Self-reinforced polyethylene and preparation method of self-reinforced polyethylene film

Abstract

The invention discloses a preparation method of self-reinforced polyethylene and a film thereof. The preparation method of the self-reinforced polyethylene comprises the following steps: (1) uniformly premixing polyethylene particles, an initiator, a cross-linking agent and a lubricant in a high-speed mixer according to a certain mass ratio, and then extruding and granulating in a double-screw extruder to obtain pre-crosslinked PE particles; and (2) uniformly mixing the pre-crosslinked PE particles and the polyethylene particles, and carrying out blending extrusion granulation in a twin-screw extruder to obtain the self-reinforced polyethylene particles. The preparation method of the self-reinforced polyethylene film comprises the step of blowing the self-reinforced polyethylene particles to obtain the self-reinforced polyethylene film. The preparation method provided by the invention improves the mechanical properties and processability of PE.

Description

Technical Field

[0001] The present invention relates to the technical field of polyethylene film processing applications, and particularly relates to a method for preparing self-reinforced polyethylene and its film. Background Art

[0002] Polyethylene (PE) is a widely used thermoplastic plastic material. With its excellent chemical resistance, low cost, easy processability and other characteristics, it occupies an important position in the fields of agricultural mulch films, packaging films and industrial films. Agricultural mulch film is a commonly used covering material for increasing soil temperature, retaining water, suppressing weed growth and increasing crop yields. However, traditional polyethylene mulch films are prone to mechanical damage during use, reducing their service life. At the same time, due to the trend of thinning of the film, higher requirements are placed on its mechanical properties and puncture resistance. In addition, the difficult recycling of agricultural mulch films has always been an environmental protection issue of global concern. Therefore, in order to further improve the mechanical properties of polyethylene films, make them suitable for more demanding use conditions, and still be able to be recycled well, the material enhancement technology has become an important research direction.

[0003] In order to improve the mechanical properties of polyethylene, in recent years, researchers have tried to improve its molecular structure through crosslinking technology. Crosslinking refers to the formation of covalent bonds or secondary valence bonds between polymer chains through chemical or physical actions, thereby constructing a three-dimensional network structure to improve the tensile strength, thermal properties and puncture resistance of the material. CN106977804A discloses a peroxide-crosslinked polyethylene, including polyethylene, porous adsorbent material, compatibilizer, antioxidant, crosslinking agent, co-crosslinking agent, lubricant. Its preparation method is to adsorb the crosslinking agent into the porous adsorbent material by using a high-speed mixer, and then blend and granulate the adsorbent material with polyethylene to obtain crosslinked polyethylene particles. CN115819872A discloses a peroxide-crosslinked polyethylene cable material for insulating layers, including low-density polyethylene resin, crosslinking agent, co-crosslinking agent, high-melting-point antioxidant, low-melting-point antioxidant. Its preparation method is to initially mix the materials by mechanical physics, then send them to an extrusion granulation system for granulation, then heat the crosslinking agent to melt it into a liquid and spray it onto the surface of the dried prefabricated particles in a vacuum drying system by a liquid atomization device, and rotate at a low speed to make the crosslinking agent liquid diffuse into the interior of the dried prefabricated particles to occur crosslinking, obtaining insulating crosslinked polyethylene with qualified strength. However, traditional crosslinking methods, such as peroxide crosslinking, radiation crosslinking and silane crosslinking, although having significant effects in enhancing mechanical properties, inevitably lead to a significant decrease in the processing performance of polyethylene materials, specifically manifested as a decrease in melt fluidity, making it difficult to carry out the film extrusion and blown film processes normally. This processing performance problem limits the wide application of crosslinked polyethylene in the field of film preparation, especially in agricultural mulch films with high processing performance requirements.

[0004] To overcome the above problems, the present invention introduces a dynamic vulcanization technology to micro-crosslink polyethylene. The dynamic vulcanization technology forms a micro-crosslinked network in the polyethylene matrix by partially crosslinking polyethylene in the molten state, rather than an overall crosslinked structure. This micro-crosslinked structure can significantly enhance the mechanical properties of polyethylene while retaining the original melt fluidity of the material, enabling it to maintain good processing performance during the film processing process. According to the principle of polymer blending modification (the so-called rule of soft wrapping hard), if the viscosity of the dispersed phase is high and the viscosity of the continuous phase is low, it is very difficult to achieve good dispersion of the dispersed phase through strong shear (the viscosity of the continuous phase is low, and the shear force cannot be transmitted to the dispersed phase). Simply adding partially crosslinked PE with a low MF value (about 1.0 or even lower) and a high melt viscosity to conventional PE (melt flow rate MF is about 4.0 g / 10 min) cannot achieve good dispersion through strong shear and form a fiber network, that is, it cannot achieve the self-reinforcing effect. The principle of dynamic vulcanization must be adopted, that is, the dispersed phase is sheared and dispersed (into a crosslinked network) while its viscosity or crosslinking is increased. This innovation significantly broadens the application potential of crosslinked polyethylene in the film field, especially in the field of agricultural mulch films. Its high mechanical properties and excellent processing performance provide a new technical path for improving the service life and environmental protection benefits of mulch films. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing self-reinforced polyethylene and its film to improve the mechanical properties and processing performance of PE.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a method for preparing self-reinforced polyethylene, including the following steps:

[0008] (1) Premix polyethylene (PE) particles, initiator, crosslinking agent, and lubricant in a high-speed mixer in a certain mass ratio, and then extrude and pelletize in a twin-screw extruder to obtain pre-crosslinked PE particles. The mass percentages of each component in the pre-crosslinked PE particles are: polyethylene 94.5 - 99.7%, initiator 0.1 - 2.0%, crosslinking agent 0.1 - 3.0%, lubricant 0.1 - 0.5%; the initiator is 1,4-bis(tert-butylperoxy)cumene (BIBP), and the crosslinking agent is triallyl isocyanurate (TAIC); the twin-screw extruder is a co-rotating parallel twin-screw extruder, the screw diameter is 20 - 75 mm, the screw length-diameter ratio is greater than 20:1 but does not exceed 56:1, the temperature range of the first to tenth sections of the twin-screw extruder is 80 - 130 °C, the die head temperature is between 110 - 130 °C, and the screw speed is controlled between 80 - 200 rpm;

[0009] (2) Mix the pre-crosslinked PE particles and polyethylene particles evenly and extrude and pelletize them in a twin-screw extruder to obtain self-reinforced polyethylene particles, where the mass percentage content of the pre-crosslinked PE particles is 10-40 wt%; the twin-screw extruder is a co-rotating parallel twin-screw extruder, the screw diameter is 20-75 mm, the screw length-diameter ratio is greater than 20:1 but not exceeding 56:1, the temperature range of the first to tenth sections of the twin-screw extruder is 150-190 °C, the die head temperature is between 150-170 °C, and the screw speed is controlled between 150-400 rpm;

[0010] In steps (1) and (2) of the present invention, the polyethylene particles refer to commercially available granular polyethylene products without modification treatment, which can be LDPE, HDPE, LLDPE, etc.

[0011] In step (1) of the present invention, the lubricant can be selected from one or more of white oil, PE wax, stearic acid, butyl stearate, monoglyceryl stearate, and oleamide.

[0012] In step (1) of the present invention, the temperature of the high-speed mixer is room temperature - 80 °C, the rotation speed is 200-1000 rpm, and the mixing time is 2-10 min.

[0013] In the second aspect, the present invention provides a method for preparing a self-reinforced polyethylene film, including:

[0014] (1) Premix polyethylene (PE) particles, initiator, crosslinking agent, and lubricant in a certain mass ratio in a high-speed mixer evenly, and then extrude and pelletize them in a twin-screw extruder to obtain pre-crosslinked PE particles. The mass percentages of each component in the pre-crosslinked PE particles are: polyethylene 94.5-99.7%, initiator 0.1-2.0%, crosslinking agent 0.1-3.0%, lubricant 0.1-0.5%; the initiator is 1,4-bis(tert-butylperoxy)cumene (BIBP), and the crosslinking agent is triallyl isocyanurate (TAIC); the twin-screw extruder is a co-rotating parallel twin-screw extruder, the screw diameter is 20-75 mm, the screw length-diameter ratio is greater than 20:1 but not exceeding 56:1, the temperature range of the first to tenth sections of the twin-screw extruder is 80-130 °C, the die head temperature is between 110-130 °C, and the screw speed is controlled between 80-200 rpm;

[0015] (2) Mix the pre-crosslinked PE particles and polyethylene particles evenly and extrude and granulate them in a twin-screw extruder to obtain self-reinforced polyethylene particles, where the mass percentage content of the pre-crosslinked PE particles is 10-40 wt%; the twin-screw extruder is a co-rotating parallel twin-screw extruder, the screw diameter is 20-75 mm, the screw length-diameter ratio is greater than 20:1 but does not exceed 56:1, the temperature range of the first to tenth sections of the twin-screw extruder is 150-190 °C, the die head temperature is between 150-170 °C, and the screw speed is controlled between 150-400 rpm;

[0016] (3) Blow the self-reinforced polyethylene particles to obtain a self-reinforced polyethylene film.

[0017] The preparation details of steps (1) and (2) are the same as those in the first aspect and will not be elaborated here.

[0018] In step (3) of the present invention, the blowing film adopts a conventional blowing film process, and the blowing film conditions are: the temperature range of the first to fourth sections of extrusion is 140-170 °C, the blow-up ratio (die diameter: film bubble diameter) is 1:2-3, and the blowing film draw ratio is 1.2.

[0019] In the preparation method of the self-reinforced polyethylene of the present invention, the initiator is 1,4-bis(tert-butylperoxy)cumene (BIBP). In a high-temperature environment, BIBP decomposes to generate free radicals, and the free radicals can chemically react with the polymer main chain to promote cross-linking between molecular chains; the cross-linking agent is triallyl isocyanurate (TAIC), and TAIC contains three acrylate groups. Under the initiation of the initiator, it reacts with the PE segments to form cross-links. First, PE, initiator, cross-linking agent, and lubricant are used to prepare pre-crosslinked PE particles through a high-speed mixer and a twin-screw extruder. Since the reaction activity of the initiator is not high at this extrusion temperature, it will not react with the PE molecular chain. Subsequently, the pre-crosslinked PE and conventional PE are melt-blended in a twin-screw extruder. Since their initial viscosities are quite similar, the pre-crosslinked PE is easily sheared by the screw / barrel into a dispersed phase. At the same time, due to the relatively high extrusion temperature, the pre-crosslinked PE undergoes a micro-crosslinking reaction with the initiator and cross-linking agent inside it to form a dispersed phase. At the same time, the initiator and cross-linking agent located at the interface cause co-crosslinking to form at the dispersed phase / continuous phase interface, obtaining self-reinforced polyethylene. This self-reinforced PE is a special multiphase system, and the physical properties of its matrix and reinforcing phase are significantly different but the chemical structures are basically the same, so it has good interfacial compatibility. Moreover, in the continuous phase of conventional PE, the crosslinked PE forms a dispersed phase network, improving the overall strength of PE; the continuous phase ensures the overall thermoplasticity and better fluidity, making the processing process easier. The obtained self-reinforced PE has better mechanical properties than conventional PE. The self-reinforced PE film obtained by blowing film in the present invention can be used as a mulch film, which is convenient to pull up and recycle in the soil.

[0020] Compared with the existing direct cross-linking PE technology, the beneficial effects of the present invention are as follows:

[0021] (1) The present invention uses a two-step method to prepare self-reinforced PE, that is, pre-cross-linked PE particles are prepared at a lower temperature first, and then dynamic cross-linking of the dispersed phase is achieved by shearing at a higher temperature. The cross-linked dispersed phase network improves the overall mechanical properties of PE, and the continuous phase ensures good processing (such as blown film) process performance of PE.

[0022] (2) The present invention uses high mixing, granulation, and blown film, and the process flow is simple, easy to operate, and suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required in the embodiments. It should be understood that the following drawings only show some embodiments and comparative examples of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0024] Figure 1 It is a schematic diagram of the experimental process and mechanism for the preparation of self-reinforced PE of the present invention;

[0025] Figure 2 It is a micrograph in a scanning electron microscope (SEM) after brittle fracture of the self-reinforced PE particles obtained in the embodiment of the present invention and the pure PE particles obtained in Comparative Example 5.

[0026] Figure 3 It is the complex viscosity (a), storage modulus graph (b) of the extruded particles tested in the advanced extensional rheometer and the torque graph (c) tested in the internal mixer torque rheometer in the examples and comparative examples. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The following further describes the present invention in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0028] For those conditions not specified in the embodiments of the present invention, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained by conventional technical means or purchased commercially.

[0029] The LDPE used in the examples is the coating-grade LDPE 1840L of Shenhua Guoneng Xinjiang Polyethylene in coal chemical industry.

[0030] Example 1

[0031] By mass percentage, the pre-crosslinked PE particles include 99.7% LDPE, 0.1% initiator (BIBP), 0.1% crosslinking agent (TAIC), and 0.1% lubricant (white oil). See Table 1 for details.

[0032] By mass percentage, the LDPE blown film material includes 70% conventional LDPE and 30% pre-crosslinked LDPE particles.

[0033] Preparation of pre-crosslinked PE particles: Weigh LDPE, initiator (BIBP), crosslinking agent (TAIC), and lubricant (white oil) according to the formula, and directly put all raw materials into a 5L high-speed mixer (LN-G5L, Guangdong Lina Industry Co., Ltd.) and blend for 2 minutes at 40°C and 300 rpm; then add the mixture to a co-rotating twin-screw extruder (φ20, L / D = 36, Nanjing Juli Chemical Machinery Co., Ltd.) for mixing, plasticizing, and extruding. After strand air-cooling and pelletizing, the required pre-crosslinked LDPE pellets are obtained; the temperatures of each section of the extruder are as follows: the temperatures of the first to tenth sections are 115, 120, 130, 135, 140, 140, 140, 140, 140, 140°C in sequence, and the die head temperature is 140°C; the rotation speed is 80 rpm.

[0034] Preparation of self-reinforced PE particles and composite films: Weigh conventional LDPE and pre-crosslinked LDPE particles according to the formula and add them to a co-rotating twin-screw extruder (φ20, L / D = 36, Nanjing Juli Chemical Machinery Co., Ltd.) for mixing, plasticizing, and extruding. After strand air-cooling and pelletizing, self-reinforced PE particles are obtained; the temperatures of each section of the extruder are as follows: the temperatures of the first to tenth sections are 130, 135, 150, 160, 165, 175, 180, 185, 185, 170°C in sequence, and the die head temperature is 170°C; the rotation speed is 150 rpm. Use a blown film machine (XH-430B, Xihua Testing Instruments Co., Ltd.) to directly blow the obtained self-reinforced PE particles to obtain LDPE films. The temperatures of the first to fourth sections of the blown film machine are 150, 160, 170, 170°C in sequence, the blow-up ratio (die diameter: bubble diameter) is 1:3, and the blowing and stretching ratio is 1.2.

[0035] The obtained film was subjected to tensile property testing in accordance with GB / T1040.3-2006 to obtain data such as tensile strength and elongation at break. The extruded self-reinforced PE pellets were kneaded in a kneading torque rheometer at a temperature of 160 °C. The sample was heated at a constant shear rate (60 rpm) at this temperature, and the torque value 5 minutes after the sample torque started to stabilize was recorded. The melt index of the material was tested using a standardized melt flow index tester. The specific method was as follows: The self-reinforced PE sample was placed in the heating barrel of the tester. At 190 °C, a load of 2.16 kg was used to melt the material at the specified temperature and pass it through a standard die, and the flow rate within 10 minutes was measured. This flow rate was expressed as grams per 10 minutes (g / 10min).

[0036] Example 2

[0037] Other conditions were the same as in Example 1, but the dosages of the initiator and crosslinking agent in the pre-crosslinked PE particles were both increased from 0.1% to 0.2%, and the LDPE dosage was reduced to 99.5%.

[0038] Example 3

[0039] Other conditions were the same as in Example 1, but the dosages of the initiator and crosslinking agent in the pre-crosslinked PE particles were both increased from 0.1% to 0.3%, and the LDPE dosage was reduced to 99.3%.

[0040] Example 4

[0041] Other conditions were the same as in Example 1, but the dosages of the initiator and crosslinking agent in the pre-crosslinked PE particles were both increased from 0.1% to 0.4%, and the LDPE dosage was reduced to 99.1%.

[0042] Control Example 1

[0043] One-step crosslinking occurring in the actual process was used as a comparison, and it was uniformly crosslinked and pelletized by extrusion with the same initiator and crosslinking agent contents.

[0044] By mass percentage, the enhanced PE pellets include 99.91% LDPE, 0.03% initiator (BIBP), 0.03% crosslinking agent (TAIC), and 0.03% lubricant (white oil). All raw materials are directly put into a 5L high-speed mixer (LN-G5L, Guangdong Lina Industry Co., Ltd.) and blended for 2 minutes at 40°C and a rotation speed of 300 rpm; then the mixture is added to a co-rotating twin-screw extruder (φ20, L / D = 36, Nanjing Juli Chemical Machinery Co., Ltd.) for mixing, plasticizing, and extrusion. After strand air-cooling and pelletizing, the required pellets are obtained; the temperatures of each section of the extruder are as follows: the temperatures of the first to tenth sections are 130, 135, 140, 140, 165, 175, 180, 185, 185, 170°C in sequence, and the die head temperature is 170°C; the rotation speed is 150 rpm. The obtained pellets are blown into films, and the film blowing parameters are the same as those in Example 1.

[0045] Test the tensile strength and elongation at break of the film, and the torque and melt index of the pellets. The test methods are the same as those in Example 1.

[0046] Control Example 2

[0047] Others are the same as Control Example 1, but the dosages of the initiator and the crosslinking agent are both increased from 0.03% to 0.06%, and the LDPE dosage is reduced to 99.85%.

[0048] Control Example 3

[0049] Others are the same as Control Example 1, but the dosages of the initiator and the crosslinking agent are both increased from 0.03% to 0.09%, and the LDPE dosage is reduced to 99.79%.

[0050] Control Example 4

[0051] Others are the same as Control Example 1, but the dosages of the initiator and the crosslinking agent are both increased from 0.03% to 0.12%, and the LDPE dosage is reduced to 99.73%.

[0052] Control Example 5

[0053] Others are the same as Control Example 1, but without using the initiator and the crosslinking agent, that is, 99.97% LDPE and 0.03% lubricant (white oil). After extrusion and film blowing, a pure LDPE film is obtained.

[0054] Table 1

[0055]

[0056] As can be seen from Table 1, when comparing the examples and control examples with the same initiator and crosslinking agent in general (the initiator and crosslinking agent added in general: Example 1 is the same as Control Example 1; Example 2 is the same as Control Example 2; Example 3 is the same as Control Example 3; Example 4 is the same as Control Example 4; Control Example 5 is LDPE without added initiator and crosslinking agent), the mechanical properties of the self-reinforced film prepared by the two-step method (example) are superior to those of the one-step crosslinking method (corresponding control example). In addition, when comparing Example 4 with the pure LDPE film (Control Example 5), the longitudinal tensile strength increased from 13.52 MPa to 20.49 MPa, which is also higher than 15.17 of Control Example 4. This shows that the mechanical properties of LDPE can be significantly improved through the self-reinforcement technology. In the control examples, as the content of the crosslinking agent increased, the mechanical properties of LDPE decreased, which may be due to the phase structure change and poor fluidity caused by over-crosslinking. Among them, it became difficult to blow film for Control Example 4. By measuring the melt index, it can be obtained that the melt index of LDPE decreased relatively after adding the initiator and crosslinking agent, but the crosslinked LDPE in the control examples decreased more. Since the self-reinforced LDPE in the examples is partially crosslinked under dynamic vulcanization to form a dispersed phase, and there is still a part of the continuous phase that is pure LDPE, it can maintain good fluidity and ensure good processing performance during the blow film processing. The same is true for torque. Torque refers to the torsional moment required during processing. The greater the processing torque, the greater the resistance suffered by the polymer material during processing, and the more difficult the processing. Although the torque of the examples is higher than that of Control Example 5, the crosslinked LDPE in the control examples increased more. This shows that crosslinking will make the processing difficult, but the self-reinforced LDPE in the examples can alleviate this non-processability to a certain extent.

[0057] It can be seen from Figure 2 that the self-reinforced LDPE prepared by the two-step method in the examples (b, c, d, e) shows obvious surface fluctuations, evolving from the initial small protrusions to the subsequent sea-island structure with a continuous lamellar structure. Generally speaking, these observation results confirm the existence of the reinforcing phase, which is responsible for the reinforcing performance, while the pure LDPE continuous phase maintains fluidity and good processing performance in the self-reinforced LDPE.

[0058] It can be seen from Figure 3It can be seen from [the relevant content] that the storage modulus, complex viscosity, and torque of the examples are lower than those of the control examples with the same cross-linking agent added. The storage modulus is the ability to store energy. Generally, the larger this value is, the stronger the elasticity. However, if it is too high, flow defects are likely to occur during the processing, such as melt fracture and die swell. Therefore, it is not suitable for processing and forming such as blown film if it is too high. The complex viscosity refers to the difficulty of deformation of the material under shear stress and is related to the rheological stress. The greater the rheological stress, the greater the complex viscosity of the polymer material. The lower complex viscosity and torque also indicate that it is easier to process by blown film. It can be concluded that the self-reinforced PE processed by the two-step process has better blown film processing performance.

Claims

1. A method for preparing self-reinforced polyethylene, characterized in that: The preparation method comprises the following steps: (1) Premixing polyethylene particles, an initiator, a crosslinking agent, and a lubricant in a high-speed mixer at a certain mass ratio, and then extruding and granulating in a twin-screw extruder to obtain pre-crosslinked PE particles, wherein the mass percentages of the components in the pre-crosslinked PE particles are: polyethylene 94.5-99.7%, initiator 0.1-2.0%, crosslinking agent 0.1-3.0%, and lubricant 0.1-0.5%; the initiator is 1,4-di-tert-butyl peroxyisopropylbenzene, and the crosslinking agent is triallyl isocyanurate; the twin-screw extruder is a co-rotating parallel twin-screw extruder, the screw diameter is 20-75 mm, the screw aspect ratio is greater than 20:1 but not more than 56:1, the temperature range of the first to tenth sections of the twin-screw extruder is 80-130° C., the die head temperature is between 110-130° C., and the screw speed is controlled between 80-200 rpm; (2) Pre-crosslinked PE particles and polyethylene particles are mixed and extruded in a twin-screw extruder to obtain reinforced polyethylene particles, wherein the mass percentage of the pre-crosslinked PE particles is 10-40wt%; the twin-screw extruder is a co-rotating parallel twin-screw extruder, the screw diameter is 20-75mm, the screw aspect ratio is greater than 20:1 but not more than 56:1, the temperature range of the first to tenth sections of the twin-screw extruder is 150-190°C, the die temperature is between 150-170°C, and the screw speed is controlled between 150-400rpm.

2. The preparation method according to claim 1, characterized in that: In steps (1) and (2), the polyethylene is LDPE, HDPE or LLDPE.

3. The preparation method according to claim 1, characterized in that: In step (1), the lubricant is selected from one or more of white oil, PE wax, stearic acid, butyl stearate, stearic acid monoglyceride, and oleamide.

4. The preparation method according to claim 1, characterized in that: In step (1), the temperature of the high-speed mixer is room temperature-80°C, the rotation speed is 200-1000 rpm, and the mixing time is 2-10 min.

5. A method for preparing a self-reinforced polyethylene film, characterized in that: The preparation method comprises: (1) Premixing polyethylene particles, an initiator, a crosslinking agent, and a lubricant in a high-speed mixer at a certain mass ratio, and then extruding and granulating in a twin-screw extruder to obtain pre-crosslinked PE particles, wherein the mass percentages of the components in the pre-crosslinked PE particles are: polyethylene 94.5-99.7%, initiator 0.1-2.0%, crosslinking agent 0.1-3.0%, and lubricant 0.1-0.5%; the initiator is 1,4-di-tert-butyl peroxyisopropylbenzene, and the crosslinking agent is triallyl isocyanurate; the twin-screw extruder is a co-rotating parallel twin-screw extruder, the screw diameter is 20-75 mm, the screw aspect ratio is greater than 20:1 but not more than 56:1, the temperature range of the first to tenth sections of the twin-screw extruder is 80-130° C., the die head temperature is between 110-130° C., and the screw speed is controlled between 80-200 rpm; (2) pre-crosslinked PE particles and polyethylene particles are mixed and extruded in a twin-screw extruder to obtain reinforced polyethylene particles, wherein the mass percentage of the pre-crosslinked PE particles is 10-40wt%; the twin-screw extruder is a co-rotating parallel twin-screw extruder, the screw diameter is 20-75mm, the screw aspect ratio is greater than 20:1 but not more than 56:1, the temperature range of the first to tenth sections of the twin-screw extruder is 150-190°C, the die temperature is between 150-170°C, and the screw speed is controlled between 150-400rpm; (3) The self-reinforced polyethylene particles are blown into a film to obtain a self-reinforced polyethylene film.

6. The preparation method according to claim 5, characterized in that: In steps (1) and (2), the polyethylene is LDPE, HDPE or LLDPE.

7. The preparation method according to claim 5, characterized in that: In step (1), the lubricant is selected from one or more of white oil, PE wax, stearic acid, butyl stearate, stearic acid monoglyceride, and oleamide.

8. The preparation method according to claim 5, characterized in that: In step (1), the temperature of the high-speed mixer is room temperature-80°C, the rotation speed is 200-1000 rpm, and the mixing time is 2-10 min.

9. The preparation method according to claim 5, characterized in that: In step (3), the film blowing adopts a conventional film blowing process, and the film blowing conditions are: the temperature range of extrusion stages one to four is 140-170° C., the blowing ratio is 1:2-3, and the film blowing stretch ratio is 1.2.

Images