.sup.4+; then depositing the mixed solution by dripping in 2 mol/L of ammonia water till pH=9, and washing and drying (at 105° C. for 2 h) the precipitate; after the treatments including a heating at 400° C. for 2 h, a heating at 700° C. for 1 h and a cooling in air, finally calcining the precipitate;

[0051] wherein a ratio of angles between centre lines of three leaves from the same trilobal spinneret hole is 1.0:1.7:1.7; wherein the ratio of lengths of two leaves forming the smallest angle to the length of the other leaf from the same trilobal spinneret hole is 3:3:2; wherein the ratio of the length to the width of the shortest leaf is 1.5:1, with the same widths of other two leaves from the same trilobal spinneret hole; wherein the shapes and sizes of three leaves from different trilobal spinneret holes are the same; wherein all the trilobal spinneret holes are distributed in concentric circles, with a center line of the leaf opposite to the smallest angle in each trilobal spinneret hole passing through the center of the circle, and pointing away from the center of the circle;

[0052] wherein the FDY process involves technological parameters: a spinning temperature of 281° C., a cooling temperature of 23° C., a cooling wind speed of 1.8 m/s, a godet roller 1 speed of 1851 m/min, a godet roller 1 temperature of 93° C., a godet roller 2 speed of 3542 m/min, a godet roller 2 temperature of 166° C., and a winding speed of 3483 m/min;

[0053] wherein the relaxation heat treatment has a temperature of 93° C., and a time of 25 minutes.

[0054] The prepared degradable polyester fiber has a three-dimensional crimp shape, and comprises a plurality of PET monofilaments containing doped ZrO.sub.2 powder in a trilobal cross-section; wherein the degradable polyester fiber comprises mechanical performance indices: a crimp shrinkage of 24%, a crimp stability of 78%, a shrinkage elongation of 57%, and a crimp elastic recovery rate of 75%, a breaking strength of 2.8 cN/dtex, an elongation at break of 49.7%, a total fineness of 143 dtex, and an intrinsic viscosity drop of 12% after a storage at 25° C. and a R.H. 65% for 60 months.

Example 4

[0055] A method for preparing a degradable polyester fiber is to cool a PET melt with an intrinsic viscosity of 0.62 dL/g by ring-blowing after extruded from a trilobal spinneret hole on a spinneret, and manufacture an FDY according to an FDY process with the PET melt, then the degradable polyester fiber is prepared after a relaxation heat treatment;

[0056] wherein the PET melt is dispersed with 0.04 wt % of doped ZrO.sub.2 powder, wherein the process of doping is evenly mixing the 2 wt % of LiNO.sub.3 aqueous solution and the 20 wt % of ZrO.sub.2 nitric acid solution in a molar ratio 8:100 of Li.sup.+ and Zr.sup.4+; then depositing the mixed solution by dripping in 2 mol/L of ammonia water till pH=9, and washing and drying (at 107° C. for 2 h) the precipitate; after the treatments including a heating at 400° C. for 3 h, a heating at 700° C. for 1 h and a cooling in air, finally calcining the precipitate;

[0057] wherein a ratio of angles between centre lines of three leaves from the same trilobal spinneret hole is 1.0:1.9:1.9; wherein the ratio of lengths of two leaves forming the smallest angle to the length of the other leaf from the same trilobal spinneret hole is 3:3:2; wherein the ratio of the length to the width of the shortest leaf is 1.8:1, with the same widths of other two leaves from the same trilobal spinneret hole; wherein the shapes and sizes of three leaves from different trilobal spinneret holes are the same; wherein all the trilobal spinneret holes are distributed in concentric circles, with a center line of the leaf opposite to the smallest angle in each trilobal spinneret hole passing through the center of the circle, and pointing away from the center of the circle;

[0058] wherein the FDY process involves technological parameters: a spinning temperature of 283° C., a cooling temperature of 23° C., a cooling wind speed of 1.9 m/s, a godet roller 1 speed of 1905 m/min, a godet roller 1 temperature of 93° C., a godet roller 2 speed of 3556 m/min, a godet roller 2 temperature of 169° C., and a winding speed of 3492 m/min;

[0059] wherein the relaxation heat treatment has a temperature of 97° C., and a time of 24 minutes.

[0060] The prepared degradable polyester fiber has a three-dimensional crimp shape, and comprises a plurality of PET monofilaments containing doped ZrO.sub.2 powder in a trilobal cross-section; wherein the degradable polyester fiber comprises mechanical performance indices: a crimp shrinkage of 24%, a crimp stability of 79%, a shrinkage elongation of 58%, and a crimp elastic recovery rate of 76%, a breaking strength of 2.8 cN/dtex, an elongation at break of 47.2%, a total fineness of 142 dtex, and an intrinsic viscosity drop of 12% after a storage at 25° C. and a R.H. 65% for 60 months.

Example 5

[0061] A method for preparing a degradable polyester fiber is to cool a PET melt with an intrinsic viscosity of 0.62 dL/g by ring-blowing after extruded from a trilobal spinneret hole on a spinneret, and manufacture an FDY according to an FDY process with the PET melt, then the degradable polyester fiber is prepared after a relaxation heat treatment;

[0062] wherein the PET melt is dispersed with 0.04 wt % of doped ZrO.sub.2 powder, wherein the process of doping is evenly mixing the 1 wt % of Zn(NO.sub.3).sub.2 aqueous solution and the 25 wt % of ZrO.sub.2 nitric acid solution in a molar ratio 6:100 of Zn.sup.2+ and Zr.sup.4+; then depositing the mixed solution by dripping in 2 mol/L of ammonia water till pH=10, and washing and drying (at 108° C. for 2 h) the precipitate; after the treatments including a heating at 400° C. for 2 h, a heating at 700° C. for 2 h and a cooling in air, finally calcining the precipitate;

[0063] wherein a ratio of angles between centre lines of three leaves from the same trilobal spinneret hole is 1.0:1.9:1.9; wherein the ratio of lengths of two leaves forming the smallest angle to the length of the other leaf from the same trilobal spinneret hole is 3:3:2; wherein the ratio of the length to the width of the shortest leaf is 1.8:1, with the same widths of other two leaves from the same trilobal spinneret hole; wherein the shapes and sizes of three leaves from different trilobal spinneret holes are the same; wherein all the trilobal spinneret holes are distributed in concentric circles, with a center line of the leaf opposite to the smallest angle in each trilobal spinneret hole passing through the center of the circle, and pointing away from the center of the circle;

[0064] wherein the FDY process involves technological parameters: a spinning temperature of 284° C., a cooling temperature of 23° C., a cooling wind speed of 2.1 m/s, a godet roller 1 speed of 1905 m/min, a godet roller 1 temperature of 94° C., a godet roller 2 speed of 3572 m/min, a godet roller 2 temperature of 173° C., and a winding speed of 3519 m/min;

[0065] wherein the relaxation heat treatment has a temperature of 101° C., and a time of 23 minutes.

[0066] The prepared degradable polyester fiber has a three-dimensional crimp shape, and comprises a plurality of PET monofilaments containing doped ZrO.sub.2 powder in a trilobal cross-section; wherein the degradable polyester fiber comprises mechanical performance indices: a crimp shrinkage of 25%, a crimp stability of 80%, a shrinkage elongation of 58%, and a crimp elastic recovery rate of 76%, a breaking strength of 2.8 cN/dtex, an elongation at break of 47.2%, a total fineness of 148 dtex, and an intrinsic viscosity drop of 13% after a storage at 25° C. and a R.H. 65% for 60 months.

Example 6

[0067] A method for preparing a degradable polyester fiber is to cool a PET melt with an intrinsic viscosity of 0.65 dL/g by ring-blowing after extruded from a trilobal spinneret hole on a spinneret, and manufacture an FDY according to an FDY process with the PET melt, then the degradable polyester fiber is prepared after a relaxation heat treatment;

[0068] wherein the PET melt is dispersed with 0.05 wt % of doped ZrO.sub.2 powder, wherein the process of doping is evenly mixing the 1 wt % of Zn(NO.sub.3).sub.2 aqueous solution and the 25 wt % of ZrO.sub.2 nitric acid solution in a molar ratio 5:100 of Zn.sup.2+ and Zr.sup.4+; then depositing the mixed solution by dripping in 2 mol/L of ammonia water till pH=10, and washing and drying (at 110° C. for 2 h) the precipitate; after the treatments including a heating at 400° C. for 2 h, a heating at 700° C. for 2 h and a cooling in air, finally calcining the precipitate;

[0069] wherein a ratio of angles between centre lines of three leaves from the same trilobal spinneret hole is 1.0:2.5:2.5; wherein the ratio of lengths of two leaves forming the smallest angle to the length of the other leaf from the same trilobal spinneret hole is 3:3:2; wherein the ratio of the length to the width of the shortest leaf is 2:1, with the same widths of other two leaves from the same trilobal spinneret hole; wherein the shapes and sizes of three leaves from different trilobal spinneret holes are the same; wherein all the trilobal spinneret holes are distributed in concentric circles, with a center line of the leaf opposite to the smallest angle in each trilobal spinneret hole passing through the center of the circle, and pointing away from the center of the circle;

[0070] wherein the FDY process involves technological parameters: a spinning temperature of 284° C., a cooling temperature of 23° C., a cooling wind speed of 2.3 m/s, a godet roller 1 speed of 1946 m/min, a godet roller 1 temperature of 95° C., a godet roller 2 speed of 3576 m/min, a godet roller 2 temperature of 174° C., and a winding speed of 3554 m/min;

[0071] wherein the relaxation heat treatment has a temperature of 101° C., and a time of 21 minutes.

[0072] The prepared degradable polyester fiber has a three-dimensional crimp shape, and comprises a plurality of PET monofilaments containing doped ZrO.sub.2 powder in a trilobal cross-section; wherein the degradable polyester fiber comprises mechanical performance indices: a crimp shrinkage of 25%, a crimp stability of 80%, a shrinkage elongation of 59%, and a crimp elastic recovery rate of 78%, a breaking strength of 3 cN/dtex, an elongation at break of 46.2%, a total fineness of 135 dtex, and an intrinsic viscosity drop of 14% after a storage at 25° C. and a R.H. 65% for 60 months.

Example 7

[0073] A method for preparing a degradable polyester fiber is to cool a PET melt with an intrinsic viscosity of 0.63 dL/g by ring-blowing after extruded from a trilobal spinneret hole on a spinneret, and manufacture an FDY according to an FDY process with the PET melt, then the degradable polyester fiber is prepared after a relaxation heat treatment;

[0074] wherein the PET melt is dispersed with 0.05 wt % of doped ZrO.sub.2 powder, wherein the process of doping is evenly mixing the 1 wt % of Mg(NO.sub.3).sub.2 aqueous solution and the 24 wt % of ZrO.sub.2 nitric acid solution in a molar ratio 8:100 of Mg.sup.2+ and Zr.sup.4+; then depositing the mixed solution by dripping in 2 mol/L of ammonia water till pH=10, and washing and drying (at 110° C. for 3 h) the precipitate; after the treatments including a heating at 400° C. for 3 h, a heating at 700° C. for 1 h and a cooling in air, finally calcining the precipitate;

[0075] wherein a ratio of angles between centre lines of three leaves from the same trilobal spinneret hole is 1.0:3.1:3.1; wherein the ratio of lengths of two leaves forming the smallest angle to the length of the other leaf from the same trilobal spinneret hole is 3:3:2; wherein the ratio of the length to the width of the shortest leaf is 2:1, with the same widths of other two leaves from the same trilobal spinneret hole; wherein the shapes and sizes of three leaves from different trilobal spinneret holes are the same; wherein all the trilobal spinneret holes are distributed in concentric circles, with a center line of the leaf opposite to the smallest angle in each trilobal spinneret hole passing through the center of the circle, and pointing away from the center of the circle;

[0076] wherein the FDY process involves technological parameters: a spinning temperature of 285° C., a cooling temperature of 24° C., a cooling wind speed of 2.3 m/s, a godet roller 1 speed of 1992 m/min, a godet roller 1 temperature of 95° C., a godet roller 2 speed of 3619 m/min, a godet roller 2 temperature of 179° C., and a winding speed of 3581 m/min;

[0077] wherein the relaxation heat treatment has a temperature of 119° C., and a time of 20 minutes.

[0078] The prepared degradable polyester fiber has a three-dimensional crimp shape, and comprises a plurality of PET monofilaments containing doped ZrO.sub.2 powder in a trilobal cross-section; wherein the degradable polyester fiber comprises mechanical performance indices: a crimp shrinkage of 26%, a crimp stability of 81%, a shrinkage elongation of 62%, and a crimp elastic recovery rate of 80%, a breaking strength of 3 cN/dtex, an elongation at break of 40.1%, a total fineness of 136 dtex, and an intrinsic viscosity drop of 15% after a storage at 25° C. and a R.H. 65% for 60 months.

Example 8

[0079] A method for preparing a degradable polyester fiber is to cool a PET melt with an intrinsic viscosity of 0.66 dL/g by ring-blowing after extruded from a trilobal spinneret hole on a spinneret, and manufacture an FDY according to an FDY process with the PET melt, then the degradable polyester fiber is prepared after a relaxation heat treatment;

[0080] wherein the PET melt is dispersed with 0.06 wt % of doped ZrO.sub.2 powder, wherein the process of doping is evenly mixing the 2 wt % of Mg(NO.sub.3).sub.2 aqueous solution and the 25 wt % of ZrO.sub.2 nitric acid solution in a molar ratio 8:100 of Mg.sup.2+ and Zr.sup.4+; then depositing the mixed solution by dripping in 2 mol/L of ammonia water till pH=10, and washing and drying (at 110° C. for 3 h) the precipitate; after the treatments including a heating at 400° C. for 3 h, a heating at 700° C. for 2 h and a cooling in air, finally calcining the precipitate;

[0081] wherein a ratio of angles between centre lines of three leaves from the same trilobal spinneret hole is 1.0:3.1:3.1; wherein the ratio of lengths of two leaves forming the smallest angle to the length of the other leaf from the same trilobal spinneret hole is 3:3:2; wherein the ratio of the length to the width of the shortest leaf is 2:1, with the same widths of other two leaves from the same trilobal spinneret hole; wherein the shapes and sizes of three leaves from different trilobal spinneret holes are the same; wherein all the trilobal spinneret holes are distributed in concentric circles, with a center line of the leaf opposite to the smallest angle in each trilobal spinneret hole passing through the center of the circle, and pointing away from the center of the circle;

[0082] wherein the FDY process involves technological parameters: a spinning temperature of 285° C., a cooling temperature of 25° C., a cooling wind speed of 2.3 m/s, a godet roller 1 speed of 2000 m/min, a godet roller 1 temperature of 95° C., a godet roller 2 speed of 3700 m/min, a godet roller 2 temperature of 180° C., and a winding speed of 3610 m/min;

[0083] wherein the relaxation heat treatment has a temperature of 120° C., and a time of 20 minutes.

[0084] The prepared degradable polyester fiber has a three-dimensional crimp shape, and comprises a plurality of PET monofilaments containing doped ZrO.sub.2 powder in a trilobal cross-section; wherein the degradable polyester fiber comprises mechanical performance indices: a crimp shrinkage of 26%, a crimp stability of 81%, a shrinkage elongation of 62%, and a crimp elastic recovery rate of 80%, a breaking strength of 3 cN/dtex, an elongation at break of 40%, a total fineness of 150 dtex, and an intrinsic viscosity drop of 16% after a storage at 25° C. and a R.H. 65% for 60 months.