High hardness epdm compound for carbon dioxide refrigeration system and preparation method thereof

Abstract

The application belongs to the technical field of rubber and plastic sealing, and particularly relates to a high-hardness EPDM rubber material for a carbon dioxide refrigeration system and a preparation method thereof. The high-hardness EPDM rubber material is composed of the following components in parts by mass: 100-150 parts of ethylene-propylene-diene rubber, 0-30 parts of silicone rubber, 0-50 parts of polyolefin elastomer, 150-200 parts of filler, 5-20 parts of pre-dispersed carbon nanotubes, 2-30 parts of plasticizer, 1-20 parts of activator, 1-8 parts of processing aid, 1-6 parts of antioxidant, 1-8 parts of vulcanization aid, 2-10 parts of vulcanizing agent and 0.5-2 parts of scorch retarder. The high-hardness EPDM rubber material prepared by the application has good processing performance, high and low temperature resistance in the range of -40-170 DEG C, resistance to carbon dioxide refrigerant / freezing oil and low permeability, and can meet the use under the harsh working condition of R744 high temperature and high pressure.

Description

Technical Field

[0001] This invention belongs to the field of rubber and plastic sealing technology, specifically relating to a high-hardness EPDM compound for carbon dioxide refrigeration systems and its preparation method. Background Technology

[0002] Since electric vehicles lack an engine to power their air conditioning compressors and cannot provide heat for winter heating, they rely on onboard batteries for heating. However, using only PTC electric heating would reduce the driving range of electric vehicles by more than 35%. Therefore, how to achieve efficient thermal management using a heat pump air conditioning system while ensuring the comfort of electric vehicles has become a pressing issue. The choice of refrigerant plays a crucial role in the design and performance of the heat pump system.

[0003] The most commonly used refrigerants in electric vehicle heat pump air conditioning systems are R134a and R1234yf, while high-end new energy vehicles generally use CO2 (R744) refrigerant in their air conditioning and thermal management systems. In 2006, the European Parliament officially passed regulations to phase out fluorinated gases, stipulating that newly developed models should stop using R134a from 2011, and newly manufactured vehicles should stop using R134a from 2017. Many companies and universities have conducted relevant research. Currently, the United States mainly promotes HFO-type substances such as R1234yf, Europe favors the natural refrigerant CO2, and the Renault-Nissan Alliance has chosen R445A as the refrigerant for automotive air conditioning. In addition, alternative refrigerants for automotive air conditioning include R152a and R290.

[0004] R134a is colorless, non-toxic, non-flammable, low in viscosity, has a high latent heat of vaporization, and a large specific heat, making it the most commonly used refrigerant in automotive air conditioning systems in developing countries. However, its high global warming potential (GWP = 1300) is facing reductions and does not meet the European MAC directive's requirement of GWP < 150 for automotive air conditioning refrigerants. Performance studies of automotive heat pump (AHP) systems using R134a as the working fluid show that compressor speed and ambient temperature are the main factors affecting system performance. Because R134a has a problem where its specific volume increases rapidly as ambient temperature decreases and its heating capacity per unit volume is relatively low, a decrease in ambient temperature will cause a significant drop in system compressor power and COP (coefficient of performance). Therefore, electric vehicles using R134a heat pumps still need to be equipped with auxiliary heating systems.

[0005] The thermophysical properties of R1234yf are similar to those of R134a. Testing has shown that its cooling capacity and COP (Coefficient of Performance) are also similar to R134a, making it a direct replacement for R134a in existing automotive air conditioning systems. Furthermore, R1234yf is slightly less toxic than R134a and exhibits slight flammability. In heat pump mode, R1234yf has a slightly higher heating capacity than R134a, but its COP is on average 3.6% lower, resulting in lower efficiency. Since the performance of R1234yf is similar to R134a, replacing R134a with R1234yf requires only minor system modifications. However, both R1234yf and R134a suffer from insufficient heating capacity; when the ambient temperature is equal to or below -10°C, PTC (Potentially Transmitted Temperature) heating is necessary.

[0006] CO2 (R744) refrigerant boasts excellent environmental performance, is non-flammable and non-toxic, has low kinematic viscosity, and is cost-effective. Due to its superior heating performance at low ambient temperatures, CO2 heat pumps have become a research hotspot in this field in recent years. For every 5°C decrease in evaporation temperature, the absorbance density of R134a and CO2 decreases by an average of 18% and 15%, respectively. At low temperatures, the flow rate and heating capacity of CO2 heat pump systems are higher than those using R134a. Through design of system components and circulation modes, electric vehicle heat pump systems using CO2 as the working fluid exhibit superior performance compared to traditional systems using R134a. A key advantage is that air conditioning heat pump systems using carbon dioxide can have very small compressors and heat exchangers. Carbon dioxide heat pumps offer strong heating capacity, energy savings, and small size, making them particularly suitable as thermal management systems for new energy vehicles. Currently, CO2 is increasingly used as the refrigerant in automotive air conditioning systems. CO2 has a high critical pressure (Pc = 7.38 MPa) and a low critical temperature (Tc = 31.25℃). To achieve good overall cooling performance, refrigeration systems using CO2 as the refrigerant must operate in the transcritical region, with operating pressures exceeding the critical pressure—significantly higher than current automotive air conditioning systems. Typically, R744 (CO2) air conditioning heat pump systems operate at pressures up to 170 bar and temperatures ranging from -40℃ to 170℃. The sealing of the refrigeration system piping needs to meet even more stringent operating conditions. Therefore, it is necessary to develop a rubber sealing material that can withstand high and low temperatures, high pressures, and the use of CO2 as the refrigerant medium.

[0007] Rubber, as a common sealing material, is easy to process, has excellent performance, and is inexpensive, making it widely used in refrigeration system sealing applications. Ethylene propylene diene monomer (EPDM) rubber is a copolymer of ethylene, propylene, and a small amount of non-conjugated diene; it is a type of ethylene propylene rubber. Because its main chain is composed of chemically stable saturated hydrocarbons, and it only contains unsaturated double bonds in its side chains, it exhibits excellent ozone resistance, heat resistance, weather resistance, and other aging resistance properties. It can be widely used in automotive parts, waterproof building materials, wire and cable sheathing, heat-resistant hoses, tapes, automotive seals, and other fields. EPDM rubber also has extensive applications in automotive refrigeration systems.

[0008] The following requirements apply to rubber sealing materials used in carbon dioxide refrigeration systems: (1) To withstand the high pressure of carbon dioxide refrigerant in the refrigeration system, the rubber sealing material is required to have a hardness range of 85 to 95 Shore A, and the high-hardness rubber material is required to have excellent processing performance; (2) The operating temperature range is -40 to 170℃, and the rubber material is required to have good high and low temperature resistance; (3) For the R744 refrigerant medium used, the rubber material is required to have good resistance to carbon dioxide and corresponding refrigeration oil; (4) As it is a rubber sealing product, the rubber material is required to have a low compression set value and a low gas permeability.

[0009] Chinese patent CN110724322A describes a sealing material and its manufacturing method for refrigerant air conditioning systems used in automotive air conditioning, household refrigeration appliances, small stationary refrigeration equipment, medium-temperature refrigeration in supermarkets, and industrial and commercial refrigeration units. The rubber seal mentioned uses HNBR material. However, this rubber material operates at temperatures ranging from -40°C to 150°C, with a maximum pressure of 4.5 MPa, and contacts refrigerants R410a and R134a. Furthermore, the patent does not evaluate the rubber product's resistance to pressure reduction and bursting in carbon dioxide refrigerants and high-pressure refrigerants, which is crucial for refrigerant sealing and leakage prevention.

[0010] Chinese patent CN112552612A describes the refrigerant and refrigeration oil resistance properties of a blend of EPDM rubber and polar rubber. However, this patent only describes the material's resistance to media at room temperature (23°C) and does not describe the material's high and low temperature performance or its resistance to carbon dioxide as a refrigerant.

[0011] Chinese patent CN116082727A describes an HNBR sealing gasket material for automotive air conditioning systems. However, this patent only describes the material's compression set and high-temperature aging resistance, without describing its resistance to carbon dioxide refrigerant and refrigeration oil. Summary of the Invention

[0012] To address some shortcomings of existing technologies and the gaps in rubber materials for carbon dioxide refrigeration systems, the present invention aims to provide a rubber compound for carbon dioxide refrigeration systems and its preparation method, particularly a rubber compound for R744 refrigeration systems in new energy vehicles and its preparation method. Its advantages include excellent long-term high-temperature resistance, high hardness and low pressure deformation, and the ability to meet the requirements of resistance to R744 refrigerant and refrigeration oil, as well as resistance to decompression bursts and low carbon dioxide permeation.

[0013] The primary objective of this invention is to provide a high-hardness EPDM compound for carbon dioxide refrigeration systems, which has good mixing and vulcanization properties, resistance to media and high and low temperatures, and low permeability.

[0014] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0015] The high-hardness EPDM compound is composed of the following parts by weight:

[0016]

[0017]

[0018] The mass fractions of silicone rubber and polyolefin elastomer are both 0 parts.

[0019] The EPDM rubber comprises one or more of the following: ENB-EPDM (a terpolymer of 6-ethylidene-2-norbornene, ethylene, and propylene); VNB-EPDM (a terpolymer of 5-vinyl-2-norbornene, ethylene, and propylene); and DCPD-EPDM (a terpolymer of dicyclopentadiene, ethylene, and propylene). The Mooney viscosity [ML(1+4)125℃] is 1–150 MU, where MU is the Mooney viscosity unit. The ethylene content ranges from 40% to 80%, the third monomer content ranges from 1% to 15%, and the rubber oil content ranges from 0 to 100 parts per 100 parts of rubber.

[0020] Preferably, the Mooney viscosity [ML(1+4)125℃] of the EPDM rubber is 1 to 70 MU, where MU is the Mooney viscosity unit.

[0021] The silicone rubber mentioned is high-temperature vulcanized silicone rubber (HTV), which includes dimethyl silicone rubber, methyl vinyl silicone rubber, methyl vinyl phenyl silicone rubber, fluorosilicone rubber, nitrile silicone rubber, silicone masterbatch, and commercially available compound rubbers premixed with silica-related additives.

[0022] The polyolefin elastomer (POE) is a thermoplastic elastomer produced by in-situ polymerization of ethylene and α-olefins using a metallocene catalyst. The crystalline regions of the polyethylene chains (resin phase) act as physical crosslinking points, exhibiting typical plastic properties. The addition of a certain amount of α-olefins (1-butene, 1-hexene, 1-octene, etc.) weakens the crystalline regions of the polyethylene chains, forming amorphous regions (rubber phase) that exhibit rubber elasticity, thus giving the product elastomer properties. This unique structure endows POE with excellent physical and mechanical properties (high elasticity, high elongation, good impact strength), good low-temperature resistance, and processing rheology. The saturated structure of the main chain also makes it superior to traditional elastomers in terms of heat aging resistance and UV resistance. Its good flowability improves filler dispersion and also enhances weld line strength in the finished product.

[0023] Preferably, the polyolefin elastomer has a specific gravity range of 0.8 to 0.9, a hardness range of 50 to 90 Shore A, and a melt index range of 0.5 to 40 g / 10 min (2.16 kg × 190 °C).

[0024] The pre-dispersed carbon nanotubes are commercially available products, containing 5% effective carbon nanotubes, 85.5% refined paraffin and mineral oil, and 9.5% solid polymer. In some specific embodiments of the invention, single-walled carbon nanotubes (TUBALL) are used. TM MATRIX 610.

[0025] The filler includes organic and inorganic fillers such as carbon black, silica, talc, polytetrafluoroethylene (PTFE) micro powder, and titanium dioxide. The filler composition by mass parts is: 65-100 parts carbon black, 30-65 parts silica, 5-25 parts talc, 5-10 parts PTFE micro powder, and 20 parts titanium dioxide.

[0026] The carbon black is composed of one or more carbon blacks with different particle sizes and structures; the carbon black includes high abrasion-resistant carbon black, reinforcing carbon black, semi-reinforcing carbon black, medium-particle thermal cracking carbon black, and spray-dried carbon black, with an average particle size ranging from 10 to 500 nanometers and a nitrogen adsorption specific surface area ranging from 5 to 150 m². 2 / g, DBP oil absorption value range: 50~150cm 3 / 100g.

[0027] Silica is composed of one or more types of silica with different specific surface areas and different degrees of structure; the nitrogen adsorption specific surface area of ​​silica ranges from 20 to 300 m². 2 / g, DBP oil absorption value range: 50~400cm³ 3 / 100g;

[0028] Preferably, the carbon black has a particle size range of 20–200 nanometers and a nitrogen adsorption specific surface area of ​​20–100 m². 2 / g, DBP oil absorption value 70~120cm 3 / 100g; the nitrogen adsorption specific surface area of ​​silica is 50-250m². 2 / g, DBP oil absorption value 100~300cm 3 / 100g; specific surface area of ​​flaky talc powder: 10-30m² 2 / g.

[0029] The plasticizers include petroleum-based plasticizers such as aromatic hydrocarbon oils, paraffin oils, naphthenic oils, and white oils; and synthetic plasticizers such as dioctyl adipate (DOA), dioctyl azelate (DOZ), dioctyl sebacate (DOS), dibutyl sebacate (DBS), diisononyl phthalate (DINP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), and butyl benzyl phthalate (BBP). Dioctyl phthalate (DOTP), polypropylene sebate, trioctyl trimellitate (NODTM), trioctyl trimellitate (TOTM), tricresyl phosphate (TCP), triphenyl phosphate (TPP), diphenyl octyl phosphate (DPOP), diphenyl toluene diphenyl phosphate (CDPP), epoxidized soybean oil, epoxidized fatty acid butyl ester, epoxidized fatty acid octyl ester, coumarone resin, pine tar, low molecular weight polymers, etc.

[0030] Preferred plasticizers include high molecular weight paraffin oil, naphthenic oil, white oil, and low molecular weight polymers.

[0031] The activator comprises a complex of zinc oxide, magnesium oxide, coupling agent, and polyol.

[0032] Preferably, the zinc oxide is active zinc oxide with an effective content greater than 90%; the magnesium oxide is active magnesium oxide with an iodine uptake value greater than 40; the coupling agent includes one or more of aminosilane, epoxysilane, vinylsilane, sulfur-containing silane, acylsilane, octylsilane, alkylsilane, piperazine silane, etc.; the polyol includes polyethylene glycol, glycerol, etc. of different molecular weights.

[0033] The processing aids include one or more of the following: fatty acids, fatty acid metal salts, fatty acid esters, octadecylamine, paraffin wax, microcrystalline wax, silicone oil, oleamide, erucamide, etc.

[0034] The antioxidants include amine antioxidants, ketone amine antioxidants, p-phenylenediamine antioxidants, phenolic antioxidants, heterocyclic antioxidants, etc. More preferably, the antioxidants include ketone amine antioxidants, such as antioxidant RD (2,2,4-trimethyl-1,2-dihydroquinoline polymer), heterocyclic antioxidants, such as MB (2-thiol-benzimidazole), ZMBI (2-thiol-benzimidazole zinc salt), and p-phenylenediamine antioxidants, such as antioxidant 445 (4,4'-bis(phenylisopropyl)diphenylamine), octyl diphenylamine (ODPA), stylated diphenylamine (SDPA), isopropylphenyl diphenylamine (CDPA), etc.

[0035] The vulcanizing aids are trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTAMA), ethylene glycol diacrylate (EGDA), ethylene glycol dimethacrylate (EGDMA), N,N′-p-phenylbismaleimide (PDM or HVA-2), zinc diacrylate (ZDA), zinc dimethacrylate (ZDMA), triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), 1,2-polybutadiene (1,2-PBR), and sulfur.

[0036] The vulcanizing agent is: dicumyl peroxide; 2,5-di(tert-butylperoxy)-2,5-dimethylhexane; tert-butylcumyl peroxide; 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyn-3; tert-butylperoxy-isopropenylcumyl peroxide; m / p-di(tert-butylperoxy)diisopropylbenzene; m-di(tert-butylperoxy)diisopropylbenzene; p-di(tert-butylperoxy)diisopropylbenzene; dicumyl peroxide; 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane; 1,1-di(tert-butylperoxy)cyclohexane; n-butyl 4,4-di(tert-butylperoxy)valerate; ethyl 3,3-di(tert-butylperoxy)butyrate; tert-butylcumyl peroxide; tert-butylperoxy-isopropenylcumyl peroxide; 3,3,5,7,7-pentanediol peroxide; Methyl-1,2,4-trioxane; 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane; m / p-di(tert-butylperoxy)diisopropylbenzene; m-di(tert-butylperoxy)diisopropylbenzene; p-di(tert-butylperoxy)diisopropylbenzene; di-tert-butylperoxide; di-tert-pentylperoxide; tert-butylperoxycarbonate-2-ethylhexyl ester; polyether polytert-butylperoxycarbonate; tert-butylperoxybenzoate; tert-butylperoxyacetic acid; tert-butylperoxymaleic acid; di(4-methylbenzoyl)peroxide; benzoyl peroxide; di(2,4-dichlorobenzoyl)peroxide; dilauryl peroxide; cumene hydroperoxide; and one or more of di(4-tert-butylcyclohexyl)peroxydicarbonate and tert-butylperoxybenzoate.

[0037] Another object of the present invention is to provide a method for preparing the above-mentioned high-hardness EPDM compound for carbon dioxide refrigeration systems, wherein the preparation method comprises the following steps:

[0038] (1) Add ethylene propylene rubber and / or silicone rubber and / or polyolefin elastomer into a mixer and stir at a speed of 20-50 r / min for 8-12 min. When the surface temperature of the mixer reaches 60-80℃, discharge the rubber compound. Adjust the roller gap of the open mill to 0.1-0.3 mm, pass through a triangular loop 6-8 times, then adjust the roller gap to 2-4 mm, and discharge and cool the sheet.

[0039] (2) Put the cooled rubber compound back into the internal mixer, then add processing aids, antioxidants, activators, pre-dispersed carbon nanotubes, and about 1 / 2 to 2 / 3 of the filler, and continue stirring at a speed of 20 to 50 r / min for 5 to 10 min;

[0040] (3) When the internal mixer reaches a surface temperature of 70-100℃, add the remaining filler and plasticizer, and stir at a speed of 20-50 r / min until the internal mixer reaches a surface temperature of 110-130℃.

[0041] (4) Put the compound obtained in step (3) into the open mill, adjust the speed of the open mill rollers to 20-30 r / min, then adjust the roller gap to 0.3-0.6 mm, and use the turning machine to feed the material for 2-4 minutes; adjust the roller gap to 2-4 mm, then discharge the sheet for cooling and let it stand for 16-24 hours.

[0042] (5) Adjust the roller gap of the open mill to 2-4 mm, adjust the roller speed of the open mill to 20-30 r / min, after wrapping the rollers, add the crosslinking agent and vulcanizing agent in multiple batches. After the material is consumed, cut the rubber on the left and right and pound the rubber 2-5 times each. Adjust the roller gap to 0.1-0.3 mm, make triangular wrapping and thin passage 6-8 times, then adjust the roller gap to 2-4 mm, sheet out, cool, and obtain the compound rubber.

[0043] (6) After the high-hardness EPDM rubber compound obtained in step (5) is left to stand for 12 to 24 hours, it is subjected to first-stage vulcanization and second-stage vulcanization to obtain the high-hardness EPDM rubber compound.

[0044] The first stage of vulcanization involves a pressure of 10–15 MPa, a vulcanization temperature of 160–190°C, and a vulcanization time of 5–15 min. The second stage of vulcanization is carried out in an oven at atmospheric pressure, with a vulcanization temperature of 150–190°C and a vulcanization time of 1–10 h.

[0045] The first stage of vulcanization aims to achieve a certain degree of cross-linking in the EPDM rubber compound, serving a shaping function. Depending on the product specifications, the vulcanization pressure is selected from 10 to 15 MPa, the vulcanization temperature from 160 to 190°C, and the vulcanization time is determined according to the optimal vulcanization time t90 measured by the vulcanizing apparatus, typically 5 to 15 minutes. The second stage of vulcanization further and fully cross-links the EPDM rubber, while simultaneously allowing low-molecular-weight compounds in the compound to volatilize, improving its physical and mechanical properties. The second stage of vulcanization can be carried out in an oven.

[0046] The application of the above-mentioned high-hardness EPDM compound in the carbon dioxide (R744) refrigeration system of new energy vehicles.

[0047] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0048] The high-hardness EPDM rubber material obtained by this invention exhibits excellent mixing and vulcanization processing performance, resistance to high and low temperatures ranging from -40 to 170°C, and resistance to carbon dioxide refrigerant / refrigeration oil, as well as low permeability. The product can meet the harsh operating conditions of R744 under high temperature and high pressure. The high-hardness EPDM rubber compound of this invention possesses excellent processing performance, resistance to carbon dioxide refrigerant / refrigeration oil, and low permeability. Products for R744 refrigeration systems made using the high-hardness EPDM rubber compound of this invention exhibit excellent application performance. Detailed Implementation

[0049] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0050] Examples 1-5 and Comparative Examples 1-6 are rubber compounds with different formulations. The components and amounts used are shown in Table 1.

[0051] The tensile properties were tested according to GB / T 528-2009 "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber"; the hot air aging properties were tested according to GB / T 3512-2014 "Accelerated Aging and Heat Resistance Tests of Vulcanized Rubber or Thermoplastic Rubber in Hot Air"; the compression set was tested according to GB / T 7759.1-2015 "Determination of Compression Set of Vulcanized Rubber or Thermoplastic Rubber - Part 1: Under Normal or High Temperature Conditions"; the low-temperature brittleness was tested according to GB / T 15256-2014 "Determination of Low-Temperature Brittleness of Vulcanized Rubber or Thermoplastic Rubber (Multiple Sample Method)"; and the glass transition temperature of the rubber was tested according to GB / T The glass transition temperature of raw rubber was determined according to GB / T 1690-2010 "Test Method for Resistance to Liquids of Vulcanized Rubber or Thermoplastic Rubber"; the resistance to refrigerant bursting performance (foaming property) was tested according to QCT 666.1-2010 "Seals for R134a of Automotive Air Conditioning"; the gas permeability test was conducted according to GB / T 7755.1-2018 "Determination of Gas Permeability of Vulcanized Rubber or Thermoplastic Rubber"; the Mooney viscosity of the compound was tested according to GB / T 1232.1-2016 "Determination of Unvulcanized Rubber Using a Disc Shear Viscometer"; and the Mooney scorch performance was tested according to GB / T 1233-2008 "Determination of Initial Vulcanization Characteristics of Unvulcanized Rubber Using a Disc Shear Viscometer".

[0052] Table 1. Raw material mass parts of Examples 1-5 and Comparative Examples 1-6

[0053]

[0054] Remark:

[0055] ① Mitsui Chemicals, Inc. of Japan produces VNB-type EPDM rubber PX-006M, with a Mooney viscosity [ML1+4 (125℃)] of approximately 69MU, an ethylene content of 60%, and a third monomer VNB content of 1.5%.

[0056] ② Mitsui Chemicals, Inc. of Japan, VNB type EPDM rubber PX-008M, Mooney viscosity [ML1+4 (125℃)] about 48MU, ethylene content 60%, third monomer VNB content 1.5%, oil extrusion 15 parts by weight / 100 parts raw rubber;

[0057] ③ Mitsui Chemicals, Inc. of Japan, VNB type EPDM rubber PX-009M, Mooney viscosity [ML1+4 (100℃)] about 10MU, Mooney viscosity [ML1+4 (125℃)] about 2MU, ethylene content 60%, third monomer VNB content 1.5%;

[0058] ④ Arlanx Newco's ENB-type EPDM rubber Keltan 2650C has a Mooney viscosity [ML1+4 (125℃)] of approximately 25MU, an ethylene content of 46%, and a third monomer ENB content of 6.0%.

[0059] ⑤ Arlanx Newco's ENB-type ethylene propylene diene monomer (EPDM) rubber Keltan 2470C, with a Mooney viscosity [ML1+4 (125℃)] of approximately 22 MU, ethylene content of 70.5%, and ENB content of 4.5%;

[0060] ⑥ Arlanx Newco ENB type EPDM rubber Keltan 13561C, Mooney viscosity [ML1+4 (125℃)] approximately 135MU, ethylene content 56%, third monomer ENB content 5.5%, oil extrusion 15 parts by weight / 100 parts raw rubber;

[0061] ⑦ Wacker Chemie R401-80, a dimethylsiloxane-based solid silicone rubber, has a hardness of approximately 80 Shore A.

[0062] ⑧ Kumho Chemical Corporation of South Korea produces ethylene propylene diene monomer (EPDM) rubber KEP-110, with an ethylene content of 52% and a Mooney viscosity of [ML1+4 (125℃)].

[0063] The content of the third monomer is 0%, with a value of 40 MU.

[0064] ⑨ DOW Company's polyolefin elastomer Engage8842 has a specific gravity of 0.857 and a melt index (190℃ / 2.16kg) of [missing value].

[0065] At 1.0 g / 10 min, the Mooney viscosity [ML1+4 (121℃)] is approximately 25 MU.

[0066] ⑩ OCSiAl's pre-dispersed single-walled carbon nanotubes, with an effective carbon nanotube content of 5%, refined paraffin and mineral oil.

[0067] 85.5%, with a solid polymer content of 9.5%.

[0068] MAGRIS's flaky talc powder has a BET specific surface area of ​​approximately 20 m². 2 / g.

[0069] Cabot N330 carbon black has a particle size of 28-36 nanometers and a nitrogen adsorption surface area of ​​approximately 80 m². 2 / g; DBP oil absorption value approximately

[0070] 102cm 3 / 100g;

[0071] Cabot N774 carbon black has a particle size of 80-170 nanometers and a nitrogen adsorption surface area of ​​approximately 25-35 m². 2 / g; DBP oil absorption value is approximately 72cm³ 3 / 100g;

[0072] Grasse silica RS60 has a nitrogen adsorption surface area of ​​approximately 50–70 m². 2 / g; DBP oil absorption value is approximately 160cm³ 3 / 100g;

[0073] Grasse silica RS120 has a nitrogen adsorption surface area of ​​approximately 110–130 m². 2 / g; DBP oil absorption value approximately 245cm³ 3 / 100g;

[0074] Sunpar 2280 paraffin oil, open cup flash point 318℃, kinematic viscosity at 40℃ 481 mmHg 2 / s;

[0075] Ricon 154D from Clayville Corporation contains 65% polybutadiene, 35% calcium silicate carrier, 90% vinyl content, and has a molecular weight of 5200.

[0076] Shanghai Nixiang peroxide scorching inhibitor NF15 has an effective content of 75% and an inorganic carrier content of 25%.

[0077] Example 1

[0078] The preparation method of high-hardness EPDM compound for R744 refrigeration system includes the following steps:

[0079] (1) Put ethylene propylene rubber, silicone rubber and polyolefin elastomer into a mixer and stir for 10 minutes at a speed of 50 r / min. When the temperature of the mixer reaches 80℃, discharge the rubber compound. Adjust the roller gap of the open mill to 0.2 mm, make a triangular wrapping process 8 times, then adjust the roller gap to 4 mm, and then sheet and cool.

[0080] (2) Put the cooled rubber compound back into the internal mixer, then add processing aids, antioxidants, activators, pre-dispersed carbon nanotubes, and about 1 / 2 filler, and continue stirring at 30 r / min for 6 min.

[0081] (3) When the internal mixer reaches 90°C, add the remaining filler and plasticizer, and stir at 30 r / min until the internal mixer reaches 110°C.

[0082] (4) Put the compound obtained in step (3) into the open mill, adjust the speed of the open mill roller to 25 r / min, then adjust the roller gap to 0.3 mm, and use the turning machine to feed the material for 2 minutes; adjust the roller gap to 4 mm to discharge the sheet for cooling, and let it stand for 16 hours.

[0083] (5) Adjust the roller gap of the open mill to 2mm, adjust the roller speed of the open mill to 25r / min, after wrapping the roller, add the crosslinking agent and vulcanizing agent in multiple batches. After the material is consumed, cut the rubber on the left and right and pound the rubber 3 times each. Adjust the roller gap to 0.1mm, make a triangular wrapping and thin passage 6 times, then adjust the roller gap to 4mm, sheet out, cool, and obtain the compound rubber.

[0084] (6) After the high-hardness EPDM rubber compound obtained in step (5) is left to stand for 16 hours, it is subjected to first-stage vulcanization and second-stage vulcanization to obtain the high-hardness EPDM rubber compound.

[0085] The first stage of vulcanization involves a pressure of 15 MPa, a vulcanization temperature of 180℃, and a vulcanization time of 5 min; the second stage of vulcanization is performed in an oven at atmospheric pressure, with a vulcanization temperature of 180℃ and a vulcanization time of 6 h.

[0086] The first stage of vulcanization aims to achieve a certain degree of cross-linking in the ethylene propylene rubber (EPR) and serves as a shaping agent. Depending on the product specifications, a vulcanization pressure of 15 MPa and a vulcanization temperature of 180°C are selected. The vulcanization time is determined according to the optimal vulcanization time t90 measured by the vulcanizing apparatus. The second stage of vulcanization further and fully cross-links the EPR and simultaneously volatilizes low-molecular-weight compounds in the rubber compound, improving its physical and mechanical properties. The second stage of vulcanization can be carried out in an oven.

[0087] The performance test results of the obtained high-hardness EPDM rubber compound are shown in Table 2.

[0088] Example 2

[0089] The preparation method of high-hardness EPDM compound for R744 refrigeration system includes the following steps:

[0090] (1) Add oil-extended ethylene propylene rubber and polyolefin elastomer into a mixer and stir for 8 minutes at a speed of 40 r / min. When the temperature of the mixer reaches 70℃, discharge the rubber compound. Adjust the roller gap of the open mill to 0.2 mm, pass through the mill in a triangular shape 6 times, then adjust the roller gap to 4 mm, and then sheet and cool.

[0091] (2) Put the cooled rubber compound back into the internal mixer, then add processing aids, antioxidants, activators, pre-dispersed carbon nanotubes, and about 1 / 2 filler, and continue stirring at 30 r / min for 5 min.

[0092] (3) When the internal mixer reaches 90°C, add the remaining filler and plasticizer, and stir at 30 r / min until the internal mixer reaches 110°C.

[0093] (4) Put the compound obtained in step (3) into the open mill, adjust the speed of the open mill roller to 25 r / min, then adjust the roller gap to 0.3 mm, and use the turning machine to feed the material for 2 minutes; adjust the roller gap to 4 mm to discharge the sheet for cooling, and let it stand for 16 hours.

[0094] (5) Adjust the roller gap of the open mill to 2mm, adjust the roller speed of the open mill to 25r / min, after wrapping the roller, add the crosslinking agent and vulcanizing agent in multiple batches. After the material is consumed, cut the rubber on the left and right and pound the rubber 3 times each. Adjust the roller gap to 0.1mm, make a triangular wrapping and thin passage 6 times, then adjust the roller gap to 4mm, sheet out, cool, and obtain the compound rubber.

[0095] (6) After the high-hardness EPDM rubber compound obtained in step (5) is left to stand for 16 hours, it is subjected to first-stage vulcanization and second-stage vulcanization to obtain the high-hardness EPDM rubber compound.

[0096] The first stage of vulcanization involves a pressure of 15 MPa, a vulcanization temperature of 180℃, and a vulcanization time of 5 min; the second stage of vulcanization is performed in an oven at atmospheric pressure, with a vulcanization temperature of 180℃ and a vulcanization time of 6 h.

[0097] The performance test results of the obtained high-hardness EPDM rubber compound are shown in Table 2.

[0098] Example 3

[0099] The preparation method of high-hardness EPDM compound for R744 refrigeration system includes the following steps:

[0100] (1) Put the two types of ethylene propylene rubber and silicone rubber into a mixer and mix them together. Stir at a speed of 50 r / min for 12 min. When the temperature of the mixer reaches 80℃, discharge the rubber compound. Adjust the roller gap of the open mill to 0.2 mm, make a triangular wrapping and thin pass 8 times, then adjust the roller gap to 4 mm, and then sheet and cool.

[0101] (2) Put the cooled rubber compound back into the internal mixer, then add processing aids, antioxidants, activators, pre-dispersed carbon nanotubes, and about 1 / 2 filler, and continue stirring at a speed of 30 r / min for 8 min;

[0102] (3) When the internal mixer reaches 90°C, add the remaining filler and plasticizer, and stir at 30 r / min until the internal mixer reaches 110°C.

[0103] (4) Put the compound obtained in step (3) into the open mill, adjust the speed of the open mill roller to 25r / min, then adjust the roller gap to 0.3mm, and use the turning machine to feed the material for 3 minutes; adjust the roller gap to 4mm to discharge the sheet for cooling, and let it stand for 16 hours.

[0104] (5) Adjust the roller gap of the open mill to 2mm, adjust the roller speed of the open mill to 25r / min, after wrapping the roller, add the crosslinking agent and vulcanizing agent in multiple batches. After the material is consumed, cut the rubber on the left and right and pound the rubber 3 times each. Adjust the roller gap to 0.1mm, make a triangular wrapping and thin pass 8 times, then adjust the roller gap to 4mm, sheet out, cool, and obtain the compound rubber.

[0105] (6) After the high-hardness EPDM rubber compound obtained in step (5) is left to stand for 16 hours, it is subjected to first-stage vulcanization and second-stage vulcanization to obtain the high-hardness EPDM rubber compound.

[0106] The first stage of vulcanization involves a pressure of 15 MPa, a vulcanization temperature of 180℃, and a vulcanization time of 5 min; the second stage of vulcanization is performed in an oven at atmospheric pressure, with a vulcanization temperature of 180℃ and a vulcanization time of 6 h.

[0107] The performance test results of the obtained high-hardness EPDM rubber compound are shown in Table 2.

[0108] Example 4

[0109] The preparation method of high-hardness EPDM compound for R744 refrigeration system includes the following steps:

[0110] (1) Add the two types of ethylene propylene rubber, silicone rubber and polyolefin elastomer into the internal mixer and mix them. Stir at 50 r / min for 12 min. When the temperature of the internal mixer reaches 80℃, discharge the rubber compound. Adjust the roller gap of the open mill to 0.1 mm, make a triangular wrapping process 8 times, then adjust the roller gap to 4 mm, and then sheet and cool.

[0111] (2) Put the cooled rubber compound back into the internal mixer, then add the processing aid, antioxidant, activator, and about 2 / 3 of the filler, and continue to stir at a speed of 40 r / min for 8 min;

[0112] (3) When the internal mixer reaches 90°C, add the remaining filler and plasticizer, and stir at 30 r / min until the internal mixer reaches 110°C.

[0113] (4) Put the compound obtained in step (3) into the open mill, adjust the speed of the open mill roller to 25r / min, then adjust the roller gap to 0.3mm, and use the turning machine to feed the material for 3 minutes; adjust the roller gap to 4mm to discharge the sheet for cooling, and let it stand for 16 hours.

[0114] (5) Adjust the roller gap of the open mill to 2mm, adjust the roller speed of the open mill to 25r / min, after wrapping the roller, add the crosslinking agent and vulcanizing agent in multiple batches. After the material is consumed, cut the rubber on the left and right and pound the rubber 3 times each. Adjust the roller gap to 0.1mm, make a triangular wrapping and thin pass 8 times, then adjust the roller gap to 4mm, sheet out, cool, and obtain the compound rubber.

[0115] (6) After the high-hardness EPDM rubber compound obtained in step (5) is left to stand for 16 hours, it is subjected to first-stage vulcanization and second-stage vulcanization to obtain the high-hardness EPDM rubber compound.

[0116] The first stage of vulcanization involves a pressure of 15 MPa, a vulcanization temperature of 180℃, and a vulcanization time of 6 min; the second stage of vulcanization is performed in an oven at atmospheric pressure, with a vulcanization temperature of 150℃ and a vulcanization time of 4 h.

[0117] The performance test results of the obtained high-hardness EPDM rubber compound are shown in Table 2.

[0118] Example 5

[0119] The preparation method of high-hardness EPDM compound for R744 refrigeration system includes the following steps:

[0120] (1) Put the two types of ethylene propylene rubber into a mixer and mix them together. Stir at a speed of 25 r / min for 8 min. When the temperature of the mixer reaches 60℃, discharge the rubber compound. Adjust the roller gap of the open mill to 0.1 mm, make a triangular wrapping process 6 times, then adjust the roller gap to 4 mm, and then sheet and cool.

[0121] (2) Put the cooled rubber compound back into the internal mixer, then add the processing aid, antioxidant, activator, about 2 / 3 of the filler, and pre-dispersed carbon nanotubes and continue stirring at 30 r / min for 5 min;

[0122] (3) When the internal mixer reaches 90°C, add the remaining filler and plasticizer, and stir at 30 r / min until the internal mixer reaches 110°C.

[0123] (4) Put the compound obtained in step (3) into the open mill, adjust the speed of the open mill roller to 25r / min, then adjust the roller gap to 0.3mm, and use the turning machine to feed the material for 3 minutes; adjust the roller gap to 4mm to discharge the sheet for cooling, and let it stand for 16 hours.

[0124] (5) Adjust the roller gap of the open mill to 2mm, adjust the roller speed of the open mill to 25r / min, after wrapping the roller, add the crosslinking agent and vulcanizing agent in multiple batches. After the material is consumed, cut the rubber on the left and right and pound the rubber 3 times each. Adjust the roller gap to 0.1mm, make a triangular wrapping and thin pass 8 times, then adjust the roller gap to 4mm, sheet out, cool, and obtain the compound rubber.

[0125] (6) After the high-hardness EPDM rubber compound obtained in step (5) is left to stand for 16 hours, it is subjected to first-stage vulcanization and second-stage vulcanization to obtain the high-hardness EPDM rubber compound.

[0126] The first stage of vulcanization involves a pressure of 15 MPa, a vulcanization temperature of 180°C, and a vulcanization time of 5 min; the second stage of vulcanization is performed in an oven at atmospheric pressure, with a vulcanization temperature of 180°C and a vulcanization time of 4 h.

[0127] The performance test results of the obtained high-hardness EPDM rubber compound are shown in Table 2.

[0128] Comparative Example 1

[0129] The preparation method is the same as in Example 1, except that the ethylene propylene rubber used in the first step is a binary ethylene propylene rubber grade, and the content of the third monomer is zero. The performance test results of the obtained rubber compound are shown in Table 2.

[0130] Comparative Example 2

[0131] The preparation method is the same as in Example 2, except that the first step uses ENB-type oil-extended EPDM rubber. The performance test results of the resulting rubber compound are shown in Table 2.

[0132] Comparative Example 3

[0133] The preparation method is the same as in Example 3, except that pre-dispersed single-walled carbon nanotubes and sheet talc Hyperplate were not added to the filler. The performance test results of the obtained rubber compound are shown in Table 2.

[0134] Comparative Example 4

[0135] The preparation method is the same as in Example 4, except that silicone rubber R401-80 and polyolefin elastomer Engage8842 were not added to the ENB-type EPDM in the first step.

[0136] The performance tests of the obtained rubber compound products are shown in Table 2.

[0137] Comparative Example 5

[0138] The preparation method is the same as in Example 5, except that no silica was added to the filler. The performance test results of the obtained rubber compound are shown in Table 2.

[0139] Comparative Example 6

[0140] The preparation method is the same as in Example 3, except that titanium dioxide and peroxide vulcanization system anti-scorching agent are not added. The performance test results of the obtained rubber compound are shown in Table 2.

[0141] Table 2 Performance Testing of High-Hardness EPDM Compounds and Products

[0142]

[0143] Notes: ◎ Excellent; ○ Good; △ Satisfactory; × Poor

[0144] As can be seen from Tables 1 and 2:

[0145] (1) By comparing Example A-1 and Comparative Example B-1, Example A-1 used VNB-type EPDM. The crosslinked molecular chains of this type of ethylene propylene rubber are fully saturated, and the low content of the third monomer VNB can significantly accelerate the vulcanization speed and improve the degree of crosslinking. Example B-1 used ethylene-propylene copolymer binary rubber. The molecular chains are fully saturated, but the lack of a third monomer results in a slow vulcanization speed and a low degree of crosslinking. Therefore, the heat resistance of A-1 and B-1 is basically the same, but B-1 has a low degree of crosslinking and a large compression set value. The rubber sealing products prepared with B-1 are prone to leakage after long-term use.

[0146] (2) A comparison was made between Example A-2 and Comparative Example B-2. Example A-2 used oil-extended VNB-EPDM, while Example B-2 used oil-extended high Mooney ENB-EPDM. The special structure of VNB-EPDM allows its crosslinking speed and degree of crosslinking with a lower third monomer content to be comparable to those of higher ENB-EPDM. However, the crosslinked molecular chains of VNB-EPDM are more regular and lack some branches, so the high-temperature heat aging resistance of A-2 is significantly better than that of B-2. Meanwhile, for B-2, high Mooney raw rubber can significantly improve physical and mechanical properties such as tensile strength and elongation at break, but it will lead to a deterioration in processing performance.

[0147] (3) By comparing Example A-3 and Comparative Example B-3, it was found that Example A-3 added flaky talc (Hyperplate) to the filler in its formulation. Since R744 refrigerant is carbon dioxide with a relatively small molecular weight, this gas is more likely to permeate through the rubber, causing a certain degree of refrigerant leakage and affecting the performance and maintenance frequency of the refrigeration system. The addition of flaky talc to the rubber can significantly reduce the permeability of small molecule gases. Example B-3 did not add flaky filler, therefore its gas permeability increased significantly. Furthermore, because Example B-3 did not contain pre-dispersed single-walled carbon nanotubes with excellent thermal conductivity, its high-temperature aging performance was poor, and its physical and mechanical properties deteriorated significantly.

[0148] (4) By comparing Example A-4 and Comparative Example B-4, Example A-4 added silicone rubber and polyolefin elastomer materials to the ENB-EPDM formulation to improve the high-temperature heat aging resistance of the rubber material. Example B-4 showed a significant performance degradation after heat aging at 170℃, and the product's pressure relief burst resistance (foaming resistance) was also poor.

[0149] (5) By comparing Example A-5 and Comparative Example B-5, it was found that Example B-5 did not use an appropriate amount of silica in the filler, resulting in poor foaming resistance of the rubber material. Example A-5 used carbon black and silica of different particle sizes, and the coupling agent connected the silica and rubber molecules through chemical cross-linking bonds, which made the rubber material more resistant to decompression bursting, less prone to tearing when small gas molecules expand, and had good foaming resistance.

[0150] (6) By comparing Example A-3 and Comparative Example B-6, it was found that B-6 did not use either titanium dioxide or peroxide scorch inhibitor. Titanium dioxide can improve the high-temperature aging resistance of rubber materials, while the scorch inhibitor can significantly improve the Mooney scorch time of high-hardness rubber materials, thus significantly improving the safety performance of vulcanization processing. Therefore, B-6 has poor heat aging resistance and low processing safety performance.

[0151] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-hardness EPDM compound for a carbon dioxide refrigeration system, characterized in that, The high-hardness EPDM compound is composed of the following parts by weight: 100-150 parts of EPDM rubber 2-30 parts of silicone rubber 3-50 parts of polyolefin elastomer 150-200 parts of filler 5-20 parts of pre-dispersed carbon nanotubes 2-30 parts plasticizer Activator 1-20 parts Processing aids 1-8 parts Anti-aging agent 1-6 parts 1-8 parts of vulcanizing aid 2-10 parts of vulcanizing agent Anti-scorching agent 0.5~2 parts; The EPDM rubber has a Mooney viscosity [ML (1+4) 125℃] of 1~70MU; an ethylene content of 40~80%; and a third monomer content of 1~15%. The filler is composed of the following components by weight: 65-100 parts carbon black, 30-65 parts silica, 5-25 parts talc, 5-10 parts polytetrafluoroethylene (PTFE) micro powder, and 20 parts titanium dioxide. The carbon black is composed of various carbon blacks with different particle sizes and structures; the silica is composed of various silicas with different specific surface areas and structures; the average particle size of the carbon black is 10-500 nanometers, and the nitrogen adsorption specific surface area is 5-150 m². 2 / g, DBP oil absorption value 50~150cm 3 / 100g; the nitrogen adsorption specific surface area of ​​the precipitated silica is 20~300 m². 2 / g, DBP oil absorption value 50~400cm 3 / 100g; the talc powder is in flake form with a specific surface area of ​​10~30 m². 2 / g; The activator is composed of zinc oxide, magnesium oxide, and a coupling agent; the zinc oxide is active zinc oxide with an effective content greater than 90%; the magnesium oxide is active magnesium oxide with an iodine uptake value greater than 40; the coupling agent includes one or more of aminosilane, epoxysilane, vinylsilane, sulfur-containing silane, acylsilane, alkylsilane, and piperazine silane.

2. The high-hardness EPDM compound for a carbon dioxide refrigeration system as described in claim 1, characterized in that, The EPDM rubber includes one or more of ENB-EPDM, VNB-EPDM, and DCPD-EPDM.

3. The high-hardness EPDM compound for a carbon dioxide refrigeration system as described in claim 1, characterized in that, The silicone rubber is a high-temperature vulcanized silicone rubber.

4. The high-hardness EPDM compound for a carbon dioxide refrigeration system as described in claim 1, characterized in that, The polyolefin elastomer has a specific gravity of 0.8~0.9, a hardness of 50~90 Shore A, and a melt index of 0.5~40 g / 10 min under test conditions of 190℃ and 2.16 kg load.

5. The high-hardness EPDM compound for a carbon dioxide refrigeration system as described in claim 1, characterized in that, The vulcanizing aids are trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, N,N′-p-phenylbismaleimide, zinc diacrylate, zinc dimethacrylate, triallyl cyanurate, triallyl isocyanurate, 1,2-polybutadiene, and sulfur.

6. The high-hardness EPDM compound for a carbon dioxide refrigeration system as described in claim 1, characterized in that, The vulcanizing agent is: dicumyl peroxide, 2,5-di(tert-butylperoxy)-2,5-dimethylhexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyn-3, m / p-di(tert-butylperoxy)diisopropylbenzene, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(tert-butylperoxy)cyclohexane, n-butyl 4,4-di(tert-butylperoxy)valerate, ethyl 3,3-di(tert-butylperoxy)butyrate, tert-butylcumyl peroxide, 3,3,5,7,7-pentamethyl-1,2-dimethylperoxybenzene, and 2,3-dimethyl-2,3-dimethylperoxybutyrate. 4-Trioxane, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane; one or more of the following: di-tert-amyl peroxide, tert-butyl peroxycarbonate-2-ethylhexyl ester, polyether polytert-butyl peroxycarbonate, tert-butyl peroxybenzoate, tert-butyl peroxyacetic acid, tert-butyl peroxymaleic acid, di(4-methylbenzoyl) peroxide, benzoyl peroxide, di(2,4-dichlorobenzoyl) peroxide, dilauryl peroxide, cumene hydroperoxide, and di(4-tert-butylcyclohexyl) peroxydicarbonate.

7. A method for preparing a high-hardness EPDM compound for a carbon dioxide refrigeration system as described in claim 1, characterized in that, The preparation method steps are as follows: (1) Put EPDM rubber, silicone rubber and polyolefin elastomer into a mixer and stir at a speed of 20~50r / min for 8~12min. When the temperature of the mixer reaches 60~80℃, discharge the rubber compound, adjust the roller gap of the open mill to 0.1~0.3mm, make a triangular wrapping and thin pass 6~8 times, then adjust the roller gap to 2~4mm, and then sheet and cool. (2) Put the cooled rubber compound back into the internal mixer, then add processing aids, antioxidants, activators, pre-dispersed carbon nanotubes, and 1 / 2 to 2 / 3 of the filler, and continue stirring at a speed of 20 to 50 r / min for 5 to 10 min; (3) When the internal mixer reaches 70~100℃, add the remaining filler and plasticizer, and stir at a speed of 20~50r / min until the internal mixer reaches 110~130℃. (4) Put the compound obtained in step (3) into the open mill, adjust the speed of the open mill rollers to 20~30 r / min, then adjust the roller gap to 0.3~0.6mm, and use the turning machine to feed the material for 2~4 minutes; adjust the roller gap to 2~4mm to discharge the sheet and cool it, and let it stand for 16~24 hours. (5) Adjust the roller gap of the open mill to 2~4mm, adjust the roller speed of the open mill to 20~30 r / min, after wrapping the roller, add vulcanizing aid and vulcanizing agent in multiple batches. After the material is consumed, cut the rubber on the left and right and pound the rubber 2~5 times each. Adjust the roller gap to 0.1~0.3mm, make triangular wrapping and thin passage 6~8 times, then adjust the roller gap to 2~4mm, sheet out, cool, and obtain the compound rubber. (6) After the high-hardness EPDM rubber compound obtained in step (5) is left to stand for 12~24h, it is subjected to first-stage vulcanization and second-stage vulcanization to obtain the high-hardness EPDM rubber compound; wherein, the pressure of the first-stage vulcanization is 10~15MPa, the vulcanization temperature is 160~190℃, and the vulcanization time is 5~15min; the second-stage vulcanization is vulcanization at normal pressure in an oven, the vulcanization temperature is 150~190℃, and the vulcanization time is 1~10h.

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