JP7811237B2 - Vinylsilane gas production method and production device - Google Patents

Description

The present invention relates to a manufacturing method and manufacturing apparatus for producing high-purity vinylsilane gas.

For example, Patent Document 1 (JP 2004-256494 A) discloses a method for producing vinylsilane by reacting acetylene with a silane compound in the presence of a titanium compound, and Patent Document 2 (International Publication WO 2006/064628) discloses a method for producing vinylsilane by reacting a vinyl halide compound with a silicon halide compound in an aprotic solvent in the presence of aluminum.

However, currently, vinylsilane gas, which has the CAS number 7291-09-0 and the structural formula CH2=CH-SiH3, is not produced industrially, and there is no integrated manufacturing process that combines the conventional methods of generation, purification, and filling. However, liquefied high-pressure gases with similar properties include carbon dioxide and organosilane gas, and there are several precedents for their purification, with reports of high-purity gases being produced by solidifying them with liquid nitrogen and evacuating them to a vacuum.

For example, Patent Document 3 (JP 2012-240870 A) discloses a system for purifying and supplying ultra-high purity liquefied carbon dioxide gas, which includes a liquefied carbon dioxide gas supply unit that supplies liquefied carbon dioxide gas recovered from a container filled with liquefied carbon dioxide gas or from a device using liquefied carbon dioxide gas; a vaporization unit that vaporizes the liquefied natural gas supplied from the liquefied carbon dioxide gas supply unit, leaving high-boiling-point liquid and solid impurities, and discharges gaseous carbon dioxide gas from the gas phase; a liquefaction unit that liquefies the gaseous carbon dioxide gas; and a gas-liquid separator that separates the liquefied carbon dioxide gas from the liquefaction unit into gas and liquid and has a discharge pipe equipped with a discharge valve that discharges low-boiling-point impurities outside the system; and a supply passage that supplies the high-purity liquefied carbon dioxide gas separated and purified by the gas-liquid separation unit to a device using ultra-high purity liquefied carbon dioxide gas via a supply valve.

Patent Document 4 (JP 2001-48519 A) discloses a purification method in which partially substituted fluorosilane gas containing low-boiling-point impurities is cooled in a container and evacuated in a solidified state, or cooled in a container and evacuated in a solidified state, and then the solidified partially substituted fluorosilane gas is vaporized, cooled again, and evacuated in a solidified state.

Japanese Patent Application Laid-Open No. 2004-256494 International Publication WO2006/064628 JP 2012-240870 A Japanese Patent Application Laid-Open No. 2001-48519

As described above, the methods disclosed in Patent Documents 3 and 4 increase the yield of carbon dioxide and organosilane gas recovery while removing only nitrogen and oxygen gases with lower boiling points than carbon dioxide or organosilane gas. However, with this method, only the lower boiling point gas components, nitrogen and oxygen, are removed for purification, and high boiling point substances are not removed. Furthermore, with typical organosilane gases, a separation-type production method is used in which the gas is first liquefied and then transferred to a separate distillation unit, where it is distilled. After distillation, a compression pump is used to compress the gas to liquefaction pressure and fill the unit. With vinylsilane gas, adiabatic compression using a compression pump can lead to a rapid reaction, making it difficult to use a compression pump.

The present invention was made in consideration of the above points, and provides a method and apparatus for producing vinylsilane that can remove high-boiling and low-boiling substances that become mixed in when vinylsilane is generated, and that can also perform purification and filling safely and at low cost.

Therefore, the present invention provides a method for producing vinylsilane, which comprises at least a generation step in which vinylsilane is continuously generated, a purification step in which the generated vinylsilane is purified, and a filling step in which the purified vinylsilane is filled into a filling container. The purification step comprises a first purification step in which high-boiling substances are separated from the vinylsilane generated in the generation step and the separated high-boiling substances are returned to the generation step, and a second purification step in which high-boiling substances are further separated from the separated vinylsilane. In the filling step, the filling container is cooled to a temperature below the freezing point of vinylsilane, and vinylsilane is filled into the filling container, and low-boiling substances are removed from the filling container.

As a result, the present invention removes most of the high-boiling substances other than vinylsilane generated in the generation stage, such as the raw materials vinyltrichlorosilane (melting point: -95°C, boiling point: 91.5°C), vinyldichlorosilane, and vinylchlorosilane, and the solvents tetrahydrofuran (melting point: -108.4°C, boiling point: 66°C) and dibutyl ether (melting point: -97.9°C, boiling point: 142°C), in the purification stage and returns them to the generation stage. Furthermore, the vinylsilane further refined in the purification stage can be solidified and recovered in the charging stage, thereby enabling the removal of low-boiling substances (such as oxygen, nitrogen, and argon gas) in the charging stage.

Furthermore, in the present invention, it is desirable that the generation stage be adjusted to a first temperature that is a predetermined value higher than the boiling point of the solvent used, and that the first purification stage be composed of an intermediate stage in which the temperature is adjusted to a second temperature that is a predetermined value lower than the first temperature, and a solvent recovery stage in which the temperature is adjusted to a third temperature in the range from the freezing point of the solvent used in the generation stage to the second temperature.

As a result, in the generation stage, the temperature is adjusted to a first temperature higher than the boiling point of the solvent, causing the vinylsilane and solvent to vaporize and reach the intermediate stage. In the intermediate stage, the temperature is adjusted to a second temperature that is a predetermined value lower than the first temperature, allowing the solvent to be fully liquefied and returned to the generation stage. Furthermore, in the solvent recovery stage following the intermediate stage, the temperature is adjusted to a third temperature that is above the freezing point of the solvent and below the second temperature, causing most of the solvent to be liquefied. Here, the liquefied solvent is returned to the generation stage via the intermediate stage, thereby suppressing temperature drops in the generation stage and allowing vinylsilane gas to be continuously generated in the generation stage.

Furthermore, it is desirable that the second purification stage be adjusted to a fourth temperature that is higher than the liquefaction temperature of vinylsilane at atmospheric pressure and lower by a predetermined value than the boiling point of the high-boiling substance.

As a result, the vinylsilane passing through the second purification stage is in the gas phase, while the high-boiling substances are in the liquid phase. As the high-boiling substances drip out during the second purification stage, the vinylsilane and the high-boiling substances are separated.

Furthermore, during the filling step, it is desirable that the filling container be adjusted to a fifth temperature that is a predetermined value lower than the freezing point of vinylsilane. In particular, it is desirable that the fifth temperature be above the melting point of the low-boiling substance and below the freezing point of vinylsilane.

As a result, the vinylsilane gas that reaches the filling stage solidifies within the filling container as the container is adjusted to the fifth temperature during the filling stage, and accumulates as a solid within the filling container. Since the low-boiling-point substances remain in the gas or liquid phase at this time, they can be removed from the vinylsilane by suction (oxygen, nitrogen, argon gas, etc.).

It is also desirable that the filled container be cooled gradually from the bottom to the top.

This ensures that vinylsilane can be reliably accumulated in the filled container from the bottom of the container.

Furthermore, the generating step, the purifying step and the filling step preferably have a sealed structure that can block the intrusion of low-boiling-point substances at a pressure of 1×10 ⁻² Torr or less (hereinafter referred to as high vacuum).

This ensures safety by preventing low-boiling-point substances, especially oxygen, from entering the path along which flammable vinylsilane travels.

Furthermore, it is desirable to use a highly airtight structure to ensure a high degree of vacuum, completely preventing the intrusion of impurity gases such as oxygen, nitrogen, and moisture, and in particular to prevent the decomposition and polymerization of vinylsilane due to the intrusion of moisture.

Furthermore, it is desirable that the filling step be performed intermittently by alternately filling with vinylsilane gas and evacuating to a vacuum.

The present invention relates to a vinylsilane production system comprising at least a generator that continuously generates vinylsilane, a purification device that purifies the generated vinylsilane, a filling device that fills a filling container with the purified vinylsilane, and a suction device that transfers vinylsilane from the generator to the purification device and the filling device. The purification device comprises a first purification device that separates high-boiling-point substances from the vinylsilane generated in the generator and returns the separated high-boiling-point substances to the generator, and a second purification device that further separates high-boiling-point substances from the separated vinylsilane. The filling device comprises a cooling device that cools the filling container to a temperature below the freezing point of vinylsilane, and a suction device that suctions low-boiling-point substances from the filling container.

As a result, the present invention allows the majority of vinylsilane generated in the generator and the high-boiling substances contained therein, such as the raw materials vinyltrichlorosilane (melting point: -95°C, boiling point: 91.5°C), vinyldichlorosilane, and vinylchlorosilane, and the solvents tetrahydrofuran (melting point: -108.4°C, boiling point: 66°C) and dibutyl ether (melting point: -97.9°C, boiling point: 142°C), to be removed in the purification device and returned to the generator. Furthermore, the vinylsilane further refined in the purification device can be solidified and recovered in the charging device, allowing low-boiling substances such as oxygen, nitrogen, and argon gas to be removed in the charging device.

Furthermore, it is desirable that the generator be adjusted to a first temperature that is a predetermined value higher than the boiling point of the solvent, and that the first purification device be composed of an intermediate container adjusted to a second temperature that is a predetermined value lower than the first temperature, and a solvent recovery container adjusted to a third temperature in the range from the freezing point of the solvent used in the generator to the second temperature.

Furthermore, it is desirable that the first purification device be positioned vertically relative to the generator. This allows the gas generated in the generator to rise to the first purification device, while the high-boiling-point substances liquefied in the first purification device can fall freely.

Furthermore, it is desirable that the temperature of the second purification device be adjusted to a predetermined value higher than the liquefaction temperature of vinylsilane at atmospheric pressure. Furthermore, the second purification device may be constructed as an upright tower of a predetermined height to ensure the reaction distance, or the reaction distance may be ensured by connecting multiple separation vessels in series. The high-boiling-point substances separated in the second purification device may be accumulated in a predetermined location, or may be circulated to the generator.

The filling device preferably includes a cooling device that adjusts the temperature of the filling container to a predetermined value lower than the freezing point of vinylsilane, and a suction device that moves vinylsilane from the generator to the upstream side of the filling container via the purification device. The cooling device preferably cools the filling container with liquid nitrogen.

As a result, the vinylsilane that has been sucked up to the upstream side of the filling container by the suction device is sucked into the filling container and solidifies as the filling container cools. This allows the vinylsilane to be accumulated. Furthermore, by arranging multiple filling containers in parallel, it becomes possible to fill them sequentially.

Furthermore, it is desirable that the cooling device gradually cools the filling container from the bottom toward the top. This allows the vinylsilane to solidify starting from the bottom of the container, thereby efficiently accumulating the vinylsilane in the filling container.

Furthermore, it is desirable that the generator, the refiner and the filling device have a sealed structure that can block the intrusion of low-boiling-point substances at a pressure of 1×10 ⁻² Torr or less (high vacuum) by the suction device.

This prevents oxygen from the air from mixing with the flammable vinylsilane passing through the device.

It is also desirable that the suction device alternately and intermittently fill and exhaust the vinylsilane. This allows exhaust from the filled container, allowing the low-boiling-point substances in the filled container to be released into the atmosphere.

As described above, the present invention enables the generation, purification, and filling of highly reactive vinylsilane gas efficiently and safely in a short period of time. Unlike common reactive gas purification methods such as adsorption and liquefaction distillation, this method is continuous and does not require large-scale equipment, as opposed to liquefying the gas first and then purifying it. Furthermore, in the case of flammable and highly reactive vinylsilane, this method eliminates the risk of ignition due to adiabatic compression in the compression pump used for liquefaction, allowing for efficient purification.

FIG. 1 is a schematic diagram illustrating the outline of the apparatus according to the present invention.

The method for producing vinylsilane according to the present invention comprises at least a generation step in which vinylsilane is continuously generated, a purification step in which the generated vinylsilane is purified, and a filling step in which the purified vinylsilane is filled into a filling container.

The generation stage generates vinylsilane gas using the required amount of raw material, such as vinyltrichlorosilane (melting point: -95°C, boiling point: 91.5°C), supplied from a raw material supply device and a solvent, such as tetrahydrofuran (melting point: -108.4°C, boiling point: 66°C) or dibutyl ether (melting point: -97.9°C, boiling point: 142°C). However, the vinylsilane gas generated in the generation stage contains high-boiling-point substances such as the solvent. Furthermore, the generation stage is adjusted to a first temperature that is a predetermined value higher than the boiling point of the solvent used.

The purification stage consists of a first purification stage in which high-boiling substances are separated from the vinylsilane generated in the generation stage and the separated high-boiling substances are returned to the generation stage, and a second purification stage in which further high-boiling substances are separated from the separated vinylsilane.

Here, the first purification stage comprises an intermediate stage adjusted to a second temperature that is a predetermined temperature lower than the first temperature, and a separation stage adjusted to a third temperature in the range from the freezing point of the solvent used in the generation stage to the second temperature. Furthermore, the second purification stage is adjusted to a fourth temperature that is higher than the liquefaction temperature of vinylsilane at atmospheric pressure and lower than the boiling point of the high-boiling substance.

In the first purification stage, high-boiling substances are liquefied in an intermediate stage adjusted to a second temperature that is a predetermined temperature lower than the first temperature, and most of the high-boiling substances are liquefied in a separation stage adjusted to a third temperature, returning to the generation stage via the intermediate stage. By providing the intermediate stage, the temperature drop in the generation stage can be suppressed, thereby maintaining continuous generation of vinylsilane gas in the generation stage.

Furthermore, during the filling step, the filling container is cooled to a temperature below the freezing point of vinylsilane, and vinylsilane is filled into the filling container, while low-boiling-point substances are removed from the solidified vinylsilane. For this purpose, during the filling step, the filling container is adjusted to a temperature that is a predetermined value lower than the freezing point of vinylsilane, and the filling container is gradually cooled from the bottom toward the top. Furthermore, during the filling step, filling with vinylsilane gas and evacuation are performed alternately and intermittently.

This allows vinylsilane to be efficiently accumulated in the filling container, while also efficiently removing low-boiling substances, such as oxygen.

Furthermore, the generation stage, the purification stage, and the filling stage have a sealed structure that can block the intrusion of low-boiling-point substances at a pressure of 1×10 ⁻² Torr or less (high vacuum), which prevents the intrusion of oxygen from the outside and ensures the reliable absorption of vinylsilane from the generation stage to the filling stage.

As shown in Figure 1, the vinylsilane production apparatus 1 according to the present invention is composed of at least a generator D equipped with a generator vessel D1 that continuously generates vinylsilane, a refiner B that refines the generated vinylsilane, and a filling device C that fills the refined vinylsilane into filling vessels C1 and C2.

The generator D generates vinylsilane gas using the required amount of raw material, such as vinyltrichlorosilane (melting point: -95°C, boiling point: 91.5°C), and solvent, such as tetrahydrofuran (melting point: -108.4°C, boiling point: 66°C) or dibutyl ether (melting point: -97.9°C, boiling point: 142°C), supplied from the raw material supply device A (raw material container A1 and solvent container A2). However, the vinylsilane gas generated by the generator D contains high-boiling-point substances such as the solvent. The generator D is also adjusted to a first temperature T1, which is a predetermined value higher than the boiling point of the solvent used.

The purification unit B is composed of a first purification unit BA that separates high-boiling substances from the vinylsilane generated in the generator D and returns the separated high-boiling substances to the generator D, and a second purification unit BB that further separates high-boiling substances from the separated vinylsilane.

Here, the first purification device BA is composed of an intermediate vessel B1, which is adjusted to a second temperature T2 that is a predetermined temperature lower than the first temperature T1, and a separation vessel B2, which is adjusted to a third temperature T3 that is in the range from the freezing point of the solvent used in the generator D to the second temperature T2. Furthermore, the second purification device BB is adjusted to a fourth temperature T4 that is higher than the liquefaction temperature of vinylsilane at atmospheric pressure and lower than the boiling point of the high-boiling substance.

In the first purification unit BA, high-boiling substances are liquefied in intermediate vessel B1, which is adjusted to a second temperature T2 that is a predetermined temperature lower than the first temperature T1. Furthermore, most of the high-boiling substances are liquefied in separation vessel B2, which is adjusted to a third temperature T3, and the liquefied gas is returned to generator D via intermediate vessel B1. By providing intermediate vessel B1, the temperature of generator D can be prevented from dropping, allowing continuous generation of vinylsilane gas in generator D to be maintained.

Furthermore, the first purification unit BA is positioned vertically relative to the generator D. This allows the gas generated in the generator D to rise to the first purification unit BA, while the high-boiling-point substances liquefied in the first purification unit BA can freely fall and return to the generator D via the intermediate vessel B1.

Furthermore, the second purification unit BB is adjusted to a third temperature T3, which is a predetermined value higher than the liquefaction temperature of vinylsilane at atmospheric pressure. The second purification unit BB may be constructed as an upright tower of a predetermined height to ensure a reaction distance, or the reaction distance may be ensured by connecting multiple separation vessels B3, B4, B5, and B6 in series. The high-boiling-point substances separated in the second purification unit BB may be accumulated in a predetermined location or circulated to the generator D. The high-boiling-point substances separated in the first purification unit BB are recovered in a recovery vessel E, but may also be returned to the generator D.

Furthermore, in the filling device C, the filling containers C1, C2 are cooled to a temperature below the freezing point of vinylsilane, and vinylsilane is filled into the filling containers C1, C2, while low-boiling-point substances are removed from the solidified vinylsilane. For this purpose, the filling device C adjusts the filling containers C1, C2 to a temperature (fifth temperature T5) that is a predetermined value lower than the freezing point of vinylsilane, and the filling containers C1, C2 are gradually cooled from the bottom toward the top. Furthermore, in the filling device C, the filling and exhaust of vinylsilane gas are alternately and intermittently performed.

This allows vinylsilane to be efficiently accumulated in the filling containers C1 and C2, while also efficiently removing low-boiling-point substances such as oxygen.

Furthermore, the generator D, the refiner B, and the filling device C have a sealed structure that can block the intrusion of low-boiling-point substances at a pressure of 1×10 ⁻² Torr or less (high vacuum) achieved by suction using a vacuum pump P. This prevents oxygen from intruding from the outside, and also ensures that vinylsilane can be reliably sucked from the generator D to the filling device C.

To implement the above control, the present invention provides on-off valves V1 to V9. In the vinylsilane production apparatus 1 configured as described above, the raw material (vinyltrichlorofuran) and solvent (tetrahydrosilane) as a high-boiling substance supplied from the material supply device A are heated and stirred in the generator vessel D1 of the generator D to a first temperature T1 (approximately 80°C), which is a predetermined value higher than the boiling point temperature of the solvent (e.g., 66°C). The vaporized vinylsilane and solvent are then raised through the intermediate vessel B1, which is adjusted to a second temperature (e.g., 5-10°C), to the separation vessel B2, which is adjusted to a third temperature (e.g., -40°C). In the intermediate vessel B1 and separation vessel B2, the vinylsilane remains in a gaseous state, while the solvent (high-boiling substance) liquefies and returns to the generator vessel D1. When it is confirmed that a sufficient amount of vinylsilane gas has been generated in the separation vessel B2, the on-off valves V1, V2, and V5 are opened and the vacuum pump P is driven to introduce the gas in the separation vessel B2 into the second purification device BB.

The second purification unit BB is equipped with multiple separation vessels B3, B4, B5, and B6, which are connected in series. The high-boiling substances separated in each of the separation vessels B3, B4, B5, and B6 are collected in a collection vessel E.

Filling of vinylsilane from the second refiner BB into the filling container B1 can be achieved, for example, by closing valve V3 and simultaneously opening valves V4 and V7 to depressurize the filling container C1. This allows the vacuum pump P to evacuate the filling container C1, while simultaneously cooling the filling container C1 with cooling device F. By closing valves V5, V6, and V7 and simultaneously opening valves V2, V3, and V4, the vinylsilane gas that has passed through the second refiner BB is drawn into the filling container C1, where it cools, solidifies, and fills the container. After this, closing valve V3 and opening valves V4 and V7 allows the vacuum pump P to evacuate the filling container C1, releasing low-boiling substances (e.g., oxygen, nitrogen, argon gas, etc.) present in the gas phase within the filling container C1 to the outside air. By intermittently alternating between the filling operation and the evacuation of the low-boiling substances, vinylsilane can be efficiently filled and the low-boiling substances can be removed.

Furthermore, when filling container C1 becomes full, by similarly operating on-off valves V6, V8, and V9 instead of on-off valves V3, V4, and V7, vinylsilane can be similarly filled into filling container C2, and low-boiling-point substances can be removed.

1 Manufacturing equipment A Material supply device B Refining device BA First refining device BB Second refining device C Filling device D Generating device E Recovery container F Cooling device P Vacuum pump V1 to V9 On-off valve

Claims (8)

A method for producing vinylsilane represented by the structural formula CH2=CH-SiH3, comprising at least a generating step of continuously generating vinylsilane, a purifying step of purifying the vinylsilane by removing high-boiling substances from the generated vinylsilane, and a filling step of filling a filling vessel with the purified vinylsilane and removing low-boiling substances from the filling vessel,
the generating step is adjusted to a first temperature higher than the boiling point of a high-boiling substance contained in the vinylsilane to be generated;
the purification step comprises a first purification step in which high boiling point substances are separated from the vinylsilane generated in the generation step and the separated high boiling point substances are returned to the generation step, and a second purification step in which the high boiling point substances are further separated from the separated vinylsilane;
the first purification stage is composed of an intermediate stage adjusted to a second temperature lower than the first temperature, and a solvent recovery stage adjusted to a third temperature higher than the freezing point of the high-boiling substance used in the generation stage and lower than the second temperature;
the second purification step is adjusted to a fourth temperature higher than the liquefaction temperature of the vinylsilane at atmospheric pressure and lower than the boiling point of the high-boiling substance;
in the filling step, the filling vessel is cooled to a fifth temperature lower than the freezing point of vinylsilane to fill the filling vessel with vinylsilane, and low-boiling-point substances contained in the vinylsilane are removed from the filling vessel by evacuation;
The high-boiling substance is one or more substances selected from vinyltrichlorosilane, vinyldichlorosilane, vinylchlorosilane, tetrahydrofuran, and dibutyl ether; and
The method for producing vinylsilane, wherein the low-boiling substance is one or more substances selected from the group consisting of oxygen, nitrogen, and argon. The method for producing vinylsilane described in claim 1, characterized in that the filling container is gradually cooled from the bottom to the top of the container. 3. The method for producing vinylsilane according to claim 1, wherein the generating step, the purifying step, and the filling step have a sealed structure capable of blocking the intrusion of low-boiling-point substances at a pressure of 1×10 ⁻² Torr or less. 4. The method for producing vinylsilane according to claim 1, wherein the filling step alternately and intermittently includes filling with vinylsilane gas and removing low-boiling-point substances by evacuation, and the removal by evacuation is performed at a pressure of 1×10 ⁻² Torr or less. An apparatus for producing vinylsilane represented by the structural formula CH2=CH-SiH3, comprising at least a generator for continuously generating vinylsilane, a purifier for purifying the generated vinylsilane by removing high-boiling substances from the vinylsilane, a filling device for filling a filling container with the purified vinylsilane and removing low-boiling substances from the filling container, and a suction device for transferring vinylsilane from the generator to the purifier and the filling device,
the generator is adjusted to a first temperature higher than the boiling point of a high-boiling substance contained in the vinylsilane to be generated;
the purification device comprises a first purification device that separates high boiling point substances from the vinylsilane generated in the generation device and returns the separated high boiling point substances to the generation device, and a second purification device that further separates high boiling point substances from the separated vinylsilane;
the first purification device is composed of an intermediate vessel adjusted to a second temperature lower than the first temperature, and a solvent recovery device adjusted to a third temperature higher than the freezing point of the high-boiling-point substance used in the generation device and lower than the second temperature;
the second purification device is adjusted to a fourth temperature that is higher than the liquefaction temperature of the vinylsilane at atmospheric pressure and lower than the boiling point of the high-boiling substance; and
the filling device cools the filling container to a fifth temperature that is lower than the freezing point of vinylsilane, filling the filling container with vinylsilane, and removing low-boiling-point substances contained in the vinylsilane from the filling container by evacuation;
The high-boiling substance is one or more substances selected from vinyltrichlorosilane, vinyldichlorosilane, vinylchlorosilane, tetrahydrofuran, and dibutyl ether; and
1. The vinylsilane production apparatus, wherein the low-boiling substance is one or more substances selected from the group consisting of oxygen, nitrogen, and argon. The vinylsilane production apparatus according to claim 5, wherein the first purification device is disposed vertically relative to the generator. The vinylsilane production apparatus according to claim 5 or 6, characterized in that the generator, the purifier, and the filling device have a sealed structure that can block the intrusion of low-boiling-point substances at a pressure of 1 x 10 ^-2 Torr or less by the suction device. The vinylsilane manufacturing apparatus according to any one of claims 5 to 7, characterized in that the suction device alternately and intermittently fills the system with vinylsilane gas and removes low-boiling-point substances by evacuation, and the removal by evacuation is carried out at a pressure of 1 x 10 ^-2 Torr or less.