A method for producing mercaptopropyltriethoxysilane

Abstract

The invention discloses a method for producing mercaptopropyl triethoxysilane, wherein chloropropyl triethoxysilane (γ2) and sodium hydrosulfide are used as raw materials, and mercaptopropyl triethoxysilane is synthesized under the action of a phase transfer catalyst, a pH regulator and an inhibitor. The reaction product is subjected to liquid separation and purification to obtain a target product. The invention has mild reaction conditions, the purity of the product mercaptopropyl triethoxysilane is greater than or equal to 98%, and the yield is greater than or equal to 95%. The invention has the advantages of simple operation, continuous controllability and high process efficiency.

Description

Technical Field

[0001] The invention relates to a method for producing mercaptopropyl triethoxysilane (KH580), and in particular to a method for producing mercaptopropyl triethoxysilane with simple operation, mild reaction conditions, continuous control and high process efficiency. Background Art

[0002] Silane coupling agent KH580 is a sulfur-containing organosilicon compound that mainly acts between rubber and silica filler to improve the performance of rubber, and can also be used as an adhesive to bond rubber to glass and metal substrates. In the synthesis method of producing mercaptopropyl triethoxysilane, the pH of the water phase must be maintained at 4-9 to allow the sodium hydrosulfide in the water phase to fully react with chloropropyl triethoxysilane, reduce side reactions and increase yield.

[0003] There are many processes for synthesizing KH580, among which phase transfer catalysis is the most important synthesis process. This synthesis process uses a certain concentration of NaHS solution and chloropropyltriethoxysilane as raw materials to obtain mercaptopropyltriethoxysilane. During the reaction, due to the presence of water, the following side reactions will occur: the ethoxy groups in chloropropyltriethoxysilane and mercaptopropyltriethoxysilane are hydrolyzed to form corresponding silanols, and under the reaction conditions (heating) of this synthesis process, the silanol molecules condense to form condensates containing Si-O-Si structures, and a large number of linear dimers or trimers are generated. Some of the polymers still contain ethoxy functional groups, which further condense to form cross-shaped solid polymers due to the presence of ethoxy functional groups. The above side reaction products will affect the main reaction in the system, prolong the reaction time, and reduce the yield and purity of the product. It is generally believed that controlling the pH of the reaction aqueous solution at 3-8 will inhibit the occurrence of the above-mentioned side reactions, so it is necessary to add a pH regulator to the organic reaction mixture before adding the NaHS solution to adjust the pH value of the reaction. Suitable pH regulators have a great influence on the synthesis process. Generally, sulfur dioxide SO2, carbon dioxide CO2, hydrogen sulfide H2S, phosphoric acid H3PO4, boric acid H3PO3, etc. are used as pH regulators. The product purity obtained by using these pH regulators is only 93%, and the yield is only about 90%.

[0004] CN107522730A discloses a method for preparing γ-mercaptopropyltriethoxysilane, which first adds industrial-grade sodium hydrosulfide and water to a reactor, stirs evenly, and slowly heats up to 60-65°C; then adjusts the pH to 7.2 with sodium bicarbonate; then adds a phase transfer catalyst and an inorganic catalyst, heats up to 75°C; after stirring for 10-15 minutes, cools to 60-70°C; adds hexamethyldisiloxane to γ-chloropropyltriethoxysilane, stirs evenly, and slowly drips into the reactor for 1-2 hours; maintains the reaction at 80-85°C for 3-5 hours, stops the reaction when the content of the raw material γ-chloropropyltriethoxysilane is less than 2%, stands and cools to room temperature, separates the liquid to remove water, performs vacuum distillation, and collects the product. The patent adds inorganic catalysts such as potassium iodide to accelerate the reaction, and uses sodium bicarbonate as a pH regulator. Sodium bicarbonate has a weak acidity adjustment ability, a short-lived effect, and releases gas during the neutralization process, increasing the pressure in the reactor, which is dangerous. In addition, the reaction needs to be carried out at a higher temperature, at which the ethoxy group is more easily hydrolyzed, resulting in more side reactions, further affecting the purity and yield of the product. Summary of the invention

[0005] Aiming at the side reactions existing in the production process of mercaptopropyltriethoxysilane, the present invention provides a method for producing mercaptopropyltriethoxysilane, which optimizes the process conditions, reduces the reaction temperature, inhibits the occurrence of side reactions, and improves the purity and yield of the product.

[0006] The specific technical solutions of the present invention are as follows:

[0007] A method for producing mercaptopropyltriethoxysilane, comprising the following steps:

[0008] (1) uniformly mixing chloropropyltriethoxysilane, a phase transfer catalyst, and a pH adjuster to obtain a solution A;

[0009] (2) Add sodium hydrosulfide and inhibitor into water until they are completely dissolved to obtain solution B;

[0010] (3) Heat both solution A and solution B to the reaction temperature, then add solution B dropwise into solution A, continue the reaction after the addition is complete, and perform post-treatment after the reaction to obtain mercaptopropyltriethoxysilane.

[0011] Further, the reaction equation is as follows:

[0012]

[0013] Furthermore, the phase transfer catalyst is tetrabutylammonium bromide, and the molar ratio of the phase transfer catalyst to chloropropyltriethoxysilane is 1:0.02-0.04.

[0014] Furthermore, the pH regulator is citric acid. The present invention uses citric acid as a pH regulator to control the pH to be stable at 4-5. Citric acid is an organic acid, which has a good regulating effect in the organic phase of the reaction, can better stabilize the pH during the reaction, make the pH value change and fluctuation during the reaction smaller, is conducive to the forward progress of the reaction, and can inhibit the occurrence of side reactions, thereby improving the purity and yield of the product.

[0015] Furthermore, the inhibitor is a sulfonyl isocyanate compound, which can inhibit the condensation of silanol molecules to form a condensate containing a Si-O-Si structure, thereby improving the reaction yield and purity. Among them, the sulfonyl isocyanate compound includes toluenesulfonyl isocyanate, benzenesulfonyl isocyanate, chlorosulfonyl isocyanate, etc., preferably chlorosulfonyl isocyanate.

[0016] Furthermore, the molar ratio of chloropropyltriethoxysilane to the inhibitor is 1:0.04-0.05.

[0017] Furthermore, the molar ratio of chloropropyltriethoxysilane to sodium hydrosulfide is 1:1.1-1.2.

[0018] Furthermore, the reaction temperature is 60-65°C.

[0019] Furthermore, the dropping speed of solution B is 2-3 ml / min. At this dropping speed, the reaction can be continued for 3-4 hours after the dropping is completed.

[0020] Furthermore, after the reaction, the organic phase is filtered and separated to obtain a crude product of mercaptopropyl triethoxysilane, and the crude product is purified by distillation to obtain a pure product of mercaptopropyl triethoxysilane.

[0021] The present invention has the following advantages:

[0022] 1. The present invention optimizes the pH regulator to adjust the reaction pH from 3-8 to 4-5, so that the pH value fluctuation during the reaction is small and the occurrence of side reactions can be suppressed, thereby improving the purity and yield of the product.

[0023] 2. The present invention adds an inhibitor during the reaction process, which can inhibit the occurrence of side reactions and further improve the purity and yield of the product.

[0024] 3. In the reaction process of the present invention, the raw materials are added in a dropwise manner, and the inhibitor is added together with sodium hydrosulfide in a dropwise manner. In the presence of the inhibitor, sodium hydrosulfide and chloropropyltriethoxysilane react, which can better inhibit the occurrence of side reactions.

[0025] 4. The method of the present invention has low reaction temperature, simple operation, continuous controllability, and high process efficiency. The yield of the obtained mercaptopropyltriethoxysilane product is greater than or equal to 95%, and the purity is greater than or equal to 98%. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The gas chromatogram of the product obtained in Example 1 is shown in FIG.

[0027] Figure 2 The gas chromatogram of the product obtained in Example 3 is shown in FIG.

[0028] Figure 3 The gas chromatogram of the product obtained in Example 4 is shown in FIG.

[0029] Figure 4 The gas chromatogram of the product obtained in Comparative Example 2 is shown in FIG.

[0030] Figure 5 The gas chromatogram of the product obtained in Comparative Example 3 is shown in FIG.

[0031] Figure 6 The gas chromatogram of the product obtained in Comparative Example 4 is shown in FIG. DETAILED DESCRIPTION

[0032] The present invention is further described below by means of specific examples. The following description is merely exemplary and does not limit the content thereof.

[0033] In the following examples, all reagents used are commercially available products, among which chloropropyltriethoxysilane (γ2), sodium hydrosulfide, tetrabutylammonium bromide, citric acid, and sulfonyl isocyanate compounds are all of industrial grade.

[0034] In the following examples, the yield is calculated as follows: mass of product / theoretical mass of product.

[0035] Example 1

[0036] 1. Take 45.8g of sodium hydrosulfide solid (content 70wt%) and 4.1g of 4-toluenesulfonyl isocyanate, add them into 30ml of water, heat to 65℃ and stir until all dissolved, and maintain this temperature for later use;

[0037] 2. Take 120g of chloropropyltriethoxysilane in a three-necked flask, add 4.8g of tetrabutylammonium bromide and 10g of citric acid in the flask in sequence, and test the solution pH to 4. Mix well and heat to 60°C for later use;

[0038] 3. Add the solution in step 1 to the solution in step 2 at a dropping speed of 2.5 ml / min. Keep the system temperature at 60-65°C during the whole process. Continue the reaction for 3 hours after the addition is completed.

[0039] 4. After the reaction is completed, the mixture is filtered and the organic phase is separated to obtain a crude product of mercaptopropyl triethoxysilane. The crude product is distilled at 90°C and 100 Pa to obtain 112.9 g of pure mercaptopropyl triethoxysilane with a purity of 98.1%. The yield is 95% based on chloropropyl triethoxysilane.

[0040] Example 2

[0041] Pure mercaptopropyl triethoxysilane was prepared according to the method of Example 1, except that the pH of the solution was adjusted to 5 with citric acid. The purity of the pure mercaptopropyl triethoxysilane finally obtained was 95.1%, and the yield was 98.2% based on chloropropyl triethoxysilane.

[0042] Example 3

[0043] Pure mercaptopropyl triethoxysilane was prepared according to the method of Example 1, except that 4.1 g of 4-toluenesulfonyl isocyanate was replaced by 3.2 g of chlorosulfonyl isocyanate. The purity of the finally obtained pure mercaptopropyl triethoxysilane was 99.2%, and the yield was 97.9% based on chloropropyl triethoxysilane.

[0044] Example 4

[0045] Pure mercaptopropyl triethoxysilane was prepared according to the method of Example 1, except that 4.1 g of 4-toluenesulfonyl isocyanate was replaced by 4.3 g of benzenesulfonyl isocyanate. The purity of the finally obtained pure mercaptopropyl triethoxysilane was 98.2%, and the yield was 95.5% based on chloropropyl triethoxysilane.

[0046] Comparative Example 1

[0047] Pure mercaptopropyl triethoxysilane was prepared according to the method of Example 1, except that the mass of sodium hydrosulfide solid (content 70wt%) was 39.8g. The purity of the finally obtained pure mercaptopropyl triethoxysilane was 95%, and the yield was 86% based on chloropropyl triethoxysilane.

[0048] Comparative Example 2

[0049] Pure mercaptopropyl triethoxysilane was prepared according to the method of Example 1, except that citric acid was replaced by phosphoric acid H3PO4, and the pH of the system was controlled to be 4. The purity of the finally obtained pure mercaptopropyl triethoxysilane was 90.1%, and the yield was 82% based on chloropropyl triethoxysilane.

[0050] Comparative Example 3

[0051] Pure mercaptopropyl triethoxysilane was prepared according to the method of Example 1, except that citric acid was replaced with sodium bicarbonate and the pH of the system was controlled to be 6-8. The purity of the finally obtained pure mercaptopropyl triethoxysilane was 91.5%, and the yield was 83% based on chloropropyl triethoxysilane.

[0052] Comparative Example 4

[0053] 1. Take 45.8g of sodium hydrosulfide solid (content 70wt%) in a three-necked flask, add 3.2g of sulfonyl isocyanate compound to 30ml of water, then add 4.8g of tetrabutylammonium bromide and 10g of citric acid, heat to 65℃ and stir until all dissolved, and maintain this temperature for later use;

[0054] 2. Take 120g of chloropropyltriethoxysilane and add it dropwise to the solution in step 1 at a dropping rate of 2.5ml / min. Keep the system temperature at 60-65°C during the whole process. Continue the reaction for 3h after the addition is completed.

[0055] 4. After the reaction is completed, the mixture is filtered and the organic phase is separated to obtain crude mercaptopropyl triethoxysilane. The crude product is distilled at 90°C and 100 Pa to obtain pure mercaptopropyl triethoxysilane with a purity of 93.7%. The yield is 84% ​​based on chloropropyl triethoxysilane.

[0056] Comparative Example 5

[0057] Pure mercaptopropyl triethoxysilane was prepared according to the method of Example 1, except that 4-toluenesulfonyl isocyanate was not added. The purity of the finally obtained pure mercaptopropyl triethoxysilane was 97.4%, and the yield was 90% based on chloropropyl triethoxysilane.

Claims

1. A method for producing mercaptopropyltriethoxysilane, characterized in that The following methods are included: (1) uniformly mixing chloropropyltriethoxysilane, a phase transfer catalyst, and a pH adjuster to obtain a solution A; (2) Add sodium hydrosulfide and inhibitor into water until they are completely dissolved to obtain solution B; (3) raising both solution A and solution B to the reaction temperature, then dropping solution B into solution A, continuing the reaction after the dropping is complete, and post-treating after the reaction to obtain mercaptopropyl triethoxysilane; The pH regulator is citric acid, which ensures that the pH of the system is 4-5 during the reaction; The inhibitor is toluenesulfonyl isocyanate, benzenesulfonyl isocyanate, chlorosulfonyl isocyanate ， The molar ratio of chloropropyltriethoxysilane to the inhibitor is 1:0.04-0.05; The drop rate of solution B is 2-3 ml / min; The molar ratio of chloropropyltriethoxysilane to sodium hydrosulfide is 1:1.1-1.

2.

2. The method according to claim 1, characterized in that: The phase transfer catalyst is tetrabutylammonium bromide.

3. The method according to claim 1, characterized in that: The molar ratio of the amount of the phase transfer catalyst to the raw material is 1:0.02-0.

04.

4. The method according to claim 1, characterized in that: The inhibitor is chlorosulfonyl isocyanate.

5. The method according to claim 1, characterized in that: The reaction temperature is 60-65°C.

6. The method according to claim 1, characterized in that: After the dripping is completed, continue the reaction for 3-4 hours.

7. The method according to claim 1, characterized in that: after the reaction, the organic phase is filtered and separated to obtain a crude product of mercaptopropyl triethoxysilane, and the crude product is distilled and purified to obtain a pure product of mercaptopropyl triethoxysilane.

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