JP2018062465A - Cyclohexasilane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide cyclohexasilane of high purity.SOLUTION: Cyclohexasilane of the present invention comprises pure cyclohexasilane in a rate of 98-100 mass%.SELECTED DRAWING: None

Description

  The present invention relates to high purity cyclohexasilane.

  Cyclohexasilane is cyclized from diphenyldichlorosilane using alkali metal, isolated from a 6-membered ring, chlorinated on silicon by contact with hydrochloric acid gas in the presence of aluminum chloride, and then lithium aluminum hydride For example, a method known in the art for reduction by contact with a metal hydride such as Hengge method (Non-Patent Document 1), trichlorosilane, N, N, N ′, N ″, N ″ -pentaethyldiethylenetriamine ( A cyclodecachlorocyclohexasilane dianion salt by cyclization coupling in the presence of a tertiary polyamine such as pedeta) or N, N, N ′, N′-tetraethylethylenediamine (teeda). It is known that it can be synthesized by a method of preparing and reducing the salt by bringing a metal hydride reducing agent into contact therewith (Patent Document 1). It has been.

Japanese Patent No. 4519955

Angew. Chem. Int. Ed. Engl., 1977, 16, 403.

  By the way, the purification method of cyclohexasilane is not known until now. Therefore, the present inventors challenged the purification, but the purification efficiency of cyclohexasilane was very poor, and it was difficult to purify it with high efficiency. Specifically, when purifying cyclohexasilane by distillation, purification efficiency could not be improved by purifying at a low temperature or purifying at a high temperature. For example, when distillation is performed at a low temperature, not only is the evaporation rate slow, but it is necessary to lower the temperature of the condenser in order to reliably condense the vaporized cyclohexasilane. The purification efficiency was inferior. In addition, when distillation was performed at a high temperature, the distillation stopped halfway, and the purification efficiency was still inferior.

  This invention is made | formed in view of the above situations, Comprising: The objective is to provide high purity cyclohexasilane.

  As a result of intensive studies to solve the above problems, the present inventors have found that a pressure region and a temperature region in which purification efficiency is improved exist specifically. Then, the crude cyclohexasilane is distilled under an absolute pressure of at least 2 kPa, and the temperature applied to the crude cyclohexasilane during the distillation is controlled to a specific range, or is further reduced to a low pressure region (for example, a medium vacuum of 0.1 to 100 Pa). If a specific distillation apparatus suitable for distillation in a high-vacuum range from 0.00001 to 0.1 Pa is employed, blockage of the condenser and stoppage of the distillation can be avoided, and purification of cyclohexasilane is achieved. The present invention has been completed by finding that the efficiency is increased.

That is, in the first method for producing cyclohexasilane according to the present invention, when distilling crude cyclohexasilane to obtain purified cyclohexasilane, the absolute pressure during distillation is 2 kPa or less, and the heating temperature of the crude cyclohexasilane is Is 25 to 100 ° C.
The second method for producing cyclohexasilane according to the present invention is characterized by using a molecular distillation apparatus or a short-path distillation apparatus in obtaining crude cyclohexasilane by distilling crude cyclohexasilane.

  The evaporator used in the distillation in the first and second cyclohexasilane production methods of the present invention is preferably a centrifugal thin film evaporator or a falling thin film evaporator. Moreover, in the said distillation in the manufacturing method of the 1st and 2nd cyclohexasilane of this invention, it is preferable to condense cyclohexasilane at -5 degreeC-30 degreeC. Further, in the first and second cyclohexasilane production methods of the present invention, the crude cyclohexasilane is preferably a reaction mixture obtained by reducing a halide of cyclohexasilane.

The cyclohexasilane of the present invention contains pure cyclohexasilane in a proportion of 98% by mass to 100% by mass. In the present invention, “pure cyclohexasilane” means cyclohexasilane having a purity of 100%.
In a preferred embodiment of the cyclohexasilane of the present invention, hexasilane is contained in a proportion of 2% by mass or less, a dimer of cyclohexasilane is contained in a proportion of 2% by mass or less, or a siloxane compound is contained in 2% by mass. Contains in the following proportions.

  In addition, when the cyclohexasilane of this invention contains pure cyclohexasilane in the ratio of less than 100 mass%, the cyclohexasilane of this invention turns into a composition containing pure cyclohexasilane and an impurity.

  According to the present invention, the pressure and temperature during distillation are set within a predetermined range, or by employing a specific distillation apparatus, it is possible to avoid clogging of the apparatus and the middle stop of distillation, and high purification efficiency. A pure cyclohexasilane can be obtained.

1 is a gas chromatography analysis chart of purified cyclohexasilane obtained in Example 1. FIG.

The first and second methods for producing cyclohexasilane of the present invention are methods in which crude cyclohexasilane is distilled to obtain purified cyclohexasilane.
For the distillation, in the first invention, the absolute pressure during distillation is 2 kPa or less, the heating temperature of the crude cyclohexasilane is 25-100 ° C., and in the second invention, a molecular distillation apparatus or a short path distillation apparatus is used. To do. According to the first or second invention, it is possible to avoid clogging of the apparatus or stop in the middle of distillation, and high purity cyclohexasilane can be obtained with good purification efficiency.

  In the first invention, the absolute pressure during distillation is 2 kPa or less, preferably 1 kPa or less, more preferably 500 Pa or less. If the absolute pressure during distillation is higher than this range, distillation stops halfway. From subsequent detailed studies by the inventors, it is speculated that this termination is due to ring-opening polymerization of cyclohexasilane during distillation. The lower limit of the pressure during distillation is not particularly limited as long as it is in a feasible range, but if the pressure is too low (the degree of vacuum is too high), the amount of evaporation of crude cyclohexasilane is small. In addition, since the restrictions on the apparatus increase, the pressure is preferably 1 Pa or more, more preferably 5 Pa or more, and further preferably 10 Pa or more.

  In the first invention, the heating temperature of the crude cyclohexasilane is 25 to 100 ° C., preferably 35 ° C. or higher, more preferably 40 ° C. or higher, still more preferably 45 ° C. or higher, and particularly preferably 50 ° C. or higher. The heating temperature is preferably 95 ° C. or lower, more preferably 90 ° C. or lower, and further preferably 85 ° C. or lower. If the heating temperature of the crude cyclohexasilane is too low, not only will the evaporation rate be slow, but it will also be necessary to lower the condenser temperature in order to reliably condense the vaporized cyclohexasilane, and solidified substances will adhere to the condenser. This makes it easier to block the device. Subsequent detailed examination by the inventors revealed that this solidified product was solid cyclohexasilane. If the condenser temperature is raised to a temperature at which the solidified product is not generated under conditions where the heating temperature is too low, the temperature difference between the heating part and the condensing part becomes smaller, the number of cyclohexasilanes not condensed increases, and the distillation yield deteriorates. To do. On the other hand, if the heating temperature of the crude cyclohexasilane is too high, distillation stops midway. From subsequent detailed studies by the inventors, it is speculated that this termination is due to ring-opening polymerization of cyclohexasilane during distillation. When the crude cyclohexasilane is purified by distillation, the purification efficiency is lowered regardless of whether the heating temperature is high or low. However, the purified cyclohexasilane can be efficiently obtained for the first time when it is distilled in a specific temperature range.

  The heating temperature of the crude cyclohexasilane means the liquid temperature of the crude cyclohexasilane heated to evaporate during distillation. For example, when the crude cyclohexasilane is evaporated in a kettle “Distillation bottom temperature” becomes the heating temperature, and when a distillation apparatus using a thin film evaporator is used, “evaporation surface temperature” becomes the heating temperature.

  In the second invention, a molecular distillation apparatus or a short path distillation apparatus is used for distillation. The terms “molecular distillation” and “short-path distillation” have various meanings depending on the times and countries, and are used in the present specification with the following meanings.

That is, according to a strict definition, molecular distillation is performed under high vacuum (for example, about 10 ⁻¹ Pa to 10 ⁻⁵ Pa), and the distance between the evaporation surface and the condensation surface is larger than the mean free path of vapor molecules. In this specification, the term “molecular distillation” refers to the meaning of molecular distillation, ie, under high vacuum (for example, about 10 ⁻¹ Pa to 10 ⁻⁵ Pa). As long as it is understood, it is used in the sense whether or not the distance between the evaporation surface and the condensation surface exceeds the mean free path of the vapor molecule. According to such molecular distillation, ideally, all evaporated vapor molecules do not collide with other vapor molecules or walls until they reach the agglomeration surface from the evaporation surface, and all the molecules enter the condenser. Aggregated.
On the other hand, short stroke distillation is performed under a medium vacuum (for example, about 10 ² Pa to 10 ⁻¹ Pa), and is characterized in that the evaporation surface and the condensation surface are arranged to face each other.

  The absolute pressure at the time of distillation in the second invention can be appropriately set within the above-described high vacuum or medium vacuum range. Further, the heating temperature of the crude cyclohexasilane on the evaporation surface is preferably, for example, 25 to 80 ° C, more preferably 25 to 75 ° C, and further preferably 40 to 70 ° C.

The molecular distillation apparatus and the short stroke distillation apparatus include an evaporator, a condenser, and a decompression unit (such as a vacuum pump).
The evaporator includes an evaporation surface that can contact the evaporation material and supply heat. Examples of the evaporator provided with the evaporation surface include a plate-like body (for example, a rectangular plate, a disk, etc.), a cylindrical body, a bottomed container, and the like. The surface of the plate-like body, the inner surface of the cylindrical body Alternatively, the outer surface, the inner surface of the container, etc. can be the evaporation surface. An evaporator such as a plate-shaped body or a cylindrical body is preferable in that the evaporation raw material can be evaporated into a thin film. When the film is evaporated in a thin film, evaporation of the evaporation material can be promoted and purification efficiency can be increased. Further, foaming and boiling of the evaporation material can be suppressed, and the heat history applied to the evaporation material can be reduced. When the evaporator is a plate-like body or a cylindrical body, the evaporator also includes forced thinning means if necessary. As the forced thinning means, for example, a wiper element that operates along the plate-like body surface or the inner or outer surface of the cylindrical body, or a forced rotating means that can generate centrifugal force by rotating the disk or cylindrical body Etc. can be used.

  The evaporator preferably used in the molecular distillation and the short path distillation is a thin film evaporator. If a thin film evaporator is used, the evaporation raw material can be evaporated into a thin film, so that evaporation of the evaporation raw material can be promoted and purification efficiency can be improved. Such heat history can be kept small. Such a thin film evaporator can be configured by appropriately combining the evaporation surfaces and forced thinning means described above. For example, if a plate-like body or a cylindrical body is provided with a wiper element or a forced rotating means as a forced thinning means, a wiper type thin film evaporator and a centrifugal thin film evaporator are obtained. Moreover, even if it is a plate-shaped body or a cylindrical body that does not have the forced thinning means, a flow-down type thin film evaporator can be obtained by arranging the evaporation surface vertically and allowing the evaporation raw material to flow from the upper portion little by little. Particularly preferable are a centrifugal thin film evaporator and a falling thin film evaporator.

The condenser includes a condensing surface for cooling the vapor molecules in contact with the vapor molecules evaporated by the evaporator.
In the apparatus used for short-path distillation, the condensation surface of the condenser is disposed relative to the evaporation surface of the evaporator. Also in the apparatus used for molecular distillation, it is preferable that the evaporation surface and the condensation surface are arranged relative to each other. However, the present invention is not limited to this, and various arrangements can be adopted within a range applicable to molecular distillation. . As an apparatus in which the evaporation surface and the condensation surface are arranged so as to face each other, for example, it has a double tube structure composed of an outer tube and an inner tube, and the inner surface of the outer tube is used as an evaporation surface or a condensation surface. An apparatus in which the outer surface of the cylinder is a condensation surface or an evaporation surface can be mentioned. When the evaporation surface and the condensation surface face each other, the area of the condensation surface is preferably equal to or greater than the area of the evaporation surface.

  The molecular distillation apparatus or short path distillation apparatus provided with the above evaporator, condenser, and decompression means is preferably a pot type distillation apparatus, a falling film type distillation apparatus, a centrifugal distillation apparatus, a concentric circular distillation apparatus, or It is classified as a Liebold mixed thin film distillation apparatus.

  The distillation apparatus used in the first invention is not particularly limited as long as it includes an evaporator, a condenser, and a decompression means. For example, a known apparatus including the above-described evaporator, condenser, etc. Various distillation apparatuses (of course, molecular distillation apparatus or short path distillation apparatus may be used) can be used. In particular, as the evaporator, the above-described thin film evaporator is also preferable in the distillation apparatus used in the first invention.

  In the first and second aspects of the invention, when a thin film evaporator is used, the thickness of the thin film formed on the evaporation surface may be set as appropriate in consideration of the evaporation rate and the like, but is 10 to 100 μm. Is more preferable, more preferably 20 to 90 μm, still more preferably 30 to 80 μm.

  In the distillation in the first and second inventions, the evaporated cyclohexasilane is preferably condensed at -5 ° C to 30 ° C. The condensation temperature is more preferably −2 ° C. to 20 ° C., further preferably 0 ° C. to 15 ° C. If the condensation temperature is in the above-mentioned range under the specific pressure condition range described above, it is possible to maintain good workability without causing cyclohexasilane to solidify and cause clogging in the apparatus.

  In the present invention, the series of operations related to the distillation (specifically, from the preparation of crude cyclohexasilane to the removal of purified cyclohexasilane) is preferably performed without exposure to the atmosphere. For example, a container for crude cyclohexasilane, a distillation apparatus (evaporator, condenser, etc.), and a container for purified cyclohexasilane are all housed in one explosion-proof booth, and the explosion-proof booth is filled with nitrogen or the like. The atmosphere may be controlled by controlling the inert gas atmosphere, or by feeding the liquid before purification or removing the condensate with an inert gas such as nitrogen gas and performing distillation in a sealed device. You may make it prevent.

  In the present invention, the preparation method of the crude cyclohexasilane to be subjected to the distillation is not particularly limited, and a known cyclohexasilane synthesis method can be appropriately employed. For example, diphenyldichlorosilane is used as a raw material, cyclized with an alkali metal, a 6-membered ring is isolated, contacted with hydrochloric acid gas in the presence of aluminum chloride to chlorinate on silicon, and then obtained cyclohexasilane A reaction mixture obtained by reducing a halide by contacting with a metal hydride such as lithium aluminum hydride can be used as crude cyclohexasilane. Also obtained by the method described in the following production examples found by the present inventors, that is, a method in which a halosilane compound such as trichlorosilane is cyclized in the presence of phosphine and the resulting halide of cyclohexasilane is reduced. The resulting reaction mixture can also be used as crude cyclohexasilane.

  In the present invention, since the crude cyclohexasilane is subjected to vacuum distillation at at least 2 kPa or less, it is desirable that the content of light-boiling components is small, and before being subjected to the distillation (vacuum distillation) according to the present invention. It is preferable to remove light boiling components such as a solvent in advance. Specifically, for example, the solvent may be distilled off under normal pressure or reduced pressure (over 2 kPa).

According to the first or second production method of the present invention, purified cyclohexasilane is usually obtained in a high purification yield of 60% or more, preferably 70% or more, more preferably 80% or more, and further preferably 90% or more. It becomes possible to obtain.
The purified cyclohexasilane obtained by the first or second production method of the present invention has a high purity. For example, in gas chromatography analysis described later in Examples, it is usually 98 area% or more, preferably 99 area% or more. More preferably, it is 99.5 area% or more, More preferably, it is 99.9 area% or more.

  The cyclohexasilane of the present invention contains pure cyclohexasilane in a proportion of 98% by mass to 100% by mass. The content of pure cyclohexasilane is preferably 99% by mass or more, more preferably 99.5% by mass or more, and further preferably 99.9% by mass or more. In addition, the method of calculating | requiring the content rate of pure cyclohexasilane can make "area%" of the cyclohexasilane in a gas chromatography analysis chart into the content rate of pure cyclohexasilane. Such cyclohexasilane of the present invention can be obtained, for example, by the above-described first or second production method of the present invention.

Impurities that the cyclohexasilane of the present invention may contain in addition to pure cyclohexasilane are not particularly limited, but are mainly hexasilane (Si ₆ H ₁₄ ), a dimer of cyclohexasilane (Si ₁₂ H ₂₂ ) or its Ring-opened compounds (compounds in which one or two rings of the dimer are opened (Si ₁₂ H ₂₄ , Si ₁₂ H ₂₆ ); collectively referred to as “cyclohexasilane dimer” in this specification) And a siloxane compound (a compound having a siloxane bond in which an oxygen atom is added to a silane hydride). Only one type of impurity may be used, or two or more types of impurities may be used.

  In a preferred embodiment of the cyclohexasilane of the present invention, hexasilane is contained in a proportion of 2% by mass or less, a dimer of cyclohexasilane is contained in a proportion of 2% by mass or less, or a siloxane compound is contained in 2% by mass. Contains in the following proportions. That is, when one or more of the three main impurities described above are contained, each is preferably 2% by mass or less, and the total content is preferably 2% by mass or less. The content of each of the three main impurities (hexasilane, cyclohexasilane dimer, and siloxane compound) is more preferably 1% by mass or less, and still more preferably 0.1% by mass or less. The lower limit is most preferably zero (ND), but it is technically difficult to reduce the hexasilane and cyclohexasilane dimer, so about 0.0001% by mass is preferable. 0.001% by mass or more is more preferable, and 0.01% by mass or more is particularly preferable. Of the three main types of silicon-containing impurities, the content of cyclohexasilane dimer is preferably within the above range.

  The high-purity cyclohexasilane (cyclohexasilane obtained by the first or second production method of the present invention or the cyclohexasilane of the present invention) as described above is, for example, a silicon raw material used for solar cells, semiconductors, etc. Useful as.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.
Purity of cyclohexasilane is capillary (J & W SCIENTIFIC Co. "DB-1 MS"; 0.25 mm × 50 m) Gas chromatograph equipped with at (manufactured by Shimadzu Corporation "GC2014"), the N ₂ carrier gas Sample injection volume 1 μL, sample injection temperature 300 ° C., column temperature 50 ° C. (holding 5 minutes) to 20 ° C./minute (temperature rising 10 minutes) to 10 ° C./minute (temperature rising 5 minutes) to 300 ° C. (holding 10) Min) and gas chromatography analysis under the conditions of the detector FID (300 ° C.).

[Production example (production of crude cyclohexasilane)]
After replacing the inside of a 300 mL four-necked flask equipped with a thermometer, a condenser, a dropping funnel and a stirrer with nitrogen gas, 5.81 g (0.022 mol) of triphenylphosphine as phosphine and 17.17 of diisopropylethylamine as a basic compound. 2 g (0.133 mol) and 1,2-dichloroethane 100 mL as a solvent were added. Subsequently, while stirring the solution in the flask, 18.0 g (0.133 mol) of trichlorosilane was slowly added dropwise as a halosilane compound from a dropping funnel at 25 ° C. After completion of dropping, the mixture was stirred as it was for 2 hours, and then reacted by heating and stirring at 60 ° C. for 8 hours. The obtained reaction solution was concentrated and washed to obtain a nonionic dodecachlorocyclohexasilane-containing compound ([Ph ₃ P] ₂ [Si ₆ Cl ₁₂ ]) as a white solid.

  In a 100 mL two-necked flask equipped with a dropping funnel and a stirrer, 2.44 g (2.18 mmol of dodecachlorocyclohexasilane-containing compound) of the obtained white solid was added and dried under reduced pressure. Next, after the inside of the flask was replaced with argon gas, 30 mL of cyclopentyl methyl ether was added as a solvent. Subsequently, while stirring the suspension in the flask, 10 mL of a lithium aluminum hydride diethyl ether solution (concentration: about 1.0 mol / L) as a reducing agent was gradually added dropwise from a dropping funnel at −20 ° C. Then, the reaction was carried out by stirring at -20 ° C for 5 hours. After the reaction, the reaction solution was filtered under a nitrogen gas atmosphere to remove the generated salt. The solvent was distilled off from the obtained filtrate under reduced pressure to obtain a colorless and transparent liquid crude cyclohexasilane.

[Example 1]
The crude cyclohexasilane obtained in the production example was subjected to an absolute pressure of 300 Pa, an evaporation surface temperature (by using a general glass vacuum distillation apparatus (a kettle, a fractionation pipe, a condenser (cooling pipe), a receiver)) Distillation was performed with the temperature of the crude cyclohexasilane in the kettle at 75 ° C. and the condensation surface temperature (set temperature of the condenser) at 5 ° C. to obtain purified cyclohexasilane. During the distillation, solidification of cyclohexasilane was not observed in the apparatus including the condenser.
When the obtained purified cyclohexasilane was analyzed by gas chromatography, the ratio of 98.9 area% for cyclohexasilane, 0.6 area% for hexasilane, and 0.5 area% for the dimer of cyclohexasilane was obtained. No siloxane compound was detected (the chart at this time is shown in FIG. 1). The distillation yield was 90%.

[Example 2]
The crude cyclohexasilane obtained in the production example was subjected to an absolute pressure of 20 Pa, an evaporation surface temperature of 45 ° C., and a condensation surface temperature of 0 ° C. using a short stroke distillation apparatus (“KDL-01” manufactured by Fintech). To obtain purified cyclohexasilane. In the apparatus including the condenser during distillation, no solidification of cyclohexasilane was observed.
When the obtained purified cyclohexasilane was analyzed by gas chromatography, the ratio of 99.1 area% of cyclohexasilane, 0.4 area% of hexasilane, and 0.5 area% of the dimer of cyclohexasilane was obtained. And no siloxane compound was detected. The distillation yield was 96%.

[Example 3]
The crude cyclohexasilane obtained in the production example was subjected to an absolute pressure of 100 Pa, an evaporation surface temperature of 60 ° C., and a condensation surface temperature of 0 ° C. using a short stroke distillation apparatus (“KDL-01” manufactured by Fintech). To obtain purified cyclohexasilane. In the apparatus including the condenser during distillation, no solidification of cyclohexasilane was observed.
When the obtained purified cyclohexasilane was analyzed by gas chromatography, the ratio of cyclohexasilane was 99.0 area%, hexasilane was 0.5 area%, and the cyclohexasilane dimer was 0.5 area%. And no siloxane compound was detected. The distillation yield was 93%.

[Comparative Example 1]
The crude cyclohexasilane was distilled in the same manner as in Example 1 except that the absolute pressure during distillation was changed from 300 Pa to 3 kPa and the temperature of the evaporation surface was changed from 75 ° C. to 130 ° C. Got. During the distillation, the solidified cyclohexasilane adhered to the condenser. After the distillation was completed, the condenser was warmed to collect the deposited cyclohexasilane as purified cyclohexasilane.
When the obtained purified cyclohexasilane was analyzed by gas chromatography, the ratio of 95.2 area% of cyclohexasilane, 2.1 area% of hexasilane, and 2.7 area% of dimer of cyclohexasilane was obtained. And no siloxane compound was detected. The distillation yield was 42%.

  The high purity purified cyclohexasilane obtained in the present invention is suitably used as a silicon raw material in applications such as solar cells and semiconductors.

Claims (4)

  Cyclohexasilane containing pure cyclohexasilane in a proportion of 98% by mass to 100% by mass.   The cyclohexasilane of Claim 1 which contains hexasilane in the ratio of 2 mass% or less.   The cyclohexasilane of Claim 1 which contains the dimer of a cyclohexasilane in the ratio of 2 mass% or less.   The cyclohexasilane of Claim 1 which contains a siloxane compound in the ratio of 2 mass% or less.

Images