Quaternary ammonium salt polymer antimicrobial material based on PVC waste and preparation method and application thereof

Abstract

The application belongs to the field of high polymer materials, relates to the resource utilization direction of plastic waste, and discloses a quaternary ammonium salt high polymer antibacterial material based on PVC waste and a preparation method thereof. The application replaces part of chlorine atoms on the PVC waste chain with quaternary ammonium salt groups having antibacterial activity through a chemical modification method, so as to obtain a high polymer antibacterial material containing chlorine atoms and quaternary ammonium salt groups; a film is prepared by adopting a solution flow casting method, and an antibacterial performance test is carried out through a film pasting contact method; test results show that the high polymer film material has 99.9% antibacterial effect on sensitive E. coli, chloramphenicol-resistant E. coli and Staphylococcus aureus. The reaction system of the application has low required temperature, small energy consumption, and does not need expensive catalyst, can realize partial dechlorination of the PVC waste while endowing the PVC waste with persistent antibacterial function, and shows great practical application potential.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of high polymer materials, and relates to the resource utilization of plastic waste. BACKGROUND

[0002] In recent years, the plastic industry has developed rapidly worldwide, and a large amount of plastic waste has been generated. Most of these wastes are non-biodegradable and can remain in the natural environment for decades or even hundreds of years, causing serious threats to the ecological environment. However, plastic waste is rich in carbon and hydrogen resources, and is therefore referred to as "resources in the wrong place". Therefore, how to realize the resource utilization of plastic waste has become a key issue for plastic pollution control and environmental protection. Among them, polyvinyl chloride (PVC), known as the "fighter of toxic plastics", is widely used in construction, wire and cable, transportation, food packaging, medical and health care, and leisure and entertainment due to its low cost, chemical corrosion resistance, acid and alkali resistance, and excellent mechanical properties. At present, the global PVC annual output has exceeded 4000 million tons, and China's output is in the first place. However, with high output comes a large amount of PVC waste that is difficult to handle. Because PVC waste contains a large amount of chlorine atoms and environmentally unfriendly additives, it has very poor biodegradability and can easily cause serious pollution to the ecological environment. Therefore, how to scientifically and reasonably dispose of PVC waste has become one of the major environmental challenges that need to be solved today.

[0003] At present, there are four methods for the treatment of PVC waste in China, including landfill, incineration, mechanical recycling and chemical recycling. However, landfill requires a large amount of land, and such methods usually release harmful organic chlorides and corrosive hydrochloric acid (HCl), which can damage recycling equipment and poison catalysts. Incineration produces a large amount of corrosive hydrochloric acid, and may also release "century poison" dioxin, and the bottom ash after incineration contains a large amount of harmful substances, causing secondary pollution. Mechanical recycling has more advantages than landfill and incineration, which can reuse PVC waste and save resources, but the mechanical stability of recycled plastics decreases step by step, and the scope of application is reduced, eventually becoming waste that harms the environment and human health. Chemical recycling refers to the use of chemical treatment to convert PVC waste into chemical raw materials, fuels or high value-added materials, including general pyrolysis, catalytic pyrolysis and wet method. However, PVC waste contains a large amount of chlorine element, and the use of general pyrolysis (hydrogenation, pyrolysis and gasification) will produce hydrochloric acid to corrode the recycling equipment and pipelines, and the chlorine-containing organic products obtained cannot be used as chemical raw materials or fuels, and even harmful substances such as dioxin, polychlorinated biphenyl, persistent organic pollutants, etc. Therefore, dechlorination is a key problem that needs to be solved to realize the resource utilization of PVC waste. It is reported that chlorinated compounds (such as chloramphenicol) are widely used due to their significant antibacterial effect, so it is worth further exploring whether PVC can be converted into high molecular antibacterial materials under the condition of incomplete dechlorination.

[0004] With the frequent outbreak of cold chain related epidemics, the surface transmission of microorganisms has attracted widespread attention. Quaternary ammonium salt antibacterial agents are widely used. Quaternary ammonium salt is a compound in which four hydrogen atoms in ammonium ion are replaced by alkyl groups, which belongs to cationic surfactants, has strong antibacterial ability, wide antibacterial spectrum and easy to obtain. Quaternary ammonium salt antibacterial agents are widely used in medical, household, water treatment and food industries. According to the latest data of the US Environmental Protection Agency, among more than 600 antibacterial disinfectants, quaternary ammonium salts account for 342, showing its importance in the field of antibacterial disinfection. However, common quaternary ammonium salt antibacterial agents usually have a relative molecular weight less than 500 (such as benzalkonium chloride), exist in the form of solution, are easy to elute and volatilize, have poor antibacterial durability, are difficult to reuse, and have low use efficiency. Patent CN201410348600.7 discloses a PVC / PVC-g-DMC antibacterial plastic and its preparation technology, which grafts PVC with quaternary ammonium salt groups. Since quaternary ammonium salt groups themselves have bactericidal properties, PVC-g-DMC itself is a high molecular antibacterial agent. According to the antibacterial performance test of plastic QB / T 2591-2003, the bactericidal rate of PVC-g-DMC to escherichia coli and staphylococcus aureus is more than 98%. However, grafting has the disadvantages of harsh reaction conditions, possible side reactions, high price of quaternary ammonium salt groups, corresponding increase in cost, non-cyclic utilization of resources, and environmental impact of waste. In contrast, the preparation of polymer antibacterial surface from PVC waste has great application potential in preventing bacterial surface transmission, and can realize cyclic utilization of resources and reduce the adverse effects on the environment. SUMMARY

[0005] To solve the above problems, the present application provides a quaternary ammonium salt high molecular antibacterial material based on PVC waste and its preparation method and application.

[0006] The technical scheme of the present application is as follows:

[0007] On the one hand, the present application provides a quaternary ammonium salt high molecular antibacterial material based on PVC waste, whose structural formula is shown as formula I:

[0008]

[0009] In the formula, m and n are natural numbers greater than 2000, and m:n=(0.9-1):1. The average molecular weight of the structural formula is 200000 Da-220000 Da.

[0010] Secondly, the present application provides a new type of quaternary ammonium salt high molecular antibacterial material (PQAM), which modifies quaternary ammonium salt groups on the long chain structure of PVC waste, so that it has both quaternary ammonium salt groups and chlorine atoms as antibacterial groups. Its preparation method is as follows:

[0011] a. Partial dechlorination of PVC waste: 4-aminobenzenethiol replaces part of the chlorine atoms in the PVC waste by a double nucleophilic substitution reaction, to obtain an intermediate product;

[0012] b. Methylation of amino group: -NH2 of the intermediate product obtained in step a reacts with iodomethane, to obtain the target product (Formula I).

[0013] In the preparation method of the quaternary ammonium salt polymer antibacterial material provided by the application, the intermediate product is obtained by a double nucleophilic substitution reaction of PVC waste and 4-aminobenzenethiol; then, -NH2 of the intermediate product is methylated by a double nucleophilic substitution reaction of iodomethane, to obtain the target product (PQAM).

[0014] In the above preparation method, the amount of the raw materials that can promote the double nucleophilic substitution reaction is feasible. In order to improve the reaction yield and the utilization rate of raw materials, preferably, the mass ratio of PVC waste to 4-aminobenzenethiol in step a is 1:(0.4-1), and the mass ratio of the intermediate product to iodomethane in step b is 1:(5-8).

[0015] The specific preparation steps are as follows:

[0016] (1) The intermediate product is obtained by a double nucleophilic substitution reaction of PVC waste and 4-aminobenzenethiol;

[0017] (2) The quaternary ammonium salt polymer antibacterial material is obtained by a double nucleophilic substitution reaction of iodomethane and the intermediate product in step (1).

[0018] Preferably, the solvent for the double nucleophilic substitution reaction in steps (1) and (2) is N,N-dimethylformamide or N,N-dimethylacetamide.

[0019] Preferably, a weak base is added to the double nucleophilic substitution reaction in steps (1) and (2), and the weak base is K2CO3 or Na2CO3.

[0020] Preferably, the molar ratio of PVC waste to 4-aminobenzenethiol in step (1) is 1:(0.4-1), and the mass ratio of the intermediate product to iodomethane in step (2) is 1:(5-8).

[0021] Preferably, the temperature of the double nucleophilic substitution reaction in step (1) is 70-90°C, and the reaction time is 5-7h; the temperature of the double nucleophilic substitution reaction in step (2) is room temperature-35°C, and the reaction time is 12-14h.

[0022] In the third aspect, a quaternary ammonium salt polymer material film / coating is obtained by dissolving the above quaternary ammonium salt polymer antibacterial material and then coating.

[0023] Fourthly, the aforementioned quaternary ammonium salt polymer film / coating is used as an antibacterial material.

[0024] Preferably, the above-mentioned antibacterial activity refers to antibacterial activity against Escherichia coli or Staphylococcus aureus.

[0025] The present invention has the following beneficial effects:

[0026] (1) This invention proposes a novel quaternary ammonium salt-based polymeric antibacterial material based on PVC waste and its preparation method. By chemical modification, some chlorine atoms on the PVC chain are replaced with quaternary ammonium salt groups with antibacterial activity, thereby obtaining a polymeric antibacterial material PQAM containing both chlorine atoms and quaternary ammonium salt groups. A film was prepared by solution casting and the antibacterial performance was tested by film-on-film contact method. The results showed that the antibacterial effect of PQAM film was negatively correlated with the initial concentration of Gram bacteria and positively correlated with the contact time. The antibacterial activity was mainly achieved through the synergistic bactericidal mechanism between the cationic quaternary ammonium salt groups and the hydrophobic long carbon chains. The antibacterial mechanism of PVC film does not only depend on its hydrophobicity, but chlorine atoms also play an important role in killing Gram-positive bacteria.

[0027] (2) The novel polymeric antibacterial material PQAM prepared in this invention has a 99.9% antibacterial effect against sensitive Escherichia coli, chloramphenicol-resistant Escherichia coli, and Staphylococcus aureus. When applied to the surface of glass jars, stainless steel door handles, and wooden boards, it exhibits good antibacterial activity against E. coli BL21 and S. aureus. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 To upgrade the functionality of PVC waste to a high-value-added quaternary ammonium salt polymeric antibacterial material (PQAM).

[0030] Figure 2 The preparation route for PQAM is shown.

[0031] Figure 3 The infrared spectrum (FT-IR) of PQAM.

[0032] Figure 4 For the proton spectrum of PQAM ( 1 H NMR).

[0033] Figure 5 Differential scanning calorimetry and thermogravimetric analysis curves of PQAM.

[0034] Figure 6 Antibacterial durability and reusability of PQAM.

[0035] Figure 7 Preparation of thin film and schematic diagram of antibacterial performance test.

[0036] Figure 8 Antibacterial activity test of PQAM thin film on E. coli BL21.

[0037] Figure 9 Antibacterial activity test of PQAM thin film on E. coli C.

[0038] Figure 10 Antibacterial activity test of PQAM thin film on S. aureus.

[0039] Figure 11 Antibacterial effect of PQAM coating on glass jar.

[0040] Figure 12 Antibacterial effect of PQAM coating on stainless steel door handle on E. coli BL21 and S. aureus.

[0041] Figure 13 Antibacterial effect of PQAM coating on wood board on E. coli BL21 and S. aureus. DETAILED DESCRIPTION

[0042] The technical solutions of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0043] The test methods used in the following experimental examples are conventional methods unless otherwise specified; the materials, reagents, etc. used are reagents and materials available through commercial channels unless otherwise specified.

[0044] The present application develops an innovative upgrade and reuse strategy Figure 1 , that is, by chemical modification method, the quaternary ammonium salt group is grafted to the PVC chain in the form of covalent bond, and is converted into a new type of quaternary ammonium salt polymer antibacterial material PQAM. This material not only maintains the original antibacterial activity of chlorine atom of PVC, but also increases the antibacterial performance of quaternary ammonium salt group.

[0045] The preparation method of the quaternary ammonium salt polymer antibacterial material PQAM is as follows: an intermediate product is obtained by a bimolecular nucleophilic substitution reaction of PVC and 4-aminobenzene sulfenol; then, the -NH2 of the intermediate product is methylated by a bimolecular nucleophilic substitution reaction of iodomethane, so as to obtain the target product (PQAM). K2CO3 or Na2CO3 is used for neutralizing HCl generated in the reaction system. The preparation method has mild reaction conditions, is easy to control, uses raw materials which are easy to obtain, and does not need to add oxidants, strong acids or strong bases and the like in the reaction process, and has strong reaction specificity; in addition, the substitution rate of chlorine atoms on the PVC and the elimination rate of HCl are controllable, the post-treatment is convenient, green and environmentally friendly, and the method is suitable for large-scale industrial production.

[0046] Example 1

[0047] In this example, the quaternary ammonium salt polymer antibacterial material (PQAM) is synthesized by a chemical modification method in two steps, as shown in the following formula (I): Figure 2 The specific steps are as follows:

[0048] (I) A three-necked flask equipped with a magnetic stirrer, an addition funnel and a condenser tube is prepared, and PVC waste (6 g, Mw value is about 130000 Da), 4-aminobenzene sulfenol (2.4 g), K2CO3 (1.33 g) and DMF (120 mL) are added into the flask. Under the protection of nitrogen, the system is heated to 70 DEG C. After 6 hours of reaction, the reaction is stopped, and after cooling to room temperature, the reaction solution is slowly poured into 200 mL of deionized water, and the solid crude product is obtained by filtration. Subsequently, it is dissolved in an appropriate amount of tetrahydrofuran (THF) for purification, and recrystallized with deionized water to obtain a solid product (intermediate product). The intermediate product is transferred to a vacuum drying oven (China Jinghong, XMTD-8222) for further drying for 48 hours.

[0049] (II) In the second step, the intermediate product (1.5 g), iodomethane (6 g) and K2CO3 (3.13 g) are added into DMF (30 mL), and the reaction liquid is heated to 35 DEG C and kept for 12 hours. After the reaction is completed, K2CO3 is removed by filtration, 1.5 g of iodomethane is added into the reaction liquid, and stirring is performed at room temperature for 2 hours. After the reaction is completed, the reaction liquid is poured into 90 mL of deionized water, and stirring is uniformly performed, and then freeze-drying is performed to obtain a solid product (i.e. PQAM, 210000 Da). Finally, the PQAM is placed in a vacuum drying oven for 48 hours. The characterization of the intermediate product and the PQAM is performed by using an infrared spectrometer (FT-IR, Thermo Fisher, Nicolet iS50, USA), a nuclear magnetic resonance instrument (NMR, Bruker, Ascend 500, Germany), a differential scanning calorimeter (DSC, TA, Q2000, USA) and a thermal gravimetric analyzer (TGA, TA, SDT-Q600, USA) and the like.

[0050] Compared to PVC, the FT-IR spectrum of the intermediate product ( Figure 3 Two new absorption peaks appeared in the sample, at 3483 cm⁻¹ and 3383 cm⁻¹. -1 Absorption peaks attributable to the stretching vibration of -NH2, 1671, 1619 and 1596 cm⁻¹ -1 The absorption peaks of the benzene ring skeletal vibrations indicate that 4-aminothiophenol successfully substituted some chlorine atoms in PVC, i.e., a bimolecular nucleophilic substitution reaction occurred. In the FT-IR spectrum of PQAM, the -NH2 absorption peak disappeared, and the absorption peaks of the benzene ring skeletal vibrations also changed significantly compared to the intermediate product. PVC's... 1 H NMR spectrum ( Figure 4 H is present at 2.23-2.57 ppm. a The absorption peak is located at 4.33-4.71 ppm for H. b The absorption peak in PQAM. 1 In the 1H NMR spectrum, H appeared at 2.71 ppm. g The absorption peak of the intermediate product disappeared, while the -NH2 absorption peak of the intermediate product disappeared. This is because -NH2 was methylated, and H... f The absorption peak split into two peaks at 6.57 and 6.75 ppm. e The absorption peak shifted from 7.08 ppm to a lower field of 7.23 ppm, indicating the formation of quaternary ammonium groups in PQAM. Furthermore, the crystallinity of PQAM was evaluated using DSC; the crystallinity of the material did not change significantly from PVC to PQAM, and the glass transition temperatures of PVC and PQAM were 80.1 °C and 79.1 °C, respectively. Next, the thermal stability of PQAM was evaluated using TGA. Figure 5 Both PQAM and PVC exhibit two-stage degradation processes. Notably, PQAM requires a temperature of 175.1°C to lose 5 wt.% of its weight, while PVC requires 274.6°C, indicating that PQAM has lower thermal stability than PVC.

[0051] The polymer material PQAM typically exists in solid form and is characterized by chemical stability, resistance to elution, and low volatility. It offers long-lasting antibacterial effects and is reusable. Figure 6 This significantly reduces the environmental impact. The antimicrobial material is suitable for product surfaces, effectively inhibiting the growth and reproduction of microorganisms on object surfaces, improving hygiene levels, reducing the risk of disease transmission, decreasing cleaning frequency, and enhancing safety. Its structure is shown in Formula I:

[0052]

[0053] Example 2

[0054] The present embodiment adopts a two-step method for synthesizing quaternary ammonium salt polymer antibacterial material (PQAM) by chemical modification, as shown in Figure 2 The specific steps are as follows:

[0055] (I) A three-necked flask equipped with a magnetic stirrer, an addition funnel and a condenser tube was prepared, and PVC waste (6 g, Mw value about 130000 Da), 4-aminobenzene sulfenamide (6 g), K2CO3 (1.33 g) and N, N-dimethylformamide (DMF, 120 mL) were added into the flask. The system was heated to 70°C under nitrogen protection. The reaction was stopped after 6 hours, and the reaction solution was slowly poured into 200 mL of deionized water after cooling to room temperature, and the solid crude product was obtained by filtration. Then, it was dissolved in an appropriate amount of tetrahydrofuran (THF) for purification, and recrystallized with deionized water to obtain a solid product (intermediate product). The intermediate product was transferred to a vacuum drying oven for further drying for 48 hours.

[0056] (II) In the second step, the intermediate product (1.5 g), iodomethane (10.5 g) and K2CO3 (3.13 g) were added to DMF (30 mL), and the reaction solution was heated to 35°C and kept for 12 hours. After the reaction was completed, K2CO3 was removed by filtration, and 1.5 g of iodomethane was added to the reaction solution, which was stirred at room temperature for 2 hours. After the reaction was completed, the reaction solution was poured into 90 mL of deionized water, stirred uniformly, and then freeze-dried to obtain a solid product (i.e. PQAM, about 220000 Da). Finally, the PQAM was placed in a vacuum drying oven for 48 hours.

[0057] Example 3

[0058] The present embodiment adopts a two-step method for synthesizing quaternary ammonium salt polymer antibacterial material (PQAM) by chemical modification, as shown in Figure 2 The specific steps are as follows:

[0059] (I) A three-necked flask equipped with a magnetic stirrer, an addition funnel and a condenser tube was prepared, and PVC waste (6 g, Mw value about 130000 Da), 4-aminobenzene sulfenamide (6 g), K2CO3 (1.33 g) and N, N-dimethylformamide (DMF, 120 mL) were added into the flask. The system was heated to 70°C under nitrogen protection. The reaction was stopped after 6 hours, and the reaction solution was slowly poured into 200 mL of deionized water after cooling to room temperature, and the solid crude product was obtained by filtration. Then, it was dissolved in an appropriate amount of tetrahydrofuran (THF) for purification, and recrystallized with deionized water to obtain a solid product (intermediate product). The intermediate product was transferred to a vacuum drying oven for further drying for 48 hours.

[0060] (II) In the second step, the intermediate product (1.5 g), methyl iodide (10.5 g) and K2CO3(3.13 g) were added to DMF (30 mL), and the reaction solution was heated to 35°C and kept for 14 h. After the reaction was completed, K2CO3was removed by filtration, 1.5 g of methyl iodide was added to the reaction solution, and the reaction was carried out at room temperature for 2 h. After the reaction was completed, the reaction solution was poured into 90 mL of deionized water, stirred uniformly, and then freeze-dried to obtain a solid product (i.e. PQAM, about 2100000 Da), and finally the PQAM was placed in a vacuum drying oven for 48 h.

[0061] Example 4

[0062] In this example, the quaternary ammonium salt polymer antibacterial material (PQAM) was synthesized in two steps by using a chemical modification method, as shown in Figure 2 , and the specific steps are as follows:

[0063] (I) A three-necked flask equipped with a magnetic stirrer, an addition funnel and a condenser tube was prepared, and PVC waste (6 g, Mwvalue about 130000 Da), 4-aminobenzene sulfenamide (4.2 g), K2CO3(1.33 g) and DMF (120 mL) were added to the flask. Under the protection of nitrogen, the system was heated to 80°C. The reaction was stopped after 5 h. After cooling to room temperature, the reaction solution was slowly poured into 200 mL of deionized water, and the solid crude product was obtained by filtration. Subsequently, it was dissolved in an appropriate amount of tetrahydrofuran (THF) for purification, and recrystallized with deionized water to obtain a solid product (intermediate product), which was transferred to a vacuum drying oven for further drying for 48 h.

[0064] (II) In the second step, the intermediate product (1.5 g), methyl iodide (10.5 g) and K2CO3(3.13 g) were added to DMF (30 mL), and the reaction solution was heated to 35°C and kept for 14 h. After the reaction was completed, K2CO3was removed by filtration, 1.5 g of methyl iodide was added to the reaction solution, and the reaction was carried out at room temperature for 2 h. After the reaction was completed, the reaction solution was poured into 90 mL of deionized water, stirred uniformly, and then freeze-dried to obtain a solid product (i.e. PQAM, about 2100000 Da), and finally the PQAM was placed in a vacuum drying oven for 48 h.

[0065] Example 5

[0066] In this example, the quaternary ammonium salt polymer antibacterial material (PQAM) was synthesized in two steps by using a chemical modification method, as shown in Figure 2 , and the specific steps are as follows:

[0067] (I) A three-necked flask equipped with a magnetic stirrer, an addition funnel and a condenser was prepared. PVC waste (6 g, Mw value of about 130,000 Da), 4-aminobenzene thiol (4.8 g), K2CO3(1.33 g) and N,N-dimethylformamide (DMF, 120 mL) were added to the flask. The system was heated to 90 °C under nitrogen protection. The reaction was stopped after 7 h. After cooling to room temperature, the reaction solution was slowly poured into 200 mL of deionized water, and the solid crude product was obtained by filtration. Subsequently, it was dissolved in an appropriate amount of tetrahydrofuran (THF) for purification, and recrystallized with deionized water to obtain a solid product (intermediate product). The intermediate product was transferred to a vacuum drying oven for further drying for 48 h.

[0068] (II) In the second step, the intermediate product (1.5 g), iodomethane (10.5 g) and K2CO3(3.13 g) were added to DMF (30 mL). The reaction solution was heated to 25 °C and maintained for 14 h. After the reaction was completed, K2CO3was removed by filtration. 1.5 g of iodomethane was added to the reaction solution, and stirred at room temperature for 2 h. After the reaction was completed, the reaction solution was poured into 90 mL of deionized water, stirred uniformly, and then freeze-dried to obtain a solid product (i.e., PQAM, about 220,000 Da). Finally, the PQAM was placed in a vacuum drying oven for 48 h.

[0069] Example 6

[0070] The quaternary ammonium salt polymer antibacterial material (PQAM) of the present embodiment was synthesized in two steps using a chemical modification method, as shown in Figure 2 The specific steps are as follows:

[0071] (I) A three-necked flask equipped with a magnetic stirrer, an addition funnel and a condenser was prepared. PVC waste (6 g, Mw value of about 130,000 Da), 4-aminobenzene thiol (4.8 g), K2CO3(1.33 g) and N,N-dimethylformamide (DMF, 120 mL) were added to the flask. The system was heated to 90 °C under nitrogen protection. The reaction was stopped after 7 h. After cooling to room temperature, the reaction solution was slowly poured into 200 mL of deionized water, and the solid crude product was obtained by filtration. Subsequently, it was dissolved in an appropriate amount of tetrahydrofuran (THF) for purification, and recrystallized with deionized water to obtain a solid product (intermediate product). The intermediate product was transferred to a vacuum drying oven for further drying for 48 h.

[0072] (II) In the second step, 1.5 g of the intermediate product, 10.5 g of iodomethane, and 3.13 g of K₂CO₃ were added to 30 mL of DMF. The reaction solution was heated to 25 °C and maintained for 14 h. After the reaction was completed, K₂CO₃ was removed by filtration. 1.5 g of iodomethane was added to the reaction solution, and the mixture was stirred at room temperature for 2 h. After the reaction was completed, the reaction solution was poured into 90 mL of deionized water, stirred evenly, and then freeze-dried to obtain a solid product (i.e., PQAM, approximately 220,000 Da). Finally, PQAM was placed in a vacuum drying oven for 48 h.

[0073] Implementation Results Example

[0074] Antibacterial films were prepared using the quaternary ammonium salt polymer material from Example 1, and their antibacterial properties were tested. Figure 7 As shown, the specific steps are as follows:

[0075] First, PVC waste (20 mg) and quaternary ammonium salt-based antibacterial polymer (20 mg) were dissolved separately in THF (2 mL). After stirring for 30 min, the solution was slowly poured into sterilized glass petri dishes and allowed to stand in a clean fume hood for 2 h. Then, the solutions were transferred to a vacuum drying oven and dried for another 48 h. Subsequent scanning electron microscopy (SEM, Hitachi, S-4800, Japan) analysis showed that all the films exhibited a rough and uneven surface, a characteristic that helps enhance the adhesion of the films to bacteria.

[0076] The antibacterial properties of the antibacterial film were tested using the film-contact method. The results showed that it had an antibacterial effect of 99.9% against sensitive Escherichia coli, chloramphenicol-resistant Escherichia coli, and Staphylococcus aureus. The antibacterial mechanism was also studied, as follows:

[0077] 1. The PQAM film material provided by this invention, prepared by solution casting, exhibits 99.9% antibacterial efficacy against sensitive Escherichia coli (E. coli BL21), chloramphenicol-resistant Escherichia coli (E. coli C), and Staphylococcus aureus (S. aureus). From... Figure 8 (a) It can be observed that E. coli BL21 cells can multiply normally in PBS. However, after adding a PQAM film to the bacterial culture, the bacterial count decreases with increasing contact time, eventually dropping to zero. Figure 8 (c) indicates that the PQAM film has significant antibacterial activity against E. coli BL21. The antibacterial rate results of the PVC film show that its antibacterial effect is negatively correlated with the initial concentration of E. coli BL21. Figure 8 (d) This means that the antibacterial effect of the PQAM film decreases as the initial bacterial concentration increases.

[0078] 2. This invention also tested the antibacterial effect of the PQAM film on E. coli C. Experimental results showed that as the contact time increased, the concentration of E. coli C continuously decreased to zero. Figure 9 (c)). Meanwhile, the antibacterial rate of the PQAM film also increased as the initial concentration of E. coli C decreased. Figure 9 (d)), this trend is consistent with the antibacterial rate of E. coli BL21 ( Figure 8 (d) This result indicates that the hydrophobicity of the material plays an important role in inhibiting the reproduction of E. coli, while the chlorine atoms on the PVC did not significantly affect the antibacterial effect. We speculate that the antibacterial activity of the PQAM film against Gram-negative bacteria is mainly achieved through a synergistic bactericidal mechanism between the cationic quaternary ammonium salt groups and the hydrophobic long carbon chains.

[0079] 3. This invention also tested the antibacterial activity of the PQAM film against *S. aureus*. From... Figure 10 As shown in (a), the concentration of *S. aureus* suspension in PBS decreases over time. Upon addition of the PQAM membrane, the bacterial count continues to decrease with increasing contact time, eventually dropping to zero. Figure 10 (c) indicates that this type of film has significant antibacterial activity against S. aureus. Figure 10 (d) shows that the antibacterial activity of the PQAM film is positively correlated with contact time and negatively correlated with the initial concentration of *S. aureus*, a trend similar to that of *E. coli*. However, compared to the antibacterial effect of *E. coli* at 24 h, the effect was significantly lower at an initial concentration of 10... 3 At CFU / mL, the inactivation time was significantly shortened to approximately 12 hours. Interestingly, when PVC film was exposed to a S. aureus suspension, the bacterial concentration also decreased continuously with increasing contact time. Figure 10 (b) This explains why PQAM films are more effective against S. aureus than against E. coli. Furthermore, it implies that the mechanism by which PVC kills S. aureus is not solely dependent on its hydrophobicity. Based on the disinfecting effect of chlorine atoms, it is speculated that chlorine atoms may play an important role in killing Gram-positive bacteria.

[0080] Application Example 1

[0081] This invention involves coating PQAM onto the surface of a glass jar to create a PQAM antibacterial surface. The bactericidal rate of the PQAM coating against *E. coli* BL21 and *S. aureus* was determined using the plate count method, with a PVC coating as a control. The PQAM coating on the glass jar exhibited 99.9% antibacterial activity against both *E. coli* BL21 and *S. aureus*. The antibacterial rate of the PQAM coating increased with prolonged contact time, consistent with the performance of the PQAM film in *E. coli* BL21 and *S. aureus* suspensions. Furthermore, the antibacterial activity of the PQAM coating against *S. aureus* was higher than that against *E. coli* BL21. Additionally, the concentration of *E. coli* BL21 increased from 3 × 10⁻⁶... 3 It takes 12 hours for CFU / mL to drop to zero. Figure 11 (a)), while the concentration of S. aureus ranged from 8 × 10 3 It only takes 6 hours for CFU / mL to drop to zero. Figure 11 (b)). The above results indicate that the PQAM coating is more effective against *S. aureus* than *E. coli* BL21, possibly due to the disinfecting properties of chlorine atoms. In conclusion, the PQAM coating adhering to glass bottles exhibits good antibacterial activity against both *E. coli* BL21 and *S. aureus*, demonstrating its potential for practical application.

[0082] Application Example 2

[0083] This invention involves coating PQAM onto stainless steel door handles to create a PQAM antibacterial surface. The bactericidal rate of the PQAM coating against *E. coli* BL21 and *S. aureus* was determined using the plate colony counting method, with a PVC coating as a control sample. The PQAM coating on the door handles exhibited 99.9% antibacterial activity against both *E. coli* BL21 and *S. aureus*. Figure 12 With prolonged contact time, the antibacterial rate of the PQAM coating increased, and the antibacterial activity of the PQAM coating against *S. aureus* was higher than that against *E. coli* BL21. This is consistent with the antibacterial effect of the PQAM coating on glass jars against both *E. coli* BL21 and *S. aureus*. Therefore, the PQAM coating attached to the steel door handle exhibits good antibacterial activity against both *E. coli* BL21 and *S. aureus*.

[0084] Application Example 3

[0085] The PQAM is coated on the wood board to make a PQAM antibacterial surface. Figure 13 The PQAM coating on the wood board shows 99.9% bacteriostatic activity on E.coli BL21 and S.aureus

[0086] In summary, the present application develops a novel functional upgrade strategy, which can controllably convert PVC waste into valuable quaternary ammonium salt polymer antibacterial material, aiming to reduce the surface spread of pathogenic bacteria, and has great application potential in cold chain packaging, public health, transportation and building fields.

[0087] The above merely describes preferred embodiments of the present application but should not be used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A quaternary ammonium salt-based polymeric antibacterial material based on PVC waste, the structural formula of which is shown in Formula I: In the formula, m and n are natural numbers greater than 2000, and m:n = (0.9-1):1, m:n≠1. The average molecular weight of this structure is 200000Da-220000Da. The preparation method is as follows: (1) PVC waste reacts with 4-aminobenzylthiophenol via a bimolecular nucleophilic substitution reaction to obtain an intermediate product; (2) Iodoform reacts with the intermediate product of step (1) via a bimolecular nucleophilic substitution reaction to obtain a quaternary ammonium salt polymeric antibacterial material.

2. The quaternary ammonium salt-based polymeric antibacterial material based on PVC waste according to claim 1, characterized in that: The solvent for the bimolecular nucleophilic substitution reaction in steps (1) and (2) is N,N-dimethylformamide or N,N-dimethylacetamide.

3. The quaternary ammonium salt-based polymeric antibacterial material based on PVC waste according to claim 2, characterized in that: K2CO3 or Na2CO3 is also added in the bimolecular nucleophilic substitution reactions in steps (1) and (2).

4. The quaternary ammonium salt-based polymeric antibacterial material based on PVC waste according to claim 1, characterized in that: In step (1), the mass ratio of PVC waste to 4-aminothiophenol is 1:(0.4-1).

5. The quaternary ammonium salt-based polymeric antibacterial material based on PVC waste according to claim 1, characterized in that: In step (2), the mass ratio of the intermediate product to iodomethane is 1:(5-8).

6. The quaternary ammonium salt polymeric antibacterial material based on PVC waste according to any one of claims 1-5, characterized in that: The temperature of the bimolecular nucleophilic substitution reaction in step (1) is 70-90℃ and the reaction time is 5-7h. The temperature of the bimolecular nucleophilic substitution reaction in step (2) is room temperature-35℃ and the reaction time is 12-14h.

7. A quaternary ammonium salt polymer film / coating, characterized in that: It is obtained by dissolving the quaternary ammonium salt polymeric antibacterial material as described in claim 6 and then coating it.

8. The application of the quaternary ammonium salt polymer film / coating as described in claim 7 as an antibacterial material.

9. The application according to claim 8, characterized in that: The antibacterial properties refer to those against Escherichia coli or Staphylococcus aureus.

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