Antibacterial plastic for bottle cap and method for preparing the same

Abstract

The application discloses a kind of bottle cap antibacterial plastics and preparation method thereof, belong to high polymer material production technical field, first, the bottle cap antibacterial plastics provided by the application includes the following mass parts raw materials: improved branched copolymer polypropylene: 70~80 parts, ZnO@ZrP core-shell powder: 2.0~3.0 parts, maleic anhydride grafting 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 parts.The bottle cap antibacterial plastics prepared by the application meets European Union EC No 1935 / 2004, Chinese GB 4806.7-2016 and other food contact material standards, provides a high reliability solution for beverage, pharmaceutical packaging.

Description

TECHNICAL FIELD

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

[0002] Plastic bottle caps are widely used in the packaging fields of beverages, medicines and cosmetics, etc. They directly contact the contents and are in a humid environment for a long time, and are easy to become a breeding ground for microorganisms. Especially in cold chain storage and transportation, high temperature and high humidity areas, the breeding of pathogenic bacteria such as Escherichia coli and Staphylococcus aureus may cause product deterioration and even food safety accidents. It is of great significance to develop plastic bottle caps with high-efficiency antibacterial properties to protect consumer health and prolong product shelf life.

[0003] The existing technology mainly adopts the method of adding silver-based, zinc-based or organic antibacterial agents (such as triclosan) to endow the plastic with antibacterial properties. However, silver ions are prone to migration, resulting in insufficient long-term effectiveness and high cost. The activity of zinc-based antibacterial agents is greatly reduced in weak acidic environment. Organic antibacterial agents have poor heat resistance (decomposition temperature < 200℃) and poor compatibility with the plastic matrix. More importantly, when the addition amount of antibacterial agent exceeds 1.5wt%, the impact toughness (decrease > 30%) and melt flow rate (decrease > 15%) of the plastic will be significantly reduced, resulting in defects such as flash and material shortage during the injection molding of the bottle cap, which seriously restricts its industrial application.

[0004] With the increasing strictness of antibacterial requirements for food contact materials in various countries (such as EU EC No 1935 / 2004 and China GB4806.7-2016), it is an urgent need in the industry to develop plastic special for bottle caps with long-term antibacterial properties, excellent processability and mechanical strength. Solving the compatibility contradiction between high addition amount of antibacterial agent and plastic matrix is a technical bottleneck that needs to be broken through in the field. SUMMARY

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

[0006] The object of the application can be achieved by the following technical solutions:

[0007] An antibacterial plastic for bottle caps comprises the following raw materials by mass:

[0008] Improved branched copolymerized polypropylene: 70-80 parts;

[0009] ZnO@ZrP core-shell powder: 2.0-3.0 parts;

[0010] Maleic anhydride grafted hydrogenated styrene-butadiene block copolymer: 5-8 parts;

[0011] Ethylene-octene copolymer: 8-12 parts;

[0012] Antioxidant 1010: 0.3-0.5 parts;

[0013] Calcium stearate: 0.5-1.0 parts.

[0014] Further, the improved branched copolymerized polypropylene comprises the following raw materials by mass fraction:

[0015] Linear copolymerized polypropylene: 100 parts;

[0016] 1,6-hexanediol diacrylate: 0.3-0.5 parts;

[0017] Dicumyl peroxide: 0.01-0.03 parts.

[0018] Further, the improved branched copolymerized polypropylene is prepared by the following steps:

[0019] The raw materials are weighed by mass fraction, the linear copolymerized polypropylene, 1,6-hexanediol diacrylate and dicumyl peroxide are mixed and added into a high-speed mixer, mixed at 800-1000 rpm for 5-10 min to obtain a mixture, and then the mixture is placed in an extruder. After completion, the extruded strip is water-cooled and granulated, vacuum dried at 90-100°C for 5-6h to obtain the improved branched copolymerized polypropylene.

[0020] Further, 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, and zone 5 170-175°C; and the screw rotation speed of the extruder is 150-200 r / min.

[0021] Further, the ZnO@ZrP core-shell powder comprises the following raw materials by mass fraction:

[0022] Nano zinc oxide: 50 parts;

[0023] Zirconium phosphate: 20-30 parts;

[0024] Silane coupling agent KH-550: 1.5-2.0 parts.

[0025] Further, the ZnO@ZrP core-shell powder is prepared by the following steps:

[0026] According to the mass parts, each raw material is weighed, first, zirconium phosphate is added to pure water according to the mass ratio of 10:1, stirred at room temperature for 10-30 min, and a zirconium phosphate suspension is obtained; then, nano-zinc oxide is added to anhydrous ethanol according to the mass ratio of 10:1, and then silane coupling agent KH-550 is added thereto under stirring, after which ultrasonic treatment is performed at 60-80 DEG C for 30 min, after which a nano-zinc oxide suspension is obtained, and then the zirconium phosphate suspension is added to the nano-zinc oxide suspension, acetic acid is used to adjust the pH of the system to 4.0-4.5, the system is heated to 70-80 DEG C and stirred for 2 h, after which spray drying is performed, and a ZnO@ZrP core-shell powder is obtained.

[0027] Further, a preparation method of the bottle cap antibacterial plastic comprises the following steps:

[0028] According to the mass parts, each raw material is weighed, the improved branched copolymerized polypropylene, ZnO@ZrP core-shell powder, maleic anhydride grafted hydrogenated styrene-butadiene block copolymer, ethylene-octene copolymer, antioxidant 1010 and calcium stearate are placed in a high-speed mixer and mixed for 5-10 min, after which a mixture is obtained, the mixture is placed in a double-screw extruder and extruded into a shape, the extruded material is then water-cooled and pelletized, and the pellets are dried at 80-100 DEG C for 4-5 h, and a bottle cap antibacterial plastic is obtained.

[0029] Further, the extrusion parameters of the double-screw extruder are as follows: zone 1, 170-180 DEG C; zone 2, 180-185 DEG C; zone 3, 185-190 DEG C; zone 4, 190-195 DEG C; zone 5, 195-200 DEG C; die temperature, 200 DEG C; and screw rotation speed, 200 r / min.

[0030] The beneficial effects of the present application are as follows:

[0031] (1) The present application solves the contradiction between high antibacterial agent addition amount and mechanical / processing performance:

[0032] In the prior art, when the antibacterial agent addition amount is >1.5 wt%, the impact toughness decreases by >30% and the melt flow rate (MFR) decreases by >15%, resulting in injection molding defects.

[0033] The effect verification of the present application is as follows: Example 8: the antibacterial agent (ZnO@ZrP) addition amount is 2.5 parts (≈2.63 wt%), the impact strength is 28.3 kJ / m 2 , and the MFR is 54.8 g / 10 min; compared with the basic linear polypropylene (melt index 60 g / 10 min), the MFR only decreases by 8.7% (<15%), and the impact strength is significantly improved (not decreased); Comparative Example 1 (without branched polypropylene): the ordinary linear polypropylene is used, and the impact strength drops to 18.2 kJ / m 2(36% lower than Example 8), MFR dropped to 46.2 g / 10min (23% lower than base value); Comparative Example 4 (POE insufficient toughening): POE dosage reduced to 5 parts (lower than the lower limit of 8 parts), impact strength only 19.5 kJ / m 2 , which proves that the toughening agent needs to be in sufficient amount.

[0034] Conclusion: Through the synergy of the improved branched polypropylene (toughening) + POE (toughening) + SEBS-g-MAH (compatibility agent), when the antibacterial agent addition amount is ≥2.0wt%, the impact strength does not decrease but increases (the highest is 28.3kJ / m 2 ), and the MFR decrease rate is ≤8.7%, which proves that the technical scheme of the present application successfully solves the performance degradation problem caused by high addition amount.

[0035] (2) The present application realizes broad-spectrum and long-acting antibacterial effect and solves the problem of inactivation in acidic environment.

[0036] In the prior art, the activity of zinc-based antibacterial agents in weak acidic environment decreases sharply, and silver-based antibacterial agents are high in cost and easy to migrate.

[0037] Effect verification of the present application: Example 8 (core-shell structure ZnO@ZrP): initial bacteriostatic rate: 99.8% for E. coli and 99.5% for Staphylococcus aureus, after soaking in acidic environment (pH=4.0) for 7 days, the bacteriostatic rate decreases only by 3.2%; Comparative Example 2 (ordinary ZnO): initial bacteriostatic rate decreases sharply (85.2% for E. coli and 82.7% for Staphylococcus aureus), and the decrease rate is as high as 42.3% after soaking in acid; other examples (7, 9): the bacteriostatic rate is all >98.5%, and the acid decay rate is ≤8.5%, which verifies the universality of the formula.

[0038] Conclusion: The core-shell structure ZnO@ZrP (ZrP coated ZnO) prepared by the present application effectively isolates weak acid erosion, so that the antibacterial agent maintains high activity (decay rate ≤5%) in acidic environment, and the technical scheme of the present application breaks through the environmental limitations of zinc-based antibacterial agents.

[0039] (3) Unsubstitutable role of compatibility agent on interface combination:

[0040] Data of Comparative Example 3: impact strength drops sharply to 16.8 kJ / m 2 (41% lower than Example 8), although the bacteriostatic rate does not decrease significantly (98.8%).

[0041] Analysis: after removing the maleic anhydride grafted SEBS, the compatibility of inorganic antibacterial powder (ZnO@ZrP) and polypropylene matrix deteriorates, resulting in a sharp decrease in impact toughness, which proves that the strengthening effect of SEBS-g-MAH on interface combination is the key to maintaining high toughness.

[0042] Finally, the core beneficial effects of the present application are summarized:

[0043] a. High antibacterial - high toughness synergy: under the antibacterial agent addition amount ≥ 2.0wt%, the impact strength of the technical scheme of the application is improved to 28.3kJ / m 2 (55% higher than the linear polypropylene baseline), MFR reduction rate ≤ 8.7%, breaking through the "high addition must be degraded" curse;

[0044] b. Long-term acid-resistant antibacterial: adding the core-shell structure ZnO@ZrP prepared by the application makes the antibacterial decay rate in acidic environment ≤ 5% (ordinary ZnO > 40%);

[0045] c. Interface strengthening mechanism: SEBS-g-MAH significantly improves the compatibility of inorganic-organic phases (impact strength decreases by 41% without this component);

[0046] d. Comprehensive performance balance: the antibacterial plastic prepared by the application for bottle cap meets the food contact material standards such as European Union EC No 1935 / 2004 and Chinese GB 4806.7-2016, and provides a high-reliability solution for beverage and pharmaceutical packaging. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the application will be clearly and completely described below in combination with the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application. Meanwhile, the raw materials, reagents or devices used in the following embodiments can be obtained from conventional commercial channels or can be obtained by existing known methods, if not otherwise specified.

[0048] Embodiment 1

[0049] Preparation of improved branched copolymerized polypropylene:

[0050] Firstly, the improved branched copolymerized polypropylene includes the following raw materials by mass fraction:

[0051] Linear copolymerized polypropylene (melt index 60g / 10min, Sinopec K8003): 100 parts;

[0052] 1,6-hexanediol diacrylate (HDDA, Aldrich reagent): 0.3 parts;

[0053] Dicumyl peroxide (DCP, National Pharmaceutical Reagent): 0.01 parts;

[0054] Then, the preparation steps of the improved branched copolymerized polypropylene are as follows:

[0055] The raw materials were weighed according to the mass parts, the linear copolymerized polypropylene, 1,6-hexanediol diacrylate and dicumyl peroxide were mixed in a high-speed mixer at 800 rpm for 5 min to obtain a mixture, and then the mixture was placed in an extruder, the temperature partition of the extruder was: 155℃ for the first zone, 160℃ for the second zone, 170℃ for the third zone, 175℃ for the fourth zone, and 170℃ for the fifth zone, the screw speed of the extruder was 150 r / min, after completion, the extruded strip was water-cooled and cut into particles, and then the particles were vacuum dried at 90℃ for 5 h to obtain the improved branched copolymerized polypropylene.

[0056] Example 2

[0057] Preparation of the improved branched copolymerized polypropylene:

[0058] Firstly, the improved branched copolymerized polypropylene included the following mass parts of raw materials:

[0059] Linear copolymerized polypropylene (melt index 60 g / 10 min, Sinopec K8003): 100 parts;

[0060] 1,6-hexanediol diacrylate (HDDA, Aldrin reagent): 0.45 parts;

[0061] Dicumyl peroxide (DCP, National Medicine Reagent): 0.025 parts;

[0062] Then, the preparation steps of the improved branched copolymerized polypropylene:

[0063] The raw materials were weighed according to the mass parts, the linear copolymerized polypropylene, 1,6-hexanediol diacrylate and dicumyl peroxide were mixed in a high-speed mixer at 1000 rpm for 10 min to obtain a mixture, and then the mixture was placed in an extruder, the temperature partition of the extruder was: 160℃ for the first zone, 165℃ for the second zone, 170℃ for the third zone, 175℃ for the fourth zone, and 170℃ for the fifth zone, the screw speed of the extruder was 200 r / min, after completion, the extruded strip was water-cooled and cut into particles, and then the particles were vacuum dried at 100℃ for 6 h to obtain the improved branched copolymerized polypropylene.

[0064] Example 3

[0065] Preparation of the improved branched copolymerized polypropylene:

[0066] Firstly, the improved branched copolymerized polypropylene included the following mass parts of raw materials:

[0067] Linear copolymerized polypropylene (melt index 60 g / 10 min, Sinopec K8003): 100 parts;

[0068] 1,6-hexanediol diacrylate (HDDA, Aldrin reagent): 0.5 parts;

[0069] Dicumyl peroxide (DCP, National Reagent): 0.03 parts;

[0070] Then, the preparation step of the improved branched copolymerized polypropylene:

[0071] According to the mass parts, the linear copolymerized polypropylene, 1,6-hexanediol diacrylate and dicumyl peroxide were mixed in a high-speed mixer, mixed at 1000 rpm for 10 min to obtain a mixture, and then the mixture was placed in an extruder. The temperature partition of the extruder was: zone one 160°C, zone two 170°C, zone three 175°C, zone four 180°C, and zone five 175°C. The screw speed of the extruder was 200 r / min. After completion, the extruded strip was water-cooled and pelletized, and then vacuum dried at 100°C for 6 h to obtain the improved branched copolymerized polypropylene.

[0072] Example 4

[0073] Preparation of ZnO@ZrP core-shell powder:

[0074] Firstly, the ZnO@ZrP core-shell powder includes the following mass parts of raw materials:

[0075] Nano-zinc oxide (ZnO, particle size 30 nm, Xuancheng Jingrui New Material): 50 parts;

[0076] Zirconium phosphate (ZrP, layered carrier, Aladdin Reagent): 20 parts;

[0077] Silane coupling agent KH-550 (Nanjing Nengxin New Material): 1.5 parts;

[0078] Then, the preparation step of the ZnO@ZrP core-shell powder:

[0079] According to the mass parts of the above raw materials, firstly, zirconium phosphate was added to pure water according to a mass ratio of 10:1, and stirred at room temperature for 10 min to obtain a zirconium phosphate suspension; then nano-zinc oxide was added to anhydrous ethanol according to a mass ratio of 10:1, and then silane coupling agent KH-550 was added thereto, after which it was ultrasonically treated at 60°C for 30 min, and then a nano-zinc oxide suspension was obtained. Then, the 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, and the system was heated to 70°C and stirred for 2 h to allow the ZrP to grow in situ on the surface of the ZnO. After completion, spray drying was performed (inlet 180°C, outlet 80°C) to obtain the ZnO@ZrP core-shell powder.

[0080] Example 5

[0081] Preparation of ZnO@ZrP core-shell powder:

[0082] Firstly, the ZnO@ZrP core-shell powder includes the following mass parts of raw materials:

[0083] Nano zinc oxide (ZnO, particle size 30 nm, Xuancheng Jingrui New Materials): 50 parts;

[0084] Zirconium phosphate (ZrP, layered carrier, Aldrin reagent): 25 parts;

[0085] Silane coupling agent KH-550 (Nanjing Nengxin New Materials): 2.0 parts;

[0086] Then, the preparation steps of ZnO@ZrP core-shell powder:

[0087] The above raw materials are weighed by mass parts. First, add zirconium phosphate to pure water according to a mass ratio of 10:1, stir at room temperature for 30 min, and obtain a zirconium phosphate suspension. Then, add nano zinc oxide to anhydrous ethanol according to a mass ratio of 10:1, and then add silane coupling agent KH-550 to the stirring. After completion, ultrasonic treatment at 80°C for 30 min is performed. After completion, a nano zinc oxide suspension is obtained. Add the zirconium phosphate suspension to the nano zinc oxide suspension, adjust the system pH to 4.2 with acetic acid, and then heat the system to 80°C for constant temperature stirring for 2h. Make ZrP grow in situ on the surface of ZnO. After completion, spray drying (inlet 180°C, outlet 80°C) is performed to obtain ZnO@ZrP core-shell powder.

[0088] Example 6

[0089] Preparation of ZnO@ZrP core-shell powder:

[0090] First, the ZnO@ZrP core-shell powder includes the following mass parts of raw materials:

[0091] Nano zinc oxide (ZnO, particle size 30 nm, Xuancheng Jingrui New Materials): 50 parts;

[0092] Zirconium phosphate (ZrP, layered carrier, Aldrin reagent): 30 parts;

[0093] Silane coupling agent KH-550 (Nanjing Nengxin New Materials): 2.0 parts;

[0094] Then, the preparation steps of ZnO@ZrP core-shell powder:

[0095] The above raw materials are weighed according to mass parts, first, zirconium phosphate is added to pure water according to a mass ratio of 10:1, stirring at room temperature for 30 min to obtain a zirconium phosphate suspension; then, nano-zinc oxide is added to anhydrous ethanol according to a mass ratio of 10:1, and then silane coupling agent KH-550 is added thereto under stirring, after which ultrasonic treatment is performed at 80℃ for 30 min, after which a nano-zinc oxide suspension is obtained, and then the zirconium phosphate suspension is added to the nano-zinc oxide suspension, acetic acid is used to adjust the pH of the system to 4.5, and the system is heated to 80℃ for constant temperature stirring for 2 h to enable in-situ growth of ZrP on the surface of ZnO, after which spray drying is performed (inlet temperature 180℃, outlet temperature 80℃) to obtain ZnO@ZrP core-shell powder.

[0096] Example 7

[0097] Preparation of antibacterial plastic for bottle caps:

[0098] First, the antibacterial plastic for bottle caps comprises the following raw materials by mass parts:

[0099] The improved branched copolymerized polypropylene prepared in Example 1: 70 parts;

[0100] The ZnO@ZrP core-shell powder prepared in Example 4: 2.0 parts;

[0101] Maleic anhydride grafted hydrogenated styrene-butadiene block copolymer: 5 parts;

[0102] Ethylene-octene copolymer: 8 parts;

[0103] Antioxidant 1010: 0.3 parts;

[0104] Calcium stearate: 0.5 parts.

[0105] Then, the preparation method of the antibacterial plastic for bottle caps comprises the following steps:

[0106] The raw materials are weighed according to mass parts, and the improved branched copolymerized 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, Engage8200, DuPont-Dow Elastomers Company, USA), antioxidant 1010 (94%, National Pharmaceutical Reagent) and calcium stearate (AR, National Pharmaceutical Reagent) are mixed in a high-speed mixer for 5 min (rotation speed 800 rpm), after which a mixture is obtained, and the mixture is placed in a twin-screw extruder for extrusion molding, the extrusion parameters of the twin-screw extruder are: zone 1 170℃, zone 2 180℃, zone 3 185℃, zone 4 190℃, zone 5 195℃, die head temperature 200℃, screw rotation speed 200 r / min, and the extruded material is then water-cooled and pelletized, and dried at 80℃ for 4 h to obtain the antibacterial plastic for bottle caps.

[0107] Example 8

[0108] Preparation of the antibacterial plastic for bottle cap:

[0109] Firstly, the antibacterial plastic for bottle cap comprises the following raw materials by mass fraction:

[0110] The improved branched copolymerized polypropylene prepared in Example 2: 75 parts;

[0111] The ZnO@ZrP core-shell powder prepared in Example 5: 2.5 parts;

[0112] Maleic anhydride grafted hydrogenated styrene-butadiene block copolymer: 7 parts;

[0113] Ethylene-octene copolymer: 10 parts;

[0114] Antioxidant 1010: 0.5 parts;

[0115] Calcium stearate: 1.0 part.

[0116] Then, the preparation method of the antibacterial plastic for bottle cap comprises the following steps:

[0117] According to the mass fraction, each raw material is weighed, the improved branched copolymerized 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, Engage8200, DuPont-Dow Elastomers Company, USA), antioxidant 1010 (94%, China Reagent) and calcium stearate (AR, China Reagent) are placed in a high-speed mixer and mixed for 10 min (rotation speed 1000 rpm), after completion, a mixture is obtained, the mixture is placed in a twin-screw extruder for extrusion molding, the extrusion parameters of the twin-screw extruder are: zone 1 175℃, zone 2 180℃, zone 3 185℃, zone 4 190℃, zone 5 195℃, die head temperature 200℃, screw rotation speed 200r / min, the extruded material is then water-cooled and pelletized, dried at 100℃ for 5h, and the antibacterial plastic for bottle cap is obtained.

[0118] Example 9

[0119] Preparation of the antibacterial plastic for bottle cap:

[0120] Firstly, the antibacterial plastic for bottle cap comprises the following raw materials by mass fraction:

[0121] The improved branched copolymerized polypropylene prepared in Example 3: 80 parts;

[0122] The ZnO@ZrP core-shell powder prepared in Example 6: 3.0 parts;

[0123] Maleic anhydride-grafted hydrogenated styrene-butadiene block copolymer: 8 parts;

[0124] Ethylene-octene copolymer: 12 parts;

[0125] Antioxidant 1010: 0.5 parts;

[0126] Calcium stearate: 1.0 part.

[0127] Then, the method for preparing antimicrobial plastic for bottle caps includes the following steps:

[0128] Weigh each raw material according to the mass percentage, including 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, Engage8200, DuPont-Dow Elastomers, USA), antioxidant 1010 (94%, Sinopharm Reagent), and calcium stearate (A R (National Pharmaceutical Reagent) was placed in a high-speed mixer and mixed for 10 minutes (1000 rpm). After mixing, a mixture was obtained. The mixture was then placed in a twin-screw extruder for extrusion molding. The extrusion parameters of the twin-screw extruder were: Zone 1 180℃, Zone 2 185℃, Zone 3 190℃, Zone 4 195℃, Zone 5 200℃, Die head temperature 200℃, and screw speed 200 r / min. The extruded material was then water-cooled and pelletized, and dried at 100℃ for 5 hours to obtain antibacterial plastic for bottle caps.

[0129] Comparative Example 1

[0130] Comparative Example 1 served as the control group for Example 8. The improved branched copolymer polypropylene prepared from the raw material in Example 2 of Example 8 was replaced with linear copolymer polypropylene (melt index 60 g / 10 min, Sinopec K8003). The remaining raw materials, raw material amounts, and preparation methods remained consistent with those in Example 8, and the antibacterial plastic for bottle caps was finally obtained.

[0131] Comparative Example 2

[0132] Comparative Example 2 served as the control group for Example 8. The ZnO@ZrP core-shell powder prepared in Example 5 of Example 8 was replaced with nano zinc oxide (ZnO, particle size 30nm, Xuancheng Jingrui New Materials). The remaining raw materials, raw material amounts, and preparation methods remained consistent with those in Example 8, and antibacterial plastic for bottle caps was finally obtained.

[0133] Comparative Example 3

[0134] Comparative Example 3 is a control group of Example 8, in which the raw material maleic anhydride grafted hydrogenated styrene-butadiene block copolymer in Example 8 is removed, and the rest of the raw materials, the amount of the raw materials, and the preparation method remain consistent with those in Example 8, finally obtaining the antibacterial plastic for bottle caps.

[0135] Comparative Example 4

[0136] Comparative Example 4 is a control group of Example 8, in which the amount of the raw material ethylene-octene copolymer in Example 8 is reduced to 5 parts (lower than the lower limit), and the rest of the raw materials, the amount of the raw materials, and the preparation method remain consistent with those in Example 8, finally obtaining the antibacterial plastic for bottle caps.

[0137] The antibacterial plastics for bottle caps prepared in Examples 7-9 and Comparative Examples 1-4 are subjected to performance tests, and the performance test process is as follows, and the test results are shown in Table 1:

[0138] (1) Antibacterial performance (GB / T 31402-2015 Test for antibacterial property of plastic surface):

[0139] Test process: The antibacterial plastics for bottle caps prepared in Examples 7-9 and Comparative Examples 1-4 are injection molded into plastic sheets (50×50×2mm), then inoculated with E. coli (ATCC 25922) / Staphylococcus aureus (ATCC 6538) suspension (concentration 1×10 5 CFU / mL), then covered with a film, incubated at 37℃ and 90% humidity for 24h, then eluted with PBS buffer, and poured into a plate to count the colonies.

[0140] Bacteriostatic rate (%) = (control group bacteria number-experimental group bacteria number) / control group bacteria number×100.

[0141] (2) Impact toughness (GB / T 1843-2008 Izod Notched Impact Strength):

[0142] Test process: The antibacterial plastics for bottle caps prepared in Examples 7-9 and Comparative Examples 1-4 are injection molded into standard notched samples (80×10×4mm, notch depth 2mm), pre-treated at 23℃ for 48h, then measured for fracture absorption energy using an impact testing machine (pendulum energy 2.75J).

[0143] (3) Melt flow rate (MFR) (GB / T 3682-2018 Melt Mass-Flow Rate of Thermoplastics):

[0144] Test procedure: The bottle cap made of antibacterial plastics prepared in Example 7 to Example 9 and Comparative Example 1 to Comparative Example 4 was pre-dried (80°C x 2h), and preheated in a melt indexer (load 2.16 kg, temperature 230°C) for 5 min. The extruded strip was cut and weighed to calculate the MFR (g / 10 min) within 10 min.

[0145] (4) Stability in acidic environment (simulating weak acid conditions):

[0146] Test procedure: The bottle cap made of antibacterial plastics prepared in Example 7 to Example 9 and Comparative Example 1 to Comparative Example 4 was soaked in a pH = 4.0 acetic acid solution (simulating beverage environment) for 7 days, and then the antibacterial property was tested (method same as 1) after taking out, and the decay of the bacteriostatic rate was calculated.

[0147] Decay rate (%) = (initial bacteriostatic rate - bacteriostatic rate after soaking) / initial bacteriostatic rate x 100.

[0148] Table 1 Test results

[0149] Item Example 7 Example 8 Example 9 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 E. coli inhibition rate (%) 98.5 99.8 99.5 99.0 85.2 99.2 99.5 S. aureus inhibition rate (%) 98.0 99.5 99.2 98.5 82.7 98.8 99.0 impact strength (kJ / m 2 ) 25.0 28.3 26.5 18.2 24.5 16.8 19.5 MFR (g / 10 min) 53.0 54.8 50.3 46.2 53.5 52.0 53.0 Attenuation of inhibition rate after acid soak (%) 8.5 3.2 5.0 7.8 42.3 8.0 4.5

[0150] Result analysis and verification:

[0151] (1) Verification of antibacterial property:

[0152] Example 8 has the highest bacteriostatic rate (99.8% / 99.5%), which is due to the core-shell structure (ZrP protects ZnO).

[0153] Comparative Example 2 (ordinary ZnO) has a bacteriostatic rate of 85.2 (acid inactivation), and the decay rate is > 40%, which proves the necessity of core-shell structure, and the bacteriostatic rate of other groups is > 98%, which shows that the basic antibacterial property of the formula is good.

[0154] (2) Impact toughness verification:

[0155] Example 8 has an impact strength of 28.3 kJ / m 2 (optimal), Comparative Example 1 (without branched polypropylene) has an impact strength of 18.2 kJ / m 2 (decrease by 36%), which reflects the toughening effect of branched structure. Comparative Example 3 (without SEBS-g-MAH) has an impact strength of 16.8 kJ / m 2 (decrease by 41%), which proves the contribution of the compatibilizer to the interfacial bonding.

[0156] (3) Verification of processability:

[0157] Example 8 MFR = 54.8 g / 10min (8.7% down from base value of 60 g / 10min), meets <10% down requirement. Comparative Example 1 MFR = 46.2 g / 10min (23% down), insufficient melt strength of linear polypropylene. All groups have MFR > 50 g / 10min, ensuring injection molding feasibility.

[0158] (3) Acid stability verification:

[0159] Example 8 decay rate only 3.2% (optimal), core-shell structure effectively protects ZnO. Comparative Example 2 decay rate 42.3%, demonstrating that ordinary ZnO fails in weak acid environment.

[0160] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting; it is also possible that the scope of the appended claims can be read to include other alternatives.

[0161] While the embodiments of the application have been illustrated and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the spirit and scope of the application, which is defined by the appended claims and their equivalents.

Claims

1. An antibacterial plastic for bottle caps, characterized in that, Includes the following quantities of raw materials: 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 parts; The improved branched copolymer polypropylene comprises the following parts by weight of raw materials: Linear copolymer polypropylene: 100 parts; 1,6-Hexanediol diacrylate: 0.3–0.5 parts; Dicumyl peroxide: 0.01–0.03 parts; 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: 1.5–2.0 parts; The ZnO@ZrP core-shell powder is prepared by the following steps: Weigh each raw material according to the mass ratio. First, add zirconium phosphate to pure water at a mass ratio of 10:1 and stir at room temperature for 10-30 minutes to obtain a zirconium phosphate suspension. Then, add nano-zinc oxide to anhydrous ethanol at a mass ratio of 10:1, and then add silane coupling agent KH-550 while stirring. After that, sonicate at 60-80℃ for 30 minutes to obtain a nano-zinc oxide suspension. Then, add zirconium phosphate suspension to the nano-zinc oxide suspension, adjust the pH of the system to 4.0-4.5 using acetic acid, and then heat the system to 70-80℃ and stir for 2 hours. After that, spray dry to obtain ZnO@ZrP core-shell powder.

2. The antibacterial plastic for bottle caps according to claim 1, characterized in that, The improved branched copolymer polypropylene is prepared by the following steps: Weigh each raw material according to the mass fraction, mix linear copolymer polypropylene, 1,6-hexanediol diacrylate and dicumyl peroxide and add to a high-speed mixer, mix at 800-1000 rpm for 5-10 min to obtain a mixture, then place the mixture in an extruder, after which the extruded strip is water-cooled and pelletized, and vacuum dried at 90-100℃ for 5-6 h to obtain the improved branched copolymer polypropylene.

3. The antibacterial plastic for bottle caps according to claim 2, characterized in that, The extruder has the following temperature zones: Zone 1 155-160℃, Zone 2 160-170℃, Zone 3 170-175℃, Zone 4 175-180℃, and Zone 5 170-175℃; the extruder screw speed is 150-200 r / min.

4. A method for preparing an antibacterial plastic for bottle caps according to any one of claims 1 to 3, characterized in that, Includes the following steps: Weigh each raw material according to the mass fraction. Place the modified branched copolymer polypropylene, ZnO@ZrP core-shell powder, maleic anhydride grafted hydrogenated styrene-butadiene block copolymer, ethylene-octene copolymer, antioxidant 1010 and calcium stearate in a high-speed mixer and mix for 5-10 minutes. After mixing, the mixture is placed in a twin-screw extruder and extruded. The extruded material is then water-cooled and pelletized, and dried at 80-100℃ for 4-5 hours to obtain antibacterial plastic for bottle caps.

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