Breathable and antistatic EVA foam material and preparation method thereof

Abstract

The invention discloses a breathable and antistatic EVA foam material and a preparation method thereof. Poly (3-hexylthiophene) (P3HT) is used as a conductive filler, CNTs-NH2 is added to make up for the problem of low conductivity of P3HT at room temperature, and a hybrid conductive network formed by interpenetrating the added CNTs-NH2 in P3HT can endow the material with better antistatic performance. Meanwhile, due to the fact that the surfaces of carbon nanotubes (CNTs) are modified and have rich-NH2 groups, the CNTs can be well compatible with a polymer matrix EVA / POE-g-MAH, the dispersity of P3HT / CNTs-NH2 conductive filler in the polymer matrix is improved, the antistatic performance of the foam material is greatly improved, the defect that antistatic components are prone to agglomeration is overcome, and the antistatic performance of the foam material is improved. The mechanical properties such as tensile strength, elongation at break and impact strength of the degradable antistatic foaming material are greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of materials, and in particular relates to a breathable and antistatic EVA foam material and a preparation method thereof. Background Art

[0002] EVA is characterized by good softness, rubber-like elasticity, good flexibility at -50°C, transparency and surface gloss, good chemical stability, good anti-aging and ozone resistance, and non-toxicity. It has good miscibility with fillers, colorability and molding processability. EVA is widely used in foamed shoe materials, films, packaging films, hot melt adhesives, wires and cables, toys and other fields. In the EVA resin used in shoe materials, the vinyl acetate content is generally 15% to 22%. Because EVA resin blended foam products have the properties of softness, good elasticity, and chemical corrosion resistance, they are widely used in the soles and interior materials of mid-to-high-end tourist shoes, hiking shoes, slippers, and sandals. In addition, this material is also used in the fields of sound insulation boards, gymnastics mats and sealing materials.

[0003] Plastic is an organic macromolecular material formed by covalent bonding, which has good insulation and water resistance. However, due to the high insulation of plastic, it brings static electricity hazards to industrial production and people's daily life. Plastic has a very high resistivity, and its volume resistance value can reach 1×10 12 Ω or more, so the surface is easily charged due to friction or other reasons and accumulates static charge. This static charge is not easy to eliminate. As the static voltage and static capacity accumulate and increase, the charged body discharge phenomenon will occur. It is easy to ignite the flammable and explosive substances in the surrounding environment, causing fires and explosions, causing huge economic losses and safety hazards to people. At the same time, due to the electrostatic adsorption characteristics, plastic products are easy to absorb dust, affecting their transparency, surface cleanliness and aesthetics, and even affecting their performance. Nano conductive modifiers have the advantages of small particle size and large specific surface area, giving nano materials a special surface effect. Nano conductive fillers have high thermal stability and can stably exist in the high temperature environment of plastic processing. They have broad prospects and wide applications in the field of plastic antistatic modification.

[0004] The method to increase the conductivity of polymers is to add fillers with high conductivity, also known as antistatic agents. Its mechanism of action is to reduce the material's obstacles to electrons, improve the material's conductive effect, enable the charge to be transferred on the surface and inside, improve the friction performance of the material surface, and avoid the generation of charge and accumulation. The antistatic properties of polymers are usually improved by adding antistatic agents. At present, there are two main ways to add antistatic agents. The first is to add the antistatic agent to the inside of the polymer, and the second is to apply the antistatic agent to the surface of the polymer. The first method can play an antistatic role for a longer time, and the second method is easy to disappear under the action of external force. To meet the antistatic properties of polymer materials, antistatic agents are generally added to the matrix material, and the main preparation methods are solution blending, melt blending, etc. Solution blending is to dissolve the plastic in an organic solvent, then add the powder filler to the organic solvent and stir evenly, and finally pour it on the mold for drying to obtain an antistatic composite material; melt blending is to blend the filler and the matrix material through an extruder to obtain an antistatic masterbatch, and then use an injection molding machine to obtain an antistatic composite material. However, the prior art generally has the problem that the antistatic agent has poor compatibility with the biodegradable base material, thereby failing to take into account both the mechanical properties and the antistatic properties of the antistatic foaming material.

[0005] Based on this, the present invention provides a breathable and antistatic EVA foam material and a preparation method thereof. Summary of the invention

[0006] The present invention selects poly (3-hexylthiophene) (P3HT) and amino carbon nanotubes (CNTs-NH2) as antistatic additives. Poly (3-hexylthiophene) (P3HT) is a conductive polymer. The polymer main chain of the conductive polymer has a conjugated large π bond. The energy of the π electrons on the large π bond is higher than that of the σ electrons on the molecular skeleton, the polarizability is stronger, and the fluidity range is large. Compared with general polymers, conductive polymers have more obvious advantages in electricity, light, magnetism and other aspects. In addition to these characteristics, conductive polymers also have application advantages such as a wide conductivity range, convenient preparation, good mechanical processing type, light weight, low price, etc. In order to improve the conductivity, carbon nanotubes (CNTs) are introduced into the P3HT matrix to construct a hybrid conductive network, and the carbon nanotubes (CNTs) are amino treated to increase the compatibility with the matrix material to improve the mechanical properties, foaming material, and antistatic properties of the foaming material.

[0007] The purpose of the present invention is to provide a carbon nanotube and P3HT antistatic composite auxiliary agent, a foaming material and a preparation method thereof, so as to solve the problem that the mechanical properties and antistatic properties of the antistatic foaming material prepared by the existing melt blending method are not well compatible.

[0008] To achieve the above object, the present invention adopts the following technical solution:

[0009] A breathable and antistatic EVA foam material comprises the following raw materials 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), 3-9 parts of composite antistatic additive, 2.5 parts of AC foaming agent, 1.5 parts of cross-linking agent, 2.5 parts of filler, 3 parts of calcium zinc stabilizer, 1 part of lubricant and 0.2 parts of release agent.

[0010] The composite antistatic additive is a P3HT / CNTs-NH2 composite, and the preparation steps include:

[0011] (1) The preparation process of P3HT is as follows: Under N2 protection, 2.27 g of anhydrous ferric chloride oxidant is added to a 250 mL flask containing 100 mL of chloroform. After stirring with a magnetic stirrer for 0.5 h, the solution turns dark green and the ferric chloride is partially dissolved. 50 mL of chloroform solution containing 0.8782 g of 3-dodecylthiophene monomer is added dropwise to the above reaction solution using a micro-syringe pump. As the polymerization reaction proceeds, the color of the solution becomes darker and HCl gas is generated; after the reaction stops, the reaction mixture is slowly poured into excess methanol for precipitation to obtain a polymer product; the product is washed with methanol several times until the filtrate is colorless to remove the residual ferric chloride; the collected product is added to a mixed solvent of 100 mL of chloroform and 100 mL of saturated hydrazine hydrate (85 wt%), stirred overnight, and the chloroform layer product is taken out using a pear-shaped separatory funnel, and then poured into excess methanol for precipitation to obtain an intrinsic polymer; the obtained polymer is placed in a Soxhlet extractor and repeatedly extracted with methanol at 65°C for 24 hours to remove impurities. The collected polymer is placed in a vacuum drying oven for drying for 12 hours to obtain poly (3-hexylthiophene) P3HT.

[0012] (2) The preparation process of CNTs-NH2 is as follows: 2g of carbon nanotubes are dissolved in a mixture of 35mL of concentrated nitric acid (70wt%) and 15mL of concentrated sulfuric acid (70wt%) for acidification, then diluted with deionized water, and the solution is removed to obtain CNTs-COOH; the obtained CNTs-COOH and 1g of condensing agent dicyclohexylcarbodiimide (DCC) are placed in a three-necked flask, and then 50mL of ethylenediamine is added and ultrasonicated for 30min. Mix well, stir and react at 120℃ for 24h. After the reaction is completed, the excess amine, DCC and by-products after the DCC reaction are ultrasonically washed with anhydrous ethanol, and the obtained product is vacuum dried at 60℃ for 24h to obtain amino carbon nanotubes CNTs-NH2.

[0013] (3) CNTs-NH2 was added to anhydrous ethanol and ultrasonicated for 20 min to be dispersed in ethanol. P3HT was then added to the suspension and stirred at 80 °C and 1500 r / min for 5 h. The obtained product was washed and vacuum dried at 60 °C for 12 h to obtain a P3HT / CNTs-NH2 composite.

[0014] Furthermore, the filler is: one or more combinations of nano zinc oxide and zinc stearate; the crosslinking agent is: dicumyl peroxide (DCP); the lubricant is: one or more combinations of stearic acid, butyl stearate, and oleamide;

[0015] Furthermore, the preparation of POE-g-MAH includes: 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 acetone solution of maleic anhydride into the POE particles, and mixing them evenly in a high-speed mixer, and standing to volatilize the acetone; the mixed material is melt-blended for 10 minutes using a torque rheometer, the rotor speed is 30r / min, the torque temperature is 165°C, and after the blending is completed, the melt is melted into sheets in an open mill.

[0016] The EVA foam material is an open-cell structure, and the preparation steps include: melt-blending EVA and LDPE, two materials with a large difference in crystallization temperature, wherein the melt structure contains two blended polymers with different crystallization temperature values, and the high crystallization temperature polymer will crystallize before the low crystallization temperature polymer, thereby generating pressure on the pore structure to cause the pores to rupture and connect to generate an open-cell structure, and at the same time, using a secondary foaming method as a compression foaming method to prepare the EVA foam material into an open-cell pore structure.

[0017] Furthermore, the preparation method of the breathable and antistatic EVA foam material is as follows: 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), 3-9 parts of composite antistatic additive, 2.5 parts of AC foaming agent, 1.5 parts of cross-linking 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 an internal mixer for blending, and then the blended product is subjected to cold and hot compression molding; specifically comprising the following steps:

[0018] (1) EVA, POE-g-MAN, LDPE and crosslinking agent were placed in a preheated internal mixer at 130°C and blended for 10 min at a speed of 30 rpm;

[0019] (2) adding a composite antistatic additive, an AC foaming agent, a filler, a calcium zinc stabilizer, a lubricant, and a release agent to the blend obtained in step (1), and continuing to mix in an internal mixer at 130° C. for 10 min;

[0020] (3) The blend obtained in step (2) is pressed into a thin sheet by an open mill and then transferred into a flat vulcanizer for compression foaming. The upper and lower template temperatures are both set to 150° C., the pressure is 10 MPa, and the compression time is 600 s. Pre-foaming is performed once. The pre-foamed semi-finished product is placed in a 60° C. forced air drying oven and dried for 12 h. Then, the upper and lower template temperatures are both adjusted to 175° C., the pressure is 20 MPa, and the compression time is 380 s. Secondary foaming is performed. After the mold is opened, the EVA foam material automatically pops out.

[0021] Preferably, the filler is nano zinc oxide; the lubricant is stearic acid; and the release agent is paraffin.

[0022] The beneficial effects of the present invention are:

[0023] The present invention uses the crystallization temperature difference method to melt blend EVA (crystallization temperature 10°C) and LDPE (crystallization temperature 90°C), two materials with a large difference in crystallization temperature. The two semi-crystalline polymers with different crystallization temperatures are melt blended to maximize the stiffness contrast between the hard and soft regions in the polymer matrix. Since the cell opening process occurs after the foam extrudate leaves the die, the foam structure is naturally cooled by the surrounding air. If the melt structure has two materials with different T c The value of the polymer blend is high T c The polymer will precede the low T c The polymer crystallizes. This means that at two T c Value between, soft section (ie low T c polymer) is almost like a liquid, while the hard section (i.e. high T c The polymer is almost solid-like, resulting in a large stiffness contrast. If the cell opening process occurs at a temperature between two T c When the value is between 0.01 and 0.17, the chance of cell opening will be greatly increased due to the large difference in stiffness. There are two blended polymers with different crystallization temperature values ​​in the melt structure. The high crystallization temperature polymer will crystallize before the low crystallization temperature polymer, thereby exerting pressure on the cell structure to cause the cells to break and connect to form an open-cell structure. At the same time, the secondary foaming method is used as the compression foaming method to make the EVA foam material into an open-cell cell structure. Since the open-cell cell structure is interconnected, the air circulation efficiency is improved and its air permeability is enhanced.

[0024] The invention adopts P3HT / CNTs-NH2 as the composite antistatic filler to prepare the EVA foam material, and the formula is scientific and reasonable, and the process flow is simple and practical. The addition of the organic conductive polymer P3HT can effectively improve the antistatic performance of the EVA foam material, and the addition of the amino carbon nanotubes can connect the P3HT to each other to form a more effective hybrid conductive network inside the filler. At the same time, since the surface of the carbon nanotubes (CNTs) has been modified and has rich -NH2 groups, it can be well compatible with the polymer matrix, improve the dispersibility of the P3HT / CNTs-NH2 antistatic composite additive in the polymer matrix, thereby greatly improving the antistatic performance of the foam material. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the Fourier infrared image of the composite wear-resistant and antistatic filler prepared by the present invention.

[0026] Figure 2 This is a scanning electron microscope image of the composite wear-resistant and antistatic filler prepared by the present invention.

[0027] Figure 3 This is a cell diagram of the EVA foam material prepared in the present invention. DETAILED DESCRIPTION

[0028] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0029] The raw material parts used in the following examples and comparative examples are parts by weight; the crystallization temperatures of the EVA and LDPE used are 10° C. and 90° C., respectively.

[0030] Example 1

[0031] (1) Preparation of polymer matrix: 70 parts of EVA, 20 parts of LDPE, 10 parts of POE-g-MAH, and 1.5 parts of cross-linking agent were placed in an internal mixer preheated at 130°C and blended for 10 min at a speed of 30 rpm;

[0032] (2) Preparation steps of composite antistatic filler P3HT / CNTs-NH2:

[0033] (2-1) The preparation process of P3HT is as follows: Under N2 protection, 2.27 g of anhydrous ferric chloride oxidant is added to a 250 mL flask containing 100 mL of chloroform. After stirring with a magnetic stirrer for 0.5 h, the solution turns dark green and the ferric chloride is partially dissolved. A micro-syringe pump is used to dropwise add 50 mL of chloroform solution containing 0.8782 g of 3-dodecylthiophene monomer into the above reaction solution. As the polymerization reaction proceeds, the color of the solution becomes darker and HCl gas is generated; after the reaction stops, the reaction mixture is slowly poured into excess methanol for precipitation to obtain a polymer product; the product is washed with methanol several times until the filtrate is colorless to remove the residual ferric chloride; the collected product is added to a mixed solvent of 100 mL of chloroform and 100 mL of saturated hydrazine hydrate (85%), stirred overnight, and the chloroform layer product is taken using a pear-shaped separatory funnel, and then poured into excess methanol for precipitation to obtain an intrinsic polymer; the obtained polymer is placed in a Soxhlet extractor and repeatedly extracted with methanol at 65°C for 24 hours to remove impurities. The collected polymer is placed in a vacuum drying oven for drying for 12 hours to obtain poly (3-hexylthiophene) P3HT.

[0034] (2-2) The preparation process of CNTs-NH2 is as follows: 2g of carbon nanotubes are dissolved in a mixture of 35mL of concentrated nitric acid (70wt%) and 15mL of concentrated sulfuric acid (70wt%) for acidification, and then diluted with deionized water, and the solution is removed to obtain CNTs-COOH. The obtained CNTs-COOH and 1g of condensation agent dicyclohexylcarbodiimide (DCC) are placed in a three-necked flask, and then 50mL of ethylenediamine is added and ultrasonically treated for 30min to mix evenly. The mixture is stirred at 120°C for 24h to react. After the reaction is completed, the excess amine, DCC and by-products of the DCC reaction are ultrasonically washed away with anhydrous ethanol. The obtained product is vacuum dried at 60°C for 24h to obtain amino carbon nanotubes CNTs-NH2.

[0035] (2-3) 2 g of CNTs-NH2 was added to anhydrous ethanol and ultrasonicated for 20 min to disperse in anhydrous ethanol. Then 1 g of P3HT was added to the suspension and stirred at 80 °C and 1500 r / min for 5 h. The obtained product was washed and vacuum dried at 60 °C for 12 h to obtain a P3HT / CNTs-NH2 composite.

[0036] (3) Preparation of composite antistatic EVA foam material:

[0037] (3-1) adding 3 parts of composite antistatic filler, 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 into an internal mixer and mixing together with the melt blend obtained in step (1) in an internal mixer at 130° C. for 10 minutes;

[0038] (3-2) The blend obtained in step (3-1) is pressed into a thin sheet by an open mill and then transferred into a flat vulcanizer for compression foaming. The upper and lower template temperatures are both set to 150°C, the pressure is 10 MPa, and the molding time is 600 s. Pre-foaming is performed once. The pre-foamed semi-finished product is placed in a 60°C forced air drying oven and dried for 12 h. Then, the upper and lower template temperatures are adjusted to 175°C, the pressure is 15 MPa, and the molding time is 380 s. Secondary foaming is performed. After the mold is opened, the EVA foam material automatically pops out.

[0039] Example 2

[0040] (1) Preparation of polymer matrix: same as in Example 1

[0041] (2) Preparation steps of composite antistatic filler P3HT / CNTs-NH2: same as Example 1

[0042] (3) Preparation of composite antistatic EVA foam material:

[0043] (3-1) adding 6 parts of composite antistatic filler, 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 into an internal mixer and mixing together with the melt blend obtained in step (1) in an internal mixer at 130° C. for 10 minutes;

[0044] (3-2) The blend obtained in step (3-1) is pressed into a thin sheet by an open mill and then transferred into a flat vulcanizer for compression foaming. The upper and lower template temperatures are both set to 150°C, the pressure is 10 MPa, and the molding time is 600 s. Pre-foaming is performed once. The pre-foamed semi-finished product is placed in a 60°C forced air drying oven and dried for 12 h. Then, the upper and lower template temperatures are adjusted to 175°C, the pressure is 15 MPa, and the molding time is 380 s. Secondary foaming is performed. After the mold is opened, the EVA foam material automatically pops out.

[0045] Example 3

[0046] (1) Preparation of polymer matrix: same as in Example 1

[0047] (2) Preparation steps of composite antistatic filler P3HT / CNTs-NH2: same as Example 1

[0048] (3) Preparation of composite antistatic EVA foam material:

[0049] (3-1) adding 9 parts of composite antistatic filler, 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 into an internal mixer and mixing together with the melt blend obtained in step (1) in an internal mixer at 130° C. for 10 minutes;

[0050] (3-2) The blend obtained in step (3-1) is pressed into a thin sheet by an open mill and then transferred into a flat vulcanizer for compression foaming. The upper and lower template temperatures are both set to 150°C, the pressure is 10 MPa, and the molding time is 600 s. Pre-foaming is performed once. The pre-foamed semi-finished product is placed in a 60°C forced air drying oven and dried for 12 h. Then, the upper and lower template temperatures are adjusted to 175°C, the pressure is 15 MPa, and the molding time is 380 s. Secondary foaming is performed. After the mold is opened, the EVA foam material automatically pops out.

[0051] Comparative Example 1 (without P3HT / CNTs-NH2 composite conductive filler)

[0052] (1) Preparation of polymer matrix: same as in Example 1

[0053] (2) Preparation of composite antistatic EVA foam material:

[0054] (2-1) adding 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 into an internal mixer and mixing together with the melt blend obtained in step (1) in an internal mixer at 130° C. for 10 minutes;

[0055] (2-2) The blend obtained in step (2-1) is pressed into a thin sheet by an open mill and then transferred into a flat vulcanizer for compression foaming. The upper and lower template temperatures are both set to 150°C, the pressure is 10 MPa, and the compression time is 600 s. Pre-foaming is performed once. The pre-foamed semi-finished product is placed in a 60°C forced air drying oven and dried for 12 h. Then, the upper and lower template temperatures are adjusted to 175°C, the pressure is 15 MPa, and the compression time is 380 s. Secondary foaming is performed. After the mold is opened, the EVA foam material automatically pops out.

[0056] Comparative Example 2 (addition of P3HT / CNTs without amination treatment)

[0057] (1) Preparation of polymer matrix: same as in Example 1

[0058] (2) Preparation steps of composite antistatic filler P3HT / CNTs:

[0059] (2-1) The preparation process of P3HT is as follows: Under N2 protection, 2.27 g of anhydrous ferric chloride oxidant is added to a 250 mL flask containing 100 mL of chloroform. After stirring with a magnetic stirrer for 0.5 h, the solution turns dark green and the ferric chloride is partially dissolved. A micro-syringe pump is used to dropwise add 50 mL of chloroform solution containing 0.8782 g of 3-dodecylthiophene monomer into the above reaction solution. As the polymerization reaction proceeds, the color of the solution becomes darker and HCl gas is generated; after the reaction stops, the reaction mixture is slowly poured into excess methanol for precipitation to obtain a polymer product; the product is washed with methanol several times until the filtrate is colorless to remove the residual ferric chloride; the collected product is added to a mixed solvent of 100 mL of chloroform and 100 mL of saturated hydrazine hydrate (85%), stirred overnight, and the chloroform layer product is taken using a pear-shaped separatory funnel, and then poured into excess methanol for precipitation to obtain an intrinsic polymer; the obtained polymer is placed in a Soxhlet extractor and repeatedly extracted with methanol at 65°C for 24 hours to remove impurities. The collected polymer is placed in a vacuum drying oven for drying for 12 hours to obtain poly (3-hexylthiophene) P3HT.

[0060] (2-2) 2 g of CNTs were added to anhydrous ethanol and ultrasonicated for 20 min to disperse in the anhydrous ethanol. Then, 1 g of P3HT was added to the suspension and stirred at 80 °C and 1500 r / min for 5 h. The obtained product was washed and vacuum dried at 60 °C for 12 h to obtain a P3HT / CNTs composite.

[0061] (3) Preparation of composite antistatic EVA foam material:

[0062] (3-1) adding 3 parts of P3HT / CNTs, 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 into an internal mixer and mixing together with the melt blend obtained in step (1) in an internal mixer at 130° C. for 10 minutes;

[0063] (3-2) The blend obtained in step (3-1) is pressed into a thin sheet by an open mill and then transferred into a flat vulcanizer for compression foaming. The upper and lower template temperatures are both set to 150°C, the pressure is 10 MPa, and the molding time is 600 s. Pre-foaming is performed once. The pre-foamed semi-finished product is placed in a 60°C forced air drying oven and dried for 12 h. Then, the upper and lower template temperatures are adjusted to 175°C, the pressure is 15 MPa, and the molding time is 380 s. Secondary foaming is performed. After the mold is opened, the EVA foam material automatically pops out.

[0064] Comparative Example 3 (adding only P3HT, without adding CNTs-NH2)

[0065] (1) Preparation of polymer matrix: same as in Example 1

[0066] (2) The preparation process of P3HT is as follows: Under N2 protection, 2.27 g of anhydrous ferric chloride oxidant is added to a 250 mL flask containing 100 mL of chloroform. After stirring with a magnetic stirrer for 0.5 h, the solution turns dark green and the ferric chloride is partially dissolved. 50 mL of chloroform solution containing 0.8782 g of 3-dodecylthiophene monomer is added dropwise to the above reaction solution using a micro-injection pump. As the polymerization reaction proceeds, the color of the solution becomes darker and HCl gas is generated; after the reaction stops, the reaction mixture is slowly poured into excess methanol for precipitation to obtain a polymer product; the product is washed with methanol several times until the filtrate is colorless to remove the residual ferric chloride; the collected product is added to a mixed solvent of 100 mL of chloroform and 100 mL of saturated hydrazine hydrate (85%), stirred overnight, and the chloroform layer product is taken using a pear-shaped separatory funnel, and then poured into excess methanol for precipitation to obtain an intrinsic polymer; the obtained polymer is placed in a Soxhlet extractor and repeatedly extracted with methanol at 65°C for 24 hours to remove impurities. The collected polymer is placed in a vacuum drying oven for drying for 12 hours to obtain poly (3-hexylthiophene) P3HT.

[0067] (3) Preparation of composite antistatic EVA foam material:

[0068] (3-1) adding 3 parts of P3HT, 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 into an internal mixer and mixing together with the melt blend obtained in step (1) in an internal mixer at 130° C. for 10 minutes;

[0069] (3-2) The blend obtained in step (3-1) is pressed into a thin sheet by an open mill and then transferred into a flat vulcanizer for compression foaming. The upper and lower template temperatures are both set to 150°C, the pressure is 10 MPa, and the molding time is 600 s. Pre-foaming is performed once. The pre-foamed semi-finished product is placed in a 60°C forced air drying oven and dried for 12 h. Then, the upper and lower template temperatures are adjusted to 175°C, the pressure is 15 MPa, and the molding time is 380 s. Secondary foaming is performed. After the mold is opened, the EVA foam material automatically pops out.

[0070] Comparative Example 4 (adding only CNTs-NH2, without adding P3HT)

[0071] (1) Preparation of polymer matrix: same as in Example 1

[0072] (2) The preparation process of CNTs-NH2 is as follows: 2g of carbon nanotubes are dissolved in a mixture of 35mL of concentrated nitric acid (70wt%) and 15mL of concentrated sulfuric acid (70wt%) for acidification, then diluted with deionized water, and the solution is removed to obtain the CNTs-COOH, the obtained CNTs-COOH and 1g of condensing agent dicyclohexylcarbodiimide (DCC) are placed in a three-necked flask, and then 50mL of ethylenediamine is added and ultrasonicated for 30min. Mix well, stir and react at 120℃ for 24h, after the reaction is completed, use anhydrous ethanol to ultrasonically wash away excess amine, DCC and by-products after the DCC reaction, and the obtained product is vacuum dried at 60℃ for 24h to obtain amino carbon nanotubes CNTs-NH2.

[0073] (3) Preparation of composite antistatic EVA foam material:

[0074] (3-1) adding 3 parts of CNTs-NH2, 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 into an internal mixer and mixing together with the melt blend obtained in step (1) in an internal mixer at 130° C. for 10 minutes;

[0075] (3-2) The blend obtained in step (3-1) is pressed into a thin sheet by an open mill and then transferred into a flat vulcanizer for compression foaming. The upper and lower template temperatures are both set to 150°C, the pressure is 10 MPa, and the molding time is 600 s. Pre-foaming is performed once. The pre-foamed semi-finished product is placed in a 60°C forced air drying oven and dried for 12 h. Then, the upper and lower template temperatures are adjusted to 175°C, the pressure is 15 MPa, and the molding time is 380 s. Secondary foaming is performed. After the mold is opened, the EVA foam material automatically pops out.

[0076] Comparative Example 5 (not using the crystallization temperature difference method and the secondary foaming method)

[0077] (1) Preparation of polymer matrix: 90 parts of EVA, 10 parts of POE-g-MAH, and 1.5 parts of cross-linking agent were placed in an internal mixer preheated at 130°C and blended for 10 min at a speed of 30 rpm;

[0078] (2) Preparation of P3HT / CNTs-NH2: Same as Example 1

[0079] (3) Preparation of open-cell breathable antistatic EVA foam material:

[0080] (3-1) adding 3 parts of antistatic additive, 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 into an internal mixer and mixing together with the melt blend obtained in step (1) in an internal mixer at 130° C. for 10 minutes;

[0081] (3-2) The blend obtained in step (3-1) is pressed into a thin sheet using an open mill and then transferred into a flat-plate vulcanizer for compression foaming. The upper and lower mold plate temperatures are both 175° C., the pressure is 15 MPa, and the compression time is 380 s. The EVA foam material is automatically ejected after the mold is opened.

[0082] The samples obtained in the embodiments and comparative examples were subjected to performance tests.

[0083] Table 1: Performance Test

[0084]

[0085]

[0086] From the test results in Table 1, in Examples 1-3, as the content of the antistatic agent increases, the tensile strength, elongation at break, and hardness of the product show different degrees of upward trends, and the surface resistivity shows a downward trend. Compared with Example 1 and Comparative Example 1, the increase in the hardness of the material will slightly reduce the resilience and compression deformation, but the impact is limited. Among them, the surface resistivity of Example 1 and Example 2 shows a significant decrease with the increase in the content of the antistatic agent, because the amount added in Example 1 is small, and a conductive network is not well formed in the material, indicating that the P3HT / CNTs-NH2 antistatic agent has an excellent modification effect on the mechanical properties and antistatic properties of the foaming material, and the surface-modified P3HT / CNTs-NH2 has good compatibility with the resin matrix. Compared with Comparative Example 2, the tensile strength, elongation at break, hardness, and antistatic properties of Comparative Example 2 have a large degree of decrease in Example 1, which is due to the poor compatibility of the inorganic filler without surface amino treatment with the organic matrix, and the obvious particle agglomeration. From the data of Comparative Examples 3 and 4, it can be seen that the antistatic property of adding conductive polymer P3HT or CNTs-NH2 alone is not as good as that of Example 1. Compared with Example 1, after not using the crystallization temperature difference method and the secondary foaming method, the mechanical properties of the material of Comparative Example 5 are not much different, but the open porosity is significantly reduced.

[0087] Figure 1 This is the Fourier infrared image of the P3HT / CNTs-NH2 antistatic additive powder, where 1590 cm -1 The characteristic peaks at 3056 cm are the stretching vibration peaks of CN and the bending vibration peaks of NH, proving that CNTs-NH2 was successfully prepared. -1 The characteristic peak at 2927cm is the stretching vibration of the CH bond on the thiophene ring. -1 and 2856cm -1 The characteristic peak at 1379 cm is the stretching vibration of the side chain alkyl group. -1 The characteristic peak at 1348 cm is the bending vibration of the side chain alkyl group. -1and 766cm -1 The characteristic peaks at 1072 cm-1 are the planar and non-planar distortion vibrations of the side chain alkyl groups. -1 and 839cm -1 The absorption peak at 1590 cm-1 is attributed to the in-plane and out-of-plane deformation vibration of the C=C double bond on the thiophene ring. -1 and 1461cm -1 The characteristic peaks at 1590 cm-1 are the antisymmetric and symmetric stretching vibrations of the C=C double bond on the thiophene ring, and coincide with the CN stretching vibration and NH bending vibration peaks of CNTs-NH2 at 1590 cm-1. -1 There is a strong peak at the

[0088] Figure 2 This is the SEM image of the P3HT / CNTs-NH2 antistatic additive. In the gaps of the material, CNTs-NH2 connects the conductive polymer P3HT in series to form a more effective hybrid conductive network, which fills the shortcoming of insufficient conductivity of P3HT at room temperature and improves the conductivity of the material.

[0089] Figure 3 The SEM image of open-cell bubbles shows that the pore structure is mostly open-cell. First, when the soft cross-section of the low-Tc polymer (LDPE) forms a smaller dispersed phase and the hard cross-section of the high-Tc polymer (EVA) forms the main melt matrix, the pore opening can be initiated and propagated by well-dispersed low-Tc polymer domains, which are surrounded by growing adjacent bubbles. These soft domains can be extended as the bubbles grow, that is, the pore wall becomes thinner until it breaks to form an open-cell structure.

[0090] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A breathable, antistatic EVA foam material, characterized in that: The raw materials of the EVA foaming material include, by weight: 70 parts of EVA, 20 parts of LDPE, 10 parts of POE-g-MAH, 3-9 parts of antistatic additives, 2.5 parts of AC foaming agents, 1.5 parts of cross-linking agents, 2.5 parts of fillers, 3 parts of calcium zinc stabilizers, 1 part of lubricants, and 0.2 parts of release agents.

2. The breathable, antistatic EVA foam material according to claim 1, characterized in that: The antistatic additive is P3HT / CNTs-NH2, and its preparation steps include: (1) Preparation of CNTs-NH2: 2 g of carbon nanotubes were dissolved in a mixture of 35 mL of concentrated nitric acid and 15 mL of concentrated sulfuric acid for acidification, then diluted with deionized water and the solution was removed to obtain CNTs-COOH; the obtained CNTs-COOH and 1 g of condensation agent dicyclohexylcarbodiimide DCC were placed in a three-necked flask, and 50 mL of ethylenediamine was added and ultrasonicated for 30 min to mix evenly, and stirred at 120 °C for 24 h. After the reaction was completed, the product was ultrasonically washed with anhydrous ethanol and vacuum dried at 60 °C for 24 h to obtain amino carbon nanotubes CNTs-NH2; (2) CNTs-NH2 was added to anhydrous ethanol and ultrasonicated for 20 min to disperse in ethanol. Then, poly (3-hexylthiophene) P3HT was added to the suspension and stirred at 80 °C at a speed of 1500 r / min for 5 h. The obtained product was washed and vacuum dried at 60 °C for 12 h to obtain P3HT / CNTs-NH2 composite.

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

4. The breathable, antistatic EVA foam material according to claim 1, characterized in that: The cross-linking agent is dicumyl peroxide.

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

6. The breathable, antistatic EVA foam material according to claim 1, characterized in that: The release agent is paraffin.

7. The breathable, antistatic EVA foam material according to claim 1, characterized in that: The preparation steps of the POE-g-MAH are as follows: 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, mixing them evenly in a high-speed mixer, and standing to volatilize the acetone; the mixed material is melt-blended for 10 minutes using a torque rheometer, the rotor speed is 30 r / min, the torque temperature is 165°C, and after the blending is completed, the melt is melted into sheets in an open mill.

8. The method for preparing the breathable and antistatic EVA foam material according to any one of claims 1 to 7, characterized in that: The EVA foam material is an open-cell structure, and the preparation steps include: melt-blending EVA and LDPE, two materials with a large difference in crystallization temperature, wherein the melt structure contains two blended polymers with different crystallization temperature values, and the high crystallization temperature polymer will crystallize before the low crystallization temperature polymer, thereby generating pressure on the pore structure to cause the pores to rupture and connect to generate an open-cell structure, and at the same time, using a secondary foaming method as a compression foaming method to prepare the EVA foam material into an open-cell pore structure.

9. The method for preparing the breathable and antistatic EVA foam material according to claim 8, characterized in that: 70 parts of EVA, 20 parts of LDPE, 10 parts of POE-g-MAH, 3-9 parts of antistatic additives, 2.5 parts of AC foaming agent, 1.5 parts of cross-linking 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 an internal mixer for blending, and then the blended product is subjected to cold and hot compression molding.

10. The method for preparing the breathable and antistatic EVA foam material according to claim 9, characterized in that: The following steps are involved: (1) EVA, LDPE, POE-g-MAH and cross-linking agent were placed in an internal mixer preheated at 130°C and blended for 10 min to obtain blend 1. The speed of the internal mixer was 30 rpm. (2) adding an antistatic agent, an AC foaming agent, a filler, a calcium zinc stabilizer, a lubricant, and a release agent to blend 1, and continuing to mix in an internal mixer at 130° C. for 10 min to obtain blend 2; (3) After blend 2 is pressed into a thin sheet using an open mixing mill, it is transferred into a flat vulcanizer for compression foaming. The upper and lower mold temperatures are both set to 150°C, the pressure is 10 MPa, and the molding time is 600 s for a pre-foaming process. The pre-foamed semi-finished product is placed in a 60°C forced air drying oven and dried for 12 h. Then, the upper and lower mold temperatures are adjusted to 175°C, the pressure is 15 MPa, and the molding time is 380 s for a secondary foaming process. After the mold is opened, the EVA foam material automatically pops out.

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