Anti-aging CPE film and preparation method thereof

Abstract

The invention relates to the technical field of plastics, and provides an anti-aging CPE film and a preparation method thereof. The anti-aging CPE film comprises a core layer and anti-aging surface layers symmetrically arranged on the outer surface of the core layer, wherein the core layer is prepared from the following raw materials in parts by weight: 55-65 parts of chlorinated polyethylene, 2-3 parts of ultra-high molecular weight polyethylene fibers, 5-8 parts of modified boehmite and 1-2 parts of auxiliaries; the anti-aging surface layer is prepared from the following raw materials in parts by weight: 50 to 60 parts of chlorinated polyethylene, 10 to 15 parts of polyolefin elastomer, 8 to 12 parts of linear low-density polyethylene, 5 to 10 parts of modified boehmite, 3 to 5 parts of cerium oxide nanoparticles, 1.5 to 2.5 parts of supported mesoporous silicon dioxide and 1.5 to 3 parts of auxiliaries. According to the anti-aging CPE film prepared in the invention, the anti-aging property of the film material is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of plastics, and in particular to an anti-aging CPE film and a preparation method thereof. Background Art

[0002] Chlorinated polyethylene (CPE), a key polymer material, has been widely used in numerous fields due to its unique molecular structure and excellent performance. CPE film, with its excellent flexibility, chemical resistance, barrier properties, and relatively low cost, plays an irreplaceable role in industries such as packaging, construction, and agriculture. However, over long-term use, CPE film is susceptible to environmental factors such as light, oxygen, heat, and humidity, causing aging. This leads to a significant decline in its physical and chemical properties, limiting its broader and more sustainable application.

[0003] Although some anti-aging CPE film products are currently available on the market, most products only improve their anti-aging properties by adding conventional anti-aging agents. These anti-aging agents can slow the aging rate of CPE films to a certain extent, but the effect is often less than ideal. For example, although some hindered amine light stabilizers and UV absorbers can absorb or block some ultraviolet rays, their anti-aging effects will gradually weaken under long-term high-intensity light conditions, and they cannot meet the requirements of some application scenarios with extremely high requirements for light aging resistance. In addition, with respect to thermal aging and oxidative aging, existing anti-aging agent systems also have certain limitations, making it difficult to fully and effectively inhibit the occurrence of various aging reactions, resulting in significant performance degradation of CPE films during long-term use. Moreover, some anti-aging CPE films can exhibit good anti-aging properties in the initial stage, but their anti-aging effects will gradually weaken as the use time increases. In order to solve the above-mentioned technical problems, the present invention proposes a new anti-aging CPE film. Summary of the Invention

[0004] The present invention proposes an anti-aging CPE film and a preparation method thereof, which improves the problem of poor light aging resistance of existing anti-aging CPE film products under long-term high-intensity light conditions, and at the same time improves the comprehensive and effective inhibition ability of the existing anti-aging agent system on thermal aging and oxidative aging, thereby reducing the performance degradation of the CPE film during long-term use.

[0005] The technical solutions of the present invention are as follows: In a first aspect, the present invention provides an anti-aging CPE film comprising a core layer and an anti-aging surface layer symmetrically arranged on the outer surface of the core layer; The core layer is composed of the following raw materials in parts by weight: 55-65 parts of chlorinated polyethylene, 2-3 parts of ultra-high molecular weight polyethylene fiber, 5-8 parts of modified boehmite, and 1-2 parts of additives; The anti-aging surface layer is composed of the following raw materials in parts by weight: 50-60 parts of chlorinated polyethylene, 10-15 parts of polyolefin elastomer, 8-12 parts of linear low-density polyethylene, 5-10 parts of modified boehmite, 3-5 parts of cerium oxide nanoparticles, 1.5-2.5 parts of supported mesoporous silica, and 1.5-3 parts of additives.

[0006] As a further technical solution, the preparation method of the modified boehmite includes: adding boehmite to anhydrous ethanol, mechanically stirring at 500-800 rpm for 30 minutes to form a uniform suspension; adding silane coupling agent KH-550 to the suspension, while raising the temperature to 50-60°C, ultrasonically treating at 500-800W and 30-40kHz for 2-3 hours, centrifuging, washing, drying, and passing through a 200-mesh sieve to obtain the product.

[0007] As a further technical solution, the weight ratio of the boehmite, anhydrous ethanol and silane coupling agent KH-550 is 100:200-300:3-5.

[0008] As a further technical solution, the boehmite includes boehmite with an average particle size of 50-100 nm and boehmite with an average particle size of 1-2 μm in a weight ratio of 1:1.

[0009] As a further technical solution, the preparation method of the loaded mesoporous silica includes: dissolving hexadecyltrimethylammonium bromide in a mixture of ethanol and water, stirring until completely dissolved, and then adding ammonia water to adjust the pH to 9-10; adding ethyl orthosilicate dropwise to the above solution at a drop rate of 0.4-0.6 mL / min, and reacting at a constant temperature of 40-50°C for 5-6 hours to generate a mesoporous SiO2 precursor; dissolving a hindered amine light stabilizer in ethanol, adding the mesoporous SiO2 precursor, and stirring at 60-70°C for 10-12 hours; after centrifugation and washing, vacuum drying at 55-65°C for 8-9 hours, heating to 500-600°C at a rate of 2°C / min, and calcining for 4-5 hours to obtain the loaded mesoporous silica.

[0010] As a further technical solution, the weight ratio of cetyltrimethylammonium bromide, ethyl orthosilicate and hindered amine light stabilizer is 3-4:20-25:5-6.

[0011] As a further technical solution, the auxiliary agents in the raw materials of the core layer and the anti-aging surface layer independently include a phosphite antioxidant, a benzotriazole ultraviolet absorber and zinc stearate in a weight ratio of 1.5-2.5:2.5-5:1-3.

[0012] As a further technical solution, the thickness of the anti-aging surface layer and the core layer are independently 10-30 μm.

[0013] In a second aspect, the present invention provides a method for preparing an anti-aging CPE film, comprising the following steps: (1) The raw materials are weighed according to the ratio and melt-blended by a twin-screw extruder at an extrusion temperature of 160-180°C, and granulated to obtain core layer masterbatch and anti-aging surface layer masterbatch respectively; (2) Add the core layer masterbatch and the anti-aging surface layer masterbatch into the hoppers of three co-extruders respectively, two of which are loaded with the surface layer masterbatch and one is loaded with the core layer masterbatch. The temperature of each extruder is controlled as follows: 165-175℃ for the core layer and 160-170℃ for the surface layer; (3) Composite extrusion is performed through a three-layer co-extrusion die, the die temperature is set to 170-180°C, and the screw speed of each extruder is adjusted to make the thickness ratio of the surface layer to the core layer reach 1:1.5-1:2; (4) Use water-cooled rollers for rapid cooling and shaping, control the cooling water temperature to 15-25°C, and then perform biaxial stretching after cooling, with a longitudinal stretching ratio of 1.5-2.0 and a transverse stretching ratio of 2.0-2.5; (5) The stretched film is introduced into a heat setting box and heat-relaxed at 80-100°C for 10-15 minutes; then rolled and slit to obtain the film.

[0014] As a further technical solution, the biaxial stretching in step (4) is carried out in two stages: first, longitudinal stretching at 50-60°C, and then transverse stretching at 70-80°C.

[0015] The present invention adopts a biaxial stretching process during the preparation process and optimizes the stretching parameters. Biaxial stretching can orient the molecular chains in the film in both the longitudinal and transverse directions, thereby improving the mechanical properties of the film. Longitudinal stretching is first performed at a lower temperature to initially orient the molecular chains in the longitudinal direction; then transverse stretching is performed at a higher temperature to further orient the molecular chains in the transverse direction. This stretching method can make the molecular chains of the film more uniform, reduce molecular chain defects and stress concentration, thereby improving the tensile strength, elongation at break and dimensional stability of the film. At the same time, biaxial stretching can also make the thickness of the film more uniform, improving the quality of the film. During the stretching process of the present invention, residual stress will be generated inside the film. The heat relaxation treatment can keep the film at a higher temperature for a period of time, allowing the molecular chains sufficient time to relax and rearrange, thereby releasing the residual stress. The release of residual stress can reduce the cracking and performance degradation caused by stress concentration during use of the film, and improve the heat aging resistance and dimensional stability of the film.

[0016] The working principle and beneficial effects of the present invention are: The present invention proposes a CPE membrane structure having a core layer and an anti-aging surface layer symmetrically arranged on the outer surface of the core layer. This layered structure can give full play to the functions of different layers. The core layer mainly provides mechanical performance support, and by adding reinforcing materials such as ultra-high molecular weight polyethylene fiber, the tensile strength and elongation at break of the membrane are improved. The anti-aging surface layer focuses on anti-aging performance, and by adding anti-aging agents such as cerium oxide nanoparticles and loaded mesoporous silica, it effectively inhibits light aging, heat aging and oxidative aging. The layered design allows the anti-aging agent to be concentrated in the surface layer, more directly resisting the erosion of the membrane by external environmental factors, while avoiding waste or performance degradation caused by uneven dispersion of the anti-aging agent in the core layer.

[0017] The present invention incorporates modified boehmite into the core layer and anti-aging surface layer. While boehmite itself possesses certain barrier properties, unmodified boehmite exhibits insufficient interfacial bonding with the substrate, prone to agglomeration and thus impairing its performance. Modifying the boehmite with the silane coupling agent KH-550 enhances the interfacial bonding between the boehmite and the substrate, reduces agglomeration, and improves the dispersibility of the boehmite within the substrate. Furthermore, boehmite of varying particle sizes exhibits distinct mechanisms of action within the CPE membrane matrix. Nanoboehmite, with its larger specific surface area, can fill the gaps between micron-sized boehmite particles, forming a denser barrier layer. This dense barrier layer effectively prevents external factors such as light and oxygen from penetrating the membrane, reducing the occurrence of photooxidation reactions and thereby enhancing the membrane's resistance to light aging. Furthermore, the stronger interfacial interaction between the nanoboehmite and the substrate can enhance the membrane's mechanical properties to a certain extent. The micron-sized boehmite acts as a skeletal support, providing the membrane with a certain degree of rigidity and strength. The synergistic effect of the two particle sizes of boehmite enables the CPE film to have better anti-aging properties while maintaining good mechanical properties.

[0018] The present invention utilizes supported mesoporous silica as a raw material, which offers advantages for improving the aging resistance of CPE membranes. The hindered amine light stabilizers (HALS) in the supported mesoporous silica can capture free radicals generated during the photoaging process, preventing the chain reaction initiated by these radicals and thereby slowing the rate of photoaging. Furthermore, the mesoporous silica itself has a certain UV shielding effect, scattering and reflecting some UV rays, reducing direct UV exposure to the membrane and further protecting it from the effects of photoaging. During thermal and oxidative aging, CPE membranes experience molecular chain breakage and crosslinking, leading to a decrease in mechanical properties. HALS is slowly released from the supported mesoporous silica, continuously exerting its antioxidant properties, inhibiting the generation and propagation of free radicals and thus reducing the occurrence of oxidative aging reactions. The barrier effect of the mesoporous silica prevents the penetration of oxidizing substances such as oxygen, reducing the oxidation rate of the membrane. In addition, the presence of supported mesoporous silica can also improve the microstructure of the membrane, reduce defects and stress concentration inside the membrane, and improve the thermal stability of the membrane, thereby comprehensively enhancing the CPE membrane's ability to inhibit thermal aging and oxidative aging, and reducing the performance degradation of the membrane during long-term use. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0020] It should be noted that the chlorinated polyethylene in the present invention, CAS No.: 63231-66-3, item No.: C909270, was purchased from Maclean Reagent; the ultra-high molecular weight polyethylene fiber, model: J200, was purchased from Jiangsu Jiujiujiu Technology Co., Ltd.; the linear low-density polyethylene, CAS No.: 9002-88-4, item No.: L790453, melt index: 40 g / 10 min, particle size: 1000 mesh, was purchased from Maclean Reagent; the polyolefin elastomer was purchased from Sanxiang Polymer Materials (Suzhou) Co., Ltd., and its model is: Japan Mitsui TAFMER (BL2481M).

[0021] Example 1 This embodiment provides an anti-aging CPE film, comprising a core layer with a thickness of 20 μm and an anti-aging surface layer with a thickness of 25 μm symmetrically arranged on the outer surface of the core layer; The core layer is composed of the following raw materials in parts by weight: 60 parts of chlorinated polyethylene, 2.5 parts of ultra-high molecular weight polyethylene fiber, 6 parts of modified boehmite and 1.5 parts of additives; The anti-aging surface layer is composed of the following raw materials in parts by weight: 55 parts of chlorinated polyethylene, 12 parts of polyolefin elastomer, 10 parts of linear low-density polyethylene, 8 parts of modified boehmite, 4 parts of cerium oxide nanoparticles, 2 parts of supported mesoporous silica, and 2.2 parts of additives.

[0022] The preparation method of modified boehmite is as follows: 50 parts of boehmite with an average particle size of 80 nm and 50 parts of boehmite with an average particle size of 1.5 μm are added to 250 parts of anhydrous ethanol, and mechanically stirred at 700 rpm for 30 minutes to form a uniform suspension; 4 parts of silane coupling agent KH-550 are added to the suspension, and the temperature is raised to 55°C, and ultrasonic treatment is performed at 600 W and 35 kHz for 2.5 hours. The suspension is then centrifuged, washed, dried, and passed through a 200-mesh sieve to obtain the product.

[0023] Among them, the preparation method of supported mesoporous silica includes: dissolving 3.5 parts of hexadecyltrimethylammonium bromide in a mixture of 60 parts of ethanol and 20 parts of water, stirring until completely dissolved, and then adding 28% mass concentration of ammonia water to adjust the pH to 9.5; adding 22 parts of ethyl orthosilicate dropwise to the above solution at a drop rate of 0.5 mL / min, reacting at a constant temperature of 45°C for 5.5 hours to generate a mesoporous SiO2 precursor; dissolving 5.5 parts of hindered amine light stabilizer Tinuvin 770 in 20 parts of ethanol, adding the mesoporous SiO2 precursor, and stirring at 65°C for 11 hours; centrifuging the product, washing it with ethanol three times, and then vacuum drying it at 60°C for 8.5 hours, heating it to 550°C at a rate of 2°C / min and calcining it for 4.5 hours to obtain supported mesoporous silica SiO2@HALS.

[0024] The additives of the core layer and the anti-aging surface layer respectively include phosphite antioxidant 168, benzotriazole ultraviolet absorber UV-234 and zinc stearate in a weight ratio of 2:3.5:2.

[0025] The method for preparing the anti-aging CPE film comprises the following steps: (1) The raw materials were weighed according to the ratio and melt-blended by a twin-screw extruder at an extrusion temperature of 170°C, and granulated to obtain core layer masterbatch and anti-aging surface layer masterbatch respectively; (2) The core layer masterbatch and the anti-aging surface layer masterbatch were added to the hoppers of three co-extruders respectively, two of which were loaded with the surface layer masterbatch and one was loaded with the core layer masterbatch. The temperature of each extruder was controlled as follows: 170°C for the core layer and 165°C for the surface layer; (3) Composite extrusion was performed through a three-layer co-extrusion die, the die temperature was set to 175°C, and the screw speed of each extruder was adjusted to make the thickness ratio of the surface layer to the core layer reach 1:1.8; (4) Rapid cooling and shaping by water-cooled rollers, controlling the cooling water temperature at 20°C, and then biaxially stretched after cooling, first longitudinally stretched at 55°C and then transversely stretched at 75°C; the longitudinal stretching ratio is 1.8 and the transverse stretching ratio is 2.2; (5) The stretched film is introduced into a heat setting box and heat-relaxed at 90°C for 12 minutes; then it is rolled up and slit to obtain the film.

[0026] Example 2 This embodiment provides an anti-aging CPE film, comprising a core layer with a thickness of 20 μm and an anti-aging surface layer with a thickness of 25 μm symmetrically arranged on the outer surface of the core layer; The core layer is composed of the following raw materials in parts by weight: 55 parts of chlorinated polyethylene, 2 parts of ultra-high molecular weight polyethylene fiber, 5 parts of modified boehmite and 1 part of additives; The anti-aging surface layer is composed of the following raw materials in parts by weight: 50 parts of chlorinated polyethylene, 10 parts of polyolefin elastomer, 8 parts of linear low-density polyethylene, 5 parts of modified boehmite, 3 parts of cerium oxide nanoparticles, 1.5 parts of supported mesoporous silica, and 1.5 parts of additives.

[0027] The preparation method of modified boehmite is as follows: 50 parts of boehmite with an average particle size of 50 nm and 50 parts of boehmite with an average particle size of 1 μm are added to 200 parts of anhydrous ethanol, and mechanically stirred at 500 rpm for 30 minutes to form a uniform suspension; 3 parts of silane coupling agent KH-550 are added to the suspension, and the temperature is raised to 50°C, and ultrasonic treatment is performed at 500W and 30kHz for 2 hours. The modified boehmite is then centrifuged, washed, dried, and passed through a 200-mesh sieve to obtain the product.

[0028] Among them, the preparation method of supported mesoporous silica includes: dissolving 3 parts of hexadecyltrimethylammonium bromide in a mixture of 60 parts of ethanol and 20 parts of water, stirring until completely dissolved, and then adding ammonia water with a mass concentration of 28% to adjust the pH to 9; adding 20 parts of ethyl orthosilicate dropwise to the above solution at a drop rate of 0.4 mL / min, reacting at a constant temperature of 40°C for 5 hours to generate a mesoporous SiO2 precursor; dissolving 5 parts of hindered amine light stabilizer Tinuvin 770 in 20 parts of ethanol, adding the mesoporous SiO2 precursor, and stirring at 60°C for 10 hours; centrifuging the product, washing it with ethanol three times, and then vacuum drying it at 55°C for 8 hours, heating it to 500°C at a rate of 2°C / min, and calcining it for 4 hours to obtain supported mesoporous silica SiO2@HALS.

[0029] The additives of the core layer and the anti-aging surface layer respectively include a phosphite antioxidant 168, a benzotriazole ultraviolet absorber UV-234 and zinc stearate in a weight ratio of 1.5:2.5:1.

[0030] The method for preparing the anti-aging CPE film comprises the following steps: (1) The raw materials were weighed according to the ratio and melt-blended in a twin-screw extruder at an extrusion temperature of 160°C, and granulated to obtain core layer masterbatch and anti-aging surface layer masterbatch respectively; (2) The core layer masterbatch and the anti-aging surface layer masterbatch were added into the hoppers of three co-extruders respectively, two of which were loaded with the surface layer masterbatch and one was loaded with the core layer masterbatch. The temperature of each extruder was controlled as follows: 165°C for the core layer and 160°C for the surface layer; (3) Composite extrusion was performed through a three-layer co-extrusion die, the die temperature was set to 170°C, and the screw speed of each extruder was adjusted to make the thickness ratio of the surface layer to the core layer reach 1:1.5; (4) Use water-cooled rollers for rapid cooling and shaping, control the cooling water temperature at 15°C, and then undergo biaxial stretching treatment after cooling, first longitudinally stretching at 50°C and then transversely stretching at 70°C; the longitudinal stretching ratio is 1.5 and the transverse stretching ratio is 2.0; (5) The stretched film is introduced into a heat setting box and heat-relaxed at 80°C for 10 minutes; then it is rolled up and slit to obtain the film.

[0031] Example 3 This embodiment provides an anti-aging CPE film, comprising a core layer with a thickness of 20 μm and an anti-aging surface layer with a thickness of 25 μm symmetrically arranged on the outer surface of the core layer; The core layer is composed of the following raw materials in parts by weight: 65 parts of chlorinated polyethylene, 3 parts of ultra-high molecular weight polyethylene fiber, 8 parts of modified boehmite and 2 parts of additives; The anti-aging surface layer is composed of the following raw materials in parts by weight: 60 parts of chlorinated polyethylene, 15 parts of polyolefin elastomer, 12 parts of linear low-density polyethylene, 10 parts of modified boehmite, 5 parts of cerium oxide nanoparticles, 2.5 parts of supported mesoporous silica, and 3 parts of additives.

[0032] The preparation method of modified boehmite is as follows: 50 parts of boehmite with an average particle size of 100 nm and 50 parts of boehmite with an average particle size of 2 μm are added to 300 parts of anhydrous ethanol, and mechanically stirred at 800 rpm for 30 minutes to form a uniform suspension; 5 parts of silane coupling agent KH-550 are added to the suspension, and the temperature is raised to 60°C, and ultrasonic treatment is performed at 800 W and 40 kHz for 3 hours. The modified boehmite is centrifuged, washed, dried, and passed through a 200-mesh sieve to obtain the product.

[0033] Among them, the preparation method of supported mesoporous silica includes: dissolving 4 parts of hexadecyltrimethylammonium bromide in a mixture of 60 parts of ethanol and 20 parts of water, stirring until completely dissolved, and then adding 28% mass concentration of ammonia water to adjust the pH to 10; adding 25 parts of ethyl orthosilicate dropwise to the above solution at a drop rate of 0.6 mL / min, reacting at a constant temperature of 50°C for 6 hours to generate a mesoporous SiO2 precursor; dissolving 6 parts of hindered amine light stabilizer Tinuvin 770 in 20 parts of ethanol, adding the mesoporous SiO2 precursor, and stirring at 70°C for 12 hours; centrifuging the product, washing it with ethanol three times, and then vacuum drying it at 65°C for 9 hours, heating it to 600°C at a rate of 2°C / min, and calcining it for 5 hours to obtain supported mesoporous silica SiO2@HALS.

[0034] The additives of the core layer and the anti-aging surface layer respectively include phosphite antioxidant 168, benzotriazole ultraviolet absorber UV-234 and zinc stearate in a weight ratio of 2.5:5:3.

[0035] The method for preparing the anti-aging CPE film comprises the following steps: (1) The raw materials were weighed according to the ratio and melt-blended by a twin-screw extruder at an extrusion temperature of 180°C, and granulated to obtain core layer masterbatch and anti-aging surface layer masterbatch respectively; (2) The core layer masterbatch and the anti-aging surface layer masterbatch were added to the hoppers of three co-extruders respectively, two of which were loaded with the surface layer masterbatch and one was loaded with the core layer masterbatch. The temperature of each extruder was controlled as follows: 175°C for the core layer and 170°C for the surface layer; (3) Composite extrusion was performed through a three-layer co-extrusion die, the die temperature was set to 180°C, and the screw speed of each extruder was adjusted to make the thickness ratio of the surface layer to the core layer reach 1:2; (4) Rapid cooling and shaping by water-cooled rollers, controlling the cooling water temperature at 25°C, and then biaxially stretched after cooling, first longitudinally stretched at 60°C, then transversely stretched at 80°C; longitudinal stretching ratio 2.0, transverse stretching ratio 2.5; (5) The stretched film is introduced into a heat setting box and heat-relaxed at 100°C for 15 minutes; then the film is rolled up and slit to obtain the film.

[0036] Example 4 This embodiment provides an anti-aging CPE film, comprising a core layer with a thickness of 20 μm and an anti-aging surface layer with a thickness of 25 μm symmetrically arranged on the outer surface of the core layer; The core layer is composed of the following raw materials in parts by weight: 55 parts of chlorinated polyethylene, 3 parts of ultra-high molecular weight polyethylene fiber, 5 parts of modified boehmite and 2 parts of additives; The anti-aging surface layer is composed of the following raw materials in parts by weight: 50 parts of chlorinated polyethylene, 15 parts of polyolefin elastomer, 8 parts of linear low-density polyethylene, 10 parts of modified boehmite, 3 parts of cerium oxide nanoparticles, 2.5 parts of supported mesoporous silica, and 1.5 parts of additives.

[0037] The preparation method of modified boehmite is as follows: 50 parts of boehmite with an average particle size of 100 nm and 50 parts of boehmite with an average particle size of 1 μm are added to 300 parts of anhydrous ethanol, and mechanically stirred at 500 rpm for 30 minutes to form a uniform suspension; 5 parts of silane coupling agent KH-550 are added to the suspension, and the temperature is raised to 50°C, and ultrasonic treatment is performed at 800 W and 30 kHz for 3 hours. The modified boehmite is centrifuged, washed, dried, and passed through a 200-mesh sieve to obtain the product.

[0038] Among them, the preparation method of supported mesoporous silica includes: dissolving 3 parts of hexadecyltrimethylammonium bromide in a mixture of 60 parts of ethanol and 20 parts of water, stirring until completely dissolved, and then adding ammonia water with a mass concentration of 28% to adjust the pH to 10; adding 20 parts of ethyl orthosilicate dropwise to the above solution at a drop rate of 0.6 mL / min, reacting at a constant temperature of 40°C for 6 hours to generate a mesoporous SiO2 precursor; dissolving 5 parts of hindered amine light stabilizer Tinuvin 770 in 20 parts of ethanol, adding the mesoporous SiO2 precursor, and stirring at 70°C for 10 hours; centrifuging the product, washing it with ethanol three times, and then vacuum drying it at 65°C for 8 hours, heating it to 600°C at a rate of 2°C / min, and calcining it for 4 hours to obtain supported mesoporous silica SiO2@HALS.

[0039] The additives of the core layer and the anti-aging surface layer respectively include phosphite antioxidant 168, benzotriazole ultraviolet absorber UV-234 and zinc stearate in a weight ratio of 2.5:5:3.

[0040] The method for preparing the anti-aging CPE film comprises the following steps: (1) The raw materials were weighed according to the ratio and melt-blended in a twin-screw extruder at an extrusion temperature of 160°C, and granulated to obtain core layer masterbatch and anti-aging surface layer masterbatch respectively; (2) The core layer masterbatch and the anti-aging surface layer masterbatch were added into the hoppers of three co-extruders respectively, two of which were loaded with the surface layer masterbatch and one was loaded with the core layer masterbatch. The temperature of each extruder was controlled as follows: 175°C for the core layer and 160°C for the surface layer; (3) Composite extrusion was performed through a three-layer co-extrusion die, the die temperature was set to 170°C, and the screw speed of each extruder was adjusted to make the thickness ratio of the surface layer to the core layer reach 1:2; (4) Rapid cooling and shaping by water-cooled rollers, controlling the cooling water temperature at 15°C, and then biaxially stretched after cooling, first longitudinally stretched at 60°C, then transversely stretched at 70°C; longitudinal stretching ratio 2.0, transverse stretching ratio 2.0; (5) The stretched film is introduced into a heat setting box and heat-relaxed at 100°C for 10 minutes; then it is rolled up and slit to obtain the film.

[0041] Comparative Example 1 Adjustments were made based on Example 1, except that the boehmite with an average particle size of 80 nm in the anti-aging surface layer and the core layer was replaced with boehmite with an average particle size of 1.5 μm.

[0042] Comparative Example 2 Adjustments were made based on Example 1. The difference from Example 1 was that unmodified dual-scale boehmite was used in the anti-aging surface layer and the core layer. The dual-scale boehmite included boehmite with an average particle size of 80 nm and boehmite with an average particle size of 1.5 μm in a mass ratio of 1:1.

[0043] Comparative Example 3 Adjustments were made based on Example 1, except that nano-cerium oxide particles were not added to the anti-aging surface layer.

[0044] Comparative Example 4 Adjustments were made based on Example 1, except that the supported mesoporous silica SiO2@HALS in the anti-aging surface layer was replaced with an equal amount of hindered amine light stabilizer Tinuvin 770.

[0045] Comparative Example 5 Adjustments were made based on Example 1. The difference from Example 1 was that the layered design of the core layer and the surface layer was cancelled, and a single-layer blended film (total thickness 70 μm) was used; The method for preparing a single-layer blend film comprises the following steps: (1) Weigh the core layer raw materials and the anti-aging surface layer raw materials according to the ratio and melt-blend them through a twin-screw extruder at an extrusion temperature of 170°C; (2) Add the masterbatch prepared in step (1) into the hopper of the extruder, control the extruder temperature to 170°C, and set the die head temperature to 175°C; (3) Rapid cooling and shaping by water-cooled rollers, controlling the cooling water temperature at 20°C, and then biaxially stretching after cooling, first longitudinally stretching at 55°C and then transversely stretching at 75°C; the longitudinal stretching ratio is 1.8 and the transverse stretching ratio is 2.2; (4) The stretched film is introduced into a heat setting box and heat-relaxed at 90°C for 12 minutes; then rolled and slit to obtain the film.

[0046] Comparative Example 6 Adjustments were made based on Example 1. The difference from Example 1 was that the ultra-high molecular weight polyethylene fiber in the core layer was replaced with ultra-high molecular weight polyethylene purchased from Dongguan Hongkuo Plastic Co., Ltd., with the brand name UHMWPE and model number X201.

[0047] Comparative Example 7 Adjustments were made based on Example 1. The difference from Example 1 was that the biaxial stretching process was changed to uniaxial stretching, the longitudinal stretching ratio was 2.0, and there was no transverse stretching.

[0048] Comparative Example 8 Adjustments were made based on Example 1, except that the heat relaxation step in the heat setting box was eliminated.

[0049] Test Example 1: The anti-aging CPE films prepared in Examples 1-4 and Comparative Examples 1-8 were subjected to the following tests: Tensile strength and elongation at break: Tested according to ASTM D882 (Testing for Tensile Properties of Plastic Films) using an electronic universal testing machine. Samples were taken in the machine direction (MD) and transverse direction (TD) of the film at a tensile speed of 50 mm / min. UV shielding rate: tested according to ASTM G154 (artificial accelerated UV aging test), UV radiation intensity 40 W / m 2 , temperature 60 ℃, humidity 50%, continuous exposure for 200 hours, use UV spectrophotometer to measure the UV transmittance of the film and calculate the shielding rate; Thermal oxidative aging resistance: Tested in accordance with GB / T 7141 (Plastics thermal aging test), the film was placed in a 60°C thermal oxidative aging chamber for 200 hours, and the tensile strength retention rate after aging was tested; The test results are shown in Table 1 below: Table 1

[0050] In view of the above, in Comparative Example 1, which only contains micron-sized boehmite, the tensile strength and UV shielding rate are significantly reduced. Micron-sized boehmite cannot fill the micropores of the matrix, and light and oxygen penetration are aggravated; the lack of nano-sized boehmite weakens the mechanical strengthening effect. In Comparative Example 2, the unmodified boehmite has the lowest elongation at break and heat aging resistance. The unmodified boehmite agglomerates due to insufficient interfacial bonding, which causes stress concentration and cracks, and is unable to effectively adsorb free radicals. In Comparative Example 3, the UV shielding rate drops to 85% without cerium oxide, and the heat aging retention rate is only 70%. The lack of cerium oxide weakens the UV absorption and free radical capture functions, accelerating photoaging. In Comparative Example 4, the heat aging retention rate is the lowest when HALS is directly added. The unloaded HALS is easy to migrate, and the slow-release function of mesoporous SiO2 is lost, resulting in rapid consumption of the antioxidant. The tensile strength and UV shielding rate of the single-layer structure of Comparative Example 5 are both lower than those of Example 1. The functions are not stratified, the antioxidant is unevenly distributed, and the mechanical anisotropy is significant. In Comparative Example 6, ultra-high molecular weight polyethylene (UHMWPE) was substituted for ultra-high molecular weight polyethylene fiber, but the fiber reinforcement effect was lost, resulting in a significant decrease in the core layer's tensile strength and elongation at break. In Comparative Example 7, uniaxial stretching resulted in a significant decrease in transverse tensile strength and elongation at break. The lack of biaxial stretching led to uneven molecular chain orientation and deterioration of transverse mechanical properties. In Comparative Example 8, the heat relaxation was eliminated, resulting in a heat aging retention rate of 60%, residual stress was not released, and interfacial delamination was exacerbated during thermal oxidative aging.

[0051] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An anti-aging CPE film, characterized in that: It comprises a core layer and an anti-aging surface layer symmetrically arranged on the outer surface of the core layer; The core layer is composed of the following raw materials in parts by weight: 55-65 parts of chlorinated polyethylene, 2-3 parts of ultra-high molecular weight polyethylene fiber, 5-8 parts of modified boehmite, and 1-2 parts of additives; The anti-aging surface layer is composed of the following raw materials in parts by weight: 50-60 parts of chlorinated polyethylene, 10-15 parts of polyolefin elastomer, 8-12 parts of linear low-density polyethylene, 5-10 parts of modified boehmite, 3-5 parts of cerium oxide nanoparticles, 1.5-2.5 parts of supported mesoporous silica, and 1.5-3 parts of additives.

2. An anti-aging CPE film according to claim 1, characterized in that, The preparation method of the modified boehmite comprises: adding boehmite to anhydrous ethanol and stirring to form a uniform suspension; adding silane coupling agent KH-550 to the suspension, heating to 50-60° C. and ultrasonically treating the suspension for 2-3 hours; centrifuging, washing, drying, and passing through a 200-mesh sieve to obtain the modified boehmite.

3. An anti-aging CPE film according to claim 2, characterized in that, The weight ratio of the boehmite, anhydrous ethanol and silane coupling agent KH-550 is 100:200-300:3-5.

4. An anti-aging CPE film according to claim 2, characterized in that, The boehmite includes boehmite with an average particle size of 50-100 nm and boehmite with an average particle size of 1-2 μm in a weight ratio of 1:

1.

5. An anti-aging CPE film according to claim 1, characterized in that: The preparation method of the loaded mesoporous silica comprises: dissolving hexadecyltrimethylammonium bromide in a mixture of ethanol and water, stirring until completely dissolved, and then adding ammonia water to adjust the pH to 9-10; adding ethyl orthosilicate dropwise to the above solution at a dropping speed of 0.4-0.6 mL / min, and reacting at a constant temperature of 40-50° C. for 5-6 hours to generate a mesoporous SiO2 precursor; dissolving a hindered amine light stabilizer in ethanol, adding the mesoporous SiO2 precursor, and stirring at 60-70° C. for 10-12 hours; centrifuging and washing, and then vacuum drying at 55-65° C. for 8-9 hours, heating to 500-600° C. and calcining for 4-5 hours to obtain the loaded mesoporous silica.

6. An anti-aging CPE film according to claim 5, characterized in that: The weight ratio of the hexadecyltrimethylammonium bromide, ethyl orthosilicate and hindered amine light stabilizer is 3-4:20-25:5-6.

7. The anti-aging CPE film according to claim 1, characterized in that: The auxiliary agents in the raw materials of the core layer and the anti-aging surface layer independently include a phosphite antioxidant, a benzotriazole ultraviolet absorber and zinc stearate in a weight ratio of 1.5-2.5:2.5-5:1-3.

8. The anti-aging CPE film according to claim 1, characterized in that: The thickness of the anti-aging surface layer and the core layer are independently 10-30 μm.

9. A method for preparing an anti-aging CPE film according to any one of claims 1 to 8, characterized in that the steps include: (1) The raw materials are weighed according to the ratio and melt-blended by a twin-screw extruder at an extrusion temperature of 160-180°C, and granulated to obtain core layer masterbatch and anti-aging surface layer masterbatch respectively; (2) Add the core layer masterbatch and the anti-aging surface layer masterbatch into the hoppers of three co-extruders respectively, two of which are loaded with the surface layer masterbatch and one is loaded with the core layer masterbatch. The temperature of each extruder is controlled as follows: 165-175℃ for the core layer and 160-170℃ for the surface layer; (3) Composite extrusion is performed through a three-layer co-extrusion die, the die temperature is set to 170-180°C, and the screw speed of each extruder is adjusted to make the thickness ratio of the surface layer to the core layer reach 1:1.5-1:2; (4) Use water-cooled rollers for rapid cooling and shaping, control the cooling water temperature to 15-25°C, and then perform biaxial stretching after cooling, with a longitudinal stretching ratio of 1.5-2.0 and a transverse stretching ratio of 2.0-2.5; (5) The stretched film is introduced into a heat setting box and heat-relaxed at 80-100°C for 10-15 minutes; then rolled and slit to obtain the film.

10. The method for preparing the anti-aging CPE film according to claim 9, characterized in that: The biaxial stretching in step (4) is carried out in two stages: firstly longitudinal stretching at 50-60°C, and then transverse stretching at 70-80°C.

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