JPS5865298A - Preparation of methylhydrodienesilanes - Google Patents

Abstract

PURPOSE:To prepare methylhydrodienesilanes useful as a modifier for various kinds of organosiloxanes and silanes, by decomposing thermally a dimethylpolysilane, subjecting formed valatile components to fractional distillation. CONSTITUTION:A dimethylpolysilane shown by the formula (n is positive integer) is decomposed thermally at >=350 deg.C, and methylhydrodienesilanes (consisting essentially of dimethylsilane) are prepared by fractional distillation from formed valatile components. When the temperature of the thermal decomposition is 650-800 deg.C, methylhydrodienesilanes are obtained in high yield, and when the thermal decomposition is carried out at 350-650 deg.C, polycarbosilane as a by- product is prepared besides methylhydrodienesilanes. USE:Methylhydrodienesilanes themselves are usable as a modifier, and preferably they are converted into methylhydrodienechlorosilanes, hydrolyzed into corresponding siloxanes, and used as modifiers.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing methylhydrogensilanes, particularly methylhydrogensilanes containing dimethylsilane as a main component.

Since methylhydrodienechlorosilanes contain an 18iH group as an active group in their molecules, they are considered useful as intermediate raw materials for producing various functional silanes and silochitins. However, the industrial production of methylhydrodienechlorosilanes is limited to a small amount as a by-product in the synthesis of methylchlorosilanes by the so-called direct method involving the reaction of methyl chloride and metal silicon; Various methods have been proposed for synthesis, but no satisfactory method has yet been established.

The present invention provides an industrially advantageous method for producing methylhydrodienesilanes, which are raw materials for producing such methylhydrodienechlorosilanes, by thermally decomposing dimethylpolysilane at a temperature of 350°C or higher, This method is characterized in that methylhydrogensilanes are collected by fractional distillation from the volatile gas components produced.

To explain this, the present inventors are currently investigating a method for producing polycarbosilane by thermal decomposition of dimethylpolysilane, and the thermal decomposition of dimethylpolysilane proceeds almost quantitatively, resulting in the formation of silicon and carbon. An organosilicon-purple-electronic compound is obtained that has the main skeleton component of
We discovered that this was mainly composed of methylhydrodiene silanes, and investigated thermal decomposition conditions to obtain these methylhydrodiene silanes in good yield.
The present invention has been completed.

That is, dimethylpolysilane, which is the starting material for the method of the present invention, is produced by the reaction of dimethyldichlorosilane and metallic sodium, and is represented by the formula; currently, it is thermally decomposed to form polycarbosilane. It is industrially produced for the purpose of making silicon carbide fibers by spinning and high-temperature treatment, and it has never been known that the volatile gas components are mainly methylhydrogen silanes. Was that.

The present invention is based on this new knowledge, and according to experiments conducted by the present inventors, the volatile gas components generated during thermal decomposition of dimethylpolysilane, that is, methylhydrogensilanes, are dimethylsilane ((OT(3) , 5in
2], and trimethylsilane ((oH,
)3stH), tetramethyldisilane ((O)T, )
2) TSi-81) ((OH3)2), hexamethyltrisilane ((OH8)2)TSi-81(C!)T3)
2-8i)T (CT-T,)2), and furthermore, this tetramethyldisilane,
Since hexamethyltrisilane can be easily converted into dimethylsilane and trimethylsilane by heating it to a higher temperature, if this volatile gas is collected by fractional distillation from the thermal decomposition process of dimethylpolysilane, the desired methyl Hydrogen silanes can be easily obtained industrially.

In addition, the present inventors studied the thermal decomposition temperature of this dimethylpolysilane and the production of volatile gases, ie, methylhydrogensilanes, and found that the thermal decomposition of this dimethylpolysilane needs to be carried out at 350°C or higher. In order to increase the yield of diene silanes, it is recommended to set the temperature as high as possible, for example, 650°C to 800°C. At this temperature, dimethylpolysilane does not pass through the formation of polycarbosilane, and most of it is converted to methylhydrogen. It was confirmed that volatile low-molecular compounds containing silanes were formed, and inorganic compounds such as sic were also produced together with this. However, this thermal decomposition temperature is 800℃
If the temperature is higher than that, the thermal decomposition reaction becomes intense and SiO, Si
The production of inorganic compounds such as
When the temperature is 50 to 500°C, a liquid organosilicon oligomer is generated together with this volatile low-molecular compound, and when this substance is then heated to 450 to 650°C, it polymerizes to become polycarbosilane, so it can be combined with methylhydrodiene silanes. If you wish to co-produce polycarbosilane, it is best to thermally decompose this dimethylpolysilane at a temperature in the range of 350 to 650°C. This will suppress the production of inorganic compounds such as Sin and 8i, and will meet the purpose. Polycarbosilane can be obtained in good yield along with methylhydrogensilanes.

The methylhydrodienesilanes collected by the method of the present invention are dimethylsilane ((OH,)28i
H2), and these are obtained as individual methylhydrogensilanes by fractional distillation, but all of these have 18iH groups as functional groups in addition to OH and 81 groups in their molecules. It is used as a modifier for various organosilochitins and silanes, but generally it is reacted with hydrogen chloride or various organochlorosilanes to form methylhydrodienechlorosilanes, and then This is often hydrolyzed to give the corresponding silochitin, which is then used as a modifying agent, for example dimethydrodiene monochlorosilane ((
OH3)2Si)(C1) is used as a modifier to introduce a 18iH group to the terminal of dimethylpolysiloxane, and also as a vinyldimethylchlorosilane obtained by the reaction of this dimethylhydrodiene monochlorosilane with acetylene.
(CH2CH)(CH8)2SIC1] is said to be useful as a modifier for introducing -(C!H20H) Si groups into the terminals of dimethylpolysiloxane.

Next, examples of the present invention will be given.

Example 1 A vertical steel reaction tube with an inner diameter of 42 mm filled with a quartz Rach ring was placed in a heating furnace with a length of 220 mm and heated to 440°C, and dimethyldichlorosilane and metallic sodium were added to it from above in xylene. The dimethylpolysilane powder obtained by reacting the dimethylpolysilane powder in the reactor was 0.217?
When it was fed using a screw feeder and pyrolyzed at a rate of /- hours, a gaseous product was obtained whose main components were 84.7% organosilicon oligomers and 15.1% dimethylsilane. It was done.

Next, the organosilicon oligomer obtained above was added to a copper reaction tube with an inner diameter of 1.5 mm heated to 720°C in a tube furnace with a length of 800 m+U using a metering pump for 0.045 n/-. When the gas was introduced at a feed rate and thermally decomposed, the gaseous matter produced was collected with dry ice and methanol.
A gas component of 86% based on the feed component was obtained, and the remainder was a pale yellow powdered inorganic compound.

When the gas components obtained in these two steps were fractionally distilled, they had the following composition.

In addition, the hexamethyltrisilane obtained here was added to 68
When introduced into a reaction tube heated to 0°C and thermally decomposed, this product contained 65.0% dimethylsilane, 7.5% trimethylsilane, 6.4% tetramethyldisilane, and 8% hexamethyltridylanph. Therefore, this yield is 86.7
% and the remainder was inorganic compounds.

Example 2 A quartz reaction tube with an inner diameter of 45 mm and a length of 1100 (Ja) with two stainless steel plates attached to the center was heated in a vertical tubular heating furnace with a heating section of 200 m + u.
It was heated to a constant temperature of .degree. C., and dimethylpolysilane powder was fed from above using a screw feeder at a feeding rate of 0.15 P/d.h to cause thermal decomposition.

As a result, 24Of dimethylpolysilane was treated in 5 hours, and the generated gaseous matter was collected in a water-cooled condenser and a dry ice methanol condenser. A product of 55% dimethylsilane, 8% trimethylsilane, and tetramethylsilane was obtained.

Example 3 500 iI of dimethylpolysilane powder obtained by the reaction of dimethyldichlorosilane and metallic sodium was placed in a quartz flask equipped with a stirrer and heated while passing a small amount of nitrogen gas, and the temperature inside the reactor reached 350°C. Sometimes a thermal decomposition polymerization reaction of dimethylpolysilane occurs,
It was observed that gaseous decomposition products were generated.

This heating was continued for 10 hours until the internal temperature reached 450°C, then kept at 450°C for 3 hours, and the molten components generated by decomposition during the volatilization were collected in a water-cooled condenser and a dry ice/methanol condenser. , 270 products were obtained, which contained 55.0% of dimethylsilane, 4.2% of trimethylsilane, 22.3% of tetramethyldisilane, 14.6% of hexamethylene, luthrine, and 3.0% of other high boilers. It consisted of 9%.

11- In this quartz flask, a solid resinous substance with a softening point of 70 to 75°C remains 211y-, and this substance has an average molecular weight of 800 and as a result of infrared analysis -8iOH2Si
- group, -8i) It was confirmed that it was a polycarbosilane exhibiting a T group bond.

patent applicant Shin-Etsu Chemical Co., Ltd. 12-

Claims (1)

[Claims] 1. A method for producing methylhydrodienesilanes, which comprises thermally decomposing dimethylpolysilane at a temperature of 350°C or higher and collecting methylhydrogensilanes by fractionation from the volatile gas components produced.