Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/21—Cyclic compounds having at least one ring containing silicon, but no carbon in the ring

Definitions

• Patent Document 1 discloses a method for producing cyclic silane compounds by dropping a silane monomer into a mixture of sodium dispersion, tetrahydrofuran (THF), and a polyether compound, and reacting the mixture at room temperature.
• THF tetrahydrofuran
• Patent Document 3 also discloses a method for producing a cyclic silane compound by 1) adding a silane monomer compound to a mixture of a sodium dispersion and a solvent and reacting the mixture, and then 2) adding a polycyclic aromatic hydrocarbon to the reaction mixture and heating to reflux.
• JP 2021-011440 A Japanese Unexamined Patent Publication No. 54-130541 JP 2019-156792 A
• the method of producing a cyclic silane compound from a silane monomer via a chain 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.
• the method as shown in Patent Document 2 has the problem that the operation is complicated because it includes a purification operation to remove the solvent from the synthesized polydimethylsilane.
• the reaction solution obtained in the first step contains a certain amount or more of components that do not contribute to the decomposition conversion reaction in the second step, so the reaction yield in the second step is likely to decrease.
• Patent Document 3 it was still necessary to use a large amount of reactant in order to obtain a high reaction yield. Therefore, it is desirable to produce in one pot and obtain a high reaction yield even with a small amount of reactant.
• the present invention was made in consideration of the above circumstances, and aims to provide a method for producing cyclic silane compounds that can produce cyclic silane compounds in one pot from silane monomers with high reaction yields, regardless of the form of the reactant used and even if the amount used is small.
• the present invention relates to a method for producing the following cyclic silane compounds.
• 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 the following formula (I) or (II) is added to the first solution or mixed into the reaction liquid:
• R a to R h each independently represent a hydrogen atom or an alkyl group;
• m1 and m2 are each an integer of 2 or more and 7 or less.
• the present invention provides a method for producing cyclic silane compounds that can produce cyclic silane compounds in one pot from silane monomers with high reaction yields, regardless of the form of the reactant used and even if the amount used is small.
• the sodium dispersion that has been used conventionally is not only expensive, but also makes it difficult to separate and recover the cyclic silane compound, as described below.
• the use of a mixture in which lump metallic sodium is dissolved in a hydrocarbon solvent has been considered as an alternative to sodium dispersion.
• 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.
• the 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-based hydrocarbon as a reaction promoter and further using a specific polyether compound in at least one of the first and second steps, preferably in the first step.
• the mechanism behind this is unclear, but is speculated to be as follows.
• the specific polyether compound is likely to increase the reactivity of the silane compound by stably capturing the oxygen atoms of the multiple ether bonds coordinated with sodium ions, which is believed to promote the polymerization reaction of the silane compound in the first step, thereby increasing the yield of the linear polysilane compound, and also promote the decomposition and conversion reaction of the linear polysilane compound in the second step.
• the specific polyether compound may be contained in the first solution or may be mixed into the reaction liquid.
• it When mixed into the reaction liquid, it may be mixed between the first and second steps, or may be mixed in the second step.
• 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 it may contain a mixture of metallic sodium (in a molten state) and a hydrocarbon solvent, and a polyether compound.
• SD sodium dispersion
• specific polyether compound or it may contain a mixture of metallic sodium (in a molten state) and a hydrocarbon solvent, and a polyether compound.
• Sodium dispersion is a dispersion of metallic sodium particles in electrical insulating oil, and has higher reactivity than lump metallic sodium.
• the average particle size of the sodium particles in SD can be 1 ⁇ m or more and 100 ⁇ m or less.
• the average particle size can be a value measured using a laser diffraction type particle size distribution measuring device or the like.
• electrical insulating oils include aliphatic hydrocarbons such as liquid paraffin and mineral oil.
• the first solution containing such a mixture can be obtained, for example, by adding metallic sodium to a hydrocarbon solvent, heating the mixture to a temperature above the melting point of metallic sodium (98°C or higher) to melt the metallic sodium, and then further mixing with a polyether compound. It can also be obtained by adding molten metallic sodium to a hydrocarbon solvent that has been heated to a temperature above the melting point of metallic sodium (98°C or higher), and then further mixing with a polyether compound.
• Such a hydrocarbon solvent may be an aliphatic hydrocarbon solvent or an aromatic hydrocarbon solvent.
• aliphatic hydrocarbon solvents include hydrocarbon solvents having 8 to 12 carbon atoms, such as octane and decane.
• aromatic hydrocarbon solvents include toluene, xylene, ethylbenzene, mesitylene, and the like. Among these, from the viewpoint of facilitating the formation of a complex between polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons and sodium, aromatic hydrocarbon solvents are preferred, toluene, xylene, and ethylbenzene are more preferred, and toluene and xylene are even more preferred.
• the content of the hydrocarbon solvent in the first solution may be such that the chain polysilane produced is sufficiently stirred and dispersed in the solvent.
• the content of the hydrocarbon solvent in the first solution is preferably 0.7 parts by mass or more relative to 10 parts by mass of the silane compound. If 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 that case, the average droplet diameter can be made smaller, so the specific surface area of sodium increases, and the reactivity of the silane compound can be further increased. If 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 viewpoint, it is more preferable that the content of the hydrocarbon solvent in the first solution is 3.0 parts by mass or more and 100.0 parts by mass or less relative to 10 parts by mass of the silane compound.
• the content of the hydrocarbon solvent in the first solution per 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.
• the metallic sodium can function primarily as a reactant in the polymerization reaction.
• the specific polyether compound is a polyether compound represented by formula (I) or (II).
• R a to R h are each independently a hydrogen atom or an alkyl group.
• R a to R h are 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 further preferably a hydrogen atom or a methyl group.
• n1 and m2 are each an integer of 2 or more and 7 or less. Among them, m1 and m2 are 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.
• the first solution may contain either the polyether compound represented by formula (I) or the polyether compound represented by formula (II), or may contain both.
• the polyether compound represented by formula (I) is preferred from the viewpoints of its high boiling point, high residual property in the reaction system under heating, and the ability to further reduce production costs.
• Examples of polyether compounds represented by formula (I) include diglyme, triglyme, and tetraglyme.
• Examples of compounds 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 promotion effect.
• 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.
• 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, and the reaction yield can be further increased.
• the molar equivalent of the polyether compound is 0.180 eq. or less, the decomposition of the cyclic silane compound, which is the final product, can be further reduced.
• the molar equivalent of the polyether compound is more preferably 0.030 eq. or more and 0.120 eq. or less.
• the first solution may further contain other solvents in addition to those mentioned above, if necessary.
• other solvents include ether-based solvents such as tetrahydrofuran, 2-methyltetrahydrofuran, diethyl ether, diisopropyl ether, and t-butyl methyl ether (excluding polyethers).
• 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).
• X1 and X2 each represent an alkoxy group or a halogen atom.
• the alkoxy group include a methoxy group and an ethoxy group.
• the halogen atom include a chlorine atom, a bromine atom, and an iodine atom. These have a large electronegativity difference with silicon and are prone to intramolecular polarization in the silane compound, so they are highly reactive and are substituents that function as leaving groups in the reaction.
• X1 and X2 are preferably halogen atoms, more preferably chlorine atoms, from the viewpoint of the reactivity of the silane compound.
• R1 and R2 are each a hydrogen atom or a hydrocarbon group.
• R1 and R2 are 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.
• n1 is an integer of 1 or more. From the viewpoint of increasing the reactivity of the silane compound, n1 is preferably 1 or 2, and more preferably 1.
• Examples of the compound represented by formula (1) include dichlorodimethylsilane, dichlorodiethylsilane, dichlorodipropylsilane, dichlorodibutylsilane, dichlorodipentylsilane, dichlorodihexylsilane, dibromodimethylsilane, dibromodiethylsilane, dibromodipropylsilane, dibromodibutylsilane, dibromodipentylsilane, dibromodihexylsilane, dichlorotetramethyldisilane, and the like. Of these, dichlorodimethylsilane is preferred.
• the silane compound may be one type or two or more types.
• the polymerization reaction of the silane compound is preferably carried out at a temperature depending on the composition of the first solution.
• the polymerization reaction is preferably carried out at a temperature between 0°C and the reflux temperature, and more preferably at room temperature.
• the polymerization reaction is preferably carried out under heating in order to carry out the polymerization reaction in a molten state of metallic sodium.
• the polymerization reaction is preferably carried out while heating to a temperature equal to or higher than the melting temperature of metallic sodium.
• 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 above reaction is preferably carried out in an inert gas atmosphere such as nitrogen or argon.
• the above reaction is also preferably carried out under normal pressure or under pressure.
• the silane compound may be added continuously or intermittently, but from the standpoint of production efficiency, it is preferable to add a constant amount continuously.
• the average addition rate of the silane compound per unit amount (mol) of metallic sodium is preferably 0.06 hr ⁇ 1 or more and 0.50 hr ⁇ 1 or less, and more preferably 0.10 hr ⁇ 1 or more and 0.30 hr ⁇ 1 or less.
• the average addition rate of the silane compound (mol ⁇ hr ⁇ 1 ) is the value obtained by dividing the total amount of the silane compound used (mol) by the addition time (hr); and the average addition rate of the silane compound (hr ⁇ 1 ) per unit amount (mol) of metallic sodium is the value obtained by dividing the average addition rate of the silane compound (mol ⁇ hr ⁇ 1 ) by the amount of metallic sodium (mol).
• the temperature of the mixed solution can be prevented from dropping below the melting temperature of sodium, and the reaction can be promoted.
• the average addition rate of the silane compound per unit amount (mol) of metallic sodium is 0.06 hr -1 or more, the total reaction time can be shortened, and the production efficiency can be increased.
• the above reaction produces a reaction liquid containing crude polydialkylsilane (chain polysilane compound).
• Chain polysilane compound has a repeating unit represented by the following formula (2).
• R 1 and R 2 in formula (2) are the same as R 1 and R 2 in formula (1).
• the groups bonded to the silicon atoms at both ends of the molecule may be hydrogen atoms, hydrocarbon groups, alkoxy groups, sodium atoms, or halogen atoms.
• the alkoxy groups or halogen atoms are the same as X1 and X2 in formula (1).
• the sodium atoms are cationized and may be coordinated to the anionized silicon atoms. Since the alkoxy groups and halogen atoms have a large electronegativity difference with the silicon atoms, they may be easily reduced by sodium and may easily generate active sites. Furthermore, since the sodium atoms have a particularly large electronegativity difference with the silicon atoms, they may easily function as active sites. Therefore, the groups at both ends of the molecule of the chain polysilane compound may be alkoxy groups, halogen atoms, or sodium atoms.
• 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.
• a polycyclic aromatic hydrocarbon or a polyphenyl-based hydrocarbon is mixed with the reaction liquid obtained in the first step to obtain a second solution.
• the polycyclic aromatic hydrocarbon or the polyphenyl-based hydrocarbon is mixed with the reaction liquid.
• the second solution preferably contains tetrahydrofuran.
• the second step is preferably carried out in a second solution in which tetrahydrofuran is further mixed into the reaction solution obtained in the first step. This allows the decomposition and conversion reaction of the chain polysilane compound to proceed to a higher degree.
• the complex between sodium and polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons, which is necessary for the decomposition and conversion reaction of the linear polysilane compound in the second step is not easily formed.
• the reaction solution contains tetrahydrofuran, a complex between sodium and polycyclic aromatic hydrocarbons or polyphenyl hydrocarbons is easily formed and easily exists stably, which can further increase the decomposition reactivity of the linear polysilane compound.
• 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.
• 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, the decomposition of the generated cyclic silane compound can be further suppressed.
• the concentration of the silane compound in the system increases, so that the reaction of the second step is easily promoted.
• 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.
• the total molar equivalent of the polycyclic aromatic hydrocarbons and polyphenyl-based 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.
• the order of mixing the reaction liquid, the polycyclic aromatic hydrocarbon or the polyphenyl-based hydrocarbon, and the tetrahydrofuran is not particularly limited.
• the reaction liquid may be added with the polycyclic aromatic hydrocarbon or the polyphenyl-based hydrocarbon and the tetrahydrofuran at the same time, or the reaction liquid may be added with tetrahydrofuran and stirred, and then the polycyclic aromatic hydrocarbon or the polyphenyl-based hydrocarbon may be added.
• the reaction liquid may be added after mixing the polycyclic aromatic hydrocarbon or the polyphenyl-based hydrocarbon and the tetrahydrofuran, or the reaction liquid may be mixed with the tetrahydrofuran and then the polycyclic aromatic hydrocarbon or the polyphenyl-based hydrocarbon may be added.
• the heating temperature may be equal to or lower than the reflux temperature, but is preferably 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.
• 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.
• the reflux temperature is a temperature that corresponds to a volume ratio of tetrahydrofuran that is greater than 68°C and less than the boiling point of the hydrocarbon solvent.
• the reaction time indicates the time elapsed after the target reaction temperature is reached.
• the reaction time depends on the temperature of the solution, but if the reaction is carried out under heating, it is preferably, for example, from 1 hour to 35 hours, and more preferably from 3 hours to 10 hours.
• 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).
• R 1 and R 2 in formula (3) are the same as R 1 and R 2 in formula (1), respectively.
• the cyclic silane may have any structure depending on R 1 and R 2 , and examples include decamethylcyclopentasilane, dodecamethylcyclohexasilane, and tetradecamethylcycloheptasilane.
• the obtained cyclic silane compound may contain a plurality of kinds of cyclic silane compounds with different n2 .
• the molar yield of the cyclic silane compound (6-membered ring) with n2 being 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.
• the first solution contains a polyether compound
• the reaction liquid is mixed with a polycyclic aromatic hydrocarbon or a polyphenyl-based hydrocarbon, but the present invention is not limited to this.
• the reaction liquid may be mixed with both a specific polyether compound and a polycyclic aromatic hydrocarbon.
• the molar equivalent of the polyether compound to the silane compound may be the same as above.
• a mixed liquid in which metallic sodium is dissolved in a hydrocarbon solvent is used, but a sodium dispersion may also be used.
• the molar equivalent of the metallic sodium particles per functional group, alkoxy group or halogen atom of the silane compound can be the same as above.
• the reaction liquid 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 liquid. In other words, even if 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 liquid obtained in the first step.
• 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.
• 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.
• 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.
• SD sodium dispersion
• 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.
• 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.
• Tests 9-13 A solution containing a cyclic silane compound was obtained in the same manner as in Test 1, except that the volume ratio of solvent A contained in the first step and THF mixed in the second step (the volume ratio of THF to the total volume of solvent A and THF in the second solution) was changed as shown in Table 1.
• 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.
• 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.
• 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.
• the total volume of toluene and tetrahydrofuran in the reaction solution was 442.2 mL relative to 10 parts by mass of metallic sodium used in the first step, and the volume ratio of tetrahydrofuran to the total volume of toluene and tetrahydrofuran was 57% by volume.
• Test 35 In the first step, a solution containing a cyclic silane compound was obtained in the same manner as in Test 34, except that the content of tetraglyme was changed as shown in Table 2.
• Test 36 A solution containing a cyclic silane compound was obtained in the same manner as in Test 35, except that in the first step, triglyme was used instead of tetraglyme.
• Test 37 A solution containing a cyclic silane compound was obtained in the same manner as in Test 35, except that in the first step, octane was used instead of toluene.
• 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.
• Tests 1, 2, 6, 7, 9-30, and 32-38 which used a specific polyether compound and a polycyclic aromatic hydrocarbon, etc., respectively, showed higher yields regardless of the form of metallic sodium compared to Tests 3-5, 8, and 31, which did not use at least one of them.
• naphthalene a polycyclic aromatic hydrocarbon
• the yield is increased by increasing the amount of tetraglyme in the first step to a certain level (Comparison between Tests 18-21 and 1). It can also be seen that tetraglyme (chain) shows a yield equivalent to that of 15-crown-5 (cyclic) (Comparison between Tests 1 and 2).
• the present invention provides a method for producing cyclic silane compounds that can produce cyclic silane compounds in one pot from silane monomers with high reaction yields, regardless of the form of the reactant used and even if the amount used is small.

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