Antibacterial high-toughness polypropylene material and application thereof

Abstract

The invention relates to an antibacterial high-toughness polypropylene material and application thereof, and belongs to the technical field of polypropylene materials. The polypropylene material consists of polypropylene resin, an antibacterial toughening agent, a compatilizer and an auxiliary agent, wherein the antibacterial toughening agent is a polyolefin elastomer with a molecular chain grafted with an antibacterial functional group, the compatilizer is maleic anhydride grafted polypropylene, and the auxiliaries are an antioxidant and a lubricant which are compounded according to a specific proportion. During preparation, the antibacterial toughening agent is prepared through a free radical grafting reaction, and then all the components are subjected to twin-screw extrusion, melt blending and granulation at the temperature of 180-210 DEG C; the material can be subjected to melt casting or film blowing forming to form a food packaging film, has efficient and lasting antibacterial property and excellent toughness, and meets the harsh requirements of food packaging.

Description

Technical Field

[0001] This invention belongs to the field of polypropylene material technology, and relates to an antibacterial and highly tough polypropylene material and its applications. Background Technology

[0002] Food packaging is a crucial link in ensuring food quality and safety and extending shelf life. Plastic packaging bags, due to their advantages such as lightweight, low cost, and ease of processing, are widely used in snack foods, fresh fruits and vegetables, and dairy products. Polypropylene, as a commonly used food packaging substrate, possesses good chemical stability, oil resistance, and recyclability, and meets the safety standards for food contact materials. Films made from polypropylene combine a certain level of mechanical strength and transparency, meeting the packaging needs of most foods and occupying a significant share of the food packaging plastics market. However, with consumers increasingly focusing on food hygiene and safety, and the growing problem of packaging damage in e-commerce logistics, the market has placed higher demands on the antibacterial properties and impact resistance of polypropylene packaging bags. Traditional pure polypropylene materials are no longer fully suitable for today's complex food packaging scenarios.

[0003] To improve the overall performance of polypropylene materials, the industry has conducted numerous improvement studies. Regarding antibacterial properties, a common approach is to directly add inorganic antibacterial agents such as silver ions, zinc oxide nanoparticles, or organic antibacterial agents such as quaternary ammonium salts and isothiazolinones to the polypropylene matrix. This inhibits microbial growth through the slow-release effect of the antibacterial components. For toughening modification, physical blending is often employed, incorporating toughening agents such as polyolefin elastomers and EPDM rubber into the polypropylene. The elastomer particles absorb energy upon impact, improving the material's brittleness. These single-function modification technologies are relatively mature and have been applied in some fields, but their limitations are gradually becoming apparent, and they struggle to simultaneously meet the dual requirements of antibacterial and toughening properties.

[0004] Existing technologies for achieving both antibacterial and toughening functions in polypropylene materials often rely on simple additive solutions, sometimes even exhibiting mutually restrictive performance characteristics. For instance, while adding inorganic antibacterial agents can enhance antibacterial efficacy, they tend to aggregate within the polypropylene matrix, affecting transparency and potentially reducing mechanical strength. Organic antibacterial agents, though dispersible, suffer from rapid migration and short-lived antibacterial effects, and some components may not meet food contact safety requirements. Conversely, while adding large amounts of toughening agents can improve toughness, it may dilute the antibacterial agent concentration, leading to a decline in antibacterial performance. Furthermore, increasing the amount of antibacterial agent to maintain antibacterial efficacy may compromise the compatibility between the toughening agent and the polypropylene matrix, affecting the toughening effect. This inherent contradiction makes it difficult for existing modified polypropylene materials to simultaneously achieve highly efficient and durable antibacterial properties, significantly improved toughness, and the safety required for food packaging, failing to meet the demanding requirements of long-term preservation of fresh food and resistance to damage during low-temperature transportation. Summary of the Invention

[0005] The purpose of this invention is to provide an antibacterial and high-toughness polypropylene material and its application. Antibacterial functional groups are introduced into the molecular chain of polyolefin elastomer through free radical grafting reaction to form a functionalized elastomer with both antibacterial and toughening properties, which breaks through the limitations of traditional antibacterial polypropylene materials.

[0006] The objective of this invention can be achieved through the following technical solutions: An antibacterial and high-toughness polypropylene material is prepared from the following components in parts by weight: 70-95 parts polypropylene resin; 5-30 parts antibacterial toughening agent; 0.5-5 parts compatibilizer; and 0.2-2 parts additives. The antibacterial toughening agent is a polyolefin elastomer with antibacterial functional groups grafted onto its molecular chain.

[0007] In this application, a polyolefin elastomer is used as the molecular backbone, which itself is an excellent toughening phase. Antimicrobial functional groups are grafted onto this flexible molecular chain through a chemical reaction. This avoids the problem of antimicrobial particle agglomeration in traditional blends, achieving uniform dispersion of the antimicrobial component in the PP matrix. The antimicrobial agent is no longer a rigid particle but becomes part of the flexible molecular chain, eliminating the problem of decreased toughness caused by poor interfacial compatibility and stress concentration. Furthermore, the antimicrobial functional groups are connected to the elastomer backbone through stable covalent bonds, making them less prone to migration into food, thus greatly improving safety and meeting the stringent requirements of food packaging regulations. The chemical bonding method ensures the durability of the antimicrobial component, avoiding the problem of premature attenuation of antimicrobial performance caused by rapid precipitation of small molecule antimicrobial agents, achieving a long-lasting and highly effective antimicrobial effect. Maleic anhydride-grafted polypropylene, as a compatibilizer, plays a connecting role in this system. The PP segment of its molecular chain is compatible with the PP matrix, while the anhydride groups can combine with the active groups on the antibacterial toughening agent molecular chain, further strengthening the interfacial adhesion between the antibacterial toughening agent and the PP matrix. This further enhances the mechanical strength of the material, making the toughening effect more significant.

[0008] As a preferred embodiment of the present invention, the polyolefin elastomer is one or more of ethylene-octene copolymer, ethylene-butene copolymer, and ethylene propylene diene monomer (EPDM) rubber.

[0009] As a preferred embodiment of the present invention, the antibacterial functional group is one or more of quaternary ammonium salt groups, guanidine salt groups, and imidazole salt groups.

[0010] Without requiring any creative effort, it is easy to conceive of the above-mentioned methods of grafting groups through free radical reactions. Since the principles and specific operating conditions of free radical reactions are generally understood by those skilled in the art, they will be briefly described again. It should be noted that the specific operating conditions of free radical reactions may be directly related to the reaction conversion rate for grafting, but they have no effect on the molecular morphology or properties of antibacterial toughening agents. That is, the specific operating conditions of free radical reactions will not significantly affect the technical functions of antibacterial toughening agents, such as antibacterial properties and toughening performance.

[0011] As a preferred embodiment of the present invention, the grafting rate of the antibacterial functional group on the polyolefin elastomer is 0.5%-5%; the grafting rate refers to the mass percentage of the antibacterial functional group monomer relative to the polyolefin elastomer.

[0012] As a preferred embodiment of the present invention, the compatibilizer is maleic anhydride-grafted polypropylene.

[0013] As a preferred embodiment of the present invention, the additive is composed of an antioxidant and a lubricant in a mass ratio of 1:0.5-2; the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1, and the lubricant is a mixture of calcium stearate and erucamide in a mass ratio of 1:1.

[0014] Furthermore, the preparation method of the aforementioned antibacterial and high-toughness polypropylene material includes the following steps: (1) The polyolefin elastomer, antibacterial functional group monomer and initiator are dissolved in ethyl acetate, and the antibacterial functional group is grafted onto the polyolefin elastomer molecular chain through free radical grafting reaction. The antibacterial toughening agent is obtained by precipitation, washing and drying. (2) After mixing polypropylene resin, antibacterial toughening agent, compatibilizer and additives obtained in step (1), the mixture is melt-blended and granulated by a twin-screw extruder.

[0015] As a preferred technical solution of the present invention, the initiator in step (1) is azobisisoheptanenitrile; the free radical grafting reaction is carried out at 60-90℃ for 2-8 hours.

[0016] As a preferred technical solution of the present invention, the processing temperature of the twin-screw extruder in step (2) is 180-210℃.

[0017] A food packaging film is made from the aforementioned antibacterial and high-toughness polypropylene material through melt casting or blown film forming.

[0018] The beneficial effects of this invention are: This invention chemically grafts antibacterial functional groups onto the molecular chain of polyolefin elastomers, enabling the antibacterial toughening agent to possess both antibacterial activity and toughening function. On the one hand, the grafted antibacterial functional groups can achieve highly efficient antibacterial activity by disrupting the cell membrane of microorganisms, and the chemical grafting avoids the migration and loss of antibacterial agents. The antibacterial rate can still be well maintained after long-term aging, solving the problems of short-term effectiveness of traditional organic antibacterial agents and agglomeration of inorganic antibacterial agents. On the other hand, the polyolefin elastomer, as a substrate, can form an elastic network in the polypropylene matrix, which absorbs energy when impacted, improving the toughness of the material. At the same time, the maleic anhydride grafted polypropylene compatibilizer optimizes the interfacial bonding, achieving a simultaneous improvement in antibacterial properties and toughness. Detailed Implementation

[0019] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0020] In the following examples and comparative examples, the ethylene-octene copolymer elastomer was purchased from Dongguan Yucheng Plastics Co., Ltd.; the ethylene-butene copolymer elastomer was purchased from Ningbo Yikun Import & Export Co., Ltd.; and the ethylene propylene diene monomer (EPDM) rubber was purchased from Boruida (Dongguan) New Materials Co., Ltd.

[0021] Example 1 An antibacterial and high-toughness polypropylene material is prepared from the following components in parts by weight: 80 parts polypropylene resin; 18 parts antibacterial toughening agent; 3 parts compatibilizer; and 1 part additive. The antibacterial toughening agent is a polyolefin elastomer with antibacterial functional groups grafted onto its molecular chain.

[0022] The polyolefin elastomer is an ethylene-octene copolymer.

[0023] The antibacterial functional group is a quaternary ammonium salt group.

[0024] The grafting rate of the antibacterial functional group on the polyolefin elastomer is 3%.

[0025] The compatibilizer is maleic anhydride-grafted polypropylene.

[0026] The additive consists of an antioxidant and a lubricant in a mass ratio of 1:1.2; the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1, and the lubricant is a mixture of calcium stearate and erucamide in a mass ratio of 1:1.

[0027] The preparation method of the antibacterial and high-toughness polypropylene material includes the following steps: (1) Dissolve polyolefin elastomer, benzyltrimethylammonium chloride and initiator in ethyl acetate, and graft antibacterial functional groups onto the polyolefin elastomer molecular chain through free radical grafting reaction, and then obtain the antibacterial toughening agent by precipitation, washing and drying. (2) After mixing polypropylene resin, antibacterial toughening agent, compatibilizer and additives obtained in step (1), the mixture is melt-blended and granulated by a twin-screw extruder.

[0028] The initiator in step (1) is azobisisoheptanenitrile; the free radical grafting reaction is carried out at 75°C for 5 hours.

[0029] The processing temperature of the twin-screw extruder in step (2) is 195°C.

[0030] A food packaging film is made from the aforementioned antibacterial and high-toughness polypropylene material through melt casting or blown film forming.

[0031] Example 2 An antibacterial and high-toughness polypropylene material is prepared from the following components in parts by weight: 70 parts polypropylene resin; 5 parts antibacterial toughening agent; 0.5 parts compatibilizer; and 0.2 parts additives. The antibacterial toughening agent is a polyolefin elastomer with antibacterial functional groups grafted onto its molecular chain.

[0032] The polyolefin elastomer is an ethylene-butene copolymer.

[0033] The antibacterial functional group is a guanidine salt group.

[0034] The grafting rate of the antibacterial functional group on the polyolefin elastomer is 0.5%.

[0035] The compatibilizer is maleic anhydride-grafted polypropylene.

[0036] The additive consists of an antioxidant and a lubricant in a mass ratio of 1:0.5; the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1, and the lubricant is a mixture of calcium stearate and erucamide in a mass ratio of 1:1.

[0037] The preparation method of the antibacterial and high-toughness polypropylene material includes the following steps: (1) Polyolefin elastomer, polyhexamethylene guanidine hydrochloride and initiator are dissolved in ethyl acetate. Antibacterial functional groups are grafted onto the polyolefin elastomer molecular chain through free radical grafting reaction. The antibacterial toughening agent is obtained by precipitation, washing and drying. (2) After mixing polypropylene resin, antibacterial toughening agent, compatibilizer and additives obtained in step (1), the mixture is melt-blended and granulated by a twin-screw extruder.

[0038] The initiator in step (1) is azobisisoheptanenitrile; the free radical grafting reaction is carried out at 60°C for 2 hours.

[0039] The processing temperature of the twin-screw extruder in step (2) is 180°C.

[0040] A food packaging film is made from the aforementioned antibacterial and high-toughness polypropylene material through melt casting or blown film forming.

[0041] Example 3 An antibacterial and high-toughness polypropylene material is prepared from the following components in parts by weight: 95 parts polypropylene resin; 30 parts antibacterial toughening agent; 5 parts compatibilizer; and 2 parts additives. The antibacterial toughening agent is a polyolefin elastomer with antibacterial functional groups grafted onto its molecular chain.

[0042] The polyolefin elastomer is ethylene propylene diene monomer (EPDM) rubber.

[0043] The antibacterial functional group is an imidazole salt group.

[0044] The grafting rate of the antibacterial functional group on the polyolefin elastomer is 0.8%.

[0045] The compatibilizer is maleic anhydride-grafted polypropylene.

[0046] The additive consists of an antioxidant and a lubricant in a mass ratio of 1:2; the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1, and the lubricant is a mixture of calcium stearate and erucamide in a mass ratio of 1:1.

[0047] The preparation method of the antibacterial and high-toughness polypropylene material includes the following steps: (1) Polyolefin elastomer, 1-butyl-3-methylimidazolium hexafluorophosphate and initiator are dissolved in ethyl acetate. The antibacterial functional group is grafted onto the polyolefin elastomer molecular chain through free radical grafting reaction. The antibacterial toughening agent is obtained by precipitation, washing and drying. (2) After mixing polypropylene resin, antibacterial toughening agent, compatibilizer and additives obtained in step (1), the mixture is melt-blended and granulated by a twin-screw extruder.

[0048] The initiator in step (1) is azobisisoheptanenitrile; the free radical grafting reaction is carried out at 60°C for 2 hours.

[0049] The processing temperature of the twin-screw extruder in step (2) is 210℃.

[0050] A food packaging film is made from the aforementioned antibacterial and high-toughness polypropylene material through melt casting or blown film forming.

[0051] Example 4 An antibacterial and high-toughness polypropylene material is prepared from the following components in parts by weight: 95 parts polypropylene resin; 5 parts antibacterial toughening agent; 5 parts compatibilizer; and 0.2 parts additives. The antibacterial toughening agent is a polyolefin elastomer with antibacterial functional groups grafted onto its molecular chain.

[0052] The polyolefin elastomer is ethylene propylene diene monomer (EPDM) rubber.

[0053] The antibacterial functional group is a quaternary ammonium salt group.

[0054] The grafting rate of the antibacterial functional group on the polyolefin elastomer is 5%.

[0055] The compatibilizer is maleic anhydride-grafted polypropylene.

[0056] The additive consists of an antioxidant and a lubricant in a mass ratio of 1:1; the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1, and the lubricant is a mixture of calcium stearate and erucamide in a mass ratio of 1:1.

[0057] The preparation method of the antibacterial and high-toughness polypropylene material includes the following steps: (1) Dissolve polyolefin elastomer, benzyltrimethylammonium chloride and initiator in ethyl acetate, and graft antibacterial functional groups onto the polyolefin elastomer molecular chain through free radical grafting reaction, and then obtain the antibacterial toughening agent by precipitation, washing and drying. (2) After mixing polypropylene resin, antibacterial toughening agent, compatibilizer and additives obtained in step (1), the mixture is melt-blended and granulated by a twin-screw extruder.

[0058] The initiator in step (1) is azobisisoheptanenitrile; the free radical grafting reaction is carried out at 90°C for 8 hours.

[0059] The processing temperature of the twin-screw extruder in step (2) is 210℃.

[0060] A food packaging film is made from the aforementioned antibacterial and high-toughness polypropylene material through melt casting or blown film forming.

[0061] Comparative Example 1 Based on Example 1, benzyltrimethylammonium chloride and ethylene-octene copolymer were added directly without grafting reaction, and the rest remained the same as in Example 1.

[0062] Comparative Example 2 Based on Example 1, the antibacterial agent was replaced with zinc-loaded zeolite, the toughening agent remained unchanged, and the mixture was added directly. The rest remained the same as in Example 1.

[0063] Comparative Example 3 Based on Example 1, the grafting of quaternary ammonium salt onto the toughening agent was replaced with grafting quaternary ammonium salt onto PP, while the rest remained the same as in Example 1. Comparative Example 4 Based on Example 1, no quaternary ammonium salt was added, and everything else remained the same as in Example 1.

[0064] Comparative Example 5 Based on Example 1, no compatibilizer was added, and everything else remained the same as in Example 1.

[0065] Comparative Example 6 Based on Example 1, no antioxidants were added to the adjuvants, and everything else remained the same as in Example 1.

[0066] Comparative Example 7 Based on Example 1, no lubricant was added to the additives, and everything else remained the same as in Example 1.

[0067] Performance testing: Antibacterial activity: The antibacterial rates of the samples prepared according to the examples and comparative examples against Staphylococcus aureus and Escherichia coli were tested according to GB / T 31402-2015 standard. Toughness: The material was injection molded into 80×10×4mm specimens with a V-shaped notch in the middle according to GB / T 1043.1-2018 standard to test the impact strength; the tensile strength at break of the specimens was tested according to GB / T 1040.3-2006 standard. Anti-aging: After UV aging for 200 hours according to GB / T 16422.3-2014 standard, the above-mentioned antibacterial and toughness performance tests were conducted again.

[0068] Table 1. Performance test results of the examples and comparative examples Table 2. Performance test results after aging for the examples and comparative examples The test results show that the samples in the examples all exhibited extremely high antibacterial rates. This is attributed to the fact that the antibacterial functional groups are uniformly and firmly distributed in the toughening phase of the elastomer through chemical bonds, achieving efficient contact sterilization. The grafted antibacterial agent becomes part of the molecular chain and does not damage the toughening phase. Comparative Example 1 shows that the effect of directly using physically mixed antibacterial agents is far worse than that of chemical grafting because the antibacterial agents have poor dispersibility and are prone to migration and loss, and are also prone to failure and migration during aging. Comparative Example 2 shows poor antibacterial effect, with the dispersibility of inorganic particles being the key bottleneck and the toughness decreasing significantly. Rigid antibacterial particles become stress concentration points, which preferentially break under impact, leading to premature material failure. Comparative Example 3 shows that grafting quaternary ammonium salts onto PP results in extremely poor toughness because grafting antibacterial agents onto rigid PP chains severely restricts molecular chain movement, leading to a surge in brittleness. Comparative Example 4 shows no antibacterial effect without the addition of antibacterial agents. Comparative Example 5 shows a slight decrease in the overall performance of the sample without the addition of compatibilizers. Comparative Examples 6-7 show that the lack of antioxidants leads to rapid aging, yellowing, and performance degradation of the materials during processing and use. The lack of lubricants leads to processing difficulties.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. An antibacterial and high-toughness polypropylene material, characterized in that, It is prepared from the following components in parts by weight: 70-95 parts polypropylene resin; 5-30 parts antibacterial toughening agent; 0.5-5 parts compatibilizer; and 0.2-2 parts additives; The antibacterial toughening agent is a polyolefin elastomer with antibacterial functional groups grafted onto its molecular chain. The antibacterial functional group is one or more of the following: quaternary ammonium salt group, guanidine salt group, and imidazole salt group.

2. The antibacterial and high-toughness polypropylene material according to claim 1, characterized in that, The polyolefin elastomer is one or more of ethylene-octene copolymer elastomer, ethylene-butene copolymer elastomer, and ethylene propylene diene monomer (EPDM) rubber.

3. The antibacterial and high-toughness polypropylene material according to claim 1, characterized in that, The grafting rate of the antibacterial functional groups on the polyolefin elastomer is 0.5%-5%.

4. The antibacterial and high-toughness polypropylene material according to claim 1, characterized in that, The compatibilizer is maleic anhydride-grafted polypropylene.

5. The antibacterial and high-toughness polypropylene material according to claim 1, characterized in that, The additive consists of an antioxidant and a lubricant in a mass ratio of 1:0.5-2; the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1, and the lubricant is a mixture of calcium stearate and erucamide in a mass ratio of 1:

1.

6. A method for preparing an antibacterial and highly tough polypropylene material as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) The polyolefin elastomer, antibacterial functional group monomer and initiator are dissolved in ethyl acetate, and the antibacterial functional group is grafted onto the polyolefin elastomer molecular chain through free radical grafting reaction. The antibacterial toughening agent is obtained by precipitation, washing and drying. (2) After mixing polypropylene resin, antibacterial toughening agent, compatibilizer and additives obtained in step (1), the mixture is melt-blended and granulated by a twin-screw extruder.

7. The method for preparing an antibacterial and high-toughness polypropylene material according to claim 6, characterized in that, The initiator in step (1) is azobisisoheptanenitrile; the free radical grafting reaction is carried out at 60-90℃ for 2-8 hours.

8. The method for preparing an antibacterial and high-toughness polypropylene material according to claim 6, characterized in that, The processing temperature of the twin-screw extruder in step (2) is 180-210℃.

9. An antibacterial and high-toughness polypropylene material as described in any one of claims 1-5, characterized in that, The aforementioned antibacterial and high-toughness polypropylene material is applied to food packaging films through melt casting or blown film molding.

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