JPH0859837A - Production of alkoxysilane - Google Patents

Abstract

PURPOSE: To produce in a high yield a halogen-free alkoxysilane which does not generate any halogen compd. such as hydrogen chloride or chlorosilane while conducting the reaction under mild conditions and thereby inhibiting side reactions. CONSTITUTION: An orthoester is reacted with a siloxane or a polysiloxane in the presence of an active hydrogen compd. and a catalyst.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an alkoxysilane, which is one of the important intermediates in the silicone industry. More specifically, the desired alkoxysilane is prepared under relatively mild conditions. The present invention relates to a method for producing a clean and high yield by a halogen-free process.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 1-132590 discloses that R ¹ _a Si (OR ² ) _4-a (wherein R ¹ represents a substituted or unsubstituted monovalent hydrocarbon group, R 1 ² represents an alkyl group, and a represents 0, 1, 2 or 3) and an alkoxysilane represented by the general formula R ³ _b SiHc (OR ² ) is reacted with a polysiloxane. _{4- (b + c)} (wherein R ² is the same as above, R ³ is a substituted or unsubstituted 1
Represents a valent hydrocarbon group, b represents 1, 2 or 3, and c
Represents 0, 1 or 2) is disclosed. According to this method, for example, tetramethoxysilane and formula Me ₃ SiO- (MeH
SiO) ₄₀ -SiOMe ₃ can be reacted with polymethylhydrogensiloxane to obtain dimethoxymethylsilane, and tetraethoxysilane and octamethylcyclotetrasiloxane represented by the formula (Me ₂ SiO) ₄ can be obtained. Can be reacted to obtain diethoxydimethylsilane. In this method, the target alkoxysilane is produced by the cleavage of the Si-O bond of the polysiloxane by the titanium compound used as a catalyst and the insertion reaction (depolymerization reaction) of the alkoxy group from the raw material alkoxysilane into that portion. It is said that.

[0003]

Since this method is a halogen-free process, it has the advantage that hydrogen chloride and chlorosilane are not by-produced, but there are many side reactions, which lowers the yield of the target product and is troublesome in the reaction process. There is a problem that a fractional distillation operation is necessary and a large amount of by-product polysiloxane is produced as a residue.

[0004]

The object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a method for producing a desired alkoxysilane in a high yield. The inventors of the present application have studied various methods for achieving such an object, and as a result, reacted an orthocarboxylic acid ester with a polysiloxane in the presence of an active hydrogen group-containing compound and a catalyst, particularly an acid. It was found that the depolymerization reaction mainly proceeds, and the amount of by-products is smaller than that in the conventional method, and the desired alkoxysilane can be produced in a high yield, and the invention of this application has been completed.

That is, the invention of the present application is a method for producing an alkoxysilane, which comprises reacting an orthoester with a siloxane or a polysiloxane in the presence of an active hydrogen group-containing compound and a catalyst, particularly an acid.

Examples of orthoesters used in the method of the present invention include orthoformate such as methyl orthoformate, ethyl orthoformate, propyl orthoformate, butyl orthoformate, octyl orthoformate, methyl orthoacetate, ethyl orthoacetate, orthoacetate. Examples thereof include orthoacetic acid esters such as propyl acetate, butyl orthoacetate, octyl orthoacetate, and methyl orthobenzoate, but are not limited thereto. Among these, orthomethyl esters such as methyl orthoformate and methyl orthoacetate are preferable in terms of reactivity.

The siloxane or polysiloxane used in the method of the present invention is a compound in which two or more silicon atoms are bonded in the molecule through oxygen atoms.

Substituents on silicon include hydrogen atom, alkyl groups, substituted alkyl groups such as chloromethyl group, alkenyl groups such as vinyl group and allyl group, aryl groups such as phenyl group and tolyl group, etc. Can be given. Of these siloxanes or polysiloxanes, those having a Si-H bond in the molecule are preferred because of quick reaction.

In the invention of this application, when the desired alkoxysilane has a Si--H bond in its molecule, the polysiloxane used as a raw material is one having a Si--H bond in the molecule. To be The structure of such a polysiloxane may be linear, branched or cyclic, or may be a mixture thereof. In such a polysiloxane, organic groups other than hydrogen atoms bonded to silicon atoms include alkyl groups, substituted alkyl groups such as chloromethyl groups, alkenyl groups such as vinyl groups and allyl groups, phenyl groups and tolyl groups. There may be mentioned aryl groups such as groups and the like. Examples of these polysiloxanes include the following.

[0010]

Embedded image (However, p and q show 0 or an integer.) A linear polysiloxane represented by the formula:

[0011]

Embedded image (However, p and q show 0 or an integer.) A linear polysiloxane represented by the formula:

[0012]

[Chemical 3] (However, m and n are 0 or integers, and m + n
Indicates an integer of 2 or more. ) A cyclic polysiloxane represented by:

[0013]

[Chemical 4] (However, Ph represents a phenyl group.)

[0014]

[Chemical 5] (However, Ph represents a phenyl group.)

The content of Si-H bond in such a polysiloxane is not particularly limited, but when the purpose is to produce an alkoxysilane having a Si-H bond in the molecule, this content is not limited. A larger amount is preferable because the yield of the desired alkoxysilane is improved. The following are more specific examples of the above polysiloxane.

[0016]

[Chemical 6]

[0017]

[Chemical 7] (CH ₃ ) ₂ HSiO consisting of _0.5 units and SiO ₂ units,
A branched polymethylhydrogensiloxane having a hydrogen atom content of 1.03% by weight and a viscosity at 25 ° C. of 24 cSt, and

[0018]

Embedded image (N represents an integer of 2 or more.)

The active hydrogen group-containing compound used in the present invention is a compound which reacts with an orthoester to produce an alcohol, or a compound containing a hydroxyl group, a carboxyl group, a mercapto group, amino or the like in the molecule. Water, alcohol, carboxylic acid, mecarptan,
Amine and the like can be used, but water, alcohol and carboxylic acid are particularly preferable.

As the alcohol used in the present invention, there are monohydric alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol and n-butanol, and polyhydric alcohols such as ethylene glycol, propylene glycol and glycerin. Examples thereof include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, and n-butanol, and methyl alcohol, ethyl alcohol, and n-butanol are particularly preferable, but not limited thereto. Examples of the carboxylic acid include formic acid, acetic acid, propionic acid, acrylic acid, and the like. Formic acid, acetic acid, and propionic acid are preferable, and acetic acid is particularly preferable, but not limited thereto.

The catalyst is preferably an acid, such as sulfuric acid or p-
Toluenesulfonic acid, hydrochloric acid, phosphoric acid, acetic acid, aluminum chloride and the like are exemplified, sulfuric acid and p-toluenesulfonic acid are preferable, and sulfuric acid is particularly preferable, but not limited thereto.

In the invention of this application, it is essential to use an active hydrogen group-containing compound. When no active hydrogen group-containing compound is used, the reaction does not proceed or is extremely slow. The reaction rate can be increased in proportion to the amount of the active hydrogen group-containing compound used. The amount of the active hydrogen group-containing compound used in the invention of this application does not necessarily need to be a stoichiometric amount. This is also a major feature of the invention of this application. That is, the amount of the active hydrogen group-containing compound used may be a so-called initiator-like amount, and even if the number of moles of the silicon atom or orthoester molecule of the polysiloxane to be used is 1/10 or less, the reaction is started at room temperature to quantitatively The desired alkoxysilane can be obtained. Therefore, it has an advantage that the desired alkoxysilane can be easily separated by distillation from the reaction solution with high purity.

The reaction of the invention of the present application is also characterized in that it does not particularly need to be heated because the reaction proceeds even at room temperature. Therefore, the reaction temperature is room temperature to 150 ° C, preferably room temperature to 120 ° C.

According to the invention of this application, the reaction can be carried out under mild conditions such as room temperature, hydrogen chloride and chlorosilane are not produced as by-products, and undesirable side reaction products are scarcely present, and a troublesome fractionation operation in the reaction step is also possible. Since it is unnecessary, a halogen-free alkoxysilane can be easily produced in high yield. In particular, an alkoxysilane having a Si-H bond in the molecule can be easily produced in high yield.

[0025]

EXAMPLES Next, the invention of the present application will be specifically described with reference to Examples and Comparative Examples. Example 1 2 with a capacity of 100 ml equipped with a reflux condenser
In the mouth _{flask, Me 3 SiO- (MeHSiO) 40} -
10.56 g of polymethyl hydrogen siloxane of SiOMe ₃ (degree of polymerization is average) (0.
164 mol) and methyl orthoformate 18.05 g (0.
170 mol), 0.46 g of methanol (0.014 m)
ol) and 20.5 mg (0.20 mmol) of sulfuric acid were stirred at room temperature. When stirred, the internal temperature becomes a little (about 5
C) was observed. After stirring for 6 hours, the reaction solution was analyzed by gas chromatography and ¹ H NMR. As a result, Me (MeO) ₂ SiH was produced in almost 100% yield based on the Si—H group in the raw material polysiloxane. It was 22.7 g of this reaction solution was placed in a 50 ml eggplant-shaped flask, and a rectification column (internal diameter: 1.5 cm, height: 9 cm,
Distilled through metal coil filling). First, set the oil bath temperature to 5
The temperature was maintained at 0 to 75 ° C, and 6.9 g of a fraction having a boiling point of about 30 ° C was taken. After that, since the boiling point started to rise, the receiver was changed to obtain 11.7 g of a colorless liquid having a boiling point of about 50 to 60 ° C. The main component of the fore-distillation is methyl formate, which contains Me (MeO) ₂ Si.
1.45 g (0.014 mol) of H was contained. Me (MeO) SiH was 11.4 g (0.10
8 mol), the isolation yield is 81% and the purity is 9
It was 8%.

Example 2 Using the same apparatus as in Example 1, 9.65 g of polymethyl hydrogen siloxane (0.15 in terms of Si--H bond) was used.
0 mol), 16.93 g (0.15 g) of methyl orthoformate
9 mol), methanol 10.01 g (0.312 mo)
1) and 0.19 mg (0.19 mmol) of sulfuric acid were stirred at room temperature. When stirred, the internal temperature dropped slightly. After continuously stirring for 2 hours, the reaction solution was measured by gas chromatography to find that it was almost 100% M (based on Si-H).
e (MeO) ₂ SiH was produced.

Example 3 Using the same apparatus as in Example 1, 10.02 g of polydimethylsiloxane (0.135 mol in terms of Si), 15.47 g (0.146 mol) of methyl orthoformate and 0.74 g of methanol (0.14 mol) were used. 023mol), sulfuric acid 20mg
(0.20 mmol) was stirred at room temperature. After stirring for 3 hours, gas chromatography showed that Me
_No formation of ₂ Si (OMe) ₂ was observed. Therefore,
Methanol and sulfuric acid were added, and the total amount was 4.94 g (0.154 mol) of methanol and 60 m of sulfuric acid, respectively.
g (0.61 mmol). After stirring at 50 ° C. for 8 hours, the reaction solution was measured by gas chromatography to find that Me ₂ Si (OMe) ₂ was produced in a 91% yield (Si standard).

Example 4 Using the same apparatus as in Example 1, 3.03 g (12.6 mmol, Si of 1,3,5,7-tetramethylsiloxane) was used.
-H bond conversion 50.4 mmol), methyl orthoformate 5.71 g (53.8 mmol), sulfuric acid 0.02 g
(0.20 mmol), 0.14 g of methanol (4.4
(mmol) was stirred at room temperature for 3 hours. 98% Me (MeO) ₂ SiH measured by gas chromatography
It was produced in a yield (based on Si-H).

Example 5 In a 200 ml three-necked flask equipped with a reflux condenser, polymethylhydrogensiloxane 50.
0 g (0.78 mol in terms of Si-H bond), methyl orthoformate 99.2 g (0.94 mol), methanol 2.50 g (0.078 mol), sulfuric acid 0.54 mg
(5.5 mmol) was added, and the mixture was stirred in an oil bath at 50 ° C for 180 minutes. When the reaction liquid was analyzed by gas chromatography, Me (MeO) ₂ SiH was produced in a yield of 93% based on the Si—H group in the raw material polysiloxane. A rectification column (inner diameter 1.
Distilled through 5 cm, height 50 cm, filled with glass beads). First, keep the oil bath temperature at 45 to 70 ° C and set the boiling point to 3
43.4 g of a distillate fraction of 2 to 37 ° C was obtained. Then boiling point 3
After taking 10.1 g of a middle distillate at 5 to 55 ° C, the boiling point is 59
67.5 g of a main fraction having a temperature of ˜61 ° C. was obtained. The main component of the previous fraction is methyl formate, and the middle fraction is methyl formate and Me (M
eO) ₂ SiH was almost half. Me in the main fraction
(MeO) ₂ SiH is 65.4 g (0.62 mol),
It contained Me ₃ SiOMe of 1.6 g (0.015 mol) and methanol of 0.1 g (0.003 mol), and the isolated yield was 79% and the purity was 97%.

Comparative Example 1 Using the same apparatus as in Example 1, 10.05 g (0.156 mol) of polymethyl hydrogen siloxane, 21.9 g (0.206 mol) of methyl orthoformate and 41 mg (0.41 mmol) of sulfuric acid were added. It was stirred. It was stirred for 3 hours while heating to _{80 ℃, Me (MeO) 2} Si
Almost no formation of H was observed. Distillation of methyl formate did not occur, and the reaction did not proceed.

Examples 6 to 10 and Comparative Example 2 Hexamethyldisiloxane 61.6 g (0.38 mo)
1) and methyl orthoformate 40.5 g (0.38 mol)
Were mixed to prepare a liquid A. Part of solution A is put in a glass container,
Water, methanol, ethanol, 1-butanol, acetic acid, and the like as active hydrogen group-containing compounds are added thereto and a sulfuric acid catalyst is reacted at room temperature. After ¹ H NMR for 20 hours and after 100 hours, the product Me ₃ SiOMe is collected. The rate (Si standard) was determined. The results are shown in the table.

[0032]

[Table 1]

Comparative Example 3 10.1 g of polymethylhydrogen siloxane was placed in a 50 ml two-necked flask equipped with a reflux condenser.
(0.16 mol in terms of Si-H bond), sulfuric acid 20 mg
(0.20 mmol), 8.7 g of methanol (0.27
mol) was added, and the mixture was heated and stirred in an oil bath at 85 ° C. for 115 minutes. SiH value is 1.01 mmol / g, the initial 88% is lost as a result of the analysis by gas chromatography Me (MeO) ₂ SiH yield 2% (SiH
It was a standard).

Comparative Example 4 A 200 ml two-necked flask was charged with 10.0 g of polymethylhydrogensiloxane (0.16 m in terms of Si--H bond).
ol), 70 mg (0.70 mmol) of sulfuric acid, and 42.2 g (1.32 mol) of methanol were added, and a rectification column (internal diameter: 1.5 cm, height: 9 c) was heated with stirring at 80 ° C. oil bath.
m, filled with a metal coil), 34.2 g of a liquid having a boiling point of 60 to 63 ° C. was distilled off. As a result of analysis by gas chromatography, the distilled liquid was 3.1 g of Me (MeO) ₂
SiH was included and the others were methanol. Me (Me
The yield of O) ₂ SiH (based on Si—H) was 19%.

[0035]

As described above, according to the invention of the present application, since an orthoester and a siloxane or a polysiloxane can be reacted in the presence of an alcohol and a catalyst under mild conditions at room temperature, undesirable side reaction products are generated. Since there is almost no, a troublesome fractionation operation in the reaction step is unnecessary, and a large amount of residue is not generated. Further, since it is a halogen-free process, it does not generate halogen compounds such as hydrogen chloride and chlorosilane. Therefore, halogen-free alkoxysilane can be easily produced in high yield.

Claims (8)

[Claims] 1. A method for producing an alkoxysilane, which comprises reacting an orthoester with a siloxane or a polysiloxane in the presence of an active hydrogen group-containing compound and a catalyst. 2. The method for producing an alkoxysilane according to claim 1, wherein the siloxane or polysiloxane has a Si—H bond in the molecule. 3. The method for producing an alkoxysilane according to claim 1, wherein the catalyst is an acid. 4. The method for producing an alkoxysilane according to claim 1, wherein the orthoester is an orthomethyl ester. 5. The method for producing an alkoxysilane according to claim 1, wherein the active hydrogen group-containing compound reacts with an orthoester to produce an alcohol. 6. The method for producing an alkoxysilane according to claim 1, wherein the active hydrogen group-containing compound is water, carboxylic acid or alcohol. 7. The method for producing an alkoxysilane according to claim 1, wherein the alkoxysilane has a Si—H bond in the molecule. 8. The method for producing an alkoxysilane according to claim 1, wherein the alkoxysilane is dimethoxymethylsilane.