Method for preparing azosilane coupling agent with symmetrical structure

Abstract

The invention discloses a method for preparing an azo silane coupling agent with a symmetrical structure, which adopts chlorosilane and biurea as reaction raw materials to synthesize the azo silane coupling agent with the symmetrical structure, the raw materials are common and easy to obtain, the cost of the raw materials is low, and the method is suitable for industrial production. And compared with a route of directly reacting amino silane with azodicarboxylate, the reaction cost is low, and industrial production is facilitated.

Description

Technical Field

[0001] This invention relates to a method for preparing a structurally symmetrical azosilane coupling agent, belonging to the field of chemical synthesis technology. Background Technology

[0002] Silane coupling agents are a class of low-molecular-weight organosilicon compounds with special structures, widely used in rubber, plastics, glass fibers, filled composites, epoxy encapsulation materials, elastomers, coatings, adhesives, and sealants. Due to their unique molecular structure, silane coupling agents can interact with both hydroxyl groups in inorganic materials and long molecular chains in organic polymers, coupling two materials with different properties and thus improving various properties of biomaterials. Therefore, silane coupling agents have become an indispensable additive in the materials industry.

[0003] However, for rubber products requiring high tensile strength and abrasion resistance, especially in tires and conveyor belts, silica is added as an effective reinforcing filler to improve the physical properties of the rubber products. Because silica contains a large number of silanol groups on its surface, it has high surface energy, can form hydrogen bonds, exhibits hydrophilicity, and is prone to agglomeration, leading to weakened rubber-filler interactions and reduced reinforcing effect. Furthermore, the silanol groups can delay rubber vulcanization. Therefore, surface modification of silica is necessary. Typically, silane coupling agents, after hydrolysis, can react with the hydroxyl groups of silica to reduce the number of hydroxyl groups, thereby improving the physical and mechanical properties of the composite material. Among these, azosilanes, with their unique azo structure, have unique applications in rubber modification.

[0004] CN105504370A and CN102822183A disclose an azo-silane coupling agent with the following chemical formula: This azo-silane coupling agent is obtained by reacting an aminosilane with an azo dicarboxylic acid compound (such as diisopropylazodicarboxylic acid ester) in an organic solvent. This method uses expensive raw materials, has high production costs, and yields products with low purity. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing structurally symmetrical azosilane coupling agents. This method uses chlorosilane and biuret as raw materials, reducing raw material costs and yielding a target product with high conversion rate and good quality. Furthermore, the preparation method is mild, simple, and easy to industrialize.

[0006] The specific technical solution of this invention is as follows: The structurally symmetrical azosilane coupling agent of the present invention has the following structural formula (Ⅰ): (I) In formula (Ⅰ): R4 is either R1 or R2; --R1 is a hydroxyl group, C1-C 18 Alkyl, C1-C 18 alkoxy groups, C5-C 18 cycloalkyl, C6-C 18 Aryl groups. Examples: -OH; -CH3; -CH2CH3; -CH2CH2CH3; -(CH2)2CH3; -(CH2)5CH3; -(CH2) 10 CH3; -(CH2) 15 CH3; -(CH2) 17 CH3;-O-CH3;-O-CH2CH3;-O-(CH2)2CH3;-O-(CH2)5CH3;-O-(CH2) 10 CH3;-O-(CH2) 17 CH3; -C5H9; -C6H 11 -C6H5; -CH2-C6H5; -C6H4-CH3, etc. Preferably, R1 is C1-C 18 The alkoxy group, more preferably a C1-C5 alkoxy group.

[0007] --R2 is C1-C 18 Alkyl, C1-C 18 alkoxy groups, C5-C 18 cycloalkyl, C6-C 18 Aryl groups. Examples: -CH3; -CH2CH3; -CH2CH2CH3; -(CH2)2CH3; -(CH2)3CH3; -(CH2)5CH3; -(CH2) 10 CH3; -(CH2) 15 CH3; -(CH2) 17 CH3;-O-CH3;-O-CH2CH3;-O-(CH2)2CH3;-O-(CH2)5CH3;-O-(CH2) 10 CH3;-O-(CH2) 17 CH3; -C5H9; -C6H 11 -C6H5; -CH2-C6H5; -C6H4-CH3, etc. Preferably, R2 is Cl-C 18 The alkoxy group, more preferably a C1-C5 alkoxy group.

[0008] --R3 is C1-C 18 Alkylene, C6-C 18Aryl groups. Examples: -CH2-; -CH2CH2-; -CH2CH2CH2-; -(CH2)5-; -(CH2) 10 -;-(CH2) 15 -;-(CH2) 18 -; -C6H4-; -CH2-C6H4-; -C6H4-CH2-, etc. Preferably, R1 is C1-C 18 The alkylene group, more preferably a C1-C5 alkylene group.

[0009] The preparation method of the structurally symmetrical azosilane coupling agent of the present invention includes the following steps: (1) Mix chlorosilane, biuret, catalyst 1 and organic solvent, and heat to reflux to obtain mixed solution A; (2) Add catalyst 2 and co-catalyst to the mixed solution A obtained in step (1), and add oxidant solution dropwise to react. After the reaction, perform post-treatment to obtain the structurally symmetrical azosilane coupling agent shown in formula (I).

[0010] The reaction equation is: Furthermore, in step (1), the chlorosilane has the following structural formula A: In the above formula A, the definitions of R1, R2, R3, and R4 are consistent with those described above.

[0011] Furthermore, in step (1), the molar ratio of chlorosilane to biuret is 1:(1 to 1.3), for example 1:1, 1:1.1, 1:1.2, 1:1.3.

[0012] Furthermore, in step (1), the catalyst 1 is one of tris(pentafluorophenyl)borane or triphenylborane.

[0013] Furthermore, in step (1), the mass ratio of chlorosilane to catalyst 1 is 1:(3%~10%), 1:3%, 1:4%, 1:5%, 1:6%, 1:7%, 1:8%, 1:9%, 1:10%.

[0014] Furthermore, in step (1), the organic solvent is a mixture of solvent A and solvent B. Solvent A is one of dichloroethane, tetrahydrofuran, acetonitrile, methyl tert-butyl ether, etc., and solvent B is one of pyridine and triethylamine. Preferably, the organic solvent is a mixture of tetrahydrofuran and pyridine.

[0015] Furthermore, in step (1), the mass ratio of solvent A to solvent B is (1-4):1, preferably 3:1.

[0016] Furthermore, in step (1), the mass ratio of chlorosilane to organic solvent is 1:(1-3).

[0017] Furthermore, in step (1), the reaction temperature is 45℃~70℃, for example 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, and the reaction time is 0.5h~2h, for example 0.5h, 1h, 1.5h, 2h.

[0018] Furthermore, in step (2), the catalyst 2 is one of sodium bromide, potassium bromide, sodium iodide, and potassium iodide.

[0019] Furthermore, in step (2), the co-catalyst is either copper chloride or vanadium chloride, and its function is to enable the oxidant to rapidly generate free radicals and promote the oxidation reaction.

[0020] Furthermore, in step (2), the oxidant is tert-butyl hydroperoxide or di-tert-butyl peroxide. Commercially available tert-butyl hydroperoxide or di-tert-butyl peroxide are generally in aqueous solution form.

[0021] Furthermore, in step (2), the molar ratio of chlorosilane to catalyst 2 is 1:(5%~20%), for example 1:5%, 1:6%, 1:7%, 1:8%, 1:9%, 1:10%, 1:11%, 1:12%, 1:13%, 1:14%, 1:15%, 1:16%, 1:17%, 1:18%, 1:19%, 1:20%.

[0022] Furthermore, in step (2), the molar ratio of chlorosilane to cocatalyst is 1:(3%~15%), for example 1:3%, 1:4%, 1:5%, 1:6%, 1:7%, 1:8%, 1:9%, 1:10%, 1:11%, 1:12%, 1:13%, 1:14%, 1:15%.

[0023] Furthermore, in step (2), the molar ratio of chlorosilane to oxidant is 1:(1 to 1.5), for example 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5.

[0024] Furthermore, in step (2), the dropping temperature of the oxidant solution is 25℃~40℃, for example 25℃, 30℃, 35℃, 40℃, and the dropping time is 15min~30min, for example 15min, 20min, 25min, 30min.

[0025] Furthermore, in step (2), after the oxidant solution is added, the reaction is kept warm for a temperature of 25℃~40℃, for example 25℃, 30℃, 35℃, 40℃, and the reaction time is 0.5h~1.5h, for example 0.5h, 1h, 1.5h.

[0026] Furthermore, in steps (1) and (2), the reaction process is carried out under the protection of inert gases such as nitrogen and argon.

[0027] Furthermore, in step (2), after the reaction, the reaction solution is post-treated to obtain the final product. The post-treatment process is as follows: the reaction solution is filtered to remove solid impurities, then water is added and stirred and washed, and after standing and separating, the organic phase is concentrated under reduced pressure to remove the organic solvent, and the final structurally symmetrical azosilane coupling agent product is obtained.

[0028] Furthermore, the mass ratio of washing water to chlorosilane is (0.5-3):1, preferably 1.5:1.

[0029] Furthermore, the temperature for vacuum concentration is 45℃~65℃, for example 45℃, 40℃, 55℃, 60℃, 65℃, and the pressure is -0.08 MPa~-0.1Mpa.

[0030] The present invention has the following beneficial effects: (1) The present invention uses chlorosilane and biuret as reaction raw materials to synthesize a symmetrical azo silane coupling agents. The raw materials are common and readily available, and the raw material cost is low. Compared with the route of directly reacting amino silane with azo dicarboxylic acid ester, the reaction cost is low and it is more conducive to industrial production.

[0031] (2) The present invention uses tris(pentafluorophenyl)borane or triphenylborane as a catalyst for the condensation reaction of chlorosilane and biuret, which improves the reaction efficiency; at the same time, the mixture is used as an organic solvent, which improves the dispersibility of the reaction and provides a reaction medium for the reaction; on the other hand, triethylamine or pyridine can be used as an acid trapping agent, which helps to capture the acid produced in the reaction, promote the forward reaction, and improve the reaction yield.

[0032] (3) In this invention, tert-butyl hydroperoxide or di-tert-butyl peroxide is used as the oxidant for the oxidation reaction, sodium bromide, potassium bromide, sodium iodide, and potassium iodide are used as the catalysts for the oxidation reaction, and copper chloride or vanadium chloride is used as the co-catalyst for the oxidation reaction. The oxidation system has high oxidation efficiency, and the yield and product purity of the obtained symmetrical azosilane coupling agent are high.

[0033] (4) The preparation method provided by the present invention has a low reaction temperature, mild operating conditions, high reaction rate, few side reactions, high and stable product yield and purity, and is easy to industrialize.

[0034] (5) The symmetrical azosilane coupling agent obtained by the present invention can be used alone or in combination with other types of coupling agents in rubber, especially tire rubber, which greatly improves the mechanical properties, weather resistance, dispersibility, molding properties and processability of rubber. Attached Figure Description

[0035] Figure 1 This is the liquid chromatogram of the final product obtained in Example 1. Detailed Implementation

[0036] The following description illustrates exemplary embodiments of the present invention, including various details to aid understanding. These should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the invention. Similarly, for clarity and brevity, descriptions of well-known functions, operations, and structures are omitted in the following description. Unless otherwise specified, the methods described in the following embodiments are conventional methods; the materials described, unless otherwise specified, are commercially available.

[0037] Unless otherwise specified, all concentrations mentioned in the following examples and comparative examples are mass percentage concentrations. In the following examples and comparative examples, the yield was calculated using the following formula: Example 1 (Ⅰ-1) A method for preparing a structurally symmetrical azosilane coupling agent as shown in formula (Ⅰ-1) includes the following steps: (1) The reaction was carried out under nitrogen protection. At room temperature, 100g of 3-chloropropyltrimethoxysilane, 65.23g of biuret, 8g of tris(pentafluorophenyl)borane and 150g of a mixture of tetrahydrofuran and pyridine (the mass ratio of tetrahydrofuran to pyridine was 3:1) were added to the reactor and refluxed at 60°C for 1h to obtain mixed solution A. (2) Adjust the temperature to 30℃, add 7.76g sodium bromide and 6.73g copper chloride to the mixed solution A obtained in step (1), and then add 77.53g of 70% tert-butyl hydrogen peroxide aqueous solution dropwise over a period of 20min. After the addition is complete, react at 30℃ for 45min.

[0038] (3) After the reaction is completed, the solid catalyst and by-products are removed by filtration. Then, 150g of water is added to the filtrate for washing. After standing and separation, the organic phase is concentrated under reduced pressure at -0.09MPa and 50℃ to remove the organic solvent, and 215.45g of target product is obtained. The product is a red oily liquid with a purity of 97.52% (liquid chromatography) and a yield of 95.02% based on 3-chloropropyltrimethoxysilane.

[0039] Example 2 The structurally symmetrical azosilane coupling agent of formula (Ⅰ-1) was prepared according to the method of Example 1, except that in step (1), "65.23g biuret" was replaced with "77.09g biuret". The final product was 214.89g, appearing as a red oily liquid with a purity of 96.81% (liquid chromatography) and a yield of 94.09% based on 3-chloropropyltrimethoxysilane.

[0040] Example 3 The structurally symmetrical azosilane coupling agent of formula (Ⅰ-1) was prepared according to the method of Example 1, except that in step (1), "8g tris(pentafluorophenyl)borane" was replaced with "8g triphenylborane". The final product was 213.56g, appearing as a red oily liquid with a purity of 97.14% (liquid chromatography) and a yield of 93.83% based on 3-chloropropyltrimethoxysilane.

[0041] Example 4 The structurally symmetrical azosilane coupling agent of formula (Ⅰ-1) was prepared according to the method of Example 1, except that in step (1), "150g of a mixture of tetrahydrofuran and pyridine (mass ratio of tetrahydrofuran to pyridine of 3:1)" was replaced with "150g of a mixture of dichloroethane and triethylamine (mass ratio of dichloroethane to triethylamine of 3:1)". Finally, 215.63g of the target product was obtained, which was a red oily liquid with a purity of 95.28% (liquid chromatography) and a yield of 92.92% based on 3-chloropropyltrimethoxysilane.

[0042] Example 5 The structurally symmetrical azosilane coupling agent of formula (Ⅰ-1) was prepared according to the method of Example 1, except that in step (1), "150g of a mixture of tetrahydrofuran and pyridine (mass ratio of tetrahydrofuran to pyridine is 3:1)" was replaced with "150g of a mixture of acetonitrile and pyridine (mass ratio of acetonitrile to pyridine is 3:1)". A total of 212.98g of the target product was obtained, which was a red oily liquid with a purity of 96.31% (liquid chromatography) and a yield of 92.77% based on 3-chloropropyltrimethoxysilane.

[0043] Example 6 The structurally symmetrical azosilane coupling agent of formula (Ⅰ-1) was prepared according to the method of Example 1, except that in step (1), "150g of a mixture of tetrahydrofuran and pyridine (mass ratio of tetrahydrofuran to pyridine is 3:1)" was replaced with "150g of a mixture of tetrahydrofuran and pyridine (mass ratio of tetrahydrofuran to pyridine is 1:1)". Finally, 214.81g of the target product was obtained, which was a red oily liquid with a purity of 96.05% (liquid chromatography) and a yield of 93.31% based on 3-chloropropyltrimethoxysilane.

[0044] Example 7 The structurally symmetrical azosilane coupling agent of formula (Ⅰ-1) was prepared according to the method of Example 1, except that in step (2), "7.76g sodium bromide and 6.73g copper chloride" were replaced with "12.51g sodium iodide and 7.89g vanadium chloride". A total of 214.65g of the target product was obtained, which was a red oily liquid with a purity of 96.47% (liquid chromatography) and a yield of 93.65% based on 3-chloropropyltrimethoxysilane.

[0045] Example 8 The symmetrical azosilane coupling agent of formula (Ⅰ-1) was prepared according to the method of Example 1, except that in step (2), "then add 77.53 g of 70% tert-butyl hydrogen peroxide solution" was replaced with "then add 88.04 g of di-tert-butyl peroxide". The final product was 213.29 g, appearing as a red oily liquid with a purity of 97.28% (liquid chromatography) and a yield of 93.84% based on 3-chloropropyltrimethoxysilane.

[0046] Example 9 The symmetrical azosilane coupling agent of formula (Ⅰ-1) was prepared according to the method of Example 1, except that in step (2), "then add 77.53g of 70% tert-butyl hydrogen peroxide solution" was replaced with "then add 96.91g of 70% tert-butyl hydrogen peroxide solution". Finally, 214.97g of the target product was obtained, which was a red oily liquid with a purity of 97.04% (liquid chromatography) and a yield of 94.35% based on 3-chloropropyltrimethoxysilane.

[0047] Example 10 (Ⅰ-2) The structurally symmetrical azosilane coupling agent of formula (Ⅰ-2) was prepared according to the method of Example 1, except that in step (1), "100g 3-chloropropyltrimethoxysilane" was replaced with "121.11g 3-chloropropyltriethoxysilane". The final product was 253.65g, appearing as a red oily liquid with a purity of 98.02% (liquid chromatography) and a yield of 94.42% based on 3-chloropropyltriethoxysilane.

[0048] Example 11 (Ⅰ-3) The symmetrical azosilane coupling agent of formula (Ⅰ-3) was prepared according to the method of Example 1, except that in step (1), "100g of 3-chloropropyltrimethoxysilane" was replaced with "91.96g of 3-chloropropylmethyldimethoxysilane". A total of 198.29g of the target product was obtained, which was a red oily liquid with a purity of 97.31% (liquid chromatography) and a yield of 94.11% based on 3-chloropropylmethyldimethoxysilane.

[0049] Comparative Example 1 The structurally symmetrical azosilane coupling agent of formula (Ⅰ-1) was prepared according to the method of Example 1, except that tris(pentafluorophenyl)borane was not added in step (1). A total of 174.59 g of the target product was obtained, which was a red oily liquid with a purity of 96.85% (liquid chromatography) and a yield of 76.48% based on 3-chloropropyltrimethoxysilane.

[0050] Comparative Example 2 The symmetrical azosilane coupling agent of formula (Ⅰ-1) was prepared according to the method of Example 1, except that in step (1), "adding 100g of 3-chloropropyltrimethoxysilane, 65.23g of biuret, 8g of tris(pentafluorophenyl)borane and 150g of a mixture of tetrahydrofuran and pyridine (mass ratio of tetrahydrofuran to pyridine is 3:1) to the reaction vessel" was replaced with "adding 100g of 3-chloropropyltrimethoxysilane, 65.23g of biuret, 8g of tris(pentafluorophenyl)borane, 112.5g of tetrahydrofuran and 37.5g of sodium carbonate to the reaction vessel". Finally, 206.53g of the target product was obtained, which was a red oily liquid with a purity of 95.17% (liquid chromatography) and a yield of 88.90% based on 3-chloropropyltrimethoxysilane.

[0051] Comparative Example 3 The structurally symmetrical azosilane coupling agent of formula (Ⅰ-1) was prepared according to the method of Example 1, except that copper chloride was not added in step (2). A total of 195.94 g of the target product was obtained, which was a red oily liquid with a purity of 95.28% (liquid chromatography) and a yield of 84.44% based on 3-chloropropyltrimethoxysilane.

[0052] Comparative Example 4 The structurally symmetrical azosilane coupling agent of formula (Ⅰ-1) was prepared according to the method of Example 1, except that no oxidant was added in step (2). A total of 187.61 g of the target product was obtained, which was a red oily liquid with a purity of 93.43% (liquid chromatography) and a yield of 79.28% based on 3-chloropropyltrimethoxysilane.

[0053] Comparative Example 5 The symmetrical azosilane coupling agent of formula (Ⅰ-1) was prepared according to the method of Example 1, except that in step (2), the following was changed: "Adjust the temperature to 30°C, add 7.76g of sodium bromide and 6.73g of copper chloride to the mixed solution A obtained in step (1), and then add 77.53g of 70% tert-butyl hydrogen peroxide solution dropwise over a period of 20 min, and react at 30°C for 45 min after the addition is complete", and "Adjust the temperature to 30°C, add 7.76g of sodium bromide, 6.73g of copper chloride and 77.53g of 70% tert-butyl hydrogen peroxide solution to the mixed solution A obtained in step (1), and react at 30°C for 60 min". Finally, 194.34g of the target product was obtained, which was a red oily liquid with a purity of 94.79% (gas chromatography and liquid chromatography), and a yield of 83.32% based on 3-chloropropyltrimethoxysilane.

[0054] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a structurally symmetrical azosilane coupling agent, characterized in that: Includes the following steps: (1) Mix the chlorosilane, biuret, catalyst 1 and organic solvent shown in formula A, and heat to react to obtain mixed solution A; (2) Add catalyst 2 and co-catalyst to the mixed solution A obtained in step (1), and add oxidant solution dropwise to react. After the reaction, perform post-treatment to obtain the structurally symmetrical azosilane coupling agent shown in formula (I). In formulas A and (I), R1 is a hydroxyl group, C1-C 18 Alkyl, C1-C 18 alkoxy groups, C5-C 18 cycloalkyl, C6-C 18 The aryl group, preferably C1-C 18 The alkoxy group, more preferably a C1-C5 alkoxy group; R2 is C1-C 18 Alkyl, C1-C 18 alkoxy groups, C5-C 18 cycloalkyl, C6-C 18 The aryl group, preferably C1-C 18 The alkoxy group, more preferably a C1-C5 alkoxy group; R3 is C1-C 18 Alkylene, C6-C 18 The arylene group, preferably C1-C 18 The alkylene group, more preferably a C1-C5 alkylene group; R4 is either R1 or R2.

2. The method according to claim 1, characterized in that: In step (1), the molar ratio of chlorosilane to biuret is 1:(1-1.3).

3. The method according to claim 1, characterized in that: In step (1), the catalyst 1 is one of tris(pentafluorophenyl)borane or triphenylborane; preferably, the mass ratio of chlorosilane to catalyst 1 is 1:(3% to 10%).

4. The method according to claim 1, characterized in that: In step (1), the organic solvent is a mixture of solvent A and solvent B. Solvent A is one of dichloroethane, tetrahydrofuran, acetonitrile, and methyl tert-butyl ether, and solvent B is one of pyridine and triethylamine. Preferably, the mass ratio of solvent A to solvent B is (1-4):

1.

5. The method according to claim 1 or 4, characterized in that: In step (1), the organic solvent is a mixture of tetrahydrofuran and pyridine.

6. The method according to claim 1, characterized in that: In step (1), the reaction temperature is 45℃~70℃ and the reaction time is 0.5h~2h.

7. The method according to claim 1, characterized in that: In step (2), the catalyst 2 is one of sodium bromide, potassium bromide, sodium iodide, and potassium iodide; preferably, in step (2), the co-catalyst is one of copper chloride or vanadium chloride; preferably, in step (2), the oxidant is tert-butyl hydroperoxide or di-tert-butyl peroxide.

8. The method according to claim 1 or 7, characterized in that: In step (2), the molar ratio of chlorosilane, catalyst 2, co-catalyst and oxidant is 1:(5%~20%):(3%~15%):(1~1.5).

9. The method according to claim 1, characterized in that: In step (2), the oxidant solution is added at a temperature of 25℃ to 40℃ and for a time of 15 min to 30 min. Preferably, in step (2), after the oxidant solution is added, the reaction time is 0.5 h to 1.5 h at a temperature of 25℃ to 40℃.

10. The method according to claim 1, characterized in that: In steps (1) and (2), the reaction process is carried out under the protection of an inert gas.

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