Composite antioxidant and preparation method therefor, and rubber product

Abstract

Provided are a composite antioxidant and a preparation method therefor, and a rubber product. The composite antioxidant comprises the following components in parts by weight: 100.0 parts of carbon black, 2.0-5.0 parts of an antioxidant, 2.0-5.0 parts of polyethylene glycol, 0.1-0.2 parts of ethylene-butylene rubber, and 0.1-2.0 parts of a silane coupling agent. By means of extensive research, it has been found that, by using polyethylene glycol as a dispersant to jointly disperse and load an antioxidant and a small amount of ethylene-butylene rubber onto a carrier, i.e., carbon black, the antioxidant, the carbon black, and the ethylene-butylene rubber form a stable binding system, so that the effect of the antioxidant can be exerted to a greater extent, and the anti-aging performance of a product containing the antioxidant is improved.

Description

A composite antioxidant and its preparation method, and rubber products Technical Field

[0001] This invention relates to the field of composite material technology, and in particular to a composite antioxidant, its preparation method, and rubber products. Background Technology

[0002] Equipment control units in power grid systems operate under various high-temperature environments. Although static sealing rings are only a small unit in the equipment control system, their performance degradation or damage can paralyze the entire system. Prolonged exposure to high temperatures reduces the size and mechanical strength of the sealing rings, making them prone to deformation and displacement. This leads to poor sealing performance, making the power system susceptible to external dust, water vapor, and other contaminants. These impurities can enter the equipment control system, adhere to electrical components, affect heat dissipation, cause localized overheating, and even trigger short circuits or discharges.

[0003] Antioxidants are usually added during the rubber manufacturing process to improve the high-temperature aging resistance of rubber products. However, the dispersion of antioxidants in the rubber matrix can have a significant impact on the high-temperature aging resistance and mechanical strength of rubber products, thereby affecting their service life.

[0004] Therefore, there is a need to provide a composite antioxidant with excellent dispersibility in a rubber matrix. Summary of the Invention

[0005] In order to improve the service life of rubber products under high temperature environment, the present invention provides a composite antioxidant with high dispersibility for use in rubber products.

[0006] The present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a composite antioxidant comprising the following components in parts by weight:

[0008] 100.0 parts carbon black, 2.0 to 5.0 parts antioxidant, 2.0 to 5.0 parts polyethylene glycol, 0.1 to 0.2 parts ethylene butadiene rubber, 0.1 to 2.0 parts silane coupling agent.

[0009] In some embodiments, the weight-average molecular weight of the polyethylene glycol is 200 to 600.

[0010] In some embodiments, the ethylene-butadiene rubber has a Mooney viscosity of 47–53 MU at ML(1+4), 100°C.

[0011] In some embodiments, the reactive monomers of the ethylene-butadiene rubber include ethylene, butene, and non-conjugated polyenes, with the mass of ethylene accounting for 48-53% of the total mass of the ethylene-butadiene rubber.

[0012] In some embodiments, the antioxidant includes at least one selected from 2-mercaptobenzimidazole zinc salt, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 2,6-di-tert-butyl-4-methylphenol, and N,N'-bis(β-naphthyl)-p-phenylenediamine.

[0013] In some embodiments, the silane coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltri(β-methoxyethoxy)silane.

[0014] In some embodiments, the particle size of the carbon black is ≤50μm.

[0015] A second aspect of the present invention provides a method for preparing the composite antioxidant described in the first aspect of the present invention, comprising the following steps:

[0016] S1 Preparation of Dispersion

[0017] According to the stated weight proportions, the antioxidant and silane coupling agent are dispersed in water to form an antioxidant dispersion; ethylene butyl rubber and silane coupling agent are dispersed in water to form an ethylene butyl rubber dispersion; and polyethylene glycol is dissolved in water to form a polyethylene glycol dispersion.

[0018] S2 granulation

[0019] The antioxidant dispersion and ethylene butyl rubber dispersion prepared in step S1 are added to the polyethylene glycol dispersion and mixed evenly with the carbon black in the specified weight to form a homogeneous slurry. The homogeneous slurry is injected into a granulation device for granulation, and then dried and sieved to obtain the composite antioxidant.

[0020] In some embodiments, the solid content of the homogenized slurry described in step S2 is 50–60 wt.%.

[0021] A third aspect of the present invention provides a rubber article comprising the following components in parts by weight:

[0022] 100.0 parts of base rubber, 40.0 to 60.0 parts of the composite antioxidant described in the first aspect of the present invention, 4.0 to 6.0 parts of vulcanizing agent, 10.0 to 20.0 parts of inorganic filler, and 0.0 to 20.0 parts of processing aid.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] This invention loads antioxidants, polyethylene glycol, and ethylene butyl rubber onto a carbon black carrier, which significantly improves the dispersibility and high-temperature aging resistance of the antioxidants in its products. Detailed Implementation

[0025] To better illustrate the purpose, technical solution, and advantages of this invention, specific embodiments will be used to further describe the invention below. However, these embodiments do not limit the invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in this technical field. Unless otherwise specified, all reagents and materials used in this invention are commercially available.

[0026] In a first aspect, the present invention provides a composite antioxidant comprising the following components in parts by weight:

[0027] 100.0 parts carbon black, 2.0 to 5.0 parts antioxidant, 2.0 to 5.0 parts polyethylene glycol, 0.1 to 0.2 parts ethylene butadiene rubber, 0.1 to 2.0 parts silane coupling agent.

[0028] Loading antioxidants onto a carrier to prepare supported composite antioxidants can improve their dispersion performance in the rubber matrix and fully leverage their high-temperature aging resistance. Carbon black, due to its excellent stability and specific surface area, is an excellent carrier for adsorption; however, it can inhibit the anti-aging effect of antioxidants. This invention, through extensive research, has found that using polyethylene glycol as a dispersant to co-disperse antioxidants and trace amounts of ethylene-butyl rubber onto a carbon black carrier allows for a stable bond between the antioxidant, carbon black, and ethylene-butyl rubber, maximizing the effectiveness of the antioxidant and enhancing the anti-aging properties of the finished product.

[0029] In the composite antioxidant of this invention, carbon black serves as a carrier, adsorbing and dispersing the antioxidant, polyethylene glycol (PEG), and ethylene butyl rubber (EBR). Specifically: 1) PEG improves the dispersibility of the antioxidant in the carbon black carrier. Furthermore, PEG adsorbed onto the carrier surface further enhances the stability of carbon black at high temperatures; it also improves the dispersion stability of the composite antioxidant in the matrix of its products, reduces the viscosity of the products during processing, and improves processing performance; 2) EBR simultaneously adsorbs both the antioxidant and carbon black, acting as a bridge between the carbon black carrier and the antioxidant, further stabilizing the anti-aging properties of the antioxidant. Therefore, the combined effect of PEG and EBR significantly reduces the influence of the carbon black carrier on the antioxidant's performance. Using carbon black as the antioxidant carrier significantly improves its dispersion stability in antioxidant products and significantly enhances the antioxidant's high-temperature aging resistance in its products.

[0030] In some embodiments, the polyethylene glycol (PEG) has a weight-average molecular weight of 200 to 600. A molecular weight within this suitable range provides the polyethylene glycol with appropriate viscosity, allowing for uniform dispersion on the carrier surface. Simultaneously, it enables more robust interaction with the carbon black surface, forming a stable dispersion system and increasing the loading of the antioxidant.

[0031] In this invention, the reactive monomers of the ethylene-butadiene rubber include ethylene, butene, and non-conjugated polyenes. The non-conjugated polyenes include, but are not limited to, at least one of 5-ethylidene-2-norbornene (ENB) and 5-vinyl-2-norbornene (VNB). The Mooney viscosity and segment composition of the ethylene-butadiene rubber affect its properties; however, since the amount of ethylene-butadiene rubber added in the composite antioxidant of this invention is extremely small, its properties have little impact on the high-temperature aging resistance of the composite antioxidant. Commonly used ethylene-butadiene rubbers in the art can be used to prepare the composite antioxidant in this invention.

[0032] In some embodiments, the ethylene-butadiene rubber has a Mooney viscosity of 47–53 MU at ML(1+4) and 100°C; and the ethylene content in the ethylene-butadiene rubber accounts for 48–53% of the total mass of the reactive monomers. When the viscosity of the ethylene-butadiene rubber and the amount of ethylene monomer are within the above-mentioned suitable ranges, the processing performance and high-temperature aging resistance of the antioxidant product can be further improved.

[0033] In this invention, the ethylene-butadiene rubber (EBT) can be prepared in-house using conventional synthetic methods in the art, or a commercially available product can be used. Commercially available products include: EBT developed by Mitsui Chemicals, a terpolymer of ethylene, butene, and 5-ethylidene-2-norbornene (ENB) synthesized using a metallocene catalyst, with two grades already commercially available (K-9330M).

[0034] In this invention, the Mooney viscosity of ethylene-butyl rubber is obtained by using a Mooney viscometer at ML(1+4) and 100°C, in accordance with the standard ASTM D1646-2019.

[0035] In some embodiments, the antioxidant includes at least one of 2-mercaptobenzimidazole zinc salt (antioxidant ZMTI), 2,2,4-trimethyl-1,2-dihydroquinoline polymer (antioxidant RD), N-isopropyl-N'-phenyl-p-phenylenediamine (antioxidant 4010NA), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (antioxidant 4020), 2,6-di-tert-butyl-4-methylphenol (antioxidant 264), and N,N'-di(β-naphthyl)-p-phenylenediamine (antioxidant DNP).

[0036] In this invention, a silane coupling agent may also be added. This silane coupling agent includes, but is not limited to, at least one of γ-aminopropyltriethoxysilane (KH550), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560), γ-methacryloyloxypropyltrimethoxysilane (KH570), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH792), N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH602), vinyltriethoxysilane (A151), vinyltrimethoxysilane (A171), and vinyltris(β-methoxyethoxy)silane (A172). The addition of the silane coupling agent can improve the dispersibility of ethylene butyl rubber and polyethylene glycol.

[0037] In some embodiments, the carbon black has a particle size ≤ 50 μm. A carbon black particle size within the aforementioned suitable range exhibits both excellent adsorption properties and dispersion stability.

[0038] In some embodiments, the composite antioxidant comprises the following components in parts by weight:

[0039] 100.0 parts carbon black, 3.0 to 5.0 parts antioxidant, 3.0 to 5.0 parts polyethylene glycol, 0.1 to 0.15 parts ethylene butadiene rubber, 1.0 to 2.0 parts silane coupling agent.

[0040] In some embodiments, the particle size of the composite antioxidant is 200–400 μm.

[0041] It is understood that the antioxidants listed herein are compounds known in the art and used for anti-aging. They primarily function as anti-aging agents in the system of this invention, and their mechanisms of action are similar. Therefore, under the stable loading system of "carbon black-butyl rubber-polyethylene glycol" provided by this invention, those skilled in the art can select one or more antioxidants from the list through conventional experiments, based on the specific performance requirements of the product (such as heat resistance, oxidation resistance, flexural strength, etc.). Similarly, it is understood that the main function of the various silane coupling agents listed herein in the system of this invention is to improve the dispersibility of butyl rubber and polyethylene glycol. Silane coupling agents with different functional groups listed herein can all achieve this function. Those skilled in the art can select suitable silane coupling agents from the list of silane coupling agents through conventional experiments, based on the specific properties of the antioxidants used and the butyl rubber. Furthermore, it is understood that the specific mass ratio of non-conjugated polyenes in ethylene-butadiene rubber is not a key technical issue, and this application does not impose any particular restrictions on this. It is sufficient to select a conventional mass ratio of non-conjugated polyenes in ethylene-butadiene rubber (e.g., 1-15%, 2-10%, or 3-8%).

[0042] A second aspect of the present invention provides a method for preparing the composite antioxidant described in the first aspect of the present invention, comprising the following steps:

[0043] S1 Preparation of Dispersion

[0044] According to the stated weight proportions, the antioxidant and silane coupling agent are dispersed in water to form an antioxidant dispersion; ethylene butyl rubber and silane coupling agent are dispersed in water to form an ethylene butyl rubber dispersion; and polyethylene glycol is dissolved in water to form a polyethylene glycol dispersion.

[0045] S2 granulation

[0046] The antioxidant dispersion and ethylene butyl rubber dispersion prepared in step S1 are added to the polyethylene glycol dispersion and mixed evenly with the carbon black in the specified weight to form a homogeneous slurry. The homogeneous slurry is injected into a granulation device for granulation, and then dried and sieved to obtain the composite antioxidant.

[0047] In some embodiments, the homogenized slurry described in step S2 has a solid content of 50–60 wt.%. Within this solid content range, the slurry has a suitable viscosity, which is beneficial for processing.

[0048] In some embodiments, the drying temperature is 150–170°C.

[0049] First, the antioxidant dispersion, ethylene butyl rubber dispersion, and polyethylene glycol dispersion are mixed to ensure that the antioxidant is fully adsorbed and adhered to the surface of the ethylene butyl rubber. Then, it is mixed with carbon black and granulated. During the granulation process, the ethylene butyl rubber and polyethylene glycol will firmly adhere to the surface of the carbon black, thus forming a stable bond system of carbon black, ethylene butyl rubber, and antioxidant.

[0050] In a third aspect, the present invention provides a rubber article comprising the following components in parts by weight: 100.0 parts of base rubber, 40.0 to 60.0 parts of the composite antioxidant described in the first aspect of the present invention, 4.0 to 6.0 parts of vulcanizing agent, 10.0 to 20.0 parts of inorganic filler, and 5.0 to 20.0 parts of processing aid.

[0051] Commonly used rubber matrices and vulcanizing agents for rubber can be used in this invention.

[0052] In some embodiments, the vulcanizing agent includes, but is not limited to, at least one of triallyl isocyanurate (TAIC) and dicumyl peroxide (DCP).

[0053] In some embodiments, the processing aids include, but are not limited to, at least one of lubricants and dispersants. Common lubricants and dispersants in the art can be used in this invention.

[0054] In some embodiments, inorganic fillers are used to enhance the mechanical strength of rubber. Common inorganic fillers in the art can be used in this invention. The inorganic fillers include, but are not limited to, at least one of calcium carbonate, talc, and metal oxides.

[0055] In some embodiments, the lubricant includes, but is not limited to, at least one of paraffin oil and stearic acid.

[0056] The following are specific embodiments of the present invention. The relevant raw materials used in the embodiments and comparative examples of the present invention are listed below:

[0057] Ethylene-butadiene rubber: prepared by the following method:

[0058] Ethylene, butene, and 5-ethylidene-2-norbornene (ENB) were used as monomers, Ziegler-Natta catalyst was used as the catalyst, and benzoyl peroxide was used as the initiator. The raw materials for the above reaction were dissolved in toluene solvent for polymerization. By adjusting the temperature, pressure, and proportion of monomers used in the polymerization reaction, different ethylene-butadiene rubbers (EBT) were prepared, as detailed in Table 1:

[0059] Table 1

[0060] Carbon Black-1: Grinded to a particle size of 10-20μm, commercially available;

[0061] Carbon black-2: Grind to a particle size of 30-50μm, commercially available;

[0062] Carbon Black-3: Grinded to a particle size of 60-80μm, commercially available;

[0063] Silica: Average particle size 200nm, commercially available;

[0064] PEG-200: Commercially available;

[0065] PEG-600: Commercially available;

[0066] PEG-2000: Commercially available;

[0067] Silane coupling agent: KH550, commercially available;

[0068] Anti-aging agent ZMTI: Commercially available;

[0069] Anti-aging agent DNP: Commercially available.

[0070] Unless otherwise specified, the raw materials used in the embodiments of the present invention are all the same commercially available raw materials. For example, the carbon black mentioned above is the same commercially available product, ground to different particle sizes.

[0071] Examples 1-15, Comparative Examples 1-7

[0072] A series of composite antioxidants are provided, and the preparation method includes the following steps:

[0073] S1 Preparation of Dispersion

[0074] According to the formulations (parts by weight) described in Tables 2-3, the antioxidant and silane coupling agent are dispersed in water to form an antioxidant dispersion; ethylene butyl rubber and silane coupling agent are dispersed in water to form an ethylene butyl rubber dispersion; and polyethylene glycol is dissolved in water to form a polyethylene glycol dispersion.

[0075] S2 granulation

[0076] The antioxidant dispersion and ethylene butyl rubber dispersion prepared in step S1 are added to the polyethylene glycol dispersion and mixed evenly with carbon black to form a homogeneous slurry (solid content of 50 wt.%). The homogeneous slurry is then poured at a rate of 70 m... 3 The compound antioxidant is fed into the granulation system at a flow rate of / h and injected into the granulation equipment for granulation. Then, it is dried in a forced-air drying oven at 170℃ to constant weight to obtain the compound antioxidant. The compound antioxidant particles with a particle size in the range of 200-400μm are screened out for later use.

[0077] It should be noted that in the embodiments of the present invention, the concentration of each raw material in its respective dispersion is not limited in step S1, and can be adjusted conventionally according to the specific dosage, as long as the dispersion and mixing in step S2 can be uniform and a homogeneous slurry can be prepared for granulation.

[0078] Table 2

[0079] Table 3

[0080] Application examples

[0081] The composite antioxidants obtained in the above examples and comparative examples were added to the rubber matrix to prepare rubber products. According to the weight parts shown in Table 4, all raw materials were mixed evenly and then vulcanized at 160°C and 15 MPa for 30 minutes to obtain the corresponding rubber products. Among them, the rubber products with the composite antioxidants prepared in Examples 1 to 15 correspond to Application Examples 1 to 15, respectively, and the rubber products with the composite antioxidants prepared in Comparative Examples 1 to 7 correspond to Comparative Application Examples 1 to 7, respectively. The "Rubber Products (Comparative)" used for comparison in Table 4 is referred to as Comparative Application Example 8.

[0082] Table 4 Rubber Products

[0083] Performance testing

[0084] 1. Initial mechanical strength test: According to the test method in standard GB / T 528-2009, after sample preparation, tensile test and Shore A hardness test were carried out at 50 mm / min in an environment of 25±2℃. The test results are detailed in Table 5.

[0085] 2. High-temperature aging resistance test: The above rubber products were placed in an environment of 100℃ and left to stand for 72 hours. After being taken out and cooled, the mechanical properties of the products after high-temperature aging were further tested according to the method described above, and the change rate (%) of the relevant mechanical properties was calculated. Taking tensile strength as an example, the change rate of tensile strength = |mechanical strength after aging - initial mechanical strength before aging| / initial mechanical strength before aging × 100%. The calculation formula for the change rate of other properties is the same. For specific test results, please refer to Table 5.

[0086] Table 5 Performance Test Results

[0087] The results above show that:

[0088] The composite antioxidant prepared by this invention has good dispersibility in the rubber matrix. Carbon black, as a carrier, further improves its dispersion stability in the matrix. The prepared rubber products have excellent initial mechanical strength and can maximize the high-temperature aging resistance of the antioxidant.

[0089] The composite antioxidant in Comparative Example 1 did not contain ethylene butadiene rubber, Comparative Example 5 did not contain polyethylene glycol, and Comparative Example 6 did not contain either polyethylene glycol or ethylene butadiene rubber. The high-temperature aging resistance of the rubber products prepared using these composite antioxidants was significantly reduced.

[0090] In Comparative Example 7, the composite antioxidant used silica as a carrier, and the initial mechanical strength of the rubber products prepared was significantly worse.

[0091] Comparative Example 2 contained a larger amount of ethylene butyl rubber. The larger amount of ethylene butyl rubber would coat and consume the antioxidant, affecting the performance of the antioxidant and significantly deteriorating the high-temperature aging resistance of the prepared rubber products.

[0092] In Comparative Examples 3 and 4, the addition of other rubber components significantly reduced the aging resistance of the resulting rubber products.

[0093] The performance comparison results of the above embodiments and comparative examples show that using polyethylene glycol as a dispersant to disperse the antioxidant and a trace amount of ethylene butadiene rubber together onto the carrier carbon black allows the antioxidant, carbon black, and ethylene butadiene rubber to form a stable bond system, which can maximize the effectiveness of the antioxidant and improve the anti-aging performance of the product.

[0094] Furthermore, Examples 6, 8, and 11-15 demonstrate that even when the carbon black particle size, PEG molecular weight, or ethylene-butadiene rubber parameters (Mooney viscosity, ethylene content) are outside the preferred range of this invention, the performance of the resulting composite antioxidant and its rubber products is still significantly superior to the comparative examples, achieving the technical effects of this invention. By selecting the preferred range of this invention, performance can be further improved.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A composite antioxidant, characterized in that, It comprises the following components in parts by weight: 100.0 parts carbon black, 2.0 to 5.0 parts antioxidant, 2.0 to 5.0 parts polyethylene glycol, 0.1 to 0.2 parts ethylene butadiene rubber, and 0.1 to 2.0 parts silane coupling agent.

2. The composite antioxidant according to claim 1, characterized in that, The weight-average molecular weight of the polyethylene glycol is 200–600.

3. The composite antioxidant according to claim 1, characterized in that, The Mooney viscosity of the ethylene-butadiene rubber at ML(1+4) and 100°C is 47–53 MU.

4. The composite antioxidant according to claim 1, characterized in that, The reactive monomers of the ethylene-butadiene rubber include ethylene, butene, and non-conjugated polyenes; the mass of ethylene accounts for 48-53% of the total mass of the ethylene-butadiene rubber.

5. The composite antioxidant according to any one of claims 1-4, characterized in that, The antioxidant comprises at least one of 2-mercaptobenzimidazole zinc salt, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 2,6-di-tert-butyl-4-methylphenol, and N,N'-di(β-naphthyl)-p-phenylenediamine.

6. The composite antioxidant according to any one of claims 1-4, characterized in that, The silane coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltri(β-methoxyethoxy)silane.

7. The composite antioxidant according to any one of claims 1-4, characterized in that, The particle size of the carbon black is ≤50μm.

8. The method for preparing the composite antioxidant according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1 Preparation of Dispersion According to the stated weight proportions, the antioxidant and silane coupling agent are dispersed in water to form an antioxidant dispersion; ethylene butyl rubber and silane coupling agent are dispersed in water to form an ethylene butyl rubber dispersion; and polyethylene glycol is dissolved in water to form a polyethylene glycol dispersion. S2 granulation The antioxidant dispersion and ethylene butyl rubber dispersion prepared in step S1 are added to the polyethylene glycol dispersion and mixed evenly with the carbon black in the specified weight to form a homogeneous slurry. The homogeneous slurry is injected into a granulation device for granulation, and then dried and sieved to obtain the composite antioxidant.

9. The method for preparing the composite antioxidant according to claim 8, characterized in that, The solid content of the homogenized slurry mentioned in step S2 is 50-60 wt.%.

10. A rubber product, characterized in that, It includes the following components in parts by weight: 100.0 parts of base rubber, 40.0 to 60.0 parts of the composite antioxidant as described in any one of claims 1 to 7, 4.0 to 6.0 parts of vulcanizing agent, 10.0 to 20.0 parts of inorganic filler, and 0.0 to 20.0 parts of processing aid.

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