Forming method of ultra-high molecular weight polyethylene fiber

Abstract

The invention discloses a forming method of ultra-high molecular weight polyethylene fibers. The forming method comprises the following steps: step 1, mixing ultra-high molecular weight polyethylene resin and a solvent to prepare a uniform suspension; step 2, preparing the suspension into a high-temperature solution, spinning, and cooling and shaping in a water bath to obtain jelly-like fibers; step 3, carrying out high-temperature ultra-time hot stretching on the jelly-like fibers; step 4, extracting and drying the jelly-like fibers subjected to high-temperature hyperfold hot stretching to remove the solvent, so as to obtain dried fibers; and step 5, carrying out low-multiple hot stretching on the dried fiber to obtain the final ultra-high molecular weight polyethylene fiber. The gel-like fiber is subjected to high-temperature ultra-time hot stretching under the condition that a solvent is not removed, so that the solvent is beneficial to promoting the orientation of fibrous extended chain crystals reserved in the gel-like fiber and the formation of high-orientation crystals such as subsequent extended chain crystals, and the mechanical property of the final fiber is greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and more specifically, to a method for forming ultra-high molecular weight polyethylene fibers. Background Art

[0002] Ultra-high molecular weight polyethylene fiber has multiple excellent properties such as light weight, high specific strength, high specific modulus, superior energy absorption, good wear resistance, corrosion resistance, and light resistance. It has been widely used in aerospace, national defense and military, security protection, marine engineering, sports equipment, power communications, medical materials, and civil ropes and nets.

[0003] Ultra-high molecular weight polyethylene fibers are usually prepared by gel spinning process. The gel spinning process is to first make a spinning solution of ultra-high molecular weight polyethylene and a suitable solvent, then form gel fibers through extrusion molding, then extract and dry the solvent in the gel fibers, and finally obtain ultra-high molecular weight polyethylene fibers through super-multiple hot drawing.

[0004] Due to the ultra-high molecular weight of the resin, the viscosity is very high when all the resin is completely dissolved, and the conditions for preparing a uniform solution are harsh, so it is difficult to obtain a high-concentration uniform solution; and because the dissolution temperature required for the resin is very high, the molecular weight of the ultra-high molecular weight polyethylene is greatly reduced, affecting the mechanical properties of the final fiber.

[0005] Patent CN115323518A discloses a process for preparing ultra-high molecular weight polyethylene fibers that retains extended chain crystals. By precisely controlling the temperature during the preparation of the ultra-high molecular weight polyethylene solution, only the folded chain lamellae with a lower melting point in the ultra-high molecular weight polyethylene are dissolved under low temperature conditions, while the extended chain crystals in the resin are partially dissolved, thereby reducing the viscosity of the ultra-high molecular weight polyethylene solution and reducing the molecular weight reduction caused by the high processing temperature. The extended chain crystals retained during the dissolution process serve as efficient nucleating agents for the crystallization of ultra-high molecular weight polyethylene, inducing the formation of extended chain crystals and folded chain lamellae during the hot stretching process after extraction and drying.

[0006] Through in-depth and systematic research on the stretching process of ultra-high molecular weight polyethylene that retains straight chain crystals, it was found that if the jelly-like fibers are subjected to ultra-multiple heat stretching, due to the presence of low molecular weight solvents, the retained fibrous straight chain crystals are easier to orient, and can promote the formation of highly oriented crystals such as straight chain crystals, thereby greatly improving the tensile strength and other properties of the final fiber, forming a unique molding method for ultra-high molecular weight polyethylene fibers. Summary of the invention

[0007] In order to further effectively improve the mechanical properties of ultra-high molecular weight polyethylene fibers, the present application provides a method for forming ultra-high molecular weight polyethylene fibers.

[0008] The present application provides a method for forming ultra-high molecular weight polyethylene fibers, which adopts the following technical solution: Step 1, mixing an ultra-high molecular weight polyethylene resin with a solvent to prepare a uniform suspension; Step 2, the suspension is made into a high-temperature solution, and after spinning, it is cooled and shaped in a water bath to obtain a jelly-like fiber; Step 3, subjecting the jelly-like fiber to high-temperature ultra-multiple heat stretching; Step 4, extracting and drying the jelly-like fibers after high-temperature super-multiple heat stretching to remove the solvent and obtain dry fibers; Step 5: The dried fiber is subjected to low-multiple heat stretching to obtain the final ultra-high molecular weight polyethylene fiber.

[0009] By adopting the above technical scheme, the jelly-like fibers are subjected to high-temperature super-multiple heat stretching without removing the solvent, so that the solvent helps to promote the orientation of fibrous straight chain crystals retained in the jelly-like fibers and the formation of highly oriented crystals such as subsequent straight chain crystals, thereby helping to significantly improve the tensile properties and other properties of the final fibers.

[0010] Preferably, in step 2, the suspension is passed through a twin-screw extruder to obtain a high-temperature solution, the feeding section temperature of the twin-screw extruder is 80-130°C, the compression section temperature is 140-200°C, the homogenization section temperature is 140-200°C, the spinning assembly temperature is 140-200°C, and the rotation speed of the twin-screw extruder is 30-400r / min.

[0011] By adopting the above technical solution, when the temperature of the compression section, homogenization section and spinning assembly of the twin-screw extruder exceeds 200°C, the extended chain crystals in the ultra-high molecular weight polyethylene resin will be dissolved. When the temperature is lower than 140°C, most of the lamellar crystals in the ultra-high molecular weight polyethylene resin will be retained, which will affect the dissolution effect of the ultra-high molecular weight polyethylene resin, causing the fluidity to decrease, and then causing the extruded jelly-like fibers to be uneven.

[0012] Preferably, the temperatures of the compression section, homogenization section and spinning assembly of the twin-screw extruder are all 145-175°C.

[0013] By adopting the above technical scheme, too high a temperature will cause most of the extended chain crystals in the ultra-high molecular weight polyethylene resin to be dissolved, while too low a temperature will cause the lamellar crystals in the ultra-high molecular weight polyethylene resin to be retained, affecting the dissolution effect, and further causing the extruded jelly-like fibers to be uneven. Therefore, the above-mentioned range of 145 to 175°C is preferred.

[0014] Preferably, the temperature of the super-multiple heat stretching of the jelly-like fibers in step 3 is 95 to 135° C., the stretching rate is 8 to 100 m / min, and the stretching ratio is 6 to 18 times.

[0015] Preferably, the stretching ratio of the super-multiple heat stretching of the jelly-like fiber is 10 to 16 times.

[0016] By adopting the above technical scheme, the thermal stretching ratio of the jelly-like fiber is low, and the number of newly formed straight chain crystals promoted by the retained straight chain crystals during the stretching process is not enough, and the mechanical properties of the final ultra-high molecular weight polyethylene fiber cannot be greatly improved; if the stretching ratio of the jelly-like fiber is too high, it will affect the stability of the fiber stretching.

[0017] Preferably, the temperature of super-heat stretching of the jelly-like fibers is 105-125°C.

[0018] By adopting the above technical scheme, the super-multiple thermal stretching temperature is low, and the orientation of the retained straight chain crystals and their promoting effect on the subsequent formation of highly oriented crystals are not obvious enough; the super-multiple thermal stretching temperature is high, and the ultra-high molecular weight polyethylene gel fibers are prone to detangling, causing unstable thermal stretching process and unstable quality of ultra-high molecular weight polyethylene fibers.

[0019] Preferably, the solvent is a mixture of one or more of decalin, white oil and long straight-chain alkanes.

[0020] By adopting the above technical scheme, the above solvents can easily dissolve the ultra-high molecular weight polyethylene resin, thereby facilitating the formation of highly oriented crystals such as the fibrous straight chain crystal orientation retained in the jelly-like fibers and subsequent straight chain crystals during the high-temperature super-multiple thermal stretching process of the ultra-high molecular weight polyethylene resin.

[0021] Preferably, the solvent is a long straight chain alkane.

[0022] By adopting the above technical scheme, the chain structure of the long straight-chain alkane is similar to the chain structure of ultra-high molecular weight polyethylene, which makes it easier to accurately control the partial solubility degree of ultra-high molecular weight polyethylene resin and the formation of highly oriented crystals during the thermal stretching of jelly-like fibers.

[0023] Preferably, the mass ratio of the ultra-high molecular weight polyethylene to the solvent in step 1 is 0.08 to 0.48.

[0024] By adopting the above technical scheme, the actual dissolved concentration is reduced by partially dissolving the ultra-high molecular weight polyethylene resin. The high rigidity of the extended chain crystals retained in the ultra-high molecular weight polyethylene resin makes the solution form characteristics similar to those of a liquid crystal solution, which can greatly reduce the viscosity of the ultra-high molecular weight polyethylene solution.

[0025] Moreover, too low an ultra-high molecular weight polyethylene resin content will result in too low an internal entanglement degree of the prepared jelly-like fiber, thereby affecting the mechanical properties. In order to maximize the production efficiency of preparing ultra-high molecular weight polyethylene fibers, a high content of ultra-high molecular weight polyethylene is preferred; however, too high an ultra-high molecular weight polyethylene resin content will affect the partial dissolution effect, thereby affecting the mechanical properties of the final ultra-high molecular weight polyethylene fiber. In order to take into account both the dissolution effect of the ultra-high molecular weight polyethylene resin and the mechanical properties of the ultra-high molecular weight polyethylene fiber, the above range is preferred.

[0026] Preferably, in step 5, the heat stretching temperature of the dried fiber is 120 to 150° C., and the stretching ratio is 1.5 to 3.5 times.

[0027] By adopting the above technical solution, the hot stretching temperature is low and the melt recrystallization effect is weak, so that the pores formed during the extraction and drying process cannot be completely eliminated; the hot stretching temperature is high, and quality instability such as yarn drawing may occur during the hot stretching preparation of ultra-high molecular weight polyethylene fibers.

[0028] However, if the thermal stretching ratio is low, the pores in the dry fiber cannot be completely eliminated, which affects the mechanical properties of the final fiber; if the stretching ratio is too high, it will affect the stability of fiber stretching.

[0029] In summary, this application has the following beneficial effects: 1. Since the jelly-like fibers in the present application are subjected to high-temperature ultra-multiple heat stretching while retaining the solvent, this not only helps to promote the orientation of the fibrous straight chain crystals retained in the jelly-like fibers, but also facilitates the formation of subsequent highly oriented crystals such as straight chain crystals, thereby greatly improving the mechanical properties of the final ultra-high molecular weight polyethylene fibers; 2. In the present application, the temperature of the compression section, homogenization section and spinning assembly of the twin-screw extruder is controlled at 140-175°C. Too high a temperature will dissolve most of the extended chain crystals in the ultra-high molecular weight polyethylene resin, while too low a temperature will retain the lamellar crystals in the ultra-high molecular weight polyethylene resin, affecting the dissolution effect, thereby causing the extruded jelly-like fibers to be uneven. Therefore, the above range is preferred; 3. In this application, long straight-chain alkanes are selected as solvents, because long straight-chain alkanes are normal alkanes with components of C12 to C16. The chain structure of long straight-chain alkanes is similar to that of ultra-high molecular weight polyethylene, which makes it easier to accurately control the retention of extended chain crystals during the dissolution of ultra-high molecular weight polyethylene resin and the formation of highly oriented crystals during the thermal stretching of jelly-like fibers; 4. In the present application, the high-temperature super-multiple thermal stretching ratio of the jelly-like fiber is 10 to 16 times. The thermal stretching ratio of the jelly-like fiber is low. The number of newly formed straight chain crystals promoted by the retained straight chain crystals during the stretching process is not enough, and the mechanical properties of the final fiber cannot be greatly improved; if the stretching ratio of the jelly-like fiber is too high, it will affect the stability of the fiber stretching. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a two-dimensional wide-angle X-ray diffraction pattern of the ultra-high molecular weight polyethylene fiber in Example 1 of the present application; Figure 2 It is a two-dimensional wide-angle X-ray diffraction pattern of the ultra-high molecular weight polyethylene fiber in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0031] The present application is further described in detail below in conjunction with the accompanying drawings, embodiments and comparative examples. Example 1

[0032] A method for forming ultra-high molecular weight polyethylene fiber, the specific steps of which are as follows: Step 1: Set the viscosity average molecular weight to 6.43×10 6 g / mol ultra-high molecular weight polyethylene resin and long straight chain alkane are mixed at a mass ratio of 0.28:1 to prepare a uniform suspension; Step 2, the suspension is fed into a twin-screw extruder to obtain a high-temperature solution, which is passed through a metering pump and a spinneret, and is cooled and shaped in a 20° C. water bath to obtain a jelly-like fiber; Step 3, subjecting the jelly-like fiber to high-temperature ultra-multiple heat stretching; Step 4, the jelly-like fiber after high-temperature super-multiple heat stretching is subjected to extraction hot air drying to remove the solvent to obtain dry fiber; Step 5: The dried fiber is subjected to low-multiple heat stretching to obtain the final ultra-high molecular weight polyethylene fiber.

[0033] Among them, the feeding section temperature of the twin-screw extruder is 105°C, the compression section temperature is 160°C, the homogenization section temperature is 160°C, the spinning assembly temperature is 160°C, and the speed of the twin-screw extruder is 210r / min. The temperature of high-temperature super-multiple thermal stretching is 115°C, the stretching rate is 54m / min, and the stretching ratio is 12 times. The low-multiple thermal stretching temperature is 135°C, and the stretching ratio is 2.5 times. Generally, the long straight-chain alkane can be a normal alkane of C12 to C16, and can be a single-length straight-chain normal alkane or a mixture of long straight-chain alkanes. The long straight-chain alkanes in this application are preferably n-pentadecane. Example 2

[0034] A method for forming ultra-high molecular weight polyethylene fiber, the specific steps of which are as follows: Step 1: Set the viscosity average molecular weight to 6.43×10 6 g / mol ultra-high molecular weight polyethylene resin and decalin are mixed at a mass ratio of 0.08:1 to prepare a uniform suspension; Step 2, the suspension is fed into a twin-screw extruder to obtain a high-temperature solution, which is passed through a metering pump and a spinneret, and is cooled and shaped in a 20° C. water bath to obtain a jelly-like fiber; Step 3, subjecting the jelly-like fiber to high-temperature ultra-multiple heat stretching; Step 4, the jelly-like fiber after high-temperature super-multiple heat stretching is subjected to extraction hot air drying to remove the solvent to obtain dry fiber; Step 5: The dried fiber is subjected to low-multiple heat stretching to obtain the final ultra-high molecular weight polyethylene fiber.

[0035] Among them, the feeding section temperature of the twin-screw extruder is 80°C, the compression section temperature is 140°C, the homogenization section temperature is 140°C, the spinning assembly temperature is 140°C, and the speed of the twin-screw extruder is 30r / min. The temperature of high-temperature super-multiple heat stretching is 95°C, the stretching rate is 8m / min, and the stretching ratio is 6 times. The low-multiple heat stretching temperature is 120°C, and the stretching ratio is 3.5 times. Example 3

[0036] A method for forming ultra-high molecular weight polyethylene fiber, the specific steps of which are as follows: Step 1: Set the viscosity average molecular weight to 6.43×10 6 g / mol ultra-high molecular weight polyethylene resin and white oil were mixed at a mass ratio of 0.48:1 to prepare a uniform suspension; Step 2, the suspension is fed into a twin-screw extruder to obtain a high-temperature solution, which is passed through a metering pump and a spinneret, and is cooled and shaped in a 20° C. water bath to obtain a jelly-like fiber; Step 3, subjecting the jelly-like fiber to high-temperature ultra-multiple heat stretching; Step 4, the jelly-like fiber after high-temperature super-multiple heat stretching is subjected to extraction hot air drying to remove the solvent to obtain dry fiber; Step 5: The dried fiber is subjected to low-multiple heat stretching to obtain the final ultra-high molecular weight polyethylene fiber.

[0037] Among them, the feeding section temperature of the twin-screw extruder is 130°C, the compression section temperature is 200°C, the homogenization section temperature is 200°C, the spinning assembly temperature is 200°C, and the speed of the twin-screw extruder is 400r / min. The temperature of high-temperature super-multiple heat stretching is 135°C, the stretching rate is 100m / min, and the stretching ratio is 18 times. The low-multiple heat stretching temperature is 150°C, and the stretching ratio is 1.5 times. Here, the white oil is Total LYRAN C360B No. 70 white oil.

[0038] Comparative Example 1 The difference between this comparative example and Example 1 is that step 3 does not exist, and step 5 is to perform multi-stage stretching of the fiber to 30 times at 120-150°C.

[0039] Comparative Example 2 The difference between this comparative example and Example 2 is that step 3 does not exist, and step 5 is to perform multi-stage stretching of the fiber to 21 times at 120-150°C.

[0040] Comparative Example 3 The difference between this comparative example and Example 3 is that step 3 does not exist, and step 5 is to perform multi-stage stretching of the fiber to 27 times at 120-150°C.

[0041] The tensile mechanical properties, thermal properties and crystallization properties of the ultra-high molecular weight polyethylene fibers of Examples 1 to 3 and Comparative Examples 1 to 3 were tested, and the specific testing methods are as follows:

[0042] Thermal properties (DSC) test Cut the ultra-high molecular weight polyethylene fiber into pieces, weigh 5-10 mg and put it in a standard aluminum crucible. Protect it with a dry nitrogen flow and use a differential scanning calorimeter (DSC) to test the thermal properties of the ultra-high molecular weight polyethylene fiber. Heat and scan from 25 °C to 200 °C at a heating rate of 10 °C / min, and record the thermal performance curve of the fiber.

[0043] Crystallinity and orientation test: The crystallinity and orientation of the ultra-high molecular weight polyethylene fibers were tested by wide angle X-ray diffraction (WAXD) with an X-ray wavelength of 0.124 nm. The two-dimensional WAXD results were collected by a Pilatus 900K detector with a resolution of 172 × 172 μm. 2 , the distance from the detector to the sample is 210 mm. The WAXD data obtained by processing with FIT2D software. The two-dimensional WAXD image is integrated in one dimension to obtain the intensity distribution curve in the 2θ direction. Then the curve is peak-fitted, the ratio of amorphous area to crystalline area is calculated, and then the crystallinity is calculated. The calculation formula is as follows: Xc=Ac / (Ac+Aa) Where Ac and Aa represent the area under the crystalline peak and amorphous peak of the I(2θ)~2θ curve, respectively.

[0044] The Hermans method is used to determine the crystal orientation of ultra-high molecular weight polyethylene fibers. The fiber axis is taken as the reference direction, and the crystal plane is set as hkl. The orientation parameter can be expressed as: in, ϕ is the azimuth, I( ϕ ) is the scattering intensity along the azimuth angle. f It can be calculated by the following formula: when f=-0.5, the normal direction of the crystal plane is perpendicular to the reference direction; when f =1, the normal direction of the crystal plane is parallel to the reference direction; when f = 0, the normal of the crystal plane is freely oriented.

[0045] Tensile mechanical properties test: The tensile mechanical properties of ultra-high molecular weight polyethylene fibers were tested at room temperature using a universal mechanical testing machine at a speed of 50 mm / min to characterize their mechanical properties. During the tensile test, at least five samples were used for each fiber to obtain the average value and standard deviation.

[0046] According to the above detection method, the test results of Examples 1 to 3 and Comparative Examples 1 to 3 were obtained, as shown in Table 1 below: Table 1 Conclusion 1: Combined with the test results of Example 1 to Example 3 and Comparative Example 1 to Comparative Example 3, respectively, and the attached Figure 1 and attached Figure 2 It can be seen from the display that when the jelly-like fibers are subjected to ultra-multiple heat stretching while retaining the solvent, the fibrous straight-chain crystals retained in the jelly-like fibers are easier to orient, and more easily promote the formation of highly oriented crystals such as subsequent straight-chain crystals, thereby effectively improving the tensile strength and tensile modulus of the final ultra-high molecular weight polyethylene fibers. Example 4

[0047] The only difference between this embodiment and embodiment 1 is that the temperatures of the compression section, the homogenization section and the spinning assembly of the twin-screw extruder in this embodiment are all 140°C. Example 5

[0048] The only difference between this embodiment and embodiment 1 is that the temperatures of the compression section, the homogenization section and the spinning assembly of the twin-screw extruder in this embodiment are all 175°C. Example 6

[0049] The only difference between this embodiment and embodiment 1 is that the temperatures of the compression section, the homogenization section and the spinning assembly of the twin-screw extruder in this embodiment are all 200°C.

[0050] Comparative Example 4 The only difference between this comparative example and Example 1 is that the temperatures of the compression section, the homogenization section and the spinning assembly of the twin-screw extruder in this comparative example are all 130°C.

[0051] Comparative Example 5 The only difference between this comparative example and Example 1 is that the temperatures of the compression section, the homogenization section and the spinning assembly of the twin-screw extruder in this comparative example are all 210°C.

[0052] According to the detection method of Table 1, the ultra-high molecular weight polyethylene fibers of Examples 4 to 6 and Comparative Examples 4 and 5 were tested, and the test results were obtained, as shown in Table 2 below: Table 2 Test items Example 4 Example 5 Example 6 Comparative Example 4 Comparative Example 5 Melting point (℃) 150.9 149.9 148.1 / 145.1 Crystallinity (%) 97 96.8 94.3 / 91.2 Orientation 0.97 0.96 0.93 / 0.91 Tensile strength (cN / dtex) 57.6±3.4 57.4±3.0 48.4±2.6 / 40.4±1.1 Tensile modulus (cN / dtex) 2712.6±90.7 2708.6±72.4 2634.1±51.5 / 1984.8±41.1 Whether the spinning is smooth and stable Smooth and stable spinning Smooth and stable spinning Smooth and stable spinning Unable to spin smoothly and stably Smooth and stable spinning Conclusion 2: By comparing the test results of Example 1, Examples 4 to 6 and Comparative Examples 4 and 5, it can be concluded that when the temperatures of the compression section, homogenization section and spinning assembly of the twin-screw extruder are controlled at 140-200°C, especially at 140-175°C, the ultra-high molecular weight polyethylene fiber finally prepared has good tensile strength and tensile modulus. Example 7

[0053] The only difference between this embodiment and embodiment 1 is that the stretching ratio of the super-multiple heat stretching of the jelly-like fiber is 10 times. Example 8

[0054] The only difference between this embodiment and embodiment 1 is that the stretching ratio of the super-multiple heat stretching of the jelly-like fiber is 6 times. Example 9

[0055] The only difference between this embodiment and embodiment 1 is that the stretching ratio of the super-multiple heat stretching of the jelly-like fiber is 16 times. Example 10

[0056] The only difference between this embodiment and embodiment 1 is that the stretching ratio of the super-multiple heat stretching of the jelly-like fiber is 18 times.

[0057] According to the detection method in Table 1, the ultra-high molecular weight polyethylene fibers of Examples 7 to 10 were tested, and the test results were obtained, as shown in Table 3 below: Table 3 Test items Example 7 Example 8 Example 9 Example 10 Melting point (℃) 149.3 147.1 151.4 151.6 Crystallinity (%) 96.3 94.1 98.4 98.6 Orientation 0.96 0.93 0.98 0.98 Tensile strength (cN / dtex) 55.9±3.0 43.6±2.4 63.6±3.4 64.1±7.2 Tensile modulus (cN / dtex) 2634.4±75.8 2186.9±67.1 2956.8±90.2 2998.4±289.4 Conclusion 3: By comparing the test results of Example 1 and Example 7 to Example 10, it can be seen that when the stretching rate of the ultra-high molecular weight polyethylene fiber is 10 to 16 times, it can not only ensure the mechanical properties of the ultra-high molecular weight polyethylene fiber, but also does not affect the stretching stability of the ultra-high molecular weight polyethylene jelly film. Embodiment 11

[0058] The only difference between this embodiment and embodiment 1 is that the temperature of super-multiple heat stretching of the jelly-like fibers in this embodiment is 105°C. Example 12

[0059] The only difference between this embodiment and embodiment 11 is that the temperature of super-multiple heat stretching of the jelly-like fibers in this embodiment is 95°C. Example 13

[0060] The only difference between this embodiment and embodiment 1 is that the temperature of super-multiple heat stretching of the jelly-like fibers in this embodiment is 125°C. Embodiment 14

[0061] The only difference between this embodiment and embodiment 13 is that the temperature of super-multiple heat stretching of the jelly-like fibers in this embodiment is 135°C.

[0062] According to the detection method in Table 1, the ultra-high molecular weight polyethylene fibers of Examples 11 to 14 were tested, and the test results were obtained, as shown in Table 4 below: Table 4 Test items Embodiment 11 Example 12 Example 13 Embodiment 14 Melting point (℃) 150.5 148.8 150.7 149.5 Crystallinity (%) 97 95.3 97 96 Orientation 0.97 0.95 0.97 0.96 Tensile strength (cN / dtex) 57.2±3.2 54.2±3.4 58.4±3.2 56.9±3.3 Tensile modulus (cN / dtex) 2724.8±83.1 2598.3±88.6 2743.8±81.3 2634.3±86.2 Conclusion 4: By comparing the test results of Example 1 and Example 11 to Example 14, it can be seen that when the temperature of the super-multiple thermal stretching of the jelly-like fiber is 105-135°C, it promotes the rapid orientation of the straight chain crystals retained in the jelly-like fiber and promotes the subsequent formation of highly oriented crystals, and the molecular chains in the jelly-like film fiber are not easy to detangle during the stretching process, and the thermal stretching process is stable. Therefore, the mechanical properties of the ultra-high molecular weight polyethylene fiber finally obtained are better. Embodiment 15

[0063] The only difference between this embodiment and embodiment 1 is that the solvent in this embodiment is decalin. Example 16

[0064] The only difference between this embodiment and embodiment 1 is that the solvent in this embodiment is white oil.

[0065] According to the detection method of Table 1, the ultra-high molecular weight polyethylene fibers of Example 15 and Example 16 were tested, and the test results were obtained, as shown in the following Table 5: Table 5 Test items Embodiment 15 Example 16 Melting point (℃) 149.4 149.1 Crystallinity (%) 95.5 95.3 Orientation 0.96 0.96 Tensile strength (cN / dtex) 57.4±3.3 58.8±3.3 Tensile modulus (cN / dtex) 2701.4±85.4 2697.3±85.2 Conclusion 5 By comparing the test results of Example 1, Example 15 and Example 16, it can be seen that the use of long straight-chain alkanes as the solvent is beneficial to improving the mechanical properties of the final ultra-high molecular weight polyethylene fiber.

[0066] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for forming ultra-high molecular weight polyethylene fibers, characterized in that: The specific steps are as follows: Step 1, mixing an ultra-high molecular weight polyethylene resin with a solvent to prepare a uniform suspension; Step 2, the suspension is made into a high-temperature solution, and after spinning, it is cooled and shaped in a water bath to obtain a jelly-like fiber; Step 3, subjecting the jelly-like fiber to high-temperature ultra-multiple heat stretching; Step 4, extracting and drying the jelly-like fibers after high-temperature super-multiple heat stretching to remove the solvent and obtain dry fibers; Step 5: The dried fiber is subjected to low-multiple heat stretching to obtain the final ultra-high molecular weight polyethylene fiber.

2. The method for forming an ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that: In step 2, the suspension is passed through a twin-screw extruder to obtain a high-temperature solution, the feeding section temperature of the twin-screw extruder is 80-130°C, the compression section temperature is 140-200°C, the homogenization section temperature is 140-200°C, the spinning assembly temperature is 140-200°C, and the rotation speed of the twin-screw extruder is 30-400r / min.

3. The method for forming an ultra-high molecular weight polyethylene fiber according to claim 2, characterized in that: The temperatures of the compression section, the homogenization section and the spinning assembly of the twin-screw extruder are all 140-175°C.

4. The method for forming an ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that: In step 3, the temperature of the super-multiple heat stretching of the jelly-like fiber is 95-135° C., the stretching rate is 8-100 m / min, and the stretching ratio is 6-18 times.

5. The method for forming an ultra-high molecular weight polyethylene fiber according to claim 4, characterized in that: The stretching ratio of the super-heat-stretching of the jelly-like fiber is 10 to 16 times.

6. The method for forming an ultra-high molecular weight polyethylene fiber according to claim 4, characterized in that: The temperature of super-heat stretching of jelly-like fibers is 105-125°C.

7. The method for forming an ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that: The solvent is a mixture of one or more of decalin, white oil and long straight-chain alkanes.

8. The method for forming an ultra-high molecular weight polyethylene fiber according to claim 7, characterized in that: The solvent is a long straight chain alkane.

9. The method for forming an ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that: The mass ratio of the ultra-high molecular weight polyethylene to the solvent in step 1 is 0.08 to 0.

48.

10. The method for forming an ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that: In step 5, the heat stretching temperature of the dried fiber is 120 to 150° C., and the stretching ratio is 1.5 to 3.5 times.

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