Anti-aging and wear-resistant BOPP (Biaxially-oriented Polypropylene) film and preparation method thereof

Abstract

The invention 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 of 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 made of polypropylene, and the thickness of the inner layer is 8-10 micrometers; the middle layer is composed of polypropylene and polyethylene, and the thickness of the middle layer is 10-12 [mu] m; the outer layer is composed of polypropylene, polyethylene and modified titanium dioxide, and the thickness of the outer layer is 3-5 microns. Nitrogen-doped titanium dioxide is prepared by a hydrothermal method, so that the anti-aging performance of the BOPP film is enhanced; polyvinylpyrrolidone improves the dispersibility of nitrogen-doped titanium dioxide, so that the preparation process is stable and controllable, and a small amount of sodium metaaluminate is added to further enhance the aging resistance and wear resistance; the titanate coupling agent enhances the interface bonding force between the inorganic nanoparticles and the organic polymer matrix, and improves the overall strength and stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of plastic films, and relates to an anti-aging and wear-resistant BOPP film and a preparation method thereof. Background Art

[0002] BOPP (biaxially oriented polypropylene) film is a film product obtained by biaxially stretching a conventional polypropylene film in the transverse and longitudinal directions. This film has good mechanical strength, physical stability, airtightness, as well as high transparency and glossiness, so it is widely used in fields such as packaging and tape base films. However, due to the presence of tertiary carbon atoms in the BOPP film, it is easily affected by light and heat and decomposed, resulting in relatively poor anti-aging performance. At the same time, although the BOPP film has good wear resistance, in some specific application scenarios, its wear resistance still needs to be further improved to meet more stringent usage requirements. Summary of the Invention

[0003] The purpose of the present invention is to provide an anti-aging and wear-resistant BOPP film and a preparation method thereof, which have the characteristics of good wear resistance and anti-aging performance.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] 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 with a thickness of 8 - 10 μm; the middle layer is composed of polypropylene and polyethylene with a thickness of 10 - 12 μm; the outer layer is composed of polypropylene, polyethylene and modified titanium dioxide with a thickness of 3 - 5 μm.

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

[0007] As a preferred technical solution of the present invention, 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 present invention, the preparation method of the modified titanium dioxide is as follows,

[0009] S4-1: Mix urea and a titanium source in a molar ratio of 1:(9 - 11) to obtain mixture A. Mix mixture A with deionized water in a mass ratio of 1:50, ultrasonicate for 1 - 2 h at 45 - 55 °C, then transfer to a reaction kettle and heat for 10 - 14 h at a heating temperature of 150 °C. Wash with deionized water and dry in a vacuum drying oven at 60 °C for 12 h. After drying, place in a ball mill and ball mill for 30 - 60 min at a ball mill speed of 150 - 250 r / min to obtain powder B;

[0010] S4-2: Add powder B to deionized water to make the solid-liquid mass ratio 10 g / L. Add polyvinylpyrrolidone and ultrasonicate for 10 - 30 min. Add sodium aluminate and stir at a speed of 600 - 700 r / min for 30 min. Adjust the pH to 9 - 10 with 1 M sodium hydroxide solution, keep stirring at the speed at 40 - 50 °C for 2 h, raise the temperature to 80 - 90 °C and let stand for 6 h. Then wash with deionized water and dry in a vacuum drying oven at 60 °C for 12 h to obtain powder C;

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

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

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

[0014] As a preferred technical solution of the present invention, in S4-3, the ball mill speed is 300 - 400 r / 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: Use a three-layer coextrusion die to separately feed the inner layer, middle layer, and outer layer raw materials into three extruders, and compound them into a melt with a three-layer structure through the die. Cool the three-layer coextruded melt into a thin sheet through a casting machine, and the casting temperature is 15 - 25 °C;

[0017] S8-2: Preheat the cooled thin sheet, the preheating temperature is 100 - 105 °C. Biaxially stretch the preheated thin sheet longitudinally and transversely to form a film, and then perform heat setting treatment, the heat setting temperature is 160 - 165 °C. Trim and wind up the stretched and heat-set film to obtain the BOPP film.

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

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

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

[0021] The middle layer is a blend layer of polypropylene and polyethylene. 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 break. The blend of polypropylene and polyethylene can improve the processing fluidity of the material, facilitate the extrusion molding of the film, and improve production efficiency. As a transition between the inner layer and the outer layer, through the reasonable ratio of polypropylene and polyethylene, the strength, flexibility, and barrier properties of the film can be balanced.

[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, the damage of ultraviolet rays to the film is reduced, and the service life of the film is extended. The Al 2 O 3 coating layer and titanate coupling agent on the surface of modified titanium dioxide 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 for film transparency in different applications. Modified titanium dioxide and its coating layer help to enhance the chemical stability of the film and resist the erosion of chemical substances such as acids and alkalis.

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

[0024] Titanium dioxide has the ability to absorb ultraviolet light, which can effectively shield ultraviolet rays, thus protecting the BOPP film from photodegradation. However, titanium dioxide exhibits high photocatalytic activity after being excited by ultraviolet light, and this activity will catalyze the degradation reaction of the BOPP film. Therefore, in the process of using titanium dioxide to enhance the light resistance of the BOPP film, it is necessary to balance the relationship between its ultraviolet light absorption and photocatalytic activity to ensure that the BOPP film can be effectively protected from light damage and unnecessary photocatalytic degradation can be avoided.

[0025] In the preparation process of modified titanium dioxide, urea decomposes into NH 3 and CO 2 under high-temperature hydrothermal conditions. The alkaline environment provided by NH 3 promotes the hydrolysis and condensation of the titanium source, forming titanium dioxide particles. During this process, some nitrogen atoms are doped into the lattice of titanium dioxide. This doping of nitrogen atoms narrows the band gap of titanium dioxide and simultaneously introduces photogenerated 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 the BOPP film, it can reduce the light damage of ultraviolet rays to the film. On the other hand, by regulating the photocatalytic activity, the adverse photoreaction of the BOPP film caused by excessive activity of titanium dioxide is avoided, thus significantly enhancing the anti-aging performance of the BOPP film.

[0026] By adding polyvinylpyrrolidone, the dispersibility of titanium dioxide particles in the solution can be significantly improved, making the particles more evenly distributed in the solution, which is beneficial to the subsequent reaction and processing processes, 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, reduce the occurrence of local agglomeration and precipitation and other phenomena, which is beneficial to improving the preparation efficiency and product quality, and can also reduce the production cost. Adding a small amount of sodium metaaluminate, sodium metaaluminate hydrolyzes under alkaline conditions to generate Al(OH) 3 colloid, and these colloids are adsorbed and deposited on the surface of some nitrogen-doped titanium dioxide particles through adsorption. Al(OH) 3 is converted into Al 2 O 3 after heat treatment, forming a coating layer. This Al 2 O 3 coating layer not only further inhibits the photocatalytic reaction and enhances the anti-aging performance of the film; at the same time, Al 2 O 3 , as a material with high hardness and high wear resistance, the existence of its coating layer also significantly improves the wear resistance of the BOPP film. Under mechanical actions such as friction and scratching, Al 2 O 3The coating layer can protect the BOPP film substrate from damage and extend the service life of the BOPP film.

[0027] One end of the titanate coupling agent forms a chemical bond with the surface hydroxyl groups of the modified titanium dioxide, connecting the inorganic nanoparticles with the organic polymer matrix, effectively enhancing the interfacial bonding force, reducing the performance degradation caused by interfacial separation or interfacial voids, and thus improving the overall strength and stability of the BOPP film. The long-chain organic groups of the titanate coupling agent extend outwards, which can form a good dispersion effect in the polymer matrix, prevent the aggregation of the modified titanium dioxide particles, is beneficial to further inhibit the photocatalytic activity, and also ensures the uniformity of the film performance, avoiding performance defects caused by too high local particle concentration.

[0028] Advantages of the present invention:

[0029] (1) For the three-layer coextruded BOPP film proposed by the present invention, the inner layer of polypropylene provides structural support and barrier properties, the middle layer of polypropylene and polyethylene blend enhances toughness and processing properties, and the outer layer adds modified titanium dioxide to significantly improve anti-aging and wear resistance, while optimizing optical properties and chemical stability. This structure realizes the comprehensive optimization and balance of the film performance, extends the service life, meets the diverse application requirements, and significantly improves the market competitiveness.

[0030] (2) Through the preparation of the modified titanium dioxide, the doping of nitrogen atoms is realized, which helps to balance the photocatalytic activity of the titanium dioxide, thereby enhancing the anti-aging performance of the BOPP film. Under the regulation of polyvinylpyrrolidone, Al(OH) generated by the hydrolysis of sodium metaaluminate 3 is converted into Al 2 O 3 through heat treatment, and a coating layer is formed 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, while preventing the aggregation of the modified titanium dioxide particles, ensuring the uniformity of the film performance, and extending the service life of the BOPP film. Specific embodiments

[0031] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following combines examples to detail the specific embodiments, structures, features and their effects according to the present invention.

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

[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 Compway Technology Co., Ltd.;

[0036] Titanium tetrachloride: purchased from Jiangsu Rain 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 Materials Technology Co., Ltd.

[0041] Example 1

[0042] An anti-aging and wear-resistant BOPP film, the BOPP film has 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 with a thickness of 9 μm; the middle layer is composed of polypropylene and polyethylene with a thickness of 11 μm; the outer layer is composed of polypropylene, polyethylene and modified titanium dioxide with a thickness of 4 μm.

[0043] Among them, the mass ratio of polypropylene to polyethylene in the middle 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: Mix urea and titanium tetrachloride according to a molar ratio of 1:10 to obtain mixture A. Mix mixture A with deionized water according to a mass ratio of 1:50, ultrasonic for 1.5 h at 50 °C, then transfer to a reaction kettle and heat for 12 h at a heating temperature of 150 °C. Wash with deionized water and dry in a vacuum drying oven at 60 °C for 12 h. After drying, place in a ball mill and ball mill for 45 min at a ball mill speed of 200 r / min to obtain powder B;

[0047] S4-2: Add powder B into deionized water to make the solid-liquid mass ratio 10 g / L. Add polyvinylpyrrolidone, and the addition amount of polyvinylpyrrolidone is 2.5% of the mass of powder B. Ultrasonic for 20 min, then add sodium aluminate, and the addition amount of sodium aluminate is 4% of the mass of powder B. Stir at a speed of 650 r / min for 30 min. Adjust the pH to 9.5 with 1 M sodium hydroxide solution, keep stirring at the speed at 45 °C for 2 h, raise the temperature to 85 °C and let it stand for 6 h. Then wash with deionized water and dry in a vacuum drying oven at 60 °C for 12 h to obtain powder C;

[0048] S4-3: Mix powder C and titanate coupling agent 401 according to the mass ratio of 98:2, put them into a ball mill and ball mill for 2.5 h at a ball mill speed of 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: Use a three-layer co-extrusion die to separately feed the inner layer, middle layer and outer layer raw materials into three extruders at a ratio. The temperature of the inner layer extruder is 250 °C, the temperature of the middle layer extruder is 255 °C, and the temperature of the outer layer extruder is 265 °C. Compound them through the die into a melt with a three-layer structure, and cool the melt of the three-layer co-extrusion into a thin sheet through a casting machine. The casting temperature is 20 °C;

[0051] S8-2: Preheat the cooled thin sheet at a preheating temperature of 102 °C. Biaxially stretch the preheated thin sheet longitudinally and transversely to form a film. The longitudinal stretching temperature is 124 °C, and the transverse stretching temperature is 160 °C. Then carry out heat setting treatment at a heat setting temperature of 162 °C. Trim and wind up the stretched and heat-set film 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 with a thickness of 9 μm; the middle layer is composed of polypropylene and polyethylene with a thickness of 11 μm; the outer layer is composed of polypropylene, polyethylene and modified titanium dioxide with a thickness of 4 μm.

[0054] Among them, 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: Mix urea and tetrabutyl titanate in a molar ratio of 1:9 to obtain mixture A. Mix mixture A with deionized water in a mass ratio of 1:50, sonicate at 45 °C for 1 h, then transfer to a reaction kettle and heat for 10 h at a heating temperature of 150 °C. Wash with deionized water and dry in a vacuum drying oven at 60 °C for 12 h. After drying, place in a ball mill and ball mill for 30 min at a ball milling speed of 150 r / min to obtain powder B;

[0058] S4-2: Add powder B to deionized water to make the solid-liquid mass ratio 10 g / L. Add polyvinylpyrrolidone, and the addition amount of polyvinylpyrrolidone is 2% of the mass of powder B. Sonicate for 10 min, add sodium aluminate, and the addition amount of sodium aluminate is 3% of the mass of powder B. Stir at a speed of 600 r / min for 30 min, adjust the pH to 9 with 1 M sodium hydroxide solution, keep stirring at a speed at 40 °C for 2 h, raise the temperature to 80 °C and let stand for 6 h. Then wash with deionized water and dry in a vacuum drying oven at 60 °C for 12 h to obtain powder C;

[0059] S4-3: Mix powder C and titanate coupling agent 401 in a mass ratio of 97:3, put into a ball mill and ball mill for 2 h at a ball milling speed of 300 r / 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: Use a three-layer co-extrusion die to send the inner layer, middle layer and outer layer raw materials into three extruders respectively according to the ratio. The temperature of the inner layer extruder is 240 °C, the temperature of the middle layer extruder is 245 °C, and the temperature of the outer layer extruder is 250 °C. Compound through the die into a melt with a three-layer structure, and cool the melt of the three-layer co-extrusion into a thin sheet through a casting machine. The casting temperature is 15 °C;

[0062] S8-2: Preheat the cooled thin sheet at a preheating temperature of 100 °C. Subject the preheated thin sheet to biaxial stretching in the longitudinal and transverse directions to form a film. The longitudinal stretching temperature is 120 °C, and the transverse stretching temperature is 155 °C. Then carry out heat setting treatment at a heat setting temperature of 160 °C. Trim and wind up the stretched and heat-set film 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, including an inner layer, a middle layer and an outer layer from inside to outside. The inner layer is composed of polypropylene with a thickness of 9 μm; the middle layer is composed of polypropylene and polyethylene with a thickness of 11 μm; the outer layer is composed of polypropylene, polyethylene and modified titanium dioxide with a thickness of 4 μm.

[0065] Among them, 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: Mix urea and titanium tetrachloride according to a molar ratio of 1:11 to obtain mixture A. Mix mixture A with deionized water according to a mass ratio of 1:50, ultrasonicate for 2 h at 55 °C, then transfer to a reaction kettle and heat for 14 h at a heating temperature of 150 °C. Wash with deionized water and dry in a vacuum drying oven at 60 °C for 12 h. After drying, place in a ball mill and ball mill for 60 min at a ball mill speed of 250 r / min to obtain powder B;

[0069] S4-2: Add powder B to deionized water so that the solid-liquid mass ratio is 10 g / L. Add polyvinylpyrrolidone, and the addition amount of polyvinylpyrrolidone is 3% of the mass of powder B. Ultrasonicate for 30 min, add sodium metaaluminate, and the addition amount of sodium metaaluminate is 5% of the mass of powder B. Stir at a speed of 700 r / min for 30 min, adjust the pH to 10 with 1 M sodium hydroxide solution, keep stirring at a speed at 50 °C for 2 h, raise the temperature to 90 °C and let stand for 6 h. Then wash with deionized water and dry in a vacuum drying oven at 60 °C for 12 h to obtain powder C;

[0070] S4-3: Mix powder C and titanate coupling agent 401 according to a mass ratio of 99:1, put them into a ball mill and ball mill for 3 h at a ball mill speed of 400 r / 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: Use a three-layer co-extrusion die to send the inner layer, middle layer and outer layer raw materials into three extruders respectively according to the proportion. The temperature of the inner layer extruder is 260 °C, the temperature of the middle layer extruder is 270 °C, and the temperature of the outer layer extruder is 270 °C. Compound them through the die into a melt of a three-layer structure, and cool the melt of the three-layer co-extrusion into a thin sheet through a casting machine. The casting temperature is 25 °C;

[0073] S8-2: Preheat the cooled thin sheet at a preheating temperature of 105°C. Then, perform biaxial stretching on the preheated thin sheet longitudinally and transversely to form a film. The longitudinal stretching temperature is 128°C, and the transverse stretching temperature is 165°C. Subsequently, conduct heat setting at a heat setting temperature of 165°C. Trim the edges and wind up the stretched and heat-set film to obtain the BOPP film.

[0074] Comparative Example 1

[0075] In the preparation of modified titanium dioxide, urea is not added, and the remaining steps are the same as those in Example 1.

[0076] Comparative Example 2

[0077] In the preparation of modified titanium dioxide, sodium metaaluminate is not added, and the remaining steps are the same as those in Example 1.

[0078] Comparative Example 3

[0079] In the preparation of modified titanium dioxide, titanate coupling agent 401 is not added, and the remaining steps are the same as those in Example 1.

[0080] Comparative Example 4

[0081] In the preparation of modified titanium dioxide, polyvinylpyrrolidone is not added, and the remaining steps are the same as those in Example 1.

[0082] Comparative Example 5

[0083] Replace the modified titanium dioxide with commercially available titanium dioxide, and the remaining steps are the same as those in Example 1. The commercially available titanium dioxide is purchased from Jinan Ruiyao Mingzhi Medical Technology Co., Ltd., with a purity of 99.8%.

[0084] Abrasion resistance test: Use a Taber rotary evaporator to test the abrasion resistance of the examples and comparative examples. The load is 2.5 N, the counter-abrasive is an H18 type grinding wheel, the rotation speed is 60 r / min, and the abrasion loss of the BOPP film is measured after 50 circles. The total mass of the BOPP film is 100 g.

[0085] Anti-aging performance test: Place the BOPP films prepared in the examples and comparative examples in an artificial accelerated aging chamber at 85°C for 96 h of hot air aging. After cooling to room temperature, measure the tensile strength after aging, and evaluate the anti-aging performance with the tensile strength retention rate. Tensile strength retention rate = tensile strength after aging / tensile strength before aging × 100%. Among them, the measurement of the tensile strength after aging and the tensile strength before aging is carried out in accordance with the standard of GB / T 13022-1991.

[0086] The experimental data are sorted out in the following table.

[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] From the data of the examples and comparative examples, it can be seen that the BOPP film prepared by the present invention has better abrasion resistance and aging resistance.

[0089] The above are only the preferred embodiments of the present invention, and do not impose any formal limitations on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the above-disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

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.

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 nano 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 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 1-2h, then transfer to a reactor and heat for 10-14h at a heating temperature of 150°C, wash with deionized water and dry in a vacuum drying oven at 60°C for 12h, and after drying, ball mill in a ball mill for 30-60min at a ball mill speed of 150-250r / min to obtain powder B; S4-2: Powder B was added to deionized water so that the solid-liquid mass ratio was 10 g / L, polyvinyl pyrrolidone was added, ultrasonication was performed for 10 to 30 min, sodium aluminate was added, stirring was performed at a speed of 600 to 700 r / min for 30 min, pH was adjusted to 9 to 10 with 1 M sodium hydroxide solution, stirring was maintained at a speed of 40 to 50° C. for 2 h, the temperature was raised to 80 to 90° C. and allowed to stand for 6 h, 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 titanate coupling agent are mixed in a mass ratio of (97-99):(1-3), and the mixture is put into a ball mill for 2-3 hours to obtain the modified titanium dioxide.

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

6. The aging-resistant and wear-resistant BOPP film according to claim 4, characterized in that: In the S4-2, the amount of polyvinyl pyrrolidone added is 2% to 3% of the mass of powder B, and the amount of sodium aluminate added is 3% to 5% of the mass of powder B.

7. The aging-resistant and wear-resistant BOPP film according to claim 4, characterized in that: The ball milling speed in S4-3 is 300-400 r / min.

8. A method for preparing an aging-resistant and wear-resistant BOPP film according to any one of claims 1 to 7, 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, compound them into a three-layer melt through the die, and cool the three-layer co-extruded melt into a thin sheet through a sheet casting machine, and the sheet casting temperature is 15-25°C; S8-2: preheating the cooled sheet at a temperature of 100 to 105°C, biaxially stretching the preheated sheet in the longitudinal and transverse directions to form a film, and then heat-setting the film at a temperature of 160 to 165°C. The stretched and heat-set film is trimmed and rolled to obtain the BOPP film.

9. The method for preparing an aging-resistant and wear-resistant BOPP film according to claim 8, 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.

10. The method for preparing an aging-resistant and wear-resistant BOPP film according to claim 8, characterized in that: In the S8-2, the longitudinal stretching temperature is 120-128°C, and the transverse stretching temperature is 155-165°C.