High-strength polypropylene packaging box plate

Abstract

The invention relates to the technical field of plates, in particular to a high-strength polypropylene packaging box plate. The high-strength polypropylene packaging box plate comprises the following components in parts by weight: 25-50 parts of polypropylene matrix resin, 15-25 parts of a toughening agent, 5-15 parts of modified nano titanium dioxide, 1-5 parts of a compatibilizer, 50-60 parts of continuous glass fibers and 1-8 parts of a lubricant. The preparation method comprises the following steps: S1, uniformly mixing polypropylene matrix resin, a flexibilizer, modified nano titanium dioxide, a compatibilizer and a lubricant, adding the mixture into an extruder, and compounding the mixture with continuous glass fibers through screw extrusion to obtain a prepreg tape; and S2, the prepreg tape is pressed into a plate through a hot press molding method, and the high-strength polypropylene packaging box plate is obtained and has excellent mechanical performance and excellent anti-aging performance at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of plates, in particular to a high-strength polypropylene packaging box plate. Background Art

[0002] High-strength polypropylene packaging boxes usually use copolymer polypropylene, modified polypropylene and other materials. These materials are specially processed and designed to withstand large loads and impacts while maintaining a light weight. By optimizing the structural design and material ratio of the box, the rigidity and compression resistance of the packaging box can be improved, thereby extending its service life and reducing transportation costs. In addition, polypropylene materials can be recycled and reused, which is in line with the current environmental protection trend.

[0003] However, the existing technology still has potential problems in some aspects. First, polypropylene material has limited UV resistance. Long-term exposure to UV rays can easily lead to material aging and deterioration, thereby reducing the strength of the packaging box, which limits its outdoor application. In addition, in some cases, if the packaging box is too strong but lacks a certain degree of flexibility, it may cause damage to the goods in the event of a collision instead of effectively absorbing the impact.

[0004] Therefore, we propose a high-strength polypropylene packaging box sheet. Summary of the invention

[0005] The object of the present invention is to provide a high-strength polypropylene packaging box plate material to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions: A high-strength polypropylene packaging box plate comprises the following components by weight: 25-50 parts of polypropylene matrix resin, 15-25 parts of toughening agent, 5-15 parts of modified nano titanium dioxide, 1-5 parts of compatibilizer, 50-60 parts of continuous glass fiber and 1-8 parts of lubricant.

[0007] Furthermore, the toughening agent is compounded by 5-10 parts of ethylene-octene copolymer and 10-15 parts of maleic anhydride grafted POE.

[0008] Furthermore, the preparation method of the modified nano titanium dioxide is as follows: Step (1): ultrasonically dispersing nano-titanium dioxide in a mixed solution of anhydrous ethanol and deionized water, adding 3-(2,3-epoxypropoxy)propyltrimethoxysilane and mixing evenly, adjusting the system pH to 4-5, reacting at 70-80° C. for 3-5 hours, and obtaining epoxidized nano-titanium dioxide after centrifugation, washing, and drying; Step (2): uniformly mixing epoxidized nano-titanium dioxide, p-aminodiphenylamine and ethanol, reacting at 30-40°C for 3-5h, then adding isocyanate ethyl methacrylate and dibutyltin dilaurate, reacting at 65-75°C for 3-5h, cooling to room temperature, filtering, washing and drying to obtain antioxidant-grafted nano-titanium dioxide; Step (3): the antioxidant grafted nano titanium dioxide, maleic anhydride modified tea polyphenols, acrylic acid, ethyl acrylate and N,N-dimethylformamide are mixed evenly, nitrogen is introduced, azobisisobutyronitrile is added, the mixture is reacted at 65-75°C for 6-10h, cooled to room temperature, and subjected to reduced pressure rotary evaporation, washing and drying to obtain modified nano titanium dioxide.

[0009] Furthermore, in the step (1), the mass ratio of nano-titanium dioxide to anhydrous ethanol, deionized water, and 3-(2,3-epoxypropoxy)propyltrimethoxysilane is 1:(10-12):(2-4):(0.3-0.5).

[0010] Furthermore, in the step (2), the mass ratio of epoxidized nano-titanium dioxide, p-aminodiphenylamine and ethanol is 1:(2-4):(10-20).

[0011] Furthermore, in step (2), the mass of ethyl isocyanate methacrylate is 3-5 times the mass of epoxidized nano-titanium dioxide, and the mass ratio of ethyl isocyanate methacrylate to dibutyltin dilaurate is 1:(0.01-0.03).

[0012] Furthermore, in step (3), the modified nano titanium dioxide comprises the following components by weight: 5-15 parts of antioxidant grafted nano titanium dioxide, 10-15 parts of maleic anhydride modified tea polyphenols, 4-8 parts of acrylic acid, 8-12 parts of ethyl acrylate, 60-80 parts of N,N-dimethylformamide, and 1-3 parts of azobisisobutyronitrile.

[0013] Furthermore, the preparation steps of the maleic anhydride modified tea polyphenols are as follows: tea polyphenols and ethyl acetate are mixed evenly, maleic anhydride and pyridine are added, reacted at 40-50°C for 5-7h, and maleic anhydride modified tea polyphenols are obtained after vacuum rotary evaporation, recrystallization, and freeze drying.

[0014] Furthermore, the mass ratio of tea polyphenols, ethyl acetate, maleic anhydride and pyridine is 1:(15-25):(0.8-1.2):(0.3-0.5).

[0015] In the above technical scheme, hydroxyl groups are generated by ring-opening reaction of epoxidized nano-titanium dioxide and p-aminodiphenylamine to achieve grafting of antioxidants, and then the reaction of hydroxyl groups with isocyanate groups is used to react with isocyanate ethyl methacrylate under the action of dibutyltin dilaurate catalyst to introduce double bonds to obtain antioxidant-grafted nano-titanium dioxide; tea polyphenols are a natural antioxidant with environmental friendliness, and tea polyphenols are modified with maleic anhydride (MA) as a modifier, which not only retains its good antioxidant properties, but also enhances its fat solubility and stability, and introduces double bonds to obtain maleic anhydride-modified tea polyphenols; modified nano-titanium dioxide is obtained by polymerization reaction using antioxidant-grafted nano-titanium dioxide, maleic anhydride-modified tea polyphenols, acrylic acid and ethyl acrylate as raw materials.

[0016] Furthermore, the compatibilizer is one or more of polypropylene-maleic anhydride graft (PP-g-MAH), polypropylene-acrylic acid graft (PP-g-MAA), and polypropylene-methyl methacrylate graft (PP-g-MMA).

[0017] Furthermore, the lubricant is one or more of fatty acid zinc and polyethylene wax.

[0018] A method for preparing a high-strength polypropylene packaging box sheet comprises the following steps: Step S1: uniformly mixing a polypropylene matrix resin, a toughening agent, modified nano titanium dioxide, a compatibilizer and a lubricant, adding the mixture into an extruder, and compounding the mixture with continuous glass fibers through screw extrusion to obtain a prepreg tape; Step S2: Pressing the prepreg tape into a sheet by a hot pressing method to obtain a high-strength polypropylene packaging box sheet.

[0019] Furthermore, the extruder is a single-screw extruder with a screw length-to-diameter ratio of 30:1. The single-screw extruder has 6 temperature zones: zone 1 100-160°C, zone 2 160-180°C, zone 3 170-190°C, zone 4 200-220°C, zone 5 200-220°C, and zone 6 200-230°C.

[0020] Furthermore, the process conditions of the hot pressing molding are: heating temperature 180-200° C., and pressure 6-8 MPa.

[0021] Compared with the prior art, the present invention has the following beneficial effects: 1. A high-strength polypropylene packaging box sheet of the present invention introduces modified nano titanium dioxide with anti-ultraviolet performance to improve the anti-aging performance and mechanical properties of polypropylene. First, the surface of the nano titanium dioxide is modified by 3-(2,3-epoxypropoxy)propyltrimethoxysilane to improve the problem that it is easy to agglomerate and difficult to disperse. Then, p-aminodiphenylamine (PPDA) is grafted on the surface to achieve the grafting of the antioxidant. Then, under the action of dibutyltin dilaurate catalyst, double bonds are introduced by reacting hydroxyl groups with ethyl isocyanate methacrylate. Finally, in order to further improve the nano In order to improve the compatibility of nano titanium dioxide with polypropylene, antioxidant-grafted nano titanium dioxide, maleic anhydride-modified tea polyphenols, acrylic acid and ethyl acrylate were used as raw materials to obtain modified nano titanium dioxide through polymerization reaction. Organic groups can be introduced on the surface of nano titanium dioxide to improve its compatibility with the polypropylene matrix, improve its dispersibility, form a stable composite material, and thus improve the mechanical properties of the material. At the same time, the introduction of antioxidants and maleic anhydride-modified tea polyphenols significantly improved the UV resistance and antioxidant capacity of polypropylene packaging box sheets, delayed the aging process of the material under light, heat and oxygen environments, and extended its service life.

[0022] 2. A high-strength polypropylene packaging box sheet of the present invention, the toughening agent is compounded by ethylene-octene copolymer and maleic anhydride grafted POE. Ethylene-octene copolymer (POE) as an elastomer can significantly improve the toughness and impact resistance of polypropylene, and reduce the risk of brittle fracture of the material when subjected to external impact; secondly, maleic anhydride grafted POE enhances the interface compatibility between components such as glass fiber and the polypropylene matrix by introducing polar groups, and further improves the mechanical properties of the material; the compound use of POE and maleic anhydride grafted POE not only maintains the lightweight characteristics of polypropylene, but also gives the material excellent fatigue resistance, thereby extending the service life of the packaging box sheet. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In this embodiment, the polypropylene matrix resin: the brand is Formosa Chemical Industry K8065 from Taiwan Province, China; the ethylene-octene copolymer: the brand is Dow POE 8540; the maleic anhydride grafted POE: the brand is Dow GR216; nano titanium dioxide: rutile type, with a particle size of 30-50nm, is sourced from Changzhou Konada New Materials Technology Co., Ltd.; the compatibilizer: maleic anhydride grafted polypropylene, the brand is Exxon PO 1020; the continuous glass fiber: the brand is Jushi 362c-1200tex; the lubricant: Honeywell polyethylene wax AC-6.

[0025] The following parts are by mass unless otherwise specified.

[0026] Embodiment 1: A method for preparing a high-strength polypropylene packaging box sheet material, comprising the following process: Step S1: 25 parts of polypropylene matrix resin, 5 parts of ethylene-octene copolymer, 10 parts of maleic anhydride grafted POE, 5 parts of modified nano titanium dioxide, 1 part of a compatibilizer and 1 part of a lubricant are mixed evenly, added into a single screw extruder, and evenly compounded with 50 parts of continuous glass fibers by screw extrusion (the screw aspect ratio is 30:1, and the temperature of the single screw extruder is set to 6 zones: zone 1 100°C, zone 2 160°C, zone 3 170°C, zone 4 200°C, zone 5 200°C, zone 6 200°C), to obtain a prepreg tape; Step S2: pressing the prepreg tape into a plate by a hot pressing method (heating temperature 180° C., pressure 6 MPa), to obtain a high-strength polypropylene packaging box plate; The preparation method of modified nano titanium dioxide is as follows: Step (1): ultrasonically disperse 5 parts of nano titanium dioxide in a mixed solution of 50 parts of anhydrous ethanol and 10 parts of deionized water, add 1.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and mix evenly, adjust the system pH to 4, react at 70°C for 3 hours, centrifuge, wash and dry to obtain epoxidized nano titanium dioxide; Step (2): 5 parts of epoxidized nano-titanium dioxide, 10 parts of p-aminodiphenylamine and 50 parts of ethanol are mixed evenly, reacted at 30°C for 3 hours, and then 15 parts of ethyl isocyanate methacrylate and 0.15 parts of dibutyltin dilaurate are added, reacted at 65°C for 3 hours, cooled to room temperature, filtered, washed and dried to obtain antioxidant-grafted nano-titanium dioxide; Step (3): 5 parts of antioxidant grafted nano titanium dioxide, 10 parts of maleic anhydride modified tea polyphenols, 4 parts of acrylic acid, 8 parts of ethyl acrylate and 60 parts of N,N-dimethylformamide are mixed evenly, nitrogen is introduced, 1 part of azobisisobutyronitrile is added, the mixture is reacted at 65°C for 6 hours, cooled to room temperature, and subjected to reduced pressure rotary evaporation, washing and drying to obtain modified nano titanium dioxide.

[0027] Embodiment 2: A high-strength polypropylene packaging box sheet, comprising the following process: Step S1: 45 parts of polypropylene matrix resin, 8 parts of ethylene-octene copolymer, 12 parts of maleic anhydride grafted POE, 10 parts of modified nano titanium dioxide, 3 parts of compatibilizer and 5 parts of lubricant are mixed uniformly, added into a single screw extruder, and uniformly compounded with 55 parts of continuous glass fiber by screw extrusion (the screw aspect ratio is 30:1, and the temperature of the single screw extruder is set to 6 zones: zone 1 150°C, zone 2 170°C, zone 3 180°C, zone 4 210°C, zone 5 210°C, zone 6 220°C), to obtain a prepreg tape; Step S2: pressing the prepreg tape into a plate by hot pressing (heating temperature 190° C., pressure 7 MPa), to obtain a high-strength polypropylene packaging box plate; The preparation method of modified nano titanium dioxide is as follows: Step (1): ultrasonically disperse 10 parts of nano titanium dioxide in a mixed solution of 110 parts of anhydrous ethanol and 30 parts of deionized water, add 4 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and mix evenly, adjust the system pH to 4.5, react at 75°C for 4 hours, centrifuge, wash and dry to obtain epoxidized nano titanium dioxide; Step (2): 10 parts of epoxidized nano-titanium dioxide, 30 parts of p-aminodiphenylamine and 150 parts of ethanol are mixed evenly, reacted at 35°C for 4 hours, and then 40 parts of ethyl isocyanate methacrylate and 0.8 parts of dibutyltin dilaurate are added, reacted at 70°C for 4 hours, cooled to room temperature, filtered, washed and dried to obtain antioxidant-grafted nano-titanium dioxide; Step (3): 10 parts of antioxidant grafted nano titanium dioxide, 12 parts of maleic anhydride modified tea polyphenols, 6 parts of acrylic acid, 10 parts of ethyl acrylate and 70 parts of N,N-dimethylformamide are mixed evenly, nitrogen is introduced, 2 parts of azobisisobutyronitrile are added, the mixture is reacted at 70°C for 7 hours, cooled to room temperature, and subjected to reduced pressure rotary evaporation, washing and drying to obtain modified nano titanium dioxide.

[0028] Embodiment 3: A high-strength polypropylene packaging box sheet, comprising the following process: Step S1: 50 parts of polypropylene matrix resin, 10 parts of ethylene-octene copolymer, 15 parts of maleic anhydride grafted POE, 15 parts of modified nano titanium dioxide, 5 parts of compatibilizer and 8 parts of lubricant are mixed uniformly, added into a single screw extruder, and uniformly compounded with 60 parts of continuous glass fiber by screw extrusion (the screw aspect ratio is 30:1, and the temperature of the single screw extruder is set to 6 zones: zone 1 160°C, zone 2 180°C, zone 3 190°C, zone 4 220°C, zone 5 220°C, zone 6 230°C), to obtain a prepreg tape; Step S2: pressing the prepreg tape into a plate by a hot pressing method (heating temperature 200° C., pressure 8 MPa), to obtain a high-strength polypropylene packaging box plate; The preparation method of modified nano titanium dioxide is as follows: Step (1): ultrasonically dispersing 15 parts of nano-titanium dioxide in a mixed solution of 180 parts of anhydrous ethanol and 60 parts of deionized water, adding 7.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and mixing evenly, adjusting the system pH to 5, reacting at 80° C. for 5 hours, and obtaining epoxidized nano-titanium dioxide after centrifugation, washing, and drying; Step (2): 15 parts of epoxidized nano-titanium dioxide, 60 parts of p-aminodiphenylamine and 300 parts of ethanol are mixed evenly, reacted at 40°C for 5 hours, and then 75 parts of ethyl isocyanate methacrylate and 2.25 parts of dibutyltin dilaurate are added, reacted at 75°C for 5 hours, cooled to room temperature, filtered, washed and dried to obtain antioxidant-grafted nano-titanium dioxide; Step (3): 15 parts of antioxidant grafted nano titanium dioxide, 15 parts of maleic anhydride modified tea polyphenols, 8 parts of acrylic acid, 12 parts of ethyl acrylate and 80 parts of N,N-dimethylformamide are mixed evenly, nitrogen is introduced, 3 parts of azobisisobutyronitrile are added, the mixture is reacted at 75°C for 8 hours, cooled to room temperature, and subjected to reduced pressure rotary evaporation, washing and drying to obtain modified nano titanium dioxide.

[0029] Comparative Example 1: A high-strength polypropylene packaging box sheet, comprising the following process: Step S1: 45 parts of polypropylene matrix resin, 8 parts of ethylene-octene copolymer, 12 parts of maleic anhydride grafted POE, 10 parts of epoxidized nano titanium dioxide, 3 parts of compatibilizer and 5 parts of lubricant are mixed uniformly, added into a single screw extruder, and uniformly compounded with 55 parts of continuous glass fiber by screw extrusion (the screw aspect ratio is 30:1, and the temperature of the single screw extruder is set to 6 zones: zone 1 150°C, zone 2 170°C, zone 3 180°C, zone 4 210°C, zone 5 210°C, zone 6 220°C), to obtain a prepreg tape; Step S2: pressing the prepreg tape into a plate by hot pressing (heating temperature 190° C., pressure 7 MPa), to obtain a high-strength polypropylene packaging box plate; Compared with Example 2, in Comparative Example 1, the modified nano-titanium dioxide is replaced with epoxidized nano-titanium dioxide of the same mass, and the other steps are the same as those of Example 2.

[0030] Comparative Example 2: A high-strength polypropylene packaging box sheet, comprising the following process: Step S1: 45 parts of polypropylene matrix resin, 8 parts of ethylene-octene copolymer, 12 parts of maleic anhydride grafted POE, 10 parts of antioxidant grafted nano titanium dioxide, 3 parts of compatibilizer and 5 parts of lubricant are mixed evenly, added into a single screw extruder, and uniformly compounded with 55 parts of continuous glass fiber by screw extrusion (the screw aspect ratio is 30:1, and the temperature of the single screw extruder is set to 6 zones: zone 1 150°C, zone 2 170°C, zone 3 180°C, zone 4 210°C, zone 5 210°C, zone 6 220°C), to obtain a prepreg tape; Step S2: pressing the prepreg tape into a plate by hot pressing (heating temperature 190° C., pressure 7 MPa), to obtain a high-strength polypropylene packaging box plate; The preparation method of antioxidant grafted nano titanium dioxide is as follows: Step (1): ultrasonically disperse 10 parts of nano titanium dioxide in a mixed solution of 110 parts of anhydrous ethanol and 30 parts of deionized water, add 4 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and mix evenly, adjust the system pH to 4.5, react at 75°C for 4 hours, centrifuge, wash and dry to obtain epoxidized nano titanium dioxide; Step (2): 10 parts of epoxidized nano-titanium dioxide, 30 parts of p-aminodiphenylamine and 150 parts of ethanol are mixed evenly, reacted at 35°C for 4 hours, and then 40 parts of ethyl isocyanate methacrylate and 0.8 parts of dibutyltin dilaurate are added, reacted at 70°C for 4 hours, cooled to room temperature, filtered, washed and dried to obtain antioxidant-grafted nano-titanium dioxide; Step (3): 10 parts of antioxidant grafted nano titanium dioxide, 6 parts of acrylic acid, 10 parts of ethyl acrylate and 70 parts of N,N-dimethylformamide are mixed evenly, nitrogen is introduced, 2 parts of azobisisobutyronitrile are added, the mixture is reacted at 70°C for 7 hours, cooled to room temperature, and subjected to vacuum rotary evaporation, washing and drying to obtain modified nano titanium dioxide; Compared with Example 2, maleic anhydride-modified tea polyphenols are not added to the modified nano-titanium dioxide in Comparative Example 2, and the other steps are the same as those in Example 2.

[0031] Comparative Example 3: A high-strength polypropylene packaging box sheet, comprising the following process: Step S1: 45 parts of polypropylene matrix resin, 8 parts of ethylene-octene copolymer, 10 parts of modified nano titanium dioxide, 3 parts of compatibilizer and 5 parts of lubricant are mixed uniformly, added into a single screw extruder, and uniformly compounded with 55 parts of continuous glass fiber by screw extrusion (the screw aspect ratio is 30:1, and the temperature of the single screw extruder is set to 6 zones: zone 1 150°C, zone 2 170°C, zone 3 180°C, zone 4 210°C, zone 5 210°C, zone 6 220°C), to obtain a prepreg tape; Compared with Example 2, Comparative Example 3 does not add maleic anhydride grafted POE, and other steps are the same as Example 2.

[0032] Experiment: Take the high-strength polypropylene packaging box plates obtained in Examples 1-3 and Comparative Examples 1-3, prepare samples, test their properties respectively and record the test results: Impact strength was tested according to GB / T 1843-2008. Tensile strength was measured on an electronic universal material testing machine according to ASTM-D638-2022. The shape of the specimen was dumbbell-shaped, the thickness was 4 mm, the width was 10 mm, and the tensile rate was 25 mm / min. UV aging test was carried out according to GB / T 16422.2-2014. The light source was a xenon arc lamp with an irradiation intensity of 0.5 W / m 2 (340nm), after UV aging the high-strength polypropylene packaging box sheet for 500h, the tensile strength before and after aging was measured, and the tensile strength retention rate was calculated. The test results are as follows:

[0033] According to the data in the above table, we can clearly draw the following conclusions: 1. Compared with Examples 1-3, the impact strength, tensile strength and tensile strength retention rate of the products obtained in Comparative Examples 1 and 2 are all reduced, indicating that the present invention can effectively improve the mechanical properties and aging resistance of the material by adding modified nano-titanium dioxide; at the same time, the introduction of an antioxidant into the modified nano-titanium dioxide and the compounding with maleic anhydride-modified tea polyphenols further enhances the aging resistance of the material.

[0034] 2. Compared with Examples 1-3, the tensile strength and impact strength of the product obtained in Comparative Example 3 are both reduced, which indicates that the present invention can enhance the interfacial compatibility with the polypropylene matrix by adding maleic anhydride grafted POE, thereby improving the tensile strength and toughness of the material; at the same time, by compounding with ethylene-octene copolymer (POE), the elastomeric properties of POE are further exerted, significantly improving the impact resistance of the material.

[0035] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A high-strength polypropylene packaging box sheet, characterized in that: The invention comprises the following components by weight: 25-50 parts of polypropylene matrix resin, 15-25 parts of toughening agent, 5-15 parts of modified nano titanium dioxide, 1-5 parts of compatibilizer, 50-60 parts of continuous glass fiber and 1-8 parts of lubricant.

2. The high-strength polypropylene packaging box sheet according to claim 1, characterized in that: The toughening agent is compounded from 5-10 parts of ethylene-octene copolymer and 10-15 parts of maleic anhydride grafted POE.

3. The high-strength polypropylene packaging box sheet according to claim 1, characterized in that: The preparation method of the modified nano titanium dioxide is as follows: Step (1): ultrasonically dispersing nano-titanium dioxide in a mixed solution of anhydrous ethanol and deionized water, adding 3-(2,3-epoxypropoxy)propyltrimethoxysilane and mixing evenly, adjusting the system pH to 4-5, reacting at 70-80° C. for 3-5 hours, and obtaining epoxidized nano-titanium dioxide after centrifugation, washing, and drying; Step (2): uniformly mixing epoxidized nano-titanium dioxide, p-aminodiphenylamine and ethanol, reacting at 30-40°C for 3-5h, then adding isocyanate ethyl methacrylate and dibutyltin dilaurate, reacting at 65-75°C for 3-5h, cooling to room temperature, filtering, washing and drying to obtain antioxidant-grafted nano-titanium dioxide; Step (3): the antioxidant grafted nano titanium dioxide, maleic anhydride modified tea polyphenols, acrylic acid, ethyl acrylate and N,N-dimethylformamide are mixed evenly, nitrogen is introduced, azobisisobutyronitrile is added, the mixture is reacted at 65-75°C for 6-10h, cooled to room temperature, and subjected to reduced pressure rotary evaporation, washing and drying to obtain modified nano titanium dioxide.

4. The high-strength polypropylene packaging box sheet according to claim 3, characterized in that: In the step (1), the mass ratio of nano-titanium dioxide to anhydrous ethanol, deionized water, and 3-(2,3-epoxypropoxy)propyltrimethoxysilane is 1:(10-12):(2-4):(0.3-0.5).

5. The high-strength polypropylene packaging box sheet according to claim 3, characterized in that: In the step (3), the modified nano titanium dioxide comprises the following components by weight: 5-15 parts of antioxidant grafted nano titanium dioxide, 10-15 parts of maleic anhydride modified tea polyphenols, 4-8 parts of acrylic acid, 8-12 parts of ethyl acrylate, 60-80 parts of N,N-dimethylformamide, and 1-3 parts of azobisisobutyronitrile.

6. The high-strength polypropylene packaging box sheet according to claim 5, characterized in that: The preparation steps of the maleic anhydride modified tea polyphenols are as follows: tea polyphenols and ethyl acetate are uniformly mixed, maleic anhydride and pyridine are added, reacted at 40-50° C. for 5-7 hours, and maleic anhydride modified tea polyphenols are obtained after vacuum rotary evaporation, recrystallization, and freeze drying.

7. The high-strength polypropylene packaging box sheet according to claim 1, characterized in that: The compatibilizer is one or more of polypropylene-maleic anhydride grafts, polypropylene-acrylic acid grafts, and polypropylene-methyl methacrylate grafts.

8. The high-strength polypropylene packaging box sheet according to claim 1, characterized in that: The lubricant is one or more of fatty acid zinc and polyethylene wax.

9. A method for preparing a high-strength polypropylene packaging box sheet, characterized in that: The steps include: Step S1: uniformly mixing a polypropylene matrix resin, a toughening agent, modified nano titanium dioxide, a compatibilizer and a lubricant, adding the mixture into an extruder, and compounding the mixture with continuous glass fibers through screw extrusion to obtain a prepreg tape; Step S2: Pressing the prepreg tape into a sheet by a hot pressing method to obtain a high-strength polypropylene packaging box sheet.

10. The method for preparing a high-strength polypropylene packaging box sheet according to claim 9, characterized in that: The process conditions of the hot pressing molding are: heating temperature 180-200° C., pressure 6-8 MPa.

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