A method for preparing uniaxially oriented ultra-high molecular weight polyethylene thin films

Abstract

This application discloses a method for preparing a uniaxially oriented ultra-high molecular weight polyethylene (UHMWPE) film, comprising the following steps: Step 1: mixing UHMWPE resin with 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 nascent film; Step 4: subjecting the nascent film to uniaxial thermal stretching to obtain the final UHMWPE uniaxially oriented film. The polyethylene wax is used to improve the melt flowability of UHMWPE, and by controlling the temperature during uniaxial thermal stretching, the polyethylene wax can participate in the crystallization of UHMWPE and retain the extended chain crystals in UHMWPE, thereby improving the mechanical properties of the UHMWPE film.

Description

Technical Field

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

[0002] Ultra-high molecular weight polyethylene (UHMWPE) is a linear thermoplastic with characteristics such as non-toxicity, excellent corrosion resistance, good chemical stability, and electrical insulation. It is widely used in new energy, marine engineering, and electronics industries.

[0003] The key technology for preparing ultra-high molecular weight polyethylene (UHMWPE) films lies in preparing UHMWPE compositions with ideal melt flowability, enabling UHMWPE to be successfully extruded. However, UHMWPE in the molten state is a rubbery, highly viscoelastic material with a melt flow index of almost zero. Consequently, UHMWPE has a very low critical shear rate, leading to defects such as melt fracture, making it difficult to form UHMWPE films using conventional polymer melt processing methods.

[0004] Polyethylene wax is an effective additive that can improve the processing flowability of polymer materials. However, commonly used polyethylene waxes have a high branching content, resulting in poor or no crystallization ability. During the cooling process after molding, they cannot participate in the crystallization of the polymer material, affecting the mechanical properties of the polymer product. Therefore, linear polyethylene wax can be used to improve the melt flowability of ultra-high molecular weight polyethylene (UHMWPE). By controlling the hot stretching temperature, the linear polyethylene wax can fully participate in the crystallization of UHMWPE during uniaxial hot stretching, thereby reducing or even eliminating the destructive effect of polyethylene wax, as a low molecular weight substance, on the mechanical properties of UHMWPE films. Analysis of UHMWPE resin reveals that it contains both ordinary folded chain lamellar crystals and extended chain crystals. Extended chain crystals possess very high mechanical properties and can also serve as highly efficient nucleating agents for linear polyethylene wax crystallization. Furthermore, the melting points of ordinary folded chain lamellar crystals and extended chain crystals differ significantly. Therefore, by controlling the plasticizing temperature, the original extended chain crystals of the UHMWPE resin can be retained, thus forming a method for preparing UHMWPE modified with polyethylene wax. Summary of the Invention

[0005] In order to improve the melt flowability of ultra-high molecular weight polyethylene (UHMWPE) to facilitate the preparation of UHMWPE films, this application provides a method for preparing uniaxially oriented UHMWPE films.

[0006] This application provides a method for preparing an ultra-high molecular weight polyethylene uniaxially oriented film, comprising the following steps:

[0007] Step 1: Mix ultra-high molecular weight polyethylene resin with polyethylene wax to obtain a mixture;

[0008] Step 2: Melt the mixture at high temperature to obtain a high-temperature melt;

[0009] Step 3: The high-temperature melt is extruded and cast to prepare the nascent film;

[0010] Step 4: Perform uniaxial thermal stretching on the nascent film to obtain the final ultra-high molecular weight polyethylene uniaxially oriented film.

[0011] By employing the above technical solution, polyethylene wax is used to improve the melt flowability of ultra-high molecular weight polyethylene (UHMWPE), enabling UHMWPE to be extruded smoothly. Furthermore, by controlling the temperature during uniaxial thermal stretching, the polyethylene wax can participate in the crystallization of UHMWPE, thereby reducing or even eliminating the destructive effect of polyethylene wax, as a low molecular weight substance, on the mechanical properties of the UHMWPE film, while preserving the original extended-chain crystals in UHMWPE, thus improving the mechanical properties of the UHMWPE film.

[0012] In addition, after the ultra-high molecular weight polyethylene film is made, there is no need to recycle the polyethylene wax, thereby reducing the preparation steps of the ultra-high molecular weight polyethylene uniaxial orientation film.

[0013] Preferably, the mixture contains 80-96 wt% ultra-high molecular weight polyethylene and 4-20 wt% polyethylene wax.

[0014] Preferably, the content of ultra-high molecular weight polyethylene is 85-92 wt%.

[0015] By adopting the above technical solution, polyethylene wax can improve the melt flowability of ultra-high molecular weight polyethylene, making it possible for ultra-high molecular weight polyethylene to be extruded and cast smoothly. The presence of a higher content of ultra-high molecular weight polyethylene helps to ensure the mechanical properties of ultra-high molecular weight polyethylene film, and the processing is more efficient.

[0016] Preferably, the polyethylene wax is a linear polyethylene wax.

[0017] By adopting the above technical solution, the linear polyethylene wax is mainly linear in structure and has ideal crystallization ability. This allows the polyethylene wax to fully participate in the crystallization process of ultra-high molecular weight polyethylene during uniaxial thermal 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 maintaining the mechanical properties of ultra-high molecular weight polyethylene film well.

[0018] Preferably, the polyethylene wax has a weight-average molecular weight of 2.0 × 10⁻⁶. 3~5.0×10 3 g / mol.

[0019] By adopting the above technical solution, low molecular weight polyethylene wax can significantly improve the melt flowability of ultra-high molecular weight polyethylene, allowing the mixture to be extruded and cast smoothly. Moreover, 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.

[0020] Preferably, in step 2, the mixture is melted at high temperature using a twin-screw extruder. 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 temperature is 160–250°C, and the screw speed of the twin-screw extruder is 10–200 rpm.

[0021] By adopting the above technical solution, when the temperature of the compression section, homogenization section, and die of the twin-screw extruder exceeds 250℃, ultra-high molecular weight polyethylene (UHMWPE) is easily degraded. When the temperature is below 160℃, the folded chain lamellar crystals in UHMWPE are retained, affecting the melt flowability of UHMWPE and resulting in uneven thickness and unsatisfactory overall quality of the prepared UHMWPE film. A screw speed of 10–200 rpm in the twin-screw extruder facilitates the mixing of UHMWPE and polyethylene wax. The low speed reduces shearing of the molecular chains, ensuring the mechanical properties of the UHMWPE film.

[0022] Preferably, the temperatures of the compression section, homogenization section, and die of the twin-screw extruder are 160–200°C.

[0023] By adopting the above technical solution, within this temperature range, the folded chain crystals in ultra-high molecular weight polyethylene resin can be fully melted, but some extended chain crystals can be retained. The retained extended chain crystals can act as nucleating agents to induce polyethylene wax to crystallize on its surface during uniaxial thermal stretching, thereby maintaining the mechanical properties of ultra-high molecular weight polyethylene film well.

[0024] Preferably, the temperature of the uniaxial thermal stretching in step 4 is 90–145°C, and the stretching ratio is 4–12 times.

[0025] Preferably, the temperature of the uniaxial thermal stretching in step 4 is 110–140°C.

[0026] By adopting the above technical solutions, 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 straightened chain crystals is low, and the quality of the resulting film is unstable; if the hot stretching temperature is too high, the linear polyethylene wax does not participate sufficiently in the crystallization of ultra-high molecular weight polyethylene, which affects the mechanical properties of ultra-high molecular weight polyethylene film.

[0027] Preferably, the stretching ratio of uniaxial thermal stretching is 8 to 12 times.

[0028] By adopting the above technical solution, when the stretching ratio is too low, the number of newly formed stretched chain crystals retained during the stretching process is insufficient, which cannot 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.

[0029] In summary, this application has the following beneficial effects:

[0030] 1. This application utilizes polyethylene wax to improve the melt flowability of ultra-high molecular weight polyethylene (UHMWPE), and by controlling the uniaxial thermal stretching temperature, the polyethylene wax can participate in the crystallization of UHMWPE, thereby improving the mechanical properties of UHMWPE film. Furthermore, the polyethylene wax added during the preparation process does not need to be recycled, which helps to reduce the preparation steps of UHMWPE uniaxial orientation film.

[0031] 2. The polyethylene wax added in this application is a linear polyethylene wax, which can improve the melt flowability of ultra-high molecular weight polyethylene, enabling ultra-high molecular weight polyethylene to be extruded and molded smoothly. Through temperature control, the linear polyethylene wax participates in the crystallization of ultra-high molecular weight polyethylene, ensuring the mechanical properties of ultra-high molecular weight polyethylene film.

[0032] 3. In this application, the temperature of the compression section, homogenization section and die head of the twin-screw extruder is controlled at 160-200℃, which can ensure that the folded chain crystals in ultra-high molecular weight polyethylene are fully melted, while the extended chain crystals are retained. The retained extended chain crystals can act as nucleating agents to induce polyethylene wax to crystallize on its surface during uniaxial thermal stretching, thereby improving the mechanical properties of ultra-high molecular weight polyethylene film. Attached Figure Description

[0033] Figure 1 This is a two-dimensional wide-angle X-ray diffraction pattern of the ultra-high molecular weight polyethylene film in Example 1 of this application.

[0034] Figure 2 This is a two-dimensional wide-angle X-ray diffraction pattern of the ultra-high molecular weight polyethylene film in Comparative Example 1 of this application. Detailed Implementation

[0035] The present application will be further described in detail below with reference to the accompanying drawings, embodiments and comparative examples. Example 1

[0036] A method for preparing an ultra-high molecular weight polyethylene uniaxially oriented film includes the following steps:

[0037] Step 1: The viscosity-average molecular weight is 5.0 × 10⁻⁶. 6 g / mol of ultra-high molecular weight polyethylene resin and a weight-average molecular weight of 4.0 × 10⁻⁶ g / mol of [unspecified material] 3 A mixture was obtained by mixing g / mol of linear polyethylene wax;

[0038] Step 2: Add the mixture to a twin-screw extruder for high-temperature melting to obtain a high-temperature melt;

[0039] Step 3: The high-temperature melt is extruded and cast through a metering pump and a slit die to obtain a primary film;

[0040] Step 4: The nascent film is subjected to uniaxial thermal stretching at 120°C with a stretching ratio of 10 times, thereby obtaining the final ultra-high molecular weight polyethylene uniaxial oriented film.

[0041] The mixture contains 88 wt% ultra-high molecular weight polyethylene and 12 wt% polyethylene wax. The feeding section temperature of the twin-screw extruder is 115℃, and the temperatures of the compression section, homogenization section, and die are all 200℃. The screw speed of the twin-screw extruder is 50 rpm. Example 2

[0042] A method for preparing an ultra-high molecular weight polyethylene uniaxially oriented film includes the following steps:

[0043] Step 1: The viscosity-average molecular weight is 5.0 × 10⁻⁶. 6 g / mol of ultra-high molecular weight polyethylene resin and a weight-average molecular weight of 1.0 × 10⁻⁶ g / mol of [unspecified material] 3 A mixture was obtained by mixing g / mol of linear polyethylene wax;

[0044] Step 2: Add the mixture to a twin-screw extruder for high-temperature melting to obtain a high-temperature melt;

[0045] Step 3: The high-temperature melt is extruded and cast through a metering pump and a slit die to obtain a primary film;

[0046] Step 4: The nascent film is subjected to uniaxial thermal stretching at 145°C with a stretching ratio of 4 times, thereby obtaining the final ultra-high molecular weight polyethylene uniaxial oriented film.

[0047] The mixture contains 96 wt% ultra-high molecular weight polyethylene and 4 wt% polyethylene wax. The feeding section temperature of the twin-screw extruder is 140℃, and the temperatures of the compression section, homogenization section, and die are all 250℃. The screw speed of the twin-screw extruder is 200 rpm. Example 3

[0048] A method for preparing an ultra-high molecular weight polyethylene uniaxially oriented film includes the following steps:

[0049] Step 1: The viscosity-average molecular weight is 5.0 × 10⁻⁶. 6 g / mol of ultra-high molecular weight polyethylene resin and a weight-average molecular weight of 6.0 × 10⁻⁶ g / mol of [unspecified material] 3 A mixture was obtained by mixing g / mol of linear polyethylene wax;

[0050] Step 2: Add the mixture to a twin-screw extruder for high-temperature melting to obtain a high-temperature melt;

[0051] Step 3: The high-temperature melt is extruded and cast through a metering pump and a slit die to obtain a primary film;

[0052] Step 4: The nascent film is subjected to uniaxial thermal stretching at 90°C with a stretching ratio of 12 times, thereby obtaining the final ultra-high molecular weight polyethylene uniaxial oriented film.

[0053] The mixture contains 80 wt% ultra-high molecular weight polyethylene and 20 wt% polyethylene wax. The feeding section temperature of the twin-screw extruder is 90℃, and the temperatures of the compression section, homogenization section, and die are all 160℃. The screw speed of the twin-screw extruder is 10 rpm.

[0054] Comparative Example 1

[0055] The only difference between this comparative example and Example 1 is that linear polyethylene wax is replaced with white oil, and the nascent gel film needs to be extracted and dried to remove the white oil before step 4, followed by uniaxial thermal stretching.

[0056] Comparative Example 2

[0057] The only difference between this comparative example and Example 2 is that linear polyethylene wax is replaced with decahydronaphthalene, and the nascent gel film needs to be extracted and dried to remove decahydronaphthalene before step 4, followed by uniaxial thermal stretching.

[0058] Comparative Example 3

[0059] The only difference between this comparative example and Example 3 is that the linear polyethylene wax is replaced with a wax with a weight-average molecular weight of 7.0 × 10⁻⁶. 4 g / mol of high-density polyethylene.

[0060] The tensile mechanical properties, thermal properties, and crystallinity 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.

[0061] Detection methods

[0062] 1. Thermal Performance (DSC) Test:

[0063] Cut the ultra-high molecular weight polyethylene uniaxially oriented film into small pieces, weigh 5-8 mg and place them in a standard aluminum crucible. Protect the crucible with a dry nitrogen gas flow and test the thermal properties of the ultra-high molecular weight polyethylene film using a differential scanning calorimeter (DSC). Heat the film from 25℃ to 200℃ at a heating rate of 10℃ / min and record the thermal property curves.

[0064] 2. Crystallinity and orientation tests:

[0065] The crystallinity and orientation of the ultra-high molecular weight polyethylene film were measured using wide-angle X-ray diffraction (WAXD) at a wavelength of 0.124 nm. Two-dimensional WAXD results were collected using a Pilatus 900K detector with a resolution of 172 × 172 μm. 2 The distance from the detector to the sample was 210 mm. WAXD data was obtained by processing the data using FIT2D software. One-dimensional integration was performed on the two-dimensional WAXD image to obtain the intensity distribution curve in the 2θ direction. Then, peak fitting was performed on the curve to calculate the ratio of amorphous to crystalline regions, and subsequently, the crystallinity was calculated. The calculation formula is as follows: Xc = Ac / (Ac + Aa),

[0066] Ac and Aa represent the areas under the crystalline peak and amorphous peak of the I(2θ)~2θ curve, respectively.

[0067] The Hermans method was used to determine the crystal orientation degree of ultrathin uniaxially oriented polyethylene films. With the film stretching direction as the reference direction and the crystal plane denoted as hkl, the orientation parameters can be expressed as:

[0068]

[0069] in, It is the azimuth angle. Let f be the scattering intensity along the azimuth angle. The orientation degree f can be calculated using the following formula:

[0070]

[0071] 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 direction of the crystal plane is freely oriented.

[0072] 3. Tensile mechanical property testing:

[0073] The tensile mechanical properties of ultra-high molecular weight polyethylene uniaxially oriented films were tested at room temperature using a universal testing machine, with a tensile speed of 50 mm / min. During the tensile tests, at least five samples were used for each type of film to obtain the mean and standard deviation.

[0074] Based on 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:

[0075] Table 1. Performance test results of ultra-high molecular weight polyethylene films in Examples 1 to 3 and Comparative Examples 1 to 3.

[0076]

[0077] Conclusion 1:

[0078] A comparison of the detection results from Examples 1 to 3 and Comparative Examples 1 to 3, and the appendix. Figure 1 and attached Figure 2 It can be seen that when linear polyethylene wax and ultra-high molecular weight polyethylene are mixed, linear polyethylene wax can effectively improve the melt flowability of ultra-high molecular weight polyethylene. Furthermore, by controlling the temperature during uniaxial hot stretching, 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 ultra-high molecular weight polyethylene film. Example 4

[0079] The only difference between this embodiment and Example 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

[0080] The only difference between this embodiment and Example 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%.

[0081] Comparative Example 4

[0082] 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%.

[0083] Comparative Example 5

[0084] 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%.

[0085] Based on 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:

[0086] Table 2 Performance test results of ultra-high molecular weight polyethylene films from Examples 1, 4 to 5, and Comparative Examples 1, 4 to 5

[0087]

[0088] Conclusion 2:

[0089] By comparing the test results of Examples 1, 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 to 96 wt%, especially when the content of ultra-high molecular weight polyethylene is 88 wt%, the ultra-high molecular weight polyethylene film finally prepared has better tensile strength and tensile modulus. Example 6

[0090] 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.

[0091] The ultra-high molecular weight polyethylene film of Example 6 was tested according to the above-described testing method, and the test results are shown in Table 3 below:

[0092] Table 3 Performance test results of ultra-high molecular weight polyethylene films from Examples 1 and 6

[0093]

[0094] Conclusion 3:

[0095] A comparison of the test results from Examples 1 and 6 shows that when the molecular structure of polyethylene wax is a linear chain, polyethylene wax is more capable of participating in the crystallization of ultra-high molecular weight polyethylene, thereby reducing or eliminating the damage to the mechanical properties of ultra-high molecular weight polyethylene film caused by polyethylene wax as a low molecular weight substance, thus preparing an ultra-high molecular weight polyethylene film with ideal performance. Example 7

[0096] The only difference between this embodiment and Example 1 is that the weight-average molecular weight of the polyethylene wax is 2.0 × 10⁻⁶. 3 g / mol. Example 8

[0097] The only difference between this embodiment and Example 1 is that the weight-average molecular weight of the polyethylene wax is 5.0 × 10⁻⁶. 3 g / mol.

[0098] Comparative Example 6

[0099] The only difference between this embodiment and Example 1 is that the weight-average molecular weight of the polyethylene wax is 8.0 × 10⁻⁶. 3 g / mol.

[0100] The ultra-high molecular weight polyethylene films of Examples 7 to 8 and Comparative Example 6 were tested according to the above-described testing methods. The test results are shown in Table 4 below:

[0101] Table 4 Performance test results of ultra-high molecular weight polyethylene films from Examples 1, 7 to 8, and Comparative Example 6

[0102]

[0103] Conclusion 4:

[0104] A comparison of the test results from Example 1, Examples 7 to 8, and Comparative Example 6 shows that when the weight-average molecular weight of polyethylene wax is 2.0 × 10⁻⁶... 3 ~5.0×10 3 Within the g / mol range, especially when the weight-average molecular weight of polyethylene wax is 4.0 × 10⁻⁶ g / mol. 3 At a concentration of g / mol, polyethylene wax can significantly improve the melt flowability of ultra-high molecular weight polyethylene, resulting in ultra-high molecular weight polyethylene films with excellent mechanical properties. Example 9

[0105] The only difference between this embodiment and Embodiment 1 is that the temperature of the compression section, homogenization section, and die of the twin-screw extruder is 160°C. Example 10

[0106] The only difference between this embodiment and Embodiment 1 is that the temperature of the compression section, homogenization section, and die of the twin-screw extruder is 250°C.

[0107] Comparative Example 7

[0108] The only difference between this comparative example and Example 1 is that the temperature of the compression section, homogenization section, and die of the twin-screw extruder is 150°C.

[0109] Comparative Example 8

[0110] The only difference between this comparative example and Example 1 is that the temperature of the compression section, homogenization section, and die of the twin-screw extruder is 270°C.

[0111] The ultra-high molecular weight polyethylene films of Examples 9 to 10 and Comparative Examples 7 to 8 were tested according to the above-described testing methods. The test results are shown in Table 5 below:

[0112] Table 5 Performance test results of ultra-high molecular weight polyethylene films from Examples 1, 9 to 10, and Comparative Examples 7 to 8

[0113]

[0114] Conclusion 5:

[0115] By comparing the test results of Examples 1, 9 to 10 and Comparative Examples 7 to 8, it can be concluded that when the temperature of the compression section, homogenization section and die head of the twin-screw extruder is between 160 and 250°C, especially when the temperature is at 200°C, the original folded chain crystals in ultra-high molecular weight polyethylene can be fully melted while the straightened chain crystals are retained. Therefore, the ultra-high molecular weight polyethylene film finally prepared has good tensile strength and tensile modulus. Example 11

[0116] The only difference between this embodiment and Embodiment 1 is that the temperature for uniaxial thermal stretching is 90°C. Example 12

[0117] The only difference between this embodiment and Embodiment 1 is that the temperature for uniaxial hot stretching is 110°C. Example 13

[0118] The only difference between this embodiment and Embodiment 1 is that the temperature for uniaxial thermal stretching is 140°C. Example 14

[0119] The only difference between this comparative example and Example 1 is that the temperature of the uniaxial thermal stretching is 145°C.

[0120] The ultra-high molecular weight polyethylene films of Examples 11 to 14 were tested according to the above-described testing methods, and the test results are shown in Table 6 below:

[0121] Table 6 Performance testing of ultra-high molecular weight polyethylene films from Examples 1, 11 to 14

[0122]

[0123] Conclusion 6:

[0124] By comparing the test results of Example 1 and Examples 11 to 14, it can be concluded that when the temperature of uniaxial thermal stretching is between 90 and 145°C, especially when the temperature of uniaxial thermal stretching is between 120°C, the ultra-high molecular weight polyethylene film finally prepared has good tensile strength and tensile modulus while ensuring the overall quality. Example 15

[0125] The only difference between this embodiment and Embodiment 1 is that the stretching ratio of uniaxial thermal stretching is 4 times. Example 16

[0126] The only difference between this embodiment and Embodiment 1 is that the stretching ratio of uniaxial thermal stretching is 8 times. Example 17

[0127] The only difference between this embodiment and Embodiment 1 is that the stretching ratio of uniaxial thermal stretching is 12 times.

[0128] The ultra-high molecular weight polyethylene films of Examples 13 to 15 were tested according to the above-described testing methods, and the test results are shown in Table 7 below:

[0129] Table 7 Performance Test Results of Ultra-High Molecular Weight Polyethylene Films from Examples 1, 15 to 17

[0130]

[0131] Conclusion 7:

[0132] By comparing the test results of Example 1 and Examples 15 to 17, it can be concluded that when the stretching ratio of uniaxial thermal 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 prepared is ideal, and it has high tensile strength and tensile modulus.

[0133] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a uniaxially oriented ultra-high molecular weight polyethylene film, characterized in that: The steps are as follows: Step 1: Mix ultra-high molecular weight polyethylene resin with polyethylene wax to obtain a mixture; Step 2: Melt the mixture at high temperature to obtain a high-temperature melt; Step 3: Extrude and cast the high-temperature melt to obtain a primary film; Step 4: Perform uniaxial thermal stretching on the nascent film to obtain the final ultra-high molecular weight polyethylene uniaxially oriented film; The polyethylene wax is a linear polyethylene wax; The weight-average molecular weight of the polyethylene wax is 2.0 × 10⁻⁶. 3 ~5.0×10 3 g / mol.

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

3. The method for preparing an ultra-high molecular weight polyethylene uniaxially oriented film according to claim 2, characterized in that: The mixture contains 85–92 wt% ultra-high molecular weight polyethylene.

4. The method for preparing an ultra-high molecular weight polyethylene uniaxially oriented film according to claim 1, characterized in that: In step 2, the mixture is melted at high temperature using a twin-screw extruder. 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 temperature is 160-250°C, and the screw speed of the twin-screw extruder is 10-200 rpm.

5. The method for preparing an ultra-high molecular weight polyethylene uniaxially oriented film according to claim 4, characterized in that: The temperature of the compression section, homogenization section, and die of the twin-screw extruder is 160–200°C.

6. The method for preparing an ultra-high molecular weight polyethylene uniaxially oriented film according to claim 1, characterized in that: In step 4, the temperature for uniaxial hot stretching is 90–145℃, and the stretching ratio is 4–12 times.

7. The method for preparing an ultra-high molecular weight polyethylene uniaxially oriented film according to claim 6, characterized in that: The temperature for uniaxial hot stretching in step 4 is 110–140°C.

8. The method for preparing an ultra-high molecular weight polyethylene uniaxially oriented film according to claim 6, characterized in that: In step 4, the stretching ratio of uniaxial thermal stretching is 8 to 12 times.

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