A polyethylene separator film with a high residual adhesion rate and a preparation method thereof

Abstract

The present invention discloses a polyethylene separator film with a high residual adhesion rate and a preparation method thereof, belonging to the technical field of separator films. The raw materials are co-extruded and blown into a film in a three-layer manner in an extruder according to the formula dosage ratio of the surface layer, the intermediate layer, and the bottom layer to obtain a separator film base film. The coating layer is prepared by mixing the raw materials evenly according to the formula dosage ratio, coating the bottom layer of the separator film base film with a coater, and drying, cross-linking, and curing to obtain the polyethylene separator film with a high residual adhesion rate. The polyethylene separator film with a high residual adhesion rate prepared by the present invention modifies high-density polyethylene with a modified composite powder, so that the separator film has good high-temperature resistance and ultraviolet resistance. A siliconophilic heat-shrinkable separator film base film is obtained by a three-layer composite method. The separator film coated with aqueous silicone oil has a high residual adhesion rate, and its performance is superior to that of the separator film coated by the solvent method, and the desiliconization rate is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of separator films, and particularly relates to a polyethylene separator film with a high residual adhesion rate and a preparation method thereof. Background Art

[0002] As a fully saturated hydrocarbon skeleton, polyethylene is one of the most important commercial polymers and is widely used as key components for pipes, plates, containers, films, cables, coatings, fibers, and other necessities. Polyethylene separator film materials are soft, have a high elongation rate, are flat and beautiful, have a relatively high dry silicon content, have a low risk of difficult peeling, are recyclable, and are green and environmentally friendly. However, their high-temperature resistance performance is very poor, and their light resistance performance is poor in outdoor light environments, and they are prone to aging and yellowing, resulting in the separation of the polyethylene separator film matrix from the aqueous silicone oil layer.

[0003] The Chinese patent application with the publication number CN117325530A discloses a heat-resistant and low-desilicon composite polyethylene separator film and a preparation method thereof. By coating silica gel glue on the original polyethylene film and using organosilicon coating cross-linking and the method of three-layer co-extrusion blow molding, it has the advantages of improving the surface strength of the film and the heat shrinkage performance of the material. However, in this solution, the improvement degree of the heat resistance performance of the original polyethylene separator film is relatively low, and it is prone to aging under the condition of ultraviolet light irradiation.

[0004] The Chinese patent application with the publication number CN117510916A discloses a preparation method of a high-temperature resistant modified polyethylene separator film. A modified polyamide obtained by polycondensation of m-phenylenediamine, isophthaloyl chloride, and phosphorus-containing m-phenylenediamine is mixed with modified polyethylene modified by vinyl nano-silica, maleic anhydride, and diisopropylbenzene peroxide to obtain a polyethylene separator film with flame retardant performance and high-temperature resistance performance. However, this solution focuses on the improvement of flame retardant performance, and the improvement of the ultraviolet light resistance ability of the polyethylene separator film is relatively small. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem of how to improve the performance of polyethylene separator films under ultraviolet light irradiation, and to provide a polyethylene separator film with a high residual adhesion rate and a preparation method thereof.

[0006] In the present invention, titanium tetrachloride is anchored on the surface of a silica carrier and oxidized into titanium dioxide, and is compounded with graphene oxide nanosheets to form a modified composite powder. By modifying high-density polyethylene with the modified composite powder, the heat resistance performance, mechanical performance, and residual adhesion rate of the polyethylene separator film are improved.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A high residual adhesion rate polyethylene separator film, comprising a surface layer, an intermediate layer, a bottom layer and a coating layer. By mass, the surface layer formulation comprises the following raw material components:

[0009] 65 - 75 parts of modified high - density polyethylene, 5 - 8 parts of linear low - density polyethylene and 20 - 25 parts of maleic anhydride grafted polyethylene.

[0010] The intermediate layer formulation comprises the following raw material components: 65 - 75 parts of modified high - density polyethylene, 10 - 12 parts of filling masterbatch and 2 - 3 parts of color masterbatch.

[0011] The bottom layer formulation comprises the following raw material components: 65 - 75 parts of modified high - density polyethylene, 5 - 8 parts of linear low - density polyethylene and 10 - 12 parts of filling masterbatch.

[0012] Furthermore, the modified high - density polyethylene is prepared by the following steps:

[0013] Step 1: Disperse the supported titanium composite powder in n - decane in a reaction kettle. Dissolve benzyl alcohol in benzene, add it to the reaction kettle, reflux and heat at 35 - 45 °C for 4 - 5 h, rotary evaporate to remove the benzene solvent, reflux and react at 170 - 180 °C for 8 - 9 h, centrifuge to collect the precipitate, wash and then vacuum dry to obtain the titanium oxide - supported composite powder.

[0014] Step 2: Modify the titanium oxide - supported composite powder with KH550 in ethanol in a reaction kettle to obtain a modified composite powder. Mix the modified composite powder with high - density polyethylene in a twin - screw extruder at 180 - 190 °C and a rotation speed of 50 - 60 rpm for 10 - 12 min to obtain the modified high - density polyethylene.

[0015] Furthermore, by mass, the coating layer formulation comprises the following raw material components: 90 - 92 parts of silicone oil, 4 - 5 parts of cross - linker, 5 - 6 parts of curing agent and 0.3 - 0.4 parts of catalyst.

[0016] Furthermore, the cross - linker is a hydrogen - containing siloxane, the curing agent is an epoxy - group silane, and the catalyst is a siloxane platinum complex.

[0017] Furthermore, in Step 1, the dosage ratio of the supported titanium composite powder, n - decane, benzyl alcohol and benzene is 30 - 40 g: 300 - 400 mL: 6 - 8 mL: 35 - 40 mL.

[0018] Furthermore, the supported titanium composite powder is prepared by the following steps:

[0019] Mix the magnesium chloride / silicon dioxide composite powder with n - hexane and titanium tetrachloride in a reaction kettle, stir at 45 - 55 °C for 3 - 4 h, centrifuge to collect the precipitate, wash and dry to obtain the supported titanium composite powder.

[0020] The dosage ratio of magnesium chloride / silica composite powder, n-hexane and titanium tetrachloride is 30 - 40 g : 600 - 700 mL : 20 - 30 mL.

[0021] Furthermore, the magnesium chloride / silica composite powder is prepared by the following steps:

[0022] The graphene dispersion and the silica dispersion are stirred at 35 - 45 °C for 3 - 4 h, and the precipitate is obtained by filtration. After washing and drying, the magnesium chloride / silica composite powder is obtained; the dosage ratio of the graphene dispersion and the silica dispersion is 400 - 500 mL : 700 - 800 mL. Further, the graphene dispersion is obtained by stirring and mixing magnesium chloride graphene, cage-shaped polyhedral oligomeric silsesquioxane and tetrahydrofuran according to the dosage ratio of 10 - 12 g : 14 - 16 g : 400 - 500 mL.

[0023] The silica dispersion is obtained by stirring and mixing silica powder, 1,4-butanediol and tetrahydrofuran according to the dosage ratio of 25 - 30 g : 12 - 15 mL : 700 - 800 mL.

[0024] Furthermore, the magnesium chloride graphene is prepared by the following steps:

[0025] The graphene oxide nanosheets are dispersed in a 1 M solution of methylmagnesium chloride in tetrahydrofuran, and ultrasonic treatment is carried out for 2 - 3 h. The precipitate is collected by centrifugation, washed and dried in vacuum to obtain magnesium chloride graphene.

[0026] Furthermore, the dosage ratio of the graphene oxide nanosheets and the methylmagnesium chloride in tetrahydrofuran solution is 10 - 12 g : 400 - 500 mL.

[0027] Furthermore, the dosage ratio of the modified composite powder and high-density polyethylene in step two is 30 - 40 g : 195 - 225 g.

[0028] Furthermore, a preparation method of a polyethylene release film with high residual adhesion rate includes the following steps:

[0029] The raw materials are co-extruded and blown into a film in three layers in an extruder according to the dosage ratio of the surface layer, the intermediate layer and the bottom layer. The extrusion and blowing temperature is 180 - 190 °C to obtain a base film of the release film. The coating layer is mixed evenly according to the dosage ratio of the raw materials, and is coated on the bottom layer of the base film of the release film by a coater. The coating thickness is 40 - 50 μm, and it is dried, cross-linked and cured at 120 - 130 °C to obtain a polyethylene release film with high residual adhesion rate.

[0030] The filling masterbatch is PE carrier filled with 10 - 20% inorganic powder, and the inorganic powder includes but is not limited to calcium carbonate and sodium sulfate.

[0031] The beneficial effects of the present invention:

[0032] (1) The high residual adhesion rate polyethylene separator film prepared by the present invention modifies high-density polyethylene with a modified composite powder, enabling the separator film to have good high-temperature resistance and ultraviolet resistance. A silicone-friendly heat-shrinkable separator film base film is obtained by a three-layer composite method. The separator film coated with aqueous silicone oil has a high residual adhesion rate, and its performance is superior to that of the separator film coated by the solvent method, with a significant reduction in the desiliconization rate.

[0033] (2) The preparation method of the present invention grafts magnesium chloride on the surface of graphene oxide and crystallizes it on the surface of silica, compounding magnesium chloride graphene on the surface of silica, reducing the agglomeration of silica; the crystallized magnesium chloride has an anchoring effect on titanium tetrachloride, enabling titanium tetrachloride to be grafted and fixed on the crystallized magnesium chloride. Through the interaction between titanium tetrachloride and benzyl alcohol in a benzene medium, a titanium halide reaction occurs, oxidizing titanium tetrachloride to form titanium oxide particles, improving the ultraviolet resistance of the titanium oxide-loaded composite powder; the modified composite powder has high bonding strength and good dispersibility in high-density polyethylene, and also has an enhancing effect on the mechanical properties of the high residual adhesion rate polyethylene separator film. Specific Embodiments

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0035] Example 1: A preparation method of a high residual adhesion rate polyethylene separator film, including the following steps:

[0036] S1. Disperse 10 g of graphene oxide nanosheets in 400 mL of 1 M methylmagnesium chloride tetrahydrofuran solution, ultrasonically treat for 2 h, centrifuge to collect the precipitate, wash the precipitate with tetrahydrofuran, and then vacuum dry at 60 °C to obtain magnesium chloride graphene.

[0037] S2. In a reaction kettle, stir 10 g of magnesium chloride graphene and 14 g of cage-shaped polyhedral oligomeric silsesquioxane in 400 mL of tetrahydrofuran at 55 °C for 3 h to obtain a graphene dispersion. Stir 25 g of silica powder, 12 mL of 1,4-butanediol, and 700 mL of tetrahydrofuran at 35 °C for 3 h to obtain a silica dispersion. Then stir 400 mL of the graphene dispersion and 700 mL of the silica dispersion at 35 °C for 3 h, filter to obtain the precipitate, wash it with n-hexane, and dry it at 40 °C for 3 h to obtain magnesium chloride / silica composite powder.

[0038] S3. Mix 30 g of magnesium chloride / silica composite powder with 600 mL of n-hexane and 20 mL of titanium tetrachloride in a reaction kettle, stir at 45 °C for 3 h, collect the precipitate by centrifugation, wash the precipitate with n-hexane, and dry at 40 °C for 3 h to obtain the titanium-loaded composite powder.

[0039] S4. Disperse 30 g of the titanium-loaded composite powder in 300 mL of n-decane in a reaction kettle. Dissolve 6 mL of benzyl alcohol in 35 mL of benzene, add it to the reaction kettle, reflux and heat at 35 °C for 4 h, remove the benzene solvent by rotary evaporation, reflux and react at 170 °C for 8 h. After cooling, collect the precipitate by centrifugation, wash the precipitate with chloroform, and dry in vacuum at 70 °C to obtain the titanium oxide-loaded composite powder.

[0040] S5. Ultrasonically disperse 30 g of the titanium oxide-loaded composite powder in 500 mL of absolute ethanol in a reaction kettle, add 8 mL of KH550, stir and react for 20 h, collect the precipitate by centrifugation, wash the precipitate with ethanol and deionized water, and dry in vacuum at 60 °C for 10 h to obtain the modified composite powder.

[0041] S6. Mix 30 g of the modified composite powder with 195 g of high-density polyethylene in a twin-screw extruder at 180 °C and a rotation speed of 50 rpm for 10 min to obtain the modified high-density polyethylene. Then mix 65 g of the modified high-density polyethylene, 5 g of linear low-density polyethylene, and 20 g of maleic anhydride-grafted polyethylene to obtain the surface layer raw material; mix 65 g of the modified high-density polyethylene, 10 g of filled masterbatch, and 2 g of color masterbatch to obtain the intermediate layer raw material; mix 65 g of the modified high-density polyethylene, 5 g of linear low-density polyethylene, and 10 g of filled masterbatch to obtain the bottom layer raw material. Co-extrude and blow-mold the surface layer raw material, intermediate layer raw material, and bottom layer raw material in a three-layer manner in an extruder, and the extrusion and blow-molding temperature is 180 °C to obtain the base film of the isolation film. Mix 90 g of silicone oil, 4 g of cross-linking agent, 5 g of curing agent, and 0.3 g of catalyst evenly to obtain the coating layer raw material. Coating the coating layer raw material on the bottom layer of the isolation film base film by a coater, with a coating thickness of 40 μm, and drying and cross-linking and curing at 120 °C to obtain the high residual adhesion rate polyethylene isolation film.

[0042] Example 2: A method for preparing a high residual adhesion rate polyethylene isolation film, comprising the following steps:

[0043] S1. Disperse 11 g of graphene oxide nanosheets in 450 mL of 1 M methylmagnesium chloride tetrahydrofuran solution, ultrasonically treat for 2.5 h, collect the precipitate by centrifugation, wash the precipitate with tetrahydrofuran, and dry in vacuum at 65 °C to obtain magnesium chloride graphene.

[0044] S2. In a reaction kettle, 11 g of magnesium chloride graphene and 15 g of cage-shaped polyhedral oligomeric silsesquioxane are stirred in 450 mL of tetrahydrofuran at 60 °C for 3.5 h to obtain a graphene dispersion. 27.5 g of silicon dioxide powder, 13.5 mL of 1,4-butanediol, and 750 mL of tetrahydrofuran are stirred at 40 °C for 3.5 h to obtain a silicon dioxide dispersion. Then, 450 mL of the graphene dispersion and 750 mL of the silicon dioxide dispersion are stirred at 40 °C for 3.5 h, and the precipitate is obtained by filtration. After washing with n-hexane, it is dried at 45 °C for 3.5 h to obtain magnesium chloride / silicon dioxide composite powder.

[0045] S3. In a reaction kettle, 35 g of the magnesium chloride / silicon dioxide composite powder is mixed with 650 mL of n-hexane and 25 mL of titanium tetrachloride, and stirred at 50 °C for 3.5 h. The precipitate is collected by centrifugation, washed with n-hexane, and dried at 45 °C for 3.5 h to obtain the titanium-loaded composite powder.

[0046] S4. In a reaction kettle, 35 g of the titanium-loaded composite powder is dispersed in 350 mL of n-decane. 7 mL of benzyl alcohol is dissolved in 37.5 mL of benzene and added to the reaction kettle. It is refluxed and heated at 40 °C for 4.5 h, and the benzene solvent is removed by rotary evaporation. It is refluxed and reacted at 175 °C for 8.5 h. After cooling, the precipitate is collected by centrifugation, washed with chloroform, and dried under vacuum at 75 °C to obtain the titanium oxide-loaded composite powder.

[0047] S5. In a reaction kettle, 35 g of the titanium oxide-loaded composite powder is ultrasonically dispersed in 600 mL of absolute ethanol, 9 mL of KH550 is added, and the reaction is stirred for 22 h. The precipitate is collected by centrifugation, washed with ethanol and deionized water, and dried under vacuum at 65 °C for 11 h to obtain the modified composite powder.

[0048] S6. In a twin-screw extruder, 35 g of the modified composite powder is mixed with 210 g of high-density polyethylene at 185 °C and a rotation speed of 55 rpm for 11 min to obtain modified high-density polyethylene. Then, 70 g of the modified high-density polyethylene, 6.5 g of linear low-density polyethylene, and 22.5 g of maleic anhydride-grafted polyethylene are mixed to obtain the surface layer raw material; 70 g of the modified high-density polyethylene, 11 g of filled masterbatch, and 2.5 g of color masterbatch are mixed to obtain the intermediate layer raw material; 70 g of the modified high-density polyethylene, 6.5 g of linear low-density polyethylene, and 11 g of filled masterbatch are mixed to obtain the bottom layer raw material. The surface layer raw material, the intermediate layer raw material, and the bottom layer raw material are co-extruded and blown into a film in an extruder at an extrusion and blowing temperature of 185 °C to obtain the base film of the isolation film. 91 g of silicone oil, 4.5 g of cross-linking agent, 5.5 g of curing agent, and 0.35 g of catalyst are mixed evenly to obtain the coating layer raw material. The coating layer raw material is coated on the bottom layer of the isolation film base film by a coater with a coating thickness of 45 μm, and dried, cross-linked, and cured at 125 °C to obtain the high-residual adhesion rate polyethylene isolation film.

[0049] Example 3: A preparation method of a polyethylene isolation film with a high residual adhesion rate, comprising the following steps:

[0050] S1. Disperse 12 g of graphene oxide nanosheets in 500 mL of 1 M methylmagnesium chloride tetrahydrofuran solution, ultrasonically treat for 3 h, centrifuge to collect the precipitate, wash the precipitate with tetrahydrofuran, and then vacuum dry at 70 °C to obtain magnesium chloride graphene.

[0051] S2. In a reaction kettle, stir 12 g of magnesium chloride graphene and 16 g of cage-shaped polyhedral oligomeric silsesquioxane in 500 mL of tetrahydrofuran at 65 °C for 4 h to obtain a graphene dispersion. Stir 30 g of silica powder, 15 mL of 1,4-butanediol, and 800 mL of tetrahydrofuran at 45 °C for 4 h to obtain a silica dispersion. Then stir 500 mL of the graphene dispersion and 800 mL of the silica dispersion at 45 °C for 4 h, filter to obtain a precipitate, wash with n-hexane, and dry at 50 °C for 4 h to obtain magnesium chloride / silica composite powder.

[0052] S3. In a reaction kettle, mix 40 g of magnesium chloride / silica composite powder with 700 mL of n-hexane and 30 mL of titanium tetrachloride, stir at 55 °C for 4 h, centrifuge to collect the precipitate, wash the precipitate with n-hexane, and dry at 50 °C for 4 h to obtain a titanium-loaded composite powder.

[0053] S4. Disperse 40 g of the titanium-loaded composite powder in 400 mL of n-decane in a reaction kettle, dissolve 8 mL of benzyl alcohol in 40 mL of benzene, add it to the reaction kettle, reflux and heat at 45 °C for 5 h, rotary evaporate to remove the benzene solvent, reflux and react at 180 °C for 9 h, cool, centrifuge to collect the precipitate, wash the precipitate with chloroform, and vacuum dry at 80 °C to obtain a titanium oxide-loaded composite powder.

[0054] S5. Ultrasonically disperse 40 g of the titanium oxide-loaded composite powder in 700 mL of absolute ethanol in a reaction kettle, add 10 mL of KH550, stir and react for 24 h, centrifuge to collect the precipitate, wash the precipitate with ethanol and deionized water, and vacuum dry at 70 °C for 12 h to obtain a modified composite powder.

[0055] S6. In a twin-screw extruder, 40 g of the modified composite powder is mixed with 225 g of high-density polyethylene at 190 °C and a rotational speed of 60 rpm for 12 min to obtain modified high-density polyethylene. Then, 75 g of the modified high-density polyethylene, 8 g of linear low-density polyethylene, and 25 g of maleic anhydride-grafted polyethylene are mixed to obtain the surface layer raw material; 75 g of the modified high-density polyethylene, 12 g of filled masterbatch, and 3 g of color masterbatch are mixed to obtain the intermediate layer raw material; 75 g of the modified high-density polyethylene, 8 g of linear low-density polyethylene, and 12 g of filled masterbatch are used to obtain the bottom layer raw material. The surface layer raw material, the intermediate layer raw material, and the bottom layer raw material are co-extruded and blown into a film in a three-layer manner in an extruder at an extrusion and blowing temperature of 190 °C to obtain the base film of the isolation film. 92 g of silicone oil, 5 g of crosslinking agent, 6 g of curing agent, and 0.4 g of catalyst are mixed evenly to obtain the coating layer raw material. The coating layer raw material is coated on the bottom layer of the isolation film base film by a coater with a coating thickness of 50 μm, and dried and crosslinked and cured at 130 °C to obtain the high residual adhesion rate polyethylene isolation film.

[0056] Principle of the invention:

[0057] By grafting magnesium chloride on the surface of graphene oxide, using the promoting crystallization effect of magnesium chloride on the surface of silica in the presence of cage-like polyhedral oligomeric silsesquioxane, magnesium chloride-graphene is crystallized on the surface of silica, reducing the agglomeration of silica. At the same time, magnesium chloride-graphene is combined on the surface of silica through cage-like polyhedral oligomeric silsesquioxane. The crystallized magnesium chloride has an anchoring effect on titanium tetrachloride, enabling titanium tetrachloride to be grafted and fixed on the crystallized magnesium chloride to obtain a titanium-loaded composite powder. Through the interaction between titanium tetrachloride and benzyl alcohol in a benzene medium, a titanium halide reaction occurs, oxidizing titanium tetrachloride to form titanium oxide particles, and oxidizing the titanium chloride grafted and loaded on the surface of magnesium chloride to form titanium oxide loaded on magnesium chloride, improving the ultraviolet resistance of the titanium oxide-loaded composite powder. Then, the titanium oxide-loaded powder is modified by a silane coupling agent to improve its compatibility with polyethylene. Finally, the modified composite powder containing graphene oxide is mixed with high-density polyethylene to obtain well-dispersed modified high-density polyethylene. The high-density polyethylene containing graphene oxide has good high-temperature resistance. At the same time, the highly dispersed titanium dioxide in the modified composite powder enhances the ultraviolet resistance of the modified high-density polyethylene. The modified composite powder has high bonding strength and good dispersion in high-density polyethylene, also enhancing the mechanical properties of the high residual adhesion rate polyethylene isolation film; the isolation film base film with siliconophilic heat shrinkage is obtained by a three-layer composite method. The isolation film coated with aqueous silicone oil has a high residual adhesion rate and better performance than the isolation film coated by the solvent method, and the desiliconization rate is significantly reduced.

[0058] Comparative Example 1: The difference from Example 1 is that in S2, graphene oxide nanosheets are used to replace magnesium chloride-graphene to prepare the high residual adhesion rate polyethylene isolation film.

[0059] Comparative Example 2: The difference from Example 1 is that in S3, titanium tetrachloride is replaced by nano-titanium dioxide with the same amount of titanium substance, and S4 is not performed to obtain a polyethylene isolation film with a high residual bonding rate.

[0060] Comparative Example 3: The difference from Example 1 is that in S5, 0.18 mol of nano titanium dioxide (the same amount of titanium substance as titanium tetrachloride in S3) and 10 g of graphene oxide nanosheets are used to replace the titanium oxide-loaded composite powder to prepare a polyethylene isolation film with a high residual bonding rate.

[0061] The sources of some reagents in the embodiments and comparative examples are as follows:

[0062] Cage polysilsesquioxane was purchased from Xi'an Qiyue Biotechnology Co., Ltd.

[0063] The silicon dioxide powder is micron silicon dioxide with a particle size of 10-50 μm, purchased from Hebei Ruihuang Metal Materials Co., Ltd.

[0064] Graphene oxide nanosheets, with a diameter of 500 nm and a thickness of 0.8-1.2 nm, were purchased from Suzhou Beike Nanotechnology Co., Ltd.

[0065] The performance tests were conducted on the high residual bonding rate polyethylene isolation films prepared in Examples 1 to 3 and Comparative Examples 1 to 3. The mechanical properties of the materials were tested using an electronic universal testing machine. The high temperature resistance of the materials was tested using a heat deformation Vicat softening point testing machine, where the heating rate was 100°C / h. The desiliconization rate was tested using the Wacker test method. Nitto 31B tape was applied to the high residual bonding rate polyethylene isolation film with a pressure roller and 20 g / cm 2 The standard stainless steel strip was placed in a 70℃ oven for 20 hours, taken out and placed at room temperature for 1 hour, and the test sample was cut out. At the same time, Nitto31B tape was applied to the Teflon film with a pressure roller and 20g / cm 2 The standard stainless steel strips were placed in a 70℃ oven for 20h. After being taken out, they were placed at room temperature for 1h. The blank samples were cut and peeled off from the isolation film and Teflon film respectively. The release force was tested. The desiliconization rate was calculated according to the formula SC=[1-(release force of test sample / release force of blank sample)]x100%. The desiliconization rate of the test sample and the blank sample was tested again after aging with ultraviolet light for 100h. The wavelength of ultraviolet light was 340nm and the irradiance was 0.4W / m 2 / nm.

[0066] The results are shown in Table 1:

[0067] Table 1: Performance test results of high residual bonding rate polyethylene isolation film

[0068] Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Tensile strength (Mpa) 18.6 18.8 18.9 17.7 16.1 14.6 Heat distortion temperature (℃) 81 81 82 75 71 62 Desilication rate (%) 7.4 7.1 6.9 7.7 8.5 9.4 Desilication rate after UV aging treatment (%) 10.8 10.4 10.2 13.6 14.7 17.3

[0069] As can be seen from Table 1, the high residual adhesion rate polyethylene separator film prepared by the present invention has good tensile strength and a relatively high heat distortion temperature, indicating that the separator film prepared by the present invention has good mechanical properties and high temperature resistance, and a low desiliconization rate, indicating a high residual grafting rate of the present invention. After ultraviolet aging treatment, the increase in the desiliconization rate is small, indicating good ultraviolet light resistance.

[0070] In Comparative Example 1, since it does not contain magnesium chloride, the binding rate of titanium tetrachloride on graphene oxide nanosheets and silica is relatively low, and the titanium content of the obtained titanium-loaded composite powder is low. The anti-ultraviolet performance of the prepared polyethylene separator film is lower than that of Examples 1-3.

[0071] In Comparative Example 2, since titanium dioxide nanoparticles are used to replace titanium tetrachloride, the binding strength between titanium dioxide nanoparticles and silica and graphene oxide nanosheets is relatively low and it is easy to fall off. Titanium dioxide nanoparticles are prone to agglomeration, which affects the mechanical properties and heat resistance of the prepared polyethylene separator film, and the improvement of the anti-ultraviolet performance is small.

[0072] In Comparative Example 3, since only titanium dioxide and graphene oxide nanosheets are modified with a silane coupling agent and then mixed with high-density polyethylene, it does not contain silica, the grafting rate with the silane coupling agent is relatively low, the dispersion of titanium dioxide in polyethylene is relatively low, and it is not compounded with graphene, and the synergistic effect with graphene nanosheets is relatively low. The prepared polyethylene separator film has poor anti-ultraviolet performance and low high temperature resistance.

[0073] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A polyethylene separator with a high residual bonding rate, comprising a surface layer, an intermediate layer, a bottom layer and a coating layer, characterized in that: The surface layer formula comprises the following raw material components by weight: 65-75 parts of modified high-density polyethylene, 5-8 parts of linear low-density polyethylene and 20-25 parts of maleic anhydride grafted polyethylene; The intermediate layer formula comprises the following raw material components: 65-75 parts of modified high-density polyethylene, 10-12 parts of filler masterbatch and 2-3 parts of color masterbatch; The bottom layer formula comprises the following raw material components: 65-75 parts of modified high-density polyethylene, 5-8 parts of linear low-density polyethylene and 10-12 parts of filler masterbatch; The modified high-density polyethylene is prepared by the following steps: Step 1: Disperse the loaded titanium composite powder in n-decane in a reaction kettle, dissolve benzyl alcohol in benzene, add the mixture into the reaction kettle, reflux and heat at 35-45° C. for 4-5 hours, remove the benzene solvent by rotary evaporation, reflux at 170-180° C. for 8-9 hours, collect the precipitate by centrifugation, wash and vacuum dry to obtain the titanium oxide loaded composite powder; Step 2: In a reaction kettle, the titanium oxide-loaded composite powder is modified with KH550 in ethanol to obtain a modified composite powder, and the modified composite powder is mixed with high-density polyethylene in a twin-screw extruder at 180-190° C. and 50-60 rpm for 10-12 minutes to obtain a modified high-density polyethylene; The loaded titanium composite powder is prepared by the following steps: The graphene dispersion and the silicon dioxide dispersion are stirred at 35-45° C. for 3-4 hours, filtered to obtain a precipitate, washed and dried to obtain a magnesium chloride / silicon dioxide composite powder; the magnesium chloride / silicon dioxide composite powder is mixed with n-hexane and titanium tetrachloride in a reaction kettle, stirred at 45-55° C. for 3-4 hours, centrifuged to collect the precipitate, washed and dried to obtain a loaded titanium composite powder; The graphene dispersion is prepared by mixing magnesium chloride graphene, cage-shaped polysilsesquioxane and tetrahydrofuran; the magnesium chloride graphene is prepared by dispersing graphene oxide nanosheets in 1M methyl magnesium chloride tetrahydrofuran solution.

2. The high residual bonding rate polyethylene separator according to claim 1, characterized in that: The coating layer formula comprises the following raw material components by weight: 90-92 parts of silicone oil, 4-5 parts of cross-linking agent, 5-6 parts of curing agent and 0.3-0.4 parts of catalyst.

3. The high residual bonding rate polyethylene separator according to claim 1, characterized in that: The amount ratio of the loaded titanium composite powder, n-decane, benzyl alcohol and benzene in step 1 is 30-40 g: 300-400 mL: 6-8 mL: 35-40 mL.

4. The high residual bonding rate polyethylene separator according to claim 1, characterized in that: The usage ratio of the magnesium chloride / silicon dioxide composite powder, n-hexane and titanium tetrachloride is 30-40 g: 600-700 mL: 20-30 mL.

5. The high residual bonding rate polyethylene separator according to claim 1, characterized in that: The usage ratio of the graphene dispersion liquid and the silicon dioxide dispersion liquid is 400-500 mL:700-800 mL.

6. The high residual bonding rate polyethylene separator according to claim 5, characterized in that: The graphene dispersion is obtained by stirring and mixing magnesium chloride graphene, cage-shaped polysilsesquioxane and tetrahydrofuran in a dosage ratio of 10-12 g: 14-16 g: 400-500 mL; The silicon dioxide dispersion is obtained by stirring and mixing silicon dioxide powder, 1,4-butanediol and tetrahydrofuran in a dosage ratio of 25-30 g: 12-15 mL: 700-800 mL.

7. The high residual bonding rate polyethylene separator according to claim 6, characterized in that: The magnesium chloride graphene is prepared by the following steps: The graphene oxide nanosheets are dispersed in a 1M methylmagnesium chloride tetrahydrofuran solution, ultrasonically treated for 2-3 hours, and the precipitate is collected by centrifugation, washed, and vacuum dried to obtain magnesium chloride graphene.

8. The high residual bonding rate polyethylene separator according to claim 7, characterized in that: The usage ratio of the graphene oxide nanosheets and the methylmagnesium chloride tetrahydrofuran solution is 10-12 g: 400-500 mL.

9. The high residual bonding rate polyethylene separator according to claim 1, characterized in that: The usage ratio of the modified composite powder and high-density polyethylene in step 2 is 30-40g:195-225g.

10. The method for preparing a polyethylene separator with a high residual bonding rate according to claim 1, characterized in that: The preparation method comprises the following steps: The raw materials are co-extruded into three layers in an extruder for film blowing according to the formula and dosage ratio of the surface layer, the middle layer and the bottom layer. The extrusion film blowing temperature is 180-190°C to obtain a base film of the isolation film. The raw materials are mixed evenly according to the formula and dosage ratio of the coating layer. The coating is applied on the bottom layer of the base film of the isolation film by a coating machine. The coating is 40-50μm thick. The coating is dried and cross-linked and cured at 120-130°C to obtain a polyethylene isolation film with a high residual bonding rate.