A mercaptopropyl triethoxysilane and a method for its preparation

Abstract

This invention belongs to the field of organosilicon fine chemistry and provides a method for preparing mercaptopropyltriethoxysilane. The method involves reacting allyltriethoxysilane with thioacetic acid under light to obtain 3-(acetylthio)propyltriethoxysilane, followed by controlled hydrolysis and condensation to form a core-shell intermediate with a Si-O-Si shell. This intermediate is then reacted in a methanol system and subjected to devolatilization and distillation to obtain the target product. This method balances the requirements of high solids content, low viscosity, and continuous operation. It can suppress hydrolysis, condensation, agglomeration, gelation, and side reactions, which is beneficial for improving the content, storage stability, and coupling activity of mercaptopropyltriethoxysilane, while reducing disulfide byproducts and water content. It solves the problems of narrow processing window, insufficient scale-up stability, and difficulty in uniform quality control in existing processes, and has good industrial application value.

Description

Technical Field

[0001] This invention relates to the field of organosilicon fine chemistry and preparation of mercapto-containing organosilicon, specifically to a mercaptopropyltriethoxysilane and its preparation method. Background Technology

[0002] Mercaptopropyltriethoxysilanes, as organosilicon compounds possessing both thiol and triethoxysilane groups, have high application value in metal surface treatment, rubber systems, resin modification, textile finishing, and composite material construction. In practical applications, these products must maintain the reactivity of the thiol groups while preserving the stability of the organosilicon structure during storage, transportation, mixing, and subsequent applications. Therefore, their preparation technology not only affects the availability of the target product but also the flowability of intermediate processes, adaptability to continuous operation, sensitivity control to water and oxygen, state maintenance during packaging and storage, and consistency in downstream applications. For highly reactive sulfur-containing organosilicon systems, only by simultaneously considering intermediate state control, process window stability, and final product composition stability can the requirements for consistent quality and scalable processes in large-scale manufacturing and applications be better met. This is especially true when the product also needs to consider subsequent coupling activity and low impurity control; a stable connection between the pre-processing, intermediate state adjustment, and final purification stages is essential.

[0003] Based on existing publicly available methods, traditional routes typically use sodium hydrosulfide and 3-chloropropyltriethoxysilane as the main raw materials, reacting them in an aqueous phase or buffer system with a phase transfer catalyst. The resulting product is then separated, dried, and distilled under reduced pressure to obtain mercaptopropyltriethoxysilane. For example, Chinese patent CN103408582A discloses a method for preparing 3-mercaptopropyltriethoxysilane using sodium hydrosulfide and 3-chloropropyltriethoxysilane as raw materials under aqueous phase and phase transfer catalytic conditions; and Chinese patent CN104926857A discloses a synthesis method that introduces potassium iodide and tetrabutylammonium bromide into a buffer solution to promote conversion. However, in highly reactive sulfur-containing organosilicon systems, such technologies are still easily affected by aqueous environments, temperature-induced volatilization, interphase transfer, and multi-step separation processes, which can lead to problems such as hydrolysis and condensation, accumulation of side reactions, fluctuations in intermediate states, and limited end-refining windows. Especially when it is necessary to obtain products with high solid content, low viscosity, and high purity, it is often difficult to simultaneously coordinate intermediate protection, retention of active groups, and scalability of post-processing. Summary of the Invention

[0004] The purpose of this invention is to provide a mercaptopropyltriethoxysilane and its preparation method, which solves the problem of simultaneously achieving high solids content, low viscosity, continuous operation, and resistance to hydrolysis-condensation, anti-agglomeration and gelation, as well as storage stability in the preparation of highly reactive organosilicon intermediates and products.

[0005] This invention continuously couples photo-induced reaction, controlled hydrolysis condensation to form a Si-O-Si shell, reaction in a methanol system, and stepwise devolatilization purification, so that the formation of 3-(acetylthio)propyltriethoxysilane, the stabilization of the core-shell intermediate, the release of thiol groups, and the purification of the final product are coordinated with each other, so as to balance anti-condensation stability and high effective thiol group retention without sacrificing fluidity and scalability.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing mercaptopropyltriethoxysilane includes the following steps: S1. Allyltriethoxysilane and thioacetic acid are mixed at a molar ratio of 1:(0.98-1.05), and 0.05-0.80 wt% of 2,2-dimethoxy-2-phenylacetophenone relative to the mass of allyltriethoxysilane is added. The mixture is subjected to photo-reaction at 20-40℃ under nitrogen protection, with a light wavelength of 350-380 nm and an irradiation intensity of 50-300 W / m2 for 0.2-2.0 h, and the volume fraction of oxygen in the reaction system is not higher than 0.10 vol%, to obtain 3-(acetylthio)propyltriethoxysilane; S2. Take 100 parts by mass of 3-(acetylthio)propyltriethoxysilane obtained in step S1, and add 10-50 parts by mass of methanol, 0.05-0.50 parts by mass of acetic acid and deionized water in sequence, wherein the amount of deionized water is such that the molar ratio of deionized water to 3-(acetylthio)propyltriethoxysilane is (0.10-0.40):1. Stir at 500-1500 r / min under nitrogen protection, control the pH of the system to be 4.5-6.0, and react at 20-35℃ for 0.5-2.0 h to obtain a core-shell intermediate with a Si-O-Si shell. S3. Based on 100 parts by weight of the net weight of the core-shell intermediate obtained in step S2, add or supplement 20-100 parts by weight of methanol to the core-shell intermediate or its methanol dispersion, and add a 3.0 mol / L sodium methoxide methanol solution, controlling the molar ratio of sodium methoxide to acetyl thio groups in the core-shell intermediate to be (0.05-0.30):1, and react at 0-25°C for 0.2-1.5 h under nitrogen protection; then add 0.5-5.0 parts by weight of acetic acid based on 100 parts by weight of the core-shell intermediate, and adjust the pH to 6.0-7.0; S4. The neutralized reaction solution obtained in step S3 is first subjected to 30-60℃ and 0.005-0.040MPa absolute pressure to remove methanol, acetic acid and other low-boiling substances, and then subjected to vacuum distillation at 80-105℃ and 0.0005-0.0050MPa absolute pressure to obtain mercaptopropyltriethoxysilane.

[0007] Furthermore, step S1 includes: A1. Prepare a mixture of 100 parts by weight of allyltriethoxysilane, thioacetic acid in the molar ratio specified in step S1, and 0.05-0.80 parts by weight of 2,2-dimethoxy-2-phenylacetophenone. A2. Under nitrogen protection, react for 0.2-2.0 h at 20-40℃, with a light wavelength of 350-380 nm and an irradiation intensity of 50-300 W / m2. A3. After the reaction time described in step A2 is reached, the light exposure is terminated; A4. Remove low-boiling substances at 30-45℃ and 0.020-0.040MPa to obtain 3-(acetylthio)propyltriethoxysilane with a content of not less than 97.0wt%.

[0008] Furthermore, step S2 includes: B1. Take 100 parts by mass of 3-(acetylthio)propyltriethoxysilane obtained in step S1, and add 10-50 parts by mass of methanol, 0.05-0.50 parts by mass of acetic acid and the corresponding amount of deionized water in the molar ratio described in step S2 in sequence; B2. Stir at 500-1500 r / min under nitrogen protection, control the pH at 4.5-6.0, the temperature at 20-35℃, and react for 0.5-2.0 h; B3. Once the reaction time described in step B2 is reached, terminate the reaction; B4. Partially remove the solvent at 25-40℃ and 0.010-0.040MPa to obtain a methanol dispersion of the core-shell intermediate with a solid content of 50-95wt%.

[0009] Furthermore, step S3 includes: C1. Take a methanol dispersion containing 100 parts by mass of the core-shell intermediate, and add 20-100 parts by mass of methanol and a sodium methoxide methanol solution with a concentration of 3.0 mol / L corresponding to the molar ratio in step S3; C2. React at 0-25℃ for 0.2-1.5h under nitrogen protection; C3. After reaching the reaction time described in step C2, add 0.5-5.0 parts by mass of acetic acid based on 100 parts by mass of the core-shell intermediate, and adjust the pH to 6.0-7.0.

[0010] Furthermore, step S4 includes: D1. Removal of methanol, acetic acid and other low-boiling substances at 30-60℃ and absolute pressure of 0.005-0.040MPa; D2. Vacuum distillation is carried out at 80-105℃ and an absolute pressure of 0.0005-0.0050MPa; D3. When the content of mercaptopropyltriethoxysilane in the distillate is not less than 99.2 wt% and the water content is not more than 0.12 wt%, the main fraction is collected.

[0011] As a concept of this invention, the present invention employs a photo-induced reaction of allyltriethoxysilane with thioacetic acid, partial hydrolysis and condensation of the core component to form a Si-O-Si shell, and then the addition of sodium methoxide methanol solution to a methanol system with pH adjustment using acetic acid. This design is primarily used to enhance the fluidity, stability, and controllable release of thiol groups during the preparation of highly reactive sulfur-containing organosilicones. By first forming 3-(acetylthio)propyltriethoxysilane and then constructing a core-shell intermediate, the hydrolysis, condensation, agglomeration, and gelation of the system can be reduced without significantly sacrificing continuous transport capacity. Subsequently, the reaction and neutralization are completed under controlled temperature and pH conditions, and with the removal of methanol, acetic acid, and other low-boiling substances, as well as vacuum distillation, it is beneficial to balance process window, impurity control, and final product purification and stability.

[0012] Furthermore, the core-shell intermediate or its methanol dispersion obtained in step S2 has a core component of 3-(acetylthio)propyltriethoxysilane obtained by photoaddition of allyltriethoxysilane and thioacetic acid, and a shell layer of Si-O-Si shell layer formed by partial hydrolysis and condensation of the core component.

[0013] Furthermore, in the core-shell intermediate or its methanol dispersion obtained in step S2, the content of 3-(acetylthio)propyltriethoxysilane in the core component is not less than 97.0 wt%, the residual amount of allyltriethoxysilane is not more than 2.0 wt%, and the water content of the core-shell intermediate obtained in step S2 is not more than 0.50 wt%.

[0014] Furthermore, the median particle size D50 of the core-shell intermediate or its methanol dispersion obtained in step S2 is 20-80 μm, the shell thickness is 50-300 nm, and the shell mass accounts for 0.2-8.0 wt% of the total mass of the core-shell intermediate.

[0015] The present invention also discloses a mercaptopropyltriethoxysilane, wherein the mercaptopropyltriethoxysilane contains not less than 99.2 wt% mercaptopropyltriethoxysilane, not more than 0.12 wt% water, not more than 0.8 wt% residual 3-(acetylthio)propyltriethoxysilane, not more than 0.8 wt% total disulfide byproducts, not more than 0.8 wt% residual allyltriethoxysilane, not more than 0.5 wt% residual thioacetic acid, not more than 0.2 wt% residual thioacetic acid, and the total amount of other components excluding water, 3-(acetylthio)propyltriethoxysilane, disulfide byproducts, allyltriethoxysilane, and thioacetic acid is not more than 0.8 wt%.

[0016] Furthermore, the content of mercaptopropyltriethoxysilane in the mercaptopropyltriethoxysilane is not less than 99.5 wt%, the water content is not more than 0.10 wt%, the residual amount of 3-(acetylthio)propyltriethoxysilane is not more than 0.30 wt%, the total amount of disulfide by-products is not more than 0.50 wt%, the residual amount of allyltriethoxysilane is not more than 0.20 wt%, the residual amount of thioacetic acid is not more than 0.10 wt%, and the total amount of other components besides water, 3-(acetylthio)propyltriethoxysilane, disulfide by-products, allyltriethoxysilane, and thioacetic acid is not more than 0.5 wt%.

[0017] Furthermore, step S1 is carried out in a continuous flow photoreactor or a plate photoreactor, and the water content of allyltriethoxysilane and thioacetic acid used in step S1 is not higher than 0.10 wt%.

[0018] Furthermore, the core-shell intermediate obtained in step S2 is sealed and packaged under an inert atmosphere, and the volume fraction of oxygen in the packaging space is not higher than 0.10 vol.

[0019] Furthermore, the main fraction collection and storage in step S4 are carried out under nitrogen protection.

[0020] Furthermore, the pH in steps S2 and S3 is the apparent pH measured at 25°C.

[0021] Furthermore, the pressure in step S4 is absolute pressure.

[0022] Furthermore, in step S1, the residual amount of allyltriethoxysilane is not higher than 2.0 wt% as an auxiliary criterion for terminating illumination.

[0023] Furthermore, step S2 uses a shell thickness of 50-300 nm or a shell mass of 0.2-8.0 wt% of the total mass of the core-shell intermediate as an auxiliary criterion for terminating the reaction.

[0024] Furthermore, in step S3, the residual amount of 3-(acetylthio)propyltriethoxysilane is not higher than 1.0 wt% as an auxiliary criterion for adding acetic acid.

[0025] Furthermore, the residual amounts of allyltriethoxysilane in step S1, 3-(acetylthio)propyltriethoxysilane in step S3, and mercaptopropyltriethoxysilane in step S4 were determined by gas chromatography, and the water content in step S4 was determined by Karl Fischer method.

[0026] Furthermore, the shell thickness of the core-shell intermediate obtained in step S2 was measured by electron microscopy, and the shell mass percentage was determined by weighing after extraction and separation and drying.

[0027] Furthermore, disulfide byproducts include bis(3-triethoxysilylpropyl)disulfide.

[0028] In this invention, 3-(acetylthio)propyltriethoxysilane plays a crucial role in constructing the target sulfur-containing organosilicon framework and maintaining the reactivity of the core component. When present in acetylthio form, it reduces the risk of oxidation and side reactions caused by premature exposure of free thiol groups. The Si-O-Si shell focuses on regulating the external microenvironment of the core component, mitigating the direct impact of moisture, oxygen, and localized heat on the core component, and improving the stability of the core-shell intermediate during transport, dispersion, and subsequent devolatilization. The combination of these two components inhibits the runaway polymerization and agglomeration of the highly reactive core component under aqueous and heated conditions, while preserving the pathway for subsequent thiol group release and purification. This simultaneously improves process stability, storage adaptability, and final product purification efficiency.

[0029] Beneficial technical effects 1. This invention uses the photo-irradiation reaction of allyltriethoxysilane and thioacetic acid to first construct 3-(acetylthio)propyltriethoxysilane, so that the highly reactive mercapto group is not exposed too early in the front-end process, thereby reducing the possibility of oxidation and side reaction accumulation, which is beneficial to improving the controllability of subsequent reactions and purification processes.

[0030] 2. In the intermediate stage, the present invention introduces a controlled Si-O-Si shell, which inhibits hydrolysis, condensation and agglomeration through the synergistic effect of the core component and the shell, so that the system can still maintain good fluidity, continuous transport adaptability and storage stability under high solid content conditions.

[0031] 3. The present invention uses a methanol system for reaction and subsequently adds acetic acid to adjust the pH, which can reduce the further amplification of side reactions while releasing thiol groups. This makes it more conducive to controlling the impact of disulfide byproducts, residual core components, residual acid and water content on the stability of the final product composition.

[0032] 4. This invention achieves a coordinated balance between process window and final product quality through a fractional purification route involving the removal of methanol, acetic acid, and other low-boiling substances and vacuum distillation. This facilitates the acquisition of mercaptopropyltriethoxysilane with high content, low impurities, low water content, and good coupling activity, and improves industrial scale-up stability. Attached Figure Description

[0033] Figure 1 The images show the FTIR full spectrum overlays of samples from Example 1, Comparative Example 3, and Comparative Example 4.

[0034] Figure 2 The TEM shell thickness difference distribution curves are for samples from Example 1, Comparative Example 3, and Comparative Example 5.

[0035] Figure 3The cumulative TEM shell thickness distribution curves are shown for samples from Example 1, Comparative Example 3, and Comparative Example 5.

[0036] Figure 4 (a) is a composite GC chromatogram of samples from Example 1, Comparative Example 6 and Comparative Example 7; Figure 4 (b) is a magnified view of the GC composite chromatogram overlay of the samples from Example 1, Comparative Example 6 and Comparative Example 7.

[0037] Figure 5 This is a point plot showing the percentage area of ​​the key GC peak for samples from Example 1, Comparative Example 6, and Comparative Example 7.

[0038] Figure 6 The graph shows the storage double Y process curves of samples from Example 1, Comparative Example 2, and Comparative Example 8.

[0039] Figure 7 The diagram shows the oxygen process in the headspace of the samples from Example 1, Comparative Example 2, and Comparative Example 8.

[0040] Figure 8 The graph shows the water content process of samples from Example 1, Comparative Example 2, and Comparative Example 8.

[0041] Figure 9 This is a macroscopic photograph of the methanol dispersion of the core-shell intermediate sample from Example 1.

[0042] Figure 10 This is a scanning electron microscope image of the core-shell intermediate of the sample from Example 1.

[0043] Figure 11 This is a transmission electron microscope image of the edge of the core-shell intermediate particles in the sample of Example 1. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0045] Example 1 S1. Photoaddition reaction: In a continuous flow reactor equipped with an ultraviolet light source, the following reactants were prepared: 100 parts by mass of allyltriethoxysilane, 37.6 parts by mass of thioacetic acid (molar ratio 1:1.01), and 0.35 parts by mass of 2,2-dimethoxy-2-phenylacetophenone. The water content of both allyltriethoxysilane and thioacetic acid was 0.06 wt%. Under nitrogen protection, the mixture was introduced into the reactor, with the temperature controlled at 30°C, the light wavelength at 365 nm, the irradiance at 150 W / m², and the residence time at 1.0 h. The volume fraction of oxygen in the reaction system was controlled below 0.05 vol%. After the reaction, the light was stopped, and low-boiling compounds were removed at 38°C and 0.030 MPa to obtain 98.5 wt% 3-(acetylthio)propyltriethoxysilane, with a residual allyltriethoxysilane content of 1.2 wt%.

[0046] S2. Controlled hydrolysis to form a shell: Take 100 parts by mass of 3-(acetylthio)propyltriethoxysilane obtained in step S1, and add 28 parts by mass of methanol, 0.25 parts by mass of acetic acid, and 1.61 parts by mass of deionized water (molar ratio to 3-(acetylthio)propyltriethoxysilane is 0.25:1). Stir at 900 r / min under nitrogen protection, control the pH of the system at 5.2 (measured at 25℃), maintain the temperature at 28℃, and react for 1.2 h. After the reaction is complete, partially remove methanol under 35℃ and 0.025 MPa conditions to obtain a core-shell intermediate methanol dispersion with a solid content of 75 wt%. The core component of the core-shell intermediate in this embodiment is 3-(acetylthio)propyltriethoxysilane, wherein the content of 3-(acetylthio)propyltriethoxysilane is 98.2 wt%. The shell layer is a Si-O-Si shell layer formed by partial hydrolysis and condensation of the core component, with a median particle size D50 of 48 μm, a shell layer thickness of 165 nm, and a shell layer mass accounting for 3.8 wt% of the total mass of the core-shell intermediate. The water content of the core-shell intermediate is 0.28 wt%.

[0047] S3. Deacetylation with a base: Take a methanol dispersion containing 100 parts by mass of the core-shell intermediate, add 55 parts by mass of methanol and 18.2 parts by volume of a 3.0 mol / L sodium methoxide methanol solution (the molar ratio of sodium methoxide to acetylacetonate in the core-shell intermediate is 0.15:1). React at 12°C for 0.8 h under nitrogen protection. At the end of the reaction, the residual amount of 3-(acetylacetonate)propyltriethoxysilane is 0.6 wt%. Subsequently, add 2.5 parts by mass of acetic acid based on 100 parts by mass of the core-shell intermediate to adjust the pH to 6.5 (measured at 25°C).

[0048] S4. Distillation purification: The neutralized reaction solution obtained in step S3 is subjected to a process at 45°C and 0.020 MPa to remove methanol, acetic acid, and other low-boiling substances. Then, vacuum distillation is performed at 92°C and 0.0025 MPa. Under nitrogen protection, the main fraction containing at least 99.2 wt% mercaptopropyltriethoxysilane and at least 0.12 wt% water is collected to obtain a high-purity mercaptopropyltriethoxysilane product. In this embodiment, the mercaptopropyltriethoxysilane product contains 99.6 wt% mercaptopropyltriethoxysilane, 0.08 wt% water, 0.18 wt% residual 3-(acetylthio)propyltriethoxysilane, 0.12 wt% total disulfide byproducts, 0.08 wt% residual allyltriethoxysilane, 0.05 wt% residual thioacetic acid, and 0.09 wt% total other components excluding water, 3-(acetylthio)propyltriethoxysilane, disulfide byproducts, allyltriethoxysilane, and thioacetic acid. The product is stored in a sealed container under nitrogen protection, with the oxygen volume fraction in the packaging space not exceeding 0.05 vol.

[0049] This embodiment employs moderately conservative process parameters, effectively balancing the stability of the intermediate with the efficiency of subsequent alkaline hydrolysis. The alkaline hydrolysis reaction is carried out under mild conditions of 12°C and a sodium methoxide molar ratio of 0.15:1, reducing the occurrence of side reactions. The final product has a mercaptopropyltriethoxysilane content of 99.6 wt%, exhibiting good overall process stability and high reproducibility. It is suitable for conventional production scenarios requiring stable product quality, and is particularly suitable for applications such as rubber, coatings, and adhesives where high product purity and batch stability are required.

[0050] Example 2 S1. Photoaddition reaction: In a plate-type photoreactor equipped with a high-intensity LED ultraviolet light source, the following ingredients were prepared: 100 parts by mass of allyltriethoxysilane, 38.4 parts by mass of thioacetic acid (molar ratio 1:1.03), and 0.55 parts by mass of 2,2-dimethoxy-2-phenylacetophenone. The water content of both allyltriethoxysilane and thioacetic acid was 0.04 wt%. Under nitrogen protection, the mixture was added to the reactor, the temperature was controlled at 35℃, the light wavelength at 360 nm, the irradiance at 220 W / m², and the reaction time was 1.5 h. The volume fraction of oxygen in the reaction system was controlled below 0.08 vol%. After the reaction was completed, the light was stopped, and low-boiling substances were removed at 40℃ and 0.035 MPa to obtain 98.8 wt% 3-(acetylthio)propyltriethoxysilane, with a residual allyltriethoxysilane content of 0.8 wt%.

[0051] S2. Controlled hydrolysis to form a shell: Take 100 parts by mass of 3-(acetylthio)propyltriethoxysilane obtained in step S1, and add 18 parts by mass of methanol, 0.35 parts by mass of acetic acid, and 0.96 parts by mass of deionized water (molar ratio to 3-(acetylthio)propyltriethoxysilane is 0.15:1). Stir at 1200 r / min under nitrogen protection, control the pH of the system at 5.5 (measured at 25℃), maintain the temperature at 25℃, and react for 1.6 h. After the reaction is complete, partially remove methanol under 38℃ and 0.032 MPa conditions to obtain a core-shell intermediate methanol dispersion with a solid content of 88 wt%. The core component of the core-shell intermediate in this embodiment is 3-(acetylthio)propyltriethoxysilane, wherein the content of 3-(acetylthio)propyltriethoxysilane is 98.5 wt%. The shell layer is a Si-O-Si shell layer formed by partial hydrolysis and condensation of the core component, with a median particle size D50 of 35 μm, a shell layer thickness of 85 nm, and the shell layer mass accounts for 1.2 wt% of the total mass of the core-shell intermediate. The water content of the core-shell intermediate is 0.15 wt%.

[0052] S3. Deacetylation with a base: Take a methanol dispersion containing 100 parts by mass of the core-shell intermediate, add 75 parts by mass of methanol and 26.7 parts by volume of a 3.0 mol / L sodium methoxide methanol solution (the molar ratio of sodium methoxide to acetylacetonate in the core-shell intermediate is 0.22:1). React at 5°C for 1.2 h under nitrogen protection. At the end of the reaction, the residual amount of 3-(acetylacetonate)propyltriethoxysilane is 0.4 wt%. Subsequently, add 3.8 parts by mass of acetic acid based on 100 parts by mass of the core-shell intermediate to adjust the pH to 6.8 (measured at 25°C).

[0053] S4. Distillation purification: The neutralized reaction solution obtained in step S3 is subjected to a process at 52°C and 0.032 MPa to remove methanol, acetic acid, and other low-boiling substances. Then, vacuum distillation is performed at 98°C and 0.0038 MPa. Under nitrogen protection, the main fraction containing at least 99.2 wt% mercaptopropyltriethoxysilane and at least 0.12 wt% water is collected to obtain a high-purity mercaptopropyltriethoxysilane product. In this embodiment, the mercaptopropyltriethoxysilane product contains 99.7 wt% mercaptopropyltriethoxysilane, 0.06 wt% water, 0.12 wt% residual 3-(acetylthio)propyltriethoxysilane, 0.08 wt% total disulfide byproducts, 0.05 wt% residual allyltriethoxysilane, and 0.03 wt% residual thioacetic acid. The total amount of other components besides water, 3-(acetylthio)propyltriethoxysilane, disulfide byproducts, allyltriethoxysilane, and thioacetic acid is 0.06 wt%. The product is stored in a sealed container under nitrogen protection, with the oxygen volume fraction in the packaging space not exceeding 0.08 vol.

[0054] This embodiment employs enhanced process conditions to improve reaction efficiency and product purity. The final product has a mercaptopropyltriethoxysilane content of 99.7 wt% and a disulfide byproduct of only 0.08 wt%. The overall process is highly efficient and produces excellent product purity, making it suitable for scenarios with high requirements for both production efficiency and product purity. It is particularly suitable for precision applications in high-end electronic materials, optical materials, and other fields where impurity content is extremely sensitive.

[0055] Example 3 S1. Photoaddition reaction: In a continuous flow reactor equipped with an ultraviolet light source, the following reactants were prepared: 100 parts by mass of allyltriethoxysilane, 36.9 parts by mass of thioacetic acid (molar ratio 1:0.99), and 0.18 parts by mass of 2,2-dimethoxy-2-phenylacetophenone. The water content of both allyltriethoxysilane and thioacetic acid was 0.08 wt%. Under nitrogen protection, the mixture was introduced into the reactor at a controlled temperature of 25°C, a light wavelength of 370 nm, an irradiance of 100 W / m², and a residence time of 0.6 h. The volume fraction of oxygen in the reaction system was controlled below 0.03 vol%. After the reaction, the light was stopped, and low-boiling compounds were removed at 35°C and 0.025 MPa to obtain 97.8 wt% 3-(acetylthio)propyltriethoxysilane, with a residual allyltriethoxysilane content of 1.8 wt%.

[0056] S2. Controlled hydrolysis to form a shell: Take 100 parts by mass of 3-(acetylthio)propyltriethoxysilane obtained in step S1, and add 40 parts by mass of methanol, 0.15 parts by mass of acetic acid, and 2.06 parts by mass of deionized water (molar ratio to 3-(acetylthio)propyltriethoxysilane is 0.32:1). Stir at 650 r / min under nitrogen protection, control the pH of the system at 4.8 (measured at 25℃), maintain the temperature at 32℃, and react for 0.8 h. After the reaction is complete, partially remove methanol under 32℃ and 0.018 MPa conditions to obtain a core-shell intermediate methanol dispersion with a solid content of 70 wt%. The core component of the core-shell intermediate in this embodiment is 3-(acetylthio)propyltriethoxysilane, wherein the content of 3-(acetylthio)propyltriethoxysilane is 97.5 wt%. The shell layer is a Si-O-Si shell layer formed by partial hydrolysis and condensation of the core component, with a median particle size D50 of 68 μm, a shell layer thickness of 245 nm, and the shell layer mass accounts for 6.5 wt% of the total mass of the core-shell intermediate. The water content of the core-shell intermediate is 0.42 wt%.

[0057] S3. Deacetylation with a base: Take a methanol dispersion containing 100 parts by mass of the core-shell intermediate, add 35 parts by mass of methanol and 12.1 parts by volume of a 3.0 mol / L sodium methoxide methanol solution (the molar ratio of sodium methoxide to acetylacetonate in the core-shell intermediate is 0.10:1). React at 18°C ​​for 0.5 h under nitrogen protection. At the end of the reaction, the residual amount of 3-(acetylacetonate)propyltriethoxysilane is 0.9 wt%. Subsequently, add 1.5 parts by mass of acetic acid based on 100 parts by mass of the core-shell intermediate to adjust the pH to 6.2 (measured at 25°C).

[0058] S4. Distillation purification: The neutralized reaction solution obtained in step S3 is subjected to a process at 38°C and 0.012 MPa to remove methanol, acetic acid, and other low-boiling substances. Then, vacuum distillation is performed at 85°C and 0.0012 MPa. Under nitrogen protection, the main fraction containing at least 99.2 wt% mercaptopropyltriethoxysilane and at least 0.12 wt% water is collected to obtain a high-purity mercaptopropyltriethoxysilane product. In this embodiment, the mercaptopropyltriethoxysilane product contains 99.5 wt% mercaptopropyltriethoxysilane, 0.09 wt% water, 0.25 wt% residual 3-(acetylthio)propyltriethoxysilane, 0.15 wt% total disulfide byproducts, 0.12 wt% residual allyltriethoxysilane, 0.07 wt% residual thioacetic acid, and the total amount of other components excluding water, 3-(acetylthio)propyltriethoxysilane, disulfide byproducts, allyltriethoxysilane, and thioacetic acid is 0.12 wt%. The product is stored in a sealed container under nitrogen protection, with the oxygen volume fraction in the packaging space not exceeding 0.05 vol.

[0059] This embodiment employs mild process conditions to optimize product purity and intermediate stability. The photoreaction uses a low irradiation intensity of 100 W / m², a temperature of 25°C, and a slightly insufficient amount of thioacetic acid (molar ratio 1:0.99). The photoinitiator dosage is low at 0.18 wt%, and the reaction time is only 0.6 h. These mild reaction conditions help reduce the formation of side reactions. The overall process is mild and by-products are well controlled, making it suitable for scenarios with high requirements for product stability and storage performance. It is particularly suitable for applications requiring long-term storage, long-distance transportation, or use under harsh environmental conditions, such as coatings for marine environments and outdoor building sealants.

[0060] Example 4 S1. Photoaddition reaction: In a plate-type photoreactor equipped with a high-intensity LED ultraviolet light source array, the following ingredients were prepared: 100 parts by mass of allyltriethoxysilane, 38.0 parts by mass of thioacetic acid (molar ratio 1:1.02), and 0.42 parts by mass of 2,2-dimethoxy-2-phenylacetophenone. The water content of both allyltriethoxysilane and thioacetic acid was 0.05 wt%. Under nitrogen protection, the mixture was added to the reactor, the temperature was controlled at 32℃, the light wavelength at 365 nm, the irradiance at 280 W / m², and the reaction time was 0.3 h. The volume fraction of oxygen in the reaction system was controlled below 0.06 vol%. After the reaction was completed, the light was stopped, and low-boiling substances were removed at 42℃ and 0.038 MPa to obtain 98.2 wt% 3-(acetylthio)propyltriethoxysilane, with a residual allyltriethoxysilane content of 1.5 wt%.

[0061] S2. Controlled hydrolysis to form a shell: Take 100 parts by mass of 3-(acetylthio)propyltriethoxysilane obtained in step S1, and add 12 parts by mass of methanol, 0.28 parts by mass of acetic acid, and 0.77 parts by mass of deionized water (molar ratio to 3-(acetylthio)propyltriethoxysilane is 0.12:1). Stir at 1000 r / min under nitrogen protection, control the pH of the system at 5.0 (measured at 25℃), maintain the temperature at 27℃, and react for 1.0 h. After the reaction is complete, partially remove methanol under 36℃ and 0.028 MPa to obtain a core-shell intermediate methanol dispersion with a solid content of 90 wt%. The core component of the core-shell intermediate in this embodiment is 3-(acetylthio)propyltriethoxysilane, wherein the content of 3-(acetylthio)propyltriethoxysilane is 98.0 wt%. The shell layer is a Si-O-Si shell layer formed by partial hydrolysis and condensation of the core component, with a median particle size D50 of 25 μm, a shell layer thickness of 62 nm, and the shell layer mass accounts for 0.5 wt% of the total mass of the core-shell intermediate. The water content of the core-shell intermediate is 0.18 wt%.

[0062] S3. Deacetylation with a base: Take a methanol dispersion containing 100 parts by mass of the core-shell intermediate, add 60 parts by mass of methanol and 32.8 parts by volume of a 3.0 mol / L sodium methoxide methanol solution (the molar ratio of sodium methoxide to acetylacetonate in the core-shell intermediate is 0.27:1). React at 2°C for 0.9 h under nitrogen protection. At the end of the reaction, the residual amount of 3-(acetylacetonate)propyltriethoxysilane is 0.5 wt%. Subsequently, add 2.8 parts by mass of acetic acid based on 100 parts by mass of the core-shell intermediate to adjust the pH to 6.6 (measured at 25°C).

[0063] S4. Distillation purification: The neutralized reaction solution obtained in step S3 is subjected to distillation at 48°C and 0.028 MPa to remove methanol, acetic acid, and other low-boiling substances. Then, it is subjected to vacuum distillation at 95°C and 0.0032 MPa. Under nitrogen protection, the main fraction with a mercaptopropyltriethoxysilane content of not less than 99.2 wt% and a water content of not more than 0.12 wt% is collected to obtain a high-purity mercaptopropyltriethoxysilane product. In this embodiment, the mercaptopropyltriethoxysilane product contains 99.6 wt% mercaptopropyltriethoxysilane, 0.07 wt% water, 0.16 wt% residual 3-(acetylthio)propyltriethoxysilane, 0.10 wt% total disulfide byproducts, 0.06 wt% residual allyltriethoxysilane, 0.04 wt% residual thioacetic acid, and a total of 0.08 wt% of other components excluding water, 3-(acetylthio)propyltriethoxysilane, disulfide byproducts, allyltriethoxysilane, and thioacetic acid. The product is stored in a sealed container under nitrogen protection, with the oxygen volume fraction in the packaging space not exceeding 0.06 vol.

[0064] This embodiment uses a specific combination of process parameters within a certain range to verify the flexibility and robustness of the method. It is suitable for scenarios that require rapid production and flexible adjustment of process parameters, and is particularly suitable for applications such as customized production of small batches and multiple varieties, pilot-scale amplification research, and sensitivity assessment of process conditions.

[0065] Comparative Example 1: Basically the same as Example 1, except that the molar ratio of allyltriethoxysilane to thioacetic acid in step S1 is 1:0.95, and other conditions remain unchanged.

[0066] Comparative Example 2: It is basically the same as Example 1, except that the volume fraction of oxygen in the reaction system in step S1 is controlled to be 0.20 vol%, and other conditions remain unchanged.

[0067] Comparative Example 3: It is basically the same as Example 1, except that the molar ratio of deionized water to 3-(acetylthio)propyltriethoxysilane in step S2 is 0.05:1, and other conditions remain unchanged.

[0068] Comparative Example 4: Basically the same as Example 1, except that the pH of the system was controlled at 6.3 in step S2 (measured at 25°C), and other conditions remained unchanged.

[0069] Comparative Example 5: It is basically the same as Example 1, except that the stirring speed in step S2 is 300 r / min, and other conditions remain unchanged.

[0070] Comparative Example 6: It is basically the same as Example 1, except that the molar ratio of sodium methoxide to acetyl thio group in the core-shell intermediate in step S3 is 0.03:1, and other conditions remain unchanged.

[0071] Comparative Example 7: It is basically the same as Example 1, except that the reaction temperature in step S3 is 30°C, while other conditions remain unchanged.

[0072] Comparative Example 8: It is basically the same as Example 1, except that the pressure of vacuum distillation in step S4 is 0.0065 MPa, and other conditions remain unchanged.

[0073] Performance testing: The contents of mercaptopropyltriethoxysilane, residual 3-(acetylthio)propyltriethoxysilane, residual allyltriethoxysilane, residual thioacetic acid, and total disulfide byproducts were determined by gas chromatography. Separation of each component was achieved by utilizing the retention differences of each component on a capillary column, and quantitative analysis was performed using fractional indices (FIDs). An internal standard method was established for the test, using a DB-5 column. The injection port temperature was set to 250℃, the column temperature program was 60℃ for 2 min, then increased to 220℃ at a rate of 8℃ / min, and the split ratio was 50:1. Each sample was measured in triplicate. The retention time, peak area, and mean ± standard deviation of each component were output to evaluate product purity and byproduct control level.

[0074] The water content in the finished product and the core-shell intermediate methanol dispersion was determined using the Karl Fischer titration method. The water content was determined by the quantitative reaction of water in the sample with the Karl Fischer reagent and the endpoint potential. During the test, the sample was injected under dry nitrogen protection, with a single sample size controlled between 0.2-1.0 g. The water content in the finished product and intermediate was determined separately, with each group tested in triplicate. The results are expressed as mean ± standard deviation. The system's ability to control low water content and its resistance to hydrolysis and polymerization were evaluated in conjunction with the increase in moisture content before and after storage. The content of each component and the water content were measured independently using different analytical methods and rounded to the appropriate decimal places. In the examples, comparative examples, and Table 1, if the sum of the percentage contents of each item differs from 100 wt% by no more than 0.5 wt%, it is considered a measurement deviation due to different analytical methods and rounding, and is not considered a compositional inconsistency.

[0075] The structural changes of the product in step S1, the core-shell intermediate in step S2, and the final mercaptopropyltriethoxysilane were analyzed using ATR-FTIR. Different chemical bonds exhibit characteristic absorptions in the infrared region, which can be used to characterize the formation of the Si-O-Si shell, the removal of acetyl thio groups, and the formation of thiol groups. The scanning range was set to 4000-650 cm⁻¹, with a resolution of 4 cm⁻¹, and a total of 32 scans were performed. Each sample was measured in triplicate, and the key absorption regions were normalized. The final output spectrum (CSV) data was then compared to characterize the structural evolution during the reaction process.

[0076] The particle size distribution of the core-shell intermediate methanol dispersion was determined by laser diffraction. The scattering angle distribution of the laser light by the particles is related to their equivalent particle size and can be used to evaluate the median particle size D50, particle size distribution width, and anti-agglomeration ability before and after cyclic transport. Anhydrous methanol was used as the dispersion medium during the test, and the shading rate was controlled within the range of 5%-15%. The initial sample and the sample after 2 hours of cyclic transport were measured. Parameters such as D10, D50, and D90 were output, and the Span value and the rate of change of D50 before and after transport were calculated. The results are expressed as mean ± standard deviation.

[0077] Cross-sectional samples of the core-shell intermediate were characterized using transmission electron microscopy. Nanoscale shell thickness was directly measured using cross-sectional imaging, and its thickness distribution was statistically analyzed using the images. The shell mass percentage was verified using an extraction-drying-weighing method. During testing, the embedded and sliced ​​samples were observed. At least 100 particles were counted for each sample, and the shell thickness of each particle was measured at at least four different orientations. Thickness CSV data was exported, and the mean, standard deviation, and box plot were provided to quantitatively evaluate shell homogeneity and the rationality of the structural design.

[0078] The rheological properties of the core-shell intermediate methanol dispersion were determined using rotational viscometry. The apparent viscosity obtained by rotational viscometers can reflect the flow resistance and continuous transport adaptability of the system under high solids content conditions. A single-cylinder rotational viscometer was used for testing at 25±0.5℃. The sample was pre-sheared for 1 min before the formal test was performed three times, and stable readings were recorded. The viscosity-shear condition data were output, and the mean ± standard deviation and thixotropic index were calculated to evaluate the low viscosity and transportability of the system.

[0079] Storage stability of mercaptopropyltriethoxysilane under nitrogen-protected sealed packaging was investigated. The oxygen content in the headspace was monitored, and the results were combined with GC and Karl Fischer assays to evaluate the product's ability to maintain purity, suppress water content, and control disulfide byproducts under low-oxygen storage conditions. Samples were stored at 25℃ for 90 days and 40℃ for 30 days, respectively. The initial oxygen volume fraction in the packaging space was controlled to be 0.10 vol% or less. Each sample was tested in triplicate. The mercaptopropyltriethoxysilane content, total disulfide byproducts, and water content were measured at each storage time point. The content retention rate, disulfide increment, and moisture increment were calculated to evaluate the product's storage stability. Table 1 shows the data after 30 days of storage. Figures 6-8 The storage process data shown correspond to storage at 40℃ for 30 days; data at 25℃ / 90 days are used for supplementary evaluation of long-term storage stability.

[0080] Figure 1The FTIR full spectrum overlays of Examples 1, 3, and 4 are shown. The overall functional groups of the samples were characterized by Fourier transform infrared spectroscopy. The differences in the response of different samples in the absorption regions related to carbonyl, alkyl, and silicon-oxygen bonds were compared. This shows that Example 1 has both the target structural unit and relatively stable shell-forming characteristics, proving that the structure of the obtained product is reasonable and the preparation route is effective.

[0081] Figure 2 The TEM shell thickness difference distribution curves of Example 1, Comparative Example 3 and Comparative Example 5 are shown. The particle shell thickness was measured by transmission electron microscopy and the distribution was fitted. The main peak position, peak width and multi-peak characteristics of different samples were compared. The results show that the thickness distribution of Example 1 is more concentrated and the deviation is smaller, while Comparative Example 5 has obvious dispersion. This proves that Example 1 is more conducive to the formation of a stable and uniform core-shell structure.

[0082] Figure 3 The cumulative distribution curves of the shell thickness of Examples 1, 3 and 5 are shown in the TEM images. The average shell thickness of the particles was statistically analyzed by transmission electron microscopy and the cumulative frequency was analyzed. The thickness range differences when different samples reached the same cumulative ratio were compared. The results show that the overall distribution of Example 1 is more stable and more concentrated, which proves that its shell formation process is more consistent.

[0083] Figure 4 (a) is a composite GC chromatogram of Example 1, Comparative Example 6 and Comparative Example 7. Gas chromatography was used to analyze the overall composition of the samples and compare the relative responses and retention time distribution of the main product peak, intermediate and by-product peaks. Figure 4 (b) is a magnified view of the GC composite chromatogram of Example 1, Comparative Example 6 and Comparative Example 7. The results show that the main peak of Example 1 is more prominent and the impurity peak is lower, proving that the preparation conditions can more effectively suppress side reactions and improve product purity.

[0084] Figure 5 The GC key peak area percentage plots for Examples 1, 6, and 7 are shown. Gas chromatography was used to quantitatively compare the main product, acetyl thio intermediate, disulfide by-product, and raw material residue. The changes in the area percentage of key components were compared. The results showed that the main product accounted for the highest proportion in Example 1, while the by-product and residual components were lower, proving that its reaction path was clearer and the product composition was better.

[0085] Figure 6 The storage double Y process curves of Example 1, Comparative Example 2 and Comparative Example 8 are shown. The changes in the content of the main product and disulfide byproducts during the storage process were examined simultaneously by combining storage stability test with composition analysis. The results show that the decrease in the main product in Example 1 was smaller and the increase in byproducts was slower, which proves that the scheme is more reasonable in maintaining product stability.

[0086] Figure 7 The head space oxygen process graphs for Example 1, Comparative Example 2, and Comparative Example 8 are shown. The changes in head space oxygen content over time for different samples were characterized using storage process monitoring methods. The results show that the oxygen content of Example 1 was lower and fluctuated less throughout the entire storage period, indicating that it was more effective in controlling the oxidizing environment and demonstrating that the sample had better storage adaptability.

[0087] Figure 8 The process flow graphs of water content in Examples 1, 2, and 8 are shown. The changes in water content of the samples were compared by the storage stability tracking test. The results show that the water content of Example 1 increased less during storage and the overall level was more stable, indicating that it has a better inhibitory effect on water introduction and accumulation, proving that the scheme is conducive to maintaining the long-term stability of the system.

[0088] Figure 9 This is a macroscopic photograph of the methanol dispersion, a core-shell intermediate from Example 1. The dispersion exhibits a uniform milky-white appearance, good flowability, and no obvious sedimentation or stratification. With a solid content of 75 wt% and a water content of only 0.28 wt%, the controlled hydrolysis conditions of pH 5.2 and 28°C effectively inhibited the deep hydrolysis of the core component. The low water content and uniform dispersion demonstrate that the system possesses good stability and reactivity in the subsequent alkaline hydrolysis step.

[0089] Figure 10 This is a scanning electron microscope (SEM) image of the core-shell intermediate from Example 1. The low-magnification image shows that the particles are spherical or near-spherical, with sizes concentrated in the range of 40-55 μm, consistent with the median particle size (D50) of 48 μm. The particles are in point contact with each other, and no significant aggregation was observed. This demonstrates that the controlled hydrolysis strategy successfully constructed a uniformly thick and structurally complete Si-O-Si coating layer, which both protects the core component and mitigates side reactions while allowing sodium methoxide solution to permeate and facilitate alkaline deacetylation.

[0090] Figure 11 The image shows a transmission electron microscope image of the edge of the core-shell intermediate particles prepared in Example 1. The image clearly shows the light and dark core-shell structure interface formed by different electron scattering capabilities at high magnification. The thickness of the outermost shell layer was measured to be about 165 nm and the coating layer was continuous and intact. This proves that the thickness of the nanoscale organosilicon shell layer was precisely controlled and effectively constructed through a mild acid catalysis strategy.

[0091] Table 1 Performance summary of examples and comparative examples As can be seen from the performance of the examples and comparative examples in Table 1, Examples 1-4 are generally superior to the comparative examples in terms of mercaptopropyltriethoxysilane content, water content, total amount of disulfide byproducts, and purity retention after 30 days of storage. This indicates a significant synergistic relationship between low-oxygen light exposure, moderate Si-O-Si shell formation, mild low-temperature deacetylation, and proper purification. Among them, Example 2 shows the best performance in terms of purity and impurity control, while Example 1 achieves the best balance between apparent viscosity, particle size, and shell thickness. In contrast, Comparative Examples 2, 4, 5, and 6 suffer from decreased purity, increased viscosity, or deteriorated storage stability due to oxygen exposure, excessive condensation, insufficient mixing, and insufficient deacetylation, respectively.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing mercaptopropyltriethoxysilane, characterized in that, Includes the following steps: S1. Allyltriethoxysilane and thioacetic acid are mixed at a molar ratio of 1:(0.98-1.05), and 0.05-0.80 wt% of 2,2-dimethoxy-2-phenylacetophenone relative to the mass of allyltriethoxysilane is added. The mixture is subjected to photo-reaction at 20-40℃ under nitrogen protection, with a light wavelength of 350-380 nm and an irradiation intensity of 50-300 W / m2 for 0.2-2.0 h, and the volume fraction of oxygen in the reaction system is not higher than 0.10 vol%, to obtain 3-(acetylthio)propyltriethoxysilane; S2. Take 100 parts by mass of 3-(acetylthio)propyltriethoxysilane obtained in step S1, and add 10-50 parts by mass of methanol, 0.05-0.50 parts by mass of acetic acid and deionized water in sequence, wherein the amount of deionized water is such that the molar ratio of deionized water to 3-(acetylthio)propyltriethoxysilane is (0.10-0.40):

1. Stir at 500-1500 r / min under nitrogen protection, control the pH of the system to be 4.5-6.0, and react at 20-35℃ for 0.5-2.0 h to obtain a core-shell intermediate with a Si-O-Si shell. S3. Based on 100 parts by weight of the net weight of the core-shell intermediate obtained in step S2, add or supplement 20-100 parts by weight of methanol to the core-shell intermediate or its methanol dispersion, and add a 3.0 mol / L sodium methoxide methanol solution, controlling the molar ratio of sodium methoxide to acetyl thio groups in the core-shell intermediate to be (0.05-0.30):1, and react at 0-25°C for 0.2-1.5 h under nitrogen protection; then add 0.5-5.0 parts by weight of acetic acid based on 100 parts by weight of the core-shell intermediate, and adjust the pH to 6.0-7.0; S4. The neutralized reaction solution obtained in step S3 is first subjected to 30-60℃ and 0.005-0.040MPa absolute pressure to remove methanol, acetic acid and other low-boiling substances, and then subjected to vacuum distillation at 80-105℃ and 0.0005-0.0050MPa absolute pressure to obtain mercaptopropyltriethoxysilane.

2. The preparation method according to claim 1, characterized in that, Step S1 includes: A1. Prepare a mixture of 100 parts by weight of allyltriethoxysilane, thioacetic acid in the molar ratio specified in step S1, and 0.05-0.80 parts by weight of 2,2-dimethoxy-2-phenylacetophenone. A2. Under nitrogen protection, react for 0.2-2.0 h at 20-40℃, with a light wavelength of 350-380 nm and an irradiation intensity of 50-300 W / m2. A3. After the reaction time described in step A2 is reached, the light exposure is terminated; A4. Remove low-boiling substances at 30-45℃ and 0.020-0.040MPa to obtain 3-(acetylthio)propyltriethoxysilane with a content of not less than 97.0wt%.

3. The preparation method according to claim 2, characterized in that, Step S2 includes: B1. Take 100 parts by mass of 3-(acetylthio)propyltriethoxysilane obtained in step S1, and add 10-50 parts by mass of methanol, 0.05-0.50 parts by mass of acetic acid and the corresponding amount of deionized water in the molar ratio described in step S2 in sequence; B2. Stir at 500-1500 r / min under nitrogen protection, control the pH at 4.5-6.0, the temperature at 20-35℃, and react for 0.5-2.0 h; B3. Once the reaction time described in step B2 is reached, terminate the reaction; B4. Partially remove the solvent at 25-40℃ and 0.010-0.040MPa to obtain a methanol dispersion of the core-shell intermediate with a solid content of 50-95wt%.

4. The preparation method according to claim 3, characterized in that, Step S3 includes: C1. Take a methanol dispersion containing 100 parts by mass of the core-shell intermediate, and add 20-100 parts by mass of methanol and a sodium methoxide methanol solution with a concentration of 3.0 mol / L corresponding to the molar ratio in step S3; C2. React at 0-25℃ for 0.2-1.5h under nitrogen protection; C3. After reaching the reaction time described in step C2, add 0.5-5.0 parts by mass of acetic acid based on 100 parts by mass of the core-shell intermediate, and adjust the pH to 6.0-7.

0.

5. The preparation method according to claim 4, characterized in that, Step S4 includes: D1. Removal of methanol, acetic acid and other low-boiling substances at 30-60℃ and absolute pressure of 0.005-0.040MPa; D2. Vacuum distillation is carried out at 80-105℃ and an absolute pressure of 0.0005-0.0050MPa; D3. When the content of mercaptopropyltriethoxysilane in the distillate is not less than 99.2 wt% and the water content is not more than 0.12 wt%, the main fraction is collected.

6. The preparation method according to any one of claims 1-5, characterized in that, The core-shell intermediate or its methanol dispersion obtained in step S2 has a core component of 3-(acetylthio)propyltriethoxysilane obtained by photoaddition of allyltriethoxysilane and thioacetic acid, and a shell layer of Si-O-Si shell layer formed by partial hydrolysis and condensation of the core component.

7. The preparation method according to claim 6, characterized in that, The core-shell intermediate obtained in step S2 or its methanol dispersion contains a core component containing 3-(acetylthio)propyltriethoxysilane with a content of not less than 97.0 wt% and an allyltriethoxysilane residue of not more than 2.0 wt%, and the water content of the core-shell intermediate obtained in step S2 is not more than 0.50 wt%.

8. The preparation method according to claim 6, characterized in that, The median particle size D50 of the core-shell intermediate or its methanol dispersion obtained in step S2 is 20-80 μm, the shell thickness is 50-300 nm, and the shell mass accounts for 0.2-8.0 wt% of the total mass of the core-shell intermediate.

9. A mercaptopropyltriethoxysilane, characterized in that, The mercaptopropyltriethoxysilane is obtained by the preparation method according to any one of claims 1-8, wherein the content of mercaptopropyltriethoxysilane is not less than 99.2 wt%, the water content is not more than 0.12 wt%, the residual amount of 3-(acetylthio)propyltriethoxysilane is not more than 0.8 wt%, the total amount of disulfide by-products is not more than 0.8 wt%, the residual amount of allyltriethoxysilane is not more than 0.5 wt%, the residual amount of thioacetic acid is not more than 0.2 wt%, and the total amount of other components other than water, 3-(acetylthio)propyltriethoxysilane, disulfide by-products, allyltriethoxysilane and thioacetic acid is not more than 0.8 wt%.

10. The mercaptopropyltriethoxysilane according to claim 9, characterized in that, The mercaptopropyltriethoxysilane contains not less than 99.5 wt% mercaptopropyltriethoxysilane, not more than 0.10 wt% water, not more than 0.30 wt% residual 3-(acetylthio)propyltriethoxysilane, not more than 0.50 wt% total disulfide byproducts, not more than 0.20 wt% residual allyltriethoxysilane, not more than 0.10 wt% residual thioacetic acid, and the total amount of other components besides water, 3-(acetylthio)propyltriethoxysilane, disulfide byproducts, allyltriethoxysilane, and thioacetic acid is not more than 0.5 wt%.

Images