Process for the preparation of methylhydrogen siloxane mixed rings and tetramethylcyclotetrasiloxane

Abstract

The application provides a preparation method of methyl hydrogen siloxane mixed ring body and tetramethylcyclotetrasiloxane. The preparation method of the methyl hydrogen siloxane mixed ring body comprises the following steps: adding a high-boiling inert cleavage diluent and an acidic rearrangement catalyst into a hydrolysate of methyl dichlorosilane, and performing vacuum distillation to obtain the methyl hydrogen siloxane mixed ring body. The preparation method provided by the application can prepare the methyl hydrogen siloxane mixed ring body with high yield and few impurities (D n H ), so that high-quality target product D4 H , secondary product D3 H , and remaining mixed ring bodies such as D5 H , D6 H can be separated and purified, and the remaining mixed ring bodies can be rearranged and cleaved with the hydrolysate again, while the solvent can be recycled and the pollution is small, and the method has good economic benefits.

Description

Technical Field

[0001] This invention relates to the field of methylhydrosiloxane mixed cyclic preparation technology, and more specifically, to a method for preparing methylhydrosiloxane mixed cyclic and tetramethylcyclotetrasiloxane. Background Technology

[0002] 1,3,5,7-Tetramethylcyclotetrasiloxane (D4) H It possesses advantages such as high purity and fixed chain segments, making it suitable for designing modified molecules and for preparing methylhydrosiloxanes and modified siloxanes with specific hydrogen contents and desired chain segment numbers. Current techniques typically involve first preparing a mixed cyclic form of methylhydrosiloxanes, and then separating and extracting 1,3,5,7-tetramethylcyclotetrasiloxane (D4) from it. H ).

[0003] However, most domestic processes for producing methylhydrocyclosiloxanes currently use concentrated sulfuric acid as a catalyst. This synthesis technology causes significant environmental pollution and wastes a large amount of freshwater resources. Furthermore, using concentrated sulfuric acid as a catalyst results in mixed cyclic D... n H The low yield, excessive impurities, and unstable quality of (n = 3, 4, 5, 6, ...) are detrimental to D4. H Separation and purification. Summary of the Invention

[0004] This invention provides a method for preparing methylhydrosiloxane mixed cyclic compounds, which can effectively improve the efficiency of methylhydrosiloxane mixed cyclic compounds (D... n H The quality and yield of 1,3,5,7-tetramethylcyclotetrasiloxane (D4) were improved through separation and purification to obtain high-quality 1,3,5,7-tetramethylcyclotetrasiloxane (D4). H ).

[0005] The present invention provides a method for preparing a mixed methylhydrosiloxane ring, which includes the following steps: adding a high-boiling-point inert cracking diluent and an acidic rearrangement catalyst to the hydrolysate of methyldichlorosilane, and then distilling under reduced pressure to obtain the mixed methylhydrosiloxane ring.

[0006] Through numerous innovative experiments, the applicant of this invention discovered that adding a high-boiling-point inert cracking diluent and an acidic rearrangement catalyst to methyldichlorosilane hydrolysate can effectively improve the methylhydrosiloxane mixed cyclic structure (D... n H (quality and yield)

[0007] In a preferred embodiment of the present application, the high-boiling inert cleavage diluent includes, but is not limited to, diethyl phthalate, dibutyl phthalate, dioctyl phthalate and other solvents that do not react with acid. In the present application, the high-boiling inert cleavage diluent preferably has a boiling point higher than 240°C, and is further preferably diethyl phthalate. The specific high-boiling inert cleavage diluent selected in the present application is used in combination with the acidic rearrangement catalyst, effectively reducing the cross-linking tendency of the cleavage material, allowing the cleavage and rearrangement process to proceed smoothly, and effectively improving the quality of the cleavage product.

[0008] In a preferred embodiment of the present application, the acidic rearrangement catalyst is glacial acetic acid, propionic acid, phosphoric acid and other weakly acidic liquid acids. The specific acidic rearrangement catalyst described above is used in the present application in combination with the high-boiling inert cleavage diluent, which, on the basis of ensuring other effects, can effectively prevent cross-linking during atmospheric cleavage. In a preferred embodiment of the present application, the acidic rearrangement catalyst is glacial acetic acid.

[0009] In a preferred embodiment of the present application, the mass ratio of the hydrolyzate of methyl dichlorosilane to the acidic rearrangement catalyst is 100:(0.5-2). In a specific embodiment of the present application, too little acidic rearrangement agent will reduce the final yield, and too much acidic rearrangement agent will cause cross-linking, thereby affecting the quality of the final product.

[0010] In a preferred embodiment of the present application, the volume ratio of the hydrolyzate of methyl dichlorosilane to the high-boiling cleavage diluent is 1:(1-3). In a specific embodiment of the present application, if the high-boiling cleavage diluent is too little or too much, the yield per unit time will decrease.

[0011] In a specific embodiment of the present application, the hydrolyzate of methyl dichlorosilane can be prepared using the hydrolysis method commonly used in the art for methyl dichlorosilane, which preferably includes the following steps: hydrolyzing methyl dichlorosilane, a solvent and water at -10-40°C, taking the oil phase, neutralizing and washing with water, and removing the solvent, i.e. the hydrolysis oil. The solvent can be one or more of cyclohexane, n-hexane, n-octane and other alkane solvents. In a specific embodiment of the present application, the volume ratio of methyl dichlorosilane to water can be 1:1. In a preferred embodiment of the present application, the hydrolysis time can be 3-5h, and too short a hydrolysis time will result in insufficient hydrolysis of methyl dichlorosilane, and too long a hydrolysis time will result in a large viscosity of the hydrolyzate, affecting the yield and quality of the final product.

[0012] In a specific embodiment of the present application, the parameters for vacuum distillation can be a temperature of 76-112°C and a pressure of -0.098MPa. That is, vacuum distillation is carried out under these parameters to obtain a methyl hydrogen siloxane mixed ring body (D n H ).

[0013] The methyl hydrogen siloxane mixed ring body (D n H ) prepared by the preparation method provided by the present application has a yield of more than 95%.

[0014] In a preferred embodiment of the present application, the obtained methyl hydrogen siloxane mixed ring body (D n H ) can be rectified and separated to obtain 1,3,5,7-tetramethylcyclotetrasiloxane (D4 H ).

[0015] That is, another object of the present application is to provide a preparation method of 1,3,5,7-tetramethylcyclotetrasiloxane, which comprises the following steps: rectifying the methyl hydrogen siloxane mixed ring body obtained by the above preparation method, rectifying under the condition of 132-137℃ and reflux ratio of 4-7:1, collecting the distillate, and obtaining 1,3,5,7-tetramethylcyclotetrasiloxane.

[0016] In a preferred embodiment of the present application, the D3 H that has been distilled out and the mixed ring body remaining after distilling out D4 H are mixed, mixed with the hydrolysate of methyl dichlorosilane (in a specific implementation operation, it is usually the hydrolysate of methyl dichlorosilane of the next batch, that is, it can be recycled batch production), cracked and rearranged, and then rectified under the condition of 132-137℃ and reflux ratio of 4-7:1, and the distillate is collected to obtain 1,3,5,7-tetramethylcyclotetrasiloxane. Therefore, the method of the present application can well recycle the remaining ring body, and can continuously obtain 1,3,5,7-tetramethylcyclotetrasiloxane in a cycle.

[0017] In a preferred embodiment of the present application, the preparation method of 1,3,5,7-tetramethylcyclotetrasiloxane comprises the following steps:

[0018] S1, after neutralizing, water washing and removing the solvent of the hydrolysate of methyl dichlorosilane, adding a high-boiling inert cracking diluent and an acidic rearrangement catalyst, and collecting the distillate at 76-112℃ / -0.098MPa by vacuum distillation, a methyl hydrogen siloxane mixed ring body is obtained;

[0019] S2, rectifying and collecting the distillate at 91-95℃ to obtain D3 H ;

[0020] S3, continuing to rectify under the condition of 132-137℃ and reflux ratio of 4-7:1, and collecting the distillate to obtain 1,3,5,7-tetramethylcyclotetrasiloxane;

[0021] S4, adding D3H hydrolyzate of methyl dichlorosilane (in a specific implementation operation, generally the hydrolyzate of methyl dichlorosilane of the next batch, i.e. the batch production can be recycled), and mixed uniformly, a high-boiling inert cleavage diluent and an acidic rearrangement agent are added to perform cleavage and rearrangement, to obtain a mixed cyclic body, which is subjected to rectification under the conditions of 132-137°C and a reflux ratio of 4-7:1, to obtain 1,3,5,7-tetramethylcyclotetrasiloxane.

[0022] The preparation method provided by the present application can prepare methylhydrogen siloxane mixed cyclic bodies (D n H ) with high yield and less impurities, so that high-quality target product D4 H can be separated and purified. H Secondary product D3 H , and the remaining mixed cyclic bodies D5 H , D6 n , etc. can be subjected to cleavage and rearrangement with the hydrolyzate again, and meanwhile, the method has the advantages of cheap and readily available raw materials, low cost, simple process, solvent recovery, and small pollution, and has good economic benefits. DETAILED DESCRIPTION

[0023] The specific implementation of the present application is described in further detail below in combination with examples. The following examples are used to illustrate the present application, but are not used to limit the scope of the present application.

[0024] Example 1

[0025] In a 500 mL three-neck flask equipped with a stirrer, a cold water bath, a constant-pressure dropping funnel, a thermometer, and a hydrogen chloride absorption device, 100 mL of water and 100 mL of cyclohexane were added, the stirring was started, and 100 mL of methyl dichlorosilane was slowly added while maintaining the temperature at 10-20°C. After the addition was completed, the stirring was continued for 1 h. The mixture was transferred to a separatory funnel, and the oil phase was separated. After the oil phase was neutralized with water, the solvent (cyclohexane) was evaporated and recovered, to obtain a hydrolyzate oil. Then, 0.5% of glacial acetic acid and diethyl phthalate (volume ratio of hydrolyzate oil: diethyl phthalate = 1:1) were added to the hydrolyzate oil, and the mixture was subjected to vacuum distillation at 76-112°C and -0.098 MPa, to obtain D n H Finally, D n H was obtained by rectification separation at 135°C and a reflux ratio of 5:1. H The purity of D4 H was 99.71% (D3 H and D5 H , etc. were subjected to cleavage and rearrangement with the hydrolyzate of the next batch again).

[0026] The specific steps for "re-cracking and rearranging the D3H obtained from distillation with the remaining D5H, D6H, etc., and the next batch of hydrolysate" are as follows:

[0027] Collect the above steps excluding D4 H The remaining cyclic compounds were mixed with the next batch of hydrolyzed oil, and 0.5% by mass of glacial acetic acid and diethyl phthalate (volume ratio of (hydrolyzed oil + remaining cyclic compounds): diethyl phthalate = 1:1) were added. The mixture was then subjected to vacuum distillation at 76–112 °C / -0.098 MPa to obtain D. n H Its composition, as shown in Table 1, was determined by gas chromatography; finally, D... n H D4 was obtained by distillation at 135℃ with a reflux ratio of 5:1. H .

[0028] Table 1 D n H Composition

[0029] D3 H / %]]> D4 H / %]]> D5 H / %]]> D6 H / %]]> ΣD 3-6 H / %]]> Yield / % 32.30 42.12 16.46 5.29 96.17 95.34

[0030] Example 2

[0031] The preparation method provided in this embodiment is the same as that in Example 1, except that the amount of glacial acetic acid added is 2% of the hydrolyzed oil, and the ratio of hydrolyzed oil to diethyl phthalate is 1:3.

[0032] D4 obtained in this embodiment H The purity was 99.81%, and the obtained D n H Its composition, as shown in Table 2, was determined by gas chromatography.

[0033] Table 2 D n H Composition

[0034] D3 H / %]]> D4 H / %]]> D5 H / %]]> D6 H / %]]> ΣD 3-6 H / %]]> Yield / % Yield / % 24.46 38.74 26.52 6.32 96.04 94.67

[0035] Finally, the method of this invention is merely a preferred embodiment and is not intended to limit the scope of protection of this invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A process for the preparation of a methylhydrogensiloxane mixed ring body, characterized by, The method comprises the following steps: adding high-boiling inert cleavage diluent and acidic rearrangement catalyst into the hydrolysate of methyl dichlorosilane, and distilling under reduced pressure to obtain methyl hydrogen siloxane mixed ring; the high-boiling inert cleavage diluent is diethyl phthalate; the acidic rearrangement catalyst is glacial acetic acid; the ratio of the hydrolysate of methyl dichlorosilane to the acidic rearrangement catalyst is 100:(0.5-2); the volume ratio of the hydrolysate of methyl dichlorosilane to the high-boiling cleavage diluent is 1:(1-3); the preparation method of the hydrolysate of methyl dichlorosilane comprises the following steps: hydrolyzing methyl dichlorosilane, a solvent and water at-10-40℃, taking the oil phase, neutralizing, washing with water, and then removing the solvent.

2. The production method according to claim 1, characterized by, In the preparation method of the hydrolysate of methyl dichlorosilane, the solvent is cyclohexane, n-hexane or n-octane.

3. The preparation method according to claim 1, characterized in that, In the preparation method of the hydrolysate of methyl dichlorosilane, the hydrolysis time is 3h-5h.

4. The method of claim 1, wherein, The parameters of the distillation under reduced pressure are 76-112℃ / -0.098MPa.

5. A process for the preparation of 1,3,5,7-tetramethylcyclotetrasiloxane, characterized in that, The method comprises the following steps: rectifying the methyl hydrogen siloxane mixed ring obtained by the preparation method in any one of claims 1-4 under the conditions of 132-137℃ and reflux ratio of (4-7):1, and collecting the distillate to obtain the product.

6. The production method according to claim 5, characterized by, Further comprising: D4 H The remaining mixed ring body after removal of D4 is mixed with methylhydrogen dichlorosilane hydrolysate to perform cracking rearrangement, and is distilled at 132-137°C under a reflux ratio of (4-7): 1 to obtain 1,3,5,7-tetramethylcyclotetrasiloxane.