An antibacterial and deodorizing EVA foam material and its preparation method

Abstract

This invention discloses an antibacterial and deodorizing EVA foam material and its preparation method, belonging to the field of polymer technology. It aims to solve the problems of easy precipitation and inactivation of antibacterial agents in existing antibacterial EVA materials, decreased mechanical properties due to fillers, and the inability of ordinary quaternary ammonium salts to withstand high-temperature processing. The material comprises an EVA matrix and an intrinsically antibacterial vinyl elastomer network running through it. Using an intrinsically antibacterial vinyl elastomer with double bonds and long-chain alkylpyridine quaternary ammonium salt side groups as the core modifier, it chemically crosslinks with the EVA matrix during the molding and foaming process, constructing an interpenetrating polymer network and permanently locking the antibacterial groups within the material network. This material exhibits long-lasting antibacterial properties, excellent resilience, and tear resistance, making it particularly suitable for manufacturing high-performance antibacterial molded foam shoe materials.

Description

Technical Field

[0001] This invention relates to the field of polymer technology, and in particular to an antibacterial and deodorizing EVA foam material and its preparation method. Background Technology

[0002] Ethylene-vinyl acetate copolymer (EVA) is widely used in the field of shoe material foaming due to its light weight, softness, good elasticity, and excellent chemical stability. However, EVA foam materials are usually closed-cell structures with poor breathability. During long-term wear, sweat accumulates on the surface of the shoe bed, easily becoming a breeding ground for bacteria and fungi, leading to odor and even foot dermatitis. Existing technologies mainly address these problems by introducing antibacterial agents through physical blending. For example, patent CN104893083A discloses an odor-resistant and antibacterial EVA shoe material using porous nano-copper oxide as an antibacterial agent; patent CN112194841A discloses an antibacterial EVA material using organic antibacterial agents and natural rubber. However, existing technologies have the following significant drawbacks:

[0003] (1) Deposition failure and poor durability: Whether it is inorganic silver / zinc ions or organic small molecule antibacterial agents, they mainly exist in the matrix in the form of physical fillers and have weak bonding with the EVA matrix. Under the friction, squeezing and water rinsing caused by daily wear, the antibacterial agents are very easy to migrate and precipitate, which leads to the rapid decay of antibacterial effect over time, and the precipitated chemical substances may cause skin allergies.

[0004] (2) Damage to mechanical properties: In order to achieve antibacterial effect, excessive inorganic powder is often required, which destroys the integrity of the EVA foam cells, resulting in a decrease in closed cell rate and poor resilience, i.e., losing the "stepping on poop" feeling.

[0005] Therefore, developing an EVA foam material that can participate in chemical cross-linking, withstand high-temperature processing, and has intrinsic antibacterial properties is key to solving the aforementioned industry pain points. Summary of the Invention

[0006] This invention aims to solve the problems of easy precipitation and failure of antibacterial agents in existing antibacterial EVA materials, decreased mechanical properties due to fillers, and poor high-temperature processing resistance of ordinary quaternary ammonium salts.

[0007] The specific technical solution is as follows: An antibacterial and deodorizing EVA foam material is made from the following raw materials in parts by weight: 60-80 parts of EVA resin, 15-25 parts of intrinsic antibacterial vinyl elastomer, 10-20 parts of polyolefin elastomer, 0.8-1.8 parts of crosslinking agent, 2.0-4.5 parts of foaming agent, and 3.7-15 parts of auxiliary agents; wherein the intrinsic antibacterial vinyl elastomer molecular chain contains double bond structural units and long-chain alkylpyridine quaternary ammonium salt antibacterial structural units.

[0008] Furthermore, the intrinsic antibacterial vinyl elastomer structure is as follows: .

[0009] Furthermore, the vinyl acetate content of the EVA resin is 18wt%-28wt%.

[0010] Furthermore, the polyolefin elastomer is an ethylene-octene copolymer or an ethylene-butene copolymer; the crosslinking agent is dicumyl peroxide or bis(tert-butylperoxyisopropyl)benzene; and the foaming agent is azodicarbonamide or 4,4'-oxobisbenzenesulfonyl hydrazine.

[0011] Furthermore, the auxiliary additives include 1.0-3.0 parts of zinc oxide activator, 0.5-2.0 parts of stearic acid lubricant, 1.0-4.0 parts of talc nucleating agent, 0.2-0.5 parts of antioxidant, and 1.0-5.0 parts of wear-resistant filler, wherein the antioxidant is a hindered phenolic antioxidant or a phosphite antioxidant; and the wear-resistant filler is silica or calcium carbonate.

[0012] Furthermore, the preparation method of the antibacterial and deodorizing EVA foam material includes the following steps: S1: Preparation of intrinsic antibacterial vinyl elastomer: 4-vinylpyridine, isooctyl acrylate and allyl methacrylate were copolymerized in ethyl acetate solvent to obtain a prepolymer solution, followed by the addition of long-chain alkyl halide 1-bromohexadecane for quaternization reaction, and the intrinsic antibacterial vinyl elastomer was obtained after post-treatment. S2: Preparation of EVA foam material: EVA resin and polyolefin elastomer are pre-mixed, and then the intrinsic antibacterial vinyl elastomer obtained in S1 and auxiliary additives are added. The mixture is continued to be intensively mixed. When the material temperature drops to below 100°C, crosslinking agent and foaming agent are added. After uniform mixing, the mixture is sheeted and cured. The EVA foam material of the present invention is obtained by compression molding, depressurization and mold opening.

[0013] Furthermore, in step S1, the molar ratio of 4-vinylpyridine, isooctyl acrylate, and allyl methacrylate is 24:70:6; and the initiator used in the copolymerization reaction is azobisisobutyronitrile.

[0014] Furthermore, the amount of 1-bromohexadecane added in step S1 is 0.75 times the molar amount of 4-vinylpyridine; the quaternization reaction is carried out under reflux conditions for 16 hours.

[0015] Furthermore, in step S2, the pre-mixing temperature is 95-105℃ and the time is 2-3 minutes; the internal mixing temperature is 110℃ and the time is 8-12 minutes.

[0016] Furthermore, the conditions for compression molding foaming in step S2 are: mold temperature 170-175℃, pressure 15-18MPa, and time 500-600 seconds.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention introduces an intrinsic antibacterial vinyl elastomer, which utilizes the active double bonds retained on its molecular chain to chemically crosslink with the EVA matrix during the foaming process, thereby constructing an interpenetrating polymer network structure of antibacterial network and EVA matrix network. This solves the problems of easy precipitation and poor water resistance of traditional physically added antibacterial agents, and achieves long-lasting antibacterial effect throughout the entire life cycle.

[0018] (2) The intrinsic antibacterial vinyl elastomer designed in this invention acts as a toughening phase in the system, which improves the resilience and wear resistance of EVA foam material. In addition, it has long-chain alkyl side groups, which play a significant compatibilizing role, making the cell structure more delicate and uniform.

[0019] (3) Through special molecular structure design, the present invention adopts a pyridine quaternary ammonium salt structure with better heat resistance or wraps the cationic center through the steric hindrance effect of hydrophobic long chain, which significantly improves the thermal decomposition temperature of antibacterial components, effectively avoids the decomposition problem in the high temperature molding and foaming process of EVA, and at the same time reduces the interference with the decomposition of foaming agent. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the preparation process of the antibacterial and deodorizing EVA foam material of the present invention; Figure 2 Fourier transform infrared spectrum of intrinsic antibacterial vinyl elastomer prepared in Example 1; Figure 3 This is a comparison chart of the test results of antibacterial rate, ammonia removal rate and compression rebound rate of the embodiments and comparative examples of the present invention. Figure 4 This is a comparison chart showing the test results of wear resistance and anti-slip performance of the embodiments and comparative examples of the present invention. Detailed Implementation

[0021] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0022] The present invention proposes an antibacterial and deodorizing EVA foam material, wherein the EVA foam material is made from the following raw materials in parts by weight: 60-80 parts of EVA resin, 15-25 parts of intrinsic antibacterial vinyl elastomer, 10-20 parts of polyolefin elastomer (POE), 0.8-1.8 parts of crosslinking agent, 2.0-4.5 parts of foaming agent, and 3.7-15 parts of auxiliary additives.

[0023] The intrinsic antibacterial vinyl elastomer is self-made in this invention. The long-chain alkyl pyridine quaternary ammonium salt grafted onto its molecular chain provides long-lasting antibacterial and deodorizing functions; the retained dangling vinyl double bond acts as a chemical anchor to participate in cross-linking, preventing precipitation and improving resilience; the long-chain alkyl provides hydrophobic compatibilizing effect.

[0024] The EVA, as the base resin of the foaming material, provides the main mechanical framework and foaming carrier, and its vinyl acetate (VA) content is 18wt%-28wt%.

[0025] The POE is an ethylene-octene copolymer or an ethylene-butene copolymer. As a toughening modifier, it improves the feel and low-temperature flexural strength of EVA foam materials, while also aiding in the dispersion of intrinsically antibacterial vinyl elastomers in the matrix.

[0026] The crosslinking agent is dicumyl peroxide (DCP) or bis(tert-butylperoxyisopropyl)benzene (BIPB), which is used to decompose at high temperature to generate free radicals, initiate crosslinking of the EVA main chain and co-crosslinking of the intrinsic antibacterial vinyl elastomer double bonds with the matrix.

[0027] The foaming agent is azodicarbonamide (AC) or 4,4'-oxobisbenzenesulfonyl hydrazine (OBSH), used to decompose and release gas to form a foam structure.

[0028] The auxiliary additives include 1.0-3.0 parts of zinc oxide activator, 0.5-2.0 parts of stearic acid lubricant, 1.0-4.0 parts of talc nucleating agent, 0.2-0.5 parts of antioxidant, and 1.0-5.0 parts of wear-resistant filler. The antioxidant is a hindered phenolic antioxidant or a phosphite antioxidant, used to inhibit the degradation of EVA and intrinsically antibacterial vinyl elastomers during high-temperature processing, thereby improving thermal stability and aging resistance. The wear-resistant filler is silica or calcium carbonate, used to improve the mechanical properties of the cell walls, enhance wear resistance, and simultaneously regulate the cell structure.

[0029] The specific preparation process is as follows, see attached. Figure 1 The following is a flowchart of the preparation process: S1. Preparation of intrinsically antimicrobial vinyl elastomers (1) Copolymerization stage: Under nitrogen protection, monomers with a molar ratio of 4-vinylpyridine (4-VP): isooctyl acrylate (2-EHA): allyl methacrylate (AMA) = 24:70:6 were dissolved in ethyl acetate, and the total solid content was controlled to be 35 wt%. Azobisisobutyronitrile (AIBN) initiator was added at 0.2 wt% of the total monomer weight, and free radical solution polymerization was carried out at 70 °C. The reaction was stirred for 12 hours to obtain a prepolymer solution containing side-hanging pyridine groups and side-hanging allyl double bonds. During the reaction, AMA mainly participated in the main chain growth through the methacrylic acid double bond, while the allyl double bond was mostly retained in the form of side chain suspension due to its low propagation rate constant.

[0030] (2) Quaternization modification stage: 1-Bromohexadecane was added to the above prepolymer solution, with a molar amount 0.75 times that of 4-VP. The mixture was heated to reflux and reacted for 16 hours. During the reaction, 1-Bromohexadecane nucleophilically alkylated the tertiary nitrogen atom on the side-attached pyridine ring. The long-chain alkyl group was directly bonded to the positively charged nitrogen atom, forming an amphiphilic polycationic structure. In this structure, the high-density positive charge center of the pyridine quaternary ammonium salt is responsible for electrostatically adsorbing bacteria and capturing acidic odor-causing molecules, while the C16 long chain synergistically inserts and disrupts the bacterial cell membrane, thus cutting off the biological source of odor while achieving physical sterilization.

[0031] (3) Post-treatment: precipitation, washing, and then vacuum drying at 40°C for 24 hours to obtain intrinsic antibacterial vinyl elastomer.

[0032] Preparation of S2. EVA foam material (1) Mixing stage: Set the internal mixer temperature to 95-105℃, add EVA resin and polyolefin elastomer POE for pre-mixing for 2-3 minutes until the matrix resin is initially melted and softened. Then add intrinsic antibacterial vinyl elastomer and auxiliary agents. Raise the temperature to 110℃ and continue mixing for 8-12 minutes. During this process, the intrinsic antibacterial vinyl elastomer has good compatibility with the vinyl acetate (VA) group of EVA through the 2-EHA flexible long chain segment on its side chain. At the same time, the long chain alkyl can interact with the POE chain segment through hydrophobic interaction and physical entanglement, so that the functional elastomer can be uniformly dispersed at the molecular level in the matrix. Due to its high molecular weight and polycationic structure, it can avoid the aggregation and precipitation of small molecule quaternary ammonium salts, ensure uniform distribution of antibacterial activity, and participate in cross-linking or form interpenetrating networks in the subsequent molding and foaming process, enhancing the integrity of the cell walls and resilience.

[0033] (2) Adding stage: When the material temperature drops below 100℃, add crosslinking agent and foaming agent, quickly and evenly knead to ensure that the crosslinking agent and foaming agent are evenly distributed in the system and at the interface with the intrinsic elastomer. Finally, extrude the film and cure for 4-8 hours.

[0034] (3) Molding and foaming stage: After cutting the film, place it in the mold of the flat vulcanizing machine. Set the mold temperature to 170-175℃, the pressure to 15-18MPa, and the time to 500-600 seconds. During the molding and foaming process, the high temperature causes the crosslinking agent to decompose and generate free radicals. These free radicals take hydrogen atoms from the EVA molecular chain, generate EVA main chain free radicals and undergo coupling crosslinking to construct a three-dimensional crosslinked network skeleton. At the same time, a small number of allyl side chains retained on the intrinsic antibacterial vinyl elastomer molecular chain can form active free radicals under the action of free radicals, which can couple or add to the EVA main chain to achieve local co-crosslinking, thereby fixing the antibacterial elastomer in the cell wall, ensuring that it is not migrated for a long time and fully exposing its antibacterial function.

[0035] (4) Mold opening: Depressurize and open the mold. The material expands instantly to obtain EVA foam material.

[0036] Example 1 Raw materials for EVA foam material preparation: 70 parts of EVA resin with a vinyl acetate content of 24 wt%, 20 parts of intrinsic antibacterial vinyl elastomer, 15 parts of ethylene-octene copolymer, 1.3 parts of DCP crosslinking agent, 3.0 parts of AC foaming agent, 2.0 parts of zinc oxide activator, 1.0 part of stearic acid lubricant, 2.5 parts of talc nucleating agent, 0.35 parts of hindered phenolic antioxidant, and 3.5 parts of silica wear-resistant filler. The preparation process is as follows: (1) Preparation of intrinsic antibacterial vinyl elastomer: Under nitrogen protection, 42 parts of 4-VP, 215 parts of 2-EHA, and 12.6 parts of AMA were dissolved in ethyl acetate, and the total solid content was controlled to be 35 wt%. 0.5 parts of AIBN were added, and free radical solution polymerization was carried out at 70 °C. The reaction was stirred for 12 hours to obtain a prepolymer solution containing side-attached pyridine groups and side-attached allyl double bonds. 91.6 parts of 1-bromohexadecane were added to the prepolymer solution. The temperature was raised to reflux, and the reaction was carried out for 16 hours. After the reaction was completed, the precipitate was washed, and then dried under vacuum at 40 °C for 24 hours to obtain the intrinsic antibacterial vinyl elastomer.

[0037] (2) Preparation of EVA foam material: Set the internal mixer temperature to 95-105℃, add EVA resin and polyolefin elastomer POE for premixing for 2 minutes until the matrix resin is initially melted and softened. Then add the intrinsic antibacterial vinyl elastomer obtained in step (1), zinc oxide activator, stearic acid lubricant, talc nucleating agent, hindered phenolic antioxidant, and silica wear-resistant filler. Raise the temperature to 110℃ and continue internal mixing for 10 minutes. When the material temperature drops below 100℃, add DCP crosslinking agent and AC foaming agent, quickly mix evenly, and finally sheet and cure for 5 hours. Cut the film and place it in the mold of the flat vulcanizing machine. Set the mold temperature to 172℃, pressure to 16MPa, and time to 550 seconds. Release the pressure and open the mold. The material expands instantly to obtain EVA foam material.

[0038] Fourier transform infrared (FT-IR) structural characterization (1) Parameter setting and detection process: The intrinsic antibacterial vinyl elastomer prepared in Example 1 was analyzed for chemical structure using a high-sensitivity Fourier transform infrared spectrometer. ATR total reflection assembly was used for direct sampling, positioned at the focal point of the infrared light path. The scanning range was set to 4000 cm⁻¹. -1 Up to 500cm -1 The mid-infrared region has a spectral resolution of 4 cm⁻¹. -1 After background subtraction, a total of 32 scans were performed.

[0039] (2) Characterization results: such as Figure 2 As shown, 1583cm -1 The peak observed at 1085 cm⁻¹ corresponds to the characteristic vibration of the pyridine ring skeleton (C=N), while the peak at 1085 cm⁻¹ corresponds to the characteristic vibration of the pyridine ring skeleton (C=N). -1 The clearly visible absorption peak is attributed to the bonding between the quaternary ammonium salt cation center and the carbon atom (CN). + ) stretching vibration; in addition, 725cm -1 The peak at this point is a planar rocking vibration characteristic of long-chain methylene groups, indicating that the hydrophobic long alkyl chain has been stably grafted. In summary, this spectrum confirms the successful construction of a polycation-long alkyl chain synergistic amphiphilic structure within the material, providing a solid chemical basis for the elastomer to achieve the dual functions of physical bacterial puncture and electrostatic adsorption deodorization.

[0040] Example 2 The intrinsic antibacterial vinyl elastomer was from the same batch as in Example 1. The raw materials for preparing the EVA foam material were: 80 parts of EVA resin with a vinyl acetate content of 18 wt%, 25 parts of intrinsic antibacterial vinyl elastomer, 20 parts of ethylene-butene copolymer, 1.8 parts of BIPB crosslinking agent, 4.5 parts of OBSH foaming agent, 3.0 parts of zinc oxide activator, 2.0 parts of stearic acid lubricant, 4.0 parts of talc nucleating agent, 0.5 parts of phosphite antioxidant, and 5.0 parts of calcium carbonate wear-resistant filler. Preparation process: pre-mixing for 3 minutes; tableting and curing for 8 hours during drug addition; during molding and foaming, the mold temperature was set at 175℃, the pressure at 18 MPa, and the time at 600 seconds. The remaining steps were the same as in Example 1.

[0041] Example 3 The intrinsic antibacterial vinyl elastomer was from the same batch as in Example 1. The raw materials for preparing the EVA foam material were: 60 parts of EVA resin with a vinyl acetate content of 28 wt%, 15 parts of the intrinsic antibacterial vinyl elastomer, 10 parts of ethylene-octene copolymer, 0.8 parts of DCP crosslinking agent, 2.0 parts of OBSH foaming agent, 1.0 part of zinc oxide activator, 0.5 parts of stearic acid lubricant, 1.0 part of talc nucleating agent, 0.2 parts of phosphite antioxidant, and 1.0 part of calcium carbonate wear-resistant filler. Preparation process: During the drug addition process, the film was extruded and cured for 4 hours; during the molding and foaming process, the mold temperature was set at 170℃, the pressure at 15 MPa, and the time at 500 seconds. The remaining steps were the same as in Example 1.

[0042] Comparative Example 1 Same as Example 1, except that no intrinsic antibacterial vinyl elastomer was added during the preparation of the EVA foam material.

[0043] Comparative Example 2 Same as Example 1, except that in the preparation of the intrinsic antibacterial vinyl elastomer, AMA was not added, but instead an equal amount of 2-EHA was used.

[0044] Comparative Example 3 Same as Example 1, except that the intrinsic antibacterial vinyl elastomer is replaced with an equal amount of the quaternary ammonium salt monomer hexadecyltrimethylammonium bromide.

[0045] Performance testing 1. Antibacterial performance test Referring to GB / T 31402-2023 "Determination of antibacterial activity of plastics and other non-porous materials", the material's sustained antibacterial ability after repeated washing was verified.

[0046] Sample preparation: The samples obtained from the examples and comparative examples were cut into 40mm × 40mm pieces and placed in a standard environment for 24 hours. Both the examples and comparative examples were subjected to 30 standard water washes before testing. A neutral detergent was used for washing at 40℃, and the samples were then air-dried.

[0047] Specific steps: Staphylococcus aureus and Escherichia coli were selected as test strains. The bacterial suspension was inoculated onto the sample surface and cultured with shaking at 37°C for 18 hours. The change in colony count before and after inoculation was measured, and the inhibition rate was calculated. Each group of samples was tested in triplicate.

[0048] 2. Ammonia removal rate test The material's ability to adsorb and neutralize ammonia was verified by referring to the gas adsorption test method in a confined space.

[0049] Sample preparation: Place a certain mass of sample in a sealed container of known volume and introduce ammonia gas with an initial concentration of 100 ppm.

[0050] Specific steps: Let the sample stand at 25℃ for 2 hours, then use a gas detector to measure the remaining ammonia concentration and calculate the removal rate. Maintain relative humidity at 50%±5% during the test. Perform three parallel tests on each sample group.

[0051] 3. Compression rebound rate test Referencing GB / T 6669-2008 "Determination of Compression Permanent Deformation of Flexible Foam Polymer Materials", the elastic recovery performance of the material was verified.

[0052] Sample preparation: The samples obtained from the examples and comparative examples were cut into 50mm×50mm×10mm specimens. The specimen surface was flat and there were no obvious bubble defects.

[0053] Specific steps: Compress to 50% of the original thickness at 70℃, maintain for 22 hours, recover for 30 minutes, measure the thickness, and calculate the rebound rate. Three parallel samples are made for each group of samples.

[0054] 4. Wear resistance test Referencing GB / T 9867-2008 "Determination of Abrasion Resistance of Vulcanized Rubber or Thermoplastic Rubber", the abrasion resistance of the material surface was verified.

[0055] Specific steps: A rotary drum abrasive mill with a drum diameter of 150mm ± 0.2mm was used. Standard alumina sandpaper with a grit size of 60# was used as the abrasive. A normal load of 10N was applied, and the abrasive stroke was set to 40m. The abrasive volume was measured. The test temperature was controlled at 23℃ ± 2℃. Each sample was tested three times.

[0056] 5. Anti-slip performance test The dynamic friction properties of the material were evaluated in accordance with GB / T 10006-2021 "Determination of the coefficient of friction of plastic films and sheets".

[0057] Specific steps: Under standard temperature and humidity conditions, measure the dynamic coefficient of friction using a coefficient of friction meter. Stainless steel or PVC plates can be used as the test substrate, and the sliding speed and load should be set according to standard parameters. Each sample group should be tested three times, and the average value should be taken.

[0058] Table 1. Test results of antibacterial rate, ammonia removal rate, and compression rebound rate for the examples and comparative examples.

[0059] Table 2. Test results of wear resistance and anti-slip performance of the examples and comparative examples.

[0060] Results Analysis (1) As shown in Tables 1 and 2, the EVA foam materials prepared in Examples 1-3 maintained a high antibacterial rate after 30 rigorous water washings, and the ammonia removal rate also met the industry's excellent standards. This indicates that the intrinsic antibacterial vinyl elastomer endows the material with excellent and long-lasting dual functions of antibacterial and deodorizing properties. In terms of physical and mechanical properties, all three examples exhibited good compression resilience, low wear volume, and excellent anti-slip properties. Among them, Example 1 showed the most balanced performance, ensuring the highest antibacterial and deodorizing efficiency while achieving the best mechanical strength and resilience, indicating that the blended network structure of the elastomer and matrix resin was the most perfect under this ratio.

[0061] (2) Compared to Example 1, Comparative Example 1 is a common EVA foam material without the addition of intrinsic antibacterial vinyl elastomer. Its antibacterial rate and ammonia removal rate are extremely low, and it basically does not have antibacterial and deodorizing functions, as shown in the attached figure. Figure 3 Furthermore, the wear volume of Example 1 is significantly smaller than that of Comparative Example 1, and the dynamic friction coefficient is significantly improved, as shown in the attached figure. Figure 4 This demonstrates that the elastomer synthesized in this invention not only serves as a functional additive, but also enhances toughness and improves surface friction properties due to its unique long-chain structure and chemical bonds formed through crosslinking agents.

[0062] (3) Comparing Example 1 and Comparative Example 2, it can be seen that when the intrinsic elastomer lacks crosslinkable AMA monomers, the antibacterial rate of the material decreases significantly after 30 water washes, and the compression rebound rate and wear resistance deteriorate, as shown in the attached figure. Figure 3 This is because the lack of chemical cross-linking points means the antibacterial components can only be physically dispersed in the matrix, making them prone to loss during washing and unable to effectively transfer stress. Comparative examples and Comparative Example 3 show that replacing the polymeric elastomer of this invention with a traditional small-molecule quaternary ammonium salt resulted in a comprehensive decline in material performance. The small-molecule antibacterial agent easily migrates and precipitates, leading to near-complete loss of antibacterial ability after washing. Simultaneously, the addition of small molecules severely disrupts the foaming pore structure of EVA, manifested as a significant decrease in compression resilience, a dramatic increase in wear volume, and a decrease in the coefficient of friction. This fully demonstrates the crucial role of the cross-linkable polymeric antibacterial agent containing double bonds used in this invention in achieving long-lasting antibacterial effects and maintaining the excellent physical properties of the material.

[0063] In summary, the antibacterial and deodorizing EVA foam material prepared by this invention, by introducing an intrinsic antibacterial vinyl elastomer containing a long-chain alkylpyridine quaternary ammonium salt structure and reactive double bonds, not only endows the material with broad-spectrum, efficient, and wash-resistant antibacterial and deodorizing functions, but also achieves a synergistic deodorization mechanism of physical sterilization and chemical neutralization. At the same time, by utilizing the reactive double bonds to chemically crosslink with the matrix resin during the foaming process, it overcomes the defects of traditional small molecule antibacterial agents, such as easy precipitation, poor wash resistance, and damage to the mechanical properties of materials, and produces a high-quality molded foam shoe material with high resilience, wear resistance, anti-slip properties, and excellent hygiene performance.

Claims

1. An antibacterial and deodorizing EVA foam material, characterized in that, The EVA foam material is made from the following raw materials in parts by weight: 60-80 parts EVA resin, 15-25 parts intrinsic antibacterial vinyl elastomer, 10-20 parts polyolefin elastomer, 0.8-1.8 parts crosslinking agent, 2.0-4.5 parts foaming agent, and 3.7-15 parts auxiliary agents. The intrinsic antibacterial vinyl elastomer contains double bond structural units and long-chain alkylpyridine quaternary ammonium salt antibacterial structural units on its molecular chain. The preparation method of the intrinsic antibacterial vinyl elastomer is as follows: a copolymerization reaction of 4-vinylpyridine, isooctyl acrylate, and allyl methacrylate is initiated in ethyl acetate solvent to obtain a prepolymer solution, followed by the addition of the long-chain alkyl halide 1-bromohexadecane for quaternization reaction, and post-treatment to obtain the intrinsic antibacterial vinyl elastomer. The molar ratio of 4-vinylpyridine, isooctyl acrylate, and allyl methacrylate is 24:70:

6. The initiator used in the copolymerization reaction is azobisisobutyronitrile.

2. The antibacterial and deodorizing EVA foam material as described in claim 1, characterized in that, The vinyl acetate content of the EVA resin is 18wt%-28wt%.

3. The antibacterial and deodorizing EVA foam material as described in claim 1, characterized in that, The polyolefin elastomer is an ethylene-octene copolymer or an ethylene-butene copolymer; the crosslinking agent is dicumyl peroxide or bis(tert-butylperoxyisopropyl)benzene; and the foaming agent is azodicarbonamide or 4,4'-oxobisbenzenesulfonyl hydrazine.

4. The antibacterial and deodorizing EVA foam material as described in claim 1, characterized in that, The auxiliary additives include 1.0-3.0 parts of zinc oxide activator, 0.5-2.0 parts of stearic acid lubricant, 1.0-4.0 parts of talc nucleating agent, 0.2-0.5 parts of antioxidant, and 1.0-5.0 parts of wear-resistant filler, wherein the antioxidant is a hindered phenolic antioxidant or a phosphite antioxidant; and the wear-resistant filler is silica or calcium carbonate.

5. A method for preparing an antibacterial and deodorizing EVA foam material according to any one of claims 1-4, characterized in that, Includes the following steps: S1: Preparation of intrinsic antibacterial vinyl elastomer: 4-vinylpyridine, isooctyl acrylate and allyl methacrylate were copolymerized in ethyl acetate solvent to obtain a prepolymer solution, followed by the addition of long-chain alkyl halide 1-bromohexadecane for quaternization reaction, and the intrinsic antibacterial vinyl elastomer was obtained after post-treatment. S2: Preparation of EVA foam material: EVA resin and polyolefin elastomer are pre-mixed, and then the intrinsic antibacterial vinyl elastomer obtained in S1 and auxiliary additives are added. The mixture is continued to be intensively mixed. When the material temperature drops to below 100°C, crosslinking agent and foaming agent are added. After uniform mixing, the mixture is sheeted and cured. The EVA foam material of the present invention is obtained by compression molding, depressurization and mold opening.

6. The method for preparing an antibacterial and deodorizing EVA foam material as described in claim 5, characterized in that, The amount of 1-bromohexadecane added in step S1 is 0.75 times the molar amount of 4-vinylpyridine; the quaternization reaction is carried out under reflux conditions for 16 hours.

7. The method for preparing an antibacterial and deodorizing EVA foam material as described in claim 5, characterized in that, In step S2, the pre-mixing temperature is 95-105℃ and the time is 2-3 minutes; the internal mixing temperature is 110℃ and the time is 8-12 minutes.

8. The method for preparing an antibacterial and deodorizing EVA foam material as described in claim 5, characterized in that, The conditions for compression molding foaming in step S2 are: mold temperature 170-175℃, pressure 15-18MPa, and time 500-600 seconds.

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