Method for producing cyclic silane compound

Abstract

This method for producing a cyclic silane compound comprises: a first step for obtaining a reaction solution containing a chain polysilane compound by subjecting a silane compound to a polymerization reaction in a first solution containing sodium; and a second step for obtaining a cyclic silane compound by subjecting the chain polysilane compound to a decomposition and conversion reaction in a second solution containing the reaction solution. Moreover, a polycyclic aromatic hydrocarbon or a polyphenyl-based hydrocarbon is incorporated in the first solution or mixed with the reaction solution, and a polyether compound represented by formula (I) or (II) is incorporated in the first solution or mixed with the reaction solution.

Description

Method for producing cyclic silane compounds

[0001] The present invention relates to a method for producing a cyclic silane compound.

[0002] Silicon carbide fiber has excellent heat resistance and oxidation resistance, even in high-temperature atmospheres of over 1,000 degrees Celsius. Taking advantage of these properties, silicon carbide fiber is expected to be used in the nuclear and aerospace fields.

[0003] Silicon carbide fibers are obtained by spinning, infusibilizing, and calcining a precursor organosilicon polymer compound such as polycarbosilane. Because oxygen-containing silicon carbide fibers decompose at high temperatures, in order to obtain ultra-heat-resistant silicon carbide fibers, it is necessary to suppress the introduction of oxygen atoms into the organosilicon polymer compound that forms the fiber. Therefore, ultra-heat-resistant silicon carbide fibers are produced by using organosilicon polymer compounds with low oxygen content and adopting a method that does not introduce oxygen during infusibilization. Polycarbosilane with an oxygen content of approximately 0.1% by weight can be obtained from cyclic silane compounds such as dodecamethylcyclohexasilane. Therefore, cyclic silane compounds are useful as raw materials for organosilicon polymer compounds that serve as precursors to silicon carbide fibers.

[0004] Various methods are known for producing a cyclic silane compound. For example, Patent Document 1 discloses a method for producing a cyclic silane compound by adding a silane monomer dropwise to a mixed solution of a sodium dispersion, tetrahydrofuran (THF), and a polyether compound, and reacting the mixture at room temperature.

[0005] Furthermore, Patent Document 2 discloses a method for producing a cyclic silane compound by: 1) adding a silane monomer dropwise to a mixed solution obtained by heating and mixing xylene and metallic sodium to cause a reaction, thereby obtaining a chain polysilane compound; and 2) heating and refluxing the purified chain polysilane compound, metallic sodium, and a polycyclic aromatic hydrocarbon in THF.

[0006] Furthermore, Patent Document 3 discloses a method for producing a cyclic silane compound by 1) adding a silane monomer compound to a mixed solution of a sodium dispersion and a solvent to cause a reaction, and then 2) adding a polycyclic aromatic hydrocarbon to the reaction solution and heating the mixture to reflux.

[0007] JP 2021-011440 A JP 54-130541 A JP 2019-156792 A

[0008] As shown in Patent Documents 2 and 3, the method of producing a cyclic silane compound from a silane monomer via a linear polysilane compound can reduce the use of expensive reactants such as sodium dispersion, compared to the method of producing a cyclic silane compound directly from a silane monomer as shown in Patent Document 1. However, the method as shown in Patent Document 2 has the problem of being complicated because it includes a purification operation for removing the solvent from the synthesized polydimethylsilane.

[0009] Therefore, it is desirable to obtain a cyclic silane compound by carrying out the second step without isolating and purifying the linear polysilane compound produced in the first step (i.e., to be able to produce a cyclic silane compound in one pot). When producing a cyclic silane compound in one pot, the reaction solution obtained in the first step contains a certain amount or more of components that do not contribute to the decomposition and conversion reaction in the second step, which tends to reduce the reaction yield in the second step. In Patent Document 3, it was still necessary to use a large amount of reactant to obtain a high reaction yield. Therefore, it is desirable to produce a cyclic silane compound in one pot and obtain a high reaction yield even with a small amount of reactant.

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a cyclic silane compound, which can produce a cyclic silane compound in one pot from a silane monomer with a high reaction yield, regardless of the form of the reactant used and even when the amount used is small.

[0011] The present invention relates to the following method for producing a cyclic silane compound.

[0012] [1] A method for producing a cyclic silane compound, comprising: a first step of polymerizing a silane compound in a first solution containing sodium to obtain a reaction liquid containing a linear polysilane compound; and a second step of decomposing and converting the linear polysilane compound in a second solution containing the reaction liquid to obtain a cyclic silane compound, wherein a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon is added to the first solution or mixed into the reaction liquid, and a polyether compound represented by the following formula (I) or (II) is added to the first solution or mixed into the reaction liquid: (In formulas (I) and (II), R ａ ~R ｈ are each independently a hydrogen atom or an alkyl group, １ and m ２are integers of 2 or more and 7 or less). [2] The method for producing a cyclic silane compound according to [1], wherein the second step is carried out in a second solution obtained by mixing tetrahydrofuran with the reaction solution. [3] The method for producing a cyclic silane compound according to [1] or [2], wherein the first solution contains a mixed solution containing metallic sodium and a hydrocarbon solvent. [4] The method for producing a cyclic silane compound according to [3], wherein the first step is carried out by heating the first solution to a temperature equal to or higher than the melting temperature of the metallic sodium. [5] The method for producing a cyclic silane compound according to any one of [1] to [4], wherein the second step is carried out by heating the chain polysilane compound in the second solution. [6] The method for producing a cyclic silane compound according to [5], wherein the heating temperature is 40°C or higher and reflux temperature or lower. [7] The method for producing a cyclic silane compound according to any one of [1] to [4], wherein the polyether compound represented by formula (I) or (II) is contained in the first solution. [8] The method for producing a cyclic silane compound according to [7], wherein the polyether compound represented by formula (I) is contained in the first solution. [9] The method for producing a cyclic silane compound according to [7] or [8], wherein the total molar equivalent of the polyether compound represented by formula (I) or (II) relative to the silicon atoms of the silane compound is 0.003 eq. or more and 0.180 eq. or less.

[10] The method for producing a cyclic silane compound according to any one of [1] to [4], wherein the polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon is mixed with the reaction solution.

[11] The method for producing a cyclic silane compound according to

[10] , wherein biphenyl, anthracene, or naphthalene is mixed with the reaction solution as the polycyclic aromatic hydrocarbon.

[12] The method for producing a cyclic silane compound according to [3] or [4], wherein the hydrocarbon solvent is an aromatic hydrocarbon solvent.

[13] The method for producing a cyclic silane compound according to [4], wherein the second solution contains the hydrocarbon solvent and tetrahydrofuran, and the volume ratio of the tetrahydrofuran contained in the second solution is 23 vol% or more and 99 vol% or less relative to the total volume of the hydrocarbon solvent and the tetrahydrofuran.

[0013] According to the present invention, it is possible to provide a method for producing a cyclic silane compound, which can produce a cyclic silane compound from a silane monomer in one pot with a high reaction yield, regardless of the form of the reactant used and even when the amount used is small.

[0014] As described above, when the first step of obtaining a chain polysilane compound from a silane monomer and the second step of obtaining a cyclic silane compound by subjecting the chain polysilane compound to a decomposition and conversion reaction are carried out in one pot, it is necessary to increase the reaction yield in the second step.

[0015] In particular, the sodium dispersions that have been used conventionally are not only expensive, but also difficult to separate and recover the cyclic silane compounds, as will be described later. Therefore, instead of sodium dispersions, the use of a mixture in which bulk metallic sodium is dissolved in a hydrocarbon solvent has been considered. However, this mixture contains a large amount of hydrocarbon solvent that does not contribute to the reaction in the second step, and therefore the reaction yield is likely to decrease.

[0016] In response to this, the present inventors have conducted extensive research and found that the yield of cyclic silane compounds can be significantly increased by using a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon as a reaction-promoting component and further using a specific polyether compound in at least one of the first and second steps, preferably in the first step.

[0017] Although the mechanism is unclear, it is speculated as follows. A specific polyether compound tends to increase the reactivity of a silane compound by stably capturing sodium ions through coordination of oxygen atoms of multiple ether bonds. This not only promotes the polymerization reaction of the silane compound and increases the yield of the linear polysilane compound in the first step, but also promotes the decomposition and conversion reaction of the linear polysilane compound in the second step.

[0018] Hereinafter, a method for producing a cyclic silane compound according to one embodiment of the present invention will be described in detail.

[0019] 1. Method for Producing Cyclic Silane Compounds As described above, a method for producing a cyclic silane compound according to one embodiment of the present invention includes: a first step of polymerizing a silane compound in a first solution containing metallic sodium to obtain a reaction solution containing a chain polysilane compound; and a second step of decomposing and converting the chain polysilane compound in a second solution containing the reaction solution to obtain a cyclic silane compound. A polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon is then added to the first solution or mixed with the reaction solution. A specific polyether compound is also added to the first solution or mixed with the reaction solution.

[0020] As described above, the polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon may be contained in the first solution or may be mixed into the reaction liquid. In particular, from the viewpoint of further suppressing decomposition of the polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon due to a side reaction with the silane compound, it is preferable to mix the polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon into the reaction liquid. When mixed into the reaction liquid, the polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon may be mixed between the first step and the second step, or may be mixed in the second step.

[0021] As described above, the specific polyether compound may be contained in the first solution or may be mixed into the reaction solution. When mixed into the reaction solution, it may be mixed between the first step and the second step, or may be mixed in the second step. Among these, from the viewpoint of further increasing the yield of the cyclic silane compound, it is preferable to contain it in the first solution.

[0022] That is, in this embodiment, it is preferable to carry out the following steps: 1) a first step of polymerizing a silane compound in a first solution containing metallic sodium and a specific polyether compound to obtain a reaction liquid containing a chain polysilane compound; and 2) a second step of decomposing and converting the chain polysilane compound in a second solution obtained by mixing a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon with the reaction liquid to obtain a cyclic silane compound.

[0023] Each step will be specifically described below.

[0024] 1-1. First Step In this embodiment, a silane compound is polymerized in a first solution containing sodium and a specific polyether compound.

[0025] The sodium in the first solution may be metallic sodium fine particles or metallic sodium in a molten state. That is, the first solution may contain a sodium dispersion (SD) and a specific polyether compound, or may contain a mixed solution containing metallic sodium (in a molten state) and a hydrocarbon solvent, and a polyether compound.

[0026] Sodium dispersion (SD) is a dispersion of metallic sodium particles in electrical insulating oil, and has higher reactivity than bulk metallic sodium. The average particle size of the sodium particles in SD can be 1 μm or more and 100 μm or less. The average particle size can be a value measured using a laser diffraction particle size distribution measuring device or the like. Examples of electrical insulating oils include aliphatic hydrocarbons such as liquid paraffin and mineral oil.

[0027] On the other hand, since the electrical insulating oil is a water-insoluble organic compound and the cyclic silane compound has a high solubility in the dispersion oil, separation and purification are likely to be difficult. Therefore, from the viewpoint of reducing production costs and facilitating separation and purification, it is desirable to reduce the amount of sodium dispersion used. Therefore, in this embodiment, it is preferable to use a mixed liquid containing metallic sodium and a hydrocarbon-based solvent.

[0028] In the mixed solution, metallic sodium is preferably in a molten state. The molten state refers to a state in which metallic sodium has been liquefied by, for example, heating, and differs from a state in which sodium is uniformly dispersed in the form of fine particles, such as in a sodium dispersion.

[0029] The first solution containing such a mixed solution can be obtained, for example, by adding metallic sodium to a hydrocarbon-based solvent, heating the mixture to a temperature equal to or higher than the melting point of metallic sodium (98° C. or higher) to melt the metallic sodium, and then further mixing in a polyether compound. Alternatively, the first solution can also be obtained by adding molten metallic sodium to a hydrocarbon-based solvent that has been heated to a temperature equal to or higher than the melting point of metallic sodium (98° C. or higher), and then further mixing in a polyether compound.

[0030] (Hydrocarbon Solvent) The hydrocarbon solvent may have a boiling point higher than the melting point of metallic sodium (98° C.). That is, the boiling point of the hydrocarbon solvent is preferably 100° C. or higher and 210° C. or lower, and more preferably 110° C. or higher and 170° C. or lower.

[0031] Such a hydrocarbon solvent may be an aliphatic hydrocarbon solvent or an aromatic hydrocarbon solvent. Examples of aliphatic hydrocarbon solvents include hydrocarbon solvents having 8 to 12 carbon atoms, such as octane and decane. Examples of aromatic hydrocarbon solvents include toluene, xylene, ethylbenzene, mesitylene, and the like. Among these, from the viewpoint of facilitating the formation of a complex between a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon and sodium, aromatic hydrocarbon solvents are preferred, with toluene, xylene, and ethylbenzene being more preferred, and toluene and xylene being even more preferred.

[0032] The content of the hydrocarbon solvent in the first solution may be such that the resulting linear polysilane is sufficiently stirred and dispersed in the solvent. For example, the content of the hydrocarbon solvent in the first solution is preferably 0.7 parts by mass or more per 10 parts by mass of the silane compound. When the content of the hydrocarbon solvent is 0.7 parts by mass or more, the volume fraction of metallic sodium decreases, making it difficult for metallic sodium droplets to coalesce. In this case, the average droplet diameter can be made smaller, the specific surface area of ​​sodium increases, and the reactivity of the silane compound can be further enhanced. When the content of the hydrocarbon solvent is 150.0 parts by weight or less, the concentration of the silane compound in the system increases, making it easier to promote the reaction in the first step. From the same perspective, the content of the hydrocarbon solvent in the first solution is more preferably 3.0 parts by mass or more and 100.0 parts by mass or less per 10 parts by mass of the silane compound.

[0033] The content of the hydrocarbon solvent in the first solution relative to 10 parts by mass of metallic sodium is preferably 1.0 parts by mass or more and 300.0 parts by mass or less, and more preferably 2.0 parts by mass or more and 250.0 parts by mass or less.

[0034] (Metallic Sodium) Metallic sodium can function mainly as a reactant in the polymerization reaction.

[0035] The molar equivalent of metallic sodium in the first solution relative to each functional group of an alkoxy group or a halogen atom of the silane compound is preferably 1.00 eq. or more and 1.80 eq. or less. When the molar equivalent of metallic sodium is 1.00 eq. or more, the rate of the polymerization reaction of the silane compound in the first step can be further increased. When the molar equivalent of metallic sodium is 1.80 eq. or less, the proportion of metallic sodium remaining unreacted can be further reduced. From the same viewpoint, the molar equivalent of metallic sodium in the first solution is more preferably 1.05 eq. or more and 1.25 eq. or less.

[0036] (Specific Polyether Compound) The specific polyether compound can stably capture sodium ions in the reaction system by coordinating oxygen atoms of multiple ether bonds to the sodium ions in the reaction system, thereby accelerating the polymerization reaction of the silane compound in the first step and the decomposition and conversion reaction of the linear polysilane compound in the second step, and producing a cyclic polysilane compound in high yield.

[0037] The specific polyether compound is a polyether compound represented by formula (I) or (II).

[0038] In formulas (I) and (II), R ａ ~R ｈ are each independently a hydrogen atom or an alkyl group. ａ ~R ｈ is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom, an ethyl group or a methyl group, and even more preferably a hydrogen atom or a methyl group.

[0039] m １ and m ２ are integers of 2 or more and 7 or less. １ and m ２is preferably an integer of 2 or more and 6 or less, and more preferably 5 from the viewpoint of selectively capturing sodium ions in the reaction system and further accelerating the reaction.

[0040] The first solution may contain only one of the polyether compound represented by formula (I) and the polyether compound represented by formula (II), or may contain both. Among them, the polyether compound represented by formula (I) is preferred from the viewpoints of having a high boiling point, remaining easily in a reaction system under heating, and being able to further reduce production costs.

[0041] Examples of the polyether compound represented by formula (I) include diglyme, triglyme, and tetraglyme. Examples of the compound represented by formula (II) include dioxane, 12-crown-4, 15-crown-5, and 18-crown-6. Among these, tetraglyme and 15-crown-5 are preferred from the viewpoint of their high reaction-accelerating effect.

[0042] The total molar equivalent of the polyether compound represented by formula (I) or (II) contained in the first solution relative to the silicon atoms of the silane compound is preferably 0.003 eq. or more and 0.180 eq. or less. When the molar equivalent of the polyether compound is 0.003 eq. or more, not only the polymerization reaction of the silane compound is further promoted, but also the decomposition conversion reaction in the second step is further promoted, thereby further increasing the reaction yield. When the molar equivalent of the polyether compound is 0.180 eq. or less, decomposition of the cyclic silane compound, which is the final product, can be further reduced. From the same viewpoint, the molar equivalent of the polyether compound is more preferably 0.030 eq. or more and 0.120 eq. or less.

[0043] The first solution may further contain a solvent other than those mentioned above, if necessary. Examples of the other solvent include ether solvents (excluding polyethers) such as tetrahydrofuran, 2-methyltetrahydrofuran, diethyl ether, diisopropyl ether, and t-butyl methyl ether.

[0044] (Silane Compound) Next, a silane compound is added to the first solution. The silane compound is preferably a compound represented by the following formula (1).

[0045] In formula (1), X １ and X ２ Each of X represents an alkoxy group or a halogen atom. Examples of the alkoxy group include a methoxy group and an ethoxy group. Examples of the halogen atom include a chlorine atom, a bromine atom, and an iodine atom. These have a large difference in electronegativity with silicon and tend to cause intramolecular polarization in the silane compound, making them highly reactive and a substituent that functions as a leaving group in the reaction. Among these, X １ and X ２ From the viewpoint of the reactivity of the silane compound, is preferably a halogen atom, more preferably a chlorine atom.

[0046] R １ and R ２ is a hydrogen atom or a hydrocarbon group. １ and R ２ is preferably a hydrocarbon group, more preferably an alkyl group having 1 to 6 carbon atoms, further preferably a methyl group or an ethyl group, and particularly preferably a methyl group.

[0047] n １ is an integer of 1 or greater. １ is preferably 1 or 2, and more preferably 1, from the viewpoint of increasing the reactivity of the silane compound.

[0048] Examples of the compound represented by formula (1) include dichlorodimethylsilane, dichlorodiethylsilane, dichlorodipropylsilane, dichlorodibutylsilane, dichlorodipentylsilane, dichlorodihexylsilane, dibromodimethylsilane, dibromodiethylsilane, dibromodipropylsilane, dibromodibutylsilane, dibromodipentylsilane, dibromodihexylsilane, and dichlorotetramethyldisilane. Among these, dichlorodimethylsilane is preferred. The silane compound may be one type or two or more types.

[0049] (Polymerization Reaction) The polymerization reaction of the silane compound is preferably carried out at a temperature according to the composition of the first solution.

[0050] For example, when the first solution contains a sodium dispersion, the polymerization reaction is preferably carried out at a temperature of 0° C. or higher and not higher than the reflux temperature, and more preferably at room temperature.

[0051] On the other hand, when the first solution contains a mixed liquid containing metallic sodium and a hydrocarbon solvent, the polymerization reaction is preferably carried out under heating in order to carry out the polymerization reaction in a molten state of metallic sodium, i.e., the polymerization reaction is preferably carried out while heating to a temperature equal to or higher than the melting temperature of metallic sodium.

[0052] The heating temperature is preferably equal to or higher than the melting temperature of metallic sodium, more preferably equal to or higher than 98°C and equal to or lower than the solvent reflux temperature, and even more preferably equal to or higher than 100°C and equal to or lower than the solvent reflux temperature. The reaction is preferably carried out in an inert gas atmosphere such as nitrogen or argon. The reaction is also preferably carried out under normal pressure or under pressure.

[0053] The addition of the silane compound may be carried out continuously or intermittently, but from the viewpoint of production efficiency, it is preferable to add the silane compound continuously at a constant amount.

[0054] The average addition rate of the silane compound per unit amount (mol) of metallic sodium was 0.06 hr. －１ Over 0.50 hours －１ Preferably, it is 0.10 hr or less. －１ 0.30hr or more －１ More preferably, it is:

[0055] Average addition rate of silane compound (mol hr －１ ) is the value obtained by dividing the total amount (mol) of the silane compound used by the addition time (hr); the average addition rate (hr) of the silane compound per unit amount (mol) of metallic sodium －１ ) is the average addition rate of the silane compound (mol·hr －１ ) divided by the amount (mol) of metallic sodium.

[0056] The average addition rate of the silane compound per unit amount (mol) of metallic sodium is 0.50 hr. －１ When the average addition rate of the silane compound per unit amount (mol) of metallic sodium is 0.06 hr or less, the temperature of the mixed solution can be more effectively prevented from dropping below the melting point of sodium, and the reaction can be more effectively promoted. －１ If the reaction time is more than this, the total reaction time can be further shortened, and production efficiency can be further improved.

[0057] From the viewpoint of increasing the amount of chain polysilane compound produced, it is preferable to continue stirring at the above reaction temperature after the addition of the silane compound is completed, preferably for 1 hour to 12 hours.

[0058] By the above reaction, a reaction liquid containing crude polydialkylsilane (chain polysilane compound) is obtained.

[0059] (Chain Polysilane Compound) The chain polysilane compound has a repeating unit represented by the following formula (2).

[0060] R in formula (2) １ and R ２ is R in formula (1). １ and R ２ is the same as

[0061] In the chain polysilane compound, the groups bonded to the silicon atoms at both ends of the molecule can be a hydrogen atom, a hydrocarbon group, an alkoxy group, a sodium atom, or a halogen atom. The alkoxy group or the halogen atom is X in formula (1). １ and X ２ The formula is the same as above. Furthermore, the sodium atom is cationized and can be coordinated to the anionized silicon atom. Since the alkoxy group and halogen atom have a large electronegativity difference with the silicon atom, they may be easily reduced by sodium and easily generate active sites. Furthermore, since the sodium atom has a particularly large electronegativity difference with the silicon atom, it may be easy to make the silicon atom function as an active site. Therefore, the groups at both molecular terminals of the chain polysilane compound may be alkoxy groups, halogen atoms, or sodium atoms.

[0062] The number of repeating units is not particularly limited, but is, for example, an integer of 2 or more, and preferably an integer of 6 or more and 12,000 or less.

[0063] 1-2. Regarding the second step: A polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon is mixed with the reaction solution obtained in the first step to obtain a second solution. In other words, without isolating the product from the reaction solution obtained in the first step, the polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon is mixed with the reaction solution.

[0064] The second solution preferably contains tetrahydrofuran. That is, the second step is preferably carried out in a second solution obtained by further mixing tetrahydrofuran with the reaction solution obtained in the first step. This allows the decomposition and conversion reaction of the chain polysilane compound to proceed more efficiently.

[0065] As described above, a complex between sodium and a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon, which is necessary for the decomposition and conversion reaction of the linear polysilane compound in Step 2, is unlikely to be formed in the hydrocarbon solvent or other solvent contained in the reaction solution obtained in Step 1. In contrast, when the reaction solution contains tetrahydrofuran, a complex between sodium and a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon is likely to be formed and remain stable, thereby further enhancing the decomposition reactivity of the linear polysilane compound.

[0066] (Tetrahydrofuran) When the second solution contains a hydrocarbon solvent and tetrahydrofuran, the amount of tetrahydrofuran added to the reaction solution is preferably an amount such that the volume ratio of tetrahydrofuran to the total volume of the hydrocarbon solvent and tetrahydrofuran in the second solution is 23% by volume or more and 99% by volume or less. When the volume ratio of tetrahydrofuran is 23% by volume or more, the decomposition and conversion reaction of the chain polysilane compound can be further promoted, and the yield of the cyclic silane compound can be further increased. When the volume ratio of tetrahydrofuran is 99% by volume or less, the volume ratio of the hydrocarbon solvent to metallic sodium can be increased, thereby enabling the synthesis of chain polysilane in the first reaction to be carried out efficiently, and thereby the yield of cyclic silane can be further increased. From the same perspective, the amount of tetrahydrofuran added to the reaction solution is more preferably an amount such that the volume ratio of tetrahydrofuran in the second solution is 25% by volume or more and 95% by volume or less, and even more preferably 35% by volume or more and 95% by volume or less.

[0067] When the second solution contains a hydrocarbon solvent and tetrahydrofuran, the total volume of the hydrocarbon solvent and tetrahydrofuran contained in the second solution is preferably 50.0 mL or more per 10 parts by mass of metallic sodium. When the total volume of the hydrocarbon solvent and tetrahydrofuran contained in the second solution is 50.0 mL or more per 10 parts by mass of metallic sodium, decomposition of the generated cyclic silane compound can be further suppressed. Furthermore, when the total volume of the hydrocarbon solvent and tetrahydrofuran contained in the second solution is 700.0 mL or less per 10 parts by mass of metallic sodium, the concentration of the silane compound in the system increases, making it easier to promote the reaction in the second step. From the same perspective, the total volume of the hydrocarbon solvent and tetrahydrofuran contained in the second solution is more preferably 50 mL or more and 600 mL or less per 10 parts by mass of metallic sodium, and particularly preferably 50 mL or more and 550 mL or less per 10 parts by mass of metallic sodium.

[0068] (Polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons) Polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons can function as catalysts for the decomposition and conversion reaction of linear polysilane compounds. Either one of polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons or both may be mixed into the reaction solution.

[0069] The polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon preferably forms a complex with sodium. Polycyclic aromatic hydrocarbons are hydrocarbon compounds containing two or more fused aromatic rings. Polyphenyl hydrocarbons are hydrocarbon compounds containing two or more aromatic rings bonded by single bonds. These compounds have conjugated π electrons in multiple aromatic rings, so they easily form complexes with sodium, and these complexes can act as reducing agents. This is thought to cleave the silicon-silicon bond of the chain polysilane compound or the bond between the silicon at the end of the chain polysilane and the functional group, promoting the decomposition and conversion reaction. Complexes of polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons with sodium are more preferably formed in the presence of tetrahydrofuran.

[0070] Examples of such polycyclic aromatic hydrocarbons include naphthalene, anthracene, phenanthrene, etc. Examples of polyphenyl aromatic hydrocarbons include biphenyl, terphenyl, etc. Among them, from the viewpoint of further promoting the decomposition conversion reaction, biphenyl, naphthalene, and anthracene are preferred, and naphthalene and biphenyl are more preferred.

[0071] The total molar equivalent of the polycyclic aromatic hydrocarbons and polyphenyl hydrocarbons in the second solution relative to the silicon atoms of the charged silane compound is preferably 0.01 eq. or more and 0.50 eq. or less. When the total molar equivalent of the polycyclic aromatic hydrocarbons and polyphenyl hydrocarbons is 0.01 eq. or more, the decomposition reaction of the chain polysilane compound is more likely to be promoted, and the yield of the cyclic silane compound is more likely to be increased. When the total molar equivalent of the polycyclic aromatic hydrocarbons and polyphenyl hydrocarbons is 0.50 eq. or less, the decomposition of the generated cyclic silane compound can be further suppressed. From the same viewpoint, the total molar equivalent of the polycyclic aromatic hydrocarbons and polyphenyl hydrocarbons is more preferably 0.04 eq. or more and 0.32 eq. or less, and particularly preferably 0.04 eq. or more and 0.24 eq. or less.

[0072] (Addition and Mixing) The order in which the reaction liquid, the polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon, and the tetrahydrofuran are mixed is not particularly limited. The polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon and the tetrahydrofuran may be added to the reaction liquid simultaneously, or tetrahydrofuran may be added to the reaction liquid and stirred, and then the polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon may be added. Alternatively, the polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon may be mixed with tetrahydrofuran, and then the reaction liquid may be added, or the reaction liquid may be mixed with tetrahydrofuran, and then the polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon may be added. In this embodiment, as an example, it is preferable to simultaneously add the polycyclic aromatic hydrocarbon or the polyphenyl hydrocarbon and the tetrahydrofuran to the reaction liquid obtained in the first step.

[0073] (Decomposition and Conversion Reaction) Then, in the obtained solution, the chain polysilane compound is subjected to a decomposition and conversion reaction to obtain a cyclic silane compound. The decomposition and conversion reaction may be carried out at room temperature or under heating. From the viewpoint of obtaining the cyclic silane compound in a higher yield, it is preferable to carry out the decomposition and conversion reaction under heating, that is, to carry out the decomposition and conversion reaction by heating the chain polysilane compound in the solution.

[0074] The heating temperature may be equal to or lower than the reflux temperature, but is, for example, equal to or higher than 40° C., more preferably equal to or higher than 50° C., and even more preferably equal to or higher than 60° C. However, the upper limit of the heating temperature is preferably equal to or lower than 200° C. from the viewpoint of suppressing decomposition of the reaction product.

[0075] When the second solution contains a hydrocarbon solvent and tetrahydrofuran, the reflux temperature is a temperature corresponding to a volume ratio of tetrahydrofuran that is greater than 68° C. and less than the boiling point of the hydrocarbon solvent.

[0076] The heating method is not particularly limited, and may be, for example, a method in which the second solution is placed in an atmosphere at a predetermined temperature, or a method in which the second solution is heated by a heater, a water bath, an oil bath, electromagnetic waves, or the like.

[0077] The reaction time refers to the time elapsed after the target reaction temperature is reached. When the reaction is carried out under heating, the reaction time is preferably, for example, from 1 hour to 35 hours, and more preferably from 3 hours to 10 hours, although it depends on the temperature of the solution.

[0078] The mechanism of the decomposition and conversion reaction is presumed to be as follows: When the bond between a group (e.g., a halogen atom) and silicon at the molecular end of a chain polysilane compound or the silicon-silicon bond is cleaved by the action of a complex formed by a polycyclic aromatic hydrocarbon or the like and sodium, the electronic state changes and active sites are generated. Subsequently, these active sites cause the molecular chain to break at predetermined intervals and undergo cyclization, producing a cyclic silane compound.

[0079] 2. Cyclic Silane Compound The cyclic silane compound obtained by the method for producing a cyclic silane compound according to this embodiment has, for example, a structure represented by the following formula (3).

[0080] R in formula (3) １ and R ２ is R in formula (1). １ and R ２ are identical to

[0081] n ２ is an integer of 3 or more. ２is preferably 3 or more and 10 or less, more preferably 5 or more and 7 or less, and even more preferably 6.

[0082] Cyclic silane is R １ and R ２ Examples include decamethylcyclopentasilane, dodecamethylcyclohexasilane, and tetradecamethylcycloheptasilane.

[0083] The resulting cyclic silane compound contains n ２ It is also possible to include multiple types of cyclic silane compounds with different n ２ The molar yield of the cyclic silane compound (6-membered ring) in which is 6 is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. The yield of the cyclic silane compound can be determined by analyzing the reaction product by gas chromatography. The measurement conditions can be the same as those in the examples described below.

[0084] 3. Modifications In the above embodiment, an example was shown in which a polyether compound was contained in the first solution and a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon was mixed into the reaction solution, but this is not limiting. For example, both a specific polyether compound and a polycyclic aromatic hydrocarbon may be mixed into the reaction solution. In this case, the molar equivalent of the polyether compound relative to the silane compound can be the same as above.

[0085] Although the above embodiment shows an example in which a mixed solution in which metallic sodium is dissolved in a hydrocarbon solvent is used, a sodium dispersion may also be used. In this case, the molar equivalent of metallic sodium particles per functional group, alkoxy group or halogen atom of the silane compound, can be the same as above.

[0086] In the above embodiment, the second step is carried out in the second solution obtained by mixing tetrahydrofuran with the reaction solution obtained in the first step, but the present invention is not limited to this.

[0087] In this embodiment, the reaction solution contains a specific polyether compound. Therefore, in the second step, a complex between sodium and a polycyclic aromatic hydrocarbon or a polyphenyl hydrocarbon can be formed without mixing tetrahydrofuran with the reaction solution. That is, even when the amount of THF used is reduced or a reaction solvent other than THF is used, the decomposition and conversion reaction of the chain polysilane compound can proceed smoothly. Therefore, the second step may be performed without mixing tetrahydrofuran with the reaction solution obtained in the first step.

[0088] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0089] [Test 1] (1) First Step: Into a 200 mL four-neck flask purged with argon, 34 mL of toluene (aromatic hydrocarbon solvent, solvent A), metallic sodium having a molar equivalent X relative to dichlorodimethylsilane of 2.4 eq., and tetraglyme (a polyether compound represented by formula (I) or (II), additive 1) having a molar equivalent Y relative to dichlorodimethylsilane of 0.04 eq. were placed, and the mixture was stirred while being heated at reflux temperature (110°C) to melt the metallic sodium. Next, 10.0 g of dichlorodimethylsilane (silane compound) was added dropwise to the resulting mixture (first solution) over 150 minutes (average addition rate of silane compound per unit amount (mol) of metallic sodium: 0.17 hr －１ ), and then the mixture was stirred at a reflux temperature in the range of 105°C to 115°C for 1.5 hours to cause a reaction. This resulted in a reaction liquid containing a chain polysilane compound. The resulting reaction liquid was cooled to room temperature. The toluene content in the mixed liquid (first solution) was 29.5 parts by mass relative to 10 parts by mass of the silane compound and 68.6 parts by mass relative to 10 parts by mass of metallic sodium.

[0090] (2) Second Step: 38 mL of tetrahydrofuran (THF) and naphthalene (polycyclic aromatic hydrocarbon, additive 2) having a molar equivalent Z relative to dichlorodimethylsilane of 0.08 eq. were simultaneously added to the reaction solution containing the chain polysilane compound, followed by stirring and mixing to prepare a solution (second solution). The resulting solution was then stirred and reacted at reflux temperature (73°C) for 6 hours while being heated in an oil bath. This resulted in a solution containing a cyclic silane compound. Note that the total volume of toluene and tetrahydrofuran in the second solution relative to 10 parts by mass of metallic sodium used in the first step was 167 mL, and the volume ratio of tetrahydrofuran to the total volume of toluene and tetrahydrofuran was 52.8% by volume.

[0091] The reaction scheme for Test 1 is shown below.

[0092] [Tests 2 to 4] Solutions containing cyclic silane compounds were obtained in the same manner as in Test 1, except that the type and amount of Additive 1 added in the first step were changed as shown in Table 1.

[0093] [Test 5] A solution containing a cyclic silane compound was obtained in the same manner as in Test 1, except that naphthalene was not mixed in the second step.

[0094] [Test 6] A solution containing a cyclic silane compound was obtained in the same manner as in Test 1, except that the type of sodium contained in the first step was changed to a sodium dispersion (SD) as shown in Table 1.

[0095] [Test 7] A solution containing a cyclic silane compound was obtained in the same manner as in Test 1, except that the reaction temperature in the first step and the type of sodium to be contained were changed as shown in Table 1.

[0096] [Test 8] A solution containing a cyclic silane compound was obtained in the same manner as in Test 1, except that the type of sodium contained in the first step was changed and tetraglyme was not contained.

[0097] [Tests 9 to 13] Solutions containing cyclic silane compounds were obtained in the same manner as in Test 1, except that the volume ratio of solvent A contained in the first step to THF mixed in the second step (the volume ratio of THF relative to the total volume of solvent A and THF in the second solution) was changed as shown in Table 1.

[0098] [Tests 14 to 17] Solutions containing cyclic silane compounds were obtained in the same manner as in Test 1, except that the total amount of solvent A added in the first step and THF mixed in the second step was changed as shown in Table 1.

[0099] [Tests 18 to 21] Solutions containing cyclic silane compounds were obtained in the same manner as in Test 1, except that the content of tetraglyme (additive 1) in the first step was changed as shown in Table 2.

[0100] [Tests 22 and 23] Solutions containing cyclic silane compounds were obtained in the same manner as in Test 1, except that the content of metallic sodium in the first step was changed as shown in Table 2.

[0101] [Tests 24 to 27] Solutions containing cyclic silane compounds were obtained in the same manner as in Test 1, except that the content of metallic sodium in the first step and the molar equivalent of Additive 2 mixed in the second step were changed as shown in Table 2.

[0102] [Test 28] A solution containing a cyclic silane compound was obtained in the same manner as in Test 1, except that the type of solvent A contained in the first step was changed as shown in Table 2.

[0103] [Test 29] A solution containing a cyclic silane compound was obtained in the same manner as in Test 1, except that the type of additive 2 mixed in the second step was changed as shown in Table 2.

[0104] [Test 30] A solution containing a cyclic silane compound was obtained in the same manner as in Test 1, except that the volume ratio of THF was kept constant and the amount of THF shown in Table 2 was added together with tetraglyme in the first step.

[0105] [Test 31] (1) First Step: A 200 mL four-neck flask purged with argon was charged with 38 mL of xylene and metallic sodium (2.15 eq. molar equivalent relative to dichlorodimethylsilane), and the mixture was heated to 120°C while stirring to melt the metallic sodium. Next, 4.9 g of dichlorodimethylsilane (silane compound) was added dropwise to the resulting mixture over 60 minutes, and the mixture was then stirred at 120°C for 7 hours to allow the reaction to proceed. This yielded a reaction solution containing a chain polysilane compound. The resulting reaction solution was cooled to room temperature. The xylene content in the mixture (first solution) was 66.2 parts by mass per 10 parts by mass of the silane compound and 164.2 parts by mass per 10 parts by mass of metallic sodium.

[0106] (2) Step 2: 50 mL of tetrahydrofuran (THF) and naphthalene (polycyclic aromatic hydrocarbon) with a molar equivalent Z relative to dichlorodimethylsilane of 0.23 eq. were added to the reaction solution containing the chain polysilane compound, followed by stirring and mixing to prepare a solution. The resulting solution was stirred at room temperature for 2 hours to react, and then heated in an oil bath at reflux temperature (74°C) for an additional 3 hours. This resulted in a solution containing a cyclic silane compound. Note that the total volume of toluene and tetrahydrofuran in the reaction solution relative to 10 parts by mass of metallic sodium used in Step 1 was 442.2 mL, and the volume ratio of tetrahydrofuran to the total volume of toluene and tetrahydrofuran was 57% by volume.

[0107] [Test 32] A solution containing a cyclic silane compound was obtained in the same manner as in Test 1, except that both tetraglyme and naphthalene were added in the first step and neither was mixed in the second step.

[0108] [Test 33] A solution containing a cyclic silane compound was obtained in the same manner as in Test 1, except that in the second step, both tetraglyme and naphthalene were mixed, and in the first step, neither was added.

[0109] [Test 34] A solution containing a cyclic silane compound was obtained in the same manner as in Test 1, except that THF was not mixed into the reaction solution in the second step.

[0110] [Test 35] A solution containing a cyclic silane compound was obtained in the same manner as in Test 34, except that in the first step, the content of tetraglyme was changed as shown in Table 2.

[0111] [Test 36] A solution containing a cyclic silane compound was obtained in the same manner as in Test 35, except that triglyme was used in place of tetraglyme in the first step.

[0112] [Test 37] A solution containing a cyclic silane compound was obtained in the same manner as in Test 35, except that octane was used instead of toluene in the first step.

[0113] [Test 38] A solution containing a cyclic silane compound was obtained in the same manner as in Test 35, except that the content of metallic sodium in the first step was changed as shown in Table 2.

[0114] The reaction products obtained in Tests 1 to 38 were analyzed by gas chromatography under the following measurement conditions.

[0115] (Gas Chromatography Measurement) Apparatus: GC-2025 (Shimadzu Corporation) Column: DB1301 (Agilent Technologies), length (30 m), diameter (0.320 m), film (0.25 m) Carrier gas: He Detector: FID

[0116] The production of cyclic silanes (dodecamethylcyclohexasilane (6-membered ring), decamethylcyclopentasilane (5-membered ring), and tetradecamethylcycloheptasilane (7-membered ring)) was confirmed, and the yields of each were determined.

[0117] The preparation conditions and evaluation results for Tests 1 to 17 are shown in Table 1, and the preparation conditions and measurement results for Tests 18 to 38 are shown in Table 2.

[0118]

[0119]

[0120] As shown in Tables 1 and 2, Tests 1, 2, 6, 7, 9 to 30, and 32 to 38, which used a specific polyether compound and a polycyclic aromatic hydrocarbon or the like, respectively, showed higher yields regardless of the form of metallic sodium, compared to Tests 3 to 5, 8, and 31, which did not use at least one of them.

[0121] In particular, it can be seen that the yield of tetraglyme (a polyether compound represented by formula (I)) is higher when it is added in the first step than when it is added in the second step (Comparison between Tests 1 and 33).

[0122] It is also clear that the yield of naphthalene (polycyclic aromatic hydrocarbon) is higher when it is added in the second step than when it is added in the first step (comparison between Tests 1 and 32).

[0123] It is also clear that the yield is increased by increasing the content of tetraglyme in the first step to a predetermined level (comparison of Tests 18 to 21 and 1). It is also clear that tetraglyme (chain) exhibits a yield equivalent to that of 15-crown-5 (cyclic) (comparison of Tests 1 and 2).

[0124] It is also clear that a high yield can be maintained even if the molar equivalent of naphthalene mixed in the second step is small (comparison of Tests 24 to 27).

[0125] It is also clear that high yields can be maintained even when other solvents are included in the first step (Compare Tests 1 and 30).

[0126] It is also clear that a good yield can be obtained even without mixing THF into the reaction solution in the second step (comparison of Tests 34 to 38 with Tests 3 to 5, 8, and 31). This is thought to be because the reaction solution contains the polyether compound added in the first step, and therefore a complex between sodium and the polycyclic aromatic hydrocarbon or polyphenyl hydrocarbon is formed in the second step, even without mixing THF into the reaction solution, and the decomposition and conversion reaction of the chain polysilane compound proceeded well.

[0127] This application claims priority from Japanese Patent Application No. 2023-140015, filed August 30, 2023, the entire contents of which are incorporated herein by reference.

[0128] According to the present invention, it is possible to provide a method for producing a cyclic silane compound, which can produce a cyclic silane compound in one pot from a silane monomer with a high reaction yield, regardless of the form of the reactant used and even if the amount used is small.

Claims

1. A method for producing a cyclic silane compound, comprising: a first step of polymerizing a silane compound in a first solution containing sodium to obtain a reaction liquid containing a linear polysilane compound; and a second step of decomposing and converting the linear polysilane compound in a second solution containing the reaction liquid to obtain a cyclic silane compound, wherein a polycyclic aromatic hydrocarbon or a polyphenyl-based hydrocarbon is added to the first solution or mixed into the reaction liquid, and a polyether compound represented by formula (I) or (II) is added to the first solution or mixed into the reaction liquid. In the formulas (I) and (II), R ａ ~R ｈ are each independently a hydrogen atom or an alkyl group; １ and m ２ are integers between 2 and 7, 2. The method for producing a cyclic silane compound according to claim 1, wherein the second step is carried out in a second solution obtained by mixing the reaction liquid with tetrahydrofuran.

3. The method for producing a cyclic silane compound according to claim 1 or 2, wherein the first solution includes a mixed solution containing metallic sodium and a hydrocarbon solvent.

4. The method for producing a cyclic silane compound according to claim 3, wherein in the first step, the first solution is heated to a melting temperature of the metallic sodium or higher.

5. The method for producing a cyclic silane compound according to claim 4, wherein the second step is carried out by heating the chain polysilane compound in the second solution.

6. The method for producing a cyclic silane compound according to claim 5, wherein the heating temperature is 40° C. or higher and reflux temperature or lower.

7. The method for producing a cyclic silane compound according to claim 4, wherein the polyether compound represented by formula (I) or (II) is contained in the first solution.

8. The method for producing a cyclic silane compound according to claim 7, wherein the polyether compound represented by formula (I) is contained in the first solution.

9. The method for producing a cyclic silane compound according to claim 7, wherein the total molar equivalent of the polyether compound represented by formula (I) or (II) relative to silicon atoms of the silane compound is 0.003 eq. or more and 0.180 eq. or less.

10. The method for producing a cyclic silane compound according to claim 4, wherein the polycyclic aromatic hydrocarbon or polyphenyl-based hydrocarbon is mixed with the reaction liquid.

11. The method for producing a cyclic silane compound according to claim 10, wherein biphenyl, anthracene or naphthalene is mixed as the polycyclic aromatic hydrocarbon in the reaction solution.

12. The method for producing a cyclic silane compound according to claim 3 or 4, wherein the hydrocarbon solvent is an aromatic hydrocarbon solvent.

13. The method for producing a cyclic silane compound described in claim 4, wherein the second solution contains the hydrocarbon solvent and tetrahydrofuran, and the volume ratio of the tetrahydrofuran contained in the second solution is 23 volume % or more and 99 volume % or less relative to the total volume of the hydrocarbon solvent and the tetrahydrofuran.

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