JP4151084B2 - Method for producing alkoxysilane - Google Patents

Description

【００３８】
【発明の効果】
反応溶媒を用いてアルコキシシランを合成する反応において、工業的に得られる汎用の反応溶媒を使用する場合でも、本発明の方法により、反応溶媒の発泡を抑制し、なおかつ高い珪素転化率および反応速度でアルコキシシランを製造することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing alkoxysilane, and more particularly to a method for suppressing foaming of a reaction solvent in a synthesis reaction.
[0002]
[Prior art]
Alkoxysilanes such as tetraethoxysilane and triethoxysilane are used as raw materials for synthetic quartz and ceramics, as raw materials for insulating and protective films for semiconductors and liquid crystals, or by hydrosilylation reaction using Si-H functional groups. In recent years, it has been increasingly used as a raw material for coupling agents.
As a conventional method for producing alkoxysilane, many methods have been performed in which metal silicon is reacted with chlorine or hydrochloric acid to produce chlorosilanes such as trichlorosilane or tetrachlorosilane, and further esterified with a lower alcohol. . However, this method is essentially a two-stage reaction and is not a complicated and economically advantageous method. In the esterification, a large amount of hydrochloric acid is produced as a by-product, and there is a problem of corrosion of the apparatus. There is a problem that separation and purification of the target product is difficult because the boiling point of the alkoxysilane and the chlorine-substituted impurity is close.
[0003]
On the other hand, a method of directly reacting metal silicon with a lower alcohol using a copper catalyst in an inert reaction solvent (hereinafter simply referred to as “reaction solvent”) has been proposed (Japanese Patent Laid-Open No. 63-41919). issue). This reaction is a one-step process, and hydrochloric acid is not produced as a by-product.
However, in practice, when carrying out the synthesis reaction, the introduction of lower alcohols into the hot reaction mixture forms undesirable bubbles, which cause the reaction mixture to foam and significantly expand its volume and eject from 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 in industrial implementation.
[0004]
In response to this foaming problem, Japanese Patent Application Laid-Open No. 8-208663 discloses a method for producing alkoxysilane using a heat transfer oil composed of substituted or unsubstituted tritoluol, tetratriol or a mixture thereof as a reaction solvent. A method of adding organopolysiloxane as a foaming agent is disclosed. However, the heat transfer oil is expensive and not economically suitable. Furthermore, the present inventors have found that organopolysiloxane not only has an effect of suppressing foaming except in combination with the limited reaction solvent, but also foaming may easily occur.
[0005]
An example of 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 is dodecylbenzene. Since the compound is produced on a large scale as a raw material for synthetic detergents, it can be obtained at a very low cost and in large quantities, and has many advantages such as non-toxicity. When the aforementioned organopolysiloxane was added as a foaming agent, there was a problem that foaming was more likely to occur.
[0006]
[Problems to be solved by the invention]
In view of the present situation, the present invention suppresses the foaming of the reaction mixture even in the case of using a general-purpose reaction solvent obtained industrially instead of a specific reaction solvent in the production method of the alkoxysilane, and silicon. It is an object of the present invention to provide a method for increasing the conversion rate and the reaction rate of.
[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 an antifoaming agent to the reaction system, and have completed the present invention.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The metal silicon used as one of the raw materials in the present invention is suitable to have a purity of 80% or more, the shape is preferably granular, and the average particle size is 2 mm or less in terms of silicon conversion and reaction rate. The average particle size is preferably 25 to 500 μm, more preferably 50 to 300 μm. In general, powdered metal silicon is not so hygroscopic, and even if it is industrially produced, the adsorbed moisture is about 3000 ppm, and it can be used in the present invention. Can also be used.
[0009]
The alkyl group in the alkyl alcohol having 1 to 4 carbon atoms (hereinafter simply referred to as “alcohol”), which is another raw material, may be either linear or fractional. Specific examples include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, iso-butanol, and t-butanol. Of these, alkoxysilanes that are inexpensive and highly reactive are produced. Alkyl alcohol having 1 to 3 carbon atoms is preferable because of its high usefulness, and methanol and ethanol having high reactivity are more preferable.
[0010]
These raw material alcohols may be used alone or as a mixture of different alcohols. When mixed, alkoxysilanes having different alkoxy groups are produced. In any case, the impurity concentration of the raw material alcohol is preferably 5% by weight or less, in particular, the water content is preferably 1% by weight or less, more preferably 0.2% by weight or less. The water content in the alcohol can be easily reduced by distilling or immersing zeolite or the like, and the alcohol thus reduced in water content can be preferably used in the present invention.
[0011]
In the present invention, commonly used catalysts such as a copper catalyst, a zinc catalyst, and a nickel catalyst can be used as the catalyst, but a copper catalyst is preferred because of its excellent reactivity.
Specifically, cuprous chloride, cupric chloride, copper bromide, copper iodide, copper fluoride, copper carbonate, copper sulfate, copper acetate, copper oxalate, copper thiocyanate, and other copper salts; Examples include copper-containing inorganic compounds such as copper, cupric oxide, cuprous hydroxide, cupric hydroxide, 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 about the level of commercially available industrial chemicals.
[0012]
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. Since the catalyst adheres to the surface of the metal silicon and exhibits catalytic activity, if the particle size is too large, the specific surface area becomes small and the efficiency as a catalyst is deteriorated. In addition, it becomes difficult to handle as a powder due to crystallization or fluidity, and as the alkoxysilane synthesis reaction proceeds, it is easily released from the silicon surface, and the released catalyst is not preferable because it causes side reactions such as alcohol decomposition.
As a method for obtaining silicon or cupric oxide powder having a desired particle size, a normal pulverization method or classification method can be used. More specifically, a pulverizing method such as a ball mill, a jet mill, and a vibration mill, and a classification method such as a sieve and a cyclone can be used.
[0013]
The amount of the catalyst used is preferably 0.5 to 50 parts by weight, more preferably 5 to 30 parts by weight with respect to 100 parts by weight of metal silicon. Outside this range, there is a risk that the conversion rate and reaction rate of metallic silicon will be significantly reduced.
As a catalyst supply method, it is common 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 on which the metal silicon is supported.
[0014]
The catalyst is preferably activated together with metallic silicon and supplied to the reaction system. As an activation method, it is preferable to heat-process at 100-600 degreeC. If it is less than 100 ° C., it takes time to activate it, so it cannot be said that it is efficient. If it exceeds 600 ° C., the catalytic action may be deactivated. More preferably, it is 130-230 degreeC.
[0015]
Since the activation time varies greatly depending on the type of catalyst and the activation temperature, it is difficult to limit the preferred range, but it is generally a long time to obtain a sufficient degree of activation when performing an activation reaction at a low temperature. Is required. However, since it is not economical to spend too much 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.
[0016]
The method of supplying metallic silicon and catalyst to the reactor is to compensate for the decrease in metallic silicon in the reactor or the deterioration of the reaction accompanying the progress of the synthesis reaction of alkoxysilane, even in the batch system in which the whole amount is initially supplied at once. Continuous addition in which the synthesis reaction is continuously performed by adjusting the supply amount may also be used.
[0017]
If the supply rate of alcohol to the reaction system in the reaction is too high, the concentration of unreacted alcohol in the product becomes too high, whereas if it is too low, the production rate of alkoxysilane per reactor volume and per hour is reduced. Therefore, the reaction takes a long time, which is not economically preferable.
Moreover, when an appropriate amount of unreacted alcohol is contained in the product, there is also a function of forming a high-boiling target product in the reaction solution out of the system without delay as bubbles in the reaction solution. For this reason, if the supply rate of alcohol is too low, the product stays in the reaction solution and is liable to cause a side reaction. Among the alkoxysilanes to be generated, the selectivity of a more useful tri-form (trialkoxysilane) There are adverse effects such as lowering the temperature and lowering the silicon conversion rate.
A preferable supply rate of the alcohol to the reaction system is 10 to 1000 mmol / hr of alcohol, more preferably 50 to 500 mmol / hr, with respect to 1 mol of metal silicon. Unreacted alcohol can be recovered and reused by a general method such as distillation.
[0018]
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 side reactions accompanying the alcohol decomposition reaction. The selectivity of silane increases, but if it is too low, the reaction rate becomes too low and the efficiency deteriorates. The reaction temperature is preferably 100 to 250 ° C, more preferably 160 to 220 ° C.
[0019]
The shape of the reactor is not limited as long as metallic silicon is kept in a good dispersion state. An external jacket for cooling or heating may be provided outside the reactor, or a thing provided with fins, coils, etc. inside the reactor to improve heat transfer. Usually, the reactor is a tube for supplying metal silicon and alcohol as reaction raw materials, a tube for discharging a reaction liquid containing the generated alkoxysilane as a main component and other by-produced silicon compounds and unreacted alcohol, and after the reaction. It has a discharge port for the remainder. The material of the reactor is not particularly limited, and quartz, glass, metal, or the like can be used.
[0020]
The reaction solvent is not particularly limited as long as it is an inert solvent that does not react with metallic silicon, the catalyst, and the generated alkoxysilane, but a solvent having a high boiling point is preferable at high temperatures. Is particularly preferable because of its large defoaming effect.
Specifically, paraffin hydrocarbons such as octane, decane, dodecane, tetradecane, hexadecane, octadecane or eicosan; diethylbenzene, trimethylbenzene, cymene, butylbenzene, butyltoluene, octylbenzene or alkylbenzene carbonization such as decylbenzene Diphenyl, diphenyl ether, monoethyl diphenyl, diethyl diphenyl or diethyl hydrocarbon such as triethyl diphenyl or hydride thereof; alkylnaphthalene hydrocarbon or hydride thereof; triphenyl hydrocarbon or hydride thereof .
[0021]
Among these, alkylbenzene hydrocarbons are preferable because they are inexpensive because they are industrially produced in large quantities as raw materials for detergents and the like, and the reaction rate of the alkoxysilane synthesis reaction and the silicon conversion rate are high. Among them, dodecylbenzene is preferably used because it has a high boiling point and is stable even when the temperature of the synthesis reaction is increased and can be obtained at a particularly low cost.
The amount of reaction solvent used should be sufficient to disperse and fluidize the metal silicon and catalyst powder. Increasing the amount of the reaction solvent facilitates removal of the heat of reaction, but it is economical to use too much. Therefore, the amount is preferably 80 to 400 parts by weight with respect to 100 parts by weight of metal silicon.
[0022]
In the method in which metal silicon and alcohol are directly reacted in a reaction solvent, the reaction mixture is easily foamed, and the feature of the present invention is to suppress foaming of the reaction mixture by adding fluorosilicone to the reaction system.
Fluorosilicone is a general term for polysiloxanes generally containing a C—F bond in a part of the side chain.
Further, the preferred degree of polymerization of the fluorosilicone (the number of siloxane units present in one molecule) is too low, it may evaporate at the reaction temperature and be lost from the reaction system. As a result, there is a risk that the effect will be reduced. Therefore, the degree of polymerization is preferably 2 to 1000, more preferably 30 to 300.
[0023]
Among the fluorosilicones, a compound having a trifluoropropylmethylsiloxane unit as a main siloxane unit is most preferable because it can be produced at a low cost and is chemically stable.
The trifluoropropylmethylsiloxane unit preferably accounts for 50% or more of all siloxane units, and more preferably 75% or more.
[0024]
If the amount of fluorosilicone added is too small, it will not be effective as an antifoaming agent, and if it is too much, it is not economical, so 0.003 to 0 parts by weight per 100 parts by weight of the reaction solvent used in the reaction. 0.5 part by weight, more preferably 0.01 to 0.2 part by weight.
In addition, in the method of directly reacting metal silicon and alcohol in a reaction solvent, a method of continuously performing a synthesis reaction by adding metal silicon and a catalyst, or reacting in batch mode and reusing the reaction solvent after completion of the reaction However, in any case, if a sufficient amount of antifoaming agent is first added to the reaction solvent, no additional addition is necessary. Alternatively, it may be added at a minimum at the beginning and added later.
[0025]
[Action]
Although it is known that the reaction mixture is easily foamed by a method in which metal silicon and alcohol are directly reacted in a reaction solvent, the mechanism of action has not yet been fully clarified. However, when 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 released copper catalyst, and water, aldehyde and ether are decomposed. As a side reaction occurs as a by-product, etc., the alkoxysilane undergoes a condensation reaction with this water to produce an alkoxysilane condensate, which forms an oil / oil system having a different molecular weight with the reaction solvent. Is guessed.
It is known that oils / oil systems having different molecular weights are likely to foam, but in the system in which alcohol bubbles are vigorously stirred as in this reaction, foaming is particularly prominent. . However, on the other hand, it is also difficult to find an effective antifoaming agent in such an oil / oil system, and the present invention has found an extremely limited antifoaming agent that can suppress foaming in such a situation. It is.
[0026]
Although there are various theories about the mechanism of defoaming, it is not yet established, but as a general trend of antifoaming agents, for example, water / oil systems are soluble in oil but hardly soluble in water. A substance having a low surface tension is preferable. Specifically, dimethylpolysiloxane disclosed in JP-A-8-208663 is well known as a substance that suppresses foaming in a water / oil system. However, it is known that when dimethylpolysiloxane is added to alkylbenzene, foaming tends to occur on the contrary (Journal of Oil Chemistry, Vol. 42, No. 10, page 98 (1993)). However, oil / oil systems are not only defoaming but also often cause foaming.
[0027]
In fact, when dimethylpolysiloxane is used as an antifoaming agent in a synthesis reaction of alkoxysilane using alkylbenzene as a reaction solvent, foaming tends to occur. Furthermore, since dimethylpolysiloxane dissolves well in both the reaction solvent and the alkoxysilane which is the reaction product, it has the effect of retaining the reaction product in the reaction solution as a surfactant, and the retained reaction product is a secondary agent. Since the reaction is likely to occur, there is an adverse effect such as formation of an alkoxysilane condensate to facilitate foaming, lowering the selectivity of more useful tri-forms of the generated alkoxysilane, and lowering the silicon conversion rate. It appears.
[0028]
On the other hand, the fluorosilicone used in the present invention dissolves well in alkoxysilane, but does not dissolve in ordinary hydrocarbon-based reaction solvents, and thus has the effect of making the generated alkoxysilane difficult to dissolve in the reaction solvent, which is harmful. Suppress side reactions. For this reason, foaming is unlikely to occur, and the selectivity of useful trialkoxysilane is high, and it is estimated that the silicon conversion rate is also increased. Also, due to this mechanism of action, the present invention is effective for a wide range of reaction solvents of ordinary hydrocarbon systems.
[0029]
【Example】
Next, the present invention will be specifically described with reference to examples and comparative examples. The selectivity of trialkoxysilane and the conversion rate of metallic silicon in the present invention are values calculated by the following equations.
Trialkoxysilane selectivity (mol%) = [(mol number of trialkoxysilane) / (mol number of trialkoxysilane + mol number of tetraalkoxysilane)] × 100
Metal silicon conversion (% by weight) = 100 − [(weight of metal silicon in reaction residue) / (weight of charged metal silicon) × 100]
[0030]
(Example 1)
Into a glass 1 liter flask equipped with an introduction tube for nitrogen and alcohol, a reaction solution thermometer, a stirrer, a reaction product discharge tube and a reaction product cooler and receiver, 600 ml of dodecylbenzene as a reaction solvent, 300 g of metallic silicon (purity 98%, average particle size 100 μm) and 25 g of cuprous chloride (average particle size 0.7 μm) were charged. Next, the catalyst was activated for 10 hours at 200 ° C. with stirring and mixing while supplying nitrogen to the reaction solution (300 ml / min). Subsequently, 0.1 g of polytrifluoropropylmethylsiloxane (degree of polymerization 140) was added to the reaction solution as an antifoaming agent. Then, while maintaining the temperature of the reaction solution at 200 ° C. and supplying nitrogen (300 ml / min), ethanol (purity 99%) was supplied to the reaction solution at 120 g / hour with stirring and mixing to react with metallic silicon.
[0031]
Five minutes after starting the supply of ethanol, the product liquid started to flow from the cooler at the end of the reaction product discharge pipe to the receiver. The composition of this product solution was analyzed by gas chromatography, and the change with time of the composition was observed. When the ethanol composition of the product solution reached 100%, the reaction was considered complete. Then, the product liquid accumulated in the receiver was analyzed by gas chromatography, and the selectivity of trialkoxysilane and the silicon conversion rate were calculated from the results of determining the amount of product produced. These results are shown in Table 1.
[0032]
(Example 2)
The same experiment as in Example 1 was performed except that methanol was used as the alcohol. The results are shown in Table 1. Compared to the results of Example 1 using ethanol, the metal silicon conversion rate was slightly improved, and the selectivity for the tri-isomer was decreased. This is probably because methanol is more reactive than ethanol in both side reactions that change to the body.
[0033]
(Example 3)
Example 1 except that therms 800 (main component triethyldiphenyl) manufactured by Nippon Steel Chemical Co., Ltd. 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 was performed. The results are shown in Table 1. Therms 800 is an oil for heat medium, and its market price is 10 times or more that of dodecylbenzene. Therefore, there is a problem in industrial use as a reaction solvent, but the result of the synthesis reaction is almost the same as in Example 1. Became.
[0034]
(Comparative Example 1)
The experiment was conducted under exactly the same conditions as in Example 1 except that no antifoam was added. The results are shown in Table 1.
In this example, since the foaming of the reaction liquid occurred during the reaction, the ethanol supply rate was reduced to prevent ejection. For this reason, it took a long time to complete the reaction, and the selectivity for the tri-isomer decreased from the time when the supply rate of ethanol was reduced. As a result, both the conversion rates of metal silicon were decreased.
[0035]
(Comparative Example 2)
The experiment was performed 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. The results are shown in Table 1.
In this example, since the foaming of the reaction liquid occurred during the reaction, the ethanol supply rate was reduced to prevent ejection. For this reason, it took a long time to complete the reaction, and both the selectivity for the tribody and the conversion rate of the metal silicon were reduced as compared with Example 1. Moreover, although the liquid volume of the reaction liquid has increased from the middle of the reaction, it seems that the reaction product has stayed.
[0036]
(Comparative Example 3)
The experiment was performed under exactly the same conditions as in Example 3 except that no antifoam was added. The results are shown in Table 1. In this example, since the foaming of the reaction liquid occurred during the reaction, the ethanol supply rate was reduced to prevent ejection. For this reason, it took a long time to complete the reaction, and the selectivity for the tori form decreased from the time when the supply rate of ethanol was reduced, and as a result, both the conversion rates of metal silicon were decreased.
[0037]
[Table 1]

[0038]
【The invention's effect】
In the reaction of synthesizing alkoxysilane using a reaction solvent, even when a general-purpose reaction solvent obtained industrially is used, the method of the present invention suppresses foaming of the reaction solvent, and also has a high silicon conversion rate and reaction rate. Alkoxysilane can be produced with this method.

Claims (2)

In alkylbenzene or triethyl diphenyl reaction solvent, by reacting an alkyl alcohol metallic silicon and 1 to 4 carbon atoms in the method for producing an alkoxysilane, was added to the fluorosilicone in the reaction system, reacting at 160 to 220 ° C. To prevent retention of reaction products during the reaction . Fluorosilicone, Ri compound der having 30 to 300 siloxane units consisting mainly of trifluoropropyl methyl siloxane units per molecule, by addition 0.003 parts by weight with respect to the reaction solvent 100 parts by weight the method of the alkoxysilane of claim 1, wherein Rukoto reacted to a selectivity of 91.5% or more metallic silicon conversion 97.3% or more and tri body.