Refrigerant-resistant EPDM sealing ring and preparation method thereof

Abstract

The invention relates to the technical field of rubber sealing materials, and particularly discloses a refrigerant-resistant EPDM (Ethylene-Propylene-Diene Monomer) sealing ring and a preparation method thereof. The refrigerant-resistant EPDM sealing ring is prepared from the following raw materials: ethylene propylene diene monomer, N-550 carbon black, stearic acid modified carbon black, paraffin oil, stearic acid, zinc oxide, an anti-aging agent, a cross-linking agent and a vulcanizing agent. Wherein the polyvinyl alcohol and the stearic acid are used for sequentially modifying the N-774 carbon black and cross-linking the polyvinyl alcohol and rubber molecules, so that the mechanical property of the material is enhanced, and the stearic acid is used for modifying the N-774 carbon black, so that the independent addition amount of the stearic acid can be reduced, and the adverse effect on the material caused by excessive stearic acid is reduced. The polyvinyl alcohol and the stearic acid have a synergistic effect, so that the N-774 carbon black is uniformly dispersed in a rubber matrix, a compact and uniform filling effect is formed, permeation of a refrigerant to the material can be reduced, and the service life of the sealing ring is prolonged.

Description

Technical Field

[0001] The present application relates to the technical field of rubber sealing materials, and in particular to a refrigerant-resistant EPDM sealing ring and a preparation method thereof. Background Art

[0002] In modern industry and electronics, seals are a key sealing component that is widely used in various devices and systems, especially in scenarios where liquid leakage or gas penetration needs to be prevented. With the development of technology, the performance requirements for seals are getting higher and higher, especially in terms of tolerance in special environments, such as high temperature resistance and solvent resistance.

[0003] In the computer CPU cooling system, the role of the sealing ring is particularly important. The system usually uses solvents such as ethylene glycol and propylene glycol as coolants. These solvents have good thermal conductivity, but they also pose severe challenges to the materials of the sealing ring. Traditional sealing ring materials are prone to swelling, deformation, or even damage when exposed to these solvents for a long time, which can cause coolant leakage and affect the normal operation of the system.

[0004] The existing sealing ring preparation process usually uses specially adjusted EPDM (ethylene propylene diene monomer) raw materials to mix with each other to make rubber raw materials, and then forms them in a high-temperature and high-pressure mold. Although the products produced by this formula have certain tensile strength and low compression permanent deformation performance, their tolerance is still limited when working in ethylene glycol and propylene glycol solutions for a long time. Especially in high temperature environments, the performance of the sealing ring will further decline, resulting in a shortened service life, which cannot meet the full life cycle requirements of the computer CPU cooling system for the sealing ring. Summary of the invention

[0005] In order to improve the tolerance of EPDM sealing rings to ethylene glycol and propylene glycol solutions, the present application provides a refrigerant-resistant EPDM sealing ring and a preparation method thereof.

[0006] In the first aspect, the present application provides a refrigerant-resistant EPDM sealing ring, which adopts the following technical solution: a refrigerant-resistant EPDM sealing ring, which is prepared by weight from the following raw materials: 110-140 parts of EPDM rubber, 50-60 parts of N-550 carbon black, 10-20 parts of stearic acid modified carbon black, 3-7 parts of paraffin oil, 0.6-0.8 parts of stearic acid, 5.5-7.5 parts of zinc oxide, 0.5-1.5 parts of antioxidant, 1-1.3 parts of crosslinking agent, and 4-6 parts of vulcanizing agent; the raw materials for preparing the stearic acid modified carbon black include N-774 carbon black, polyvinyl alcohol, stearic acid and crosslinking agent, and the weight ratio of the N-774 carbon black, polyvinyl alcohol, stearic acid and crosslinking agent is 10:(2-4):(0.3-0.5):(0.12-0.18).

[0007] By adopting the above technical scheme, the sealing ring of the present application adopts EPDM as the base material, and adopts N-550 carbon black and stearic acid modified carbon black to synergistically enhance the EPDM. Among them, the hydroxyl group on the surface of N-774 carbon black reacts with the hydroxyl group of polyvinyl alcohol, so that polyvinyl alcohol is successfully grafted on the surface of N-774 carbon black. In addition, the carboxyl group of stearic acid reacts with the hydroxyl group of N-774 carbon black, thereby connecting stearic acid to the surface of N-774 carbon black. Polyvinyl alcohol reacts with the active group on the rubber molecular chain under the action of the crosslinking agent to form a covalent bond connection, thereby achieving chemical crosslinking between the two, thereby enhancing the mechanical properties of the material, such as tensile strength, tear strength, etc., and can also improve its aging resistance, solvent resistance, etc. In addition, since excessive addition of carbon black will affect the hardness of EPDM, the present application adopts N-550 carbon black and stearic acid modified carbon black for compounding, which can reduce the compression permanent deformation performance of rubber while increasing the hardness of rubber. Stearic acid can improve the dispersion of various raw materials in EPDM rubber, allowing it to penetrate into the EPDM macromolecular chain to form a stable network structure to improve the tensile strength, hardness and other mechanical properties of the material. In addition, the use of stearic acid to modify N-774 carbon black can reduce the amount of stearic acid added alone, thereby reducing the adverse effects of excessive stearic acid on the material. Vulcanizing agents and zinc oxide can increase the vulcanization speed and cross-linking degree, making the EPDM rubber have a higher degree of vulcanization. Paraffin oil has good compatibility with EPDM rubber and can improve the processing performance of EPDM rubber.

[0008] Preferably, the preparation method of the stearic acid modified carbon black is: (1) dissolving polyvinyl alcohol in deionized water to obtain a polyvinyl alcohol solution, adding N-774 carbon black and a crosslinking agent to the polyvinyl alcohol solution at 40-50° C., stirring for reaction for 2-3 hours, and drying to obtain polyvinyl alcohol grafted carbon black; (2) Dispersing stearic acid in ethanol at 80-100° C. to obtain a dispersion, then adding polyvinyl alcohol grafted carbon black to the dispersion and reacting for 25-35 minutes to obtain stearic acid modified carbon black.

[0009] Preferably, the cross-linking agent in step (1) is glutaraldehyde.

[0010] By adopting the above technical solution, N-774 carbon black is modified with polyvinyl alcohol and stearic acid to reduce the agglomeration state of N-774 carbon black, so that it is more evenly dispersed in the rubber matrix, forming a dense and uniform filling effect, which can reduce the penetration of refrigerant into the material, thereby improving the sealing ring's tolerance to ethylene glycol and propylene glycol solutions. The modified carbon black chemically bonds with EPDM rubber to form an organic-inorganic hybrid reinforcement system, which has a good reinforcement effect on the EPDM rubber airway.

[0011] Preferably, the EPDM rubber is prepared by mixing ARLANXEO 10660C EPDM rubber and ARLANXEO 4869C EPDM rubber in a weight ratio of (9-11):(2-3).

[0012] By adopting the above technical solution, the EPDM rubber in the present application is prepared by mixing two different types of EPDM rubber raw materials, and the prepared material has good chemical corrosion resistance and durability.

[0013] Preferably, the antioxidant is at least one of antioxidant RD, antioxidant MB, antioxidant MTI, antioxidant 445, and antioxidant 264.

[0014] By adopting the above technical solution, adding an antioxidant can improve the heat resistance of EPDM rubber, delay the aging of EPDM rubber, and extend the service life of the sealing ring.

[0015] Preferably, the vulcanizing agent is at least one of di-tert-butyl peroxide diisopropylbenzene, N,N'-bisfurfurylideneacetone, and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0016] By adopting the above technical solution, the vulcanizing agent can form a uniform and stable cross-linked network structure during the vulcanization process, thereby improving the strength and elasticity of the sealing ring. An appropriate amount of vulcanizing agent can ensure that the vulcanization reaction is complete without causing excessive cross-linking and causing the material to become brittle and hard.

[0017] Preferably, the cross-linking agent is at least one of triallyl isocyanurate, triallyl cyanurate and cross-linking agent CA94-50.

[0018] By adopting the above technical solution, the cross-linking agent forms a stable three-dimensional network structure in the EPDM rubber, which can effectively improve the tensile strength, tensile stress and tear strength of the rubber. At the same time, it further enhances the sealing ring's tolerance to refrigerants such as ethylene glycol and propylene glycol.

[0019] Preferably, the particle size of the N-550 carbon black is 40-60 nm, and the particle size of the N-774 carbon black is 110-120 nm.

[0020] By adopting the above technical solution, carbon black with different particle sizes can be filled in the rubber matrix more evenly and can form more bonding points with the rubber molecules, thereby providing a stronger reinforcement effect.

[0021] In the second aspect, the present application provides a method for preparing a refrigerant-resistant EPDM sealing ring using the following technical solution: A method for preparing a refrigerant-resistant EPDM sealing ring comprises the following steps: S1: weighing raw materials according to the component ratio, melt-mixing EPDM rubber, N-550 carbon black, stearic acid-modified carbon black, paraffin oil, stearic acid, zinc oxide, and antioxidant at 120-130° C. to obtain a premix; then uniformly mixing the premix with a crosslinking agent and a vulcanizing agent, vulcanizing at 120-160° C., and obtaining refrigerant-resistant EPDM particles after the reaction is completed; S2: Inject refrigerant-resistant EPDM particles into a mold using a molding device to obtain a sealing ring blank; place the sealing ring blank in a high-pressure reactor, introduce supercritical N2, foam and mold it in an environment with a pressure of 22-26Mpa, and keep it warm for 1-2h to obtain a refrigerant-resistant EPDM sealing ring.

[0022] Preferably, the vulcanization in step S1 includes a first vulcanization and a second vulcanization, wherein the first vulcanization temperature is 150-160°C, the time is 10-20 min, and the pressure is 13-17 MPa; the second vulcanization temperature is 120-140°C, the time is 30-40 min, and the pressure is 8-10 MPa.

[0023] By adopting the above technical solution, the above preparation method can evenly disperse N-550 carbon black and stearic acid modified carbon black in the EPDM rubber matrix, form a three-dimensional cross-linked network after vulcanization, improve the density of the rubber matrix, and the prepared sealing ring maintains good tolerance to ethylene glycol and propylene glycol at high temperature. In addition, the use of two-stage vulcanization can further increase the cross-linking density of the rubber, reduce the number of small molecules, and reduce compression permanent deformation.

[0024] In summary, the present application includes at least one of the following beneficial technical effects: The sealing ring of the present application adopts EPDM as the base material, and adopts N-550 carbon black and stearic acid modified carbon black to synergistically enhance the EPDM. Among them, the hydroxyl group on the surface of N-774 carbon black reacts with the hydroxyl group of polyvinyl alcohol, so that polyvinyl alcohol is successfully grafted on the surface of N-774 carbon black. In addition, the carboxyl group of stearic acid reacts with the hydroxyl group of N-774 carbon black, thereby connecting stearic acid to the surface of N-774 carbon black. Under the action of the crosslinking agent, polyvinyl alcohol reacts with the active group on the rubber molecular chain to form a covalent bond connection, thereby achieving chemical crosslinking between the two, thereby enhancing the mechanical properties of the material, such as tensile strength, tear strength, etc., and can also improve its aging resistance, solvent resistance, etc. In addition, since excessive addition of carbon black will affect the hardness of EPDM, the present application adopts N-550 carbon black and stearic acid modified carbon black for compounding, which can reduce the compression permanent deformation performance of rubber while increasing the hardness of rubber. Stearic acid can improve the dispersion of various raw materials in EPDM rubber, allowing it to penetrate into the EPDM macromolecular chain to form a stable network structure to improve the tensile strength, hardness and other mechanical properties of the material. In addition, the use of stearic acid to modify N-774 carbon black can reduce the amount of stearic acid added alone, thereby reducing the adverse effects of excessive stearic acid on the material. Vulcanizing agents and zinc oxide can increase the vulcanization speed and cross-linking degree, making the EPDM rubber have a higher degree of vulcanization. Paraffin oil has good compatibility with EPDM rubber and can improve the processing performance of EPDM rubber. DETAILED DESCRIPTION

[0025] The present application is further described in detail below with reference to the embodiments.

[0026] Preparation Example Preparation Example 1 Stearic acid modified carbon black: (1) 20 g of polyvinyl alcohol (Changchen 9002-89-5) was dissolved in 100 mL of deionized water to obtain a polyvinyl alcohol solution, 100 g of N-774 carbon black and 1.2 g of glutaraldehyde were added to the polyvinyl alcohol solution at 40° C., stirred for reaction for 2 h, and dried to obtain polyvinyl alcohol grafted carbon black; (2) 3 g of stearic acid was dispersed in ethanol at 80° C. to obtain a dispersion, and then polyvinyl alcohol grafted carbon black was added to the dispersion and reacted for 25 minutes to obtain stearic acid modified carbon black.

[0027] Preparation Example 2 Stearic acid modified carbon black: (1) 30 g of polyvinyl alcohol (Changchen 9002-89-5) was dissolved in 100 mL of deionized water to obtain a polyvinyl alcohol solution, 100 g of N-774 carbon black and 1.5 g of glutaraldehyde were added to the polyvinyl alcohol solution at 45° C., stirred for reaction for 2.5 h, and dried to obtain polyvinyl alcohol grafted carbon black; (2) 4 g of stearic acid was dispersed in ethanol at 90° C. to obtain a dispersion, and then polyvinyl alcohol grafted carbon black was added to the dispersion and reacted for 30 minutes to obtain stearic acid modified carbon black.

[0028] Preparation Example 3 Stearic acid modified carbon black: (1) 40 g of polyvinyl alcohol (Changchen 9002-89-5) was dissolved in 100 mL of deionized water to obtain a polyvinyl alcohol solution, 100 g of N-774 carbon black and 1.8 g of glutaraldehyde were added to the polyvinyl alcohol solution at 50° C., stirred for reaction for 3 h, and dried to obtain polyvinyl alcohol grafted carbon black; (2) Dispersing 5 g of stearic acid in ethanol at 100° C. to obtain a dispersion, then adding polyvinyl alcohol grafted carbon black to the dispersion and reacting for 35 minutes to obtain stearic acid modified carbon black.

[0029] Preparation Example 4 The difference between this preparation example and preparation example 2 is that an equal amount of isobutyraldehyde is used instead of glutaraldehyde in step (1).

[0030] Preparation Example 5 The difference between this preparation example and preparation example 2 is that in step (1), an equal amount of N-550 carbon black is used instead of N-774 carbon black. Example

[0031] Example 1 A refrigerant-resistant EPDM sealing ring comprises the following raw materials: 900g EPDM rubber (ARLANXEO 10660C), 200g EPDM rubber (ARLANXEO 4869C), 500g N-550 carbon black, 100g stearic acid modified carbon black (prepared in Preparation Example 1), 30g paraffin oil, 6g stearic acid, 55g zinc oxide (ZNO-80), 3g antioxidant RD and 2g antioxidant MB, 10g triallyl cyanurate, 40g N,N'-disfurfurylideneacetone.

[0032] The method for preparing the refrigerant-resistant EPDM sealing ring of this embodiment comprises the following steps: First, the raw materials are weighed according to the component ratio, and ethylene propylene diene monomer rubber, N-550 carbon black, stearic acid modified carbon black, paraffin oil, stearic acid, zinc oxide, antioxidant RD and antioxidant MB are melt-kneaded at 120° C. to obtain a premix; then the premix is ​​uniformly mixed with triallyl cyanurate and N,N'-difurfurylideneacetone, and the first vulcanization is carried out at 150° C. and a pressure of 13 MPa for 10 min, and then the second vulcanization is carried out at 120° C. and a pressure of 8 MPa for 30 min, and after the reaction is completed, refrigerant-resistant EPDM particles are obtained; then, the refrigerant-resistant EPDM particles are injected into a mold using a molding device to obtain a sealing ring blank; finally, the sealing ring blank is placed in a high-pressure reactor, supercritical N2 is introduced, and foaming is carried out in an environment with a pressure of 22 MPa, and the temperature is kept for 1 hour to obtain a refrigerant-resistant EPDM sealing ring.

[0033] Example 2 A refrigerant-resistant EPDM sealing ring comprises the following raw materials: 1000g EPDM rubber (ARLANXEO 10660C), 300g EPDM rubber (ARLANXEO 4869C), 550g N-550 carbon black, 150g stearic acid modified carbon black (prepared in Preparation Example 2), 50g paraffin oil, 7g stearic acid, 65g zinc oxide (ZNO-80), 10g antioxidant 445, 12g triallyl isocyanurate, 50g di-tert-butyl peroxide diisopropylbenzene.

[0034] The method for preparing the refrigerant-resistant EPDM sealing ring of this embodiment comprises the following steps: First, the raw materials are weighed according to the component ratio, and ethylene propylene diene monomer rubber, N-550 carbon black, stearic acid modified carbon black, paraffin oil, stearic acid, zinc oxide, and antioxidant 445 are melt-kneaded at 125° C. to obtain a premix; then the premix is ​​uniformly mixed with triallyl isocyanurate and di-tert-butyl peroxide diisopropylbenzene, and the first vulcanization is carried out at 155° C. and a pressure of 15 MPa for 15 min, and then the second vulcanization is carried out at 130° C. and a pressure of 9 MPa for 35 min. After the reaction is completed, refrigerant-resistant EPDM particles are obtained; then, the refrigerant-resistant EPDM particles are injected into a mold using a molding device to obtain a sealing ring blank; finally, the sealing ring blank is placed in a high-pressure reactor, supercritical N2 is introduced, and foaming is carried out in an environment with a pressure of 24 MPa, and the temperature is kept for 1.5 hours to obtain a refrigerant-resistant EPDM sealing ring.

[0035] Example 3 A refrigerant-resistant EPDM sealing ring comprises the following raw materials: 1100g EPDM rubber (ARLANXEO 10660C), 250g EPDM rubber (ARLANXEO 4869C), 600g N-550 carbon black, 200g stearic acid modified carbon black (prepared in Preparation Example 3), 70g paraffin oil, 8g stearic acid, 65g zinc oxide (ZNO-80), 15g antioxidant 264, 13g crosslinking agent CA94-50, 60g 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0036] The method for preparing the refrigerant-resistant EPDM sealing ring of this embodiment comprises the following steps: First, the raw materials are weighed according to the component ratio, and ethylene propylene diene monomer rubber, N-550 carbon black, stearic acid modified carbon black, paraffin oil, stearic acid, zinc oxide, and antioxidant 264 are melt-kneaded at 130° C. to obtain a premix; then the premix is ​​uniformly mixed with a cross-linking agent CA94-50 and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, and the first vulcanization is performed at 160° C. and a pressure of 17 MPa for 20 min, and then the second vulcanization is performed at 140° C. and a pressure of 10 MPa for 40 min. After the reaction is completed, refrigerant-resistant EPDM particles are obtained; then, the refrigerant-resistant EPDM particles are injected into a mold using a molding device to obtain a sealing ring blank; finally, the sealing ring blank is placed in a high-pressure reactor, supercritical N2 is introduced, and foaming is performed in an environment with a pressure of 26 MPa, and the temperature is kept for 2 hours to obtain a refrigerant-resistant EPDM sealing ring.

[0037] Example 4 The difference between this embodiment and embodiment 2 is that the stearic acid modified carbon black prepared in preparation example 4 is used.

[0038] Comparative Example Comparative Example 1 A refrigerant-resistant EPDM sealing ring, which differs from Example 2 in that the stearic acid-modified carbon black prepared in Preparation Example 5 is used.

[0039] Comparative Example 2 A refrigerant-resistant EPDM sealing ring, which differs from Example 2 in that an equal amount of N-774 carbon black is used instead of stearic acid-modified carbon black.

[0040] Comparative Example 3 A refrigerant-resistant EPDM sealing ring, which differs from Example 2 in that an equal amount of oleic acid-modified carbon black is used instead of stearic acid-modified carbon black.

[0041] Wherein, the preparation method of oleic acid modified carbon black is: (1) 30 g of polyvinyl alcohol (Changchen 9002-89-5) was dissolved in 100 mL of deionized water to obtain a polyvinyl alcohol solution, 100 g of N-774 carbon black and 1.5 g of glutaraldehyde were added to the polyvinyl alcohol solution at 45° C., stirred for reaction for 2.5 h, and dried to obtain polyvinyl alcohol grafted carbon black; (2) 4 g of oleic acid was dispersed in ethanol at 90° C. to obtain a dispersion, and then polyvinyl alcohol grafted carbon black was added to the dispersion and reacted for 30 minutes to obtain oleic acid-modified carbon black.

[0042] Comparative Example 4 A refrigerant-resistant EPDM sealing ring, which differs from Example 2 in that an equal amount of polyvinyl alcohol grafted carbon black is used instead of stearic acid modified carbon black.

[0043] Wherein, the preparation method of polyvinyl alcohol grafted carbon black is: Dissolve 30g of polyvinyl alcohol (Changchen 9002-89-5) in 100mL of deionized water to obtain a polyvinyl alcohol solution. Add 100g of N-774 carbon black and 1.5g of glutaraldehyde to the polyvinyl alcohol solution at 45°C, stir and react for 2.5h, and dry to obtain polyvinyl alcohol grafted carbon black.

[0044] Comparative Example 5 A refrigerant-resistant EPDM sealing ring, which differs from Example 2 in that no N-550 carbon black is added.

[0045] Comparative Example 6 A refrigerant-resistant EPDM sealing ring, which differs from Example 2 in that stearic acid-modified carbon black is not added.

[0046] Comparative Example 7 A refrigerant-resistant EPDM sealing ring, which differs from Example 2 in that N-550 carbon black and stearic acid-modified carbon black are not added.

[0047] Performance testing The refrigerant-resistant EPDM sealing rings prepared in Examples 1-4 and Comparative Examples 1-7 were subjected to hardness test, compression set test, tensile strength test, elongation at break test, weather resistance test, and high and low temperature resistance test. The test results are recorded in Table 1.

[0048] Hardness test: According to GB / T 531.2-2009 standard, the obtained refrigerant-resistant EPDM sealing ring is subjected to a hardness test.

[0049] Permanent deformation test: According to GB / T7759.2-2014 standard, it is expressed by testing its 0℃ / 72h compression permanent deformation percentage.

[0050] Tensile strength and elongation at break: The tensile strength and elongation at break were tested according to ASTM-D3574-08.

[0051] Weather resistance: According to GB T 3511-2018 and GB / T16422.2-2014, irradiate the sample for 168 hours, test and calculate the performance retention percentage of its tensile strength in %.

[0052] High and low temperature resistance test: The refrigerant-resistant sealing ring for new energy vehicle air conditioning prepared in the embodiments and comparative examples was placed in a 100°C environment for 5 hours, then placed in a -20°C environment for 5 hours, and cycled 100 times. The tensile strength performance retention percentage was tested and calculated in %.

[0053] Table 1 According to the data in Example 2 and Example 4 and Table 1, the two aldehyde groups in the glutaraldehyde molecule can react with more hydroxyl groups, so that the reaction between glutaraldehyde and polyvinyl alcohol is faster and it is easier to form a cross-linked product. Therefore, the modification effect of polyvinyl alcohol on N-774 carbon black in Example 2 is more obvious, forming a stable three-dimensional network structure, which can effectively improve the tensile strength, tensile stress and tear strength of the rubber, and at the same time, enhance the sealing ring's tolerance to refrigerants such as ethylene glycol and propylene glycol.

[0054] According to the data in Example 2, Comparative Example 1 and Table 1, it can be seen that adding N-550 carbon black alone will have an adverse effect on the hardness of EPDM rubber. However, compounding N-550 carbon black with stearic acid modified carbon black can increase the hardness of rubber while reducing the compression permanent deformation performance of rubber.

[0055] According to the data in Example 2, Comparative Example 2 and Table 1, it can be seen that N-774 carbon black is easily agglomerated when added to EPDM rubber without modification, thereby affecting the performance of the material. However, the modified N-774 carbon black can be evenly dispersed in the rubber matrix to form a stable three-dimensional network structure, which can effectively improve the tensile strength, tensile stress and tear strength of the rubber, and at the same time, further enhance the tolerance of the sealing ring to refrigerants such as ethylene glycol and propylene glycol.

[0056] According to the data in Example 2, Comparative Examples 3-4 and Table 1, it can be seen that polyvinyl alcohol and stearic acid are used to synergistically modify N-774 carbon black, so that polyvinyl alcohol and stearic acid are grafted onto the surface of carbon black at the same time. Among them, polyvinyl alcohol forms chemical crosslinks with rubber molecules, thereby enhancing the mechanical properties of the material, such as tensile strength, tear strength, etc., and can also improve its aging resistance and solvent resistance; stearic acid is used to modify N-774 carbon black, which can reduce the amount of stearic acid added alone, thereby reducing the adverse effects of excessive stearic acid on the material, thereby improving the compatibility of N-774 carbon black with rubber.

[0057] According to the data in Example 2, Comparative Examples 5-7 and Table 1, it can be seen that N-550 carbon black and stearic acid modified carbon black are used to synergistically reinforce EPDM rubber. N-550 carbon black has a good dispersion effect, which can increase the hardness and strength of the sealing ring, while stearic acid modified carbon black forms a dense and uniform filling effect in the rubber, which can reduce the penetration of refrigerant into the material, thereby improving the sealing ring's tolerance to ethylene glycol and propylene glycol solutions.

[0058] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A refrigerant-resistant EPDM sealing ring, characterized in that: The invention is prepared from the following raw materials by weight: 110-140 parts of EPDM rubber, 50-60 parts of N-550 carbon black, 10-20 parts of stearic acid modified carbon black, 3-7 parts of paraffin oil, 0.6-0.8 parts of stearic acid, 5.5-7.5 parts of zinc oxide, 0.5-1.5 parts of antioxidant, 1-1.3 parts of crosslinking agent, 4-6 parts of vulcanizing agent; The raw materials for preparing the stearic acid modified carbon black include N-774 carbon black, polyvinyl alcohol, stearic acid and a crosslinking agent, and the weight ratio of the N-774 carbon black, polyvinyl alcohol, stearic acid and the crosslinking agent is 10: (2-4): (0.3-0.5): (0.12-0.18).

2. A refrigerant-resistant EPDM sealing ring according to claim 1, characterized in that: The preparation method of the stearic acid modified carbon black is: (1) dissolving polyvinyl alcohol in deionized water to obtain a polyvinyl alcohol solution, adding N-774 carbon black and a crosslinking agent to the polyvinyl alcohol solution at 40-50° C., stirring for 2-3 hours, and drying to obtain polyvinyl alcohol grafted carbon black; (2) dispersing stearic acid in ethanol at 80-100° C. to obtain a dispersion, then adding polyvinyl alcohol grafted carbon black to the dispersion and reacting for 25-35 minutes to obtain stearic acid modified carbon black; The cross-linking agent in step (1) is glutaraldehyde.

3. The refrigerant-resistant EPDM sealing ring according to claim 1, characterized in that: The EPDM rubber is prepared by mixing ARLANXEO 10660C EPDM rubber and ARLANXEO 4869C EPDM rubber in a weight ratio of (9-11):(2-3).

4. The refrigerant-resistant EPDM sealing ring according to claim 1, characterized in that: The antioxidant is at least one of antioxidant RD, antioxidant MB, antioxidant MTI, antioxidant 445, and antioxidant 264.

5. The refrigerant-resistant EPDM sealing ring according to claim 1, characterized in that: The vulcanizing agent is at least one of di-tert-butyl peroxide diisopropylbenzene, N,N'-bisfurfurylideneacetone and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

6. The refrigerant-resistant EPDM sealing ring according to claim 1, characterized in that: The cross-linking agent is at least one of triallyl isocyanurate, triallyl cyanurate and cross-linking agent CA94-50.

7. The refrigerant-resistant EPDM sealing ring according to claim 1, characterized in that: The particle size of the N-550 carbon black is 40-60 nm, and the particle size of the N-774 carbon black is 110-120 nm.

8. A method for preparing a refrigerant-resistant EPDM sealing ring according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: weighing raw materials according to the component ratio, melt-mixing EPDM rubber, N-550 carbon black, stearic acid-modified carbon black, paraffin oil, stearic acid, zinc oxide, and antioxidant at 120-130° C. to obtain a premix; then uniformly mixing the premix with a crosslinking agent and a vulcanizing agent, vulcanizing at 120-160° C., and obtaining refrigerant-resistant EPDM particles after the reaction is completed; S2: Inject refrigerant-resistant EPDM particles into a mold using a molding device to obtain a sealing ring blank; place the sealing ring blank in a high-pressure reactor, introduce supercritical N2, foam and mold it in an environment with a pressure of 22-26Mpa, and keep it warm for 1-2h to obtain a refrigerant-resistant EPDM sealing ring.

9. The method for preparing a refrigerant-resistant EPDM sealing ring according to claim 8, characterized in that: The vulcanization in step S1 includes a first vulcanization and a second vulcanization. The first vulcanization temperature is 150-160° C., the time is 10-20 min, and the pressure is 13-17 MPa; the second vulcanization temperature is 120-140° C., the time is 30-40 min, and the pressure is 8-10 MPa.

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