Antibacterial plastic and preparation method thereof

Abstract

The invention discloses an antibacterial plastic and a preparation method thereof, belongs to the technical field of high polymer materials, and provides introduction of functional master batch into polypropylene aiming at the problems of short aging, potential safety hazards and difficulty in inhibition of a biological membrane caused by migration of an antibacterial agent. The master batch is prepared from a carrier PP, a sulfhydrylated mesoporous silica loaded chlorhexidine gluconate slow-release unit and sulfurized chitosan with biological adhesion, and is matched with PP-g-MAH, an antioxidant and a lubricating agent through twin-screw melt blending. The preparation method comprises the following steps: firstly preparing functional master batches, and then compounding the functional master batches with matrix resin and extruding to form granules; the process temperature is 180-210 DEG C; the test shows that the initial antibacterial rate gt; the biofilm amount is obviously reduced, and the biofilm is suitable for medical instruments and food packaging. The problems of heat resistance and compatibility are solved, the release of the antibacterial agent is controlled, the migration risk is reduced, and the mechanical property is basically maintained.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to an antibacterial plastic and its preparation method. Background Technology

[0002] Plastic products are widely used in medical devices, food packaging, public facilities, and household appliances due to their advantages such as light weight, durability, and low cost. However, the surface of ordinary plastics is extremely prone to becoming a breeding ground for bacteria, fungi, and other microorganisms, which can not only cause cross-infection and threaten public health, but also lead to material aging, discoloration, and odor, thus shortening the lifespan of the products.

[0003] To impart antibacterial properties to plastics, current technologies typically employ the method of adding antibacterial agents to the plastic matrix. Currently, the main antibacterial agents are divided into three categories: Inorganic antibacterial agents, represented by nano-silver and nano-zinc oxide, have the advantages of broad antibacterial spectrum and good efficacy. However, their core drawback lies in the ion migration problem. Nano-silver or zinc ions exert their bactericidal effect by continuously migrating from the plastic matrix to the surface. This leads to continuous consumption of the antibacterial agent, and the antibacterial effect decays sharply over time, resulting in poor timeliness. Furthermore, the migrating heavy metal ions may enter the human body or the environment, posing potential biosafety risks and environmental pollution.

[0004] Organic antibacterial agents, represented by quaternary ammonium salts and triclosan, typically suffer from poor heat resistance. They are prone to decomposition and inactivation during the high-temperature melting and processing of plastics (above 200°C), significantly reducing the antibacterial properties of the final product. Furthermore, some organic antibacterial agents also exhibit a narrow antibacterial spectrum and are prone to causing bacterial resistance.

[0005] Natural antibacterial agents, such as chitosan, have the advantages of being safe and environmentally friendly. However, their disadvantages include relatively weak antibacterial ability and extremely poor compatibility with non-polar plastic matrices (such as polypropylene and polyethylene), making them difficult to disperse evenly and severely affecting the mechanical properties of the material.

[0006] In summary, existing technologies, when attempting to solve the problem of antibacterial properties in plastics, have always faced a dilemma: how to balance the "immediacy" and "long-lasting" antibacterial effects, and how to ensure that the added antibacterial components, while playing their role, do not harm the human body and the environment, and do not damage the original physical and mechanical properties of the plastic.

[0007] Furthermore, most existing technologies focus only on the killing effect on planktonic bacteria (i.e., antibacterial rate), neglecting a more serious objective problem in practical applications—the formation of bacterial biofilms. Once bacteria adhere to a material surface, they secrete extracellular polysaccharides and other substances to encapsulate themselves, forming a complex biofilm. Bacteria within biofilms are hundreds or even thousands of times more resistant to antibiotics and antibacterial agents than planktonic bacteria, making them extremely difficult to eliminate and a root cause of persistent problems such as medical device-related infections and food industry pipeline contamination. Currently, almost all antibacterial plastics on the market lack effective resistance to biofilm formation.

[0008] Therefore, there is an urgent need in this field to develop a new type of antimicrobial plastic that can not only solve the technical problems of existing antimicrobial agents such as easy migration, short duration of action, and low safety, but also further inhibit the formation of bacterial biofilms, thereby providing a more durable, safer, and more comprehensive solution to microbial contamination. Summary of the Invention

[0009] In view of the technical problems in the background art, such as the short antibacterial effect due to easy migration of antibacterial agents, the existence of safety hazards, and the inability to effectively inhibit biofilm formation, the purpose of this invention is to provide an antibacterial plastic and its preparation method.

[0010] The objective of this invention can be achieved through the following technical solutions: An antibacterial plastic is prepared from the following raw materials in parts by weight: Plastic matrix resin: 100 parts; Functional masterbatch: 3-10 parts; Compatibilizer: 1-5 parts; Antioxidant: 0.1–0.5 parts; Lubricant: 0.1–0.5 parts; The functional masterbatch is prepared from the following raw materials in parts by weight: Carrier resin: 100 parts; Surface-thiolized modified mesoporous silica loaded with sustained-release antibacterial unit: 20-40 parts; Sulfated chitosan with bioadhesive properties: 5-15 parts.

[0011] The first core improvement of this invention lies in the structural improvement and functional combination of the traditional antibacterial agent carrier (mesoporous silica) and antibacterial agent (chlorhexidine gluconate) to construct the "surface-thiol-modified mesoporous silica-supported sustained-release antibacterial unit".

[0012] Furthermore, the plastic matrix resin is PPH-T03 type polypropylene; the compatibilizer is maleic anhydride-grafted polypropylene, and the grafting rate of the maleic anhydride-grafted polypropylene is 0.8% to 1.5%; the antioxidant is antioxidant 1010; the lubricant is ethylene bis-stearamide; and the carrier resin is PPH-T03 type polypropylene.

[0013] Furthermore, the surface-thiol-modified mesoporous silica-supported sustained-release antibacterial unit is prepared by the following steps: A1. Dry mesoporous silica at 110-130℃ for 4-6 hours. Add the dried mesoporous silica to anhydrous toluene and ultrasonically disperse for 20-50 minutes. Add (3-mercaptopropyl)trimethoxysilane and stir the reaction at 80-100℃ for 10-14 hours. After the reaction is completed, cool, filter, wash, and vacuum dry to obtain mercapto-modified mesoporous silica. A2. Chlorhexidine gluconate was dissolved in a 40% (v / v) aqueous ethanol solution, and thiolized mesoporous silica was added. The mixture was stirred at room temperature for 20–28 hours, and then filtered, washed, and vacuum dried to obtain a mesoporous silica-supported slow-release antibacterial unit.

[0014] Furthermore, the ratio of dried mesoporous silica, anhydrous toluene, and (3-mercaptopropyl)trimethoxysilane described in A1 is 100g:1000mL:5-15g.

[0015] Furthermore, the ratio of chlorhexidine gluconate, aqueous ethanol solution, and thiolated mesoporous silica in A2 is 20-30g:500mL:100g.

[0016] The second core improvement of this invention lies in the molecular chain modification of the traditional natural antibacterial agent (chitosan) to prepare the "sulfurized chitosan with bioadhesive properties".

[0017] Furthermore, the bioadhesive-resistant sulfurized chitosan is prepared by the following steps: Chitosan was dissolved in an aqueous acetic acid solution and stirred until dissolved. Then, N-acetylcysteine ​​and water-soluble carbodiimide hydrochloride were added to the solution and stirred at room temperature in the dark for 16–24 hours. After the reaction was completed, the reaction solution was placed in a dialysis bag and dialyzed in deionized water for 48–72 hours. Finally, it was freeze-dried to obtain sulfurized chitosan with bioadhesive properties.

[0018] Furthermore, the volume fraction of the acetic acid aqueous solution is 1% to 2%; the molecular weight cutoff of the dialysis bag is 10,000 Da.

[0019] Furthermore, the ratio of chitosan, aqueous acetic acid solution, N-acetylcysteine, and water-soluble carbodiimide hydrochloride is 20g:2000mL:2~6g:1~3g.

[0020] The present invention also provides a method for preparing the above-mentioned antibacterial plastic, comprising the following steps: S1. Mix the carrier resin, surface-thiolized mesoporous silica loaded with slow-release antibacterial unit and bioadhesive sulfide chitosan according to the weight parts for 5-10 minutes to obtain mixture A. Add mixture A to a twin-screw extruder for melt blending, extrusion, water cooling and pelletizing to obtain functional masterbatch. S2. Mix the plastic matrix resin, functional masterbatch, compatibilizer, antioxidant and lubricant according to the weight parts for 5 to 10 minutes to obtain mixture B. Add mixture B to a twin-screw extruder for melt blending, extrusion, water cooling and pelletizing to obtain antibacterial plastic.

[0021] Furthermore, the twin-screw extruder described in S1 has a screw diameter of 35mm, a length-to-diameter ratio of 40:1, and a screw speed of 200-300rpm; the temperature settings for each zone of the twin-screw extruder are as follows: Zone 1 170-180℃, Zone 2 180-190℃, Zone 3 190-200℃, Zone 4 195-205℃, and die head temperature 190-200℃.

[0022] Furthermore, the screw speed of the twin-screw extruder in S2 is 300-400 rpm; the temperature of each zone of the twin-screw extruder is set as follows: Zone 1 180-190℃, Zone 2 190-200℃, Zone 3 200-210℃, Zone 4 205-215℃, and the die head temperature 200-210℃.

[0023] The beneficial effects of this invention are: This invention provides an antibacterial plastic and its preparation method. The invention introduces two core units through a functional masterbatch: a surface-thiolized modified mesoporous silica-supported slow-release antibacterial unit and bioadhesive-modified chitosan, achieving a combined performance of "high initial antibacterial activity + long-lasting antibacterial effect + strong anti-biofilm activity." Detailed analysis follows: (1) High initial and long-lasting antibacterial properties are achieved simultaneously: A. Examples 7-9 showed initial antibacterial rates of ≥98.5% (maximum 99.8%) for both strains, and maintained ≥94.0% (maximum 98.4%) after 30 days of aging. These results indicate that samples prepared under actual processing conditions such as twin-screw extrusion at 190-215°C exhibit significant initial antibacterial effects and retain high levels of antibacterial activity even after 30 days of simulated PBS immersion.

[0024] B. Key Control Verification: Example 8 and Comparative Example 3 showed similar initial antibacterial rates (e.g., 99.5% vs 99.1% for Escherichia coli), but significant differences after aging (96.8% vs 74.5% for Escherichia coli, 97.2% vs 78.0% for Staphylococcus aureus). Simply changing the "whether or not it is thiolated" resulted in a significant difference in long-term effectiveness, indicating that "thiolation modification of mesoporous silica" is key to improving long-term effectiveness. Comparative Examples 4 and 6 (with the antibacterial unit removed or replaced with commercially available mesoporous silica) showed antibacterial rates of only 15%–35% initially and after aging, further demonstrating that the "loaded sustained-release antibacterial unit" is the main contributor to antibacterial activity.

[0025] (2) Strong resistance to biofilm formation: A. The biofilm content in Examples 7-9 was low (OD570=0.30 / 0.18 / 0.12), with Example 9 having the lowest (0.12), indicating that the biofilm inhibition ability is enhanced with the increase of the content of functional masterbatch and the two core components.

[0026] B. Key Control Verification: The OD of Example 8 was 0.18; when sulfurized chitosan was removed (Comparative Example 5), the OD surged to 0.80; and when ordinary chitosan was used as a substitute (Comparative Example 7), the OD was 0.55. Furthermore, the antibacterial rates of all three were >95%, indicating that the difference in anti-biofilm activity is mainly determined by "sulfurized chitosan," and the antibacterial rate itself is not equivalent to anti-biofilm ability. Comparative Examples 4 / 6 (without or with replaced antibacterial units) had ODs of 0.40 / 0.50, both significantly higher than Example 8, indicating that the synergistic effect of the two core components is superior.

[0027] (3) The necessity and synergistic effect of the components have been systematically proven: A. Non-functional masterbatch (Comparative Example 2): Completely lacks antibacterial and anti-biofilm functions.

[0028] B. Only the surface state of the carrier was changed (Example 8 vs Comparative Example 3): the initial results were similar, but the long-term effects were significantly different, confirming the long-term significance of "thiolization modification".

[0029] C. Removal or replacement of the antimicrobial unit with an inactive carrier (Comparative Example 4 / 6): The antimicrobial and antibiofilm capabilities were significantly lost, indicating that the "loaded sustained-release antimicrobial unit" was the main source of function.

[0030] D. Removal or replacement of sulfurized chitosan (Comparative Examples 5 / 7): The antimicrobial rate remained high, but the biofilm content increased significantly, confirming that "sulfurized chitosan" is the key to anti-biofilm activity.

[0031] (4) The mechanical properties are basically maintained, and the modified chitosan has better compatibility: A. The tensile strength of Examples 7-9 was 31.5-32.0 MPa and the elongation at break was 320%-340%, which was only slightly lower than that of Comparative Example 2 (32.5 MPa and 350%), indicating that the mechanical properties were basically maintained while the function was obtained.

[0032] B. The elongation at break of Comparative Example 7 (ordinary chitosan) decreased to 300%, which is lower than the 330% of Example 8, indicating that the "sulfurization modification" has better compatibility and less impact on toughness.

[0033] (5) Principle Analysis: A. Sustained Release and Long-Lasting Effect: The difference in antibacterial rate after aging between Example 8 and Comparative Example 3 directly indicates that "thiolization modification" makes the release of antibacterial agents from mesoporous silica more controlled, slowing down excessive loss and thus maintaining a higher antibacterial rate after 30 days. The low antibacterial rates of Comparative Examples 4 / 6 further illustrate that only "thiolized and loaded with antibacterial agents" units can provide effective and sustained antibacterial action.

[0034] B. Evidence chain for anti-biofilm mechanism: Under the premise of similar antibacterial rate, Example 8 and Comparative Examples 5 / 7 showed a significant difference in biofilm amount (0.18 vs 0.80 / 0.55), proving that "sulfurized chitosan with bioadhesive properties" is the key factor in inhibiting biofilm formation; its "sulfurization" modification can significantly reduce the OD value and reduce the negative impact on mechanical toughness compared with ordinary chitosan (330% vs 300%).

[0035] C. Synergistic Enhancement: In Examples 7-9, with the increase of functional masterbatch and two core components, the antibacterial durability and anti-biofilm ability were simultaneously enhanced (e.g., Example 9 had the highest antibacterial rate and lowest OD after aging), indicating that the two functional components work synergistically in the same system: the slow-release antibacterial unit provides high initial and long-lasting killing effect, and sulfurized chitosan inhibits biofilm formation. Together, they achieve the comprehensive performance of "high efficiency + long-lasting effect + anti-biofilm".

[0036] (6) In conclusion: A. This invention, through the introduction of functional masterbatch, for the first time clearly demonstrated the combined performance of "high initial antibacterial activity + long-lasting antibacterial activity + strong anti-biofilm activity" in the same polypropylene system through comparative experiments. Compared with the dilemma in the prior art, the antibacterial rate of Examples 7-9 remained at 94.0%-98.4% after 30 days of aging, and the biofilm amount was significantly reduced (minimum 0.12), effectively making up for the shortcomings of poor timeliness and lack of anti-biofilm ability in the prior art.

[0037] B. The key mechanism stems from the synergistic effect of two improvements: the thiolized mesoporous silica-supported sustained-release antibacterial unit significantly enhances the long-lasting effect; and the bioadhesive-enhancing sulfide chitosan significantly inhibits biofilm formation. The data from the examples all demonstrate significant advantages compared to comparative examples where either component was removed or replaced.

[0038] C. While maintaining functionality, the mechanical properties of the material are basically controllable, and there is clear evidence that sulfurization modification improves compatibility and reduces toughness loss (Comparative Example 7 vs Example 8). Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Meanwhile, unless otherwise specified, the raw materials, reagents, or devices used in the following embodiments can be obtained from conventional commercial channels or by existing known methods. The specifications of some raw materials are as follows: Polypropylene (PP): China Petroleum & Chemical Corporation, PPH-T03 (injection molding grade), melt index 25 g / 10min.

[0040] Mesoporous silica (MCM-41, Pioneer Nano, pore size 5-20nm).

[0041] (3-Mercaptopropyl)trimethoxysilane (MPTMS): Commercially available, analytical grade.

[0042] Chlorhexidine gluconate: Commercially available, pharmaceutical grade, purity >99%.

[0043] Chitosan: Commercially available, degree of deacetylation 95%, viscosity-average molecular weight 200,000.

[0044] N-acetylcysteine: Commercially available, analytical grade.

[0045] Water-soluble carbodiimide hydrochloride (EDC): Commercially available, analytical grade.

[0046] Maleic anhydride-grafted polypropylene (PP-g-MAH): Commercially available, grafting rate 1.0%.

[0047] Antioxidant 1010 and lubricant EBS: both are commercially available industrial grade. Example

[0048] Preparation of surface-thiol-modified mesoporous silica-supported sustained-release antibacterial unit: (1) Place commercially available mesoporous silica in a vacuum drying oven and dry it at 110°C for 4 hours; (2) 100g of dried mesoporous silica was added to a three-necked flask containing 1000mL of anhydrous toluene and ultrasonically dispersed for 20 minutes. Mechanical stirring was then turned on, and 5g of (3-mercaptopropyl)trimethoxysilane (MPTMS) was added. The mixture was stirred at 80°C for 10 hours. After the reaction was completed, the mixture was naturally cooled to obtain the product. The product was filtered and washed three times each with anhydrous toluene and anhydrous ethanol. Then, it was vacuum dried at 80°C for 6 hours to obtain thiolized mesoporous silica with thiol groups (-SH) grafted on its surface.

[0049] (3) Dissolve 20g of medical-grade broad-spectrum antibacterial agent chlorhexidine gluconate in 500mL of 40% ethanol aqueous solution, add 100g of thiolized mesoporous silica prepared in step (2), stir and adsorb at room temperature for 20 hours, so that chlorhexidine gluconate molecules enter the pores of silica through physical adsorption, then filter, wash away the unadsorbed antibacterial agent on the surface with a small amount of ethanol, and then vacuum dry at 50℃ for 6 hours. After completion, the surface thiolized modified mesoporous silica loaded with sustained-release antibacterial unit is obtained. Example

[0050] Preparation of surface-thiol-modified mesoporous silica-supported sustained-release antibacterial unit: (1) Place commercially available mesoporous silica in a vacuum drying oven and dry it at 120°C for 5 hours; (2) 100g of dried mesoporous silica was added to a three-necked flask containing 1000mL of anhydrous toluene and ultrasonically dispersed for 30 minutes. Mechanical stirring was then turned on, and 10g of (3-mercaptopropyl)trimethoxysilane (MPTMS) was added. The mixture was stirred at 90°C for 12 hours. After the reaction was completed, the mixture was naturally cooled to obtain the product. The product was filtered and washed three times each with anhydrous toluene and anhydrous ethanol. Then, it was vacuum dried at 80°C for 12 hours to obtain thiolized mesoporous silica with thiol groups (-SH) grafted on its surface.

[0051] (3) Dissolve 25g of medical-grade broad-spectrum antibacterial agent chlorhexidine gluconate in 500mL of 40% ethanol aqueous solution, add 100g of the thiolized mesoporous silica prepared in step (2), stir and adsorb at room temperature for 24 hours, so that chlorhexidine gluconate molecules enter the pores of silica through physical adsorption, then filter, wash away the unadsorbed antibacterial agent on the surface with a small amount of ethanol, and then vacuum dry at 60℃ for 12 hours. After completion, the surface thiolized modified mesoporous silica loaded with sustained-release antibacterial unit is obtained. Example

[0052] Preparation of surface-thiol-modified mesoporous silica-supported sustained-release antibacterial unit: (1) Place commercially available mesoporous silica in a vacuum drying oven and dry it at 130°C for 6 hours; (2) 100g of dried mesoporous silica was added to a three-necked flask containing 1000mL of anhydrous toluene and ultrasonically dispersed for 50 minutes. Mechanical stirring was then turned on, and 15g of (3-mercaptopropyl)trimethoxysilane (MPTMS) was added. The mixture was stirred at 100℃ for 14 hours. After the reaction was completed, the mixture was naturally cooled to obtain the product. The product was filtered and washed three times each with anhydrous toluene and anhydrous ethanol. Then, it was vacuum dried at 80℃ for 12 hours to obtain thiolized mesoporous silica with thiol groups (-SH) grafted on its surface.

[0053] (3) Dissolve 30g of medical-grade broad-spectrum antibacterial agent chlorhexidine gluconate in 500mL of 40% ethanol aqueous solution, add 100g of the thiolized mesoporous silica prepared in step (2), stir and adsorb at room temperature for 28 hours, so that chlorhexidine gluconate molecules enter the pores of silica through physical adsorption, then filter, wash away the unadsorbed antibacterial agent on the surface with a small amount of ethanol, and then vacuum dry at 70℃ for 12 hours. After completion, the surface thiolized modified mesoporous silica loaded with sustained-release antibacterial unit is obtained.

[0054] Comparative Example 1 Comparative Example 1 served as the control group for Example 2. The mercapto process of the mesoporous silica in Example 2 was removed, while the remaining raw materials, amounts of raw materials, and preparation steps remained consistent with those in Example 2, as follows: (1) Place commercially available mesoporous silica in a vacuum drying oven and dry it at 120°C for 5 hours; (2) Dissolve 25g of medical-grade broad-spectrum antibacterial agent chlorhexidine gluconate in 500mL of 40% ethanol aqueous solution, add 100g of dried mesoporous silica, stir and adsorb at room temperature for 24 hours, then filter, wash away the unadsorbed antibacterial agent on the surface with a small amount of ethanol, and then vacuum dry at 60℃ for 12 hours. After completion, mesoporous silica-supported slow-release antibacterial unit is obtained. Example

[0055] Preparation of bioadhesive chitosan: 20g of commercially available chitosan was dissolved in 2000mL of 1% acetic acid aqueous solution and stirred until completely dissolved. Then, 2g of N-acetylcysteine ​​was added as a thiol source and 1g of water-soluble carbodiimide hydrochloride (EDC) was added as a coupling agent. The mixture was stirred and reacted at room temperature (20℃) in the dark for 16 hours. After the reaction was completed, the reaction solution was placed in a dialysis bag (molecular weight cutoff 10000 Da) and dialyzed in deionized water for 48 hours, with the deionized water being replaced every 8 hours. Finally, the mixture was freeze-dried to obtain white flocculent sulfurized chitosan with bioadhesive properties. Example

[0056] Preparation of bioadhesive chitosan: 20g of commercially available chitosan was dissolved in 2000mL of 2% acetic acid aqueous solution and stirred until completely dissolved. Then, 4g of N-acetylcysteine ​​was added as a thiol source and 2g of water-soluble carbodiimide hydrochloride (EDC) was added as a coupling agent. The mixture was stirred and reacted at room temperature (25℃) in the dark for 24 hours. After the reaction was completed, the reaction solution was placed in a dialysis bag (molecular weight cutoff 10000 Da) and dialyzed in deionized water for 64 hours, with the deionized water being replaced every 8 hours. Finally, the mixture was freeze-dried to obtain white flocculent sulfurized chitosan with bioadhesive properties. Example

[0057] Preparation of bioadhesive chitosan: 20g of commercially available chitosan was dissolved in 2000mL of 2% acetic acid aqueous solution and stirred until completely dissolved. Then, 6g of N-acetylcysteine ​​was added as a thiol source and 3g of water-soluble carbodiimide hydrochloride (EDC) was added as a coupling agent. The mixture was stirred and reacted at room temperature (30℃) in the dark for 24 hours. After the reaction was completed, the reaction solution was placed in a dialysis bag (molecular weight cutoff 10000 Da) and dialyzed in deionized water for 72 hours, with the deionized water being replaced every 8 hours. Finally, the mixture was freeze-dried to obtain white flocculent sulfurized chitosan with bioadhesive properties. Example

[0058] Preparation of antibacterial plastics: (1) Preparation of functional masterbatch: 1000g of carrier resin (polypropylene, PPH-T03), 200g of surface thiol-modified mesoporous silica-loaded slow-release antibacterial unit prepared in Example 1 and 50g of bioadhesive sulfide chitosan prepared in Example 4 were premixed in a high-speed mixer at 800rpm for 5 minutes to obtain mixture A. Then, mixture A was added to a twin-screw extruder (screw diameter 35mm, length-to-diameter ratio 40:1) for melt blending, extrusion, water cooling and pelletizing to obtain functional masterbatch. The temperature of each zone of the twin-screw extruder was set as follows: zone 1 170℃, zone 2 180℃, zone 3 190℃, zone 4 195℃, die head temperature 190℃, and screw speed 200rpm.

[0059] (2) Preparation of antibacterial plastic: 10 kg of plastic matrix resin (polypropylene, PPH-T03), 0.3 kg of functional masterbatch obtained in step (1), 0.1 kg of compatibilizer maleic anhydride grafted polypropylene (PP-g-MAH, grafting rate 0.8%~1.5%), 10 g of antioxidant 1010 and 10 g of lubricant ethylene bis-stearamide (EBS) are mixed in a high-speed mixer for 5 minutes to obtain mixture B. Then, mixture B is added to a twin-screw extruder for melt blending, extrusion, water cooling and pelletizing to obtain antibacterial plastic. The temperature of each zone of the twin-screw extruder is set according to the processing temperature of the plastic matrix resin: Zone 1 180℃, Zone 2 190℃, Zone 3 200℃, Zone 4 205℃, die head temperature 200℃, and screw speed 300 rpm. Example

[0060] Preparation of antibacterial plastics: (1) Preparation of functional masterbatch: 1000g of carrier resin (polypropylene, PPH-T03), 300g of surface thiol-modified mesoporous silica-loaded slow-release antibacterial unit prepared in Example 2, and 100g of bioadhesive sulfide chitosan prepared in Example 5 were premixed in a high-speed mixer at 1000rpm for 10 minutes to obtain mixture A. Then, mixture A was added to a twin-screw extruder (screw diameter 35mm, length-to-diameter ratio 40:1) for melt blending, extrusion, water cooling, and pelletizing to obtain functional masterbatch. The temperature of each zone of the twin-screw extruder was set as follows: Zone 1 175℃, Zone 2 185℃, Zone 3 195℃, Zone 4 200℃, die head temperature 195℃, and screw speed 300rpm.

[0061] (2) Preparation of antibacterial plastic: 10 kg of plastic matrix resin (polypropylene, PPH-T03), 1.0 kg of functional masterbatch obtained in step (1), 0.5 kg of compatibilizer maleic anhydride grafted polypropylene (PP-g-MAH, grafting rate 0.8%~1.5%), 50 g of antioxidant 1010 and 50 g of lubricant ethylene bis-stearamide (EBS) are mixed in a high-speed mixer for 10 minutes to obtain mixture B. Then, mixture B is added to a twin-screw extruder for melt blending, extrusion, water cooling and pelletizing to obtain antibacterial plastic. The temperature of each zone of the twin-screw extruder is set according to the processing temperature of the plastic matrix resin: Zone 1 185℃, Zone 2 195℃, Zone 3 205℃, Zone 4 210℃, die head temperature 205℃, and screw speed 400 rpm. Example

[0062] Preparation of antibacterial plastics: (1) Preparation of functional masterbatch: 1000g of carrier resin (polypropylene, PPH-TO3), 400g of surface thiol-modified mesoporous silica-supported slow-release antibacterial unit prepared in Example 3 and 150g of bioadhesive sulfide chitosan prepared in Example 6 were premixed in a high-speed mixer at 1000rpm for 10 minutes to obtain mixture A. Then, mixture A was added to a twin-screw extruder (screw diameter 35mm, length-to-diameter ratio 40:1) for melt blending, extrusion, water cooling and pelletizing to obtain functional masterbatch. The temperature of each zone of the twin-screw extruder was set as follows: zone 1 180℃, zone 2 190℃, zone 3 200℃, zone 4 205℃, die head temperature 200℃, and screw speed 300rpm.

[0063] (2) Preparation of antibacterial plastic: 10 kg of plastic matrix resin (polypropylene, PPH-T03), 1.0 kg of functional masterbatch obtained in step (1), 0.5 kg of compatibilizer maleic anhydride grafted polypropylene (PP-g-MAH, grafting rate 0.8%~1.5%), 50 g of antioxidant 1010 and 50 g of lubricant ethylene bis-stearamide (EBS) are mixed in a high-speed mixer for 10 minutes to obtain mixture B. Then, mixture B is added to a twin-screw extruder for melt blending, extrusion, water cooling and pelletizing to obtain antibacterial plastic. The temperature of each zone of the twin-screw extruder is set according to the processing temperature of the plastic matrix resin: Zone 1 190℃, Zone 2 200℃, Zone 3 210℃, Zone 4 215℃, die head temperature 210℃, and screw speed 400 rpm.

[0064] Comparative Example 2 Comparative Example 2 was the control group of Example 8. Step (1) was removed, and 1.0 kg of functional masterbatch was removed in step (2). The remaining raw materials, raw material amounts and preparation steps were kept consistent with those in Example 8, and antibacterial plastic was finally obtained.

[0065] Comparative Example 3 Comparative Example 3 served as the control group for Example 8. In Example 8, 300g of the surface-thiolized modified mesoporous silica-supported slow-release antibacterial unit prepared in Example 2 was replaced with 300g of the mesoporous silica-supported slow-release antibacterial unit prepared in Comparative Example 1. The remaining raw materials, raw material amounts, and preparation steps remained consistent with those in Example 8, and antibacterial plastic was finally obtained.

[0066] Comparative Example 4 Comparative Example 4 served as the control group for Example 8. 300g of the surface-thiolized modified mesoporous silica-loaded slow-release antibacterial unit prepared in Example 2 was removed from Example 8, while the remaining raw materials, raw material amounts, and preparation steps remained consistent with those in Example 8, ultimately yielding antibacterial plastic.

[0067] Comparative Example 5 Comparative Example 5 served as the control group for Example 8. 100g of the bioadhesive sulfurized chitosan prepared in Example 5 was removed from Example 8, while the remaining raw materials, raw material amounts, and preparation steps remained consistent with those in Example 8, ultimately yielding antibacterial plastic.

[0068] Comparative Example 6 Comparative Example 6 served as the control group for Example 8. In Example 8, 300g of the surface-thiolized modified mesoporous silica-supported slow-release antibacterial unit prepared in Example 2 was replaced with 300g of commercially available mesoporous silica. The remaining raw materials, raw material amounts, and preparation steps remained consistent with those in Example 8, ultimately yielding antibacterial plastic.

[0069] Comparative Example 7 Comparative Example 7 served as the control group for Example 8. In Example 8, 100g of the bioadhesive sulfurized chitosan prepared in Example 5 was replaced with 100g of commercially available chitosan. The remaining raw materials, raw material amounts, and preparation steps remained consistent with those in Example 8, ultimately yielding antibacterial plastic.

[0070] Test Example 1 The antibacterial plastics prepared in Examples 7 to 9 and Comparative Examples 2 to 7 were subjected to performance tests. The performance test process is as follows, and the test results are shown in Table 1: 1. Long-lasting antibacterial performance test: Test method: Refer to "GB / T 31402-2015 Plastics - Test method for antibacterial properties of plastic surfaces".

[0071] (1) Sample preparation: The antibacterial plastics prepared in Examples 7 to 9 and Comparative Examples 2 to 7 were injection molded into standard sample pieces of 50mm×50mm×2mm.

[0072] (2) Aging treatment (simulating long-term effectiveness): Each set of samples (except those used for initial testing) was immersed in phosphate buffered saline (PBS, pH=7.4) and placed in a 37°C constant temperature shaking incubator. The PBS solution was changed daily for 30 days. This process was designed to simulate the slow dissolution and consumption of antimicrobial agents during long-term use. After 30 days, the samples were removed, rinsed with sterile water, and dried for later use.

[0073] (3) Antibacterial test: Take 3 "initial sample" and 3 "sample after 30 days of aging". Add bacterial suspensions of *Escherichia coli* (ATCC 8739) and *Staphylococcus aureus* (ATCC 6538) (concentration 10) to each sample. 5 Apply 0.1 mL (CFU / mL) to the sample surface and cover with a sterile film. Incubate the inoculated sample in a constant temperature incubator at 37℃ and humidity >90% for 24 hours. Elute the bacteria on the sample surface with elution buffer and calculate the viable bacteria count using the plate count method. Antibacterial rate R(%) = [(BC) / B] × 100%, where B is the number of viable bacteria on Comparative Example 2 (blank control group) and C is the number of viable bacteria on the test sample.

[0074] 2. Anti-biofilm formation performance test: Test method: Crystal violet staining method.

[0075] (1) Sample preparation: The antibacterial plastics prepared in Examples 7 to 9 and Comparative Examples 2 to 7 were injection molded into circular sheets with a diameter of 15 mm and sterilized with ethylene oxide.

[0076] (2) Biofilm culture: Sterile samples were placed into 24-well culture plates, and 2 mL of TSB medium containing Staphylococcus aureus (initial bacterial concentration 10) was added to each well. 6 (CFU / mL).

[0077] (3) Place it in a constant temperature shaker at 37℃ and slowly shake it for 72 hours to allow the bacteria to grow fully and form a biofilm.

[0078] (4) Staining and Quantification: Carefully aspirate the culture medium, gently wash three times with PBS buffer to remove airborne bacteria, add 2 mL of methanol for fixation for 15 minutes, then aspirate the methanol and allow the sample to air dry. Add 2 mL of 0.1% (w / v) crystal violet solution for staining for 20 minutes, carefully rinse the sample with deionized water to remove excess dye, then dry. Add 2 mL of 33% glacial acetic acid to each well, shake for 15 minutes to fully dissolve the crystal violet bound to the biofilm, and take the solution. Measure the absorbance (OD570 value) at 570 nm using a microplate reader. The higher the OD value, the greater the biofilm content.

[0079] 3. Mechanical property testing: Test method: Refer to GB / T 1040.2-2006 Determination of tensile properties of plastics.

[0080] (1) Sample preparation: The antibacterial plastics prepared in Examples 7 to 9 and Comparative Examples 2 to 7 were injection molded into dumbbell-shaped standard tensile specimens according to the standard.

[0081] (2) Performance testing: Using a universal testing machine, tensile tests were conducted on the specimens at a tensile speed of 50 mm / min at room temperature, and the tensile strength and elongation at break were recorded. Five specimens were tested in each group, and the average value of the results was taken.

[0082] Table 1 Test Results project Example 7 Example 8 Example 9 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Initial antibacterial rate (%, E. coli) 98.5 99.5 99.7 0.0 99.1 28.0 99.3 18.0 99.4 Antibacterial rate (%, E. coli) after 30 days of aging 94.0 96.8 98.0 0.0 74.5 25.0 95.0 15.0 95.8 Initial antibacterial rate (%, Staphylococcus aureus) 98.8 99.6 99.8 0.0 99.3 35.0 99.4 28.0 99.5 Antibacterial rate (%, Staphylococcus aureus) after 30 days of aging 94.5 97.2 98.4 0.0 78.0 32.0 95.5 25.0 96.2 Biofilm quantity (OD570 value) 0.30 0.18 0.12 1.20 0.22 0.40 0.80 0.50 0.55 Tensile strength (MPa) 32.0 31.8 31.5 32.5 31.8 32.0 31.7 31.6 31.2 Elongation at break (%) 340 330 320 350 328 335 327 325 300 Analysis of the data in Table 1: 1. Overall effect analysis of functional masterbatch (comparative example 8 and comparative example 2): (1) Differences in technical solutions: The only difference between the technical solution of Comparative Example 2 and Example 8 is that no functional masterbatch was added. Comparative Example 2 only contains plastic matrix resin (polypropylene), compatibilizer, antioxidant and lubricant.

[0083] (2) Test Result Analysis: A. Antibacterial properties: Table 1 shows that the initial antibacterial rate and the antibacterial rate after 30 days of aging of Comparative Example 2 were both 0.0% against both Escherichia coli and Staphylococcus aureus. This indicates that the pure polypropylene matrix without functional masterbatch does not possess any antibacterial ability.

[0084] B. Anti-biofilm properties: The biofilm amount (OD570 value) of Comparative Example 2 was 1.20, which was the highest among all test groups. This indicates that a large number of bacterial biofilms can easily form on the surface of pure polypropylene materials.

[0085] C. Mechanical properties: The tensile strength (32.5 MPa) and elongation at break (350%) of Comparative Example 2 represent the basic mechanical properties of the pure polypropylene matrix.

[0086] Conclusion: By comparing with Example 8 (initial antibacterial rate >99%, antibacterial rate after aging >96%, biofilm amount 0.18), it can be clearly concluded that functional masterbatch is the core key component that enables plastics to acquire antibacterial and anti-biofilm formation capabilities. Without functional masterbatch, the product does not possess the claimed functions.

[0087] 2. Analysis of the effect of thiolization (-SH) modification on the surface of mesoporous silica (Comparative Example 8 and Comparative Example 3): (1) Differences in technical solutions: Compared with Example 8, the antibacterial unit in the functional masterbatch of Comparative Example 3 was replaced by "surface-thiolized modified mesoporous silica-supported sustained-release antibacterial unit" (prepared in Example 2) with "mesoporous silica-supported sustained-release antibacterial unit" (prepared in Comparative Example 1) without thiolization modification. All other components and amounts were exactly the same.

[0088] (2) Test Result Analysis: A. Long-lasting antibacterial properties: Initial antibacterial rate: The initial antibacterial rates of Comparative Example 3 (Escherichia coli - 99.1%, Staphylococcus aureus - 99.3%) were very close to those of Example 8 (Escherichia coli - 99.5%, Staphylococcus aureus - 99.6%), indicating that the unmodified carrier can also load and release antibacterial agents, showing excellent antibacterial effects in the initial stage.

[0089] Antibacterial rate after 30 days of aging: The antibacterial rate of Comparative Example 3 after aging (Escherichia coli - 74.5%, Staphylococcus aureus - 78.0%) was significantly lower than that of Example 8 (Escherichia coli - 96.8%, Staphylococcus aureus - 97.2%). The decrease in antibacterial rate was much greater than that of Example 8.

[0090] B. Anti-biofilm performance: The biofilm amount (OD570 value) of Comparative Example 3 was 0.22, which was slightly higher than 0.18 of Example 8, but still showed a better anti-biofilm effect.

[0091] Conclusion: Comparing the data from Example 8 and Comparative Example 3 demonstrates that thiolation modification of the mesoporous silica surface is key to achieving "long-lasting" antibacterial properties. Although the initial antibacterial effects were not significantly different, after 30 days of simulated dissolution aging, the antibacterial performance retention rate of the thiolated modified sample (Example 8) was much higher than that of the unmodified sample (Comparative Example 3). This indicates that thiolation effectively slows down the release rate of the antibacterial agent and prevents its rapid loss, thereby significantly improving the antibacterial duration of the material.

[0092] 3. Necessity analysis of surface-thiolized modified mesoporous silica-supported slow-release antibacterial unit (comparative Example 8 with Comparative Examples 4 and 6): (1) Differences in technical solutions: Comparative Example 4: Compared with Example 8, the "surface-thiolized mesoporous silica-supported slow-release antibacterial unit" was completely removed from the functional masterbatch, and only sulfurized chitosan was retained.

[0093] Comparative Example 6: Compared with Example 8, the antimicrobial unit in the functional masterbatch was replaced with an equal amount of commercially available mesoporous silica that had not undergone any treatment.

[0094] (2) Test Result Analysis: A. Antibacterial properties: The initial and post-aging antibacterial rates of Comparative Examples 4 and 6 were very low (between 15.0% and 35.0%), which were almost negligible compared to Example 8 (>96%). This indicates that sulfurized chitosan alone or pure mesoporous silica does not possess effective antibacterial capabilities.

[0095] B. Anti-biofilm properties: The biofilm amounts of Comparative Example 4 (OD570=0.40) and Comparative Example 6 (OD570=0.50) were much higher than those of Example 8 (0.18), indicating that their ability to inhibit biofilm formation was weaker.

[0096] Conclusion: These two comparative examples demonstrate, from both positive and negative perspectives, that the surface-thiolized mesoporous silica-supported slow-release antibacterial unit is the main contributor to antibacterial and anti-biofilm properties and is an indispensable core component. The absence of this component (Comparative Example 4) or its replacement with an inactive pure carrier (Comparative Example 6) results in a near-complete loss of product functionality.

[0097] 4. Necessity and role analysis of sulfurized chitosan with bioadhesive properties (Comparative Example 8 with Comparative Examples 5 and 7): (1) Differences in technical solutions: Comparative Example 5: Compared with Example 8, the functional masterbatch completely removed "bioadhesive sulfurized chitosan".

[0098] Comparative Example 7: Compared to Example 8, the sulfurized chitosan in the functional masterbatch was replaced with an equal amount of unmodified commercially available ordinary chitosan.

[0099] (2) Test Result Analysis: A. Antibacterial properties: The initial and aging antibacterial rates of Comparative Examples 5 and 7 were both very high (>95%), which are very close to the data of Example 8. This indicates that in this technical solution, the antibacterial properties are mainly provided by the "surface-thiol-modified mesoporous silica-supported slow-release antibacterial unit", and the direct contribution of sulfurized chitosan or ordinary chitosan to the antibacterial rate is not significant.

[0100] B. Anti-biofilm properties: This is the key difference. The biofilm amount (OD570 value) of Example 8 was 0.18, while the OD value of Comparative Example 5 (with sulfurized chitosan removed) was 0.80, and the OD value of Comparative Example 7 (replaced with ordinary chitosan) was 0.55. The relationship among the three is: Example 8 << Comparative Example 7 < Comparative Example 5.

[0101] C. Mechanical properties: It is worth noting that the elongation at break of Comparative Example 7 (300%) was the lowest among all the samples containing additives, lower than that of Example 8 (330%), indicating that the direct addition of unmodified chitosan may have a certain negative impact on the toughness of the material.

[0102] Conclusion: Comparing Example 8 and Comparative Example 5, it is clear that sulfurized chitosan with bioadhesive properties is the key component for achieving highly efficient anti-biofilm formation capabilities. Without it, even if the material has a high antibacterial rate, it cannot effectively inhibit biofilm formation (OD value increases sharply from 0.18 to 0.80).

[0103] Meanwhile, comparing Example 8 and Comparative Example 7 demonstrates that "sulfurization" modification of chitosan is necessary. The modified sulfurized chitosan (Example 8, OD=0.18) exhibits a stronger ability to inhibit biofilm formation than unmodified ordinary chitosan (Comparative Example 7, OD=0.55). Furthermore, the modification improves its compatibility with the matrix and has a smaller negative impact on mechanical properties.

[0104] 5. Overall Conclusion: (1) The core of this invention lies in the functional masterbatch, which endows polypropylene plastic, which originally does not have antibacterial and anti-biofilm properties, with excellent functionality.

[0105] (2) The surface-thiolized modified mesoporous silica-supported slow-release antibacterial unit is the key to achieving efficient and long-lasting antibacterial effects. Among them, surface thiolization is the core technical means to ensure the long-lasting antibacterial performance.

[0106] (3) Sulfurized chitosan with bioadhesive properties is key to achieving excellent resistance to biofilm formation. Furthermore, sulfur modification of chitosan is necessary, as it can significantly enhance the anti-biofilm effect and improve compatibility with the plastic matrix.

[0107] (4) By combining the above two functional components in the functional masterbatch, the present invention has successfully prepared an antibacterial plastic with both high long-lasting antibacterial rate and strong resistance to biofilm formation, while basically maintaining the original excellent mechanical properties of the matrix material.

[0108] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0109] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can 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, characterized by, Prepared from the following raw materials by weight parts: Plastic matrix resin: 100 parts; Functional masterbatch: 3-10 parts; Compatibility agent: 1-5 parts; Antioxidant: 0.1-0.5 parts; Lubricant: 0.1-0.5 parts; The functional masterbatch is prepared from the following raw materials by weight parts: Carrier resin: 100 parts; Surface thiol-modified mesoporous silica loaded sustained-release antibacterial unit: 20-40 parts; Sulfurized chitosan with biological adhesion: 5-15 parts.

2. An antibacterial plastic according to claim 1, wherein The plastic matrix resin is PPH-T03 type polypropylene; the compatibility agent is maleic anhydride grafted polypropylene, the grafting rate of the maleic anhydride grafted polypropylene is 0.8%-1.5%; the antioxidant is antioxidant 1010; the lubricant is ethylene bis stearamide; the carrier resin is PPH-T03 type polypropylene.

3. The antimicrobial plastic according to claim 1, wherein The surface thiol-modified mesoporous silica loaded sustained-release antibacterial unit is prepared by the following steps: A1, dry the mesoporous silica at 110-130℃ for 4-6 hours, add the dried mesoporous silica into anhydrous toluene, ultrasonic dispersion for 20-50 minutes, add (3-mercaptopropyl) trimethoxysilane, stir at 80-100℃ for 10-14 hours, after the reaction is completed, cool, filter, wash, vacuum dry to obtain thiol-modified mesoporous silica; A2, dissolve chlorhexidine gluconate in a 40% volume fraction of ethanol aqueous solution, add thiol-modified mesoporous silica, stir at room temperature for 20-28 hours, then filter, wash, vacuum dry to obtain mesoporous silica loaded sustained-release antibacterial unit.

4. An antibacterial plastic according to claim 3, wherein The amount ratio of the dried mesoporous silica, anhydrous toluene and (3-mercaptopropyl) trimethoxysilane in A1 is 100g:1000mL:5-15g.

5. An antibacterial plastic according to claim 3, wherein The amount ratio of chlorhexidine gluconate, ethanol aqueous solution and thiol-modified mesoporous silica in A2 is 20-30g:500mL:100g.

6. The antimicrobial plastic according to claim 1, wherein The sulfurized chitosan with biological adhesion is prepared by the following steps: Dissolve chitosan in acetic acid aqueous solution, stir to dissolve, then add N-acetyl cysteine and water-soluble carbodiimide hydrochloride, stir at room temperature for 16-24 hours in the dark, after the reaction is completed, pack the reaction solution into a dialysis bag, dialyze in deionized water for 48-72 hours, then freeze-dry to obtain sulfurized chitosan with biological adhesion.

7. An antibacterial plastic according to claim 6, wherein The amount ratio of chitosan, acetic acid aqueous solution, N-acetyl cysteine and water-soluble carbodiimide hydrochloride is 20g:2000mL:2-6g:1-3g.

8. A process for the preparation of an antibacterial plastic according to any one of claims 1 to 7, characterized in that, Including the following steps: S1, mix the carrier resin, surface thiol-modified mesoporous silica loaded sustained-release antibacterial unit and sulfurized chitosan with biological adhesion according to weight parts for 5-10 minutes to obtain mixture A, add mixture A into a twin-screw extruder for melt blending, extrusion, water cooling and pelletizing to obtain a functional masterbatch; S2, the plastic matrix resin, functional master batch, compatibilizer, antioxidant and lubricant are mixed according to weight parts for 5-10 minutes to obtain a mixture B, and the mixture B is added into a double screw extruder for melt blending, extrusion, water cooling and granulation, thus obtaining the antibacterial plastic.

9. A method of producing an antibacterial plastic according to claim 8, characterized in that, The screw diameter of the double screw extruder in S1 is 35 mm, the length-diameter ratio is 40:1, and the screw rotation speed is 200-300 rpm; the temperature of each zone of the double screw extruder is set as follows: zone 1, 170-180℃; zone 2, 180-190℃; zone 3, 190-200℃; zone 4, 195-205℃; and the die temperature, 190-200℃.

10. The method of claim 8, wherein the antimicrobial plastic is prepared by adding the antimicrobial agent to the plastic in the form of a masterbatch. 5 The screw rotation speed of the double screw extruder in S2 is 300-400 rpm; the temperature of each zone of the double screw extruder is set as follows: zone 1, 180-190℃; zone 2, 190-200℃; zone 3, 200-210℃; zone 4, 205-215℃; and the die temperature, 200-210℃.