Preparation method and application of white carbon black synergistically modified based on silane and natural antioxidant

Abstract

The invention relates to the technical field of rubber reinforcing agents, and discloses a preparation method and application of white carbon black synergistically modified based on silane and a natural antioxidant. The preparation method comprises the following steps: putting pre-dried silicon dioxide and a silane coupling agent into a reactor, and stirring at high temperature to react to obtain silane modified white carbon black; and then stirring the silane modified white carbon black and a natural antioxidant for reaction to obtain the synergistically modified white carbon black. Through two-step solvent-free reaction, an organic molecular layer with functions of improving dispersibility and providing lasting anti-aging is constructed on the surface of silicon dioxide, and synergistic modification of silicon dioxide is realized.

Description

Technical Field

[0001] This invention relates to the technical field of rubber reinforcing agents, specifically to a preparation method and application of silica based on the synergistic modification of silica by silane and natural antioxidants. Background Technology

[0002] Silica (SiO2) is a crucial reinforcing filler in the rubber industry. Compared to traditional carbon black fillers, silica-filled rubber composites can significantly reduce tire rolling resistance, thereby improving vehicle fuel economy, while maintaining good anti-skid performance. This makes it a key material for achieving tire energy conservation, safety, and environmental protection goals. However, the inherent physicochemical properties of silica present significant challenges to its application in rubber systems.

[0003] The surface of silica particles is rich in silanol groups (Si-OH). These highly polar groups form a dense network of hydrogen bonds, leading to strong spontaneous agglomeration of filler particles in non-polar rubber matrices (such as styrene-butadiene rubber (SBR) and butadiene rubber (BR)). This agglomeration not only severely affects the uniformity of filler dispersion in rubber but also significantly weakens its effective reinforcing effect. This is because the reinforcing effect largely depends on the large effective contact area and strong interfacial bonding between the filler and rubber molecular chains. The presence of agglomerates prevents effective stress transfer and dispersion in the composite material, causing stress to concentrate at defects, thus leading to a decrease in mechanical properties, particularly tensile strength, tear strength, and abrasion resistance.

[0004] To overcome the dispersion and interfacial compatibility problems of silica, the most widely adopted technology in industry and academia is the use of silane coupling agents. Among them, bis-(γ-triethoxysilylpropyl)tetrasulfide (commonly known as Si69) is the most representative variety used in the tire industry. Silane coupling agent molecules typically possess two different functional groups: one end is a silanoxy group capable of condensing with the silanol groups on the silica surface, and the other end is an organic functional group (such as polysulfide bonds) capable of reacting with the rubber molecular chain (especially during vulcanization). Through this "bridging" effect, silane coupling agents can effectively reduce the surface energy of silica, weaken the filler-filler interaction (i.e., reduce the Payne effect), and significantly enhance the interfacial bonding between filler and rubber. Chinese invention patent CN113801376A discloses a method for improving the surface activity of carbon black by high-temperature heat treatment of pyrolysis, the principle of which is also related to improving the surface properties of fillers; however, this method is energy-intensive and not highly targeted towards silica. However, although silane modification technology is very mature, it mainly solves the problems of dispersion and basic adhesion. For another critical threat faced by rubber products during long-term use—thermo-oxidative aging—silane modification alone offers limited benefits. Rubber molecular chains are prone to chain breakage or cross-linking under the combined effects of heat and oxygen, leading to hardening and brittleness or softening and stickiness, resulting in a sharp deterioration in mechanical properties.

[0005] To address the aging problem of rubber, the traditional method is to directly add small-molecule antioxidants, such as phenolic antioxidant 2246, during the mixing process. These antioxidants can slow down the aging process by capturing free radicals. However, small-molecule antioxidants tend to migrate and volatilize within the rubber matrix. Over time, they gradually migrate from the rubber interior to the surface and precipitate, forming what is known as "blooming." Blooming not only affects the appearance of the product, but more importantly, it leads to a decrease in the effective concentration of antioxidants, preventing them from providing sustained and long-term protection for the rubber, and causing the anti-aging efficacy to rapidly decline over time.

[0006] To overcome the migration problem of small-molecule antioxidants, researchers have proposed strategies for immobilizing antioxidants, with loading or grafting antioxidants onto filler surfaces becoming a research hotspot. For example, Chinese invention patent CN120513274A discloses a method for modifying silica using platinum-based acid, which improves the thermal stability of composite materials. Similarly, Chinese invention patent CN120519034A discloses a method for preparing and applying polymer-coupled grafted modified silica. This method first uses a silane coupling agent to vinyl-functionalize nano-silica, then mercapto-modifies a hydroxyl-terminated polymer, and finally grafts the two together via click chemistry to obtain polymer-modified silica nanoparticles. This product significantly improves compatibility with polyethylene oxide (PEO) and exhibits excellent dispersibility in a PEO matrix. However, these methods generally rely on solvent-assisted processes. While the use of solvents facilitates the diffusion and contact of reactant molecules, it inevitably introduces several drawbacks: First, organic solvents (such as toluene and ethanol) are expensive, and require complex distillation and recovery equipment in post-processing, increasing equipment investment and operating costs. Second, the use of large quantities of solvents poses safety hazards such as combustion and explosion, requiring high levels of protection in production sites. Third, the volatilization and emission of solvents can harm the environment and the health of operators, which is inconsistent with the modern industrial trend towards green and environmentally friendly development. Finally, and most importantly, the complex process and demanding production conditions of solvent methods make it difficult to achieve economical, stable, and safe commercial application on large-scale industrial production lines.

[0007] In summary, existing technologies for modifying silica face a dilemma: traditional silane modification improves dispersion but lacks anti-aging properties; while solvent-based methods with loaded antioxidants can immobilize antioxidants, their complexity, high cost, and environmental pollution make industrialization difficult; and early solvent-free solid-phase modification suffers from shortcomings in dispersion and compatibility. Therefore, there is an urgent need in this field for a novel technological solution that can overcome this dilemma. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for preparing silica based on the synergistic modification of silane and natural antioxidants, and its application.

[0009] To achieve the above objectives, the technical solution of the present invention is: a method for preparing silica based on the synergistic modification of silane and natural antioxidants, comprising the following steps: (1) Silane pretreatment: Pre-dried silica and silane coupling agent are placed in a reactor and stirred continuously at 100~130℃ for 2~6 hours to obtain silane modified silica; (2) Antioxidant grafting: Silane-modified silica and natural antioxidants are continuously stirred at 50~80℃ for 2~6 hours to obtain synergistically modified silica.

[0010] Further; the pre-drying treatment in step (1) is to dry at 80~110℃ for 1~4 hours.

[0011] Further; the silane coupling agent in step (1) is γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560), and the mass ratio of silicon dioxide to silane coupling agent is 100:(6~10), preferably, the mass ratio is 100:8.

[0012] Further; the natural antioxidant mentioned in step (2) is curcumin, and the mass ratio of silicon dioxide to natural antioxidant is 100:(5~8), preferably, the mass ratio is 100:6.67.

[0013] Furthermore, it also includes step (3): vacuum drying the synergistic modified silica at 70~90℃ for 1~3 hours to obtain powdered synergistic modified silica.

[0014] Another technical solution of the present invention is: a synergistically modified silica prepared by the preparation method described above.

[0015] Another technical solution of the present invention is: a rubber composite material including the aforementioned synergistic modified silica, the preparation method being as follows: raw rubber, synergistic modified silica, silica and minor components are mixed in an internal mixer to obtain a compound, wherein the mass ratio of raw rubber, synergistic modified silica, silica and minor components is 100∶(20~40)∶(20~40)∶(2~6), then the compound and vulcanization system are placed in an open mill at a mass ratio of (150~160)∶(3~4), and the mixture is rolled and rolled, then pressed into a set thickness, and after standing at room temperature, the compound is placed on a flat vulcanizing machine for vulcanization, thus obtaining the synergistic modified silica / rubber composite material.

[0016] Furthermore, the raw rubber is selected from one or more of styrene-butadiene rubber (SBR), natural rubber (NR), and butadiene rubber (BR); the minor components include zinc oxide, stearic acid, and Si69; and the vulcanization system includes sulfur, accelerator, and antioxidant.

[0017] Further; the mass ratio of zinc oxide, stearic acid and Si69 is (1~3):(1~3):5, the accelerator is selected from accelerator CZ (N-cyclohexyl-2-benzothiazole sulfenamide) and accelerator DPG (diphenylguanidine), the mass ratio of accelerator CZ to accelerator DPG is (1~2):(1~2), the antioxidant is selected from one or more of protective wax, antioxidant RD and antioxidant 4020, and the mass ratio of sulfur, accelerator and antioxidant is (1~2):(2~4):(0~3).

[0018] Furthermore, the vulcanization temperature is 150℃, the pressure is 10MPa, and the vulcanization time is 1.3t90.

[0019] The beneficial effects of this invention are as follows: This invention constructs an organic molecular layer on the surface of silica through a two-step solvent-free reaction, which combines improved dispersibility with durable anti-aging properties, thus achieving synergistic modification of silica. The prepared synergistically modified silica exhibits excellent dispersibility in a rubber matrix, good interfacial compatibility, and durable resistance to thermo-oxidative aging. This results in rubber composites exhibiting high mechanical strength, high elasticity, and excellent thermo-oxidative aging stability, meeting the stringent requirements of high-performance rubber products. Attached Figure Description

[0020] Figure 1 This is a diagram illustrating the synergistic modification mechanism of Embodiment 3 of the present invention; Figure 2 These are Fourier transform infrared spectra of silicon dioxide and MS and MSJ of the present invention. Detailed Implementation

[0021] Example 1:

[0022] A method for preparing silane-modified silica: Silica was dried at 100℃ for 2 hours to obtain dried silica. 90 g of the dried silica and 7.2 g of KH560 were placed in a three-necked flask with a heatable stirrer. The mixture was mechanically stirred continuously at 120℃ for 4 hours under solvent-free conditions to complete the silanization reaction, yielding silane-modified silica (MS). The Fourier transform infrared (FT-IR) spectrum of MS is shown below. Figure 2 As shown, MS exhibits a distinct absorption peak at 2954 cm⁻¹, which is attributed to the asymmetric stretching vibration of the CH bond, directly originating from the methylene (-CH₂-) and methyl (-CH₃) groups in the KH₅₆₀ molecular chain. The appearance of this characteristic peak confirms that KH₅₆₀ has successfully grafted onto the fumed silica surface via a condensation reaction between the silanol groups generated from its hydrolysis and the silanol groups on the fumed silica surface, forming a covalent bond.

[0023] Preparation of silica / natural rubber composite materials: The internal mixer temperature was adjusted to 90℃ and the speed to 60 r / min. 100 g of natural rubber was added and mixed for 50 s. Then, small components (2 g zinc oxide, 2 g stearic acid, 5 g Si69) and 30 g MS were added. After the top bolt was lowered, the mixture was mixed for 1 min 20 s. Finally, 30 g of silica was added, bringing the total mixing time to 6 min 30 s. The discharge temperature was 145℃, yielding the compound. The compound and vulcanization system (1.3 g DPG accelerator, 1.2 g CZ accelerator, and 1 g sulfur) were placed in an open mill with the roll gap adjusted to wrap the rolls. Triangular wrapping and rolling were performed three times each, followed by sheeting to the set thickness. The sheet was then allowed to stand at room temperature for 12 h. The resulting compound was then vulcanized on a flat vulcanizing machine at 150℃ and 10 MPa for 1.3 min 90 s, yielding the modified silica / natural rubber composite material.

[0024] Example 2:

[0025] A method for preparing silane-modified silica: MS is prepared in the same way as in Example 1.

[0026] Preparation of silica / natural rubber composite material: The difference from Example 1 is that 2 grams of curcumin are added to the internal mixer, that is, 100 grams of natural rubber are added and mixed for 50 seconds, and small ingredients (2 grams of zinc oxide, 2 grams of stearic acid, 5 grams of Si69), 30 grams of MS and 2 grams of curcumin are added. After the top plug is dropped, the mixture is mixed for 1 minute and 20 seconds.

[0027] Example 3

[0028] A method for preparing silica based on the synergistic modification of silane and natural antioxidants: (1) Silane pretreatment: MS was prepared in the same way as in Example 1.

[0029] (2) Synergistic modification of silica: After cooling MS to 50°C, 6 g of curcumin was added, and the reaction was continued at 50°C under solvent-free conditions for 4 hours. During this process, the active epoxy groups introduced by KH560 on the MS surface undergo a ring-opening reaction with the phenolic hydroxyl groups on the curcumin molecules, thereby chemically grafting curcumin onto the silica surface in the form of covalent bonds. After the reaction, the resulting solid product was vacuum dried at 80°C for 2 hours to completely remove moisture and unreacted volatile substances, finally obtaining a dry, uniform powder product, which is curcumin and silane synergistic modified silica (MSJ). Its chemical grafting structure was characterized by FT-IR, such as... Figure 2 As shown, MSJ exhibited a characteristic absorption peak at 1509 cm⁻¹ for the vibration of the benzene ring skeleton in the curcumin molecule, proving that curcumin had been successfully grafted.

[0030] Preparation of synergistically modified silica / natural rubber composites: The difference from Example 1 is that MSJ was used instead of MS.

[0031] Comparative Example 1: Preparation of silica / natural rubber composite material: The difference from Example 2 is that silica is used instead of MS.

[0032] Comparative Example 2: Preparation of silica / natural rubber composite material: The difference from Example 2 is that antioxidant 4020 is used instead of curcumin.

[0033] Performance testing: The rubber composite materials prepared in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2 were subjected to various performance tests, and the results are shown in Table 1: Table 1 performance hardness 100% constant tensile stress 300% calming stress Tensile strength Elongation at break Thermo-oxidative aging coefficient RPA unit Shaw Brothers A MPa MPa MPa % N·m Comparative Example 1 73 2.45 9.63 23.79 566.03 0.55 1974 Comparative Example 2 74 3.17 12.94 26.76 531.05 0.7 1442 Example 1 76.5 3.91 14.79 471.63 25.2 0.52 1489 Example 2 76 3.29 12.34 538.79 25.06 0.56 1824 Example 3 75.5 2.74 10.28 565.01 24.86 0.72 1049 According to the performance test data in Table 1, the synergistically modified silica (MSJ) prepared by chemical grafting in this invention exhibits excellent comprehensive performance in rubber composites. In terms of mechanical properties, the MSJ-containing sample (Example 3) achieves the best balance between reinforcement and toughness, with a tensile strength of 24.86 MPa while maintaining a high elongation at break of 565.01% and a moderate 300% modulus of elongation (10.28 MPa). In contrast, the MSJ-containing sample (Example 1), although possessing the highest 300% modulus of elongation (14.79 MPa) and hardness (76.5), suffers from insufficient toughness; while the physically blended curcumin sample (Example 2) experiences a decline in mechanical properties due to interfacial compatibility issues. This indicates that the chemical grafting method can retain the reinforcing effect of silane modification while avoiding the damage to the network structure caused by physical blending.

[0034] In terms of resistance to thermo-oxidative aging, the sample containing MSJ showed the best performance, with an aging coefficient as high as 0.72, surpassing the traditional antioxidant 4020 (0.7) and all other comparative samples. This result fully demonstrates the unique advantages of chemical grafting: by covalently fixing curcumin to the surface of silica, the problem of easy migration and volatilization of small molecule antioxidants is effectively solved, achieving long-lasting and efficient protection. Meanwhile, the aging coefficients of the samples in Comparative Example 1 and Example 2 were only 0.55 and 0.56, respectively, further highlighting the key role of chemical fixation in maintaining the stability of anti-aging performance.

[0035] From the perspective of filler dispersibility, the RPA test results showed that the MSJ sample had the lowest RPA value (1049 N·m), indicating that its filler network was the weakest and its silica dispersion in the rubber matrix was the best. In contrast, the RPA value of the sample containing unmodified silica (Comparative Example 1) was as high as 1974 N·m, showing strong filler agglomeration and Payne effect. Even the sample containing KH560 silanized modified silica (Example 1, RPA = 1489 N·m) still had lower dispersibility than the chemically grafted sample. This indicates that the chemical grafting of curcumin further enhanced the steric hindrance effect between silica particles, effectively preventing secondary agglomeration of the filler and achieving a more uniform dispersion.

[0036] In summary, the modified silica of this invention, through a chemical grafting strategy, simultaneously achieves excellent dispersibility, good mechanical property balance, and long-lasting resistance to thermo-oxidative aging in the rubber matrix. It successfully solves the technical problem of difficulty in balancing dispersibility and functionality in traditional modification methods, and provides a green and efficient solution for the development of high-performance rubber composite materials.

[0037] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

Claims

1. A method for preparing silica based on the synergistic modification of silane and natural antioxidants, characterized in that, Includes the following steps: (1) Silane pretreatment: Pre-dried silica and silane coupling agent are placed in a reactor and stirred continuously at 100~130℃ for 2~6 hours to obtain silane modified silica; (2) Antioxidant grafting: Silane-modified silica and natural antioxidants are continuously stirred at 50~80℃ for 2~6 hours to obtain synergistically modified silica.

2. The preparation method of silica based on the synergistic modification of silane and natural antioxidants according to claim 1, characterized in that: The pre-drying process described in step (1) involves drying at 80~110℃ for 1~4 hours.

3. The preparation method of silica based on the synergistic modification of silane and natural antioxidants according to claim 1, characterized in that: The silane coupling agent mentioned in step (1) is γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and the mass ratio of silicon dioxide to silane coupling agent is 100:(6~10).

4. The preparation method of silica based on the synergistic modification of silane and natural antioxidants according to claim 1, characterized in that: The natural antioxidant mentioned in step (2) is curcumin, and the mass ratio of silicon dioxide to natural antioxidant is 100:(5~8).

5. The preparation method of silica based on the synergistic modification of silane and natural antioxidants according to claim 1, characterized in that, It also includes step (3): vacuum drying the synergistic modified silica at 70~90℃ for 1~3 hours to obtain powdered synergistic modified silica.

6. A synergistically modified silica prepared by the preparation method according to any one of claims 1 to 5.

7. The application of the synergistically modified silica as described in claim 6 in rubber composite materials, characterized in that, The preparation method of the rubber composite material is as follows: raw rubber, synergistic modified silica, silica and minor ingredients are mixed in an internal mixer to obtain a compound, wherein the mass ratio of raw rubber, synergistic modified silica, silica and minor ingredients is 100:(20~40):(20~40):(2~6). Then the compound and vulcanization system are placed in an open mill at a mass ratio of (150~160):(3~4) for triangular wrapping and rolling. Then the compound is pressed into a sheet of a set thickness. After standing at room temperature, the compound is placed on a flat vulcanizing machine for vulcanization to obtain a rubber composite material containing synergistic modified silica.

8. The rubber composite material according to claim 7, characterized in that: The raw rubber is selected from one or more of styrene-butadiene rubber, natural rubber, and butadiene rubber; the minor components include zinc oxide, stearic acid, and Si69; the vulcanization system includes sulfur, accelerator, and antioxidant.

9. The rubber composite material according to claim 8, characterized in that: The mass ratio of zinc oxide, stearic acid and Si69 is (1~3):(1~3):

5. The accelerator is selected from accelerator CZ and accelerator DPG. The mass ratio of accelerator CZ to accelerator DPG is (1~2):(1~2). The antioxidant is selected from one or more of protective wax, antioxidant RD and antioxidant 4020. The mass ratio of sulfur, accelerator and antioxidant is (1~2):(2~4):(0~3).

10. The rubber composite material according to claim 7, characterized in that: The vulcanization temperature is 150℃, the pressure is 10MPa, and the vulcanization time is 1.3t90.

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