EPDM sealing ring material for glycol refrigerant and preparation method thereof

Abstract

This invention belongs to the technical field of rubber sealing materials, specifically relating to an EPDM sealing ring material for diol refrigerants and its preparation method. The EPDM sealing ring material for diol refrigerants is composed of the following components in parts by weight: 50-70 parts of first EPDM, 30-50 parts of second EPDM, 5-12 parts of modified EPDM masterbatch, 25-45 parts of carbon black, 1-2.5 parts of antioxidant, 0.3-1.5 parts of polyethylene wax, 0.8-1.6 parts of peroxide vulcanizing agent, and 1.1-3 parts of crosslinking agent; the modified EPDM masterbatch is prepared by premixing modified flake boron nitride with reactive liquid EPDM. The sealing ring prepared by this invention retains excellent mechanical properties even after prolonged immersion in propylene glycol and high / low temperature cycling.

Description

Technical Field

[0001] This invention belongs to the technical field of rubber sealing materials, specifically relating to an EPDM sealing ring material for diol refrigerants and its preparation method. Background Technology

[0002] Computer CPU liquid cooling systems typically consist of a closed cooling loop formed by a cold plate, circulating pump, piping, connectors, and heatsink, using an aqueous solution of ethylene glycol or propylene glycol as the cooling medium. Sealing rings, as sealing elements, are commonly placed between the cold plate interface, pump and valve connections, and liquid reservoir components to prevent coolant leakage and are critical components affecting the long-term reliability of the liquid cooling system.

[0003] Ethylene propylene diene monomer (EPDM) rubber, due to its highly saturated main chain, possesses excellent weather resistance, heat aging resistance, and resistance to polar media, making it a common material for manufacturing sealing rings in liquid cooling systems. However, the performance characteristics of existing EPDM sealing rings are primarily focused on initial hardness, tensile strength, elongation at break, and conventional compression set. In contrast, sealing rings in CPU liquid cooling systems require prolonged contact with high-temperature ethylene glycol or propylene glycol coolants and continuous compression. They are also subject to thermal cycling caused by equipment start-up and shutdown, as well as pressure fluctuations generated by the circulating pump.

[0004] Existing technologies typically reduce rubber swelling by increasing filler content or adjusting crosslinking density. For example, Chinese patent application CN108395631A discloses a high-temperature resistant EPDM rubber and its preparation method, using an odorless DCP-TAIC peroxide vulcanization system for EPDM rubber, with N550 carbon black as a reinforcing filler and paraffin oil as a plasticizer to improve the rubber's high-temperature aging resistance. However, paraffin oil is a non-reactive mineral plasticizer, which may be extracted or migrated by the coolant during long-term immersion in a high-temperature polar diol-water medium, causing changes in rubber hardness, crosslinking density, and elasticity. Furthermore, the N550 carbon black filler content in this method is 60-90 parts; excessive amounts can easily reduce the rubber's flexibility and interfacial adhesion.

[0005] Therefore, there is a need to develop an EPDM sealing ring material for diol refrigerants that combines excellent resistance to refrigerant swelling, low compression set, low additive precipitation, and strong interfacial bonding, suitable for liquid cooling sealing conditions in CPUs, power batteries, and energy storage devices. Summary of the Invention

[0006] Existing EPDM sealing rings cannot simultaneously achieve coolant barrier properties, heat aging resistance, elastic recovery, and long-term sealing performance. To address this deficiency, this invention provides an EPDM sealing ring material for diol refrigerants and its preparation method.

[0007] To achieve the objectives of this invention, the following technical solution is adopted: In a first aspect, the present invention provides an EPDM sealing ring material for diol refrigerants, comprising the following components in parts by weight: 50-70 parts of first EPDM, 30-50 parts of second EPDM, 5-12 parts of modified EPDM masterbatch, 25-45 parts of carbon black, 1-2.5 parts of antioxidant, 0.3-1.5 parts of polyethylene wax, 0.8-1.6 parts of peroxide vulcanizing agent, and 1.1-3 parts of crosslinking agent; The modified EPDM masterbatch is prepared by premixing modified flake boron nitride with reactive liquid EPDM.

[0008] In the above technical solution, the first EPDM and the second EPDM work together as the base rubber matrix, and a modified EPDM masterbatch is introduced. The modified EPDM masterbatch includes modified flake boron nitride and reactive liquid EPDM: the reactive liquid EPDM participates in vulcanization crosslinking, replacing traditional paraffin-based plasticizers and reducing small molecule migration and media extraction; the modified flake boron nitride constructs a labyrinth barrier pathway, enhancing the filler's performance. The rubber interface bonding stability; carbon black, as a reinforcing filler, adjusts the hardness of the rubber compound and improves its mechanical strength and compression resilience; antioxidants, polyethylene wax and other additives can inhibit the thermo-oxidative aging of rubber and improve the flowability of the mixture; peroxide vulcanizing agents and crosslinking agents form a stable crosslinking network to ensure heat resistance and low compression set performance.

[0009] Furthermore, in the first EPDM: the ethylene content is 60%~70%, the third monomer content is 4%~7%, and the Mooney viscosity is 55~80; in the second EPDM: the ethylene content is 45%~58%, the third monomer content is 5%~10%, and the Mooney viscosity is 20~50.

[0010] In the above technical solution, the first EPDM is a high-ethylene-content EPDM, which provides excellent tensile strength, heat resistance and barrier properties against diol refrigerants; the second EPDM is a medium-ethylene-content EPDM, which imparts good low-temperature elasticity, flexibility and processing fluidity to the rubber compound; the two work together to balance the resistance to media and the processability.

[0011] Furthermore, the reactive liquid EPDM is a liquid EPDM with a diene monomer content of 3% to 10%.

[0012] In the above technical solution, the molecular chain has double bond groups that can participate in peroxide sulfidation, which can crosslink with the EPDM matrix, avoiding the extraction and migration of traditional mineral oil plasticizers by diol refrigerant and reducing the risk of pollution.

[0013] Furthermore, the modified EPDM masterbatch is prepared by the following method: (1) Disperse the flake boron nitride in a 15%~25% hydrogen peroxide aqueous solution, stir at 60~80℃ for 2~6h, filter, wash and dry to obtain activated flake boron nitride; (2) Add activated sheet boron nitride to the hydrolysate of silane coupling agent, stir and react at 60~80℃ for 1~4h, wash, and heat treat at 100~120℃ for 1~3h to obtain modified sheet boron nitride. (3) Add the modified flake boron nitride and reactive liquid EPDM to the kneading equipment and knead for 20 to 60 minutes at 70 to 110°C. Vacuum devolatilization is then performed to obtain the modified EPDM masterbatch.

[0014] In the above technical solution, the preparation method can suppress the agglomeration of boron nitride powder, reduce dust during mixing, and facilitate the formation of a continuous interface composed of plate boron nitride, silane layer, liquid EPDM, and solid EPDM after vulcanization.

[0015] Further, in step (1), the ratio of the amount of the sheet-like boron nitride to the aqueous hydrogen peroxide solution is 1 g: (8~15) mL.

[0016] In the above technical solution, this ratio can ensure that boron nitride is fully suspended and wetted, and that activation is uniform.

[0017] Further, in step (2), the silane coupling agent hydrolysate is prepared by the following method: adding silane coupling agent KH-570 to an ethanol aqueous solution with a concentration of 90%~95%, adjusting the pH value to 4~5.5, stirring for 0.5~2h, and obtaining the silane coupling agent hydrolysate.

[0018] In the above technical solution, the silane coupling agent hydrolysate is fully hydrolyzed and has a suitable concentration, which allows silane molecules to be effectively grafted onto the activated boron nitride surface.

[0019] Furthermore, the mass ratio of the silane coupling agent KH-570 to the aqueous ethanol solution is 1:(60~90).

[0020] In the above technical solution, controlling the concentration of silane in the hydrolysate ensures that there is sufficient silane for surface grafting while avoiding excessive silane concentration that could lead to self-polymerization.

[0021] Furthermore, the amount of the coupling agent KH-570 is 3% to 6% of the mass of the activated flake boron nitride.

[0022] In the above technical solution, the dosage range can form a complete graft layer on the surface of the boron nitride sheet.

[0023] Further, in step (3), the mass ratio of the modified flake boron nitride to the reactive liquid EPDM is 1:(0.4~1).

[0024] In the above technical solution, the ratio ensures that the liquid EPDM wets and coats the boron nitride flakes; if there is too little liquid EPDM, the coating will be incomplete and the powder will easily agglomerate again; if there is too much liquid EPDM, the masterbatch will become sticky and clump, which is not conducive to subsequent mixing and processing with solid EPDM.

[0025] Furthermore, the peroxide sulfiding agent is selected from at least one of di-tert-butylperoxydiisopropylbenzene and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0026] In the above technical solution, both peroxides are high-temperature peroxides, which are suitable for the vulcanization temperature of EPDM. They are not easily affected by other components in the system during the vulcanization process, and the crosslinking efficiency is stable. The C-C bonds generated by the peroxide vulcanization have excellent thermal stability, which gives the vulcanized rubber excellent heat aging resistance and extremely low compression set.

[0027] Furthermore, the crosslinking agent is prepared by mixing crosslinking agent TAIC and crosslinking agent N,N'-m-phenylenebismaleimide in a mass ratio of (1~3):1.

[0028] In the above technical solution, TAIC improves the efficiency of free radical crosslinking and increases the crosslinking density; N,N' m-phenylene bismaleimide further enhances the heat resistance stability of the cross-linked network. The two work synergistically to reduce compression set under high temperature conditions and improve the long-term sealing reliability of the sealing ring.

[0029] Secondly, the present invention provides a method for preparing the above-mentioned EPDM sealing ring material for diol refrigerants, comprising the following steps: S1: Add the first EPDM and the second EPDM to the internal mixer and plasticize at 60~90℃ for 1~3 minutes. Then add 1 / 3 part by weight of carbon black, modified EPDM masterbatch, antioxidant and polyethylene wax in sequence and mix at 90~120℃ for 5~10 minutes. Then add the remaining carbon black and mix evenly. Discharge, cool and let stand for 8~24 hours to obtain a first compound rubber. S2: Add a section of compound rubber to the open mill. When the rubber temperature is below 70°C, add peroxide vulcanizing agent and crosslinking agent, and mix for 3-8 minutes to obtain the final compound rubber. S3: The final rubber compound is vulcanized to obtain EPDM sealing ring material for diol refrigerant.

[0030] Further, in step S3, the vulcanization process is as follows: the temperature of the first vulcanization is 165~180℃, the pressure of the first vulcanization is 10~18MPa, and the time of the first vulcanization is 8~20min; a second vulcanization is carried out at a temperature of 140~150℃ for 2~6h.

[0031] In the above technical solution, the entire preparation process is controllable and suitable for industrial production.

[0032] In summary, the beneficial effects of this invention are: 1. This invention uses EPDM with high ethylene and high Mooney content and medium ethylene and low Mooney content to balance the rubber compound's resistance to diol refrigerants, heat resistance, and molding performance. 2. This invention pre-prepares modified EPDM masterbatch by kneading silane-grafted boron nitride with reactive liquid EPDM, effectively alleviating boron nitride powder agglomeration; after sulfidation, a multi-level covalent continuous interface is constructed, utilizing the boron nitride lamellar labyrinth effect to hinder the penetration of small diol molecules and reduce volume swelling. 3. This invention combines TAIC and N,N'-m-phenylenebismaleimide as a crosslinking agent to form a highly thermally stable CC crosslinking network, resulting in low permanent compression deformation of the sealing ring; 4. The sealing ring prepared by this invention retains its mechanical properties well after long-term propylene glycol immersion and high and low temperature cycle impact, and has no defects such as blistering or swelling. It can be used for sealing of diol refrigerant pipelines in liquid cooling circuits. Detailed Implementation

[0033] The present invention will be further described below with reference to specific embodiments.

[0034] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples and comparative examples are commercially available.

[0035] First EPDM: Ethylene propylene diene monomer (EPDM) rubber, with an ethylene content of 60%~70%, a third monomer content of 4%~7%, and a Mooney viscosity of 55~80.

[0036] Second EPDM: Ethylene propylene diene monomer (EPDM) rubber, with an ethylene content of 45%~58%, a third monomer content of 5%~10%, and a Mooney viscosity of 20~50.

[0037] Reactive liquid EPDM: Diene-based liquid EPDM, with a diene monomer content of 3%~10%.

[0038] Plate-shaped boron nitride: average plate diameter 4μm, average thickness 80nm, purity ≥98%.

[0039] Carbon black: N550 carbon black.

[0040] Antioxidant: Antioxidant 445.

[0041] Preparation Example Preparation Example 1 (1) Disperse the flake boron nitride in a 25% hydrogen peroxide aqueous solution at a ratio of 1g:10mL, stir at 65℃ for 4h, filter and wash until the filtrate is neutral, and dry at 60℃ for 12h to obtain activated flake boron nitride. (2) Add 0.5g of silane coupling agent KH-570 to 45g of 90% ethanol aqueous solution, adjust the pH value to 4, stir for 2h to obtain silane coupling agent hydrolysate; add 10g of activated flake boron nitride to silane coupling agent hydrolysate, stir and react at 70℃ for 4h, wash, heat treat at 100℃ for 2h to obtain modified flake boron nitride; (3) Modified flake boron nitride and reactive liquid EPDM are added to a kneading device at a mass ratio of 1:0.6 and kneaded at 75°C for 40 min. Vacuum devolatilization is then performed to obtain modified EPDM masterbatch.

[0042] Preparation Example 2 (1) Disperse the flake boron nitride in a 25% hydrogen peroxide aqueous solution at a ratio of 1g:12mL, stir at 70℃ for 3h, filter and wash until the filtrate is neutral, and dry at 60℃ for 12h to obtain activated flake boron nitride. (2) Add 0.4g of silane coupling agent KH-570 to 32g of 95% ethanol aqueous solution, adjust the pH value to 4.5, stir for 1.5h to obtain silane coupling agent hydrolysate; add 10g of activated flake boron nitride to silane coupling agent hydrolysate, stir and react at 60℃ for 3h, wash, and heat treat at 120℃ for 1.5h to obtain modified flake boron nitride; (3) Add modified flake boron nitride and reactive liquid EPDM to a kneading device at a mass ratio of 1:0.5, knead at 100°C for 30 min, and then vacuum devolatilize to obtain modified EPDM masterbatch.

[0043] Preparation Example 3 (1) Disperse the flake boron nitride in a 20% hydrogen peroxide aqueous solution at a ratio of 1g:15mL, stir at 80℃ for 5h, filter and wash until the filtrate is neutral, and dry at 60℃ for 12h to obtain activated flake boron nitride. (2) Add 0.6g of silane coupling agent KH-570 to 45g of 95% ethanol aqueous solution, adjust the pH value to 5, stir for 2h to obtain silane coupling agent hydrolysate; add 10g of activated flake boron nitride to silane coupling agent hydrolysate, stir and react at 75℃ for 4h, wash, and heat treat at 110℃ for 3h to obtain modified flake boron nitride; (3) Modified flake boron nitride and reactive liquid EPDM are added to a kneading device at a mass ratio of 1:0.8 and kneaded at 90°C for 50 min. Vacuum devolatilization is then performed to obtain modified EPDM masterbatch.

[0044] Example Example 1 This embodiment of an EPDM sealing ring material for diol refrigerants is composed of the following components by mass: First EPDM 65g, Second EPDM 35g, Modified EPDM Masterbatch 10g, Carbon Black 35g, Antioxidant 2.5g, Polyethylene Wax 1g, Peroxide Vulcanizing Agent 1.2 parts, Crosslinking Agent 2.3g; The first EPDM has an ethylene content of 65%, a third monomer content of 4%, and a Mooney viscosity of 60. The second EPDM has an ethylene content of 48%, a third monomer content of 6%, and a Mooney viscosity of 30. The modified EPDM masterbatch is the modified EPDM masterbatch obtained in Preparation Example 1; The peroxide sulfide agent is di-tert-butylperoxide diisopropylbenzene; The crosslinking agent was prepared by mixing crosslinking agent TAIC and crosslinking agent N,N'-m-phenylenebismaleimide in a mass ratio of 2:1. The specific steps for preparing the EPDM sealing ring material for diol refrigerant in this embodiment are as follows: S1: Add the first EPDM and the second EPDM to the internal mixer and plasticize at 70°C for 2 minutes. Then add 1 / 3 part by weight of carbon black, modified EPDM masterbatch, antioxidant and polyethylene wax in sequence and mix at 110°C for 8 minutes. Then add the remaining carbon black and mix evenly. Discharge, cool and let stand for 12 hours to obtain a first compound. S2: Add a section of compound rubber to the open mill. When the rubber temperature is below 70°C, add peroxide vulcanizing agent and crosslinking agent, and mix for 5 minutes to obtain the final compound rubber. S3: The final compound is vulcanized using a flatbed vulcanizing machine. The temperature of the first vulcanization is 165℃, the pressure of the first vulcanization is 12MPa, and the time of the first vulcanization is 10min. A second vulcanization is carried out at a temperature of 145℃ for 6h to obtain the EPDM sealing ring material for diol refrigerant.

[0045] Example 2 This embodiment of an EPDM sealing ring material for diol refrigerants is composed of the following components by mass: First EPDM 58g, Second EPDM 40g, Modified EPDM Masterbatch 7g, Carbon Black 40g, Antioxidant 2.5g, Polyethylene Wax 1.5g, Peroxide Vulcanizing Agent 1 part, Crosslinking Agent 2.5g; The first EPDM has an ethylene content of 65%, a third monomer content of 4%, and a Mooney viscosity of 60. The second EPDM has an ethylene content of 48%, a third monomer content of 6%, and a Mooney viscosity of 30. The modified EPDM masterbatch is the modified EPDM masterbatch obtained in Preparation Example 1; The peroxide sulfide is 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; The crosslinking agent was prepared by mixing crosslinking agent TAIC and crosslinking agent N,N'-m-phenylenebismaleimide in a mass ratio of 1.5:1. The specific steps for preparing the EPDM sealing ring material for diol refrigerant in this embodiment are as follows: S1: Add the first EPDM and the second EPDM to the internal mixer and plasticize at 80°C for 1.5 min. Then add 1 / 3 part by weight of carbon black, modified EPDM masterbatch, antioxidant and polyethylene wax in sequence and mix at 95°C for 6 min. Then add the remaining carbon black and mix evenly. Discharge, cool and let stand for 20 h to obtain a first compound. S2: Add a section of compound rubber to the open mill. When the rubber temperature is below 70°C, add peroxide vulcanizing agent and crosslinking agent, and mix for 4 minutes to obtain the final compound rubber. S3: The final compound is vulcanized using a flatbed vulcanizing machine. The temperature of the first vulcanization is 170℃, the pressure of the first vulcanization is 15MPa, and the time of the first vulcanization is 15min. A second vulcanization is carried out at a temperature of 140℃ for 5h to obtain the EPDM sealing ring material for diol refrigerant.

[0046] Example 3 This embodiment of an EPDM sealing ring material for diol refrigerants is composed of the following components by mass: First EPDM 62g, Second EPDM 37g, Modified EPDM Masterbatch 8g, Carbon Black 30g, Antioxidant 2g, Polyethylene Wax 0.9g, Peroxide Vulcanizing Agent 1.5 parts, Crosslinking Agent 2g; The first EPDM has an ethylene content of 70%, a third monomer content of 5%, and a Mooney viscosity of 70. The second EPDM has an ethylene content of 50%, a third monomer content of 8%, and a Mooney viscosity of 40. The modified EPDM masterbatch is the modified EPDM masterbatch obtained in Preparation Example 2; The peroxide sulfide is 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; The crosslinking agent was prepared by mixing crosslinking agent TAIC and crosslinking agent N,N'-m-phenylenebismaleimide in a mass ratio of 1.5:1. The specific steps for preparing the EPDM sealing ring material for diol refrigerant in this embodiment are as follows: S1: Add the first EPDM and the second EPDM to the internal mixer and plasticize at 65°C for 3 minutes. Then add 1 / 3 mass of carbon black, modified EPDM masterbatch, antioxidant and polyethylene wax in sequence and mix at 100°C for 7 minutes. Then add the remaining carbon black and mix evenly. Discharge, cool and let stand for 10 hours to obtain a first compound. S2: Add a section of compound rubber to the open mill. When the rubber temperature is below 70°C, add peroxide vulcanizing agent and crosslinking agent, and mix for 6 minutes to obtain the final compound rubber. S3: The final compound is vulcanized using a flatbed vulcanizing machine. The temperature of the first vulcanization is 170℃, the pressure of the first vulcanization is 10MPa, and the time of the first vulcanization is 12min. A second vulcanization is carried out at a temperature of 150℃ for 4h to obtain the EPDM sealing ring material for diol refrigerant.

[0047] Example 4 This embodiment of an EPDM sealing ring material for diol refrigerants is composed of the following components by mass: First EPDM 68g, Second EPDM 45g, Modified EPDM Masterbatch 11g, Carbon Black 35g, Antioxidant 1.5g, Polyethylene Wax 1.5g, Peroxide Vulcanizing Agent 1.4 parts, Crosslinking Agent 2.8g; The first EPDM has an ethylene content of 70%, a third monomer content of 5%, and a Mooney viscosity of 70. The second EPDM has an ethylene content of 50%, a third monomer content of 8%, and a Mooney viscosity of 40. The modified EPDM masterbatch is the modified EPDM masterbatch obtained in Preparation Example 3; The peroxide sulfide agent is di-tert-butylperoxide diisopropylbenzene; The crosslinking agent was prepared by mixing crosslinking agent TAIC and crosslinking agent N,N'-m-phenylenebismaleimide in a mass ratio of 2.5:1. The specific steps for preparing the EPDM sealing ring material for diol refrigerant in this embodiment are as follows: S1: Add the first EPDM and the second EPDM to the internal mixer and plasticize at 90°C for 2 minutes. Then add 1 / 3 part by weight of carbon black, modified EPDM masterbatch, antioxidant and polyethylene wax in sequence and mix at 90°C for 8 minutes. Then add the remaining carbon black and mix evenly. Discharge, cool and let stand for 12 hours to obtain a first compound. S2: Add a section of compound rubber to the open mill. When the rubber temperature is below 70°C, add peroxide vulcanizing agent and crosslinking agent, and mix for 5 minutes to obtain the final compound rubber. S3: The final compound is vulcanized using a flatbed vulcanizing machine. The temperature of the first vulcanization is 175℃, the pressure of the first vulcanization is 12MPa, and the time of the first vulcanization is 15min. A second vulcanization is carried out at a temperature of 145℃ for 5h to obtain the EPDM sealing ring material for diol refrigerant.

[0048] Comparative Example Comparative Example 1 The difference from Example 1 is that: In this comparative example, an equal amount of the first EPDM was used instead of the second EPDM, and the other raw materials and preparation methods were the same as in Example 1.

[0049] Comparative Example 2 The difference from Example 1 is that: In this comparative example, an equal amount of reactive liquid EPDM was used instead of modified EPDM masterbatch, and the other raw materials and preparation methods were the same as in Example 1.

[0050] Comparative Example 3 The difference from Example 1 is that: In this comparative example, an equal amount of modified flake boron nitride was used instead of modified EPDM masterbatch, and the remaining raw materials and preparation methods were the same as in Example 1.

[0051] Comparative Example 4 The difference from Example 1 is that: In the preparation method of the EPDM sealing ring material for diol refrigerant in this comparative example, modified boron nitride and reactive liquid EPDM are directly added to the internal mixer, and the other raw materials and preparation methods are the same as in Example 1.

[0052] Comparative Example 5 The difference from Example 1 is that: In this comparative example, the crosslinking agent is TAIC, and the other raw materials and preparation methods are the same as in Example 1.

[0053] Related performance tests The EPDM sealing ring material for the diol refrigerant prepared in Examples 1-4 and Comparative Examples 1-5 was subjected to relevant performance tests. The test results are shown in Tables 1 and 2.

[0054] Hardness test: The test sample shall be tested for hardness in accordance with GB / T 531.1-2008 standard.

[0055] Tensile strength and elongation at break: The test samples were tested for tensile strength and elongation at break according to GB / T 528-2021.

[0056] Compression set test: The test sample is prepared according to the high temperature standard GB / T 7759.1-2015 30%. 135℃ The compression set test was performed using the 120h (1h rebound) standard.

[0057] High and low temperature shock test: The test sample is subjected to high and low temperature shock test, and then the test is carried out in cycles of -40℃ for 2 hours and 85℃ for 2 hours for 125 times; for a total of 500 hours, the sample is placed at room temperature for 1 hour and the performance change rate is tested.

[0058] Propylene glycol immersion test: The test sample was immersed in PG25 propylene glycol at 85℃ for 1000h, and its performance changes were tested.

[0059] Table 1 Initial physical properties and high and low temperature shock test results

[0060] Table 2. Performance test results after propylene glycol immersion at 85℃ for 1000h

[0061] From Tables 1 and 2, we can see that: The EPDM sealing ring materials obtained in Examples 1-4 of this invention have a hardness in the range of 70-75HA, a tensile strength ≥15MPa, and low compression set. After 500 hours of high and low temperature cycling, the tensile and elongation retention rates are both greater than 85%, and the appearance is intact. After long-term immersion in propylene glycol refrigerant at 85℃ for 1000 hours, the volume change rate and mass change rate are low, and the resistance to swelling by diol refrigerant is excellent.

[0062] Comparative Example 1 lacks the plasticizing and synergistic effect of the second EPDM, resulting in poorer processability, uneven filler dispersion, decreased uniformity of vulcanization network, increased compression set, and significantly increased swelling after immersion in the medium.

[0063] In Comparative Example 2, the system lacked modified sheet boron nitride, thus lacking the two-dimensional sheet labyrinth barrier effect. The overall barrier reinforcement effect was insufficient, resulting in increased changes in the volume and mass of the refrigerant during immersion.

[0064] Comparative Example 3 directly added modified flake boron nitride, which dispersed poorly during mixing and was prone to forming agglomerates. Although its performance was slightly better than that of Comparative Example 2, its overall performance was still not as good as that of Example 1.

[0065] Comparative Example 4 shows that pre-kneading to prepare the masterbatch helps to further optimize the packer dispersion and overall performance.

[0066] Comparative Example 5 lacked the synergistic effect of N,N'-m-phenylenebismaleimide, resulting in insufficient crosslinking density and network heat resistance, leading to deterioration of high-temperature compression set.

[0067] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. An EPDM sealing ring material for diol refrigerants, characterized in that, It consists of the following components in parts by weight: 50-70 parts of first EPDM, 30-50 parts of second EPDM, 5-12 parts of modified EPDM masterbatch, 25-45 parts of carbon black, 1-2.5 parts of antioxidant, 0.3-1.5 parts of polyethylene wax, 0.8-1.6 parts of peroxide vulcanizing agent, and 1.1-3 parts of crosslinking agent; The modified EPDM masterbatch is prepared by premixing modified flake boron nitride with reactive liquid EPDM.

2. The EPDM sealing ring material for diol refrigerant according to claim 1, characterized in that, In the first EPDM: the ethylene content is 60%~70%, the third monomer content is 4%~7%, and the Mooney viscosity is 55~80; in the second EPDM: the ethylene content is 45%~58%, the third monomer content is 5%~10%, and the Mooney viscosity is 20~50.

3. The EPDM sealing ring material for diol refrigerant according to claim 1, characterized in that, The reactive liquid EPDM is a liquid EPDM with a diene monomer content of 3% to 10%.

4. The EPDM sealing ring material for diol refrigerant according to claim 1, characterized in that, The modified EPDM masterbatch is prepared by the following method: (1) Disperse the flake boron nitride in a 15%~25% hydrogen peroxide aqueous solution, stir at 60~80℃ for 2~6h, filter, wash and dry to obtain activated flake boron nitride; (2) Add activated sheet boron nitride to the hydrolysate of silane coupling agent, stir and react at 60~80℃ for 1~4h, wash, and heat treat at 100~120℃ for 1~3h to obtain modified sheet boron nitride. (3) Add the modified flake boron nitride and reactive liquid EPDM to the kneading equipment and knead for 20-60 min at 70-110℃. Vacuum devolatilization is then performed to obtain the modified EPDM masterbatch.

5. The EPDM sealing ring material for diol refrigerant according to claim 4, characterized in that, In step (1), the ratio of the amount of the flake boron nitride to the aqueous hydrogen peroxide solution is 1 g: (8~15) mL.

6. The EPDM sealing ring material for diol refrigerant according to claim 4, characterized in that, In step (2), the silane coupling agent hydrolysate is prepared by the following method: adding silane coupling agent KH-570 to an aqueous ethanol solution with a concentration of 90%~95%, adjusting the pH value to 4~5.5, stirring for 0.5~2h, and obtaining the silane coupling agent hydrolysate; The mass ratio of the silane coupling agent KH-570 to the ethanol aqueous solution is 1:(60~90); The amount of coupling agent KH-570 used is 3% to 6% of the mass of the activated flake boron nitride.

7. The EPDM sealing ring material for diol refrigerant according to claim 4, characterized in that, In step (3), the mass ratio of the modified flake boron nitride to the reactive liquid EPDM is 1:(0.4~1).

8. The EPDM sealing ring material for diol refrigerant according to claim 1, characterized in that, The peroxide sulfiding agent is selected from at least one of di-tert-butylperoxydiisopropylbenzene and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

9. The EPDM sealing ring material for diol refrigerant according to claim 1, characterized in that, The crosslinking agent is prepared by mixing crosslinking agent TAIC and crosslinking agent N,N'-m-phenylenebismaleimide in a mass ratio of (1~3):

1.

10. A method for preparing an EPDM sealing ring material for diol refrigerants according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1: Add the first EPDM and the second EPDM to the internal mixer and plasticize at 60~90℃ for 1~3 minutes. Then add 1 / 3 part by weight of carbon black, modified EPDM masterbatch, antioxidant and polyethylene wax in sequence and mix at 90~120℃ for 5~10 minutes. Then add the remaining carbon black and mix evenly. Discharge, cool and let stand for 8~24 hours to obtain a first compound rubber. S2: Add a section of compound rubber to the open mill. When the rubber temperature is below 70°C, add peroxide vulcanizing agent and crosslinking agent, and mix for 3-8 minutes to obtain the final compound rubber. S3: The final rubber compound is vulcanized to obtain EPDM sealing ring material for diol refrigerant.

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