Method for improving crimp shrinkage of polylactic acid ultra-high elastic fiber

Abstract

The invention discloses a method for improving the crimp shrinkage rate of polylactic acid ultrahigh-elastic fibers, and belongs to the technical field of fibers. Two polylactic acid POYs sequentially pass through a raw yarn frame, a first roller, a deformation hot box and a cooling plate and then are input into a false twister to be twisted in the same direction, two fibers output from the false twister are input into the same second roller together to be plied, plied tows sequentially pass through a network nozzle, an auxiliary roller, a shaping hot box and a feeding roller and then are subjected to oiling and winding treatment, and the polylactic acid POYs are obtained. The ultrahigh-elasticity fiber is prepared. The finished product fiber formed by stranding and elasticizing the two strands of yarns can be a single-strand yarn elasticized fiber, so that the crimp shrinkage rate of the polylactic acid ultrahigh-elastic fiber is improved, and the subsequent dyeing quality risk is overcome.

Description

Technical Field

[0001] The present invention relates to the field of fiber technology, and more particularly to a method for improving the curling shrinkage rate of polylactic acid ultra-elastic fiber. Background Art

[0002] With rising living standards, people's demands for quality in clothing are increasing, particularly in terms of softness and stretch. Fiber softness and stretch are primarily measured by crimp shrinkage (CC), and current texturing processes primarily increase the CC value of ultra-high-stretch fibers by adjusting the texturing speed, draw ratio (DR), and D / Y ratio. However, when consumers demand even higher CC values ​​for ultra-high-stretch yarns, such as a CC of 30% or higher for 83dtex / 72f ultra-high-stretch fibers, current single-strand processing methods struggle to meet these requirements. Even with reduced texturing speeds from 700m / min to 550m / min, DR from 1.72 to 1.63, and D / Y ratio from 1.72 to 1.75, CC values ​​still fall below 30%. This results in reduced production and increased energy consumption, failing to meet customer expectations. Furthermore, the reduction in DR from 1.72 to 1.63 results in incomplete drafting of the fibers, which in turn poses risks to dyeing quality in subsequent weaving processes. Therefore, alternative solutions are urgently needed. Summary of the Invention

[0003] The object of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a method for improving the curl shrinkage rate of polylactic acid ultra-high elastic fiber. The finished fiber formed by twisting and stretching two strands of yarn can be indistinguishable from a single-strand stretched fiber, thereby improving the curl shrinkage rate of the polylactic acid ultra-high elastic fiber and overcoming the quality risk of subsequent dyeing.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for improving the crimp shrinkage of polylactic acid ultra-high elastic fiber comprises the following steps: two polylactic acid POY yarns are sequentially passed through a raw yarn rack, a roller, a deformation hot box, and a cooling plate, and then fed into a false twister for co-directional twisting; the two fibers respectively exiting the false twister are fed together into the same second roller for plying; the plying yarn bundles are sequentially passed through a network nozzle, an auxiliary roller, a setting hot box, and a feeding roller, and then subjected to oiling and winding treatment to produce ultra-high elastic fiber.

[0006] The present invention is further configured such that the temperatures of the two deformation hot boxes are both 170-175° C., and the two setting hot boxes are both closed.

[0007] The present invention is further configured such that the twisting tension of the two false twisters is 17.5-18.2N, and the untwisting tension is 27.4-28.5N.

[0008] The present invention is further configured such that the stretching ratio is 1.72-1.74.

[0009] The present invention is further configured such that the processing speed is 690-720 m / min.

[0010] The present invention is further configured such that the D / Y ratio is 1.71-1.73.

[0011] The present invention is further configured such that the network pressure is 0.12 MPa.

[0012] The present invention is further configured such that the oiling rate is 3-3.5%.

[0013] The present invention is further configured such that the winding tension is 12.5-13.4N.

[0014] In summary, the present invention has the following beneficial effects:

[0015] The present invention adopts a bidirectional plying process [two identical polylactic acid POY precursor yarns (with a fineness half that of a single strand of polylactic acid POY precursor yarn used in conventional methods for preparing ultra-high elastic fiber) are respectively twisted in the same direction in two false twisters, and then plyed in the same two rollers before being drafted and shaped together] for preparation. The two yarns are well-coordinated and not easily separated, achieving a realistic effect (if the finished fiber mesh is not carefully observed or the finished fiber dots are broken up, the naked eye cannot detect that the two yarns are plyed together, and it would be mistaken for a single strand of yarn that has been stretched). This not only improves the curl shrinkage rate of the polylactic acid ultra-high elastic fiber, but also effectively overcomes the quality risks of subsequent dyeing. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the appearance of the fiber prepared in Example 1;

[0017] Figure 2 This is the appearance of the fiber prepared in Comparative Example 1. DETAILED DESCRIPTION

[0018] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0019] The method for improving the crimp shrinkage of polylactic acid ultra-elastic fiber of the present invention comprises the following steps: two identical polylactic acid POY yarns are sequentially passed through a yarn rack, a roller, a texturing hot box, and a cooling plate, and then respectively fed into a false twister for co-directional twisting (i.e., one polylactic acid POY yarn is processed through the yarn rack, a roller, a texturing hot box, a cooling plate, and a false twister, while the other polylactic acid POY yarn is also processed through the yarn rack, a roller, a texturing hot box, a cooling plate, and a false twister, and the processing methods of each step are the same); the two fibers respectively exiting the false twister are simultaneously fed into the same two rollers for plying; the ply-plying yarn bundles are sequentially passed through a network nozzle, an auxiliary roller, a setting hot box, and a feed roller, and then subjected to oiling and winding processes to produce ultra-elastic fiber.

[0020] During preparation, the temperature of the two deformation hot boxes is 170-175°C, and the two setting hot boxes are closed; the twisting tension of the two false twisters is 17.5-18.2N, and the untwisting tension is 27.4-28.5N; the stretching ratio is 1.72-1.74; the processing speed is 690-720m / min; the D / Y ratio is 1.71-1.73; the network pressure is 0.12MPa; the oiling rate is 3-3.5%; and the winding tension is 12.5-13.4N.

[0021] Example 1

[0022] Two 73dtex / 36f polylactic acid POY yarns are sequentially passed through the raw yarn rack, a roller, a texturing hot box, and a cooling plate, and then respectively input into the false twister for co-directional twisting. The two fibers coming out of the false twister are fed into the same two rollers for plying. After plying, the tows are sequentially passed through the network nozzle, auxiliary roller, setting hot box, and feeding roller, and then oiled and wound to produce ultra-high elastic fiber. Among them, the temperature of the two texturing hot boxes is 170℃, and the two setting hot boxes are both closed; the twisting tension of the two false twisters is 18N, and the untwisting tension is 28N; the draw ratio is 1.735; the processing speed is 700m / min; the D / Y ratio is 1.72; the network pressure is 0.12MPa; the oiling rate is 3.5%; and the winding tension is 13N.

[0023] Comparative Example 1: Preparation of ultra-high elastic yarn using conventional process

[0024] A 136 dtex / 72 f polylactic acid POY yarn (the breaking strength of the polylactic acid POY yarn is 2.6 cn / dtex, same as that of the 73 dtex / 36 f polylactic acid POY yarn of Example 1) was sequentially passed through a yarn guide, a first roller, a texturing heat box, a cooling plate, a false twister, a second roller, a network nozzle, an auxiliary roller, a setting heat box, a feed roller, and then was subjected to oiling and winding treatment to produce an ultrahigh elastic fiber of the same linear density specification as Example 1. Different from Example 1, in this comparative example, the temperature of the texturing heat box was 170°C, and the setting heat box was closed; the twisting tension of the false twister was 30 N, and the untwisting tension was 23 N; the draw ratio was 1.63; the processing speed was 550 m / min; the D / Y ratio was 1.75; the network pressure was 0.12 MPa; the oiling rate was 3.5%; and the winding tension was 13 N. It was found through experimental research that the process parameters of this comparative example were the optimal parameters for preparing an 83 dtex / 72 f ultrahigh elastic fiber from a 136 dtex / 72 f polylactic acid PLA yarn.

[0025] The fibers prepared in Example 1 and Comparative Example 1 were tested for performance (the breaking strength and elongation at break were tested in accordance with GB / T 14344-2022 “Chemical Fiber Filament Tensile Property Test Method”; the oil content was tested in accordance with GB / T 6504-2017 “Chemical Fiber Oil Content Test Method”; the boiling water shrinkage was tested in accordance with GB / T 6505-2017 “Chemical Fiber Filament Thermal Shrinkage Test Method”; the network degree was tested in accordance with the provisions of FZ / T 50001-2016 “Synthetic Fiber Filament Network Degree Test Method”; the crimp shrinkage was tested in accordance with GB / T 6506-2017 “Synthetic Fiber Textured Yarn Crimp Performance Test Method”; and the fiber torque (i.e., twist) was tested using a direct counting method: the two ends of the ultrahigh elastic fiber were clamped on a twist tester, one end was fixed, and the other end was rotated around the axis in the untwisting direction until the single fibers in the ultrahigh elastic fiber were completely flattened, and the number of twists removed was the number of twists in the length of the ultrahigh elastic fiber sample). The test results are shown in Table 1. As shown in Table 1, the crimp shrinkage (CC index) of the two PLA yarns after being twisted in the same direction and then plied increased significantly, which met the customer's requirement for a CC value of more than 30%.

[0026] Table 1

[0027]

[0028] The dyeing M rate (referring to GB / T 6508-2015 "Test Method for Dyeing Evenness of Polyester Filament") and AA rate [dyeing AA rate = ((weight of fibers with dyeing evenness gray card grade ≥ 4.5) / total weight of all dyed fibers) × 100%; dyeing evenness gray card grade: refer to FZ / T 50008 Test Method for Dyeing Evenness of Nylon Filament] of the fibers prepared in Example 1 and Comparative Example 1 were tested respectively. The results showed that the dyeing M rate of the fibers prepared in Example 1 was 98%, and the AA rate reached over 95%. However, the dyeing M rate of the fibers prepared in Comparative Example 1 was significantly lower, reaching 85%, and the AA rate was only 80%. At the same time, due to insufficient single-strand drafting of the fibers in Comparative Example 1, tight spots were easily generated, resulting in tight twist and obvious color difference in the fibers. In addition, warp willows in the fabric caused quality problems.

[0029] The fibers prepared in Example 1 and Comparative Example 1 were made into fabrics using the same process, and it was found that the planar effects of the two fabrics were almost the same.

[0030] Comparative Example 2

[0031] Fibers were prepared as in Example 1, but the processing speed was set at 650 m / min.

[0032] Comparative Example 3

[0033] Fibers were prepared according to the method of Example 1, except that the temperature of both deformation ovens was set to 163°C.

[0034] Comparative Example 4

[0035] Fibers were prepared according to the method of Example 1, except that the draw ratio was set to 1.69.

[0036] Comparative Example 5

[0037] Fibers were prepared as in Example 1, but with a D / Y ratio of 1.75.

[0038] The performance tests of the fibers prepared in Comparative Examples 2 to 5 were conducted respectively, and it was found that their curl shrinkage rates were between 20-28%, which could not reach above 30%. The fabric dyeing M rate was between 85-95%, and the AA rate was between 80-90%. The dyeing was uneven and the color difference was obvious.

[0039] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for increasing the crimp shrinkage of polylactic acid ultra-elastic fiber, characterized in that: Two polylactic acid POY yarns are passed through the raw yarn rack, a roller, a deformation hot box, and a cooling plate in sequence, and then input into the false twister for co-directional twisting. The two fibers coming out of the false twister are input into the same second roller for plying. After plying, the yarn bundles are passed through the network nozzle, auxiliary roller, setting hot box, and feeding roller in sequence, and then oiled and wound to produce ultra-high elastic fiber.

2. The method for improving the crimp shrinkage of polylactic acid ultra-elastic fiber according to claim 1, characterized in that: The temperature of the two deformation hot boxes is 170-175℃, and the two setting hot boxes are closed.

3. The method for improving the crimp shrinkage of polylactic acid ultra-elastic fiber according to claim 1, characterized in that: The twisting tension of the two false twisters is 17.5-18.2N, and the untwisting tension is 27.4-28.5N.

4. The method for improving the crimp shrinkage of polylactic acid ultra-elastic fiber according to claim 1, characterized in that: The stretching ratio is 1.72-1.

74.

5. The method for improving the crimp shrinkage of polylactic acid ultra-elastic fiber according to claim 1, characterized in that: The processing speed is 690-720m / min.

6. The method for improving the crimp shrinkage of polylactic acid ultra-elastic fiber according to claim 1, characterized in that: The D / Y ratio is 1.71-1.

73.

7. The method for improving the crimp shrinkage of polylactic acid ultra-elastic fiber according to claim 1, characterized in that: The network pressure is 0.12MPa.

8. The method for improving the crimp shrinkage of polylactic acid ultra-elastic fiber according to claim 1, characterized in that: The oiling rate is 3-3.5%.

9. The method for improving the crimp shrinkage of polylactic acid ultra-elastic fiber according to claim 1, characterized in that: The winding tension is 12.5-13.4N.

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