Preparation method of ultra-high molecular weight polyethylene uniaxially oriented film

Abstract

The invention discloses a preparation method of an ultra-high molecular weight polyethylene uniaxially oriented film, which comprises the following steps: step 1, mixing ultra-high molecular weight polyethylene resin and polyethylene wax to obtain a mixture; 2, melting the mixture at a high temperature to obtain a high-temperature melt; 3, the high-temperature melt is subjected to extrusion casting, and a primary film is obtained; and 4, carrying out uniaxial hot stretching on the primary film to obtain the final ultrahigh molecular weight polyethylene uniaxial oriented film. The melt flowability of the ultra-high molecular weight polyethylene is improved by utilizing the polyethylene wax, the polyethylene wax can participate in crystallization of the ultra-high molecular weight polyethylene by controlling the temperature in uniaxial hot stretching, and extended chain crystals in the ultra-high molecular weight polyethylene are reserved, so that the mechanical property of the ultra-high molecular weight polyethylene film is improved.

Description

Technical Field

[0001] The present application relates to the field of polymer material technology, and in particular to a method for preparing an ultra-high molecular weight polyethylene uniaxially oriented film. Background Art

[0002] Ultra-high molecular weight polyethylene is a linear thermoplastic plastic with the characteristics of non-toxicity, excellent corrosion resistance, good chemical stability and electrical insulation. It is widely used in new energy fields, marine engineering fields and electronic industry fields.

[0003] The key technology for preparing ultra-high molecular weight polyethylene film is to prepare an ultra-high molecular weight polyethylene composition with ideal melt fluidity so that the ultra-high molecular weight polyethylene can be smoothly extruded. However, ultra-high molecular weight polyethylene is a rubber-like high-viscosity elastic body in the melt state, and the melt flow index is almost zero. Therefore, the critical shear rate of ultra-high molecular weight polyethylene is very low, which makes ultra-high molecular weight polyethylene prone to melt fracture and other defects. It is difficult to use conventional polymer melt processing methods to form ultra-high molecular weight polyethylene films.

[0004] Polyethylene wax is an effective additive that can improve the processing fluidity of polymer materials, but the commonly used polyethylene wax has a high content of branches, so it has no crystallization ability or very weak crystallization ability. It cannot participate in the crystallization of polymer materials during the cooling process after processing and molding, which will affect the mechanical properties of polymer products. Therefore, linear polyethylene wax can be selected to improve the melt fluidity of ultra-high molecular weight polyethylene. By controlling the hot stretching temperature, the linear polyethylene wax can fully participate in the crystallization of ultra-high molecular weight polyethylene during the uniaxial hot stretching process, thereby reducing or even eliminating the damage of polyethylene wax as a low molecular weight substance to the mechanical properties of ultra-high molecular weight polyethylene film. Through the analysis and research of ultra-high molecular weight polyethylene resin, it is found that ultra-high molecular weight polyethylene resin contains both ordinary folded chain lamellae and extended chain crystals, among which the extended chain crystals have very high mechanical properties and can also be used as efficient nucleating agents for the crystallization of linear polyethylene wax. There is a large difference in the melting points of ordinary folded chain lamellae and extended chain crystals. Therefore, the original extended chain crystals of ultra-high molecular weight polyethylene resin can be retained by controlling the plasticizing temperature, thereby forming a preparation method of ultra-high molecular weight polyethylene modified by polyethylene wax. Summary of the invention

[0005] In order to improve the melt fluidity of ultra-high molecular weight polyethylene to facilitate the preparation of ultra-high molecular weight polyethylene film, the present application provides a method for preparing an ultra-high molecular weight polyethylene uniaxially oriented film.

[0006] The present application provides a method for preparing an ultra-high molecular weight polyethylene uniaxially oriented film, comprising the following steps: Step 1: mixing an ultra-high molecular weight polyethylene resin and a polyethylene wax to obtain a mixture; Step 2: Melting the mixture at high temperature to obtain a high-temperature melt; Step 3: Extruding and casting the high-temperature melt to prepare a primary film; Step 4: Perform uniaxial heat stretching on the nascent film to obtain the final ultra-high molecular weight polyethylene uniaxially oriented film.

[0007] By adopting the above technical solution, polyethylene wax is used to improve the melt fluidity of ultra-high molecular weight polyethylene, so that ultra-high molecular weight polyethylene can be smoothly extruded. And by controlling the temperature during the uniaxial heat stretching process, the polyethylene wax can participate in the crystallization of ultra-high molecular weight polyethylene, thereby reducing or even eliminating the damage of polyethylene wax as a low molecular weight substance to the mechanical properties of ultra-high molecular weight polyethylene film, and retaining the original extended chain crystals in the ultra-high molecular weight polyethylene, thereby improving the mechanical properties of the ultra-high molecular weight polyethylene film.

[0008] In addition, after the ultra-high molecular weight polyethylene film is produced, the polyethylene wax does not need to be recovered, thereby reducing the preparation steps of the ultra-high molecular weight polyethylene uniaxially oriented film.

[0009] Preferably, the content of ultra-high molecular weight polyethylene in the mixture is 80-96 wt%, and the content of polyethylene wax is 4-20 wt%.

[0010] Preferably, the content of the ultra-high molecular weight polyethylene is 85-92 wt%.

[0011] By adopting the above technical solution, polyethylene wax can improve the melt fluidity of ultra-high molecular weight polyethylene, so that ultra-high molecular weight polyethylene can be smoothly extruded and cast. The presence of a higher content of ultra-high molecular weight polyethylene helps to ensure the mechanical properties of the ultra-high molecular weight polyethylene film, and the processing process is more efficient.

[0012] Preferably, the polyethylene wax is linear polyethylene wax.

[0013] By adopting the above technical scheme, the linear polyethylene wax is mainly straight-chain as a whole, and its crystallization ability is ideal, so that the polyethylene wax can fully participate in the crystallization process of ultra-high molecular weight polyethylene during uniaxial heat stretching, thereby reducing or even eliminating the damage of polyethylene wax as a low molecular weight substance to the mechanical properties of ultra-high molecular weight polyethylene film, and the mechanical properties of ultra-high molecular weight polyethylene film can be well maintained.

[0014] Preferably, the weight average molecular weight of the polyethylene wax is 2.0×10 3 ~5.0×10 3 g / mol.

[0015] By adopting the above technical scheme, low molecular weight polyethylene wax can greatly improve the melt fluidity of ultra-high molecular weight polyethylene, so that the mixture can be smoothly extruded and cast, and during the stretching process, linear polyethylene wax can participate in the crystallization of ultra-high molecular weight polyethylene, which can well maintain the mechanical properties of ultra-high molecular weight polyethylene film.

[0016] Preferably, the mixture in step 2 is melted at high temperature by a twin-screw extruder, the feeding section temperature of the twin-screw extruder is 90-140°C, the compression section temperature is 160-250°C, the homogenization section temperature is 160-250°C, the die head temperature is 160-250°C, and the screw speed of the twin-screw extruder is 10-200rpm.

[0017] By adopting the above technical solution, when the compression section, homogenization section and die temperature of the twin-screw extruder exceed 250°C, the ultra-high molecular weight polyethylene is easy to degrade. When the temperature is lower than 160°C, the folded chain lamellae in the ultra-high molecular weight polyethylene will be retained, affecting the melt fluidity of the ultra-high molecular weight polyethylene, which in turn leads to uneven thickness of the prepared ultra-high molecular weight polyethylene film and unsatisfactory overall quality. The screw speed of the twin-screw extruder is 10 to 200 rpm, which is helpful for mixing the ultra-high molecular weight polyethylene and polyethylene wax. The low speed can reduce the shearing of the molecular chain and ensure the mechanical properties of the ultra-high molecular weight polyethylene film.

[0018] Preferably, the temperature of the compression section, homogenization section and die head of the twin-screw extruder is preferably 160-200°C.

[0019] By adopting the above technical scheme, within this temperature range, the folded chain lamellae in the ultra-high molecular weight polyethylene resin can be fully melted, but some straight chain crystals can be retained. The retained straight chain crystals can act as nucleating agents during the uniaxial heat stretching process to induce the polyethylene wax to crystallize on its surface, thereby well maintaining the mechanical properties of the ultra-high molecular weight polyethylene film.

[0020] Preferably, the temperature of the uniaxial heat stretching in step 4 is 90 to 145° C., and the stretching ratio is 4 to 12 times.

[0021] Preferably, the temperature of the uniaxial heat stretching in step 4 is 110-140°C.

[0022] By adopting the above technical scheme, if the hot stretching temperature is too low, hot stretching is difficult to carry out and the hot stretching process is unstable, the formation efficiency of straight chain crystals is low, and the quality of the obtained film is unstable; if the hot stretching temperature is too high, the linear polyethylene wax will not participate enough in the crystallization of ultra-high molecular weight polyethylene, which will affect the mechanical properties of the ultra-high molecular weight polyethylene film.

[0023] Preferably, the stretching ratio of the uniaxial heat stretching is 8 to 12 times.

[0024] By adopting the above technical scheme, when the stretching ratio is too low, the number of newly formed straight chain crystals promoted by the straight chain crystals retained during the stretching process is not large enough to significantly improve the mechanical properties of the final ultra-high molecular weight polyethylene film; when the stretching ratio is too high, it will affect the stability of the ultra-high molecular weight polyethylene film.

[0025] In summary, this application has the following beneficial effects: 1. The present application utilizes polyethylene wax to improve the melt fluidity of ultra-high molecular weight polyethylene, and by controlling the uniaxial heat stretching temperature, the polyethylene wax can participate in the crystallization of ultra-high molecular weight polyethylene, thereby improving the mechanical properties of the ultra-high molecular weight polyethylene film. In addition, during the preparation process, the added polyethylene wax does not need to be recycled, which helps to reduce the preparation steps of the ultra-high molecular weight polyethylene uniaxially oriented film; 2. The polyethylene wax added in this application is linear polyethylene wax, which can improve the melt fluidity of ultra-high molecular weight polyethylene, so that the ultra-high molecular weight polyethylene can be smoothly extruded and molded, and through temperature control, the linear polyethylene wax participates in the crystallization of ultra-high molecular weight polyethylene, thereby ensuring the mechanical properties of the ultra-high molecular weight polyethylene film; 3. In the present application, the compression section, homogenization section and die temperature of the twin-screw extruder are controlled at 160-200°C, which can ensure that the folded chain lamellae in the ultra-high molecular weight polyethylene are fully melted, while the straight chain crystals are retained. The retained straight chain crystals can act as nucleating agents during the uniaxial heat stretching process to induce the polyethylene wax to crystallize on its surface, thereby improving the mechanical properties of the ultra-high molecular weight polyethylene film. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a two-dimensional wide-angle X-ray diffraction pattern of the ultra-high molecular weight polyethylene film in Example 1 of the present application.

[0027] Figure 2 It is a two-dimensional wide-angle X-ray diffraction pattern of the ultra-high molecular weight polyethylene film in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0028] The present application is further described in detail below in conjunction with the accompanying drawings, embodiments and comparative examples. Example 1

[0029] A method for preparing an ultra-high molecular weight polyethylene uniaxially oriented film comprises the following steps: Step 1: Set the viscosity average molecular weight to 5.0×10 6 g / mol ultra-high molecular weight polyethylene resin and a weight average molecular weight of 4.0×10 3 g / mol of linear polyethylene wax are mixed to obtain a mixture; Step 2: adding the mixture to a twin-screw extruder for high-temperature melting to obtain a high-temperature melt; Step 3: The high-temperature melt is extruded and cast through a metering pump and a slit die to obtain a primary film; Step 4: The nascent film is subjected to uniaxial heat stretching at a temperature of 120° C. with a stretching ratio of 10 times, thereby obtaining a final ultra-high molecular weight polyethylene uniaxially oriented film.

[0030] The content of ultra-high molecular weight polyethylene in the mixture is 88wt%, and the content of polyethylene wax is 12wt%. The temperature of the feeding section of the twin-screw extruder is 115°C, the temperature of the compression section, the homogenization section and the die head are 200°C, and the screw speed of the twin-screw extruder is 50rpm. Example 2

[0031] A method for preparing an ultra-high molecular weight polyethylene uniaxially oriented film comprises the following steps: Step 1: Set the viscosity average molecular weight to 5.0×10 6 g / mol ultra-high molecular weight polyethylene resin and a weight average molecular weight of 1.0×10 3 g / mol of linear polyethylene wax are mixed to obtain a mixture; Step 2: adding the mixture to a twin-screw extruder for high-temperature melting to obtain a high-temperature melt; Step 3: The high-temperature melt is extruded and cast through a metering pump and a slit die to obtain a primary film; Step 4: The nascent film is subjected to uniaxial heat stretching at a temperature of 145° C. with a stretching ratio of 4 times, thereby obtaining a final ultra-high molecular weight polyethylene uniaxially oriented film.

[0032] The content of ultra-high molecular weight polyethylene in the mixture is 96wt%, and the content of polyethylene wax is 4wt%. The temperature of the feeding section of the twin-screw extruder is 140°C, the temperatures of the compression section, homogenization section and die head are all 250°C, and the screw speed of the twin-screw extruder is 200rpm. Example 3

[0033] A method for preparing an ultra-high molecular weight polyethylene uniaxially oriented film comprises the following steps: Step 1: Set the viscosity average molecular weight to 5.0×10 6 g / mol ultra-high molecular weight polyethylene resin and a weight average molecular weight of 6.0×10 3 g / mol of linear polyethylene wax are mixed to obtain a mixture; Step 2: adding the mixture to a twin-screw extruder for high-temperature melting to obtain a high-temperature melt; Step 3: The high-temperature melt is extruded and cast through a metering pump and a slit die to obtain a primary film; Step 4: The nascent film is subjected to uniaxial heat stretching at a temperature of 90° C. with a stretching ratio of 12 times, thereby obtaining a final ultra-high molecular weight polyethylene uniaxially oriented film.

[0034] The content of ultra-high molecular weight polyethylene in the mixture is 80wt%, and the content of polyethylene wax is 20wt%. The temperature of the feeding section of the twin-screw extruder is 90°C, the temperature of the compression section, the homogenization section and the die head are 160°C, and the screw speed of the twin-screw extruder is 10rpm.

[0035] Comparative Example 1 The only difference between this comparative example and Example 1 is that the linear polyethylene wax is replaced by white oil, and before step 4, the primary gel film needs to be extracted and dried to remove the white oil, and then uniaxially hot stretched.

[0036] Comparative Example 2 The only difference between this comparative example and Example 2 is that the linear polyethylene wax is replaced by decalin, and before step 4, the primary gel film needs to be extracted and dried to remove the decalin, and then uniaxially hot stretched.

[0037] Comparative Example 3 The difference between this comparative example and Example 3 is that the linear polyethylene wax is replaced by a polyethylene wax having a weight average molecular weight of 7.0×10 4 g / mol of high-density polyethylene.

[0038] The tensile mechanical properties, thermal properties and crystallization properties of the ultra-high molecular weight polyethylene films of Examples 1 to 3 and Comparative Examples 1 to 3 were tested. The specific testing methods are as follows: Detection Methods 1. Thermal properties (DSC) test: Cut the ultra-high molecular weight polyethylene uniaxially oriented film into small pieces, weigh 5 to 8 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 film. 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 film.

[0039] 2. Crystallinity and orientation test: The crystallinity and orientation of the ultra-high molecular weight polyethylene film 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 Pilatus900K detector with a resolution of 172×172 μm. 2, the distance from the detector to the sample is 210mm. 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 to calculate the ratio of amorphous area to crystalline area, and then the crystallinity is calculated. The calculation formula is as follows: Xc=Ac / (Ac+Aa), Where Ac and Aa represent the areas under the crystalline peak and amorphous peak of the I(2θ)~2θ curve, respectively.

[0040] The Hermans method is used to determine the crystal orientation of ultra-thin molecular weight polyethylene uniaxially oriented films. Taking the film stretching direction as the reference direction and the crystal plane as hkl, the orientation parameter can be expressed as:

[0041] in, is the azimuth, is the scattering intensity along the azimuth angle. The orientation degree f can be calculated by the following formula:

[0042] 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.

[0043] 3. Tensile mechanical properties test: The tensile mechanical properties of the ultra-high molecular weight polyethylene uniaxially oriented film were tested at room temperature using a universal mechanical testing machine, and the mechanical properties were characterized by stretching at a speed of 50 mm / min. During the tensile test, at least five samples were used for each film to obtain the average value and standard deviation.

[0044] 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 Performance test table of ultra-high molecular weight polyethylene films in Examples 1 to 3 and Comparative Examples 1 to 3

[0045] Conclusion 1: Combined with the test results of Example 1 to Example 3 and Comparative Example 1 to Comparative Example 3, the following Figure 1 and attached Figure 2It can be seen that when linear polyethylene wax and ultra-high molecular weight polyethylene are mixed, the linear polyethylene wax can effectively improve the melt fluidity of ultra-high molecular weight polyethylene, and by controlling the temperature during uniaxial hot stretching, the linear polyethylene wax can fully participate in the crystallization of ultra-high molecular weight polyethylene, thereby effectively improving the tensile strength and tensile modulus of the ultra-high molecular weight polyethylene film. Example 4

[0046] The only difference between this embodiment and embodiment 1 is that the content of ultra-high molecular weight polyethylene in the mixture is 80 wt %, and the content of polyethylene wax is 20 wt %. Example 5

[0047] The only difference between this embodiment and embodiment 1 is that the content of ultra-high molecular weight polyethylene in the mixture is 96 wt %, and the content of polyethylene wax is 4 wt %.

[0048] Comparative Example 4 The only difference between this comparative example and Example 1 is that the content of ultra-high molecular weight polyethylene in the mixture is 75 wt %, and the content of polyethylene wax is 25 wt %.

[0049] Comparative Example 5 The only difference between this comparative example and Example 1 is that the content of ultra-high molecular weight polyethylene in the mixture is 98 wt %, and the content of polyethylene wax is 2 wt %.

[0050] According to the above detection method, the detection results of the ultra-high molecular weight polyethylene films of Examples 4 to 5 and Comparative Examples 4 to 5 were obtained, and the detection results are shown in Table 2 below: Table 2 Performance test table of ultra-high molecular weight polyethylene films of Example 1, Example 4 to Example 5 and Comparative Example 1, Comparative Example 4 to Comparative Example 5

[0051] Conclusion 2: By comparing the test results of Example 1, Examples 4 to 5 and Comparative Examples 4 to 5, it can be concluded that when the content of ultra-high molecular weight polyethylene in the mixture is 80-96wt%, especially when the content of ultra-high molecular weight polyethylene is 88wt%, the ultra-high molecular weight polyethylene film finally prepared has good tensile strength and tensile modulus. Example 6

[0052] The only difference between this embodiment and embodiment 1 is that the polyethylene wax is a branched polyethylene wax with a branching degree of 110 / 1000C.

[0053] The ultra-high molecular weight polyethylene film of Example 6 was tested according to the above-mentioned testing method, and the test results are shown in Table 3 below: Table 3 Performance test table of ultra-high molecular weight polyethylene films of Example 1 and Example 6

[0054] Conclusion 3: By comparing the test results of Example 1 and Example 6, it can be concluded that when the molecular structure of the polyethylene wax is a linear chain, the polyethylene wax is more able to participate in the crystallization of ultra-high molecular weight polyethylene, thereby reducing or eliminating the damage of the polyethylene wax as a low molecular weight substance to the mechanical properties of the ultra-high molecular weight polyethylene film, thereby preparing an ultra-high molecular weight polyethylene film with ideal performance. Example 7

[0055] The difference between this embodiment and embodiment 1 is that the weight average molecular weight of the polyethylene wax is 2.0×10 3 g / mol. Example 8

[0056] The difference between this embodiment and embodiment 1 is that the weight average molecular weight of the polyethylene wax is 5.0×10 3 g / mol.

[0057] Comparative Example 6 The difference between this embodiment and embodiment 1 is that the weight average molecular weight of the polyethylene wax is 8.0×10 3 g / mol.

[0058] The ultra-high molecular weight polyethylene films of Examples 7 to 8 and Comparative Example 6 were tested according to the above-mentioned testing method, and the test results are shown in Table 4 below: Table 4 Performance test table of ultra-high molecular weight polyethylene films of Example 1, Example 7 to Example 8 and Comparative Example 6

[0059] Conclusion 4: Combining the test results of Example 1, Example 7 to Example 8 and Comparative Example 6, it can be concluded that when the weight average molecular weight of polyethylene wax is 2.0×10 3 ~5.0×10 3 g / mol range, especially when the weight average molecular weight of polyethylene wax is 4.0×10 3 g / mol, polyethylene wax can greatly improve the melt fluidity of ultra-high molecular weight polyethylene, and the obtained ultra-high molecular weight polyethylene film has excellent mechanical properties. Example 9

[0060] The only difference between this embodiment and embodiment 1 is that the temperature of the compression section, homogenization section and die head of the twin-screw extruder is 160°C. Example 10

[0061] The only difference between this embodiment and embodiment 1 is that the temperature of the compression section, homogenization section and die head of the twin-screw extruder is 250°C.

[0062] Comparative Example 7 The only difference between this comparative example and Example 1 is that the temperature of the compression section, homogenization section and die head of the twin-screw extruder is 150°C.

[0063] Comparative Example 8 The only difference between this comparative example and Example 1 is that the temperature of the compression section, homogenization section and die head of the twin-screw extruder is 270°C.

[0064] The ultra-high molecular weight polyethylene films of Examples 9 and 10 and Comparative Examples 7 and 8 were tested according to the above-mentioned testing method. The test results are shown in Table 5 below: Table 5 Performance test table of ultra-high molecular weight polyethylene films of Example 1, Example 9 to Example 10 and Comparative Example 7 to Comparative Example 8

[0065] Conclusion 5: By comparing the test results of Example 1, Examples 9 to 10 and Comparative Examples 7 to 8, it can be concluded that when the compression section, homogenization section and die temperature of the twin-screw extruder are at 160-250°C, especially when the temperature is at 200°C, the original folded chain lamellae in the ultra-high molecular weight polyethylene can be fully melted and the straight chain crystals are retained. Therefore, the ultra-high molecular weight polyethylene film finally prepared has good tensile strength and tensile modulus. Embodiment 11

[0066] The only difference between this embodiment and embodiment 1 is that the temperature of uniaxial heat stretching is 90°C. Example 12

[0067] The only difference between this embodiment and embodiment 1 is that the temperature of uniaxial heat stretching is 110°C. Example 13

[0068] The only difference between this embodiment and embodiment 1 is that the temperature of uniaxial heat stretching is 140°C. Embodiment 14

[0069] The only difference between this comparative example and Example 1 is that the temperature of uniaxial heat stretching is 145°C.

[0070] The ultra-high molecular weight polyethylene films of Examples 11 to 14 were tested according to the above-mentioned testing method, and the test results are shown in Table 6 below: Table 6 Performance test table of ultra-high molecular weight polyethylene films of Example 1, Example 11 to Example 14

[0071] Conclusion 6: By comparing the test results of Example 1 and Examples 11 to 14, it can be concluded that when the temperature of uniaxial hot stretching is between 90 and 145°C, especially when the temperature of uniaxial hot stretching is at 120°C, the ultra-high molecular weight polyethylene film finally prepared has good tensile strength and tensile modulus while ensuring the overall quality. Embodiment 15

[0072] The only difference between this embodiment and embodiment 1 is that the stretching ratio of the uniaxial heat stretching is 4 times. Example 16

[0073] The only difference between this embodiment and embodiment 1 is that the stretching ratio of the uniaxial heat stretching is 8 times. Embodiment 17

[0074] The only difference between this embodiment and embodiment 1 is that the stretching ratio of the uniaxial heat stretching is 12 times.

[0075] The ultra-high molecular weight polyethylene films of Examples 13 to 15 were tested according to the above-mentioned testing method, and the test results are shown in Table 7 below: Table 7 Performance test table of ultra-high molecular weight polyethylene films of Example 1, Example 15 to Example 17

[0076] Conclusion 7: By comparing the test results of Example 1 and Examples 15 to 17, it can be concluded that when the stretching ratio of uniaxial heat stretching is in the range of 4 to 12 times, especially when the stretching ratio is 10 times, the overall quality of the ultra-high molecular weight polyethylene film finally prepared is ideal and has higher tensile strength and tensile modulus.

[0077] 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 preparing an ultra-high molecular weight polyethylene uniaxially oriented film, characterized in that: The steps are as follows: Step 1: mixing an ultra-high molecular weight polyethylene resin and a polyethylene wax to obtain a mixture; Step 2: Melting the mixture at high temperature to obtain a high-temperature melt; Step 3: Extruding and casting the high temperature melt to obtain a primary film; Step 4: Perform uniaxial heat stretching on the nascent film to obtain the final ultra-high molecular weight polyethylene uniaxially oriented film.

2. The method for preparing a uniaxially oriented ultra-high molecular weight polyethylene film according to claim 1, characterized in that: The content of ultra-high molecular weight polyethylene in the mixture is 80-96 wt %, and the content of polyethylene wax is 4-20 wt %.

3. The method for preparing a uniaxially oriented ultra-high molecular weight polyethylene film according to claim 2, characterized in that: The content of ultra-high molecular weight polyethylene in the mixture is 85-92 wt %.

4. The method for preparing a uniaxially oriented ultra-high molecular weight polyethylene film according to claim 1, characterized in that: The polyethylene wax is linear polyethylene wax.

5. The method for preparing a uniaxially oriented ultrahigh molecular weight polyethylene film according to claim 4, characterized in that: The weight average molecular weight of the polyethylene wax is 2.0×10 3 ~5.0×10 3 g / mol.

6. The method for preparing a uniaxially oriented ultrahigh molecular weight polyethylene film according to claim 1, characterized in that: In step 2, the mixture is melted at high temperature by a twin-screw extruder, wherein the temperature of the feeding section of the twin-screw extruder is 90-140°C, the temperature of the compression section is 160-250°C, the temperature of the homogenization section is 160-250°C, the die head temperature is 160-250°C, and the screw speed of the twin-screw extruder is 10-200rpm.

7. The method for preparing a uniaxially oriented ultrahigh molecular weight polyethylene film according to claim 6, characterized in that: The temperatures of the compression section, homogenization section and die head of the twin-screw extruder are 160-200°C.

8. The method for preparing a uniaxially oriented ultra-high molecular weight polyethylene film according to claim 1, characterized in that: The temperature of the uniaxial heat stretching in step 4 is 90 to 145° C., and the stretching ratio is 4 to 12 times.

9. The method for preparing a uniaxially oriented ultra-high molecular weight polyethylene film according to claim 8, characterized in that: The temperature of the uniaxial heat stretching in step 4 is 110-140°C.

10. The method for preparing a uniaxially oriented ultrahigh molecular weight polyethylene film according to claim 8, characterized in that: The stretching ratio of the uniaxial heat stretching in step 4 is 8 to 12 times.

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