Air-permeable, antistatic EVA foam material and method for producing same

Abstract

The application discloses a kind of breathable, antistatic EVA foamed material and preparation method thereof.Poly (3-hexylthiophene) (P3HT) is used as conductive filler, and CNTs-NH2 is added to compensate for the low conductivity of P3HT at room temperature, and the hybrid conductive network formed by the CNTs-NH2 inserted in P3HT can give the material better antistatic performance.At the same time, the surface of carbon nanotubes (CNTs) is modified with abundant -NH2 groups, which can be well compatible with the polymer matrix EVA / POE-g-MAH, improving the dispersibility of P3HT / CNTs-NH2 conductive filler in the polymer matrix, thus greatly improving the antistatic performance of the foamed material, and improving the defect that the antistatic component is easy to agglomerate, greatly improving the tensile strength, elongation at break, impact strength and other mechanical properties of the degradable antistatic foamed material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of materials, and particularly relates to a breathable and antistatic 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 aging resistance 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, electric 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 the shoe soles and inner decoration materials of high-grade tourist shoes, mountaineering shoes, slippers and sandals. In addition, the material is also used in the fields of soundproof boards, gymnastic mats and sealing materials.

[0003] Plastic is an organic macromolecular material formed by covalent bond, and has the characteristics of good insulation and water resistance. However, due to the high insulation of plastic, it brings electrostatic hazards to industrial production and people's daily life. Plastic has very high resistivity, and its bulk resistance value can reach 1x10 12 Ω or above, so the surface is easy to charge and accumulate static electricity due to friction or other reasons. Such static electricity is not easy to eliminate. With the accumulation and increase of electrostatic voltage and electrostatic capacity, the discharge phenomenon of the charged body occurs. It is easy to ignite the flammable and explosive substances existing in the surrounding environment to cause fire and explosion, which causes huge economic losses and safety hazards to people. At the same time, due to the electrostatic adsorption characteristics, plastic products are easy to adsorb dust, which affects the transparency, surface cleanliness and aesthetic appearance, and even affects the performance. Nano conductive modifier has the advantages of small particle size and large specific surface area, and endows nano materials with special surface effect. Nano conductive filler has high thermal stability and can exist stably in the high temperature environment of plastic processing. They have broad prospects and wide application in the field of plastic antistatic modification.

[0004] The method for increasing the conductivity of the polymer is to add a filler with high conductivity, also known as an antistatic agent. Its mechanism of action is to reduce the barrier of the material to electrons, improve the conductivity of the material, enable the transfer of electric charges on the surface and inside, improve the friction performance of the material surface, avoid the generation of electric charges and accumulation. Generally, the antistatic performance of the polymer is improved by adding an antistatic agent. At present, there are mainly two ways to add the antistatic agent, the first way is to add the antistatic agent into the polymer, and the second way is to coat the antistatic agent on the surface of the polymer. The first way can last longer to play the antistatic effect, and the second way is easy to disappear under external force. To meet the antistatic performance of the high polymer material, the antistatic agent is generally added to the base material, mainly using solution blending, melt blending and other preparation methods. The solution blending is to dissolve the plastic in an organic solvent, then the powder filler is added to the organic solvent and stirred uniformly, and finally the antistatic composite material is obtained by pouring in the mold and drying. The melt blending is to blend the filler and the base material through an extruder to prepare an antistatic master batch, and then an antistatic composite material is prepared by an injection molding machine. However, the existing technology generally has the problem that the compatibility of the antistatic agent with the biodegradable base material is poor, so that the mechanical properties and the antistatic performance of the antistatic foaming material cannot be considered.

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

[0006] The present application selects poly(3-hexylthiophene) (P3HT) and amino-functionalized carbon nanotubes (CNTs-NH2) as antistatic additives. Poly(3-hexylthiophene) (P3HT) is a conductive polymer. The conductive polymer has a conjugated pi bond on the polymer backbone, and the pi electrons on the large pi bond have higher energy than the sigma electrons on the molecular skeleton, can be more polarizable, and have a wide range of flowability. 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 the application advantages of wide conductivity range, easy preparation, good mechanical processing type, light weight, low price and the like. In order to improve the electrical conductivity, carbon nanotubes (CNTs) are introduced into the P3HT matrix to construct a hybrid conductive network, and the carbon nanotubes (CNTs) are subjected to amino functionalization to increase the compatibility with the base material and improve the mechanical properties, foaming material and antistatic performance of the foaming material.

[0007] The present application provides a carbon nanotube and P3HT antistatic composite additive, a foaming material and a preparation method thereof, to solve the problem that the mechanical properties and the antistatic performance of the antistatic foaming material prepared by the existing melt blending method cannot be well compatible.

[0008] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0009] A breathable, antistatic EVA foaming material, wherein the raw materials used include: 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 crosslinking 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, and stirred for 0.5 h by a magnetic stirrer, and the solution is 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 into the above reaction solution by a micro-injection pump. As the polymerization reaction proceeds, the color of the solution becomes deeper and is accompanied by the generation of HCl gas; after the reaction stops, the reaction mixture is slowly poured into excess methanol to settle, and the polymer product is obtained; the product is washed with methanol for several times until the filtrate is colorless to remove the residual ferric chloride; the collected product is added into a mixed solvent of 100 mL of chloroform and 100 mL of saturated hydrazine hydrate (85 wt%), and stirred overnight, and then the chloroform layer product is taken out by a pear-shaped separatory funnel, and then poured into excess methanol to settle, and the intrinsic state polymer is obtained; the obtained polymer is placed in a Soxhlet extractor, and repeatedly extracted with methanol at 65℃ for 24 h to remove impurities. The collected polymer is dried in a vacuum drying oven for 12 h to obtain poly(3-hexylthiophene) P3HT.

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

[0013] (3) CNTs-NH2 was added into anhydrous ethanol and dispersed in ethanol by ultrasonic for 20 min, then P3HT was added into the suspension and stirred at 80℃ for 5 h at a speed of 1500 r / min, the obtained product was washed and dried at 60℃ for 12 h to obtain P3HT / CNTs-NH2 composite.

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

[0015] Further, the preparation of POE-g-MAH includes: weighing 0.4 parts by weight of maleic anhydride, dissolving 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 mixing uniformly in a high-speed mixer, and volatilizing acetone after standing; 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 blending, the melt is opened into a sheet on an open mill.

[0016] 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, the melt structure has two kinds of blended polymers with different crystallization temperature values, the polymer with high crystallization temperature will crystallize before the polymer with low crystallization temperature, thereby generating pressure on the bubble structure to make the bubble structure broken and connected to form an open cell structure, and a secondary foaming method is used as a mold foaming method to prepare the EVA foaming material into an open cell structure.

[0017] Further, the preparation method of the air-permeable and antistatic EVA foaming material includes: placing 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 a composite antistatic 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 into a banbury mixer for blending, and then cold and hot mold pressing the blended product; specifically including the following steps:

[0018] (1) EVA, POE-g-MAN, LDPE, and a crosslinking agent are placed into a preheated banbury mixer at 130℃ and blended for 10 min, and the banbury mixer speed is 30 rpm;

[0019] (2) A composite antistatic additive, an AC foaming agent, a filler, a calcium-zinc stabilizer, a lubricant, and a release agent are added into the blended product obtained in step (1), and the mixture is further mixed in the banbury mixer at 130℃ for 10 min;

[0020] (3) The blend obtained in step (2) is pressed into thin sheets by an open mill and then transferred to a flat vulcanizing machine for molding and foaming. The temperature of the upper and lower molds is set to 150℃, the pressure is 10MPa, and the molding time is 600s for the first pre-foaming. The pre-foamed semi-finished product is placed in a 60℃ forced-air drying oven for 12h. Then the temperature of the upper and lower molds is adjusted to 175℃, the pressure is 20MPa, and the molding time is 380s for the second foaming. After the mold is opened, the EVA foam material is automatically ejected.

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

[0022] The beneficial effects of this invention are as follows:

[0023] 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.

[0024] The EVA foaming material formula prepared by adopting P3HT / CNTs-NH2 as the composite antistatic filler 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 property of the EVA foaming material, and the addition of the amino-functionalized carbon nanotube can connect the P3HT together to form a more effective hybrid conductive network inside the filler. Meanwhile, the surface of the carbon nanotube (CNTs) is modified and has rich -NH2 groups, which can be well compatible with the polymer matrix, thereby improving the dispersibility of the P3HT / CNTs-NH2 antistatic composite additive in the polymer matrix, and greatly improving the antistatic property of the foaming material. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The Fourier infrared spectrum of the composite wear-resistant antistatic filler prepared in the application.

[0026] Figure 2 The scanning electron microscope image of the composite wear-resistant antistatic filler prepared in the application.

[0027] Figure 3 The cell diagram of the EVA foaming material prepared in the application. DETAILED DESCRIPTION

[0028] In order to make the content of the application more convenient to understand, the technical solutions of the application will be further described in combination with specific embodiments, but the application is not limited to this.

[0029] 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℃ and 90℃ respectively.

[0030] Example 1

[0031] (1) Preparation of the polymer matrix: 70 parts of EVA, 20 parts of LDPE, 10 parts of POE-g-MAH, and 1.5 parts of crosslinking agent were put into a preheated mixing mill at 130℃ and blended for 10 min, and the rotation speed of the mixing mill was 30 rpm;

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

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

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

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

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

[0037] (3-1) 3 parts of the 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 part of release agent are added into a Banbury mixer together with the molten blend obtained in step (1) and continue to mix in the Banbury mixer at 130°C for 10 min;

[0038] (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℃, the pressure is 10 MPa, the molding time is 600 s, and one-step pre-foaming is performed. The pre-foamed semi-finished product is placed in a 60℃ air-drying oven for drying for 12 h, then the temperature of the upper and lower mold plates is adjusted to 175℃, the pressure is 15 MPa, the molding time is 380 s, and two-step foaming is performed. After the mold is opened, the EVA foaming material is automatically ejected.

[0039] Example 2

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

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

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

[0043] (3-1) 6 parts of the 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 are added into the internal mixer and the molten blend obtained in step (1) is continuously mixed in the internal mixer at 130℃ for 10 min;

[0044] (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℃, the pressure is 10 MPa, the molding time is 600 s, and one-step pre-foaming is performed. The pre-foamed semi-finished product is placed in a 60℃ air-drying oven for drying for 12 h, then the temperature of the upper and lower mold plates is adjusted to 175℃, the pressure is 15 MPa, the molding time is 380 s, and two-step foaming is performed. After the mold is opened, the EVA foaming material is automatically ejected.

[0045] Example 3

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

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

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

[0049] (3-1) 9 parts of the 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 are added into the internal mixer and the molten blend obtained in step (1) is continuously mixed in the internal mixer at 130℃ for 10 min;

[0050] (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℃, the pressure is 10 MPa, the molding time is 600 s, and a pre-foaming is performed, the pre-foamed semi-finished product is placed in a 60℃ air drying oven for drying for 12 h, then the temperature of the upper and lower mold plates is adjusted to 175℃, the pressure is 15 MPa, the molding time is 380 s, and a second foaming is performed, and the EVA foaming material is automatically ejected after the mold is opened.

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

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

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

[0054] (2-1) 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 are added into the internal mixer, and the obtained molten blend in step (1) is continuously mixed in the internal mixer at 130℃ for 10 min;

[0055] (2-2) After the blend obtained in step (2-1) 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℃, the pressure is 10 MPa, the molding time is 600 s, and a pre-foaming is performed, the pre-foamed semi-finished product is placed in a 60℃ air drying oven for drying for 12 h, then the temperature of the upper and lower mold plates is adjusted to 175℃, the pressure is 15 MPa, the molding time is 380 s, and a second foaming is performed, and the EVA foaming material is automatically ejected after the mold is opened.

[0056] Comparative Example 2 (P3HT / CNTs is added without amino group treatment)

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

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

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

[0060] (2-2) 2 g of CNTs is added to anhydrous ethanol and ultrasonically dispersed for 20 min, then 1 g of P3HT is added to the suspension and stirred at 80°C at a speed of 1500 r / min for 5 h, the obtained product is washed and vacuum dried at 60°C for 12 h to obtain a P3HT / CNTs composite.

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

[0062] (3-1) 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 are added into the internal mixer together with the melt blend obtained in step (1) and continue to mix in the internal mixer at 130°C for 10 min;

[0063] (3-2) The blend obtained in step (3-1) is pressed into a sheet by using an open mill and then transferred 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, and the mold pressing time is 600 s for primary foaming, and the pre-foamed semi-finished product is dried in a 60°C air-drying oven for 12 h, 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, and the EVA foaming material is automatically ejected after the mold is opened.

[0064] Comparative Example 3 (only P3HT is added without CNTs-NH2)

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

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

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

[0068] (3-1) 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 are added into the mixer together with the melt blend obtained in step (1) and continue to mix in the mixer at 130°C for 10 min;

[0069] (3-2) The blend obtained in step (3-1) is pressed into a sheet using an open mill and then transferred into a flat curing press for mold foaming, the temperature of the upper and lower mold plates is set to 150°C, the pressure is 10 MPa, and the mold pressing time is 600 s for the first pre-foaming, and the pre-foamed semi-finished product is placed in a 60°C air-drying oven for drying for 12 h, 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 the second foaming, and the EVA foaming material is automatically ejected after the mold is opened.

[0070] Comparative Example 4 (only CNTs-NH2 is added without P3HT)

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

[0072] (2) The preparation process of CNTs-NH2 is as follows: 2 g of carbon nanotubes is dissolved in a mixture of 35 mL of concentrated nitric acid (70 wt%) and 15 mL of concentrated sulfuric acid (70 wt%) for acidification treatment, and then diluted with deionized water, and the solution is removed to obtain the CNTs-COOH. The obtained CNTs-COOH and 1 g of condensing agent dicyclohexyl carbodiimide (DCC) are placed in a three-necked flask, and then 50 mL of ethylenediamine is added and ultrasonicated for 30 min. After mixing uniformly, the mixture is stirred at 120°C for 24 h. After the reaction is completed, the excess amine, DCC and by-product after DCC reaction are washed away by ultrasonicating with anhydrous ethanol. The obtained product is vacuum dried at 60°C for 24 h to obtain amino-functionalized carbon nanotubes CNTs-NH2.

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

[0074] (3-1) 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 are added into the internal mixer, and the obtained melt blend of step (1) is continuously mixed in the internal mixer at 130°C for 10 min;

[0075] (3-2) The blend obtained in step (3-1) is 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 is set to 150°C, the pressure is 10 MPa, and the mold pressing time is 600 s for the first pre-foaming. The pre-foamed semi-product is dried in a 60°C air-drying oven 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 the second foaming. After the mold is opened, the EVA foaming material is automatically ejected.

[0076] Comparative Example 5 (without using the crystallization temperature difference method and the second foaming method)

[0077] (1) Preparation of the polymer matrix: 90 parts of EVA, 10 parts of POE-g-MAH, and 1.5 parts of crosslinking agent are put into an internal mixer preheated at 130°C and blended for 10 min, and the rotation speed of the internal mixer is 30 rpm;

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

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

[0080] (3-1) 3 parts of antistatic 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 are added into the internal mixer, and the obtained melt blend of step (1) is continuously mixed in the internal mixer at 130°C for 10 min;

[0081] (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 to mold and foam. The temperature of the upper and lower mold plates was 175°C, the pressure was 15 MPa, and the molding time was 380 s. After the mold was opened, the EVA foamed material was automatically ejected.

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

[0083] Table 1: Performance tests

[0084]

[0085]

[0086] From the test results in Table 1, it can be seen that in Examples 1-3, with the increase of the content of the antistatic agent, the tensile strength, elongation at break and hardness of the product showed different degrees of upward trend, and the surface resistivity showed a downward trend. Compared with Example 1 and Comparative Example 1, the hardness of the material increased, which slightly reduced the resilience and compression deformation, but the impact was limited. The surface resistivity of Example 1 and Example 2 showed a large decrease with the increase of the content of the antistatic agent, because the amount of P3HT / CNTs-NH2 antistatic agent added in Example 1 was small, and it did not form a good conductive network in the material, indicating that P3HT / CNTs-NH2 antistatic agent had excellent modification effect on the mechanical properties and antistatic properties of the foamed material, and the surface modified P3HT / CNTs-NH2 had good compatibility with the resin matrix. Compared with Example 1 and Comparative Example 2, the tensile strength, elongation at break, hardness and antistatic properties of Comparative Example 2 all showed a large degree of decrease, because the inorganic filler without surface aminoization treatment had poor compatibility with the organic matrix, and the particle agglomeration was obvious. From the data of Comparative Examples 3 and 4, it can be seen that the antistatic property of the conductive polymer P3HT or CNTs-NH2 alone was not as good as that of Example 1. Compared with Example 1, the mechanical properties of Comparative Example 5 were not much different, but the open porosity decreased significantly without using the crystallization temperature difference method and the secondary foaming method.

[0087] Figure 1 The Fourier infrared spectrum of P3HT / CNTs-NH2 antistatic agent powder, wherein the characteristic peak at 1590 cm -1 is the stretching vibration of C-N and the bending vibration of N-H, proving that CNTs-NH2 is successfully prepared, the characteristic peak at 3056 cm -1 is the stretching vibration of C-H bond on thiophene ring, the characteristic peaks at 2927 cm -1 and 2856 cm -1 are the stretching vibrations of alkyl side chains, the characteristic peak at 1379 cm -1 is the bending vibration of alkyl side chain, and the characteristic peak at 1348 cm -1and 766cm -1 The characteristic peak at 1072 cm⁻¹ represents the planar and non-planar torsional 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 vibrations of the C=C double bond on the thiophene ring. -1 and 1461cm -1 The characteristic peak at 1590 cm⁻¹ corresponds to the antisymmetric and symmetric stretching vibrations of the C=C double bond on the thiophene ring, and coincides with the CN stretching vibration and NH bending vibration peaks of CNTs-NH₂ at 1590 cm⁻¹. -1 A relatively strong peak is observed at this location.

[0088] Figure 2 The image shows the SEM image of the P3HT / CNTs-NH2 antistatic additive. In the spacers of the material, CNTs-NH2 connects the conductive polymer P3HT in series, forming a more effective hybrid conductive network. This compensates for the insufficient conductivity of P3HT at room temperature and improves the conductivity of the material.

[0089] Figure 3 The SEM image of the open-cell structure shows that the cell structure is mostly open-cell structure. First, when the soft cross-section of the low-Tc polymer (LDPE) forms a small dispersed phase, while the hard cross-section of the high-Tc polymer (EVA) forms the main melt matrix, the cell opening can be initiated and propagated through the well-dispersed low-Tc polymer domains. These domains are surrounded between the growing adjacent cells. These soft structural domains can extend as the cells grow, that is, the cell walls become thinner and eventually rupture 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 within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A breathable, antistatic 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, 3-9 parts of antistatic aid, 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 antistatic aid is P3HT / CNTs-NH2, and the preparation steps thereof include: (1) Preparation of CNTs-NH2: 2g of carbon nanotubes is dissolved in a mixed solution of 35mL of concentrated nitric acid and 15mL of concentrated sulfuric acid for acidification treatment, and then diluted with deionized water, and the solution is removed to obtain CNTs-COOH; the obtained CNTs-COOH and 1g of condensing agent dicyclohexyl carbodiimide DCC are placed in a three-necked flask, 50mL of ethylenediamine is added, and ultrasonic treatment is performed for 30min, and then mixed uniformly, and then stirred at 120℃ for 24h, and after the reaction is completed, the product is washed with anhydrous ethanol, and then vacuum dried at 60℃ for 24h to obtain amino-functionalized carbon nanotubes CNTs-NH2; (2) The CNTs-NH2 is added into anhydrous ethanol and ultrasonically treated for 20min, dispersed in ethanol, and then poly(3-hexylthiophene) P3HT is added into the suspension, and then stirred at 1500r / min at 80℃ for 5h, and then the obtained product is washed and vacuum dried at 60℃ for 12h to obtain a P3HT / CNTs-NH2 composite.

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

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

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

5. The breathable, antistatic EVA foamed material according to claim 1, characterized in that: The release agent is paraffin wax.

6. The breathable, antistatic EVA foam material according to claim 1, characterized in that: The preparation steps of the POE-g-MAH are as follows: 0.4 parts by weight of maleic anhydride is weighed, and the maleic anhydride is dissolved in acetone to prepare a solution; 4 parts by weight of polyolefin elastomer POE particles are weighed, the acetone solution of maleic anhydride is sprayed into the POE particles, and then mixed uniformly in a high-speed mixer, and then the acetone is volatilized after standing; the mixture is melt blended for 10min by using a torque rheometer, the rotor speed is 30r / 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, antistatic EVA foam material according to any one of claims 1 to 6, characterized in that: The EVA foaming material is of open-cell structure, and the preparation steps include: melt blending two materials with large difference in crystallization temperature, i.e. EVA and LDPE, at the same time, using a secondary foaming method as a mold pressing foaming method to prepare the EVA foaming material into an open-cell pore structure.

8. The process for preparing a breathable, antistatic EVA foamed material according to claim 7, characterized in that: 70 parts of EVA, 20 parts of LDPE, 10 parts of POE-g-MAH, 3-9 parts of antistatic aid, 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.

9. The process for preparing a breathable, antistatic EVA foam material according to claim 8, characterized in that: The steps include: (1) EVA, LDPE, POE-g-MAH, and crosslinking agent are put into a preheated banbury mixer at 130℃ for 10min to obtain a blend 1, and the speed of the banbury mixer is 30rpm; (2) The antistatic aid, AC foaming agent, filler, calcium-zinc stabilizer, lubricant, and release agent were added into the blend 1, and the mixing was continued in the internal mixer at 130 °C for 10 min to obtain a blend 2; (3) The blend 2 was pressed into a sheet by an open mill and then was transferred into a flat vulcanizing machine for mold foaming. The temperature of the upper and lower mold plates was set to 150 °C, the pressure was 10 MPa, the mold pressing time was 600 s, and the pre-foaming was performed. The pre-foamed semi-product was dried in a 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, the mold pressing time was 380 s, and the secondary foaming was performed. After the mold was opened, the EVA foaming material was automatically ejected.

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