A polythiooctanoic acid-based silane coupling agent and its application in the preparation of rubber composites

Abstract

This invention provides a polythiooctanoic acid-based silane coupling agent and its application in the preparation of rubber composites. The high-density silane coupling agent with side chains of this invention can covalently couple with inorganic fillers at multiple sites during rubber blending and vulcanization, bridging the rubber backbone and significantly enhancing the organic-inorganic interface interaction. Simultaneously, this invention interpenetrates and entangles with the rubber molecular chains, forming a physical cross-linked network, improving the mechanical strength of the rubber composite. The disulfide bonds on the backbone exhibit dynamic covalent properties; they can break and dissipate energy under external forces, improving toughness, and can recombine under mild conditions, endowing the material with self-healing capabilities. Furthermore, the multi-site covalent coupling and envelope effect of this invention effectively prevent the migration and diffusion of inorganic fillers in the rubber matrix, giving the material excellent stability and long-term durability, significantly extending its service life.

Description

Technical Field

[0001] This invention belongs to the field of silane coupling agent technology, specifically relating to a polythiooctanoic acid-based silane coupling agent and its application in the preparation of rubber composite materials. Background Technology

[0002] With the advancement of modernization and the growing acceptance of green and environmentally friendly concepts, the development of rubber composite materials with excellent comprehensive performance and durability has become particularly important. In industrial production, nano-inorganic fillers (such as carbon black, silica, and clay) are compounded with rubber to enhance material properties. However, due to the thermodynamic incompatibility between inorganic fillers and the organic rubber matrix, simple physical mixing is insufficient to achieve uniform dispersion of the inorganic fillers within the rubber matrix. This leads to the easy aggregation of inorganic fillers, resulting in defects and stress concentration points within the rubber composite material, thus diminishing the reinforcing effect.

[0003] Silane coupling agents are a class of organosilicon compounds with a special structure, generally represented by the formula RSiX3. Here, R represents active groups such as amino, mercapto, vinyl, and epoxy groups, which possess strong reactivity with the polymer matrix; X is typically an alkoxy or acyloxy group capable of hydrolysis. When silane coupling agents are added to polymer composite systems, they can undergo condensation reactions with hydroxyl groups in inorganic materials and also interact physically or chemically with polymer chains, thus bridging the organic and inorganic components and significantly improving the overall performance of the polymer composite. Based on this, numerous studies have reported the application of small-molecule silane coupling agents in rubber composites, achieving significant practical applications and economic value.

[0004] However, the rapid development of modern industry has placed higher demands on the performance of rubber composites. The core issue lies in further enhancing the organic-inorganic interfacial interaction between rubber and inorganic fillers, thereby maximizing the functional properties of the inorganic reinforcing fillers. Therefore, it is necessary to improve the bridging force of existing small-molecule silane coupling agents and enrich the types of interactions between them and the polymer matrix. This will help to further improve the mechanical properties and stability of rubber composites to meet the higher demands of production and daily life. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a polythiooctanoic acid silane coupling agent.

[0006] Another object of the present invention is to provide the application of the above-mentioned polythiooctanoic acid silane coupling agent in the preparation of rubber composite materials.

[0007] The technical solution of the present invention is as follows:

[0008] A polythiooctanoic acid silane coupling agent, the structural formula of which is: Where R is selected from n1 = 5 - 2000, n2 = 2 - 5.

[0009] In a preferred embodiment of the present invention, its structural formula is as follows: n = 5 - 2000.

[0010] The above-mentioned polythioctic acid-based silane coupling agent is prepared by condensing a silane coupling agent with a terminal group of -NH2, -SH, -OH or epoxy group with thioctic acid to obtain a silane coupling agent polymer monomer containing a dithiopentane ring, and then preparing it by ring-opening polymerization.

[0011] The application of the above-mentioned polythiooctanoic acid-based silane coupling agent in the preparation of rubber composite materials.

[0012] In a preferred embodiment of the present invention, the rubber composite material is prepared by uniformly mixing a matrix rubber, the polythiooctanoic acid-based silane coupling agent, an inorganic filler, zinc oxide, stearic acid, a vulcanizing agent, an accelerator, an antioxidant, and paraffin wax, followed by vulcanization and hot pressing; the surface of the inorganic filler contains active hydrogen sites (preferably hydroxyl groups), which can undergo a condensation reaction with the polythiooctanoic acid-based silane coupling agent.

[0013] More preferably, the matrix rubber is selected from natural rubber, styrene-butadiene rubber, cis-butadiene rubber and chloroprene rubber, and the inorganic filler is selected from silica, metal-organic framework (MOF), two-dimensional transition metal carbide (MXene), silicate, inorganic metal oxide and hydroxide.

[0014] More preferably, the mass ratio of the matrix rubber, polythiooctanoic acid silane coupling agent, inorganic filler, zinc oxide, stearic acid, vulcanizing agent, accelerator, antioxidant and paraffin is 60-100:1-30:10-80:2-4:1-3:1-4:1-4:1-3:1-3.

[0015] A rubber composite material, characterized in that its raw materials include the above-mentioned polythiooctanoic acid silane coupling agent.

[0016] In a preferred embodiment of the present invention, it is prepared by uniformly mixing a base rubber, the polythiooctanoic acid silane coupling agent, an inorganic filler, zinc oxide, stearic acid, a vulcanizing agent, an accelerator, an antioxidant, and paraffin wax, followed by vulcanization and hot pressing; the surface of the inorganic filler contains active hydrogen sites (preferably hydroxyl groups), which can undergo a condensation reaction with the polythiooctanoic acid silane coupling agent.

[0017] More preferably, the matrix rubber is selected from natural rubber, styrene-butadiene rubber, cis-butadiene rubber and chloroprene rubber, and the inorganic filler is selected from silica, metal-organic framework (MOF), two-dimensional transition metal carbide (MXene), silicate, inorganic metal oxide and hydroxide.

[0018] More preferably, the mass ratio of the matrix rubber, polythiooctanoic acid silane coupling agent, inorganic filler, zinc oxide, stearic acid, vulcanizing agent, accelerator, antioxidant, and paraffin wax is 60-100:1-30:10-80:2-4:1-3:1-4:1-4:1-3:1-3

[0019] The beneficial effects of this invention are:

[0020] 1. The polythioctic acid-based silane coupling agent of the present invention is prepared by ring-opening polymerization of a silane coupling agent containing thioctic acid. Due to the high reactivity of the dithiopentane, this polymerization reaction is carried out under mild conditions and is simple to operate. During rubber blending and vulcanization, the high-density silane coupling agent grafted onto the side chain of the polythioctic acid-based silane coupling agent can covalently couple inorganic fillers at multiple sites and bridge the rubber backbone. Compared with small molecule silane coupling agents, this multi-site synergistic coupling effect significantly enhances the organic-inorganic interface interaction. Furthermore, during processing, the polythioctic acid-based silane coupling agent interpenetrates and entangles with the rubber molecular chains, forming a rich physical cross-linked network, thereby significantly increasing the mechanical strength of the rubber composite material.

[0021] 2. The disulfide bonds on the main chain of the polythiooctanoic acid-based silane coupling agent of this invention possess dynamic covalent chemical properties. Under external force, the disulfide bonds can break, releasing energy and dissipating it, thereby improving the toughness of the rubber composite material. Simultaneously, these disulfide bonds can recombine under mild conditions, endowing the material with excellent self-healing capabilities. By adjusting the molecular weight, molecular weight distribution, and blending ratio of this polythiooctanoic acid-based silane coupling agent with rubber, the comprehensive properties of the rubber composite material can be broadly tunable to meet the needs of different application scenarios.

[0022] 3. Based on the inherent properties of inorganic fillers, customized and functionalized rubber composite materials can be prepared. The multi-site covalent coupling and the encapsulation effect of the polythiooctanoic acid-based silane coupling agent of this invention effectively prevent the migration and diffusion of inorganic fillers in the rubber matrix during long-term storage or use. Therefore, this rubber composite material not only has excellent stability but also long-term durability, significantly extending the service life of the material. Attached Figure Description

[0023] Figure 1Optical photographs of the thioctic acid-containing silane coupling agent monomer LMTES and the polythioctic acid-based silane coupling agent p(LMTES) prepared in Example 1 of this invention.

[0024] Figure 2 The infrared spectrum of the polythiooctanoic acid silane coupling agent p(LMTES) prepared in Example 1 of this invention is shown.

[0025] Figure 3 The infrared spectrum of the polythiooctanoic acid silane coupling agent p(LATES) prepared in Example 2 of this invention is shown.

[0026] Figure 4 The UV-Vis absorption spectra of the thioctic acid-containing silane coupling agent polymer monomer LMTES and the polythioctic acid-based silane coupling agent p(LMTES) prepared in Example 1 of this invention are shown.

[0027] Figure 5 The vulcanization curves of the rubber composite materials obtained in Examples 1 and 2 of this invention are shown.

[0028] Figure 6 This is an optical photograph of the rubber composite material obtained in Example 1 of the present invention. Detailed Implementation

[0029] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.

[0030] Example 1

[0031] (1) The synthetic route of the thiooctanoic acid-containing silane coupling agent S-(3-(triethoxysilyl)propyl)5-(1,2-dithiocyclopentan-3-yl)thiovalerate (LMTES) is as follows:

[0032]

[0033] Specifically, the reaction mixture consisted of: lipoic acid (LA) (5.12 g, 24.8 mmol) and N,N′-carbonyldiimidazole (CDI) (4.83 g, 29.8 mmol) placed in a round-bottom flask, and 30 mL of tetrahydrofuran (THF) was added at room temperature. The reaction mixture was refluxed for 1 h, and the byproduct CO2 gas was expelled within 10-15 min. After reflux, the mixture was cooled to room temperature, and one equivalent of mercaptopropyltriethoxysilane (MPTES) was added, followed by heating for another 8 h. After the reaction was complete, the mixture was washed with a suitable amount of 25 wt% brine, extracted with dichloromethane (DCM), and the organic phase was dried with anhydrous sodium sulfate (Na2SO4) to remove the solvent, yielding the following product: Figure 1 The target product shown is LMTES.

[0034] (2) The synthetic route of the polysilane coupling agent p(LMTES) is as follows:

[0035]

[0036] Specifically, the process involves dissolving the above-mentioned LMTES (5 g, 11.7 mmol) in 20 mL of dry THF, then adding 5 μL of trifluoromethanesulfonic acid (TfOH), stirring the mixture for 2 h, and terminating the polymerization with 1-propanethiol. The solvent is evaporated, the resulting crude product is washed with ethanol (EtOH) and dried under vacuum at 40 °C to constant weight to obtain the target product, polythiooctanoic acid silane coupling agent p (LMTES), with a number average molecular weight of... polydispersion coefficient Its infrared spectrum is as follows Figure 2 As shown.

[0037] (3) Preparation of inorganic filler MOF: 5-(pyrimidinyl)isophthalic acid (4 mmol, 0.98 g) and Zn(NO3)2·6H2O (6 mmol, 1.78 g) were dissolved in 50 mL of DMF / H2O (v / v = 1:1). After stirring for 30 min, the solution was transferred to a hydrothermal reactor and reacted at 120 °C for 72 h. After the reaction was completed, the solution was cooled to room temperature at a rate of 5 °C / h to obtain MOF crystals.

[0038] (4) By weight, 100 parts of natural rubber, 4 parts of polysilane coupling agent p (LMTES), 40 parts of inorganic filler MOF, 2 parts of stearic acid, 3 parts of zinc oxide, 2 parts of antioxidant N-isopropyl-N-phenyl-p-phenylenediamine, 2.5 parts of sulfur, 1.4 parts of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of paraffin wax are mixed in an internal mixer for 8 minutes, and then sheeted out through a two-roll mill to obtain the rubber prepolymer. Figure 5 As shown in the vulcanization curve, the optimal vulcanization time, determined by a rotorless vulcanizer, was 10.8 min. The product was then obtained by hot pressing at 15 MPa and 150°C for 10.8 min using a flatbed hot press. Figure 6 The rubber composite material shown.

[0039] Example 2

[0040] The difference between this embodiment and Embodiment 1 is that the polysilane coupling agent in the rubber composite material is p(LATES).

[0041] (1) The synthetic route of LATES is as follows:

[0042]

[0043] Specifically, the preparation of the lipoic acid-containing silane coupling agent 5-(1,2-dithiocyclopentan-3-yl)-N-(3-(triethoxysilyl)propyl)pentanamide (LATES) was carried out as follows: Under nitrogen (N2) protection, aminopropyltriethoxysilane (APTES) (4.80 g, 21.7 mmol) was dissolved in 30 mL of dry dichloromethane (DCM). Then, lipoic acid (LA) (5.12 g, 24.8 mmol) and N,N-dicyclohexylcarbodiimide (DCC) (4.92 g, 23.8 mmol) were successively added to the mixture, and the mixture was stirred for 2.5 h. After the reaction was completed, the solvent was removed by filtration to obtain the crude product. Dry toluene was added to remove the solvent again, and this process was repeated three times to obtain the target product LATES.

[0044] (2) The synthetic route of the polythiooctanoic acid silane coupling agent p(LATES) is as follows:

[0045]

[0046] Specifically, the process involves dissolving the above-mentioned LATES (5 g, 12.2 mmol) in 20 mL of dry DCM, then adding 5 μL of trifluoromethanesulfonic acid (TfOH), stirring the mixture for 2 h, and terminating the polymerization with 1-propanethium. The solvent is evaporated, the resulting crude product is washed with ethanol (EtOH) and dried under vacuum at 40 °C to constant weight to obtain the polysilane coupling agent p(LATES), with a number average molecular weight of... polydispersion coefficient Its infrared spectrum is as follows Figure 3 As shown.

[0047] (3) Preparation of vulcanized rubber: By weight, 100 parts of natural rubber, 4 parts of polythiooctanoic acid silane coupling agent p (LATES), 40 parts of inorganic filler MOF prepared in Example 1, 2 parts of stearic acid, 3 parts of zinc oxide, 2 parts of antioxidant N-isopropyl-N-phenyl p-phenylenediamine, 2.5 parts of sulfur, 1.4 parts of accelerator N-cyclohexyl-2-benzothiazole sulfenamide and 1 part of paraffin wax were mixed in an internal mixer for 8 minutes, and then sheeted out by an open mill to obtain rubber prepolymer.

[0048] The remaining steps are the same as in Example 1, and a rubber composite material is obtained, the vulcanization curve of which is shown below. Figure 5 As shown.

[0049] Example 3

[0050] The difference between this embodiment and Example 1 is that the inorganic filler is silica. Specifically, by weight, 100 parts of styrene-butadiene rubber, 4 parts of polythiooctanoic acid silane coupling agent p (LMTES), 40 parts of inorganic filler silica, 2 parts of stearic acid, 3 parts of zinc oxide, 2 parts of antioxidant N-isopropyl-N-phenyl-p-phenylenediamine, 2.5 parts of sulfur, 1.4 parts of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of paraffin wax are mixed in an internal mixer for 8 minutes, and then sheeted out through a two-roll mill to obtain the rubber prepolymer.

[0051] The remaining steps are the same as in Example 1, and a rubber composite material is obtained.

[0052] Example 4

[0053] The difference between this embodiment and Example 1 is that the inorganic filler is aluminum hydroxide. Specifically, by weight, 100 parts of styrene-butadiene rubber, 4 parts of polythiooctanoic acid silane coupling agent p (LMTES), 40 parts of inorganic filler aluminum hydroxide, 2 parts of stearic acid, 3 parts of zinc oxide, 2 parts of antioxidant N-isopropyl-N-phenyl-p-phenylenediamine, 2.5 parts of sulfur, 1.4 parts of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of paraffin wax are mixed in an internal mixer for 8 minutes, and then sheeted out through an open mill to obtain the rubber prepolymer.

[0054] The remaining steps are the same as in Example 1, and a rubber composite material is obtained.

[0055] Example 5

[0056] The difference between this embodiment and Example 1 is that the rubber matrix is ​​styrene-butadiene rubber. Specifically, by weight, 100 parts of styrene-butadiene rubber, 4 parts of polythiooctanoic acid silane coupling agent p (LMTES), 40 parts of inorganic filler MOF, 2 parts of stearic acid, 3 parts of zinc oxide, 2 parts of antioxidant N-isopropyl-N-phenyl-p-phenylenediamine, 2.5 parts of sulfur, 1.4 parts of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of paraffin wax are mixed in an internal mixer for 8 minutes, and then sheeted out through a two-roll mill to obtain the rubber prepolymer.

[0057] The remaining steps are the same as in Example 1, and a rubber composite material is obtained.

[0058] Comparative Example 1

[0059] The difference between this comparative example and Example 1 is that the polysilane coupling agent p (LMTES) was not added. Specifically, by weight, 100 parts of natural rubber, 40 parts of inorganic filler MOF, 2 parts of stearic acid, 3 parts of zinc oxide, 2 parts of antioxidant N-isopropyl-N-phenyl-p-phenylenediamine, 2.5 parts of sulfur, 1.4 parts of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of paraffin wax were mixed in an internal mixer for 8 minutes, and then sheeted out through a two-roll mill to obtain the rubber prepolymer.

[0060] The remaining steps are the same as in Example 1, and a comparative rubber composite material is obtained.

[0061] Comparative Example 2

[0062] The difference between this comparative example and Example 1 is that the polythioctic acid-containing silane coupling agent LMTES is used instead of the polythioctic acid-based silane coupling agent p(LMTES). Specifically, by weight, 100 parts of natural rubber, 40 parts of inorganic filler MOF, 4 parts of LMTES, 2 parts of stearic acid, 3 parts of zinc oxide, 2 parts of antioxidant N-isopropyl-N-phenyl-p-phenylenediamine, 2.5 parts of sulfur, 1.4 parts of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of paraffin wax are mixed in an internal mixer for 8 minutes, and then sheeted out through an open mill to obtain the rubber prepolymer.

[0063] The remaining steps are the same as in Example 1, and a comparative rubber composite material is obtained.

[0064] Comparative Example 3

[0065] The difference between this comparative example and Example 2 is that the thioctic acid-containing silane coupling agent LATES is used instead of the polythioctic acid-based silane coupling agent p(LATES). Specifically, by weight, 100 parts of natural rubber, 40 parts of inorganic filler MOF, 4 parts of LATES, 2 parts of stearic acid, 3 parts of zinc oxide, 2 parts of antioxidant N-isopropyl-N-phenyl-p-phenylenediamine, 2.5 parts of sulfur, 1.4 parts of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of paraffin wax are mixed in an internal mixer for 8 minutes, and then sheeted out through an open mill to obtain the rubber prepolymer.

[0066] The remaining steps are the same as in Example 2, and a comparative rubber composite material is obtained.

[0067] Comparative Example 4

[0068] The difference between this comparative example and Example 3 is that the thioctic acid-containing silane coupling agent LMTES is used instead of the polythioctic acid-based silane coupling agent p(LMTES). Specifically, by weight, 100 parts of styrene-butadiene rubber, 4 parts of LMTES, 40 parts of inorganic filler silica, 2 parts of stearic acid, 3 parts of zinc oxide, 2 parts of antioxidant N-isopropyl-N-phenyl-p-phenylenediamine, 2.5 parts of sulfur, 1.4 parts of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of paraffin wax are mixed in an internal mixer for 8 minutes, and then sheeted out through an open mill to obtain the rubber prepolymer.

[0069] The remaining steps are the same as in Example 3, and a comparative rubber composite material is obtained.

[0070] Comparative Example 5

[0071] The difference between this comparative example and Example 4 is that the polythioctic acid-containing silane coupling agent LMTES is used instead of the polythioctic acid-based silane coupling agent p(LMTES). Specifically, by weight, 100 parts of styrene-butadiene rubber, 4 parts of LMTES, 40 parts of inorganic filler aluminum hydroxide, 2 parts of stearic acid, 3 parts of zinc oxide, 2 parts of antioxidant N-isopropyl-N-phenyl-p-phenylenediamine, 2.5 parts of sulfur, 1.4 parts of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 1 part of paraffin wax are mixed in an internal mixer for 8 minutes, and then sheeted out through an open mill to obtain the rubber prepolymer.

[0072] The remaining steps are the same as in Example 4, to obtain the comparative rubber composite material.

[0073] Test method:

[0074] The following tests were conducted on the performance of Embodiments 1 to 5 and Comparative Examples 1 to 6 of the present invention. The test items and methods are as follows:

[0075] Structural characterization of polythiooctanoic acid silane coupling agents: The chemical structure of polythiooctanoic acid silane coupling agents was characterized by Fourier transform infrared (FTIR) spectroscopy (Nicoleti S10, USA) using attenuated total reflectance (ATR) method, with a wavenumber range of 500-4000 cm⁻¹. -1 The number of scans was 32. The absorption spectra of thioctic acid-containing silane coupling agents and polythioctic acid-based silane coupling agents were characterized by a UV-Vis spectrometer (Shimadzu UV-2550, Japan), with a test wavelength range of 200-800 nm.

[0076] Determination of vulcanization curve: The vulcanization curve of the rubber composite material prepared above was tested using a BL-6190 rotorless vulcanizer (Baisheng Machinery Equipment Factory). According to GB / T 9869-2014 standard, the temperature was set to 150℃ and the time was set to 30min. The vulcanization curve of the compound was measured, and the vulcanization time T was determined. 90 .

[0077] Stress-strain performance test: According to the method specified in GB / T 528-2009, the 100% constant elongation stress, 300% constant elongation stress, tensile strength and elongation at break of the rubber composite material prepared as described above are determined.

[0078] Toughness characterization: The toughness of rubber is characterized by comparing the integral area of ​​the stress-strain curve.

[0079] Crosslinking density test: The crosslinking density of vulcanized rubber was determined using the equilibrium expansion method. 1 g of vulcanized rubber was immersed in 30 mL of toluene for 3 days, with the toluene replaced every 24 hours. After immersion, the solvent was quickly absorbed with filter paper, and the sample mass was recorded as m1. The sample was then dried to constant weight and recorded as m2. The crosslinking density V of the sample was determined. c Calculated according to the Flory-Rehner equation:

[0080]

[0081] In the formula, M c The molecular weight between cross-linking points is calculated using the following formula:

[0082]

[0083] In the formula, ρ p The density of NR is 0.912 g / cm³. 3 V s The molar volume of toluene is 106.3 cm³. 3 / mol), χ is the interaction parameter between NR and toluene, V r V represents the volume fraction of the swollen sample. r Calculated using the following formula:

[0084]

[0085] In the formula, m f ρ represents the mass of the filler material in the sample. s The density of toluene is 0.866 g / cm³. 3 )

[0086] All test results are shown in Tables 1 and 2.

[0087] Table 1 Test results of Examples 1 to 5

[0088]

[0089] Table 2 shows the test results of Comparative Examples 1 to 5.

[0090]

[0091] Experimental data analysis:

[0092] Figure 1 These are optical photographs of the thioctic acid-containing silane coupling agent LMTES and the polythioctic acid-based silane coupling agent p(LMTES) prepared in Example 1. Before polymerization, LMTES is a flowable yellow liquid, and after ring-opening polymerization, p(LMTES) is a yellow blocky solid. Figure 4The figure shows the UV-Vis absorption spectra of LMTES and p(LMTES). Due to the 1,2-dithiopentane structure, the LMTES monomer exhibits an absorption peak at 330 nm. After ring-opening polymerization of the dithiopentane, p(LMTES) contains only linear disulfide bonds, thus the absorption peak at 330 nm disappears. These results demonstrate that the thiooctanoic acid-containing silane coupling agent LMTES was successfully ring-opened to obtain the polythiooctanoic acid-based silane coupling agent p(LMTES).

[0093] The test data for Examples 1 to 5 and Comparative Examples 1 to 6 are shown in Tables 1 and 2 above. The test results show that Example 1 has a 100% constant elongation stress of 3.4 MPa, a 300% constant elongation stress of 11.2 MPa, a tensile strength of 31.8 MPa, and an elongation at break of 608%. Compared to Comparative Example 1 without the addition of polythiooctanoic acid silane coupling agent, its tensile strength, constant elongation stress, elongation at break, and toughness are significantly improved. The vulcanization time (T) of Example 1... 90 The vulcanization time of the first example was 10.8 min, while that of the comparative example 1 was 20.3 min. This indicates that the polythiooctanoic acid silane coupling agent can improve the dispersion compatibility of inorganic filler MOF in the rubber matrix, avoid the adsorption of rubber additives by inorganic fillers, shorten the vulcanization time, and significantly enhance the interaction between organic and inorganic components, thereby improving the mechanical properties of the rubber composite material.

[0094] Combining the experimental results of Examples 1 and 2, it is shown that changing the chemical structure of the silane coupling agent in the polythiooctanoic acid-based silane coupling agent does not affect the reinforcing effect of the inorganic filler MOF on the rubber composite material. This is because the terminal active groups of the silane coupling agent only condense with thioctic acid to achieve covalent coupling, without affecting the interfacial modification between the polythiooctanoic acid-based silane coupling agent and the inorganic filler. Combining Examples 1 and Examples 3 to 4, it can be seen that, in addition to the inorganic filler MOF, the polythiooctanoic acid-based silane coupling agent is also effective in reinforcing inorganic fillers such as silica and aluminum hydroxide in rubber. This is because the surfaces of these inorganic fillers contain active hydroxyl groups that can undergo condensation reactions with the polythiooctanoic acid-based silane coupling agent, thereby exerting the reinforcing effect of the inorganic filler in the rubber matrix. Combining the experimental results of Examples 1 and 5, it is confirmed that changing the rubber matrix has almost no impact on the interfacial regulation performance of the polythiooctanoic acid-based silane coupling agent for inorganic fillers in rubber. The above results indicate that polythiooctanoic acid-based silane coupling agents are highly efficient and universally applicable in improving the comprehensive mechanical properties of rubber composites with inorganic fillers containing active hydroxyl groups on their surfaces.

[0095] The effects of polythiooctanoic acid-based silane coupling agents and small-molecule silane coupling agents on the comprehensive mechanical properties of rubber composites were compared. The tensile strength, stress at a given elongation, and toughness of Examples 1, 3, and 4 were significantly improved compared to Comparative Examples 2, 4, and 5. The crosslinking density of the rubber composites was determined by the equilibrium swelling method; the crosslinking density of Examples 1, 3, and 4 was higher than that of Comparative Examples 2, 4, and 5. This is because, compared to small-molecule silane coupling agents, polythiooctanoic acid-based silane coupling agents can covalently couple inorganic fillers at multiple sites. Furthermore, they can construct a physical crosslinking network through interpenetration and entanglement with rubber molecular chains, resulting in a higher crosslinking density. Under external force, the breaking of dynamic disulfide bonds on the main chain of the polythiooctanoic acid-based silane coupling agent has an energy dissipation effect, thus enhancing the comprehensive mechanical properties.

[0096] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A polysulfoacitic silane coupling agent characterized by: The structural formula is wherein R is selected from , , and n1= 5-2000, n2 = 2-5.

2. A lipo-hydroxythioic acid silane coupling agent as claimed in claim 1, wherein: The structural formula is or , n = 5-2000.

3. Use of the polysulfoacitic silane coupling agent of claim 1 or 2 in the preparation of a rubber composite.

4. Use according to claim 3, wherein: The rubber composite is prepared by uniformly mixing the base rubber, the polysulfoacitic silane coupling agent, an inorganic filler, zinc oxide, stearic acid, a vulcanizing agent, an accelerator, an antioxidant, and a paraffin wax, and then vulcanizing and hot-pressing; the inorganic filler has active hydrogen sites on the surface and can undergo condensation reaction with the polysulfoacitic silane coupling agent.

5. The use according to claim 4, characterized in that: The base rubber is selected from natural rubber, styrene-butadiene rubber, cis-butadiene rubber, and chlorobutadiene rubber, and the inorganic filler is selected from white carbon black, metal organic frameworks, two-dimensional transition metal carbides, silicates, inorganic metal oxides, and hydroxides.

6. Use according to claim 5, wherein: The mass ratio of the base rubber, the polysulfoacitic silane coupling agent, the inorganic filler, zinc oxide, stearic acid, the vulcanizing agent, the accelerator, the antioxidant, and the paraffin wax is 60-100: 1-30: 10-80: 2-4: 1-3: 1-4: 1-4: 1-3: 1-3.

7. A rubber composite material characterized by: The raw materials thereof include the polysulfoacitic silane coupling agent of claim 1 or 2.

8. A rubber composite material as claimed in claim 7, characterised in that: The rubber composite is prepared by uniformly mixing the base rubber, the polysulfoacitic silane coupling agent, an inorganic filler, zinc oxide, stearic acid, a vulcanizing agent, an accelerator, an antioxidant, and a paraffin wax, and then vulcanizing and hot-pressing; the inorganic filler has active hydrogen sites on the surface and can undergo condensation reaction with the polysulfoacitic silane coupling agent.

9. A rubber composite material as claimed in claim 8, characterised in that: The base rubber is selected from natural rubber, styrene-butadiene rubber, cis-butadiene rubber, and chlorobutadiene rubber, and the inorganic filler is selected from white carbon black, metal organic frameworks, two-dimensional transition metal carbides, silicates, inorganic metal oxides, and hydroxides.

10. A rubber composite material as claimed in claim 9, characterised in that: The mass ratio of the base rubber, the polysulfoacitic silane coupling agent, the inorganic filler, zinc oxide, stearic acid, the vulcanizing agent, the accelerator, the antioxidant, and the paraffin wax is 60-100: 1-30: 10-80: 2-4: 1-3: 1-4: 1-4: 1-3: 1-3. The raw materials thereof include the polysulfoacitic silane coupling agent of claim 1 or 2. The rubber composite is prepared by uniformly mixing the base rubber, the polysulfoacitic silane coupling agent, an inorganic filler, zinc oxide, stearic acid, a vulcanizing agent, an accelerator, an antioxidant, and a paraffin wax, and then vulcanizing and hot-pressing; the inorganic filler has active hydrogen sites on the surface and can undergo condensation reaction with the polysulfoacitic silane coupling agent. The base rubber is selected from natural rubber, styrene-butadiene rubber, cis-butadiene rubber, and chlorobutadiene rubber, and the inorganic filler is selected from white carbon black, metal organic frameworks, two-dimensional transition metal carbides, silicates, inorganic metal oxides, and hydroxides. The mass ratio of the base rubber, the polysulfoacitic silane coupling agent, the inorganic filler, zinc oxide, stearic acid, the vulcanizing agent, the accelerator, the antioxidant, and the paraffin wax is 60-100: 1-30: 10-80: 2-4: 1-3: 1-4: 1-4: 1-3: 1-3.

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