Polyphenylene ether, method for producing the same, thermosetting composition, prepreg, and laminate

Abstract

A polyphenylene ether which is characterized by comprising a repeating unit that is derived from a phenol of formula (1), a repeating unit that is derived from a phenol of formula (2) and a structural unit that is derived from a phenol of formula (3).

Description

Technical Field

[0001] The present invention relates to polyphenylene ether, a method for producing the same, a thermosetting composition, a prepreg, and a laminate.

Background Art

[0002] Polyphenylene ether (hereinafter also referred to as "PPE") has excellent high-frequency characteristics, flame retardancy, and heat resistance, and is therefore widely used as a material for products and parts in the electrical and electronic fields, the automotive field, the food and packaging fields, and other various industrial material fields. In particular, in recent years, taking advantage of its low dielectric characteristics and heat resistance, its application as an electronic material such as a substrate material and as a modifier in various applications has been promoted.

[0003] However, generally, high molecular weight polyphenylene ether having a repeating unit derived from monohydric phenol represented by 2,6-dimethylphenol dissolves in a highly toxic solvent such as chloroform, but is difficult to dissolve at high concentrations in aromatic solvents such as toluene known as good solvents at room temperature, and is insoluble in ketone solvents such as methyl ethyl ketone. Therefore, for example, when used as a wiring board material, it is difficult to handle resin varnish solutions such as toluene and methyl ethyl ketone.

[0004] °>Patent Document 1 discloses that polyphenylene ether having a low molecular weight and a specific particle size is excellent in solubility in solvents such as methyl ethyl ketone. Patent Document 2 describes a modified polyphenylene ether compound having a predetermined polyphenylene ether moiety in its molecular structure and having at least one p-vinylbenzyl group, m-vinylbenzyl group, or the like at this molecular terminal. Furthermore, Patent Document 3 describes a modified polymer having a polyphenylene ether moiety in its molecular structure and having a methacryl group at this molecular terminal.

[0005] In order to easily ensure the heat resistance of polyphenylene ether for substrate applications, like the compounds disclosed in Patent Document 2 and Patent Document 3, a method of increasing the crosslinking density of a thermosetting polyphenylene ether and a thermosetting crosslinking agent is effective. Therefore, a polyfunctional polyphenylene ether having multiple terminals in one molecule is required. For this reason, low-molecular polyfunctional polyphenylene ethers obtained by polymerization in the presence of a polyfunctional phenol compound have been proposed in Patent Documents 4, 5, and 6. Since these polyfunctional polyphenylene ethers have a branched structure, at the same molecular weight, the solution viscosity is lower than that of a linear polymer, and they have higher fluidity than a linear polymer at the same molecular weight. Therefore, a polymer with a relatively high molecular weight can be used in the curing process, and an improvement in the physical properties of the cured product can be expected. In addition, since the number of crosslinking reaction points increases, in addition to contributing to the above-mentioned improvement in physical properties, it can also be expected that the crosslinking reaction control will be easier to perform.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0007] As mentioned above, while documents such as Patent Document 1 disclose methods for producing low-molecular-weight polyphenylene ethers and polyfunctional polyphenylene ethers to improve the solvent solubility of polyphenylene ethers, simply reducing the molecular weight of polyphenylene ether does not significantly improve its solubility at room temperature in common ketone solvents such as methyl ethyl ketone, and is still insufficient.

[0008] This invention has been made in view of the above problems, and aims to provide a polyphenylene ether with excellent solubility in general-purpose ketone solvents and a method for producing the same. It also aims to provide a thermosetting composition, a prepreg, and a laminate using the polyphenylene ether. [Means for solving the problem]

[0009] In other words, the present invention is as follows: [1] It includes a repeating unit derived from phenol of formula (1) below, a repeating unit derived from phenol of formula (2) below, and a structural unit derived from phenol of formula (3) below. It is a polyphenylene ether, which is an oxidation polymerization product. The phenol in formula (3) above is A phenol compound having two phenol units in its molecule, selected from the group consisting of 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 4,4'-methylenebis(2,6-dimethylphenol), bis(4-hydroxy-3-methylphenyl)sulfide, bis(4-hydroxy-3,5-dimethylphenyl)sulfone, α,α'-bis(4-hydroxy-3,5-dimethylphenyl)-1,4-diisopropylbenzene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane, and 1,1-bis(2-methyl-4-hydroxy-5-t-butylphenyl)butane, or 4,4'-[(3-hydroxyphenyl)methylene]bis(2,6-dimethylphenol), 4,4'-[(3-hydroxyphenyl)methylene]bis(2,3,6-trimethylphenol), 4,4'-[(4-hydroxyphenyl)methylene]bis(2,6-dimethylphenol), 4,4'-[(4-hydroxyphenyl)methylene]bis(2,3,6-trimethylphenol), 4,4'-[(2-hydroxy-3-methoxyphenyl)methylene]bis(2,6-dimethylphenol), 4,4'-[(3,4-dihydroxyphenyl)methylene [Len]bis(2,6-dimethylphenol), 4,4'-[(3,4-dihydroxyphenyl)methylene]bis(2,3,6-trimethylphenol), 2,2'-[(4-hydroxyphenyl)methylene]bis(3,5,6-trimethylphenol), 4,4'-[4-(4-hydroxyphenyl)cyclohexylidene]bis(2,6-dimethylphenol), 4,4'-[(2-hydroxyphenyl)methylene]-bis(2,3,6-trimethylphenol), 4,4'-[1-[4-[1-(4-hydroxy-3,5-dimethylphenyl)-1- [methylethyl]phenyl]ethylidene]bis(2,6-dimethylphenol], 4,4'-[1-[4-[1-(4-hydroxy-3-fluorophenyl)-1-methylethyl]phenyl]ethylidene]bis(2,6-dimethylphenol], 2,6-bis[(4-hydroxy-3,5-dimethylphenyl)ethyl]-4-methylphenol, 2,6-bis[(4-hydroxy-2,3,6-trimethylphenyl)methyl]-4-methylphenol, 2,6-bis[(4-hydroxy-3,5,6-trimethylphenyl)methyl]-4-ethylpheno Lu, 2,4-bis[(4-hydroxy-3-methylphenyl)methyl]-6-methylphenol, 2,6-bis[(4-hydroxy-3-methylphenyl)methyl]-4-methylphenol, 2,4-bis[(4-hydroxy-3-cyclohexylphenyl)methyl]-6-methylphenol, 2,4-bis[(4-hydroxy-3-methylphenyl)methyl]-6-cyclohexylphenol, 2,4-bis[(4-hydroxy-2,3,6-trimethylphenyl)methyl]-6-cyclohexylphenol, 3,6-bis[(4-hydroxy-3,5-dimethylphenyl)methyl]-1,2-benzenediol, 4,6-bis[(4-hydroxy-3,5-dimethylphenyl)methyl]-1,3-benzenediol, 2,4,6-tris[(4-hydroxy-3,5-dimethylphenyl)methyl]-1,3-benzenediol, 2,4,6-tris[(2-hydroxy-3,5-dimethylphenyl)methyl]-1,3-benzenediol, 2,2'-methylenebis[6-[(4 / 2-hydroxy-2,5 / 3,6-dimethylphenyl)methyl [(4-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol], 2,2'-methylenebis[6-[(4-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol], 2,2'-methylenebis[6-[(4 / 2-hydroxy-2,3,5 / 3,4,6-trimethylphenyl)methyl]-4-methylphenol], 2,2'-methylenebis[6-[(4-hydroxy-2,3,5-trimethylphenyl)methyl]-4-methylphenol], 4,4'-methylenebis[ 2-[(2,4-dihydroxy-3-methylphenyl)methyl]-3,6-dimethylphenol], 6,6'-methylenebis[4-[(4-hydroxy-3,5-dimethylphenyl)methyl]-1,2,3-benzenetriol], 4,4'-cyclohexyllidenbis[2-cyclohexyl-6-[(4-hydroxy-3,5-dimethylphenyl)methyl]phenol], 4,4'-cyclohexyllidenbis[2-cyclohexyl-6-[(4-hydroxy-2-methyl- A phenol compound having three or more phenol units in its molecule, selected from the group consisting of 5-cyclohexylphenyl)methylphenol, 4,4',4'',4'''-(1,2-ethanediylidene)tetrakis(2,6-dimethylphenol), 4,4',4'',4'''-(1,4-phenylenedimethylidene)tetrakis(2,6-dimethylphenol), and 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, The number-average molecular weight in terms of polystyrene is 500 to 15,000. A polyphenylene ether characterized by the following features. [ka] (In formula (1), R41 , , , 3 , , , 3 , , 43 , , 42 , 41 , 21 , , , , 21 , , is each independently an optionally substituted saturated hydrocarbon group having 1 to 6 carbon atoms, an optionally substituted aryl group having 6 to 12 carbon atoms, or a halogen atom, and R 12 is each independently the hydrogen atom, an optionally substituted hydrocarbon group having 1 to 6 carbon atoms, an optionally substituted aryl group having 6 to 12 carbon atoms,or a halogen atom.)<0000၁၄၄><0000၁၄၅>[Chemical formula][[ID=-7]]<0000၁၄၆><0000၁၄၇><0000၁၄၈> [[ID=1O]](In formula (2), R 22 is each independently the hydrogen atom, an optionally substituted saturated or unsaturated hydrocarbon group having from 1 to ~20 carbon atoms, an optionally substituted aryl group having 6 to 12 carbon atoms, or a halogen atom, and two Rs[[ID=ー{13}]] 22 are not both hydrogen atoms, and R<00০০০০৫>[[ID═16]]is a partial structure represented by the following formula (4).)<0000၁၄၉> [[ID=-18]]<००оо२५०> [Chemical formula]<0000၁၅၁> <0000၁၅၂> <0000၁၅з> (In formula (3), X is an arbitrary linking group having a valency,a is an integer of 2 to 6, and R 3 is either a linear alkyl group having from 1 to 8 carbon atoms or a partial structure represented by the following formula (4), and is bonded to at least one of the carbon atoms at the 2-position or the 6-position with the carbon atom to which -OH is bonded as the 1-position on the benzene ring, and k is each independently an integer of 1 to 4.)<00OO၁း၄> <७७७७१५५> [[ID={28}]]{[Chemical formula]} <00००१५६> [[ID=зо]]<0000၁၅۷> <0000၁၅۸> )(In formula (4), R [[ID=m 41 is each independently an optionally substituted linear alkyl group having 1 to 8 carbon atoms, or a cyclic alkyl structure having 3 to 8 carbon atoms to which two Rs<000८००८>[[end]]are bonded, and R <000000۹>[[ends]]is each independently an optionally subtracted diene group having 1 to 8 carbon atoms, bls each independently 0 or 1, and R 43 [[ends]][[ID=4{}]]is either the hydrogen atom, an optionally substituted alkyl group having 1 to 8 carbon atoms, or an optionally substituted phenyl group.) [[ID=4{1}]] [[ends]] The partial structure represented by the formula (4 in which R 21 [[ends]]in the formula (2) and R<२२०००१२>[[ends]]The substructures represented by formula (4) above may be the same or different. [2] In at least one of the repeating units derived from phenol in formula (2), R 21 The polyphenylene ether described in [1], wherein is a t-butyl group. [3] A polyphenylene ether according to [1] or [2], having at least one substructure selected from the group consisting of the following formulas (5), (6), (7), and (8). [ka] [ka] [ka] (In formula (7), R 7 (This is a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, and the saturated or unsaturated hydrocarbon may have substituents to the extent that it satisfies the condition of having 1 to 10 carbon atoms.) [ka] (In formula (8), R 8 R is a saturated or unsaturated divalent hydrocarbon group having 1 to 10 carbon atoms, and the saturated or unsaturated divalent hydrocarbon may have substituents to the extent that it satisfies the condition of having 1 to 10 carbon atoms. 9 (This is a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, and the saturated or unsaturated hydrocarbon may have substituents to the extent that it satisfies the condition of having 1 to 10 carbon atoms.) [4] A method for producing a polyphenylene ether according to any one of [1] to [3], comprising the step of carrying out oxidative polymerization of the phenol of formula (1), the phenol of formula (2), and the phenol of formula (3). [5] A thermosetting polyphenylene ether containing any of the polyphenylene ethers described in [1] to [4]. sex composition. [6] The base material and the thermosetting method described in [5]. sex A prepreg is a composite containing a composition. [7] The prepreg according to [6], wherein the substrate is glass cloth. [8] A laminate comprising a cured prepreg according to [6] or [7] and a metal foil. [Effects of the Invention]

[0010] According to the present invention, a polyphenylene ether exhibiting excellent solubility in general-purpose ketone solvents and a method for producing the same can be provided. Furthermore, a thermosetting composition, a prepreg, and a laminate using the polyphenylene ether can be provided. [Modes for carrying out the invention]

[0011] The following describes in detail embodiments for carrying out the present invention (hereinafter referred to as "this embodiment"). This embodiment is an example for illustrating the present invention, and the present invention is not limited to this embodiment. The present invention can be appropriately modified and implemented within the scope of its gist.

[0012] In this embodiment, polyphenylene ether in which some or all of the hydroxyl groups contained in the polyphenylene ether have been modified may be simply referred to as "polyphenylene ether." Therefore, when the term "polyphenylene ether" is used, it includes both unmodified polyphenylene ether and modified polyphenylene ether, unless otherwise inconsistent. In this specification, A(numerical value) to B(numerical value) means A or greater and B or less. In this specification, substituents include, for example, saturated or unsaturated hydrocarbon groups having 1 to 10 carbon atoms, aryl groups having 6 to 10 carbon atoms, and halogen atoms.

[0013] <Polyphenylene ether> The polyphenylene ether of this embodiment is a polyphenylene ether comprising a repeating unit derived from the phenol of formula (1) below, a repeating unit derived from the phenol of formula (2) below, and a structural unit derived from the phenol of formula (3) below, and the repeating unit in the compound may consist only of the repeating unit derived from the phenol of formula (1) below, the repeating unit derived from the phenol of formula (2) below, and the structural unit derived from the phenol of formula (3) below. [ka] (In formula (1), R 11 Each of these is independently a saturated hydrocarbon group having 1 to 6 carbon atoms which may be substituted, an aryl group having 6 to 12 carbon atoms which may be substituted, or a halogen atom, and R 12 Each of these is independently a hydrogen atom, an optionally substituted C1-C6 hydrocarbon group, an optionally substituted C6-C12 aryl group, or a halogen atom. [ka] (In formula (2), R 22 Each of these is independently a hydrogen atom, an optionally substituted saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms, an optionally substituted aryl group having 6 to 12 carbon atoms, or a halogen atom, and the two R 22 Both are not hydrogen atoms, R 21 This is a substructure represented by the following equation (4). [ka] (In equation (3), X is any a-valent linking group, a is an integer from 2 to 6, R 3 (This is either a linear alkyl group having 1 to 8 carbon atoms or a substructure represented by the following formula (4), where the carbon atom of the benzene ring to which the -O- is bonded is considered as position 1, and it is bonded to at least one of the carbon atoms at positions 2 or 6, with k being an integer from 1 to 4.) [ka] (In formula (4), R41 Each of these is independently a linear alkyl group having 1 to 8 carbon atoms, which may be substituted, or two R 41 It is a cyclic alkyl structure with 1 to 8 carbon atoms bonded together, R 42 Each is independently an alkylene group having 1 to 8 carbon atoms, which may be substituted, and each is independently 0 or 1, R 43 (This is one of the following: a hydrogen atom, an optionally substituted C1-C8 alkyl group, or an optionally substituted phenyl group.)

[0014] In the above equation (1), R 11 Each of these is preferably independently a saturated hydrocarbon group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, more preferably a methyl group or a phenyl group, and even more preferably a methyl group. In formula (1), the two R 11 It is preferable that both have the same structure. The above R 11 Substituents for saturated hydrocarbon groups having 1 to 6 carbon atoms and aryl groups having 6 to 12 carbon atoms include saturated or unsaturated hydrocarbon groups having 1 to 10 carbon atoms, aryl groups having 6 to 10 carbon atoms, and halogen atoms.

[0015] In the above equation (1), R 12 Each of them is preferably a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, and more preferably a hydrogen atom or a methyl group. In formula (1), the two R 12 These are preferably different, and more preferably one is a hydrogen atom and the other is a hydrocarbon group having 1 to 6 carbon atoms (preferably a methyl group). The above R 12 Substituents for the hydrocarbon group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include saturated or unsaturated hydrocarbon groups having 1 to 10 carbon atoms, aryl groups having 6 to 10 carbon atoms, and halogen atoms.

[0016] In equation (2) above, R 22Each of these is preferably independently a hydrogen atom, a saturated or unsaturated hydrocarbon group having 1 to 15 carbon atoms, or an aryl group having 6 to 12 carbon atoms that may be substituted with an alkyl group having 1 to 6 carbon atoms; more preferably a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, or an aryl group having 6 to 10 carbon atoms that may be substituted with an alkyl group having 1 to 6 carbon atoms; and even more preferably a hydrogen atom or a methyl group. In formula (2), the two R 22 It is preferable that they are different, and more preferably that one is a hydrogen atom and the other is a hydrocarbon group having 1 to 6 carbon atoms (preferably a methyl group). The above R 22 Substituents in saturated or unsaturated hydrocarbon groups having 1 to 20 carbon atoms and aryl groups having 6 to 12 carbon atoms include saturated or unsaturated hydrocarbon groups having 1 to 10 carbon atoms, aryl groups having 6 to 10 carbon atoms, and halogen atoms.

[0017] In the above equation (3), R 3 Each of these is independently one of a linear alkyl group having 1 to 8 carbon atoms, such as a methyl group, an ethyl group, or an n-propyl group, and one of the substructures represented by formula (4) above, and it is preferable that they are a methyl group or the structure of formula (4) above. Each of the a substructures may be the same or different. In particular, from the viewpoint of obtaining a polyphenylene ether with even better solubility in the solvent and an even higher glass transition temperature after curing, it is preferable that each of the a substructures is the same. In the above formula (3), k is an integer from 1 to 4, and preferably an integer from 2 to 4. R 3 The R bonded to the benzene ring is positioned at position 2 and / or 6, with the carbon atom to which the -O- bond is attached being at position 1. 3 When is a linear alkyl group having 1 to 8 carbon atoms, it is preferable that it is bonded to both the 2nd and 6th positions, and R bonded to the 2nd and / or 6th positions 3 If the substructure is represented by formula (4), it is preferable that it is bonded to only one of either the 2nd or 6th position. R in equation (2) above 21 and R in equation (3) above 3If both are substructures (functional groups) represented by formula (4) (i.e., both the phenol compound represented by formula (2) and the phenol compound represented by formula (3) are substituted with the substructures (functional groups) represented by formula (4)), the structures of each substructure (functional group) represented by formula (4) may be the same or different.

[0018] In formula (3) above, X is any a-valent linking group and is not particularly limited, but examples include hydrocarbon groups such as chain hydrocarbons and cyclic hydrocarbons; hydrocarbon groups containing one or more atoms selected from nitrogen, phosphorus, silicon, and oxygen; atoms such as nitrogen, phosphorus, and silicon; or groups combining these. X may be a linking group excluding single bonds. X may be a linking group that links a substructures together. As for X above, R is connected via a single bond or an ester bond, etc. 3 R 3 R 3 Examples include α-valent heterocyclic skeletons bonded to a benzene ring. Here, the alkyl skeleton is not particularly limited, but examples include a chain hydrocarbon with 2 to 6 carbon atoms and at least a branched chain (e.g., a chain saturated hydrocarbon) in which the branched ends are directly bonded to the benzene ring of the substructure (it is sufficient that a benzene ring is bonded to a branched end, and there may be branched ends that are not bonded to a benzene ring). Also, the aryl skeleton is not particularly limited, but examples include a benzene ring, a mesitylene group, or a 2-hydroxy-5-methyl-1,3-phenylene group bonded via a single bond or an alkyl chain, R 3 Examples include skeletons that bond to a benzene ring to which R is attached. Furthermore, there are no particular limitations on the heterocyclic skeleton, but for example, a triazine ring is bonded via a single bond or alkyl chain, 3 Examples include skeletons that bond to the benzene ring to which the compound is attached.

[0019] In the above formula (3), a is an integer between 2 and 6, preferably between 2 and 4.

[0020] The substructure represented by formula (4) above is preferably a group containing secondary and / or tertiary carbons, such as an isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, tert-amyl group, 2,2-dimethylpropyl group, cyclohexyl group, or a structure having a phenyl group at its terminal, more preferably a tert-butyl group or a cyclohexyl group, and even more preferably a tert-butyl group. The above R 41 Substituents in a linear alkyl group having 1 to 8 carbon atoms, the above R 42 Substituents in the alkylene group having 1 to 8 carbon atoms, and the above R 43 Examples of substituents on the C1-C8 alkyl group and phenyl group include C1-C10 saturated or unsaturated hydrocarbon groups, C6-C10 aryl groups, and halogen atoms. As mentioned above, R in equation (2) 21 is a substructure represented by equation (4), and R in equation (3) 3 These substructures may be represented by equation (4), and these substructures represented by equation (4) may be the same or different.

[0021] In this embodiment, the structure of polyphenylene ether can be identified by analyzing it using techniques such as NMR and mass spectrometry. A specific method for identifying the structure of polyphenylene ether involves performing field desorption mass spectrometry (FD-MS), which is known to be less prone to fragmentation, and estimating the repeating units based on the spacing of the detected ions. Furthermore, a method for estimating the structure of polyphenylene ether can be proposed by combining electron ionization (EI) peak analysis of fragment ions with structural analysis by NMR.

[0022] In this embodiment, from the viewpoint of obtaining a polyphenylene ether with excellent solvent solubility and low dielectric loss tangent, the repeating units derived from phenol of formula (2) are preferably 10 mol% or more, more preferably 15 mol% or more, and even more preferably 20 mol% or more, relative to a total of 100 mol% of the repeating units derived from phenol of formula (1) and the repeating units derived from phenol of formula (2). Furthermore, the repeating units derived from phenol of formula (2) are preferably 95 mol% or less, more preferably 90 mol% or less, and even more preferably 85 mol% or less. From a similar viewpoint, the repeating units derived from phenol of formula (1) are preferably 90 mol% or less, more preferably 85 mol% or less, and even more preferably 80 mol% or less. Furthermore, the repeating units derived from phenol of formula (1) are preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 15 mol% or more.

[0023] In this embodiment, with respect to 100 mol% of the monomer units contained in the polyphenylene ether (for example, all monomer units derived from phenol contained in the polyphenylene ether), the total molar ratio of the repeating units derived from phenol of formula (1) and the repeating units derived from phenol of formula (2) is preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 85 mol% or more. Furthermore, the above total molar ratio is preferably 99.9 mol% or less, more preferably 99 mol% or less, and even more preferably 98 mol% or less.

[0024] In this embodiment, with respect to 100 mol% of monomer units contained in the polyphenylene ether (for example, all monomer units derived from phenol contained in the polyphenylene ether), the molar ratio of the structural unit derived from phenol of formula (3) is preferably 0.1 mol% or more, more preferably 1 mol% or more, even more preferably 2 mol% or more, and from the viewpoint of monomer reactivity, preferably 30 mol% or less, more preferably 20 mol% or less, and even more preferably 15 mol% or less. Furthermore, the molar ratio of the total repeating units derived from phenol of formula (1) and the repeating units derived from phenol of formula (2) to the structural units derived from phenol of formula (3) (total repeating units derived from phenol of formula (1) and the repeating units derived from phenol of formula (2): structural units derived from phenol of formula (3)) is preferably 99.5:0.5 to 70:30, more preferably 99:1 to 80:20, even more preferably 98.5:1.5 to 85:15, and particularly preferably 98:2 to 92:8.

[0025] The repeating unit derived from the phenol of formula (1) contained in the polyphenylene ether of this embodiment may be one type or multiple types. Furthermore, the repeating unit derived from the phenol of formula (2) contained in the polyphenylene ether of this embodiment may be one type or multiple types. Furthermore, the repeating unit derived from the phenol of formula (3) contained in the polyphenylene ether of this embodiment may be one type or multiple types. The proportions of the repeating units derived from phenol in formula (1), the repeating units derived from phenol in formula (2), and the structural units derived from phenol in formula (3) are, for example, 1 1H NMR, 13 It can be determined using analytical techniques such as 13C NMR, and more specifically, it can be measured by the method described in the examples below.

[0026] Since the phenol in formula (1) does not have an unsubstituted ortho position (i.e., hydrogen atoms are not bonded to the two ortho carbon atoms of the carbon atom to which the hydroxyl group is bonded), it can react with other phenolic monomers only at the phenolic hydroxyl group and the para carbon atom. Therefore, the repeating units derived from formula (1) include repeating units having the structure of formula (9) below. [ka] (In formula (9), R 11 and R 12 This is the same as equation (1).

[0027] The phenol of formula (2) can react with another phenolic monomer at either the ortho or para position of the phenol, in addition to the phenolic hydroxyl group. Therefore, repeating units derived from the phenol of formula (2) have the structures of formula (10), formula (11), or combinations thereof. [ka] [ka] (R in equations (10) and (11)) 21 , R 22 This is the same as equation (2).

[0028] If the phenol of formula (3) does not have an unsubstituted ortho position, the structural unit derived from the phenol of formula (3) has the structure of formula (12) below. If the phenol of formula (3) has an unsubstituted ortho position, the structure derived from the phenol of formula (3) has the structure of formula (12) below, the structure of formula (13) below, or a combination thereof. [ka] [ka] (R in equations (12) and (13)) 3 This is the same as equation (3).

[0029] The polyphenylene ether in this embodiment may be a modified polyphenylene ether in which the hydroxyl groups contained in the polyphenylene ether are modified into functional groups (for example, functional groups containing unsaturated carbon bonds).

[0030] The polyphenylene ether in this embodiment may have at least one substructure selected from the group consisting of the following formulas (5), (6), (7), and (8). [ka] [ka] [ka] (In formula (7), R 7 R is a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, and the saturated or unsaturated hydrocarbon is R 7 The substituents may be present within the range of 1 to 10 total carbon atoms. [ka] (In formula (8), R 8 R is a saturated or unsaturated divalent hydrocarbon group having 1 to 10 carbon atoms, and the above saturated or unsaturated divalent hydrocarbon is R 8 The substituents may be within the range of 1 to 10 carbon atoms, R 9 R is a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, and the saturated or unsaturated hydrocarbon is R 9 The substituents may be present within the range of 1 to 10 total carbon atoms. Furthermore, at least one substructure selected from the group consisting of formulas (5), (6), (7), and (8) above may be directly bonded to the oxygen of the hydroxyl group contained in the polyphenylene ether.

[0031] The ratio of repeating units derived from phenol of formula (1) and repeating units derived from phenol of formula (2) in a modified polyphenylene ether into which a substructure represented by at least one selected from the group consisting of formulas (5), (6), (7), and (8) above has been introduced is, for example, 1 1H NMR, 13 It can be determined using analytical techniques such as 13C NMR, and more specifically, it can be measured by the method described in the examples below.

[0032] In this embodiment, the polyphenylene ether preferably has a number-average molecular weight on a polystyrene basis of 500 to 15,000, more preferably 1,000 to 14,000, and even more preferably 1,500 to 13,000, from the viewpoint of achieving both heat resistance and easy handling of solution viscosity. The number-average molecular weight is determined by the method described in the examples below.

[0033] <Method for producing polyphenylene ether> The polyphenylene ether of this embodiment can be obtained, for example, by a method that includes at least a step of oxidative polymerization of a monovalent phenol compound represented by formula (1) and formula (2) and a polyvalent phenol compound represented by formula (3). In the oxidative polymerization step, it is preferable to oxidatively polymerize a raw material containing at least the phenol of formula (1), the phenol of formula (2), and the phenol of formula (3).

[0034] Examples of monovalent phenol compounds represented by the above formula (1) include 2,6-dimethylphenol, 2-methyl-6-ethylphenol, 2,6-diethylphenol, 2-ethyl-6-n-propylphenol, 2-methyl-6-chlorophenol, 2-methyl-6-bromophenol, 2-methyl-6-n-propylphenol, 2-ethyl-6-bromophenol, 2-methyl-6-n-butylphenol, 2,6-di-n-propylphenol, 2-ethyl-6-chlorophenol, 2-methyl-6-phenylphenol, 2,6-diphenylphenol, 2-methyl-6-tolylphenol, 2,6-ditolylphenol, 2,3,6-trimethylphenol, 2,3-diethyl-6-n-propylphenol, 2,3,6-tributylphenol, 2,6-di-n-butyl-3-methylphenol, 2,6-dimethyl-3-n-butylphenol, and 2,6-dimethyl-3-t-butylphenol. In particular, 2,6-dimethylphenol, 2,3,6-trimethylphenol, and 2,6-diphenylphenol are preferred because they are inexpensive and readily available. The monovalent phenol compound represented by formula (1) above may be used individually or in combination of multiple types.

[0035] Examples of monovalent phenol compounds represented by formula (2) above include 2-isopropyl-5-methylphenol, 2-cyclohexyl-5-methylphenol, 2-tert-butyl-5-methylphenol, and 2-isobutyl-5-methylphenol. From the viewpoint of suppressing multi-branching and gelation, 2-t-butyl-5-methylphenol and 2-cyclohexyl-5-methylphenol, which have bulky substituents, are more preferred. The monovalent phenol compound represented by formula (2) above may be used individually or in combination of multiple types.

[0036] Among the polyvalent phenol compounds represented by formula (3) above, examples of phenol compounds having two phenol units in the molecule include 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 4,4'-methylenebis(2,6-dimethylphenol), bis(4-hydroxy-3-methylphenyl)sulfide, bis(4-hydroxy-3,5-dimethylphenyl)sulfone, α,α'-bis(4-hydroxy-3,5-dimethylphenyl)-1,4-diisopropylbenzene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane, and 1,1-bis(2-methyl-4-hydroxy-5-t-butylphenyl)butane. In particular, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane and 1,1-bis(2-methyl-4-hydroxy-5-t-butylphenyl)butane are preferred because they are inexpensive and readily available.

[0037] Furthermore, among the polyvalent phenol compounds represented by the above formula (3), phenol compounds having three or more phenol units in the molecule include, for example, 4,4'-[(3-hydroxyphenyl)methylene]bis(2,6-dimethylphenol), 4,4'-[(3-hydroxyphenyl)methylene]bis(2,3,6-trimethylphenol), 4,4'-[(4-hydroxyphenyl)methylene]bis(2,6-dimethylphenol), 4,4'-[(4-hydroxyphenyl)methylene]bis(2,3,6-trimethylphenol), and 4,4'-[(2 [(4-hydroxy-3-methoxyphenyl)methylene]bis(2,6-dimethylphenol), 4,4'-[(4-hydroxy-3-ethoxyphenyl)methylene]bis(2,3,6-trimethylethylphenol), 4,4'-[(3,4-dihydroxyphenyl)methylene]bis(2,6-dimethylphenol), 4,4'-[(3,4-dihydroxyphenyl)methylene]bis(2,3,6-trimethylphenol), 2,2'-[(4-hydroxyphenyl)methylene]bis(3,5,6-trimethylphenol), 4,4'-[4-(4-hydroxyphenyl)methylene]bis(3,5,6-trimethylphenol] [phenyl)cyclohexylidene]bis(2,6-dimethylphenol), 4,4'-[(2-hydroxyphenyl)methylene]-bis(2,3,6-trimethylphenol), 4,4'-[1-[4-[1-(4-hydroxy-3,5-dimethylphenyl)-1-methylethyl]phenyl]ethylidene]bis(2,6-dimethylphenol), 4,4'-[1-[4-[1-(4-hydroxy-3-fluorophenyl)-1-methylethyl]phenyl]ethylidene]bis(2,6-dimethylphenol), 2,6-bis[(4-hydroxy-3,5-dimethylethyl] [(4-hydroxyphenyl)ethyl]-4-methylphenol, 2,6-bis[(4-hydroxy-2,3,6-trimethylphenyl)methyl]-4-methylphenol, 2,6-bis[(4-hydroxy-3,5,6-trimethylphenyl)methyl]-4-ethylphenol, 2,4-bis[(4-hydroxy-3-methylphenyl)methyl]-6-methylphenol, 2,6-bis[(4-hydroxy-3-methylphenyl)methyl]-4-methylphenol, 2,4-bis[(4-hydroxy-3-cyclohexylphenyl)methyl]-6-methylphenol, 2,4-bis[(4-hydroxy-3-methylphenyl)methyl]-6-cyclohexylphenol, 2,4-bis[(2-hydroxy-5-methylphenyl)methyl]-6-cyclohexylphenol, 2,4-bis[(4-hydroxy-2,3,6-trimethylphenyl)methyl]-6-cyclohexylphenol, 3,6-bis[(4-hydroxy-3,5-dimethylphenyl)methyl]-1,2-benzenediol, 4,6-bis[(4-hydroxy-3,5-dimethylphenyl)methyl]-1,3-benzenediol, 2,4,6 -Tris[(4-hydroxy-3,5-dimethylphenyl)methyl]-1,3-benzenediol, 2,4,6-Tris[(2-hydroxy-3,5-dimethylphenyl)methyl]-1,3-benzenediol, 2,2'-Methylenebis[6-[(4 / 2-hydroxy-2,5 / 3,6-dimethylphenyl)methyl]-4-methylphenol], 2,2'-Methylenebis[6-[(4-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol], 2,2'-Methylenebis[6-[(4 / 2-hydroxy-2,3,5 / 3 [4,6-trimethylphenyl)methyl]-4-methylphenol], 2,2'-methylenebis[6-[(4-hydroxy-2,3,5-trimethylphenyl)methyl]-4-methylphenol], 4,4'-methylenebis[2-[(2,4-dihydroxyphenyl)methyl]-6-methylphenol], 4,4'-methylenebis[2-[(2,4-dihydroxyphenyl)methyl]-3,6-dimethylphenol], 4,4'-methylenebis[2-[(2,4-dihydroxy-3-methylphenyl)methyl]-3,6-dimethylphenol 4,4'-methylenebis[2-[(2,3,4-trihydroxyphenyl)methyl]-3,6-dimethylphenol], 6,6'-methylenebis[4-[(4-hydroxy-3,5-dimethylphenyl)methyl]-1,2,3-benzenetriol], 4,4'-cyclohexyllidenbis[2-cyclohexyl-6-[(2-hydroxy-5-methylphenyl)methyl]phenol], 4,4'-cyclohexyllidenbis[2-cyclohexyl-6-[(4-hydroxy-3,5-dimethylphenyl)methyl]phenol], 4,Examples include 4'-cyclohexyllidenebis[2-cyclohexyl-6-[(4-hydroxy-2-methyl-5-cyclohexylphenyl)methyl]phenol], 4,4'-cyclohexyllidenebis[2-cyclohexyl-6-[(2,3,4-trihydroxyphenyl)methyl]phenol], 4,4',4'',4'''-(1,2-ethanediylidene)tetrakis(2,6-dimethylphenol), 4,4',4'',4'''-(1,4-phenylenedimethylidene)tetrakis(2,6-dimethylphenol), and 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane. Among these, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane is particularly preferred due to its low cost and easy availability. The polyvalent phenol compound represented by formula (3) above may be used individually or in combination of multiple types.

[0038] The number of phenolic hydroxyl groups in the polyvalent phenol compound represented by formula (3) above is not particularly limited as long as it is between 2 and 6, but from the viewpoint of making it easier to control the thermosetting rate, it is preferably between 2 and 4.

[0039] Typically, in the oxidative polymerization of phenols having a hydrogen atom in the ortho position (e.g., 2-methylphenol, 2,5-dimethylphenol, 2-phenylphenol), ether bonds can be formed even at the ortho position. This makes it difficult to control the bonding position of the phenol compound during oxidative polymerization, resulting in branched polymers with high molecular weight, ultimately generating gel components that are insoluble in solvents. On the other hand, when a phenol having a bulky substituent at one ortho position, as represented by formula (2) above, is used, even though it has a hydrogen atom at the opposite ortho position, it becomes possible to control the bonding position of the phenol compound during oxidative polymerization, suppressing gelation and allowing the acquisition of a solvent-soluble polyphenylene ether.

[0040] (Oxidative polymerization process) In the method for producing polyphenylene ether, an aromatic solvent, which is a good solvent for polyphenylene ether, can be used as the polymerization solvent in the oxidative polymerization step. Here, a good solvent for polyphenylene ether is a solvent that can dissolve polyphenylene ether. Examples of such solvents include aromatic hydrocarbons such as benzene, toluene, xylene (including o-, m-, and p- isomers), and ethylbenzene, as well as halogenated hydrocarbons such as chlorobenzene and dichlorobenzene; and nitro compounds such as nitrobenzene.

[0041] In this embodiment, a known catalyst system generally usable for the production of polyphenylene ether can be used as the polymerization catalyst. Commonly known catalyst systems consist of a transition metal ion having redox activity and an amine compound that can form a complex with the transition metal ion. Examples include catalyst systems consisting of a copper compound and an amine compound, a manganese compound and an amine compound, and a cobalt compound and an amine compound. Since the polymerization reaction proceeds efficiently under slightly alkaline conditions, a small amount of alkali or further amine compounds may be added.

[0042] The polymerization catalyst preferred in this embodiment is a catalyst comprising a copper compound, a halogen compound, and an amine compound as catalyst components, and more preferably a catalyst containing a diamine compound represented by the following formula (14) as the amine compound.

[0043] [ka] In formula (14), R 14 , R 15 , R 16 , R 17 Each of these is independently a hydrogen atom and a linear or branched alkyl group having 1 to 6 carbon atoms, and not all of them are hydrogen atoms at the same time. 18 This is an alkylene group having 2 to 5 carbon atoms and being linear or methyl-branched.

[0044] Examples of copper compounds used as catalyst components are listed below. Suitable copper compounds include cuprous compounds, cupric compounds, or mixtures thereof. Examples of cupric compounds include cupric chloride, cupric bromide, cupric sulfate, and cupric nitrate. Examples of cuprous compounds include cuprous chloride, cuprous bromide, cuprous sulfate, and cuprous nitrate. Among these, particularly preferred metallic compounds are cuprous chloride, cupric chloride, cuprous bromide, and cupric bromide. These copper salts may also be synthesized at the time of use from oxides (e.g., cuprous oxide), carbonates, hydroxides, and corresponding halogens or acids. A frequently used method is to prepare them by mixing the previously exemplified cuprous oxide with hydrogen halides (or solutions of hydrogen halides).

[0045] Examples of halogen compounds include hydrogen chloride, hydrogen bromide, hydrogen iodide, sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide, potassium iodide, tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, tetraethylammonium chloride, tetraethylammonium bromide, and tetraethylammonium iodide. These can be used as aqueous solutions or in solutions with a suitable solvent. These halogen compounds can be used individually or in combination of two or more. Preferred halogen compounds are aqueous solutions of hydrogen chloride and aqueous solutions of hydrogen bromide.

[0046] The amount of these compounds used is not particularly limited, but it is preferably between 2 and 20 times the amount of halogen atoms relative to the molar amount of copper atoms, and the preferred amount of copper atoms to use per 100 moles of phenol compound added to the polymerization reaction is in the range of 0.02 moles to 0.6 moles.

[0047] Next, we list examples of diamine compounds that serve as catalyst components. For example, N,N,N',N'-tetramethylethylenediamine, N,N,N'-trimethylethylenediamine, N,N'-dimethylethylenediamine, N,N-dimethylethylenediamine, N-methylethylenediamine, N,N,N',N'-tetraethylethylenediamine, N,N,N'-triethylethylenediamine, N,N'-diethylethylenediamine, N,N'-diethylethylenediamine, N-ethylethylenediamine, N,N-dimethyl-N'-ethylethylenediamine, N,N'-dimethyl-N-ethylethylenediamine, Nn-propylethylenediamine, N,N'-n-propylethylenediamine, Ni-propylethylenediamine, N,N'-i-propylethylenediamine, Nn-butylethylenediamine Examples include methyl ethylenediamine, N,N'-n-butylethylenediamine, Ni-butylethylenediamine, N,N'-i-butylethylenediamine, Nt-butylethylenediamine, N,N'-t-butylethylenediamine, N,N,N'-tetramethyl-1,3-diaminopropane, N,N,N'-trimethyl-1,3-diaminopropane, N,N'-dimethyl-1,3-diaminopropane, N-methyl-1,3-diaminopropane, N,N,N',N'-tetramethyl-1,3-diamino-1-methylpropane, N,N,N',N'-tetramethyl-1,3-diamino-2-methylpropane, N,N,N',N'-tetramethyl-1,4-diaminobutane, and N,N,N',N'-tetramethyl-1,5-diaminopentane. For this embodiment, preferred diamine compounds are those in which the alkylene group connecting the two nitrogen atoms has two or three carbon atoms. The amount of these diamine compounds used is not particularly limited, but it is preferably in the range of 0.01 moles to 10 moles per 100 moles of the phenol compound added to the polymerization reaction.

[0048] In this embodiment, the polymerization catalyst may include primary amines and secondary monoamines as constituent components. Examples of secondary monoamines, but not limited to the following, include dimethylamine, diethylamine, di-n-propylamine, di-i-propylamine, di-n-butylamine, di-i-butylamine, di-t-butylamine, dipentylamines, dihexylamines, dioctylamines, didecylamines, dibenzylamines, methylethylamine, methylpropylamine, methylbutylamine, cyclohexylamine, N-phenylmethanolamine, N-phenylethanolamine, N-phenylpropanolamine, N-(m-methylphenyl)ethanolamine, N-(p-methylphenyl)ethanolamine, N-(2',6'-dimethylphenyl)ethanolamine, N-(p-chlorophenyl)ethanolamine, N-ethylaniline, N-butylaniline, N-methyl-2-methylaniline, N-methyl-2,6-dimethylaniline, and diphenylamine.

[0049] The polymerization catalyst in this embodiment may also include a tertiary monoamine compound. A tertiary monoamine compound is an aliphatic tertiary amine, including alicyclic tertiary amines. Examples include trimethylamine, triethylamine, tripropylamine, tributylamine, triisobutylamine, dimethylethylamine, dimethylpropylamine, allyldiethylamine, dimethyl-n-butylamine, diethylisopropylamine, and N-methylcyclohexylamine. These tertiary monoamines may be used individually or in combination of two or more types. The amount used is not particularly limited, but it is preferably in the range of 15 moles or less per 100 moles of the phenol compound added to the polymerization reaction.

[0050] In this embodiment, there are no limitations on adding surfactants that are conventionally known to have an effect of improving polymerization activity. Examples of such surfactants include trioctylmethylammonium chloride, known by the trade names Aliquat 336 and Capriquat. The amount used is preferably in a range not exceeding 0.1% by mass relative to 100% by mass of the total amount of the polymerization reaction mixture.

[0051] In this embodiment, the oxygen-containing gas used in polymerization can be pure oxygen, a mixture of oxygen and an inert gas such as nitrogen in any proportion, air, or a mixture of air and an inert gas such as nitrogen in any proportion. While atmospheric pressure is sufficient for the system pressure during the polymerization reaction, it can be reduced or increased as needed.

[0052] The polymerization temperature is not particularly limited, but if it is too low, the reaction will not proceed easily, and if it is too high, the reaction selectivity may decrease or a gel may form. Therefore, it is preferably in the range of 0 to 60°C, more preferably 10 to 40°C.

[0053] In the method for producing polyphenylene ether, polymerization can also be carried out in a poor solvent such as alcohol.

[0054] (Copper extraction and by-product removal process) In this embodiment, there are no particular restrictions on the post-treatment method after the polymerization reaction is completed. Typically, an acid such as hydrochloric acid or acetic acid, or ethylenediaminetetraacetic acid (EDTA) and its salts, nitrilotriacetic acid and its salts, etc., are added to the reaction solution to deactivate the catalyst. In addition, the removal of divalent phenol by-products generated by the polymerization of polyphenylene ether can be carried out using conventionally known methods. If the metal ions that act as catalysts are substantially deactivated as described above, the mixture can be decolorized simply by heating it. Alternatively, it is also possible to add the required amount of a known reducing agent. Examples of known reducing agents include hydroquinone and sodium dithionite.

[0055] (liquid-liquid separation process) In the method for producing polyphenylene ether, water may be added to extract the compound from which the copper catalyst has been deactivated, followed by liquid-liquid separation into an organic phase and an aqueous phase. The copper catalyst may then be removed from the organic phase by removing the aqueous phase. This liquid-liquid separation step is not particularly limited, but examples include static separation and separation by centrifugation. To promote the above liquid-liquid separation, known surfactants may be used.

[0056] (concentration / drying process) Next, in the method for producing polyphenylene ether according to this embodiment, the organic phase containing the polyphenylene ether after liquid-liquid separation may be concentrated and dried by volatilizing the solvent.

[0057] Methods for volatilizing the solvent contained in the organic phase are not particularly limited, but include methods such as transferring the organic phase to a high-temperature concentration tank and distilling off the solvent to concentrate it, or using equipment such as a rotary evaporator to distill off toluene and concentrate it.

[0058] The drying temperature in the drying process is preferably at least 60°C, more preferably 80°C or higher, even more preferably 120°C or higher, and most preferably 140°C or higher. Drying polyphenylene ether at a temperature of 60°C or higher efficiently reduces the content of high-boiling point volatile components in the polyphenylene ether powder.

[0059] To efficiently obtain polyphenylene ether, methods such as increasing the drying temperature, increasing the vacuum level in the drying atmosphere, and stirring during drying are effective, but increasing the drying temperature is particularly preferable from the viewpoint of manufacturing efficiency. In the drying process, it is preferable to use a dryer equipped with a mixing function. Examples of dryers equipped with a mixing function include agitation type dryers and tumbling type dryers. This allows for a larger processing volume and maintains high productivity.

[0060] The polyphenylene ether of this embodiment can also be produced by a redistribution reaction in which the polyphenylene ether derived from the phenol of formula (1) is equilibrated with the phenol compound of formula (2) and the phenol compound of formula (3) in the presence of an oxidizing agent. The redistribution reaction is known in the art and is described, for example, in U.S. Patent No. 3,496,236 by Cooper et al. and U.S. Patent No. 5,880,221 by Liska et al.

[0061] (Denaturation reaction process) There are no limitations on the method for introducing functional groups to the hydroxyl groups of unmodified polyphenylene ether. For example, it can be obtained by the formation of an ester bond between the hydroxyl groups of unmodified polyphenylene ether and a carboxylic acid having a carbon-carbon double bond (hereinafter referred to as carboxylic acid). Various known methods can be used to form the ester bond. For example, a. reaction between a carboxylic acid halide and the hydroxyl group at the polymer end, b. formation of an ester bond by reaction with a carboxylic acid anhydride, c. direct reaction with a carboxylic acid, and d. transesterification reaction are examples. Method a, the reaction with a carboxylic acid halide, is one of the most common methods. As the carboxylic acid halide, chlorides and bromides are commonly used, but other halogens may also be used. The reaction may be either a direct reaction with the hydroxyl group or a reaction with an alkali metal salt of the hydroxyl group. Since acids such as hydrogen halides are generated in the direct reaction between a carboxylic acid halide and the hydroxyl group, a weak base such as an amine may be present to trap the acid. In the reaction with carboxylic acid anhydride (b) and the direct reaction with carboxylic acid (c), compounds such as carbodiimides or dimethylaminopyridine may be present to activate the reaction site and promote the reaction. In the case of the transesterification reaction (d), it is desirable to remove the alcohols produced as needed. Known metal catalysts may also be present to promote the reaction. After the reaction, the polymer solution may be washed with water, an acidic or alkaline aqueous solution to remove by-products such as amine salts, or the polymer solution may be dropped into a poor solvent such as an alcohol and the target product may be recovered by reprecipitation. Alternatively, after washing the polymer solution, the solvent may be removed under reduced pressure and the polymer may be recovered.

[0062] The method for producing modified polyphenylene ether according to this embodiment is not limited to the method for producing modified polyphenylene ether according to this embodiment described above, and the order and number of times of the above-described oxidative polymerization step, copper extraction and by-product removal step, liquid-liquid separation step, and concentration and drying step may be adjusted as appropriate.

[0063] (Polyphenylene ether solution) The polyphenylene ether solution of this embodiment contains at least the polyphenylene ether of this embodiment and a ketone solvent, and may also contain other components. Furthermore, it may contain a solvent other than a ketone solvent. Examples of the ketone solvents mentioned above include acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, diisobutyl ketone, and cyclohexanone. The ratio of the total mass of the polyphenylene ether and the ketone-based solvent to 100% by mass of the above polyphenylene ether solution is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 100% by mass. The preferred mass ratio of the polyphenylene ether to 100% by mass of the polyphenylene ether solution is 1 to 40% by mass. Furthermore, the preferred mass ratio of the ketone solvent to 100% by mass of the polyphenylene ether solution is 60 to 99% by mass. The above polyphenylene ether solution can be prepared, for example, by mixing the above polyphenylene ether, the above ketone solvent, and any other components or other solvents.

[0064] <Thermosetting composition> The polyphenylene ether of this embodiment can be used as a raw material for a thermosetting composition. The thermosetting composition is not particularly limited as long as it contains polyphenylene ether, but it preferably further contains a crosslinking agent and an organic peroxide, and optionally further contains a thermoplastic resin, a flame retardant, other additives, silica filler, solvent, etc. The components of the thermosetting composition of this embodiment are described below.

[0065] (Polyphenylene ether) As described above, the polyphenylene ether of this embodiment may be used as a single resin in the thermosetting composition, or in combination with other polyphenylene ethers having different structures, or in combination with various known additives. When used in combination with other components, the polyphenylene ether content in the thermosetting composition is preferably 0.5 to 95% by mass, more preferably 20 to 93% by mass, and even more preferably 40 to 90% by mass.

[0066] (Crosslinking agent) In the thermosetting composition of this embodiment, any crosslinking agent having the ability to cause or promote a crosslinking reaction can be used. The crosslinking agent preferably has a number-average molecular weight of 4,000 or less. When the number-average molecular weight of the crosslinking agent is 4,000 or less, the increase in viscosity of the thermosetting composition can be suppressed, and good resin fluidity can be obtained during heat molding. The number-average molecular weight is often a value measured using a general molecular weight measurement method, specifically a value measured using GPC.

[0067] From the viewpoint of crosslinking reaction, the crosslinking agent preferably has an average of two or more carbon-carbon unsaturated double bonds per molecule. The crosslinking agent may consist of one type of compound or two or more types of compounds. In this specification, "carbon-carbon unsaturated double bond" refers to a double bond located at the branched end of the main chain when the crosslinking agent is a polymer or oligomer. An example of a carbon-carbon unsaturated double bond is the 1,2-vinyl bond in polybutadiene.

[0068] When the number-average molecular weight of the crosslinking agent is less than 600, the number of carbon-carbon unsaturated double bonds per molecule of the crosslinking agent (average value) is preferably 2 to 4. When the number-average molecular weight of the crosslinking agent is 600 or more and less than 1,500, the number of carbon-carbon unsaturated double bonds per molecule of the crosslinking agent (average value) is preferably 4 to 26. When the number-average molecular weight of the crosslinking agent is 1,500 or more and 4,000 or less, the number of carbon-carbon unsaturated double bonds per molecule of the crosslinking agent (average value) is preferably 26 to 60. When the number-average molecular weight of the crosslinking agent is within the above range, having the number of carbon-carbon unsaturated double bonds equal to or greater than the specified value further enhances the reactivity of the crosslinking agent in the thermosetting composition of this embodiment, further improves the crosslinking density of the cured product of the thermosetting composition, and as a result can provide even better heat resistance. On the other hand, when the number-average molecular weight of the crosslinking agent is within the above range, having the number of carbon-carbon unsaturated double bonds equal to or less than the specified value further enhances the resin fluidity during heat molding.

[0069] Examples of crosslinking agents include triallyl isocyanurate compounds such as triallyl isocyanurate (TAIC), triallyl cyanurate compounds such as triallyl cyanurate (TAC), polyfunctional methacrylate compounds having two or more methacrylic groups in the molecule, polyfunctional acrylate compounds having two or more acrylic groups in the molecule, polyfunctional vinyl compounds having two or more vinyl groups in the molecule such as polybutadiene, vinyl benzyl compounds such as divinylbenzene having a vinylbenzyl group in the molecule, and polyfunctional maleimide compounds having two or more maleimide groups in the molecule such as 4,4'-bismaleimidediphenylmethane. These crosslinking agents can be used individually or in combination of two or more. Among these, it is preferable that the crosslinking agent contains at least one compound selected from the group consisting of triallyl cyanurate, triallyl isocyanurate, and polybutadiene. By including at least one of the compounds described above as a crosslinking agent, the thermosetting composition exhibits improved compatibility and coating properties between the crosslinking agent and polyphenylene ether, and tends to exhibit improved substrate properties when mounted on an electronic circuit board.

[0070] The mass ratio of polyphenylene ether to crosslinking agent (polyphenylene ether:crosslinking agent) is preferably 25:75 to 95:5, and more preferably 32:68 to 85:15, from the viewpoint of further improving the compatibility between the crosslinking agent and polyphenylene ether, the coatability of the thermosetting composition, and the characteristics of the mounted electronic circuit board.

[0071] (organic peroxide) In this embodiment, any organic peroxide having the ability to promote the polymerization reaction of a thermosetting composition containing polyphenylene ether and a crosslinking agent can be used. Examples of organic peroxides include benzoyl peroxide, cumene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexine-3, di-t-butyl peroxide, t-butylcumyl peroxide, di(2-t-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, dicumyl peroxide, di-t-butylperoxyisophthalate, t-butylperoxybenzoate, 2,2-bis(t-butylperoxy)butane, 2,2-bis(t-butylperoxy)octane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, di(trimethylsilyl)peroxide, and trimethylsilyltriphenylsilyl peroxide. Furthermore, radical generators such as 2,3-dimethyl-2,3-diphenylbutane can also be used as reaction initiators for thermosetting compositions. Among these, 2,5-dimethyl-2,5-di(t-butylperoxy)hexine-3, di(2-t-butylperoxyisopropyl)benzene, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane are preferred from the viewpoint of providing a cured product with excellent heat resistance and mechanical properties, as well as lower dielectric constant and dielectric loss tangent.

[0072] The 1-minute half-life temperature of the organic peroxide is preferably 155 to 185°C, more preferably 160 to 180°C, and even more preferably 165 to 175°C. Having the 1-minute half-life temperature of the organic peroxide within the range of 155 to 185°C tends to result in improved compatibility between the organic peroxide and polyphenylene ether, better coating properties of the thermosetting composition, and superior characteristics of the mounted electronic circuit board. In this specification, the 1-minute half-life temperature is defined as the temperature at which the time required for an organic peroxide to decompose and its amount of reactive oxygen species to be halved is 1 minute. The 1-minute half-life temperature is determined by dissolving an organic peroxide in a radical-inert solvent, such as benzene, at a concentration of 0.05 to 0.1 mol / L, and then thermally decomposing the organic peroxide solution under a nitrogen atmosphere.

[0073] Examples of organic peroxides with a 1-minute half-life temperature in the range of 155-185°C include t-hexylperoxyisopropyl monocarbonate (155.0°C), t-butylperoxy-3,5,5-trimethylhexanoate (166.0°C), t-butylperoxylaurate (159.4°C), t-butylperoxyisopropyl monocarbonate (158.8°C), t-butylperoxy-2-ethylhexyl monocarbonate (161.4°C), t-hexylperoxybenzoate (160.3°C), and 2,5-dimethyl-2,5-di(benzoylperoxy)hexane (158.2°C). Examples include t-butylperoxyacetate (159.9°C), 2,2-di-(t-butylperoxy)butane (159.9°C), t-butylperoxybenzoate (166.8°C), n-butyl4,4-di-(t-butylperoxy)valerate (172.5°C), di(2-t-butylperoxyisopropyl)benzene (175.4°C), dicumyl peroxide (175.2°C), di-t-hexyl peroxide (176.7°C), 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (179.8°C), and t-butylcumyl peroxide (173.3°C).

[0074] The content of the organic peroxide is preferably 0.05 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, and even more preferably 1.5 parts by mass or more, based on 100 parts by mass of the total of the polyphenylene ether and the crosslinking agent, from the viewpoint of further improving the compatibility between the organic peroxide and the polyphenylene ether and the coating properties of the thermosetting composition, and preferably 5 parts by mass or less, more preferably 4.5 parts by mass or less, from the viewpoint of having excellent substrate properties when the thermosetting composition is mounted on an electronic circuit board.

[0075] (thermoplastic resin) The thermoplastic resin is preferably at least one selected from the group consisting of block copolymers of vinyl aromatic compounds and olefin-based alkene compounds and their hydrogenated products (hydrogenated block copolymers obtained by hydrogenating block copolymers of vinyl aromatic compounds and olefin-based alkene compounds), and homopolymers of vinyl aromatic compounds. Furthermore, the weight-average molecular weight of the thermoplastic resin is preferably more than 50,000 and 780,000 or less, more preferably 60,000 to 750,000, and even more preferably 70,000 to 700,000, from the viewpoint of further improving compatibility with polyphenylene ether, resin fluidity, coatability of the thermosetting composition, and heat resistance during curing. When a thermosetting composition contains polyphenylene ether, a crosslinking agent, and an organic peroxide, along with a thermoplastic resin having the type and weight-average molecular weight described above, the compatibility between the polyphenylene ether and other components, as well as the coatability on substrates, tends to be good, and consequently, the substrate characteristics when incorporated into an electronic circuit board may also be excellent. The weight-average molecular weight is determined using gel permeation chromatography (GPC).

[0076] The content of units derived from vinyl aromatic compounds in the block copolymer or its hydrogenated product is preferably 20% by mass or more, more preferably 22% by mass or more, 24% by mass or more, 26% by mass or more, 28% by mass or more, 30% by mass or more, and 32% by mass or more. The upper limit is preferably 70% by mass or less, more preferably 69% by mass or less, 68% by mass or less, and 67% by mass or less. When the content of units derived from vinyl aromatic compounds in the block copolymer or its hydrogenated product is 20 to 70% by mass, the compatibility with polyphenylene ether is further improved and / or the adhesion strength with metal foil tends to be further improved.

[0077] Examples of vinyl aromatic compounds include those having an aromatic ring and a vinyl group within the molecule, such as styrene. The olefinic alkene compound can be any alkene having a linear or branched structure within the molecule, such as ethylene, propylene, butylene, isobutylene, butadiene, and isoprene. As for the thermoplastic resin, from the viewpoint of having even better compatibility with polyphenylene ether, it is preferable that it be at least one selected from the group consisting of styrene-butadiene block copolymer, styrene-ethylene-butadiene block copolymer, styrene-ethylene-butylene block copolymer, styrene-butadiene-butylene block copolymer, styrene-isoprene block copolymer, styrene-ethylene-propylene block copolymer, styrene-isobutylene block copolymer, hydrogenated styrene-butadiene block copolymer, hydrogenated styrene-ethylene-butadiene block copolymer, hydrogenated styrene-butadiene-butylene block copolymer, hydrogenated styrene-isoprene block copolymer, and styrene homopolymer (polystyrene), and more preferably one or more selected from the group consisting of styrene-butadiene block copolymer, hydrogenated styrene-butadiene block copolymer, and polystyrene.

[0078] The hydrogenation rate in the above-mentioned hydrogenated product is not particularly limited, and some carbon-carbon unsaturated double bonds derived from the olefinic alkene compound may remain.

[0079] The content of the thermoplastic resin is preferably 2 to 20 parts by mass, more preferably 3 to 19 parts by mass, even more preferably 4 to 18 parts by mass, and particularly preferably 5 to 17 parts by mass, based on 100 parts by mass of the total of the polyphenylene ether and the crosslinking agent. When this content is within the above numerical range, the thermosetting composition of this embodiment tends to have even better compatibility and coating properties between the thermoplastic resin and the polyphenylene ether, and to have even better substrate properties when mounted on an electronic circuit board.

[0080] Furthermore, the thermosetting composition of this embodiment may also include thermoplastic resins other than those described above, having the same type and weight-average molecular weight.

[0081] (Flame retardant) The thermosetting composition of this embodiment preferably contains a flame retardant. The flame retardant is not particularly limited as long as it is incompatible with other components in the thermosetting composition after curing, from the viewpoint of improving heat resistance. Preferably, the flame retardant is incompatible with the polyphenylene ether and / or crosslinking agent in the thermosetting composition after curing. Examples of flame retardants include inorganic flame retardants such as antimony trioxide, aluminum hydroxide, magnesium hydroxide, and zinc borate; aromatic bromine compounds such as hexabromobenzene, decabromodiphenylethane, 4,4-dibromoviphenyl, and ethylenebistetrabromophthalimide; and phosphorus-based flame retardants such as resorcinol bis-diphenyl phosphate and resorcinol bis-dixylenyl phosphate. These flame retardants may be used individually or in combination of two or more. Among these, decabromodiphenylethane is preferred as the flame retardant from the viewpoint of superior compatibility between the flame retardant and polyphenylene ether, coating properties of the thermosetting composition, and characteristics of the mounted electronic circuit board.

[0082] The amount of flame retardant is not particularly limited, but from the viewpoint of maintaining flame retardancy at the V-0 level of UL standard 94, it is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, per 100 parts by mass of the total of the polyphenylene ether resin and the crosslinking agent. Furthermore, from the viewpoint of maintaining a low dielectric constant and dielectric loss tangent of the resulting cured product, the amount of flame retardant is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and even more preferably 40 parts by mass or less.

[0083] (Silica filler) The thermosetting composition of this embodiment may contain a silica filler. Examples of silica fillers include natural silica, fused silica, synthetic silica, amorphous silica, aerosil, and hollow silica. The silica filler content may be 10 to 100 parts by mass per 100 parts by mass of the total of the polyphenylene ether resin and the crosslinking agent. Furthermore, the silica filler may be surface-treated with a silane coupling agent or the like.

[0084] The thermosetting composition of this embodiment may further contain additives such as heat stabilizers, antioxidants, UV absorbers, surfactants, lubricants, solvents, etc., in addition to the flame retardant and silica filler. The thermosetting composition of this embodiment, when it contains a solvent, can be in the form of a varnish in which the solid components in the thermosetting composition are dissolved or dispersed in the solvent, and a resin film can be formed from the thermosetting composition of this embodiment.

[0085] (solvent) From the viewpoint of solubility, preferred solvents include aromatic compounds such as toluene and xylene, methyl ethyl ketone (MEK), cyclopentanone, cyclohexanone, and chloroform. These solvents may be used individually or in combination of two or more.

[0086] <Prepreg> The prepreg of this embodiment comprises a substrate and the thermosetting composition of this embodiment described above, and is preferably a composite comprising the substrate and the thermosetting composition of this embodiment impregnated or coated onto the substrate. The prepreg can be obtained, for example, by impregnating a substrate such as glass cloth with the varnish of the thermosetting composition, and then drying off the solvent using a hot air dryer or the like.

[0087] Examples of substrates include various glass cloths such as roving cloth, cloth, chopped mat, and surfacing mat; asbestos cloth, metal fiber cloth, and other synthetic or natural inorganic fiber cloths; woven or nonwoven fabrics obtained from liquid crystal fibers such as fully aromatic polyamide fibers, fully aromatic polyester fibers, and polybenzoxazole fibers; natural fiber cloths such as cotton cloth, linen cloth, and felt; natural cellulose-based substrates such as carbon fiber cloth, kraft paper, cotton paper, and cloths obtained from paper-glass blended yarns; and polytetrafluoroethylene porous films. Glass cloth is preferred among these. These substrates may be used individually or in combination of two or more.

[0088] The proportion of the thermosetting composition solids (components of the thermosetting composition other than the solvent) in the prepreg of this embodiment is preferably 30 to 80% by mass, and more preferably 40 to 70% by mass. When the above proportion is 30% by mass or more, the insulation reliability tends to be even better when the prepreg is used for electronic circuit boards, etc. When the above proportion is 80% by mass or less, the mechanical properties such as the flexural modulus tend to be even better in applications such as electronic circuit boards.

[0089] <Laminate> The laminate of this embodiment preferably comprises a cured prepreg of this embodiment and a metal foil, and is a metal-clad laminate obtained by laminating and curing the thermosetting composition of this embodiment or the prepreg of this embodiment and the metal foil. The metal-clad laminate preferably has a form in which the cured prepreg (hereinafter also referred to as the "cured composite") and the metal foil are laminated and in close contact, and is suitably used as a material for electronic substrates. Examples of metal foils include aluminum foil and copper foil, and among these, copper foil is preferred because of its low electrical resistance. The cured composite material combined with metal foil can consist of one or multiple sheets, and depending on the application, the metal foil is layered on one or both sides of the composite material to form a laminate.

[0090] One method for manufacturing a metal-clad laminate is to form a composite (for example, the aforementioned prepreg) composed of a thermosetting composition and a substrate, then layer this with a metal foil, and finally cure the thermosetting composition to obtain a laminate in which the cured composite and the metal foil are laminated. One particularly preferred application of the metal-clad laminate is a printed circuit board. Preferably, in a printed circuit board, at least a portion of the metal foil is removed from the metal-clad laminate.

[0091] <Printed wiring board> The printed circuit board of this embodiment is obtained by removing at least a portion of the metal foil from the metal-clad laminate of this embodiment. The printed circuit board of this embodiment can typically be formed by a pressure-heat molding method using the prepreg of this embodiment described above. The base material is the same as that described above regarding the prepreg. The printed circuit board of this embodiment, by containing the thermosetting composition of this embodiment, has excellent heat resistance and electrical properties (low dielectric constant and low dielectric loss tangent), can further suppress fluctuations in electrical properties due to environmental changes, and has excellent insulation reliability and mechanical properties. [Examples]

[0092] The embodiment will be described in more detail below based on the following examples, but this embodiment is not limited to the following examples.

[0093] First, the measurement methods and evaluation criteria for each physical property are described below.

[0094] (1) The molar ratio of repeating units derived from phenol of formula (1) or formula (2) to the total of repeating units derived from phenol of formula (1) and repeating units derived from phenol of formula (2) contained in unmodified polyphenylene ether, and the molar ratio of structural units derived from phenol of formula (3) to unmodified polyphenylene ether. The unmodified polyphenylene ethers obtained in the examples and comparative examples were dissolved in deuterated chloroform, and tetramethylsilane was used as an internal standard. 1 ¹H-NMR measurements were performed using a JEOL 500MHz instrument. Before measurement, the unmodified polyphenylene ether was held at 140°C and 1 mmHg for 8 hours to remove volatile components such as toluene and water, and the measurement was performed on the dried unmodified polyphenylene ether. The signals of the units derived from phenol in formulas (1), (2), and (3) were identified, and their respective proportions were calculated. For example, in the unmodified polyphenylene ether obtained in Example 1, the signal derived from the repeating unit derived from the phenol of formula (1), i.e., the 2,6-dimethylphenol-derived structure (2,6-dimethylphenylene unit), the signal derived from the repeating unit derived from the phenol of formula (2), i.e., the 2-tert-butyl-5-methylphenol-derived structure (2-tert-butyl-5-methylphenylene unit), and the signal derived from the structural unit derived from the phenol of formula (3), i.e., the 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane-derived structure (2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane unit) were analyzed as follows. The peaks of the repeating units derived from each phenol appear in the following region. Peaks originating from hydrogen atoms of the methyl groups of the 2,6-dimethylphenylene unit, the 2-tert-butyl-5-methylphenylene unit, and the 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane unit (6H, 3H, and 18H, respectively): 1.60-2.50 ppm (excluding the peak originating from hydrogen atoms of the methyl group of toluene). Peak (9H) originating from the hydrogen atom of the tert-butyl group in the 2-tert-butyl-5-methylphenylene unit: 1.00~1.52 ppm (excluding the peak originating from the hydrogen atom of water). Peak (4H) originating from hydrogen atoms inside the 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane unit: 6.85~7.00 ppm By examining the integral value of the above signal, the integral value per proton of the peak originating from the hydrogen atom of the methyl group of the 2,6-dimethylphenylene unit can be determined using the following formula (1). F = {C - 3 × (D / 9) - 18 × (E / 4)} / 6 ... Formula (1) Integrated values ​​of peaks derived from the methyl group of the C:2,6-dimethylphenylene unit, 2-tert-butyl-5-methylphenylene unit, and 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane unit. D: Integrated value of the peak derived from tert-butyl in the 2-tert-butyl-5-methylphenylene unit. E: Integrated value of the peak originating from the hydrogen atom inside the 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane unit. F: Integral value per proton of the methyl-derived peak of the 2,6-dimethylphenylene unit Furthermore, the ratio (mol%) of the repeating units derived from formula (1) or formula (2) to the total of the repeating units derived from formula (1) and the repeating units derived from formula (2) can be calculated using the following formulas (2) and (3). The percentage (mol%) of repeating units derived from phenol in equation (1) = F / {(D / 9)+F} × 100 ...Equation (2) The percentage (mol%) of repeating units derived from phenol in equation (2) = (D / 9) / {(D / 9)+F} × 100 ... Equation (3) Furthermore, the percentage (mol%) of repeating units derived from phenol in formula (3) relative to unmodified polyphenylene ether can be calculated using the following formula (4). The percentage (mol%) of repeating units derived from phenol in equation (3) = (E / 4) / {(D / 9)+F+(E / 4)}×100 ...Equation (4)

[0095] (2) The molar ratio of repeating units derived from phenol of formula (1) or formula (2) to the total of repeating units derived from phenol of formula (1) and repeating units derived from phenol of formula (2) contained in the modified polyphenylene ether, and the molar ratio of structural units derived from phenol of formula (3) to the modified polyphenylene ether. The modified polyphenylene ethers obtained in the examples and comparative examples were dissolved in the measurement solvent (deuterated chloroform with one drop of deuterium water added to eliminate the hydroxyl group), and tetramethylsilane was used as an internal standard. 1 ¹H-NMR measurements were performed using a JEOL 500MHz instrument. Before measurement, the modified polyphenylene ether was held at 140°C and 1 mmHg for 8 hours to remove volatile components such as toluene and water, and the measurement was performed on the dried modified polyphenylene ether. The signals of the units derived from phenol in formulas (1), (2), and (3) were identified, and their respective proportions were calculated. For example, in the modified polyphenylene ether obtained in Example 9, the following methods were used to assign signals to the repeating units derived from the phenol of formula (1), i.e., the 2,6-dimethylphenol-derived structure (2,6-dimethylphenylene unit), the repeating units derived from the phenol of formula (2), i.e., the 2-tert-butyl-5-methylphenol-derived structure (2-tert-butyl-5-methylphenylene unit), the structural units derived from the phenol of formula (3), i.e., the 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane-derived structure (2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane unit), and the signals derived from substructures selected from the group consisting of formulas (5), (6), (7), or (8), i.e., the methacrylic group-derived structure. The peaks of the repeating units derived from each phenol appear in the following regions. Peaks originating from hydrogen atoms of the methyl group of the 2,6-dimethylphenylene unit, 2-tert-butyl-5-methylphenylene unit, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane unit, and methacrylic group (6H, 3H, 18H, and 3H, respectively): 1.60-2.50 ppm (excluding the peak originating from the hydrogen atom of the methyl group of toluene). Peak (9H) originating from the hydrogen atom of the tert-butyl group in the 2-tert-butyl-5-methylphenylene unit: 1.00~1.52 ppm (excluding the peak originating from the hydrogen atom of water). Peak (4H) originating from hydrogen atoms inside the 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane unit: 6.85~7.00 ppm Peak (1H) originating from one hydrogen atom of the methylene group of the methacrylic group: 4.4~5.8 ppm By examining the integral value of the above signal, the integral value per proton of the peak originating from the hydrogen atom of the methyl group of the 2,6-dimethylphenylene unit can be determined using the following formula (5). F = {C - 3 × (D / 9) - 18 × (E / 4) - 3 × (H / 1)} / 6 ... Formula (5) Integrated values ​​of peaks derived from the methyl group of the C:2,6-dimethylphenylene unit, 2-tert-butyl-5-methylphenylene unit, and 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane unit. D: Integrated value of the peak derived from tert-butyl in the 2-tert-butyl-5-methylphenylene unit. E: Integrated value of the peak originating from the hydrogen atom inside the 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane unit. F: Integral value per proton of the methyl-derived peak of the 2,6-dimethylphenylene unit H: Integrated value of the peak originating from one hydrogen atom of the methylene group of the methacrylic group. Furthermore, the ratio (mol%) of the repeating units derived from the phenol of formula (1) or formula (2) to the total of the repeating units derived from the phenol of formula (1) and the repeating units derived from the phenol of formula (2) can be calculated using the following formulas (6) and (7). The percentage (mol%) of repeating units derived from phenol in equation (1) = F / {(D / 9) + F} × 100 ... Equation (6) The percentage (mol%) of repeating units derived from phenol in equation (2) = (D / 9) / {(D / 9)+F} × 100 ... Equation (7) Furthermore, the percentage (mol%) of the repeating units derived from phenol in formula (3) relative to the modified polyphenylene ether can be calculated using the following formula (8). The percentage (mol%) of repeating units derived from phenol in equation (3) = (E / 4) / {(D / 9)+F+(E / 4)}×100 ...Equation (8)

[0096] (3) Number average molecular weight (Mn) A gel permeation chromatography system (product name: LC2030S) manufactured by Shimadzu Corporation was used as the measuring instrument. A calibration curve was created using standard polystyrene and ethylbenzene, and the number-average molecular weight (Mn) of the obtained polyphenylene ether was measured using this calibration curve. Standard polystyrenes used had molecular weights of 3,650,000, 2,170,000, 1,090,000, 681,000, 204,000, 52,000, 30,200, 13,800, 3,360, 1,300, and 550. The column used consisted of two Showa Denko K-805L columns connected in series. Chloroform was used as the solvent, with a solvent flow rate of 1.0 mL / min and a column temperature of 40°C. A 1 g / L chloroform solution of polyphenylene ether was prepared and used as the sample for measurement. The UV wavelength of the detection unit was set to 254 nm for standard polystyrene and 283 nm for polyphenylene ether. Based on the above measurement data, the number-average molecular weight (Mn) (g / mol) was calculated from the percentage of peak areas on the curve showing the molecular weight distribution obtained by GPC.

[0097] (4) Long-term solubility in methyl ethyl ketone (MEK long-term solubility) Two g of polyphenylene ether and two g of methyl ethyl ketone were weighed into a transparent glass screw tube. A 50% by mass methyl ethyl ketone solution was prepared by stirring for one hour using a stirring bar and a magnetic stirrer, and then left at 20°C for seven days. After seven days, the solution was judged as "○" (good) if it remained transparent, "△" if it was partially cloudy (the upper part of the solution was clear, but the lower part was cloudy), and "×" (poor) if the entire solution was cloudy.

[0098] (5) Viscosity (liquid viscosity) of polyphenylene ether solution with toluene Two g of polyphenylene ether and three g of toluene were weighed into a transparent glass screw-top tube. A 40% by mass toluene solution was prepared by stirring for one hour using a stirring bar and a magnetic stirrer. The viscosity of this solution was measured using a B-type viscometer at 25°C and 30 rpm.

[0099] (6) Dielectric properties of the cured product of the thermosetting composition The dielectric properties (dielectric constant and dielectric loss tangent) of the laminates manufactured in the examples and comparative examples were measured at 10 GHz using the cavity resonance method. A network analyzer (N5230A, Agilent Technologies) and a cavity resonator (Cavity Resornator CP series, Kanto Electronics Applied Development Co., Ltd.) were used as the measurement equipment. The laminates were cut into strips approximately 2 mm wide, 50 mm long, and 0.5 mm thick, with the warp threads of the glass cloth as the longer side. Next, they were dried in an oven at 105°C ± 2°C for 2 hours, and then left to stand for 24 ± 5 ​​hours in an environment of 23°C and 50 ± 5% relative humidity. After that, the dielectric properties (dielectric constant and dielectric loss tangent) were measured using the above measurement equipment in an environment of 23°C and 50 ± 5% relative humidity.

[0100] The following describes the methods for producing polyphenylene ether in each example and comparative example.

[0101] (Example 1) A 1.5-liter jacketed reactor, equipped with a sparger for introducing oxygen-containing gas at the bottom, stirring turbine blades and baffles, and a reflux condenser in the vent gas line at the top of the reactor, was filled with a pre-prepared mixture of 0.10 g of cuprous oxide and 0.77 g of 47% hydrogen bromide, along with 0.25 g of N,N'-di-t-butylethylenediamine, 3.62 g of dimethyl-n-butylamine, 1.19 g of di-n-butylamine, 894 g of toluene, 23.28 g of 2,6-dimethylphenol, 73.03 g of 2-tert-butyl-5-methylphenol, and 3.69 g of 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane. Then, while vigorously stirring, air was introduced into the reactor at a rate of 1.05 L / min through the sparger, and the polymerization temperature was adjusted by passing a heat transfer medium through the jacket to maintain a temperature of 20°C. 150 minutes after the introduction of air, the air supply was stopped, and the reactor was replaced with nitrogen gas. Then, 1.10 g of tetrasodium ethylenediaminetetraacetate tetrahydrate (reagent manufactured by Dojin Chemical Laboratories) was added to the polymerization mixture as an aqueous solution in 100 g of water. Next, the mixture was heated to 70°C, and copper extraction was carried out at 70°C for 2 hours. Subsequently, the mixture was separated by static separation into an unmodified polyphenylene ether solution (organic phase) and an aqueous phase to which the catalyst metal had been transferred. The organic phase was concentrated using a rotary evaporator until the polymer concentration reached 25% by mass. The above solution was mixed with methanol in a ratio of 6 to the polymer solution, and the polymer was precipitated. Wet polyphenylene ether was obtained by vacuum filtration using a glass filter. The wet polyphenylene ether was then washed with methanol in a ratio of 3 to the wet polyphenylene ether. The above washing operation was repeated three times. Next, the wet polyphenylene ether was held at 140°C and 1 mmHg for 120 minutes to obtain dry polyphenylene ether. The obtained polyphenylene ether was subjected to the measurements described above. The results of each analysis are shown in Table 1.

[0102] (Example 2) The procedure was carried out in the same manner as in Example 1, except that the phenolic raw materials were 22.00 g of 2,6-dimethylphenol, 69.01 g of 2-tert-butyl-5-methylphenol, and 8.98 g of 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane. The results of each analysis are shown in Table 1.

[0103] (Example 3) The procedure was carried out in the same manner as in Example 1, except that the phenolic raw materials were 20.00 g of 2,6-dimethylphenol, 62.75 g of 2-tert-butyl-5-methylphenol, and 17.25 g of 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane. The results of each analysis are shown in Table 1.

[0104] (Example 4) The procedure was carried out in the same manner as in Example 1, except that the phenolic raw materials were 18.16 g of 2,6-dimethylphenol, 56.97 g of 2-tert-butyl-5-methylphenol, and 24.87 g of 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane. The results of each analysis are shown in Table 1.

[0105] (Example 5) The procedure was carried out in the same manner as in Example 1, except that the phenolic raw materials were 16.72 g of 2,6-dimethylphenol, 52.45 g of 2-tert-butyl-5-methylphenol, and 30.83 g of 1,1-bis(2-methyl-4-hydroxy-5-t-butylphenyl)butane (ADEKA: AO-40). The results of each analysis are shown in Table 1.

[0106] (Example 6) The procedure was carried out in the same manner as in Example 1, except that the phenolic raw materials were 60.99 g of 2,6-dimethylphenol, 9.11 g of 2-tert-butyl-5-methylphenol, and 29.90 g of 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane (ADEKA: AO-30). The results of each analysis are shown in Table 1.

[0107] (Example 7) The procedure was carried out in the same manner as in Example 1, except that the phenolic raw materials were 25.52 g of 2,6-dimethylphenol, 34.31 g of 2-tert-butyl-5-methylphenol, and 40.18 g of 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane (ADEKA: AO-30). The results of each analysis are shown in Table 1.

[0108] (Example 8) The procedure was carried out in the same manner as in Example 1, except that the phenolic raw materials were 14.79 g of 2,6-dimethylphenol, 46.40 g of 2-tert-butyl-5-methylphenol, and 38.81 g of 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane (ADEKA: AO-30). The results of each analysis are shown in Table 1.

[0109] (Example 9) Similar to Example 1, oxidative polymerization, copper extraction, liquid-liquid separation, and concentration using a rotary evaporator were performed, and a polymer solution with a polymer concentration of 25% by mass was used as the stock solution for the modification reaction. A 500 mL three-necked flask, equipped with a nitrogen gas introduction line at the top of the reactor and a reflux condenser on the vent gas line at the top of the reactor, was purged with nitrogen. Then, 200 g of unmodified polyphenylene ether solution and 0.94 g of 4-dimethylaminopyridine were added. While stirring, 43 mL of triethylamine was added using a syringe. Next, 14.9 mL of methacryloyl chloride was taken with a syringe and added dropwise to the system at room temperature. For one hour after the completion of the dropwise addition, the flask was heated in an oil bath at 90°C and stirring was continued. Afterward, the mixture was further heated in the oil bath and the reaction continued under reflux. Four hours after the start of reflux, heating was stopped, and after returning to room temperature, 5 g of methanol was added to halt the reaction. Next, the reaction solution was filtered using a glass filter to obtain a solution from which the by-product triethylammonium salt had been removed. This solution was mixed with methanol in a ratio of 10 to the polymer solution, and the polymer was precipitated. Wet polyphenylene ether was obtained by vacuum filtration using a glass filter. Furthermore, the wet polyphenylene ether was washed with methanol in an amount such that the ratio of methanol to wet polyphenylene ether was 2.5. This washing procedure was repeated three times. Then, the wet polyphenylene ether was maintained at 100°C and 1 mmHg for 8 hours to obtain dry polyphenylene ether. 1 ¹H NMR measurements confirmed the presence of proton peaks originating from the olefin of the methacrylic group, leading to the conclusion that the hydroxyl group had been modified into a methacrylic group. Next, 79 parts by mass of modified polyphenylene ether, 20 parts by mass of TAIC (manufactured by Nippon Chemical Corporation), and 1 part by mass of organic peroxide (perbutyl P, manufactured by NOF Corporation) were added to toluene, stirred, and dissolved to obtain a varnish (solid content concentration 58% by mass). After impregnating L glass cloth (manufactured by Asahi Schwebel Co., Ltd., style: 2116) with this varnish, the excess varnish was scraped off by passing it through a predetermined slit, and the prepreg was dried in a drying oven at 105°C for a predetermined time to remove the toluene and obtain a prepreg. This prepreg was cut to a predetermined size, and the solid content of the thermosetting composition in the prepreg was calculated by comparing the mass of the prepreg with the mass of glass cloth of the same size, and it was found to be 52% by mass. A copper-clad laminate was obtained by stacking a predetermined number of these prepregs, and then applying copper foil (manufactured by Furukawa Electric Industry Co., Ltd., 35 μm thick, GTS-MP foil) to both sides of the stacked prepregs, and then performing a vacuum press. In this vacuum pressing process, first, the material was heated from room temperature at a heating rate of 2°C / min while applying a pressure of 40 kg / cm². 2 The conditions are as follows: After the temperature reaches 200°C, the temperature is maintained at 200°C while the pressure is 40 kg / cm². 2 The conditions of a 60-minute duration were also adopted. Next, a laminate (approximately 0.5 mm thick) was obtained by removing the copper foil from the copper-clad laminate by etching. The dielectric properties of the laminate obtained by the method described above were measured. The results of each analysis are shown in Table 2.

[0110] (Example 10) Similar to Example 2, oxidative polymerization, copper extraction, liquid-liquid separation, and concentration using a rotary evaporator were performed, and the mixture was further maintained at 100°C and 1 mmHg for 2 hours to obtain a dry polyphenylene ether. After methacrylic modification was performed in the same manner as in Example 9, except that the above dry polyphenylene ether was used as the raw material for the modification reaction, a laminate was prepared and its dielectric properties were measured. The results of each analysis are shown in Table 2.

[0111] (Example 11) Similar to Example 3, oxidative polymerization, copper extraction, liquid-liquid separation, and concentration using a rotary evaporator were performed, and the mixture was further maintained at 100°C and 1 mmHg for 2 hours to obtain a dry polyphenylene ether. After methacrylic modification was performed in the same manner as in Example 9, except that the above dry polyphenylene ether was used as the raw material for the modification reaction, a laminate was prepared and its dielectric properties were measured. The results of each analysis are shown in Table 2.

[0112] (Example 12) Similar to Example 4, oxidative polymerization, copper extraction, liquid-liquid separation, and concentration using a rotary evaporator were performed, and the mixture was further maintained at 100°C and 1 mmHg for 2 hours to obtain a dry polyphenylene ether. After methacrylic modification was performed in the same manner as in Example 9, except that the above dry polyphenylene ether was used as the raw material for the modification reaction, a laminate was prepared and its dielectric properties were measured. The results of each analysis are shown in Table 2.

[0113] (Example 13) Similar to Example 5, oxidative polymerization, copper extraction, liquid-liquid separation, and concentration using a rotary evaporator were performed, and the mixture was further maintained at 100°C and 1 mmHg for 2 hours to obtain a dry polyphenylene ether. After methacrylic modification was performed in the same manner as in Example 9, except that the above dry polyphenylene ether was used as the raw material for the modification reaction, a laminate was prepared and its dielectric properties were measured. The results of each analysis are shown in Table 2.

[0114] (Example 14) Similar to Example 6, oxidative polymerization, copper extraction, liquid-liquid separation, and concentration using a rotary evaporator were performed, and the mixture was further maintained at 100°C and 1 mmHg for 2 hours to obtain a dry polyphenylene ether. After methacrylic modification was performed in the same manner as in Example 9, except that the above dry polyphenylene ether was used as the raw material for the modification reaction, a laminate was prepared and its dielectric properties were measured. The results of each analysis are shown in Table 2.

[0115] (Example 15) Similar to Example 7, oxidative polymerization, copper extraction, liquid-liquid separation, and concentration using a rotary evaporator were performed, and the mixture was further maintained at 100°C and 1 mmHg for 2 hours to obtain a dry polyphenylene ether. Methacrylic modification was performed in the same manner as in Example 9, except that the above dry polyphenylene ether was used as the raw material for the modification reaction, and then laminates were prepared and their dielectric properties were measured. The results of each analysis are shown in Table 2.

[0116] (Example 16) Similar to Example 8, oxidative polymerization, copper extraction, liquid-liquid separation, and concentration using a rotary evaporator were performed, and the mixture was further maintained at 100°C and 1 mmHg for 2 hours to obtain a dry polyphenylene ether. After methacrylic modification was performed in the same manner as in Example 9, except that the above dry polyphenylene ether was used as the raw material for the modification reaction, a laminate was prepared and its dielectric properties were measured. The results of each analysis are shown in Table 2.

[0117] (Comparative Example 1) The procedure was carried out in the same manner as in Example 1, except that the phenol raw materials were 79.45 g of 2,6-dimethylphenol and 20.55 g of 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane. The results of each analysis are shown in Table 1.

[0118] (Comparative Example 2) The procedure was carried out in the same manner as in Example 1, except that the phenolic raw materials were 66.86 g of 2,6-dimethylphenol and 33.14 g of 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane (ADEKA: AO-30). The results of each analysis are shown in Table 1.

[0119] (Comparative Example 3) The procedure was carried out in the same manner as in Example 1, except that the phenolic raw materials were 55.95 g of 2,6-dimethylphenol and 44.05 g of 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane (ADEKA: AO-30). The results of each analysis are shown in Table 1.

[0120] (Comparative Example 4) Similar to Comparative Example 1, oxidative polymerization, copper extraction, liquid-liquid separation, and concentration using a rotary evaporator were performed, and the mixture was further maintained at 100°C and 1 mmHg for 2 hours to obtain a dry polyphenylene ether. After methacrylic modification was performed in the same manner as in Example 9, except that the above dry polyphenylene ether was used as the raw material for the modification reaction, a laminate was prepared and its dielectric properties were measured. The results of each analysis are shown in Table 2.

[0121] (Comparative Example 5) Similar to Comparative Example 2, oxidative polymerization, copper extraction, liquid-liquid separation, and concentration using a rotary evaporator were performed, and the mixture was further maintained at 100°C and 1 mmHg for 2 hours to obtain a dry polyphenylene ether. After methacrylic modification was performed in the same manner as in Example 9, except that the above dry polyphenylene ether was used as the raw material for the modification reaction, a laminate was prepared and its dielectric properties were measured. The results of each analysis are shown in Table 2.

[0122] (Comparative Example 6) Similar to Comparative Example 3, oxidative polymerization, copper extraction, liquid-liquid separation, and concentration using a rotary evaporator were performed, and the mixture was further maintained at 100°C and 1 mmHg for 2 hours to obtain a dry polyphenylene ether. After methacrylic modification was performed in the same manner as in Example 9, except that the above dry polyphenylene ether was used as the raw material for the modification reaction, a laminate was prepared and its dielectric properties were measured. The results of each analysis are shown in Table 2.

[0123] [Table 1]

[0124] [Table 2]

[0125] As shown in Tables 1 and 2, by comparing with the comparative example, the polyphenylene ether of the example was used to obtain a polyphenylene ether with excellent solubility in methyl ethyl ketone and low viscosity in toluene solution. Furthermore, the laminate using polyphenylene ether according to the examples showed superior dielectric properties compared to the laminate using polyphenylene ether in the comparative example. [Industrial applicability]

[0126] The polyphenylene ether of the present invention exhibits excellent solvent solubility, and the thermosetting composition containing it has excellent dielectric properties, thus possessing industrial value for use in electronic materials.

Claims

1. A polyphenylene ether which is an oxidative polymerization product comprising a repeating unit derived from phenol of formula (1) below, a repeating unit derived from phenol of formula (2) below, and a structural unit derived from phenol of formula (3) below, The phenol in formula (3) above is A phenol compound having two phenol units in its molecule, selected from the group consisting of 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 4,4'-methylenebis(2,6-dimethylphenol), bis(4-hydroxy-3-methylphenyl)sulfide, bis(4-hydroxy-3,5-dimethylphenyl)sulfone, α,α'-bis(4-hydroxy-3,5-dimethylphenyl)-1,4-diisopropylbenzene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane, and 1,1-bis(2-methyl-4-hydroxy-5-t-butylphenyl)butane, or 4,4'-[(3-hydroxyphenyl)methylene]bis(2,6-dimethylphenol), 4,4'-[(3-hydroxyphenyl)methylene]bis(2,3,6-trimethylphenol), 4,4'-[(4-hydroxyphenyl)methylene]bis(2,6-dimethylphenol), 4,4'-[(4-hydroxyphenyl)methylene]bis(2,3,6-trimethylphenol), 4,4'-[(2-hydroxy-3-methoxyphenyl)methylene]bis(2,6-dimethylphenol), 4,4'-[(3,4-dihydroxyphenyl)methylene [Len]bis(2,6-dimethylphenol), 4,4'-[(3,4-dihydroxyphenyl)methylene]bis(2,3,6-trimethylphenol), 2,2'-[(4-hydroxyphenyl)methylene]bis(3,5,6-trimethylphenol), 4,4'-[4-(4-hydroxyphenyl)cyclohexylidene]bis(2,6-dimethylphenol), 4,4'-[(2-hydroxyphenyl)methylene]-bis(2,3,6-trimethylphenol), 4,4'-[1-[4-[1-(4-hydroxy-3,5-dimethylphenyl)-1- [methylethyl]phenyl]ethylidene]bis(2,6-dimethylphenol), 4,4'-[1-[4-[1-(4-hydroxy-3-fluorophenyl)-1-methylethyl]phenyl]ethylidene]bis(2,6-dimethylphenol), 2,6-bis[(4-hydroxy-3,5-dimethylphenyl)ethyl]-4-methylphenol, 2,6-bis[(4-hydroxy-2,3,6-trimethylphenyl)methyl]-4-methylphenol, 2,6-bis[(4-hydroxy-3,5,6-trimethylphenyl)methyl]-4-ethylpheno 2,4-bis[(4-hydroxy-3-methylphenyl)methyl]-6-methylphenol, 2,6-bis[(4-hydroxy-3-methylphenyl)methyl]-4-methylphenol, 2,4-bis[(4-hydroxy-3-cyclohexylphenyl)methyl]-6-methylphenol, 2,4-bis[(4-hydroxy-3-methylphenyl)methyl]-6-cyclohexylphenol, 2,4-bis[(4-hydroxy-2,3,6-trimethylphenyl)methyl]-6-cyclohexylphenol, 3,6-bis[(4-hydroxy-3,5-dimethylphenyl)methyl]-1,2-benzenediol, 4,6-bis[(4-hydroxy-3,5-dimethylphenyl)methyl]-1,3-benzenediol, 2,4,6-tris[(4-hydroxy-3,5-dimethylphenyl)methyl]-1,3-benzenediol, 2,4,6-tris[(2-hydroxy-3,5-dimethylphenyl)methyl]-1,3-benzenediol, 2,2'-methylenebis[6-[(4 / 2-hydroxy-2,5 / 3,6-dimethylphenyl)methyl [(4-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol], 2,2'-methylenebis[6-[(4-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol], 2,2'-methylenebis[6-[(4 / 2-hydroxy-2,3,5 / 3,4,6-trimethylphenyl)methyl]-4-methylphenol], 2,2'-methylenebis[6-[(4-hydroxy-2,3,5-trimethylphenyl)methyl]-4-methylphenol], 4,4'-methylenebis[ 2-[(2,4-dihydroxy-3-methylphenyl)methyl]-3,6-dimethylphenol], 6,6'-methylenebis[4-[(4-hydroxy-3,5-dimethylphenyl)methyl]-1,2,3-benzenetriol], 4,4'-cyclohexylidenebis[2-cyclohexyl-6-[(4-hydroxy-3,5-dimethylphenyl)methyl]phenol], 4,4'-cyclohexylidenebis[2-cyclohexyl-6-[(4-hydroxy-2-methyl- A phenol compound having three or more phenol units in its molecule, selected from the group consisting of 5-cyclohexylphenyl)methyl[phenol], 4,4',4'',4'''-(1,2-ethanediylidene)tetrakis(2,6-dimethylphenol), 4,4',4'',4'''-(1,4-phenylenedimethylidene)tetrakis(2,6-dimethylphenol), and 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, The number-average molecular weight in terms of polystyrene is 500 to 15,000. A polyphenylene ether characterized by the following features. 【Chemistry 1】 (In formula (1), R １１ Each of these is independently a saturated hydrocarbon group having 1 to 6 carbon atoms which may be substituted, an aryl group having 6 to 12 carbon atoms which may be substituted, or a halogen atom, and R １２ Each of these is independently a hydrogen atom, an optionally substituted C1-C6 hydrocarbon group, an optionally substituted C6-C12 aryl group, or a halogen atom. 【Chemistry 2】 (In formula (2), R ２２ Each of these is independently a hydrogen atom, an optionally substituted saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms, an optionally substituted aryl group having 6 to 12 carbon atoms, or a halogen atom, and two R ２２ Both are not hydrogen atoms, R ２１ This is a substructure represented by the following formula (4). 【Transformation 3】 (In equation (3), X is any a-valent linking group, a is an integer from 2 to 6, R ３ (This is either a linear alkyl group having 1 to 8 carbon atoms or a substructure represented by the following formula (4), where the carbon atom of the benzene ring to which the -OH group is bonded is considered as position 1, and it is bonded to at least one of the carbon atoms at positions 2 or 6, and k is an integer from 1 to 4 independently.) 【Chemistry 4】 (In formula (4), R ４１ is each independently a linear alkyl group having 1 to 8 carbon atoms which may be substituted, or a cyclic alkyl structure having 3 to 8 carbon atoms to which two R ４１ are bonded, R ４２ is each independently an alkylene group having 1 to 8 carbon atoms which may be substituted, b is each independently 0 or 1, and R ４３ is either a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may be substituted, or a phenyl group which may be substituted.) R in formula (2) above ２１ The substructure represented by formula (4) and R of formula (3) ３ The substructures represented by formula (4) above may be the same or different.

2. In at least one of the repeating units derived from phenol of formula (2), R ２１ The polyphenylene ether according to claim 1, wherein is a t-butyl group.

3. The polyphenylene ether according to claim 1 or 2, having at least one substructure selected from the group consisting of formulas (5), (6), (7), and (8) below. 【Transformation 5】 【Transformation 6】 【Transformation 7】 (In formula (7), R ７ (This is a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, and the saturated or unsaturated hydrocarbon may have substituents to the extent that it satisfies the condition of having 1 to 10 carbon atoms.) 【Transformation 8】 (In formula (8), R ８ R is a saturated or unsaturated divalent hydrocarbon group having 1 to 10 carbon atoms, and the saturated or unsaturated divalent hydrocarbon may have substituents to the extent that it satisfies the condition of having 1 to 10 carbon atoms. ９ (This is a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, and the saturated or unsaturated hydrocarbon may have substituents to the extent that it satisfies the condition of having 1 to 10 carbon atoms.)

4. A method for producing a polyphenylene ether according to any one of claims 1 to 3, comprising the step of carrying out oxidative polymerization of the phenol of formula (1), the phenol of formula (2), and the phenol of formula (3).

5. A thermosetting composition comprising the polyphenylene ether described in any one of claims 1 to 3.

6. A prepreg that is a composite comprising a substrate and the thermosetting composition described in claim 5.

7. The prepreg according to claim 6, wherein the substrate is glass cloth.

8. A laminate comprising a cured prepreg according to claim 6 or 7 and a metal foil.

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