JPH10338696A - Production of alkoxysilane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an alkoxysilane for a raw material, etc. for a synthetic quartz and a ceramic in high reaction rate and conversion by reacting metal silicon with a specific alkyl alcohol in an inert reaction solvent in the presence of a fluorosilicone. SOLUTION: This method for producing an alkoxysilane by reacting metal silicon with a 1-4C alkyl alcohol in an inert reaction solvent is carried out by adding 0.003-0.5 pt.wt. fluorosilicone having 30-300 siloxane units consisting essentially of trifluoropropylmethylsiloxane units in a molecule in 100 pts.wt. inert reaction solvent to the reaction system. The method can inhibits foaming of the reaction mixture even in the case in which an industrially available conventional reaction solvent is used, and further can provide the object alkoxysilane with a heightened conversion of silicon and reaction rate. The alkoxysilane is useful as a raw material for a synthetic quartz and a ceramic, a raw material for an insulating membrane and a protecting membrane of a semiconductor and a liquid crystal, a raw material for a silane coupling agent, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an alkoxysilane, and more particularly to a method for suppressing foaming of a reaction solvent in a synthesis reaction.

[0002]

2. Description of the Related Art Alkoxysilanes such as tetraethoxysilane and triethoxysilane are used as raw materials for synthetic quartz and ceramics, as raw materials for insulating films and protective films for semiconductors and liquid crystals, or using Si-H functional groups. In recent years, it has been increasingly used as a raw material of a silane coupling agent by a hydrosilylation reaction. As a conventional method for producing an alkoxysilane, a method of reacting metal silicon with chlorine or hydrochloric acid to produce chlorosilanes such as trichlorosilane or tetrachlorosilane, and further performing an esterification reaction with a lower alcohol has been frequently performed. . However, this method is essentially a two-step reaction, is complicated and is not an economically advantageous method. In esterification, a large amount of hydrochloric acid is produced as a by-product, so that there is a problem of corrosion of the apparatus. And the chlorine-substituted impurities have similar boiling points, which makes it difficult to separate and purify the target product.

On the other hand, there has been proposed a method of directly reacting metallic silicon with a lower alcohol using a copper catalyst in an inert reaction solvent (hereinafter simply referred to as "reaction solvent") (Japanese Patent Application Laid-open No. Sho. 63-41919). Since this reaction is a one-step reaction and does not produce hydrochloric acid as a by-product, it is a method that can be carried out industrially well. However, in practice when introducing the lower alcohol into the hot reaction mixture when carrying out the synthesis reaction, undesirable bubbles are formed, which cause the reaction mixture to foam and remarkably expand its volume and squirt out of the reactor There is a risk. In order to avoid this, for example, it is necessary to remarkably suppress the supply amount of the lower alcohol, and this synthesis reaction has a problem when industrially carried out.

To solve the problem of foaming, Japanese Patent Application Laid-Open No. Hei 8-208663
Discloses a method for adding an organopolysiloxane as an antifoaming agent in a method for producing an alkoxysilane using a heat medium oil comprising a substituted or unsubstituted tritoluol, tetratriol or a mixture thereof as a reaction solvent. ing. However, the heat transfer oil is expensive and not economically suitable. Furthermore, the present inventors have found that the organopolysiloxane has no effect of suppressing foaming except for the combination with the limited reaction solvent, and conversely, foaming is likely to occur.

As a reaction solvent used in a method for producing an alkoxysilane in which metal silicon and a lower alcohol are directly reacted using a copper catalyst, for example, dodecylbenzene can be mentioned. Since this compound is produced on a large scale as a raw material for synthetic detergents, it can be obtained at very low cost and in large quantities and has many advantages such as no toxicity. When the above-mentioned organopolysiloxane is added as a foaming agent, there is a problem that foaming is more likely to occur.

[0006]

DISCLOSURE OF THE INVENTION In view of the above-mentioned circumstances, the present invention provides a method for producing an alkoxysilane, in which, even when an industrially obtained general-purpose reaction solvent is used in place of a specific reaction solvent, the reaction is carried out. An object of the present invention is to provide a method for suppressing foaming of the mixture and increasing the conversion rate and reaction rate of silicon.

[0007]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by adding fluorosilicone as a defoaming agent to a reaction system. The invention has been completed.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The metal silicon used as one of the raw materials in the present invention is suitably one having a purity of 80% or more, the shape is preferably granular, and the average particle diameter is 2 mm or less. It is preferable because the conversion and the reaction rate are increased, more preferably the average particle size is 25 to 500 μm, and particularly preferably the average particle size is 50 to 300 μm. Generally, metallic silicon powder is not so hygroscopic, and even if it is manufactured industrially, it has an adsorbed moisture of about 3000 ppm, which is acceptable for use in the present invention. Can also be used.

Another raw material, an alkyl alcohol having 1 to 4 carbon atoms (hereinafter simply referred to as "alcohol").
In the above, the alkyl group may be either linear or branched. Specifically, methanol, ethanol, n-
Propanol, iso-propanol, n-butanol, sec-butanol, iso-butanol and t
-Butanol, but among them, alkyl alcohols having 1 to 3 carbon atoms are preferable because they are inexpensive, highly reactive, and the usefulness of the resulting alkoxysilane is high,
Highly reactive methanol and ethanol are more preferred.

These raw material alcohols may be used alone or as a mixture of different alcohols, and when mixed, an alkoxysilane having a different alkoxy group is produced. In any case, it is preferable that the impurity concentration of the raw material alcohol is 5% by weight or less, and it is particularly preferable that the water content is suppressed to 1% by weight or less, more preferably 0.2% by weight or less. Moisture in alcohol can be easily reduced by immersion in distillation or zeolite,
The alcohol whose water content has been reduced in this way can be preferably used in the present invention.

In the present invention, as the catalyst, a commonly used catalyst such as a copper catalyst, a zinc catalyst and a nickel catalyst can be used, but a copper-based catalyst is preferable because of its excellent reactivity. Specifically, cuprous chloride, cupric chloride, copper bromide,
Copper salts such as copper iodide, copper fluoride, copper carbonate, copper sulfate, copper acetate, copper oxalate, copper thiocyanate; cuprous oxide, cupric oxide, cuprous hydroxide, cupric hydroxide, Copper-containing inorganic compounds such as copper cyanide and copper sulfide; organic copper compounds such as methyl copper and ethyl copper; and metallic copper. The purity can be used as long as it is at least about the level of commercially available industrial chemicals.

Among these catalysts, those suitable for the present invention are powders having a particle size of 0.1 to 50 μm, more preferably 0.5 to 10 μm. Due to the mechanism by which the catalyst adheres to the surface of metallic silicon and exhibits catalytic activity, if the particle size is too large, the specific surface area becomes small and the efficiency as a catalyst deteriorates. It is difficult to handle as a powder due to poor binding and fluidity, and it is easily released from the silicon surface as the synthesis reaction of alkoxysilane proceeds, and the released catalyst is not preferred because it causes side reactions such as decomposition of alcohol. As a method for obtaining silicon or cupric oxide powder having a desired particle size, a usual pulverization method or a classification method can be used. More specifically, a pulverization method such as a ball mill, a jet mill, and a vibration mill, and a classification method such as a sieve and a cyclone are exemplified.

The amount of the catalyst used is preferably 0.5 to 50 parts by weight, more preferably 5 to 30 parts by weight, based on 100 parts by weight of metallic silicon. Outside this range, the conversion and reaction rate of metallic silicon may be significantly reduced. As a method of supplying the catalyst, it is general to supply the reaction system separately from the metal silicon. However, the catalyst may be mixed with the metal silicon in advance, or a catalyst supporting the metal silicon may be supplied.

The catalyst is preferably activated together with the silicon metal and supplied to the reaction system. The activation method is 100
It is preferable to heat-treat at -600 ° C. If the temperature is lower than 100 ° C., it takes a long time to activate the catalyst, which is not efficient. If the temperature is higher than 600 ° C., the catalyst may be deactivated. The temperature is more preferably 130 to 230 ° C.

Since the activation time varies greatly depending on the type of catalyst and the activation temperature, it is difficult to limit the preferable range. However, in general, in order to obtain a sufficient degree of activation when performing the activation reaction at a low temperature. Requires a long time. However, since it is not economical to take a long time, it is practically 24 hours or less, more preferably 12 hours or less. The activation reaction is preferably performed in an inert gas atmosphere to avoid side reactions.

The method of supplying metal silicon and a catalyst to a reactor is not limited to a batch method in which the entire amount is initially supplied at once, even if the amount of metal silicon in the reactor is reduced or the reaction is reduced as the synthesis reaction of alkoxysilane proceeds. Continuous addition may be performed in which the synthesis reaction is continuously performed by adjusting the supply amount so as to compensate.

If the rate of supply of alcohol to the reaction system in the reaction is too high, the concentration of unreacted alcohol in the product becomes too high, while if it is too low, the rate of formation of alkoxysilane per reactor volume and per hour is made too low. Is small, so that the reaction takes a long time, which is not economically preferable. In addition, the fact that an appropriate amount of unreacted alcohol is contained in the product also serves as a bubble in the reaction solution to send out the high-boiling target product in the reaction solution to the outside of the system without delay. For this reason, if the supply rate of the alcohol is too low, the product stays in the reaction solution to easily cause a side reaction, and the selectivity of a more useful tri-form (trialkoxysilane) among the produced alkoxysilanes is increased. And the conversion rate of silicon is reduced. The preferred supply rate of the alcohol to the reaction system is 10 to 1000 mmol / hour of alcohol, more preferably 50 to 500 mmol / hour, per mole of metal silicon. Unreacted alcohol can be recovered and reused by a general method such as distillation.

The higher the reaction temperature, the higher the reaction rate. However, if the reaction temperature is too high, the catalyst may be deactivated due to a side reaction accompanying the decomposition reaction of the alcohol. The selectivity of the trialkoxysilane is high, but if it is too low, the reaction rate becomes too low, and the efficiency becomes poor. The preferred reaction temperature is 100
To 250 ° C, more preferably 160 to 220 ° C.

The shape of the reactor is not limited as long as the silicon metal is kept in a good dispersion state. An outer jacket for cooling or heating may be provided outside the reactor, or a fin, a coil or the like may be provided inside the reactor to improve heat transfer. Usually, the reactor is a pipe for supplying metal silicon and alcohol as reaction raw materials, a pipe for discharging a reaction solution containing the produced alkoxysilane as a main component and other by-product silicon compounds and unreacted alcohol, and a pipe after the reaction. It is equipped with an outlet for residue. The material of the reactor is not particularly limited, and quartz, glass, metal, or the like can be used.

The reaction solvent is not particularly limited as long as it is an inert solvent which does not react with the metal silicon, the catalyst and the alkoxysilane to be formed. However, a solvent having a high boiling point and a high stability is preferable. It is particularly preferable because the defoaming effect when added is large. Specifically, octane, decane, dodecane, tetradecane,
Paraffinic hydrocarbons such as hexadecane, octadecane or eicosane; alkylbenzene hydrocarbons such as diethylbenzene, trimethylbenzene, cymene, butylbenzene, butyltoluene, octylbenzene and decylbenzene; diphenyl, diphenylether, monoethyldiphenyl and diethyldiphenyl Are diphenyl hydrocarbons such as triethyldiphenyl or hydrides thereof; alkylnaphthalene hydrocarbons or hydrides thereof; and triphenyl hydrocarbons or hydrides thereof.

Of these, alkylbenzene hydrocarbons are inexpensive because they are industrially produced in large quantities as raw materials for detergents and the like, and are preferable because they have a high reaction rate and a high silicon conversion rate for the synthesis reaction of alkoxysilane. . Above all, dodecylbenzene is preferably used because it has a high boiling point and is stable even when the temperature of the synthesis reaction is raised, and can be obtained at a particularly low cost. The amount of the reaction solvent used may be sufficient to disperse and fluidize the silicon metal or the catalyst powder.If the amount is large, it is easy to remove the reaction heat, but it is economical to use too much. Therefore, it is preferable to use metal silicon 10
It is 80 to 400 parts by weight with respect to 0 parts by weight.

In the method of directly reacting metal silicon and alcohol in a reaction solvent, the reaction mixture is liable to foam, and the feature of the present invention is to suppress the foaming of the reaction mixture by adding fluorosilicone to the reaction system. It is.
Fluorosilicone generally means C-F
It is a general term for polysiloxane containing a bond. If the fluorosilicone has a preferable degree of polymerization (the number of siloxane units present in one molecule), if it is too low, it may evaporate at the reaction temperature and be lost from the reaction system,
If it is too high, the effect as an antifoaming agent may be reduced. Therefore, the degree of polymerization is preferably from 2 to 1,000, and more preferably from 30 to 300.

Among the fluorosilicone compounds, compounds having a trifluoropropylmethylsiloxane unit as a main siloxane unit are most preferable because they can be produced at low cost and are chemically stable. The trifluoropropylmethylsiloxane unit preferably accounts for 50% or more of all siloxane units, and more preferably 75% or more.

If the amount of the fluorosilicone is too small, the effect as an antifoaming agent is not obtained, and if it is too large, it is not economical. 003 to 0.5 parts by weight,
More preferably, it is 0.01 to 0.2 parts by weight. Also,
In the method of directly reacting metal silicon and an alcohol in a reaction solvent, a method of continuously performing a synthesis reaction by adding a metal silicon and a catalyst, or a method of reacting in a batch system and reusing the reaction solvent after the reaction is completed, etc. As is known, in any case,
If a sufficient amount of the antifoaming agent is initially added to the reaction solvent, no additional addition is required. Alternatively, a method in which the amount is initially added to a minimum and then added later may be adopted.

[0025]

It is known that a reaction mixture is liable to foam by a method of directly reacting metal silicon and an alcohol in a reaction solvent, but its mechanism of action has not yet been completely elucidated. However, considering a system in which an alcohol and metal silicon are reacted at a reaction temperature of 100 to 250 ° C. using a copper catalyst as the most general method, the alcohol is decomposed by the liberated copper catalyst, and water, aldehyde and ether are decomposed. Because of the side reaction that produces by-products, etc., this water causes the condensation reaction of alkoxysilane to produce an alkoxysilane condensate, which creates an oil / oil system with a different molecular weight between the reaction solvent and the reaction solvent. Is assumed. It is known that oils / oils having different molecular weights easily foam.
In a system in which alcohol is blown vigorously while blowing bubbles as in this reaction, it is presumed that foaming particularly occurs remarkably. However, on the other hand, it is also a fact that it is difficult to find an effective antifoaming agent in such an oil / oil system, and the present invention has found an extremely limited antifoaming agent capable of suppressing foaming in such a situation. It is.

Although there are various theories regarding the mechanism of action of the defoamer, it has not been determined yet. However, as a generally known tendency of the defoamer, for example, a water / oil system is soluble in oil but not water. A substance which is hardly soluble and has a small surface tension is preferred. Specifically, dimethylpolysiloxane disclosed in JP-A-8-2088663 is well known as a substance which suppresses foaming in a water / oil system. However, it is known that the addition of dimethylpolysiloxane to alkylbenzene makes foaming easier (Oil Chemistry Journal Vol. 42, No. 10, p. 98 (1.
As described in (993)), even if the defoaming effect is large in the water / oil system, the oil / oil system often has no defoaming property, and on the contrary, it often causes foaming.

When dimethylpolysiloxane is actually used as a defoaming agent in a synthesis reaction of alkoxysilane using alkylbenzene as a reaction solvent, foaming easily occurs. Furthermore, since dimethylpolysiloxane is well soluble in both the reaction solvent and the reaction product, alkoxysilane, it has the effect of retaining the reaction product in the reaction solution as a surfactant. Because the reaction is likely to occur, an alkoxysilane condensate is generated to facilitate foaming, and among the generated alkoxysilanes, the selectivity of more useful tri-forms is reduced,
Adverse effects such as lowering the silicon conversion rate appear.

On the other hand, the fluorosilicone used in the present invention, although well soluble in alkoxysilane, does not dissolve in ordinary hydrocarbon-based reaction solvents, and thus has the effect of making the formed alkoxysilane difficult to dissolve in the reaction solvent. Suppresses harmful side reactions. For this reason, it is presumed that the foaming hardly occurs, the selectivity of useful trialkoxysilane is high, and the silicon conversion rate is increased. Also, due to this mechanism of action, the present invention is effective for a wide range of reaction solvents of ordinary hydrocarbons.

[0029]

Next, the present invention will be specifically described with reference to examples and comparative examples. The selectivity of trialkoxysilane and the conversion of metallic silicon in the present invention are values calculated by the following equations. -Selectivity of trialkoxysilane (mol%) = [(mol of trialkoxysilane) / (mol of trialkoxysilane + mol of tetraalkoxysilane)] x 100-Metal silicon conversion (wt%) = 100 − [(Weight of metallic silicon in reaction residue) / (weight of charged metallic silicon) × 1
00]

(Example 1) A 1-liter glass flask equipped with an inlet tube for nitrogen and alcohol, a reaction liquid thermometer, a stirrer, a discharge tube for the reaction product, and a cooler and a receiver for the reaction product was used. , Dodecylbenzene 60 as a reaction solvent
0 ml, metallic silicon (purity 98%, average particle size 100 μm)
300 g and cuprous chloride (average particle size 0.7 μm) 25
g. Then, while supplying nitrogen to the reaction solution (3.
(00 ml / min) The catalyst was activated at 200 ° C. for 10 hours under stirring and mixing. Then, as an antifoaming agent, polytrifluoropropylmethylsiloxane (degree of polymerization 140)
0.1 g was added to the reaction. And the temperature of the reaction solution is 2
While maintaining the temperature at 00 ° C and supplying nitrogen (300 ml / min)
Under stirring and mixing, ethanol (purity 99%) was added to the reaction solution in an amount of 1%.
It was fed at a rate of 20 g / h to react with the metallic silicon.

Five minutes after the start of the supply of ethanol, the product liquid began to flow from the cooler in front of the reaction product discharge pipe to the receiver. The composition of the product solution was analyzed by gas chromatography to observe the change over time in the composition. When the ethanol composition of the product solution reached 100%, the reaction was considered to be completed. The product liquid collected in the receiver was analyzed by gas chromatography, and the selectivity of trialkoxysilane and the silicon conversion were calculated from the result of obtaining the amount of product generated. Table 1 shows the results.

Example 2 The same experiment as in Example 1 was performed except that methanol was used as the alcohol.
Table 1 shows the results. Example 1 using ethanol
The conversion of metal silicon was slightly improved compared to the result of the above, and the selectivity of the tri-isomer was reduced. This is because methanol is more reactive than ethanol.

(Example 3) Thermes 800 (manufactured by Nippon Steel Chemical Co., Ltd., triethyldiphenyl) was used as a reaction solvent, and 0.1 g of polytrifluoropropylmethylsiloxane (degree of polymerization 100) was added as an antifoaming agent. The same experiment as in Example 1 was performed except for the above. Table 1 shows the results. Therms 800 is a heat medium oil, and its market price is more than 10 times that of dodecylbenzene. Therefore, there is a problem in using it as a reaction solvent industrially. However, the result of the synthesis reaction is almost the same as in Example 1. Became.

(Comparative Example 1) An experiment was performed under the same conditions as in Example 1 except that no defoaming agent was added. Table 1 shows the results. In this example, since the reaction solution foamed during the reaction, the ethanol supply speed was reduced to prevent ejection. Therefore, it took a long time to complete the reaction, and the selectivity of the tri-form was reduced from the point of time when the supply rate of ethanol was reduced, and as a result, both the conversion rates of the metallic silicon were reduced.

(Comparative Example 2) An experiment was carried out under exactly the same conditions as in Example 1 except that 0.1 g of dimethylpolysiloxane (molecular weight 1250) was added as an antifoaming agent. Table 1 shows the results.
Shown in In this example, since the reaction solution foamed during the reaction, the ethanol supply speed was reduced to prevent ejection.
Therefore, it took a long time to complete the reaction, and
Both the selectivity of the tri-isomer and the conversion of the metallic silicon were lower than those of the above. In addition, although the amount of the reaction solution increased during the course of the reaction, it is considered that the stagnation of the reaction product occurred.

Comparative Example 3 An experiment was performed under the same conditions as in Example 3 except that no defoaming agent was added. Table 1 shows the results. In this example, since the reaction solution foamed during the reaction, the ethanol supply speed was reduced to prevent ejection. For this reason, it took a long time until the reaction was completed, and the selectivity of the tri-form was lowered from the point of time when the supply rate of ethanol was reduced, and as a result, both the conversion rates of metallic silicon were lowered.

[0037]

[Table 1] _{* 1} : Trialkoxysilane corresponding to alcohol _{* 2} : Tetraalkoxysilane corresponding to alcohol _{* 3} : Mainly dialkoxysilane

[0038]

According to the method of the present invention, in the reaction for synthesizing an alkoxysilane using a reaction solvent, even when a general-purpose reaction solvent obtained industrially is used, foaming of the reaction solvent is suppressed and a high silicon Alkoxysilanes can be produced at conversions and reaction rates.

Claims (3)

[Claims] 1. A method for producing alkoxysilane by reacting metal silicon with an alkyl alcohol having 1 to 4 carbon atoms in an inert reaction solvent, wherein fluorosilicon is added to the reaction system. A method for producing silane. 2. The method for producing alkoxysilane according to claim 1, wherein the fluorosilicone is a compound having 30 to 300 siloxane units in a molecule mainly composed of trifluoropropylmethylsiloxane units. 3. The method according to claim 1, wherein the addition amount of the fluorosilicone is 0.003 to 0.5 part by weight based on 100 parts by weight of the inert reaction solvent. .