JPH0977779A - Purification of silane compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently accomplish purification to highly pure dimethoxymethylsilane which is suitable as a raw material for silicones and has excellent storage stability by distilling a mixture that contains dimethoxymethylsilane and methanol together with a specific extractant, and distilling off the methanol. SOLUTION: This purification method purifies dimethoxymethylsilane from a mixture that contains dimethoxymethylsilane (A1 ) and methanol (A2 ) by distilling the mixture in the presence of methyl format (B) as an extractant to distill off A2 , and, where necessary, further distilling the residue containing A1 and B to distill off the component B. Preferably, the distilled-off component B or component B separated from the methanol which contains the distilled-off component B is recycled to the component A, and component B is added 30% or more to the component A.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying dimethoxymethylsilane, which is one of important intermediates in the silicone industry, and more specifically, it purifies dimethoxymethylsilane with high purity and high yield. Is the way to do it.

[0002]

Dimethoxymethylsilane is one of the key intermediates in the silicone industry. Dimethoxymethylsilane is often produced using methanol as a raw material. In addition, dimethoxymethylsilane produces methanol when decomposed. Therefore, dimethoxymethylsilane often coexists with methanol. Methanol is
Since the reactivity of the dimethoxymethylsilane with the SiH group is high, it causes a decrease in storage stability. In addition, the reactivity as a reaction intermediate is adversely affected. Therefore, it is important to separate methanol from the mixed liquid of dimethoxymethylsilane and methanol, but since the difference in boiling point between dimethoxymethylsilane and methanol is only 3 to 4 ° C, it is difficult to separate both by a distillation method. Is.

[0003]

The inventors of the present application measured the gas-liquid equilibrium relationship between dimethoxymethylsilane and methanol and found that dimethoxymethylsilane: methanol =
It was found to form an azeotrope (boiling point about 50 ° C.) in a ratio of 6: 4. Further, from the result that the difference from the diagonal line is small especially in the high concentration region of dimethoxymethylsilane, it was found that the separability of dimethoxymethylsilane and methanol is very poor as shown in FIG. In such a case, the dimethoxymethylsilane / methanol mixed solution cannot be separated by distillation, and the methanol concentration in the dimethoxymethylsilane is distilled without being lowered. The problem to be solved by the invention of this application is that dimethoxymethylsilane and methanol, which are difficult to separate, are distilled in the presence of methyl formate to purify dimethoxymethylsilane to obtain dimethoxymethylsilane having a low methanol concentration. It is to provide a method of manufacturing.

[0004]

Means for Solving the Problems The inventors of the present application have
Various compounds that change the vapor-liquid equilibrium relationship between dimethoxymethylsilane and methanol were investigated. As a result, they have found that methyl formate acts as an extractant for the binary system of dimethoxymethylsilane and methanol, and completed the invention of this application. That is, the present invention relates to a method for purifying dimethoxymethylsilane by separating dimethoxymethylsilane and methanol by an extractive distillation method using methyl formate as an extractant from a mixed solution containing dimethoxymethylsilane and methanol.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The effect of distillation separation in the presence of methyl formate will be described with reference to FIG. When the gas-liquid equilibrium relationship between dimethoxymethylsilane and methanol in the presence of methyl formate is illustrated, the gas-liquid equilibrium curve shifts to the liquid phase side.
Therefore, dimethoxymethylsilane and methanol can be separated by distillation using methyl formate as an extractant. Methyl formate is preferably 20% or more, particularly preferably 30% or more. In particular, it was found that dimethoxymethylsilane and methanol do not azeotrope when methyl formate is mixed in the liquid phase at a ratio of 30% or more.

Further, the inventors of the present application measured the gas-liquid equilibrium relationship between methyl formate and dimethoxymethylsilane, and found that methyl formate and dimethoxymethylsilane did not form an azeotropic mixture and had good separability. . That is, by separating methyl formate added as an extractant and dimethoxymethylsilane, the product dimethoxymethylsilane and the extractant methyl formate can be recovered with high purity.

Further, methyl formate and methanol have a boiling point difference of 33 ° C., do not form an azeotropic mixture, and have relatively good separability. That is, since methyl formate and methanol can be well separated by distillation, methyl formate as an extractant can be recovered with high purity.

The extractive distillation method of dimethoxymethylsilane and methanol in the presence of methyl formate will be described with reference to FIG. The distillation process basically consists of two distillation columns 1 and 2. In the extractive distillation column, by distilling in the presence of methyl formate, methanol containing methyl formate is distilled off, and dimethoxymethylsilane and methanol are separated. Dimethoxymethylsilane containing methyl formate is recovered from the bottom of the extractive distillation column, and the extractant recovery column separates methyl formate and dimethoxymethylsilane.By distilling off methyl formate, dimethoxymethylsilane is obtained from the bottom of the column. To be The methyl formate recovered from the top of the tower is recycled to the extractive distillation tower. Since the boiling point of methyl formate is 31 ° C., it is necessary to feed the recovered methyl formate to the bottom side of the raw material feed stage to maintain the methyl formate concentration in the column. When a large amount of methyl formate is distilled from the top together with methanol in the distillation column, it is preferable to further provide a recovery column to separate methanol and methyl formate, and to recycle the recovered methyl formate to the extractive distillation column. . When starting the distillation apparatus, methyl formate is fed from the bottom of the extractive distillation column. When the apparatus is in a steady state, the methyl formate feed is stopped and the methyl formate recovered from the extractant recovery column is recycled, so there is no need to newly feed methyl formate.

[0009] In the dimethoxymethylsilane synthesis reaction (Japanese Patent Application No. 6-248300) using siloxane or polysiloxane as a raw material, methyl formate is produced as a by-product. In this case, it is not necessary to add new methyl formate.

[0010]

EFFECTS OF THE INVENTION According to the invention of this application, high-purity dimethoxymethylsilane can be easily purified by efficiently distilling and separating methanol from dimethoxymethylsilane.

[Brief description of drawings]

Figure 1: Vapor-liquid equilibrium diagram of dimethoxymethylsilane and methanol

Figure 2: Vapor-liquid equilibrium diagram of dimethoxymethylsilane and methanol in the presence of methyl formate.

FIG. 3 Flow chart of distillation separation

[Explanation of symbols]

 1 distillation tower 2 distillation tower

Claims (5)

[Claims] 1. A method for purifying dimethoxymethylsilane, which comprises distilling a mixed solution containing dimethoxymethylsilane and methanol in the presence of methyl formate to distill off methanol. 2. The method for purifying dimethoxymethylsilane according to claim 1, wherein after distilling off methanol, the remaining dimethoxymethylsilane and methyl formate are distilled to distill off methyl formate. 3. The method for purifying dimethoxymethylsilane according to claim 1 or 2, wherein the distilled methyl formate is recycled to a mixed solution of dimethoxymethylsilane and methanol. 4. The method according to claim 1, wherein methyl formate is separated from methanol containing distilled methyl formate, and the separated methyl formate is recycled to a mixed solution of dimethoxymethylsilane and methanol. A method for purifying dimethoxymethylsilane as described. 5. The method for purifying dimethoxymethylsilane according to any one of claims 1 to 4, wherein the mixed solution of dimethoxymethylsilane and methanol has 30% or more of methyl formate.