A method for producing an ultra-high molecular weight polyethylene biaxially oriented film

Abstract

The application discloses a preparation method of an ultra-high molecular weight polyethylene biaxial orientation film and relates to the field of polymer materials, and comprises the following steps: step 1, mixing ultra-high molecular weight polyethylene and polyethylene wax to obtain a composition; step 2, melt plasticizing the obtained composition, and forming a thin-walled tubular film through extrusion after melt plasticizing; and step 3, obtaining the final ultra-high molecular weight polyethylene film through blowing, traction and winding of the thin-walled tubular film. The polyethylene wax is used to improve the melt flowability of the ultra-high molecular weight polyethylene, and through control of a blowing process, the polyethylene wax can participate in the crystallization of the ultra-high molecular weight polyethylene, so that the mechanical property of the ultra-high molecular weight polyethylene biaxial orientation film is improved.

Description

Technical Field

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

[0002] Ultra-high molecular weight polyethylene is a linear thermoplastic engineering plastic with super wear resistance, self-lubrication, relatively high strength, stable chemical properties and strong anti-aging performance. Therefore, it has a wide range of applications. In the new energy field, it can be used as a lithium-ion battery separator. In the marine engineering field, it can be used as an anti-corrosion, anti-rust and anti-adhesion veneer and coating material for the surface of ships. In the food field, it can be used as a packaging material for food and medicinal materials.

[0003] Existing ultra-high molecular weight polyethylene (UHMWPE) films are typically produced using a wet extrusion process. In this process, UHMWPE is first mixed with a suitable solvent, then extruded and cast to form a gel film. The gel film is then subjected to simultaneous or stepwise biaxial heat stretching, and finally the solvent within the gel film is extracted and dried to produce the finished film. However, during the preparation of these UHMWPE films, the added solvent needs to be recovered, making the process environmentally unfriendly, lengthy, and costly. Furthermore, the UHMWPE films produced using the wet extrusion process are porous membranes.

[0004] The addition of linear polyethylene wax can effectively improve the melt fluidity of ultra-high molecular weight polyethylene, and by controlling the temperature, the linear polyethylene wax can participate in the crystallization of ultra-high molecular weight polyethylene, thereby ensuring the mechanical properties of the ultra-high molecular weight polyethylene film. The added linear polyethylene wax does not need to be recycled, and the composition is then blown and stretched, which helps to improve the longitudinal and transverse mechanical properties of the ultra-high molecular weight polyethylene film, thereby forming a preparation method for ultra-high molecular weight polyethylene biaxially oriented film. Summary of the Invention

[0005] In order to solve the problem that the preparation process of ultra-high molecular weight polyethylene film is long and environmentally unfriendly, the present application provides a method for preparing ultra-high molecular weight polyethylene biaxially oriented film.

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

[0007] Step 1: mixing ultra-high molecular weight polyethylene and polyethylene wax to obtain a composition;

[0008] Step 2: Melting and plasticizing the obtained composition, and then extruding it to form a thin-walled tubular film;

[0009] Step 3: The thin-walled tubular film is blown, drawn and rolled to obtain the final ultra-high molecular weight polyethylene film.

[0010] By adopting the above technical solution, polyethylene wax is used to improve the melt fluidity of ultra-high molecular weight polyethylene (UHMWPE), allowing the UHMWPE to be smoothly extruded. Furthermore, by controlling the blow molding process, the polyethylene wax fully participates in the crystallization of the UHMWPE during the blow molding process, thereby reducing or even eliminating the damage caused by the polyethylene wax, a low molecular weight substance, to the mechanical properties of the UHMWPE film, thereby improving the mechanical properties of the UHMWPE film. After the UHMWPE biaxially oriented film is produced, the added polyethylene wax does not need to be recycled, effectively reducing the production process flow of the UHMWPE biaxially oriented film.

[0011] Preferably, when the mass of the composition is 100 wt%, the content of ultra-high molecular weight polyethylene is 90-99 wt%, and the content of polyethylene wax is 1-10 wt%.

[0012] By adopting the above technical solution, the UHMWPE content in the composition reaches over 90wt%. The UHMWPE can improve the mechanical properties of the film. The low content of polyethylene wax can enhance the melt flow of the UHMWPE and participate in the crystallization of the UHMWPE during the blow molding process, effectively maintaining the mechanical properties of the UHMWPE film. With this selection of mass content ratios, the UHMWPE film can achieve both high mechanical properties and greater processing efficiency.

[0013] Preferably, the polyethylene wax is linear polyethylene wax.

[0014] By adopting the above technical solution, linear polyethylene wax and ultra-high molecular weight polyethylene are mixed. The molecular chain of the linear polyethylene wax is mainly straight chain, and its crystallization ability is ideal, so that the polyethylene wax can fully participate in the crystallization of the ultra-high molecular weight polyethylene during the blow molding process, thereby reducing or even 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, and can well maintain the mechanical properties of the ultra-high molecular weight polyethylene film.

[0015] Preferably, the weight average molecular weight of the polyethylene wax is 1.0×10 3 ~6.0×10 3 g / mol.

[0016] By adopting the above technical solution, low molecular weight polyethylene wax can significantly improve the melt fluidity of ultra-high molecular weight polyethylene, so that the composition can be smoothly extruded and blow-molded. 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.

[0017] Preferably, the composition in step 2 is melt-plasticized by an extruder, the feeding section temperature of the 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 extruder is 10~200rpm.

[0018] By adopting the above technical solution, when the extruder temperature is too high, the ultra-high molecular weight polyethylene (UHMWPE) is easily degraded, resulting in reduced mechanical properties of the UHMWPE film. When the extruder temperature is too low, the melt fluidity of the UHMWPE is affected, and the composition cannot be fully melted, resulting in the UHMWPE being unable to be smoothly extruded. When the extruder screw speed is within the above range, it facilitates the mixing of the UHMWPE and the polyethylene wax. The low speed can reduce shearing of the molecular chains, thereby ensuring the mechanical properties of the UHMWPE film.

[0019] Preferably, the temperature of the compression section of the extruder is 190-230°C, the temperature of the homogenization section is 190-230°C, and the temperature of the die head is 190-230°C.

[0020] By adopting the above technical solution, when the temperature of the extruder is within the above range, the composition can be fully melted, and the degradation of ultra-high molecular weight polyethylene can be greatly alleviated or even eliminated, thereby ensuring the melt fluidity of the ultra-high molecular weight polyethylene while improving the mechanical properties of the ultra-high molecular weight polyethylene film.

[0021] Preferably, in step 3, the inflation of the thin-walled tubular film requires blowing compressed air around the thin-walled tubular film through an air ring to cool the film, and the wind speed of the compressed air is 0.1-1.4 m / s.

[0022] By adopting the above technical solution, when the wind speed is too fast, the cooling rate of the ultra-high molecular weight polyethylene film is too fast, resulting in insufficient participation of the linear polyethylene wax in the crystallization process of the ultra-high molecular weight polyethylene, affecting the mechanical properties of the ultra-high molecular weight polyethylene film; when the wind speed is too slow, it will affect the wall thickness uniformity and overall quality of the ultra-high molecular weight polyethylene film.

[0023] Preferably, in step 3, the longitudinal stretching ratio of the ultra-high molecular weight polyethylene film is controlled by the drawing ratio, and the longitudinal stretching ratio is 3 to 8 times, and the transverse stretching ratio of the ultra-high molecular weight polyethylene film is controlled by the blowing ratio, and the transverse stretching ratio is 1.5 to 5 times.

[0024] Preferably, the longitudinal stretching ratio is 3-8 times.

[0025] By adopting the technical scheme, when the longitudinal stretching ratio is too low, the mechanical properties of the final ultra-high molecular weight polyethylene film cannot be greatly improved, and when the longitudinal stretching ratio is too high, the overall quality of the ultra-high molecular weight polyethylene film is affected.

[0026] Preferably, the transverse stretching ratio is 2-4 times.

[0027] By adopting the technical scheme, when the transverse stretching ratio is too low, the transverse mechanical properties of the ultra-high molecular weight polyethylene film are poor, and when the transverse stretching ratio is too high, the ultra-high molecular weight polyethylene film is unstable and prone to wrinkles or rupture.

[0028] In summary, the present application has the following beneficial effects:

[0029] 1. The present application uses polyethylene wax to improve the melt flowability of ultra-high molecular weight polyethylene. By controlling the blowing process, the polyethylene wax can participate in the crystallization of ultra-high molecular weight polyethylene, improving the mechanical properties of the ultra-high molecular weight polyethylene film. In the preparation process, the added polyethylene wax does not need to be recycled, effectively reducing the preparation steps of the ultra-high molecular weight polyethylene film.

[0030] 2. In the present application, the air speed for blowing compressed air around the thin-walled tubular film is 0.1-1.4 m / s. Within this range of air speed, the linear polyethylene wax can fully participate in the crystallization of ultra-high molecular weight polyethylene, improving the mechanical properties of the ultra-high molecular weight polyethylene film, and ensuring the uniformity of the wall thickness and the overall quality stability of the ultra-high molecular weight polyethylene film.

[0031] 3. In the present application, the longitudinal stretching ratio of the ultra-high molecular weight polyethylene film is 4-6 times, and the transverse stretching ratio is 2-4 times, thereby ensuring the overall quality of the ultra-high molecular weight polyethylene film while improving the longitudinal and transverse mechanical properties of the ultra-high molecular weight polyethylene film. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is the differential scanning calorimetry (DSC) graph of the ultra-high molecular weight polyethylene biaxially oriented film in Example 1 of the present application.

[0033] Figure 2 is the differential scanning calorimetry (DSC) graph of the ultra-high molecular weight polyethylene biaxially oriented film in Comparative Example 4 of the present application. DETAILED DESCRIPTION Example 1

[0034] A preparation method of an ultra-high molecular weight polyethylene biaxially oriented film, comprising the following steps:

[0035] Step 1, mixing ultra-high molecular weight polyethylene with viscosity average molecular weight of 4.14 x 10 6 g / mol and linear polyethylene wax with weight average molecular weight of 4.0 x 10 3 g / mol to obtain a composition;

[0036] Step 2, adding the obtained composition into a single screw extruder for melt plasticization, and after melt plasticization, extruding a thin-walled tubular film through a die head;

[0037] Step 3, blowing the thin-walled tubular film by compressed air, pulling through a herringbone clamp and a traction roller, and finally winding, and in the blowing process, controlling the traction ratio and the blow ratio to control the longitudinal and transverse stretching multiples of the ultra-high molecular weight polyethylene film respectively, to obtain the final ultra-high molecular weight polyethylene film.

[0038] In the composition, the content of the ultra-high molecular weight polyethylene is 95 wt%, and the content of the polyethylene wax is 5 wt%. The feeding section temperature of the single screw extruder is 115°C, the compression section temperature is 190°C, the homogenization section temperature is 190°C, and the die head temperature is 190°C. The screw rotation speed of the single screw extruder is 50 rpm. The air speed of the compressed air is 0.7 m / s, the longitudinal stretching ratio of the ultra-high molecular weight polyethylene film is 5 times, and the transverse stretching ratio is 3 times. Example 2

[0039] A preparation method of an ultra-high molecular weight polyethylene biaxially oriented film, comprising the following steps:

[0040] Step 1, mixing ultra-high molecular weight polyethylene with viscosity average molecular weight of 4.14 x 10 6 g / mol and linear polyethylene wax with weight average molecular weight of 1.0 x 10 3 g / mol to obtain a composition;

[0041] Step 2, adding the obtained composition into a single screw extruder for melt plasticization, and after melt plasticization, extruding a thin-walled tubular film through a die head;

[0042] Step 3, blowing the thin-walled tubular film by compressed air, pulling through a herringbone clamp and a traction roller, and finally winding, and in the blowing process, controlling the traction ratio and the blow ratio to control the longitudinal and transverse stretching multiples of the ultra-high molecular weight polyethylene film respectively, to obtain the final ultra-high molecular weight polyethylene film.

[0043] The composition contained 99% ultra-high molecular weight polyethylene (UHMWPE) and 1% polyethylene wax. The single-screw extruder had a feed section temperature of 140°C, a compression section temperature of 190°C, a homogenization section temperature of 190°C, and a die head temperature of 190°C. The screw speed of the single-screw extruder was 10 rpm. The compressed air velocity was 0.1 m / s. The longitudinal stretch ratio of the UHMWPE film was 3 times, and the transverse stretch ratio was 1.5 times. Example 3

[0044] A method for preparing an ultra-high molecular weight polyethylene biaxially oriented film comprises the following steps:

[0045] Step 1: The viscosity average molecular weight is 4.14×10 6 g / mol ultra-high molecular weight polyethylene and a weight average molecular weight of 6.0×10 3 g / mol linear polyethylene waxes are mixed to obtain a composition;

[0046] Step 2: adding the obtained composition into a single-screw extruder for melt plasticization, and then extruding through a die head to form a thin-walled tubular film after melt plasticization;

[0047] Step 3: The thin-walled tubular film is blown with compressed air, pulled by a herringbone plywood and a pulling roller, and finally wound up. During the blow molding process, the longitudinal and transverse stretching multiples of the ultra-high molecular weight polyethylene film are controlled by controlling the pulling ratio and the blowing ratio, respectively, to obtain the final ultra-high molecular weight polyethylene film.

[0048] The composition contained 90% ultra-high molecular weight polyethylene (UHMWPE) and 10% polyethylene wax. The single-screw extruder had a feed section temperature of 90°C, a compression section temperature of 190°C, a homogenization section temperature of 190°C, and a die head temperature of 190°C. The screw speed of the single-screw extruder was 200 rpm. The compressed air velocity was 1.4 m / s. The longitudinal stretch ratio of the UHMWPE film was 8 times, and the transverse stretch ratio was 5 times.

[0049] Comparative Example 1

[0050] The only difference between this comparative example and Example 1 is that the linear polyethylene wax is replaced by a polyethylene wax having a weight average molecular weight of 68.5×10 3 g / mol of high-density polyethylene.

[0051] Comparative Example 2

[0052] The only difference between this comparative example and Example 2 is that no flow modifier is added in step 1.

[0053] Comparative Example 3

[0054] The only difference between this comparative example and Example 3 is that the linear polyethylene wax is replaced by a low density polyethylene with a weight average molecular weight of 41.3 x 10 3 g / mol.

[0055] The tensile mechanical properties, thermal properties and crystallization properties of the ultra-high molecular weight polyethylene films of Examples 1-3 and Comparative Examples 1-3 were tested, and the specific testing methods are as follows:

[0056] Testing methods

[0057] 1. Thermal property (DSC) test:

[0058] 5-8 milligrams of ultra-high molecular weight polyethylene film was weighed in a standard aluminum crucible, protected by a stream of dry nitrogen, and the thermal properties of the ultra-high molecular weight polyethylene film were tested using a differential scanning calorimeter (DSC) device, heated and scanned from 25°C to 200°C at a heating rate of 10°C / min, and the thermal property curve of the film was recorded.

[0059] 2. Crystallinity and orientation test:

[0060] The crystallinity of the ultra-high molecular weight polyethylene film was tested by wide-angle X-ray diffraction (WAXD) device, and the X-ray wavelength was 0.124 nm. The two-dimensional WAXD results were collected by a Pilatus 900K detector with a resolution of 172 x 172 μm 2 , and the distance between the detector and the sample was 210 mm. The WAXD data obtained were processed using FIT2D software. The two-dimensional WAXD graph was integrated in one dimension to obtain the intensity distribution curve in the 2θ direction. Then the curve was peak-fitted to calculate the ratio of amorphous and crystalline regions, and then the crystallinity was 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.

[0061] 3. Tensile mechanical property test:

[0062] The tensile mechanical properties of the ultra-high molecular weight polyethylene 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.

[0063] According to the above testing methods, the test results of Examples 1-3 and Comparative Examples 1-3 are shown in Table 1 below:

[0064] Table 1 Performance test table of ultra-high molecular weight polyethylene films of Examples 1-3 and Comparative Examples 1-3

[0065]

[0066] Conclusion 1:

[0067] By comparing the test results of Examples 1 to 3 and Comparative Examples 1 to 3, it can be concluded that mixing linear polyethylene wax and ultra-high molecular weight polyethylene, on the one hand, improves the melt fluidity of ultra-high molecular weight polyethylene, so that the ultra-high molecular weight polyethylene can be smoothly extruded and blown into film. On the other hand, by controlling the blow molding process during the preparation process, the linear polyethylene wax can fully participate in the crystallization of the ultra-high molecular weight polyethylene, thereby improving the tensile strength and elongation at break of the ultra-high molecular weight polyethylene film. Example 4

[0068] The only difference between this embodiment and embodiment 1 is that the content of ultra-high molecular weight polyethylene in the composition is 90 wt %, and the content of polyethylene wax is 10 wt %. Example 5

[0069] The only difference between this embodiment and embodiment 1 is that the content of ultra-high molecular weight polyethylene in the composition is 99 wt %, and the content of polyethylene wax is 1 wt %.

[0070] Comparative Example 4

[0071] The only difference between this comparative example and Example 1 is that the content of the ultra-high molecular weight polyethylene in the composition is 85 wt %, and the content of the polyethylene wax is 15 wt %.

[0072] According to the above-mentioned detection method, the detection results of the ultra-high molecular weight polyethylene films of Examples 4 to 5 and Comparative Example 4 were obtained, and the detection results are shown in Table 2 below:

[0073] Table 2 Performance test table of ultra-high molecular weight polyethylene films of Example 1, Example 4 to Example 5 and Comparative Example 4

[0074]

[0075] Conclusion 2:

[0076] Combined with the test results of Example 1, Example 4 to Example 5 and Comparative Example 4 and the attached Figure 1 and attached Figure 2 By comparison, it can be concluded that when the content of ultra-high molecular weight polyethylene in the composition is between 90 and 99 wt%, especially when the content of ultra-high molecular weight polyethylene is 95 wt%, the prepared ultra-high molecular weight polyethylene film has better tensile strength and elongation at break.

[0077] Example 6

[0078] The only difference between this embodiment and embodiment 1 is that the linear polyethylene wax is replaced by a polyethylene wax with a branching degree of 50 / 1000C.

[0079] The ultra-high molecular weight polyethylene film of Example 6 was tested according to the above-mentioned testing method. The test results are shown in Table 3 below:

[0080] Table 3 Performance test table of ultra-high molecular weight polyethylene films of Example 1 and Example 6

[0081]

[0082] Conclusion 3:

[0083] 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 can participate in the crystallization of the ultra-high molecular weight polyethylene, thereby reducing or even eliminating the damage to the mechanical properties of the ultra-high molecular weight polyethylene film caused by the polyethylene wax as a low molecular weight substance, thereby preparing an ultra-high molecular weight polyethylene film with ideal performance. Example 7

[0084] The only difference between this embodiment and embodiment 1 is that the weight average molecular weight of the polyethylene wax is 1.0×10 3 g / mol. Example 8

[0085] The only difference between this embodiment and embodiment 1 is that the weight average molecular weight of the polyethylene wax is 6.0×10 3 g / mol.

[0086] Comparative Example 5

[0087] The only difference between this comparative example and Example 1 is that the weight average molecular weight of the polyethylene wax is 8.0×10 3 g / mol.

[0088] The ultra-high molecular weight polyethylene films of Examples 7 to 8 and Comparative Example 5 were tested according to the above-mentioned testing method. The test results are shown in Table 4 below:

[0089] Table 4 Performance test table of ultra-high molecular weight polyethylene films of Example 1, Example 7 to Example 8 and Comparative Example 5

[0090]

[0091] Conclusion 4:

[0092] Combining the test results of Example 1, Example 7 to Example 8 and Comparative Example 5, it can be concluded that when the weight average molecular weight of the polyethylene wax is 1.0×10 3 ~6.0×10 3When the polyethylene wax has a molecular weight of 0.17477 W / mol, the melt fluidity of ultra-high molecular weight polyethylene can be greatly improved, so that the composition can be smoothly extruded and blown into film. Moreover, since the polyethylene wax can participate in the crystallization of ultra-high molecular weight polyethylene during the stretching process, the prepared ultra-high molecular weight polyethylene film has excellent mechanical properties. Example 9

[0093] The only difference between this embodiment and embodiment 1 is that the temperature of the compression section, homogenization section and die head of the extruder is 160°C. Example 10

[0094] The only difference between this embodiment and embodiment 1 is that the temperature of the compression section, homogenization section and die head of the extruder is 230°C. Example 11

[0095] The only difference between this embodiment and embodiment 1 is that the temperature of the compression section, homogenization section and die head of the extruder is 250°C.

[0096] Comparative Example 6

[0097] 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 extruder is 150°C.

[0098] Comparative Example 7

[0099] The only difference between this comparative example and Example 1 is that the temperatures of the compression section, homogenization section and die head of the extruder are 270°C.

[0100] The ultra-high molecular weight polyethylene films of Examples 9 to 11 and Comparative Examples 6 to 7 were tested according to the above-mentioned testing method. The test results are shown in Table 5 below:

[0101] Table 5 Performance test table of ultra-high molecular weight polyethylene films of Example 1, Example 9 to Example 11 and Comparative Examples 6 to Comparative Examples 7

[0102]

[0103] Conclusion 5:

[0104] By comparing the test results of Example 1, Examples 9 to 11 and Comparative Examples 6 to 7, it can be concluded that when the temperatures of the compression section, homogenization section and die head of the extruder are in the range of 160~250°C, especially at 190°C, the fluidity of the ultra-high molecular weight polyethylene melt is better, thereby improving the tensile strength and elongation at break of the ultra-high molecular weight polyethylene film. Example 12

[0105] The only difference between this embodiment and embodiment 1 is that the wind speed of the compressed air is 0.1 m / s. Example 13

[0106] The only difference between this embodiment and embodiment 1 is that the wind speed of the compressed air is 0.3 m / s. Example 14

[0107] The only difference between this embodiment and embodiment 1 is that the wind speed of the compressed air is 1 m / s. Example 15

[0108] The only difference between this embodiment and embodiment 1 is that the wind speed of the compressed air is 1.4 m / s.

[0109] The ultra-high molecular weight polyethylene films of Examples 12 to 14 were tested according to the above-mentioned testing method. The test results are shown in Table 6 below:

[0110] Table 6 Performance test table of ultra-high molecular weight polyethylene films of Example 1 and Example 12 to Example 15

[0111]

[0112] Conclusion 6:

[0113] By comparing the test results of Example 1 and Examples 12 to 15, it can be concluded that when the wind speed of the compressed air is 0.1~1.4 m / s, especially when the wind speed is 0.7 m / s, the linear polyethylene wax can fully participate in the crystallization of ultra-high molecular weight polyethylene, ensuring the mechanical properties of the ultra-high molecular weight polyethylene film, and the wall thickness uniformity of the prepared ultra-high molecular weight polyethylene film is high, and the overall quality is ideal. Example 16

[0114] The only difference between this embodiment and embodiment 1 is that the longitudinal stretching ratio of the ultra-high molecular weight polyethylene film is 3 times. Example 17

[0115] The only difference between this embodiment and embodiment 1 is that the longitudinal stretching ratio of the ultra-high molecular weight polyethylene film is 4 times. Example 18

[0116] The only difference between this embodiment and embodiment 1 is that the longitudinal stretching ratio of the ultra-high molecular weight polyethylene film is 6 times. Example 19

[0117] The only difference between this embodiment and embodiment 1 is that the longitudinal stretching ratio of the ultra-high molecular weight polyethylene film is 8 times.

[0118] Comparative Example 8

[0119] The only difference between this comparative example and Example 1 is that the longitudinal stretching ratio of the ultra-high molecular weight polyethylene film is 2 times.

[0120] Comparative Example 9

[0121] The only difference between this comparative example and Example 1 is that the longitudinal stretching ratio of the ultra-high molecular weight polyethylene film is 10 times.

[0122] The ultra-high molecular weight polyethylene films of Examples 16 to 19 and Comparative Examples 8 to 9 were tested according to the above-mentioned testing method. The test results are shown in Table 7 below:

[0123] Table 7 Performance test table of ultra-high molecular weight polyethylene films of Example 1, Example 16 to Example 19 and Comparative Examples 8 to Comparative Examples 9

[0124]

[0125] Conclusion 7:

[0126] By comparing the test results of Example 1, Examples 16 to 19, and Comparative Examples 8 to 9, it can be concluded that when the longitudinal stretching ratio of the ultra-high molecular weight polyethylene film is between 3 and 8 times, especially at 5 times, the obtained ultra-high molecular weight polyethylene film can have good tensile strength and elongation at break while ensuring the overall quality. Example 20

[0127] The only difference between this embodiment and embodiment 1 is that the transverse stretching ratio of the ultra-high molecular weight polyethylene film is 1.5 times. Example 21

[0128] The only difference between this embodiment and embodiment 1 is that the transverse stretching ratio of the ultra-high molecular weight polyethylene film is 2 times. Example 22

[0129] The only difference between this embodiment and embodiment 1 is that the transverse stretching ratio of the ultra-high molecular weight polyethylene film is 4 times. Example 23

[0130] The only difference between this embodiment and embodiment 1 is that the transverse stretching ratio of the ultra-high molecular weight polyethylene film is 5 times.

[0131] Comparative Example 10

[0132] The only difference between this comparative example and Example 1 is that the transverse stretching ratio of the ultra-high molecular weight polyethylene film is 7 times.

[0133] The ultra-high molecular weight polyethylene films of Examples 20 to 23 and Comparative Example 10 were tested according to the above-mentioned testing method. The test results are shown in Table 8 below:

[0134] Table 8 Performance test table of ultra-high molecular weight polyethylene films of Example 1, Examples 20 to 23 and Comparative Example 10

[0135]

[0136] Conclusion 8:

[0137] By comparing the test results of Example 1, Examples 20 to 23 and Comparative Example 10, it can be concluded that when the transverse stretching ratio of the ultra-high molecular weight polyethylene film is between 1.5 and 5 times, especially at 3 times, the transverse mechanical properties of the obtained ultra-high molecular weight polyethylene film are ideal, and the ultra-high molecular weight polyethylene film is relatively stable.

[0138] 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 non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing an ultra-high molecular weight polyethylene biaxially oriented film, characterized in that: The steps are as follows: Step 1: mixing ultra-high molecular weight polyethylene and polyethylene wax to obtain a composition; Step 2: Melting and plasticizing the obtained composition, and then extruding it to form a thin-walled tubular film; Step 3: The thin-walled tubular film is inflated, drawn, and rolled to obtain the final ultra-high molecular weight polyethylene film; The content of ultra-high molecular weight polyethylene in the composition is 90-99 wt %, and the content of polyethylene wax is 1-10 wt %; The polyethylene wax is linear polyethylene wax; The weight average molecular weight of the polyethylene wax is 1.0×10 3 ~6.0×10 3 g / mol; In step 2, the composition is melt-plasticized by an extruder, wherein the temperature of the feeding section of the 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 temperature of the die head is 160-250° C., and the screw speed of the extruder is 10-200 rpm; In step 3, the thin-walled tubular film needs to be inflated by blowing compressed air around the thin-walled tubular film through an air ring, and the wind speed of the compressed air is 0.1~1.4 m / s; In step 3, the longitudinal stretching ratio of the ultra-high molecular weight polyethylene film is controlled by the drawing ratio, and the longitudinal stretching ratio is 3 to 8 times. The transverse stretching ratio of the ultra-high molecular weight polyethylene film is controlled by the blowing ratio, and the transverse stretching ratio is 1.5 to 5 times.

2. The method for preparing a biaxially oriented ultra-high molecular weight polyethylene film according to claim 1, wherein: The temperature of the compression section of the extruder is 190-230°C, the temperature of the homogenization section is 190-230°C, and the temperature of the die head is 190-230°C.

3. The method for preparing a biaxially oriented ultra-high molecular weight polyethylene film according to claim 1, wherein: The longitudinal stretching ratio is 4 to 6 times.

4. The method for preparing a biaxially oriented ultra-high molecular weight polyethylene film according to claim 1, wherein: The transverse stretching ratio is 2~4 times.

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