Environment-friendly bio-based reinforced rubber compound and preparation method thereof

Abstract

This invention discloses an environmentally friendly bio-based reinforcing compound and its preparation method. The compound, by weight, comprises: 100 parts EPDM rubber, 15-25 parts modified epoxidized soybean oil, 40-60 parts silane-modified rice husk ash silica, 2-2.5 parts peroxide, 1.5-2.5 parts crosslinking agent, and 5-7 parts additives. The modified epoxidized soybean oil is prepared by reacting epoxidized soybean oil with N-(2-hydroxyethyl)itaconic acid monoamide, followed by a reaction with a bio-based quaternary ammonium salt. This invention uses bio-based materials to replace traditional petroleum-based materials, resulting in excellent environmental performance. The introduction of modified epoxidized soybean oil significantly improves the compatibility and dispersibility of the bio-based reinforcing material with the rubber matrix, giving the compound excellent tensile strength, elongation at break, damping properties, antibacterial properties, and fatigue resistance. It can be widely used in automotive seals, shock absorbers, and other fields.

Description

Technical Field

[0001] This invention relates to the field of rubber compound technology, specifically to an environmentally friendly bio-based reinforcing rubber compound and its preparation method. Background Technology

[0002] Ethylene propylene diene monomer (EPDM) rubber is a synthetic rubber with excellent weather resistance, ozone resistance, aging resistance, and electrical insulation properties, widely used in automotive seals, building waterproofing materials, and wire and cable sheathing. However, pure EPDM rubber has poor mechanical properties, requiring the addition of reinforcing fillers to improve its strength and performance. Traditional rubber reinforcing materials mainly rely on petroleum-based products, such as carbon black and fumed silica. These materials not only consume non-renewable petroleum resources but also cause environmental pollution during production and use. With increasing environmental awareness and the promotion of sustainable development concepts, the development of environmentally friendly bio-based rubber reinforcing materials has become an important direction for the industry.

[0003] Rice husk ash silica is a silica material extracted from rice husks, an agricultural waste. It boasts advantages such as wide availability, low cost, and renewability, making it an ideal alternative to traditional petroleum-based reinforcing materials. However, the surface of rice husk ash silica contains a large number of hydroxyl groups, resulting in poor compatibility with the rubber matrix and difficulty in uniform dispersion within the rubber, leading to poor reinforcing effects. Furthermore, plasticizers are typically added to rubber formulations to improve processing performance. Plasticizers used in ethylene propylene rubber (EPR) are usually processing oils or handling oils, primarily to improve the processing performance of EPR and reduce compound costs. The addition of plasticizers reduces intermolecular forces in rubber, improving chain mobility. Plasticizers also wet fillers, promoting filler dispersion, reducing compound viscosity, increasing EPR plasticity, and saving processing energy and reducing machine wear. Additionally, plasticizers can significantly improve the low-temperature resistance, elongation at break, and hardness of the finished product. Because EPR has excellent fillerability, the addition of plasticizers can significantly reduce its cost. However, traditional petroleum-based plasticizers (such as paraffin oil and aromatic oil) also present environmental problems. While bio-based plasticizers, such as epoxidized soybean oil, are environmentally friendly, they have poor compatibility with EPDM rubber, easily migrating and leaching out, affecting the long-term performance of rubber products. Furthermore, traditional automotive seals and shock absorbers are prone to mold and bacteria growth in long-term humid environments, not only affecting their lifespan but also potentially releasing odors and allergens. Existing petroleum-based plasticizers (such as phthalates) and conventional fillers (such as carbon black and precipitated silica) lack antibacterial activity, requiring the addition of small-molecule antibacterial agents (such as triclosan and isothiazolinones). However, these substances face REACH regulations or the risk of migration and leaching.

[0004] Therefore, developing a bio-based reinforcing compound that combines environmental protection and antibacterial properties with excellent mechanical properties, and solving the problems of poor compatibility and dispersibility between bio-based materials and rubber matrices, is of great significance for promoting the green development of the rubber industry. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an environmentally friendly bio-based reinforcing compound and its preparation method, aiming to solve the following technical problems: (1) Existing rubber reinforcing materials rely on petroleum-based products, which do not meet the requirements of environmental protection and sustainable development; (2) Bio-based plasticizers have poor compatibility with the rubber matrix and are prone to migration and precipitation; (3) Rice husk ash and carbon black have poor dispersibility in rubber and limited reinforcing effect; (4) Traditional antibacterial small molecules are prone to precipitation.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An environmentally friendly bio-based reinforcing compound comprises, by weight: 100 parts EPDM rubber, 15-25 parts modified epoxidized soybean oil, 40-60 parts silane-modified rice husk ash carbon black, 2-2.5 parts peroxide, 1.5-2.5 parts crosslinking agent, and 5-7 parts additives; wherein the modified epoxidized soybean oil is a product obtained by reacting epoxidized soybean oil with N-(2-hydroxyethyl)itaconic acid monoamide and then with bio-based quaternary ammonium salt.

[0007] The structural formulas of the N-(2-hydroxyethyl)itaconic acid monoamide and the bio-based quaternary ammonium salt are shown in Formula 1 and Formula 2, respectively: Formula 1; Equation 2, where R represents a long carbon chain with 13 to 17 carbon atoms.

[0008] In one specific embodiment, the peroxide is selected from one or more of dicumyl peroxide and bis-tert-butyl dicumyl peroxide; the crosslinking agent is selected from one or more of triallyl isocyanurate, trimethylolpropane trimethacrylate, triallyl cyanurate, and tri(2-hydroxyethyl)isocyanurate triacrylate.

[0009] In one specific embodiment, the additives include 3-5 parts zinc oxide, 1.0-1.5 parts lubricant, and 1.5-2.0 parts antioxidant. The lubricant is selected from one or more of stearic acid, zinc stearate, polyethylene wax, oxidized polyethylene wax, butyl stearate, and monoglyceride. The antioxidant is selected from one or more of antioxidant 445, antioxidant RD, antioxidant MB, antioxidant MBZ, and antioxidant 264.

[0010] In one specific embodiment, the EPDM rubber has an ENB content of 4.5~5.5wt% and a Mooney viscosity of 45~90MU (ML 1+4, 125°C).

[0011] In one specific embodiment, the silane-modified rice husk ash carbon black is surface-modified using silane coupling agent KH-570, and the amount of silane used is 0.5~2wt% of the mass of rice husk ash carbon black.

[0012] In one specific embodiment, the preparation method of the modified epoxidized soybean oil includes the following steps: heating the epoxidized soybean oil to 115~120℃, adding N-(2-hydroxyethyl)itacin monoamide and a catalyst, controlling the molar ratio of carboxyl groups to epoxy groups to be 1:1~1:1.5, and reacting until the acid value is <5 mg KOH / g; cooling to 75~85℃, adding a bio-based quaternary ammonium salt, the molar ratio of the bio-based quaternary ammonium salt to N-(2-hydroxyethyl)itacin monoamide to be 0.8~1.2:1, heating to 100~130℃ and reacting until the epoxy value reaches 0.5~2.0wt% and the reaction is stopped, and the modified epoxidized soybean oil is obtained after purification.

[0013] In one specific embodiment, the method for preparing the bio-based quaternary ammonium salt includes the following steps: S1. Saturated fatty acids with 14-18 carbon atoms are reacted with 3-(dimethylamino)-1-propane in the presence of a catalyst at 140-160°C for 6-10 hours to obtain N-(3-dimethylaminopropyl) fatty acid amide; the molar ratio of saturated fatty acid to 3-(dimethylamino)-1-propane is 1:1.0-1.2. S2. N-(3-dimethylaminopropyl) fatty acid amide and epichlorohydrin are reacted in an organic solvent at 50-70℃ for 4-8 hours to obtain a 3-chloro-2-hydroxypropyl quaternary ammonium salt intermediate; the molar ratio of epichlorohydrin to N-(3-dimethylaminopropyl) fatty acid amide is 0.8-1.2:1; the 3-chloro-2-hydroxypropyl quaternary ammonium salt intermediate is reacted under alkaline conditions at 30-50℃ for 1-4 hours, and after neutralization and purification, a bio-based quaternary ammonium salt is obtained.

[0014] Preferably, the saturated fatty acid is selected from one or more of stearic acid, palmitic acid, and myristic acid.

[0015] In one specific embodiment, the preparation method of the N-(2-hydroxyethyl)itaconic acid monoamide includes the following steps: Under nitrogen protection, itaconic anhydride was dissolved in an organic solvent and cooled to below 25°C in an ice-water bath. Ethanolamine was added dropwise, and the dropping rate was controlled to maintain the reaction temperature below 25°C. After the addition was complete, the mixture was brought to room temperature and reacted for 2-4 hours. After the reaction was completed, it was quenched with dilute acid, the pH was adjusted to 5-6, the solvent was removed under reduced pressure, and after washing, recrystallization, and vacuum drying, N-(2-hydroxyethyl)itaconic acid monoamide was obtained. The molar ratio of itaconic anhydride to ethanolamine was 1:1-1.2.

[0016] Another objective of this invention is to protect the preparation method of the aforementioned environmentally friendly bio-based reinforcing compound, comprising the following steps: EPDM rubber is fed into an internal mixer at 75-85°C and masticated for 1.5-2.5 minutes; modified epoxidized soybean oil is added, and the temperature is raised to 115-125°C and mixing is continued for 3.5-4.5 minutes; silane-modified rice husk ash carbon black is added in batches, and the temperature is maintained at 115-125°C for 4.5-5.5 minutes; additives are added and mixing is continued for 1.5-2.5 minutes, followed by discharge to obtain a masterbatch; the masterbatch is transferred to a two-roll mill, and a crosslinking agent and peroxide are added and mixed for 5-7 minutes; the rubber sheet is placed in a flat vulcanizing apparatus at 175-185°C and 14-16 MPa for 25-35 minutes to obtain the environmentally friendly bio-based reinforcing compound.

[0017] In one specific embodiment, the silane-modified rice husk ash carbon black is added in 2-4 batches, with an interval of 0.8-1.2 minutes between each batch. The roller temperature of the open mill is <70°C, preferably 45-50°C for the front roller and 40-45°C for the rear roller. The gap between the thin rollers is 0.8-1.2 mm.

[0018] Another objective of this invention is to protect the application of the aforementioned environmentally friendly bio-based reinforcing compound in the fields of automotive seals and shock-absorbing products.

[0019] Beneficial effects

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention uses rice husk ash and carbon black as reinforcing fillers and modified epoxidized soybean oil as plasticizer. Both are bio-based materials with renewable sources, which can significantly reduce dependence on petroleum resources, reduce carbon emissions, and meet the requirements of green environmental protection and sustainable development. Specifically, the modified epoxidized soybean oil preferentially reacts with the carboxyl group of the bridging agent N-(2-hydroxyethyl)itaconic acid monoamide through the epoxy group of epoxidized soybean oil, retaining the active primary hydroxyl group and avoiding the premature cross-linking that may be caused by the direct reaction between epoxidized soybean oil and itaconic acid. Then, the primary hydroxyl group reacts with the bio-based quaternary ammonium salt with epoxy group to introduce double bonds, quaternary ammonium cations and long carbon chains. The long carbon chain increases the compatibility of modified epoxidized soybean oil with EPDM rubber, reducing the probability of bio-based plasticizers migrating and precipitating out of EPDM rubber during the mixing stage. Quaternary ammonium cations achieve antibacterial function through electrostatic interactions and membrane disruption. Double bonds allow modified epoxidized soybean oil to react with double bonds on EPDM rubber / silane-modified rice husk silica or crosslinking agents during vulcanization to form a crosslinking network, thus solving the problem of plasticizer precipitation during rubber use. Furthermore, surface modification of rice husk silica using a silane coupling agent with double bonds introduces double-bonded functional groups to its surface, reducing surface hydroxyl groups and significantly improving the compatibility and dispersibility of silica with the rubber matrix. This allows silica to be uniformly dispersed in the rubber matrix and chemically bonded to the rubber matrix during subsequent vulcanization, fully exerting its reinforcing effect.

[0021] (2) Through the synergistic effect of modified epoxidized soybean oil and silane-modified rice husk ash carbon black, the present invention enables the compound to have excellent tensile strength, elongation at break, antibacterial properties and fatigue resistance, good damping properties, high damping coefficient, excellent heat aging resistance and low compression set, which meets the requirements of automotive seals, shock absorbers and other application scenarios. Attached Figure Description

[0022] Figure 1 A schematic diagram of the synthetic route for N-(2-hydroxyethyl)itaconic acid monoamide and bio-based quaternary ammonium salt; Figure 2 A schematic diagram of the synthetic route for modified epoxidized soybean oil; Figure 3 Infrared spectra of epoxidized soybean oil and modified epoxidized soybean oil. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0025] The raw materials used in the examples and comparative examples are described below: EPDM rubber: ENB content 5.0wt%, Mooney viscosity 70MU (ML 1+4, 125℃), Nordel™ IP4570, DOW; Epoxidized soybean oil: epoxidation value 6.0-6.2wt%, Qilu Petrochemical; Bio-based quaternary ammonium salt 1: Self-made, preparation method as follows: S1. In a three-necked flask equipped with a magnetic stirrer, condenser, and fractionating head, under nitrogen protection, 0.55 mol of 3-(dimethylamino)-1-propylamine, 0.05 mol of sodium fluoride catalyst, and 0.5 mol of stearic acid were added to the flask. Calcium chloride was added to the fractionating head as a dehydrating agent. The reaction system was heated to 85°C, and stirring was started at 200 rpm to allow the stearic acid to completely melt and initially mix with 3-(dimethylamino)-1-propylamine. The temperature was then slowly increased to 150°C, and the reaction was continued under nitrogen protection with stirring for 8 hours. The reaction progress was monitored by thin-layer chromatography. After the reaction was complete, unreacted dimethylaminopropylamine was removed by rotary evaporation. The product was washed repeatedly with a 2:1 mixture of acetone and water until colorless, filtered, and dried to obtain N-(3-dimethylaminopropyl)stearamide in 99% yield. The structure of the product was confirmed by 1H NMR spectroscopy as follows: 1 H NMR (500 MHz, CDCl3): δ0.89(t, 3H, -CH3), 1.27 (m, 28H, -(CH2) 14 ), 1.62 (m, 2H,-CH2CH2CO-), 1.65 (p,2H, -NHCH2CH2CH2N(CH3)2), 2.14 (t, 2H, -CH2CO-), 2.23 (s, 6H, N(CH3)2), 2.37 (t, 2H,-CH2N(CH3)2), 3.33 (dt, 2H, NHCH2CH2CH2N(CH3)2), 6.90 (s, 1H, NH).

[0026] S2. In a three-necked flask equipped with a magnetic stirrer, reflux condenser, and constant-pressure dropping funnel, nitrogen gas was introduced for protection. 0.1 mol of N-(3-dimethylaminopropyl)stearamide was dissolved in an appropriate amount of isopropanol, and a small amount of glacial acetic acid was added to adjust the pH to 5-6. 0.1 mol of epichlorohydrin was slowly added dropwise to the reaction system, controlling the dropping rate to maintain the reaction temperature. After the addition was complete, the temperature was raised to 60°C and the reaction was maintained for 6 hours. The reaction progress was monitored by TLC until the tertiary amine was essentially converted. After the reaction was complete, the solvent and unreacted epichlorohydrin were removed by vacuum distillation to obtain a 3-chloro-2-hydroxypropyl quaternary ammonium salt intermediate. 0.09 mol of the 3-chloro-2-hydroxypropyl quaternary ammonium salt intermediate was dissolved in an appropriate amount of deionized water and heated to 40°C until completely dissolved, preparing a 10 wt% NaOH aqueous solution. 40 ml of NaOH solution was slowly added dropwise to the reaction system with stirring, and the temperature was controlled at 40 °C. The reaction was maintained at this temperature for 3 hours. The endpoint was determined by monitoring the epoxy value or organochlorine content of the system. The pH was adjusted to neutral with dilute hydrochloric acid, and water was removed by vacuum distillation. The residue was purified by recrystallization from acetone, filtered, and dried to obtain N-(3-dimethylaminopropyl)stearamide glycidyl ether quaternary ammonium salt, with a yield of 90%. The structure of the product was confirmed by 1H NMR spectroscopy as follows: 1 H NMR (500 MHz, CDCl3): δ0.91 (t, 3H, -CH3), 1.29 (m, 28H, -(CH2) 14 ), 1.63 (m, 2H,-CH2CH2CO-), 2.15 (p,2H, -NHCH2CH2CH2N + ), 2.26 (t, 2H, -CH2CO-), 3.26 (dt, 2H, NHCH2CH2CH2N + ), 3.38(s, 6H, N + (CH3)2-), 3.79 (t, 4H, -CH2N + (CH3)2CH2-), 3.83 (dd, 2H, epoxy-CH2), 4.04 (m, 1H, epoxy-CH), 7.57 (s, 1H, NH).

[0027] Bio-based Quaternary Ammonium Salt 2: The difference from Bio-based Quaternary Ammonium Salt 1 is that stearic acid is replaced with palmitic acid; Bio-based Quaternary Ammonium Salt 3: Compared with Bio-based Quaternary Ammonium Salt 1, the difference is that stearic acid is replaced with myristic acid; Bio-based Quaternary Ammonium Salt 4: The difference from Bio-based Quaternary Ammonium Salt 1 is that stearic acid is replaced with lauric acid; N-(2-hydroxyethyl)itaconic acid monoamide: prepared in-house, the preparation method is as follows: In a four-necked round-bottom flask equipped with a mechanical stirrer, a constant-pressure dropping funnel, a thermometer, and a nitrogen inlet tube, under nitrogen protection, 0.1 mol itaconic anhydride and 50 mL tetrahydrofuran were added to the flask and stirred until completely dissolved. Under ice-water bath cooling and nitrogen protection, 0.1 mol ethanolamine was added through the constant-pressure dropping funnel, controlling the dropping rate to keep the system temperature below 25°C. After the addition was complete, the ice bath was removed, and the mixture was heated to room temperature and stirred for 3 hours. The reaction progress was monitored using thin-layer chromatography (TLC). After the reaction was complete, a small amount of dilute hydrochloric acid was added to the reaction system to quench the reaction and adjust the pH to 5-6. The solvent was removed by rotary evaporation under reduced pressure. The crude product could be washed with a small amount of cold water and then recrystallized with ethyl acetate or acetone. The purified product was dried under vacuum at 40-50°C, with a yield of 95%. The structure of the product was confirmed by 1H NMR as follows: 1 H NMR (500 MHz, CDCl3): δ 3.01 (s, 2H, -CH2CONH-), 3.30 (dt, 2H, -NHCH2-), 3.64 (t, 2H, -CH2OH), 4.85 (br s, 1H, -OH), 5.71 (s, 1H, =CH2), 5.82 (s, 1H, =CH2), 7.75 (s, 1H, -NH-), 11.67 (br s, 1H, -COOH).

[0028] Modified epoxidized soybean oil 1: Homemade, preparation method as follows: In a dry reactor equipped with a stirrer, reflux condenser, and thermometer, epoxidized soybean oil is added, and nitrogen is introduced to purge the air. The epoxidized soybean oil is heated to 120°C, and N-(2-hydroxyethyl)itacin monoamide is slowly added with stirring, typically controlling the molar ratio of carboxyl to epoxy groups at 1:1.2. Stannous octoate (1 wt% of total material mass) is added as a catalyst. The reaction is maintained at 115–120°C, and the acid value of the system is measured every hour. When the acid value drops to <5 mg KOH / g, the reaction system is cooled to 80°C, and bio-based quaternary ammonium salt is slowly added with stirring, controlling the amount of bio-based quaternary ammonium salt 1 to be the same molar amount as N-(2-hydroxyethyl)itacin monoamide. After the addition is complete, the system temperature is raised to 100–110°C, and the reaction is continued with stirring at this temperature for 4 hours. The reaction endpoint is determined by measuring the epoxy value of the system. Heating is stopped when the epoxy value reaches 1.5 wt%. The product was cooled to room temperature and dissolved in ethyl acetate. The organic phase was washed successively with saturated brine and dilute alkaline solution. After washing, the organic phase was dried with anhydrous sodium sulfate and filtered to remove the drying agent. The organic solvent was then removed by vacuum distillation or rotary evaporation to obtain modified epoxidized soybean oil 1. The infrared spectra of modified epoxidized soybean oil and epoxidized soybean oil were obtained (FTIR-850, Tianjin Gangdong Technology Co., Ltd., scanning range 500~4000 cm⁻¹).-1 The resolution is 4cm. -1 (32 scans) Figure 3 As shown.

[0029] Modified epoxidized soybean oil 2: Compared with modified epoxidized soybean oil 1, the difference is that bio-based quaternary ammonium salt 1 is replaced with bio-based quaternary ammonium salt 2; Modified epoxidized soybean oil 3: Compared with modified epoxidized soybean oil 1, the difference is that bio-based quaternary ammonium salt 1 is replaced with bio-based quaternary ammonium salt 3; Modified epoxidized soybean oil 4: Compared with modified epoxidized soybean oil 1, the difference is that bio-based quaternary ammonium salt 1 is replaced with bio-based quaternary ammonium salt 4; Rice husk ash-white carbon black: SiO2≥90%, specific surface area 150~300 m² / g, 200 mesh sieve residue≤5%, moisture content≤6%, Yihai Kerry; Silane-modified rice husk fumed silica: KH-570 was diluted with anhydrous ethanol to a concentration of 10 wt%, and water of 10% of the mass of KH-570 was added to promote pre-hydrolysis. The rice husk fumed silica was then added to a high-speed mixer, stirred, and the speed was set to 800 rpm. The jacket was heated to 80°C. The KH-570 silane solution was evenly sprayed onto the fumed silica using a sprayer for 15 minutes. After spraying, stirring was continued for 30 minutes to maintain the temperature and promote the reaction using frictional heat. The modified rice husk fumed silica was then transferred to a rotary dryer and dried at 110°C for 60 minutes to remove ethanol and residual moisture. After drying, the material was pulverized by air jet milling or mechanical milling to a D50 of 3~8 μm. The amount of silane used was 1 wt% of the mass of the fumed silica.

[0030] Peroxide: dicumyl peroxide, commercially available; Crosslinking agent: triallyl isocyanurate, commercially available; Zinc oxide: 300±50nm, purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Lubricant: Zinc stearate, commercially available; Antioxidant: Antioxidant 445 and antioxidant MB are compounded in a mass ratio of 3:1 and are commercially available.

[0031] Unless otherwise specified, all components and raw materials used in the embodiments and comparative examples of this invention are commercially available, and the same type of components and raw materials are used in each parallel experiment.

[0032] Examples and Comparative Examples An environmentally friendly bio-based reinforcing compound, the weight parts of which are shown in Table 1, is prepared as follows: EPDM rubber was added to an internal mixer at 80°C and 40 rpm for 2 minutes until the compound wrapped around the rollers and had a smooth surface. Modified epoxidized soybean oil was added, and the temperature was raised to 120°C and mixing continued for 4 minutes. Silane-modified rice husk ash and carbon black were added in batches (20 parts each time, 1 minute interval), and the temperature was maintained at 120°C for 5 minutes. Additions (zinc oxide, lubricant, antioxidant) were added and mixed for 2 minutes. The mixture was then discharged to obtain the masterbatch, with a discharge temperature ≤130°C and a sheet thickness of 4-5 mm. The mixture was allowed to cool naturally to room temperature and stand for at least 4 hours. The masterbatch was then transferred to an open mill (front roller 45°C, rear roller 40°C) and passed through it 2-3 times (roller gap 1 mm) to soften the compound and allow it to wrap around the rollers. Then, a crosslinking agent was added and cut 3 times each on the left and right sides. Next, peroxide was added and cut 5 times each on the left and right sides, followed by 3 triangular wraps. The roller gap was adjusted to 2.5 mm, and the sheet thickness was 2.5 mm. mm, cut into sheets suitable for mold size, place the sheets in a conventional flat vulcanizing apparatus at 180℃ and 15MPa for 30 minutes to obtain the vulcanized environmentally friendly bio-based reinforcing compound.

[0033] Table 1 Environmentally friendly bio-based reinforcing compound (parts by weight)

[0034] The environmentally friendly bio-based reinforcing compound prepared in the examples and comparative examples was subjected to the following performance tests, and the results are shown in Table 2.

[0035] 1. Damping coefficient (tanδ) max The damping coefficient of the rubber compound was tested using a dynamic mechanical analyzer.

[0036] 2. Tensile strength and elongation at break: According to GB / T 528-2009 standard, using type I dumbbell-shaped specimens, with a tensile rate of 500 mm / min, the tensile strength and elongation at break of the compound were tested using a universal testing machine.

[0037] 3. Compression permanent deformation rate: According to GB / T 7759.1-2015, Method A (constant deformation), compression rate 25%, 70℃×22h, residual deformation rate was measured 30 min after unloading.

[0038] 4. Fatigue resistance: According to GB / T 1688-2008 standard, using type I dumbbell-shaped specimens, frequency 2 Hz, constant maximum elongation of 50%, after each stretching, the specimen recovers to zero strain / zero stress, and the number of cycles at which the specimen breaks is recorded as the tensile fatigue life of the compound.

[0039] 5. Heat aging resistance: After aging at 150℃ for 168h according to GB / T 3512-2014, the tensile strength is tested according to GB / T 528, and the retention rate is calculated as (after aging / before aging × 100%).

[0040] 6. Antibacterial performance test: The test was conducted according to GB / T 31402-2015, evaluating the antibacterial rate of the vulcanized rubber against *Escherichia coli* (ATCC 25922) and *Staphylococcus aureus* (ATCC 6538). A 50mm × 50mm sample was cut and inoculated with bacterial solution (10... 5 The antibacterial rate was calculated after incubation at 35℃ for 24 hours (CFU / mL).

[0041] Table 2 Performance test results of environmentally friendly bio-based reinforcing compound after vulcanization

[0042] As can be seen from the test results in Table 2, the environmentally friendly bio-based reinforcing compounds prepared in Examples 1-4 of this invention exhibit excellent performance in all performance indicators. The bio-based quaternary ammonium salt used in Comparative Example 1 has a carbon chain R length of only 11 carbon atoms, which is not compatible with EPDM rubber and cannot be stably dispersed in the compound. After vulcanization, it gradually migrates to the surface, forming oily or waxy precipitates that contaminate the mold and damage interfacial adhesion. Comparative Example 2 uses unmodified epoxidized soybean oil instead of modified epoxidized soybean oil. Its tensile strength, elongation at break, damping coefficient, and fatigue resistance are significantly lower than those in Examples 1-4, indicating that modified epoxidized soybean oil plays an important role in improving the overall performance of the compound. Comparative Example 3 uses unmodified rice husk fumed silica instead of silane-modified rice husk fumed silica. Its tensile strength and elongation at break decrease significantly, while its compression set increases significantly, indicating that silane modification significantly improves the dispersibility and reinforcing effect of fumed silica in rubber. Comparative Examples 4 and 5 investigated the effect of modified epoxidized soybean oil dosage on performance. In Comparative Example 4, insufficient dosage resulted in limited performance improvement; in Comparative Example 5, excessive dosage actually decreased tensile strength and increased compression set. This indicates that the dosage of modified epoxidized soybean oil needs to be controlled within a reasonable range to achieve the best results.

[0043] In summary, this invention successfully prepared a compound rubber material with both environmentally friendly antibacterial properties and excellent mechanical properties through the synergistic effect of modified epoxidized soybean oil and silane-modified rice husk ash carbon black, which has good application prospects.

[0044] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. An environmentally friendly bio-based reinforcing compound, characterized in that, The product comprises, by weight, 100 parts EPDM rubber, 15-25 parts modified epoxidized soybean oil, 40-60 parts silane-modified rice husk ash carbon black, 2-2.5 parts peroxide, 1.5-2.5 parts crosslinking agent, and 5-7 parts additives; the modified epoxidized soybean oil is a product obtained by reacting epoxidized soybean oil with N-(2-hydroxyethyl)itaconic acid monoamide and then with a bio-based quaternary ammonium salt; the structural formulas of the N-(2-hydroxyethyl)itaconic acid monoamide and the bio-based quaternary ammonium salt are shown in Formula 1 and Formula 2, respectively. Formula 1; Equation 2, where R represents a long carbon chain with 13 to 17 carbon atoms.

2. The environmentally friendly bio-based reinforcing compound as described in claim 1, characterized in that, The peroxide is selected from one or more of dicumyl peroxide and bis-tert-butyl dicumyl peroxide; the crosslinking agent is selected from one or more of triallyl isocyanurate, trimethylolpropane trimethacrylate, triallyl cyanurate, and tri(2-hydroxyethyl)isocyanurate triacrylate.

3. The environmentally friendly bio-based reinforcing compound as described in claim 1, characterized in that, The additives include 3-5 parts zinc oxide, 1.0-1.5 parts lubricant, and 1.5-2.0 parts antioxidant. The lubricant is selected from one or more of stearic acid, zinc stearate, polyethylene wax, oxidized polyethylene wax, butyl stearate, and monoglyceride. The antioxidant is selected from one or more of antioxidant 445, antioxidant RD, antioxidant MB, antioxidant MBZ, and antioxidant 264.

4. The environmentally friendly bio-based reinforcing compound as described in claim 1, characterized in that, The EPDM rubber has an ENB content of 4.5~5.5wt% and a Mooney viscosity of 45~90MU (ML 1+4, 125℃).

5. The environmentally friendly bio-based reinforcing compound as described in claim 1, characterized in that, The silane-modified rice husk ash carbon black is surface modified using silane coupling agent KH-570, with the amount of silane used being 0.5~2wt% of the mass of the rice husk ash carbon black.

6. The environmentally friendly bio-based reinforcing compound as described in claim 1, characterized in that, The method for preparing the modified epoxidized soybean oil includes the following steps: heating the epoxidized soybean oil to 115~120℃, adding N-(2-hydroxyethyl)itacin monoamide and a catalyst, controlling the molar ratio of carboxyl groups to epoxy groups to be 1:1~1.5, and reacting until the acid value is <5 mg KOH / g; cooling to 75~85℃, adding a bio-based quaternary ammonium salt, the molar ratio of the bio-based quaternary ammonium salt to N-(2-hydroxyethyl)itacin monoamide to be 0.8~1.2:1, heating to 100~130℃ and reacting until the epoxy value reaches 0.5~2.0wt%, then stopping the reaction, and purifying to obtain the modified epoxidized soybean oil.

7. The environmentally friendly bio-based reinforcing compound as described in claim 1, characterized in that, The preparation method of the bio-based quaternary ammonium salt includes the following steps: S1. Saturated fatty acids with 14-18 carbon atoms are reacted with 3-(dimethylamino)-1-propane in the presence of a catalyst at 140-160°C for 6-10 hours to obtain N-(3-dimethylaminopropyl) fatty acid amide; the molar ratio of saturated fatty acid to 3-(dimethylamino)-1-propane is 1:1.0-1.

2. S2. N-(3-dimethylaminopropyl) fatty acid amide and epichlorohydrin are reacted in an organic solvent at 50-70℃ for 4-8 hours to obtain a 3-chloro-2-hydroxypropyl quaternary ammonium salt intermediate; the molar ratio of epichlorohydrin to N-(3-dimethylaminopropyl) fatty acid amide is 0.8-1.2:1; the 3-chloro-2-hydroxypropyl quaternary ammonium salt intermediate is reacted under alkaline conditions at 30-50℃ for 1-4 hours, and after neutralization and purification, a bio-based quaternary ammonium salt is obtained.

8. The method for preparing the environmentally friendly bio-based reinforcing compound according to any one of claims 1 to 7, characterized in that, The process includes the following steps: EPDM rubber is fed into an internal mixer at 75-85°C and masticated for 1.5-2.5 minutes; Add modified epoxidized soybean oil, raise the temperature to 115~125℃ and continue mixing for 3.5~4.5 minutes; Add silane-modified rice husk ash and carbon black in batches, maintain the temperature at 115~125℃, and continue mixing for 4.5~5.5 minutes; add the additives and mix for 1.5~2.5 minutes, then discharge the rubber to obtain the masterbatch. Transfer the masterbatch to a two-roll mill, add the crosslinking agent and peroxide, and mix for 5~7 minutes; place the rubber sheet in a flat vulcanizing apparatus at 175~185℃ and 14~16MPa for 25~35 minutes to obtain an environmentally friendly bio-based reinforcing compound.

9. The preparation method of the environmentally friendly bio-based reinforcing compound as described in claim 8, characterized in that, The silane-modified rice husk ash carbon black is added in 2 to 4 batches, with an interval of 0.8 to 1.2 minutes between each batch. The roller temperature of the open mill is <70℃, and the thin roller gap is 0.8 to 1.2 mm.

10. The application of the environmentally friendly bio-based reinforcing compound as described in any one of claims 1 to 7 in the fields of automotive seals and shock-absorbing products.

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