Modified lignin bio-based anti-aging agent and application thereof in rubber tire

Abstract

The invention relates to the technical field of anti-aging agents, in particular to a modified lignin bio-based anti-aging agent and application thereof in rubber tires. The anti-aging agent comprises the following components: 30-40 parts of modified lignin, 3-5 parts of a silane coupling agent, 5-10 parts of white carbon black, 1-3 parts of polyethylene wax and 100-120 parts of a carrier. The anti-aging agent provided by the invention adopts bio-based components, can effectively reduce pollution, improves the compatibility of lignin and rubber by modifying lignin, ensures uniform dispersion of modified lignin, improves the bonding strength of lignin and a rubber matrix interface, and the modified lignin can be synergistically dispersed with white carbon black to play a reinforcing role, so that the service life of the anti-aging agent is prolonged, and the service life of the anti-aging agent is prolonged. And the mechanical properties such as tensile strength and tearing strength of the rubber are effectively improved while the filler consumption is reduced.

Description

Technical Field

[0001] This invention relates to the field of antioxidant technology, specifically to a modified lignin-based antioxidant and its application in rubber tires. Background Technology

[0002] Tires are a crucial component of modern automobiles, enduring various deformations, loads, forces, and extreme temperatures during driving. Their performance directly impacts driving economy and safety. However, during use, tire temperatures can reach 60-80°C or even higher due to friction with the road surface. This accelerates the reaction between oxygen and rubber molecules, leading to tire aging and affecting the tire's mechanical properties.

[0003] Therefore, antioxidants need to be added to tires during the production process to improve their anti-aging properties. Existing antioxidants mainly include amines, phenols, thioesters, and phosphites. However, most of these antioxidants are derived from non-renewable petrochemical products, and their production and use can cause environmental pollution.

[0004] Because lignin contains a large number of hindered phenolic structures, it has a certain ability to capture free radicals and is a natural anti-aging agent, thus having great application potential in the field of rubber anti-aging agents. However, lignin itself has poor anti-aging properties and is difficult to effectively inhibit the aging process of rubber. In addition, lignin has poor dispersion in the rubber matrix and weak interfacial bonding with the rubber matrix, which may lead to a decrease in the mechanical properties of rubber products after the addition of lignin. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a modified lignin-based bio-based antioxidant and its application in rubber tires.

[0006] The technical solution of the present invention is: a modified lignin bio-based antioxidant, comprising the following components by weight: 30-40 parts modified lignin, 3-5 parts silane coupling agent, 5-10 parts silica, 1-3 parts polyethylene wax, and 100-120 parts carrier.

[0007] Note: The above antioxidant uses bio-based components, which can effectively reduce pollution. By modifying lignin, the compatibility between lignin and rubber is improved, ensuring uniform dispersion of modified lignin and increasing the bonding strength between lignin and the rubber matrix. Furthermore, the modified lignin can synergistically disperse with silica to play a reinforcing role. While reducing the amount of filler, it effectively improves the mechanical properties of rubber, such as tensile strength and tear strength.

[0008] Furthermore, the carrier is any one of EPDM rubber, polypropylene, polyethylene, or vinyl acetate.

[0009] Note: The above-mentioned carrier can effectively disperse modified lignin and is well compatible with the rubber matrix, so that the antioxidant components can be effectively dispersed in the rubber matrix along with the carrier.

[0010] Furthermore, the silane coupling agent is KH-550 or KH-560.

[0011] Note: The above-mentioned silane coupling agent can enhance the interfacial bonding force between modified lignin and the rubber matrix, so that the modified lignin is fully dispersed in the rubber matrix.

[0012] Furthermore, the method for preparing the modified lignin includes the following steps: S1. Add alkali lignin to the solvent and stir for 10-20 min. Then add bromododecane to obtain the first mixture. Adjust the pH of the first mixture to 11-12 with a 20-30% sodium hydroxide solution. Then stir at 80-100℃ for 2-4 h to obtain the first reaction solution. The mass ratio of alkali lignin, bromododecane and solvent is 1:0.3-0.5:10-15. S2. Adjust the pH of the first reaction solution to 3-4 using dilute hydrochloric acid with a mass concentration of 15-20%, then filter to obtain solid particles. After washing the solid particles, alkylated lignin is obtained. S3. Add p-hydroxybenzoic acid to thionyl chloride and reflux at 60-70°C for 2-3 hours. After vacuum distillation, pretreated p-hydroxybenzoic acid is obtained. The mass ratio of p-hydroxybenzoic acid to thionyl chloride is 1:3-4. S4. Add alkylated lignin to dimethyl sulfoxide and stir at 50-60°C for 20-30 min to obtain a second mixture; the mass ratio of alkylated lignin to dimethyl sulfoxide is 1:8-10. S5. Place the second mixture into the reactor and evacuate the reactor until the pressure inside the reactor reaches 1000~3000Pa. Then, pressurize the reactor with inert gas until the pressure inside the reactor reaches 0.1~0.15MPa. Add pyridine to the reactor, then stop pressurizing and heat the reactor until the temperature inside the reactor reaches 40~50℃. Add pretreated p-hydroxybenzoic acid to the reactor, then heat and pressurize the reactor until the temperature inside the reactor reaches 100~120℃ and the pressure reaches 0.2~0.3MPa. Maintain the temperature and pressure for 2~4 hours to obtain the second reaction solution. The amount of pyridine added accounts for 1~3% of the initial mass of the second mixture, and the amount of pretreated p-hydroxybenzoic acid added accounts for 4~6% of the initial mass of the second mixture. S6. The second reaction liquid is added dropwise to ice water, filtered to obtain a precipitate, and the precipitate is washed and dried to obtain modified lignin.

[0013] Explanation: The above modification method first alkylates lignin to improve its compatibility with rubber, and then grafts p-hydroxybenzoic acid onto lignin through ester bonds to improve the antioxidant properties of lignin. This allows the modified lignin to be effectively dispersed in the rubber matrix and to scavenge free radicals, thereby improving the anti-aging properties of the rubber.

[0014] Furthermore, the solvent is prepared by mixing urea, imidazole, and deionized water in a mass ratio of 1:0.4~0.6:70~80.

[0015] Note: The above solvent can effectively dissolve alkali lignin, ensuring that alkali lignin can fully participate in the reaction, thereby guaranteeing the modification effect of lignin.

[0016] Further, in step S1, the alkali lignin is pretreated before being added to the solvent. The pretreatment method is as follows: the alkali lignin is added to an ethanol solution with a mass concentration of 70-80%, and ultrasonically treated at 20-30°C for 1-2 hours. The power of the ultrasonic treatment is 150-300W and the frequency is 20-40kHz.

[0017] Note: Pretreatment can reduce the aggregation of alkali lignin, fully expose the phenolic hydroxyl groups on the surface of alkali lignin, and improve the reactivity of alkali lignin.

[0018] Furthermore, in step S6, the temperature of the ice water is 0~5℃, and the volume ratio of the second reaction liquid to the ice water is 1:6~7.

[0019] Note: Limiting the temperature of the ice water allows for full extraction of modified lignin, thus increasing the yield of modified lignin.

[0020] Further, the preparation method of the antioxidant is as follows: the modified lignin, silane coupling agent and carrier are placed in a mixer according to the specified weight parts, and mixed at 80~100℃ for 1~3 min, then fumed silica and polyethylene wax are added; then the temperature is raised to 150~170℃ and mixed at a speed of 60~80 r / min for 5~8 min; then the temperature is raised again to 175~185℃ and mixed at a speed of 50~60 r / min for 2~3 min to obtain a mixed masterbatch; the mixed masterbatch is extruded and granulated using a screw extruder at 160~170℃ to obtain the antioxidant.

[0021] Note: By loading raw materials into a carrier to form an antioxidant, the dispersibility of the antioxidant in the rubber matrix can be effectively improved.

[0022] On the other hand, the present invention also provides an application of a modified lignin bio-based antioxidant in rubber tires.

[0023] Note: The above-mentioned antioxidants are highly compatible with rubber tires and can reduce the amount of fillers used in rubber tires. Furthermore, the antioxidants can effectively improve the anti-aging and UV resistance of rubber tires, preventing the rapid decline in performance after a period of use and extending the service life of rubber tires. They are also directly compatible with existing tire mixing and vulcanization production lines, requiring no additional equipment modifications and reducing technology replacement costs.

[0024] Furthermore, the application method is as follows: during the rubber compounding process of rubber tires, the antioxidant is added to the rubber matrix, and the amount of antioxidant added accounts for 5 to 10% of the total mass of the rubber matrix.

[0025] Note: Limiting the amount of antioxidant added can ensure the anti-aging performance of rubber tires and prevent the performance of rubber tires from deteriorating.

[0026] The beneficial effects of this invention are: (1) The antioxidant of this invention uses bio-based components, which can effectively reduce pollution. By modifying lignin, the compatibility between lignin and rubber is improved, ensuring that the modified lignin is evenly dispersed, improving the bonding strength between lignin and rubber matrix. Furthermore, the modified lignin can be synergistically dispersed with silica to play a reinforcing role. While reducing the amount of filler, it effectively improves the mechanical properties of rubber such as tensile strength and tear strength.

[0027] (2) The modification method of the present invention first modifies lignin by alkylation to improve the compatibility between lignin and rubber, and then grafts p-hydroxybenzoic acid onto lignin through esterification reaction to improve the antioxidant properties of lignin, so that the modified lignin can be effectively dispersed in the rubber matrix and free radicals can be removed, thereby improving the anti-aging properties of rubber.

[0028] (3) The application method of the present invention is to load the antioxidant raw material into the carrier to make the antioxidant, and then add the antioxidant into the rubber matrix. This not only improves the dispersibility of the antioxidant in the rubber matrix, but also can be directly adapted to the existing tire mixing and vulcanization production line without additional equipment modification, thus reducing the cost of technology replacement. Detailed Implementation

[0029] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0030] Example 1: A modified lignin bio-based antioxidant, comprising the following components by weight: 35 parts modified lignin, 4 parts silane coupling agent, 8 parts silica, 2 parts polyethylene wax, and 110 parts carrier; the carrier is EPDM rubber; the silane coupling agent is KH-550. The method for preparing modified lignin includes the following steps: S1. Add alkali lignin to the solvent and stir for 15 min. Then add bromododecane to obtain the first mixture. Adjust the pH of the first mixture to 11.5 with a 25% sodium hydroxide solution. Then stir at 90℃ for 3 h to obtain the first reaction solution. The mass ratio of alkali lignin, bromododecane and solvent is 1:0.4:12. The solvent is prepared by mixing urea, imidazole, and deionized water in a mass ratio of 1:0.5:75; S2. The pH of the first reaction solution was adjusted to 3.5 using 18% hydrochloric acid, followed by filtration to obtain solid particles. After washing the solid particles, alkylated lignin was obtained. Deionized water was used for washing. S3. Add p-hydroxybenzoic acid to thionyl chloride and reflux at 65°C for 2.5 h. After vacuum distillation, pretreated p-hydroxybenzoic acid is obtained. The mass ratio of p-hydroxybenzoic acid to thionyl chloride is 1:3.5. The pressure during vacuum distillation is 0.08 MPa and the temperature is 50°C. S4. Add alkylated lignin to dimethyl sulfoxide and stir at 55°C for 25 min to obtain a second mixture; the mass ratio of alkylated lignin to dimethyl sulfoxide is 1:9. S5. Place the second mixture into the reactor and evacuate the reactor until the pressure inside the reactor reaches 2000 Pa. Then, pressurize the reactor with inert gas until the pressure inside the reactor reaches 0.12 MPa. Add pyridine to the reactor, then stop pressurizing and heat the reactor until the temperature inside the reactor reaches 45°C. Add pretreated p-hydroxybenzoic acid to the reactor, then heat and pressurize the reactor until the temperature inside the reactor reaches 110°C and the pressure reaches 0.25 MPa. Maintain the temperature and pressure for 3 hours to obtain the second reaction solution. The amount of pyridine added accounts for 2% of the initial mass of the second mixture, and the amount of pretreated p-hydroxybenzoic acid added accounts for 5% of the initial mass of the second mixture. S6. The second reaction solution is added dropwise to ice water, filtered to obtain a precipitate, and the precipitate is washed and dried to obtain modified lignin; wherein, the temperature of the ice water is 2℃, and the volume ratio of the second reaction solution to the ice water is 1:6.5; deionized water is used for washing, and the drying temperature is 80℃ and the drying time is 2h. Before adding alkali lignin to the solvent, it is pretreated by adding alkali lignin to a 75% ethanol solution and ultrasonically treating it at 25°C for 1.5 hours. The ultrasonic power is 220W and the frequency is 30kHz. In this embodiment, nitrogen is used as the inert gas. The preparation method of the above antioxidant is as follows: Modified lignin, silane coupling agent and carrier are placed in a mixer according to the specified weight parts, and mixed at 90°C for 2 minutes. Then, silica and polyethylene wax are added. The temperature is then raised to 160°C and mixed at 70 r / min for 7 minutes. The temperature is then raised to 180°C and mixed at 55 r / min for 2.5 minutes to obtain a mixed masterbatch. The mixed masterbatch is extruded and granulated at 165°C using a screw extruder to obtain the antioxidant.

[0031] The above-mentioned modified lignin bio-based antioxidant was applied to rubber tires. The application method was as follows: during the rubber compounding process of rubber tires, the antioxidant was added to the rubber matrix. The amount of antioxidant added accounted for 8% of the total mass of the rubber matrix. The rubber matrix was styrene-butadiene rubber.

[0032] Example 2: This example is basically the same as Example 1, except that a modified lignin bio-based antioxidant, by weight, includes the following components: 30 parts modified lignin, 3 parts silane coupling agent, 5 parts fumed silica, 1 part polyethylene wax, and 100 parts carrier.

[0033] Example 3: This example is basically the same as Example 1, except that a modified lignin bio-based antioxidant, by weight, includes the following components: 40 parts modified lignin, 5 parts silane coupling agent, 10 parts fumed silica, 3 parts polyethylene wax, and 120 parts carrier.

[0034] Example 4: This example is basically the same as Example 1, except that the mass ratio of alkali lignin, bromododecane and solvent is 1:0.3:10.

[0035] Example 5: This example is basically the same as Example 1, except that the mass ratio of alkali lignin, bromododecane and solvent is 1:0.5:15.

[0036] Example 6: This example is basically the same as Example 1, except that the pH value of the first mixture is adjusted to 11 using a 25% sodium hydroxide solution.

[0037] Example 7: This example is basically the same as Example 1, except that the pH value of the first mixture is adjusted to 12 using a 25% sodium hydroxide solution.

[0038] Example 8: This example is basically the same as Example 1, except that the mass ratio of p-hydroxybenzoic acid to thionyl chloride is 1:3.

[0039] Example 9: This example is basically the same as Example 1, except that the mass ratio of p-hydroxybenzoic acid to thionyl chloride is 1:4.

[0040] Example 10: This example is basically the same as Example 1, except that the mass ratio of alkylated lignin to dimethyl sulfoxide is 1:8.

[0041] Example 11: This example is basically the same as Example 1, except that the mass ratio of alkylated lignin to dimethyl sulfoxide is 1:10.

[0042] Example 12: This example is basically the same as Example 1, except that pyridine is added to the reactor when the pressure inside the reactor reaches 0.1 MPa.

[0043] Example 13: This example is basically the same as Example 1, except that pyridine is added to the reactor when the pressure inside the reactor reaches 0.15 MPa.

[0044] Example 14: This example is basically the same as Example 1, except that the amount of pyridine added accounts for 1% of the initial mass of the second mixture.

[0045] Example 15: This example is basically the same as Example 1, except that the amount of pyridine added accounts for 3% of the initial mass of the second mixture.

[0046] Example 16: This example is basically the same as Example 1, except that pretreated p-hydroxybenzoic acid is added to the reactor when the temperature inside the reactor reaches 40°C.

[0047] Example 17: This example is basically the same as Example 1, except that pretreated p-hydroxybenzoic acid is added to the reactor when the temperature inside the reactor reaches 50°C.

[0048] Example 18: This example is basically the same as Example 1, except that the amount of p-hydroxybenzoic acid added after pretreatment accounts for 4% of the initial mass of the second mixture.

[0049] Example 19: This example is basically the same as Example 1, except that the amount of p-hydroxybenzoic acid added after pretreatment accounts for 6% of the initial mass of the second mixture.

[0050] Example 20: This example is basically the same as Example 1, except that the temperature and pressure inside the reactor are maintained for 3 hours until the temperature reaches 100°C and the pressure reaches 0.2MPa.

[0051] Example 21: This example is basically the same as Example 1, except that the temperature and pressure inside the reactor are maintained for 3 hours until the temperature reaches 120°C and the pressure reaches 0.3MPa.

[0052] Example 22: This example is basically the same as Example 1, except that the power during ultrasonic processing is 150W and the frequency is 20kHz.

[0053] Example 23: This example is basically the same as Example 1, except that the power during ultrasonic treatment is 300W and the frequency is 40kHz.

[0054] Example 24: This example is basically the same as Example 1, except that the amount of antioxidant added accounts for 5% of the total mass of the rubber matrix.

[0055] Example 25: This example is basically the same as Example 1, except that the amount of antioxidant added accounts for 10% of the total mass of the rubber matrix.

[0056] Comparative Example 1: Referring to Example 1, the modified lignin was replaced with commercially available antioxidant D.

[0057] Comparative Example 2: Referring to Example 1, the modified lignin was replaced with unmodified lignin.

[0058] Comparative Example 3: Referring to Example 1, after adding pyridine and p-hydroxybenzoic acid to the reactor, the pressure inside the reactor was kept constant at 0.12 MPa.

[0059] Comparative Example 4: Referring to Example 1, no pretreatment of alkali lignin was performed.

[0060] Experimental Example: To investigate the influence of parameters from each embodiment and comparative example on the performance of antioxidants, antioxidants from each embodiment and comparative example were added to a rubber matrix to prepare rubber samples. Tensile strength tests were performed on the rubber samples from each embodiment and comparative example. Subsequently, the rubber samples from each embodiment and comparative example were aged at 100℃ for 72 hours. Tensile strength tests were then performed on the aged rubber samples, and the rate of decrease in tensile strength after aging was calculated. The specific investigation is as follows: 1. Investigate the influence of antioxidant components on antioxidant performance. Using Examples 1, 2, and 3, as well as Comparative Examples 1 and 2, as experimental comparisons, the performance of antioxidants with different components is shown in Table 1 below: Table 1. Performance of antioxidants with different components

[0061] As shown in Table 1, compared with Examples 1, 2, and 3, the rubber sample of Example 1 had the highest tensile strength and the lowest rate of decrease in tensile strength, indicating that the antioxidant in Example 1 had the best performance. This may be because the antioxidant in Example 1 was most uniformly dispersed in the rubber. Therefore, the antioxidant composition selected in Example 1 was the best.

[0062] Compared with Comparative Examples 1 and 2, in Example 1, the tensile strength of the rubber sample decreased and the rate of decrease in tensile strength increased after using commercially available antioxidants or replacing modified lignin with unmodified lignin. This may be because the modified lignin in Example 1 has better free radical scavenging ability and better dispersion in the rubber. Therefore, the antioxidant component selected in Example 1 is optimal.

[0063] 2. Investigate the effect of the composition of the first mixture on the performance of the antioxidant. Using Examples 1, 4, and 5 as experimental comparisons, the antioxidant performance of the first mixture with different components is shown in Table 2 below: Table 2. Antioxidant performance of different components in the first mixture.

[0064] As shown in Table 2, compared with Examples 1, 4, and 5, the rubber sample of Example 1 had the highest tensile strength and the lowest rate of decrease in tensile strength, indicating that the antioxidant of Example 1 had the best performance. This may be because the alkali lignin in the first mixture of Example 1 can be fully alkylated and modified. Therefore, the first mixture component selected in Example 1 was the best.

[0065] 3. Investigate the effect of pH value of the first mixture on the performance of the antioxidant. Using Examples 1, 6, and 7 as comparative experiments, the antioxidant performance of the first mixture at different pH values ​​is shown in Table 3 below: Table 3. Antioxidant performance of the first mixture at different pH values.

[0066] As shown in Table 3, compared with Examples 1, 6, and 7, the rubber sample of Example 1 had the highest tensile strength and the lowest rate of decrease in tensile strength, indicating that the antioxidant performance of Example 1 was the best. This may be because the alkali lignin and bromododecane could fully react at the pH value of the first mixture selected in Example 1, thus the pH value of the first mixture selected in Example 1 was the best.

[0067] 4. Investigate the effect of the ratio of p-hydroxybenzoic acid to thionyl chloride on the performance of antioxidants. Using Examples 1, 8, and 9 as comparative experiments, the antioxidant properties of different ratios of p-hydroxybenzoic acid and thionyl chloride are shown in Table 4 below: Table 4. Antioxidant properties at different ratios of p-hydroxybenzoic acid and thionyl chloride

[0068] As shown in Table 4, compared with Examples 1, 8, and 9, the rubber sample of Example 1 had the highest tensile strength and the lowest rate of decrease in tensile strength, indicating that the antioxidant performance of Example 1 was the best. This may be because the p-hydroxybenzoic acid and thionyl chloride ratio selected in Example 1 allowed for sufficient reaction between the two substances. Therefore, the p-hydroxybenzoic acid and thionyl chloride ratio selected in Example 1 was the optimal one.

[0069] 5. Investigate the effect of the second mixture composition on the performance of the antioxidant. Using Examples 1, 10, and 11 as comparative experiments, the antioxidant performance of the second mixture with different components is shown in Table 5 below: Table 5. Antioxidant performance of different components in the second mixture.

[0070] As shown in Table 5, compared with Examples 1, 10, and 11, the rubber sample of Example 1 had the highest tensile strength and the lowest rate of decrease in tensile strength, indicating that the antioxidant of Example 1 had the best performance. This may be because the alkylated lignin in the second mixture selected in Example 1 can be fully dispersed in dimethyl sulfoxide, so the second mixture selected in Example 1 is the best.

[0071] 6. Investigate the effect of reactor pressure on antioxidant performance when pyridine is added. Using Examples 1, 12, and 13 as experimental comparisons, the antioxidant performance under different reactor pressures with added pyridine is shown in Table 6 below: Table 6. Antioxidant performance under different reactor pressures with added pyridine

[0072] As shown in Table 6, compared with Examples 1, 12, and 13, the rubber sample of Example 1 had the highest tensile strength and the lowest rate of decrease in tensile strength, indicating that the antioxidant performance of Example 1 was the best. This may be because when pyridine was added in Example 1, the pressure inside the reactor was such that pyridine and the pretreated p-hydroxybenzoic acid could fully participate in the reaction. Therefore, the pressure inside the reactor was the best when pyridine was added in Example 1.

[0073] 7. Investigate the effect of pyridine dosage on the performance of antioxidants. Using Examples 1, 14, and 15 as comparative experiments, the antioxidant properties at different pyridine addition levels are shown in Table 7 below: Table 7. Antioxidant performance at different pyridine addition levels

[0074] As shown in Table 7, compared with Examples 1, 14, and 15, the rubber sample of Example 1 had the highest tensile strength and the lowest rate of decrease in tensile strength, indicating that the antioxidant performance of Example 1 was the best. This may be because the p-hydroxybenzoic acid after pretreatment can fully react with alkylated lignin at the pyridine addition amount selected in Example 1. Therefore, the pyridine addition amount selected in Example 1 was the best.

[0075] 8. Investigate the effect of the addition temperature of pretreated p-hydroxybenzoic acid on the performance of antioxidants. Using Examples 1, 16, and 17 as experimental comparisons, the antioxidant properties of pretreated p-hydroxybenzoic acid at different addition temperatures are shown in Table 8 below: Table 8 Antioxidant properties of pretreated p-hydroxybenzoic acid at different addition temperatures

[0076] As shown in Table 8, compared with Examples 1, 16, and 17, the rubber sample of Example 1 had the highest tensile strength and the lowest rate of decrease in tensile strength, indicating that the antioxidant performance of Example 1 was the best. This may be because the p-hydroxybenzoic acid pretreated at the selected temperature for adding p-hydroxybenzoic acid in Example 1 had the best reactivity. Therefore, the selected temperature for adding p-hydroxybenzoic acid pretreated in Example 1 was the best.

[0077] 9. Investigate the effect of the amount of pretreated p-hydroxybenzoic acid added on the performance of antioxidants. Using Examples 1, 18, and 19 as comparative experiments, the antioxidant properties of pretreated p-hydroxybenzoic acid with different addition amounts are shown in Table 9 below: Table 9. Antioxidant performance of pretreated p-hydroxybenzoic acid at different dosages

[0078] As shown in Table 9, compared with Examples 1, 18, and 19, the rubber sample of Example 1 had the highest tensile strength and the lowest rate of decrease in tensile strength, indicating that the antioxidant performance of Example 1 was the best. This may be because the alkylated lignin reacted most fully with the pretreated p-hydroxybenzoic acid at the amount of pretreated p-hydroxybenzoic acid selected in Example 1. Therefore, the amount of pretreated p-hydroxybenzoic acid selected in Example 1 was the best.

[0079] 10. Investigate the effects of temperature and pressure inside the reactor on the performance of antioxidants. Using Examples 1, 20, 21 and Comparative Example 3 as experimental comparisons, the performance of the antioxidant under different temperatures and pressures inside the reactor is shown in Table 10 below: Table 10. Performance of antioxidants under different temperatures and pressures inside the reactor.

[0080] As shown in Table 10, compared with Examples 1, 20, and 21, the rubber sample of Example 1 had the highest tensile strength and the lowest rate of decrease in tensile strength, indicating that the antioxidant performance of Example 1 was the best. This may be because the modified lignin yield was the highest and the byproducts were the fewest under the selected temperature and pressure in the reactor of Example 1. Therefore, the selected temperature and pressure in the reactor of Example 1 was the best.

[0081] Compared with Comparative Example 3, after the pressure inside the reactor was kept constant, the tensile strength of the rubber sample decreased and the rate of decrease in tensile strength increased. This may be because there are more by-products, which leads to more impurities in the modified lignin. Therefore, the reactor pressure selected in Example 1 is optimal.

[0082] 11. Investigating the effects of ultrasonic treatment parameters on the performance of antioxidants. Using Examples 1, 22, 23 and Comparative Example 4 as experimental comparisons, the performance of the antioxidant under different ultrasonic treatment parameters is shown in Table 11 below: Table 11. Performance of antioxidants under different parameters of ultrasonic treatment

[0083] As shown in Table 11, compared with Examples 1, 22, and 23, the rubber sample of Example 1 had the highest tensile strength and the lowest rate of decrease in tensile strength, indicating that the antioxidant of Example 1 had the best performance. This may be because the surface reactivity of alkali lignin was best under the ultrasonic treatment parameters selected in Example 1. Therefore, the ultrasonic treatment parameters selected in Example 1 were the best.

[0084] Compared with Comparative Example 4, Example 1 showed that without ultrasonic treatment, the tensile strength of the rubber sample decreased and the rate of decrease in tensile strength increased. This may be because the surface activity of alkali lignin was poor, which affected the modification effect. Therefore, the ultrasonic treatment parameters selected in Example 1 were optimal.

[0085] 12. Investigate the effect of the amount of antioxidant added on the performance of antioxidants. Using Examples 1, 24, and 25 as comparative experiments, the performance of antioxidants at different addition amounts is shown in Table 12 below: Table 12 Performance of antioxidants at different dosages

[0086] As shown in Table 12, compared with Examples 1, 24, and 25, the rubber sample of Example 1 had the highest tensile strength and the lowest rate of decrease in tensile strength, indicating that the antioxidant in Example 1 had the best performance. This may be because the antioxidant selected in Example 1 can be fully dispersed in the rubber sample at the selected amount of antioxidant addition, so the antioxidant addition amount selected in Example 1 is the optimal.

Claims

1. A modified lignin-based bio-based antioxidant, characterized in that, By weight, it includes the following components: 30-40 parts modified lignin, 3-5 parts silane coupling agent, 5-10 parts silica, 1-3 parts polyethylene wax, and 100-120 parts carrier.

2. The modified lignin-based antioxidant according to claim 1, characterized in that, The carrier is any one of EPDM rubber, polypropylene, polyethylene, or vinyl acetate.

3. The modified lignin-based antioxidant according to claim 1, characterized in that, The silane coupling agent is KH-550 or KH-560.

4. The modified lignin-based antioxidant according to claim 1, characterized in that, The method for preparing the modified lignin includes the following steps: S1. Add alkali lignin to the solvent and stir for 10-20 min. Then add bromododecane to obtain the first mixture. Adjust the pH of the first mixture to 11-12 with a 20-30% sodium hydroxide solution. Then stir at 80-100℃ for 2-4 h to obtain the first reaction solution. The mass ratio of alkali lignin, bromododecane and solvent is 1:0.3-0.5:10-15. S2. Adjust the pH of the first reaction solution to 3-4 using dilute hydrochloric acid with a mass concentration of 15-20%, then filter to obtain solid particles. After washing the solid particles, alkylated lignin is obtained. S3. Add p-hydroxybenzoic acid to thionyl chloride and reflux at 60-70°C for 2-3 hours. After vacuum distillation, pretreated p-hydroxybenzoic acid is obtained. The mass ratio of p-hydroxybenzoic acid to thionyl chloride is 1:3-4. S4. Add alkylated lignin to dimethyl sulfoxide and stir at 50-60°C for 20-30 min to obtain a second mixture; the mass ratio of alkylated lignin to dimethyl sulfoxide is 1:8-10. S5. Place the second mixture into the reactor and evacuate the reactor until the pressure inside the reactor reaches 1000~3000Pa. Then, pressurize the reactor with inert gas until the pressure inside the reactor reaches 0.1~0.15MPa. Add pyridine to the reactor, then stop pressurizing and heat the reactor until the temperature inside the reactor reaches 40~50℃. Add pretreated p-hydroxybenzoic acid to the reactor, then heat and pressurize the reactor until the temperature inside the reactor reaches 100~120℃ and the pressure reaches 0.2~0.3MPa. Maintain the temperature and pressure for 2~4 hours to obtain the second reaction solution. The amount of pyridine added accounts for 1~3% of the initial mass of the second mixture, and the amount of pretreated p-hydroxybenzoic acid added accounts for 4~6% of the initial mass of the second mixture. S6. The second reaction liquid is added dropwise to ice water, filtered to obtain a precipitate, and the precipitate is washed and dried to obtain modified lignin.

5. The modified lignin-based antioxidant according to claim 4, characterized in that, In step S1, the solvent is prepared by mixing urea, imidazole, and deionized water in a mass ratio of 1:0.4~0.6:70~80.

6. The modified lignin-based antioxidant according to claim 4, characterized in that, In step S1, the alkali lignin is pretreated before being added to the solvent. The pretreatment method is as follows: the alkali lignin is added to an ethanol solution with a mass concentration of 70-80%, and ultrasonically treated at 20-30°C for 1-2 hours. The power of the ultrasonic treatment is 150-300W and the frequency is 20-40kHz.

7. The modified lignin-based antioxidant according to claim 4, characterized in that, In step S6, the temperature of the ice water is 0~5℃, and the volume ratio of the second reaction liquid to the ice water is 1:6~7.

8. The modified lignin-based antioxidant according to claim 1, characterized in that, The preparation method of the antioxidant is as follows: Modified lignin, silane coupling agent, and carrier are placed in a mixer according to the specified weight proportions and mixed at 80-100°C for 1-3 minutes. Then, silica and polyethylene wax are added. The temperature is then raised to 150-170°C and mixed at 60-80 r / min for 5-8 minutes. The temperature is then raised again to 175-185°C and mixed at 50-60 r / min for 2-3 minutes to obtain a mixed masterbatch. The mixed masterbatch is then extruded and granulated using a screw extruder at 160-170°C to obtain the antioxidant.

9. The application of a modified lignin bio-based antioxidant as described in any one of claims 1 to 8 in rubber tires.

10. The application according to claim 9, characterized in that, The application method is as follows: during the rubber compounding process of rubber tires, the antioxidant is added to the rubber matrix, and the amount of antioxidant added accounts for 5 to 10% of the total mass of the rubber matrix.

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