Method for decomposing polyphenylene sulfide resin, and method for producing benzene and bis(trialkylsilyl) sulfide

Abstract

To provide a method for decomposing a polyphenylene sulfide resin which can obtain a decomposition product from a polyphenylene sulfide resin with a high yield, and a method for producing benzine and bis(trialkylsilyl)sulfide.SOLUTION: A method for decomposing a polyphenylene sulfide resin includes a step of reacting a polyphenylene sulfide resin with a hydrosilane in the presence of a palladium complex catalyst having a ligand.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for decomposing polyphenylene sulfide resin. Further, the present invention relates to a method for producing benzene and bis(trialkylsilyl) sulfide by the above method.

Background Art

[0002] Polyphenylene sulfide resin belongs to super engineering plastics and has mechanical strength, rigidity, heat resistance, flame retardancy, chemical resistance, electrical properties, dimensional stability, etc., so it is widely used in various applications such as electrical and electronic parts, household electrical appliance parts, automotive parts, and mechanical parts (for example, see Patent Document 1). In recent years, the demand for recycling these wastes has increased, and the reuse of polyphenylene sulfide resin has been studied.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, since polyphenylene sulfide resin is excellent in chemical resistance, heat resistance, etc., it has been very difficult to decompose. Therefore, an object of the present invention is to provide a method for decomposing polyphenylene sulfide resin that can obtain decomposition products in a high yield. Further, an object of the present invention is to provide a method for producing benzene and bis(trialkylsilyl) sulfide that can obtain benzene and bis(trialkylsilyl) sulfide in a high yield using the above method.

Means for Solving the Problems

[0005] As a result of intensive studies by the present inventors to solve the above problems, it has been found that the above problems can be solved by reacting a polyphenylene sulfide resin with a hydrosilane in the presence of a palladium complex catalyst having a ligand, and the present invention has been completed. That is, the present invention is as follows.

[0006] [1] A method for decomposing a polyphenylene sulfide resin, comprising a step of reacting a polyphenylene sulfide resin with a hydrosilane in the presence of a palladium complex catalyst having a ligand. [2] The method for decomposing a polyphenylene sulfide resin according to [1], wherein the ligand is an N-heterocyclic carbene compound or a phosphine compound. [3] The palladium source of the palladium complex catalyst includes at least one selected from the group consisting of allylpalladium (II) chloride dimer, (2-butenyl)chloropalladium dimer, palladium(π-cinnamyl)chloride dimer, palladium(II) trifluoroacetate, palladium(II) trimethylacetate, palladium(II) acetate, palladium(II) chloride, palladium(II) nitrate, palladium(II) bromide, palladium(II) iodide, palladium(II) sulfate, palladium(II) oxide, palladium(II) tetrafluoroborate tetrakis(acetonitrile) complex, tetrakis(triphenylphosphine)palladium(0), palladium(II) acetylacetonate, palladium(II) hexafluoroacetylacetonate, chloro(1,5-cyclooctadiene)methylpalladium(II), (η5-2,4-cyclopentadien-1-yl)[(1,2,3-η)-1-phenyl-2-propenyl]palladium, bis(benzonitrile)palladium(II) bromide, bis(dibenzylideneacetone)palladium(0), tris(dibenzylideneacetone)dipalladium(0), dichloro(1,5-cyclooctadiene)palladium(II), dichloro(norbornadiene)palladium(II), dichlorobis(acetonitrile)palladium(II) and dichlorobis(benzonitrile)palladium(II), and is a method for decomposing the polyphenylene sulfide resin according to [1] or [2]. [4] The method for decomposing the polyphenylene sulfide resin according to [1], wherein the palladium complex catalyst having the ligand contains at least one selected from the group consisting of chloro[[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](N,N-dimethylbenzylamine)palladium(II)], chloro[(1,3-dimesitylimidazol-2-ylidene)(N,N-dimethylbenzylamine)palladium(II)], chloro[[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](acetanilide)palladium(II)], chloro[[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](4'-methoxyacetanilide)palladium(II)], and chloro[[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](N,N-dimethyl-3,5-dimethoxybenzylamine)palladium(II)]. [5] The method for decomposing the polyphenylene sulfide resin according to any one of [1] to [4], wherein the hydrosilane contains at least one selected from the group consisting of diethylsilane, phenylsilane, diphenylsilane, triphenylsilane, diphenylmethylsilane, methylphenylsilane, dimethylphenylsilane, diphenylethylsilane, diethylphenylsilane, trimethylsilane, triethylsilane, tert-butyldimethylsilane, trimethoxysilane, triethoxysilane, diethoxyphenylsilane, diethoxymethylsilane, dimethoxymethylsilane, ethoxydimethylsilane, and tris(trimethylsilyl)silane. [6] The method for decomposing the polyphenylene sulfide resin according to any one of [1] to [5], wherein the reaction temperature in the step of reacting is 50 to 300 °C. [7] A method for producing benzene, comprising the step of decomposing the polyphenylene sulfide resin by the method according to any one of [1] to [6] to obtain benzene. [8] A method for producing bis(trialkylsilyl)sulfide, comprising the step of decomposing the polyphenylene sulfide resin by the method according to any one of [1] to [6] to obtain bis(trialkylsilyl)sulfide.

Advantages of the Invention

[0007] According to the present invention, a method for decomposing a polyphenylene sulfide resin capable of obtaining decomposition products from the polyphenylene sulfide resin in a high yield can be provided. Further, according to the present invention, a method for producing benzene and bis(trialkylsilyl) sulfide capable of obtaining benzene and bis(trialkylsilyl) sulfide in a high yield by using the above method can be provided.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, the decomposition reaction and production method of the present invention will be described in detail. The following is an example (representative example) of the present invention, and the present invention is not limited thereto.

[0009] [Decomposition Reaction of Polyphenylene Sulfide Resin] The method for decomposing a polyphenylene sulfide resin (hereinafter sometimes abbreviated as PPS resin) according to the present embodiment includes a step of reacting the PPS resin and hydrosilane in the presence of a palladium complex catalyst having a ligand.

[0010] The reaction mechanism by which the PPS resin is decomposed is presumed as follows. The carbon-sulfur bond of the PPS resin undergoes oxidative addition to the palladium(0) complex generated from the palladium complex in the reaction system, and a complex having benzene and a sulfur functional group on palladium is formed. A ligand exchange reaction occurs between this complex and the silicon-hydrogen bond of hydrosilane, the palladium(0) complex undergoes oxidative desorption, and a carbon-hydrogen bond and a silicon-sulfur bond are formed, thereby decomposing the carbon-sulfur bond that is the main chain of the PPS resin. The palladium(0) complex acts as a catalyst again, and as the above decomposition reaction further proceeds, the PPS resin is finally depolymerized into benzene and bis(trialkylsilyl) sulfide. Thus, it is presumed that by using hydrosilane and a palladium complex catalyst having a ligand, the PPS resin can be efficiently depolymerized under mild conditions that do not require a high reaction temperature.

[0011] (Polyphenylene sulfide resin) The PPS resin used in this embodiment is a polymer having p-phenylene sulfide as a main structural unit, and may contain, in addition to the p-phenylene unit, a phenylene sulfide sulfone unit and a phenylene sulfide ketone unit, and may be a random copolymer, a block copolymer, or a mixture thereof.

[0012] The form of the PPS resin is not particularly limited, and may be powder, granules, pellets, fibers, films, molded articles, etc.

[0013] The number average molecular weight of the PPS resin depends on its raw materials and methods and is not particularly limited. For example, it may be 1,000 or more, and may also be 5,000 or more. Further, the number average molecular weight of the PPS resin may be, for example, 500,000 or less, and may also be 100,000 or less.

[0014] (Hydrosilane) Hydrosilane is not particularly limited as long as it is a compound having a hydrogen atom directly bonded to a silicon atom, and is preferably a compound represented by the following formula (1).

[0015] [Chemical formula]

[0016] (In formula (1), R 1 represents a hydrocarbon group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or a trialkylsilyl group, and a is an integer of 1 to 3.)

[0017] In formula (1), R 1 Examples of include an alkyl group having 1 to 20 carbon atoms, an alicyclic alkyl group having 3 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 5 to 20 carbon atoms, an aralkyl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a trialkylsilyl group, etc. When a is 1 or 2, R1 may be the same or different from each other.

[0018] The alkyl group having 1 to 20 carbon atoms preferably has 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, and still more preferably 1 to 4 carbon atoms. Specific examples of the alkyl group having 1 to 20 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a t-butyl group, an n-pentyl group, a 1,1-dimethylpropyl group, an n-hexyl group, an n-heptyl group, an n-octyl group and the like.

[0019] The alicyclic alkyl group having 3 to 20 carbon atoms preferably has 3 to 12 carbon atoms, more preferably 3 to 10 carbon atoms, and still more preferably 4 to 8 carbon atoms. Specific examples of the alicyclic alkyl group having 3 to 20 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclohexyl group, a norbornyl group, an adamantyl group and the like.

[0020] The alkenyl group having 2 to 20 carbon atoms preferably has 2 to 12 carbon atoms, more preferably 2 to 8 carbon atoms, and still more preferably 2 to 4 carbon atoms. Specific examples of the alkenyl group having 2 to 20 carbon atoms include an ethenyl group, a propenyl group, a butenyl group, a pentenyl group, a hexenyl group, an octenyl group and the like.

[0021] The alkynyl group having 2 to 20 carbon atoms preferably has 2 to 12 carbon atoms, more preferably 2 to 8 carbon atoms, and still more preferably 2 to 4 carbon atoms. Specific examples of the alkynyl group having 2 to 20 carbon atoms include an ethynyl group, a propynyl group, a butynyl group, a pentynyl group, a hexynyl group, an octynyl group and the like.

[0022] The aryl group having 5 to 20 carbon atoms preferably has 6 to 16 carbon atoms, more preferably 6 to 12 carbon atoms, and still more preferably 6 to 10 carbon atoms. Specific examples of the aryl group having 5 to 20 carbon atoms include a phenyl group, a tolyl group, a naphthyl group and the like.

[0023] The above aralkyl group having 6 to 20 carbon atoms preferably has 7 to 17 carbon atoms, more preferably 7 to 13 carbon atoms, and even more preferably 7 to 11 carbon atoms. Specific examples of the aralkyl group having 6 to 20 carbon atoms include a benzyl group, a 1-methylbenzyl group, a 1,1-dimethylbenzyl group, and the like.

[0024] The above alkoxy group having 1 to 20 carbon atoms preferably has 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, and even more preferably 1 to 4 carbon atoms. Specific examples of the alkoxy group having 1 to 20 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, a t-butoxy group, an n-pentoxy group, a 1,1-dimethylpropoxy group, an n-hexoxy group, an n-heptoxy group, an n-octoxy group, a phenoxy group, and the like.

[0025] In the above trialkylsilyl group, the carbon of the alkyl group preferably has 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms, even more preferably 1 to 4 carbon atoms, and particularly preferably a methyl group or an ethyl group. Specific examples of the trialkylsilyl group include a trimethylsilyl group and a triethylsilyl group.

[0026] The hydrosilane is more preferably a compound represented by the following formula (2).

[0027]

Chemical formula

[0028] (In formula (2), R 2 ~R 4 each independently represents a hydrocarbon group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or a trialkylsilyl group.)

[0029] R 2 ~R 4The hydrocarbon group having 1 to 20 carbon atoms, the alkoxy group having 1 to 20 carbon atoms, and the trialkylsilyl group represented by R 1 Examples of the hydrocarbon group having 1 to 20 carbon atoms, the alkoxy group having 1 to 20 carbon atoms, and the trialkylsilyl group described above as [R] are the same, and the preferable ranges are also the same.

[0030] More specifically, the hydrosilane includes diethylsilane, phenylsilane, diphenylsilane, triphenylsilane, diphenylmethylsilane, methylphenylsilane, dimethylphenylsilane, diphenylethylsilane, diethylphenylsilane, trimethylsilane, triethylsilane, tert-butyldimethylsilane, trimethoxysilane, triethoxysilane, diethoxyphenylsilane, diethoxymethylsilane, dimethoxymethylsilane, ethoxydimethylsilane, tris(trimethylsilyl)silane and the like. Among these, the hydrosilane is preferably trimethylsilane, triethylsilane, tert-butyldimethylsilane, and more preferably triethylsilane. The hydrosilane may be used alone or in combination of two or more.

[0031] The amount of the hydrosilane used is 20 molar equivalents or less, preferably 15 molar equivalents or less, and more preferably 10 molar equivalents or less with respect to the number of moles of the p-phenylene sulfide unit in the PPS resin. Also, the amount used is 0.5 molar equivalent or more, preferably 1.0 molar equivalent or more, and more preferably 1.5 molar equivalents or more with respect to the number of moles of the p-phenylene sulfide unit in the PPS resin. When the amount of the hydrosilane used is within the above range, the reaction proceeds rapidly and decomposition products tend to be obtained in a high yield.

[0032] (Palladium complex catalyst) The palladium complex catalyst used in this embodiment is a palladium complex catalyst having a ligand.

[0033] As the palladium complex catalyst having a ligand, those with various structures can be used. For example, chloro[[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](N,N-dimethylbenzylamine)palladium(II)] (trade name: SingaCycle-A1, manufactured by Tokyo Chemical Industry Co., Ltd.), chloro[(1,3-dimesitylimidazol-2-ylidene)(N,N-dimethylbenzylamine)palladium(II)] (trade name: SingaCycle-E1, manufactured by Tokyo Chemical Industry Co., Ltd.), chloro[[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](acetanilide)palladium(II)] (trade name: SingaCycle-A3, manufactured by Tokyo Chemical Industry Co., Ltd.), chloro[[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](4'-methoxyacetanilide)palladium(II)] (trade name: SingaCycle-A4, manufactured by Tokyo Chemical Industry Co., Ltd.), chloro[[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](N,N-dimethyl-3,5-dimethoxybenzylamine)palladium(II)] (trade name: SingaCycle-A2, manufactured by Tokyo Chemical Industry Co., Ltd.) and the like can be used. The palladium complex catalyst having a ligand may be used alone or in combination of two or more.

[0034] In addition, in this embodiment, in the reaction system, a palladium source and a ligand can be mixed to generate and use a palladium complex catalyst having a ligand.

[0035] <Palladium source> Palladium sources include, for example, allylpalladium(II) chloride dimer, (2-butenyl)chloropalladium dimer, palladium(π-cinnamyl) chloride dimer, palladium(II) trifluoroacetate, palladium(II) pivalate, palladium(II) acetate, palladium(II) chloride, palladium(II) nitrate, palladium(II) bromide, palladium(II) iodide, palladium(II) sulfate, palladium(II) oxide, palladium(II) tetrafluoroborate tetraacetonitrile complex, tetrakis(triphenylphosphine)palladium(0), palladium(II) acetylacetonate, palladium(II) hexafluoroacetylacetonate, chloro(1,5-cyclooctadiene)methylpalladium(II), (η5-2,4-cyclopentadien-1-yl)[(1,2,3-η)-1-phenyl-2-propenyl]palladium, bis(benzonitrile)palladium(II) bromide, bis(dibenzylideneacetone)palladium(0), tris(dibenzylideneacetone)dipalladium(0), dichloro(1,5-cyclooctadiene)palladium(II), dichloro(norbornadiene)palladium(II), dichlorobis(acetonitrile)palladium(II), dichlorobis(benzonitrile)palladium(II), etc. Among these, from the viewpoint of obtaining decomposition products in high yields, allylpalladium(II) chloride dimer, palladium(II) acetate, and palladium(II) chloride are preferred as the palladium source. The palladium source may be used alone or in combination of two or more.

[0036] <Ligand> The ligand is not limited in its type and structure as long as it has the property of being able to form a complex with the above palladium source.

[0037] Examples of the ligand include diamine compounds, diketone compounds, diene compounds, bipyridine compounds, N-heterocyclic carbene (hereinafter sometimes abbreviated as NHC) compounds, phosphine compounds, and the like. Among these, NHC compounds and phosphine compounds are preferred as the ligand, and NHC compounds are more preferred from the viewpoint of being bulky and having high electron-donating properties. The ligand may be used alone or in combination of two or more.

[0038] The diamine compound is preferably a diamine compound having 1 to 12 carbon atoms, and examples thereof include ethylenediamine, tetramethylethylenediamine, phenylenediamine, and the like. The diketone compound is preferably a diketone compound having 3 to 15 carbon atoms, and examples thereof include 2,4-pentanedione (acetylacetone), 2,4-hexanedione, 3,5-heptanedione, 2-methyl-3,5-hexanedione, 6-methyl-2,4-heptanedione, 2,6-dimethyl-3,5-heptanedione, 2,2-dimethyl-3,5-hexanedione, 2,2,6,6-tetramethyl-3,5-heptanedione, and the like. The diene compound is preferably a diene compound having 5 to 25 carbon atoms, and examples thereof include norbornadiene, 1,5-cyclooctadiene, dibenzylideneacetone, and the like. Examples of the bipyridine compound include bipyridine which may have a substituent selected from the group consisting of an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 18 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and an aryloxy group having 6 to 18 carbon atoms.

[0039] <<N-heterocyclic carbene compound>> Carbene is a state having a divalent carbon atom without charge, and an NHC compound is a compound in which a carbon atom of a nitrogen-containing heterocycle is in a state where it can coordinate to a palladium atom in a carbene state or a divalent carbon atom state.

[0040] Examples of the nitrogen-containing heterocyclic ring in the NHC compound include a 3- to 8-membered, preferably 4- to 6-membered monocyclic, polycyclic, or condensed nitrogen-containing heterocyclic ring having at least one nitrogen atom and optionally containing 1 to 3 heteroatoms such as oxygen atoms and / or sulfur atoms.

[0041] Specific NHC compounds include, for example, imidazolylidenes derived from imidazole, dihydroimidazolylidenes derived from dihydroimidazole, dihydropyrimidinylidenes derived from dihydropyrimidine, hexahydro-1,3-diazepinylidenes derived from tetrahydro-1,3-diazepine, thiazolylidenes derived from thiazole, dihydrothiazolylidenes derived from dihydrothiazole, oxazolylidenes derived from oxazole, dihydrooxazolylidenes derived from dihydrooxazole, tetrahydropyrimidinylidenes derived from tetrahydropyrimidine, pyrimidinylidenes derived from pyrimidine, triazolylidenes derived from triazole, and salts thereof. The type of the counter anion of the salt form is not particularly limited. The counter anion is usually a halogen ion (F - , Cl - , Br - or I - ), but may also be a nitrate ion (NO 3- ), an acetate ion (CH3COO - ), a trifluoroacetate ion (CF3COO - ), a tetrafluoroborate ion (BF 4- ), etc.

[0042] Among the above, as the NHC compound used as a ligand, imidazol-2-ylidenes represented by the following formula (3), imidazolinium salts which are salts of dihydroimidazolylidenes represented by the following formula (4), and imidazolium salts which are salts of imidazolylidenes represented by the following formula (5) are more preferable.

[0043]

Chemical formula

[0044] [Chemical formula]

[0045] [Chemical formula]

[0046] (In formulas (3), (4), and (5), R 5 , R 5 ’, R 7 , R 7 ’, R 9 , and R 9 ’ each independently represent a hydrocarbon group or a heterocyclic group having 1 to 20 carbon atoms, and these hydrocarbon groups and heterocyclic groups having 1 to 20 carbon atoms may have substituents. Also, in formulas (3), (4), and (5), R 6 , R 6 ’, R 8 , R 8 ’, R 10 , and R 10 ’ each independently represent a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a heterocyclic group, or an amine group, and the hydrocarbon groups and heterocyclic groups having 1 to 20 carbon atoms may have substituents. In formula (3), R 5 and R 5 ’, R 5 and R 6 , R 6 and R 6 ’ and R 6 ’ and R 5 ’ may each independently combine with each other to form a ring together with adjacent atoms. Also, in formula (4), R 7 and R 7 ’, R 7 and R 8 , R 8 and R 8 ’, R 8 ’ and R 7 ’ may each independently combine to form a ring together with adjacent atoms. In formula (5), R 9 and R 9 ’, R 9 and R 10 , R 10and R 10 ’ and R 10 ’ and R 9 ’ may each independently combine with each other to form a ring together with adjacent atoms. In Formulas (4) and (5), X - represents a counter anion.)

[0047] The substituents that the hydrocarbon group and heterocyclic group having 1 to 20 carbon atoms may have are not particularly limited, and examples thereof include a hydroxyl group, a halogen atom (such as fluorine, chlorine, bromine, iodine, etc.), a nitro group, an alkyl group, an alkoxy group, an alkylthio group, an aryl group, an aryloxy group, an arylthio group, an arylalkyl group, an arylalkoxy group, an arylalkylthio group, an arylalkenyl group, an arylalkynyl group, an amino group, a substituted amino group, an acyl group, an acyloxy group, an amide group, a carboxyl group, a substituted carboxyl group, a cyano group, etc. When there are a plurality of substituents, they may be the same or different.

[0048] R 5 , R 5 ’, R 7 , R 7 ’, R 9 and R 9 ’ The hydrocarbon group having 1 to 20 carbon atoms in is the same group as the hydrocarbon group having 1 to 20 carbon atoms described above as R 1 in the above formula (1). Examples of the heterocyclic group in R 5 , R 5 ’, R 7 , R 7 ’, R 9 and R 9 ’ include an aliphatic heterocyclic group and an aromatic heterocyclic group.

[0049] Examples of the aliphatic heterocyclic group include a 3-8-membered, preferably 4-6-membered, monocyclic aliphatic heterocyclic group, polycyclic or condensed aliphatic heterocyclic group, each of which has 2 to 14 carbon atoms and contains at least one heteroatom such as a nitrogen atom, an oxygen atom or a sulfur atom. Specific examples of the aliphatic heterocyclic group include a 2-pyrrolidyl group, a 2-piperidinyl group, a 2-piperazinyl group, a 2-morpholinyl group, a 2-tetrahydrofuryl group, a 2-tetrahydropyranyl group, and a 2-tetrahydrothienyl group.

[0050] Examples of aromatic heterocyclic groups include 5- or 6-membered monocyclic heteroaryl groups, polycyclic or fused ring heteroaryl groups having 2 to 15 carbon atoms and containing at least one heteroatom such as a nitrogen atom, an oxygen atom or a sulfur atom. Specific examples thereof include a 2-furyl group, a 3-furyl group, a 2-thienyl group, a 3-thienyl group, a 2-pyridyl group, a 3-pyridyl group, a 2-pyrimidyl group, a 2-pyrazyl group, a 2-imidazolyl group, a 4-imidazolyl group, a 2-oxazolyl group, a 2-thiazolyl group, a 2-benzofuryl group, a 3-benzofuryl group, a 2-benzothienyl group, a 3-benzothienyl group, a 2-quinolyl group, a 3-quinolyl group, a 1-isoquinolyl group, a 2-benzimidazolyl group, a 2-benzoxazolyl group and a 2-benzothiazolyl group.

[0051] R 6 , R 6’ , R 8 , R 8’ , R 10 and R 10’ As the hydrocarbon group and heterocyclic group having 1 to 20 carbon atoms in R 5 , R 5’ , R 7 , R 7’ , R 9 and R 9’ Examples of R include the same groups as the above-mentioned hydrocarbon groups and heterocyclic groups having 1 to 20 carbon atoms. 6 , R 6’ , R 8 , R 8’ , R 10 and R 10’Examples of the amino group in [Compound Name] may have a substituent. For example, at least one hydrogen atom of the amino group may be independently substituted with an alkyl group, aryl group, aralkyl group, alkenyl group, or alkynyl group, such as an amino group. Specifically, N,N-diethylamino group, N,N-diisopropylamino group, N,N-dicyclohexylamino group, N,N-diphenylamino group, N-naphthyl-N-phenylamino group, and N,N-dibenzylamino group, etc. may be mentioned. Further, when having two substituents, they may be bonded to each other to form a ring. Specifically, 1-pyrrolidinyl group and 1-piperidinyl group, etc. may be mentioned.

[0052] Specific examples of the imidazole-2-ylidenes represented by formula (3) include, for example, 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene, 1,3-dimethylimidazole-2-ylidene, 1,3-diisopropylimidazole-2-ylidene, 1,3-di-tert-butylimidazole-2-ylidene, 1,3-dicyclohexylimidazole-2-ylidene, 1,3-bis(2,4,6-trimethylphenyl)imidazole-2-ylidene, 1,3-dimethylbenzimidazole-2-ylidene, 1,3-diisopropylbenzimidazole-2-ylidene, 1,3-di-tert-butylbenzimidazole-2-ylidene, 1,3-dicyclohexylbenzimidazole-2-ylidene, 1,3-bis(2,4,6-trimethylphenyl)benzimidazole-2-ylidene, 1,3,4,5-tetramethylimidazole-2-ylidene, 1,3-diisopropyl-4,5-dimethylimidazole-2-ylidene, 1,3-di-tert-butyl-4,5-dimethylimidazole-2-ylidene, 1,3-dicyclohexyl-4,5-dimethylimidazole-2-ylidene, and 1,3-bis(2,4,6-trimethylphenyl)-4,5-dimethylimidazole-2-ylidene, etc.

[0053] Specific examples of the imidazolinium salt represented by the formula (4) include, for example, 1,3-bis(2,4,6-trimethylphenyl)imidazolinium chloride, 1,3-bis(2,4,6-trimethylphenyl)imidazolinium tetrafluoroborate, 1,3-bis(2,6-diisopropylphenyl)imidazolinium chloride, 1,3-bis(2,6-diisopropylphenyl)imidazolinium tetrafluoroborate, 1,3-bis(1-adamantyl)imidazolinium chloride, 1,3-bis(1-adamantyl)imidazolinium tetrafluoroborate, 1,3-di(tert-butyl)imidazolinium tetrafluoroborate, 1,3-di(isopropyl)imidazolinium tetrafluoroborate, etc.

[0054] Specific examples of the imidazolium salt represented by the formula (5) include, for example, 1,3-dicyclohexylimidazolium chloride, 1,3-bis(1-adamantyl)benzimidazolium chloride, 1,3-bis(1-adamantyl)imidazolium chloride, 1,3-bis(1-adamantyl)imidazolium tetrafluoroborate, 1,3-dimesitylimidazolium chloride, 1,3-bis(2,6-diisopropylphenyl)imidazolium chloride, 1,3-di(isopropyl)imidazolium chloride, 1,3-di(isopropyl)imidazolium tetrafluoroborate, 1,3-dimethyl-1H-benzimidazolium iodide, 1,3-dicyclohexylbenzimidazolium iodide, 1,3-di(tert-butyl)benzimidazolium chloride, 1,3-di(tert-butyl)imidazolium tetrafluoroborate, 1,3-di(tert-butyl)imidazolium chloride, 1,3-bis(phenylmethyl)imidazolium chloride, etc.

[0055] Preferable specific examples of the above NHC compound can include the following compounds.

[0056]

Chemical formula

[0057] The compound of formula (3-1) is 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene. The compound of formula (4-1) is 1,3-bis(2,4,6-trimethylphenyl)imidazolinium chloride. The compound of formula (5-1) is 1,3-dicyclohexylimidazolinium chloride. The compound of formula (5-2) is 1,3-bis(1-adamantyl)imidazolinium tetrafluoroborate. The compound of formula (5-3) is 1,3-dimesitylimidazolinium chloride.

[0058] <<Phosphine Compound>> The phosphine compound used as the ligand has a general formula of R 11 R 12 R 13 P (wherein R 11 , R 12 and R 13 are each independently a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms), and there is no particular limitation as long as it is a compound represented by this formula.

[0059] Specific examples of the phosphine compound include, for example, trimethylphosphine, triethylphosphine, triisopropylphosphine, tri-tert-butylphosphine, di-tert-butylmethylphosphine, tricyclopentylphosphine, tricyclohexylphosphine, butyldi-1-adamantylphosphine, tris(1-adamantyl)phosphine, triphenylphosphine, tritolylphosphine, trimesitylphosphine, trinaphthylphosphine, tris(2,4,6-trimethoxyphenyl)phosphine, 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl, 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl, 2-dicyclohexylphosphino-2',6'-diisopropoxybiphenyl and the like. Among these, from the viewpoint of having a bulky and high electron-donating property, tricyclohexylphosphine, di-tert-butylmethylphosphine, butyldi-1-adamantylphosphine and tris(1-adamantyl)phosphine are preferred as the phosphine compound.

[0060] The usage amount of the ligand is 10 molar equivalents or less, preferably 5 molar equivalents or less, and more preferably 3 molar equivalents or less, relative to the palladium source. Also, the usage amount is 0.01 molar equivalent or more, preferably 0.1 molar equivalent or more, and more preferably 1 molar equivalent or more, relative to the palladium source.

[0061] The usage amount of the palladium complex catalyst having a ligand may be a so-called catalytic amount, which is 10 mol% or less, preferably 5 mol% or less, and more preferably 3 mol% or less, relative to the number of moles of p-phenylene sulfide units in the PPS resin. Also, the usage amount is 0.01 mol% or more, preferably 0.1 mol% or more, and more preferably 1 mol% or more, relative to the number of moles of p-phenylene sulfide units in the PPS resin.

[0062] In this embodiment, a base may be mixed and used as a catalyst together with the palladium complex catalyst. By adding the base in a catalytic amount, the reaction activity of the palladium complex catalyst having a ligand is improved, and the reaction tends to proceed with high efficiency. Examples of the base that can be used in this embodiment include organic bases such as trimethylamine, triethylamine, diethylamine, tripropylamine, tributylamine, dibutylamine, piperidine, and pyridine, and inorganic bases such as lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, potassium phosphate, lithium tert-butoxide, sodium tert-butoxide, potassium tert-butoxide, lithium bis(trimethylsilyl)amide, sodium bis(trimethylsilyl)amide, potassium bis(trimethylsilyl)amide, sodium hydroxide, potassium hydroxide, sodium hydride, potassium fluoride, and cesium fluoride. Among them, inorganic bases are preferred, and potassium tert-butoxide is more preferred. The usage amount of the base is not particularly limited, and for example, an equimolar amount may be used relative to the ligand.

[0063] (Reaction conditions) The decomposition reaction of this embodiment is preferably carried out in the presence of a solvent. As the reaction solvent, those that do not inhibit the progress of the reaction are preferred. For example, aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane and heptane, alicyclic hydrocarbons such as cyclohexane, aromatic halogenated hydrocarbons such as chlorobenzene and dichlorobenzene, aliphatic halogenated hydrocarbons such as dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane, trichloroethylene, and tetrachloroethylene, ethers such as diethyl ether, isopropyl ether, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1-methoxy-2-(2-methoxyethoxy)ethane, TBME (t-butyl methyl ether), and CPME (cyclopentyl methyl ether), esters such as ethyl acetate and ethyl propionate, amides such as dimethylformamide, dimethylacetamide, and N-methyl-2-pyrrolidone, amines such as triethylamine, tributylamine, and N,N-dimethylaniline, pyridines such as pyridine and picoline, alcohols such as methanol, ethanol, n-propanol, and ethylene glycol, acetonitrile, dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, acetone, water, etc. can be mentioned. Among these, toluene and xylene are preferred as the solvent. The solvent may be used alone or in combination of two or more.

[0064] The reaction temperature can be selected in the range from room temperature to the boiling point temperature of the reaction solvent used, but is preferably room temperature to 500 °C, more preferably 50 to 300 °C, and still more preferably 50 to 200 °C. The reaction time is 0.1 to 1000 hours, preferably 0.5 to 100 hours. The reaction may be carried out at normal pressure or under pressure, and may be continuous or batchwise. The reaction is preferably carried out in an inert gas atmosphere such as nitrogen or argon.

[0065] When the decomposition method of the present embodiment described above is used, decomposition products can be obtained from PPS resin. The decomposition products may contain compounds other than benzene and bis(trialkylsilyl)sulfide described later. Examples of the compounds other than benzene and bis(trialkylsilyl)sulfide include diphenyl sulfide, 1,4-bis(phenylthio)benzene, bis{4-(phenylthio)phenyl}sulfide, phenyl(trialkylsilyl)sulfide, 1,4-di(trialkylsilylsulfide)benzene, and the like.

[0066] [Method for producing benzene] The method for producing benzene according to the present embodiment includes a step of decomposing PPS resin by the above-described method to obtain benzene.

[0067] Benzene can be obtained by isolating benzene from the decomposition products containing benzene obtained by the above-described method. The method for isolating benzene is not particularly limited, and benzene can be isolated by general methods such as solvent extraction, column chromatography, preparative thin-layer chromatography, preparative liquid chromatography, recrystallization, distillation, sublimation, and the like.

[0068] The production method according to the present embodiment may further include a step of separating and recovering unreacted PPS resin. By recovering and reusing PPS resin, the yield of benzene can be further increased.

[0069] [Method for producing bis(trialkylsilyl)sulfide] The method for producing bis(trialkylsilyl)sulfide according to the present embodiment includes a step of decomposing PPS resin by the above-described method to obtain bis(trialkylsilyl)sulfide.

[0070] The alkyl in bis(trialkylsilyl)sulfide is, for example, an alkyl having 1 to 20 carbon atoms. Examples of bis(trialkylsilyl)sulfide include bis(trimethylsilyl)sulfide, bis(triethylsilyl)sulfide, bis(tributylsilyl)sulfide, and the like. Bis(trialkylsilyl)sulfide is known to be a compound with high resource utilization value that can be used, for example, as a raw material for semiconductor particles.

[0071] Bis(trialkylsilyl)sulfide is obtained by isolating bis(trialkylsilyl)sulfide from the decomposition products containing bis(trialkylsilyl)sulfide obtained by the above-mentioned method. The method for isolating bis(trialkylsilyl)sulfide is not particularly limited, and bis(trialkylsilyl)sulfide can be isolated by general methods such as solvent extraction, column chromatography, preparative thin-layer chromatography, preparative liquid chromatography, recrystallization, distillation, sublimation, etc.

[0072] The production method according to this embodiment may further include a step of separating and recovering the unreacted PPS resin. By recovering and reusing the PPS resin, the yield of bis(trialkylsilyl)sulfide can be further increased.

Examples

[0073] Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. (Example 1)

[0074]

Chemical formula

[0075] In an argon atmosphere, 10.8 mg (number of moles of p-phenylene sulfide unit = 0.1 mmol) of polyphenylene sulfide (PPS) resin, 46.4 mg (0.4 mmol) of triethylsilane, allyl palladium (II) chloride dimer ([Pd(allyl)Cl]2) as a palladium source, and butyldi-1-adamantylphosphine (PBu(1-adamantyl)2) as a ligand were added to 0.5 ml of xylene in amounts of 1 mol% each based on the number of moles of the p-phenylene sulfide unit of the PPS resin, and the mixture was stirred at 150 °C for 15 hours for reaction. After the reaction time elapsed, the reaction product was allowed to cool naturally to room temperature, 3.7 mg of undecane was added as an internal standard substance, and benzene and bis(triethylsilyl)sulfide (BTESiS) were quantified using a gas chromatograph FID analyzer (equipment name: GC-2014, manufactured by Shimadzu Corporation).

[0076] The yield of the decomposition product was calculated using the following formula. The results are shown in Table 1. Yield [%] = {number of moles of decomposition product [mol] / number of moles of p-phenylene sulfide unit of the charged PPS resin [mol]} × 100

[0077] (Example 2) The same operation as in Example 1 was carried out except that tris(1-adamantyl)phosphine (P(1-adamantyl)3) was used instead of butyldi-1-adamantylphosphine (PBu(1-adamantyl)2) as the ligand. The results are shown in Table 1.

[0078] (Example 3) The same operation as in Example 1 was carried out except that 1,3-dimesitylimidazolium chloride (IMes·HCl) was used instead of butyldi-1-adamantylphosphine (PBu(1-adamantyl)2) as the ligand, and potassium tert-butoxide (KOtBu) was added in an amount of 1 mol% based on the number of moles of the p-phenylene sulfide unit of the PPS resin as the base. The results are shown in Table 1.

[0079] (Example 4) Except that 1,3-bis(2,4,6-trimethylphenyl)imidazolinium chloride (SIMes·HCl) was used instead of butyldi-1-adamantylphosphine (PBu(1-adamantyl)2) as the ligand, and potassium tert-butoxide (KOtBu) was added at 1 mol% based on the number of moles of p-phenylene sulfide units of the PPS resin as the base, the same operations as in Example 1 were carried out. The results are shown in Table 1.

[0080] (Example 5) Except that 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) was used instead of butyldi-1-adamantylphosphine (PBu(1-adamantyl)2) as the ligand, the same operations as in Example 1 were carried out. The results are shown in Table 1.

[0081] (Example 6) Except that 1,3-bis(1-adamantyl)imidazolium tetrafluoroborate (IAd·HBF4) was used instead of butyldi-1-adamantylphosphine (PBu(1-adamantyl)2) as the ligand, and potassium tert-butoxide (KOtBu) was added at 1 mol% based on the number of moles of p-phenylene sulfide units of the PPS resin as the base, the same operations as in Example 1 were carried out. The results are shown in Table 1.

[0082] (Example 7) Except that 1,3-dicyclohexylimidazolium chloride (IcHex·HCl) was used instead of butyldi-1-adamantylphosphine (PBu(1-adamantyl)2) as the ligand, and potassium tert-butoxide (KOtBu) was added at 1 mol% based on the number of moles of p-phenylene sulfide units of the PPS resin as the base, the same operations as in Example 1 were carried out. The results are shown in Table 1.

[0083] (Examples 8 and 9) Except that the reaction temperatures and reaction times described in Table 1 were respectively changed, the same operations as in Example 7 were respectively carried out. The results are shown in Table 1.

[0084] (Example 10) The same operation as in Example 7 was carried out except that palladium(II) acetate (Pd(OAc)2) was used instead of allylpalladium(II) chloride dimer ([Pd(allyl)Cl]2) as the palladium source. The results are shown in Table 1.

[0085] (Example 11) The same operation as in Example 7 was carried out except that bis(dibenzylideneacetone)palladium(0) (Pd(dba)2) was used instead of allylpalladium(II) chloride dimer ([Pd(allyl)Cl]2) as the palladium source. The results are shown in Table 1.

[0086] (Example 12) Under an argon atmosphere, 10.8 mg of polyphenylene sulfide (PPS) resin (number of moles of p-phenylene sulfide unit = 0.1 mmol), 46.4 mg of triethylsilane (0.4 mmol), and chloro[[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](N,N-dimethylbenzylamine)palladium(II)] (trade name: Singacycle-A1, manufactured by Tokyo Chemical Industry Co., Ltd.) as a palladium complex catalyst having a ligand were added in an amount of 1 mol% based on the number of moles of the p-phenylene sulfide unit of the PPS resin to 0.5 ml of xylene, and the mixture was stirred at a reaction temperature of 150 °C for 15 hours for reaction. After the reaction time elapsed, the reaction product was allowed to cool naturally to room temperature, 3.7 mg of undecane was added as an internal standard substance, and benzene and bis(triethylsilyl)sulfide (BTESiS) were quantified using a gas chromatograph FID analyzer (equipment name: GC-2014, manufactured by Shimadzu Corporation). The yield of the decomposition product was calculated by the calculation formula described in Example 1. The results are shown in Table 1.

[0087] (Comparative Example 1) [Chemical formula]

[0088] In an argon atmosphere, 10.8 mg (number of moles of p-phenylene sulfide unit = 0.1 mmol) of polyphenylene sulfide (PPS) resin, 46.4 mg (0.4 mmol) of triethylsilane, and 10 mol% of bis(1,5-cyclooctadiene)nickel(0) (Ni(cod)2), a nickel complex catalyst having a ligand as a catalyst, were added to 0.5 ml of xylene with respect to the number of moles of p-phenylene sulfide unit of the PPS resin. The mixture was stirred at a reaction temperature of 150 °C for 15 hours to effect the reaction. After the lapse of the reaction time, the reaction product was allowed to cool naturally to room temperature, 3.7 mg of undecane was added as an internal standard substance, and benzene and bis(triethylsilyl)sulfide (BTESiS) were quantified using a gas chromatograph FID analyzer (equipment name: GC-2014, manufactured by Shimadzu Corporation). The yield of the decomposition product was calculated using the calculation formula described in Example 1. The results are shown in Table 2.

[0089] (Comparative Example 2) The same operation as in Comparative Example 1 was carried out except that palladium carbon (Pd / C) in which palladium metal was dispersed on activated carbon as a carrier was added in an amount of 3 mol% with respect to the number of moles of p-phenylene sulfide unit of the PPS resin instead of adding 10 mol% of bis(1,5-cyclooctadiene)nickel(0) (Ni(cod)2) as a catalyst with respect to the number of moles of p-phenylene sulfide unit of the PPS resin. The results are shown in Table 2.

[0090] (Comparative Example 3) The same operation as in Comparative Example 1 was carried out except that palladium(II) chloride (PdCl2) was added in an amount of 3 mol% with respect to the number of moles of p-phenylene sulfide unit of the PPS resin instead of adding 10 mol% of bis(1,5-cyclooctadiene)nickel(0) (Ni(cod)2) as a catalyst with respect to the number of moles of p-phenylene sulfide unit of the PPS resin. The results are shown in Table 2.

[0091]

Table 1

[0092]

Table 2

[0093] As shown in Tables 1 and 2, the methods of Examples 1 to 12 using a palladium complex catalyst having a hydrosilane and a ligand were found to be able to decompose the PPS resin under very mild conditions (reaction temperature 100 °C or 150 °C) and obtain benzene and bis(triethylsilyl)sulfide in high yields. On the other hand, the methods of Comparative Examples 1 to 3 without using a palladium complex catalyst having a ligand were unable to efficiently decompose the PPS resin and could not obtain benzene and bis(triethylsilyl)sulfide in high yields.

[0094] Examples 1 to 7 show that when an N-heterocyclic carbene compound is used as a ligand, there is a tendency to efficiently decompose the PPS resin. Examples 8 and 9 show that even when the reaction temperature is 100 °C, the PPS resin can be efficiently decomposed, and there is a tendency to further decompose the PPS resin by increasing the reaction time. Examples 7, 10 and 11 show that when allylpalladium(II) chloride dimer ([Pd(allyl)Cl]2) is used as a palladium source, there is a tendency to efficiently decompose the PPS resin.

Claims

1. A method for decomposing a polyphenylene sulfide resin, comprising a step of reacting a polyphenylene sulfide resin with a hydrosilane in the presence of a palladium complex catalyst having a ligand, wherein the hydrosilane is a compound represented by the following formula (2). 【Chemical 1】 (In formula (2), R ２ to R ４ each independently represents an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, an alkynyl group having 2 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a trimethylsilyl group, or a triethylsilyl group, which has no substituent.)

2. The method for decomposing a polyphenylene sulfide resin according to claim 1, wherein the ligand is an N-heterocyclic carbene compound or a phosphine compound.

3. The palladium source of the palladium complex catalyst includes at least one selected from the group consisting of allylpalladium (II) chloride dimer, (2-butenyl)chloropalladium dimer, palladium (π-cinnamyl) chloride dimer, palladium (II) trifluoroacetate, palladium (II) trimethylacetate, palladium (II) acetate, palladium (II) chloride, palladium (II) nitrate, palladium (II) bromide, palladium (II) iodide, palladium (II) sulfate, palladium (II) oxide, palladium (II) tetrafluoroborate tetrakis(acetonitrile) complex, tetrakis(triphenylphosphine)palladium(0), palladium (II) acetylacetonate, palladium (II) hexafluoroacetylacetonate, chloro(1,5-cyclooctadiene)methylpalladium(II), (η5-2,4-cyclopentadien-1-yl)[(1,2,3-η)-1-phenyl-2-propenyl]palladium, bis(benzonitrile)palladium(II) bromide, bis(dibenzylideneacetone)palladium(0), tris(dibenzylideneacetone)dipalladium(0), dichloro(1,5-cyclooctadiene)palladium(II), dichloro(norbornadiene)palladium(II), dichlorobis(acetonitrile)palladium(II) and dichlorobis(benzonitrile)palladium(II). The method for decomposing a polyphenylene sulfide resin according to claim 1 or 2.

4. The method for decomposing a polyphenylene sulfide resin according to claim 1, wherein the palladium complex catalyst having the ligand contains at least one selected from the group consisting of chloro[[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](N,N-dimethylbenzylamine)palladium(II)], chloro[(1,3-dimesitylimidazol-2-ylidene)(N,N-dimethylbenzylamine)palladium(II)], chloro[[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](acetanilide)palladium(II)], chloro[[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](4'-methoxyacetanilide)palladium(II)], and chloro[[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](N,N-dimethyl-3,5-dimethoxybenzylamine)palladium(II)].

5. The method for decomposing a polyphenylene sulfide resin according to any one of claims 1 to 4, wherein the hydrosilane contains at least one selected from the group consisting of trimethylsilane, triethylsilane, tert-butyldimethylsilane, trimethoxysilane, triethoxysilane, diethoxymethylsilane, dimethoxymethylsilane, ethoxydimethylsilane, and tris(trimethylsilyl)silane.

6. The method for decomposing a polyphenylene sulfide resin according to any one of claims 1 to 5, wherein the reaction temperature in the step of reacting is 50 to 300 °C.

7. A method for producing benzene, comprising a step of decomposing the polyphenylene sulfide resin by the method according to any one of claims 1 to 6 to obtain benzene.

8. A method for producing bis(trialkylsilyl) sulfide, comprising a step of decomposing the polyphenylene sulfide resin by the method according to any one of claims 1 to 6 to obtain bis(trimethylsilyl) sulfide, bis(triethylsilyl) sulfide, or bis(tributylsilyl) sulfide.

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