Antibacterial plastic for bottle caps and preparation method of antibacterial plastic

Abstract

The invention discloses antibacterial plastic for bottle caps and a preparation method of the antibacterial plastic, and belongs to the technical field of high polymer material production. The antibacterial plastic for the bottle cap, provided by the invention, is prepared from the following raw materials in parts by mass: 70 to 80 parts of improved branched co-polypropylene, 2.0 to 3.0 parts of ZnO and ZrP core-shell powder, 5 to 8 parts of maleic anhydride grafted hydrogenated styrene-butadiene block copolymer, 8 to 12 parts of ethylene-octylene copolymer, 0.3 to 0.5 part of antioxidant 1010 and 0.5 to 1.0 part of calcium stearate. The prepared antibacterial plastic for the bottle cap meets the food contact material standards of European Union EC No 1935 / 2004, China GB 4806.7-2016 and the like, and a high-reliability solution is provided for beverage and medicine packaging.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer material production, and particularly relates to an antibacterial plastic for bottle caps and a preparation method thereof. Background Art

[0002] Plastic bottle caps are widely used in packaging for beverages, pharmaceuticals, and cosmetics. Their direct contact with the contents and prolonged exposure to moisture make them a breeding ground for microbial growth. This is particularly true in cold chain storage and transportation, or in areas with high temperatures and humidity. The growth of pathogens like Escherichia coli and Staphylococcus aureus can lead to product spoilage and even food safety incidents. Developing plastic bottle caps with highly effective antimicrobial properties is crucial for protecting consumer health and extending product shelf life.

[0003] Existing technologies mostly use the method of adding silver, zinc or organic antimicrobial agents (such as triclosan) to give plastics antimicrobial properties. However, the easy migration of silver ions leads to insufficient long-term effectiveness and high costs; the activity of zinc-based antimicrobial agents is greatly reduced in weakly acidic environments; and organic antimicrobial agents have problems such as poor heat resistance (decomposition temperature <200°C) and poor compatibility with plastic matrices. More importantly, when the amount of antimicrobial agent added exceeds 1.5wt%, it will significantly deteriorate the impact toughness of the plastic (decrease by >30%) and melt flow rate (decrease by >15%), resulting in defects such as flash and material shortages during bottle cap injection molding, seriously restricting its industrial application.

[0004] With increasingly stringent antimicrobial requirements for food contact materials (e.g., EU EC No. 1935 / 2004 and China GB4806.7-2016), the industry urgently needs to develop specialized plastics for bottle caps that combine long-lasting antimicrobial properties with excellent processability and mechanical strength. Addressing the compatibility conflict between high-dosage antimicrobial agents and the plastic matrix remains a critical technical bottleneck in this field. Summary of the Invention

[0005] The core problem to be solved by the present invention is: how to avoid a significant decrease in the impact toughness and melt flow rate of the plastic while ensuring that the addition amount of the antibacterial agent is ≥2.0wt%, while achieving broad-spectrum and long-lasting antibacterial properties. To this end, the present invention provides an antibacterial plastic for bottle caps and a preparation method thereof.

[0006] The purpose of the present invention can be achieved through the following technical solutions: An antibacterial plastic for bottle caps, comprising the following raw materials in parts by weight: Improved branched copolymer polypropylene: 70-80 parts; ZnO@ZrP core-shell powder: 2.0-3.0 parts; Maleic anhydride grafted hydrogenated styrene-butadiene block copolymer: 5-8 parts; Ethylene-octene copolymer: 8-12 parts; Antioxidant 1010: 0.3-0.5 parts; Calcium stearate: 0.5-1.0 part.

[0007] Furthermore, the improved branched copolymer polypropylene comprises the following raw materials in parts by weight: Linear copolymer polypropylene: 100 parts; 1,6-Hexanediol diacrylate: 0.3-0.5 parts; Dicumyl peroxide: 0.01 to 0.03 parts.

[0008] Furthermore, the improved branched copolymer polypropylene is prepared by the following steps: The raw materials were weighed in parts by mass, and linear copolymer polypropylene, 1,6-hexanediol diacrylate and diisopropylbenzene peroxide were mixed and added to a high-speed mixer. The mixture was mixed at 800-1000 rpm for 5-10 minutes to obtain a mixture. The mixture was then placed in an extruder. After completion, the extruded material strips were water-cooled and pelletized, and vacuum-dried at 90-100° C. for 5-6 hours to obtain an improved branched copolymer polypropylene.

[0009] Furthermore, the temperature zones of the extruder are: zone 1 155-160°C, zone 2 160-170°C, zone 3 170-175°C, zone 4 175-180°C, zone 5 170-175°C; the screw speed of the extruder is 150-200r / min.

[0010] Furthermore, the ZnO@ZrP core-shell powder includes the following raw materials in parts by weight: Nano zinc oxide: 50 parts; Zirconium phosphate: 20-30 parts; Silane coupling agent KH-550: 1.5 to 2.0 parts.

[0011] Furthermore, the ZnO@ZrP core-shell powder is prepared by the following steps: The raw materials were weighed in parts by mass. First, zirconium phosphate was added to pure water in a mass ratio of 10:1 and stirred at room temperature for 10 to 30 minutes to obtain a zirconium phosphate suspension. Then, nano zinc oxide was added to anhydrous ethanol in a mass ratio of 10:1, and a silane coupling agent KH-550 was added thereto with stirring. After completion, the mixture was ultrasonically treated at 60 to 80°C for 30 minutes to obtain a nano zinc oxide suspension. The zirconium phosphate suspension was then added to the nano zinc oxide suspension, and the pH of the system was adjusted to 4.0 to 4.5 using acetic acid. The system was then heated to 70 to 80°C and stirred at a constant temperature for 2 hours. After completion, the mixture was spray-dried to obtain a ZnO@ZrP core-shell powder.

[0012] Furthermore, a method for preparing an antibacterial plastic for a bottle cap comprises the following steps: The raw materials were weighed in parts by mass, and the improved branched copolymer polypropylene, ZnO@ZrP core-shell powder, maleic anhydride grafted hydrogenated styrene-butadiene block copolymer, ethylene-octene copolymer, antioxidant 1010 and calcium stearate were placed in a high-speed mixer and mixed for 5 to 10 minutes to obtain a mixture. After the mixture was completed, the mixture was placed in a twin-screw extruder for extrusion molding, and the extrudate was then water-cooled and pelletized, and dried at 80 to 100° C. for 4 to 5 hours to obtain an antibacterial plastic for bottle caps.

[0013] Furthermore, the extrusion parameters of the twin-screw extruder are: zone 1 170-180°C, zone 2 180-185°C, zone 3 185-190°C, zone 4 190-195°C, zone 5 195-200°C, die head temperature 200°C, screw speed 200r / min.

[0014] Beneficial effects of the present invention: (1) The present invention solves the contradiction between high addition amount of antimicrobial agent and mechanical / processing properties: In the prior art, when the amount of antimicrobial agent added is greater than 1.5 wt%, the impact toughness decreases by more than 30% and the melt flow rate (MFR) decreases by more than 15%, resulting in injection molding defects.

[0015] The effect of the present invention is verified: Example 8: The antibacterial agent (ZnO@ZrP) is added in an amount of 2.5 parts (≈2.63wt%), and the impact strength reaches 28.3 kJ / m 2 , MFR is 54.8 g / 10min, compared with the basic linear polypropylene (melt index 60g / 10min), MFR only decreased by 8.7% (<15%), and the impact strength was significantly improved (not decreased); Comparative Example 1 (unbranched polypropylene): using ordinary linear polypropylene, the impact strength plummeted to 18.2 kJ / m 2 (a decrease of 36% compared with Example 8), MFR dropped to 46.2 g / 10min (a decrease of 23% compared with the base value); Comparative Example 4 (POE toughening is insufficient): POE dosage is reduced to 5 parts (below the lower limit of 8 parts), and the impact strength is only 19.5 kJ / m 2 , proving that the toughening agent needs to be sufficient to work synergistically.

[0016] Conclusion: The present invention uses the synergistic effect of improved branched polypropylene (toughening) + POE (toughening) + SEBS-g-MAH (compatibilizer) to increase the impact strength (maximum 28.3 kJ / m) instead of decreasing when the antibacterial agent addition amount is ≥ 2.0 wt%. 2 ), the MFR decrease rate is ≤8.7%, which proves that the technical solution of the present invention successfully solves the performance degradation problem caused by high addition amount.

[0017] (2) The present invention achieves broad-spectrum and long-lasting antibacterial effect, overcoming the problem of inactivation in acidic environments: In the existing technology, the activity of zinc-based antibacterial agents drops sharply in a weakly acidic environment, and silver-based antibacterial agents are expensive and easy to migrate.

[0018] Verification of the effect of the present invention: Example 8 (core-shell structure ZnO@ZrP): initial antibacterial rate: Escherichia coli 99.8%, Staphylococcus aureus 99.5%, after soaking in an acidic environment (pH = 4.0) for 7 days, the antibacterial rate decayed by only 3.2%; Comparative Example 2 (ordinary ZnO): the initial antibacterial rate dropped sharply (Escherichia coli 85.2%, Staphylococcus aureus 82.7%), and the attenuation rate after acidic soaking was as high as 42.3%; other examples (7, 9): the antibacterial rates were all greater than 98.5%, and the acidic attenuation rate was ≤8.5%, verifying the universality of the formula.

[0019] Conclusion: The core-shell structure ZnO@ZrP (ZrP coated ZnO) prepared by the present invention effectively isolates weak acid corrosion, allowing the antibacterial agent to maintain high activity in an acidic environment (attenuation rate ≤ 5%). The technical solution of the present invention breaks through the environmental limitations of zinc-based antibacterial agents.

[0020] (3) The irreplaceable role of compatibilizers in interfacial bonding: Comparative Example 3 data: impact strength plummets to 16.8 kJ / m 2 (a decrease of 41% compared to Example 8), although the inhibition rate did not decrease significantly (98.8%).

[0021] Analysis: After removing the maleic anhydride grafted SEBS, the compatibility of the inorganic antibacterial powder (ZnO@ZrP) with the polypropylene matrix deteriorated, resulting in a sharp drop in impact toughness, proving that the strengthening effect of SEBS-g-MAH on interfacial bonding is the key to maintaining high toughness.

[0022] Finally, the core beneficial effects of the present invention are summarized as follows: a. High antibacterial and high toughness synergy: When the antibacterial agent addition amount is ≥2.0wt%, the impact strength of the technical solution of the present invention is increased to 28.3kJ / m 2 (+55% compared to the linear polypropylene baseline), MFR reduction rate ≤ 8.7%, breaking the curse of "high addition will lead to deterioration"; b. Long-lasting acid-resistant antibacterial effect: Adding the core-shell structure ZnO@ZrP prepared by the present invention makes the antibacterial decay rate in acidic environment ≤5% (common ZnO>40%); c. Interface strengthening mechanism: SEBS-g-MAH significantly improves the compatibility of inorganic and organic phases (impact strength decreases by 41% without this component); d. Comprehensive performance balance: The antibacterial plastic for bottle caps prepared by the present invention meets food contact material standards such as EU EC No. 1935 / 2004 and China GB 4806.7-2016, providing a high-reliability solution for beverage and pharmaceutical packaging. DETAILED DESCRIPTION

[0023] Below in conjunction with the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, it is obvious that described embodiment is only a part of embodiment of the present invention, rather than whole embodiment. Based on the embodiment in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise all fall within the scope of protection of the present invention. Meanwhile, raw materials, reagents or devices used in the following examples, unless otherwise specified, can be obtained from conventional commercial channels, or can be obtained by existing known methods.

[0024] Example 1

[0025] Preparation of improved branched copolymer polypropylene: First, the improved branched copolymer polypropylene includes the following raw materials in parts by weight: Linear copolymer polypropylene (melt index 60g / 10min, Sinopec K8003): 100 parts; 1,6-Hexanediol diacrylate (HDDA, Aladdin reagent): 0.3 parts; Dicumyl peroxide (DCP, Sinopharm Reagent): 0.01 parts; Then, the preparation steps of the improved branched copolymer polypropylene are: The raw materials were weighed in parts by mass, and linear copolymer polypropylene, 1,6-hexanediol diacrylate and diisopropylbenzene peroxide were mixed and added to a high-speed mixer and mixed at 800 rpm for 5 minutes to obtain a mixture. The mixture was then placed in an extruder. The temperature zones of the extruder were: zone 1 155°C, zone 2 160°C, zone 3 170°C, zone 4 175°C, zone 5 170°C, and the screw speed of the extruder was 150 r / min. After completion, the extruded material strips were water-cooled and pelletized, and vacuum-dried at 90°C for 5 hours to obtain an improved branched copolymer polypropylene.

[0026] Example 2

[0027] Preparation of improved branched copolymer polypropylene: First, the improved branched copolymer polypropylene includes the following raw materials in parts by weight: Linear copolymer polypropylene (melt index 60g / 10min, Sinopec K8003): 100 parts; 1,6-Hexanediol diacrylate (HDDA, Aladdin reagent): 0.45 parts; Dicumyl peroxide (DCP, Sinopharm Reagent): 0.025 parts; Then, the preparation steps of the improved branched copolymer polypropylene are: The raw materials were weighed in parts by mass, and linear copolymer polypropylene, 1,6-hexanediol diacrylate and diisopropylbenzene peroxide were mixed and added to a high-speed mixer. The mixture was mixed at 1000 rpm for 10 minutes to obtain a mixture, and then the mixture was placed in an extruder. The temperature zones of the extruder were: zone 1 160°C, zone 2 165°C, zone 3 170°C, zone 4 175°C, zone 5 170°C, and the screw speed of the extruder was 200 r / min. After completion, the extruded material strips were water-cooled and pelletized, and vacuum-dried at 100°C for 6 hours to obtain an improved branched copolymer polypropylene.

[0028] Example 3

[0029] Preparation of improved branched copolymer polypropylene: First, the improved branched copolymer polypropylene includes the following raw materials in parts by weight: Linear copolymer polypropylene (melt index 60g / 10min, Sinopec K8003): 100 parts; 1,6-Hexanediol diacrylate (HDDA, Aladdin reagent): 0.5 parts; Dicumyl peroxide (DCP, Sinopharm Reagent): 0.03 parts; Then, the preparation steps of the improved branched copolymer polypropylene are: The raw materials were weighed in parts by mass, and linear copolymer polypropylene, 1,6-hexanediol diacrylate and diisopropylbenzene peroxide were mixed and added to a high-speed mixer. The mixture was mixed at 1000 rpm for 10 minutes to obtain a mixture, and then the mixture was placed in an extruder. The temperature zones of the extruder were: zone 1 160°C, zone 2 170°C, zone 3 175°C, zone 4 180°C, zone 5 175°C, and the screw speed of the extruder was 200 r / min. After completion, the extruded material strips were water-cooled and pelletized, and vacuum-dried at 100°C for 6 hours to obtain an improved branched copolymer polypropylene.

[0030] Example 4

[0031] Preparation of ZnO@ZrP core-shell powder: First, the ZnO@ZrP core-shell powder includes the following raw materials in parts by weight: Nano zinc oxide (ZnO, particle size 30 nm, Xuancheng Jingrui New Materials): 50 parts; Zirconium phosphate (ZrP, layered support, Aladdin reagent): 20 parts; Silane coupling agent KH-550 (Nanjing Nengde New Materials): 1.5 parts; Then, the preparation steps of ZnO@ZrP core-shell powder are as follows: The above raw materials were weighed in parts by mass. First, zirconium phosphate was added to pure water in a mass ratio of 10:1 and stirred at room temperature for 10 minutes to obtain a zirconium phosphate suspension. Then, nano zinc oxide was added to anhydrous ethanol in a mass ratio of 10:1, and then a silane coupling agent KH-550 was added thereto with stirring. After completion, ultrasonic treatment was carried out at 60°C for 30 minutes to obtain a nano zinc oxide suspension. Then, zirconium phosphate suspension was added to the nano zinc oxide suspension, and the pH of the system was adjusted to 4.0 with acetic acid. The system was then heated to 70°C and stirred at a constant temperature for 2 hours to allow ZrP to grow in situ on the ZnO surface. After completion, the system was spray dried (inlet 180°C, outlet 80°C) to obtain ZnO@ZrP core-shell powder.

[0032] Example 5

[0033] Preparation of ZnO@ZrP core-shell powder: First, the ZnO@ZrP core-shell powder includes the following raw materials in parts by weight: Nano zinc oxide (ZnO, particle size 30 nm, Xuancheng Jingrui New Materials): 50 parts; Zirconium phosphate (ZrP, layered support, Aladdin reagent): 25 parts; Silane coupling agent KH-550 (Nanjing Nengde New Materials): 2.0 parts; Then, the preparation steps of ZnO@ZrP core-shell powder are as follows: The above raw materials were weighed in parts by mass. First, zirconium phosphate was added to pure water in a mass ratio of 10:1 and stirred at room temperature for 30 minutes to obtain a zirconium phosphate suspension. Then, nano zinc oxide was added to anhydrous ethanol in a mass ratio of 10:1, and a silane coupling agent KH-550 was added thereto with stirring. After completion, the reaction was ultrasonically treated at 80°C for 30 minutes to obtain a nano zinc oxide suspension. The zirconium phosphate suspension was then added to the nano zinc oxide suspension, and the pH of the system was adjusted to 4.2 with acetic acid. The system was then heated to 80°C and stirred at a constant temperature for 2 hours to allow ZrP to grow in situ on the ZnO surface. After completion, the reaction was spray-dried (inlet 180°C, outlet 80°C) to obtain ZnO@ZrP core-shell powder.

[0034] Example 6 Preparation of ZnO@ZrP core-shell powder: First, the ZnO@ZrP core-shell powder includes the following raw materials in parts by weight: Nano zinc oxide (ZnO, particle size 30 nm, Xuancheng Jingrui New Materials): 50 parts; Zirconium phosphate (ZrP, layered support, Aladdin reagent): 30 parts; Silane coupling agent KH-550 (Nanjing Nengde New Materials): 2.0 parts; Then, the preparation steps of ZnO@ZrP core-shell powder are as follows: The above raw materials were weighed in parts by mass. First, zirconium phosphate was added to pure water in a mass ratio of 10:1 and stirred at room temperature for 30 minutes to obtain a zirconium phosphate suspension. Then, nano zinc oxide was added to anhydrous ethanol in a mass ratio of 10:1, and a silane coupling agent KH-550 was added thereto with stirring. After completion, the reaction was ultrasonically treated at 80°C for 30 minutes to obtain a nano zinc oxide suspension. The zirconium phosphate suspension was then added to the nano zinc oxide suspension, and the pH of the system was adjusted to 4.5 with acetic acid. The system was then heated to 80°C and stirred at a constant temperature for 2 hours to allow ZrP to grow in situ on the ZnO surface. After completion, the reaction was spray-dried (inlet 180°C, outlet 80°C) to obtain ZnO@ZrP core-shell powder.

[0035] Example 7 Preparation of antibacterial plastics for bottle caps: First, the antibacterial plastic for bottle caps includes the following raw materials in parts by weight: Improved branched copolymer polypropylene prepared in Example 1: 70 parts; ZnO@ZrP core-shell powder prepared in Example 4: 2.0 parts; Maleic anhydride grafted hydrogenated styrene-butadiene block copolymer: 5 parts; Ethylene-octene copolymer: 8 parts; Antioxidant 1010: 0.3 parts; Calcium stearate: 0.5 parts.

[0036] Then, the preparation method of the antibacterial plastic for bottle caps comprises the following steps: The raw materials were weighed according to their mass parts, and the improved branched copolymer polypropylene prepared in Example 1, the ZnO@ZrP core-shell powder prepared in Example 4, maleic anhydride grafted hydrogenated styrene-butadiene block copolymer (SEBS-g-MAH, M1913, Asahi Kasei Corporation, Japan), ethylene-octene copolymer (POE, Engage 8200, DuPont-Dow Elastomers Company, USA), antioxidant 1010 (94%, Sinopharm Reagent) and calcium stearate were added. (AR, Sinopharm Reagent) was placed in a high-speed mixer and mixed for 5 minutes (speed 800 rpm). After completion, a mixture was obtained, and the mixture was placed in a twin-screw extruder for extrusion molding. The extrusion parameters of the twin-screw extruder were: zone 170°C, zone 2 180°C, zone 3 185°C, zone 4 190°C, zone 5 195°C, head temperature 200°C, screw speed 200r / min, and the extrudate was then water-cooled and pelletized, and dried at 80°C for 4 hours to obtain antibacterial plastic for bottle caps.

[0037] Example 8 Preparation of antibacterial plastics for bottle caps: First, the antibacterial plastic for bottle caps includes the following raw materials in parts by weight: Improved branched copolymer polypropylene prepared in Example 2: 75 parts; ZnO@ZrP core-shell powder prepared in Example 5: 2.5 parts; Maleic anhydride grafted hydrogenated styrene-butadiene block copolymer: 7 parts; Ethylene-octene copolymer: 10 parts; Antioxidant 1010: 0.5 parts; Calcium stearate: 1.0 part.

[0038] Then, the preparation method of the antibacterial plastic for bottle caps comprises the following steps: The raw materials were weighed according to their mass parts, and the improved branched copolymer polypropylene prepared in Example 2, the ZnO@ZrP core-shell powder prepared in Example 5, maleic anhydride grafted hydrogenated styrene-butadiene block copolymer (SEBS-g-MAH, M1913, Asahi Kasei Corporation, Japan), ethylene-octene copolymer (POE, Engage 8200, DuPont-Dow Elastomers Company, USA), antioxidant 1010 (94%, Sinopharm Reagent) and calcium stearate (A R, Sinopharm Reagent) was placed in a high-speed mixer and mixed for 10 minutes (speed 1000 rpm). After completion, a mixture was obtained, and the mixture was placed in a twin-screw extruder for extrusion molding. The extrusion parameters of the twin-screw extruder were: zone 1 175°C, zone 2 180°C, zone 3 185°C, zone 4 190°C, zone 5 195°C, head temperature 200°C, screw speed 200 r / min, and the extrudate was then water-cooled and pelletized, and dried at 100°C for 5 hours to obtain an antibacterial plastic for bottle caps.

[0039] Example 9 Preparation of antibacterial plastics for bottle caps: First, the antibacterial plastic for bottle caps includes the following raw materials in parts by weight: 80 parts of the improved branched copolymer polypropylene prepared in Example 3; ZnO@ZrP core-shell powder prepared in Example 6: 3.0 parts; Maleic anhydride grafted hydrogenated styrene-butadiene block copolymer: 8 parts; Ethylene-octene copolymer: 12 parts; Antioxidant 1010: 0.5 parts; Calcium stearate: 1.0 part.

[0040] Then, the preparation method of the antibacterial plastic for bottle caps comprises the following steps: The raw materials were weighed according to their mass parts, and the improved branched copolymer polypropylene prepared in Example 3, the ZnO@ZrP core-shell powder prepared in Example 6, maleic anhydride grafted hydrogenated styrene-butadiene block copolymer (SEBS-g-MAH, M1913, Asahi Kasei Corporation, Japan), ethylene-octene copolymer (POE, Engage 8200, DuPont-Dow Elastomers Company, USA), antioxidant 1010 (94%, Sinopharm Reagent) and calcium stearate (A R, Sinopharm Reagent) was placed in a high-speed mixer and mixed for 10 minutes (speed 1000 rpm). After completion, a mixture was obtained, and the mixture was placed in a twin-screw extruder for extrusion molding. The extrusion parameters of the twin-screw extruder were: zone 180°C, zone 2 185°C, zone 3 190°C, zone 4 195°C, zone 5 200°C, head temperature 200°C, screw speed 200 r / min, and the extrudate was then water-cooled and pelletized, and dried at 100°C for 5 hours to obtain an antibacterial plastic for bottle caps.

[0041] Comparative Example 1 Comparative Example 1 is the control group of Example 8, in which the improved branched copolymer polypropylene prepared in Example 2 of the raw material in Example 8 is replaced by the raw material linear copolymer polypropylene (melt index 60 g / 10 min, Sinopec K8003), and the remaining raw materials, raw material amounts and preparation methods are kept consistent with those in Example 8, and finally an antibacterial plastic for bottle caps is obtained.

[0042] Comparative Example 2 Comparative Example 2 is the control group of Example 8. The ZnO@ZrP core-shell powder prepared in Example 5 in Example 8 is replaced by raw material nano zinc oxide (ZnO, particle size 30 nm, Xuancheng Jingrui New Materials). The remaining raw materials, raw material amounts and preparation methods remain the same as in Example 8, and finally an antibacterial plastic for bottle caps is obtained.

[0043] Comparative Example 3 Comparative Example 3 is the control group of Example 8, except that the raw material maleic anhydride grafted hydrogenated styrene-butadiene block copolymer in Example 8 is removed, and the remaining raw materials, raw material amounts and preparation method are kept consistent with those in Example 8, and finally an antibacterial plastic for bottle caps is obtained.

[0044] Comparative Example 4 Comparative Example 4 is the control group of Example 8. The amount of the raw material ethylene-octene copolymer in Example 8 is reduced to 5 parts (below the lower limit), and the remaining raw materials, raw material amounts and preparation methods remain the same as in Example 8, and finally an antibacterial plastic for bottle caps is obtained.

[0045] The performance tests were conducted on the antibacterial plastics for bottle caps prepared in Examples 7 to 9 and Comparative Examples 1 to 4. The performance test process is as follows, and the test results are shown in Table 1: (1) Antibacterial properties (GB / T 31402-2015 Test for antibacterial properties of plastic surfaces): Test process: The bottle caps prepared in Examples 7 to 9 and Comparative Examples 1 to 4 were injection molded into plastic sheets (50×50×2 mm) with antibacterial plastic, and then inoculated with Escherichia coli (ATCC 25922) / Staphylococcus aureus (ATCC 6538) suspension (concentration 1×10 5 CFU / mL), then covered with a film, cultured at 37°C and 90% humidity for 24 h, then eluted with PBS buffer and poured onto plates to count colonies.

[0046] Inhibition rate (%) = (number of colonies in the control group - number of colonies in the experimental group) / number of colonies in the control group × 100.

[0047] (2) Impact toughness (GB / T 1843-2008 Izod notched impact strength): Testing process: The bottle caps prepared in Examples 7 to 9 and Comparative Examples 1 to 4 were injection molded into standard notched specimens (80×10×4 mm, notch depth 2 mm) using antibacterial plastic, pretreated at 23°C for 48 h, and then measured for fracture absorption energy using an impact tester (pendulum energy 2.75 J).

[0048] (3) Melt flow rate (MFR) (GB / T 3682-2018 Thermoplastics melt mass flow rate): Testing Procedure: The antibacterial plastics used in bottle caps prepared in Examples 7-9 and Comparative Examples 1-4 were pre-dried (80°C for 2 hours) and preheated for 5 minutes in a melt indexer (2.16 kg load, 230°C). Strips extruded within 10 minutes were then cut and weighed to calculate the MFR (g / 10 min).

[0049] (4) Stability in acidic environment (simulated weak acid conditions): Test process: The bottle caps prepared in Examples 7 to 9 and Comparative Examples 1 to 4 were soaked in an acetic acid solution with a pH of 4.0 (simulating a beverage environment) for 7 days, and then the antibacterial properties were tested (the same method as 1) after removal, and the attenuation of the inhibition rate was calculated.

[0050] Attenuation rate (%) = (initial inhibition rate - inhibition rate after immersion) / initial inhibition rate × 100.

[0051] Table 1 Test results project Example 7 Example 8 Example 9 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Escherichia coli inhibition rate (%) 98.5 99.8 99.5 99.0 85.2 99.2 99.5 Staphylococcus aureus inhibition rate (%) 98.0 99.5 99.2 98.5 82.7 98.8 99.0 <![CDATA[Impact strength (kJ / m 2 )]]> 25.0 28.3 26.5 18.2 24.5 16.8 19.5 MFR (g / 10min) 53.0 54.8 50.3 46.2 53.5 52.0 53.0 Attenuation of antibacterial rate after acid immersion (%) 8.5 3.2 5.0 7.8 42.3 8.0 4.5 Result analysis and verification: (1) Antibacterial verification: Example 8 has the highest antibacterial rate (99.8% / 99.5%), which is due to the core-shell structure (ZrP protecting ZnO).

[0052] The antibacterial rate of comparative example 2 (ordinary ZnO) is 85.2 (acid inactivation), and the attenuation rate is greater than 40%, which proves the necessity of the core-shell structure. The antibacterial rates of other groups are all greater than 98%, indicating that the basic antibacterial properties of the formula are good.

[0053] (2) Impact toughness verification: Example 8 Impact strength 28.3 kJ / m 2 (optimal), the impact strength of comparative example 1 (unbranched polypropylene) dropped to 18.2 kJ / m 2 (36% decrease), reflecting the toughening effect of the branched structure. Comparative Example 3 (without SEBS-g-MAH) has an impact strength of 16.8 kJ / m 2 (41% decrease), proving the contribution of the compatibilizer to the interfacial bonding.

[0054] (3) Processability verification: Example 8 had an MFR of 54.8 g / 10min (an 8.7% decrease from the baseline value of 60 g / 10min), meeting the requirement of a decrease of less than 10%. Comparative Example 1 had an MFR of 46.2 g / 10min (a 23% decrease), due to insufficient melt strength of the linear polypropylene. All groups had an MFR greater than 50 g / 10min, ensuring injection molding feasibility.

[0055] (3) Acid stability verification: The attenuation rate of Example 8 is only 3.2% (optimal), indicating that the core-shell structure effectively protects ZnO. The attenuation rate of Comparative Example 2 is 42.3%, proving that ordinary ZnO fails in a weak acid environment.

[0056] It should be noted that, in this document, terms such as "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0057] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An antibacterial plastic for bottle caps, characterized in that: Including the following raw materials by weight: Improved branched copolymer polypropylene: 70-80 parts; ZnO@ZrP core-shell powder: 2.0-3.0 parts; Maleic anhydride grafted hydrogenated styrene-butadiene block copolymer: 5-8 parts; Ethylene-octene copolymer: 8-12 parts; Antioxidant 1010: 0.3-0.5 parts; Calcium stearate: 0.5-1.0 part.

2. The antibacterial plastic for bottle caps according to claim 1, characterized in that: The improved branched copolymer polypropylene comprises the following raw materials in parts by weight: Linear copolymer polypropylene: 100 parts; 1,6-Hexanediol diacrylate: 0.3-0.5 parts; Dicumyl peroxide: 0.01 to 0.03 parts.

3. The antibacterial plastic for bottle caps according to claim 2, characterized in that: The improved branched copolymer polypropylene is prepared by the following steps: The raw materials were weighed in parts by mass, and linear copolymer polypropylene, 1,6-hexanediol diacrylate and diisopropylbenzene peroxide were mixed and added to a high-speed mixer. The mixture was mixed at 800-1000 rpm for 5-10 minutes to obtain a mixture. The mixture was then placed in an extruder. After completion, the extruded material strips were water-cooled and pelletized, and vacuum-dried at 90-100° C. for 5-6 hours to obtain an improved branched copolymer polypropylene.

4. The antibacterial plastic for bottle caps according to claim 3, characterized in that: The temperature zones of the extruder are: zone 1 155-160° C., zone 2 160-170° C., zone 3 170-175° C., zone 4 175-180° C., zone 5 170-175° C.; the screw speed of the extruder is 150-200 r / min.

5. The antibacterial plastic for bottle caps according to claim 1, characterized in that: The ZnO@ZrP core-shell powder comprises the following raw materials in parts by weight: Nano zinc oxide: 50 parts; Zirconium phosphate: 20-30 parts; Silane coupling agent KH-550: 1.5 to 2.0 parts.

6. The antibacterial plastic for bottle caps according to claim 5, characterized in that: The ZnO@ZrP core-shell powder is prepared by the following steps: The raw materials were weighed in parts by mass. First, zirconium phosphate was added to pure water in a mass ratio of 10:1 and stirred at room temperature for 10 to 30 minutes to obtain a zirconium phosphate suspension. Then, nano zinc oxide was added to anhydrous ethanol in a mass ratio of 10:1, and a silane coupling agent KH-550 was added thereto with stirring. After completion, the mixture was ultrasonically treated at 60 to 80°C for 30 minutes to obtain a nano zinc oxide suspension. The zirconium phosphate suspension was then added to the nano zinc oxide suspension, and the pH of the system was adjusted to 4.0 to 4.5 using acetic acid. The system was then heated to 70 to 80°C and stirred at a constant temperature for 2 hours. After completion, the mixture was spray-dried to obtain a ZnO@ZrP core-shell powder.

7. A method for preparing an antibacterial plastic for bottle caps according to any one of claims 1 to 6, characterized in that: The following steps are involved: The raw materials were weighed in parts by mass, and the improved branched copolymer polypropylene, ZnO@ZrP core-shell powder, maleic anhydride grafted hydrogenated styrene-butadiene block copolymer, ethylene-octene copolymer, antioxidant 1010 and calcium stearate were placed in a high-speed mixer and mixed for 5 to 10 minutes to obtain a mixture. After the mixture was completed, the mixture was placed in a twin-screw extruder for extrusion molding, and the extrudate was then water-cooled and pelletized, and dried at 80 to 100° C. for 4 to 5 hours to obtain an antibacterial plastic for bottle caps.

8. The method for preparing an antibacterial plastic for bottle caps according to claim 7, characterized in that: The extrusion parameters of the twin-screw extruder are: zone 1 170-180°C, zone 2 180-185°C, zone 3 185-190°C, zone 4 190-195°C, zone 5 195-200°C, die head temperature 200°C, screw speed 200r / min.