A method for preparing a thio-carboxylate silane coupling agent

Abstract

The application discloses a preparation method of a thio-carboxylic acid ester silane coupling agent, and comprises the following steps: S1: deionized water and an organic solvent are matched into a water-organic mixed solvent; sodium sulfide is added and stirred until no solid particles are generated, then a phase transfer catalyst is added and octanoyl chloride is added dropwise, after dropwise addition is completed, secondary stirring is carried out, and a sodium thio-octanoate water-organic mixed catalytic liquid is prepared; S2: chloromethylphenethyltriethoxysilane and chloropropyltriethoxysilane are added into the catalytic liquid obtained in S1; then the pH value of the system is adjusted to weak alkalinity, the stirring speed is increased, and after temperature is increased, constant-temperature stirring reaction is carried out; S3: the reaction liquid is allowed to stand and phase separation is carried out, the organic phase is taken and washed to neutral; the organic phase after water washing is subjected to gradient reduced-pressure rectification, and finally, the product is obtained. The preparation method realizes high-efficiency cooperation of directional thio-substitution of chloropropyltriethoxysilane and more than 99% retention of benzyl chlorine groups of chloromethylphenethyltriethoxysilane, the stability and batch consistency of the reaction are good, and the product is high in purity and good in stability.

Description

Technical Field

[0001] This invention relates to the field of organic materials technology, and specifically to a method for preparing a thiocarboxylic acid ester silane coupling agent. Background Technology

[0002] 3-Octaylthio-1-propyltriethoxysilane (NXT silane), as a high-performance thiocarboxylic acid ester silane coupling agent, is widely used in the field of rubber composites due to its excellent coupling properties with rubber fillers. Its mainstream industrial synthesis process is the phase transfer catalytic aqueous / water-organic mixed phase method, which uses octayl chloride and sodium sulfide as raw materials to prepare sodium thiooctanoate, which then undergoes a nucleophilic substitution reaction with 3-chloropropyltriethoxysilane under the catalysis of a phase transfer catalyst. The product yield and purity are excellent. Chloromethylphenethyltriethoxysilane is a key coupling agent intermediate for high-end composite materials. The benzylic chlorine group in the molecule endows it with high interfacial bonding strength with inorganic fillers and engineering plastic substrates. The mainstream industrial preparation method is a two-step method of hydrosilylation-continuous alcoholysis. However, its benzylic chlorine group is highly sensitive to aqueous phase, high temperature, and acid-base environment, and is prone to side reactions such as hydrolysis and elimination, which places strict requirements on the reaction system. However, while using NXT silane alone can meet the low VOC requirement, it has shortcomings in terms of interfacial bonding strength and material mechanical property enhancement. While using chloromethylphenethyltriethoxysilane alone can improve interfacial bonding performance, it is difficult to meet the current industry's environmental requirements for low VOC. Neither of them can simultaneously meet the dual application requirements of low VOC emissions and enhanced interfacial performance when used alone, which has become a key issue restricting the upgrading and development of high-end rubber composite materials.

[0003] To achieve VOC reduction and performance enhancement, a chemical co-reaction synthesis technology for chloromethylphenylethyltriethoxysilane and NXT silane needs to be developed. However, current technologies only allow for the stepwise synthesis of the two silanes followed by physical mixing. This method requires two distillation purification processes, resulting in a long production process, high energy consumption, and high industrialization costs. Furthermore, the composite system exhibits poor compatibility and is prone to stratification during room temperature storage, leading to loss of homogeneity and affecting application performance. If chloromethylphenylethyltriethoxysilane is directly introduced into the phase transfer catalytic synthesis system of NXT silane for one-step co-reaction, current technologies fail to address the compatibility issues between the two systems. This can easily lead to the elimination of benzylic chlorine groups (benzylic chlorine retention rate ≤70%) and silane hydrolysis, causing damage to its structure and properties. This core technical challenge remains unresolved. Meanwhile, existing NXT silane phase transfer catalytic synthesis processes suffer from drawbacks such as limited catalyst types and coarse process control parameters. They lack precise control over key parameters like feedstock moisture content, material droplet acceleration rate, and temperature / pH accuracy, easily leading to uneven mass transfer in the reaction system, frequent side reactions, poor batch repeatability in industrial production, and large fluctuations in product purity and yield. In summary, current technologies struggle to achieve efficient composite preparation of two high-performance silanes. There is an urgent need to develop a one-step composite silane coupling agent preparation process that can precisely protect the benzylic chlorine group of chloromethylphenethyltriethoxysilane while meeting the requirements of NXT silane phase transfer catalytic synthesis, and also features catalyst diversification and refined process control, thereby overcoming the multiple shortcomings of existing technologies. Summary of the Invention

[0004] To address the issue that a single silane coupling agent cannot simultaneously achieve both VOC reduction and performance enhancement, this invention provides a method for preparing a thiocarboxylic acid ester silane coupling agent.

[0005] The technical solution adopted in this invention is: a method for preparing a thiocarboxylic acid ester silane coupling agent, comprising the following steps: S1: Mix deionized water with an organic solvent to prepare a water-organic mixed solvent; add sodium sulfide to the water-organic mixed solvent and stir until there are no solid particles, then add phase transfer catalyst and add octanoyl chloride dropwise. After the addition is complete, stir twice to obtain sodium thiooctanoate water-organic mixed catalyst solution. S2: Add chloromethylphenylethyltriethoxysilane and chloropropyltriethoxysilane to the sodium thiooctanoate aqueous-organic mixed catalyst solution obtained in S1; then adjust the pH of the system to weakly alkaline, increase the stirring rate, and stir the reaction at a constant temperature after heating. S3: After the reaction in step S2 is completed, the reaction solution is allowed to stand and the organic phase is separated. The organic phase is washed until neutral and then allowed to stand. The organic phase after washing is subjected to gradient vacuum distillation to obtain chloromethylphenethyltriethoxysilane-NTX silane composite thiocarboxylic acid ester silane coupling agent.

[0006] This application employs a phase transfer catalyst to enhance water-organic phase mass transfer, thereby improving reaction rate and selectivity; in-situ synthesis avoids intermediate decomposition and enhances process stability; a weakly alkaline system inhibits silane hydrolysis and reduces byproducts; the resulting composite coupling agent possesses both thiocarboxylic acid ester and benzylic chloride dual reaction sites, achieving synergistic enhancement of interfacial bonding, crosslinking efficiency, and filler dispersion, and features low VOC, high purity, and excellent overall performance, making it more suitable for industrial production.

[0007] Preferably, in S1, the volume ratio of deionized water to organic solvent is 1:1 to 2:1, the mass-volume ratio of sodium sulfide to water-organic mixed solvent is 0.010 to 0.030 g / mL, and the molar ratio of octanoyl chloride to sodium sulfide is 1:1.1 to 1.3.

[0008] Preferably, the organic solvent in S1 is toluene, xylene, and / or C1-C4 fatty alcohols, wherein the fatty alcohols are preferably ethanol or isopropanol; the phase transfer catalyst is a quaternary ammonium salt catalyst, a quaternary phosphorus salt catalyst, or a nonionic polyether catalyst.

[0009] Preferably, the quaternary ammonium salt catalyst is tetrapropylammonium bromide, tetrabutylammonium bromide, benzyltriethylammonium chloride or methyltrioctylammonium chloride, and its mass is 0.3% to 2% of octanoyl chloride.

[0010] Preferably, the quaternary phosphonium salt catalyst is tetrabutylphosphonium bromide or benzyltributylphosphonium bromide, and its mass is 0.4% to 1.8% of octanoyl chloride.

[0011] Preferably, the nonionic polyether catalyst is PEG400, PEG600 or polyethylene glycol dialkyl ether, and its mass is 0.8% to 3% of octanoyl chloride.

[0012] Preferably, the secondary stirring rate in S1 is 200~300 r / min, the temperature during secondary stirring is 20~30℃, the secondary stirring time is 1-2 hours, and the dropping time of octanoyl chloride is 0.5~2h.

[0013] Preferably, the molar ratio of sodium thiooctanoate to chloropropyltriethoxysilane in the sodium thiooctanoate water-organic mixed catalyst solution is 1:1.05 to 1.2, and the mass ratio of chloromethylphenylethyltriethoxysilane to chloropropyltriethoxysilane in S2 is 1:9 to 3:7. The pH of the system is adjusted with sodium carbonate or sodium bicarbonate solution.

[0014] Preferably, the stirring rate in S2 is increased to 300~400 r / min, the pH is adjusted to 7-8, and the temperature is slowly increased to 40~60℃ at a rate of 5~8℃ / h, and the reaction is carried out under constant temperature and stirring for 1~2 hours.

[0015] Preferably, the reaction solution in S3 is allowed to stand for 30-40 minutes, and the organic phase is washed 3-4 times with water at a stirring rate of 150-200 r / min each time. After washing, it is allowed to stand for 20 minutes until the system is neutral. The gradient vacuum distillation conditions are as follows: first, a primary removal of at least a small amount of solvent and low-boiling substances is carried out under a vacuum of -0.08 to -0.09 MPa and a temperature of 70-80°C until no distillate is obtained; then, a secondary removal is carried out under a vacuum of -0.095 to -0.1 MPa and a temperature of 85-100°C until no trace impurities are obtained.

[0016] The beneficial effects of this invention are: This invention provides a one-step phase transfer catalysis method for preparing composite silane coupling agents, achieving highly efficient synergy between the directional thiolation of chloropropyltriethoxysilane and the retention of over 99% of the benzylic chlorine group in chloromethylphenethyltriethoxysilane. Simultaneously, a refined process control system is established to improve the stability and batch consistency of the core reaction, resulting in high purity and good stability. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with preferred embodiments.

[0018] Example 1: S1: In a 50L stainless steel reactor, add 8L of deionized water and 8L of toluene (water:organic solvent volume ratio 1:1), then add 2.2mol of sodium sulfide. The mass-volume ratio of sodium sulfide to the water-toluene mixed solvent is 0.0107 g / mL. Stir until the sodium sulfide is completely dissolved. Then, control the temperature at 25℃±0.5℃ and add 2.0mol of octanoyl chloride dropwise over 1.63h. Simultaneously, add 1.15% (by mass) of tetrabutylammonium bromide of octanoyl chloride. After the addition is complete, stir at a constant temperature (25℃±0.5℃) at 250r / min for 1.5h to obtain a sodium thiooctanoate water-organic mixed catalyst solution. S2: Then add 1.0 kg of chloromethylphenylethyltriethoxysilane and 9.0 kg of chloropropyltriethoxysilane (mass ratio 1:9) to the reactor, with a molar ratio of sodium thiooctanoate to chloropropyltriethoxysilane of 1:1.1. Increase the stirring speed to 350 r / min, adjust the pH of the system to 7.5±0.2 with sodium carbonate, and heat to 50℃±0.5℃ at a heating rate of 6℃ / h and react at this temperature for 4h. S3: After the reaction, allow the mixture to stand for 35 minutes and discard the aqueous phase. Wash the organic phase three times with water at a stirring rate of 180 r / min, allowing it to stand for 20 minutes after each wash until the system is neutral. Perform gradient vacuum distillation on the washed organic phase: first, remove low-boiling substances and solvent under vacuum of -0.085 MPa and 75℃; then, remove trace impurities a second time under vacuum of -0.098 MPa and 90℃ to obtain the composite silane coupling agent. The results showed a benzylic chloride retention rate of 99.6%, an NXT silane yield of 96.2%, and a composite product purity of 99.3%.

[0019] Example 2: S1: In a 1000L (1m³) stainless steel reactor, add 240L of deionized water and 120L of xylene (water:organic solvent volume ratio 2:1), then add 46mol of sodium sulfide. The mass-volume ratio of sodium sulfide to the total volume of the water-organic mixed solvent is 0.0199 g / mL. Stir until the sodium sulfide is completely dissolved. Then, control the temperature at 28℃±0.5℃ and add 40mol of octanoyl chloride dropwise over 0.5h. At the same time, add 1.0% (by mass) of tetrabutylphosphonium bromide of octanoyl chloride. After the addition is complete, stir at 280r / min at a constant temperature (28℃±0.5℃) for 1h to obtain sodium thiooctanoate catalyst solution. S2: Then add 30 kg of chloromethylphenylethyltriethoxysilane and 180 kg of chloropropyltriethoxysilane (mass ratio 1:6) to the reactor, with a molar ratio of sodium thiooctanoate to chloropropyltriethoxysilane of 1:1.1. Increase the stirring speed to 380 r / min, adjust the pH of the system to 7.2±0.2 with sodium bicarbonate, and heat to 55℃±0.5℃ at a heating rate of 5℃ / h and react at this temperature for 3.5h. S3: After the reaction, allow the mixture to stand for 30 minutes and discard the aqueous phase. Wash the organic phase four times with water at a stirring rate of 190 r / min, allowing it to stand for 20 minutes after each wash until the system is neutral. Perform gradient vacuum distillation on the washed organic phase: first, remove low-boiling substances and solvent under vacuum of -0.088 MPa and 78℃; then, remove trace impurities a second time under vacuum of -0.099 MPa and 95℃ to obtain the composite silane coupling agent. The results showed a benzylic chloride retention rate of 99.7%, an NXT silane yield of 96.5%, and a composite product purity of 99.4%.

[0020] Example 3: S1: In a 3000L (3m³) stainless steel reactor, add 630L of deionized water and 420L of anhydrous ethanol (water:organic solvent volume ratio 1.5:1), then add 144mol of sodium sulfide. The mass-volume ratio of sodium sulfide to the total volume of the water-organic mixed solvent is 0.0283 g / mL. Stir until the sodium sulfide is completely dissolved. Then, control the temperature at 22℃±0.5℃ and add 120mol of octanoyl chloride dropwise over a period of 0.54h. At the same time, add 2.0% (by mass) of PEG-400 of octanoyl chloride. After the addition is complete, stir at a constant temperature (22℃±0.5℃) at 220r / min for 2h to obtain sodium thiooctanoate catalyst solution. S2: Subsequently, 180 kg of chloromethylphenylethyltriethoxysilane and 540 kg of chloropropyltriethoxysilane (mass ratio 1:3) were added to the reactor, with a molar ratio of sodium thiooctanoate to chloropropyltriethoxysilane of 1:1.15. The stirring speed was increased to 320 r / min, and the pH of the system was adjusted to 7.8±0.2 with a sodium carbonate-sodium bicarbonate mixed solution. The temperature was increased to 45℃±0.5℃ at a heating rate of 7℃ / h and kept at the temperature for 4.5h. S3: After the reaction, allow the mixture to stand for 40 minutes and discard the aqueous phase. Wash the organic phase three times with water at a stirring rate of 170 r / min, allowing it to stand for 20 minutes after each wash until the system is neutral. Perform gradient vacuum distillation on the washed organic phase: first, remove low-boiling substances and solvent under vacuum of -0.089 MPa and 79℃; then, remove trace impurities a second time under vacuum of -0.099 MPa and 98℃ to obtain the composite silane coupling agent. The results showed a benzylic chloride retention rate of 99.8%, an NXT silane yield of 95.8%, and a composite product purity of 99.5%. Example 4

[0021] S1: In a 500L stainless steel reactor, add 150L of deionized water and 75L of toluene (water:organic solvent volume ratio 2:1), then add 33mol of sodium sulfide. The mass-volume ratio of sodium sulfide to the total volume of the water-organic mixed solvent is 0.030g / mL. Stir until the sodium sulfide is completely dissolved. Then, control the temperature at 30℃±0.5℃ and add 30mol of octanoyl chloride dropwise over 0.6h. At the same time, add 2.0% (by mass) of benzyltriethylammonium chloride. After the addition is complete, stir at 300r / min at a constant temperature (30℃±0.5℃) for 2h to obtain sodium thiooctanoate catalyst solution. S2: Then, 27 kg of chloromethylphenylethyltriethoxysilane and 63 kg of chloropropyltriethoxysilane (mass ratio 3:7) were added to the reactor, and the molar ratio of sodium thiooctanoate to chloropropyltriethoxysilane was 1:1.2. The stirring speed was increased to 400 r / min, the pH of the system was adjusted to 8.0±0.2 with sodium carbonate, the temperature was increased to 60℃±0.5℃ at a heating rate of 8℃ / h, and the reaction was stirred at a constant temperature for 5h.

[0022] S3: After the reaction is complete, let stand for 40 min and discard the aqueous phase; wash the organic phase with water 4 times with a stirring rate of 200 r / min, letting it stand for 20 min after each wash, until the system is neutral. Perform gradient vacuum distillation on the washed organic phase: first remove low-boiling substances and solvent under vacuum of -0.09 MPa and temperature of 80℃, and then remove trace impurities a second time under vacuum of -0.1 MPa and temperature of 100℃ to obtain the composite silane coupling agent.

[0023] Test results: Benzyl chloride retention rate 99.5%, NXT silane yield 95.9%, and composite product purity 99.2%. Example 5

[0024] S1: In a 300L stainless steel reactor, add 60L of deionized water and 60L of anhydrous ethanol (water:organic solvent volume ratio 1:1), then add 13.2mol of sodium sulfide. The mass-volume ratio of sodium sulfide to the total volume of the water-organic mixed solvent is 0.0105g / mL. Stir until the sodium sulfide is completely dissolved. Then, control the temperature at 20℃±0.5℃ and add 12mol of octanoyl chloride dropwise over 1.95h. At the same time, add 0.3% (by mass) of methyltrioctylammonium chloride. After the addition is complete, stir at 200r / min at a constant temperature (20℃±0.5℃) for 1h to obtain sodium thiooctanoate catalyst solution. S2: Then add 6 kg of chloromethylphenylethyltriethoxysilane and 54 kg of chloropropyltriethoxysilane (mass ratio 1:9) to the reactor, with a molar ratio of sodium thiooctanoate to chloropropyltriethoxysilane of 1:1.05; increase the stirring speed to 300 r / min, adjust the pH of the system to 7.0±0.2 with sodium bicarbonate, and heat to 40℃±0.5℃ at a heating rate of 5℃ / h and stir at a constant temperature for 3h.

[0025] S3: After the reaction is complete, let stand for 30 min and discard the aqueous phase; wash the organic phase three times with water at a stirring rate of 150 r / min, letting it stand for 20 min after each wash, until the system is neutral. Perform gradient vacuum distillation on the washed organic phase: first remove low-boiling substances and solvent under vacuum of -0.08 MPa and 70℃, then remove trace impurities a second time under vacuum of -0.095 MPa and 85℃ to obtain the composite silane coupling agent.

[0026] Test results: Benzyl chloride retention rate 99.4%, NXT silane yield 96.4%, and composite product purity 99.4%. Example 6

[0027] S1: In a 2000L (2m³) stainless steel reactor, add 320L of deionized water and 160L of xylene (water:organic solvent volume ratio 2:1), then add 70.4mol of sodium sulfide. The mass-volume ratio of sodium sulfide to the total volume of the water-organic mixed solvent is 0.029g / mL. Stir until the sodium sulfide is completely dissolved. Then, control the temperature at 29℃±0.5℃ and add 64mol of octanoyl chloride dropwise over a period of 0.74h. At the same time, add 1.8% (by mass) of benzyltributylphosphonium bromide. After the addition is complete, adjust the stirring speed to a constant temperature (29℃±0.5℃) at 290r / min and stir for 1.9h to obtain sodium thiooctanoate catalyst solution. S2: Subsequently, 72 kg of chloromethylphenylethyltriethoxysilane and 168 kg of chloropropyltriethoxysilane (mass ratio 3:7) were added to the reactor, with a molar ratio of sodium thiooctanoate to chloropropyltriethoxysilane of 1:1.2; the stirring speed was increased to 390 r / min, the pH of the system was adjusted to 7.9±0.2 with a sodium carbonate-sodium bicarbonate mixed solution, the temperature was increased to 58℃±0.5℃ at a heating rate of 7.5℃ / h, and the reaction was stirred at a constant temperature for 4.8 h.

[0028] S3: After the reaction is complete, let stand for 39 min and discard the aqueous phase; wash the organic phase with water 4 times with a stirring rate of 190 r / min, letting it stand for 20 min after each wash until the system is neutral. Perform gradient vacuum distillation on the washed organic phase: first remove low-boiling substances and solvent under vacuum of -0.089 MPa and temperature of 79℃, and then remove trace impurities a second time under vacuum of -0.099 MPa and temperature of 98℃ to obtain the composite silane coupling agent.

[0029] Test results: Benzyl chloride retention rate 99.7%, NXT silane yield 95.8%, and composite product purity 99.1%. Example 7

[0030] S1: In a 400L stainless steel reactor, add 80L of deionized water and 80L of isopropanol (water:organic solvent volume ratio 1:1), then add 17.6mol of sodium sulfide. The mass-volume ratio of sodium sulfide to the total volume of the water-organic mixed solvent is 0.011g / mL. Stir until the sodium sulfide is completely dissolved. Then, control the temperature at 21℃±0.5℃ and add 16mol of octanoyl chloride dropwise over 2 hours. Simultaneously, add 0.4% (by mass) of tetrabutylphosphonium bromide of octanoyl chloride. After the addition is complete, stir at a constant temperature (21℃±0.5℃) at 210r / min for 1.1 hours to obtain sodium thiooctanoate catalyst solution.

[0031] S2: Subsequently, 8 kg of chloromethylphenylethyltriethoxysilane and 72 kg of chloropropyltriethoxysilane (mass ratio 1:9) were added to the reactor, with a molar ratio of sodium thiooctanoate to chloropropyltriethoxysilane of 1:1.05; the stirring speed was increased to 310 r / min, the pH of the system was adjusted to 7.1±0.2 with sodium bicarbonate, and the temperature was increased to 42℃±0.5℃ at a heating rate of 5.5℃ / h and stirred at a constant temperature for 3.2 h.

[0032] S3: After the reaction is complete, let stand for 31 min and discard the aqueous phase; wash the organic phase three times with water at a stirring rate of 160 r / min, letting it stand for 20 min after each wash until the system is neutral. Perform gradient vacuum distillation on the washed organic phase: first remove low-boiling substances and solvent under vacuum of -0.082 MPa and 72 °C, then remove trace impurities a second time under vacuum of -0.096 MPa and 87 °C to obtain the composite silane coupling agent.

[0033] Test results: Benzyl chloride retention rate 99.4%, NXT silane yield 96.5%, and composite product purity 99.5%. Example 8

[0034] S1: In a 2500L (2.5m³) stainless steel reactor, add 700L of deionized water and 350L of isopropanol (water:organic solvent volume ratio 2:1), then add 154mol of sodium sulfide. The mass-volume ratio of sodium sulfide to the total volume of the water-organic mixed solvent is 0.029g / mL. Stir until the sodium sulfide is completely dissolved. Then, control the temperature at 30℃±0.5℃ and add 140mol of octanoyl chloride dropwise over a period of 1.52h. At the same time, add 3.0% (by mass) of PEG600 of octanoyl chloride. After the addition is complete, stir at 300r / min at a constant temperature (30℃±0.5℃) for 2h to obtain sodium thiooctanoate catalyst solution.

[0035] S2: Subsequently, 135 kg of chloromethylphenylethyltriethoxysilane and 315 kg of chloropropyltriethoxysilane (mass ratio 3:7) were added to the reactor, with a molar ratio of sodium thiooctanoate to chloropropyltriethoxysilane of 1:1.2; the stirring speed was increased to 400 r / min, the pH of the system was adjusted to 8.0±0.2 with sodium carbonate, the temperature was increased to 60℃±0.5℃ at a heating rate of 8℃ / h and stirred at a constant temperature for 5h.

[0036] S3: After the reaction is complete, let stand for 40 min and discard the aqueous phase; wash the organic phase with water 4 times with a stirring rate of 200 r / min, letting it stand for 20 min after each wash, until the system is neutral. Perform gradient vacuum distillation on the washed organic phase: first remove low-boiling substances and solvent under vacuum of -0.09 MPa and temperature of 80℃, and then remove trace impurities a second time under vacuum of -0.1 MPa and temperature of 100℃ to obtain the composite silane coupling agent.

[0037] Test results: Benzyl chloride retention rate 99.7%, NXT silane yield 95.7%, and composite product purity 99.0%. Example 9

[0038] S1: Add 500L of deionized water and 500L of anhydrous ethanol to a 2000L (2m³) stainless steel reactor (water:organic solvent volume ratio 1:1), then add 55mol of sodium sulfide. The mass-volume ratio of sodium sulfide to the total volume of the water-organic mixed solvent is 0.0105g / mL. Stir until the sodium sulfide is completely dissolved. Then, control the temperature at 20℃±0.5℃ and add 50mol of octanoyl chloride dropwise over a period of 1.63h. At the same time, add 0.8% by mass of polyethylene glycol dialkyl ether of octanoyl chloride. After the addition is complete, stir at a constant temperature (20℃±0.5℃) at 200r / min for 1h to obtain sodium thiooctanoate catalyst solution.

[0039] S2: Then add 50 kg of chloromethylphenylethyltriethoxysilane and 450 kg of chloropropyltriethoxysilane (mass ratio 1:9) to the reactor, with a molar ratio of sodium thiooctanoate to chloropropyltriethoxysilane of 1:1.05; increase the stirring speed to 300 r / min, adjust the pH of the system to 7.0±0.2 with sodium bicarbonate, and heat to 40℃±0.5℃ at a heating rate of 5℃ / h and stir at a constant temperature for 3h.

[0040] S3: After the reaction is complete, let stand for 30 min and discard the aqueous phase; wash the organic phase three times with water at a stirring rate of 150 r / min, letting it stand for 20 min after each wash, until the system is neutral. Perform gradient vacuum distillation on the washed organic phase: first remove low-boiling substances and solvent under vacuum of -0.08 MPa and 70℃, then remove trace impurities a second time under vacuum of -0.095 MPa and 85℃ to obtain the composite silane coupling agent.

[0041] Test results: Benzyl chloride retention rate 99.5%, NXT silane yield 96.6%, and composite product purity 99.6%.

[0042] Comparative Example 1 The silane used is NXT silane from Momentive Performance Materials, Inc.; the chloromethylphenylethyltriethoxysilane used is ChangFu® CBE33 from Hubei Changfu Chemical Co., Ltd. The two silanes were mixed at a mass ratio of 1:9 (consistent with Example 1) and stirred at room temperature for 30 minutes to obtain a physically mixed composite silane.

[0043] Test and application results: The initial benign chloride retention rate of the composite silane obtained in Comparative Example 1 was 99.5%, and the NXT silane purity was 99.4%. After 7 days of sealed storage at room temperature, obvious oil-water separation occurred. After 15 days of storage, the benign chloride retention rate decreased to 92.3%, and the NXT silane purity decreased to 91.5%. Under the same conditions, when the composite silane obtained in Comparative Example 1 was applied to rubber filler coupling under the same conditions as in Example 1, the filler dispersion uniformity was poor, the rubber-filler interfacial bonding strength decreased by 38% compared to Example 1, and the wear resistance of the rubber compound decreased by 29%.

[0044] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also within the protection scope of the present invention.

Claims

1. A method for preparing a thiocarboxylic acid ester silane coupling agent, characterized in that, Includes the following steps: S1: Mix deionized water with an organic solvent to prepare a water-organic mixed solvent; add sodium sulfide to the water-organic mixed solvent and stir until there are no solid particles, then add phase transfer catalyst and add octanoyl chloride dropwise. After the addition is complete, stir twice to obtain sodium thiooctanoate water-organic mixed catalyst solution. S2: Add chloromethylphenylethyltriethoxysilane and chloropropyltriethoxysilane to the sodium thiooctanoate aqueous-organic mixed catalyst solution obtained in S1; then adjust the pH of the system to weakly alkaline, increase the stirring rate, and stir the reaction at a constant temperature after heating. S3: After the reaction in step S2 is completed, the reaction solution is allowed to stand and the organic phase is separated. The organic phase is washed until neutral. The organic phase after water washing is subjected to gradient vacuum distillation to obtain chloromethylphenethyltriethoxysilane-NTX silane composite thiocarboxylic acid ester silane coupling agent.

2. The preparation method according to claim 1, characterized in that, In S1, the volume ratio of deionized water to organic solvent is 1:1 to 2:1, the mass-volume ratio of sodium sulfide to water-organic mixed solvent is 0.010 to 0.030 g / mL, and the molar ratio of octanoyl chloride to sodium sulfide is 1:1.1 to 1.

2.

3. The preparation method according to claim 1, characterized in that, The organic solvent in S1 is toluene, xylene, and / or C1-C4 fatty alcohols; the phase transfer catalyst is a quaternary ammonium salt catalyst, a quaternary phosphorus salt catalyst, or a nonionic polyether catalyst.

4. The preparation method according to claim 3, characterized in that, The quaternary ammonium salt catalyst is tetrapropylammonium bromide, tetrabutylammonium bromide, benzyltriethylammonium chloride or methyltrioctylammonium chloride, and its mass is 0.3% to 2% of octanoyl chloride.

5. The preparation method according to claim 3, characterized in that, The quaternary phosphonium salt catalyst is tetrabutylphosphonium bromide or benzyltributylphosphonium bromide, and its mass is 0.4% to 1.8% of octanoyl chloride.

6. The preparation method according to claim 3, characterized in that, The nonionic polyether catalyst is PEG400, PEG600 or polyethylene glycol dialkyl ether, and its mass is 0.8% to 3% of octanoyl chloride.

7. The preparation method according to claim 1, characterized in that, The secondary stirring rate in S1 is 200~300 r / min, the temperature during secondary stirring is 20~30℃, the secondary stirring time is 1-2 hours, and the dropping time of octanoyl chloride is 0.5~2h.

8. The preparation method according to claim 1, characterized in that, The molar ratio of sodium thiooctanoate to chloropropyltriethoxysilane in the sodium thiooctanoate aqueous-organic mixed catalyst solution is 1:1.05 to 1.2, and the mass ratio of chloromethylphenylethyltriethoxysilane to chloropropyltriethoxysilane in S2 is 1:9 to 3:

7. The pH of the system is adjusted with sodium carbonate and / or sodium bicarbonate solution.

9. The preparation method according to claim 1, characterized in that, Increase the stirring rate in S2 to 300-400 r / min, adjust the pH to 7-8, and slowly increase the temperature to 40-60℃ at a rate of 5-8℃ / h, then stir the reaction at a constant temperature for 3-5 hours.

10. The preparation method according to claim 1, characterized in that, The reaction solution in S3 was allowed to stand for 30-40 minutes. The organic phase was washed 3-4 times, with a stirring rate of 150-200 r / min each time. After washing, it was allowed to stand for 20 minutes until the system was neutral. The gradient vacuum distillation conditions were as follows: first, a first removal was carried out under a vacuum of -0.08 to -0.09 MPa and a temperature of 70-80℃, and then a second removal was carried out under a vacuum of -0.095 to -0.1 MPa and a temperature of 85-100℃.