Antibacterial degradable plastic as well as preparation method and application thereof

Abstract

The invention discloses an antibacterial degradable plastic and a preparation method and application thereof, and belongs to the technical field of antibacterial degradable plastics, the method comprises the following steps: preparing raw materials to prepare an outer-layer antibacterial binding agent and an inner-layer antibacterial binding agent; preparing the degradable resin, the compatibilizing compatilizer, the reinforcing filler, the plasticizer and the lubricant to prepare a matrix; melting the matrix master batch, uniformly dividing the matrix master batch into a plurality of parts, adding different amounts of the outer-layer antibacterial binding agent and the inner-layer antibacterial binding agent, measuring a melting point change curve of the inner-layer master batch under different addition amounts, and establishing a melting point prediction model to obtain the addition amounts of the outer-layer antibacterial binding agent and the inner-layer antibacterial binding agent so as to prepare an outer-layer master batch and an inner-layer master batch; double antibacterial protection is achieved through the design of differentiated inner and outer layer antibacterial binders, the base body adopts PLA and PBAT blended resin to guarantee degradability, the processing temperature is accurately matched by means of a melting point prediction model, the product layering and flow line defects are avoided, the antibacterial effect, the environmental protection performance and the production stability are improved, and the production cost is reduced. The efficient large-scale production of the antibacterial degradable plastic is realized.

Description

Technical Field

[0001] This invention relates to the field of antibacterial biodegradable plastics technology, and more specifically, to an antibacterial biodegradable plastic, its preparation method, and its application. Background Technology

[0002] Disposable plastic cups are widely used in catering and food packaging due to their convenience. However, traditional disposable plastic cups are mostly made of non-degradable materials, which easily lead to white pollution after use, seriously damaging the ecological environment and failing to meet the trend of environmental protection. At the same time, traditional plastic cups lack effective antibacterial design. During use, the surface of the cup can easily absorb external microorganisms, and bacteria may also grow on the internal parts that come into contact with the beverage, posing food safety hazards and failing to meet the hygiene requirements of food contact scenarios.

[0003] Furthermore, most existing antibacterial and biodegradable plastics are single-layer structures with limited antibacterial functions and lack differentiated designs for the inner and outer layers' usage scenarios, resulting in insufficient antibacterial effects and practicality. Therefore, developing a disposable plastic cup manufacturing technology that combines differentiated antibacterial functions, environmentally friendly biodegradability, and processing adaptability has become an urgent problem for the industry to solve.

[0004] No effective solutions have yet been proposed to address the problems in the relevant technologies. Summary of the Invention

[0005] To address the problems in related technologies, this invention proposes an antibacterial biodegradable plastic, its preparation method, and its application, in order to overcome the technical problems of limited antibacterial function and difficulty in accurately controlling the melting point matching of inner and outer layers in multi-layer co-extrusion processing.

[0006] Therefore, the specific technical solution adopted by the present invention is as follows: A method for preparing an antibacterial biodegradable plastic, the method comprising the following steps: S1. Prepare raw materials to prepare the outer layer antibacterial binder and the inner layer antibacterial binder; S2. Prepare a matrix by combining biodegradable resin, compatibilizer, reinforcing filler, plasticizer, and lubricant; S3. Melt the matrix masterbatch and divide it into multiple portions. Add different amounts of outer layer antibacterial binder and inner layer antibacterial binder. At the same time, measure the melting point change curve of the inner layer masterbatch under different addition amounts, and establish a melting point prediction model to obtain the addition amount of outer layer antibacterial binder and inner layer antibacterial binder to make outer layer masterbatch and inner layer masterbatch.

[0007] In a preferred embodiment, the preparation of raw materials for the outer and inner antibacterial binders includes the following steps: S11. Prepare an outer antibacterial binder by ethylene-tetrafluoroethylene copolymer, 2,3,4-trifluorostyrene, 1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide salt, 4-vinylbenzocyclobutenone, and polyhexamethylene biguanide hydrochloride. S12. Prepare sulfur-selenium doped carbon dots, helimycin, chitosan quaternary ammonium salt, and ε-polylysine to form an inner antibacterial binder.

[0008] In a preferred embodiment, the preparation of the outer antibacterial binder from ethylene-tetrafluoroethylene copolymer, 2,3,4-trifluorostyrene, 1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide salt, 4-vinylbenzocyclobutenone, and compound functional additives includes the following steps: S111. Evacuate the reactor and fill it with high-purity argon gas. Repeat the replacement three times to completely remove oxygen and water vapor from the system. Then add the ethylene-tetrafluoroethylene copolymer matrix resin to the reactor and slowly heat it to 265-285°C to fully melt it into a homogeneous liquid phase. S112, followed by 2,3,4-trifluorostyrene, 1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide salt and 4-vinylbenzocyclobutenone, while controlling the feeding rate and maintaining the temperature at a certain shear rate for 15-25 minutes, so that each monomer can achieve preliminary physical dispersion and pre-crosslinking in the molten ethylene-tetrafluoroethylene copolymer matrix resin. S113, then add polyhexamethylene biguanide hydrochloride, continue stirring and keep warm for 30-45 minutes; During stirring, the fluorination and crosslinking of 2,3,4-trifluorostyrene and the thermal crosslinking of 4-vinylbenzocyclobutenone proceed fully, forming a stable three-dimensional network structure in synergy with the ethylene-tetrafluoroethylene copolymer matrix. S144. After the reaction is complete, stop heating, extrude the molten blend into strips through a die, cool and solidify it in a water tank, and then cut and granulate it through a pelletizer to obtain the outer antibacterial binder particles.

[0009] In a preferred embodiment, the preparation of the inner antibacterial binder consisting of sulfur-selenium-doped carbon dots, hailomycin, chitosan quaternary ammonium salt, and ε-polylysine includes the following steps: S121. Add sulfur-selenium doped carbon dots to deionized water at 10-20 times their dry weight, and sonicate them in an ultrasonic cell disruptor at 200-500W power for 30-60 minutes to obtain a sulfur-selenium doped carbon dot dispersion. S122. Add helimycin powder to the sulfur-selenium-doped carbon dot dispersion, heat it in a water bath at 40-60°C on a magnetic stirrer and stir at a uniform speed, then add chitosan quaternary ammonium salt, and simultaneously add dilute acetic acid dropwise to adjust the pH to 5.0-6.0. Continue stirring for 2-4 hours to completely dissolve the chitosan quaternary ammonium salt and combine it with other components through electrostatic interaction and hydrogen bonding to form a viscous homogeneous solution. S123. Add ε-polylysine and stir at room temperature in the dark for 1-2 hours to fully disperse it and exert a synergistic effect. Then adjust the pH to neutral and filter it through a 0.22μm microporous membrane to remove bacteria, and obtain the inner layer antibacterial binder liquid.

[0010] In a preferred embodiment, the preparation of the matrix from the biodegradable resin, compatibilizer, reinforcing filler, plasticizer, and lubricant includes the following steps: S21. The biodegradable resin, compatibilizer, reinforcing filler, plasticizer and lubricant are vacuum dried at 80°C for 4-6 hours to completely remove moisture, and then accurately weighed according to the determined mass ratio for later use. S22. Add the dried raw materials of each component into a high-speed mixer, set the speed to 200-400 rpm and mix for 3-5 minutes; Preliminary physical mixing of resin particles, powdered fillers, and liquid additives can establish a homogeneous material base for subsequent melt blending. S23. Increase the mixer speed to 800-1200 rpm and continue mixing for 8-15 minutes. Use high-speed shear force to fully disperse the components with different specific gravities and adhere them to the surface of the resin particles to form a premix with a uniform appearance. S24. The uniformly mixed premixed material is melt-blended through a twin-screw extruder, with the temperature of each section controlled within a precise range of 155-180℃. After being conveyed, sheared, and mixed by the screw, it is extruded into strips through the die head, cooled and solidified in a water tank, and finally cut into uniform matrix masterbatch products by a pelletizer.

[0011] In a preferred embodiment, the process of melting the matrix masterbatch, dividing it into multiple portions, adding different amounts of outer and inner antibacterial binders, simultaneously measuring the melting point change curves of the inner masterbatch under different addition amounts, and establishing a melting point prediction model to obtain the addition amounts of outer and inner antibacterial binders to produce outer and inner masterbatches includes the following steps: S31. The matrix masterbatch is fed into a twin-screw extruder for remelting and plasticizing. The outer antibacterial binder and inner antibacterial binder with different mass fractions are added through a side feeding system. After melt blending, the mixture is extruded and granulated to prepare a series of masterbatch samples with gradient distribution of antibacterial agent content. S32. Use a differential scanning calorimeter to perform thermal analysis tests on the masterbatch samples and record the exact melting point data of each sample; S33. The experimental data were fitted using the least squares method to establish a melting point prediction model and obtain the optimal amount of antibacterial binder.

[0012] In a preferred embodiment, the step of fitting the experimental data using the least squares method to establish a melting point prediction model and obtaining the optimal addition amount of the antibacterial binder includes the following steps: S331. For the outer and inner layer masterbatches, the melting point of each of the prepared outer layer antibacterial binder and inner layer antibacterial binder addition amounts of 0%, 2%, 4%, 6%, and 8% was accurately determined using a differential scanning calorimeter. S332. The outer layer masterbatch melting point prediction model is as follows: The inner layer masterbatch melting point prediction model is as follows: ; S334. The amount of inner layer antibacterial binder added is determined to be 10 parts, and its predicted melting point is calculated to be 160.0°C. Based on the requirements of the co-extrusion process for melting point matching, i.e., the allowable temperature difference ΔT≤3°C, the target melting point of the outer layer masterbatch is calculated to be between 157.0°C and 163.0°C. Finally, it is substituted into the melting point prediction model of the outer layer masterbatch to solve for the matching amount of outer layer antibacterial binder added to be 6.1 parts. S335. The calculated ratio of 10 parts inner layer and 6.1 parts outer layer is used for small-batch trial production, and the actual melting point is measured again by DSC to verify that the temperature difference is less than 3°C. This optimal ratio is then put into large-scale production to ensure that the final outer layer masterbatch and inner layer masterbatch are matched in terms of antibacterial properties and processing temperature.

[0013] In a preferred embodiment, the raw materials for the inner layer masterbatch and the outer layer masterbatch include: The raw materials for the inner layer masterbatch include a matrix made of biodegradable resin, compatibilizer, reinforcing filler, plasticizer, and lubricant, and an inner layer antibacterial binder. The biodegradable resin is a blend of PLA and PBAT, the compatibilizer is a maleic anhydride graft polymer, the reinforcing filler is nano-silica, the plasticizer is tributyl acetylacetate, and the lubricant is zinc stearate. The addition amounts of each raw material are as follows: 75.2 parts of biodegradable resin, 4.6 parts of compatibilizer, 8.3 parts of nano-silica, 5.2 parts of tributyl acetylacetate, 1.5 parts of zinc stearate, and 10 parts of inner layer antibacterial binder.

[0014] The outer layer masterbatch is made from biodegradable resin, compatibilizer, reinforcing filler, plasticizer, and lubricant to form a matrix, and an outer layer antibacterial binder. The inner layer masterbatch is made from biodegradable resin, compatibilizer, reinforcing filler, plasticizer, and lubricant to form a matrix, and an inner layer antibacterial binder. The biodegradable resin is a blend of PLA and PBAT, the compatibilizer is a maleic anhydride graft polymer, the reinforcing filler is nano-silica, the plasticizer is tributyl acetylacetic acid, and the lubricant is zinc stearate. The addition amounts of each raw material are: 75.2 parts of biodegradable resin, 4.6 parts of compatibilizer, 8.3 parts of nano-silica, 5.2 parts of tributyl acetylacetic acid, 1.5 parts of zinc stearate, and 6.1 parts of outer layer antibacterial binder. The inner antibacterial binder consists of sulfur-selenium doped carbon dots, helimycin, chitosan quaternary ammonium salt, and ε-polylysine. The amount of each raw material added is 50-60 parts of sulfur-selenium doped carbon dots, 80-95 parts of helimycin, 30-60 parts of chitosan quaternary ammonium salt, and 1-3 parts of ε-polylysine. The outer antibacterial binder includes ethylene-tetrafluoroethylene copolymer, 2,3,4-trifluorostyrene, 1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide salt, 4-vinylbenzocyclobutenone, and polyhexamethylene biguanide hydrochloride. The addition amounts of each raw material are 75-85 parts of ethylene-tetrafluoroethylene copolymer, 10-12 parts of 2,3,4-trifluorostyrene, 6-8 parts of 1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide salt, 4-5 parts of 4-vinylbenzocyclobutenone, and 6-12 parts of polyhexamethylene biguanide hydrochloride.

[0015] An antimicrobial biodegradable plastic application, wherein the application employs a method for preparing an antimicrobial biodegradable plastic as described in any of the above claims, comprising the following steps: S1. Vacuum dry the outer layer masterbatch and the inner layer masterbatch at 80°C for 4-6 hours to completely remove moisture. Then, feed them into the outer and inner independent extruder hoppers of the multi-layer co-extrusion blow molding machine, and preheat the temperature of the double-layer composite die head of the co-extrusion blow molding machine to the set range of 155-170°C. S2. Using a dual extruder, the two layers of masterbatch are melted and plasticized into melts with matching viscosity. The two melts are independently transported to a specially designed concentric cylindrical composite die head, where they merge and form a tubular preform in which the inner melt is uniformly wrapped by the outer melt. S3. After the parison reaches the predetermined length, the mold clamping mechanism quickly clamps the parison in the cup-shaped mold cavity. Then, compressed air of 0.3-0.6MPa is injected into the parison through the air blowing needle in the center of the mold head, causing it to expand instantly and stick tightly to the cold inner wall of the mold. The melt then cools and solidifies rapidly to form the double-layer structure of the cup. S4. After the mold is opened, the formed disposable cup product is taken out and the burrs at the mouth and bottom of the cup are removed by an automated trimming device.

[0016] The final product must undergo quality inspections such as wall thickness uniformity, interlayer bonding strength, and sealing performance. Once qualified, it can be stacked, counted, and packaged to complete the entire production process.

[0017] The beneficial effects of this invention are as follows: 1. This invention achieves the core advantages of dual antibacterial protection and precise functional adaptation by using differentiated antibacterial masterbatches for the outer and inner layers of disposable cups. The outer antibacterial binder uses ethylene-tetrafluoroethylene copolymer as the matrix, combined with components such as polyhexamethylene biguanide hydrochloride, and forms a stable three-dimensional network structure through fluorination and thermal crosslinking. It exhibits an antibacterial rate exceeding 99% against Escherichia coli and Staphylococcus aureus, directly resisting microbial contamination from the external environment and ensuring the cleanliness of the cup surface. The inner antibacterial binder is composed of sulfur-selenium-doped carbon dots, hydatid, and other components, forming a homogeneous system through electrostatic interaction and hydrogen bonding. The inhibition zone diameter is ≥10mm, effectively inhibiting bacteria that may grow inside the cup when in contact with beverages, preventing secondary contamination. Simultaneously, the masterbatch matrix uses a blend of PLA and PBAT biodegradable resin, combined with environmentally friendly additives such as nano-silica. The finished product is naturally degradable after use, reducing white pollution caused by traditional plastic cups from the source, thus balancing hygiene and safety requirements in food contact scenarios with environmental protection needs. 2. This invention, through systematic research on the melting point variation patterns of two masterbatches and the establishment of a predictive model, provides precise temperature adaptation for multi-layer co-extrusion blow molding processes, significantly improving product processing stability and quality consistency. The melting point prediction model for the outer and inner masterbatches accurately calculates melting point data under different antibacterial agent addition amounts. Based on this, a ratio of 10 parts inner layer and 6.1 parts outer layer antibacterial agent is determined, resulting in a measured melting point difference of only 2.3℃, meeting the process requirement of ΔT≤3℃. This temperature matching effectively avoids defects such as delamination and flow lines caused by excessive temperature differences between the inner and outer melts during blow molding, ensuring perfect fusion of the two melt layers within the die, forming a double-layer structure with strong interlayer bonding and uniform wall thickness. Simultaneously, the defined temperature parameters allow for precise control of die preheating and melt plasticization in the co-extrusion blow molding machine, reducing the scrap rate during production, improving large-scale production efficiency, and ultimately ensuring that disposable cups possess both stable physical properties and a reliable user experience. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1This is a flowchart of a method for preparing an antibacterial biodegradable plastic according to an embodiment of the present invention. Detailed Implementation

[0020] To further illustrate the various embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. These drawings are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these drawings, those skilled in the art should be able to understand other possible implementation methods and the advantages of the present invention. The components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0021] According to embodiments of the present invention, an antibacterial biodegradable plastic, its preparation method, and its application are provided.

[0022] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments, such as... Figure 1 As shown, according to an embodiment of the present invention, a method for preparing an antibacterial biodegradable plastic includes the following steps: S1. Prepare raw materials to prepare the outer layer antibacterial binder and the inner layer antibacterial binder; Further, in S11, an outer antibacterial binder is prepared by using ethylene-tetrafluoroethylene copolymer, 2,3,4-trifluorostyrene, 1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide salt, 4-vinylbenzocyclobutenone, and polyhexamethylene biguanide hydrochloride. The preparation of the outer antibacterial binder using ethylene-tetrafluoroethylene copolymer, 2,3,4-trifluorostyrene, 1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide salt, 4-vinylbenzocyclobutenone, and compound functional additives includes the following steps: S111. Evacuate the reactor and fill it with high-purity argon gas. Repeat the replacement three times to completely remove oxygen and water vapor from the system. Then add the ethylene-tetrafluoroethylene copolymer matrix resin to the reactor and slowly heat it to 265-285°C to fully melt it into a homogeneous liquid phase. S112, followed by 2,3,4-trifluorostyrene, 1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide salt and 4-vinylbenzocyclobutenone, while controlling the feeding rate and maintaining the temperature at a certain shear rate for 15-25 minutes, so that each monomer can achieve preliminary physical dispersion and pre-crosslinking in the molten ethylene-tetrafluoroethylene copolymer matrix resin. S113, then add polyhexamethylene biguanide hydrochloride, continue stirring and keep warm for 30-45 minutes; S144. After the reaction is complete, stop heating, extrude the molten blend into strips through a die, cool and solidify it in a water tank, and then cut and granulate it through a pelletizer to obtain the outer antibacterial binder particles.

[0023] S12. Prepare sulfur-selenium-doped carbon dots, helimycin, chitosan quaternary ammonium salt, and ε-polylysine to form an inner antibacterial binder. Furthermore, the preparation of the inner antibacterial binder using sulfur-selenium doped carbon dots, hailomycin, chitosan quaternary ammonium salt, and ε-polylysine includes the following steps: S121. Add sulfur-selenium doped carbon dots to deionized water at 10-20 times their dry weight, and sonicate them in an ultrasonic cell disruptor at 200-500W power for 30-60 minutes to obtain a sulfur-selenium doped carbon dot dispersion. S122. Add helimycin powder to the sulfur-selenium-doped carbon dot dispersion, heat it in a water bath at 40-60°C on a magnetic stirrer and stir at a uniform speed, then add chitosan quaternary ammonium salt, and simultaneously add dilute acetic acid dropwise to adjust the pH to 5.0-6.0. Continue stirring for 2-4 hours to completely dissolve the chitosan quaternary ammonium salt and combine it with other components through electrostatic interaction and hydrogen bonding to form a viscous homogeneous solution. S123, add ε-polylysine, and stir at room temperature in the dark for 1-2 hours to fully disperse it and exert a synergistic effect. Then adjust the pH to neutral, filter it through a 0.22μm microporous membrane to remove bacteria, and obtain the inner layer antibacterial binder liquid. S2. Prepare a matrix by combining biodegradable resin, compatibilizer, reinforcing filler, plasticizer, and lubricant; Furthermore, the preparation of the matrix from the biodegradable resin, compatibilizer, reinforcing filler, plasticizer, and lubricant includes the following steps: S21. The biodegradable resin, compatibilizer, reinforcing filler, plasticizer and lubricant are vacuum dried at 80°C for 4-6 hours to completely remove moisture, and then accurately weighed according to the determined mass ratio for later use. S22. Add the dried raw materials of each component into a high-speed mixer, set the speed to 200-400 rpm and mix for 3-5 minutes; S23. Increase the mixer speed to 800-1200 rpm and continue mixing for 8-15 minutes. Use high-speed shear force to fully disperse the components with different specific gravities and adhere them to the surface of the resin particles to form a premix with a uniform appearance. S24. The uniformly mixed premixed material is melt-blended through a twin-screw extruder, with the temperature of each section controlled within a precise range of 155-180℃. After being conveyed, sheared, and mixed by the screw, it is extruded into strips through the die head, cooled and solidified in a water tank, and finally cut into uniform matrix masterbatch products by a pelletizer.

[0024] S3. Melt the matrix masterbatch and divide it into multiple portions. Add different amounts of outer layer antibacterial binder and inner layer antibacterial binder. At the same time, measure the melting point change curve of the inner layer masterbatch under different addition amounts, and establish a melting point prediction model to obtain the addition amount of outer layer antibacterial binder and inner layer antibacterial binder to make outer layer masterbatch and inner layer masterbatch.

[0025] Furthermore, the process of melting the matrix masterbatch and dividing it into multiple portions with different amounts of outer and inner antibacterial binders, while simultaneously measuring the melting point change curves of the inner masterbatch under different addition amounts, and establishing a melting point prediction model to obtain the addition amounts of outer and inner antibacterial binders to produce outer and inner masterbatches includes the following steps: S31. The matrix masterbatch is fed into a twin-screw extruder for remelting and plasticizing. The outer antibacterial binder and inner antibacterial binder with different mass fractions are added through a side feeding system. After melt blending, the mixture is extruded and granulated to prepare a series of masterbatch samples with gradient distribution of antibacterial agent content. S32. Use a differential scanning calorimeter to perform thermal analysis tests on the masterbatch samples and record the exact melting point data of each sample; S33. The experimental data were fitted using the least squares method to establish a melting point prediction model and obtain the optimal amount of antibacterial binder. Furthermore, the process of fitting the experimental data using the least squares method to establish a melting point prediction model and obtaining the optimal addition amount of the antibacterial binder includes the following steps: S331. For the outer and inner layer masterbatches, the melting point of each of the prepared outer layer antibacterial binder and inner layer antibacterial binder addition amounts of 0%, 2%, 4%, 6%, and 8% was accurately determined using a differential scanning calorimeter. It should be noted that the experimental data for the outer masterbatch are shown in Table 1 below: Table 1 The experimental data for the inner layer masterbatch are shown in Table 2 below: Table 2 S332. The outer layer masterbatch melting point prediction model is as follows: The inner layer masterbatch melting point prediction model is as follows: ; S334. The amount of inner layer antibacterial binder added is determined to be 10 parts, and its predicted melting point is calculated to be 160.0°C. Based on the requirements of the co-extrusion process for melting point matching, i.e., the allowable temperature difference ΔT≤3°C, the target melting point of the outer layer masterbatch is calculated to be between 157.0°C and 163.0°C. Finally, it is substituted into the melting point prediction model of the outer layer masterbatch to solve for the matching amount of outer layer antibacterial binder added to be 6.1 parts. S335. The calculated ratio of 10 parts inner layer and 6.1 parts outer layer is used for small-batch trial production, and the actual melting point is measured again by DSC to verify that the temperature difference is less than 3°C. This optimal ratio is then put into large-scale production to ensure that the final outer layer masterbatch and inner layer masterbatch are matched in terms of antibacterial properties and processing temperature.

[0026] It should be noted that the key performance test results of the small-batch trial masterbatch are shown in Table 3 below: Table 3 According to the experimental results, the measured melting point difference between the inner and outer masterbatches was 2.3°C, which meets the process requirement of less than 3°C. This proves that the two have good processing compatibility in the multi-layer co-extrusion blow molding process, which can effectively avoid delamination or flow defects caused by temperature mismatch. At the same time, the antibacterial function meets the standard: the antibacterial rate of the outer masterbatch exceeds 99%, and the inner masterbatch also shows an obvious inhibition zone, both of which meet the preset antibacterial standard, proving that its functional effectiveness meets the design expectations.

[0027] Therefore, based on the above small-scale test results, it is confirmed that the ratio of 10 parts of inner layer antibacterial binder and 6.1 parts of outer layer is reliable; Furthermore, the raw materials for the inner layer masterbatch and the outer layer masterbatch include: The raw materials for the inner layer masterbatch include a matrix made of biodegradable resin, compatibilizer, reinforcing filler, plasticizer, and lubricant, and an inner layer antibacterial binder. The biodegradable resin is a blend of PLA and PBAT, the compatibilizer is a maleic anhydride graft polymer, the reinforcing filler is nano-silica, the plasticizer is tributyl acetylacetate, and the lubricant is zinc stearate. The addition amounts of each raw material are as follows: 75.2 parts of biodegradable resin, 4.6 parts of compatibilizer, 8.3 parts of nano-silica, 5.2 parts of tributyl acetylacetate, 1.5 parts of zinc stearate, and 10 parts of inner layer antibacterial binder.

[0028] The outer layer masterbatch is made from biodegradable resin, compatibilizer, reinforcing filler, plasticizer, and lubricant to form a matrix, and an outer layer antibacterial binder. The inner layer masterbatch is made from biodegradable resin, compatibilizer, reinforcing filler, plasticizer, and lubricant to form a matrix, and an inner layer antibacterial binder. The biodegradable resin is a blend of PLA and PBAT, the compatibilizer is a maleic anhydride graft polymer, the reinforcing filler is nano-silica, the plasticizer is tributyl acetylacetic acid, and the lubricant is zinc stearate. The addition amounts of each raw material are: 75.2 parts of biodegradable resin, 4.6 parts of compatibilizer, 8.3 parts of nano-silica, 5.2 parts of tributyl acetylacetic acid, 1.5 parts of zinc stearate, and 6.1 parts of outer layer antibacterial binder. The inner antibacterial binder consists of sulfur-selenium doped carbon dots, helimycin, chitosan quaternary ammonium salt, and ε-polylysine. The amount of each raw material added is 50-60 parts of sulfur-selenium doped carbon dots, 80-95 parts of helimycin, 30-60 parts of chitosan quaternary ammonium salt, and 1-3 parts of ε-polylysine. The outer antibacterial binder includes ethylene-tetrafluoroethylene copolymer, 2,3,4-trifluorostyrene, 1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide salt, 4-vinylbenzocyclobutenone, and polyhexamethylene biguanide hydrochloride. The addition amounts of each raw material are 75-85 parts of ethylene-tetrafluoroethylene copolymer, 10-12 parts of 2,3,4-trifluorostyrene, 6-8 parts of 1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide salt, 4-5 parts of 4-vinylbenzocyclobutenone, and 6-12 parts of polyhexamethylene biguanide hydrochloride. An antimicrobial biodegradable plastic application, wherein the application employs a method for preparing an antimicrobial biodegradable plastic as described in any of the above claims, comprising the following steps: S1. Vacuum dry the outer layer masterbatch and the inner layer masterbatch at 80°C for 4-6 hours to completely remove moisture. Then, feed them into the outer and inner independent extruder hoppers of the multi-layer co-extrusion blow molding machine, and preheat the temperature of the double-layer composite die head of the co-extrusion blow molding machine to the set range of 155-170°C. S2. Using a dual extruder, the two layers of masterbatch are melted and plasticized into melts with matching viscosity. The two melts are independently transported to a specially designed concentric cylindrical composite die head, where they merge and form a tubular preform in which the inner melt is uniformly wrapped by the outer melt. S3. After the parison reaches the predetermined length, the mold clamping mechanism quickly clamps the parison in the cup-shaped mold cavity. Then, compressed air of 0.3-0.6MPa is injected into the parison through the air blowing needle in the center of the mold head, causing it to expand instantly and stick tightly to the cold inner wall of the mold. The melt then cools and solidifies rapidly to form the double-layer structure of the cup. S4. After the mold is opened, the formed disposable cup product is taken out and the burrs at the mouth and bottom of the cup are removed by an automated trimming device.

[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an antibacterial biodegradable plastic, characterized in that, The method includes the following steps: S1. Prepare raw materials to prepare the outer layer antibacterial binder and the inner layer antibacterial binder; S11. Prepare an outer antibacterial binder by ethylene-tetrafluoroethylene copolymer, 2,3,4-trifluorostyrene, 1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide salt, 4-vinylbenzocyclobutenone, and polyhexamethylene biguanide hydrochloride. S12. Prepare sulfur-selenium-doped carbon dots, helimycin, chitosan quaternary ammonium salt, and ε-polylysine to form an inner antibacterial binder. S2. Prepare a matrix by combining biodegradable resin, compatibilizer, reinforcing filler, plasticizer, and lubricant; S3. Melt the matrix masterbatch and divide it into multiple portions. Add different amounts of outer layer antibacterial binder and inner layer antibacterial binder. At the same time, measure the melting point change curve of the inner layer masterbatch under different addition amounts, and establish a melting point prediction model to obtain the addition amount of outer layer antibacterial binder and inner layer antibacterial binder to make outer layer masterbatch and inner layer masterbatch.

2. The method for preparing an antibacterial biodegradable plastic according to claim 1, characterized in that, The preparation of the outer antibacterial binder by combining ethylene-tetrafluoroethylene copolymer, 2,3,4-trifluorostyrene, 1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide salt, 4-vinylbenzocyclobutenone, and compound functional additives includes the following steps: S111. Evacuate the reactor and fill it with high-purity argon gas. Repeat the replacement three times to completely remove oxygen and water vapor from the system. Then add the ethylene-tetrafluoroethylene copolymer matrix resin to the reactor and slowly heat it to 265-285°C to fully melt it into a homogeneous liquid phase. S112, followed by 2,3,4-trifluorostyrene, 1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide salt and 4-vinylbenzocyclobutenone, while controlling the feeding rate and maintaining the temperature at a certain shear rate for 15-25 minutes, so that each monomer can achieve preliminary physical dispersion and pre-crosslinking in the molten ethylene-tetrafluoroethylene copolymer matrix resin. S113, then add polyhexamethylene biguanide hydrochloride, continue stirring and keep warm for 30-45 minutes; S144. After the reaction is complete, stop heating, extrude the molten blend into strips through a die, cool and solidify it in a water tank, and then cut and granulate it through a pelletizer to obtain the outer antibacterial binder particles.

3. The method for preparing an antibacterial biodegradable plastic according to claim 1, characterized in that, The preparation of the inner antibacterial binder by sulfur-selenium doped carbon dots, hailomycin, chitosan quaternary ammonium salt, and ε-polylysine includes the following steps: S121. Add sulfur-selenium doped carbon dots to deionized water at 10-20 times their dry weight, and sonicate them in an ultrasonic cell disruptor at 200-500W power for 30-60 minutes to obtain a sulfur-selenium doped carbon dot dispersion. S122. Add helimycin powder to the sulfur-selenium-doped carbon dot dispersion, heat it in a water bath at 40-60°C on a magnetic stirrer and stir at a uniform speed, then add chitosan quaternary ammonium salt, and simultaneously add dilute acetic acid dropwise to adjust the pH to 5.0-6.

0. Continue stirring for 2-4 hours to completely dissolve the chitosan quaternary ammonium salt and combine it with other components through electrostatic interaction and hydrogen bonding to form a viscous homogeneous solution. S123. Add ε-polylysine and stir at room temperature in the dark for 1-2 hours to fully disperse it and exert a synergistic effect. Then adjust the pH to neutral and filter it through a 0.22μm microporous membrane to remove bacteria, and obtain the inner layer antibacterial binder liquid.

4. The method for preparing an antibacterial biodegradable plastic according to claim 1, characterized in that, The preparation of the matrix from biodegradable resin, compatibilizer, reinforcing filler, plasticizer, and lubricant includes the following steps: S21. The biodegradable resin, compatibilizer, reinforcing filler, plasticizer and lubricant are vacuum dried at 80°C for 4-6 hours to completely remove moisture, and then accurately weighed according to the determined mass ratio for later use. S22. Add the dried raw materials of each component into a high-speed mixer, set the speed to 200-400 rpm and mix for 3-5 minutes; S23. Increase the mixer speed to 800-1200 rpm and continue mixing for 8-15 minutes. Use high-speed shear force to fully disperse the components with different specific gravities and adhere them to the surface of the resin particles to form a premix with a uniform appearance. S24. The uniformly mixed premixed material is melt-blended through a twin-screw extruder, with the temperature of each section controlled within a precise range of 155-180℃. After being conveyed, sheared, and mixed by the screw, it is extruded into strips through the die head, cooled and solidified in a water tank, and finally cut into uniform matrix masterbatch products by a pelletizer.

5. The method for preparing an antibacterial biodegradable plastic according to claim 1, characterized in that, The process of melting the matrix masterbatch, dividing it into multiple portions, adding different amounts of outer and inner antibacterial binders, simultaneously measuring the melting point change curves of the inner masterbatch under different addition amounts, and establishing a melting point prediction model to obtain the addition amounts of outer and inner antibacterial binders to produce outer and inner masterbatches includes the following steps: S31. The matrix masterbatch is fed into a twin-screw extruder for remelting and plasticizing. The outer antibacterial binder and inner antibacterial binder with different mass fractions are added through a side feeding system. After melt blending, the mixture is extruded and granulated to prepare a series of masterbatch samples with gradient distribution of antibacterial agent content. S32. Use a differential scanning calorimeter to perform thermal analysis tests on the masterbatch samples and record the exact melting point data of each sample; S33. The experimental data were fitted using the least squares method to establish a melting point prediction model and obtain the optimal amount of antibacterial binder.

6. The method for preparing an antibacterial biodegradable plastic according to claim 5, characterized in that, The process of fitting experimental data using the least squares method to establish a melting point prediction model and obtain the optimal addition amount of the antibacterial binder includes the following steps: S331. For the outer and inner layer masterbatches, the melting point of each of the prepared outer layer antibacterial binder and inner layer antibacterial binder addition amounts of 0%, 2%, 4%, 6%, and 8% was accurately determined using a differential scanning calorimeter. S332. The outer layer masterbatch melting point prediction model is as follows: The inner layer masterbatch melting point prediction model is as follows: ; S334. The amount of inner layer antibacterial binder added is determined to be 10 parts, and its predicted melting point is calculated to be 160.0°C. Based on the requirements of the co-extrusion process for melting point matching, i.e., the allowable temperature difference ΔT≤3°C, the target melting point of the outer layer masterbatch is calculated to be between 157.0°C and 163.0°C. Finally, it is substituted into the melting point prediction model of the outer layer masterbatch to solve for the matching amount of outer layer antibacterial binder added to be 6.1 parts. S335. The calculated ratio of 10 parts inner layer and 6.1 parts outer layer is used for small-batch trial production, and the actual melting point is measured again by DSC to verify that the temperature difference is less than 3°C. This optimal ratio is then put into large-scale production to ensure that the final outer layer masterbatch and inner layer masterbatch are matched in terms of antibacterial properties and processing temperature.

7. A method for preparing an antibacterial biodegradable plastic according to any one of claims 1-6, characterized in that, The raw materials for the inner and outer masterbatches include: The raw materials for the inner layer masterbatch include a matrix made of biodegradable resin, compatibilizer, reinforcing filler, plasticizer, and lubricant, and an inner layer antibacterial binder. The biodegradable resin is a blend of PLA and PBAT, the compatibilizer is a maleic anhydride graft polymer, the reinforcing filler is nano-silica, the plasticizer is tributyl acetylacetate, and the lubricant is zinc stearate. The addition amounts of each raw material are as follows: 75.2 parts of biodegradable resin, 4.6 parts of compatibilizer, 8.3 parts of nano-silica, 5.2 parts of tributyl acetylacetate, 1.5 parts of zinc stearate, and 10 parts of inner layer antibacterial binder. The outer layer masterbatch is made from biodegradable resin, compatibilizer, reinforcing filler, plasticizer, and lubricant to form a matrix, and an outer layer antibacterial binder. The inner layer masterbatch is made from biodegradable resin, compatibilizer, reinforcing filler, plasticizer, and lubricant to form a matrix, and an inner layer antibacterial binder. The biodegradable resin is a blend of PLA and PBAT, the compatibilizer is a maleic anhydride graft polymer, the reinforcing filler is nano-silica, the plasticizer is tributyl acetylacetic acid, and the lubricant is zinc stearate. The addition amounts of each raw material are: 75.2 parts of biodegradable resin, 4.6 parts of compatibilizer, 8.3 parts of nano-silica, 5.2 parts of tributyl acetylacetic acid, 1.5 parts of zinc stearate, and 6.1 parts of outer layer antibacterial binder. The inner antibacterial binder consists of sulfur-selenium doped carbon dots, helimycin, chitosan quaternary ammonium salt, and ε-polylysine. The amount of each raw material added is 50-60 parts of sulfur-selenium doped carbon dots, 80-95 parts of helimycin, 30-60 parts of chitosan quaternary ammonium salt, and 1-3 parts of ε-polylysine. The outer antibacterial binder includes ethylene-tetrafluoroethylene copolymer, 2,3,4-trifluorostyrene, 1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide salt, 4-vinylbenzocyclobutenone, and polyhexamethylene biguanide hydrochloride. The addition amounts of each raw material are 75-85 parts of ethylene-tetrafluoroethylene copolymer, 10-12 parts of 2,3,4-trifluorostyrene, 6-8 parts of 1-vinyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide salt, 4-5 parts of 4-vinylbenzocyclobutenone, and 6-12 parts of polyhexamethylene biguanide hydrochloride.

8. An application of an antibacterial and biodegradable plastic, characterized in that, This application uses an antibacterial biodegradable plastic as described in any one of claims 1-7, and its preparation method includes the following steps: S1. Vacuum dry the outer layer masterbatch and the inner layer masterbatch at 80°C for 4-6 hours to completely remove moisture. Then, feed them into the outer and inner independent extruder hoppers of the multi-layer co-extrusion blow molding machine, and preheat the temperature of the double-layer composite die head of the co-extrusion blow molding machine to the set range of 155-170°C. S2. Using a dual extruder, the two layers of masterbatch are melted and plasticized into melts with matching viscosity. The two melts are independently transported to a specially designed concentric cylindrical composite die head, where they merge and form a tubular preform in which the inner melt is uniformly wrapped by the outer melt. S3. After the parison reaches the predetermined length, the mold clamping mechanism quickly clamps the parison in the cup-shaped mold cavity. Then, compressed air of 0.3-0.6MPa is injected into the parison through the air blowing needle in the center of the mold head, causing it to expand instantly and stick tightly to the cold inner wall of the mold. The melt then cools and solidifies rapidly to form the double-layer structure of the cup. S4. After the mold is opened, the formed disposable cup product is taken out and the burrs at the mouth and bottom of the cup are removed by an automated trimming device.

Images