JP3277770B2 - Method for producing polysilane - Google Patents

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 a polysilane by improving a conventional method for producing a polysilane by a wurtz type condensation method and obtaining a high molecular weight polysilane in a high yield.

[0002]

2. Description of the Related Art Polysilane has attracted attention as a compound useful as a precursor of silicon carbide ceramics, a photoresist material, a photopolymerization initiator, a photoconductive material, a nonlinear optical material, and the like. Soluble polysilane found (West, R. et al, JA)
m. Chem. Soc. 1981, 103, 7352)
Since then, polysilanes have been studied in a wide variety of ways, including their production methods and their applications.

Hitherto, as a method for producing this polysilane, a method based on desalting condensation of a diorganodihalosilane with an alkali metal has been adopted, and it has long been known as a so-called Wurtz type condensation method (Kipping, F., et al.).
S. J. Chem. Soc. 1921, 119, 83
0. Burkhard, C .; J. Am. Chem. S
oc. 1949, 71, 963. ).

[0004] However, polysilanes produced by the Wurtz type condensation method generally have low yields, and are particularly important for high molecular weight polymers which are regarded as important in terms of handling and molding properties in molding processes such as film formation or spinning. Has a very low yield.
When the reaction is carried out in an aromatic solvent such as toluene or an ether solvent, the yield of polysilane is improved, but the molecular weight is reduced and the production ratio of the high molecular weight product is 20% in the aromatic solvent. %, Hardly formed in an ether solvent. On the other hand, performing the reaction in an alkane is known to increase the molecular weight and increase the yield by increasing the reaction temperature, and is effective when a high molecular weight product is intended.

For example, in the case of polymethylphenylsilane,
Trujillo (J. Organomet. Che
m. 1980, 198, C27), or Taylo
r (JP-A-63-286433, GB87-10)
531) are reported to be obtained with a yield of 65% and 57%, respectively, but when they are obtained as polysilanes having low dispersity by reprecipitation purification, only 43% and 35% are obtained. Also, Zeigler (Tokuheihei 1-503237)
Discloses a method for obtaining a polysilane in high yield by adjusting the relative solubility parameter with a solvent, but this method also has a maximum of 45%.
It is.

[0006] As described above, the reason why the yield of the high molecular weight compound is low is that polysilane produced from organodihalosilane and alkali metal is not only a high molecular weight compound but also a cyclic or chain oligosilane or a low molecular weight polysilane. This is because production is inevitable and the yield is reduced.

Therefore, a method for obtaining a high molecular weight polysilane in a high yield is desired.

The present invention has been made in view of the above circumstances, and has as its object to provide a practical production method capable of obtaining a high-molecular-weight polysilane in a high yield.

[0009]

Means for Solving the Problems and Embodiments of the Invention The present inventors have conducted intensive studies to achieve the above object, and as a result, polysilane was produced by the reaction of diorganodihalosilane with an alkali metal. When low-molecular-weight polysilanes containing cyclic or chain-like oligosilanes are produced as by-products (hereinafter, these by-products are referred to as low-molecular-weight products), these by-product low-molecular-weight products react with alkali metals again to produce polysilanes. Was obtained.

That is, in general, in the wurtz type condensation method using an alkali metal, an alcohol is used for the purpose of securing the safety against the alkali metal in the post-treatment process after completion of the reaction or for removing the alkali metal ion or the halogen ion.
An operation of contacting with water or water is performed. By this operation, the alkali metal is brought into a safe state, but at the same time, the chlorine atom bonded to the terminal of the low molecular weight by-product undergoes alcohol decomposition or hydrolysis to produce silanol or siloxane, and the alkali metal is no longer alkali. It does not participate in the reaction with metals. Unless these compounds converted to silanol or siloxane are used as new by-products as by-products, they are discarded, resulting in an increase in production costs.

However, when this low-molecular-weight product is again subjected to a reaction between a diorganodihalosilane and an alkali metal without contact with alcohol or water, the molecular weight increases and finally the diorganodihalosilane Polysilane equivalent to a high molecular weight polysilane produced only from the above can be obtained. Further, when subjected to a reaction with a diorganodihalosilane which is a monomer, the polysilane produced and obtained when only diorganodihalosilane is used is obtained. It has been found that it is possible to obtain a high-molecular-weight polysilane in a much larger amount than the amount of the high-molecular-weight polysilane.

In this case, as described above, polysilane is produced by the reaction between the diorganodihalosilane and the alkali metal, and a low-molecular-weight product is also produced as a by-product. It is difficult to dissolve in the aliphatic hydrocarbon solvent, and after the reaction, it exists in a form insoluble in the solvent together with the by-product alkali metal halide, and the by-product low-molecular-weight compound is soluble in the solvent. Thus, the reaction mixture of the diorganodihalosilane and the alkali metal is filtered,
The present inventors have found that a high molecular weight polysilane can be obtained in good yield by adding diorganodihalosilane and an alkali metal to the obtained filtrate and reacting again, and have accomplished the present invention.

Accordingly, the present invention provides a method for reacting a diorganodihalosilane with an alkali metal in an aliphatic hydrocarbon solvent, filtering the resulting reaction mixture, and then adding the diorganodihalosilane and the alkali to the filtrate. A method for producing a polysilane, characterized in that a low-molecular-weight polysilane in the filtrate is converted into a high-molecular-weight polysilane by reacting with a metal.

Hereinafter, the present invention will be described in more detail. As the diorganodihalosilane used in the production method of the present invention, a silicon compound represented by the following general formula (1) or a silicon compound represented by the following general formula (1) is used. A mixture of the compound and a silicon compound represented by the following general formula (2) is suitably used.

[0015]

Embedded image

However, R ^{1 to} R ⁴ represent a hydrogen atom or a C ¹ -C 1
18, preferably 1 to 12 unsubstituted or substituted monovalent hydrocarbon groups, which may be the same or different from each other.

Here, examples of the monovalent hydrocarbon group include an alkyl group such as methyl, ethyl, propyl, and butyl; an alkenyl group such as vinyl and allyl; an aryl group such as phenyl; and an aralkyl group such as benzyl.

As the alkali metal, lithium, sodium and potassium are used, and sodium is particularly preferable. The amount of the alkali metal used is 1 to 1.5 equivalents of diorganodihalosilane, more preferably 1.05 to 1.3 equivalents. When the amount is less than 1 equivalent, the alkali metal as a condensing agent becomes insufficient and the yield is lowered, and at the same time, the low molecular weight is gradually increased in the process of reusing the low molecular weight many times to cause imbalance. Therefore, an undesirable case occurs. Further, use exceeding 1.5 equivalents may not work effectively for improving the yield or increasing the molecular weight.

As the solvent, diorganodihalosilanes and aliphatic hydrocarbons such as hexane, octane and dodecane which are stable to alkali metals are preferred. Aromatic hydrocarbons and ether compounds that easily dissolve high molecular weight polysilanes are effective as reaction solvents,
It is not preferable because it is difficult to separate the high-molecular-weight product and the low-molecular-weight product after the reaction by filtration.

The reaction temperature is preferably at least the melting point of the alkali metal. Although the reaction proceeds at a temperature lower than the melting point, the reaction speed is low and it takes a long time to complete the reaction, which is not economically preferable. Also, the reaction temperature is related to the solubility of the produced polysilane high molecular weight substance,
It affects the molecular weight of the resulting polysilane high molecular weight. That is, the higher the temperature, the higher the molecular weight range of the soluble polysilane increases, and as a solution, it is involved in the reaction with the alkali metal and is converted into a higher molecular weight polysilane,
Polysilanes in the high molecular weight range that can no longer be dissolved are excluded from the reaction system as insoluble forms in the solvent. As described above, the molecular weight of the polysilane which becomes insoluble in the solvent after the completion of the reaction increases as the reaction temperature increases. This makes it possible to adjust the molecular weight of the polysilane obtained by controlling the reaction temperature.

As for the reaction time, at least a time until the heat generation by the reaction is completed is required. Since the reaction involves a large amount of heat, a method of detecting the end of the heat generation is to control the change in the amount of reflux when the reaction is carried out under reflux of the solvent, or to control the temperature at a constant temperature equal to or lower than the boiling point of the solvent. In this case, this can be achieved by a heater output for temperature control or the like. The upper limit of the reaction time is preferably within 2 hours, particularly preferably within 1 hour. When the reaction time exceeds 2 hours, the yield and molecular weight of polysilane hardly increase, and it is not economical.

The reaction is performed in an inert atmosphere such as a nitrogen atmosphere while avoiding contact with water, air and the like.

The reaction mixture obtained by the reaction under the above conditions is then cooled, if necessary, and then appropriately passed through a filter layer in an inert atmosphere to separate into a filter cake and a filtrate. In this case, in the cooling process of the reaction mixture, in addition to the high molecular weight insoluble at a predetermined reaction temperature, polysilane having a lower molecular weight is precipitated in the cooling process. If only a high molecular weight substance that is insoluble at a predetermined reaction temperature is desired, it is not preferable because the polysilane having a lower molecular weight becomes unnecessary and is separated and discarded in the subsequent purification process. Therefore, it is more preferable to filter the reaction mixture at a temperature equal to or close to the reaction temperature, since polysilane having a lower molecular weight is excluded as a solution on the filtrate side, and can be subjected to the reaction again. Further, since the load in the purification process is reduced, it is effective as a method for efficiently producing a high molecular weight polysilane having a narrow molecular weight range. The filtration is performed in an inert atmosphere, and the filtrate is reacted under an inert atmosphere as described above, avoiding contact with not only alcohol and water but also air.

In the present invention, an alkali metal and a diorganodihalosilane are added to the by-product low-molecular-weight polysilane thus separated, particularly the filtrate, and the reaction is carried out again. In this case, the filtrate obtained by filtering the reaction mixture can be directly used for the reaction. As a reaction method at that time, (1) a method in which a predetermined amount of an alkali metal is added to the filtrate, the temperature is raised to a predetermined temperature, and then diorganodihalosilane is dropped, (2) Conversely, a predetermined amount is added to the filtrate. Is added, and the temperature is raised, and then the alkali metal is gradually added in a solid state or in a heated, molten liquid state. Further, (3) a so-called continuous reaction method in which a mixture of the filtrate, diorganodihalosilane, and alkali metal are continuously supplied to the reaction layer in an equivalent amount, and the reaction liquid generated successively is discharged. Can also.

Here, as the diorganodihalosilane to be added, the same diorganodihalosilane as used initially can be used in the same amount. At this time, the concentration of the silicon compound in the reaction solution increases due to the addition of the low-molecular-weight compound contained in the filtrate to the amount of diorganodihalosilane used in the first reaction, so that it is possible to appropriately dilute the compound. It is. However, in the mixture of the reaction products, the component that hinders stirring is mainly by-produced salt, so even if low-molecular-weight products that have already undergone considerable desalination condensation increase in the system, It does not usually need to be diluted as it does not affect the stirring and the reaction. Therefore, the solvent contained in the filtrate can be used as it is. That is, it is only necessary to add diorganodihalosilane and an alkali metal to the filtrate and react them, and it is not necessary to add a new solvent. Usually, the amount of the solvent used is 300 ml or more, preferably 500 ml or more, per 1 mol of diorganodihalosilane. Further, the addition amount of the alkali metal is preferably 1 to 1.5 equivalents to the total amount of the low molecular weight compound and the added diorganodihalosilane in the filtrate. Further, the reaction conditions in this case may be the same as the reaction conditions described above. In the present invention, the above operations can be repeatedly performed.

In the present invention, a low molecular weight compound having a weight average molecular weight of less than 100,000 is converted to a high molecular weight polysilane having a weight average molecular weight larger than that of the low molecular weight compound used, in particular, a weight average molecular weight of 100,000. It can be converted to high molecular weight polysilanes of 000 or more. Preferably, a low molecular weight compound having a weight average molecular weight of less than 50,000 is converted to a high molecular weight polysilane having a weight average molecular weight larger than that of the low molecular weight used, in particular, having a weight average molecular weight of 50,000 or more, especially 100,000 or more. It can be converted to high molecular weight polysilane. More preferably,
Weight average molecular weight of 30,000 or less, especially 20,000
A low molecular weight compound having a weight average molecular weight of 50,000 or more, particularly 100,000 or more can be converted into a low molecular weight compound having a weight average molecular weight of 50,000 or more, particularly 100,000 or more.

The filter cake obtained by filtering the reaction mixture is treated with alcohol or water to remove the residual alkali metal and dissolve and remove the alkali metal halide to obtain a crude polysilane polymer. Obtain and further purify. Refining methods are already known in various literatures and patents, for example, a typical method is to dissolve polysilane in its parent solvent and then add a poor solvent for polysilane to solidify the polysilane, so-called recrystallization. Alternatively, a method called reprecipitation is suitable.

The polysilane obtained by the present invention is represented by the following general formula (3) when using the diorganodihalosilanes of the above formulas (1) and (2).

[0029]

Embedded image (However, R ^{1 to} R ⁴ are the same as described above. Further, n is an integer of 1 or more, m is an integer of 0 or more, and n + m ≧ 10.)

Here, various yields based on conventionally known polysilane production methods are described. However, the numerical values of these yields are intended for polysilanes having a very wide molecular weight range. Molecular weight of about 100,00
In order to obtain a high molecular weight compound having a molecular weight range of 0 or more, purification results in a large decrease in yield. On the other hand, the high molecular weight polysilane obtained by the present invention has a feature that the molecular weight distribution is narrow and polysilane having an average molecular weight of about 100,000 or higher can be easily obtained in high yield. .

[0031]

According to the present invention, low-molecular-weight polysilane containing cyclic or chain-like oligosilane by-produced during the production of polysilane is brought into contact with diorganodihalosilane again without contact with alcohol or water. By reacting with a metal and converting it to a high molecular weight polysilane, a high molecular weight substance can be obtained economically and in high yield.

[0032]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Reference Examples, Examples, and Comparative Examples, but the present invention is not limited to the following Examples.

Reference Example 1 A 300 ml four-necked round bottom separable flask was charged with a stirrer, a Dimroth condenser, a thermometer,
A 50 ml dropping funnel was provided, and the container was left overnight with aeration of dry nitrogen. 5.06 g of metallic sodium in the vessel
(0.22 mol) and 140 ml of dried dodecane were charged and heated to 190 ° C. on an oil bath. On the other hand, 19.1 g of phenylmethyldichlorosilane (0.1
mol), while maintaining the inside of the flask at 190 ° C., 1
The solution was slowly dropped over 5 minutes. After completion of the dropwise addition, the temperature was maintained at 190 ° C. for another 45 minutes, and the reaction was terminated after cooling. Then, the mixture was filtered with a glass filter under a nitrogen stream, and washed with 10 ml of dodecane to obtain a filter residue and a filtrate. The filter cake was further sufficiently washed with n-octane, further washed with methanol and then with water, and dried to obtain 8.6 g of a crude product (yield: 71%). G of this polysilane crude product
As a result of PC measurement, the weight average molecular weight was 138,00.
It was 0. This crude product was dissolved in 260 ml of toluene, washed three times with a separating funnel, dried over magnesium sulfate, and filtered. Then, 500 ml of acetone was gradually added thereto with stirring with a magnetic stirrer to carry out reprecipitation, followed by filtration and drying to obtain 5.2 g of purified polysilane (yield 43%, weight average molecular weight 198,00).
0).

[Comparative Example 1] The filtrate obtained in Reference Example 1 was divided into two parts, and one of them was washed three times with a separating funnel and washed with water.
Dry over anhydrous magnesium sulfate. This solution contains low-molecular-weight oligosilanes according to GPC.
As a result of the measurement, it was found (see the chromatogram before the reaction in FIG. 1).

To the dodecane solution containing this low molecular weight substance was added 0.5 g of metallic sodium, and the temperature was raised to 190 ° C. and maintained for 4.5 hours. As a result of treatment in the same manner as described above and measurement of GPC, there was no sign of an increase in the molecular weight, which was exactly the same as the chromatogram before the reaction (see FIG. 1).

[Experimental Example] The other of the filtrate obtained in Comparative Example 1 was not subjected to any treatment, and was kept under a nitrogen atmosphere, added with 0.5 g of metallic sodium, and maintained at 190 ° C. for 3 hours. As a result of the measurement, a clear increase in the molecular weight was observed as shown in FIG.

Examples 1 to 5 A polysilane was synthesized in the same manner as in Reference Example 1, and a filter cake and a filtrate were obtained by filtration. The cake was treated in the same manner as in Reference Example 1 (Reference Example 2).

Next, the obtained filtrate was newly charged into a flask, 5.06 g of metallic sodium was added, and the temperature was raised to 190 ° C. 19.1 g of phenylmethyldichlorosilane was put into the dropping funnel, and the mixture was gradually dropped over 15 minutes while keeping the inside of the flask at 190 ° C. After completion of the dropwise addition, the temperature was maintained at 190 ° C. for another 45 minutes, and the reaction was terminated after cooling. The cake was treated in the same manner as in Reference Example 1 (Example 1). The filtrate was subjected to the next reaction for reuse. Hereinafter, similarly, 4
The reaction was repeated twice (Examples 2 to 5).

Each crude product was dissolved in toluene so as to have a concentration of 10% by weight, and twice the volume of acetone used was added to carry out reprecipitation purification. Table 1 shows these results.
It was shown to.

[0040]

[Table 1]

The amount of phenylmethyldichlorosilane used in the total of five reactions was 95.5 g. Based on this, the yield of the crude product and the purified product was calculated five times. 89.5%, the yield of the purified product was 51.7%, and the improvement of the yield was confirmed. GPC charts of the crude product and the purified product of Example 1 are shown in FIG.

Examples 6 to 8 Polysilane was synthesized in the same manner as in Reference Example 1 (Reference Example 3). The obtained filtrate and 19.1 g of phenylmethyldichlorosilane were charged into a flask, and the temperature was raised to 190 ° C. 12.65 g of metal sodium dispersion (manufactured by Aldrich, 40% light oil dispersion) was gradually added over 10 minutes, and thereafter, the reaction was terminated at 190 ° C. for 45 minutes (Example 6). Hereinafter, two reactions were similarly repeated using the obtained filtrate. Table 2 shows these results.
It was shown to.

[0043]

[Table 2]

The amount of phenylmethyldichlorosilane used in the total of three reactions was 57.3 g. Based on this, the yield of the crude product and the purified product was calculated three times. 89.4% and the purified product yield was 50.8%, confirming the improvement of the yield.

Examples 9 to 11 Polysilane was synthesized in the same manner as in Reference Example 1. After completion of the reaction, the reaction solution was immediately filtered through a closed glass filter without cooling. The cake was treated in the same manner as in Reference Example 1 (Reference Example 4).

The obtained filtrate and 19.1 g of phenylmethyldichlorosilane were charged into a flask and heated to 190 ° C. Next, the reaction was carried out in the same manner as in Example 6. Hereinafter, two reactions were similarly repeated. Table 3 shows the results.

[0047]

[Table 3]

The amount of phenylmethyldichlorosilane used in the three reactions was 57.3 g. Based on this, the yield of the crude product and the purified product was calculated three times. 75.2% and the yield of the purified product was 68.6%.
It was confirmed that the yield of polysilane was greatly improved because the ratio of the reuse of the low-molecular-weight product was increased by the filtration under hot conditions.

[Brief description of the drawings]

FIG. 1 is a GPC chart of a reaction product obtained by using a post-processed low molecular weight product of Comparative Example 1.

FIG. 2 is a GPC chart of a reaction product obtained by using an untreated low molecular weight product of an experimental example.

FIG. 3 is a GPC chart of the crude polysilane obtained in Example 1.

Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08G 77/60

Claims (1)

(57) [Claims] 1. A diorganodihalosilane and an alkali metal are reacted in an aliphatic hydrocarbon solvent, the obtained reaction mixture is filtered, and then the diorganodihalosilane and the alkali metal are added to the filtrate. And converting the low molecular weight polysilane in the filtrate to a high molecular weight polysilane.