A method for preparing 3-thiocyano propyl triethoxysilane by aqueous phase

Abstract

The present application relates to a kind of water phase method preparation 3-thiocyanate propyl triethoxysilane method, the present application is catalytic synthesis 3-thiocyanate propyl triethoxysilane using water phase method, using the mixed solution of water and ethanol as solvent makes sodium thiocyanate fully dissolved, overcome the problem that sodium thiocyanate cannot be fully dissolved or dissolved time is too long using organic solvent in solvent method, while using sodium bicarbonate as buffer agent makes the pH of system between 8-9, avoid the problem of hydrolysis in subsequent drop and reaction process, improve the reaction yield, the highest yield reaches 92.10%.By the water phase after separation into saturated sodium chloride solution to organic phase is washed, improve the utilization of reaction solution.

Description

Technical Field

[0001] This invention relates to a method for preparing 3-thiocyanopropyltriethoxysilane using an aqueous phase method, belonging to the field of chemical synthesis technology. Background Technology

[0002] 3-Thiocyanopropyltriethoxysilane (trade name Si-264 from Degussa, Germany) can be used as a coupling agent to improve the tear resistance, abrasion resistance, and flexural crack resistance of vulcanizates, and also increase the resistance of natural rubber vulcanizates to vulcanization reduction. Its properties are more stable than bis-(triethoxysilylpropyl)tetrasulfide (trade name Si-69 from Degussa, Germany). Thiocyanosilane itself is light in color, so it can be used in some light-colored rubber products, such as white rubber shoe soles.

[0003] Currently, there are two main methods for synthesizing thiocyanosilanes: the aqueous phase method and the solvent method. Both methods utilize phase transfer catalysts to catalyze the condensation of thiocyanate salts and 3-chloropropylalkoxysilanes to prepare 3-thiocyanopropyltriethoxysilane. The solvent method primarily uses N,N-dimethylformamide (DMF) as a solvent to synthesize 3-thiocyanopropyltriethoxysilane. This process has high reaction efficiency and is favored by many companies. However, this method uses a large amount of organic solvent, and DMF residues are easily left in the finished product, affecting the use of subsequent products. Furthermore, the product is prone to yellowing and has poor stability. The aqueous phase method uses water as a solvent, avoiding the use of organic solvents, making the synthesis process more environmentally friendly. However, it faces the challenge of silanes being easily hydrolyzed in water.

[0004] Chinese patent document CN 102731560 A discloses a method for synthesizing thiocyanopropyltriethoxysilane. Although the system separates into an aqueous phase and an organic phase after the reaction, the organic phase still contains some toluene, requiring toluene treatment and posing a potential environmental pollution hazard. Chinese patent document CN 1265396A discloses a method for preparing thiocyanopropyltriethoxysilane by reacting chloropropyltriethoxysilane with a sodium cyanate solution in ethanol. Although only ethanol is used as the solvent, the distillation time is excessively long. Chinese patent document CN 105061485 A discloses a method for synthesizing thiocyanopropyltrialkoxysilane. This method uses a self-made catalyst to catalyze the synthesis of thiocyanopropyltrialkoxysilane and sodium thiocyanate under specific reaction conditions. The treatment with a single catalyst requires 6.5-10.5 hours, a lengthy process that is not conducive to industrial application.

[0005] Therefore, there is an urgent need for a novel aqueous phase method for preparing 3-thiocyanopropyltriethoxysilane with short reaction time and high yield of the target product. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention employs an aqueous phase method to synthesize 3-thiocyanopropyltriethoxysilane. This method features short reaction time, high yield of the target product, and no organic waste liquid generation.

[0007] This invention is achieved through the following technical solution:

[0008] A method for preparing 3-thiocyanopropyltriethoxysilane using an aqueous phase method includes the following steps:

[0009] 1) Add sodium thiocyanate to a mixed solvent of water and alcohol, add sodium bicarbonate, mix, stir and heat until sodium thiocyanate and sodium bicarbonate are completely dissolved, and add phase transfer catalyst;

[0010] 2) Add γ-chloropropyltriethoxysilane dropwise. After the addition is complete, react for 1.5-2 hours to obtain the crude product.

[0011] 3) After separation, sodium chloride was added to the aqueous phase to saturate it, and the organic phase was washed. The filtered solution was then distilled to obtain a colorless and transparent 3-thiocyanopropyltriethoxysilane product.

[0012] According to a preferred embodiment of the present invention, in step 1), the alcohol in the mixed solvent of water and alcohol is ethanol, isopropanol, or methanol.

[0013] According to a preferred embodiment of the present invention, in step 1), the mass ratio of alcohol to water in the mixed solvent of water and alcohol is 1:(3-6).

[0014] More preferably, in step 1), the mass ratio of alcohol to water in the mixed solvent of water and alcohol is 1:4.5-5.

[0015] According to a preferred embodiment of the present invention, in step 1), the mass ratio of sodium thiocyanate to the mixed solvent of water and alcohol is 1:6.5-7.5.

[0016] According to a preferred embodiment of the present invention, in step 1), the amount of sodium bicarbonate added is such that the pH reaches 8–9.

[0017] According to a preferred embodiment of the present invention, in step 1), the heating temperature is 60-70°C.

[0018] According to a preferred embodiment of the present invention, in step 1), the phase transfer catalyst is one of tetrabutylammonium chloride, tetrabutylammonium bromide, and hexadecyltrimethylammonium bromide.

[0019] More preferably, in step 1), the phase transfer catalyst is tetrabutylammonium bromide.

[0020] According to a preferred embodiment of the present invention, in step 1), the amount of phase transfer catalyst used is 2.5-3.5% of the mass of sodium thiocyanate.

[0021] According to a preferred embodiment of the present invention, in step 2), the molar ratio of γ-chloropropyltriethoxysilane to sodium thiocyanate is 1:1.03-1.05.

[0022] Most preferably, in step 2), the molar ratio of γ-chloropropyltriethoxysilane to sodium thiocyanate is 1:1.04.

[0023] According to a preferred embodiment of the present invention, in step 2), the time for adding γ-chloropropyltriethoxysilane is 0.5 h.

[0024] According to a preferred embodiment of the present invention, in step 2), the reaction temperature is between 80-90°C.

[0025] According to a preferred embodiment of the present invention, in step 2), the reaction time is 1.5-2 hours.

[0026] This invention employs an aqueous phase method for the catalytic synthesis of 3-thiocyanopropyltriethoxysilane. A mixed solution of water and ethanol is used as the solvent to ensure complete dissolution of sodium thiocyanate, overcoming the problems of insufficient dissolution or excessively long dissolution times associated with solvent-based methods using organic solvents. Simultaneously, sodium bicarbonate is used as a buffer to maintain the system pH between 8 and 9, avoiding hydrolysis issues during subsequent dropwise addition and the reaction process, thus improving the reaction yield, which reaches a maximum of 92.10%. Furthermore, by converting the separated aqueous phase into a saturated sodium chloride solution to wash the organic phase, the utilization rate of the reaction solution is improved. Detailed Implementation

[0027] The following embodiments are given to further illustrate the present invention. However, it should be noted that the following embodiments are illustrative and not limiting, and should not be used to limit the scope of protection of the present invention.

[0028] Example 1

[0029] A method for preparing 3-thiocyanopropyltriethoxysilane using an aqueous phase method, comprising the following steps:

[0030] 83.5 g of sodium thiocyanate was added to a mixed solvent of water and alcohol (480 g of water and 100 g of ethanol), and 0.18 g of sodium bicarbonate was added as a buffer. The mixture was stirred and heated to 65 °C. After 5 minutes, the sodium thiocyanate and sodium bicarbonate were completely dissolved. The pH of the system was controlled at 8. 2.5 g of tetrabutylammonium bromide was added, and after stirring for 5 minutes, 239.84 g of γ-chloropropyltriethoxysilane was added dropwise. The addition was completed in 0.5 hours. After the addition was completed, the mixture was reacted at 85 °C for 2 hours to obtain the crude product.

[0031] The liquid was separated into an organic phase on top and an aqueous phase on the bottom. Sodium chloride was added to the aqueous phase to saturate it. The organic phase was washed with the treated aqueous phase and then adsorbed with 4g of activated carbon. After filtration, it was subjected to vacuum distillation. After 1.5 hours, a transparent liquid thiocyanopropyltriethoxysilane was obtained, with a content of 98.61% and a product yield of 92.10%.

[0032] Example 2

[0033] A method for preparing 3-thiocyanopropyltriethoxysilane using an aqueous phase method, comprising the following steps:

[0034] 83.5 g of sodium thiocyanate was added to a mixed solvent of water and alcohol (480 g of water and 100 g of isopropanol), and 0.18 g of sodium bicarbonate was added as a buffer. The mixture was stirred and heated to 68 °C. After 4 minutes, the sodium thiocyanate and sodium bicarbonate were completely dissolved. The pH of the system was controlled at 9. 2.5 g of tetrabutylammonium bromide was added, and after stirring for 5 minutes, 238.47 g of γ-chloropropyltriethoxysilane was added dropwise. The addition was completed in 35 minutes. After the addition was completed, the mixture was reacted at 86 °C for 2 hours to obtain the crude product.

[0035] The liquid was separated into an organic phase on top and an aqueous phase on the bottom. A certain amount of sodium chloride was added to the aqueous phase to saturate it. The organic phase was washed with the treated lower aqueous phase and then adsorbed with 4g of activated carbon. After filtration, it was subjected to vacuum distillation. After 1.8 hours, a transparent liquid thiocyanopropyltriethoxysilane was obtained, with a content of 98.30% and a product yield of 91.13%.

[0036] Example 3

[0037] A method for preparing 3-thiocyanopropyltriethoxysilane using an aqueous phase method, comprising the following steps:

[0038] 83.5 g of sodium thiocyanate was added to a mixed solvent of water and alcohol (480 g of water and 100 g of methanol), and 0.18 g of sodium bicarbonate was added as a buffer. The mixture was stirred and heated to 70 °C. After 3.5 minutes, the sodium thiocyanate and sodium bicarbonate were completely dissolved. The pH of the system was controlled at 8. 2.5 g of tetrabutylammonium bromide was added, and after stirring for 5 minutes, 236.21 g of γ-chloropropyltriethoxysilane was added dropwise. The addition was completed in 28 minutes. After the addition was completed, the mixture was reacted at 86 °C for 1.5 hours to obtain the crude product.

[0039] The liquid was separated into an organic phase on top and an aqueous phase on the bottom. A certain amount of sodium chloride was added to the aqueous phase to saturate it. The organic phase was washed with the treated lower aqueous phase and then adsorbed with 4g of activated carbon. After filtration, it was subjected to vacuum distillation. After 1.6 hours, a transparent liquid thiocyanopropyltriethoxysilane product was obtained, with a content of 97.96% and a product yield of 90.01%.

[0040] Example 4

[0041] A method for preparing 3-thiocyanopropyltriethoxysilane using an aqueous phase method, comprising the following steps:

[0042] 83.5 g of sodium thiocyanate was added to a mixed solvent of water and alcohol (480 g of water and 100 g of ethanol), and 0.18 g of sodium bicarbonate was added as a buffer. The mixture was stirred and heated to 67 °C. After 5 minutes, the sodium thiocyanate and sodium bicarbonate were completely dissolved. The pH of the system was controlled at 8. 2.5 g of cetyltrimethylammonium bromide was added, and after stirring for 5 minutes, 239.84 g of γ-chloropropyltriethoxysilane was added dropwise. The addition was completed in 0.5 hours. After the addition was completed, the mixture was reacted at 86 °C for 2 hours to obtain the crude product.

[0043] The liquid was separated into an organic phase on top and an aqueous phase on the bottom. Sodium chloride was added to the aqueous phase to saturate it. The organic phase was washed with the treated lower aqueous phase and then adsorbed with 4g of activated carbon. After filtration, it was subjected to vacuum distillation. After 1.5 hours, a transparent liquid thiocyanopropyltriethoxysilane was obtained, with a content of 97.8% and a product yield of 89.89%.

[0044] Example 5

[0045] A method for preparing 3-thiocyanopropyltriethoxysilane using an aqueous phase method, comprising the following steps:

[0046] 83.5g of sodium thiocyanate was added to a mixed solvent of water and alcohol (480g of water and 100g of ethanol), and 0.18g of sodium bicarbonate was added as a buffer. The mixture was stirred and heated to 65°C. After 5 minutes, the sodium thiocyanate and sodium bicarbonate were completely dissolved. The pH of the system was controlled at 8. 2.5g of tetrabutylammonium chloride was added, and after stirring for 5 minutes, 239.84g of γ-chloropropyltriethoxysilane was added dropwise. The addition was completed in 0.5 hours. After the addition was completed, the mixture was reacted at 85°C for 2 hours to obtain the crude product.

[0047] The liquid was separated into an organic phase on top and an aqueous phase on the bottom. Sodium chloride was added to the aqueous phase to saturate it. The organic phase was washed with the treated aqueous phase and then adsorbed with 4g of activated carbon. After filtration, it was subjected to vacuum distillation. After 1.5 hours, a transparent liquid thiocyanopropyltriethoxysilane was obtained, with a content of 97.48% and a product yield of 89.23%.

[0048] Comparative Example 1

[0049] The method described in the same way as in Example 1 differs in that:

[0050] Add 83.5g of sodium thiocyanate to 580g of water, and proceed as in Example 1.

[0051] A transparent liquid thiocyanopropyltriethoxysilane product was obtained, with a content of 82.3% and a product yield of 79.8%.

[0052] Comparative Example 2

[0053] The method described in the same way as in Example 1 differs in that:

[0054] Add 83.5g of sodium thiocyanate to 580g of ethanol, and proceed as in Example 1.

[0055] A transparent liquid thiocyanopropyltriethoxysilane product was obtained, with a content of 80.8% and a product yield of 77.5%.

[0056] Comparative Example 3

[0057] The method described in the same way as in Example 1 differs in that:

[0058] Sodium bicarbonate was not added; all other procedures were carried out as in Example 1.

[0059] A transparent liquid thiocyanopropyltriethoxysilane product was obtained, with a content of 60.23% and a product yield of 56.4%.

Claims

1. A method for preparing 3-thiocyanopropyltriethoxysilane using an aqueous phase method, comprising the following steps: 1) Add sodium thiocyanate to a mixed solvent of water and alcohol, add sodium bicarbonate, mix, stir, and heat until sodium thiocyanate and sodium bicarbonate are completely dissolved, and add a phase transfer catalyst; the alcohol in the mixed solvent of water and alcohol is ethanol, isopropanol, or methanol; the mass ratio of alcohol to water in the mixed solvent of water and alcohol is 1:(3-6), the mass ratio of sodium thiocyanate to the mixed solvent of water and alcohol is 1:6.5-7.5, the amount of sodium bicarbonate added is to make the pH reach 8-9, the heating temperature is 60-70℃, and the phase transfer catalyst is tetrabutylammonium bromide; the amount of phase transfer catalyst is 2.5-3.5% of the mass of sodium thiocyanate; 2) Add γ-chloropropyltriethoxysilane dropwise. After the addition is complete, react for 1.5-2 hours to obtain the crude product. 3) After separation, sodium chloride was added to the aqueous phase to saturate it, and the organic phase was washed. The filtered solution was then distilled to obtain a colorless and transparent 3-thiocyanopropyltriethoxysilane product.

2. The method according to claim 1, characterized in that, In step 2), the molar ratio of γ-chloropropyltriethoxysilane to sodium thiocyanate is 1:1.03-1.

05.

3. The method according to claim 1, characterized in that, In step 2), the time for adding γ-chloropropyltriethoxysilane is 0.5-0.6 hours.

4. The method according to claim 1, characterized in that, In step 2), the reaction temperature is between 80-90℃.

5. The method according to claim 1, characterized in that, In step 2), the reaction time is 1.5-2 hours.