A gs-g-sal filler, its preparation method and application

Abstract

This invention discloses a GS-g-SAL filler, its preparation method, and its application, belonging to the technical field of rubber fillers and rubber composite materials. The GS-g-SAL filler is obtained by surface grafting modification of sulfonated alkali lignin with glyceryl stearate as a grafting agent; the mass ratio of glyceryl stearate to sulfonated alkali lignin is 9:25. This invention effectively shields the association between polar groups by constructing a "hydrophilic core-hydrophobic shell" structure on the SAL surface, significantly improving the dispersibility and interfacial bonding of the filler in the rubber matrix. This invention has the following advantages: First, the raw materials are widely available and inexpensive. Second, the process is simple and environmentally friendly. Third, it can effectively improve the mechanical properties, processing properties, and aging resistance of NRL / WRP rubber composites, reduce production costs, realize the high-value utilization of biomass fillers, and has broad industrial application prospects.

Description

Technical Field

[0001] This invention belongs to the technical field of rubber fillers and rubber composite materials, specifically relating to a GS-g-SAL filler, its preparation method and application. Background Technology

[0002] Natural rubber latex (NRL) is widely used in the manufacturing of tires, seals, and shock absorbers due to its excellent elasticity, toughness, and processing adaptability. However, the relative scarcity of domestic natural rubber resources, coupled with its high cost, restricts its large-scale promotion. Meanwhile, waste rubber powder (WRP), as a recycled product of waste rubber products, is abundant and inexpensive. Blending it with natural rubber latex to prepare NRL / WRP composites can achieve resource recycling of waste rubber and reduce overall raw material costs, aligning with the trend of green and environmentally friendly industries. However, waste rubber powder itself has low surface activity and poor interfacial affinity with the natural rubber latex matrix. Direct addition often leads to a significant decrease in the mechanical and processing properties of the composite material, making it difficult to meet practical application requirements.

[0003] To address this issue, reinforcing fillers are often introduced into the system. Al, a byproduct primarily derived from the paper industry, is abundant and inexpensive. Its molecular structure is rich in active functional groups, theoretically possessing the potential to serve as a reinforcing filler for rubber. However, lignin itself has numerous polar hydroxyl groups on its surface, creating a significant polarity difference with the non-polar rubber matrix. This results in poor interfacial compatibility, making it prone to agglomeration in rubber and hindering the establishment of an effective stress transfer network, thus affecting the mechanical strength and long-term performance of the composite material.

[0004] Preliminary studies indicate that ultrasonic-assisted sulfonation can significantly disrupt the aggregation morphology of lignin, increase its specific surface area, and thus improve its dispersion in rubber. However, the sulfonation process introduces a large number of sulfonic acid groups, further enhancing the polarity and hydrophilicity of lignin. This exacerbates the interfacial compatibility issues between lignin and the hydrophobic NRL / WRP rubber matrix, making it difficult to fundamentally improve thermodynamic instability and form effective interfacial bonding. This limits stress transfer and performance improvement of the composite material.

[0005] Currently, various modification methods for SAL (Solid Alkali) have been explored, including alkylation and silane coupling agent modification. However, these methods are typically complex, costly, and difficult to balance with environmental considerations. Furthermore, the improvement in interfacial compatibility between modified SAL and the NRL / WRP matrix is ​​still insufficient, making it difficult to simultaneously enhance the mechanical properties, processing flowability, and aging resistance of the composite material, thus failing to meet the comprehensive requirements of practical industrial applications. Therefore, ensuring good dispersion of lignin in the system while effectively enhancing its interfacial bonding with the rubber matrix has become a core technical challenge that urgently needs to be addressed to improve the overall performance of NRL / WRP composite materials. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to provide a GS-g-SAL filler, its preparation method and application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A GS-g-SAL filler is obtained by surface grafting modification of sulfonated alkali lignin with glyceryl stearate as a grafting agent; the mass ratio of glyceryl stearate to sulfonated alkali lignin is (3~15):25.

[0008] Based on the above scheme, the mass ratio of stearic acid glyceride to sulfonated alkali lignin is 9:25.

[0009] The preparation method of the above GS-g-SAL packing material includes the following steps: The sulfonated alkali lignin solution was mixed with a mixture of 1.5% to 7.5% anhydrous glycerol stearate and ethanol, wherein the mass ratio of glycerol stearate to sulfonated alkali lignin was (3~15):25. The mixed reaction system was reacted at 70℃ and 1000 rpm for 4 hours. After the reaction was completed, the mixture was centrifuged, the precipitate was collected, washed, and dried to obtain the GS-g-SAL packing material.

[0010] Based on the above scheme, the sulfonated alkali lignin is prepared by the following method: Add alkali lignin to anhydrous ethanol, followed by sodium hydroxide solution, and stir to mix. Add sodium sulfite aqueous solution dropwise to the mixture, and adjust the pH of the mixture to 9-10 using dilute hydrochloric acid. Place the reaction system at 60℃ and 1000 rpm for 3 hours. When the reaction has proceeded for 1 hour and 30 minutes, sonicate for 5 minutes at a power of 55W. After sonication, proceed with the subsequent reaction. After the reaction is complete, adjust the pH of the mixture to neutral using dilute hydrochloric acid, centrifuge to collect the precipitate, wash the precipitate repeatedly with deionized water until the supernatant is neutral, and then dry it to obtain the final product.

[0011] The above-mentioned GS-g-SAL filler is used in the preparation of rubber composite materials with low Mooney viscosity, high wear resistance, high tensile strength and excellent anti-aging properties.

[0012] A rubber composite material is prepared from the following components in parts by mass: 85-95 parts natural latex, 9-11 parts of the above-mentioned GS-g-SAL filler, 9-11 parts of waste rubber powder, 25-35 parts of precipitated silica, 1.5-2.5 parts of antioxidant 4020, 4.5-5.5 parts of zinc oxide, 1.5-2.5 parts of stearic acid, 0.5-1.5 parts of FP-80G, 0.5-1.5 parts of sulfur, 1.4-1.6 parts of accelerator CZ, and 1.4-1.6 parts of accelerator DM.

[0013] Based on the above scheme, the rubber composite material is prepared from the following components in parts by mass: 90 parts natural latex, 10 parts of the above-mentioned GS-g-SAL filler, 10 parts waste rubber powder, 30 parts fumed silica, 2 parts antioxidant 4020, 5 parts zinc oxide, 2 parts stearic acid, 1 part FP-80G, 1 part sulfur, 1.5 parts accelerator CZ, and 1.5 parts accelerator DM.

[0014] Based on the above scheme, the preparation method of the rubber composite material is as follows: (1) Dilute natural latex with deionized water to a solid content of 40%, then add fumed silica and mix to obtain mixture A; (2) The GS-g-SAL filler and waste adhesive powder are mixed with deionized water to obtain mixture B; (3) Pour mixture B into mixture A to obtain mixture C. Slowly pour mixture C into 1% calcium chloride solution under stirring to flocculate. Dry the resulting flocculent block to obtain masterbatch. (4) The masterbatch obtained in step (3) is mixed with zinc oxide, stearic acid, antioxidant 4020 and FP-80G, and then sulfur, accelerator CZ and accelerator DM are added and mixed evenly; after vulcanization, the rubber composite material is obtained.

[0015] Based on the above scheme, the vulcanization conditions in step (4) are a temperature of 150°C, a pressure of 10 MPa, and a time of 1.3 × Tc90.

[0016] The above-mentioned rubber composite materials are used in the manufacture of tires, seals or shock-absorbing components.

[0017] Advantages of the technical solution of this invention This invention modifies SAL with GS to create a hydrophobic core-hydrophobic shell structure, which effectively shields the association of polar groups in the SAL molecule, significantly improves its interfacial compatibility with the nonpolar NRL / WRP rubber matrix, avoids filler agglomeration, and fully utilizes the reinforcing effect of SAL. The GS-g-SAL filler preparation method of this invention is simple and convenient to operate, requires no complex equipment, uses widely available and environmentally friendly raw materials, and enables high-value utilization of sulfonated alkali lignin, a biomass resource, reducing filler preparation costs. Compared with existing modification methods, it is more suitable for large-scale industrial production. Furthermore, the NRL / WRP rubber composite material of this invention, through the synergistic reinforcing effect of GS-g-SAL and silica, has the following advantages: First, it significantly improves the tensile strength, tear strength, and other mechanical properties of the composite material, improves processing fluidity by reducing Mooney viscosity, and enhances aging resistance by increasing the retention rate of thermo-oxidative aging strength. This effectively compensates for the performance degradation caused by the addition of waste rubber powder, achieving efficient recycling of waste rubber resources and further reducing the production cost of the composite material. Second, the composite material preparation process is simple and controllable, compatible with existing rubber processing equipment, requires no equipment modification, has low production costs, is environmentally friendly, and the prepared composite material has excellent comprehensive performance, making it widely applicable in tires, seals, shock-absorbing products, and other fields, with broad industrial application prospects. Attached Figure Description

[0018] Figure 1 shows the infrared spectra of GS, SAL and GS-g-SAL materials; Figure 2 shows scanning electron microscope images of different GS-g-SAL-X materials; Figure 3 shows the water contact angle test results of SAL and different GS-g-SAL-X materials; Figure 4 shows a comparison of the Mooney viscosity of different GS-g-SAL-X composite materials; Figure 5. Tensile strength and elongation at break of different GS-g-SAL-X composite materials; Figure 6. Tear strength and hardness of different GS-g-SAL-X composite materials; Figure 7 shows a comparison of DIN wear of different GS-g-SAL-X composite materials; Figure 8 shows the G'-Strain curves of different GS-g-SAL-X composite materials; Figure 9 shows a comparison of the aging performance of different GS-g-SAL-X composite materials. Detailed Implementation

[0019] The terminology used in this invention, unless otherwise specified, generally has the meanings commonly understood by those skilled in the art. The invention is further described in detail below with reference to specific embodiments and data. The following embodiments are merely illustrative and are not intended to limit the scope of the invention in any way.

[0020] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the experimental materials, reagents, and chemicals used in the following embodiments can be obtained through general channels.

[0021] The principle of the technical solution of this invention: SAL molecules are rich in polar groups such as hydroxyl and sulfonic acid groups, thus exhibiting hydrophilicity. This presents a significant polarity difference with the hydrophobic rubber matrix. When these two materials with such large polarity differences are blended, the system has a high free energy, tending towards phase separation. This leads to SAL aggregation within the rubber matrix, preventing the formation of effective interfacial bonding. GS contains long-chain alkyl hydrophobic segments. When grafted onto the SAL surface, these hydrophobic segments covalently coat the lignin particles, forming a hydrophobic shell. The modified SAL exhibits a significantly increased water contact angle, achieving a transformation from hydrophilic to hydrophobic. Its surface energy matches that of the rubber matrix, reducing interfacial tension and significantly improving the thermodynamic compatibility of the two phases. According to the principle of "like dissolves like," the hydrophobic long-chain alkyl groups have good affinity with rubber molecular chains, forming molecular chain entanglements at the interface and enhancing interfacial bonding strength.

[0022] Unmodified SAL particles exhibit strong self-aggregation due to hydrogen bonding of surface polar groups, forming large agglomerates. After graft modification, the long-chain alkyl groups on the surface form a steric hindrance layer around the particles, effectively shielding the hydrogen bonding association between the core polar groups. When the modified particles approach each other, the long-chain alkyl groups generate steric repulsion, preventing secondary agglomeration and thus dispersing SAL in the rubber matrix.

[0023] The formation of the hydrophobic shell enhances the interfacial bonding between the modified SAL and the rubber matrix, effectively transferring stress from the rubber to the rigid lignin particles, thus providing reinforcement. Simultaneously, the interfacial bonding layer can induce molecular chain slippage and crack deflection under stress, thereby improving tensile strength, tear strength, and elongation at break. The long-chain alkyl groups on the surface act as lubricants during processing, reducing Mooney viscosity, and form a solid lubricating film during friction to improve wear resistance. The dense hydrophobic layer blocks oxygen diffusion, delaying thermo-oxidative aging. Insufficient grafting leads to inadequate hydrophobicity, while excessive grafting causes long-chain entanglement and agglomeration. The composite material exhibits optimal overall performance when the grafting concentration reaches 4.5%.

[0024] In the following examples, the AL used was provided by Beijing Huamaike Biotechnology Co., Ltd.; GS was provided by Xilong Scientific Co., Ltd.; anhydrous ethanol was provided by Shanghai Maclean Biochemical Technology Co., Ltd.; the solid content of natural latex was 61%; 120-mesh waste rubber powder was provided by Jiangxi Kangdi New Materials Co., Ltd.; precipitated silica was provided by Shandong Lianke Technology Co., Ltd.; zinc oxide was provided by Weifang Aolong Zinc Industry Co., Ltd.; antioxidant 4020 was provided by Wuhan Lingfan Technology Co., Ltd.; sulfur was provided by Luoyang Tianzhidao New Materials Technology Co., Ltd.; and the remaining materials FP-80G, accelerator CZ, and accelerator DM were all commercially available and used in accordance with regulations.

[0025] The sulfonated alkali lignin (SAL) is prepared by the following method: First, add 200 mL of anhydrous ethanol and 50 g of AL to a beaker, followed by 50 mL of 10% sodium hydroxide solution. Stir thoroughly with a glass rod until the mixture is homogeneous. Then, add 20 g of sodium sulfite solution (pre-dissolved in 100 mL of water) dropwise, and adjust the pH of the mixture to 9-10 using dilute hydrochloric acid. Place the reaction system in a magnetic water bath at 60°C and 1000 rpm for 3 hours. After 1 hour and 30 minutes of reaction, remove the beaker from the magnetic water bath and sonicate it for 5 minutes at a power of 55 W. Then, place the beaker back in the magnetic water bath for subsequent experimental reactions. After the reaction is complete, adjust the pH of the mixture to neutral using dilute hydrochloric acid. The sample is then centrifuged, and the precipitate is collected. The precipitate was repeatedly washed with deionized water until the supernatant was neutral, then transferred to an oven and dried at 50°C for 36 hours until constant weight was obtained, thus yielding the ultrasonically treated sulfonated alkali lignin sample. The molecular formula of the sulfonated alkali lignin is (C9H). 7.5 O 4.3 S) n Free sulfonic acid groups are attached to the molecule. SO3H has no sodium ions in its molecular structure.

[0026] Example 1 A GS-g-SAL filler is obtained by surface modification of ultrasonic SAL using glyceryl stearate (GS) as a grafting agent.

[0027] The specific steps are as follows: The ultrasonically treated SAL was prepared into a 100 mL solution with a mass fraction of 25%, and 200 mL of a 1.5% (w / w) mixture of glyceryl stearate and anhydrous ethanol was added. The reaction system was placed in a magnetic water bath and reacted at 70 °C and 1000 rpm for 4 hours. After the reaction was completed, the mixture was centrifuged, the precipitate was collected, washed, and dried in an oven at 50 °C for 36 hours until constant weight was obtained, yielding the GS-g-SAL packing material, denoted as GS-g-SAL-1.5.

[0028] Example 2 A GS-g-SAL filler is obtained by surface modification of ultrasonic SAL using glyceryl stearate (GS) as a grafting agent.

[0029] The specific steps are as follows: The ultrasonically treated SAL was prepared into a 100 mL solution with a mass fraction of 25%, and 200 mL of a 3% (w / w) mixture of glyceryl stearate and anhydrous ethanol was added. The reaction system was placed in a magnetic water bath and reacted at 70 °C and 1000 rpm for 4 hours. After the reaction was completed, the mixture was centrifuged, the precipitate was collected, washed, and dried in an oven at 50 °C for 36 hours until constant weight was obtained, yielding the GS-g-SAL packing material, denoted as GS-g-SAL-3.

[0030] Example 3 A GS-g-SAL filler is obtained by surface modification of ultrasonic SAL using glyceryl stearate (GS) as a grafting agent.

[0031] The specific steps are as follows: The ultrasonically treated SAL was prepared into a 100 mL solution with a mass fraction of 25%, and 200 mL of a 4.5% (w / w) mixture of glyceryl stearate and anhydrous ethanol was added. The reaction system was placed in a magnetic water bath and reacted at 70 °C and 1000 rpm for 4 hours. After the reaction was completed, the mixture was centrifuged, the precipitate was collected, washed, and dried in an oven at 50 °C for 36 hours until constant weight was obtained, yielding the GS-g-SAL packing material, denoted as GS-g-SAL-4.5.

[0032] Example 4 A GS-g-SAL filler is obtained by surface modification of ultrasonic SAL using glyceryl stearate (GS) as a grafting agent.

[0033] The specific steps are as follows: The ultrasonically treated SAL was prepared into a 100 mL solution with a mass fraction of 25%, and 200 mL of a 6% (w / w) mixture of glyceryl stearate and anhydrous ethanol was added. The reaction system was placed in a magnetic water bath and reacted at 70 °C and 1000 rpm for 4 hours. After the reaction was completed, the mixture was centrifuged, the precipitate was collected, washed, and dried in an oven at 50 °C for 36 hours until constant weight was obtained, yielding the GS-g-SAL packing material, denoted as GS-g-SAL-6.

[0034] Example 5 A GS-g-SAL filler is obtained by surface modification of ultrasonic SAL using glyceryl stearate (GS) as a grafting agent.

[0035] The specific steps are as follows: The ultrasonically treated SAL was prepared into a 100 mL solution with a mass fraction of 25%, and 200 mL of a 7.5% (w / w) mixture of glyceryl stearate and anhydrous ethanol was added. The reaction system was placed in a magnetic water bath and reacted at 70 °C and 1000 rpm for 4 hours. After the reaction was completed, the mixture was centrifuged, the precipitate was collected, washed, and dried in an oven at 50 °C for 36 hours until constant weight was obtained, yielding the GS-g-SAL packing material, denoted as GS-g-SAL-7.5.

[0036] Infrared spectral analysis of GS-g-SAL packing material Infrared spectra of GS, SAL, and GS-g-SAL materials prepared by grafting the two are as follows: Figure 1 As shown, the GS-g-SAL material here was prepared in Example 3, and GS is at 2908 cm⁻¹. -1 With 2848 cm -1 Two sharp absorption peaks were observed, one induced by the -CH2- asymmetric vibration and the other by the symmetric stretching vibration. Simultaneously, the C=O and COC bonds in its ester structure showed peaks at 1730 cm⁻¹. -1 and 1173 cm -1 The location yielded a strong characteristic response. After the grafting reaction, the obtained GS-g-SAL composite product spectrum completely retained the typical absorption signal derived from the GS aliphatic segment, directly confirming that the hydrophobic segment had been successfully grafted into the system. Observation of the SAL spectrum after ultrasonic treatment revealed that at 3400 cm⁻¹... -1The presence of a free -OH absorption band in the vicinity indicates a decrease in the intensity of the characteristic hydroxyl response at this specific position in the spectral curve of the corresponding GS-g-SAL product. This weakening of the absorption band demonstrates that the densely distributed polar hydroxyl groups on the lignin framework, acting as highly active sites, underwent chemical grafting and esterification reactions with the GS molecules. It is this molecular-scale bonding that consumes the free hydroxyl groups, thus laying the foundation for a subsequent leap in macroscopic interfacial compatibility at the underlying chemical structure level.

[0037] Infrared spectral analysis of GS-g-SAL packing material Scanning electron microscopy was performed on the GS-g-SAL fillers prepared by the methods in Examples 1-5, with sulfonated alkali lignin not grafted with GS as a control. The results are as follows: Figure 2 As shown in the figure, SAL treated with ultrasound for only 20 minutes exhibits a rough and highly fragmented surface morphology. Due to the lack of a surface shielding layer, its microstructure exhibits the irregular, loosely aggregated network characteristic of natural polymers. When the GS concentration is 1.5% and 3%, the surface of the modified lignin tends to be smooth, indicating that the hydrophobic segments have initially played a modifying role, but the continuity of the formed coating layer is poor, and exposed and void distributions are still visible in the interface area. As the GS concentration is further increased to 4.5%, the microstructure of the material reaches a more ideal equilibrium state. At this time, the particle size distribution is highly uniform, the surface is continuous, smooth, and the structure is dense. This morphological feature indicates that the long-chain alkyl groups have constructed a complete hydrophobic "shell" around the lignin core, effectively shielding the mutual attraction between the polar bonds in the core, thereby fundamentally inhibiting the occurrence of secondary aggregation. However, when the GS concentration rises to 6% or even 7.5%, the excessive flexible long-chain lipid molecules not only fail to further optimize the shell structure, but also cause a negative aggregation effect due to intense physical entanglement. Under high magnification, severe boundary adhesion between modified particles can be clearly observed, the original phase boundaries are blurred, and they re-evolve into large-scale blocky aggregates in the matrix, resulting in a sharp deterioration in the dispersibility of the material.

[0038] Water contact angle analysis of GS-g-SAL-X material The water contact angles of the GS-g-SAL fillers prepared by the methods in Examples 1-5 were tested, with sulfonated alkali lignin without GS grafting used as a control. The results are shown in Table 1. Figure 3As shown, the contact angle directly indicates whether a material surface is hydrophilic or hydrophobic. Table 1 shows that the unmodified SAL has a contact angle of only 60°, which is relatively low. This is because the lignin molecular network contains a large number of polar oxygen-containing functional groups, which absorb water. After graft modification, the contact angle of GS-g-SAL gradually increases. When the GS concentration is 1.5%, the contact angle rises to 70.7°, exhibiting some hydrophobic ability. As the concentration continues to increase, the contact angle successively crosses nodes of 82.1°, 87.9°, and 89.6°. When the GS concentration reaches 7.5%, the contact angle finally reaches 96.8°, indicating that the material surface has completely transformed from a hydrophilic state to a typical hydrophobic state.

[0039] Table 1 Water contact angles of SAL and GS-g-SAL

[0040] Example 6 A rubber composite material using GS-g-SAL-1.5 prepared in Example 1 as a reinforcing filler.

[0041] Its specific formula (parts by weight, phr) is as follows: 90 parts natural latex; GS-g-SAL-1.510 copies; 10 parts of waste glue powder; 30 parts of silica; Anti-aging agent 4020, 2 parts; 5 parts zinc oxide; Stearic acid 2 parts; FP-80G 1 copy; 1 part sulfur; Accelerator CZ 1.5 parts; Accelerator DM 1.5 parts; The specific preparation method is as follows: (1) Accurately weigh each component in the formula: (2) Dilute natural latex with deionized water to a solid content of 40%, then add fumed silica and stir evenly to obtain mixture A; mix GS-g-SAL-1.5 with waste rubber powder with deionized water to obtain mixture B; pour mixture B into mixture A and stir evenly to obtain mixture C, then slowly pour it into 2000 mL of 1% calcium chloride solution while stirring. After flocculation is completed, wash the flocculated gel block with deionized water and dry it at 50℃ for 36 h to constant weight to obtain masterbatch.

[0042] (3) The masterbatch obtained in step (2) is mixed with zinc oxide, stearic acid, antioxidant 4020, and FP-80G in a mixer. Then, sulfur, accelerator CZ, and accelerator DM are added in a two-roll mill and mixed evenly. Vulcanization is carried out at a vulcanization temperature of 150℃, a vulcanization pressure of 10MPa, and a vulcanization time of 1.3×Tc90. After vulcanization, the sample is cooled to room temperature for at least 8 hours to obtain the GS-g-SAL-1.5 / NRL / WRP rubber composite material.

[0043] Example 7 A rubber composite material using GS-g-SAL-3 prepared in Example 2 as a reinforcing filler.

[0044] Except for GS-g-SAL-3, the other components and preparation methods are the same as in Example 6; thus, the GS-g-SAL-3 / NRL / WRP rubber composite material is obtained.

[0045] Example 8 A rubber composite material using GS-g-SAL-4.5 prepared in Example 3 as a reinforcing filler.

[0046] Except for GS-g-SAL-4.5, the other components and preparation methods are the same as in Example 6; thus, the GS-g-SAL-4.5 / NRL / WRP rubber composite material is obtained.

[0047] Example 9 A rubber composite material using GS-g-SAL-6 prepared in Example 4 as a reinforcing filler.

[0048] Except for GS-g-SAL-6, the other components and preparation methods are the same as in Example 6; thus, the GS-g-SAL-6 / NRL / WRP rubber composite material is obtained.

[0049] Example 10 A rubber composite material using GS-g-SAL-7.5 prepared in Example 4 as a reinforcing filler.

[0050] Except for GS-g-SAL-7.5, the other components and preparation methods are the same as in Example 6; thus, the GS-g-SAL-7.5 / NRL / WRP rubber composite material is obtained.

[0051] Comparison Examples A rubber composite material was prepared using ultrasonic SAL without GS grafting agent modification as filler, with the remaining formulation, preparation steps, and process parameters the same as in Example 6. A GS-g-SAL / NRL / WRP rubber composite material was thus obtained.

[0052] Effect of GS-g-SAL-X on the processing properties of NRL / WRP composites The Mooney viscosity of the rubber composites prepared by the methods described in Examples 6-10 and the comparative examples was determined using a rubber Mooney viscosity tester according to GB / T 1232.1-2016. The results are as follows: Figure 4 As shown in the figure, the data indicates that the Mooney viscosity of the unmodified SAL rubber composite material (GS-g-SAL-0) prepared by ultrasonic treatment is relatively high at 39.815, mainly due to the large interfacial friction between the lignin polar aggregates and the rubber. After graft modification, the Mooney viscosity exhibits a U-shaped trend of first decreasing and then increasing: when the GS concentration increases from 1.5% to 4.5%, the viscosity drops to the lowest point of 27.573, because the grafted GS is hydrophobic, reducing flow resistance; however, when the GS concentration exceeds 4.5%, the viscosity rises back to 33.431, because the excessive flexible long chains induce intermolecular physical entanglement, causing the modified particles to re-aggregate, which in turn hinders chain segment slippage.

[0053] Effect of GS-g-SAL-X on the vulcanization properties of NRL / WRP composites The vulcanization characteristics of the rubber composites prepared by the methods described in Examples 6-10 and the comparative examples were determined using a rotorless vulcanizer according to GB / T 16584-1996. The results are shown in Table 2. The Tc90 and Tc10 of the rubber composite prepared by ultrasonic treatment of unmodified SAL (GS-g-SAL-0) were 5.735 min and 2.537 min, respectively. After introducing GS-grafted lignin, the vulcanization cycle of each experimental group generally showed a shortening trend. Among them, the Tc90 of GS-g-SAL-3 was shortened to 5.495 min, a decrease of about 4.2%; while the Tc10 of GS-g-SAL-4.5 decreased to 2.497 min. With the increase of GS concentration, MH-ML showed a trend of first increasing and then decreasing: from 10.871 dN·m in the control group to a peak of 11.926 dN·m at 4.5%, and then falling back to 11.345 dN·m. The upward phase benefits from the effective participation of lignin surface active sites after hydrophobic grafting in cross-linking, which improves interfacial fusion; the downward phase is due to the introduction of excessive long-chain molecules, which increases steric hindrance and hinders the formation of effective cross-linking bonds.

[0054] Table 2. Vulcanization characteristics of NRL / WRP composites of GS-g-SAL-X

[0055] Effect of GS-g-SAL-X on the Mechanical Properties of NRL / WRP Composites The mechanical properties of the rubber composites prepared by the methods described in Examples 6-10 and the comparative examples were determined according to GB / T 528-2009 using an electronic universal tensile testing machine and GB / T 39693.7-2022 using a hardness tester. The results are as follows: Figure 5 and Figure 6 As shown, the tensile strength of the unmodified SAL rubber composite material (GS-g-SAL-0) prepared by ultrasonic treatment was 26.74 MPa, and the elongation at break was 556.72%. With the gradual increase of GS concentration, the tensile properties and ductility of the material improved simultaneously, reaching the optimal balance point of mechanical properties at GS-g-SAL-4.5. At this point, the tensile strength of the composite rubber increased to 27.83 MPa, an increase of 4.1% compared to the control group; the elongation at break increased to 593.12%; the tear strength reached a peak of 67.31 N / mm, an increase of 8.0% compared to the control group; and the hardness also increased to a maximum value of 57. This indicates that modifying lignin with an appropriate amount of GS can make it disperse evenly in the rubber, forming an efficient "force transfer network," resulting in stronger overall material performance. However, once the GS concentration exceeds 4.5%, the excess long-chain molecules cause the lignin particles to re-agglomerate, disrupting the original continuous interface. This easily leads to stress concentration points and structural defects within the material, weakening cohesion and causing a decline in mechanical properties.

[0056] Effect of GS-g-SAL-X on the wear resistance of NRL / WRP composites The abrasion resistance data of the rubber composites prepared by the methods described in Examples 6-10 and the comparative examples were determined using a DIN abrasion tester according to GB / T 9867-2008. The results are as follows: Figure 7 As shown, the DIN wear volume of all modified groups was lower than that of the unmodified ultrasonic control group. With increasing GS concentration, the wear volume showed a stepwise decreasing trend: from 174.53 mm for GS-g-SAL-1.5. 3 It gradually decreased, reaching its lowest point of 135.53 mm at GS-g-SAL-6. 3 Compared to the control group, the wear resistance of this formulation improved by 29.82%. This is because after GS is grafted onto SAL, the long alkyl chains increase the compatibility between lignin and the rubber matrix, reduce the existence of stress concentration points, and prevent lignin particles from easily detaching during friction. When the GS concentration is too high, self-polymerization can easily occur due to intermolecular hydrogen bonds or van der Waals forces, leading to filler agglomeration in the rubber matrix. Agglomerates not only fail to strengthen the matrix but also become stress concentration points, weakening its wear resistance.

[0057] Effect of GS-g-SAL-X on the processing properties of NRL / WRP composites The G'-Strain curves of the rubber composites prepared by the methods described in Examples 6-10 and the comparative examples were measured using an RPA2000 rubber processing analyzer from Alpha Technologies, USA. The results are as follows: Figure 8As shown, GS-g-SAL-4.5 exhibits a lower initial storage modulus and a smaller Payne effect, indicating that the filler achieves good dispersion in the rubber matrix and that the filler-filler interaction is weak. This suggests that the long alkyl-linked branches of GS effectively suppress the self-aggregation of lignin particles through steric hindrance, achieving optimal physical dispersion. This uniform dispersion avoids stress concentration caused by filler agglomeration, while the GS segments enhance the compatibility and physical entanglement between the filler and the rubber matrix. In contrast, although GS-g-SAL-6 and GS-g-SAL-7.5 form a dense filler network and achieve higher static stiffness, their severe Payne effect foreshadows serious internal defects, making them prone to microcrack initiation under large strain or dynamic loads.

[0058] Effect of GS-g-SAL-X on the aging properties of NRL / WRP composites The strength retention rate and aging performance of the rubber composite materials prepared in Examples 6-10 and the comparative examples, after being dried in an oven at 100°C for 48 hours, were tested using an electronic universal tensile testing machine. The results are shown in Table 3 and... Figure 9 As shown, with the increase of GS concentration, the strength of the composite material initially increases and then decreases. The GS-g-SAL-4.5 group achieved the highest tensile strength and strength retention rate after aging, significantly better than the unmodified control group. This is because lignin itself contains abundant phenolic hydroxyl structures, which can act as natural antioxidants to capture free radicals generated during aging. Appropriate GS grafting modification further optimizes its uniform dispersion in the rubber matrix, forming a denser physical barrier. However, when the GS concentration reaches 6%, severe filler agglomeration leads to increased interfacial defects, and stress concentration points during aging are more prone to inducing microcrack propagation, resulting in a decrease in the retention rate to 83.61%.

[0059] Table 3 Strength retention rate of NRL / WRP composite material of GS-g-SAL-X

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A GS-g-SAL packing material, characterized in that, The GS-g-SAL filler was obtained by surface grafting modification of sulfonated alkali lignin with glyceryl stearate as a grafting agent; the mass ratio of glyceryl stearate to sulfonated alkali lignin was (3~15):

25.

2. The GS-g-SAL packing according to claim 1, characterized in that, The mass ratio of stearic acid glyceride to sulfonated alkali lignin is 9:

25.

3. The preparation method of the GS-g-SAL packing material according to claim 1, characterized in that, The steps are as follows: The sulfonated alkali lignin solution was mixed with a mixture of 1.5% to 7.5% anhydrous glycerol stearate and ethanol, wherein the mass ratio of glycerol stearate to sulfonated alkali lignin was (3~15):

25. The mixed reaction system was reacted at 70℃ and 1000 rpm for 4 hours. After the reaction was completed, the mixture was centrifuged, the precipitate was collected, washed, and dried to obtain the GS-g-SAL packing material.

4. The preparation method of the GS-g-SAL filler according to claim 3, characterized in that, The sulfonated alkali lignin is prepared by the following method: Add alkali lignin to anhydrous ethanol, followed by sodium hydroxide solution, and stir to mix. Add sodium sulfite aqueous solution dropwise to the mixture, and adjust the pH of the mixture to 9-10 using dilute hydrochloric acid. Place the reaction system at 60℃ and 1000 rpm for 3 hours. When the reaction has proceeded for 1 hour and 30 minutes, sonicate for 5 minutes at a power of 55W. After sonication, proceed with the subsequent reaction. After the reaction is complete, adjust the pH of the mixture to neutral using dilute hydrochloric acid, centrifuge to collect the precipitate, wash the precipitate repeatedly with deionized water until the supernatant is neutral, and then dry it to obtain the final product.

5. The application of the GS-g-SAL filler according to claim 1 or 2 in the preparation of rubber composite materials with low Mooney viscosity, high wear resistance, high tensile strength and excellent anti-aging properties.

6. A rubber composite material, characterized in that, It is prepared from the following components in parts by mass: 85-95 parts of natural latex, 9-11 parts of GS-g-SAL filler as described in claim 1 or 2, 9-11 parts of waste rubber powder, 25-35 parts of silica, 1.5-2.5 parts of antioxidant 4020, 4.5-5.5 parts of zinc oxide, 1.5-2.5 parts of stearic acid, 0.5-1.5 parts of FP-80G, 0.5-1.5 parts of sulfur, 1.4-1.6 parts of accelerator CZ, and 1.4-1.6 parts of accelerator DM.

7. The rubber composite material according to claim 6, characterized in that, It is prepared from the following components in parts by mass: 90 parts of natural latex, 10 parts of GS-g-SAL filler as described in claim 1 or 2, 10 parts of waste rubber powder, 30 parts of fumed silica, 2 parts of antioxidant 4020, 5 parts of zinc oxide, 2 parts of stearic acid, 1 part of FP-80G, 1 part of sulfur, 1.5 parts of accelerator CZ, and 1.5 parts of accelerator DM.

8. The rubber composite material according to claim 6 or 7, characterized in that, The preparation method is as follows: (1) Dilute natural latex with deionized water to a solid content of 40%, then add fumed silica and mix to obtain mixture A; (2) The GS-g-SAL filler and waste adhesive powder are mixed with deionized water to obtain mixture B; (3) Pour mixture B into mixture A to obtain mixture C. Slowly pour mixture C into a 1% calcium chloride solution under stirring to flocculate. Dry the resulting flocculent block to obtain masterbatch. (4) The masterbatch obtained in step (3) is mixed with zinc oxide, stearic acid, antioxidant 4020 and FP-80G, and then sulfur, accelerator CZ and accelerator DM are added and mixed evenly; after vulcanization, the rubber composite material is obtained.

9. The rubber composite material according to claim 8, characterized in that, The vulcanization conditions in step (4) are a temperature of 150°C, a pressure of 10 MPa, and a time of 1.3 × Tc90.

10. The use of the rubber composite material according to any one of claims 6 to 9 in the manufacture of tires, seals or shock-absorbing elements.

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