Valve chamber cover gasket and preparation method thereof

Abstract

The invention relates to the technical field of rubber sealing materials, and particularly discloses a valve chamber cover gasket and a preparation method thereof. Wherein the valve chamber cover pad is prepared from the following raw materials: acrylate rubber, a curing cross-linking agent, modified carbon black, silica, a high-temperature plasticizer, an anti-aging agent, a release agent and a flow promoter; the preparation raw materials of the modified carbon black comprise carbon black, a coating monomer and an initiator, and the mass ratio of the carbon black to the coating monomer to the initiator is 1: (0.1-0.2): (0.01-0.03). According to the invention, the mechanical properties of the acrylate rubber in a wide temperature range can be effectively improved, and material hardening and embrittlement are reduced.

Description

Technical Field

[0001] This invention relates to the field of rubber sealing materials technology, and more particularly to valve cover gaskets and their preparation methods. Background Technology

[0002] The valve cover gasket is a key sealing component between the cylinder head and the valve cover of an automobile engine. Its main function is to prevent engine oil leakage, isolate high-temperature gases in the combustion chamber and external impurities. Its sealing performance is directly related to the engine's operational reliability and service life.

[0003] Acrylic rubber, a high-molecular elastomer synthesized from acrylate and a small amount of crosslinked monomers, has become a commonly used material in automotive sealing products due to its excellent high-temperature resistance and oil resistance, meeting the basic sealing requirements of engines under complex operating conditions. In existing technologies, valve cover gaskets are typically made of acrylic rubber through molding or injection molding processes. However, when faced with extreme temperature fluctuations, especially at low temperatures, the molecular structure of acrylic rubber may gradually age, leading to hardening and embrittlement. After long-term operation, this can easily cause problems such as seal failure and oil leakage. Summary of the Invention

[0004] In order to improve the mechanical properties of acrylate rubber over a wide temperature range and reduce material hardening and embrittlement, this application provides a valve cover gasket and its preparation method.

[0005] Firstly, the valve cover gasket provided in this application adopts the following technical solution: The valve cover gasket, by weight, is made from the following raw materials: Acrylic rubber 80-100 parts, curing crosslinking agent 2.07-3.07 parts, modified carbon black 55-65 parts, silica 10-13 parts, high-temperature plasticizer 3.75-4.25 parts, antioxidant 1-2 parts, release agent 2.94-4.94 parts, flow aid 2.6-3.4 parts; The raw materials for preparing the modified carbon black include carbon black, coating monomers and initiators, and the mass ratio of carbon black, coating monomers and initiators is 1:(0.1-0.2):(0.01-0.03).

[0006] By adopting the above technical solution, the valve cover gasket of this application uses acrylate rubber as the base rubber and modified carbon black and silica as synergistic reinforcements for the acrylate rubber. Silica possesses good filling properties and stability, improving the physical properties of the material. Modified carbon black, due to its unique coating monomers, enhances its compatibility and dispersibility with the acrylate rubber. Specifically, the coating monomers combine with carbon black in a certain proportion, forming a specific chemical structure on the carbon black surface, enhancing the interaction between the carbon black and the rubber matrix. When modified carbon black and silica work together, on the one hand, the overall strength and toughness of the material are improved; on the other hand, the stability of the material at extreme temperatures is enhanced, reducing the hardening and embrittlement of the acrylate rubber at low temperatures.

[0007] Simultaneously, under the action of the crosslinking agent, the molecular chains of acrylate rubber are effectively crosslinked to form a stable three-dimensional network structure. Modified carbon black and silica are uniformly dispersed in this network, further enhancing the network's mechanical properties and thermal stability. Specifically, the amine-based curing crosslinking agent can react with the active groups on the acrylate rubber molecular chains to construct a dense and flexible crosslinking system. This system is not prone to hardening due to restricted molecular chain movement at low temperatures. Instead, it can buffer the stress caused by temperature changes through the flexible chain segments introduced by the monomer coating on the surface of modified carbon black. Combined with the filling and supporting effect of silica, this allows the valve cover gasket to maintain good elasticity and sealing performance over a wide temperature range.

[0008] Preferably, the coating monomers comprise methyl methacrylate, hexyl acrylate, acrylic acid, diethylene glycol diacrylate, and diethylene glycol monomethyl ether acrylate in a mass ratio of 1:(0.5-0.55):(0.03-0.05):(0.1-0.15):(0.2-0.3).

[0009] By adopting the above technical solutions, the above-mentioned proportions of coating monomers can achieve complementary functions: methyl methacrylate imparts appropriate rigidity to the carbon black surface, enhancing its supporting role as a filler; hexyl acrylate has a long carbon chain, which effectively alleviates stress concentration inside the material at low temperatures by introducing flexible segments; the polar groups of acrylic acid can improve the interfacial bonding force between modified carbon black and acrylate rubber matrix, promoting uniform dispersion; diethylene glycol diacrylate, as a crosslinking monomer, can form a local crosslinking network on the carbon black surface, further strengthening the entanglement between carbon black and rubber molecular chains; diethylene glycol monomethyl ether acrylate, as a long-branched low-temperature oil-resistant monomer containing ether bonds, can further improve the oil resistance and elastic recovery ability of modified carbon black in low-temperature environments. Synergistically acting with other coating monomers, the modified carbon black possesses multiple functions such as rigid support, flexible buffering, interfacial reinforcement, and oil and low-temperature resistance, thereby significantly improving the sealing reliability and service life of the valve cover gasket under extreme temperature fluctuations.

[0010] Preferably, the method for preparing the modified carbon black includes the following steps: Water and emulsifier are added to a reaction vessel and stirred until homogeneous. Then, the coated monomer is added and stirred until homogeneous. Carbon black is then added and stirred until homogeneous. The mixture is heated and stirred until homogeneous. The temperature is increased and an initiator is added to carry out the reaction. After the reaction is completed, the product is cooled, filtered, and dried to obtain modified carbon black.

[0011] By employing the above technical solution, the emulsification process ensures that the coated monomers are uniformly polymerized on the carbon black surface to form a dense and functionalized coating layer, effectively suppressing the agglomeration of carbon black particles and improving their dispersibility in the acrylate rubber matrix. First, an emulsifier is used to form stable emulsion droplets of the coated monomers, which are then mixed and emulsified with carbon black, allowing the carbon black particles to be fully immersed in the emulsion environment. The subsequent heating and emulsification step further promotes the adsorption and pre-dispersion of the coated monomers on the carbon black surface, laying a uniform interfacial foundation for the subsequent polymerization reaction. After heating and adding an initiator, the coated monomers polymerize in situ on the carbon black surface. The resulting polymer chains are tightly bonded to the carbon black surface through physical adsorption or chemical bonding, endowing the carbon black surface with specific chemical structures and functional groups, thereby enhancing the interfacial bonding force between the modified carbon black and the rubber matrix, enabling it to exert better filling, reinforcing, and low-temperature modification effects in the rubber network.

[0012] Preferably, the mass ratio of the emulsifier to carbon black is (0.3-0.4):1, and the emulsifier includes emulsifier OP-10 and sodium dodecyl sulfate in a mass ratio of 1:(0.8-1); the initiator is potassium persulfate.

[0013] By adopting the above technical solution, the emulsifier OP-10 and sodium dodecyl sulfate are compounded at a mass ratio of 1:(0.8-1) to achieve a synergistic emulsifying effect, resulting in good emulsification performance, improved stability of the emulsion system, and promotion of uniform dispersion of the coated monomers. Potassium persulfate is selected as the initiator. As a water-soluble initiator, it can uniformly decompose in the emulsion system to generate free radicals, efficiently initiating the in-situ polymerization of the coated monomers on the carbon black surface. The reaction process is mild and controllable, thus ensuring a uniform and functionally stable coating layer structure of the modified carbon black, further enhancing the overall performance of the valve cover gasket.

[0014] Preferably, the acrylate rubber is a carboxyl-based acrylate rubber.

[0015] By adopting the above technical solution, the carboxyl acrylate rubber molecular chain contains abundant carboxyl active groups, which can undergo a highly efficient cross-linking reaction with the amine curing cross-linking agent used in this application to form a denser and more flexible three-dimensional network structure. This not only enhances the high temperature resistance and oil corrosion resistance of the rubber matrix, but also maintains the appropriate mobility of the molecular chain in low temperature environments, effectively alleviating the dynamics of the material.

[0016] Preferably, the curing crosslinking agent is an amine curing crosslinking agent, which includes one or two of hexamethylenediamine carbamate and di-o-tolueneguanidine.

[0017] By adopting the above technical solution, hexamethylenediamine carbamate can slowly release active amine groups during vulcanization, which can cross-link with the carboxyl groups on the acrylate rubber molecular chain to form a uniform and flexible three-dimensional cross-linked network; di-o-tolueneguanidine has both cross-linking promotion and heat aging resistance functions, which can accelerate the cross-linking reaction process while improving the structural stability of the material under high temperature conditions.

[0018] Preferably, the high-temperature plasticizer includes one or more of Adico RS-705, Adico RS-107, Rohm and Haas TP-95, and Rohm and Haas TP-759.

[0019] By adopting the above technical solutions, the high-temperature plasticizers of the above models all have low volatility, high compatibility and excellent high and low temperature resistance. They can be tightly combined with the acrylic rubber matrix, maintain the material's softness and elastic recovery ability in high-temperature environments, and avoid the decrease in sealing performance caused by plasticizer migration. At low temperatures, they can effectively reduce the glass transition temperature of the rubber molecular chain and inhibit the hardening and embrittlement of the material.

[0020] Preferably, the antioxidant includes one or more of antioxidant 445, antioxidant RD, antioxidant MB, and antioxidant 264.

[0021] By adopting the above technical solution, adding an anti-aging agent can effectively slow down the aging rate of the valve cover gasket material, prevent the material from hardening and becoming brittle due to aging during long-term use, avoid sealing failure and oil leakage caused by material aging, thereby improving the service life of the valve cover gasket and the reliability of engine operation.

[0022] Preferably, the release agent includes one or both of stearic acid and PE wax.

[0023] By adopting the above technical solutions, stearic acid, as a fatty acid-based mold release agent, has good lubricity and can effectively reduce the friction between the valve cover gasket and the mold surface during the vulcanization molding process, preventing the product from sticking to the mold; PE wax has excellent thermal stability and is not easily decomposed in a high-temperature vulcanization environment, and can form a uniform isolation film on the surface of the product, further improving the demolding effect.

[0024] Preferably, the flow aid includes one or both of isopentyl stearate and flow aid WS180.

[0025] By adopting the above technical solutions, isoprene tetraol stearate, as a polyol ester flow aid, has excellent lubrication and dispersibility, which can effectively reduce the melt viscosity during rubber mixing and promote the uniform dispersion of fillers such as modified carbon black and silica in the acrylate rubber matrix. Flow aid WS180 has both lubrication and interface optimization functions, which can enhance the interaction between fillers and rubber molecular chains, reduce internal friction loss during processing, improve material flowability and mold filling during vulcanization molding, ensure the valve cover gasket product has accurate dimensions and dense structure, and optimize its sealing performance and mechanical stability in a wide temperature range.

[0026] Secondly, the method for preparing the valve cover gasket provided in this application adopts the following technical solution: The method for preparing a valve cover gasket includes the following steps: Acrylic rubber, modified carbon black, silica, high-temperature plasticizer, antioxidant, release agent, and flow aid are melt-blended at 140-150℃ to obtain a premix. A curing crosslinking agent is added to the premix, mixed evenly, and vulcanized at 150-180℃. After the gate is repaired, a second vulcanization is performed to obtain the valve cover gasket.

[0027] By adopting the above technical solution, modified carbon black, due to the good compatibility between its surface coating layer and the rubber matrix, can be uniformly dispersed in the rubber matrix with components such as silica and high-temperature plasticizers, forming a premixed system in which the components work synergistically. After adding the curing crosslinking agent, the reaction between the agent and the active groups on the rubber molecular chains provides suitable activation energy, promoting the rapid and uniform construction of a three-dimensional crosslinked network. Simultaneously, the filler particles are stably embedded in the network structure, further enhancing the material's mechanical strength and sealing stability. Secondary vulcanization after gate trimming effectively eliminates residual stress within the product, improves the density and uniformity of the crosslinked network, and significantly enhances the material's dimensional stability and performance durability under long-term high and low temperature cycling conditions. Ultimately, a valve cover gasket with excellent low-temperature embrittlement resistance, high-temperature aging resistance, and long-term sealing performance is obtained.

[0028] This application has the following beneficial effects: The valve cover gasket of this application uses acrylic rubber as the base rubber, and modified carbon black and silica are used to synergistically reinforce the acrylic rubber. Silica possesses good filling properties and stability, improving the physical properties of the material. The modified carbon black, due to its unique coating monomers, enhances its compatibility and dispersibility with the acrylic rubber. Specifically, the coating monomers combine with carbon black in a certain proportion, forming a specific chemical structure on the carbon black surface, enhancing the interaction between the carbon black and the rubber matrix. When modified carbon black and silica work together, they improve the overall strength and toughness of the material, and enhance its stability at extreme temperatures, reducing the hardening and embrittlement of the acrylic rubber at low temperatures.

[0029] Simultaneously, under the action of the crosslinking agent, the molecular chains of acrylate rubber are effectively crosslinked to form a stable three-dimensional network structure. Modified carbon black and silica are uniformly dispersed in this network, further enhancing the network's mechanical properties and thermal stability. Specifically, the amine-based curing crosslinking agent can react with the active groups on the acrylate rubber molecular chains to construct a dense and flexible crosslinking system. This system is not prone to hardening due to restricted molecular chain movement at low temperatures. Instead, it can buffer the stress caused by temperature changes through the flexible chain segments introduced by the monomer coating on the surface of modified carbon black. Combined with the filling and supporting effect of silica, this allows the valve cover gasket to maintain good elasticity and sealing performance over a wide temperature range. Detailed Implementation

[0030] The present application will be further described in detail below with reference to the embodiments.

[0031] Preparation Example 1 The preparation method of modified carbon black includes the following steps: Carbon black, coating monomer, and initiator are weighed according to a mass ratio of 1:0.1:0.01; the carbon black is specifically N-550 carbon black; the coating monomer is a compound of methyl methacrylate, hexyl acrylate, acrylic acid, diethylene glycol diacrylate, and diethylene glycol monomethyl ether acrylate in a mass ratio of 1:0.5:0.03:0.1:0.2; the initiator is potassium persulfate; the emulsifier is weighed, wherein the mass ratio of emulsifier to carbon black is 0.3:1, and the emulsifier is a compound of emulsifier OP-10 and sodium dodecyl sulfate in a mass ratio of 1:0.8.

[0032] Water, emulsifier OP-10, and sodium dodecyl sulfate were added to a reaction vessel and stirred until homogeneous. Methyl methacrylate, hexyl acrylate, acrylic acid, diethylene glycol diacrylate, and diethylene glycol monomethyl ether acrylate were then added and stirred until homogeneous. N-550 carbon black was added and stirred until emulsified. The mixture was heated to 60°C and stirred until emulsification continued. The temperature was then raised to 80°C, and potassium persulfate was added to react for 4 hours. After the reaction was completed, the product was cooled, filtered, and dried to obtain modified carbon black.

[0033] Preparation Example 2 The preparation method of modified carbon black includes the following steps: Carbon black, coating monomer, and initiator are weighed according to a mass ratio of 1:0.15:0.02; the carbon black is specifically N-550 carbon black; the coating monomer is a compound of methyl methacrylate, hexyl acrylate, acrylic acid, diethylene glycol diacrylate, and diethylene glycol monomethyl ether acrylate in a mass ratio of 1:0.53:0.04:0.13:0.25; the initiator is potassium persulfate; the emulsifier is weighed, wherein the mass ratio of emulsifier to carbon black is 0.35:1, and the emulsifier is a compound of emulsifier OP-10 and sodium dodecyl sulfate in a mass ratio of 1:0.9.

[0034] Water, emulsifier OP-10, and sodium dodecyl sulfate were added to a reaction vessel and stirred until homogeneous. Methyl methacrylate, hexyl acrylate, acrylic acid, diethylene glycol diacrylate, and diethylene glycol monomethyl ether acrylate were then added and stirred until homogeneous. N-550 carbon black was added and stirred until homogeneous. The mixture was heated to 65°C and stirred until homogeneous. The temperature was then raised to 85°C, and potassium persulfate was added. The reaction was carried out for 4 hours. After the reaction was completed, the product was cooled, filtered, and dried to obtain modified carbon black.

[0035] Preparation Example 3 The preparation method of modified carbon black includes the following steps: Carbon black, coating monomer, and initiator are weighed according to a mass ratio of 1:0.2:0.03; the carbon black is specifically N-550 carbon black; the coating monomer is a compound of methyl methacrylate, hexyl acrylate, acrylic acid, diethylene glycol diacrylate, and diethylene glycol monomethyl ether acrylate in a mass ratio of 1:0.55:0.05:0.15:0.3; the initiator is potassium persulfate; the emulsifier is weighed, wherein the mass ratio of emulsifier to carbon black is 0.4:1, and the emulsifier is a compound of emulsifier OP-10 and sodium dodecyl sulfate in a mass ratio of 1:1.

[0036] Water, emulsifier OP-10, and sodium dodecyl sulfate were added to a reaction vessel and stirred until homogeneous. Methyl methacrylate, hexyl acrylate, acrylic acid, diethylene glycol diacrylate, and diethylene glycol monomethyl ether acrylate were then added and stirred until homogeneous. N-550 carbon black was added and stirred until homogeneous. The mixture was heated to 70°C and stirred until homogeneous. The temperature was then raised to 90°C, and potassium persulfate was added to react for 4 hours. After the reaction was completed, the product was cooled, filtered, and dried to obtain modified carbon black.

[0037] Preparation Example 4 The difference between this preparation example and preparation example 3 is that hexyl acrylate is replaced by ethyl acrylate in equal mass.

[0038] Preparation Example 5 The difference between this preparation example and preparation example 3 is that the same mass of diethylene glycol monomethyl ether acrylate is replaced with methoxyethyl acrylate.

[0039] Example 1 The preparation method of the valve cover gasket includes the following steps: Raw materials were weighed according to the following proportions by weight: 80 parts acrylate rubber, 2.07 parts curing crosslinking agent, 55 parts modified carbon black, 10 parts silica, 3.75 parts high-temperature plasticizer, 1 part antioxidant, 2.94 parts release agent, and 2.6 parts flow aid. The acrylate rubber was a carboxyl-type acrylate rubber, brand name Dewey Technology ACM 4211. The curing crosslinking agent was a compound of hexamethylenediamine carbamate and di-o-tolueneguanidine in a mass ratio of 1:0.2. The modified carbon black was prepared according to Preparation Example 1. The high-temperature plasticizer was specifically Adico RS-705. The antioxidant was a compound of antioxidant RD and antioxidant MB in a mass ratio of 1:0.7. The release agent was specifically stearic acid. The flow aid was specifically isoprene tetraethanolamine stearate.

[0040] Acrylic rubber, modified carbon black, silica, Adico RS-705, antioxidants RD and MB, stearic acid, and isopentyl stearate were melt-blended at 140°C to obtain a premix. Hexamethylenediamine carbamate and di-o-tolueneguanidine were added to the premix, mixed evenly, and vulcanized at 160°C for 8 minutes. After the gate was trimmed, a second vulcanization was performed at 155°C for 4 hours to obtain the valve cover gasket.

[0041] Example 2 The preparation method of the valve cover gasket includes the following steps: The raw materials were weighed according to the following proportions by weight: 90 parts of acrylate rubber, 2.57 parts of curing crosslinking agent, 60 parts of modified carbon black, 11.5 parts of silica, 4 parts of high-temperature plasticizer, 1.5 parts of antioxidant, 3.94 parts of release agent, and 3 parts of flow aid. The acrylate rubber was a carboxyl-type acrylate rubber, brand name Dewey Technology ACM 4211. The curing crosslinking agent was a compound of hexamethylene diamine carbamate and di-o-tolueneguanidine in a mass ratio of 1:0.2. The modified carbon black was prepared according to Preparation Example 2. The high-temperature plasticizer was Rohm and Haas TP-95. The antioxidant was antioxidant 264. The release agent was PE wax. The flow aid was flow aid WS180.

[0042] Acrylic rubber, modified carbon black, silica, Rohm and Haas TP-95, antioxidant 264, PE wax, and flow aid WS180 were melt-blended at 145°C to obtain a premix. Hexamethylene diamine carbamate and di-o-tolueneguanidine were added to the premix, mixed evenly, and vulcanized at 165°C for 6 minutes. After repairing the sprue, a second vulcanization was performed at 160°C for 4 hours to obtain the valve cover gasket.

[0043] Example 3 The preparation method of the valve cover gasket includes the following steps: Raw materials were weighed according to the following proportions by weight: 100 parts acrylate rubber, 3.07 parts curing crosslinking agent, 65 parts modified carbon black, 13 parts silica, 4.25 parts high-temperature plasticizer, 2 parts antioxidant, 4.94 parts release agent, and 3.4 parts flow aid. The acrylate rubber was a carboxyl-type acrylate rubber, brand name Dewey Technology ACM 4211. The curing crosslinking agent was a compound of hexamethylene diamine carbamate and di-o-tolueneguanidine in a mass ratio of 1:0.2. The modified carbon black was prepared according to Preparation Example 3. The high-temperature plasticizer was Rohm and Haas TP-759. The antioxidant was antioxidant 445. The release agent was stearic acid. The flow aid was flow aid WS180.

[0044] Acrylic rubber, modified carbon black, silica, Rohm and Haas TP-759, antioxidant 445, stearic acid, and flow aid WS180 were melt-blended at 150°C to obtain a premix. Hexamethylene diamine carbamate and di-o-tolueneguanidine were added to the premix, mixed evenly, and vulcanized at 170°C for 5 minutes. After the gate was trimmed, a second vulcanization was performed at 162°C for 4 hours to obtain the valve cover gasket.

[0045] Example 4 The difference between this embodiment and Example 3 is that the modified carbon black prepared in Example 4 is used.

[0046] Example 5 The difference between this embodiment and Example 3 is that the modified carbon black prepared in Example 5 is used.

[0047] Example 6 The difference between this embodiment and Embodiment 3 is that the acrylate rubber used is active chloroacrylate rubber, with the brand name Dewey Technology ACM 101X.

[0048] Comparative Example 1 The method for preparing the valve cover gasket differs from that in Example 3 in that the modified carbon black is replaced by N-550 carbon black.

[0049] Comparative Example 2 The method for preparing the valve cover gasket differs from that in Example 3 in that modified carbon black is not added.

[0050] Comparative Example 3 The method for preparing the valve cover gasket differs from that in Example 3 in that silica is not added. Performance testing

[0051] According to GB / T 531.1-2008 standard, the hardness (Shore A type) of the valve cover gaskets prepared in Examples 1-6 and Comparative Examples 1-3 was tested, and the results are recorded in Table 1.

[0052] According to GB / T 528-2009 standard, the tensile strength, 100% tensile strength at a constant elongation, and elongation at break of the valve cover gaskets prepared in Examples 1-6 and Comparative Examples 1-3 were tested, and the results are recorded in Table 1.

[0053] According to GB / T 529-2009 standard, the tear strength of the valve cover gaskets prepared in Examples 1-6 and Comparative Examples 1-3 was tested, and the results are recorded in Table 1.

[0054] According to GB / T 7759.1-2015 standard, the compression set properties of the valve cover gaskets prepared in Examples 1-6 and Comparative Examples 1-3 were tested under the conditions of 150℃ for 70 hours. The results are recorded in Table 1.

[0055] According to GB / T 1682-2014 standard, the brittle temperature of the valve cover gaskets prepared in Examples 1-6 and Comparative Examples 1-3 was tested, and the results are recorded in Table 2.

[0056] According to GB / T 1690-2010 standard, the oil resistance of valve cover gaskets prepared in Examples 1-6 and Comparative Examples 1-3 was tested. The samples were immersed in IRM903 test oil at 150°C for 70 hours. After the test, the samples were removed and wiped clean. The weight and volume change rate were measured within 30 minutes. The results are recorded in Table 2.

[0057] Table 1

[0058] Table 2

[0059] A comparison of Examples 3 and 4, along with the data in Tables 1-2, reveals that replacing hexyl acrylate with ethyl acrylate in Example 3 (i.e., Example 4) resulted in varying degrees of decrease in the mechanical properties, low-temperature toughness, and oil resistance of the valve cover gasket, with a significant reduction in low-temperature resistance. This indicates that hexyl acrylate plays a crucial role in improving material properties during the preparation of modified carbon black. Its longer carbon chain structure may impart superior flexibility and compatibility to the coating layer, facilitating the uniform dispersion of modified carbon black within the acrylate rubber matrix, thereby synergistically enhancing the material's mechanical strength, low-temperature stability, and oil-resistant sealing performance.

[0060] Based on the comparison between Examples 3 and 5 and the data in Tables 1-2, it can be seen that after replacing the diethylene glycol monomethyl ether acrylate in Example 3 with methoxyethyl acrylate (i.e., Example 5), the hardness, tensile strength, 100% tensile strength at a given elongation, elongation at break, and tear strength of the valve cover gasket all decreased, while the compression set increased, the brittle temperature rose, and the volume and mass change rate after oil immersion also increased significantly. This may be because diethylene glycol monomethyl ether acrylate plays a key role in the coating monomer system of modified carbon black. The longer ether segments in its molecular structure can further optimize the flexibility and polarity matching of the coating layer, enhance the interfacial bonding force between the modified carbon black and the acrylate rubber matrix, and thus improve the mechanical properties, low-temperature toughness, and oil-resistant sealing stability of the material.

[0061] Based on the comparison between Example 3 and Example 6 and the data in Table 1-2, it can be seen that the thermal decomposition temperature of the amide bond formed by the carboxyl acrylate rubber and the curing crosslinking agent system selected in this application is higher than that of the amine salt bond formed by the reaction of chlorinated hydrocarbons and amines. This causes the active chlorinated rubber to be prone to crosslinking bond breakage at high temperatures, resulting in increased compression set.

[0062] Based on the comparison between Example 3 and Comparative Example 1, and the data in Tables 1-2, it can be seen that after replacing the modified carbon black with unmodified N-550 carbon black, all mechanical properties of the valve cover gasket decreased significantly, the compression set increased, the brittle temperature increased significantly, and the oil resistance also deteriorated markedly. This fully demonstrates that the modified carbon black effectively improves the overall performance of the material through the synergistic effect of the flexible segments coated on the surface and the silica.

[0063] Based on the comparison between Example 3 and Comparative Example 2 and the data in Table 1-2, it can be seen that the material performance of Comparative Example 2 deteriorated further when no modified carbon black was added. This indicates that modified carbon black is one of the core functional fillers for improving the performance of valve cover gaskets. Its uniform dispersion in the rubber matrix can not only play an effective reinforcing role, but also form a good interface bond with the matrix through the flexible acrylate segments coated on the surface, and work with silica to optimize the cross-linking network structure of the material, thereby significantly improving mechanical strength, oil resistance sealing performance and low temperature toughness.

[0064] Based on the comparison between Example 3 and Comparative Example 3, and the data in Tables 1-2, it can be seen that in Comparative Example 3 without silica, the compression set increased, and the mechanical properties and low-temperature resistance decreased slightly. This verifies the importance of silica's filling and supporting role in maintaining the material's elasticity and sealing performance over a wide temperature range. Silica, as an auxiliary functional filler, can form a synergistic effect with modified carbon black, further reducing the material's compression set and enhancing its tear strength and low-temperature brittleness resistance.

[0065] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A valve cover gasket, characterized in that, It is prepared from the following raw materials in parts by weight: Acrylic rubber 80-100 parts, curing crosslinking agent 2.07-3.07 parts, modified carbon black 55-65 parts, silica 10-13 parts, high-temperature plasticizer 3.75-4.25 parts, antioxidant 1-2 parts, release agent 2.94-4.94 parts, flow aid 2.6-3.4 parts; The raw materials for preparing the modified carbon black include carbon black, coating monomers and initiators, and the mass ratio of carbon black, coating monomers and initiators is 1:(0.1-0.2):(0.01-0.03).

2. The valve cover gasket according to claim 1, characterized in that, The coating monomers comprise methyl methacrylate, hexyl acrylate, acrylic acid, diethylene glycol diacrylate, and diethylene glycol monomethyl ether acrylate in a mass ratio of 1:(0.5-0.55):(0.03-0.05):(0.1-0.15):(0.2-0.3).

3. The valve cover gasket according to claim 1, characterized in that, The method for preparing the modified carbon black includes the following steps: Water and emulsifier are added to a reaction vessel and stirred until homogeneous. Then, the coated monomer is added and stirred until homogeneous. Carbon black is then added and stirred until homogeneous. The mixture is heated and stirred until homogeneous. The temperature is increased and an initiator is added to carry out the reaction. After the reaction is completed, the product is cooled, filtered, and dried to obtain modified carbon black.

4. The valve cover gasket according to claim 3, characterized in that, The mass ratio of the emulsifier to carbon black is (0.3-0.4):1, and the emulsifier includes emulsifier OP-10 and sodium dodecyl sulfate in a mass ratio of 1:(0.8-1); the initiator is potassium persulfate.

5. The valve cover gasket according to claim 1, characterized in that, The acrylate rubber is a carboxyl-type acrylate rubber.

6. The valve cover gasket according to claim 1, characterized in that, The curing crosslinking agent is an amine curing crosslinking agent, which includes one or two of hexamethylenediamine carbamate and di-o-tolueneguanidine.

7. The valve cover gasket according to claim 1, characterized in that, The high-temperature plasticizer includes one or more of Adico RS-705, Adico RS-107, Rohm and Haas TP-95, and Rohm and Haas TP-759.

8. The valve cover gasket according to claim 1, characterized in that, Antioxidants include one or more of antioxidant 445, antioxidant RD, antioxidant MB, and antioxidant 264.

9. The valve cover gasket according to claim 1, characterized in that, The release agent includes one or two of stearic acid and PE wax; the flow aid includes one or two of isopentyl stearate and flow aid WS180.

10. A method for preparing a valve cover gasket according to any one of claims 1-9, characterized in that, Includes the following steps: Acrylic rubber, modified carbon black, silica, high-temperature plasticizer, antioxidant, release agent, and flow aid are melt-blended at 140-150℃ to obtain a premix. A curing crosslinking agent is added to the premix, mixed evenly, and vulcanized at 150-180℃. After the gate is repaired, a second vulcanization is performed to obtain the valve cover gasket.

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