Aging and wear resistant bopp film and preparation method thereof

Abstract

The application relates to an anti-aging and wear-resistant BOPP film and a preparation method thereof, and belongs to the technical field of plastic films. The BOPP film is a three-layer co-extrusion structure, and comprises an inner layer, an intermediate layer and an outer layer from inside to outside. The inner layer is composed of polypropylene and has a thickness of 8-10 mu m; the intermediate layer is composed of polypropylene and polyethylene and has a thickness of 10-12 mu m; and the outer layer is composed of polypropylene, polyethylene and modified titanium dioxide and has a thickness of 3-5 mu m. Nitrogen-doped titanium dioxide is prepared through a hydrothermal method to enhance the anti-aging performance of the BOPP film; polyvinylpyrrolidone improves the dispersibility of the nitrogen-doped titanium dioxide, so that the preparation process is stable and controllable; the addition of a small amount of sodium metaaluminate further enhances the anti-aging performance and wear resistance; and a titanate coupling agent enhances the interfacial bonding force between inorganic nanoparticles and an organic polymer matrix, and improves the overall strength and stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of plastic films, and relates to an aging-resistant and wear-resistant BOPP film and a preparation method thereof. BACKGROUND

[0002] BOPP (biaxially oriented polypropylene) film is a film product obtained through biaxial stretching treatment in the transverse and longitudinal directions on the basis of conventional polypropylene film. The film has good mechanical strength, physical stability, air tightness, and relatively high transparency and gloss, and is widely used in the fields of packaging, adhesive tape base film and the like. However, due to the presence of tertiary carbon atoms in the BOPP film, the BOPP film is prone to decomposition under the influence of light and heat, resulting in relatively poor aging resistance. Meanwhile, although the wear resistance of the BOPP film is good, in some specific application scenarios, it is still necessary to further improve the wear resistance of the BOPP film to meet more stringent use requirements. SUMMARY

[0003] The application aims to provide an aging-resistant and wear-resistant BOPP film and a preparation method thereof, which have good wear resistance and aging resistance.

[0004] The object of the application can be achieved by the following technical solutions.

[0005] An aging-resistant and wear-resistant BOPP film, which is a three-layer co-extrusion structure and comprises an inner layer, an intermediate layer and an outer layer from inside to outside, wherein the inner layer is composed of polypropylene and has a thickness of 8-10 microns; the intermediate layer is composed of polypropylene and polyethylene and has a thickness of 10-12 microns; and the outer layer is composed of polypropylene, polyethylene and modified titanium dioxide and has a thickness of 3-5 microns.

[0006] As a preferred technical solution of the application, the mass ratio of polypropylene to polyethylene in the intermediate layer is (7-9):(1-3).

[0007] As a preferred technical solution of the application, the mass ratio of polypropylene, polyethylene and modified nano-titanium dioxide in the outer layer is 10:(3-5):(0.5-1).

[0008] As a preferred technical solution of the application, the preparation method of the modified titanium dioxide is as follows,

[0009] S4-1: urea and titanium source are mixed according to a molar ratio of 1:(9-11) to obtain a mixture A, the mixture A is mixed with deionized water according to a mass ratio of 1:50, ultrasonic treatment is carried out at 45-55 DEG C for 1-2h, then transferred to a reaction kettle for heating for 10-14h, the heating temperature is 150 DEG C, washed with deionized water and placed in a vacuum drying oven at 60 DEG C for drying for 12h, after drying, placed in a ball mill for ball milling for 30-60min, the ball milling speed is 150-250r / min, to obtain powder B;

[0010] S4-2: powder B is added to deionized water to make the solid-liquid mass ratio 10g / L, polyvinylpyrrolidone is added, ultrasonic treatment is carried out for 10-30min, sodium metaaluminate is added, stirring is carried out at a speed of 600-700r / min for 30min, 1M sodium hydroxide solution is used to adjust the pH to 9-10, stirring is carried out at a speed of 40-50 DEG C for 2h, the temperature is raised to 80-90 DEG C and kept for 6h, then washed with deionized water and placed in a vacuum drying oven at 60 DEG C for drying for 12h, to obtain powder C;

[0011] S4-3: powder C is mixed with titanate coupling agent according to a mass ratio of (97-99):(1-3), put into a ball mill for ball milling for 2-3h, to obtain the modified titanium dioxide.

[0012] As a preferred technical scheme of the present application, the titanium source in S4-1 is one of titanium tetrachloride and tetrabutyl titanate.

[0013] As a preferred technical scheme of the present application, the addition amount of polyvinylpyrrolidone in S4-2 is 2%-3% of the mass of powder B, and the addition amount of sodium metaaluminate is 3%-5% of the mass of powder B.

[0014] As a preferred technical scheme of the present application, the ball milling speed in S4-3 is 300-400r / min.

[0015] A preparation method of an anti-aging and wear-resistant BOPP film, the specific steps of the preparation method are as follows,

[0016] S8-1: the inner layer, the intermediate layer and the outer layer raw materials are respectively sent into three extruders according to the proportion by using a three-layer co-extrusion die, the three-layer co-extruded melt is cooled and cast into a sheet by a sheet casting machine, and the sheet casting temperature is 15-25 DEG C;

[0017] S8-2: the cooled sheet is subjected to preheating treatment, the preheating temperature is 100-105 DEG C, the preheated sheet is subjected to bidirectional stretching in the longitudinal and transverse directions to form a film, then subjected to heat setting treatment, the heat setting temperature is 160-165 DEG C, and the stretched and heat set film is subjected to edge cutting and winding treatment, to obtain the BOPP film.

[0018] As a preferred technical solution of the present application, the temperature of the inner layer extruder in S8-1 is 240-260℃, the temperature of the middle layer extruder is 245-270℃, and the temperature of the outer layer extruder is 240-270℃.

[0019] As a preferred technical solution of the present application, the longitudinal stretching temperature in S8-2 is 120-128℃, and the transverse stretching temperature is 155-165℃.

[0020] The BOPP film of the present application is a three-layer co-extrusion structure. First, the inner layer is a polypropylene layer. Polypropylene is used as the inner layer material, which has cost-effectiveness and good basic physical properties. The inner layer provides basic structural support for the film while maintaining appropriate flexibility and strength. In addition, polypropylene has certain gas and moisture barrier ability, which helps to protect the items inside the BOPP film package from the external environment.

[0021] The middle layer is a polypropylene and polyethylene blend layer. The addition of polyethylene effectively improves the toughness of the middle layer, enabling the film to better absorb energy when subjected to impact or stretching, and not easily broken. The blending of polypropylene and polyethylene can improve the processing flowability of the material, which is beneficial to the extrusion molding of the film and improves the production efficiency. As a transition between the inner layer and the outer layer, the middle layer can balance the strength, flexibility and barrier properties of the film through the reasonable proportioning of polypropylene and polyethylene.

[0022] The outer layer is a composite layer of polypropylene, polyethylene and modified titanium dioxide. The addition of modified titanium dioxide significantly enhances the anti-aging performance of the outer layer. By balancing its photocatalytic activity, it reduces the damage of ultraviolet light to the film, prolonging the service life of the film. The Al2O3 coating layer on the surface of the modified titanium dioxide and the action of titanate coupling agent significantly improve the hardness and wear resistance of the outer layer, enabling the film to maintain better integrity under mechanical actions such as friction and scratching. The addition of modified titanium dioxide can also adjust the light transmittance and haze of the outer layer to meet the requirements of different applications for the transparency of the film. Modified titanium dioxide and its coating layer help to improve the chemical stability of the film, resisting the erosion of acid and alkali and other chemicals.

[0023] The anti-aging and wear-resistant BOPP film with three-layer co-extrusion structure realizes the optimization and balance of performance through the reasonable selection and proportioning of the components of each layer. The inner layer provides basic structural support and barrier properties, the middle layer enhances the toughness and processing performance of the film, and the outer layer significantly improves the anti-aging performance and wear resistance through the addition of modified titanium dioxide, while optimizing the optical properties and chemical stability.

[0024] Titanium dioxide has the ability to absorb ultraviolet light, which can effectively shield ultraviolet light and protect BOPP film from photodegradation. However, titanium dioxide exhibits high photocatalytic activity when excited by ultraviolet light, which can catalyze the degradation of BOPP film. Therefore, in the process of using titanium dioxide to enhance the light resistance of BOPP film, it is necessary to balance the relationship between its ultraviolet light absorption and photocatalytic activity, to ensure that it can effectively protect BOPP film from light damage and avoid unnecessary photocatalytic degradation.

[0025] During the preparation of modified titanium dioxide, urea is decomposed into NH3 and CO2 under high-temperature hydrothermal conditions. The alkaline environment provided by NH3 promotes the hydrolysis and condensation of the titanium source, forming titanium dioxide particles. In this process, some nitrogen atoms are doped into the crystal lattice of titanium dioxide, which narrows the band gap of titanium dioxide and introduces electron-hole recombination centers, effectively balancing its ultraviolet light absorption and photocatalytic activity. On the one hand, the ultraviolet light absorption ability of titanium dioxide is retained, and when added to BOPP film, it can reduce the photodamage of ultraviolet light to the film; on the other hand, by regulating the photocatalytic activity, it avoids the adverse photochemical reactions of BOPP film caused by excessive activity of titanium dioxide, thereby significantly enhancing the anti-aging performance of BOPP film.

[0026] The addition of polyvinylpyrrolidone can significantly improve the dispersibility of titanium dioxide particles in solution, making the particles more uniformly distributed in the solution, which is beneficial to the subsequent reaction and processing process, and can also improve the performance of the final product. In addition, the addition of polyvinylpyrrolidone can make the preparation process of modified titanium dioxide more stable and controllable, reducing the occurrence of local agglomeration and precipitation, which is beneficial to improving the preparation efficiency and product quality, and can also reduce the production cost. A small amount of sodium metaaluminate is added, which hydrolyzes to form Al(OH)3 colloid under alkaline conditions. These colloids are deposited on the surface of some nitrogen-doped titanium dioxide particles. After heat treatment, Al(OH)3 is converted to Al2O3, forming a coating layer. This Al2O3 coating layer not only further inhibits the photocatalytic reaction and enhances the anti-aging performance of the film; at the same time, Al2O3 as a high-hardness and high-wear-resistant material, the existence of its coating layer also significantly improves the wear resistance of BOPP film. Under the action of friction and scraping, the Al2O3 coating layer can protect the BOPP film matrix from damage and prolong the service life of the BOPP film.

[0027] The long-chain organic group of the titanate coupling agent extends outward, which can form a good dispersion effect in the polymer matrix, prevents the agglomeration of modified titanium dioxide particles, is conducive to the further inhibition of photocatalytic activity, and also ensures the uniformity of the film performance, avoiding performance defects caused by too high local particle concentration.

[0028] The beneficial effects of the present application are:

[0029] (1) The three-layer co-extrusion BOPP film proposed in the present application provides structural support and barrier properties through the inner layer of polypropylene, enhances toughness and processing performance through the middle layer of polypropylene and polyethylene blending, and significantly improves aging resistance and wear resistance through the addition of modified titanium dioxide in the outer layer, while optimizing optical properties and chemical stability. This structure realizes the overall optimization and balance of the film performance, prolongs the service life, meets the diversified application requirements, and significantly improves the market competitiveness.

[0030] (2) Through the preparation of modified titanium dioxide, nitrogen atom doping is realized, which helps to balance the photocatalytic activity of titanium dioxide, thereby enhancing the anti-aging performance of the BOPP film. Under the regulation of polyvinylpyrrolidone, Al(OH)3 generated by the hydrolysis of sodium metaaluminate is converted into Al2O3 by heat treatment, forming a coating layer on the surface of part of the titanium dioxide, further improving the anti-aging performance and wear resistance of the film. The titanate coupling agent enhances the interfacial bonding force between the inorganic nanoparticles and the organic polymer matrix, improves the overall strength and stability of the film, prevents the agglomeration of modified titanium dioxide particles, ensures the uniformity of the film performance, and prolongs the service life of the BOPP film. DETAILED DESCRIPTION

[0031] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the specific embodiments, structures, features and effects according to the present application are described in detail as follows in combination with examples.

[0032] In the examples and comparative examples of the present application:

[0033] Polypropylene: purchased from Sigma Aldrich (Shanghai) Trading Co., Ltd.;

[0034] Polyethylene: purchased from Shanghai Dingfen Chemical Technology Co., Ltd.;

[0035] Urea: purchased from Beijing Comphuivi Technology Co., Ltd.;

[0036] Titanium tetrachloride: purchased from Jiangsu Lein Environmental Protection Technology Co., Ltd.

[0037] Tetrabutyl titanate: purchased from Nanjing Tengchuan Technology Co., Ltd.

[0038] Polyvinylpyrrolidone: purchased from Hefei Tianjian Chemical Co., Ltd.

[0039] Sodium metaaluminate: purchased from Shandong Qiangsen Chemical Co., Ltd.

[0040] Titanate coupling agent 401: purchased from Nanjing Feiteng New Material Technology Co., Ltd.

[0041] Example 1

[0042] A kind of anti-aging wear-resistant BOPP film, the BOPP film is three-layer co-extrusion structure, including inner layer, intermediate layer and outer layer from inside to outside, the inner layer is composed of polypropylene, and the thickness is 9 μm;The intermediate layer is composed of polypropylene and polyethylene, and the thickness is 11 μm;The outer layer is composed of polypropylene, polyethylene and modified titanium dioxide, and the thickness is 4 μm.

[0043] The mass ratio of polypropylene and polyethylene in the intermediate layer is 8:2.

[0044] The mass ratio of polypropylene, polyethylene and modified nano-titanium dioxide in the outer layer is 10:4:0.8.

[0045] The preparation method of the modified titanium dioxide is as follows,

[0046] S4-1: urea and titanium tetrachloride are mixed according to a molar ratio of 1:10 to obtain a mixture A, the mixture A is mixed with deionized water according to a mass ratio of 1:50, ultrasonic is carried out at 50℃ for 1.5h, then it is transferred to a reaction kettle and heated for 12h, the heating temperature is 150℃, it is washed with deionized water and dried in a 60℃ vacuum drying box for 12h, after drying, it is placed in a ball mill and ball milled for 45min, the ball milling speed is 200r / min, to obtain powder B;

[0047] S4-2: powder B is added to deionized water to make the solid-liquid mass ratio 10g / L, polyvinylpyrrolidone is added, the addition amount of polyvinylpyrrolidone is 2.5% of the mass of powder B, ultrasonic is carried out for 20min, sodium metaaluminate is added, the addition amount of sodium metaaluminate is 4% of the mass of powder B, stirring is carried out at a speed of 650r / min for 30min, 1M sodium hydroxide solution is used to adjust the pH to 9.5, the temperature is kept at 45℃ and the stirring speed is kept for 2h, then the temperature is raised to 85℃ and kept for 6h, then it is washed with deionized water and dried in a 60℃ vacuum drying box for 12h, to obtain powder C;

[0048] S4-3: mixing the powder C and the titanate coupling agent 401 according to a mass ratio of 98:2, putting into a ball mill, ball milling for 2.5 h, the ball milling speed is 350 r / min, to obtain the modified titanium dioxide.

[0049] A preparation method of an anti-aging and wear-resistant BOPP film, the specific steps of the preparation method are as follows,

[0050] S8-1: using a three-layer co-extrusion die, the inner layer, the middle layer and the outer layer raw materials are respectively sent into three extruders according to the proportion, the temperature of the inner layer extruder is 250℃, the temperature of the middle layer extruder is 255℃, the temperature of the outer layer extruder is 265℃, the three-layer structure melt is compounded through the die, and the three-layer co-extrusion melt is cooled and cast into a sheet through a sheet casting machine, and the sheet casting temperature is 20℃;

[0051] S8-2: the cooled sheet is preheated, the preheating temperature is 102℃, the preheated sheet is stretched in longitudinal and transverse directions to form a film, the longitudinal stretching temperature is 124℃, the transverse stretching temperature is 160℃, then heat setting treatment is carried out, the heat setting temperature is 162℃, the stretched and heat set film is edge cut and wound to obtain the BOPP film.

[0052] Example 2

[0053] An anti-aging and wear-resistant BOPP film, the BOPP film is a three-layer co-extrusion structure, including an inner layer, a middle layer and an outer layer from inside to outside, the inner layer is composed of polypropylene, and the thickness is 9μm; the middle layer is composed of polypropylene and polyethylene, and the thickness is 11μm; the outer layer is composed of polypropylene, polyethylene and modified titanium dioxide, and the thickness is 4μm.

[0054] The mass ratio of polypropylene and polyethylene in the middle layer is 7:3.

[0055] The mass ratio of polypropylene, polyethylene and modified nano-titanium dioxide in the outer layer is 10:3:0.5.

[0056] The preparation method of the modified titanium dioxide is as follows,

[0057] S4-1: mixing urea and tetrabutyl titanate according to a molar ratio of 1:9 to obtain a mixture A, mixing the mixture A with deionized water according to a mass ratio of 1:50, ultrasonicating at 45℃ for 1h, then transferring to a reaction kettle and heating for 10h, the heating temperature is 150℃, washing with deionized water and drying in a 60℃ vacuum drying box for 12h, after drying, putting into a ball mill and ball milling for 30min, the ball milling speed is 150r / min, to obtain powder B;

[0058] S4-2: Powder B is added to deionized water to make the solid-liquid mass ratio 10 g / L, polyvinylpyrrolidone is added, the addition amount of polyvinylpyrrolidone is 2% of the mass of powder B, ultrasonic for 10 min, sodium metaaluminate is added, the addition amount of sodium metaaluminate is 3% of the mass of powder B, stirring at a speed of 600 r / min for 30 min, adjusting pH to 9 with 1M sodium hydroxide solution, maintaining the stirring speed at 40℃ for 2h, increasing the temperature to 80℃ and standing for 6h, then washing with deionized water and drying in a 60℃ vacuum drying oven for 12h to obtain powder C;

[0059] S4-3: Powder C is mixed with titanate coupling agent 401 according to a mass ratio of 97:3, and is put into a ball mill for ball milling for 2h at a ball milling speed of 300r / min to obtain the modified titanium dioxide.

[0060] A preparation method of an anti-aging and wear-resistant BOPP film, the specific steps of the preparation method are as follows,

[0061] S8-1: The inner layer, the middle layer and the outer layer raw materials are respectively sent into three extruders according to the proportion by using a three-layer co-extrusion die, the temperature of the inner layer extruder is 240℃, the temperature of the middle layer extruder is 245℃, and the temperature of the outer layer extruder is 250℃, the three-layer structure melt is compounded by the die, and the three-layer co-extrusion melt is cast into a sheet by a sheet casting machine, and the sheet casting temperature is 15℃;

[0062] S8-2: The cooled sheet is preheated, the preheating temperature is 100℃, the preheated sheet is stretched in the longitudinal and transverse directions to form a film, the longitudinal stretching temperature is 120℃, the transverse stretching temperature is 155℃, then heat setting treatment is carried out, the heat setting temperature is 160℃, and the stretched and heat set film is subjected to edge cutting and winding treatment to obtain the BOPP film.

[0063] Example 3

[0064] An anti-aging and wear-resistant BOPP film, the BOPP film is a three-layer co-extrusion structure, and comprises an inner layer, a middle layer and an outer layer from inside to outside, the inner layer is composed of polypropylene and has a thickness of 9μm, the middle layer is composed of polypropylene and polyethylene and has a thickness of 11μm, and the outer layer is composed of polypropylene, polyethylene and modified titanium dioxide and has a thickness of 4μm.

[0065] The mass ratio of polypropylene to polyethylene in the middle layer is 9:1.

[0066] The mass ratio of polypropylene, polyethylene and modified nano-titanium dioxide in the outer layer is 10:5:1.

[0067] The preparation method of the modified titanium dioxide is as follows,

[0068] S4-1: urea and titanium tetrachloride were mixed according to a molar ratio of 1:11 to obtain a mixture A, the mixture A was mixed with deionized water according to a mass ratio of 1:50, ultrasonic treatment was performed at 55℃ for 2h, then transferred to a reaction kettle for heating for 14h, the heating temperature was 150℃, washed with deionized water and placed in a 60℃ vacuum drying box for drying for 12h, after drying, placed in a ball mill for ball milling for 60min, the ball milling speed was 250r / min, to obtain powder B;

[0069] S4-2: powder B was added to deionized water to obtain a solid-liquid mass ratio of 10g / L, polyvinylpyrrolidone was added, the addition amount of polyvinylpyrrolidone was 3% of the mass of powder B, ultrasonic treatment was performed for 30min, sodium metaaluminate was added, the addition amount of sodium metaaluminate was 5% of the mass of powder B, stirring was performed at a speed of 700r / min for 30min, 1M sodium hydroxide solution was used to adjust the pH to 10, the temperature was kept at 50℃ for 2h, the temperature was then increased to 90℃ and kept for 6h, then washed with deionized water and placed in a 60℃ vacuum drying box for drying for 12h, to obtain powder C;

[0070] S4-3: powder C was mixed with titanate coupling agent 401 according to a mass ratio of 99:1, put into a ball mill for ball milling for 3h, the ball milling speed was 400r / min, to obtain the modified titanium dioxide.

[0071] A preparation method of an anti-aging and wear-resistant BOPP film, the specific steps of the preparation method are as follows,

[0072] S8-1: the inner layer, the middle layer and the outer layer raw materials were respectively sent into three extruders according to the proportion by using a three-layer co-extrusion die, the temperature of the inner layer extruder was 260℃, the temperature of the middle layer extruder was 270℃, the temperature of the outer layer extruder was 270℃, the three-layer structure melt was compounded by the die, and the three-layer co-extrusion melt was cooled and cast into a sheet by a sheet casting machine, and the sheet casting temperature was 25℃;

[0073] S8-2: the cooled sheet was preheated, the preheating temperature was 105℃, the preheated sheet was stretched in the longitudinal and transverse directions to form a film, the longitudinal stretching temperature was 128℃, the transverse stretching temperature was 165℃, then heat setting treatment was performed, the heat setting temperature was 165℃, and the stretched and heat set film was subjected to edge cutting and winding treatment to obtain the BOPP film.

[0074] Comparative Example 1

[0075] In the preparation of the modified titanium dioxide, urea was not added, and the remaining steps were consistent with Example 1.

[0076] Comparative Example 2

[0077] The modified titanium dioxide is prepared without adding sodium metaaluminate, and the remaining steps are consistent with Example 1.

[0078] Comparative Example 3

[0079] The modified titanium dioxide is prepared without adding titanium ester coupling agent 401, and the remaining steps are consistent with Example 1.

[0080] Comparative Example 4

[0081] The modified titanium dioxide is prepared without adding polyvinylpyrrolidone, and the remaining steps are consistent with Example 1.

[0082] Comparative Example 5

[0083] The modified titanium dioxide is replaced by commercially available titanium dioxide, and the remaining steps are consistent with Example 1. The commercially available titanium dioxide is purchased from Jinan Ruiaomingzhi Medical Technology Co., Ltd., and the purity is 99.8%.

[0084] Abrasion resistance test: the Taber rotary evaporimeter is used to test the abrasion resistance of the examples and the comparative examples, the load is 2.5N, the counter-abrasion part is H18 type grinding wheel, the rotation speed is 60r / min, and the abrasion amount of the BOPP film is tested after 50 circles, and the total mass of the BOPP film is 100g.

[0085] Anti-aging performance test: the BOPP films prepared by the examples and the comparative examples are respectively placed in an artificial accelerated aging oven at 85℃ for 96h of hot air aging, and the tensile strength after aging is measured after cooling to room temperature, and the anti-aging performance is evaluated by the tensile strength retention rate. Tensile strength retention rate = tensile strength after aging / tensile strength before aging x 100%. The tensile strength after aging and the tensile strength before stretching are tested according to the standard GB / T 13022-1991.

[0086] The experimental data is arranged as follows.

[0087] Wear amount (mg) Tensile strength retention rate (%) Example 1 0.4 99.7 Example 2 0.5 99.4 Example 3 0.4 99.5 Comparative Example 1 0.7 98.1 Comparative Example 2 1.2 96.8 Comparative Example 3 0.6 98.5 Comparative Example 4 0.5 99.1 Comparative Example 5 2.0 95.2

[0088] It can be seen from the data of the examples and the comparative examples that the BOPP film prepared by the application has better abrasion resistance and aging resistance.

[0089] The above is only a preferred embodiment of the application, and does not limit the application in any form. Although the application has been disclosed as above with a preferred embodiment, it is not intended to limit the application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the application, and any simple modification, equivalent change and modification of the above examples according to the technical essence of the application are still within the scope of the technical solution of the application.

Claims

1. An aging-resistant and wear-resistant BOPP film, characterized in that: The BOPP film is a three-layer co-extruded structure, including an inner layer, a middle layer and an outer layer from the inside to the outside. The inner layer is composed of polypropylene and has a thickness of 8 to 10 μm; the middle layer is composed of polypropylene and polyethylene and has a thickness of 10 to 12 μm; the outer layer is composed of polypropylene, polyethylene and modified titanium dioxide and has a thickness of 3 to 5 μm. Wherein, the preparation method of the modified titanium dioxide is as follows: S4-1: Mix urea and a titanium source in a molar ratio of 1:(9-11) to obtain a mixture A, mix the mixture A with deionized water in a mass ratio of 1:50, ultrasonicate at 45-55°C for 1-2 hours, transfer the mixture to a reactor, and heat it at 150°C for 10-14 hours. Wash the mixture with deionized water and dry it in a vacuum drying oven at 60°C for 12 hours. After drying, mill the mixture in a ball mill at a speed of 150-250 rpm for 30-60 minutes to obtain powder B. S4-2: Powder B was added to deionized water to a solid-liquid mass ratio of 10 g / L, polyvinyl pyrrolidone was added, and the mixture was ultrasonicated for 10 to 30 min. Sodium aluminate was added and stirred at 600 to 700 rpm for 30 min. The pH was adjusted to 9 to 10 with 1 M sodium hydroxide solution. The mixture was stirred at 40 to 50°C for 2 h, the temperature was raised to 80 to 90°C, and the mixture was allowed to stand for 6 h. The mixture was then washed with deionized water and dried in a vacuum drying oven at 60°C for 12 h to obtain powder C. S4-3: Powder C and a titanate coupling agent are mixed in a mass ratio of (97-99):(1-3), and the mixture is put into a ball mill for ball milling for 2-3 hours to obtain the modified titanium dioxide.

2. The aging-resistant and wear-resistant BOPP film according to claim 1, characterized in that: The mass ratio of polypropylene to polyethylene in the intermediate layer is (7-9): (1-3).

3. The aging-resistant and wear-resistant BOPP film according to claim 1, characterized in that: The mass ratio of polypropylene, polyethylene and modified titanium dioxide in the outer layer is 10: (3-5): (0.5-1).

4. The aging-resistant and wear-resistant BOPP film according to claim 1, characterized in that: The titanium source in S4-1 is one of titanium tetrachloride and tetrabutyl titanate.

5. The aging-resistant and wear-resistant BOPP film according to claim 1, characterized in that: The amount of polyvinyl pyrrolidone added in S4-2 is 2% to 3% of the mass of powder B, and the amount of sodium metaaluminate added is 3% to 5% of the mass of powder B.

6. The aging-resistant and wear-resistant BOPP film according to claim 1, characterized in that: The ball milling speed in S4-3 is 300-400 r / min.

7. A method for preparing an aging-resistant and wear-resistant BOPP film according to any one of claims 1 to 6, characterized in that: The specific steps of the preparation method are as follows: S8-1: Use a three-layer co-extrusion die to feed the inner layer, middle layer and outer layer raw materials into three extruders in proportion. The three-layer melt is compounded through the die to form a three-layer structure. The three-layer co-extruded melt is cooled and cast into thin sheets through a sheet casting machine. The casting temperature is 15-25°C. S8-2: The cooled sheet is preheated at a temperature of 100 to 105°C, and the preheated sheet is biaxially stretched in the longitudinal and transverse directions to form a film, which is then heat-set at a temperature of 160 to 165°C. The stretched and heat-set film is trimmed and rolled to obtain the BOPP film.

8. The method for preparing an aging-resistant and wear-resistant BOPP film according to claim 7, characterized in that: In the S8-1, the temperature of the inner layer extruder is 240-260°C, the temperature of the middle layer extruder is 245-270°C, and the temperature of the outer layer extruder is 240-270°C.

9. The method for preparing an aging-resistant and wear-resistant BOPP film according to claim 7, characterized in that: In the S8-2, the longitudinal stretching temperature is 120-128°C, and the transverse stretching temperature is 155-165°C.