A method for preparing a structurally symmetrical azosilane coupling agent

Abstract

The invention discloses a method for preparing a structurally symmetrical azosilane coupling agent, wherein chlorosilane is used as a raw material, and first reacts with amino ester to obtain amino ester silane; then the amino ester silane reacts with hydrazine hydrate to generate an azosilane coupling agent precursor; finally, the precursor is subjected to the action of an oxidant to obtain a final target product. The raw materials of the invention are common and easily available, the price is low, the reaction temperature is not high, the operating conditions are mild, the reaction rate is high, the side reactions are few, the product yield and purity are high, the production cost is reduced, and it is easy to industrialize production.

Description

Technical Field

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

[0002] Silane coupling agents are a class of low molecular weight organic silicon compounds with special structures, which are widely used in rubber, plastic, glass fiber, filling composite materials, epoxy packaging materials, elastomers, coatings, adhesives and sealants. Due to its special molecular structure, silane coupling agents can interact with both hydroxyl groups in inorganic substances and long molecular chains in organic polymers, coupling two materials with different properties, thereby improving various properties of biomaterials. Therefore, silane coupling agents have become one of the indispensable additives in the materials industry.

[0003] However, for rubber products that require high tensile strength and wear resistance, especially for tires and conveyor belts, etc., rubber products add silica as an effective reinforcing filler to improve the physical properties of rubber products. Since the surface of silica contains a large number of silanol groups, it has a high surface energy, can form hydrogen bonds, shows hydrophilicity, and is very easy to agglomerate with each other, resulting in a weakening of the rubber-filler interaction and a decrease in the reinforcement effect. Secondly, the hydroxyl groups will also cause the rubber to delay vulcanization. Therefore, it is necessary to modify the surface of silica. Generally, silane coupling agents can react with the hydroxyl groups of silica after hydrolysis to reduce the number of hydroxyl groups, thereby improving the physical and mechanical properties of the composite material. Among them, azosilane, with its unique azo structure, has a unique application in rubber modification.

[0004] CN105504370A and CN102822183A disclose an azo-silane coupling agent, the chemical formula of which is (R 1 ) 3-a (R 2 ) a Si-R I -NH-C(O)-N=NC(O)-NH-R I -Si(R 1 ) 3-a (R 2 ) a I. The azo-silane coupling agent is obtained by reacting aminosilane with an azodicarboxyl compound (such as diisopropyl azodicarboxylate) in an organic solvent. The raw materials used in this method are expensive, the production cost is high, and the purity of the obtained product is low. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for preparing a structurally symmetrical azosilane coupling agent. The method has common and easily available raw materials, mild operating conditions, high reaction rate, high reaction efficiency, high product yield and purity, low production cost, and is suitable for large-scale industrial production.

[0006] The structurally symmetrical azosilane coupling agent of the present invention has the structural formula described in the following formula (I):

[0007] (R1) x (R2) 3-x -Si-R3-NH-C(O)-N=NC(O)-NH-R3-Si-(R1) x (R2) 3-x (Ⅰ)

[0008] in:

[0009] --R1 is hydroxyl, C1-C 18 Alkyl, C1-C 18 Alkoxy, C5-C 18 Cycloalkyl, C6-C 18 For example: -OH; -CH3; -CH2CH3; -(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.

[0010] --R2 is C1-C 18 Alkyl, C1-C 18 Alkoxy, C5-C 18 Cycloalkyl, C6-C 18 For example: -CH3; -CH2CH3; -(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.

[0011] --x is equal to 1, 2, or 3.

[0012] --R3 is C1-C 18 Alkylene, C6-C 18 For example: -CH2-; -CH2 CH2-; -CH2CH2CH2-; -(CH2)5-; -(CH2) 10 -; -(CH2) 15 -; -(CH2) 18 -; -C6H4-; -CH2-C6H4-; -C6H4-CH2-, etc.

[0013] The method for preparing the structurally symmetrical azosilane coupling agent of the present invention comprises the following steps:

[0014] (1) reacting an amino ester of formula (II) with a chlorosilane of formula (III) to obtain an amino ester silane of formula (IV);

[0015] (2) reacting the amino ester silane of formula (IV) with hydrazine hydrate in the presence of a catalyst to obtain an azosilane coupling agent precursor of formula (V);

[0016] (3) Finally, the azosilane coupling agent precursor of formula (V) is reacted with an oxidant to obtain the final target product, a structurally symmetrical azosilane coupling agent of formula (I).

[0017] Furthermore, in step (1), the structural formula of the amino ester is:

[0018] NH2-C(O)-O-R5(Ⅱ)

[0019] In formula (II), R5 is C1-C 18 Alkyl, C5-C 18 Cycloalkyl, C6-C 18 For example: -CH3; -CH2CH3; -(CH2)2CH3; -(CH2)3CH3; -(CH2)5CH3; -(CH2) 10 CH3; -(CH2) 15 CH3; -(CH2) 17 CH3; -C5H9; -C6H 11 ; -C6H5; -CH2-C6H5; -C6H4-CH3, etc.

[0020] Furthermore, in step (1), the structural formula of the chlorosilane is:

[0021] (R1) x (R2) 3-x -Si-R3-Cl(Ⅲ)

[0022] In formula (III), the definitions of R1, R2, R3 and x are consistent with those in the above formula (I).

[0023] Furthermore, in step (1), the amino ester silane has the structural formula:

[0024] (R1) x (R2) 3-x -Si-R3-NH-C(O)-O-R5(Ⅳ)

[0025] In formula (IV), the definitions of R1, R2, R3 and x are consistent with those in the above formula (I), and the definition of R5 is consistent with that in the above formula (II).

[0026] Furthermore, in step (1), the reaction is carried out in the presence of an organic solvent, and the organic solvent is used as a reaction medium, preferably an organic amine organic solvent, and at least one of pyridine, triethylamine, N,N-dimethylaniline (DMA), tri-n-butylamine, etc. can be selected. On the one hand, such organic solvents can improve the dispersibility of the reaction as an organic solvent and provide a reaction medium for the reaction. On the other hand, they can act as an acid binding agent to remove the hydrogen chloride generated by the reaction, promote the reaction to proceed in the forward direction, and improve the yield of the reaction.

[0027] Furthermore, in step (1), the mass ratio of the organic solvent to the amino ester of formula (II) can be (2-5):1, for example, 2:1, 3:1, 4:1, 5:1.

[0028] Furthermore, in step (1), the molar ratio of the chlorosilane of formula (III) to the amino ester of formula (II) is 1:(1-1.2), for example, 1:1, 1:1.1, 1:1.2.

[0029] Furthermore, in step (1), the chlorosilane of formula (III) is preferably added dropwise to the mixture of the amino ester of formula (II) and the organic solvent, the dropping temperature is 40°C to 70°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, and the dropping time is 30min to 45min, for example, 30min, 35min, 40min, 45min.

[0030] Furthermore, in step (1), after the dropwise addition is completed, the reaction is continued at 40°C to 70°C for 30min to 90min. The reaction time can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, and the reaction time can be 30min, 40min, 50min, 60min, 70min, 80min, 90min.

[0031] Furthermore, in step (1), after the reaction is completed, the by-products are filtered out, and the filtrate is subjected to reduced pressure distillation to recover the organic solvent to obtain the amino ester silane of formula (IV). The reduced pressure distillation temperature varies depending on the type of organic solvent selected, and the vacuum degree of the reduced pressure distillation is generally 0.08 MPa to 0.1 MPa.

[0032] Furthermore, in step (2), the structural formula of the azosilane coupling agent precursor is:

[0033] (R1) x (R2) 3-x -Si-R3-NH-C(O)-NH-NH-C(O)-NH-R3-Si-(R1) x (R2) 3-x (V)

[0034] In formula (V), R1, R2, R3 and x are defined as in the above formula (I).

[0035] Furthermore, in step (2), hydrazine hydrate is present in the form of a solution, preferably a high concentration hydrazine hydrate solution, such as 75-85 wt %.

[0036] Furthermore, in step (2), the molar ratio of hydrazine hydrate to the chlorosilane of formula (III) is (1-1.1):1.

[0037] Furthermore, in step (2), the reaction is carried out in the presence of an organic solvent, and the organic solvent as the reaction medium can be selected from at least one of dichloromethane, tetrahydrofuran, N,N-dimethylamide, acetonitrile, etc. The mass ratio of the organic solvent to the hydrazine hydrate solution is (2 to 6):1, for example, 2:1, 3:1, 4:1, 5:1, 6:1.

[0038] Furthermore, in step (2), the catalyst is an ethanol solution of sodium ethoxide with a mass fraction of 25% to 30%, and the mass ratio of the ethanol solution of sodium ethoxide with a mass fraction of 25% to 30% to the hydrazine hydrate solution is (5% to 20%): 1, such as 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%: 1. The catalyst is sodium ethoxide. Since sodium ethoxide is relatively active and will rapidly decompose into sodium hydroxide and ethanol when dissolved in water, it is selected to be added in the form of an ethanol solution. The sodium ethoxide ethanol solution of this concentration is convenient for feeding and makes the reaction more gentle.

[0039] Furthermore, in step (2), it is preferred to first mix the hydrazine hydrate solution, the organic solvent and the catalyst, and then dropwise add the product of step (1) into the resulting mixture.

[0040] Further, in step (2), the reaction temperature is 40°C to 60°C, for example 40°C, 45°C, 50°C, 55°C, 60°C. The reaction time is 30min to 2h, for example 30min, 35min, 40min, 45min, 50min, 55min, 60min, 65min, 70min, 75min, 80min, 85min, 90min, 95min, 100min, 105min, 110min, 115min, 120min.

[0041] Furthermore, in step (2), after the reaction is completed, a quencher is added to terminate the reaction, the quencher is liquid pure acetic acid, and the mass ratio of acetic acid to hydrazine hydrate solution is (0.5% to 5%): 1, for example 0.5%: 1, 1%: 1, 1.5%: 1, 2%: 1, 2.5%: 1, 3%: 1, 3.5%: 1, 4%: 1, 4.5%: 1, 5%: 1.

[0042] Furthermore, in step (2), the temperature of the quenching reaction is 20°C to 30°C, for example, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, and the time of the quenching reaction is 5 min to 15 min, for example, 5 min, 10 min, 15 min.

[0043] Furthermore, in step (2), after the quenching reaction, the water in the reaction solution is removed, and the dehydration method can be distillation, reduced pressure distillation, adding a dehydrating agent, etc., preferably adding a dehydrating agent. The dehydrating agent is preferably a water-absorbing resin, such as SAP super absorbent resin, and examples thereof include polyacrylate, starch acrylate polymer, starch-acrylonitrile graft copolymer, acrylamide-acrylonitrile-acrylic acid terpolymer, etc. Preferably, the mass ratio of the dehydrating agent to the hydrazine hydrate solution is (3% to 8%): 1, such as 3%: 1, 4%: 1, 5%: 1, 6%: 1, 7%: 1, 8%: 1. After dehydration, the resin is filtered to remove the resin, and the filtrate does not need to be extracted and separated from the azosilane coupling agent precursor, and can be directly used in the next step of the reaction.

[0044] Further, in step (3), the oxidant is one of dichloroisocyanuric acid (TCCA) / acid-binding agent oxidation system, sodium bromide / chlorine / acid-binding agent oxidation system, diacetoxyphenyliodide (PIDA), bis(trifluoroacetoxy)phenyliodide (PIFA), etc. Among them, the acid-binding agent can be an alkaline substance such as pyridine and triethylamine.

[0045] Further, in step (3), when the oxidant is a dichloroisocyanuric acid (TCCA) / acid binding agent oxidation system, dichloroisocyanuric acid (TCCA) acts as an oxidant, and the acid binding agent can better promote the oxidation reaction. The molar ratio of dichloroisocyanuric acid (TCCA) to hydrazine hydrate is (0.5-2.5):1, for example, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, and the mass ratio of the acid binding agent to the hydrazine hydrate solution is (5%-10%):1, for example, 5%:1, 6%:1, 7%:1, 8%:1, 9%:1, 10%:1.

[0046] Further, in step (3), when the oxidant is a sodium bromide / chlorine / acid binding agent oxidation system, the bromine generated by the reaction of sodium bromide and chlorine acts as an oxidant, and the acid binding agent can better promote the oxidation reaction. The molar ratio of sodium bromide to hydrazine hydrate is (0.5-2.5):1, for example, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, chlorine is continuously introduced into the reaction system, and the pressure in the reaction system is ensured to be below 0.1Mpa to ensure safety. The mass ratio of the acid binding agent to the hydrazine hydrate solution is (5%-10%):1, for example, 5%:1, 6%:1, 7%:1, 8%:1, 9%:1, 10%:1.

[0047] Furthermore, in step (3), the molar ratio of diacetoxyphenyliodoacetyl (PIDA) to hydrazine hydrate is (0.5-2.5):1, for example, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1.

[0048] Furthermore, in step (3), the molar ratio of bis(trifluoroacetoxy)phenyliodoacetyl (PIFA) to hydrazine hydrate is (0.5-2.5):1, for example, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1.

[0049] Furthermore, in step (3), there is no special requirement for the mixing order of the reactants. Preferably, dichloroisocyanuric acid (TCCA), diacetoxyphenyliodoacetyl (PIDA), and bis(trifluoroacetoxy)phenyliodoacetyl (PIFA) are added in the form of an organic solvent solution, and sodium bromide is added in the form of a solid powder. The organic solvent used can be at least one of dichloromethane, tetrahydrofuran, N,N-dimethylformamide, acetonitrile, etc.

[0050] Furthermore, in step (3), the reaction temperature is 20°C to 35°C, for example, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, and the reaction time is 30min to 60min, for example, 30min, 35min, 40min, 45min, 50min, 55min, 60min.

[0051] Furthermore, in step (3), after the reaction is completed, the reaction solution is post-treated to obtain the final product, and the post-treatment includes: recovering the organic solvent by vacuum rotary evaporation, washing the residue with a detergent, filtering after washing, and vacuum rotary evaporating the filtrate to remove the detergent to obtain the final product.

[0052] Furthermore, in step (3), the detergent is a mixture of heptane and isopropyl ether (volume ratio is 1:1), and the mass of the mixture of heptane and isopropyl ether and the mass of the azosilane coupling agent precursor of formula (VI) are (0.5-2):1, for example, 0.5:1, 1:1, 1.5:1, 2:1.

[0053] Furthermore, in step (3), the drying temperature of the two vacuum rotary evaporation dryings is 55°C to 65°C, the drying pressure is -0.08MPa to -0.1MPa, and the drying time is 0.5h to 3h. The purpose of the first vacuum rotary evaporation drying is to remove the organic solvent, and the purpose of the second vacuum rotary evaporation drying is to remove the detergent (a mixture of heptane and isopropyl ether).

[0054] Furthermore, in steps (1), (2) and (3), the reaction processes are all carried out under the protection of an inert gas such as nitrogen.

[0055] The present invention has the following beneficial effects:

[0056] (1) The present invention uses chlorosilane as a raw material, firstly reacts an amino ester to synthesize the corresponding amino ester silane, then reacts with hydrazine hydrate to generate a precursor, and finally oxidatively dehydrogenates the target structure to obtain a symmetrical azo silane coupling agent under the action of an oxidant. In this synthesis method, various raw materials are common and easy to obtain, and the cost of raw materials is low. Compared with the route of directly using amino silane to react with azodicarboxylate, the reaction cost is low, and it is more conducive to industrial production.

[0057] (2) The present invention uses pyridine, triethylamine, N,N-dimethylaniline (DMA), tri-n-butylamine, etc. as the organic solvent for the first step reaction, which can also serve as an acid binding agent to neutralize the hydrochloric acid generated by the reaction, thereby promoting the reaction to proceed in the forward direction.

[0058] (3) The present invention uses an ethanol solution of sodium ethoxide as a strong catalyst for the second step reaction, which has a mild reaction, helps to improve the reaction efficiency, shortens the reaction time, and reduces the production cost.

[0059] (4) The oxidant used in the present invention is one of the oxidation system of dichloroisocyanuric acid (TCCA) / acid-binding agent (pyridine or triethylamine), the oxidation system of sodium bromide / chlorine / acid-binding agent (pyridine or triethylamine), diacetoxyphenyliodide (PIDA), and bis(trifluoroacetoxy)phenyliodide (PIFA). The oxidation system has a low price, high oxidation efficiency, short reaction time, and a more gentle and controllable oxidation process, so that the oxidation reaction proceeds more thoroughly in the forward direction. Among them, the more preferred oxidant is the oxidation system of dichloroisocyanuric acid (TCCA) / acid-binding agent, because the oxidant not only has a high oxidation efficiency, but is also cheap and easy to obtain, and the yield and product purity of the obtained structurally symmetrical azosilane coupling agent are higher.

[0060] (5) The preparation method provided by the present invention has low reaction temperature, mild operating conditions, high reaction rate, few side reactions, high and stable product yield and purity, and is easy for industrial production.

[0061] (6) The structurally symmetrical azosilane coupling agent obtained by the present invention can be applied to rubber, especially tire rubber, alone or in combination with other types of coupling agents, to greatly improve the mechanical properties, weather resistance, dispersibility, formability, process operability, etc. of the rubber. DETAILED DESCRIPTION

[0062] The following is a description of exemplary embodiments of the present invention, including various details of the embodiments of the present invention to facilitate understanding, which should be considered as merely exemplary. Therefore, it should be recognized by those of ordinary skill in the art that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for the sake of clarity and conciseness, descriptions of well-known functions, operations and structures are omitted in the following description. The methods described in the following embodiments, unless otherwise specified, are conventional methods; the materials, unless otherwise specified, can be obtained from commercial sources.

[0063] In the following examples and comparative examples, unless otherwise specified, the concentrations are all mass percentage concentrations.

[0064] Example 1

[0065] (CH3-0)3-Si-(CH2)3-NH-C(O)-N=NC(O)-NH-(CH2)3-Si-(0-CH3)3 (Ⅰ-1)

[0066] A method for preparing a structurally symmetrical azosilane coupling agent of formula (I-1) comprises the following steps:

[0067] 1) 49.20 g of ethyl carbamate was dissolved in 150 g of triethylamine, and the reactor was placed under a nitrogen atmosphere; the temperature was raised to 55° C., 100 g of 3-chloropropyltrimethoxysilane was added dropwise to the reactor, and the reaction was carried out at a temperature of 55° C. to 60° C. for 1 h; after the reaction was completed, the by-product was filtered out, and the filtrate was distilled under reduced pressure at 60° C. and -0.090 MPa to recover triethylamine to obtain [3-(trimethoxysilyl)propyl]ethyl carbamate.

[0068] 2) At room temperature, 32.98 g of 80% hydrazine hydrate was dissolved in 100 g of tetrahydrofuran, and then placed in a clean reactor under a nitrogen atmosphere; 3 g of 25% sodium ethoxide ethanol solution was added to the reactor, and then at 45° C., the [3-(trimethoxysilyl)propyl]urethane obtained in step 1) was added dropwise to the reactor, the temperature was controlled to be 45° C. to 50° C., and the reaction was carried out in this temperature range for 90 min; after the reaction was completed, the temperature was cooled to room temperature and 0.5 g of acetic acid was added to quench the reaction for 5 min, and then 1.5 g of SAP super absorbent resin was added to the reaction system at room temperature, and the reaction solution was stirred for 15 min and filtered to fully remove water from the reaction solution. The filtrate was a tetrahydrofuran solution of azosilane precursor.

[0069] 3) Add 3g of pyridine to the tetrahydrofuran solution of the azosilane precursor obtained in step 2) under a nitrogen atmosphere, then add 122.41g of a 60% by mass dichloroisocyanuric acid (TCCA) tetrahydrofuran solution to the reactor at 25°C, and react at room temperature for 45min. After the reaction is completed, the organic solvent is recovered by vacuum rotary drying at 60°C and a vacuum degree of 0.09MPa, and the residual paste is washed with a mixture of heptane and isopropyl ether (volume ratio of 1:1), and then filtered. The filtrate is vacuum rotary dried at 60°C and a vacuum degree of 0.09MPa to obtain the final structurally symmetrical azosilane product as shown in formula (I-1), which has the appearance of a red oily liquid.

[0070] Example 2

[0071] A structurally symmetrical azosilane coupling agent of formula (I-1) was prepared according to the method of Example 1, except that in step (1), "49.20 g of ethyl carbamate was dissolved in 150 g of triethylamine" was replaced by "53.67 g of ethyl carbamate was dissolved in 150 g of triethylamine".

[0072] Example 3

[0073] A structurally symmetrical azosilane coupling agent of formula (I-1) was prepared according to the method of Example 1, except that: in step (2), "32.98 g of 80% hydrazine hydrate was dissolved in 100 g of tetrahydrofuran at room temperature" was replaced by "34.55 g of 80% hydrazine hydrate was dissolved in 100 g of tetrahydrofuran at room temperature"; and in step (3), "122.41 g of 60% dichloroisocyanuric acid (TCCA) in tetrahydrofuran was then added dropwise to the reaction kettle at 25°C" was replaced by "128.24 g of 60% dichloroisocyanuric acid (TCCA) in tetrahydrofuran was then added dropwise to the reaction kettle at 25°C".

[0074] Example 4

[0075] A structurally symmetrical azosilane coupling agent of formula (I-1) was prepared according to the method of Example 1, except that in step (2), "after the reaction is completed, the temperature is cooled to room temperature and 0.5 g of acetic acid is added to quench the reaction for 5 min" is replaced by "after the reaction is completed, the temperature is cooled to room temperature and 2.5 g of acetic acid is added to quench the reaction for 5 min".

[0076] Example 5

[0077] A structurally symmetrical azosilane coupling agent of formula (I-1) was prepared according to the method of Example 1, except that: in step (2), "at room temperature, 32.98 g of 80% by mass hydrazine hydrate was dissolved in 100 g of tetrahydrofuran" was replaced by "at room temperature, 32.98 g of 80% by mass hydrazine hydrate was dissolved in 100 g of dichloromethane".

[0078] Example 6

[0079] A structurally symmetrical azosilane coupling agent of formula (I-1) was prepared according to the method of Example 1, except that: in step (2), "then 1.5 g of SAP super absorbent resin was added to the reaction system at room temperature, stirred for 15 min and filtered" was replaced by "then 2.5 g of SAP super absorbent resin was added to the reaction system at room temperature, stirred for 15 min and filtered".

[0080] Example 7

[0081] A structurally symmetrical azosilane coupling agent of formula (I-1) was prepared according to the method of Example 1, except that in step (3), "adding 3 g of pyridine to the tetrahydrofuran solution of the azosilane precursor obtained in step 2) under a nitrogen atmosphere" was replaced by "adding 3 g of triethylamine recovered in step 1) to the tetrahydrofuran solution of the azosilane precursor obtained in step 2) under a nitrogen atmosphere".

[0082] Example 8

[0083] A structurally symmetrical azosilane coupling agent of formula (I-1) was prepared according to the method of Example 1, except that: in step (3), "then 122.41 g of a 60% by mass solution of dichloroisocyanuric acid (TCCA) in tetrahydrofuran was added dropwise to the reactor at 25°C" was replaced by "then 32.61 g of solid sodium bromide was added to the reactor at 25°C, and chlorine gas was continuously bubbled into the bottom of the reactor to maintain the pressure in the reactor below 0.1 MPa".

[0084] Example 9

[0085] A structurally symmetrical azosilane coupling agent of formula (I-1) was prepared according to the method of Example 1, except that: in step (3), "adding 3 g of pyridine to the tetrahydrofuran solution of the azosilane precursor obtained in step 2) under a nitrogen atmosphere, and then adding dropwise 122.41 g of a 60% by mass solution of dichloroisocyanuric acid (TCCA) in tetrahydrofuran to the reaction kettle at 25° C." was replaced by "adding dropwise 169.90 g of a 60% by mass solution of diacetoxyphenyliodoacetate (PIDA) in tetrahydrofuran to the tetrahydrofuran solution of the azosilane precursor obtained in step 2) under a nitrogen atmosphere at 25° C."

[0086] Example 10

[0087] A structurally symmetrical azosilane coupling agent of formula (I-1) was prepared according to the method of Example 1, except that: in step (3), "3 g of pyridine was added to the tetrahydrofuran solution of the azosilane precursor obtained in step 2) under a nitrogen atmosphere, and then 122.41 g of a 60% by mass solution of dichloroisocyanuric acid (TCCA) in tetrahydrofuran was added dropwise to the reaction kettle at 25°C" was replaced by "226.88 g of a 60% by mass solution of bis(trifluoroacetoxy)phenyliodoacetyl (PIFA) in tetrahydrofuran was added dropwise to the tetrahydrofuran solution of the azosilane precursor obtained in step 2) under a nitrogen atmosphere at 25°C".

[0088] Embodiment 11

[0089] (CH3)3-Si-(CH2)3-NH-C(O)-N=NC(O)-NH-(CH2)3-Si-(CH3)3(Ⅰ-2)

[0090] The structurally symmetrical azosilane coupling agent of formula (I-2) was synthesized according to the method of Example 1, except that: in step (1), "raising the temperature to 55°C and adding 100g of 3-chloropropyltrimethoxysilane dropwise to the reaction kettle" was replaced by "raising the temperature to 55°C and adding 75.88g of (3-chloropropyl)trimethylsilane dropwise to the reaction kettle".

[0091] Comparative Example 1

[0092] A structurally symmetrical azosilane coupling agent of formula (I-1) was prepared according to the method of Example 1, except that: in step (2), "after the reaction is completed, the temperature is cooled to room temperature and 0.5 g of acetic acid is added to quench the reaction for 5 minutes, and then 1.5 g of SAP super absorbent resin is added to the reaction system at room temperature" is replaced by "after the reaction is completed, the temperature is cooled to room temperature, the reaction is continuously stirred at room temperature for 5 minutes, and then 1.5 g of SAP super absorbent resin is added to the reaction system at room temperature".

[0093] Comparative Example 2

[0094] A structurally symmetrical azosilane coupling agent of formula (I-1) was prepared according to the method of Example 1, except that: in step (3), "then 122.41 g of a 60% by mass solution of dichloroisocyanuric acid (TCCA) in tetrahydrofuran was added dropwise to the reaction kettle at 25°C" was replaced by "then 93.39 g of a 60% by mass solution of N-bromosuccinimide (NBS) in tetrahydrofuran was added dropwise to the reaction kettle at 25°C".

[0095] Comparative Example 3

[0096] A structurally symmetrical azosilane coupling agent of formula (I-1) was prepared according to the method of Comparative Example 2, except that: in step (2), "at room temperature, 32.98 g of hydrazine hydrate with a mass fraction of 80% was dissolved in 100 g of tetrahydrofuran" was replaced by "at room temperature, 32.98 g of hydrazine hydrate with a mass fraction of 80% was dissolved in 100 g of dichloromethane".

[0097] Comparative Example 4

[0098] A structurally symmetrical azosilane coupling agent of formula (I-1) was prepared according to the method of Example 1, except that: in step (2), "add 3 g of 25% sodium ethoxide ethanol solution to the reactor, and then begin to dropwise add the [3-(trimethoxysilyl)propyl]urethane obtained in step 1) to the reactor at 45°C" was replaced by "then begin to dropwise add the [3-(trimethoxysilyl)propyl]urethane obtained in step 1) to the reactor at 45°C".

[0099] The purity of the structurally symmetrical azosilane coupling agents obtained in the examples of the present invention and the comparative examples was detected by gas chromatography, and the yield was calculated by the following formula. The specific results are shown in Table 1.

[0100]

[0101] Table 1

[0102]

[0103]

[0104] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a structurally symmetrical azosilane coupling agent, characterized in that include: In the first step, the amino ester of formula (II) NH2-C(O)-O-R5(Ⅱ) With chlorosilane of formula (III) (R1) x (R2) 3-x -Si-R3-Cl(Ⅲ) The reaction yields an aminoester silane of formula (IV): (R1) x (R2) 3-x -Si-R3-NH-C(O)-O-R5(Ⅳ); In the second step, the amino ester silane of formula (IV) reacts with hydrazine hydrate under the action of a catalyst to obtain a silane of formula (V) Azosilane coupling agent precursor: (R1) x (R2) 3-x -Si-R3-NH-C(O)-NH-NH-C(O)-NH-R3-Si-(R1) x (R2) 3-x (Ⅴ); In the third step, the azosilane coupling agent precursor of formula (V) is reacted with an oxidant to obtain a structurally symmetrical azosilane coupling agent of formula (I): (R1) x (R2) 3-x -Si-R3-NH-C(O)-N=NC(O)-NH-R3-Si-(R1) x (R2) 3-x (Ⅰ); In formula (I), formula (II), formula (III), formula (IV) and formula (V), R1 is hydroxyl, C1-C 18 Alkyl, C1-C 18 Alkoxy, C5-C 18 Cycloalkyl, C6-C 18 The aromatic group; R2 is C1-C 18 Alkyl, C1-C 18 Alkoxy, C5-C 18 Cycloalkyl, C6-C 18 The aromatic group; R3 is C1-C 18 Alkylene, C6-C 18 arylene; R5 is C1-C 18 Alkyl, C5-C 18 Cycloalkyl, C6-C 18 The aromatic group; x is an integer from 1 to 3.

2. The preparation method according to claim 1, characterized in that: R1 is -OH; -CH3; -CH2CH3; <h2 style=";text-align:left;direction:ltr">-(CH2)2CH3;-(CH2)5CH3;-(CH2)<h2 style=";text-align:left;direction:ltr"> 10 <h2 style=";text-align:left;direction:ltr"> CH3;-(CH2)<h2 style=";text-align:left;direction:ltr"> 15 <h2 style=";text-align:left;direction:ltr"> CH3;-(CH2)<h2 style=";text-align:left;direction:ltr"> 17 <h2 style=";text-align:left;direction:ltr"> CH3;-O-CH3; <h2 style=";text-align:left;direction:ltr">-O-CH2CH3;-O-(CH2)2CH3;-O-(CH2)5CH3;-O-(CH2)<h2 style=";text-align:left;direction:ltr"> 10 <h2 style=";text-align:left;direction:ltr"> CH3;-O-(CH2)<h2 style=";text-align:left;direction:ltr"> 17 <h2 style=";text-align:left;direction:ltr"> CH3;-C5H9; -C6H 11 ;-C6H5;-CH2-C6H5;-C6H4-CH3; R2 is -CH3; -CH2CH3; -(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; R3 is -CH2-; -CH2 CH2-; -CH2CH2CH2-; -(CH2)5-; -(CH2) 10 -; -(CH2) 15 -; -(CH2) 18 -;-C6H4-;-CH2-C6H4-;-C6H4-CH2-; R5 is -CH3; -CH2CH3; -(CH2)2CH3; -(CH2)3CH3; -(CH2)5CH3; -(CH2) 10 CH3; -(CH2) 15 CH3; -(CH2) 17 CH3;-C5H9;-C6H 11 ;-C6H5;-CH2-C6H5;-C6H4-CH3。 3. The preparation method according to claim 1, characterized in that: in the first step, at least one of the following conditions is included: Condition 1: the molar ratio of the chlorosilane of formula (III) to the amino ester of formula (II) is 1: (1-1.2); Condition 2: the reaction is carried out in the presence of an organic solvent, and the organic solvent is preferably an organic amine, more preferably at least one of pyridine, triethylamine, N,N-dimethylaniline, and tri-n-butylamine; Condition 3, the reaction temperature is 40°C to 70°C; Condition 4: The reaction time is 30 min to 90 min.

4. The preparation method according to claim 1, The method is characterized in that: in the second step, at least one of the following conditions is included: Condition 1: The molar ratio of hydrazine hydrate to the chlorosilane of formula (III) is (1-1.1):1; Condition 2: hydrazine hydrate exists in the form of a solution, and the concentration of the hydrazine hydrate solution is 75-85wt%; Condition 3: The catalyst is an ethanol solution of sodium ethoxide with a mass fraction of 25% to 30%; The reaction is carried out in the presence of an organic solvent, and the organic solvent is preferably at least one of dichloromethane, tetrahydrofuran, N,N-dimethylamide, and acetonitrile; Condition 3, the reaction temperature is 40°C to 60°C; Condition 4: Reaction time is 30 min to 2 h.

5. The preparation method according to claim 4, characterized in that: In the second step, the mass ratio of the ethanol solution of sodium ethoxide with a mass fraction of 25% to 30% to hydrazine hydrate is (5% to 20%):

1.

6. The preparation method according to claim 1, characterized in that: in the third step, the oxidant is one of dichloroisocyanuric acid / acid binding agent oxidation system, sodium bromide / chlorine / acid binding agent oxidation system, diacetoxybenzyl iodide, and bis(trifluoroacetoxy)benzyl iodide.

7. The preparation method according to claim 6, characterized in that: in the third step, at least one of the following conditions is included: Condition 1: In the dichloroisocyanuric acid / acid-binding agent oxidation system, the molar ratio of dichloroisocyanuric acid to hydrazine hydrate is (0.5-2.5):1, and the mass ratio of the acid-binding agent to hydrazine hydrate is (5%-10%):1; Condition 2: In the sodium bromide / chlorine / acid-binding agent oxidation system, the molar ratio of sodium bromide to hydrazine hydrate is (0.5-2.5):1, the mass ratio of the acid-binding agent to hydrazine hydrate is (5%-10%):1, and the chlorine gas keeps the system pressure below 0.1 MPa; Condition 3: the molar ratio of diacetoxybenzene iodide to hydrazine hydrate is (0.5-2.5):1; Condition 4: The molar ratio of bis(trifluoroacetoxy)benzene iodoacetyl to hydrazine hydrate is (0.5-2.5):

1.

8. The preparation method according to claim 1, 6 or 7, characterized in that: in the third step, at least one of the following conditions is included: Condition 1: The reaction is carried out in the presence of an organic solvent, and the organic solvent is preferably one or more of dichloromethane, tetrahydrofuran, N,N-dimethylamide, and acetonitrile; Condition 2: reaction temperature is 20°C to 35°C; Condition 3: The reaction time is 30 min to 60 min.

9. The preparation method according to claim 1, characterized in that: In the second step, after the reaction is completed, a quencher is added to terminate the reaction, and then the water in the reaction solution is removed; preferably, the quencher is acetic acid, and the mass ratio of acetic acid to hydrazine hydrate is (0.5% to 5%): 1; preferably, the temperature of the quenching reaction is 20°C to 30°C, and the time of the quenching reaction is 5min to 15min.

10. The preparation method according to any one of claims 1 to 9, characterized in that: In the first step, the second step and the third step, the reaction processes are all carried out under the protection of inert gas.

Images