UHMWPE dry spinning process and fiber preparation method

Abstract

The application provides a new UHMWPE dry spinning process and fiber preparation method, which greatly shortens the dry spinning process flow and reduces the operation cost of the device on the basis of the existing dry spinning technology, improves the production efficiency of the device on the basis of ensuring the fiber quality. Mainly including the preparation unit of nascent gel wet yarn and the subsequent multi-stage high-drawing unit; the preparation unit of nascent gel wet yarn comprises the following steps: the gel melt of UHWMPE resin is extruded at high speed and high pressure through the spinneret plate provided with an inverted cone type spinneret hole, is gathered, enters the condensing bath tank provided with a gathering roller and a godet roller below the spinneret plate, and after the godet roller and the godet roller, enters the multi-stage high-drawing unit through the multi-roller drawing machine; the multi-stage high-drawing unit comprises the following steps: multi-stage drawing is carried out through at least three steam azeotropic drawing heat boxes with different temperatures and pressures; the gathering roller, the godet roller and the condensing bath tank can move up and down.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, especially the technology of dry spinning for preparing ultra-high molecular weight polyethylene fibers, specifically to process parameters and equipment in the fiber spinning process and ultra-high molecular weight polyethylene fibers. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) fiber is also known as high-strength, high-modulus polyethylene fiber. Currently, the processing and preparation of this fiber has been industrialized. The more mature process routes are dry spinning route and wet spinning route, depending on the raw material solvent used.

[0003] Internationally, the wet spinning route is represented by Honeywell's Dyneema® in the United States. Its process involves using low-volatile solvents (mineral oil, white oil, etc.) to prepare ultra-high molecular weight polyethylene gel fibers. After extrusion from the spinneret, the gel fibers are solidified in a water bath (or a mixed bath of water and ethylene glycol, etc.) to obtain wet gel fibers containing low-volatile solvents. This wet gel fiber is then subjected to multi-stage extraction using a high-volatile extractant and a continuous extraction device to displace the low-volatile solvents, yielding the gel fibers (the mixture of extractant, solvent, and water is collected and sent to a distillation unit for separation and recovery). The extractant in the gel fibers undergoes continuous multi-stage drying to fully vaporize and escape, resulting in dry gel fibers. These dry fibers are then subjected to high-ratio drawing to obtain high-strength, high-modulus polyethylene fibers. In China, this fiber preparation technology, developed by Donghua University, has been industrialized in over a dozen companies, including Beijing Tongyi, Hunan Zhongtai, Zhejiang Dacheng, Shandong Aidi, and Beijing Weiya.

[0004] Internationally, the dry spinning route is represented by Dyneema® from DSM in the Netherlands. This method uses a highly volatile decahydronaphthalene solvent to prepare the spinning solution for ultra-high molecular weight polyethylene (UHMWPE). After the spinning solution is extruded from the spinneret, the decahydronaphthalene vaporizes and escapes, resulting in dry gel-fibers. These fibers are then subjected to high-ratio drawing to obtain high-strength, high-modulus polyethylene fibers. This process was developed relatively late in China. In 2008, Yizheng Chemical Fiber (utilizing the first-generation product technology from this project, developed in cooperation with the applicant) built and put into operation the first 300t / a high-performance polyethylene fiber dry spinning industrial plant. Currently, its capacity has reached 3300 tons, making it the only company in China using dry spinning to produce UHMWPE fibers.

[0005] In the large-scale trials and industrial-scale implementation of dry spinning, the preparation of low-entanglement nascent gel wet filaments, the amount of solvent evaporation on the filament surface during high-ratio drawing of the filament bundle, and the spinning speed all have a significant impact on the fiber performance indicators. In the technology provided by Chinese Patent CN110079881B, the fibers are not subjected to high-ratio drawing in a constant-temperature freezing chamber or a sealed hot chamber. The gel precursor filament still contains spinning solvent containing no less than 30% of the precursor filament weight, which is detrimental to the drawing process in subsequent steps, and the residual solvent in the fiber also limits its application range. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a new UHMWPE dry spinning process and fiber preparation method, which greatly shortens the dry spinning process flow, reduces the operating cost of the equipment, and improves the production efficiency of the equipment while ensuring fiber quality, based on the existing dry spinning technology.

[0007] The main technical solution of this invention is a UHMWPE dry spinning process, characterized in that it includes a primary gel wet filament preparation unit and a subsequent multi-stage high-ratio drawing unit; the primary gel wet filament preparation unit includes: UHMWPE resin gel melt being extruded at high speed and high pressure through a spinneret with inverted conical spinnerets, bundled, and then entering a condensation bath located below the spinneret and equipped with a bundle roller and a guide roller; after exiting the condensation bath, it enters the multi-stage high-ratio drawing unit through a multi-roller drawing machine; the multi-stage high-ratio drawing unit includes: at least three steam azeotropic drawing hot boxes with different temperatures and pressures for multi-stage drawing; the bundle roller, guide roller, and condensation bath can all move up and down.

[0008] Furthermore, after the prepared raw material liquid has swollen and homogenized, it is used to form a gel melt through a twin-screw extruder. The gel melt, after passing through a booster pump and a metering pump, enters the nascent gel wet filament preparation unit. The pressure of the gel melt exiting the booster pump is 2.0-6.5 MPa, preferably 3.0-5.5 MPa, and more preferably 3.5-4.5 MPa.

[0009] Furthermore, the inverted conical spinneret is a circular hole, comprising upper and lower sections, the upper section being an inverted conical shape and the lower section being a straight cylindrical shape; the ratio of D / d in the external dimensions of the inverted conical spinneret is 3:1~15:1, preferably 5:1-12:1, more preferably 6:1-8:1, H / h is 2:1~10:1, preferably 3:1-8:1, more preferably 4:1-6:1; the ratio of (H+h) / d is 15:1-40:1, preferably 18:1-35:1, more preferably 20:1-30:1, where D is the upper diameter, d is the lower diameter, H is the height of the upper inverted conical section, and h is the height of the lower straight cylindrical section.

[0010] Furthermore, the extrusion rate of the nascent gel wet filaments exiting the inverted conical spinneret is 5-30 m / min, preferably 10-20 m / min, and more preferably 10-15 m / min.

[0011] Furthermore, the residence time of the nascent gel wet filaments exiting the inverted conical spinneret in the condensation bath is 5-50s, preferably 10-30s, and more preferably 10-20s.

[0012] Furthermore, the multi-roller drawing machine is a five-roller drawing machine with a drawing ratio of 1-3 times, preferably 1-2 times, and more preferably 1-1.5 times.

[0013] Furthermore, the nascent gel wet filaments are subjected to three or four stages of stretching through three or four steam azeotropic stretching chambers.

[0014] Furthermore, the extrusion speed of the last stage of multi-stage drawing is 150-600 m / min, preferably 200-500 m / min, and more preferably 300-400 m / min.

[0015] This invention also provides a method for preparing UHMWPE fibers. The raw yarn prepared by the above-mentioned dry spinning process of this invention is stored in a static room for 24-48 hours and then sent to the post-spinning unit for multi-stage hot drawing to prepare ultra-high molecular weight polyethylene fine denier fibers of different specifications. The yarn bundle is then wound on a winding machine to obtain the finished UHMWPE fiber.

[0016] Preferably, the residual solvent content in the finished fiber is 5-50 ppm, more preferably 10-30 ppm, and even more preferably 10-20 ppm.

[0017] Generally, the specific implementation process of the UHMWPE dry spinning process provided by the present invention is briefly described as follows.

[0018] (1) After pre-swelling UHWMPE resin with a molecular weight range of 2 million to 4 million with solvent decahydronaphthalene at a rate of not less than 10% of the total mass of raw materials, it is fed into a parallel twin-screw extruder for further swelling, dissolution and conveying to form a gel melt. The pressure of the melt after passing through the booster pump and metering pump is maintained at 3.5-4.5 MPa. It is extruded at high speed and high pressure at 10-15 m / min through an inverted conical spinneret (11) with a length-to-diameter ratio [(H+h) / d] of 20:1. The nascent wet gel filaments from the conical spinneret are bundled and sent to a five-roller drawing machine. The spinneret drawing ratio of the filaments in this process is 1.0-1.5 times. At the same time, the residence time of the filament bundle in the condensation bath below the spinneret does not exceed 10-20 s. The residence time of the filament bundle can be adjusted by the up-and-down movable bundling roller (3) and guide roller (4) set in the condensation bath.

[0019] (2) The nascent gel wet filaments from the five-roller drawing machine are drawn in at least three stages in a steam azeotropic heating box, wherein the ratio of the first stage drawing is not higher than 10 times, the ratio of the second stage drawing is not higher than 30 times, the ratio of the third stage drawing is not higher than 5 times, and the speed of the filament bundle exiting the third stage azeotropic drawing heating box is 300-400 m / min.

[0020] The method for preparing UHMWPE fibers provided by the present invention, after the nascent filaments are subjected to multi-stage stretching in a steam azeotropic heating box and then subjected to drying heating box and post-spinning stretching treatment, the residual solvent content in the finished fiber is 5-50ppm, preferably 10-30ppm, and more preferably 10-20ppm.

[0021] Beneficial Effects: This invention significantly shortens the spinning process and reduces operating costs compared to existing dry spinning technology, while improving production efficiency while ensuring fiber quality. Improved spinneret and spinneret orifice design reduces shearing forces during high-pressure gel fluid transport, thus mitigating molecular weight degradation caused by mechanical forces during spinning. Higher spinneret extrusion speeds and lower nozzle drafting ratios ensure that the low entanglement state of the viscoelastic gel exiting the spinneret is not damaged by excessive drafting. Multi-stage drafting within the steam azeotropic heating chamber ensures high fiber drafting ratios, resulting in high strength and high modulus characteristics. This invention significantly shortens the original process flow, effectively improves the fineness uniformity of UHMWPE fibers prepared by dry spinning, and greatly reduces equipment operating costs. Attached Figure Description

[0022] Figure 1 This is a partial flowchart of the dry spinning process provided in the embodiments of the present invention.

[0023] Figure 2 This is a top view of the spinneret in the embodiment.

[0024] Figure 3 This is a schematic cross-sectional view of the spinneret in the embodiment.

[0025] Figure 4 This is an enlarged schematic diagram of the spinneret hole in the embodiment.

[0026] In the diagram, 1-spinneret; 2-condensation bath; 3-bundling roller; 4-guide roller; 5-drawing machine; 11-spinneret orifice. Implementation

[0027] The present invention will now be described in detail with reference to embodiments and accompanying drawings. Example

[0028] (I) A Reference for a Dry Spinning Process of UHMWPE Figure 1The system mainly includes a primary gel wet filament preparation unit (A) and a subsequent multi-stage high-ratio drawing unit (B). The primary gel wet filament preparation unit (A) mainly includes a spinneret 1 with inverted conical spinneret holes 11, a condenser bath 2 with a bundle roller 3 and a guide roller 4 located below the spinneret 1, and a five-roller drawing machine 5 located after the condenser bath 2; the multi-stage high-ratio drawing unit (B) mainly includes three steam azeotropic drawing heat boxes (B1, B2, B3) with different temperatures and pressures; the bundle roller 3, the guide roller 4, and the condenser bath 2 can all move up and down.

[0029] (II) Dry spinning process: UHWMPE resin with a viscosity-average molecular weight range of 2 million-4 million is pre-swelled with solvent decahydronaphthalene and other additives at an amount of not less than 10% of the total raw material mass. The resin is then fed into a parallel twin-screw extruder for further swelling, dissolution and conveying to form a gel melt. The pressure of the melt after passing through a booster pump and a metering pump is maintained at 3.5-4.5 MPa. After being extruded at high speed and high pressure through an inverted conical spinneret with a length-to-diameter ratio [(H+h) / d]20:1, the melt is bundled and briefly enters a condensation bath located below the spinneret. It then enters a steam azeotropic heat box multi-stage drawing unit (B) through a five-roll drawing machine for three-stage drawing. The filament bundle exiting the azeotropic heat box passes through a five-roll drawing machine and enters a drying heat box for drying. Finally, it is wound to obtain ultra-high molecular weight polyethylene fiber filament.

[0030] (III) Fiber preparation process: After the above-mentioned raw yarn is stored in the static room for 24-48 hours, it is sent to the post-spinning machine for multi-stage hot stretching to prepare ultra-high molecular weight polyethylene fine denier fibers of different specifications. The yarn bundle is then wound on a winding machine to obtain UHMWPE fiber finished products.

[0031] The data in the examples were obtained after the device operated stably for 4-12 hours under the set process parameters. The fineness and mechanical properties of the finished fiber were determined according to the national standard GB / T19975-2005. Example 1

[0032] UHWMPE resin with a viscosity-average molecular weight range of 2 million to 4 million was pre-swelled with solvent decahydronaphthalene and other additives at an amount not less than 10% of the total raw material mass. The mixture was then fed into a parallel twin-screw extruder for further swelling, dissolution, and transport to form a gel melt. The melt pressure was maintained at 3.5 ± 0.1 MPa after passing through a booster pump and a metering pump. The melt was then extruded through an inverted conical spinneret (11) with an aspect ratio [(H+h) / d] of 22 at a speed of 12 m / min in a condenser bath (2). The residence time is 10±1s, the nozzle draw ratio of the gel filament bundle is 1, and it enters the steam azeotropic heat box multi-stage draw unit (B) through the five-roller drawer (5) for three-stage draw. The draw ratio in the azeotropic heat box (B1) is 1.1 times, the draw ratio in the azeotropic heat box (B2) is 10 times, and the draw ratio in the azeotropic heat box (B3) is 2.3 times. The filament bundle exiting the azeotropic heat box (B3) passes through the five-roller drawer at a linear speed of 300m / min, enters the drying heat box for drying, and is then wound to obtain ultra-high molecular weight polyethylene fiber filament.

[0033] The precursor fibers obtained from the dry spinning process for preparing UHMWPE of the present invention are stored in a static room for 24 hours and then sent to the post-spinning stage. They are then subjected to hot drawing under the following conditions: first-stage hot drawing temperature 143°C, draw ratio 3; second-stage hot drawing temperature 147°C, draw ratio 5; and third-stage hot drawing temperature 148°C, draw ratio 1.1. Ultra-high molecular weight polyethylene fine denier fibers are prepared. The fiber bundles are then wound on a winding machine to obtain finished UHMWPE fibers. Samples are taken for relevant mechanical property testing and analysis. The results are shown in Table 1. Example 2

[0034] UHWMPE resin with a viscosity-average molecular weight range of 2 million to 4 million was pre-swelled with solvent decahydronaphthalene and other additives at an amount not less than 10% of the total raw material mass. The mixture was then fed into a parallel twin-screw extruder for further swelling, dissolution, and transport to form a gel melt. The melt pressure was maintained at 3.7 ± 0.1 MPa after passing through a booster pump and a metering pump. The melt was then extruded through an inverted conical spinneret (11) with an aspect ratio [(H+h) / d] of 22 at a speed of 15 m / min in a condenser bath (2). The residence time is 8±1s, the nozzle draw ratio of the gel filament bundle is 1.2, and it enters the steam azeotropic heat box multi-stage draw unit (B) through the five-roller drawer (5) for three-stage draw. The draw ratio in the azeotropic heat box (B1) is 1.2 times, the draw ratio in the azeotropic heat box (B2) is 12 times, and the draw ratio in the azeotropic heat box (B3) is 1.7 times. The filament bundle exiting the azeotropic heat box (B3) passes through the five-roller drawer at a linear speed of 300m / min, enters the drying heat box for drying, and is then wound to obtain ultra-high molecular weight polyethylene fiber filament.

[0035] The precursor fibers obtained from the dry spinning process for preparing UHMWPE of the present invention are stored in a static room for 24 hours and then sent to the post-spinning stage. They are then subjected to hot drawing under the following conditions: first-stage hot drawing temperature 142°C, draw ratio 2; second-stage hot drawing temperature 146°C, draw ratio 6; and third-stage hot drawing temperature 148°C, draw ratio 1.2. Ultra-high molecular weight polyethylene fine denier fibers are prepared. The fiber bundles are then wound on a winding machine to obtain finished UHMWPE fibers. Samples are taken for relevant mechanical property testing and analysis. The results are shown in Table 1. Example 3

[0036] UHWMPE resin with a viscosity-average molecular weight range of 2 million to 4 million was pre-swelled with solvent decahydronaphthalene and other additives at an amount not less than 10% of the total raw material mass. The mixture was then fed into a parallel twin-screw extruder for further swelling, dissolution, and transport to form a gel melt. The melt pressure was maintained at 4.0 ± 0.1 MPa after passing through a booster pump and a metering pump. The melt was then extruded through an inverted conical spinneret (11) with an aspect ratio [(H+h) / d] of 22 at a speed of 14 m / min in a condenser bath (2). The residence time is 9±1s, the nozzle draw ratio of the gel filament bundle is 1.1, and it enters the steam azeotropic heat box multi-stage draw unit (B) through the five-roller drawer (5) for three-stage draw. The draw ratio in the azeotropic heat box (B1) is 1.0 times, the draw ratio in the azeotropic heat box (B2) is 14 times, and the draw ratio in the azeotropic heat box (B3) is 1.8 times. The filament bundle exiting the azeotropic heat box (B3) passes through the five-roller drawer at a linear speed of 350m / min, enters the drying heat box for drying, and is then wound to obtain ultra-high molecular weight polyethylene fiber filament.

[0037] The precursor fibers obtained from the dry spinning process for preparing UHMWPE of the present invention are stored in a static room for 24 hours and then sent to the post-spinning stage. They are then subjected to hot drawing under the following conditions: first-stage hot drawing temperature 140°C, first-stage drawing ratio 1.5 times; second-stage hot drawing temperature 143°C, drawing ratio 4 times; third-stage hot drawing temperature 147°C, drawing ratio 1.5 times. Ultra-high molecular weight polyethylene fine denier fibers are prepared. The fiber bundles are then wound on a winding machine to obtain finished UHMWPE fibers. Samples are taken for relevant mechanical property testing and analysis. The results are shown in Table 1. Example 4

[0038] UHWMPE resin with a viscosity-average molecular weight range of 2 million to 4 million was pre-swelled with solvent decahydronaphthalene and other additives at an amount not less than 10% of the total raw material mass. The mixture was then fed into a parallel twin-screw extruder for further swelling, dissolution, and transport to form a gel melt. The melt pressure was maintained at 4.2 ± 0.1 MPa after passing through a booster pump and a metering pump. The melt was then extruded through an inverted conical spinneret (11) with an aspect ratio [(H+h) / d] of 28 at a speed of 16 m / min in a condenser bath (2). The residence time is 7±1s, the nozzle draw ratio of the gel filament bundle is 1.3, and it enters the steam azeotropic heat box multi-stage draw unit (B) through a five-roller drawer (5) for three-stage draw. The draw ratio in the azeotropic heat box (B1) is 1.1 times, the draw ratio in the azeotropic heat box (B2) is 12.8 times, and the draw ratio in the azeotropic heat box (B3) is 1.5 times. The filament bundle exiting the azeotropic heat box (B3) passes through the five-roller drawer at a linear speed of 340m / min, enters the drying heat box for drying, and is then wound to obtain ultra-high molecular weight polyethylene fiber filament.

[0039] The precursor fibers obtained from the dry spinning process for preparing UHMWPE of the present invention are stored in a static room for 24 hours and then sent to the post-spinning stage. They are then subjected to hot drawing under the following conditions: first-stage hot drawing temperature 143°C, draw ratio 2.0 times; second-stage hot drawing temperature 146°C, draw ratio 5 times; third-stage hot drawing temperature 148°C, draw ratio 2.0 times. Ultra-high molecular weight polyethylene fine denier fibers are prepared. The fiber bundles are then wound on a winding machine to obtain finished UHMWPE fibers. Samples are taken for relevant mechanical property testing and analysis. The results are shown in Table 1. Example 5

[0040] UHWMPE resin with a viscosity-average molecular weight range of 2 million to 4 million was pre-swelled with solvent decahydronaphthalene and other additives at an amount not less than 10% of the total raw material mass. The mixture was then fed into a parallel twin-screw extruder for further swelling, dissolution, and transport to form a gel melt. The melt pressure was maintained at 4.0 ± 0.1 MPa after passing through a booster pump and a metering pump. The melt was then extruded at a speed of 10 m / min through an inverted conical spinneret (11) with an aspect ratio [(H+h) / d] of 28 into a condenser bath (2). The residence time is 11±1s, the nozzle draw ratio of the gel filament bundle is 1, and it enters the steam azeotropic heat box multi-stage draw unit (B) through the five-roller drawer (5) for three-stage draw. The draw ratio in the azeotropic heat box (B1) is 1.5 times, the draw ratio in the azeotropic heat box (B2) is 15 times, and the draw ratio in the azeotropic heat box (B3) is 1.6 times. The filament bundle exiting the azeotropic heat box (B3) passes through the five-roller drawer at a linear speed of 350m / min, enters the drying heat box for drying, and is then wound to obtain ultra-high molecular weight polyethylene fiber filament.

[0041] The precursor fibers obtained from the dry spinning process for preparing UHMWPE of the present invention are stored in a static room for 24 hours and then sent to the post-spinning stage. They are then subjected to hot drawing under the following conditions: first-stage hot drawing temperature 140°C, first-stage drawing ratio 1.8 times; second-stage hot drawing temperature 145°C, drawing ratio 6 times; third-stage hot drawing temperature 146°C, drawing ratio 1.8 times. Ultra-high molecular weight polyethylene fine denier fibers are prepared. The fiber bundles are then wound on a winding machine to obtain finished UHMWPE fibers. Samples are taken for relevant mechanical property testing and analysis. The results are shown in Table 1. Example 6

[0042] UHWMPE resin with a viscosity-average molecular weight range of 2 million to 4 million was pre-swelled with solvent decahydronaphthalene and other additives at an amount not less than 10% of the total raw material mass. The mixture was then fed into a parallel twin-screw extruder for further swelling, dissolution, and transport to form a gel melt. The melt pressure was maintained at 4.2 ± 0.1 MPa after passing through a booster pump and a metering pump. The melt was then extruded at a speed of 12 m / min through an inverted conical spinneret (11) with an aspect ratio [(H+h) / d] of 28 into a condenser bath (2). The residence time is 10±1s, the nozzle draw ratio of the gel filament bundle is 1.1, and it enters the steam azeotropic heat box multi-stage draw unit (B) through a five-roller drawer (5) for three-stage draw. The draw ratio in the azeotropic heat box (B1) is 1.2 times, the draw ratio in the azeotropic heat box (B2) is 15 times, and the draw ratio in the azeotropic heat box (B3) is 1.5 times. The filament bundle exiting the azeotropic heat box (B3) passes through the five-roller drawer at a linear speed of 320m / min, enters the drying heat box for drying, and is then wound to obtain ultra-high molecular weight polyethylene fiber filament.

[0043] The precursor fibers obtained from the dry spinning process for preparing UHMWPE of the present invention are stored in a static room for 24 hours and then sent to the post-spinning stage. They are then subjected to hot drawing under the following conditions: first-stage hot drawing temperature 142°C, first-stage drawing ratio 2.0 times; second-stage hot drawing temperature 146°C, drawing ratio 5 times; third-stage hot drawing temperature 149°C, drawing ratio 2.0 times, to prepare ultra-high molecular weight polyethylene fine denier fibers. The fiber bundles are then wound on a winding machine to obtain finished UHMWPE fibers. Samples are taken for relevant mechanical property testing and analysis, and the results are shown in Table 1. Example 7

[0044] UHWMPE resin with a viscosity-average molecular weight range of 2 million to 4 million was pre-swelled with solvent decahydronaphthalene and other additives at an amount not less than 10% of the total raw material mass. The mixture was then fed into a parallel twin-screw extruder for further swelling, dissolution, and transport to form a gel melt. The melt pressure was maintained at 4.5 ± 0.1 MPa after passing through a booster pump and a metering pump. The melt was then extruded through an inverted conical spinneret (11) with an aspect ratio [(H+h) / d] of 28 at a speed of 18 m / min in a condenser bath (2). The residence time is 7±1s, the nozzle draw ratio of the gel filament bundle is 1.5, and it enters the steam azeotropic heat box multi-stage draw unit (B) through the five-roller drawer (5) for three-stage draw. The draw ratio in the azeotropic heat box (B1) is 1.1 times, the draw ratio in the azeotropic heat box (B2) is 14 times, and the draw ratio in the azeotropic heat box (B3) is 1.5 times. The filament bundle exiting the azeotropic heat box (B3) passes through the five-roller drawer at a linear speed of 400m / min, enters the drying heat box for drying, and is then wound to obtain ultra-high molecular weight polyethylene fiber filament.

[0045] The precursor fibers obtained from the dry spinning process for preparing UHMWPE of the present invention are stored in a static room for 24 hours and then sent to the post-spinning stage. They are then subjected to hot drawing under the following conditions: first-stage hot drawing temperature 144°C, draw ratio 3.0; second-stage hot drawing temperature 147°C, draw ratio 6; and third-stage hot drawing temperature 148°C, draw ratio 1.5. Ultra-high molecular weight polyethylene fine denier fibers are prepared. The fiber bundles are then wound on a winding machine to obtain finished UHMWPE fibers. Samples are taken for relevant mechanical property testing and analysis. The results are shown in Table 1.

[0046] Table 1. Test Analysis Results of Examples

[0047]

[0048] This invention significantly shortens the spinning process and reduces operating costs compared to existing dry spinning technologies, while improving production efficiency while maintaining fiber quality. Improved spinneret and orifice design reduces shear forces during high-pressure gel fluid transport, thus mitigating molecular weight degradation caused by mechanical forces during spinning. Higher spinneret extrusion speeds and lower nozzle draw ratios ensure that the low entanglement state of the viscoelastic gel at the spinneret is not damaged by excessive draw. Multi-stage draw within the steam azeotropic heating chamber ensures high fiber draw ratios, resulting in high strength and high modulus. This significantly shortens the original process flow, effectively improves the fineness uniformity of UHMWPE fibers prepared by dry spinning, and greatly reduces equipment operating costs.

Claims

1. A dry spinning process for UHMWPE, characterized in that, It includes a primary gel wet filament preparation unit and a subsequent multi-stage high-ratio drawing unit. The primary gel wet filament preparation unit includes: UHWMPE resin gel melt is extruded at high speed and high pressure through a spinneret with inverted conical spinnerets, bundled, and then enters a condensation bath located below the spinneret, equipped with a bundling roller and a guide roller. After exiting the condensation bath, it enters the multi-stage high-ratio drawing unit through a multi-roller drawing machine with a drawing ratio of 1-1.5 times. The multi-stage high-ratio drawing unit includes: at least three steam azeotropic drawing chambers with different temperatures and pressures for multi-stage drawing, with the final stage of multi-stage drawing having a filament exit speed of 300-400 m / min. The bundling roller, guide roller, and condensation bath can all move up and down. The inverted conical spinneret is a circular hole comprising two sections: an upper section that is inverted conical and a lower section that is cylindrical. The external dimensions of the inverted conical spinneret have the following ratios: D / d = 6:1-8:1, H / h = 4:1-6:1, and (H+h) / d = 20:1-30:

1. Here, D is the upper diameter, d is the lower diameter, H is the height of the upper inverted conical section, and h is the height of the lower cylindrical section. The extrusion rate of the nascent gel wet filaments extruded from the inverted conical spinneret is 5-30 m / min; the residence time of the nascent gel wet filaments extruded from the inverted conical spinneret in the condensation bath is 5-50 s.

2. The UHMWPE dry spinning process according to claim 1, characterized in that, After the prepared raw material solution has swollen and homogenized, it is extruded through a twin-screw extruder to form a gel melt. The gel melt, after passing through a booster pump and a metering pump, enters the nascent gel wet filament preparation unit. The pressure of the gel melt exiting the booster pump is 2.0-6.5 MPa.

3. The UHMWPE dry spinning process according to claim 2, characterized in that, The pressure of the gel melt exiting the booster pump is 3.0-5.5 MPa.

4. The UHMWPE dry spinning process according to claim 3, characterized in that, The pressure of the gel melt exiting the booster pump is 3.5-4.5 MPa.

5. The UHMWPE dry spinning process according to claim 1, characterized in that, The extrusion rate of the nascent gel wet filaments extruded from the inverted conical spinneret is 10-20 m / min.

6. The UHMWPE dry spinning process according to claim 5, characterized in that, The extrusion rate of the nascent gel wet filaments extruded from the inverted conical spinneret is 10-15 m / min.

7. The UHMWPE dry spinning process according to claim 1, characterized in that, The residence time of the nascent gel wet filaments extruded from the inverted conical spinneret in the condensation bath is 10-30 seconds.

8. The UHMWPE dry spinning process according to claim 7, characterized in that, The residence time of the nascent gel wet filaments extruded from the inverted conical spinneret in the condensation bath is 10-20 seconds.

9. The UHMWPE dry spinning process according to claim 1, characterized in that, The multi-roller drawing machine is a five-roller drawing machine.

10. The UHMWPE dry spinning process according to claim 1, characterized in that, The nascent gel wet filaments are subjected to three or four stages of drawing through three or four steam azeotropic drawing chambers.

11. A method for preparing UHMWPE fibers, characterized in that, The raw yarn prepared by the spinning process described in any one of claims 1-10 is stored in a static room for 24-48 hours and then sent to the post-spinning unit for multi-stage hot stretching to prepare ultra-high molecular weight polyethylene fine denier fibers of different specifications. The yarn bundle is then wound on a winding machine to obtain the finished UHMWPE fiber.

12. The method for preparing UHMWPE fibers according to claim 11, characterized in that, The residual solvent content in the finished fiber is 5-50 ppm.

13. The method for preparing UHMWPE fibers according to claim 12, characterized in that, The residual solvent content in the finished fiber is 10-30 ppm.

14. The method for preparing UHMWPE fibers according to claim 13, characterized in that, The residual solvent content in the finished fiber is 10-20 ppm.

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