Preparation method of methacryloyloxypropyltriacetoxysilane

Abstract

The invention provides a preparation method of methacryloyloxypropyltriacetoxysilane, and relates to the field of organic silicon synthesis, the preparation method comprises the following steps: adding a solvent, sodium acetate and a first polymerization inhibitor into a reaction container; under the protection of inert gas, dropwise adding methacryloyloxypropyl trichlorosilane and a second polymerization inhibitor; after dropwise adding is completed, continuously reacting for a period of time, filtering to remove solid salt, and distilling to remove the solvent to obtain a finished product methacryloyloxypropyltriacetoxysilane; according to the method, sodium acetate and methacryloyloxypropyltrichlorosilane are taken as raw materials, two polymerization inhibitors, namely p-hydroxyanisole and 2, 6-di-tert-butyl p-cresol, are compounded for use, a specific polymerization inhibitor adding sequence is adopted, and methacryloyloxypropyltriacetoxysilane can be synthesized under the condition that a catalyst is not used.

Description

Technical Field

[0001] This invention relates to the field of organosilicon synthesis technology, specifically to a method for preparing methacryloyloxypropyltriacetoxysilane. Background Technology

[0002] Methacryloxypropyltriacetoxysilane is a common crosslinking agent, and there are two main existing synthetic methods. One is the addition-acylation method, in which allyl methacrylate and trichlorosilane undergo hydrosilylation to obtain methacryloxypropyltrichlorosilane, which is then synthesized by acylation with glacial acetic acid or acetic anhydride. The other is the acylation-condensation method, in which chloropropyltrichlorosilane undergoes acylation with glacial acetic acid or acetic anhydride to obtain chloropropyltriacetoxysilane, which is then prepared by condensation with sodium methacrylate. However, both of these synthetic methods suffer from long synthetic routes, and due to the photosensitive and thermosensitive nature of the product, it is prone to crosslinking and solidification during the addition reaction and distillation process, affecting product purity, and making industrial production difficult.

[0003] To address this issue, prior art patent application CN114315890A discloses a method for preparing methacryloyloxypropyltriacetoxysilane. The method involves mixing methacryloyloxypropyltrimethoxysilane, a polymerization inhibitor, and a catalyst, adding acetic anhydride, and conducting an acyloxy group exchange reaction under stirring, heating, and slight negative pressure conditions to obtain a reaction product. The reaction product is then subjected to vacuum distillation to remove and recover residual acetic anhydride, yielding a crude product. Activated carbon is added to the crude product to adsorb residual catalyst, followed by filtration to obtain methacryloyloxypropyltriacetoxysilane.

[0004] However, the aforementioned existing technologies involve the use of catalysts such as ytterbium trifluoromethanesulfonate, lanthanum trifluoromethanesulfonate, or europium trifluoromethanesulfonate, which are corrosive, and require subsequent steps to adsorb residual catalysts using activated carbon. The synthesis process is relatively complex, and the color of the product cannot be guaranteed. Summary of the Invention

[0005] This invention addresses the aforementioned problems in the prior art by providing a method for preparing methacryloyloxypropyltriacetoxysilane, which requires no catalyst, simplifies the synthesis process, and produces a product with low color.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a method for preparing methacryloxypropyltriacetoxysilane, characterized by comprising the following steps: Solvent, sodium acetate, and the first polymerization inhibitor are added to the reaction vessel at room temperature; Under inert gas protection, methacryloyloxypropyltrichlorosilane and a second polymerization inhibitor are added dropwise; After the addition is complete, continue the reaction for a period of time, filter to remove the solid salt, and distill to remove the solvent to obtain the finished product, methacryloyloxypropyltriacetoxysilane.

[0007] Furthermore, the molar ratio of chlorine atoms to sodium acetate in the methacryloxypropyltrichlorosilane is 1:3-3.5, preferably 1:3.1.

[0008] Furthermore, the first polymerization inhibitor is p-hydroxyanisole (MEHQ), and the amount of the first polymerization inhibitor is 50-150 ppm of the total mass of methacryloyloxypropyltrichlorosilane and acetate, preferably 76 ppm.

[0009] Furthermore, the second polymerization inhibitor is 2,6-di-tert-butyl-p-cresol (BHT), and the amount of the second polymerization inhibitor does not exceed 2‰ of the mass of methacryloyloxypropyltrichlorosilane, preferably 1‰.

[0010] Furthermore, the solvent is ethyl acetate.

[0011] Furthermore, after the addition is complete, the reaction is stopped when the pH of the reaction solution reaches 5-7 (preferably pH 6).

[0012] Furthermore, the inert gas is nitrogen.

[0013] Furthermore, the reaction temperature is controlled at 15-45℃, preferably 20-40℃.

[0014] Further, the distillation operation is as follows: the filtrate and washing salt solution are desolventized under vacuum until the internal temperature reaches 90°C and then the distillation stops. Nitrogen protection is used for cooling to obtain the finished product, methacryloyloxypropyltriacetoxysilane. Specifically, negative pressure distillation is carried out at a vacuum degree of 700-730 mmHg and a processing time of more than 1 hour at 90°C.

[0015] Furthermore, to ensure product yield, after filtering to remove solid salt, the solvent is used to perform a salt washing operation to obtain a salt washing solution. The filtrate and the salt washing solution are distilled together, and the finished product, methacryloyloxypropyltriacetoxysilane, is obtained after distillation. Its specifications are: color value less than 1, chloride ion content: <10ppm, and purity of ≥97%.

[0016] The beneficial effects of the present invention are as follows: The present invention uses sodium acetate and methacryloxypropyltrichlorosilane as raw materials, combined with two polymerization inhibitors, p-hydroxyanisole and 2,6-di-tert-butyl-p-cresol, and adopts a specific order of addition of polymerization inhibitors, to synthesize methacryloxypropyltriacetoxysilane under conditions without the use of a catalyst. On the one hand, it effectively prevents polymerization of the finished product during distillation due to excessively high bottom temperature, resulting in a product purity of over 97%, a color of <1, and a chloride ion content of <10ppm, ensuring product quality. On the other hand, the process of this invention only requires removing the solvent from the synthesis solution, leaving only the product at the bottom of the vessel. Under nitrogen protection, the temperature is controlled at 15-45℃, which is a low temperature condition and eliminates the need for activated carbon adsorption, thus simplifying the process, saving significant energy consumption, and reducing production costs. On the other hand, the combined use of the above-mentioned polymerization inhibitors eliminates the need for special removal during later product storage, preventing contamination of the finished product's appearance and color. Furthermore, these inhibitors can be used as antioxidants and anti-aging agents, simplifying the removal of polymerization inhibitors from the finished product and reducing production costs. Finally, by monitoring the pH of the synthesis solution during the synthesis process to between 5 and 7, it is possible to more clearly and intuitively determine whether the reaction has been completed, facilitating operation. Detailed Implementation

[0017] The principles and features of the present invention are described below. The embodiments given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0018] Example 1 The preparation method of methacryloyloxypropyltriacetoxysilane in this embodiment is carried out according to the following steps: Step 1: Add 97.56g (1.132mol) of ethyl acetate and 97.56g (1.189mol) of sodium acetate to the bottom of the reactor at room temperature, and then add 0.015g (76ppm) of p-hydroxyanisole (MEHQ) polymerization inhibitor. Step 2: Under nitrogen protection, heat to 20°C and begin adding 100g (0.382mol) of methacryloyloxypropyltrichlorosilane and 0.1g of 2,6-di-tert-butyl-p-cresol (BHT) (the amount of BHT is 1‰ of the amount of methacryloyloxypropyltrichlorosilane).

[0019] Step 3: After the addition is complete, continue to keep the reaction at a constant temperature. During the reaction, take a sample to test the pH of the reaction solution. Stop the reaction when the pH reaches 6 (reaction time 2 hours) and proceed to the next step. Step 4: Filter the synthesis solution using a filter to obtain the filtrate, and then wash the salt with the solvent ethyl acetate to obtain the washing solution; Step 5: The filtrate and washing brine are subjected to vacuum distillation to remove low-temperature silane. The vacuum degree is 700-730 mmHg. Distillation is stopped when the internal temperature reaches 90℃ and no more distillation occurs. The mixture is then cooled under nitrogen protection. The final product, methacryloxypropyltriacetoxysilane, is obtained at the bottom of the vessel. The product has a color value <1 (Hach colorimeter), a yield of 90%, a purity of 98%, and a chloride ion content <10 ppm.

[0020] Example 2 Step 1: Add 97.56g (1.132mol) of ethyl acetate and 97.56g (1.189mol) of sodium acetate to the bottom of the reactor at room temperature, and then add 0.015g (76ppm) of p-hydroxyanisole (MEHQ) polymerization inhibitor. Step 2: Under nitrogen protection, heat to 17°C and begin adding 100g (0.382mol) of methacryloyloxypropyltrichlorosilane and 0.1g of 2,6-di-tert-butyl-p-cresol (BHT) (the amount of BHT is 1‰ of the amount of methacryloyloxypropyltrichlorosilane).

[0021] Step 3: After the addition is complete, continue to keep the reaction at a constant temperature. During the reaction, take a sample to test the pH of the reaction solution. Stop the reaction when the pH reaches 6 (reaction time 2 hours) and proceed to the next step. Step 4: Filter the synthesis solution using a filter to obtain the filtrate, and then wash the salt with the solvent ethyl acetate to obtain the washing solution; Step 5: The filtrate and washing salt solution are subjected to vacuum distillation to remove low concentrations. The vacuum degree is 700-730 mmHg. Distillation is stopped when the internal temperature reaches 90℃ and no more distillation occurs. The product, methacryloxypropyltriacetoxysilane, is obtained at the bottom of the vessel. The product has a color of <1, a yield of 91%, and a purity of 97.84%.

[0022] Example 3 Step 1: Add 97.56g (1.132mol) of ethyl acetate and 97.56g (1.189mol) of sodium acetate to the bottom of the reactor at room temperature, and then add 0.029g (150ppm) of p-hydroxyanisole (MEHQ) polymerization inhibitor. Step 2: Under nitrogen protection, heat to 20°C and begin adding 100g (0.382mol) of methacryloyloxypropyltrichlorosilane and 0.1g of 2,6-di-tert-butyl-p-cresol (BHT) (the amount of BHT is 1‰ of the amount of methacryloyloxypropyltrichlorosilane).

[0023] Step 3: After the addition is complete, continue to keep the reaction at a constant temperature. During the reaction, take a sample to test the pH of the reaction solution. Stop the reaction when the pH reaches 6 (reaction time 2 hours) and proceed to the next step. Step 4: Filter the synthesis solution using a filter to obtain the filtrate, and then wash the salt with the solvent ethyl acetate to obtain the washing solution; Step 5: The filtrate and washing salt solution are subjected to vacuum distillation to remove the low-purity liquid. The negative pressure vacuum degree is 700-730 mmHg. The distillation is stopped when the internal temperature reaches 90℃ and no more distillation occurs. The product is methacryloyloxypropyltriacetoxysilane with a purity of 97.64% obtained from the bottom of the vessel.

[0024] Example 4 Step 1: Add 97.56g (1.132mol) of ethyl acetate and 97.56g (1.189mol) of sodium acetate to the bottom of the reactor at room temperature, and then add 0.01g (50ppm) of p-hydroxyanisole (MEHQ) polymerization inhibitor. Step 2: Under nitrogen protection, heat to 20°C and begin adding 100g (0.382mol) of methacryloyloxypropyltrichlorosilane and 0.1g of 2,6-di-tert-butyl-p-cresol (BHT) (the amount of BHT is 1‰ of the amount of methacryloyloxypropyltrichlorosilane).

[0025] Step 3: After the addition is complete, continue to keep the reaction at a constant temperature. During the reaction, take a sample to test the pH of the reaction solution. Stop the reaction when the pH reaches 6 (reaction time 2 hours) and proceed to the next step. Step 4: Filter the synthesis solution using a filter to obtain the filtrate, and then wash the salt with the solvent ethyl acetate to obtain the washing solution; Step 5: Vacuum distillation is performed on the filtrate and washing salt solution to remove low-purity liquid. The negative pressure vacuum degree is 700-730 mmHg. The distillation is stopped when the internal temperature reaches 90℃ and no more distillation occurs. The product is methacryloyloxypropyltriacetoxysilane with a purity of 98.54% obtained from the bottom of the vessel.

[0026] Comparative Example 1 The preparation method of the methacryloyloxypropyltriacetoxysilane in this comparative example is basically the same as that in Example 1, except that the polymerization inhibitor BHT is replaced with an equal mass of MEHQ.

[0027] The results showed that the product yield was 65.81% and the content was 89.66%. This was because polymerization occurred in the vessel during the distillation and washing of the brine, which led to a decrease in product yield.

[0028] Comparative Example 2 The preparation method of the methacryloyloxypropyltriacetoxysilane in this comparative example is basically the same as that in Example 1, except that the polymerization inhibitor BHT and MEHQ are added before the reaction.

[0029] The results showed that when the polymerization inhibitors BHT and MEHQ were added simultaneously before the reaction, the yield of the finished product was 77.47%, the content was 94.95%, and the color of the finished product was 390.

[0030] Comparative Example 3 The preparation method of the methacryloyloxypropyltriacetoxysilane in this comparative example is basically the same as that in Example 1, except that the solvent is replaced with n-hexane.

[0031] The results showed that the reaction rate was significantly slower. After 5 hours of reaction, the yield of the product was only 32.6% (with no industrial value) and the content was 90.20%.

[0032] Comparative Example 4 The preparation method of the methacryloyloxypropyltriacetoxysilane in this comparative example is basically the same as that in Example 1, except that the solvent is replaced with xylene.

[0033] The results showed that xylene has a high boiling point and is difficult to remove completely from the finished product, resulting in a low content in the finished product. The yield of the finished product was 70.21%, and the content was 95.8%. Furthermore, the presence of xylene is detrimental to the downstream application of the product.

[0034] The instrument used to detect the color of the finished product is a Hash colorimeter, model LICO690; the instrument used to detect chloride ions in the finished product is an automatic precipitation titrator, model ET28.

[0035] Table 1

[0036] As shown in Table 1, without the use of a catalyst, the purity of the methacryloxypropyltriacetoxysilanes obtained in each embodiment of the present invention is above 97%, and the color value is <1. In contrast, in Comparative Example 1, after replacing the composite polymerization inhibitor with a single polymerization inhibitor, both the product purity and yield significantly decreased. In Comparative Example 2, after adjusting the order of adding the polymerization inhibitors, the product purity decreased slightly, the yield significantly decreased, and the color value significantly increased. In Comparative Examples 3 and 4, after changing the solvent, the product yield and purity decreased to varying degrees, and even the reaction time was prolonged, resulting in low efficiency.

Claims

1. A method for preparing methacryloyloxypropyltriacetoxysilane, characterized in that, Includes the following steps: Solvent, sodium acetate, and the first polymerization inhibitor are added to the reaction vessel; Under inert gas protection, methacryloyloxypropyltrichlorosilane and a second polymerization inhibitor are added dropwise; After the addition is complete, continue the reaction for a period of time, filter to remove the solid, and distill to remove the solvent to obtain the finished product, methacryloyloxypropyltriacetoxysilane.

2. The method for preparing methacryloyloxypropyltriacetoxysilane according to claim 1, characterized in that, The first polymerization inhibitor is p-hydroxyanisole (MEHQ).

3. The method for preparing methacryloyloxypropyltriacetoxysilane according to claim 1 or 2, characterized in that, The amount of the first polymerization inhibitor is 50-150 ppm of the total mass of the raw materials, namely methacryloyloxypropyltrimethoxysilane and sodium acetate.

4. The method for preparing methacryloyloxypropyltriacetoxysilane according to claim 1, characterized in that, The second polymerization inhibitor is 2,6-di-tert-butyl-p-cresol (BHT).

5. The method for preparing methacryloyloxypropyltriacetoxysilane according to claim 1 or 4, characterized in that, The amount of the second polymerization inhibitor shall not exceed 2‰ of the mass of methacryloyloxypropyltrichlorosilane.

6. The method for preparing methacryloyloxypropyltriacetoxysilane according to claim 1, characterized in that, The solvent is ethyl acetate.

7. The method for preparing methacryloyloxypropyltriacetoxysilane according to claim 1, characterized in that, After the addition is complete, the reaction is stopped when the pH of the reaction solution reaches 5-7.

8. The method for preparing methacryloyloxypropyltriacetoxysilane according to claim 1, characterized in that, The inert gas is nitrogen.

9. The method for preparing methacryloyloxypropyltriacetoxysilane according to claim 1, characterized in that, The reaction temperature is controlled between 15-45℃.

10. The method for preparing methacryloyloxypropyltriacetoxysilane according to claim 1, characterized in that, The distillation is a negative pressure distillation with a vacuum degree of 700-730 mmHg. After distillation, methacryloyloxypropyltriacetoxysilane with a purity of over 97% and a color value of less than 1 is obtained.

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