Low-odor, high-mechanical-property EPDM foam material and preparation method thereof

Abstract

The application provides a low-cost, low-odor, low-VOC-emission and excellent-mechanical-property EPDM (Ethylene Propylene Diene Rubber) foaming material and a preparation method thereof, and belongs to the technical field of high polymer materials. The application realizes slow release control by adopting a PVA / SiO2 composite coated citric acid-sodium bicarbonate foaming agent, and is synergistically compounded with odorless organic foaming agent 4,4'-oxobisbenzenesulfonylhydrazide (OBSH), so as to optimize the cell structure through a binary foaming system (CO2+N2). The foaming agent applied in the EPDM foam material can significantly improve the mechanical property of the EPDM foaming material, effectively reduces the VOC emission, has good environmental protection and stability, and is suitable for automobile, rail transit and other fields, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high polymer materials, and particularly relates to a preparation method of an environmentally friendly foaming agent, and based on this, a low-cost, low-odor, low-VOC-emission and excellent mechanical property EPDM (ethylene propylene diene rubber) foaming material and a preparation method thereof are developed. BACKGROUND

[0002] EPDM (ethylene propylene diene rubber) foam is widely used in sealing, sound insulation and pressure-resistant cushioning fields due to its excellent weather resistance, heat resistance, ozone resistance and elasticity. However, the current EPDM foam material still has the following problems: the environmental friendliness of traditional foaming agents is insufficient, many foaming agents (such as azo foaming agents AC and OBSH) may release toxic volatile organic compounds (VOCs), which do not meet modern environmental regulations; the bubble structure control is poor, the conventional sodium bicarbonate-citric acid system releases gas too quickly, resulting in uneven bubble size and affecting the mechanical properties of the foam; the mechanical properties are limited, and the existing environmentally friendly EPDM foam often has uneven bubble structure or improper foaming ratio control, resulting in a decrease in mechanical properties such as tensile strength, tear strength and wear resistance; the storage stability is poor, and some inorganic foaming agents may fail or foam unevenly due to their strong hygroscopicity after long-term storage. Therefore, there is an urgent need for an environmentally friendly, low-VOC and high-mechanical-property EPDM foam material to meet the needs of automotive, rail transportation and other industrial applications. SUMMARY

[0003] The present application aims to provide a low-cost, low-odor, low-VOC-emission and excellent mechanical property EPDM (ethylene propylene diene rubber) foaming material and a preparation method thereof. The present application uses PVA / SiO2 to complexly wrap the citric acid-sodium bicarbonate foaming agent to achieve slow-release control, prevent premature decomposition and improve storage stability, and combines with OBSH to form a binary foaming system (CO2+N2) to optimize the bubble structure, improve the compression resistance of the material, and reduce VOC emissions.

[0004] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0005] A low-odor and high-mechanical-property EPDM (ethylene propylene diene rubber) foaming material, by weight, the raw materials used therein include: 100 parts of EPDM, 6 parts of carbon black, 40 parts of light calcium carbonate, 15 parts of paraffin oil, 10 parts of zinc oxide, 1 part of vulcanizing agent, 1.5 parts of accelerator, 2 parts of stearic acid, 1 part of lubricant and 10 parts of foaming agent.

[0006] In this invention, the ethylene propylene diene monomer (EPDM) rubber (EPDM) can be made from environmentally friendly raw rubbers, including Lanxess Keltan Eco5470, ExxonMobil Vistalon 2504 Eco, Dow Chemical's Nordel IP 3430 Bio, and South Korea's Kumho Petrochemical's KEP 460 Bio. These EPDM compounds are primarily composed of bio-based raw materials (approximately 70% derived from sugarcane ethylene conversion), offering excellent environmental performance and a low carbon footprint. Keltan Eco 5470, in particular, combines high performance with environmental advantages, making it particularly suitable for environmentally friendly sealing strips, automotive parts, and industrial rubber products. Furthermore, these EPDM compounds contain less than 5% ethylidene norbornene (ENB), ensuring a good cure rate while effectively reducing odor emissions during the foaming process and during product use, further meeting environmental and low-pollution requirements.

[0007] In the present invention, the carbon black can be selected from Orion NEROX 505, NEROX 510, Cabot BlackPearls 800, and Degussa Special Black 550. These carbon blacks all exhibit excellent dispersibility, stability, and environmental performance. The preferred NEROX 505 features a small particle size (4 nm), low sulfur content, and low VOC emissions, reducing pollutant emissions from rubber materials and complying with environmental regulations such as RoHS and REACH. In the present invention, the carbon black has a BET specific surface area of ​​50-150 m² / g, a pH of 6-9, a carbon content of ≥95%, and a dispersibility of ≥90%. It is also produced using a clean furnace process to reduce harmful emissions and enhance the product's environmental performance.

[0008] In the present invention, the paraffin oil is preferably SK YUBASE 8, American Sun Sanepar 936, Sunpar 2280, or Nytex 4700. These environmentally friendly paraffin oils have a saturated hydrocarbon content of ≥90%, an aromatic hydrocarbon content of ≤1%, a kinematic viscosity of 10-50 cSt at 40°C, a kinematic viscosity of 2-8 cSt at 100°C, a flash point of ≥200°C, a pour point of ≤-10°C, low VOC emissions, and a low sulfur content (≤10 ppm). They comply with REACH regulations or FDA standards, ensuring the environmental safety and long-term stability of rubber products.

[0009] In the present invention, zinc oxide acts as a heat stabilizer and an activator.

[0010] In the present invention, the vulcanizing agent includes any one of sulfur, zinc dibenzyldithiocarbamate, dibenzoyl peroxide, dicumyl peroxide, and the like.

[0011] In the present application, the accelerator comprises zinc dibenzyl dithiocarbamate (ZBEC) and / or tetra-benzyl thiuram disulfide (TBZTD), preferably a mixture of zinc dibenzyl dithiocarbamate and tetra-benzyl thiuram disulfide.

[0012] In the present application, the lubricant is polyethylene glycol.

[0013] In the present application, the foaming agent is a mixture of 4,4'-oxybisbenzenesulfonyl hydrazide (OBSH) and modified sodium bicarbonate, with a mass ratio of 1:(1-3). The mixed gas produced by OBSH and modified sodium bicarbonate is a mixture of N2 and CO2, which can optimize the uniformity of foaming, improve the stability of the cell structure of the material, and reduce the amount of OBSH used while ensuring that the shrinkage of the foamed material is less than 10%, thereby reducing costs while better maintaining environmental performance.

[0014] In the present application, the preparation method of the modified sodium bicarbonate comprises the following steps:

[0015] (a) Dissolve 5g of PVA in 100mL of water, heat to 80℃, stir for 2h, then add 10g of citric acid, stir until uniform, then slowly add 10g of NaHCO3 (100-500 mesh), continue stirring for 30min, then dry in an oven at 80℃ to obtain PVA-coated citric acid-NaHCO3 particles;

[0016] (b) Disperse 2g of SiO2 nano-powder in 50mL of ethanol solution with a volume concentration of 50%, ultrasonic for 30min, then add the PVA-coated citric acid-NaHCO3 particles prepared in step (a), stir for 1h, then centrifuge at 8000rpm for 10min, collect the particles and dry;

[0017] (c) Add 1g of KH-550 to 100mL of anhydrous ethanol, stir until uniform, then add the particles prepared in step (b) and stir until they are uniformly dispersed in the solution, then stir at room temperature for 1h and dry at 50℃ for 12h.

[0018] In the present application, the dispersibility of the foaming agent in the rubber matrix is improved by adjusting the mesh number (100 mesh~500 mesh) of sodium bicarbonate, thereby improving the mechanical properties of the EPDM foamed material. Meanwhile, the sodium bicarbonate is surface modified by citric acid, which increases the decomposition temperature and makes it more consistent with the foaming curve of rubber, and can improve its dispersibility in the formula and reduce the problem of cell shrinkage. The coating of polyvinyl alcohol (PVA) and SiO2 composite layer on the surface of sodium bicarbonate can make it more stable in the foaming process and release gas more uniformly, thereby optimizing the foaming structure of EPDM and improving the resilience and dimensional stability of the foamed material. In addition, the silane coupling agent modified silica powder and PVA coated citric acid-sodium bicarbonate can improve the interfacial compatibility of the filler and the rubber matrix, improve the processing performance of the material, reduce the emission of volatile organic compounds (VOC) during the foaming process, and make the EPDM foamed material superior to the prior art in environmental protection, mechanical properties and durability. It has a wide application prospect, including high-performance sealing, shock-absorbing materials and lightweight high-strength elastomer fields.

[0019] The preparation method of the EPDM foamed material comprises the following steps:

[0020] 1) Put EPDM, carbon black, light calcium carbonate, zinc oxide, lubricant, stearic acid and half of the amount of paraffin oil into a mixer for primary mixing, so that the materials are uniformly dispersed, and then pass out the sheet, to obtain the first stage rubber;

[0021] 2) Put the first stage rubber, accelerator, vulcanizing agent, foaming agent and remaining paraffin oil into the mixer for secondary mixing, so that the materials are uniformly mixed, and then pass out the sheet, to obtain the mixed rubber;

[0022] 3) The mixed rubber is sequentially extruded, once vulcanized and twice vulcanized, to finally obtain the EPDM foamed material.

[0023] In the present application, the temperature of the primary mixing is 90~110℃, and the time is 10~12 min; the temperature of the sheet passing out is 30~50℃, and the thickness of the sheet is 1~3mm.

[0024] In the present application, the temperature of the secondary mixing is 60~90℃, and the time is 2~5 min; the temperature of the sheet passing out is 80~100℃, and the thickness of the sheet is 2~4mm.

[0025] In the present application, the temperature of the extrusion is 100~120℃.

[0026] In the present application, the temperature of the first vulcanization is 130-135 DEG C, and the time is 20-30 min. The lower temperature of the first vulcanization makes OBSH decompose, the colloid expand to a certain extent, the hardness decrease, the volume increase, and the colloid has a certain cross-linking degree, so that the colloid has enough strength to support the pores and improve the anti-shrinkage performance.

[0027] In the present application, the temperature of the second vulcanization is 150-155 DEG C, preferably 151-154 DEG C, and further preferably 152-153 DEG C; the time of the second vulcanization is 10-30 min, preferably 12-28 min, and further preferably 15-25 min.

[0028] In the present application, through the process of the second vulcanization, the synthesized foaming agent is fully decomposed, the colloid volume is further increased, and the internal structure of the EPDM foaming material is optimized. At the same time, after the EPDM product is vulcanized to a certain extent, even if it is not continuously heated, it can still continue to occur deep vulcanization reaction under the action of residual heat or in the storage process, or even further cross-linking under dynamic load conditions. Therefore, the main purpose of the second vulcanization is to promote the further cross-linking of the EPDM product, significantly improve its mechanical properties, reduce the compression permanent deformation rate, thereby enhancing its long-term use stability and durability, and making its application advantages in the field of high-performance seals, shock-absorbing materials and weather-resistant elastomers more prominent.

[0029] The EPDM foaming material provided by the present application can be applied in the fields of automobiles, rail transportation, etc.

[0030] The present application has the following advantages:

[0031] (1) Low cost and excellent mechanical properties: the present application can bring more uniform foaming effect in EPDM by optimizing the mesh number of sodium bicarbonate, improve its mechanical properties, elasticity, processing performance, and thermal and acoustic insulation performance. The fine cell structure and stable foaming effect have a significant effect on improving the comprehensive performance and application performance of EPDM. At the same time, the PVA / SiO2 composite coating technology can effectively control the foaming process and improve the compression deformation resistance of the material. In addition, by compounding the PVA / SiO2 composite coated citric acid-sodium bicarbonate foaming agent with OBSH, the dispersibility of the foaming agent in the EPDM matrix is effectively improved, and the problems of pore shrinkage and unevenness of the traditional sodium carbonate foaming agent are solved.

[0032] (2) Low VOC emission, in line with environmental regulations: The present application optimizes the rubber formulation and uses low VOC emission raw materials, effectively reducing the VOC emission of EPDM foamed material, in line with the requirements of China's "Solid Waste Pollution Environment Prevention Law of the People's Republic of China" and EU REACH and RoHS environmental regulations. The use of silane coupling agent modified microcapsule blowing agent reduces the use of traditional azo blowing agent, further reducing the emission of volatile organic compounds.

[0033] (3) Low odor, excellent environmental performance: High-purity PVA and SiO2 nanometer coating are used, not only optimizing the release rate of the blowing agent, but also effectively reducing the irritating gas that may be produced during foaming, so that the odor level of EPDM foamed material at room temperature is <2.5 level, and the odor level is ≤3.5 level under the condition of 80℃ water bath heating. The promoter is selected as TBZTD and ZBEC, which can avoid the generation of nitrous acid amine and improve the environmental performance. The carbon black is selected as NEROX 505 with small specific surface area, which reduces the surface oxygen-containing functional groups and improves the anti-fouling performance and long-term use performance of the material. The paraffin oil is selected as YUBASE8 with flash point higher than 260℃ and low aromatic group content, which reduces odor residue.

[0034] (4) Using binary foaming system (CO2+N2), regulating the bubble hole distribution and improving the bubble hole uniformity. The present application significantly reduces the problems of bubble hole collapse and local bubble hole too large by compounding PVA / SiO2 composite coated citric acid-sodium bicarbonate blowing agent with OBSH, which can improve the mechanical properties of ternary ethylene propylene rubber foamed material. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 DTA curve of sodium bicarbonate and PVA / SiO2 composite coated citric acid-sodium bicarbonate prepared in Example 1. As can be seen from the figure, the decomposition temperature of the modified sodium bicarbonate is increased from the original value to a more suitable range for rubber foaming (150-170℃), and the decomposition interval is significantly reduced, which makes it better match the EPDM vulcanization and foaming curve, and improves the stability of the bubble hole structure.

[0036] Figure 2 Optical microscope pictures of EPDM foamed materials prepared by using the blowing agents of Example 1 (a) and Comparative Examples 5~9 (b-e). As can be seen from the figure, with the decrease of the particle size of sodium bicarbonate, the bubble hole size of EPDM foamed material gradually decreases, and the distribution of bubble hole is more uniform, the number of white spots is obviously reduced, and the dispersity is significantly improved. This shows that the particle size of the optimized coated and modified sodium bicarbonate can effectively improve the dispersity of the blowing agent, thereby enhancing the uniformity of the bubble hole structure and improving the overall performance of the material.

[0037] Figure 3Thermogravimetric curve of the EPDM foamed material prepared by using the foaming agent of Example 1. As can be seen from the figure, the prepared EPDM foamed material has high thermal stability, which helps to improve the heat resistance and flame retardance of the product during long-term use. DETAILED DESCRIPTION

[0038] A low-odor, high-mechanical-property EPDM foamed material, the raw materials used by weight parts include: 100 parts of EPDM, 6 parts of carbon black, 40 parts of modified sodium bicarbonate, 15 parts of paraffin oil, 10 parts of zinc oxide, 1 part of vulcanizing agent, 1.5 parts of accelerator, 2 parts of stearic acid, 1 part of lubricant, and 10 parts of foaming agent. The preparation method comprises the following steps:

[0039] 1) Put EPDM, carbon black, light calcium carbonate, zinc oxide, lubricant, stearic acid, and half of the paraffin oil into a mixer, mix once at 90-110°C for 10-12 min to make the materials uniformly dispersed, and then pass out a sheet at 30-50°C to obtain a first-stage rubber with a thickness of 1-3 mm;

[0040] 2) Put the first-stage rubber, accelerator, vulcanizing agent, foaming agent, and the remaining paraffin oil into a mixer, mix twice at 60-90°C for 2-5 min to make the materials uniformly mixed, and then pass out a sheet at 80-100°C to obtain a mixed rubber with a thickness of 2-4 mm;

[0041] 3) Extrude the mixed rubber at 100-120°C, vulcanize once at 130-135°C for 20-30 min, and vulcanize twice at 150-155°C for 10-30 min to finally obtain an EPDM foamed material.

[0042] The foaming agent is a mixture of 4,4'-oxybisbenzenesulfonyl hydrazide (OBSH) and modified sodium bicarbonate in a mass ratio of 1:(1-3).

[0043] The preparation method of the modified sodium bicarbonate comprises the following steps:

[0044] (a) Dissolve 5g of PVA in 100mL of water, heat to 80°C, stir for 2h, then add 10g of citric acid, stir until uniform, then slowly add 10g of NaHCO3 (100-500 mesh), continue stirring for 30min, and then dry in an oven at 80°C to obtain PVA-coated citric acid-NaHCO3 particles;

[0045] (b) 2g SiO2nanopowder was dispersed in 50mL ethanol solution with volume concentration of 50%, and ultrasonic for 30min. Then the PVA coated citric acid-NaHCO3particles prepared in step (a) were added, stirred for 1h, centrifuged at 8000rpm for 10min, and the particles were collected and dried;

[0046] (c) 1g KH-550 was added into 100mL anhydrous ethanol, stirred uniformly, and the particles prepared in step (b) were added and dispersed uniformly in the solution. Then the solution was stirred at room temperature for 1h, and dried at 50℃ for 12h.

[0047] The technical solutions provided by the present application are described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the present application.

[0048] In the examples, the ethylene propylene rubber was Keltan Eco 5470 from Lanxess. The carbon black was NEROX505 from Ocelon. The paraffin oil was YUBASE 8 from SK. The vulcanizing agent was sulfur. The accelerator was a mixture of zinc dibenzyl dithiocarbamate and tetra-benzyl thiuram disulfide with a mass ratio of 1:1. The lubricant was polyethylene glycol 2000.

[0049] Preparation of the foaming agent in Example 1

[0050] 1) 5g PVA was dissolved in 100mL water, heated to 80℃, and stirred for 2h. Then 10g citric acid was added and stirred uniformly. 10g NaHCO3(500 mesh) was slowly added, and stirred for 30min. Then the mixture was dried in an oven at 80℃ to obtain PVA coated citric acid-NaHCO3particles.

[0051] 2) 2g SiO2nanopowder was dispersed in 50mL ethanol solution with volume concentration of 50%, and ultrasonic for 30min. Then the PVA coated citric acid-NaHCO3particles prepared in step (a) were added, stirred for 1h, centrifuged at 8000rpm for 10min, and the particles were collected and dried.

[0052] 3) 1g KH-550 was added into 100mL anhydrous ethanol, stirred uniformly, and the particles prepared in step (b) were added and dispersed uniformly in the solution. Then the solution was stirred at room temperature for 1h, and dried at 50℃ for 12h to obtain PVA / SiO2complex coated citric acid-sodium bicarbonate.

[0053] 4) 5 parts of PVA / SiO2complex coated citric acid-sodium bicarbonate and 5 parts of 4,4'-oxobisbenzenesulfonyl hydrazide were mixed uniformly to prepare a foaming agent, which was labeled as foaming agent A.

[0054] Preparation of the foaming agent in Example 2

[0055] 1) 5 g PVA was dissolved in 100 mL water, heated to 80°C, stirred for 2 h, then 10 g citric acid was added, stirred evenly, then 10 g NaHCO3 (500 mesh) was slowly added, stirred for 30 min, then dried in an oven at 80°C to obtain PVA-coated citric acid-NaHCO3 particles;

[0056] 2) 2 g SiO2 nano powder was dispersed in 50 mL ethanol solution with a volume concentration of 50%, ultrasonic for 30 min, then the PVA-coated citric acid-NaHCO3 particles prepared in step (a) were added, stirred for 1 h, then centrifuged at 8000 rpm for 10 min, the particles were collected and dried;

[0057] 3) 1 g KH-550 was added to 100 mL anhydrous ethanol, stirred evenly, then the particles prepared in step (b) were added and uniformly dispersed in the solution, then stirred at room temperature for 1 h, dried at 50°C for 12 h, to obtain PVA / SiO2 composite coated citric acid-sodium bicarbonate;

[0058] 4) According to the weight parts, 7 parts of PVA / SiO2 composite coated citric acid-sodium bicarbonate and 5 parts of 4,4'-oxobisbenzenesulfonyl hydrazide were mixed to form a foaming agent, labeled as foaming agent B.

[0059] Preparation of foaming agent

[0060] 1) 5 g PVA was dissolved in 100 mL water, heated to 80°C, stirred for 2 h, then 10 g citric acid was added, stirred evenly, then 10 g NaHCO3 (500 mesh) was slowly added, stirred for 30 min, then dried in an oven at 80°C to obtain PVA-coated citric acid-NaHCO3 particles;

[0061] 2) 2 g SiO2 nano powder was dispersed in 50 mL ethanol solution with a volume concentration of 50%, ultrasonic for 30 min, then the PVA-coated citric acid-NaHCO3 particles prepared in step (a) were added, stirred for 1 h, then centrifuged at 8000 rpm for 10 min, the particles were collected and dried;

[0062] 3) 1 g KH-550 was added to 100 mL anhydrous ethanol, stirred evenly, then the particles prepared in step (b) were added and uniformly dispersed in the solution, then stirred at room temperature for 1 h, dried at 50°C for 12 h, to obtain PVA / SiO2 composite coated citric acid-sodium bicarbonate;

[0063] 4) According to the weight parts, 10 parts of PVA / SiO2 composite coated citric acid-sodium bicarbonate and 5 parts of 4,4'-oxobisbenzenesulfonyl hydrazide were mixed to form a foaming agent, labeled as foaming agent C.

[0064] Comparative Example 1 OBSH

[0065] Take 4,4'-oxobisbenzenesulfonyl hydrazide as foaming agent, marked as foaming agent D.

[0066] Comparative Example 2 PVA / SiO2 composite coated sodium bicarbonate without citric acid

[0067] 1) Take 5g PVA and dissolve in 100mL water, heated to 80℃, stirred for 2h, then slowly add 10g NaHCO3(500 mesh), continue to stir for 30min, then dried in an oven at 80℃, to obtain PVA coated NaHCO3 particles;

[0068] 2) Take 2g SiO2 nano powder and disperse in 50mL volume concentration of 50% ethanol solution, ultrasonic for 30min, then add PVA coated NaHCO3 particles prepared in step (a), stir for 1h, then centrifuge at 8000rpm for 10min, collect the particles and dry;

[0069] 3) Take 1g KH-550 and add to 100mL anhydrous ethanol, stir evenly, add the particles prepared in step (b), make them evenly dispersed in the solution, then stir at room temperature for 1h, dry at 50℃ for 12h, to obtain PVA / SiO2 composite coated sodium bicarbonate;

[0070] 4) According to the weight parts, take 5 parts of PVA / SiO2 composite coated sodium bicarbonate and 5 parts of 4,4'-oxobisbenzenesulfonyl hydrazide to prepare foaming agent, marked as foaming agent E.

[0071] Comparative Example 3 PVA / SiO2 composite coated citric acid-sodium bicarbonate without silane modification

[0072] 1) Take 5g PVA and dissolve in 100mL water, heated to 80℃, stirred for 2h, then add 10g citric acid, stir evenly, then slowly add 10g NaHCO3(500 mesh), continue to stir for 30min, then dried in an oven at 80℃, to obtain PVA coated citric acid-NaHCO3 particles;

[0073] 2) Take 2g SiO2 nano powder and disperse in 50mL volume concentration of 50% ethanol solution, ultrasonic for 30min, then add PVA coated citric acid-NaHCO3 particles prepared in step (a), stir for 1h, then centrifuge at 8000rpm for 10min, collect the particles and dry, to obtain PVA / SiO2 composite coated citric acid-sodium bicarbonate without silane modification;

[0074] 3) 5 parts of the mixture of citric acid and sodium bicarbonate without silane modification PVA / SiO2 composite coating and 5 parts of 4,4'-oxobisbenzenesulfonylhydrazide were mixed as foaming agent, marked as foaming agent F.

[0075] Comparative Example 4: mixture of citric acid and sodium bicarbonate

[0076] 1) 10 g of citric acid was mixed with 10 g of NaHCO3 (500 mesh) and stirred continuously for 30 min to obtain a mixture;

[0077] 2) 5 parts of the mixture of step 1) and 5 parts of 4,4'-oxobisbenzenesulfonylhydrazide were mixed as foaming agent, marked as foaming agent G.

[0078] Comparative Examples 5-9

[0079] NaHCO3 (500 mesh) used in Example 1 was replaced with NaHCO3 (100 mesh), NaHCO3 (200 mesh), NaHCO3 (300 mesh), and NaHCO3 (400 mesh), respectively, and other operations were the same as in Example 1 to obtain foaming agents H, I, J, and K.

[0080] Application Example

[0081] The preparation steps of a ternary ethylene propylene rubber foaming material are as follows:

[0082] 1) 100 parts of EPDM, 6 parts of carbon black, 40 parts of light calcium carbonate, 10 parts of zinc oxide, 1 part of lubricant, 2 parts of stearic acid, and 7.5 parts of paraffin oil were added to a mixing machine, and once mixing was carried out at 100°C for 10 min to uniformly disperse the materials, and then a sheet was thinly passed out at 50°C to obtain a first-stage rubber with a thickness of 2 mm;

[0083] 2) The first-stage rubber, 1.5 parts of an accelerator, 1 part of a vulcanizing agent, the remaining paraffin oil, and 10 parts of the foaming agent prepared in the example or comparative example were added to the mixing machine, and secondary mixing was carried out at 60°C for 5 min to uniformly mix the materials, and then a sheet was thinly passed out at 80°C to obtain a mixed rubber with a thickness of 3 mm;

[0084] 3) The mixed rubber was sequentially extruded at 100°C, once vulcanized at 130°C for 20 min, and twice vulcanized at 150°C for 10 min to finally obtain a ternary ethylene propylene rubber foaming material.

[0085] Table 1: Comparison results of properties of ternary ethylene propylene rubber foaming materials prepared using foaming agents of examples and comparative examples

[0086]

[0087] As can be seen from Table 1, the EPDM foamed material doped with PVA / SiO2 composite coated citric acid-sodium bicarbonate has significantly better mechanical properties such as tensile strength, tear strength and elongation at break than the EPDM foamed material prepared by using traditional OBSH foaming agent (Comparative Example 1). Meanwhile, as can be seen from Examples 1 to 3, with the increase of the content of modified sodium bicarbonate in the foaming agent, the shrinkage of the EPDM foamed material gradually increases. In order to ensure the dimensional stability of the EPDM foamed material, the shrinkage of the material should be controlled at about 10%, and at this time, the tensile strength of the prepared EPDM foamed material is as high as 1130 kPa, which is about 55% higher than the tensile strength of the EPDM foamed material foamed by OBSH (730 kPa), and the tear strength is about 24% higher, which can ensure the stability and optimization of other properties. In addition, by comparing the EPDM foamed materials prepared by using sodium bicarbonate with different particle sizes (100-500 mesh), it can be seen that with the decrease of the particle size, the mechanical properties of the material are improved, and the cell structure is more stable.

[0088] Table 2 Test results of the EPDM foamed material prepared by using the foaming agent of Example 1

[0089]

[0090] It is further verified from the data in Table 2 that the EPDM foamed material prepared by using the foaming agent of Example 1 has reached the lowest level in environmental protection indexes such as odor, VOC (volatile organic compound) emission and atomization value, has more excellent environmental protection performance, and can meet more stringent environmental protection and low pollution requirements.

[0091] In summary, the present application provides an EPDM foamed material which has environmental protection, high mechanical properties, good dimensional stability and excellent cell structure, and is suitable for high-performance applications such as automobile sealing parts, rail transit sealing pads, industrial shock-absorbing materials, etc., and has wide industrial application prospects.

[0092] The above only describes the preferred embodiments of the present application, and any changes and modifications made within the scope of the present application should be included in the scope of the present application.

Claims

1. A low odor, high mechanical property, EPDM foam material, characterized in that, The raw materials used include, by weight parts: 100 parts of ethylene propylene diene rubber, 6 parts of carbon black, 40 parts of light calcium carbonate, 15 parts of paraffin oil, 10 parts of zinc oxide, 1 part of vulcanizing agent, 1.5 parts of accelerator, 2 parts of stearic acid, 1 part of lubricant, 10 parts of foaming agent; The foaming agent is a mixture of 4,4'-oxybisbenzenesulfonyl hydrazide and modified sodium bicarbonate, and the mass ratio of the two is 1:(1-3); The preparation method of the modified sodium bicarbonate comprises the following steps: (a) Dissolve 5g of PVA in 100mL of water, heat to 80℃, stir for 2h, then add 10g of citric acid, stir evenly, then slowly add 10g of NaHCO3, continue to stir for 30min, then dry at 80℃ to obtain PVA-coated citric acid-NaHCO3 particles; (b) Disperse 2g of SiO2 nano powder in 50mL of ethanol solution with a volume concentration of 50%, ultrasonic for 30min, then add the PVA-coated citric acid-NaHCO3 particles prepared in step (a), stir for 1h, then centrifuge at 8000rpm for 10min, collect the particles and dry; (c) Take 1g of KH-550 and add it to 100mL of anhydrous ethanol, stir until uniform, then add the particles prepared in step (b) and stir at room temperature for 1h, then dry at 50℃ for 12h to obtain the modified sodium bicarbonate; The NaHCO3 used is 100-500 mesh.

2. The EPDM foam material according to claim 1, characterized in that, The vulcanizing agent includes any one of sulfur, zinc dibenzyl dithiocarbamate, dibenzoyl peroxide and dicumyl peroxide.

3. The EPDM foam material according to claim 1, characterized in that, The accelerator includes at least one of zinc dibenzyl dithiocarbamate and tetrabenzyl thiuram disulfide.

4. A process for the production of a foamed ethylene-propylene-diene rubber material according to claim 1, characterized in that The method comprises the following steps: 1) Put the ethylene propylene diene rubber, carbon black, light calcium carbonate, zinc oxide, lubricant, stearic acid and half of the paraffin oil into a mixer for primary mixing, so that the materials are uniformly dispersed, then pass out the sheet thinly to obtain the first stage rubber; 2) Put the first stage rubber, accelerator, vulcanizing agent, foaming agent and the remaining paraffin oil into the mixer for secondary mixing, so that the materials are uniformly mixed, then pass out the sheet thinly to obtain the mixed rubber; 3) Extrude, primary vulcanize and secondary vulcanize the mixed rubber in sequence to finally obtain the ethylene propylene diene rubber foaming material.

5. The process for the preparation of a ternary ethylene propylene rubber foamed material according to claim 4, characterized in that, The temperature of the primary mixing in step 1) is 90-110℃, and the time is 10-12min.

6. The process for preparing a ternary ethylene propylene rubber foamed material according to claim 4, characterized in that, The temperature of the secondary mixing in step 2) is 60-90℃, and the time is 2-5min.

7. The process for preparing a foamed ethylene propylene diene rubber material according to claim 4, characterized in that, The temperature of the extrusion in step 3) is 100-120℃.

8. The process for preparing a foamed EPDM material according to claim 4, characterized in that, The temperature of the primary vulcanization in step 3) is 130-135℃, and the time is 20-30min; the temperature of the secondary vulcanization is 150-155℃, and the time is 10-30min.

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