Silane cross-linking agent for sealant and preparation method of silane cross-linking agent

Abstract

The invention relates to the technical field of cross-linking agents, in particular to a silane cross-linking agent for sealant and a preparation method thereof.The preparation method comprises the following steps that diacetylmonoxime, an organic solvent, anion exchange resin and a molecular sieve are mixed in proportion, vinyl trichlorosilane is slowly and dropwise added, the reaction temperature is not higher than 30 DEG C in the dropwise adding process, after dropwise adding is completed, the reaction continues for 1.5-2.5 h, and the silane cross-linking agent for sealant is obtained; and performing post-treatment on the product to obtain the silane cross-linking agent, wherein the molecular sieve is a high-temperature-resistant water-absorbing molecular sieve. The prepared water-absorbing molecular sieve and the oxyhydrogen anion exchange resin participate in the reaction to prepare the silane cross-linking agent, so that the reaction can be carried out in the forward direction, the conversion rate and the product yield of diacetylmonoxime are improved, the generation of a byproduct diacetylmonoxime hydrochloride is reduced, the traditional method of adsorbing hydrochloric acid by using excessive diacetylmonoxime is avoided, and the production cost is reduced. And the generation of diacetylmonoxime hydrochloride with thermal instability is obviously reduced, so that the reaction safety is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of crosslinking agents, and particularly to a silane crosslinking agent for sealants and a preparation method thereof. Background Art

[0002] Sealants, also known as room temperature vulcanized silicone rubbers, are polymers of polysiloxanes with a Si-O-Si main chain. Due to the high bond energy of the Si-O bond, they have very excellent high temperature resistance (can be used for a long time at 150°C - 200°C) and UV resistance. In addition, due to the relatively long Si-O bond and large Si-O-Si bond angle, the main chain can rotate freely, and the glass transition temperature is very low, having excellent cold resistance (can still maintain good elasticity at -60°C). The common types on the market can be divided into three types: acetic acid removal type, ketoxime removal type, and alcohol removal type. Among them, the storage property and adhesiveness of the alcohol removal type silicone sealant are not as good as those of the ketoxime removal type silicone sealant under certain conditions. The acid removal type sealant has a pungent smell and is corrosive to metals.

[0003] Sealants mainly consist of 107 rubber (hydroxyl-terminated polydimethylsiloxane), fillers, crosslinking agents, catalysts, coupling agents, and other additives. The role of the crosslinking agent is to link the chain-shaped 107 into a network crosslinked structure, directly affecting the crosslinking density of the sealant system, visually manifested in the apparent density of the silicone rubber and resulting in hardness. Vinyl tributanone oxime silane (VOS), as a crosslinking agent for neutral fast-curing one-component room temperature vulcanized silicone rubber, is commonly used in high-performance one-component formulations, which can better solve the disadvantages of slow vulcanization speed and low bonding strength of neutral one-component silicone rubber. By controlling its dosage, it can enhance the crosslinking points, which is beneficial to the construction of the conductive network and improves the conductivity. And the presence of vinyl in VOS makes the ketoxime group directly connected to the silicon atom on it have a relatively high activity and a relatively fast hydrolysis speed. Therefore, the surface drying time of the sealant can be adjusted by changing the content of VOS. And because VOS can better react with the silicon hydroxyl groups in 107 rubber to form a dense network structure, its tensile strength and elongation at break are both improved. However, when the proportion of VOS increases, the reaction speed between silane molecules becomes faster, reducing the amount of silane that can effectively react with 107 rubber, resulting in a decrease in the crosslinking density of the vulcanizate and a decline in mechanical properties.

[0004] The existing patent CN031311575.5 relates to the raw material components of vinyltris(methylethylketoxime)silane. The solvent is changed to petroleum ether with a boiling point of 60 - 90 °C and a water content of 100 ppm, and methyl ethyl ketoxime with a water content < 1000 ppm. The weight percentages of the raw material components in the total amount are adjusted to obtain a target product with a purity above 97%, a yield of 55% - 62%, and the product appearance is colorless or light-colored. The existing patent CN201810138622.9 relates to a continuous reaction system for vinyltris(methylethylketoxime)silane. By using a cluster tube reactor module connected in series up and down to form a cluster tube template combination application, the reaction temperature can be accurately controlled, safe and reliable, and continuous feeding of the reactor can be achieved. Precise batching under DCS control improves production efficiency and reduces energy consumption, and greatly reduces the labor intensity of operators. The existing patent CN202010252128.2 relates to a preparation method of vinyltris(methylethylketoxime)silane. It mainly synthesizes a tungsten silicate solid crystal with a microporous structure and combines it with traditional desiccants calcium oxide and anhydrous calcium chloride to prepare a composite strong microporous desiccant for drying the raw material methyl ethyl ketoxime, so as to greatly reduce the water content in methyl ethyl ketoxime, reducing the water content in methyl ethyl ketoxime from 1500 - 2500 ppm to below 200 ppm. The existing patent CN202011512002.0 relates to the preparation of a catalyst for synthesizing vinyltris(methylethylketoxime)silane. In this paper, cheap and non-toxic cyanuric acid and cyanamide are used as precursors, and a compound microemulsion is used as a template agent to prepare porous graphitic carbon nitride; then, ethylenediamine is grafted onto the material surface in an ethylene glycol environment to prepare a supported amino porous graphitic carbon nitride powder. Grafting amino groups on the material surface can promote the deposition of metal ions on the material surface, create more catalytic sites, and enhance the catalytic ability.

[0005] The reaction yield of vinyltris(methylethylketoxime)silane prepared by some of the above methods is about 65%. The method described in patent CN202011512002.0 can reach about 80%. However, by-products HCl will be generated during the synthesis reaction. Currently, the existing process mainly uses excessive methyl ethyl ketoxime to adsorb hydrochloric acid. While reducing the content of hydrochloric acid, heat-unstable substances methyl ethyl ketoxime hydrochloride will also be produced. At the same time, this substance is immiscible with the solvent and the product, which will increase the viscosity of the reaction system and the dispersibility of the materials. Summary of the Invention

[0006] In view of this, the present invention provides a silane crosslinking agent for sealants and its preparation method, aiming to reduce the content of by-product methyl ethyl ketoxime hydrochloride, improve the conversion rate of methyl ethyl ketoxime and the product yield.

[0007] The technical solution of the present invention is realized as follows:

[0008] The present invention provides a preparation method of a silane cross-linking agent for sealant, comprising the following steps:

[0009] Mix methyl ethyl ketoxime, organic solvent, anion exchange resin and molecular sieve in proportion, slowly dropwise add vinyltrichlorosilane, and during the dropping process, the reaction temperature is not greater than 30 °C. After the dropping is completed, continue to react for 1.5 - 2.5 h, and the product is post-treated to obtain the silane cross-linking agent. The molecular sieve is a high-temperature resistant water-absorbing molecular sieve.

[0010] This reaction belongs to the O-alkylation reaction of methyl ethyl ketoxime. The reaction system is conducive to proceeding in the forward reaction direction under alkaline conditions. In this method, the hydroxide form anion exchange resin reduces the pH value in the system while adsorbing and removing chloride ions, which is beneficial to improving the product yield. Hydrochloric acid is generated during the reaction process. In the original process, methyl ethyl ketoxime is used to adsorb the hydrochloric acid generated by the reaction. On the one hand, it can prevent the reaction kettle from being corroded by hydrochloric acid, and on the other hand, it can prevent excessive acid and avoid incomplete reaction. However, using methyl ethyl ketoxime to adsorb acid will generate heat-unstable methyl ethyl ketoxime hydrochloride, which is prone to thermal decomposition at a certain temperature, releasing a large amount of heat and having certain potential safety hazards. The present invention uses the hydroxide form anion exchange resin to adsorb and exchange chloride ions, which is beneficial for the methyl ethyl ketoxime negative ion to attack vinyltrichlorosilane and carry out SN2 nucleophilic reaction to make the reaction proceed in the forward direction. The principle of the hydroxide form anion exchange resin adsorbing and exchanging chloride ions is as follows:

[0011]

[0012] During the process of adsorbing chloride ions by the hydroxide form anion exchange resin, water will be generated, which will affect the yield of the target product. The present invention uses a high-temperature resistant water-absorbing molecular sieve to absorb the water produced in the system and avoid the hydrolysis of the product to form dimers and trimers.

[0013] On the basis of the above technical solutions, preferably, the preparation method of the molecular sieve is as follows:

[0014] S1. Mix tetraethyl orthosilicate and tetraethylammonium hydroxide solution at room temperature, dropwise add the methanol solution of 171 - 560 silane mixture, and continue to react at room temperature for 1.5 - 2.5 h after the dropping is completed to obtain solution A;

[0015] S2. Dissolve sodium aluminate in deionized water to obtain solution B, add solution A to solution B, and stir and react at room temperature for 0.5 - 1.5 h to obtain a gel;

[0016] S3. Carry out crystallization treatment on the gel, and after crystallization is completed, dry and calcine to obtain the molecular sieve.

[0017] The water-absorbing molecular sieve prepared by the present invention is prepared using organosilicon as a template agent. Due to its strong affinity for silicates and aluminosilicates, the organosilane template agent can easily form silicon-oxygen-silicon or silicon-oxygen-aluminum covalent bonds with silanol groups or aluminum hydroxide groups through the hydrolysis of silyl groups in an aqueous solution in a silicate gel or a silicon-based precursor. The organosilylated zeolite gel forms inorganic-organic composite seeds during crystallization. The template agent causes a blocking and occupying effect in space as the zeolite framework grows due to its strong chemical binding with silicon source or aluminum source molecules. After calcining to remove the template agent, a hierarchical pore zeolite material with a zeolite crystal form is finally prepared. After hydrolysis, the siloxy groups in the template agent form hydroxyl groups, and the hydroxyl groups condense with the silanol groups on the surface of the zeolite crystal to form Si-O-Si bonds, enabling the template agent molecules to be connected to the zeolite surface, thereby preventing crystal growth and forming nanoscale zeolites.

[0018] Based on the above technical solution, preferably, in step S1, the addition amounts of tetraethyl orthosilicate, tetraethylammonium hydroxide solution, and methanol solution of 171-560 silane mixture are 10-20 g: 20-40 mL: 3-6 mL. The tetraethylammonium hydroxide solution is an aqueous solution with a mass fraction of 25%, and the concentration of the methanol solution of 171-560 silane mixture is 5%-10%.

[0019] Based on the above technical solution, preferably, in step S2, the addition amounts of sodium aluminate and deionized water are 4-8 g: 20 mL.

[0020] Based on the above technical solution, preferably, in step S3, the crystallization treatment specifically includes: statically pre-crystallizing the gel at 70-90 °C for 22-26 h at low temperature, and then raising the temperature to 140-180 °C for high-temperature crystallization for 3-5 d.

[0021] In the present invention, first, low-temperature pre-crystallization is carried out at 70-90 °C for 22-26 h, mainly promoting the formation of a large number of small crystal nuclei and laying a foundation for subsequent crystal growth. Subsequently, high-temperature crystallization is carried out at 140-180 °C for 3-5 d to accelerate crystal growth. This step-by-step process not only separates nucleation from crystal growth but also significantly improves crystal quality, reduces defects, and increases crystallinity and purity. By controlling the conditions of low-temperature pre-crystallization, the crystal size and distribution can be precisely controlled. In addition, this method helps to optimize the hierarchical pore structure and form a synergistic structure of micropores, mesopores, and macropores. Step-by-step crystallization also improves the thermal stability and chemical stability of the product, while improving the effect of the template agent, promoting the full interaction between the template agent and the aluminosilicate precursor, and guiding the formation and growth of the crystal framework. Although the entire process takes a long time, the low energy consumption in the low-temperature pre-crystallization stage balances the high energy consumption in the high-temperature crystallization to a certain extent, improving the overall energy efficiency.

[0022] On the basis of the above technical solutions, preferably, in step S3, the drying temperature is 100 - 120 °C, and the drying time is 1 - 2 h; the calcination temperature is 550 - 700 °C, and the calcination time is 8 - 12 h.

[0023] On the basis of the above technical solutions, preferably, the mass ratio of methyl ethyl ketoxime, organic solvent and vinyl trichlorosilane is 1:1 - 1.5:0.2 - 0.4, and the addition amount of the anion exchange resin is 5 - 15% of the mass of methyl ethyl ketoxime.

[0024] On the basis of the above technical solutions, preferably, the anion exchange resin is a hydroxide - type anion exchange resin, and the dropping rate of vinyl trichlorosilane is 1.5 - 2.0 mL / min. By controlling the dropping rate of vinyl trichlorosilane, the reaction rate is controlled to avoid the sudden rise in temperature caused by too fast reaction, which is difficult to control.

[0025] On the basis of the above technical solutions, preferably, the post - treatment specifically includes: after the reaction is completed, the product is allowed to stand for liquid - liquid separation, and the upper clear liquid is taken for vacuum distillation. The distillation temperature is 90 - 110 °C, and the vacuum pressure is 30 KPa.

[0026] The present invention provides a silane cross - linker for sealant, and the silane cross - linker is prepared by using the preparation method described in any one of the above.

[0027] The silane cross - linker for sealant and its preparation method of the present invention have the following

[0028] Advantages:

[0029] (1) By using the prepared water - absorbing molecular sieve and hydroxide - type anion exchange resin to participate in the reaction to prepare the silane cross - linker, it is beneficial to the forward progress of the reaction, improves the conversion rate of methyl ethyl ketoxime and the product yield, and reduces the generation of by - product methyl ethyl ketoxime hydrochloride. It not only avoids the traditional method of using excessive methyl ethyl ketoxime to adsorb hydrochloric acid, but also significantly reduces the generation of thermally unstable methyl ethyl ketoxime hydrochloride, thereby improving the safety of the reaction. While improving the product quality and production efficiency, it also enhances the safety and controllability of the production process, providing a new, more efficient, safe and environmentally friendly way for the industrial production of sealant silane cross - linker;

[0030] (2) By using the hydroxide - type anion exchange resin, the chloride ions in the reaction system are effectively adsorbed and removed. It not only avoids the disadvantages of using excessive methyl ethyl ketoxime to adsorb hydrochloric acid in the traditional method, but also effectively promotes the formation of methyl ethyl ketoxime anions and promotes the SN2 nucleophilic reaction, thereby improving the selectivity and efficiency of the reaction. Secondly, by reducing the chloride ions in the system, the generation of corrosive by - products is significantly reduced, improving the service life of the equipment and the safety of production;

[0031] (3) By using silicone as a template agent and adopting a stepwise crystallization strategy combining low-temperature pre-crystallization and high-temperature crystallization, the obtained molecular sieve has a hierarchical pore structure and a nano-scale zeolite structure, which can effectively absorb the water generated in the reaction system, thus avoiding the hydrolysis of the product, effectively inhibiting the formation of by-products such as dimers and trimers, and significantly improving the yield and purity of the target product; at the same time, the high-temperature resistance of the molecular sieve ensures that it can continuously and effectively play its role throughout the reaction process, and can maintain stable structure and complete function even at a relatively high reaction temperature. Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0033] Figure 1 Scanning electron microscope image of the water-absorbing molecular sieve prepared in Example 1 of the present invention;

[0034] Figure 2 Infrared spectrum of the silane coupling agent prepared in Example 1 of the present invention. Detailed Embodiments

[0035] The following will describe clearly and completely the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0036] The raw materials of the embodiments of the present invention are all purchased from conventional channels. Among them, the 171-560 silane mixture is purchased from New Blue Sky New Materials Co., Ltd., with the model LT-171 / LT-560.

[0037] Example 1

[0038] This embodiment provides a preparation method of a silane crosslinking agent for sealant, comprising the following steps: Add 532 g of butanone oxime, 700 g of petroleum ether, 53.2 g of hydroxide-type anion exchange resin and water-absorbing molecular sieve, stir for 20 min to mix evenly, then add 162 g of vinyltrichlorosilane to a constant-pressure separatory funnel, control the dropping rate at 1.8 mL / min. After the dropping is completed, continue the reaction, stop stirring, let it stand and cool down. The upper clear liquid is neutralized with liquid ammonia and filtered by suction, and then the clear liquid is subjected to vacuum distillation, control the kettle temperature at 100 °C and the vacuum pressure at 30 KPa to obtain the product. After drying the lower-layer precipitate of the reaction and sieving to separate the resin and the molecular sieve, the resin is regenerated.

[0039] Among them, the preparation method of the water-absorbing molecular sieve is as follows:

[0040] S1. Mix 15 g of tetraethyl orthosilicate and 30 mL of tetraethylammonium hydroxide solution (TEAH, 25% aqueous solution) evenly by stirring at room temperature for 30 min, then slowly dropwise add 4.5 mL of methanol solution of 171-560 silane mixture under vigorous stirring. After the dropping is completed, continue the reaction at room temperature for 2 h to obtain solution A;

[0041] S2. Dissolve 6 g of sodium aluminate in 20 mL of deionized water and stir at room temperature until it is dissolved and clarified to obtain solution B. Under vigorous stirring, gradually add solution A to solution B, and stir and react at room temperature for 1 h to obtain a milky white gel;

[0042] S3. Transfer the above gel to a polytetrafluoroethylene inner liner and place it in a high-temperature kettle for static low-temperature precrystallization at 80 °C for 24 h, and then raise the temperature to 160 °C for high-temperature crystallization for 4 d. After the crystallization is completed, take it out, quickly cool it with tap water, dry the crystallized product with deionized water at 110 °C, and then calcine it in a muffle furnace at 600 °C for 10 h to remove various template agents to obtain a white powder molecular sieve.

[0043] The content of vinyltrichlorosilane in the product of this embodiment is 96.21%, the product chromaticity is No. 10, and the content of butanone oxime hydrochloride accounts for 5% of the reactant system.

[0044] As Figure 1 shown, Figure 1 The electron microscope image of the molecular sieve is shown. It can be clearly seen from the figure that the prepared sample is spherical particles with a particle size of about 500-900 nm and a smooth surface. In particular, there are no small nanocrystalline aggregates similar to those found before on the surface, and the large particles are not composed of nanocrystals. The mass transfer rate and reaction rate of the nanoscale mesoporous material in the catalytic reaction are also significantly improved.

[0045] As Figure 2 shown, Figure 2The infrared spectrum of the silane coupling agent prepared in Example 1 is shown, where 1190.82 cm -1 is the hydroxyl absorption peak, and 1073.88 cm -1 is the stretching vibration of the ether group, and 2943.54 cm -1 is the absorption peak of C-H stretching vibration, and 2840.86 cm -1 is the absorption peak of C-H stretching vibration of Si–OCH3. 560 epoxy ring-opening addition 171, without vinyl (around 1645 cm -1 ), and epoxy (1280 - 1240 cm -1 , 950 - 810 cm -1 , 840 - 750 cm -1 ) characteristic peaks.

[0046] Example 2

[0047] This example provides a preparation method of a silane cross-linking agent for sealant, including the following steps: 532 g of butanone oxime, 532 g of petroleum ether, 26.5 g of hydroxide form anion exchange resin and water-absorbing molecular sieve are stirred for 20 min to be mixed evenly, then 106.4 g of vinyltrichlorosilane is added to a constant pressure separating funnel, the dropping rate is controlled at 1.5 mL / min, after the dropping is completed, the reaction continues, the stirring is stopped and the mixture is allowed to stand and cool down. The upper clear liquid is neutralized and filtered by liquid ammonia, and then the clear liquid is subjected to vacuum rectification, controlling the kettle temperature at 90 °C and the vacuum pressure at 30 KPa to obtain the product. After drying the lower layer precipitate of the reaction and sieving to separate the resin and the molecular sieve, the resin is regenerated.

[0048] Among them, the preparation method of the water-absorbing molecular sieve is as follows:

[0049] S1. 10 g of tetraethyl orthosilicate and 20 mL of tetraethylammonium hydroxide solution (TEAH, 25% aqueous solution) are stirred at room temperature for 30 min to be mixed evenly, then 3 mL of methanol solution of 171 - 560 silane mixture is slowly added dropwise under vigorous stirring. After the dropping is completed, the reaction continues at room temperature for 1.5 h to obtain solution A;

[0050] S2. 4 g of sodium aluminate is dissolved in 20 mL of deionized water and stirred at room temperature until it is dissolved and clarified to obtain solution B. Under vigorous stirring, solution A is gradually added to solution B, and the mixture is stirred and reacted at room temperature for 0.5 h to obtain a milky white gel;

[0051] S3. Transfer the above gel to a polytetrafluoroethylene liner and place it in an autoclave for static low-temperature pre-crystallization at 70 °C for 26 h, and then raise the temperature to 140 °C for high-temperature crystallization for 5 d. After the crystallization is completed, take it out and quickly cool it with tap water. Dry the crystallization product with deionized water at 110 °C, and then calcine it in a muffle furnace at 550 °C for 12 h to remove various templating agents, obtaining white powder molecular sieve.

[0052] The content of vinyltrichlorosilane in the product of this example is 95.92%, the product chromaticity is No. 10, and the content of butanone oxime hydrochloride accounts for 4.8% of the reactant system.

[0053] Example 3

[0054] This example provides a preparation method of a silane cross-linking agent for sealant, which includes the following steps: Add 532 g of butanone oxime, 798 g of petroleum ether, 79.5 g of hydroxide-type anion exchange resin and water-absorbing molecular sieve, stir for 20 min to mix evenly, then add 212.8 g of vinyltrichlorosilane to a constant-pressure separating funnel, control the dropping rate at 2.0 mL / min. After the dropping is completed, continue the reaction, stop stirring and let it stand to cool down. The upper clear liquid is neutralized and filtered by ammonia, and then the clear liquid is subjected to vacuum rectification, control the kettle temperature at 110 °C, and the vacuum pressure at 30 KPa to obtain the product. After drying the lower-layer precipitate of the reaction and sieving to separate the resin and the molecular sieve, regenerate the resin.

[0055] Among them, the preparation method of the water-absorbing molecular sieve is as follows:

[0056] S1. Add 20 g of tetraethyl orthosilicate and 40 mL of tetraethylammonium hydroxide solution (TEAH, 25% aqueous solution), stir at room temperature for 30 min to mix evenly, and then slowly drop 6 mL of methanol solution of 171-560 silane mixture under vigorous stirring. After the dropping is completed, continue to react at room temperature for 2.5 h to obtain solution A;

[0057] S2. Dissolve 8 g of sodium aluminate in 20 mL of deionized water, stir at room temperature until it is dissolved and clarified to obtain solution B. Under vigorous stirring, gradually add solution A to solution B, and stir and react at room temperature for 1.5 h to obtain a milky white gel;

[0058] S3. Transfer the above gel to a polytetrafluoroethylene liner and place it in an autoclave for static low-temperature pre-crystallization at 90 °C for 22 h, and then raise the temperature to 180 °C for high-temperature crystallization for 3 d. After the crystallization is completed, take it out and quickly cool it with tap water. Dry the crystallization product with deionized water at 110 °C, and then calcine it in a muffle furnace at 700 °C for 8 h to remove various templating agents, obtaining white powder molecular sieve.

[0059] In this example, the content of vinyltrichlorosilane in the product is 95.21%, the colority of the product is No. 10, and the content of butanone oxime hydrochloride accounts for 4.5% of the reactant system.

[0060] Example 4

[0061] This example provides a preparation method of a silane crosslinking agent for sealant, which includes the following steps: Add 532 g of butanone oxime, 600 g of petroleum ether, 50 g of hydroxide-type anion exchange resin and water-absorbing molecular sieve, stir for 20 min to mix evenly, then add 200 g of vinyltrichlorosilane to a constant-pressure separating funnel, control the dropping rate at 1.6 mL / min. After the dropping is completed, continue the reaction, stop stirring, let it stand and cool down. The upper clear liquid is neutralized and filtered by liquid ammonia, and then the clear liquid is subjected to vacuum rectification. Control the kettle temperature at 95 °C and the vacuum pressure at 30 KPa to obtain the product. After drying the lower-layer precipitate of the reaction and sieving to separate the resin and molecular sieve, regenerate the resin.

[0062] Among them, the preparation method of the water-absorbing molecular sieve is as follows:

[0063] S1. Mix 17 g of tetraethyl orthosilicate and 25 mL of tetraethylammonium hydroxide solution (TEAH, 25% aqueous solution) by stirring at room temperature for 30 min. Then, slowly and gradually drop 4 mL of the methanol solution of the 171-560 silane mixture under vigorous stirring. After the dropping is completed, continue the reaction at room temperature for 2.2 h to obtain solution A;

[0064] S2. Dissolve 5 g of sodium aluminate in 20 mL of deionized water and stir at room temperature until it is dissolved and clarified to obtain solution B. Under vigorous stirring, gradually add solution A to solution B, and stir and react at room temperature for 0.8 h to obtain a milky white gel;

[0065] S3. Transfer the above gel to a polytetrafluoroethylene inner liner and place it in a high-temperature kettle for static low-temperature precrystallization at 85 °C for 23 h, and then raise the temperature to 170 °C for high-temperature crystallization for 3.5 d. After the crystallization is completed, take it out and quickly cool it with tap water. Dry the crystallized product with deionized water at 110 °C, and then calcine it in a muffle furnace at 600 °C for 11 h to remove various template agents to obtain a white powder molecular sieve.

[0066] In this example, the content of vinyltrichlorosilane in the product is 94.81%, the colority of the product is No. 10, and the content of butanone oxime hydrochloride accounts for 6.1% of the reactant system.

[0067] Comparative Example 1

[0068] This comparative example provides a preparation method of a silane crosslinking agent for sealant, including the following steps: Add 585.2 g of butanone oxime, 700 g of petroleum ether and water-absorbing molecular sieve, stir for 20 min to mix evenly, then add 162 g of vinyltrichlorosilane to a constant pressure separating funnel, control the dropping rate at 1.8 mL / min. After the dropping is completed, continue the reaction, stop stirring, let it stand and cool down. The upper clear liquid is neutralized and filtered with liquid ammonia, and then the clear liquid is subjected to vacuum distillation. Control the kettle temperature at 100 °C and the vacuum pressure at 30 KPa to obtain the product.

[0069] Among them, the preparation method of the water-absorbing molecular sieve is as follows:

[0070] S1. Mix 15 g of tetraethyl orthosilicate and 30 mL of tetraethylammonium hydroxide solution (TEAH, 25% aqueous solution) evenly by stirring at room temperature for 30 min, and then slowly dropwise add 4.5 mL of the methanol solution of 171-560 silane mixture under vigorous stirring. After the dropping is completed, continue the reaction at room temperature for 2 h to obtain solution A;

[0071] S2. Dissolve 6 g of sodium aluminate in 20 mL of deionized water and stir at room temperature until it is dissolved and clarified to obtain solution B. Under vigorous stirring, gradually and slowly add solution A to solution B, and stir and react at room temperature for 1 h to obtain a milky white gel;

[0072] S3. Transfer the above gel to a polytetrafluoroethylene inner liner and place it in a high-temperature kettle for static low-temperature precrystallization at 80 °C for 24 h, and then raise the temperature to 160 °C for high-temperature crystallization for 4 d. After the crystallization is completed, take it out, quickly cool it with tap water, dry the crystallized product with deionized water at 110 °C, and then calcine it in a muffle furnace at 600 °C for 10 h to remove various template agents to obtain white powder molecular sieve.

[0073] The content of vinyltrichlorosilane in the product of this comparative example is 90.75%, the product chromaticity is No. 10, and the content of butanone oxime hydrochloride accounts for 8.4% of the reactant system.

[0074] Comparative Example 2

[0075] This comparative example provides a preparation method of a silane crosslinking agent for sealant, including the following steps: Add 532 g of butanone oxime, 700 g of petroleum ether, 53.2 g of hydroxide-type anion exchange resin and water-absorbing molecular sieve, stir for 20 min to mix evenly, then add 162 g of vinyltrichlorosilane to a constant pressure separating funnel, control the dropping rate at 1.8 mL / min. After the dropping is completed, continue the reaction, stop stirring, let it stand and cool down. The upper clear liquid is neutralized and filtered with liquid ammonia, and then the clear liquid is subjected to vacuum distillation. Control the kettle temperature at 100 °C and the vacuum pressure at 30 KPa to obtain the product. After drying the lower layer precipitate of the reaction and sieving to separate the resin and the molecular sieve, the resin is regenerated.

[0076] Among them, the water-absorbing molecular sieve is 4A molecular sieve, purchased from Zibo Jiulong Chemical Technology Co., Ltd. The 4A molecular sieve is spherical, with a diameter of 1.4 - 2.5 mm, a particle size qualification rate ≥ 95%, and a static water adsorption ≥ 20.5%.

[0077] The content of vinyltrichlorosilane in the product of this comparative example is 85.36%, the product chromaticity is No. 10, and the content of butanone oxime hydrochloride accounts for 7.3% of the reactant system.

[0078] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a silane crosslinking agent for sealant, characterized in that: It includes the following steps: Mix methyl ethyl ketoxime, organic solvent, anion exchange resin, and molecular sieve in proportion, slowly dropwise add vinyltrichlorosilane, and during the dropping process, the reaction temperature is not higher than 30 °C. After the dropping is completed, continue to react for 1.5 - 2.5 h, and obtain the silane crosslinking agent through post-treatment of the product. The molecular sieve is a high-temperature resistant water-absorbing molecular sieve.

2. The preparation method of a silane crosslinking agent for sealant according to claim 1, characterized in that: The preparation method of the molecular sieve is as follows: S1. Mix tetraethyl orthosilicate and tetraethylammonium hydroxide solution at room temperature, dropwise add a methanol solution of 171 - 560 silane mixture, and continue to react at room temperature for 1.5 - 2.5 h after the dropping is completed to obtain solution A; S2. Dissolve sodium aluminate in deionized water to obtain solution B, add solution A to solution B, and stir and react at room temperature for 0.5 - 1.5 h to obtain a gel; S3. Perform crystallization treatment on the gel, and after the crystallization is completed, dry and calcine to obtain the molecular sieve.

3. The preparation method of a silane crosslinking agent for sealant according to claim 2, characterized in that: In step S1, the addition amounts of tetraethyl orthosilicate, tetraethylammonium hydroxide solution, and methanol solution of 171 - 560 silane mixture are 10 - 20 g: 20 - 40 mL: 3 - 6 mL. The tetraethylammonium hydroxide solution is an aqueous solution with a mass fraction of 25%, and the concentration of the methanol solution of 171 - 560 silane mixture is 5% - 10%.

4. The preparation method of a silane crosslinking agent for sealant according to claim 2, wherein: In step S2, the addition amounts of sodium aluminate and deionized water are 4 - 8 g: 20 mL.

5. The preparation method of a silane crosslinking agent for sealant according to claim 1, wherein: In step S3, the crystallization treatment specifically includes: statically pre-crystallize the gel at 70 - 90 °C for 22 - 26 h at low temperature, and then raise the temperature to 140 - 180 °C for high-temperature crystallization for 3 - 5 d.

6. The preparation method of a silane crosslinking agent for sealant according to claim 1, characterized in that: In step S3, the drying temperature is 100 - 120 °C, and the drying time is 1 - 2 h; the calcination temperature is 550 - 700 °C, and the calcination time is 8 - 12 h.

7. The preparation method of a silane crosslinking agent for sealant according to claim 1, characterized in that: The mass ratio of methyl ethyl ketoxime, organic solvent, and vinyltrichlorosilane is 1: 1 - 1.5: 0.2 - 0.4, and the addition amount of the anion exchange resin is 5 - 15% of the mass of methyl ethyl ketoxime.

8. The preparation method of a silane crosslinking agent for sealant according to claim 1, characterized in that: The anion exchange resin is a hydroxide-type anion exchange resin, the organic solvent is petroleum ether, and the dropping rate of vinyltrichlorosilane is 1.5 - 2.0 mL / min.

9. The preparation method of a silane crosslinking agent for sealant according to claim 1, wherein: The post-treatment specifically includes: after the reaction is completed, let the product stand for layering, take the upper clear liquid for vacuum distillation, the distillation temperature is 90 - 110 °C, and the vacuum pressure is 30 KPa.

10. A silane crosslinking agent for sealant, characterized in that: The silane crosslinking agent is prepared by using the preparation method described in any one of claims 1 - 9.

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