Forming method of ultra-high molecular weight polyethylene strip

Abstract

The invention discloses a forming method of an ultra-high molecular weight polyethylene strip, which comprises the following steps: step 1, mixing ultra-high molecular weight polyethylene resin and a low molecular weight solvent to prepare a uniform suspension, then extruding at high temperature, and cooling and shaping to obtain a gel film; step 2, carrying out single-axis high-temperature ultra-time hot stretching on the gel film; 3, extracting the stretched gel film to remove the low-molecular-weight solvent, and drying with hot air to obtain a dried film; 4, longitudinally cutting the dry film to form strips; and step 5, carrying out low-multiple uniaxial thermal stretching on the strip to remove pores so as to obtain the final ultra-high molecular weight polyethylene strip. The gel film is subjected to uniaxial hot stretching under the condition that a low-molecular-weight solvent is not removed, and the low-molecular-weight solvent is beneficial to promoting orientation of fibrous extended-chain crystals reserved in the gel film and formation of high-orientation crystals such as subsequent extended-chain crystals, so that the tensile mechanical property and other properties of a final strip are improved.

Description

Technical Field

[0001] The present application relates to the field of polymer technology, and more specifically, to a method for molding ultra-high molecular weight polyethylene strips. Background Art

[0002] Ultra-high molecular weight polyethylene is a thermoplastic engineering plastic with excellent comprehensive properties, and its molecular weight is generally 1-6 million or even higher. Films made of ultra-high molecular weight polyethylene have excellent wear resistance and good anti-adhesion ability, and are widely used in civil, medical, military and other fields. Therefore, its industrial production is of great significance. For many years, technicians in ultra-high molecular weight polyethylene materials and related fields have been exploring a method suitable for the industrial production of ultra-high molecular weight polyethylene films. In particular, how to obtain ultra-high molecular weight polyethylene strips with excellent performance has become a technical problem that people in related fields have been eager to solve.

[0003] To prepare ultra-high molecular weight polyethylene strips with excellent mechanical properties, a gel molding method can be used. First, the ultra-high molecular weight polyethylene is mixed with a suitable solvent and dissolved at high temperature to form a solution, and then gel molding is used to form a gel film. The gel film is first extracted and dried, and then the dry film is cut to form strips, and then uniaxial multi-stage heat stretching is performed to obtain finished ultra-high molecular weight polyethylene strips.

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

[0005] Patent CN115302751A discloses a process for preparing ultra-high molecular weight polyethylene film with retained straight chain crystals. By precisely controlling the temperature during the preparation of the ultra-high molecular weight polyethylene solution, only the folded chain lamellae with a lower melting point in the ultra-high molecular weight polyethylene are dissolved under low temperature conditions, while the partial dissolution of the straight chain crystals in the resin is retained, thereby reducing the viscosity of the ultra-high molecular weight polyethylene solution and reducing the molecular weight reduction caused by the high processing temperature. The straight chain crystals retained during the dissolution process serve as efficient nucleating agents for the crystallization of ultra-high molecular weight polyethylene, inducing the formation of straight chain crystals and folded chain lamellae during the hot stretching process after extraction and drying.

[0006] Through in-depth and systematic research on the stretching process of ultra-high molecular weight polyethylene that retains straight chain crystals, it was found that if the gel film is subjected to uniaxial heat stretching, due to the presence of low molecular weight solvents, the retained fibrous straight chain crystals are easier to orient, and it is easier to promote the formation of highly oriented crystals such as subsequent straight chain crystals, thereby greatly improving the tensile mechanical properties and other properties of the final strip, forming a unique ultra-high molecular weight polyethylene strip molding process. Summary of the invention

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

[0008] The present application provides a method for forming an ultra-high molecular weight polyethylene strip, comprising the following steps: Step 1: Mixing ultra-high molecular weight polyethylene resin and low molecular weight solvent to form a uniform suspension, then extruding at high temperature, and cooling and shaping to obtain a gel film; Step 2: subjecting the gel film to uniaxial high-temperature ultra-multiple thermal stretching; Step 3: extracting the stretched gel film to remove the low molecular weight solvent, and then drying it with hot air to obtain a dry film; Step 4: Cut the dried film longitudinally to form strips; Step 5: The strip is subjected to low-multiple uniaxial heat stretching to remove pores and obtain the final ultra-high molecular weight polyethylene strip.

[0009] By adopting the above technical scheme, the gel film is subjected to uniaxial heat stretching without removing the low molecular weight solvent. In this way, the low molecular weight solvent helps to promote the orientation of the fibrous straight chain crystals retained in the gel film and the formation of highly oriented crystals such as subsequent straight chain crystals, thereby helping to significantly improve the tensile properties and other properties of the final strip.

[0010] Preferably, during the high-temperature extrusion process in step 1, the feeding section temperature of the twin-screw extruder used is 80-130°C, the compression section temperature is 130-200°C, the homogenization section temperature is 130-200°C, the die head temperature is 130-200°C, and the speed of the twin-screw extruder is 30-400r / min.

[0011] By adopting the above technical solution, when the temperature of the compression section, homogenization section and die head of the twin-screw extruder exceeds 200°C, most of the extended chain crystals in the ultra-high molecular weight polyethylene resin will be dissolved. When the temperature is lower than 130°C, the lamellar crystals in the ultra-high molecular weight polyethylene resin will almost be retained, which will affect the dissolution effect of the ultra-high molecular weight polyethylene resin and cause the fluidity to decrease, thereby causing the extruded jelly film to be uneven.

[0012] Preferably, the compression section, homogenization section and die head temperature of the twin-screw extruder are 130-170°C.

[0013] By adopting the above technical scheme, when the temperature of the compression section, homogenization section and die head of the twin-screw extruder is controlled at 130-170°C, it is beneficial for most of the straight chain crystals in the ultra-high molecular weight polyethylene resin to be retained without being dissolved, and at the same time, it also ensures the fluidity of the ultra-high molecular weight polyethylene resin after dissolution, making the gel film uniform.

[0014] Preferably, the temperature of the uniaxial super-multiple thermal stretching in step 2 is 90 to 130° C., the stretching rate is 5 to 80 m / min, and the stretching ratio is 6 to 18 times.

[0015] Preferably, the temperature of the uniaxial super-multiple thermal stretching is 100-120°C.

[0016] By adopting the above technical scheme, the heat stretching temperature is low, and the orientation of the retained straight chain crystals and their promoting effect on the subsequent formation of highly oriented crystals are not obvious enough; the heat stretching temperature is high, and the ultra-high molecular weight polyethylene gel film is prone to detangling, resulting in a decrease in the mechanical properties of the strip, instability in the heat stretching process and instability in the film quality.

[0017] Preferably, the stretching rate of the uniaxial high-temperature super-multiple thermal stretching is 10 to 60 m / min.

[0018] By adopting the above technical solution, the stretching rate is low, and the oriented molecular chains are more easily deoriented under the action of low molecular weight solvents, thereby affecting the mechanical properties of the final ultra-high molecular weight polyethylene strips and also affecting the production efficiency; while too high a stretching rate will affect the stability of the gel film stretching.

[0019] Preferably, the stretching ratio of the uniaxial high-temperature super-multiple thermal stretching is 10 to 15 times.

[0020] By adopting the above technical solution, the uniaxial thermal stretching ratio of the gel film is low, and the number of newly formed straight chain crystals promoted by the retained straight chain crystals during the stretching process is insufficient to significantly improve the mechanical properties of the final strip; if the uniaxial stretching ratio of the gel film is too high, it will affect the stretching stability.

[0021] Preferably, the low molecular weight solvent is a mixture of one or more of decalin, white oil or long straight chain alkanes.

[0022] By adopting the above technical scheme, the above low molecular weight solvents can dissolve the ultra-high molecular weight polyethylene resin relatively easily, thereby facilitating the formation of retained fibrous straight chain crystal orientation and subsequent straight chain crystals and other highly oriented crystals during the thermal stretching process of the gel film.

[0023] Preferably, the low molecular weight solvent is a long straight chain alkane.

[0024] By adopting the above technical scheme, since the long straight-chain alkanes are normal alkanes with components of C12 to C16, and the chain structure of the long straight-chain alkanes is similar to the chain structure of ultra-high molecular weight polyethylene, it is easier to accurately control the retention of extended chain crystals during the dissolution of ultra-high molecular weight polyethylene resin and the formation of highly oriented crystals during the thermal stretching of the gel film.

[0025] Preferably, the mass ratio of the ultra-high molecular weight polyethylene to the low molecular weight solvent in step 1 is (0.18-0.45):1.

[0026] By adopting the above technical solution, the method of partially dissolving a small amount of ultra-high molecular weight polyethylene resin reduces the actual dissolved concentration, and the high rigidity of the retained extended chain crystals makes the solution form characteristics similar to liquid crystal solutions, which can greatly reduce the viscosity of the ultra-high molecular weight polyethylene solution. However, too low a resin content will lead to too low an internal entanglement degree of the prepared jelly film, thereby affecting the mechanical properties, and too high a resin content will affect the partial dissolution effect. In order to take into account both the dissolution effect of the ultra-high molecular weight polyethylene resin and the mechanical properties of the strip, the above range is preferred.

[0027] Preferably, in step 5, the temperature for heat stretching the strip after extraction and drying is 120 to 150° C., and the stretching ratio is 1.5 to 4 times.

[0028] By adopting the above technical solutions, the heat stretching temperature is low, and the melt recrystallization effect is weak, so the pores caused by extraction drying cannot be completely eliminated; the heat stretching temperature is high, and detangling is easy to occur in the ultra-high molecular weight polyethylene film, causing problems such as unstable heat stretching process and unstable film quality. At the same time, the longitudinal heat stretching multiple is low, and the pores in the dried film cannot be completely eliminated, affecting the mechanical properties of the final film; too high a uniaxial stretching multiple will affect the stability of film stretching.

[0029] In summary, this application has the following beneficial effects: 1. Since the jelly film in the present application is subjected to uniaxial high-temperature ultra-multiple thermal stretching without removing the low molecular weight solvent, this not only helps to promote the orientation of the fibrous straight chain crystals retained in the jelly film, but also facilitates the formation of subsequent highly oriented crystals such as straight chain crystals, thereby greatly improving the tensile properties and other properties of the final ultra-high molecular weight polyethylene strip; 2. In the present application, the compression section, homogenization section and die head temperature of the twin-screw extruder are controlled at 130-170° C., which is beneficial for most of the extended chain crystals in the ultra-high molecular weight polyethylene resin to be retained without being dissolved, and also ensures the fluidity of the ultra-high molecular weight polyethylene resin after dissolution, so that the produced jelly film is more uniform; 3. In this application, long straight-chain alkanes are selected as low molecular weight solvents, because long straight-chain alkanes are normal alkanes with components of C12 to C16. The chain structure of long straight-chain alkanes is similar to that of ultra-high molecular weight polyethylene, which makes it easier to accurately control the retention of extended chain crystals during the dissolution of ultra-high molecular weight polyethylene resin and the formation of highly oriented crystals during the thermal stretching of the gel film; 4. In the present application, the ratio of the uniaxial high-temperature ultra-multiple thermal stretching of the gel film is 10 to 15 times, which can orient the fibrous straight chain crystals in the ultra-high molecular weight polyethylene resin, thereby ensuring the mechanical properties of the ultra-high molecular weight polyethylene strips, while not affecting the stability of the uniaxial high-temperature ultra-multiple thermal stretching of the gel film. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the X-ray diffraction pattern of the ultra-high molecular weight polyethylene strip in Example 1 of the present application.

[0031] Figure 2 It is the X-ray diffraction pattern of the ultra-high molecular weight polyethylene strip in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0032] The present application is further described in detail below in conjunction with the accompanying drawings, embodiments and comparative examples. Example 1

[0033] A method for forming an ultra-high molecular weight polyethylene strip comprises the following steps: Step 1: The viscosity average molecular weight is 7.12×10 6 g / mol ultra-high molecular weight polyethylene resin and long straight-chain alkane are mixed at a mass ratio of 0.32:1 to prepare a uniform suspension, which is then fed into a twin-screw extruder for high-temperature dissolution to obtain a solution, which is then passed through a metering pump and a slit die, and cooled and shaped by a 20°C polished cold roller to obtain a gel film; Step 2: subjecting the gel film to uniaxial high-temperature ultra-multiple thermal stretching; Step 3: immersing the stretched gel film in an extraction tank with ultrasound to extract and remove the long straight-chain alkanes, and then drying with hot air to obtain a dry film; Step 4: Cut the dried film longitudinally to form strips; Step 5: The strip is subjected to uniaxial heat stretching at a temperature of 135° C. to remove pores, with a stretching ratio of 3 times, thereby obtaining the final ultra-high molecular weight polyethylene strip.

[0034] Among them, the feeding section temperature of the twin-screw extruder is 105°C, the compression section temperature is 170°C, the homogenization section temperature is 170°C, the die head temperature is 170°C, and the speed of the twin-screw extruder is 200r / min. The temperature of the uniaxial super-multiple thermal stretching of the gel film is 100°C, the stretching rate is 45m / min, and the stretching ratio is 10 times. Generally, the long straight-chain alkane can be a normal alkane of C12 to C16, and can be a single-length straight-chain normal alkane or a mixture of long straight-chain alkanes. In the following embodiments, unless otherwise specified, n-pentadecane is preferably used. Example 2

[0035] A method for forming an ultra-high molecular weight polyethylene strip comprises the following steps: Step 1: The viscosity average molecular weight is 7.12×10 6 g / mol ultra-high molecular weight polyethylene resin and decalin are mixed at a mass ratio of 0.18:1 to prepare a uniform suspension, which is then fed into a twin-screw extruder for high-temperature dissolution to obtain a solution, which is then passed through a metering pump and a slit die, and cooled and shaped by a 10°C polished cold roller to obtain a gel film; Step 2: subjecting the gel film to uniaxial high-temperature ultra-multiple thermal stretching; Step 3: immersing the stretched gel film in an extraction tank with ultrasound to extract and remove decalin, and then drying with hot air to obtain a dry film; Step 4: Cut the dried film longitudinally to form strips; Step 5: The strip is subjected to uniaxial heat stretching at a temperature of 120° C. to remove pores, with a stretching ratio of 4 times, thereby obtaining the final ultra-high molecular weight polyethylene strip.

[0036] The feeding section temperature of the twin-screw extruder is 80°C, the compression section temperature is 130°C, the homogenization section temperature is 130°C, the die head temperature is 130°C, and the speed of the twin-screw extruder is 30r / min. The temperature of the uniaxial super-multiple thermal stretching of the gel film is 90°C, the stretching rate is 5m / min, and the stretching ratio is 6 times. Example 3

[0037] A method for forming an ultra-high molecular weight polyethylene strip comprises the following steps: Step 1: The viscosity average molecular weight is 7.12×10 6 g / mol ultra-high molecular weight polyethylene resin and white oil were mixed at a mass ratio of 0.45:1 to prepare a uniform suspension, and then sent to a twin-screw extruder for high-temperature dissolution to obtain a solution, which was passed through a metering pump and a slit die, and then cooled and shaped by a 30°C polished cold roller to obtain a gel film; Step 2: subjecting the gel film to uniaxial high-temperature ultra-multiple thermal stretching; Step 3: immersing the stretched gel film in an extraction tank with ultrasound to extract and remove the white oil, and then drying it with hot air to obtain a dry film; Step 4: Cut the dried film longitudinally to form strips; Step 5: The strip is subjected to uniaxial heat stretching at a temperature of 150° C. to remove pores, with a stretching ratio of 1.5 times, thereby obtaining the final ultra-high molecular weight polyethylene strip.

[0038] The feeding section temperature of the twin-screw extruder is 130°C, the compression section temperature is 200°C, the homogenization section temperature is 200°C, the die head temperature is 200°C, and the speed of the twin-screw extruder is 400r / min. The temperature of the uniaxial super-multiple thermal stretching of the gel film is 130°C, the stretching rate is 80m / min, and the stretching ratio is 18 times. Here, the white oil is Total LYRAN C360B No. 70 white oil.

[0039] Comparative Example 1 The difference between this comparative example and Example 1 is that step 2 is not included and in step 5, multi-stage stretching to 30 times is performed at 120-150°C.

[0040] Comparative Example 2 The difference between this comparative example and Example 2 is that step 2 is not included and in step 5, multi-stage stretching to 24 times is performed at 120-150°C.

[0041] Comparative Example 3 The difference between this comparative example and Example 3 is that step 2 is not included and in step 5, multi-stage stretching to 27 times is performed at 120-150°C.

[0042] The tensile mechanical properties, thermal properties and crystallization properties of the ultra-high molecular weight polyethylene strips of Examples 1 to 3 and Comparative Examples 1 to 3 were tested. The specific testing methods are as follows:

[0043] Thermal performance test Cut the ultra-high molecular weight polyethylene strip into small pieces, weigh 5 to 10 mg and put it in a standard aluminum crucible. Protect it with a dry nitrogen flow and use a differential scanning calorimeter (DSC) to test the thermal properties of the ultra-high molecular weight polyethylene strip. 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 strip.

[0044] Crystallinity and orientation test The crystallinity and orientation of the ultra-high molecular weight polyethylene strips were tested by wide angle X-ray diffraction (WAXD) with an X-ray wavelength of 0.124 nm. The two-dimensional WAXD results were collected by a Pilatus 900K detector with a resolution of 172 × 172 μm. 2, the distance from the detector to the sample is 210 mm. The WAXD data obtained by processing with FIT2D software. The two-dimensional WAXD image is integrated in one dimension to obtain the intensity distribution curve in the 2θ direction. Then the curve is peak-fitted, the ratio of amorphous area to crystalline area is calculated, and then the crystallinity is calculated. The calculation formula is as follows: Xc=Ac / (Ac+Aa), where Ac and Aa represent the area under the crystalline peak and amorphous peak of the I(2θ)~2θ curve, respectively.

[0045] The Hermans method is used to determine the crystal orientation of ultra-thin molecular weight polyethylene strips. Taking the strip stretching direction as the reference direction and the crystal plane as hkl, the orientation parameter can be expressed as: in, Ф is the azimuth, I( Ф ) is the scattering intensity along the azimuth angle. f It can be calculated by the following formula: when f =-0.5, the normal direction of the crystal plane is perpendicular to the reference direction; when f =1, the normal direction of the crystal plane is parallel to the reference direction; when f = 0, the normal of the crystal plane is freely oriented.

[0046] Tensile mechanical properties test: The tensile mechanical properties of the ultra-high molecular weight polyethylene strips were tested at room temperature using a universal mechanical testing machine. The strips were stretched at a speed of 50 mm / min to characterize their mechanical properties. At least five samples were used for each strip to obtain the average value and standard deviation.

[0047] 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

[0048] Test items Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Melting point (℃) 150.5 148.2 149.1 145.5 143.0 144.2 Crystallinity (%) 96.9 94.4 95.2 93.1 91.1 92.0 Orientation 0.95 0.93 0.94 0.91 0.89 0.90 Tensile strength (GPa) 5.04±0.25 4.29±0.21 4.64±0.22 3.51±0.18 3.10±0.16 3.31±0.17 Tensile modulus (GPa) 185.16±9.32 152.67±7.68 159.74±7.89 132.3±6.58 121.8±6.02 125.8±6.12

[0049] The test results of Example 1 to Example 3 were compared with those of Comparative Examples 1 to Comparative Examples 3, and the attached Figure 1 and attached Figure 2 It can be seen from the demonstration that when the low molecular weight solvent is not removed, the uniaxial high temperature ultra-multiple thermal stretching of the gel film can more easily retain the fibrous straight chain crystal orientation and promote the formation of highly oriented crystals such as subsequent straight chain crystals, thereby effectively improving the tensile strength and tensile modulus of the final ultra-high molecular weight polyethylene strip. Example 4

[0050] The only difference between this comparative example and Example 1 is that the compression section, homogenization section and die head temperature of the twin-screw extruder are 200°C. Example 5

[0051] 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 130°C.

[0052] Comparative Example 4 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 120°C.

[0053] Comparative Example 5 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 210°C.

[0054] The ultra-high molecular weight strips of Example 4 and Example 5 and Comparative Example 4 and Comparative Example 5 were tested according to the testing method in Table 1. Meanwhile, the testing results of the ultra-high molecular weight polyethylene strips are shown in Table 2 below. Table 2

[0055] Test items Example 4 Example 5 Comparative Example 4 Comparative Example 5 Melting point (℃) 150.6 148.1 / 145.2 Crystallinity (%) 96.8 93.4 / 91.4 Orientation 0.94 0.93 / 0.91 Tensile strength (GPa) 4.89±0.29 4.14±0.24 / 3.45±0.19 Tensile modulus (GPa) 178.23±11.25 140.34±8.98 / 134.65±6.68 Film forming ability Smooth and stable film formation Smooth and stable film formation Unable to form a stable film Smooth and stable film formation

[0056] By comparing the test results of Example 1, Example 4, Example 5 and Comparative Example 4 and Comparative Example 5, it can be seen that when the temperature of the compression section, homogenization section and die head of the twin-screw extruder is controlled at 130-200°C, especially at 130-170°C, the ultra-high molecular weight polyethylene strips finally prepared have good tensile strength and tensile modulus. Example 6

[0057] The only difference between this embodiment and embodiment 1 is that the low molecular weight solvent is decalin. Example 7

[0058] The only difference between this embodiment and embodiment 1 is that the low molecular weight solvent is white oil.

[0059] The ultra-high molecular weight polyethylene strips of Example 6 and Example 7 were tested according to the testing method of Table 1. The test results are shown in Table 3 below. Table 3

[0060] Test items Example 6 Example 7 Melting point (℃) 149.1 149 Crystallinity (%) 95.2 95 Orientation 0.94 0.94 Tensile strength (GPa) 4.89±0.26 4.81±0.26 Tensile modulus (GPa) 174.8±9.23 173.9±9.21

[0061] By comparing the test results of Example 1, Example 6 and Example 7, it can be seen that the low molecular weight solvent is a long straight chain alkane, which is beneficial to improving the mechanical properties of the final ultra-high molecular weight polyethylene strip. Example 8

[0062] The only difference between this embodiment and embodiment 1 is that the stretching ratio of the uniaxial super-multiple thermal stretching of the jelly film is 15 times. Example 9

[0063] The only difference between this embodiment and embodiment 1 is that the stretching ratio of the uniaxial super-multiple thermal stretching of the jelly film is 6 times. Example 10

[0064] The only difference between this embodiment and embodiment 1 is that the stretching ratio of the uniaxial super-multiple thermal stretching of the jelly film is 18 times.

[0065] The ultra-high molecular weight polyethylene strips of Examples 8 to 10 were tested according to the testing method in Table 1. The specific test results are shown in Table 4 below. Table 4

[0066] Test items Example 8 Example 9 Example 10 Melting point (℃) 151.2 148.9 151.3 Crystallinity (%) 97.4 94.9 97.5 Orientation 0.96 0.93 0.96 Tensile strength (GPa) 5.48±0.29 4.23±0.20 5.54±0.58 Tensile modulus (GPa) 197.63±11.24 155.21±7.84 199.88±21.44 Film forming ability Smooth and stable film formation Smooth and stable film formation The film is easy to break during stretching

[0067] By comparing the test results of Example 1 and Example 8 to Example 10, it can be seen that when the stretching rate of the uniaxial super-multiple thermal stretching of the jelly film is 10 to 15 times, it can not only ensure the mechanical properties of the ultra-high molecular weight polyethylene strips, but also does not affect the stretching stability of the ultra-high molecular weight polyethylene jelly film. Embodiment 11

[0068] The difference between this embodiment and embodiment 1 is that the temperature of the uniaxial super-multiple thermal stretching of the gel film is 120°C. Example 12

[0069] The difference between this embodiment and embodiment 1 is that the temperature of the uniaxial super-multiple heat stretching of the jelly film is 90°C. Example 13

[0070] The difference between this embodiment and embodiment 1 is that the temperature of uniaxial super-multiple thermal stretching of the gel film is 130°C.

[0071] The ultra-high molecular weight polyethylene strips of Examples 11 to 13 were tested according to the testing method in Table 1. The specific test results are shown in Table 5 below. Table 5

[0072] Test items Embodiment 11 Example 12 Example 13 Melting point (℃) 151.5 148.3 149.4 Crystallinity (%) 97.3 94.4 95.8 Orientation 0.96 0.93 0.94 Tensile strength (GPa) 5.42±0.25 4.42±0.28 4.82±0.26 Tensile modulus (GPa) 195.65±9.37 164.18±10.52 179.54±10.24

[0073] By comparing the test results of Example 1 and Example 11 to Example 13, it can be seen that when the temperature of the uniaxial super-multiple thermal stretching of the gel film is 100-120°C, the retained straight chain crystals can be quickly oriented and promote the formation of subsequent highly oriented crystals, and the molecular chains in the gel film are not easy to detangle during the stretching process, and the thermal stretching process is stable, thereby making the final ultra-high molecular weight polyethylene strip have better mechanical properties.

[0074] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for forming an ultra-high molecular weight polyethylene strip, characterized in that: The following steps are included: Step 1: Mixing ultra-high molecular weight polyethylene resin and low molecular weight solvent to form a uniform suspension, then extruding at high temperature, and cooling and shaping to obtain a gel film; Step 2: subjecting the gel film to uniaxial high-temperature ultra-multiple thermal stretching; Step 3: extracting the stretched gel film to remove the low molecular weight solvent, and then drying it with hot air to obtain a dry film; Step 4: Cut the dried film longitudinally to form strips; Step 5: The strip is subjected to low-multiple uniaxial heat stretching to remove pores and obtain the final ultra-high molecular weight polyethylene strip.

2. The method for forming an ultra-high molecular weight polyethylene strip according to claim 1, characterized in that: In step 1, high-temperature extrusion is achieved by a twin-screw extruder, the feeding section temperature of the twin-screw extruder is 80-130°C, the compression section temperature is 130-200°C, the homogenization section temperature is 130-200°C, the die head temperature is 130-200°C, and the rotation speed of the twin-screw extruder is 30-400r / min.

3. The method for forming an ultra-high molecular weight polyethylene strip according to claim 2, characterized in that: The temperatures of the compression section, homogenization section and die head of the twin-screw extruder are 130-170°C.

4. The method for forming an ultra-high molecular weight polyethylene strip according to claim 1, characterized in that: The temperature of the uniaxial super-multiple heat stretching in step 2 is 90 to 130° C., the stretching rate is 5 to 80 m / min, and the stretching ratio is 6 to 18 times.

5. The method for forming an ultra-high molecular weight polyethylene strip according to claim 4, characterized in that: The temperature of the uniaxial heat stretching of the gel film is 100-120°C.

6. The method for forming an ultra-high molecular weight polyethylene strip according to claim 4, characterized in that: The stretching ratio during the uniaxial heat stretching process is 10 to 15 times.

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

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

9. The method for forming an ultra-high molecular weight polyethylene strip according to claim 7, characterized in that: The mass ratio of the ultra-high molecular weight polyethylene resin to the low molecular weight solvent in step 1 is (0.18-0.45):

1.

10. The method for forming an ultra-high molecular weight polyethylene strip according to claim 1, characterized in that: In step 5, the temperature of thermal stretching of the strip after extraction and drying is 120-150° C., and the stretching ratio is 1.5-4 times.

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