Rubber composition and preparation method thereof

Abstract

The invention relates to the technical field of rubber compositions, and provides a rubber composition which comprises rubber, carbon black, a vulcanizing agent, an accelerant, an activating agent, an anti-aging agent and modified nano attapulgite, and the nano attapulgite is obtained by modifying with a silane coupling agent and 2-imidazole-1-ethylamine. The modified nano attapulgite delays the transfer of heat to the interior of the rubber and limits the propagation speed of thermal decomposition reaction through the nano-scale physical barrier effect, and the thermal barrier effect is beneficial to improving the thermal stability of the material and prolonging the service life of the material; the modification treatment also enhances the interface bonding force between the nano attapulgite and the rubber, and is beneficial to the effective transfer of stress, so that the prepared rubber composition has excellent heat resistance and mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of rubber compositions, and in particular to a rubber composition and a preparation method thereof. Background Art

[0002] Rubber materials are widely used in a variety of fields, including automotive, aerospace, electronics, and construction. They are particularly important in critical components such as seals, shock absorbers, and conveyor belts used in high-temperature environments. Their thermal stability is directly related to the product's service life and safety. However, most general-purpose rubbers (such as natural rubber, styrene-butadiene rubber, and butadiene rubber) are susceptible to molecular chain breakage, crosslinking disruption, or oxidative degradation under prolonged heat exposure, leading to decreased mechanical properties, surface cracking, and even failure. Therefore, effectively improving the thermal stability of rubber compositions has become a key technical challenge in the development of high-performance rubber materials.

[0003] In order to improve the heat resistance of rubber, traditional methods mainly focus on optimizing the vulcanization system, adding antioxidants, and introducing inorganic fillers. For example, the use of highly active accelerators and vulcanizing agents can enhance the crosslinking density and improve the thermal resistance of the material; the addition of antioxidants helps to inhibit oxidation reactions caused by free radicals. In addition, fillers such as carbon black, white carbon black, and clay are also widely used to improve the thermal stability and mechanical strength of rubber. However, these methods still have limitations in practical applications, such as poor filler dispersion, weak interfacial bonding, and insufficient durability, making it difficult to meet long-term service requirements in extremely high temperature environments. Therefore, there is an urgent need to develop a new rubber composition and its preparation method to achieve a significant improvement in heat resistance and stability while taking into account mechanical properties. Summary of the Invention

[0004] In view of this, the present invention provides a rubber composition having good heat resistance and stability while taking into account mechanical properties, and a preparation method thereof.

[0005] The technical solution of the present invention is achieved as follows: On the one hand, the present invention provides a rubber composition, including rubber, carbon black, a vulcanizing agent, an accelerator, an activator, an antioxidant, and modified nano-attapulgite, wherein the nano-attapulgite is modified with a silane coupling agent and 2-imidazole-1-ylethylamine.

[0006] At high temperatures, rubber molecular chains are prone to oxidative cracking or cross-linking network destruction; the modified nano-attapulgite delays the transfer of heat into the rubber through its nanoscale physical barrier effect and limits the propagation speed of thermal decomposition reactions; this "thermal barrier effect" helps to improve the thermal stability of the material and extend its service life. In addition, the physical barrier effect is combined with the chemical antioxidant effect of the antioxidant to form a "physical + chemical" dual protection mechanism, which significantly extends the service life of rubber at high temperatures.

[0007] The siloxane groups (Si–O–Si) of the silane coupling agent undergo a condensation reaction with the hydroxyl groups on the attapulgite surface, firmly grafting the polymer onto the surface. Simultaneously, the epoxy groups participate in the cross-linking reaction during rubber vulcanization, forming chemical bonds that bridge the rubber matrix and filler, enhancing interfacial adhesion. The imidazole rings undergo a ring-opening reaction with the epoxy groups on the silane coupling agent, forming a more stable covalent bond, further strengthening the chemical connection between the filler and rubber. The modifier, through chemical bonding and interfacial reinforcement, enhances the filler / rubber interface, forming a strong interfacial bond, preventing filler shedding or phase separation at high temperatures, and improving the overall thermal conductivity and thermal stability of the composite.

[0008] In composite filler systems, nano-attapulgite acts as a "bridge" or "connector," forming a denser network with carbon black, which helps improve the thermal stability of rubber compositions. Furthermore, the modified attapulgite surface contains active sites that promote crosslinking reactions, increase crosslink density, and enhance the heat resistance of vulcanized rubber.

[0009] On the basis of the above technical solution, preferably, calculated by weight, it includes 100 parts of rubber, 30-80 parts of carbon black, 1.5-5 parts of vulcanizer, 0.5-2 parts of accelerator, 4-7 parts of activator, 1-3 parts of antioxidant, and 5-15 parts of modified nano-attapulgite.

[0010] On the basis of the above technical solution, preferably, the preparation method of the modified nano-attapulgite comprises the following steps: S1, adding ethanol solution to a reaction kettle, adding attapulgite until the solid content is 5% to 10%, stirring evenly, and then slowly adding the ethanol solution of the silane coupling agent dropwise, controlling the pH value of the reaction solution to 4 to 6, and stirring the reaction at 60 to 80° C. for 2 to 3 hours; after the reaction is completed, filtering, washing, and drying to obtain silane coupling agent-modified attapulgite; S2, dispersing the silane coupling agent modified attapulgite in step S1 in an ethanol solution with a solid content of 5% to 10%, then adding an ethanol solution of 2-imidazole-1-ylethylamine, controlling the pH value of the reaction solution to 5.5 to 6.5, and reflux reacting at 70 to 90° C. for 2 to 4 hours; after the reaction is completed, cooling, filtering, washing, and drying to obtain the modified attapulgite.

[0011] On the basis of the above technical solution, preferably, the silane coupling agent is 3% to 8% of the mass of the attapulgite, and the 2-imidazole-1-ylethylamine is 3% to 5% of the mass of the attapulgite.

[0012] Based on the above technical solution, preferably, in steps S1 and S2, the volume concentration of the ethanol solution is 50%-75%.

[0013] On the basis of the above technical solution, preferably, the silane coupling agent is one of γ-glycidyloxypropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane.

[0014] On the basis of the above technical solution, preferably, the rubber composition further comprises a rare earth salt, and the mass ratio of the rare earth salt to the rubber is 1-3:100.

[0015] On the basis of the above technical solution, preferably, the rare earth salt is one or more combinations of cerium acetylacetonate, cerium citrate, lanthanum stearate and lanthanum polycarboxylate.

[0016] Rare earth ion Ce 3+ 、La 3+ The valence-modifying properties of rare earth acetylacetonate effectively capture free radicals, inhibiting the oxidative degradation of rubber at high temperatures. Rare earth acetylacetonate and rare earth citrate, with their functional ligands, act like surfactants in rubber, helping to better disperse carbon black fillers and reduce agglomeration.

[0017] Rare earth salts can be adsorbed onto the surface of attapulgite through electrostatic interactions or coordination, further enhancing its compatibility with the rubber matrix and achieving a more uniform distribution. Rare earth ions can also participate in interfacial reactions, forming a stable metal-organic interface layer and improving the interfacial bonding strength of the composite material.

[0018] The addition of nano-attapulgite improves the hardness and modulus of the material; rare earth salts promote the optimization of the cross-linking structure, giving the material better friction and shear resistance; the combined effect of the two also improves the tensile strength, elongation at break and tear strength.

[0019] Based on the above technical solution, preferably, the rubber is one or more combinations of natural rubber, styrene-butadiene rubber, chloroprene rubber and butadiene rubber; the carbon black is one or both of carbon black N220 and carbon black N550; the vulcanizing agent is phenolic resin, the accelerator is one or more of 2-mercaptobenzothiazole, N-cyclohexyl-2-benzothiazole sulfenamide, N,N'-diphenyl-thiourea and 2-mercaptobenzothiazole; the activator is one or both of stearic acid and zinc oxide; and the antioxidant is one or more of antioxidant RD, antioxidant 4010NA and antioxidant MB.

[0020] On the other hand, the present invention also provides a method for preparing a rubber composition, comprising the following steps: adding the rubber into an internal mixer and mixing at 90-120°C; then adding carbon black, modified nano-attapulgite and 1 / 3-2 / 3 of the mass of an activator and continuing to mix until the materials are evenly dispersed; adding a vulcanizing agent, an accelerator, an antioxidant, a rare earth salt and the remaining activator, adjusting the temperature to 70-90°C, and continuing to mix for 2-3 minutes to ensure that the components are fully mixed; vulcanizing the mixed rubber material, the vulcanization temperature is 130-180°C, and the vulcanization time is 10-60 minutes.

[0021] The rubber composition and preparation method of the present invention have the following advantages over the prior art: (1) The modified nano-attapulgite delays the transfer of heat to the inside of the rubber and limits the propagation speed of the thermal decomposition reaction through its nano-scale physical barrier effect; this "thermal barrier effect" helps to improve the thermal stability of the material and extend its service life; the nano-attapulgite doubly modified with silane coupling agent and 2-imidazole-1-ylethylamine also has good surface lipophilicity and dispersibility, allowing it to be evenly distributed in the rubber matrix; after modification, the nano-attapulgite forms a denser network structure with carbon black, which helps to improve thermal stability and strength; the modification treatment also enhances the interfacial bonding force between the nano-attapulgite and the rubber, which is conducive to the effective transfer of stress, thereby improving mechanical properties such as tensile strength and tear strength.

[0022] (2) Rare earth acetylacetonate and rare earth citrate contain functional ligands that act like surfactants in rubber, helping to better disperse carbon black fillers and reduce agglomeration. Furthermore, the addition of nano-attapulgite improves the material's hardness and modulus; rare earth salts promote the optimization of the cross-linking structure, giving the material better abrasion and shear resistance; the combined effect of the two also improves tensile strength, elongation at break, and tear strength. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] The natural rubber was Hainan Baodao Rubber, model SCR-WF; the styrene-butadiene rubber, model NS612, was purchased from ZEON Chemical Co., Ltd.; carbon black N220 and N550 were purchased from Tianjin Tianyi Century Chemical Co., Ltd.; and the antioxidants RD, 4010NA, and MB were purchased from Shanghai Jiacheng Chemical Co., Ltd.

[0025] Before use, the attapulgite was dried (oven-dried at 105°C), ground in a ball mill, and passed through a 100-mesh sieve to obtain nano-attapulgite.

[0026] Example 1 The rubber composition of this embodiment includes: 4 kg of natural rubber, 3 kg of styrene-butadiene rubber, 3 kg of chloroprene rubber, 3 kg of carbon black N220, 3 kg of carbon black N550, 0.3 kg of phenolic resin, 0.1 kg of 2-mercaptobenzothiazole, 0.05 kg of N-cyclohexyl-2-benzothiazolesulfenamide, 0.3 kg of stearic acid, 0.3 kg of zinc oxide, 0.2 kg of antioxidant RD, and 1 kg of modified nano-attapulgite.

[0027] The modified nano-attapulgite is obtained by modification with a silane coupling agent and 2-imidazole-1-ylethylamine. The preparation method comprises the following steps: S1. Add 20 L of ethanol aqueous solution (70% v / v) and 1.5 kg of attapulgite to a reactor until the solid content reaches 7.5%. After stirring evenly, slowly add 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane solution (0.09 kg of 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane dissolved in 1 L of 70% v / v ethanol solution) at a rate of 2 mL / min. Control the pH value of the reaction solution to 6 (adjust with 0.1 mol / L dilute hydrochloric acid or NaOH). After the addition is complete, stir and react at 75°C for 2.5 h. After the reaction is completed, filter (0.45 μm filter membrane), wash (wash with deionized water until neutral), and dry at 80°C to constant weight to obtain silane coupling agent-modified attapulgite. S2, dispersing the silane coupling agent-modified attapulgite obtained in step S1 (ultrasonic dispersion at 40 kHz for 30 min) in 20 L of ethanol aqueous solution (70% v / v), adding 2-imidazole-1-ylethylamine solution (0.06 kg of 2-imidazole-1-ylethylamine dissolved in 1 L of 70% v / v ethanol solution) under stirring, continuing to dissolve it, controlling the pH value of the reaction solution to 6 (adjusted by 0.1 mol / L dilute hydrochloric acid or NaOH), and then refluxing the reaction at 85°C for 3 h; after the reaction, cooling to room temperature, filtering (0.45 μm filter membrane), washing (washing with deionized water until neutral), and drying at 80°C to constant weight to obtain modified attapulgite.

[0028] The rubber composition of this embodiment is prepared by adding natural rubber, styrene-butadiene rubber, and chloroprene rubber to an internal mixer and mixing at 100°C; then, adding carbon black N220 and N550, modified nano-attapulgite, and 1 / 2 the mass of activator (stearic acid and zinc oxide) and continuing to mix until the materials are uniformly dispersed; adding phenolic resin, 2-mercaptobenzothiazole, N-cyclohexyl-2-benzothiazolesulfenamide, antioxidant RD, and the remaining activator (stearic acid and zinc oxide), adjusting the temperature to 80°C, and continuing to mix for 3 minutes to ensure that all components are fully mixed; and vulcanizing the mixed rubber at a vulcanization temperature of 150°C and a vulcanization time of 30 minutes.

[0029] Example 2 The difference between Example 2 and Example 1 is that 0.1 kg of cerium acetylacetonate and 0.1 kg of lanthanum stearate are added, and the other components are the same.

[0030] The rubber composition of this embodiment is prepared by adding natural rubber, styrene-butadiene rubber, and chloroprene rubber to an internal mixer and mixing at 100°C; then, adding carbon black N220 and N550, modified nano-attapulgite, and 1 / 2 the mass of activator (stearic acid and zinc oxide) and continuing to mix until the materials are uniformly dispersed; adding phenolic resin, 2-mercaptobenzothiazole, N-cyclohexyl-2-benzothiazolesulfenamide, antioxidant RD, cerium acetylacetonate, lanthanum stearate, and the remaining activator (stearic acid and zinc oxide), adjusting the temperature to 80°C, and continuing to mix for 3 minutes to ensure that all components are fully mixed; and vulcanizing the mixed rubber at a vulcanization temperature of 150°C and a vulcanization time of 30 minutes.

[0031] Example 3 The rubber composition of this embodiment includes: 2 kg of natural rubber, 3 kg of chloroprene rubber and 5 kg of butadiene rubber, 3 kg of carbon black N220, 0.2 kg of phenolic resin, 0.05 kg of 2-mercaptobenzothiazole, 0.5 kg of zinc oxide, 0.1 kg of antioxidant MB, 0.1 kg of lanthanum polycarboxylate and 0.8 kg of modified nano-attapulgite.

[0032] The modified nano-attapulgite is obtained by modification with a silane coupling agent and 2-imidazole-1-ylethylamine. The preparation method comprises the following steps: S1. Add 20 L of 50% v / v ethanol aqueous solution and 1 kg of attapulgite to a reactor until the solid content is 5%. Stir evenly. Then, slowly add γ-glycidyloxypropyltrimethoxysilane solution (0.03 kg of γ-glycidyloxypropyltrimethoxysilane dissolved in 1 L of 50% v / v ethanol aqueous solution) at a rate of 2 mL / min. Control the pH value of the reaction solution to 4 (adjust with 0.1 mol / L dilute hydrochloric acid or NaOH). After the addition is complete, stir and react at 60°C for 3 h. After the reaction is completed, filter (0.45 μm filter membrane), wash (wash with deionized water until neutral), and dry at 80°C to constant weight to obtain silane coupling agent-modified attapulgite. S2, dispersing the silane coupling agent-modified attapulgite obtained in step S1 (ultrasonic dispersion at 40 kHz for 30 min) in 20 L of ethanol aqueous solution (50% v / v), adding 2-imidazole-1-ylethylamine solution (0.04 kg of 2-imidazole-1-ylethylamine dissolved in 1 L of 50% v / v ethanol aqueous solution) under stirring, continuing stirring to dissolve, controlling the pH value of the reaction solution to 5.5 (adjusted by 0.1 mol / L dilute hydrochloric acid or NaOH), and then refluxing the reaction at 70°C for 4 h; after the reaction, cooling to room temperature, filtering (0.45 μm filter membrane), washing (washing with deionized water until neutral), and drying at 80°C to constant weight to obtain modified attapulgite.

[0033] The rubber composition of this embodiment is prepared by adding natural rubber, chloroprene rubber and butadiene rubber to an internal mixer and mixing at 90°C; then adding carbon black N220, modified nano-attapulgite and 1 / 3 of the mass of zinc oxide and continuing to mix until the materials are uniformly dispersed; adding phenolic resin, 2-mercaptobenzothiazole, antioxidant MB, lanthanum polycarboxylate and the remaining zinc oxide, adjusting the temperature to 90°C, and continuing to mix for 2 minutes to ensure that all components are fully mixed; and vulcanizing the mixed rubber at a vulcanization temperature of 130°C and a vulcanization time of 60 minutes.

[0034] Example 4 The rubber composition of this embodiment includes: 10 kg of butadiene rubber, 5 kg of carbon black N550, 0.15 kg of phenolic resin, 0.5 kg of N-cyclohexyl-2-benzothiazole sulfenamide, 0.5 kg of N,N'-diphenyl-thiourea, 0.4 kg of stearic acid, 0.15 kg of antioxidant RD, 0.15 kg of lanthanum stearate and 0.5 kg of modified nano-attapulgite.

[0035] The modified nano-attapulgite is obtained by modification with a silane coupling agent and 2-imidazole-1-ylethylamine. The preparation method comprises the following steps: S1. Add 20 L of ethanol aqueous solution (55% v / v) and 1 kg of attapulgite to a reactor until the solid content is 5%. After stirring evenly, slowly add γ-mercaptopropylmethyldimethoxysilane solution (0.05 kg of γ-mercaptopropylmethyldimethoxysilane is dissolved in 1 L of 55% v / v ethanol solution) at a rate of 2 mL / min. Control the pH value of the reaction solution to 6 (adjust with 0.1 mol / L dilute hydrochloric acid or NaOH). After the addition is complete, stir and react at 70°C for 2.5 hours. After the reaction is completed, filter (0.45 μm filter membrane), wash (wash with deionized water until neutral), and dry at 80°C to constant weight to obtain silane coupling agent-modified attapulgite. S2, dispersing the silane coupling agent-modified attapulgite obtained in step S1 (ultrasonic dispersion at 40 kHz for 30 min) in 20 L of ethanol aqueous solution (55% v / v), adding 2-imidazole-1-ylethylamine solution (0.05 kg of 2-imidazole-1-ylethylamine dissolved in 1 L of 55% v / v ethanol solution) under stirring, continuing stirring to dissolve, controlling the pH value of the reaction solution to 6.5 (adjusted by 0.1 mol / L dilute hydrochloric acid or NaOH), and then refluxing the reaction at 80°C for 3 h; after the reaction, cooling to room temperature, filtering (0.45 μm filter membrane), washing (washing with deionized water until neutral), and drying at 80°C to constant weight to obtain modified attapulgite.

[0036] The preparation method of the rubber composition of this embodiment is as follows: adding butadiene rubber to an internal mixer and mixing at 100°C; then adding carbon black N550, modified nano-attapulgite and 1 / 3 of the mass of stearic acid and continuing to mix until the materials are evenly dispersed; adding phenolic resin, N-cyclohexyl-2-benzothiazole sulfenamide and N,N'-diphenyl-thiourea, antioxidant RD, lanthanum stearate and the remaining stearic acid, adjusting the temperature to 70°C, and continuing to mix for 3 minutes to ensure that all components are fully mixed; the mixed rubber is vulcanized at a vulcanization temperature of 140°C and a vulcanization time of 30 minutes.

[0037] Example 5 The rubber composition of this embodiment includes: 3kg of styrene-butadiene rubber, 3kg of chloroprene rubber, 4kg of butadiene rubber, 4kg of carbon black N220, 4kg of carbon black N550, 0.4kg of phenolic resin, 0.1kg of 2-mercaptobenzothiazole, 0.1kg of N-cyclohexyl-2-benzothiazolesulfenamide, 0.3kg of stearic acid, 0.4kg of zinc oxide, 0.25kg of antioxidant RD, 0.1kg of cerium acetylacetonate, 0.1kg of cerium citrate, 0.1kg of lanthanum stearate, and 1.5kg of modified nano-attapulgite.

[0038] The modified nano-attapulgite is obtained by modification with a silane coupling agent and 2-imidazole-1-ylethylamine. The preparation method comprises the following steps: S1. Add 20 L of ethanol aqueous solution (75% v / v) and 2 kg of attapulgite to a reactor until the solid content is 10%. After stirring evenly, slowly add γ-mercaptopropylmethyldimethoxysilane solution (0.16 kg of γ-mercaptopropylmethyldimethoxysilane is dissolved in 1 L of 75% v / v ethanol solution) at a rate of 2 mL / min. Control the pH value of the reaction solution to 5 (adjust with 0.1 mol / L dilute hydrochloric acid or NaOH). After the addition is complete, stir and react at 80°C for 2 h. After the reaction is completed, filter (0.45 μm filter membrane), wash (wash with deionized water until neutral), and dry at 80°C to constant weight to obtain silane coupling agent-modified attapulgite. S2, dispersing the silane coupling agent-modified attapulgite obtained in step S1 (ultrasonic dispersion) in 20 L of ethanol aqueous solution (75% v / v), adding 2-imidazole-1-ylethylamine solution (0.06 kg of 2-imidazole-1-ylethylamine dissolved in 1 L of 75% v / v ethanol solution) under stirring, continuing stirring to dissolve, controlling the pH value of the reaction solution to 6 (adjusted by 0.1 mol / L dilute hydrochloric acid or NaOH), and then refluxing the reaction at 90°C for 2 h; after the reaction, cooling to room temperature, filtering (0.45 μm filter membrane), washing (washing with deionized water until neutral), and drying at 80°C to constant weight to obtain modified attapulgite.

[0039] The rubber composition of this embodiment is prepared by adding styrene-butadiene rubber, chloroprene rubber, and cis-1,4-butadiene rubber to an internal mixer and mixing at 120°C; then adding carbon black N220, carbon black N550, modified nano-attapulgite, and 2 / 3 of the mass of activator (stearic acid and zinc oxide) and continuing to mix until the materials are uniformly dispersed; adding phenolic resin, 2-mercaptobenzothiazole, N-cyclohexyl-2-benzothiazolesulfenamide, antioxidant RD, cerium acetylacetonate, cerium citrate, lanthanum stearate, and the remaining activator (stearic acid and zinc oxide), adjusting the temperature to 90°C, and continuing to mix for 3 minutes to ensure that all components are fully mixed; and vulcanizing the mixed rubber material at a vulcanization temperature of 170°C and a vulcanization time of 40 minutes.

[0040] Example 6 The rubber composition of this embodiment includes: 2.5 kg of natural rubber, 2.5 kg of styrene-butadiene rubber, 2.5 kg of chloroprene rubber, 2.5 kg of butadiene rubber, 3 kg of carbon black N220, 4 kg of carbon black N550, 0.5 kg of phenolic resin, 0.2 kg of 2-mercaptobenzothiazole, 0.5 kg of zinc oxide, 0.2 kg of antioxidant 4010NA, 0.1 kg of antioxidant MB, 0.1 kg of cerium citrate, 0.15 kg of lanthanum polycarboxylate, and 1.3 kg of modified nano-attapulgite.

[0041] The modified nano-attapulgite is obtained by modification with a silane coupling agent and 2-imidazole-1-ylethylamine. The preparation method comprises the following steps: S1, add 20L of ethanol aqueous solution (60% v / v) and 1.5kg of attapulgite to a reactor to a solid content of 7.5%, stir evenly, and then slowly add 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane solution (0.06kg of 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane is dissolved in 1L of 60% v / v ethanol solution) at a rate of 2 mL / min, and control the pH value of the reaction solution to 4 (adjusted by 0.1mol / L dilute hydrochloric acid or NaOH). After the addition is complete, stir and react at 80°C for 2h; after the reaction is completed, filter (0.45μm filter membrane), wash (wash with deionized water until neutral), and dry at 80°C to constant weight to obtain silane coupling agent modified attapulgite; S2, dispersing the silane coupling agent-modified attapulgite obtained in step S1 (ultrasonic dispersion at 40 kHz for 30 min) in 20 L of ethanol aqueous solution (60% v / v), adding 2-imidazole-1-ylethylamine solution (0.06 kg of 2-imidazole-1-ylethylamine dissolved in 1 L of 60% v / v ethanol solution) under stirring, continuing stirring to dissolve it, controlling the pH value of the reaction solution to 6 (adjusted by 0.1 mol / L dilute hydrochloric acid or NaOH), and then refluxing the reaction at 90°C for 2 h; after the reaction, cooling to room temperature, filtering (0.45 μm filter membrane), washing (washing with deionized water until neutral), and drying at 80°C to constant weight to obtain modified attapulgite.

[0042] The preparation method of the rubber composition of this embodiment is as follows: natural rubber, styrene-butadiene rubber, chloroprene rubber, and cis-1,4-dimethyl-1,6-dioxane rubber are added to an internal mixer and mixed at 120°C; then carbon black N220, carbon black N550, modified nano-attapulgite, and 1 / 3-2 / 3 of the mass of zinc oxide are added and mixing is continued until the materials are evenly dispersed; phenolic resin, 2-mercaptobenzothiazole, antioxidant 4010NA, antioxidant MB, cerium citrate, lanthanum polycarboxylate, and the remaining zinc oxide are added, the temperature is adjusted to 90°C, and mixing is continued for 2 minutes to ensure that all components are fully mixed; the mixed rubber is vulcanized at a vulcanization temperature of 180°C and a vulcanization time of 10 minutes.

[0043] Comparative Example 1 Compared with Example 1, in Comparative Example 1, the attapulgite is not modified but added directly, and the rest of the contents are the same as in Example 1.

[0044] Comparative Example 2 Compared with Example 1, in Comparative Example 2, the modified attapulgite is attapulgite modified with a silane coupling agent, and no 2-imidazole-1-ylethylamine is added for modification. The rest of the contents are the same as in Example 1.

[0045] Comparative Example 3 Compared with Example 1, Comparative Example 3 uses 2-imidazol-1-ylethylamine-modified attapulgite, without adding a silane coupling agent for modification, and the rest of the contents are the same as Example 1.

[0046] The preparation method of modified attapulgite is as follows: attapulgite is dispersed (ultrasonic dispersion) in 20 L of ethanol aqueous solution (70% v / v), 2-imidazole-1-ylethylamine solution is added under stirring (1 L of 70% v / v ethanol solution dissolves 0.06 kg of 2-imidazole-1-ylethylamine), and stirring is continued to dissolve it. The pH value of the reaction solution is controlled to 6 (adjusted by 0.1 mol / L dilute hydrochloric acid or NaOH), and then refluxed at 85°C for 3 hours; after the reaction is completed, it is cooled to room temperature, filtered (0.45 μm filter membrane), washed (washed with deionized water to neutrality), and dried at 80°C to constant weight to obtain modified attapulgite.

[0047] Comparative Example 4 Compared with Example 1, the amount of modified attapulgite in Comparative Example 4 exceeds the specified range, specifically 2 kg, and the rest is the same as Example 1.

[0048] Comparative Example 5 Compared with Example 2, in Comparative Example 5, the amount of rare earth salt used exceeds the specified range, specifically 0.5 kg. The rest of the contents are the same as in Example 1.

[0049] Comparative Example 6 Compared with Example 2, Comparative Example 6 is the same as Example 1, except that the rare earth salt is cerium nitrate.

[0050] The synthetic rubber compositions were subjected to the following tests: Heat stability: The prepared rubber composition was exposed to 120°C for 10 days. The change in tensile strength and elongation at break were measured before and after the test. The test method refers to GB / T 528-2009. Change (%) = (before test - after test) / after test × 100%.

[0051] Carbon black aggregation: After the prepared rubber composition is stored at room temperature for 30 days, the change in storage modulus ΔG' (test conditions: 0.25%-100%, @60°C) before and after storage (day 1 and day 30) is measured using a rubber processing analyzer to determine whether secondary aggregation has occurred during storage. The calculation formula is: ΔG' change rate (%) = (ΔG' before storage - ΔG' after storage) / ΔG' before storage × 100% The test results are shown in Table 1.

[0052]

[0053] The lower the rate of change in tensile strength and elongation at break, the better, indicating that the material maintains good mechanical properties after high-temperature aging. Example 2 exhibits optimal performance, demonstrating that rare earth salts (particularly cerium acetylacetonate + lanthanum stearate) possess excellent resistance to thermal oxidative aging. The unmodified attapulgite in Comparative Example 1 exhibits poor compatibility with rubber, resulting in a weak interface and accelerated degradation at high temperatures. Comparative Examples 2 and 3 demonstrate that while modification with silane or imidazole alone has some effect, it is not as effective as the synergistic effect of both. In Comparative Example 4, excessive addition of modified attapulgite may cause filler agglomeration, forming stress concentration points and reducing thermal stability. In Comparative Example 5, excessive rare earth salts may affect the vulcanization reaction or produce side reactions, which in turn may be detrimental to performance improvement. Comparative Example 6 exhibits moderate performance. While cerium nitrate also offers some antioxidant benefits, its dispersibility and rubber adhesion are inferior to those of organic ligand-complexed rare earth salts.

[0054] The lower the ΔG' change rate, the better, indicating that no obvious secondary aggregation of carbon black occurs during the parking process. Example 2 is the lowest, indicating that rare earth salts not only improve thermal stability, but also help improve filler dispersion, which may be due to the adsorption of rare earth ions on the filler surface, thereby enhancing the interaction with rubber. Comparative Example 1 is the highest, indicating that unmodified attapulgite cannot effectively prevent carbon black aggregation, and may even become an aggregation center. Comparative Examples 2 and 3 show that a single modifier cannot provide sufficient interfacial anchoring. In Comparative Example 4, excessive filler will lead to excessive local concentration, thereby promoting carbon black aggregation. Comparative Example 5 has some improvement but not significant. Excessive rare earth salts may change the rheological behavior of the rubber, but fail to completely inhibit aggregation. Comparative Example 6 is worse than Comparative Examples 1-4, but not as good as Example 2, indicating that although cerium nitrate has some auxiliary effect, it is not as good as organic ligand rare earth in terms of dispersibility and interfacial bonding.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A rubber composition, characterized in that: The invention comprises rubber, carbon black, vulcanizing agent, accelerator, activator, antioxidant and modified nano attapulgite. The nano attapulgite is modified by a silane coupling agent and 2-imidazole-1-ylethylamine.

2. A rubber composition according to claim 1, characterized in that: Calculated by weight, the composition includes 100 parts of rubber, 30-80 parts of carbon black, 1.5-5 parts of vulcanizing agent, 0.5-2 parts of accelerator, 4-7 parts of activator, 1-3 parts of antioxidant and 5-15 parts of modified nano-attapulgite.

3. A rubber composition according to claim 1, characterized in that: The preparation method of the modified nano-attapulgite comprises the following steps: S1, adding ethanol solution to a reaction kettle, adding attapulgite until the solid content is 5% to 10%, stirring evenly, and then slowly adding the ethanol solution of the silane coupling agent dropwise, controlling the pH value of the reaction solution to 4 to 6, and stirring the reaction at 60 to 80° C. for 2 to 3 hours; after the reaction is completed, filtering, washing, and drying to obtain silane coupling agent-modified attapulgite; S2, dispersing the silane coupling agent modified attapulgite in step S1 in an ethanol solution with a solid content of 5% to 10%, then adding an ethanol solution of 2-imidazole-1-ylethylamine, controlling the pH value of the reaction solution to 5.5 to 6.5, and reflux reacting at 70 to 90° C. for 2 to 4 hours; after the reaction is completed, cooling, filtering, washing, and drying to obtain the modified attapulgite.

4. A rubber composition according to claim 3, characterized in that: The silane coupling agent accounts for 3% to 8% of the mass of the attapulgite, and the 2-imidazole-1-ylethylamine accounts for 3% to 5% of the mass of the attapulgite.

5. A rubber composition according to claim 3, characterized in that: In steps S1 and S2, the volume concentration of the ethanol solution is 50%-75%.

6. A rubber composition according to claim 1, characterized in that: The silane coupling agent is one of γ-glycidyloxypropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane.

7. A rubber composition according to claim 2, characterized in that: The rubber composition further comprises a rare earth salt, and the mass ratio of the rare earth salt to the rubber is 1-3:

100.

8. A rubber composition according to claim 7, characterized in that: The rare earth salt is one or more of cerium acetylacetonate, cerium citrate, lanthanum stearate and lanthanum polycarboxylate.

9. A rubber composition according to claim 7, characterized in that: The rubber is one or more combinations of natural rubber, styrene-butadiene rubber, chloroprene rubber and butadiene rubber; the carbon black is one or both of carbon black N220 and carbon black N550; the vulcanizing agent is phenolic resin; the accelerator is one or more of 2-mercaptobenzothiazole, N-cyclohexyl-2-benzothiazolesulfenamide, N,N'-diphenyl-thiourea and 2-mercaptobenzothiazole; the activator is one or both of stearic acid and zinc oxide; and the antioxidant is one or more of antioxidant RD, antioxidant 4010NA and antioxidant MB.

10. A method for preparing a rubber composition according to any one of claims 7 to 9, characterized in that: The method comprises the following steps: adding rubber into an internal mixer and mixing at 90-120°C; then adding carbon black, modified nano-attapulgite and 1 / 3-2 / 3 of the mass of an activator and continuing to mix until the materials are evenly dispersed; adding a vulcanizing agent, an accelerator, an antioxidant, a rare earth salt and the remaining activator, adjusting the temperature to 70-90°C, and continuing to mix for 2-3 minutes to ensure that all components are fully mixed; and vulcanizing the mixed rubber material at a vulcanization temperature of 130-180°C and a vulcanization time of 10-60 minutes.

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