Antibacterial plastic and preparation method thereof

Abstract

The invention provides antibacterial polypropylene plastic, and aims to obtain a composite antibacterial agent with the advantages of an inorganic antibacterial agent and an organic antibacterial agent by compounding the inorganic antibacterial agent and the organic antibacterial agent, and the antibacterial polypropylene plastic which is good in antibacterial property, good in migration resistance, good in mechanical property, good in mechanical property, good in mechanical property and the like is obtained by adding the obtained composite antibacterial agent into the polypropylene plastic. The invention discloses antibacterial polypropylene plastic with long-acting antibacterial property.

Description

Technical Field

[0001] The invention relates to an antibacterial plastic, in particular to an antibacterial polypropylene plastic. Background Art

[0002] With the continuous development of the economy and society, more and more plastic products have penetrated into people's lives. Plastics are materials with polymers as the main component, which can be processed into a certain shape under certain conditions and can maintain their shape at room temperature. There are many types of plastics, and the commonly used ones are polyethylene, polypropylene, polyvinyl chloride, polystyrene, etc. By adding fillers, plasticizers, colorants and other additives to the matrix, it can be given properties such as light weight, high strength, corrosion resistance, heat resistance, impact resistance, and tensile resistance.

[0003] Polypropylene (PP) is a general-purpose plastic with excellent mechanical properties and low cost. It is widely used in automotive parts, home appliances, toys, kitchen appliances, medical and other fields. These products often come into contact with human skin, and a large number of bacteria are often attached to the surface of the products. These harmful bacteria will continue to spread and transfer, threatening the health of people who have come into contact with them. Adding antibacterial agents to plastics is an effective measure to improve the antibacterial properties of plastics.

[0004] There are many types of antimicrobial agents, including inorganic antimicrobial agents, organic antimicrobial agents and natural antimicrobial agents. Types of inorganic antimicrobial agents include silver ions, copper ions, zinc ions, zinc oxide, titanium dioxide, etc. Inorganic antimicrobial agents have high safety, heat resistance and durability, and are widely used in the fields of fiber, plastic and building materials. The disadvantage is that inorganic antimicrobial agents are relatively expensive, have a delayed antibacterial effect, cannot kill bacteria as quickly as organic antimicrobial agents, and have almost no inhibitory effect on fungi and molds. Organic antimicrobial agents are mainly antimicrobial agents with quaternary ammonium salts, biguanides, alcohols, chlorine-containing hydrochloric acid, organic halides, organic metal compounds, phenols, pyridines, imidazoles, iodides, etc. as main ingredients. The advantages of organic antimicrobial agents are fast sterilization speed, high efficiency and low price, but organic antimicrobial agents generally have poor heat resistance and are prone to drug resistance. Natural antimicrobial agents come from extracts of animals and plants, belong to organic antimicrobial agents, and have the characteristics of natural environmental protection, non-toxicity, good biocompatibility, etc. Types of natural antibacterial agents include chitosan, chitin, mugwort, aloe vera, etc.

[0005] At present, the research work on the antibacterial properties of polypropylene mainly focuses on the single use or physical mixing of antibacterial agents. For example, Lou Xiaoan et al. prepared antibacterial materials by mixing silver, zinc and organic polymer antibacterial agents with polypropylene (PP) through a twin-screw extruder, studied the effects of different types of antibacterial agents on the properties of PP, and evaluated the antibacterial activity, high-temperature anti-yellowing effect and timeliness of antibacterial materials. The results showed that silver, zinc and organic polymer antibacterial agents had little effect on the mechanical properties of the materials. In terms of antibacterial efficiency, organic antibacterial agents were superior to silver and zinc antibacterial agents, but organic antibacterial agents were significantly inferior to silver and zinc antibacterial agents in terms of high-temperature anti-yellowing. Li Jie et al. used isothiazolinone antibacterial agents to develop antibacterial polypropylene, studied the effects of granulation temperature, injection temperature, ultraviolet aging, discoloration inhibitors, etc. on the yellow index and color difference of antibacterial polypropylene, and analyzed the thermal stability of isothiazolinone by thermogravimetric / infrared synchronous thermal analyzer. The results showed that when the content of 4,5-dichloro-2-n-octyl-4-isothiazoline-3-one in the discoloration-resistant antibacterial polypropylene reached 0.25% (w), the antibacterial rate against Escherichia coli and Staphylococcus aureus was greater than 99% after the sample was boiled in water at 50 ℃ for 16 h.

[0006] Based on the existing research work, this application combines the advantages and disadvantages of organic antimicrobial agents and inorganic antimicrobial agents, and organically combines inorganic antimicrobial agents and organic antimicrobial agents through chemical modification. The prepared composite antimicrobial agent has the heat resistance and durability of inorganic antimicrobial agents, and at the same time, the high efficiency of organic antimicrobial agents. Summary of the invention

[0007] The purpose of the present invention is to obtain a composite antibacterial agent having the advantages of both inorganic antibacterial agents and organic antibacterial agents by compounding an inorganic antibacterial agent and an organic antibacterial agent, and to add the obtained composite antibacterial agent to polypropylene plastic to obtain an antibacterial polypropylene plastic with good antibacterial performance, good migration resistance and long-term antibacterial property.

[0008] The purpose of the present invention is achieved through the following technical solutions: An antibacterial plastic, which is composed of the following raw materials by weight: 100 parts of polypropylene resin, 3-5 parts of composite antibacterial agent, 1-2 parts of dispersant, 2-3 parts of antioxidant, and 0.1-0.3 parts of initiator; Furthermore, as a preferred technical solution of the present invention, the dispersant is selected from one or a combination of two or more of stearic acid, polyethylene wax, and liquid paraffin.

[0009] Furthermore, as a preferred technical solution of the present invention, the antioxidant is selected from: a combination of antioxidant 1010 and antioxidant 168 in a dosage ratio of 1:1.

[0010] Furthermore, as a preferred technical solution of the present invention, the initiator is selected from: dibenzoyl peroxide, methyl ethyl ketone peroxide, or a combination of two thereof.

[0011] Furthermore, the present invention also provides a preparation process of an antibacterial plastic material, and the specific operation steps are as follows: According to the proportion, 100 parts of polypropylene resin, 3-8 parts of composite antibacterial agent, 1-2 parts of dispersant, 2-3 parts of antioxidant and 0.1-0.3 parts of initiator are put into a high-speed mixer, and mixed at a speed of 600-800rpm for 10-30min to make the materials dispersed evenly. After mixing evenly, the materials are discharged and cooled. The cooled mixture is sent to a twin-screw extruder for melt extrusion to obtain a strip material. The extruded strip material is cooled in a water tank, pulled into a pelletizer for granulation, and dried to obtain a polypropylene antibacterial plastic.

[0012] In the preparation process, the temperature of the first zone of the twin-screw extruder is controlled at 155-165°C, the temperature of the second zone is controlled at 175-185°C, the temperature of the third zone is controlled at 185-195°C, the temperature of the fourth zone is controlled at 205-215°C, the temperature of the fifth zone is controlled at 205-215°C, and the temperature of the sixth zone is controlled at 195-205°C.

[0013] Furthermore, as a preferred technical solution of the present invention, the composite antibacterial agent is quaternary ammonium salt chitosan modified nano-TiO2 composite particles, and its preparation process is as follows: Step 1: Add nano-TiO2 with a median particle size D50 of 10-50nm to 100-300mL of 95% ethanol aqueous solution for ultrasonic dispersion. After the ultrasonic dispersion, add aminosilane coupling agent and triethylamine under magnetic stirring, stir at 70-80°C, reflux reaction for 7-8h, cool to room temperature after the reaction, filter in turn, wash repeatedly with toluene and ethanol, and then dry in an oven to obtain modified nano-TiO2; Step 2: dissolve chitosan in 100-200 mL of 2% acetic acid aqueous solution, add sodium hydroxide solution to adjust the pH to 8-9, heat to 80°C, add isopropanol solution of 2,3-epoxypropyltrimethylammonium chloride, stir to react for 3-5h, add anhydrous ethanol to precipitate, filter, and dry the filter cake to obtain quaternary ammonium salt chitosan; Step 3: Prepare 200-500 mL of a mixed solution of N,N-dimethylformamide and water, wherein the volume percentage of water does not exceed 50% of the total volume of the solution; Step 4: Add the modified nano-TiO2 prepared in step 1 and the quaternary ammonium salt chitosan prepared in step 2 to the mixed solution obtained in step 3, and drop 10-30mL of N,N-dimethylformamide solution containing maleic anhydride into the above mixed solution, and continue stirring and refluxing for 4-6h. The reaction temperature does not exceed 45°C. After the reaction is completed, centrifuge, wash, and dry to obtain quaternary ammonium salt chitosan modified nano-TiO2 composite particles.

[0014] In the step 1, the mass ratio of the nano-TiO2, aminosilane coupling agent and triethylamine is 3-6:5-10:1; In the step 2, the mass ratio of chitosan to 2,3-epoxypropyltrimethylammonium chloride is 5-6:1-3; In the step 4, the mass ratio of the modified nano-TiO2, quaternary ammonium salt chitosan and maleic anhydride is 7-8:2-3:1.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The composite antibacterial agent prepared by the present invention is based on inorganic nano-TiO2. The antibacterial mechanism of inorganic nano-TiO2 lies in photocatalysis. It can immediately exert antibacterial effects in a light environment, but the inorganic particles have compatibility problems with polymers. The present application introduces amino groups into the surface of inorganic nano-TiO2 by condensing the silanol groups generated by hydrolysis of aminosilane coupling agent with the hydroxyl groups on the surface of inorganic nano-TiO2, and modifies the inorganic nano-TiO2 to improve its compatibility and reactivity. Subsequently, maleic anhydride is used as a bridge to react the anhydride groups of maleic anhydride with the amino groups on the surface of inorganic nano-TiO2 and the amino groups of chitosan quaternary ammonium salt, so as to organically combine inorganic nano-TiO2 with chitosan quaternary ammonium salt, thereby obtaining a composite antibacterial agent with high antibacterial efficiency, which can give full play to the characteristics of long-term antibacterial property of inorganic nano-TiO2 and the characteristics of high antibacterial efficiency of chitosan quaternary ammonium salt. (2) The maleic anhydride used in the present invention organically bonds the inorganic nano-TiO2 with the chitosan quaternary ammonium salt, thereby improving the compatibility of the inorganic nano-TiO2 with the polypropylene resin matrix and avoiding the precipitation problem of the chitosan quaternary ammonium salt. At the same time, the introduced double bond functional groups can undergo polymerization reaction with the small amount of double bond groups remaining in the polypropylene resin matrix under the action of the initiator, thereby grafting the composite antibacterial agent onto the polypropylene molecular chain, further improving its long-term antibacterial property. DETAILED DESCRIPTION

[0016] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be appreciated by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work, all belong to the scope of protection of the present invention. If specific conditions are not indicated in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0017] Preparation Example 1: The composite antibacterial agent is a quaternary ammonium salt chitosan modified nano-TiO2 composite particle, and its preparation process is as follows: Step 1: 8 g of nano-TiO2 with a median particle size D50 of 30 nm was added to 150 mL of 95% ethanol aqueous solution for ultrasonic dispersion. After the ultrasonic dispersion, 12 g of 3-aminopropyltrimethoxysilane and 2 g of triethylamine were added under magnetic stirring, stirred at 75 ° C, and refluxed for 7 h. After the reaction was completed, it was cooled to room temperature, filtered in turn, washed repeatedly with toluene and ethanol, and then placed in an oven to dry to obtain modified nano-TiO2; Step 2: Dissolve 5 g of chitosan in 100 mL of 2% acetic acid aqueous solution, add sodium hydroxide solution to adjust the pH to 8, heat to 80°C, add 4 g of 2,3-epoxypropyltrimethylammonium chloride isopropanol solution, wherein the mass fraction of 2,3-epoxypropyltrimethylammonium chloride in the isopropanol solution is 50%, stir and react for 4 h, add anhydrous ethanol to precipitate, filter, and dry the filter cake to obtain quaternary ammonium salt chitosan; Step 3: Prepare 200 mL of a mixed solution of N,N-dimethylformamide and water, wherein the volume percentage of water accounts for 20% of the total volume of the mixed solution; Step 4: Add 7g of modified nano-TiO2 prepared in step 1 and 3g of quaternary ammonium chitosan prepared in step 2 to the mixed solution obtained in step 3, and drop 20mL of N,N-dimethylformamide solution containing 1g of maleic anhydride into the mixed solution, and continue stirring and refluxing for 5h. The reaction temperature does not exceed 45°C. After the reaction is completed, centrifuge, wash and dry to obtain quaternary ammonium chitosan modified nano-TiO2 composite particles.

[0018] Example 1 An antibacterial plastic is composed of the following raw materials in parts by weight: 100 parts of polypropylene resin, 3 parts of the composite antibacterial agent obtained in Preparation Example 1, 1 part of stearic acid, 1 part of antioxidant 1010, 1 part of antioxidant 168, and 0.2 parts of dibenzoyl peroxide; The preparation process of antibacterial plastic material is as follows: According to the ratio, 100 parts of polypropylene resin, 3 parts of the composite antibacterial agent obtained in Preparation Example 1, 1 part of stearic acid, 1 part of antioxidant 1010, 1 part of antioxidant 168, and 0.2 part of initiator dibenzoyl peroxide are put into a high-speed mixer and mixed for 20 minutes. The speed is maintained at 800 rpm to make the materials evenly dispersed. After the materials are evenly mixed, the materials are discharged and cooled. The cooled mixed material is sent to a twin-screw extruder for melt extrusion to obtain a strip material. The extruded strip material is cooled in a water tank, pulled into a pelletizer for granulation, and dried to obtain a polypropylene antibacterial plastic. In the preparation process, the temperature of the first zone of the twin-screw extruder is controlled to be 155°C, the temperature of the second zone is 175°C, the temperature of the third zone is 185°C, the temperature of the fourth zone is 205°C, the temperature of the fifth zone is 205°C, and the temperature of the sixth zone is 195°C.

[0019] Example 2 An antibacterial plastic, composed of the following raw materials in parts by weight: 100 parts of polypropylene resin, 5 parts of the composite antibacterial agent obtained in Preparation Example 1, 2 parts of polyethylene wax, 1 part of antioxidant 1076, 1 part of antioxidant 168, and 0.1 part of methyl ethyl ketone peroxide; The preparation process of antibacterial plastic material is as follows: According to the ratio, 100 parts of polypropylene resin, 5 parts of the composite antibacterial agent obtained in Preparation Example 1, 2 parts of polyethylene wax, 2 parts of antioxidant 1076, 1 part of antioxidant 168, and 0.1 part of initiator methyl ethyl ketone peroxide were put into a high-speed mixer and mixed for 15 minutes. The speed was kept at 700 rpm to make the materials evenly dispersed. After the materials were evenly mixed, the materials were discharged and cooled. The cooled mixed material was sent to a twin-screw extruder for melt extrusion to obtain a strip material. The extruded strip material was cooled in a water tank, pulled into a pelletizer for granulation, and dried to obtain a polypropylene antibacterial plastic. In the preparation process, the temperature of the first zone of the twin-screw extruder was controlled to be 160°C, the temperature of the second zone was 180°C, the temperature of the third zone was 185°C, the temperature of the fourth zone was 210°C, the temperature of the fifth zone was 205°C, and the temperature of the sixth zone was 195°C.

[0020] Example 3 An antibacterial plastic, composed of the following raw materials in parts by weight: 100 parts of polypropylene resin, 8 parts of the composite antibacterial agent obtained in Preparation Example 1, 2 parts of liquid paraffin, 1 part of antioxidant 1076, 1 part of antioxidant 168, and 0.3 parts of methyl ethyl ketone peroxide; The preparation process of antibacterial plastic material is as follows: According to the ratio, 100 parts of polypropylene resin, 8 parts of the composite antibacterial agent obtained in Preparation Example 1, 2 parts of liquid paraffin, 1 part of antioxidant 1076, 1 part of antioxidant 168, and 0.3 parts of initiator methyl ethyl ketone peroxide are put into a high-speed mixer and mixed for 15 minutes. The speed is maintained at 800 rpm to make the materials evenly dispersed. After the materials are evenly mixed, the materials are discharged and cooled. The cooled mixed material is sent to a twin-screw extruder for melt extrusion to obtain a strip material. The extruded strip material is cooled in a water tank, pulled into a pelletizer for granulation, and dried to obtain a polypropylene antibacterial plastic. In the preparation process, the temperature of the first zone of the twin-screw extruder is controlled to be 165°C, the temperature of the second zone is 185°C, the temperature of the third zone is 185°C, the temperature of the fourth zone is 210°C, the temperature of the fifth zone is 205°C, and the temperature of the sixth zone is 195°C.

[0021] Comparative Example 1 An antibacterial plastic is composed of the following raw materials in parts by weight: 100 parts of polypropylene resin, 3 parts of unmodified nano-TiO2 with a median particle size D50 of 30 nm, 1 part of stearic acid, 1 part of antioxidant 1010, 1 part of antioxidant 168, and 0.2 part of dibenzoyl peroxide; The preparation process of antibacterial plastic material is as follows: According to the ratio, 100 parts of polypropylene resin, 3 parts of unmodified nano-TiO2 with a median particle size D50 of 30 nm, 1 part of stearic acid, 1 part of antioxidant 1010, 1 part of antioxidant 168, and 0.2 parts of initiator dibenzoyl peroxide are put into a high-speed mixer and mixed for 20 minutes. The rotation speed is maintained at 800 rpm to make the materials evenly dispersed. After the materials are evenly mixed, the materials are discharged and cooled. The cooled mixed material is sent to a twin-screw extruder for melt extrusion to obtain a strip material. The extruded strip material is cooled in a water tank, pulled into a pelletizer for granulation, and dried to obtain a polypropylene antibacterial plastic. In the preparation process, the temperature of the first zone of the twin-screw extruder is controlled to be 155° C., the temperature of the second zone is 175° C., the temperature of the third zone is 185° C., the temperature of the fourth zone is 205° C., the temperature of the fifth zone is 205° C., and the temperature of the sixth zone is 195° C.

[0022] Comparative Example 2 An antibacterial plastic is composed of the following raw materials in parts by weight: 100 parts of polypropylene resin, 3 parts of quaternary ammonium salt chitosan obtained in step 2 of Preparation Example 1, 1 part of stearic acid, 1 part of antioxidant 1010, 1 part of antioxidant 168, and 0.2 parts of dibenzoyl peroxide; The preparation process of antibacterial plastic material is as follows: According to the ratio, 100 parts of polypropylene resin, 3 parts of quaternary ammonium salt chitosan obtained in step 2 of Preparation Example 1, 1 part of stearic acid, 1 part of antioxidant 1010, 1 part of antioxidant 168, and 0.2 part of initiator dibenzoyl peroxide are put into a high-speed mixer and mixed for 20 minutes. The speed is maintained at 800 rpm to make the materials evenly dispersed. After the materials are evenly mixed, the materials are discharged and cooled. The cooled mixture is sent to a twin-screw extruder for melt extrusion to obtain a strip material. The extruded strip material is cooled in a water tank, pulled into a pelletizer for granulation, and dried to obtain a polypropylene antibacterial plastic. In the preparation process, the temperature of the first zone of the twin-screw extruder is controlled to be 155°C, the temperature of the second zone is 175°C, the temperature of the third zone is 185°C, the temperature of the fourth zone is 205°C, the temperature of the fifth zone is 205°C, and the temperature of the sixth zone is 195°C.

[0023] Comparative Example 3 An antibacterial plastic is composed of the following raw materials in parts by weight: 100 parts of polypropylene resin, 2.1 parts of unmodified nano-TiO2 with a median particle size D50 of 30 nm, 0.9 parts of quaternary ammonium salt chitosan obtained in step 2 of Preparation Example 1, 1 part of stearic acid, 1 part of antioxidant 1010, 1 part of antioxidant 168, and 0.2 parts of dibenzoyl peroxide; The preparation process of antibacterial plastic material is as follows: According to the ratio, 100 parts of polypropylene resin, 2.1 parts of unmodified nano-TiO2 with a median particle size D50 of 30 nm, 0.9 parts of quaternary ammonium salt chitosan obtained in step 2 of Preparation Example 1, 1 part of stearic acid, 1 part of antioxidant 1010, 1 part of antioxidant 168, and 0.2 parts of initiator dibenzoyl peroxide are put into a high-speed mixer and mixed for 20 minutes. The speed is maintained at 800 rpm to make the materials evenly dispersed. After the materials are evenly mixed, the discharging is cooled, and the cooled mixture is sent to a twin-screw extruder for melt extrusion to obtain a strip material. The extruded strip material is cooled in a water tank, pulled into a pelletizer for granulation, and dried to obtain a polypropylene antibacterial plastic. In the preparation process, the temperature of the first zone of the twin-screw extruder is controlled to be 155°C, the temperature of the second zone is 175°C, the temperature of the third zone is 185°C, the temperature of the fourth zone is 205°C, the temperature of the fifth zone is 205°C, and the temperature of the sixth zone is 195°C.

[0024] Test Example 1 The antibacterial plastics prepared in Examples 1-3 and Comparative Examples 1-3 were injection molded into test samples using a horizontal injection molding machine, and then relevant performance tests were performed on each test sample. The test methods for the various properties of antibacterial plastic materials are as follows: Test tensile strength according to ASTM D-638 standard; Test flexural strength and flexural modulus according to ASTM D-790; Notched impact performance test according to ASTM D-256 standard; The specific test results are shown in Table 1 below: Table 1 Mechanical properties test results

[0025] Test Example 2 The antibacterial performance test was conducted on the antibacterial plastic material test samples prepared in Examples 1-3 and Comparative Examples 1-3. The specific antibacterial performance test method was based on GB / T 31402-2015, and the antibacterial rate of each test sample was examined. The specific test results are shown in Table 2 below: Table 2: Inhibition rate against Staphylococcus aureus and Escherichia coli (%)

[0026] According to the experimental results in Table 1 and Table 2, the antibacterial polypropylene plastics prepared in Examples 1-3 of the present application are superior to those in Comparative Examples 1-3 in terms of antibacterial properties and mechanical properties. The antibacterial polypropylene plastics prepared in the present invention combine the advantages and disadvantages of organic antibacterial agents and inorganic antibacterial agents. By chemically modifying the inorganic antibacterial agents and the organic antibacterial agents, the prepared composite antibacterial agent has the durability of the inorganic antibacterial agent and the high efficiency of the organic antibacterial agent.

[0027] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the defined scope, they should all fall within the protection scope of the present invention.

Claims

1. An antibacterial plastic material, characterized in that: The raw materials are composed of the following components according to weight: 100 parts of polypropylene resin, 3-5 parts of composite antibacterial agent, 1-2 parts of dispersant, 2-3 parts of antioxidant, and 0.1-0.3 parts of initiator; The composite antibacterial agent is a quaternary ammonium salt chitosan modified nano-TiO2 composite particle, and its preparation process is as follows: Step 1: Add nano-TiO2 with a median particle size D50 of 10-50nm to 100-300mL of 95% ethanol aqueous solution for ultrasonic dispersion. After the ultrasonic dispersion, add aminosilane coupling agent and triethylamine under magnetic stirring, stir at 70-80°C, reflux reaction for 7-8h, cool to room temperature after the reaction, filter in turn, wash repeatedly with toluene and ethanol, and then dry in an oven to obtain modified nano-TiO2; Step 2: dissolve chitosan in 100-200 mL of 2% acetic acid aqueous solution, add sodium hydroxide solution to adjust the pH to 8-9, heat to 80°C, add isopropanol solution of 2,3-epoxypropyltrimethylammonium chloride, stir to react for 3-5h, add anhydrous ethanol to precipitate, filter, and dry the filter cake to obtain quaternary ammonium salt chitosan; Step 3: Prepare 200-500 mL of a mixed solution of N,N-dimethylformamide and water, wherein the volume percentage of water does not exceed 50% of the total volume of the solution; Step 4: Add the modified nano-TiO2 prepared in step 1 and the quaternary ammonium salt chitosan prepared in step 2 to the mixed solution prepared in step 3, and drop 10-30mL of N,N-dimethylformamide solution containing maleic anhydride into the mixed solution, and continue stirring and refluxing for 4-6h. The reaction temperature does not exceed 45°C. After the reaction is completed, centrifuge, wash, and dry to obtain quaternary ammonium salt chitosan modified nano-TiO2 composite particles.

2. The antibacterial plastic material according to claim 1, characterized in that: The dispersant is selected from: stearic acid, polyethylene wax, liquid paraffin, one or a combination of two or more thereof.

3. The antibacterial plastic material according to claim 1, characterized in that: The antioxidant is selected from: a combination of antioxidant 1010 and antioxidant 168 in a usage ratio of 1:

1.

4. The antibacterial plastic material according to claim 1, characterized in that: The initiator is selected from: dibenzoyl peroxide, methyl ethyl ketone peroxide, or a combination of the two.

5. The antibacterial plastic material according to claim 1, characterized in that: In the step 1, the mass ratio of the nano-TiO2, aminosilane coupling agent and triethylamine is 3-6:5-10:

1.

6. The antibacterial plastic material according to claim 1, characterized in that: In the step 2, the mass ratio of the chitosan to 2,3-epoxypropyltrimethylammonium chloride is 5-6:1-3.

7. The antibacterial plastic material according to claim 1, characterized in that: In the step 4, the mass ratio of the modified nano-TiO2, quaternary ammonium salt chitosan and maleic anhydride is 7-8:2-3:

1.

8. The process for preparing the antibacterial plastic material according to any one of claims 1 to 7, characterized in that: The preparation process of the antibacterial plastic material is as follows: 100 parts of polypropylene resin, 3-8 parts of composite antibacterial agent, 1-2 parts of dispersant, 2-3 parts of antioxidant and 0.1-0.3 parts of initiator are put into a high-speed mixer according to the proportion, and mixed at a rotation speed of 600-800rpm for 10-30min to make the materials dispersed evenly, and the materials are discharged and cooled after being evenly mixed, and the cooled mixed materials are sent to a twin-screw extruder for melt extrusion to obtain a strip material, and the extruded strip material is cooled in a water tank, pulled into a pelletizer for granulation, and dried to obtain a polypropylene antibacterial plastic.

9. The process for preparing an antibacterial plastic material according to claim 8, characterized in that: The temperature of zone 1 of the twin-screw extruder is 155-165°C, the temperature of zone 2 is 175-185°C, the temperature of zone 3 is 185-195°C, the temperature of zone 4 is 205-215°C, the temperature of zone 5 is 205-215°C, and the temperature of zone 6 is 195-205°C.

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