Breathable and antibacterial EVA foaming material and preparation method thereof

Abstract

The application discloses a kind of breathable, antibacterial EVA foaming material and preparation method thereof.The open hole structure is by adding the polymer LDPE with EVA melt blending of larger crystallization temperature difference, simultaneously using secondary foaming method to make open hole structure, so that the composite material has better air flowability.By loading "CS / AgNPs" nanoparticles on graphene oxide with large specific surface area and persistent stability, and adding MnO2 as catalyst, a "GO-SH / MnO2 / CS / AgNPs" composite material is constructed for antibacterial.The "GO-SH / MnO2 / CS / AgNPs" composite material constructed in this way has higher antibacterial activity and better stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of materials, and particularly relates to a breathable and antibacterial EVA foaming material and a preparation method thereof. BACKGROUND

[0002] EVA has the characteristics of good softness, rubber-like elasticity, good flexibility at-50 DEG C, transparency and surface gloss, good chemical stability, good anti-aging and ozone resistance, and no toxicity. The mixing property with fillers, coloring property and forming processability are good. EVA is widely used in foaming shoe materials, films, packaging films, hot melt adhesives, wires and cables, toys and the like. In the EVA resin used in shoe materials, the content of vinyl acetate is generally 15% to 22%. Since the EVA resin blended foaming product has the properties of softness, good elasticity, chemical corrosion resistance and the like, it is widely used in shoe soles and interior materials of high-grade travel shoes, mountaineering shoes, slippers and sandals. In addition, the material is also used in the fields of sound insulation boards, gymnastic mats and sealing materials. However, shoe materials, gymnastic mats and the like inevitably need to be in direct contact with various places for a long time, which will bring opportunities for the breeding of various bacteria thereon, and therefore, it is of great value to research the EVA foaming material with antibacterial property for its application in the field of shoe materials and the like.

[0003] The traditional method for improving the antibacterial property of high polymer materials is to directly add traditional antibacterial agents such as nano-zinc oxide, nano-silicon dioxide and chitosan, and to directly melt blend the antibacterial additives with the matrix. However, most of the nano-metal oxides and other antibacterial agents are strong hydrophilic materials, while most of the high polymer materials are hydrophobic materials, which leads to poor compatibility of the antibacterial additives with the matrix, and the antibacterial additives cannot be stably and uniformly distributed in the matrix, so that the overall antibacterial effect of the product is poor.

[0004] Chitosan (CS) particles have good antibacterial property. Chitosan is a product obtained by removing part of acetyl groups from chitin, a natural polysaccharide, and has physiological functions such as biodegradability, biocompatibility, non-toxicity, bacteriostasis, anticancer, lipid-lowering, immune enhancement and the like, and is widely used in antibacterial agents, medical fibers, medical dressings, artificial tissue materials, drug release materials, gene transduction carriers, biological medical fields, medical absorbable materials and the like. Metal nano materials mainly include gold nanoparticles, silver nanoparticles, copper nanoparticles and metal oxide nanoparticles. Among them, silver nanoparticles AgNPs are concerned for their broad-spectrum antibacterial ability caused by the action mode of destroying bacterial cell membranes and intracellular components.

[0005] Based on this, the present application provides a breathable and antibacterial EVA foaming material and a preparation method thereof. SUMMARY

[0006] The application makes the EVA foaming material into an open-cell structure by a secondary foaming method and a crystallization temperature difference method, the cells of the open-cell polymer foaming material are interconnected, the gas phase and the polymer phase in the polymer foaming body are continuous phases, and fluid can pass through the foaming body.

[0007] The application constructs a "GO-SH / MnO2 / CS / AgNPs" composite material for antibiosis by loading MnO2 and "CS / AgNPs" nanoparticles on graphene oxide (GO) with large specific surface area and long-term stability. The thiol-functionalized graphene oxide (GO-SH) is a good nanomaterial support matrix, in which "-SH" represents a thiol group. The nanoparticles are uniformly distributed on the surface of the support matrix through the interaction between the thiol groups and the CS / AgNPs nanoparticles. The construction of the composite material can utilize the biocompatibility, surface roughness and morphology of the support matrix to improve the antibiosis performance of the nanoparticles. The "GO-SH / MnO2 / CS / AgNPs" composite material constructed in this way has higher antibiosis activity and better stability.

[0008] The application aims to provide an EVA foaming material with both air permeability and antibiosis performance and a preparation method thereof.

[0009] To achieve the above object, the application adopts the following technical scheme:

[0010] The open-cell air-permeable and antibacterial EVA foaming material comprises the following raw materials in parts by weight: 70 parts of EVA (ethylene-vinyl acetate), 20 parts of LDPE (low-density polyethylene), 10 parts of POE-g-MAH (maleic anhydride grafted polyolefin elastomer), 1-3 parts of a composite antibacterial additive, 2.5 parts of an AC foaming agent, 1.5 parts of a crosslinking agent, 2.5 parts of a filler, 3 parts of a calcium-zinc stabilizer, 1 part of a lubricant and 0.2 parts of a release agent.

[0011] Further, the composite antibacterial additive is GO-SH / MnO2 / CS / AgNPs. The preparation steps of the POE-g-MAH include: weighing 0.4 parts by weight of maleic anhydride MAH, dissolving the MAH in acetone to prepare a solution. Weighing 4 parts by weight of polyolefin elastomer POE particles, spraying the acetone solution of MAH into the POE particles, and uniformly mixing in a high-speed mixer, and volatilizing the acetone after standing. The mixture is melt blended for 10 min by using a torque rheometer, the rotor speed is 30 r / min, the torque temperature is 165 DEG C, and the melt is opened into a sheet on an open mill after the blending is completed.

[0012] Further, the preparation steps of the composite antibacterial adjuvant (GO-SH / MnO2 / CS / AgNPs) include:

[0013] (1) Preparation of graphene oxide (GO): 0.5 g of graphite powder and 24 mL of H2SO4 solution were stirred at room temperature for about 2 h. Then, the mixture was cooled to 3 °C, and 1.2 g of KMnO4 was slowly added to the mixture. Next, the mixture was heated to 30-35 °C and stirred for 24 h. Then, 20 mL of deionized water was added to the mixture and stirred for 5 min. Finally, 10 mL of distilled water and 5 mL of 30 wt% H2O2 solution were added to the mixture to complete the reaction. The resulting mixture was washed with a 5 wt% HCL solution in deionized water until the pH reached 5-6, and GO was obtained after vacuum drying at 50 °C for 24 h.

[0014] (2) Preparation of GO-SH / MnO2: First, 5.0 grams of 4-aminothiophenol and 80 mL of 1M HC1 solution were added to a three-necked flask, and the reaction temperature was raised to 50 °C under stirring conditions until the 4-aminothiophenol was completely dissolved. Then, NaNO2 solution (10.0 grams of NaNO2 dissolved in 100 mL of deionized water) was added dropwise to the reaction mixture under ice bath conditions until the gas bubbles completely disappeared. After that, 5.0 grams of GO were dispersed in 200 mL of deionized water and then added to the above solution. After stirring for 12 h under ice bath, the mixture was washed with acetone, ethanol, and deionized water. Finally, GO-SH was obtained after vacuum drying at 50 °C for 24 h. 2.0 grams of GO-SH were ultrasonically dispersed in 100 mL of pure water, and 20 mL of potassium permanganate solution (15 mg / L) was added dropwise under stirring, followed by the addition of 12 mL of formamide under ultrasonication for 30 min. The precipitate was collected by centrifugation and washed with pure water three times, and then oven dried for 12 h to obtain GO-SH / MnO2.

[0015] (3) Preparation of CS / AgNPs: 2 g of CS was dissolved in 200 mL of an acetic acid aqueous solution (0.1 wt%), and placed in an oil bath pot for stirring, while 10 mL of freshly prepared 5 mg / mL AgNO3 solution was added dropwise during stirring. After heating to 95 °C under stirring, 0.1 g / mL of NaOH solution was added dropwise until the solution turned yellow, and then the reaction was terminated after stirring at 95 °C for 20 min. The precipitate was collected by centrifugation, and the product was washed with deionized water three times, and then vacuum dried at 60 °C for 1 h to obtain CS / AgNPs.

[0016] (4) Preparation of GO-SH / MnO2 / CS / AgNPs: GO-SH / MnO2 was dispersed in deionized water, and then CS / AgNPs was added into the suspension, the mass ratio of GO-SH / MnO2 and CS / AgNPs was 1:2, magnetic stirring was carried out at room temperature for 5 hours, then the mixture was washed with deionized water for three times, after centrifugation, the product was vacuum dried at 70℃ for 12h to obtain GO-SH / MnO2 / CS / AgNPs.

[0017] Further, the EVA foaming material is of open-cell structure, and the preparation steps include: melt blending EVA and LDPE which have a large difference in crystallization temperature, and there are two kinds of blended polymers with different crystallization temperature values in the melt structure, the polymer with high crystallization temperature crystallizes before the polymer with low crystallization temperature, thereby producing pressure on the cell structure to make the cells break and connect to form open-cell structure, and a secondary foaming method is used as a mold foaming method to make the EVA foaming material into open-cell structure.

[0018] Further, the preparation method of the breathable and antibacterial EVA foaming material: 70 parts of EVA (ethylene-vinyl acetate), 20 parts of LDPE (low-density polyethylene), 10 parts of POE-g-MAH (maleic anhydride modified polyolefin elastomer), 1-3 parts of composite antibacterial additive, 2.5 parts of AC foaming agent, 1.5 parts of crosslinking agent, 2.5 parts of filler, 3 parts of calcium-zinc stabilizer, 1 part of lubricant, and 0.2 parts of release agent are put into a banbury mixer for blending, and then the blended product is cold and hot mold pressed; specifically including the following steps:

[0019] (1) EVA, POE-g-MAN, LDPE and crosslinking agent are put into a preheated banbury mixer at 130℃ for 10min, and the rotation speed of the banbury mixer is 30rpm;

[0020] (2) The composite antibacterial additive, AC foaming agent, filler, calcium-zinc stabilizer, lubricant and release agent are added into the blended product obtained in step (1), and the blending is continued in the banbury mixer at 130℃ for 10min;

[0021] (3) The blended product obtained in step (2) is pressed into a sheet by an open mill and then moved into a flat vulcanizing machine for mold foaming, the temperature of the upper and lower mold plates is set to 150℃, the pressure is 10MPa, the mold pressing time is 600s, and the pre-foaming is carried out, then the pre-foamed semi-finished product is dried in a 60℃ air drying oven for 12h, then the temperature of the upper and lower mold plates is adjusted to 175℃, the pressure is 15MPa, the mold pressing time is 380s, and the secondary foaming is carried out, and the breathable and antibacterial EVA foaming material is automatically ejected after the mold is opened.

[0022] The filler is one or more of nano zinc oxide and zinc stearate;

[0023] The crosslinking agent is dicumyl peroxide;

[0024] The lubricant is one or more of stearic acid, butyl stearate, and oleamide.

[0025] Preferably, the filler is nano zinc oxide; the lubricant is stearic acid; and the release agent is paraffin wax.

[0026] The beneficial effects of this invention are as follows:

[0027] This invention employs a crystallization temperature difference method to melt-blend two materials with significantly different crystallization temperatures: EVA (crystallization temperature 10℃) and LDPE (crystallization temperature 90℃). The melt blending of these two semi-crystalline polymers with different crystallization temperatures maximizes the stiffness contrast between the hard and soft regions in the polymer matrix. Since the opening process occurs after the foam extruder leaves the mold, the foam structure is naturally cooled by the surrounding air. If the melt structure has two different crystallization temperatures... c High T values ​​in blended polymers c Polymers will precede low T c Polymer crystallization. This means that in two T... c Between values, soft cross section (i.e., low T) c The polymer is almost like a liquid, while the hard cross-section (i.e., high T) c The polymer is almost solid, resulting in a large contrast in stiffness. If the cell opening process occurs within a temperature range between two T... c When the values ​​are between [values ​​missing], the chance of the cells opening will be greatly increased due to the large difference in stiffness. In a melt structure containing two blended polymers with different crystallization temperatures, the polymer with the higher crystallization temperature will crystallize before the polymer with the lower crystallization temperature, thus exerting pressure on the cell structure, causing the cells to rupture and connect, creating an open-cell structure. Simultaneously, a secondary foaming method is used as a molding foaming method to create an open-cell structure in EVA foam material. Because the open-cell structure is interconnected internally, it improves airflow efficiency and enhances its permeability.

[0028] This invention utilizes GO-SH / MnO2 / CS / AgNPs as a composite antibacterial agent to prepare a highly efficient antibacterial EVA foam material. The formulation is scientifically sound, and the process is simple and practical. The heterogeneous structure of CS encapsulating AgNPs enhances the material's oxygen vacancy concentration, oxygen storage capacity, and redox activity. Loading CS / AgNPs with GO-SH promotes their uniform distribution within the aggregate, thereby improving antibacterial performance.

[0029] The addition of a low content of two-dimensional nanofiller in the matrix is an effective strategy to improve the antibacterial performance of the polymer, because they have superior ability to penetrate the bacterial biofilm, so GO and CS / AgNPs are selected to construct the composite antibacterial material, in addition, the construction of the composite material can also use the biocompatibility, surface roughness and morphology of the support matrix to improve the antibacterial performance of the nanoparticles, so as to have higher antibacterial activity and better stability. Among them, in view of the efficiency and uniformity of the loading of CS / AgNPs on the surface of GO, GO-SH is obtained by modifying the thiol group of GO, so that GO becomes a good nanomaterial support matrix. Through the interaction between the thiol group and the CS / AgNPs nanoparticles, the CS / AgNPs nanoparticles are uniformly distributed on the surface of the GO-SH support matrix. In addition, there are a large number of H2O2 in the microenvironment of bacterial infection, and since MnO2 is an effective catalyst for triggering the decomposition of H2O2 into H2O and O2, the application utilizes MnO2 to synergistically antibacterial, and MnO2 can decompose the environment conducive to bacterial growth. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The Fourier infrared spectrum of the composite antibacterial aid of Example 1 is shown in the figure;

[0031] Figure 2 The scanning electron microscope image of the composite antibacterial aid of Example 1 is shown in the figure;

[0032] Figure 3 The scanning electron microscope image of the cell of Example 1 is shown in the figure;

[0033] Figure 4 The schematic diagram of the antibacterial test is shown in the figure. DETAILED DESCRIPTION

[0034] In order to make the content described in the application more convenient to understand, the technical solutions described in the application will be further described below in combination with specific embodiments, but the application is not limited to this.

[0035] The raw material parts used in the following examples and comparative examples are weight parts; the crystallization temperatures of the EVA and LDPE used are 10 DEG C and 90 DEG C respectively.

[0036] Example 1

[0037] (1) Preparation of the polymer matrix: 70 parts of EVA, 20 parts of LDPE, 10 parts of POE-g-MAH, 1.5 parts of crosslinking agent were put into a preheated mixing mill at 130 DEG C and blended for 10 min, and the speed of the mixing mill was 30 rpm;

[0038] (2) Preparation steps of the composite antibacterial aid GO-SH / MnO2 / CS / AgNPs:

[0039] (2-1) Preparation of graphene oxide (GO): 0.5 g of graphite powder and 24 mL of concentrated H2SO4 solution (70 wt%) were stirred at room temperature for about 2 h. Then, the mixture was cooled to 3 °C, and 1.2 g of KMnO4 was slowly added to the mixture. Next, the mixture was heated to 30 °C and stirred for 24 h. Then, 20 mL of deionized water was added to the mixture and stirred for 5 min. Finally, 10 mL of distilled water and 5 mL of 30 wt% H2O2 solution were added to the mixture to complete the reaction. The resulting mixture was washed with 5 wt% HCL in deionized water until the pH reached 5-6, and was vacuum dried at 50 °C for 24 h to obtain GO.

[0040] (2-2) Preparation of GO-SH / MnO2: First, 5.0 g of 4-aminobenzenethiol and 80 mL of 1 M HC1 solution were added to a three-necked flask, and the reaction temperature was increased to 50 °C under stirring until the 4-aminobenzenethiol was completely dissolved. Then, NaNO2 solution (10.0 g of NaNO2 dissolved in 100 mL of deionized water) was added dropwise to the reaction mixture under ice bath-50 °C conditions until the gas bubbles completely disappeared. After that, 5.0 g of GO was dispersed in 200 mL of deionized water and then added to the above solution. After stirring for 12 h under ice bath, the mixture was washed with acetone, ethanol, and deionized water. Finally, it was vacuum dried at 50 °C for 24 h to obtain GO-SH. 2.0 g of GO-SH was ultrasonically dispersed in 100 mL of pure water, and 20 mL of potassium permanganate solution (15 mg / L) was added dropwise under stirring, followed by the addition of 12 mL of formamide under ultrasonication for 30 min. The precipitate was collected by centrifugation and washed with pure water three times, and oven dried for 12 h to obtain GO-SH / MnO2.

[0041] (2-3) Preparation of nano CS / AgNPs: First, 2 g of CS was dissolved in 200 mL of an aqueous acetic acid solution (0.1 wt%), and placed in an oil bath pot for stirring, while 10 mL of freshly prepared AgNO3 (5 mg / mL) solution was added dropwise during stirring. After heating to 95 °C with stirring, 0.1 g / mL of NaOH solution was added dropwise until the solution turned yellow, and then the reaction was terminated after stirring at 95 °C for 20 min. The product was washed with deionized water three times, and then vacuum dried at 60 °C for 1 h to obtain CS / AgNPs.

[0042] (2-4) Preparation of GO-SH / MnO2 / CS / AgNPs: 1 g of GO-SH / MnO2 was dispersed in 250 mL of deionized water, and then 2 g of nano CS / AgNPs was added to the suspension, which was magnetically stirred at room temperature for 5 h. After washing the mixture with deionized water three times, it was centrifuged, and the product was vacuum dried at 70 °C for 12 h to obtain GO-SH / MnO2 / CS / AgNPs.

[0043] (3) Preparation of the open-cell breathable antibacterial EVA foaming material:

[0044] (3-1) 1 part of the composite antibacterial aid, 2.5 parts of the AC foaming agent, 2.5 parts of the filler, 3 parts of the calcium-zinc stabilizer, 1 part of the lubricant, and 0.2 parts of the release agent were added into the internal mixer and the molten blend obtained in step (1) was continuously mixed in the internal mixer at 130°C for 10 min;

[0045] (3-2) After the blend obtained in step (3-1) was pressed into a sheet by the open mill, it was moved into the flat vulcanizing machine for molding and foaming, the temperature of the upper and lower mold plates was set to 150°C, the pressure was 10 MPa, the molding time was 600 s, and the pre-foaming was performed once, then the pre-foamed semi-product was placed in the 60°C air-drying oven for drying for 12 h, then the temperature of the upper and lower mold plates was adjusted to 175°C, the pressure was 15 MPa, the molding time was 380 s, and the foaming was performed twice, and the open-cell breathable antibacterial EVA foaming material was automatically ejected after the mold was opened.

[0046] Example 2

[0047] (1) Preparation of the polymer matrix: same as in Example 1

[0048] (2) Preparation of GO-SH / MnO2 / CS / AgNPs: same as in Example 1

[0049] (3) Preparation of the open-cell breathable antibacterial EVA foaming material:

[0050] (3-1) 2 parts of the composite antibacterial aid, 2.5 parts of the AC foaming agent, 2.5 parts of the filler, 3 parts of the calcium-zinc stabilizer, 1 part of the lubricant, and 0.2 parts of the release agent were added into the internal mixer and the molten blend obtained in step (1) was continuously mixed in the internal mixer at 130°C for 10 min;

[0051] (3-2) After the blend obtained in step (3-1) was pressed into a sheet by the open mill, it was moved into the flat vulcanizing machine for molding and foaming, the temperature of the upper and lower mold plates was set to 150°C, the pressure was 10 MPa, the molding time was 600 s, and the pre-foaming was performed once, then the pre-foamed semi-product was placed in the 60°C air-drying oven for drying for 12 h, then the temperature of the upper and lower mold plates was adjusted to 175°C, the pressure was 15 MPa, the molding time was 380 s, and the foaming was performed twice, and the open-cell breathable antibacterial EVA foaming material was automatically ejected after the mold was opened.

[0052] Example 3

[0053] (1) Preparation of the polymer matrix: same as in Example 1

[0054] (2) Preparation of GO-SH / / MnO2 / CS / AgNPs: same as in Example 1

[0055] (3) Preparation of the open-cell, breathable and antibacterial EVA foaming material:

[0056] (3-1) 3 parts of the composite antibacterial additive, 2.5 parts of the AC foaming agent, 2.5 parts of the filler, 3 parts of the calcium-zinc stabilizer, 1 part of the lubricant, and 0.2 parts of the release agent were added into the mixer and the molten blend obtained in step (1) was continuously mixed in the mixer at 130°C for 10 min;

[0057] (3-2) After the blend obtained in step (3-1) was pressed into a sheet by the open mill, it was moved into the flat vulcanizing machine for molding and foaming, the temperature of the upper and lower mold plates was set to 150°C, the pressure was 10 MPa, the molding time was 600 s, and the pre-foaming was performed once, then the pre-foamed semi-product was dried in the 60°C air-drying oven for 12 h, and then the temperature of the upper and lower mold plates was adjusted to 175°C, the pressure was 15 MPa, and the molding time was 380 s, and the foaming was performed twice, and the open-cell, breathable and antibacterial EVA foaming material was automatically ejected after the mold was opened.

[0058] Comparative Example 1 (without GO-SH / MnO2 / CS / AgNPs antibacterial agent)

[0059] (1) Preparation of the polymer matrix: same as Example 1

[0060] (2) Preparation of the open-cell, breathable and antibacterial EVA foaming material:

[0061] (2-1) 2.5 parts of the AC foaming agent, 2.5 parts of the filler, 3 parts of the calcium-zinc stabilizer, 1 part of the lubricant, and 0.2 parts of the release agent paraffin were added into the mixer and the molten blend obtained in step (1) was continuously mixed in the mixer at 130°C for 10 min;

[0062] (2-2) After the blend obtained in step (2-1) was pressed into a sheet by the open mill, it was moved into the flat vulcanizing machine for molding and foaming, the temperature of the upper and lower mold plates was set to 150°C, the pressure was 10 MPa, the molding time was 600 s, and the pre-foaming was performed once, then the pre-foamed semi-product was dried in the 60°C air-drying oven for 12 h, and then the temperature of the upper and lower mold plates was adjusted to 175°C, the pressure was 15 MPa, and the molding time was 380 s, and the foaming was performed twice, and the open-cell, breathable and antibacterial EVA foaming material was automatically ejected after the mold was opened.

[0063] Comparative Example 2 (GO-SH / MnO2 and CS / AgNPs were not subjected to any composite treatment and were added into the system separately)

[0064] (1) Preparation of the polymer matrix: same as Example 1

[0065] (2) Preparation of GO-SH / MnO2 and CS / AgNPs: same as Example 1

[0066] (3) Preparation of open-cell, air-permeable and antibacterial EVA foaming material:

[0067] (3-1) 1 part of GO-SH / MnO2 and CS / AgNPs directly and simply mixed at a mass ratio of 1:2, 2.5 parts of AC foaming agent, 2.5 parts of filler, 3 parts of calcium-zinc stabilizer, 1 part of lubricant, and 0.2 part of release agent were added into the mixing mill together with the molten blend obtained in step (1) and continued to be mixed in the mixing mill at 130℃ for 10 min;

[0068] (3-2) The blend obtained in step (3-1) was pressed into a sheet by an open mill and then transferred into a flat vulcanizing machine for mold foaming, the temperature of the upper and lower mold plates was set to 150℃, the pressure was 10 MPa, the mold pressing time was 600 s, and a first pre-foaming was performed. The pre-foamed semi-finished product was placed in a 60℃ air-drying oven for drying for 12 h, and then the temperature of the upper and lower mold plates was adjusted to 175℃, the pressure was 15 MPa, and the mold pressing time was 380 s, and a second foaming was performed. After the mold was opened, the air-permeable and antibacterial EVA foaming material was automatically ejected.

[0069] Comparative Example 3 (GO was compounded with MnO2 and CS / AgNPs according to the above method, but GO was not modified by thiol)

[0070] (1) Preparation of the polymer matrix: same as Example 1

[0071] (2) Preparation of GO / MnO2 / CS / AgNPs:

[0072] (2-1) Preparation of GO and CS / AgNPs: same as Example 1

[0073] (2-2) Preparation of GO / MnO2 / CS / AgNPs: 2.0 grams of GO was ultrasonically dispersed in 100 mL of pure water, 20 mL of potassium permanganate solution (15 mg / L) was added dropwise under stirring, then 12 mL of formamide was added and ultrasonically treated for 30 min. The precipitate was collected by centrifugation and washed with pure water three times, and then dried in an oven for 12 h to obtain GO / MnO2. 1 g of GO / MnO2 was dispersed in 250 ml of deionized water, and then 2 g of nano CS / AgNPs was added to the suspension, and stirred magnetically at room temperature for 5 hours. The mixture was washed with deionized water, and the product was dried in a vacuum oven at 70℃ for 12 h to obtain GO / MnO2 / CS / AgNPs.

[0074] (3) Preparation of open-cell, air-permeable and antibacterial EVA foaming material:

[0075] (3-1) Put 1 part of GO / MnO2 / CS / AgNPs, 2.5 parts of AC foaming agent, 2.5 parts of filler, 3 parts of calcium-zinc stabilizer, 1 part of lubricant, and 0.2 part of release agent into the internal mixer and continue to mix the molten blend obtained in step (1) in the internal mixer at 130°C for 10 min;

[0076] (3-2) After the blend obtained in step (3-1) is pressed into a sheet with an open mill, it is moved into a flat vulcanizing machine for mold foaming, the temperature of the upper and lower mold plates is set to 150°C, the pressure is 10 MPa, the mold pressing time is 600 s, and primary foaming is performed. The pre-foamed semi-finished product is placed in a 60°C air-drying oven for drying for 12 h, and then the temperature of the upper and lower mold plates is adjusted to 175°C, the pressure is 15 MPa, and the mold pressing time is 380 s for secondary foaming. After the mold is opened, the air-permeable antibacterial EVA foaming material automatically pops out.

[0077] Comparative Example 4 (GO-SH is compounded with CS / AgNPs according to the above method, but without adding MnO2)

[0078] (1) Preparation of the polymer matrix: same as in Example 1

[0079] (2) Nanometer CS / AgNPs are compounded with GO-SH:

[0080] (2-1) Preparation of GO-SH: same as in Example 1

[0081] (2-2) Preparation of CS / AgNPs: same as in Example 1

[0082] (2-3) Preparation of GO-SH / CS / AgNPs: 1 g of GO-SH is dispersed in 250 ml of deionized water, and then 2 g of nanometer CS / AgNPs is added to the suspension. The mixture is magnetically stirred at room temperature for 5 hours, and then the mixture is washed with deionized water and centrifuged. The product is vacuum dried at 70°C for 12 h to obtain GO-SH / CS / AgNPs.

[0083] (3) Preparation of the open-cell air-permeable antibacterial EVA foaming material:

[0084] (3-1) Put 1 part of GO-SH / CS / AgNPs, 2.5 parts of AC foaming agent, 2.5 parts of filler, 3 parts of calcium-zinc stabilizer, 1 part of lubricant, and 0.2 part of release agent into the internal mixer and continue to mix the molten blend obtained in step (1) in the internal mixer at 130°C for 10 min;

[0085] (3-2) After the blend obtained in step (3-1) is pressed into a sheet by an open mill, it is moved into a flat vulcanizing machine for molding and foaming, the temperature of the upper and lower mold plates is set to 150°C, the pressure is 10 MPa, the molding time is 600 s, and one-time pre-foaming is performed. The pre-foamed semi-finished product is placed in a 60°C air-drying oven for drying for 12 h, and then the temperature of the upper and lower mold plates is adjusted to 175°C, the pressure is 15 MPa, and the molding time is 380 s for two-time foaming. After the mold is opened, the air-permeable antibacterial EVA foaming material is automatically ejected.

[0086] Comparative Example 5 (without using the crystallization temperature difference method and the two-time foaming method)

[0087] (1) Preparation of the polymer matrix: 90 parts of EVA, 10 parts of POE-g-MAH, 1.5 parts of a crosslinking agent were placed in a preheated mixing mill at 130°C and blended for 10 min, and the rotation speed of the mixing mill was 30 rpm;

[0088] (2) Preparation of GO-SH / / MnO2 / CS / AgNPs: same as Example 1

[0089] (3) Preparation of the open-cell air-permeable antibacterial EVA foaming material:

[0090] (3-1) 1 part of the composite antibacterial aid, 2.5 parts of AC foaming agent, 2.5 parts of filler, 3 parts of calcium-zinc stabilizer, 1 part of lubricant, and 0.2 parts of release agent were added into the mixing mill together with the molten blend obtained in step (1) and continued to be mixed in the mixing mill at 130°C for 10 min;

[0091] (3-2) After the blend obtained in step (3-1) is pressed into a sheet by an open mill, it is moved into a flat vulcanizing machine for molding and foaming, the temperature of the upper and lower mold plates is set to 150°C, the pressure is 10 MPa, the molding time is 600 s, and one-time pre-foaming is performed. The pre-foamed semi-finished product is placed in a 60°C air-drying oven for drying for 12 h, and then the temperature of the upper and lower mold plates is adjusted to 175°C, the pressure is 15 MPa, and the molding time is 380 s for two-time foaming. After the mold is opened, the air-permeable antibacterial EVA foaming material is automatically ejected.

[0092] The samples obtained in the examples and comparative examples were tested for performance.

[0093] Table 1: Performance test

[0094]

[0095] Table 2: Luminescence value test of samples

[0096]

[0097] Table 3: Bacteriostatic rate test of samples

[0098]

[0099] The anti-bacterial performance test method and its steps are as follows: self-made fluorescent E. coli is used to verify the experiment for 5 min, 30 min and 60 min at different positions of the sample, the test method is as follows: 500 μL of luminescent bacteria liquid is added at different positions of the sample, 200 μL of test luminescent average value is taken after a specified time, and a schematic diagram is as shown in Figure 4 . (The range of luminescent bacteria is 3.0 x 10 6 6.0 x 10 6 The luminescent value is tested and the bacteriostatic rate is calculated, and the results are shown in Tables 2 and 3 (with Comparative Example 1 as a control group).

[0100] From the test results in Table 1, in Example 1 and Comparative Example 5, after the EVA foam is not made into an open-cell structure, the mechanical properties of the product show a slight upward trend, which is because the closed-cell structure makes the foam cell walls connected to each other, which can improve the mechanical properties of the foam, but the open-cell rate shows a significant downward trend, indicating that after the material is made into an open-cell structure, the open-cell rate is significantly improved, which strengthens the air flow rate of the product and improves the air permeability. In Examples 1-3, with the increase of the content of the composite antibacterial additive, the tensile strength, cell density, hardness and elongation at break of the product all show an upward trend, and the resilience is slightly reduced, and most of the mechanical properties are better than those of Comparative Example 1 without the addition of the composite antibacterial additive. However, the hardness of the material is slightly reduced due to the addition of the antibacterial additive filler, which slightly reduces the resilience and compression deformation of the material. Compared with Comparative Example 1, the open-cell rate is slightly reduced due to the addition of the GO-SH / MnO2 / CS / AgNPs composite antibacterial additive, indicating that the GO-SH / MnO2 / CS / AgNPs composite antibacterial additive has a good modification effect on the mechanical properties of the foaming material, and has little effect on the resilience, open-cell rate and compression deformation of the foaming material. Moreover, the composite antibacterial additive has good compatibility with the resin matrix. From the data of Comparative Example 2, compared with Example 1, the mechanical properties and foaming properties (open-cell rate) of Comparative Example 2 are greatly reduced, and most of the mechanical properties of Comparative Example 2 are not increased but decreased compared with Comparative Example 1 without the addition of the modifier. This is because nano-CS / AgNPs and graphene oxide have high surface energy, and the particle agglomeration is obvious without any surface treatment, and the surface energy is greatly reduced after the composite material is constructed, which is more conducive to the dispersion of the antibacterial additive in the resin matrix, so the modification effect of the composite antibacterial additive is better. In Comparative Example 3, the graphene oxide is not modified by thiol groups, and the degree of compounding of CS / AgNPs nanoparticles and graphene oxide matrix is reduced. Due to the influence of the surface energy in the material, the dispersion degree of the composite additive in the matrix is not as good as that of Example 1, and the mechanical properties and foaming properties (open-cell rate) of the obtained product are greatly reduced compared with Example 1. The mechanical properties and foaming properties of Comparative Example 4 are not significantly different from those of Example 1.

[0101] From the test results in Table 2 and Table 3, compared with Comparative Example 1 without adding any antibacterial agent, from Example 1 to Example 3, the antibacterial ability of the sample at 5 min, 10 min, 60 min is greatly increased with the increase of the content of the composite antibacterial agent, which shows that the GO-SH / MnO2 / CS / AgNPs has good antibacterial effect and good compatibility with the matrix. From the data of Comparative Example 2, GO-SH / MnO2 and CS / AgNPs are not compounded and added to the matrix, and each reacts and plays a role in the mixing process, and the multi-hydroxy polymer graphene oxide and CS / AgNPs with high surface energy are easy to agglomerate in the melting process, so the antibacterial effect is far less than that of the GO-SH / MnO2 / CS / AgNPs added to the matrix after compounding; and Comparative Example 3 only compounds graphene oxide and MnO2, CS / AgNPs, due to the lack of interaction between thiol groups and CS / AgNPs nanoparticles, there is still a part of self-aggregation, and the antibacterial agent is less stable in structure than GO-SH / MnO2 / CS / AgNPs containing thiol groups, so the antibacterial effect is less than that of GO-SH / MnO2 / CS / AgNPs, which shows that the thiol functionalization of GO in the composite antibacterial agent can maximize the antibacterial effect. Comparative Example 4 uses GO-SH and CS / AgNPs to construct a composite material but does not add MnO2, which lacks MnO2 as a catalyst to decompose the H2O2 environment conducive to bacterial growth, so the material is less effective than GO-SH / MnO2 / CS / AgNPs in inhibiting bacterial growth and destroying the bacterial growth environment, and the antibacterial performance is significantly lower than that of Example 1.

[0102] Figure 1 The Fourier infrared spectrum of the powder of GO-SH / MnO2 / CS / AgNPs composite antibacterial agent, wherein the peaks at 3460 cm -1 -1 of CS / AgNPs and GO-SH, the absorption peak at 2920 cm -1 is the stretching vibration peak of alkyl, the absorption peak at 2540 cm -1 is the vibration peak of -SH, the characteristic peak at 1632 cm -1 corresponds to the stretching vibration of C=C bond of carbon skeleton, which may also belong to the bending vibration absorption peak of C-OH, the bands observed at 1390 cm -1 and 1352 cm -1 are caused by the shear vibration of -NH2 group and the stretching vibration of polymer glucoside bond, the absorption peak at 1141 cm -1 is the anti-symmetric vibration of C-O-C, and the characteristic peak of MnO2 at 506 cm -1 represents the symmetric stretching vibration of Mn-O bond.

[0103] Figure 2For the SEM image of the composite material, it can be seen that the GO matrix after thiol modification uniformly disperses the nano CS / AgNPs, which can prove that the introduction of thiol groups in the GO matrix plays an important role in preventing the agglomeration of nanoparticles.

[0104] Figure 3 For the SEM image of the open cell foam, it can be seen that the foam structure is mostly open structure. First, when the low Tc polymer (LDPE) soft section forms smaller dispersed phase, and the high Tc polymer (EVA) hard section forms the main melt matrix, the foam opening can be started and propagated through the well-dispersed low Tc polymer domain, and these domains are surrounded between the adjacent growing cells. These soft domains can be elongated as the cell grows, that is, the cell wall thins to break to form an open structure.

[0105] The above only describes the preferred embodiments of the present application, and any changes and modifications made within the scope of the patent application of the present application shall be within the scope of the present application.

Claims

1. A breathable, antibacterial EVA foamed material, characterized by: The raw materials of the EVA foaming material include: 70 parts of EVA, 20 parts of LDPE, 10 parts of POE-g-MAH, 1-3 parts of composite antibacterial additive, 2.5 parts of AC foaming agent, 1.5 parts of crosslinking agent, 2.5 parts of filler, 3 parts of calcium zinc stabilizer, 1 part of lubricant, and 0.2 parts of release agent. The composite antibacterial additive is GO-SH / MnO2 / CS / AgNPs, and the preparation steps thereof include: (1) Preparation of GO-SH: first, 5g of 4-aminothiophenol and 80mL of 1M HCl solution are added to a three-necked flask, and the reaction temperature is raised to 50℃ under stirring until the 4-aminothiophenol is completely dissolved; then, 1.5mol / L NaNO2 solution is added dropwise to the reaction mixture under ice bath conditions until the gas bubbles completely disappear; after that, 5g of graphene oxide GO is added in the form of a deionized water dispersion, and stirring is carried out under ice bath for 12h, followed by washing with acetone, ethanol and deionized water; finally, vacuum drying is carried out at 50℃ for 24h to obtain GO-SH; (2) Preparation of CS / AgNPs: 2g of chitosan CS is dissolved in 200mL of 0.1wt% acetic acid aqueous solution, and placed in an oil bath for stirring, while 10mL of freshly prepared 5mg / mL AgNO3 solution is added dropwise during stirring; after heating to 95℃ under stirring, 0.1g / mL NaOH solution is added dropwise until the solution turns yellow, and then the reaction is terminated after stirring at 95℃ for 20min; the product is washed with deionized water three times, and then vacuum dried at 60℃ for 1h to obtain CS / AgNPs; (3) Preparation of GO-SH / MnO2 / CS / AgNPs: 2g of GO-SH is ultrasonically dispersed in 100mL of pure water, and 20mL of 15mg / L potassium permanganate solution is added dropwise under stirring, followed by the addition of 12mL of formamide and ultrasonic treatment for 30min; the precipitate is collected by centrifugation, washed with pure water three times, and oven dried for 12h to obtain GO-SH / MnO2; then, GO-SH / MnO2 is dispersed in deionized water, and CS / AgNPs is added; magnetic stirring is carried out at room temperature for 5h, followed by washing with deionized water three times; after centrifugation, the product is vacuum dried at 70℃ for 12h to obtain GO-SH / MnO2 / CS / AgNPs.

2. The breathable, antibacterial EVA foamed material according to claim 1, characterized in that: The mass ratio of GO-SH / MnO2 and CS / AgNPs in step (3) is 1:

2.

3. The breathable, antibacterial EVA foamed material according to claim 1, characterized in that: The filler is one or more of nano-zinc oxide and zinc stearate.

4. The breathable, antibacterial EVA foamed material according to claim 1, characterized in that: The crosslinking agent is dicumyl peroxide.

5. The breathable, antibacterial EVA foamed material according to claim 1, characterized in that: The lubricant is one or more of stearic acid, butyl stearate and oleamide.

6. The breathable, antibacterial EVA foamed material according to claim 1, characterized in that: The POE-g-MAH preparation comprises: weighing 0.4 parts by weight of maleic anhydride, dissolving the maleic anhydride in acetone to prepare a solution; weighing 4 parts by weight of polyolefin elastomer POE particles, spraying the maleic anhydride acetone solution into the POE particles, and uniformly mixing in a high-speed mixer, and standing to volatilize the acetone; the mixture is melt blended for 10 min using a torque rheometer, the rotor speed is 30 r / min, the torque temperature is 165℃, and after the blending is completed, the melt is opened into a sheet on an open mill.

7. Process for the production of a breathable, antibacterial EVA foamed material according to any one of claims 1-6, characterized in that: The EVA foaming material is of an open-cell structure, and the preparation steps comprise: melt blending EVA and LDPE, two materials with a large difference in crystallization temperature, and using a secondary foaming method as a mold foaming method to prepare the EVA foaming material into an open-cell pore structure.

8. The process for the preparation of a breathable, antibacterial EVA foamed material according to claim 7, characterized by the fact that: 70 parts of EVA, 20 parts of LDPE, 10 parts of POE-g-MAH, 1-3 parts of a composite antibacterial aid, 2.5 parts of an AC foaming agent, 1.5 parts of a crosslinking agent, 2.5 parts of a filler, 3 parts of a calcium-zinc stabilizer, 1 part of a lubricant, and 0.2 parts of a release agent are put into a banbury mixer for blending, and then the blended product is cold and hot mold pressed.

9. The process for the preparation of a breathable, antibacterial EVA foamed material according to claim 8, characterized in that: The method comprises the following steps: 1) EVA, LDPE, POE-g-MAH, and a crosslinking agent are put into a preheated banbury mixer at 130℃ for 10 min to obtain a blend 1, and the banbury mixer speed is 30 rpm; 2) a composite antibacterial aid, an AC foaming agent, a filler, a calcium-zinc stabilizer, a lubricant, and a release agent are added to the blend 1, and the mixture is continuously mixed in the banbury mixer at 130℃ for 10 min to obtain a blend 2; 3) the blend 2 is pressed into a sheet by an open mill and then moved into a flat vulcanizing machine for mold foaming, the upper and lower mold plate temperatures are both set to 150℃, the pressure is 10 MPa, the mold pressing time is 600 s, and a first pre-foaming is performed; the pre-foamed semi-finished product is dried in a 60℃ air-drying oven for 12 h, then the upper and lower mold plate temperatures are both adjusted to 175℃, the pressure is 15 MPa, the mold pressing time is 380 s, and a second foaming is performed; after the mold is opened, the air-permeable and antibacterial EVA foaming material is automatically ejected.

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