A method for preparing highly dispersed silica and its application in reinforcing green tires

Abstract

The present invention belongs to the technical field of white carbon black preparation, and discloses a method for preparing highly dispersed white carbon black and its application in reinforcing green tires. The method uses SiO2 wet gel obtained by precipitation as raw material, and is synergistically modified under certain conditions by phenyltrimethoxysilane (PTMS) and vinyltrimethoxysilane (A171), with a modification temperature of 70-90°C, a modification time of 30-150 min, a modified pH of 2.5-4.5, a PTMS to A171 mass ratio of 5:2, and a modifier amount of 3.5%-17.5% of the total mass of the SiO2 wet gel, to prepare highly dispersed and strong low-temperature flexible white carbon black for reinforcing green tires. The product obtained by the present invention reduces the number of hydroxyl groups on the surface of white carbon black, improves the processing performance and mechanical properties of rubber, and enhances the low-temperature flexibility and anti-wet skid performance of the tread rubber. The process of the present invention is simple, easy to industrialize, and has good application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of white carbon black preparation, and particularly relates to a method for preparing highly dispersed white carbon black and its application in reinforcing green tires. Background Art

[0002] Silica, also known as hydrated silicon dioxide (SiO2·nH2O), is a white powder or granular material that is non-toxic, stable, heat-resistant, and electrically insulating. Silica, used as a reinforcing agent in tire rubber, reduces rolling resistance and contributes to energy conservation and consumption reduction, making it an ideal raw material for "green tires." However, silica's surface contains a large number of silanol groups, which are highly reactive, making it hydrophilic, poorly dispersible, and prone to agglomeration. This results in poor compatibility at the rubber matrix-silica interface when combined with rubber, resulting in poor mechanical properties of the rubber compound and increased adsorption of accelerators and antioxidants, which reduces the vulcanization rate. Therefore, silane coupling agents are often used to modify and optimize surface properties. This primarily involves condensing the silanol groups generated by the hydrolysis of the silane coupling agent with the surface silanol groups of the silica particles to reduce the surface silanol number and improve silica's dispersibility in tire rubber. However, the effectiveness of this modification is influenced by numerous factors, such as the alkyl group of the silane coupling agent and, in particular, the modification conditions. The hydrolyzed hydroxyl groups of the silane coupling agent also undergo self-condensation, which can affect the properties of the modified material. Research on the modification of silica to improve its dispersibility in tire rubber compounds, enhance processing performance, save energy and reduce consumption, and improve the tire's anti-skid performance is a hot topic in the industry. Summary of the Invention

[0003] To address the above technical issues, the present invention aims to provide a method for preparing highly dispersed and highly low-temperature-flexible silica for reinforcing green tires. Compared to conventional silica, the silica prepared by this method exhibits significantly lower surface hydroxyl numbers, increased activation and lipophilicity, and enhanced hydrophobicity. When applied to styrene-butadiene rubber (SBR), this method significantly improves tire processing performance and enhances its dispersibility in the rubber compound. Furthermore, it also enhances mechanical and dynamic mechanical properties, thereby achieving high dispersion, strong low-temperature flexibility, and high wet-skid resistance.

[0004] Based on the above objectives, the present invention adopts a technical solution of synergistic modification of phenyltrimethoxysilane and vinyltrimethoxysilane.

[0005] Specifically, the present invention first provides a method for preparing highly dispersed silica, comprising the following steps: adding a certain amount of wet silica gel, deionized water, and a silane coupling agent, vinyltrimethoxysilane (A171), into a reactor; stirring and heating in an oil bath to a certain temperature; adjusting the temperature to a set pH value; then adding a certain proportion of pre-hydrolyzed silane coupling agent, phenyltrimethoxysilane (PTMS), to carry out a modification reaction for a certain period of time; and washing with alcohol, filtering, and drying after the reaction to obtain a highly dispersed and strong low-temperature flexible silica for reinforcing green tires.

[0006] Among them, the total mass of the modifier PTMS and A171 is 3.5%-17.5% of the mass of the SiO2 wet gel; the mass ratio of PTMS:A171 is 5:2; preferably, the total mass of the modifier PTMS and A171 is 14%-17.5% of the mass of the SiO2 wet gel.

[0007] The mass ratio of the wet silica gel to deionized water is 2:1.

[0008] The modification temperature is 70-90° C., the modification time is 30-150 min, and the modification pH is 2.5-4.5; preferably, the modification temperature is 80° C., the modification time is 90 min, and the modification pH is 3.5.

[0009] The PTMS pre-hydrolysis solution is obtained by hydrolyzing PTMS in a solvent of anhydrous ethanol and water, the hydrolysis pH is 4.0, and the mass ratio of PTMS to anhydrous ethanol and water is 5:14:5.

[0010] The silica prepared by the present invention has the following beneficial effects: compared with unmodified precipitated silica and silica modified with a single modifier, the number of surface hydroxyl groups is reduced and the hydrophobicity is improved, thus solving the problem of poor dispersion of silica in the rubber matrix. The activation degree reaches 100%, the lipophilicity reaches 10.1%, and the number of surface hydroxyl groups is 0.924 / nm. 2 .

[0011] The present invention also provides a method for using the white carbon black prepared by the above method to reinforce green tires, which has strong low-temperature flexibility and high wet-skid resistance.

[0012] Styrene-butadiene rubber (SBR) is a commonly used green tire tread compound. When applied to SBR, the silica prepared in this invention exhibits a significantly improved performance compared to unmodified silica reinforcement, due to the simultaneous grafting of benzene rings and unsaturated double bonds on the surface. This allows the modified silica to participate in the vulcanization of the rubber, increasing the crosslink density of the rubber compound and, in turn, enhancing the silica's reinforcing effect. Curing time is reduced by 68.8%, and Mooney viscosity by 61.3%, simplifying processing. The modified silica also increases tensile strength by 14.0%, elongation at break by 11.3%, and modulus at 300% and 500% elongation by 43.4% and 31.3%, respectively, enhancing mechanical properties. Furthermore, the modified silica exhibits a reduced Payne effect and a lowered ΔG′, improving its dispersion in the rubber matrix, with increases in tanδ (-10°C) and tanδ (0°C), and significantly increasing shear compliance across the board. This improved dispersion of the modified silica in the rubber compound also results in greater viscous resistance and traction at ambient temperatures, enhancing the low-temperature flexibility and wet skid resistance of the tread compound. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The shear storage modulus-strain curves of the rubber materials of Example 1 and Comparative Examples 1, 2, and 3 are shown;

[0014] Figure 2 The graph shows the rubber loss factor-temperature curve of Example 1 and Comparative Examples 1, 2, and 3.

[0015] Figure 3 The shear compliance-temperature curves of the rubber materials of Example 1 and Comparative Examples 1, 2, and 3 are shown. DETAILED DESCRIPTION

[0016] The present invention is not limited to the following specific embodiments. Based on the disclosure of the present invention, a person skilled in the art may adopt a variety of other specific embodiments to implement the present invention. Any simple changes or modifications made to the design structure and concept of the present invention fall within the scope of protection of the present invention. It should be noted that the embodiments and features of the embodiments of the present invention may be combined with each other unless they conflict.

[0017] The present invention is further described in detail below in conjunction with the embodiments:

[0018] Example 1

[0019] 500g SiO2 wet gel (855MP, BET 180m 2 / g) was added to a reactor, followed by 250g of deionized water and Al71. The mixture was stirred and heated in an oil bath to 80°C. The modified pH was adjusted to 3.5. Pre-hydrolyzed PTMS (phenyltrimethoxysilane was pre-hydrolyzed using an ethanol solution as the hydrolysis solvent, with 50g of PTMS, 140g of ethanol, and 50g of water, respectively, and a hydrolysis pH of 4.0) was then added. The total mass of PTMS and Al71 was 70g, with a PTMS:A171 mass ratio of 5:2. The reaction was continued for 90 minutes. After the reaction, the mixture was washed with alcohol, filtered, and dried to obtain a highly dispersed, strong, low-temperature, flexible silica for reinforcing green tires.

[0020] Example 2

[0021] 500g of wet SiO2 gel was added to a reactor, along with 250g of deionized water and Al71. The mixture was stirred and heated in an oil bath to 80°C. The pH of the modified mixture was adjusted to 3.5. Pre-hydrolyzed PTMS (12.5g of PTMS, 35g of ethanol, and 12.5g of water, with a hydrolysis pH of 4.0) was then added. The total mass of the modifier was 17.5g. The PTMS:Al71 ratio was 5:2, and the reaction time was 90 minutes. After the reaction, the mixture was washed with alcohol, filtered, and dried to produce a highly dispersed, strong, low-temperature, flexible silica for reinforcing green tires.

[0022] Example 3

[0023] 500g of wet SiO2 gel was added to a reactor, along with 250g of deionized water and Al71. The mixture was stirred and heated in an oil bath to 80°C. The pH of the modified mixture was adjusted to 3.5. Pre-hydrolyzed PTMS (25g of PTMS, 70g of ethanol, and 25g of water, with a hydrolysis pH of 4.0) was then added. The total mass of the modifier was 35g, and the PTMS:Al71 ratio was 5:2. The reaction was continued for 90 minutes. After the reaction, the mixture was washed with alcohol, filtered, and dried to obtain a highly dispersed, strong, low-temperature, flexible silica for reinforcing green tires.

[0024] Example 4

[0025] 500g of wet SiO2 gel was added to a reactor, along with 250g of deionized water and Al71. The mixture was stirred and heated in an oil bath to 80°C. The pH of the modified mixture was adjusted to 3.5. Pre-hydrolyzed PTMS (37.5g of PTMS, 105g of ethanol, and 37.5g of water, with a hydrolysis pH of 4.0) was then added. The total mass of the modifier was 52.5g. The PTMS:Al71 ratio was 5:2, and the reaction time was 90 minutes. After the reaction, the mixture was washed with alcohol, filtered, and dried to produce a highly dispersed, strong, low-temperature, flexible silica for reinforcing green tires.

[0026] Example 5

[0027] 500g of wet SiO2 gel was added to a reactor, along with 250g of deionized water and Al71. The mixture was stirred and heated in an oil bath to 80°C. The pH of the modified mixture was adjusted to 3.5. Pre-hydrolyzed PTMS (62.5g of PTMS, 175g of ethanol, and 62.5g of water, with a hydrolysis pH of 4.0) was then added. The total mass of the modifier was 87.5g. The PTMS:Al71 ratio was 5:2, and the reaction time was 90 minutes. After the reaction, the mixture was washed with alcohol, filtered, and dried to produce a highly dispersed, strong, low-temperature, flexible silica for reinforcing green tires.

[0028] Example 6

[0029] 500g of wet SiO2 gel was added to a reactor, along with 250g of deionized water and Al71. The mixture was stirred and heated in an oil bath to 70°C. The pH of the modified mixture was adjusted to 3.5. Pre-hydrolyzed PTMS (25g of PTMS, 70g of ethanol, and 25g of water, with a hydrolysis pH of 4.0) was then added. The total weight of the modifier was 35g, and the PTMS:Al71 ratio was 5:2. The reaction was continued for 90 minutes. After the reaction, the mixture was washed with alcohol, filtered, and dried to obtain a highly dispersed, strong, low-temperature, flexible silica for reinforcing green tires.

[0030] Example 7

[0031] 500g of wet SiO2 gel was added to a reactor, along with 250g of deionized water and Al71. The mixture was stirred and heated in an oil bath to 90°C. The pH of the modified mixture was adjusted to 3.5. Pre-hydrolyzed PTMS (25g of PTMS, 70g of ethanol, and 25g of water, with a hydrolysis pH of 4.0) was then added. The total weight of the modifier was 35g, and the PTMS:Al71 ratio was 5:2. The reaction lasted for 90 minutes. After the reaction, the mixture was washed with alcohol, filtered, and dried to produce a highly dispersed, strong, low-temperature, flexible silica for reinforcing green tires.

[0032] Example 8

[0033] 500g of wet SiO2 gel was added to a reactor, along with 250g of deionized water and Al71. The mixture was stirred and heated in an oil bath to 80°C. The pH of the modified mixture was adjusted to 3.5. Pre-hydrolyzed PTMS (25g of PTMS, 70g of ethanol, and 25g of water, with a hydrolysis pH of 4.0) was then added. The total weight of the modifier was 35g, and the PTMS:Al71 ratio was 5:2. The reaction was continued for 30 minutes. After the reaction, the mixture was washed with alcohol, filtered, and dried to obtain a highly dispersed, strong, low-temperature, and flexible silica for reinforcing green tires.

[0034] Example 9

[0035] 500g of wet SiO2 gel was added to a reactor, along with 250g of deionized water and Al71. The mixture was stirred and heated in an oil bath to 80°C. The pH of the modified mixture was adjusted to 3.5. Pre-hydrolyzed PTMS (25g of PTMS, 70g of ethanol, and 25g of water, with a hydrolysis pH of 4.0) was then added. The total weight of the modifier was 35g, and the PTMS:Al71 ratio was 5:2. The reaction was continued for 150 minutes. After the reaction, the mixture was washed with alcohol, filtered, and dried to obtain a highly dispersed, strong, low-temperature, flexible silica for reinforcing green tires.

[0036] Example 10

[0037] 500g of wet SiO2 gel was added to a reactor, along with 250g of deionized water and Al71. The mixture was stirred and heated in an oil bath to 80°C. The pH of the modified mixture was adjusted to 2.5. Pre-hydrolyzed PTMS (25g of PTMS, 70g of ethanol, and 25g of water, with a hydrolysis pH of 4.0) was then added. The total weight of the modifier was 35g, and the PTMS:Al71 ratio was 5:2. The reaction was continued for 90 minutes. After the reaction, the mixture was washed with alcohol, filtered, and dried to obtain a highly dispersed, strong, low-temperature, and flexible silica for reinforcing green tires.

[0038] Example 11

[0039] 500g of wet SiO2 gel was added to a reactor, along with 250g of deionized water and Al71. The mixture was stirred and heated in an oil bath to 80°C. The pH of the modified mixture was adjusted to 4.5. Pre-hydrolyzed PTMS (25g of PTMS, 70g of ethanol, and 25g of water, with a hydrolysis pH of 4.0) was then added. The total weight of the modifier was 35g, and the PTMS:Al71 ratio was 5:2. The reaction was continued for 90 minutes. After the reaction, the mixture was washed with alcohol, filtered, and dried to obtain a highly dispersed, strong, low-temperature, flexible silica for reinforcing green tires.

[0040] Comparative Example 1

[0041] The SiO2 wet gel is dried to obtain a highly dispersed and strong low-temperature flexible white carbon black for reinforcing green tires.

[0042] Comparative Example 2

[0043] 500g of wet SiO2 gel was added to a reactor, along with 250g of deionized water. The mixture was stirred and heated in an oil bath to 80°C. The modified pH was adjusted to 3.5. 70g of pre-hydrolyzed PTMS (hydrolysis conditions were the same as in Example 1) was then added for 90 minutes. After the reaction, the mixture was washed with alcohol, filtered, and dried to obtain a highly dispersed, strong, low-temperature, flexible silica for reinforcing green tires.

[0044] Comparative Example 3

[0045] 500g of wet SiO2 gel was added to a reactor, along with 250g of deionized water. The mixture was stirred and heated in an oil bath to 90°C. The pH of the modified mixture was adjusted to 3.5. 70g of pre-hydrolyzed A171 (hydrolysis conditions were the same as in Example 1) was then added for 90 minutes. After the reaction, the mixture was washed with alcohol, filtered, and dried to obtain a highly dispersed, strong, low-temperature, flexible silica for reinforcing green tires.

[0046] Comparative Example 4

[0047] 500g of wet SiO2 gel was added to a reactor, along with 250g of deionized water. The mixture was stirred and heated in an oil bath to 80°C. The pH of the modified mixture was adjusted to 3.5. Pre-hydrolyzed PTMS and Al71 (50g PTMS, 20g Al71, 140g ethanol, 50g water, and a hydrolysis pH of 4.0) were then added. The total mass of the modifier was 70g, and the PTMS:Al71 ratio was 5:2. The reaction lasted for 90 minutes. After the reaction, the mixture was washed with alcohol, filtered, and dried to produce a highly dispersed, strong, low-temperature, and flexible silica for reinforcing green tires.

[0048] The test methods for each performance parameter are as follows:

[0049] (1) Determination of activation degree:

[0050] Measure 50 mL of distilled water and place it in a 100 mL beaker. Add 1.0 g of silica. Stir for 30 minutes and let it stand for 24 hours. Separate the silica that sinks to the bottom, dry it, and weigh it. Then calculate the activation degree according to the following formula:

[0051]

[0052] (2) Determination of lipophilicity:

[0053] Measure 50 mL of distilled water and place it in a 100 mL beaker. Add 1.0 g of silica. Use anhydrous ethanol titration to soak the powder until it is completely submerged in the water phase. Record the amount of anhydrous ethanol added (V (mL)) at this time. Then calculate the lipophilicity according to the following formula:

[0054]

[0055] (3) Determination of hydroxyl content:

[0056] This study determined the number of surface hydroxyl groups on modified silica according to the specific measurement procedures in T / FSI 049-2020. Weigh 2.0 g of silica into a 200 mL beaker, add 25 mL of anhydrous ethanol, and then add 75 mL of a 20% NaCl solution. After magnetic stirring, adjust the pH of the test solution to 4 by adding a 0.1 mol / L NaOH (or 0.1 mol / L HCl) standard solution. Then, slowly add 0.1 mol / L NaOH to bring the pH to 9, maintaining the pH constant for 20 seconds. The number of hydroxyl groups (N) per square nanometer of silica surface was calculated according to the formula:

[0057]

[0058] N A : Avogadro's constant

[0059] C: The exact concentration of the NaOH standard solution (mol / L)

[0060] V: Volume consumed by adding 0.1 mol / L NaOH to adjust the pH value of the solution from 4 to 9 (mL)

[0061] M: mass of silica (g).

[0062] S: Specific surface area of ​​the sample (nm 2 / g)

[0063] (4) Preparation and vulcanization of rubber mix:

[0064] Rubber mixing was carried out according to HG / T2404-2020, "Identification of Precipitated Hydrated Silica in Styrene-Butadiene Rubber." The formula is: 200g SBR, 100g silica, 10g ZnO, 2g stearic acid, 6g polyethylene glycol, 2.4g DM accelerator, 1.4g M accelerator, 1g DPG accelerator, and 4g sulfur. The silica-SBR mixture was then vulcanized at 160°C on a flat-plate vulcanizer.

[0065] (5) Performance determination of rubber mix:

[0066] The Mooney viscosity of rubber was tested according to GB / T1232 "Unvulcanized rubber - Determination by disc shear viscometer - Part 1: Determination of Mooney viscosity".

[0067] The vulcanization characteristics of rubber were tested according to GB / T9869-1997 “Determination of vulcanization characteristics of rubber compounds (disc oscillation vulcanometer method)”.

[0068] The stress-strain characteristics test is carried out according to GB / T528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber".

[0069] The performance of the rubber compounds was tested using an RPA rubber processing analyzer. The strain sweep conditions were: frequency 1 Hz, temperature 70 °C, and strain range 0.1%–100%.

[0070] The RPA rubber processing analyzer was used to perform temperature scanning on the rubber compound to test the changes in the dynamic properties of the rubber. The scanning conditions were: strain 0.25%, frequency 10 Hz, and temperature range -20℃ to 70℃.

[0071] The performance of the white carbon black obtained in the above examples and comparative examples was tested, and the test results are shown in Table 1.

[0072] Table 1 Performance test table of white carbon black in various embodiments and comparative examples

[0073]

[0074] The white carbon blacks in Examples 1-5 and Comparative Examples 1-4 in the above examples were tested for rubber refining performance. The test results are shown in Table 2.

[0075] Table 2 White carbon black rubber mixing performance test table of each embodiment and comparative example

[0076]

[0077] As can be seen from Examples 1-5 and Comparative Examples 1-4, the addition of an appropriate amount of composite modifier to the silica provided by the present invention reduces the number of surface hydroxyl groups, significantly improves the activation and lipophilicity, and thus enhances hydrophobicity, thereby resolving the problem of poor dispersibility of silica in the rubber matrix. The activation degree reaches 100%, the lipophilicity reaches 10.1%, and the surface hydroxyl number is reduced to 0.924 / nm. 2 .

[0078] When applied to styrene-butadiene rubber (SBR), compared to unmodified silica / SBR, the surface grafting of benzene rings and unsaturated double bonds creates greater steric hindrance for the benzene rings, requiring greater van der Waals forces for molecular slip. The unsaturated double bonds, on the other hand, can participate in the vulcanization of the rubber. The combined effect of these two modifiers increases the crosslink density of the rubber compound, thereby enhancing the reinforcing effect of silica. This modifier also achieves better results than single-modifier modification. The curing time is reduced by 68.8%, the Mooney viscosity by 61.3%, and the processing difficulty is reduced. The tensile strength is increased by 14.0%, the elongation at break by 11.3%, and the modulus of 300% and 500% elongation by 43.4% and 31.3%, respectively, enhancing mechanical strength.

[0079] After the white carbon black of Example 1 and Comparative Examples 1, 2, and 3 were applied to styrene-butadiene rubber, the rubber was subjected to dynamic mechanical property testing using a rubber processing analyzer. The test data are shown in Table 3.

[0080] Table 3 Dynamic mechanical properties of the rubber materials of Example 1 and the comparative examples

[0081]

[0082] From the analysis of the data in the table, it can be seen that the dynamic mechanical properties of the composite modified product in Example 1 are improved compared with the unmodified silica / SBR and the single-modifier silica / SBR. Among them, the Payne effect of the PTMS+A171 modified silica / SBR is greatly weakened compared with the unmodified silica / SBR, and ΔG′ decreases by 88.7%. Its dispersibility in the rubber matrix is ​​greatly improved, and tanδ (-10℃) increases by 94.6%, and tanδ (0℃) increases by 112.0%. The shear compliance is greatly improved across the board, among which the shear compliance (0℃) increases by 149.2%, the shear compliance (-10℃) increases by 150.0%, and the shear compliance (30℃) increases by 162.5%. The above data fully demonstrate that the PTMS+A171 modified silica / SBR of the present invention has improved dispersibility in the rubber material compared with the unmodified silica / SBR, and obtains greater viscous resistance and traction under normal low temperature environment, thereby improving the low-temperature flexibility of the tread rubber.

[0083] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A method for preparing white carbon black, characterized in that: The invention comprises the following steps: adding silicon dioxide wet gel, deionized water and vinyl trimethoxysilane into a reaction kettle, stirring and heating to 70-90°C; adjusting the modified pH to 2.5-4.5, adding phenyl trimethoxysilane pre-hydrolysis solution, heating to 70-90°C for modification reaction, and washing with alcohol, filtering and drying after the reaction to obtain white carbon black; the total mass of the vinyl trimethoxysilane and the phenyl trimethoxysilane is 3.5%-17.5% of the mass of the silicon dioxide wet gel; the mass ratio of the phenyl trimethoxysilane in the vinyl trimethoxysilane and the phenyl trimethoxysilane pre-hydrolysis solution is 5:2; and the phenyl trimethoxysilane pre-hydrolysis solution is prepared by the following method: hydrolyzing phenyl trimethoxysilane in anhydrous ethanol and water solvent, the hydrolysis pH is 4.0, and the mass ratio of phenyl trimethoxysilane to anhydrous ethanol and water is 5:14:

5.

2. The method for preparing white carbon black according to claim 1, wherein: The total mass of the vinyltrimethoxysilane and phenyltrimethoxysilane is 14%-17.5% of the mass of the silicon dioxide wet gel.

3. The method for preparing white carbon black according to claim 1, wherein: The modified pH is 3.

5.

4. The method for preparing white carbon black according to claim 1, wherein: The modification reaction time is 30-150 min.

5. The method for preparing white carbon black according to claim 4, wherein: The modification reaction time is 90 min.

6. White carbon black prepared by the method according to any one of claims 1 to 5.

7. Use of the white carbon black according to claim 6 in reinforcing green tires.

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