Rubber-plastic composite material based on ethylene propylene diene monomer and production process thereof

Abstract

The invention relates to the technical field of materials, and discloses a rubber-plastic composite material based on ethylene propylene diene monomer and a production process thereof.The composite material is prepared by taking ethylene propylene diene monomer and ethylene-vinyl acetate copolymer as base materials and modified palygorskite functional materials and the like as auxiliary materials through banburying, extrusion and vulcanization foaming processes. Wherein the modified palygorskite functional material is prepared by modifying the surface of palygorskite with a macromolecular polymer formed by alternately connecting methyltrisiloxane-phosphorus derivatives, and the palygorskite can efficiently exert the advantages of serving as an inorganic additive, so that the mechanical strength of the rubber and plastic composite material is improved; the phosphorus element of the macromolecular polymer can promote rapid formation of a compact carbon layer on the surface of the material during combustion, and the silicon element can form silicon oxide to be deposited on the surface of the carbon layer, so that the strength of the carbon layer is improved, the high-strength carbon layer is formed, and the flame retardant property of the rubber and plastic composite material is effectively improved through cooperation with the palygorskite.

Description

Technical Field

[0001] The present invention relates to the field of material technology, and in particular to a rubber-plastic composite material based on EPDM rubber and a production process thereof. Background Art

[0002] Rubber-plastic composite foam material is made of rubber and plastic as the base material through a vulcanization foaming process. Due to the closed bubble structure inside the material, the density can be significantly reduced. This feature not only reduces product weight and transportation costs, but also facilitates installation and construction. Therefore, it has excellent sound insulation, shock absorption, and heat insulation effects, and is therefore widely used in various industries.

[0003] Among many rubber substrates, EPDM rubber has become one of the key substrates for rubber-plastic composite foam materials due to its excellent mechanical properties, weather resistance, corrosion resistance and ozone resistance. Ethylene-vinyl acetate copolymer has good flexibility and chemical corrosion resistance. Therefore, using EPDM rubber and ethylene-vinyl acetate copolymer as substrates, the advantages of each other can be utilized to complement each other to produce rubber-plastic composite foam materials with excellent performance.

[0004] Although the rubber-plastic composite foam material has excellent properties, it is very easy to burn due to the special bubble structure, and it is also accompanied by the phenomenon of molten droplets, which causes the fire to spread rapidly. At present, when fires are frequent, this undoubtedly has a huge negative impact on the application prospects of the rubber-plastic composite foam material. The prior art generally achieves the purpose of improving the flame retardant properties of rubber-plastic materials by adding flame retardants. For example, the invention patent with publication number CN111662512B discloses a rubber-plastic foam material and a preparation method thereof, and flame retardant modification is achieved by adding a high content of inorganic flame retardant. However, too high a content of inorganic flame retardant will have a negative effect on the mechanical properties of the material. Based on this, the present invention provides a rubber-plastic composite material that can solve the problems existing in the prior art. Summary of the invention

[0005] In order to solve the problems mentioned in the background technology, the object of the present invention is to provide a rubber-plastic composite material based on EPDM rubber and a production process thereof.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A rubber-plastic composite material based on EPDM rubber, comprising the following raw materials in parts by weight: 35-45 parts of EPDM rubber; 10-15 parts of ethylene-vinyl acetate copolymer; Chlorinated paraffin oil 15-20 parts; 3-6.5 parts of modified palygorskite functional material; 5 - 10 parts of foaming agent; 0.2 - 0.5 parts of vulcanizing agent; 1 - 2 parts of zinc oxide; 2 - 6 parts of accelerator; 0.5 - 1 part of carbon black; 5 - 12 parts of polyethylene wax.

[0007] As a further scheme of the present invention, the modified palygorskite functional material is prepared by the following method: Step 1: Add palygorskite to tetrahydrofuran, after ultrasonic dispersion, raise the temperature to 50 - 60 °C, then continue to add dimethylchlorosilane and accelerator. After adding, keep warm and stir for 4 - 6 h, then stop heating, cool down and discharge the material, centrifuge to obtain solid materials, and after washing and vacuum drying, obtain organically modified palygorskite; Step 2: Disperse the organically modified palygorskite in N,N - dimethylformamide medium to form a uniform dispersion liquid, then add an excessive amount of diallyl - substituted phosphorus derivative and catalyst to the dispersion liquid, start heating, raise the temperature to 80 - 90 °C, keep warm and stir for 2 - 4 h, then continue to add an excessive amount of methyltrisiloxane derivative. After adding, stir evenly, then raise the temperature to 90 - 100 °C, continuously keep warm and stir for 12 - 16 h, then stop heating, cool down and discharge the material, and the modified palygorskite functional material can be obtained.

[0008] As a further scheme of the present invention, in Step 1, the accelerator is triethylamine.

[0009] As a further scheme of the present invention, in Step 2, the preparation method of the diallyl - substituted phosphorus derivative is as follows: Add diallylcarbamoyl chloride and phosphoryl chloride compound to toluene, raise the temperature to 50 - 60 °C, stir until completely dissolved, then introduce nitrogen protection, and then raise the temperature to 80 - 90 °C, continuously keep warm and stir for 6 - 12 h, rotary evaporate to remove the solvent, cool down and discharge the material, and after purification treatment, the diallyl - substituted phosphorus derivative can be obtained.

[0010] As a further scheme of the present invention, the phosphoryl chloride compound is any one of diisobutyl phosphite, diisopropyl phosphite, diisooctyl phosphite or dibenzyl phosphite.

[0011] As a further scheme of the present invention, the molar ratio of diallylcarbamoyl chloride to phosphoryl chloride compound is 1:1.

[0012] As a further scheme of the present invention, in Step 2, the catalyst is chloroplatinic acid.

[0013] As a further solution of the present invention, in step two, the methyltrisiloxane derivative is 1,1,3,3,5,5-hexamethyltrisiloxane or 1,1,3,3,5,5,7,7-octamethyltetrasiloxane.

[0014] In the above technical solution, first, dimethylchlorosilane is used as a modifier. Under the action of a promoter, the Si-Cl in its structure can be substituted with the surface hydroxyl groups of palygorskite to achieve the organic modification of palygorskite, and the organic palygorskite is prepared. Then, under the action of a chloroplatinic acid catalyst, the Si-H on the surface of the organic palygorskite can carry out a hydrosilylation reaction with the unsaturated alkenyl substituents in the structure of the diallyl-substituted phosphorus derivative. The excessive diallyl-substituted phosphorus derivative and methyltrisiloxane derivative in the system will carry out continuous hydrosilylation reactions on the surface of palygorskite, thereby forming a macromolecular polymer with alternating connections of methyltrisiloxane-phosphorus derivatives on the surface of palygorskite, and the modified palygorskite functional material is prepared.

[0015] Among them, the diallyl-substituted phosphorus derivative is prepared by using diallylcarbamoyl chloride and phosphoryl chloride compounds as reactants, and utilizing the principle that the acyl chloride groups in their structures can react with P-H to obtain a diallyl-substituted phosphorus derivative containing two equivalents of unsaturated alkenyl substituents in its structure.

[0016] As a further solution of the present invention, the blowing agent is azodicarbonamide; the vulcanizing agent is sulfur; the promoter is a mixture of promoter DPTT and promoter EZ, and the mass ratio is 1:0.5 - 1.

[0017] A production process of a rubber and plastic composite material based on ethylene-propylene-diene monomer rubber comprises the following steps: The first step, prepare each raw material according to the weight parts; The second step, add ethylene-propylene-diene monomer rubber, ethylene-vinyl acetate copolymer, chlorinated paraffin oil, modified palygorskite functional material, blowing agent, zinc oxide, carbon black and polyethylene wax into a kneader, knead and mix evenly at a temperature of 130 - 140 °C, then transfer to an open mill, open mill and calender into sheets, and let stand for 24 - 36 h after natural cooling to form a precursor material; The third step, in the way of secondary open milling, add the vulcanizing agent and the promoter into the precursor material, mix evenly, then transfer to an extruder for extrusion, control the head temperature at 50 - 70 °C, add the extruded rubber material into an oven for vulcanization and foaming. The vulcanization and foaming are carried out at six different temperatures, which are 130 ± 2 °C, 140 ± 2 °C, 155 ± 2 °C, 170 ± 2 °C, 183 ± 2 °C, 190 ± 2 °C respectively. After completion, cool by air cooling, and that's it.

[0018] The beneficial effects of the present invention: In the present invention, a macromolecular polymer with alternating methyltrisiloxane-phosphorus derivatives is modified on the surface of palygorskite as a modified palygorskite functional material. Since the macromolecular polymer forms a "transition" between palygorskite and ethylene propylene diene monomer (EPDM), the interfacial compatibility between palygorskite and EPDM can be improved. On the one hand, it can promote palygorskite to effectively exert its advantages as an inorganic additive and improve the mechanical strength of the rubber-plastic composite material. In addition, the phosphorus element in the macromolecular polymer structure can promote the rapid formation of a dense carbon layer on the material surface during combustion to prevent continuous combustion. The silicon element can form silicon oxides deposited on the surface of the carbon layer to improve the strength of the carbon layer, thereby isolating oxygen and heat outside through the carbon layer. At the same time, the layer-chain structure of palygorskite can cooperate with the carbon layer to prevent the continuous progress of combustion, thereby effectively improving the flame retardancy of the rubber-plastic composite material.

[0019] Of course, it is not necessary for any product implementing the present invention to achieve all the above-mentioned advantages simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 It is an infrared test chart of a diallyl-substituted phosphorus derivative. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0023] Example 1

[0024] A rubber-plastic composite material based on ethylene propylene diene monomer (EPDM) includes the following raw materials by weight: 35 parts of ethylene propylene diene monomer (EPDM); 10 parts of ethylene-vinyl acetate copolymer; 15 parts of chlorinated paraffin oil; 3 parts of modified palygorskite functional material; 5 parts of blowing agent azodicarbonamide; 0.2 part of sulfur; 1 part of zinc oxide; 2 parts of accelerator; 0.5 parts of carbon black; 5 parts of polyethylene wax.

[0025] The production process of the rubber-plastic composite material includes the following steps: First step, prepare each raw material according to the weight parts; Second step, add ethylene propylene diene monomer rubber, ethylene-vinyl acetate copolymer, chlorinated paraffin oil, modified palygorskite functional material, foaming agent azodicarbonamide, zinc oxide, carbon black and polyethylene wax into a kneader, knead and mix evenly under the temperature condition of 130 °C, then transfer to an open mill, open mill and calender into sheets, and let it stand for 24 h after natural cooling to form a precursor material; Third step, in the way of secondary open milling, add sulfur and accelerator into the precursor material, mix evenly, then transfer to an extruder for extrusion, control the head temperature at 50 °C, add the extruded rubber material into an oven for vulcanization and foaming, and the vulcanization and foaming are carried out at six different temperatures, which are 130 ± 2 °C, 140 ± 2 °C, 155 ± 2 °C, 170 ± 2 °C, 183 ± 2 °C, 190 ± 2 °C respectively. After completion, cool it by air cooling, and that's it.

[0026] The accelerator is a mixture of accelerator DPTT and accelerator EZ, and the mass ratio is 1:1, the same below.

[0027] The modified palygorskite functional material is prepared by the following method: Step one, add 1.8 g of palygorskite into tetrahydrofuran, ultrasonically disperse evenly, then raise the temperature to 50 °C, continue to add 3.4 g of dimethylchlorosilane and 0.5 g of triethylamine. After adding, keep stirring at a constant temperature for 6 h, then stop heating, cool down and discharge, centrifuge out the solid material, and carry out washing and vacuum drying treatment to obtain organically modified palygorskite; Step two, disperse 1.5 g of organically modified palygorskite in N,N-dimethylformamide medium to form a uniform dispersion liquid, then add 5.5 g of diallyl-substituted phosphorus derivative and 0.01 g of chloroplatinic acid into the dispersion liquid, start heating, raise the temperature to 85 °C, keep stirring at a constant temperature for 3 h, then continue to add 4.8 g of 1,1,3,3,5,5,7,7-octamethyltetrasiloxane. After adding, stir evenly, then raise the temperature to 95 °C, keep stirring at a constant temperature for 15 h, then stop heating, cool down and discharge, and the modified palygorskite functional material can be obtained.

[0028] The preparation method of the diallyl-substituted phosphorus derivative is as follows: Add 0.4 g of diallylcarbamoyl chloride and 0.42 g of diisopropyl phosphite to toluene, heat to 55°C, stir until completely dissolved, introduce nitrogen protection, then raise the temperature to 85°C, keep stirring for 9 hours, remove the solvent by rotary evaporation, cool and discharge the material, and purify it to obtain a diene-substituted phosphorus-containing derivative.

[0029] Figure 1 This is the infrared test image of the diene-substituted phosphorus-containing derivative, where 3000-3100cm -1 The characteristic absorption peak at 1762 cm is attributed to the CH characteristic absorption peak in the unsaturated olefinic functional group. -1 The characteristic absorption peak at 1294 cm is the C=O characteristic absorption peak. -1 The characteristic absorption peak at 2350-2440cm is attributed to the characteristic absorption peak of P=O. -1 Obvious pH characteristic absorption peaks were observed.

[0030] Example 2

[0031] A rubber-plastic composite material based on EPDM rubber, comprising the following raw materials in parts by weight: 36 parts of EPDM rubber; 12 parts of ethylene-vinyl acetate copolymer; Chlorinated paraffin oil 18 parts; 6 parts of modified palygorskite functional material; 8 parts of foaming agent; Sulfur 0.3 parts; 1.5 parts of zinc oxide; 4 parts of accelerator; 0.8 parts of carbon black; 6 parts of polyethylene wax.

[0032] The production process of the rubber-plastic composite material comprises the following steps: The first step is to prepare all the raw materials according to the weight. Step 2: Add EPDM rubber, ethylene-vinyl acetate copolymer, chlorinated paraffin oil, modified palygorskite functional material, foaming agent, zinc oxide, carbon black and polyethylene wax into an internal mixer, mix them evenly at 135°C, transfer them to an open mixer, roll them into sheets, cool them naturally and leave them for 36 hours to form a precursor material; The third step is to add sulfur and accelerator to the precursor material in a secondary open refining manner. After mixing, transfer it to the extruder for extrusion. Control the head temperature at 60°C and add the extruded rubber material into the oven for vulcanization and foaming. The vulcanization and foaming are carried out at six different temperatures, namely 130±2°C, 140±2°C, 155±2°C, 170±2°C, 183±2°C, and 190±2°C. After completion, cool it with air cooling.

[0033] Example 3

[0034] A rubber-plastic composite material based on EPDM rubber, comprising the following raw materials in parts by weight: 45 parts of EPDM rubber; 15 parts of ethylene-vinyl acetate copolymer; 20 parts of chlorinated paraffin oil; 6.5 parts of modified palygorskite functional material; 10 parts of foaming agent; 0.5 parts of sulfur; 2 parts of zinc oxide; 6 parts of accelerator; 1 part of carbon black; 12 parts of polyethylene wax.

[0035] The production process of the rubber-plastic composite material comprises the following steps: The first step is to prepare all the raw materials according to the weight. Step 2: Add EPDM rubber, ethylene-vinyl acetate copolymer, chlorinated paraffin oil, modified palygorskite functional material, foaming agent, zinc oxide, carbon black and polyethylene wax into an internal mixer, mix them evenly at 140°C, transfer them to an open mixer, roll them into sheets, cool them naturally and leave them for 36 hours to form a precursor material. The third step is to add sulfur and accelerator to the precursor material in a secondary open milling manner. After mixing, transfer it to the extruder for extrusion. Control the head temperature at 70°C and add the extruded rubber material into the oven for vulcanization and foaming. The vulcanization and foaming are carried out at six different temperatures, namely 130±2°C, 140±2°C, 155±2°C, 170±2°C, 183±2°C, and 190±2°C. After completion, cool it with air cooling.

[0036] Comparative Example 1 A rubber-plastic composite material based on EPDM rubber, comprising the following raw materials in parts by weight: 36 parts of EPDM rubber; 12 parts of ethylene-vinyl acetate copolymer; Chlorinated paraffin oil 18 parts; 6 parts of palygorskite; 8 parts of foaming agent; 0.3 part of sulfur; 1.5 parts of zinc oxide; 4 parts of accelerator; 0.8 part of carbon black; 6 parts of polyethylene wax.

[0037] The production process of the rubber-plastic composite material includes the following steps: First step: Prepare each raw material according to the weight parts; Second step: Add ethylene propylene diene monomer (EPDM), ethylene-vinyl acetate copolymer (EVA), chlorinated paraffin oil, palygorskite, foaming agent, zinc oxide, carbon black and polyethylene wax into a kneader, knead and mix evenly under the temperature condition of 135 °C, then transfer to a two-roll mill, open mill and calender into sheets, and let it stand for 36 h after natural cooling to form a precursor; Third step: In the way of secondary open milling, add sulfur and accelerator into the precursor, mix evenly, then transfer to an extruder for extrusion, control the head temperature at 60 °C, add the extruded rubber compound into an oven for vulcanization and foaming. The vulcanization and foaming are carried out at six different temperatures, which are 130±2 °C, 140±2 °C, 155±2 °C, 170±2 °C, 183±2 °C, 190±2 °C respectively. After that, cool it by air cooling to finish.

[0038] Comparative Example 2 A rubber-plastic composite material based on ethylene propylene diene monomer (EPDM), by weight, includes the following raw materials: 36 parts of ethylene propylene diene monomer (EPDM); 12 parts of ethylene-vinyl acetate copolymer (EVA); 18 parts of chlorinated paraffin oil; 8 parts of foaming agent; 0.3 part of sulfur; 1.5 parts of zinc oxide; 4 parts of accelerator; 0.8 part of carbon black; 6 parts of polyethylene wax.

[0039] The production process of the rubber-plastic composite material includes the following steps: First step: Prepare each raw material according to the weight parts; Second step: Add ethylene propylene diene monomer (EPDM), ethylene-vinyl acetate copolymer (EVA), chlorinated paraffin oil, foaming agent, zinc oxide, carbon black and polyethylene wax into a kneader, knead and mix evenly under the temperature condition of 135 °C, then transfer to a two-roll mill, open mill and calender into sheets, and let it stand for 36 h after natural cooling to form a precursor; Step 3: Add sulfur and accelerators to the precursor material in a secondary kneading manner. After mixing evenly, transfer it to an extruder for extrusion. Control the head temperature at 60°C. Add the extruded rubber compound to an oven for vulcanization and foaming. The vulcanization and foaming are carried out at six different temperatures, namely 130±2°C, 140±2°C, 155±2°C, 170±2°C, 183±2°C, and 190±2°C. After completion, cool it by air cooling, and that's it.

[0040] Performance Testing Make the rubber-plastic composites in the examples and comparative examples into test specimens that meet the specifications for various performance tests. According to the standard GB / T 2406.2-2009, conduct the flame retardancy performance test. According to the standard GB / T 8813-2020, conduct the compressive strength test. The test results are shown in the following table:

[0041] Analyzing the test results, it can be seen that the rubber-plastic composites prepared by directly adding unmodified palygorskite as an additive have obviously poor mechanical properties and flame retardancy performance. This is because after losing the surface modification, it is impossible to form a dense carbon layer using the phosphorus and silicon flame retardant elements in the modifier, and agglomeration may have occurred, resulting in the above phenomena.

[0042] In this article, specific examples are used to elaborate on the principles and implementation methods of the present invention. The descriptions of the above examples are only used to help understand the method and its core idea of the present invention, including the best mode, and also enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of the present invention patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A rubber and plastic composite material based on ethylene-propylene-diene monomer rubber, characterized in that, Comprising the following raw materials by weight parts: Ethylene propylene diene monomer rubber: 35 - 45 parts; Ethylene - vinyl acetate copolymer: 10 - 15 parts; Chlorinated paraffin oil: 15 - 20 parts; Modified palygorskite functional material: 3 - 6.5 parts; Blowing agent: 5 - 10 parts; Vulcanizing agent: 0.2 - 0.5 parts; Zinc oxide: 1 - 2 parts; Accelerator: 2 - 6 parts; Carbon black: 0.5 - 1 part; Polyethylene wax: 5 - 12 parts.

2. The rubber-plastic composite material based on ethylene-propylene-diene monomer rubber according to claim 1, wherein The modified palygorskite functional material is prepared by the following method: Step 1: Under the action of an accelerator, palygorskite is surface - modified with dimethylchlorosilane to obtain organophilic palygorskite; Step 2: In an N,N - dimethylformamide medium, using a diallyl - substituted phosphorus derivative as a linker, under the action of a catalyst, the organophilic palygorskite is linked with a methyltrisiloxane derivative. The excess diallyl - substituted phosphorus derivative and methyltrisiloxane derivative added are in - situ polymerized on the surface of the organophilic palygorskite to obtain the modified palygorskite functional material.

3. The rubber-plastic composite material based on ethylene-propylene-diene monomer rubber according to claim 2, characterized in that In Step 1, the accelerator is triethylamine.

4. The rubber-plastic composite material based on ethylene propylene diene monomer rubber according to claim 2, characterized in that In Step 2, the diallyl - substituted phosphorus derivative is prepared by reacting diallylcarbamoyl chloride and a phosphoryl chloride compound as raw materials.

5. The rubber-plastic composite material based on ethylene-propylene-diene monomer rubber according to claim 4, wherein, The phosphoryl chloride compound is any one of di - isobutyl phosphite, di - isopropyl phosphite, di - isooctyl phosphite or dibenzyl phosphite.

6. The rubber and plastic composite material based on ethylene-propylene-diene monomer rubber according to claim 4, wherein The molar ratio of the diallylcarbamoyl chloride to the phosphoryl chloride compound is 1:

1.

7. The rubber and plastic composite material based on ethylene propylene diene monomer rubber according to claim 2, characterized in that, In Step 2, the catalyst is chloroplatinic acid.

8. The rubber-plastic composite material based on ethylene-propylene-diene monomer rubber according to claim 2, wherein, In Step 2, the methyltrisiloxane derivative is 1,1,3,3,5,5 - hexamethyltrisiloxane or 1,1,3,3,5,5,7,7 - octamethyltetrasiloxane.

9. An ethylene-propylene-diene rubber-based rubber-plastic composite material according to claim 1, characterized in that, The blowing agent is azodicarbonamide; the vulcanizing agent is sulfur; the accelerator is a mixture of accelerator DPTT and accelerator EZ, and the mass ratio is 1:0.5 - 1.

10. A production process of a rubber-plastic composite material based on ethylene-propylene-diene monomer rubber as described in claim 1, characterized in that, Including the following steps: The first step: Prepare each raw material according to the weight parts; The second step: Add ethylene propylene diene monomer rubber, ethylene - vinyl acetate copolymer, chlorinated paraffin oil, modified palygorskite functional material, blowing agent, zinc oxide, carbon black and polyethylene wax into a kneader. After kneading and mixing evenly at a temperature of 130 - 140 °C, transfer it to an open mill, roll it out into sheets, and let it stand for 24 - 36 h after natural cooling to form a precursor material; The third step: In the way of secondary open - milling, add the vulcanizing agent and accelerator into the precursor material, mix them evenly, then transfer them to an extruder for extrusion. Control the head temperature at 50 - 70 °C. Add the extruded rubber material into an oven for vulcanization and foaming. The vulcanization and foaming are carried out at six different temperatures, which are 130 ± 2 °C, 140 ± 2 °C, 155 ± 2 °C, 170 ± 2 °C, 183 ± 2 °C, 190 ± 2 °C respectively. After completion, cool it by air cooling.

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