Preparation method of methyl alkoxy acetoxysilane with low crystallization temperature

Abstract

The invention relates to the technical field of preparation of silane cross-linking agents, and particularly discloses a preparation method of methyl alkoxyacetoxysilane with low crystallization temperature, which comprises the following steps: by taking methyl triacetoxysilane and methyl trimethoxy silane as raw materials, reacting under the catalytic action of an acidic phosphazene catalyst to obtain methyl alkoxyacetoxysilane with low crystallization temperature; and the methyl alkoxy acetoxysilane product with low crystallization temperature is generated. The method can overcome the problems of low production efficiency, high energy consumption, low conversion rate and the like in the prior art, does not need to separate the catalyst, and is simple to operate, low in production cost, high in production efficiency, safe, environment-friendly and suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of silane crosslinking agents, and particularly relates to a method for preparing low crystallization temperature methyl alkoxy acetoxy silane. Background Art

[0002] Room temperature vulcanized silicone rubber has excellent weather resistance, electrical insulation and other characteristics, and is widely used in various industries. Its characteristics are that it can be vulcanized and formed at room temperature, and it is extremely convenient to use.

[0003] The crosslinking agent for RTV silicone rubber is mainly methyltriacetoxysilane, but because methyltriacetoxysilane cannot be used normally in certain specific fields or when the temperature is low in winter, this greatly limits its application areas. Therefore, it is of great significance to develop a crosslinking agent product for RTV silicone rubber with a low crystallization temperature.

[0004] CN115322438A discloses a methyl alkoxy acetoxy silane mixture with a low crystallization temperature, a preparation method and an application thereof. The methyl alkoxy acetoxy silane mixture product is obtained by modifying methyl triacetoxy silane with different types of alcohols. The process produces organic acid as a by-product, which will seriously affect the product quality if not removed. However, the boiling points of the alkoxy tri-substituted and di-substituted products are close to those of the acid, so there is a problem that the by-product organic acid is difficult to separate, resulting in the inability to properly reuse the by-product and low product yield. CN103450246A discloses a method for preparing methylacetoxymethoxysilane, wherein methyltriacetoxysilane and methyltrimethoxysilane are mixed and then heated to react to obtain a methylacetoxymethoxysilane product. The process does not produce by-products and does not require post-processing, but has problems such as low raw material conversion rate and low production efficiency. Summary of the invention

[0005] The invention provides a method for preparing methyl alkoxy acetoxy silane with a low crystallization temperature, which can quickly and efficiently prepare methyl alkoxy acetoxy silane.

[0006] The technical solution of the present invention is to provide a method for preparing low crystallization temperature methyl alkoxy acetoxy silane, the specific steps of which are: The product is prepared by taking methyltrimethoxysilane and methyltriacetoxysilane as raw materials, adding a phosphazene catalyst, and heating to carry out a reaction.

[0007] Furthermore, the mass ratio of the methyltrimethoxysilane to the methyltriacetoxysilane is 0.2-0.6.

[0008] In a more preferred embodiment, the mass ratio of methyltrimethoxysilane to methyltriacetoxysilane is 0.4.

[0009] Further, the amount of the phosphazene catalyst added is 5-20 ppm of the total mass of the material. In a more preferred embodiment, the amount of the phosphazene catalyst added is 10 ppm of the total mass of the material.

[0010] Furthermore, after adding the catalyst, the temperature is raised to 70-120° C. for reaction. In a more preferred embodiment, after adding the catalyst, the reaction temperature is 100° C. The reaction time is 0.5-2 h.

[0011] The phosphazene catalyst involved in the present invention can be prepared by using phosphorus pentachloride and ammonium chloride as raw materials, adding chlorobenzene, heating to react until a homogeneous phase is formed, and then removing chlorobenzene by reduced pressure distillation.

[0012] The present invention has the following beneficial effects: The present invention can prepare methyl alkoxy acetoxy silane by a one-step method, and adopts a phosphazene catalyst for catalysis, and no by-products are generated during the reaction, the reaction rate is fast, the product conversion rate is high, the process conditions are simple, the reaction cycle is greatly shortened, the production efficiency is improved, and it is easy to realize industrialization. When the phosphazene catalyst is used to catalyze the reaction of methyl trimethoxy silane and methyl triacetoxy silane, it can be controlled at about 10 ppm to meet the catalytic demand, and the excessive dosage is avoided, and the product color is aggravated. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a gas chromatogram of the methyl alkoxy acetoxy silane product obtained in Example 1 of the present invention.

[0014] Figure 2 This is a gas chromatogram of the methyl alkoxy acetoxy silane product obtained in Example 2 of the present invention.

[0015] Figure 3 This is a gas chromatogram of the methyl alkoxy acetoxy silane product obtained in Example 7 of the present invention. DETAILED DESCRIPTION

[0016] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0017] The phosphazene catalysts used in the following examples can be prepared by themselves or purchased from the market.

[0018] How to prepare it yourself: The phosphazene catalyst is prepared by using solid phosphorus pentachloride and ammonium chloride as raw materials (molar ratio is 4:1), adding chlorobenzene to mix and disperse thoroughly, setting the external temperature at 140°C to reflux for 7 hours until a homogeneous phase is obtained, and then removing chlorobenzene by reduced pressure distillation at 120°C to obtain the catalyst.

[0019] Example 1 Preparation method of methyl alkoxy acetoxy silane: Methyltrimethoxysilane and methyltriacetoxysilane were added into the reactor at a mass ratio of 0.4:1, and the temperature was raised to 120°C for 8 hours. After the reaction was completed, the color change of the product was observed. The obtained material was methylalkoxyacetoxysilane. The chromatogram is shown in Figure 1 , it can be seen from the figure that the product components are mainly methyltrimethoxysilane (position 2) and methyltriacetoxysilane and its polymers (positions 5 and 8), and only a small part undergoes substitution reaction (positions 3 and 4).

[0020] Example 2 Preparation method of methyl alkoxy acetoxy silane: Methyltrimethoxysilane and methyltriacetoxysilane were added into the reactor at a mass ratio of 0.4:1, and 1% of the total mass of D001 resin (the resin was dried before use) was added. The temperature was raised to 120°C for reaction for 8 hours, and the temperature was lowered and filtered. The filtrate was collected as the product, methylalkoxyacetoxysilane. When the reaction was completed, the color change of the product was observed.

[0021] The obtained material was tested, and the specific chromatogram is shown in Figure 2 From the figure, it can be seen that a large amount of acetic acid (position 1) is generated as a byproduct in the reaction. It is speculated that there may be a small amount of water that has not been evaporated in the acidic resin, which causes the product to hydrolyze and generate acetic acid as a byproduct. In addition, there is still a lot of trimethylolpropane that does not participate in the reaction, and the product conversion rate is low. Considering that the removal of acetic acid will bring out trimethylolpropane, no distillation and deacetic acid treatment was performed before the later evaluation.

[0022] Example 3 Preparation method of methyl alkoxy acetoxy silane: Methyltrimethoxysilane and methyltriacetoxysilane were added into the reactor in a mass ratio of 0.4:1, and 5% of the total mass of acetic acid was added. The temperature was raised to 120°C and reacted for 8 hours. After the reaction was completed, the by-product acetic acid was distilled out under reduced pressure at 100°C to obtain the product methylalkoxyacetoxysilane, and the color change of the product was observed.

[0023] It should be noted that the methyltriacetoxysilane raw material itself contains acetic acid, but due to its low content (<3%), it cannot promote the forward reaction. When too little acetic acid is added, there is almost no catalytic effect. When too much acetic acid is added, further distillation and separation are required, and the catalytic effect is still poor.

[0024] Example 4 Preparation method of methyl alkoxy acetoxy silane: Methyltrimethoxysilane and methyltriacetoxysilane were added into the reactor at a mass ratio of 0.4:1, and concentrated sulfuric acid (mass concentration is 98%) of 1% of the total mass of the two was added. The temperature was raised to 120°C and reacted for 8 hours. After the reaction was completed, the color change was observed.

[0025] The obtained material methylalkoxyacetoxysilane is yellowish with a slight red color. Analysis shows that the reason is that the concentrated sulfuric acid itself contains a very small amount of metal iron ions which causes the product to change color.

[0026] Example 5 The preparation method of methyl alkoxy acetoxy silane comprises the following steps: Methyltrimethoxysilane and methyltriacetoxysilane were added into the reactor at a mass ratio of 0.4:1, and 1% of the total mass of AlCl3 was added. The temperature was raised to 120°C for reaction for 8 hours, and the temperature was lowered and filtered. The filtrate was collected as the product, methylalkoxyacetoxysilane. When the reaction was completed, the color change was observed.

[0027] Example 6 The preparation method of low crystallization temperature methyl alkoxy acetoxy silane comprises the following steps: Methyltrimethoxysilane and methyltriacetoxysilane were added into the reactor at a mass ratio of 0.4:1, and 10 ppm of the total mass of the acidic phosphazene catalyst was added. The temperature was raised to 70°C and reacted for 2 hours to obtain methylalkoxyacetoxysilane product. After the reaction was completed, the color change was observed.

[0028] Example 7 The preparation method of low crystallization temperature methyl alkoxy acetoxy silane comprises the following steps: Methyltrimethoxysilane and methyltriacetoxysilane were added into the reactor at a mass ratio of 0.4:1, and 10 ppm of the total mass of the acidic phosphazene catalyst was added. The temperature was raised to 100°C and reacted for 1 hour to obtain methylalkoxyacetoxysilane product. After the reaction was completed, the color change was observed.

[0029] The obtained material was tested, and the specific chromatogram is shown in Figure 3 ,It can be seen from the figure that there is almost no methyltrimethoxysilane (position 2) in the product, indicating that the conversion rate of the raw material methyltrimethoxysilane is high and it is effectively converted into mono- and di-substituted products (positions 4 and 3).

[0030] Example 8 The preparation method of low crystallization temperature methyl alkoxy acetoxy silane comprises the following steps: Methyltrimethoxysilane and methyltriacetoxysilane were added into the reactor at a mass ratio of 0.4:1, and 10 ppm of the total mass of the acidic phosphazene catalyst was added. The temperature was raised to 120° C. and reacted for 1 hour to obtain a methylalkoxyacetoxysilane product. After the reaction was completed, the color change was observed.

[0031] Example 9 The preparation method of low crystallization temperature methyl alkoxy acetoxy silane comprises the following steps: Methyltrimethoxysilane and methyltriacetoxysilane were added into the reactor at a mass ratio of 0.4:1, and 10 ppm of the total mass of the acidic phosphazene catalyst was added. The temperature was raised to 120°C and reacted for 0.5 h to obtain methylalkoxyacetoxysilane product. After the reaction was completed, the color change was observed.

[0032] Example 10 Only methyltrimethoxysilane and methyltriacetoxysilane are in a mass ratio of 0.2:1, and the rest is the same as Example 7.

[0033] Embodiment 11 Only methyltrimethoxysilane and methyltriacetoxysilane are in a mass ratio of 0.6:1, and the rest is the same as Example 7.

[0034] The performance tests were conducted on the products obtained in Examples 1 to 11. Specifically, the crystallization rate and the mechanical properties of the products were compared.

[0035] (1) Comparison of crystallization performance: The methyl alkoxy acetoxy silane products in Examples 1-11 were placed in a -15°C refrigerator for one day, and then methyl triacetoxy silane seed crystals were added. The products were placed in the refrigerator for another week, and the crystallization rates of the products before and after the addition of seed crystals were observed.

[0036] (2) Comparison of mechanical properties: 107 glue (viscosity 20000cp), dimethyl silicone oil (viscosity 20cp) and fumed silica were added into a planetary mixer at a ratio of 1:0.05:0.2 and stirred at normal pressure until homogeneous to obtain a base glue. After vacuum stirring for 30 min, a mixture of methyl alkoxyacetoxy silane as a cross-linking agent and dibutyl tin dilaurate catalyst was added to the base glue in a certain ratio (base glue: cross-linking agent: dibutyl tin dilaurate = 1:6%:0.2%). The mixture was vacuum stirred for 15 min and a film was made to evaluate its surface drying time and mechanical properties.

[0037] The performance of the films in Examples 1-11 was evaluated. The surface drying time was tested according to GB / T 13477.5-2002; the tensile strength and elongation were tested according to GT / T 528-2009; and the hardness was tested according to HG / T2368-2011.

[0038] The results of the comparative experiments of the products obtained in Examples 1 to 11 are shown in Table 1.

[0039] Table 1

[0040] As can be seen from Table 1, the methyl alkoxy acetoxy silane product synthesized by the method provided by the present invention does not crystallize when a seed is added at a low temperature of -15°C, and has excellent mechanical properties; the present invention uses phosphazene as a catalyst, effectively improves the reaction rate of methyl trimethoxy silane and methyl triacetoxy silane and the conversion rate of raw materials, shortens the reaction cycle, and can achieve reaction equilibrium by only reacting 10 ppm for 1 hour. The conversion rate of methyl trimethoxy silane is ≥99%, and there is no need to separate the catalyst again, which greatly reduces the production cost, shortens the reaction cycle, improves the conversion rate of raw materials, and the process is simple and continuous, and it is easy to realize industrial production.

[0041] Comparison of Example 1 with Examples 2-11 shows that without the catalytic action of a catalyst, the reaction efficiency of methyltrimethoxysilane and methyltriacetoxysilane is very low, almost no reaction, the product can be regarded as a physical mixture of the two raw materials, the modified product has low activity, a long surface drying time, incomplete curing, and poor mechanical properties.

[0042] Comparing Examples 2-5 with Examples 6-11, the following conclusions were drawn: (1) D001 resin (macroporous strong acid ion exchange resin), acetic acid, concentrated sulfuric acid, AlCl3 and acidic phosphazene catalyst all had catalytic effects on the reaction system of methyltrimethoxysilane and methyltriacetoxysilane. In comparison, the homemade acidic phosphazene catalyst had the highest catalytic activity. The reaction equilibrium could be achieved with only 10 ppm reaction for 1 h. The conversion rate of methyltrimethoxysilane was ≥99%, which greatly improved the reaction rate and product conversion rate, shortened the reaction cycle, and was beneficial to improving product production capacity; (2) The trace amount of water in the catalyst had a great influence on the reaction system of methyltrimethoxysilane and methyltriacetoxysilane. When the acidic resin was used as the catalyst, the acetic acid content in the product increased, and after being placed in a -15°C refrigerator for one day, the product was fully crystallized without adding seed crystals. The reason for this was that the trace amount of water in the resin hydrolyzed part of the raw materials, the crystallization temperature of acetic acid was low, and the acetic acid crystals acted as seed crystals to induce product crystallization.

[0043] By comparing Examples 6-11, the following conclusions can be drawn: (1) The reaction efficiency of the acidic phosphazene catalyst is low at 70°C. Heating can greatly increase the reaction rate of the system, but too high a temperature will cause the product color to darken. 100°C is preferably the optimal reaction temperature; (2) The acidic phosphazene catalyst has a high catalytic activity, and the amount used is extremely small, and separation is not required. It has no effect on the use of the next product, and the production cost is low.

[0044] By comparing Examples 7, 10, and 11, the following conclusions can be drawn: when the amount of the modified substance methyltrimethoxysilane added is small, the modified groups are insufficient, and the product is still fully crystallized after adding seeds at low temperatures; when the amount of the modified substance methyltrimethoxysilane added is large, methyltrimethoxysilane and its substituents will reach an equilibrium, and there is still a large amount of methyltrimethoxysilane in the system, resulting in reduced product activity, and then reduced product hardness and mechanical properties.

[0045] The above embodiments describe the preferred implementation of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing low crystallization temperature methyl alkoxy acetoxy silane, characterized in that: The specific steps are: The product is prepared by taking methyltrimethoxysilane and methyltriacetoxysilane as raw materials, adding a phosphazene catalyst, and heating to carry out a reaction.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the methyltrimethoxysilane to the methyltriacetoxysilane is 0.2-0.

6.

3. The preparation method according to claim 2, characterized in that: The mass ratio of the methyltrimethoxysilane to the methyltriacetoxysilane is 0.

4.

4. The preparation method according to claim 1, characterized in that: The added amount of phosphazene catalyst accounts for 5-20 ppm of the total mass of the material.

5. The preparation method according to claim 4, characterized in that: The added amount of phosphazene catalyst accounts for 10 ppm in the total mass of the material.

6. The preparation method according to any one of claims 1 to 4, characterized in that: After adding the catalyst, the temperature is raised to 70-120°C for reaction.

7. The preparation method according to claim 6, characterized in that: After adding the catalyst, the temperature was raised to 100°C for reaction.

8. The preparation method according to claim 6, characterized in that: The reaction time is 0.5-2h.

9. The preparation method according to claim 8, characterized in that: The reaction time is 1h.

10. The preparation method according to claim 1, characterized in that: The phosphazene catalyst is prepared by using solid phosphorus pentachloride and ammonium chloride as raw materials, adding chlorobenzene to fully mix and disperse, reflux reaction to a homogeneous phase, and then removing chlorobenzene by reduced pressure distillation.

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