Preparation method of thiocarboxylate silane

Abstract

The invention provides a preparation method of thiocarboxylate silane, which comprises the following steps: 1) uniformly mixing thiocarboxylic acid with a solvent, and then adding 3-chloropropyltrialkoxysilane for reaction to obtain a reaction solution containing thiocarboxylate silane; and 2) adding organic amine into the reaction liquid in the step 1) for neutralization, then adding sodium alkoxide for stirring, and then filtering and removing the solvent to obtain the thiocarboxylate silane. According to the preparation method, the use of water is avoided in the whole reaction process, the raw materials are not subjected to hydrolysis reaction, the selectivity is high, and the product purity is high. A phase transfer catalyst is not needed in the production process, phase separation operation is not needed, and the technological process is simplified.

Description

Technical Field

[0001] The invention relates to a method for preparing a silane coupling agent, in particular to a method for preparing a thiocarboxylate silane coupling agent. Background Art

[0002] Sulfur-containing silane coupling agents are an important class of silane coupling agents, which are widely used in the rubber vulcanization process. Thiocarboxylate silane coupling agents are one of them. At present, the most commonly used method for industrial production is mainly the aqueous phase method. That is, a thiocarboxylate solution is reacted with 3-chloropropyltrialkoxysilane to obtain a thiocarboxylate silane coupling agent. Among them, the thiocarboxylate is prepared by reacting an aqueous solution of sulfide or hydrosulfide with an acyl chloride. The aqueous phase synthesis involves water throughout the process. The acyl chloride will react with water to reduce the selectivity of the main reaction, and the alkoxysilane will hydrolyze and condense in water to generate heavy components, especially when the pH value of the aqueous phase deviates from neutrality, the hydrolysis is more obvious, and the reaction in the aqueous phase will increase the water content of the product, which is not conducive to product storage.

[0003] In order to solve the problem of raw material and product hydrolysis, patent CN103709189A proposes a solvent-free process for preparing thiocarboxylate silane coupling agent. That is, 3-mercaptopropyltrialkoxysilane is reacted with acyl chloride, and a solvent is added to the reaction between the two to control the reaction rate and absorb the generated hydrogen chloride. However, the yield is low, and the cost of 3-mercaptopropyltrialkoxysilane is high, which limits its application in industrial production.

[0004] CN103709188B uses acyl chloride and sodium sulfide aqueous solution to react to generate sodium thiocarboxylate, which is then reacted with allyl chloride to produce thiocarboxylate allyl ester, and then added with trialkoxysilane under platinum catalyst conditions to obtain thiocarboxylate silane product after liquid separation and low boiling point removal. This method separates liquid before adding alkoxysilane, avoids hydrolysis and condensation of alkoxy groups, and improves the yield and purity of the product. However, the hydrolysis problem of acyl chloride is not solved. Summary of the invention

[0005] In view of this, the inventors of the present application have found that the aqueous phase method uses a thiocarboxylate solution as an intermediate raw material, and the preparation and use of the thiocarboxylate solution must be completed in a water system. If thiocarboxylic acid can be used instead of the thiocarboxylate solution to react with 3-chloropropyltriethoxysilane, the use of water can be avoided, solving the problem of alkoxy hydrolysis and condensation. Based on this, the present invention provides an anhydrous preparation process for thiocarboxylate silane.

[0006] The preparation method of the present invention has the advantages that the use of water is avoided in the entire reaction process, and no wastewater is generated in the production process. No hydrolysis process occurs in the raw materials and the products, and the selectivity and conversion rate are high, and the product purity is high. No phase transfer catalyst is required in the production process, and no phase separation operation is required, which greatly simplifies the process flow.

[0007] In order to achieve the above purpose, the following operation method is adopted:

[0008] The present invention provides a method for preparing thiocarboxylate silane, the steps comprising:

[0009] 1) mixing the thiocarboxylic acid and the solvent uniformly, and then adding 3-chloropropyltriethoxysilane to react to obtain a reaction solution containing thiocarboxylate silane;

[0010] 2) adding an organic amine to the reaction solution of step 1) for neutralization, then adding sodium alcoholate for stirring, and then filtering and removing the solvent to obtain the thiocarboxylate silane.

[0011] The thiocarboxylate silane described in the present invention has a structure shown in the following formula (1):

[0012]

[0013] In the formula, R1 is an alkyl group, an aryl group, or an aralkyl group, preferably a C1-C5 alkyl group, a C6 aryl group, or a C6-C10 aralkyl group, more preferably a C1-C5 alkyl group, and further preferably a methyl group or an ethyl group;

[0014] R2 is a straight-chain alkyl group, a branched-chain alkyl group, or an aralkyl group, preferably a C6-C12 straight-chain alkyl group, a C6-C10 branched-chain alkyl group, or a C6 aralkyl group, more preferably a C6-C12 straight-chain alkyl group, and further preferably an octyl group, a heptyl group, and the like.

[0015] In some embodiments, the thiocarboxylic acid in step 1) has a structure as shown in the following formula (2):

[0016]

[0017] In the formula, R2 is the same as R2 in formula (1), that is, R2 is a straight-chain alkyl group, a branched-chain alkyl group, or an aralkyl group, preferably a C6-C12 straight-chain alkyl group, a C6-C10 branched-chain alkyl group, or a C6 aralkyl group, more preferably a C6-C12 straight-chain alkyl group, and further preferably a straight-chain octyl group, a heptyl group, etc.

[0018] Preferably, the thiocarboxylic acid is selected from one or more of thioheptanoic acid, thiohexanoic acid, thiooctanoic acid, thiononanoic acid, thiodecanoic acid, and thioisooctanoic acid, more preferably one or more of thiooctanoic acid and thioheptanoic acid.

[0019] The thiocarboxylic acid described in the present invention is an existing product that has been disclosed, and can be a common commercially available product obtained through commercial channels, or can be prepared by technicians based on existing processes, for example, by the method disclosed in the reference document "Study on Preparation Process of Thioacetic Acid". The present invention has no special requirements for its source and is not specifically limited herein.

[0020] Specifically, one of the preparation processes of the thiocarboxylic acid is to react a carboxylic acid (e.g., heptanoic acid, hexanoic acid, octanoic acid, nonanoic acid, decanoic acid, etc.) with an excess sulfide (e.g., phosphorus pentasulfide, arsenic pentasulfide, etc.) to generate a thiocarboxylic acid. The reaction is a solid-liquid reaction to generate a liquid-solid mixture of thiocarboxylic acid and an oxide, which is filtered to obtain a thiocarboxylic acid. The actual operation and reaction conditions can be optimized by technicians based on known processes according to actual needs, and the present invention will not repeat them in detail.

[0021] In some embodiments, the 3-chloropropyltrialkoxysilane in step 1) has a structure shown in the following formula (3):

[0022]

[0023] In the formula, R1 is an alkyl group, an aryl group, or an aralkyl group, preferably a C1-C5 alkyl group, a C6 aryl group, or a C6-C10 aralkyl group, more preferably a C1-C5 alkyl group, and further preferably a methyl group or an ethyl group;

[0024] Preferably, the 3-chloropropyltrialkoxysilane is selected from one or more of 3-chloropropyltriethoxysilane and 3-chloropropyltrimethoxysilane.

[0025] In some embodiments, the solvent in step 1) has no special requirements and can be any conventional solvent for this type of reaction in the art, for example, one or more of ethanol, isopropanol, petroleum ether, alkane, toluene, and xylene can be selected.

[0026] In some embodiments, the mass ratio of the thiocarboxylic acid to 3-chloropropyltriethoxysilane in step 1) is 1:1.2-2.5, such as 1:1.2, 1:1.5, 1:1.7, 1:2, 1:2.2, 1:2.5, etc., preferably 1:1.5-1.7;

[0027] The amount of the solvent used is 70-100 wt % of the mass of the thiocarboxylic acid, for example 70%, 80%, 90%, 100%, etc.

[0028] In some embodiments, in step 1), the reaction temperature is 40-70°C, such as 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, etc., and the reaction time is 30-140min, such as 30min, 50min, 70min, 90min, 110min, 130min, 140min, etc.;

[0029] Preferably, the reaction pressure is 40-60 kPaA, such as 40 kPaA, 45 kPaA, 50 kPaA, 55 kPaA, 60 kPaA, etc.

[0030] In some specific embodiments, during the reaction process of step 1), the 3-chloropropyltriethoxysilane is added continuously, in batches, or dropwise; preferably, the addition time is 20-40 min, and the addition time is included in the aforementioned reaction time. In practical application, a slight excess of 3-chloropropyltriethoxysilane can be maintained during the reaction.

[0031] Specifically, in step 1) of the present invention, the thiocarboxylic acid and the solvent are mixed evenly, and then 3-chloropropyltriethoxysilane is added dropwise. The reaction process is carried out under negative pressure, so that the generated hydrogen chloride can be removed in time. At the same time, the tail gas pipeline can also be connected to a vacuum pump through an absorption bottle filled with alkali solution (such as soda lime); the reaction process reaction formula is as follows:

[0032]

[0033] In some specific embodiments, the organic amine in step 2) is selected from one or more of alkylamines, alcoholamines, and amides, preferably alkylamines, and more preferably one or more of triethylamine, tripropylamine, and tributylamine.

[0034] In some specific embodiments, the sodium alkoxide in step 2) is selected from one or more of sodium methoxide and sodium ethoxide.

[0035] In some specific embodiments, the amount of the organic amine added in step 2) is 1-2.2 wt % of the mass of the thiocarboxylic acid in step 1), for example, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, etc.;

[0036] The amount of sodium alkoxide added is 1-2.2 wt % of the mass of the thiocarboxylic acid in step 1), for example, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, etc.

[0037] In some specific embodiments, in step 2), the neutralization is carried out after adding the organic amine, and the temperature is 40-70°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, etc., and the time is 5-20 min, for example, 5 min, 7 min, 10 min, 12 min, 15 min, 18 min, 20 min, etc.

[0038] In some specific embodiments, in step 2), the stirring after adding sodium alkoxide is performed at a temperature of 40-70°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, etc., and the time is 10-50 min, for example, 10 min, 20 min, 30 min, 40 min, 50 min, etc.

[0039] Specifically, in step 2) of the present invention, an organic amine is first added to the system after the reaction in step 1) to neutralize the residual hydrogen chloride, and then sodium alcoholate is added and stirred to convert the Si-Cl generated by hydrogen chloride and silyloxy back to silyloxy. After conventional filtration, desolventizing and other operations, thiocarboxylate silane can be obtained.

[0040] The thiocarboxylate silane prepared by the method of the present invention can be used as a silane coupling agent and has a wide range of applications in the rubber vulcanization process.

[0041] Compared with the prior art, the preparation method of the present invention has the following advantages:

[0042] The entire process avoids the use of water, and neither the raw materials nor the products will be hydrolyzed, with high selectivity and high product purity. No phase transfer catalyst or phase separation operation is required during the production process, which greatly simplifies the process and achieves high product purity. DETAILED DESCRIPTION

[0043] The following examples will further illustrate the method provided by the present invention, but the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the rights claimed by the present invention.

[0044] Unless otherwise specified, the reagents, materials and instruments used in the following examples are conventional reagents, conventional materials and conventional instruments in the art and can be obtained commercially.

[0045] Thiocarboxylic acid: prepared by the method disclosed in the reference "Study on the Preparation Process of Thioacetic Acid", specifically,

[0046] 1. Thioctanoic acid is prepared by the following method:

[0047] 1000g of 99%wt pure n-octanoic acid was placed on the bottom of a 2L round-bottom flask, 312g of flaky phosphorus pentasulfide from which metal impurities had been removed was added to the bottom solution, and 20g of a 95wt% methanol aqueous solution was mixed as a catalyst, and reacted in a round-bottom flask at 40°C and normal pressure for 4.5h to obtain a mother liquor. The solid-liquid separation was performed by suction filtration to obtain a liquid phase mixture. The mixture was deweighted with a scraper. The scraper heat source temperature was set at 230°C and the pressure was set to 10kPaA. After deweighting, the mixture entered the distillation tower for vacuum distillation, with a top temperature of 148°C, a bottom temperature of 169°C, and a pressure of 10kPaA. 409g of thiooctanoic acid was extracted from the top of the distillation tower, and 453g of octanoic acid was extracted from the bottom of the tower for reuse. The thiooctanoic acid content in the product was 99.5% by gas chromatography.

[0048] 2. Thioisooctanoic acid: According to the above preparation method, the n-octanoic acid raw material is replaced by isooctanoic acid, and other operations remain unchanged to obtain 405 g of thioisooctanoic acid. The thioisooctanoic acid content in the product detected by gas chromatography is 99.1%.

[0049] 3. Thioheptanoic acid: According to the above preparation method, the n-octanoic acid raw material is replaced by n-heptanoic acid, the scraper heat source temperature is set to 216°C, and other operations remain unchanged to obtain 396g of thioheptanoic acid. The thiooctanoic acid content in the product detected by gas chromatography is 99.2%.

[0050] Embodiment 1:

[0051] Preparation of 3-thiooctanoate-propyltriethoxysilane

[0052] 1) 409g of thiooctanoic acid was placed on the bottom of a 2L round-bottom flask, and its tail gas line was connected to a vacuum pump through an absorption bottle filled with soda lime. Stirring was started, 300g of ethanol was added and mixed evenly, the vacuum pump was turned on and the pressure dropped to 40kPaA, while the oil bath was heated to 50°C, and then 621g of 3-chloropropyltriethoxysilane (control of slight excess) was slowly added with a peristaltic pump, the addition time was 30min, and the oil bath was maintained at 50°C and the reaction continued for 10min.

[0053] 2) Add 5g of triethylamine to the reaction solution, neutralize at 50°C for 10min; add 5g of sodium ethoxide, maintain stirring at 50°C for 30min. After completion, remove the precipitated salt by suction filtration (diatomaceous earth can be added as a filter aid), and obtain an ethanol solution of 3-thiooctanoate-propyltriethoxysilane in the liquid phase. Distill and remove ethanol at 60°C and 20kPaA to obtain 937g of product.

[0054] The product was detected by gas chromatography, and the content of 3-thiooctanoate-propyltriethoxysilane was 98.7%; the conversion rate of the raw material 3-chloropropyltriethoxysilane was 99.2%, and the selectivity was 99.2%.

[0055] Example 2

[0056] Preparation of 3-thioisooctanoate-propyltriethoxysilane

[0057] 1) 405g of thioisooctanoic acid was placed on the bottom of a 2L round-bottom flask, and its tail gas line was connected to a vacuum pump through an absorption bottle filled with soda lime. Stirring was started, 400g of ethanol was added and mixed evenly, the vacuum pump was turned on and the pressure dropped to 60kPaA, while the oil bath was heated to 70°C, and then 618g of 3-chloropropyltriethoxysilane (control of slight excess) was slowly added with a peristaltic pump, the addition time was 20min, and the oil bath was maintained at 70°C and the reaction continued for 10min.

[0058] 2) Add 9g of tributylamine to the reaction solution, neutralize at 70°C for 5min; add 9g of sodium ethoxide, maintain stirring at 70°C for 10min. After completion, remove the precipitated salt by suction filtration (diatomaceous earth can be added as a filter aid), and obtain an ethanol solution of 3-thioisooctanoate-propyltriethoxysilane in the liquid phase. Distill and remove ethanol at 60°C and 20kPaA to obtain 942g of product.

[0059] The product was detected by gas chromatography, and the content of 3-thioisooctanoate-propyltriethoxysilane was 98.3%, the conversion rate of the raw material 3-chloropropyltriethoxysilane was 98.7%, and the selectivity was 98.3%.

[0060] Example 3

[0061] Preparation of 3-thioheptanoate-propyltrimethoxysilane

[0062] 1) 396 g of thioheptanoic acid was placed on the bottom of a 2 L round bottom flask, and its tail gas line was connected to a vacuum pump through an absorption bottle filled with soda lime. Stirring was started, 300 g of isopropanol was added and mixed evenly, the vacuum pump was turned on and the pressure was reduced to 30 kPaA, while the oil bath was heated to 40°C, and then 663 g of 3-chloropropyltrimethoxysilane (control of slight excess) was slowly added with a peristaltic pump, the addition time was 40 min, and the oil bath was maintained at 40°C and the reaction was continued for 20 min.

[0063] 2) Add 5g of tripropylamine to the reaction solution, neutralize at 40°C for 20min; add 5g of sodium ethoxide, maintain stirring at 40°C for 50min. After completion, remove the precipitated salt by suction filtration (diatomaceous earth can be added as a filter aid), and obtain an isopropanol solution of 3-thiooctanoate-propyltrimethoxysilane in the liquid phase. Distill and remove isopropanol at 80°C and 20kPaA to obtain 960g of product.

[0064] The product was detected by gas chromatography, and the content of 3-thioheptanoate-propyltrimethoxysilane was 97.6%, the conversion rate of the raw material 3-chloropropyltrimethoxysilane was 99.2%, and the selectivity was 98.1%.

[0065] Comparative Example 1

[0066] The preparation method is similar to that in Example 1, except that triethylamine is not added for neutralization in step 2), and other operations and conditions remain unchanged.

[0067] The product was detected by gas chromatography, and the content of 3-thiooctanoate-propyltriethoxysilane was 84.9%, the conversion rate of the raw material 3-chloropropyltriethoxysilane was 98.7%, and the selectivity was 85.4%.

[0068] Comparative Example 2

[0069] The preparation method was prepared with reference to Example 1, except that in step 2), an equal amount of sodium hydroxide was replaced by triethylamine, and other operations and conditions remained unchanged.

[0070] The product was detected by gas chromatography, and the content of 3-thiooctanoate-propyltriethoxysilane was 89.3%, the conversion rate of the raw material 3-chloropropyltriethoxysilane was 98.4%, and the selectivity was 90.2%.

[0071] Comparative Example 3

[0072] The preparation method is similar to that in Example 1, except that sodium ethoxide is not added in step 2), and other operations and conditions remain unchanged.

[0073] The product was detected by gas chromatography, and the content of 3-thiooctanoate-propyltriethoxysilane was 85.9%, the conversion rate of the raw material 3-chloropropyltriethoxysilane was 98.2%, and the selectivity was 86.9%.

[0074] Comparative Example 4

[0075] The preparation method was prepared by referring to Example 1, except that in step 2), an equal amount of ether was replaced by sodium ethoxide, and other operations and conditions remained unchanged.

[0076] The product was detected by gas chromatography, and the content of 3-thiooctanoate-propyltriethoxysilane was 90.6%, the conversion rate of the raw material 3-chloropropyltriethoxysilane was 99%, and the selectivity was 91.2%.

Claims

1. A method for preparing thiocarboxylate silane, characterized in that the steps include: 1) mixing the thiocarboxylic acid and the solvent uniformly, and then adding 3-chloropropyltriethoxysilane to react to obtain a reaction solution containing thiocarboxylate silane; 2) adding an organic amine to the reaction solution of step 1) for neutralization, then adding sodium alcoholate for stirring, and then filtering and removing the solvent to obtain the thiocarboxylate silane.

2. The preparation method according to claim 1, characterized in that: The thiocarboxylic acid in step 1) has a structure as shown in the following formula (2): In the formula, R2 is a straight-chain alkyl group, a branched-chain alkyl group, or an aralkyl group, preferably a C6-C12 straight-chain alkyl group, a C6-C10 branched-chain alkyl group, or a C6 aralkyl group, more preferably a C6-C12 straight-chain alkyl group, and further preferably a straight-chain octyl group, a heptyl group, or the like. Preferably, the thiocarboxylic acid is selected from one or more of thioheptanoic acid, thiohexanoic acid, thiooctanoic acid, thiononanoic acid, thiodecanoic acid, and thioisooctanoic acid, more preferably one or more of thiooctanoic acid and thioheptanoic acid.

3. The preparation method according to claim 1, characterized in that: Step 1) The 3-chloropropyltriethoxysilane has a structure as shown in the following formula (3): In the formula, R1 is an alkyl group, an aryl group, or an aralkyl group, preferably a C1-C5 alkyl group, a C6 aryl group, or a C6-C10 aralkyl group, more preferably a C1-C5 alkyl group, and further preferably a methyl group or an ethyl group; Preferably, the 3-chloropropyltrialkoxysilane is selected from one or more of 3-chloropropyltriethoxysilane and 3-chloropropyltrimethoxysilane.

4. The preparation method according to claim 1, characterized in that: Step 1) The solvent is selected from one or more of ethanol, isopropanol, petroleum ether, alkanes, toluene and xylene.

5. The preparation method according to any one of claims 1 to 4, characterized in that: Step 1) the mass ratio of the thiocarboxylic acid to 3-chloropropyltriethoxysilane is 1:1.2-2.5, preferably 1:1.5-1.7; and / or The amount of the solvent used in step 1) is 70-100 wt% of the mass of the thiocarboxylic acid.

6. The preparation method according to claim 1, characterized in that: Step 1) The reaction temperature is 40-70°C and the reaction time is 30-140min; and / or In step 1), the reaction pressure is 40-60 kPaA.

7. The preparation method according to claim 1 or 6, characterized in that: During the reaction of step 1), the 3-chloropropyltriethoxysilane is added continuously, in batches, or dropwise; Preferably, the feeding time is 20-40 min.

8. The preparation method according to claim 1, characterized in that: Step 2) the organic amine is selected from one or more of alkylamines, alcoholamines, and amides, preferably alkylamines, more preferably one or more of triethylamine, tripropylamine, and tributylamine; and / or Step 2) the sodium alkoxide is selected from one or more of sodium methoxide and sodium ethoxide.

9. The preparation method according to claim 1 or 8, characterized in that: The amount of the organic amine added in step 2) is 1-2.2 wt% of the mass of the thiocarboxylic acid in step 1); and / or The amount of sodium alkoxide added in step 2) is 1-2.2 wt% of the mass of the thiocarboxylic acid in step 1).

10. The preparation method according to claim 1, characterized in that: Step 2) adding an organic amine and then neutralizing at a temperature of 40-70° C. for 5-20 min; and / or Step 2) adding sodium alkoxide and stirring at a temperature of 40-70° C. for 10-50 min.

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