Polyphenylene ether, its production method, thermosetting composition, prepreg, and laminate

Abstract

To provide a polyphenylene ether excellent in solubility in a general-purpose ketone-based solvent, a production method of the same, a thermosetting composition using the polyphenylene ether, prepreg, and laminate.SOLUTION: A polyphenylene ether includes: 5-85 mol% of a repeating unit derived from a phenol of formula (1); and 15-95 mol% of a repeating unit derived from a phenol of formula (2) based on 100 mol% of a total of the repeating unit derived from the phenol of formula (1) and the repeating unit derived from the phenol of formula (2), where the reduced viscosity (η sp / c) measured at 30°C by a chloroform solution of a concentration of 0.5 g / dL is 0.03-0.30 dL / g.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Polyphenylene ether (hereinafter 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, automotive, food, and packaging fields, as well as in various other industrial materials. In particular, in recent years, its low dielectric properties and heat resistance have led to its application as a modifier in electronic materials such as circuit board materials and in a variety of other applications.

[0003] However, while high-molecular-weight polyphenylene ethers with repeating units derived from monohydric phenols, such as 2,6-dimethylphenol, are soluble in highly toxic solvents such as chloroform, they are poorly soluble at high concentrations at room temperature in aromatic solvents such as toluene, which are known to be good solvents, and are insoluble in ketone solvents such as methyl ethyl ketone. Therefore, when used as a wiring board material, for example, it is difficult to handle resin varnish solutions in toluene or methyl ethyl ketone.

[0004] Patent Document 1 discloses that polyphenylene ethers having a low molecular weight and a specific particle size have excellent solubility in solvents such as methyl ethyl ketone. Furthermore, Patent Document 2 describes a modified polyphenylene ether compound having a specific polyphenylene ether moiety in its molecular structure and having at least one p-ethenylbenzyl group, m-ethenylbenzyl group, or the like at the molecular end. Furthermore, Patent Document 3 describes a modified polymer having a polyphenylene ether moiety in its molecular structure and having a methacryl group at the molecular end. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-99824 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-339328 [Patent Document 3] Special Publication No. 2008-510059 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, Patent Documents 1 to 3 disclose methods for producing polyphenylene ethers and the like with reduced molecular weight to improve the solvent solubility of polyphenylene ethers, but simply reducing the molecular weight of polyphenylene ethers does not significantly improve the solubility at room temperature in general-purpose ketone solvents such as methyl ethyl ketone, and the improvement is still insufficient. In particular, a method for improving the long-term solvent solubility in ketone solvents is desired.

[0007] The present invention has been made in view of the above-mentioned problems, and aims to provide a polyphenylene ether having excellent solubility in general-purpose ketone solvents and a method for producing the same, as well as a thermosetting composition, a prepreg, and a laminate using the polyphenylene ether. [Means for solving the problem]

[0008] That is, the present invention is as follows. [1] The repeating unit derived from a phenol of the following formula (1) comprises 5 to 85 mol % of the repeating unit derived from a phenol of the following formula (1) and 15 to 95 mol % of the repeating unit derived from a phenol of the following formula (2), relative to 100 mol % in total of the repeating unit derived from a phenol of the following formula (1) and the repeating unit derived from a phenol of the following formula (2), The reduced viscosity (ηsp / c) measured in a chloroform solution with a concentration of 0.5 g / dL at 30°C is 0.03 to 0.30 dL / g. A polyphenylene ether characterized by: [ka] (In formula (1), R 11 each independently represents 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; R 12 are each independently a 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. [ka] (In formula (2), R 22 are each 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 are not both hydrogen atoms, and R 21 is a partial structure represented by the following formula (3). [ka] (In formula (3), R 31 are each independently an optionally substituted linear alkyl group having 1 to 8 carbon atoms, or two R 31 is a cyclic alkyl structure having 1 to 8 carbon atoms to which R 32 each independently represents an optionally substituted alkylene group having 1 to 8 carbon atoms; each b independently represents 0 or 1; R 33 is a hydrogen atom, an optionally substituted alkyl group having 1 to 8 carbon atoms, or an optionally substituted phenyl group. [2] The polyphenylene ether according to [1], wherein the partial structure represented by the formula (3) is a t-butyl group. [3] The polyphenylene ether according to [1] or [2], having an average number of hydroxyl groups per molecule of less than 2.5. [4] The polyphenylene ether according to any one of [1] to [3], which has an average number of hydroxyl groups of less than 0.2 per molecule. [5] The polyphenylene ether according to any one of [1] to [4], which has at least one partial structure selected from the group consisting of the following formula (4), formula (5), formula (6), and formula (7), and has an average number of hydroxyl groups per molecule of less than 0.2: [ka] [ka] [ka] (In formula (6), R 6 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 a substituent as long as the condition of having 1 to 10 carbon atoms is satisfied. [ka] (In formula (7), R 7 is a saturated or unsaturated divalent hydrocarbon group having 1 to 10 carbon atoms, and the saturated or unsaturated divalent hydrocarbon may have a substituent within the range of satisfying the condition of having 1 to 10 carbon atoms, and R 8 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 a substituent as long as the condition of having 1 to 10 carbon atoms is satisfied. [6] The polyphenylene ether according to any one of [1] to [5], which contains a repeating unit derived from a monohydric phenol having at least one unsaturated hydrocarbon group on a carbon atom in the ortho position relative to a carbon atom to which a phenol hydroxyl group is bonded. [7] The polyphenylene ether according to [6], wherein the monohydric phenol is 2-allylphenol or 2-methyl-6-allylphenol. [8] A method for producing polyphenylene ether according to any one of [1] to [7], comprising a step of oxidatively polymerizing a phenol of the formula (1) and a phenol of the formula (2). [9] A polyphenylene ether solution comprising the polyphenylene ether according to any one of [1] to [7] and a ketone solvent.

[10] A thermosetting composition comprising the polyphenylene ether according to any one of [1] to [7].

[11] A prepreg comprising a substrate and the thermosetting composition according to

[10] .

[12] The prepreg according to

[11] , wherein the substrate is glass cloth.

[13] A laminate comprising a cured product of the prepreg according to

[11] or

[12] and a metal foil. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a polyphenylene ether having excellent solubility in a general-purpose ketone solvent, a method for producing the same, and a thermosetting composition, a prepreg, and a laminate using the polyphenylene ether. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a mode for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. The following present embodiment is an example for explaining the present invention, and the present invention is not limited to only this present embodiment, and the present invention can be carried out by appropriately modifying it within the scope of its gist.

[0011] In the present 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 specified. In this specification, A (numeric value) to B (numeric value) means greater than or equal to A and less than or equal to B. In addition, in this specification, examples of the substituent include saturated or unsaturated hydrocarbon groups having 1 to 10 carbon atoms, aryl groups having 6 to 10 carbon atoms, and halogen atoms.

[0012] <Polyphenylene ether> The polyphenylene ether of the present embodiment contains at least a repeating unit derived from a phenol of the following formula (1) and a repeating unit derived from a phenol of the following formula (2), and the repeating units in the compound may consist solely of a repeating unit derived from a phenol of the following formula (1) and a repeating unit derived from a phenol of the following formula (2). [ka] (In formula (1), R 11 each independently represents 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; R 12 are each independently a 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. [ka] (In formula (2), R 22 are each 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 are not both hydrogen atoms, and R 21 is a partial structure represented by the following formula (3). [ka] (In formula (3), R 31 are each independently an optionally substituted linear alkyl group having 1 to 8 carbon atoms, or two R 31 is a cyclic alkyl structure having 1 to 8 carbon atoms to which R 32each independently represents an optionally substituted alkylene group having 1 to 8 carbon atoms; each b independently represents 0 or 1; R 33 is either a hydrogen atom, an optionally substituted alkyl group having 1 to 8 carbon atoms, or an optionally substituted phenyl group.

[0013] In the above formula (1), R 11 are each independently preferably 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. 11 Preferably, both have the same structure. Above R 11 Substituents in the saturated 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.

[0014] In the above formula (1), R 12 are each independently preferably a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, more preferably a hydrogen atom or a methyl group. 12 are preferably different, and it is more preferable that one is a hydrogen atom and the other is a hydrocarbon group having 1 to 6 carbon atoms (preferably a methyl group). 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.

[0015] In the above formula (2), R 22 are each independently preferably 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 which 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 which may be substituted with an alkyl group having 1 to 6 carbon atoms, and even more preferably a hydrogen atom or a methyl group. 22are preferably different, and it is more preferable that one is a hydrogen atom and the other is a hydrocarbon group having 1 to 6 carbon atoms (preferably a methyl group). Above R 22 Examples of the substituent in the saturated or unsaturated hydrocarbon group having 1 to 20 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] The partial structure represented by the above formula (3) is preferably a group containing a secondary and / or tertiary carbon, such as an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a tert-amyl group, a 2,2-dimethylpropyl group, a cyclohexyl group, or a structure having a phenyl group at the end of any of these groups, more preferably a tert-butyl group or a cyclohexyl group, and even more preferably a tert-butyl group. In addition, the above R 31 the substituent in the linear alkyl group having 1 to 8 carbon atoms, 32 The substituents in the alkylene group having 1 to 8 carbon atoms and the above R 33 Examples of the substituent on the alkyl group having 1 to 8 carbon atoms and the phenyl group 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 this embodiment, the structure of polyphenylene ether can be identified by analyzing the polyphenylene ether using techniques such as NMR and mass spectrometry. A specific method for identifying the structure of polyphenylene ether is to perform field desorption mass spectrometry (FD-MS), which is known to be less susceptible to fragmentation, and estimate the repeating units based on the intervals between detected ions. Furthermore, the structure of polyphenylene ether can be estimated by combining peak analysis of fragment ions using electron ionization (EI) and structural analysis by NMR.

[0018] The polyphenylene ether of this embodiment contains 5 to 85 mol % of repeating units derived from a phenol of formula (1) and 15 to 95 mol % of repeating units derived from a phenol of formula (2), relative to a total of 100 mol % of repeating units derived from a phenol of formula (1) and repeating units derived from a phenol of formula (2). From the viewpoint of obtaining a polyphenylene ether having excellent solvent solubility and a low dielectric loss tangent, the repeating units derived from a phenol of formula (2) are preferably 18 mol % or more, more preferably 20 mol % or more. From the same viewpoint, the repeating units derived from a phenol of formula (1) are preferably 82 mol % or less, more preferably 80 mol % or less. The polyphenylene ether of the present embodiment may contain one or more types of repeating units derived from the phenol of formula (1), and may contain one or more types of repeating units derived from the phenol of formula (2).

[0019] The total molar amount of the repeating units derived from phenol of formula (1) and the repeating units derived from phenol of formula (2) relative to 100 mol % of the monomer units contained in the polyphenylene ether of the present embodiment (for example, all monomer units derived from phenol contained in the polyphenylene ether) is preferably 75 mol % or more, more preferably 90 mol % or more, and even more preferably 95 mol % or more.

[0020] The respective ratios of the repeating units derived from the phenol of formula (1) and the repeating units derived from the phenol of formula (2) are, for example, 1 H NMR, 13 It can be determined using an analytical method such as C NMR, and more specifically, it can be measured by the method described in the Examples below.

[0021] Since the phenol of formula (1) has no unsubstituted ortho-positions (i.e., no hydrogen atoms are bonded to the carbon atoms two ortho to the carbon atom to which the hydroxyl group is bonded), it can react with another phenolic monomer only at the carbon atom para to the phenolic hydroxyl group. Therefore, the repeating unit derived from formula (1) includes a repeating unit having the structure of formula (8) below. [ka] (In formula (8), R 11 and R 12 is the same as equation (1).

[0022] In addition to the phenolic hydroxyl group, the phenol of formula (2) can react with another phenolic monomer at either the ortho- or para-position of the phenol. Thus, the repeating unit derived from the phenol of formula (2) has a monomer unit of formula (9), formula (10), or a combination thereof: [ka] [ka] (R in Equation (9) and Equation (10) 21 , R 22 is the same as equation (2).

[0023] The reduced viscosity of the polyphenylene ether in this embodiment measured in a chloroform solution having a concentration of 0.5 g / dL at 30° C. is preferably 0.03 to 0.30 dL / g, and more preferably 0.06 to 0.30 dL / g. The reduced viscosity can be appropriately selected depending on the application. For example, if it is desired to further improve the fluidity when dissolved in a solvent for preparing a varnish in the process of applying it to a substrate material, a low reduced viscosity is preferred. The reduced viscosity can be measured by the method described in the Examples below.

[0024] The polyphenylene ether of this embodiment may contain, as an impurity (sometimes simply referred to as "impurity A" in this specification), a terpolymer containing a structure derived from a dihydric phenol of the following formula (11) in addition to the phenol of formula (1) and the phenol of formula (2). The polyphenylene ether of this embodiment may be a mixture of the above polyphenylene ether and the above impurity A. The molar ratio of impurity A to 100 mol % of the polyphenylene ether of this embodiment is preferably 10 mol % or less, and more preferably 5 mol % or less. The impurity A can be synthesized, for example, as a terpolymer containing a structure derived from a dihydric phenol where z=0 in formula (11) by reacting the following formula (12), which is generated as a by-product during the oxidative polymerization of a monohydric phenol, with a polyphenylene ether composed of the monohydric phenol. [ka] (In formula (11), R 11 and R 12 is the same as formula (1), z is 0 or 1, and Y is [ka] (In the formula, R 41 are each independently any one of an optionally substituted hydrocarbon group having 1 to 6 carbon atoms, an optionally substituted aryl group having 6 to 12 carbon atoms, and a halogen atom. [ka] (In formula (12), R 11 and R 12 is the same as equation (1).

[0025] In the present embodiment, the average number of hydroxyl groups in the unmodified polyphenylene ether is preferably less than 2.5 per molecule, more preferably less than 2.2 per molecule, and even more preferably less than 2.0 per molecule. If the average number of hydroxyl groups exceeds 2.5 per molecule, it means that the polyphenylene ether is a multi-branched unmodified polyphenylene ether whose structure cannot be controlled. The average number of hydroxyl groups can be measured by the method described in the Examples below.

[0026] The polyphenylene ether in this embodiment may be a modified polyphenylene ether in which hydroxyl groups contained in the polyphenylene ether are modified into functional groups (for example, functional groups containing unsaturated carbon bonds). In the case of the modified polyphenylene ether, the average number of hydroxyl groups is preferably less than 0.2 per molecule, more preferably less than 0.1 per molecule, and even more preferably less than 0.01 per molecule.

[0027] The polyphenylene ether in this embodiment may have at least one partial structure selected from the group consisting of the following formulas (4), (5), (6), and (7). [ka] [ka] [ka] (In formula (6), R 6 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 6 may have a substituent within the range of a total carbon number of 1 to 10.) [ka] (In formula (7), R 7 is a saturated or unsaturated divalent hydrocarbon group having 1 to 10 carbon atoms, and the saturated or unsaturated divalent hydrocarbon is R7 may have a substituent within the range of 1 to 10 carbon atoms in total, and R 8 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 8 may have a substituent within the range of a total carbon number of 1 to 10.) The partial structure represented by at least one selected from the group consisting of the above formula (4), formula (5), formula (6), and formula (7) may be directly bonded to a hydroxyl group contained in the polyphenylene ether.

[0028] The ratio of the repeating unit derived from phenol of formula (1) and the repeating unit derived from phenol of formula (2) contained in the modified polyphenylene ether into which at least one partial structure represented by formula (4), formula (5), formula (6), and formula (7) has been introduced is, for example, 1 H NMR, 13 It can be determined using an analytical method such as C NMR, and more specifically, it can be measured by the method described in the Examples below.

[0029] The polyphenylene ether of this embodiment may contain a monohydric phenol having at least one unsaturated hydrocarbon group on the carbon atom ortho-positioned relative to the carbon atom to which the hydroxyl group of the phenol is bonded. The monohydric phenol preferably has one unsaturated hydrocarbon group bonded to the carbon atom ortho-positioned relative to the carbon atom to which the hydroxyl group of the phenol is bonded. The unsaturated hydrocarbon may be bonded to one of the carbon atoms ortho-positioned relative to the carbon atom to which the hydroxyl group of the phenol is bonded, or one of the unsaturated hydrocarbons may be bonded to one of the carbon atoms ortho-positioned relative to the carbon atom to which the hydroxyl group of the phenol is bonded. The monohydric phenol having at least one unsaturated hydrocarbon group on the carbon atom ortho-positioned relative to the carbon atom to which the hydroxyl group of the phenol is bonded refers to a monohydric phenol different from the phenol of formula (1) or formula (2). The unsaturated hydrocarbon group is preferably an unsaturated hydrocarbon group having 3 to 10 carbon atoms, and more preferably an unsaturated hydrocarbon group having 3 to 5 carbon atoms. Examples of such unsaturated hydrocarbon groups include alkenyl groups (e.g., vinyl group, allyl group, etc.) and alkynyl groups (e.g., ethynyl group, 1-propynyl, 2-propynyl, etc.). The unsaturated hydrocarbon may have a substituent as long as it satisfies the condition of having 3 to 10 carbon atoms.

[0030] The introduction rate of the monohydric phenol having at least one unsaturated hydrocarbon group on a carbon atom in the ortho position relative to the carbon atom to which the phenol hydroxyl group is bonded may be adjusted as appropriate to adjust the number of curable functional groups, but the monohydric phenol having at least one unsaturated hydrocarbon group on a carbon atom in the ortho position relative to the carbon atom to which the phenol hydroxyl group is bonded is preferably 0.1 to 30 mol %, and more preferably 0.1 to 25 mol %, relative to the total of phenol of formula (1) and the monohydric phenol having at least one unsaturated hydrocarbon group on a carbon atom in the ortho position relative to the carbon atom to which the phenol hydroxyl group is bonded. In the polyphenylene ether of this embodiment, the molar ratio of the repeating units derived from the monohydric phenol having at least one unsaturated hydrocarbon group on a carbon atom in the ortho position relative to the carbon atom to which the hydroxyl group of the phenol is bonded to the sum of the repeating units derived from the phenol of formula (1) and the repeating units derived from the monohydric phenol having at least one unsaturated hydrocarbon group on a carbon atom in the ortho position relative to the carbon atom to which the hydroxyl group of the phenol is bonded is preferably 0.1 to 40 mol %, and more preferably 0.1 to 10 mol %.

[0031] <Method of producing polyphenylene ether> The polyphenylene ether of the present embodiment can be obtained, for example, by a method including at least a step of oxidatively polymerizing a monohydric phenol compound represented by the above formula (1) or formula (2). The above oxidative polymerization step preferably involves oxidatively polymerizing a raw material containing at least the above phenol of formula (1) and the phenol of formula (2).

[0032] Examples of the monohydric phenol compound 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. Among these, 2,6-dimethylphenol, 2,3,6-trimethylphenol, and 2,6-diphenylphenol are particularly preferred because they are inexpensive and easily available. The monohydric phenol compound represented by the above formula (1) may be used singly or in combination of two or more kinds.

[0033] Examples of the monohydric phenol compound represented by the above formula (2) include 2-isopropyl-5-methylphenol, 2-cyclohexyl-5-methylphenol, 2-tert-butyl-5-methylphenol, 2-isobutyl-5-methylphenol, etc. 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 monohydric phenol compounds represented by the above formula (2) may be used singly or in combination of two or more kinds.

[0034] The step of carrying out the oxidative polymerization may be, for example, a step of carrying out oxidative polymerization of a raw material containing, in addition to the phenol of formula (1) and the phenol of formula (2), a monohydric phenol having at least one unsaturated hydrocarbon group on a carbon atom ortho to the carbon atom to which the hydroxyl group of the phenol is bonded. The monohydric phenol having at least one unsaturated hydrocarbon group on the carbon atom in the ortho position relative to the carbon atom to which the phenol hydroxyl group is bonded is preferably a monohydric phenol in which at least one (preferably one) unsaturated hydrocarbon group is bonded to the carbon atom in the ortho position and hydrogen atoms are bonded to the carbon atoms in the meta and para positions, more preferably 2-allylphenol or 2-allyl-6-methylphenol, and even more preferably 2-allylphenol. The monohydric phenol having at least one unsaturated hydrocarbon group on the carbon atom ortho to the carbon atom to which the phenol hydroxyl group is bonded may be used alone or in combination of two or more kinds.

[0035] Normally, in the oxidative polymerization of phenols having a hydrogen atom at the ortho position (for example, 2-methylphenol, 2,5-dimethylphenol, 2-phenylphenol), an ether bond can also be formed at the ortho position, making it difficult to control the bonding position of the phenol compound during oxidative polymerization. As a result, a high-molecular-weight polymer is obtained that is polymerized in a branched manner with an average of three or more hydroxyl groups per molecule, and ultimately a gel component that is insoluble in solvents is generated (see the oxidative polymerization of 2,5-dimethylphenol and 2,6-dimethylphenol in Reference Example 1 below). On the other hand, when a phenol having a bulky substituent at one ortho-position, as represented by the above formula (2), is used, it becomes possible to control the bonding position of the phenol compound during oxidative polymerization, even though it has a hydrogen atom at the ortho-position on the opposite side, and polyphenylene ether having an average of less than 2.5 hydroxyl groups per molecule can be obtained. Furthermore, when a phenol having a bulky substituent at one ortho position represented by the above formula (2) is used, even when a monohydric phenol having a non-bulky substituent (e.g., a hydrogen atom, an allyl group, a methyl group, an ethyl group, a methoxy group, etc.) at the ortho position of the oxygen atom of the phenol is used as the third component, gelation does not occur and a polyphenylene ether having an average of less than 2.5 hydroxyl groups per molecule can be obtained.

[0036] The molecular weight of the polyphenylene ether in this embodiment can be adjusted by the molar ratio of the repeating units derived from the above formula (2) to the sum of the repeating units derived from the above formula (1) and the repeating units derived from the above formula (2). That is, when the molar ratio of the repeating units derived from the above formula (2) is high, the achieved molecular weight (reduced viscosity) can be lowered, and when the molar ratio of the repeating units derived from the above formula (2) is low, the molecular weight (reduced viscosity) can be adjusted to be high. Although the reason for this is not clear, it is presumed that the bulky substitution at the ortho position of the above formula (2) suppresses the increase in molecular weight.

[0037] (Oxidative polymerization process) In the method for producing polyphenylene ether, an aromatic solvent that 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, and examples of such solvents include aromatic hydrocarbons such as benzene, toluene, xylene (including o-, m-, and p-isomers), and ethylbenzene; halogenated hydrocarbons such as chlorobenzene and dichlorobenzene; and nitro compounds such as nitrobenzene.

[0038] The polymerization catalyst used in this embodiment may be a known catalyst system that can generally be used for producing polyphenylene ether. Commonly known catalyst systems include those that consist of a transition metal ion having oxidation-reduction ability and an amine compound that can form a complex with the transition metal ion, such as a catalyst system consisting of a copper compound and an amine compound, a catalyst system consisting of a manganese compound and an amine compound, or a catalyst system consisting of a cobalt compound and an amine compound. Because the polymerization reaction proceeds efficiently under slightly alkaline conditions, a small amount of alkali or an additional amine compound may be added.

[0039] The polymerization catalyst preferably used in the present embodiment is a catalyst containing 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 (13) as the amine compound:

[0040] [ka] In formula (13), R 14 , R 15 , R 16 , R 17 are each independently a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, provided that all of them are not hydrogen atoms at the same time. 18 is a linear or methyl-branched alkylene group having 2 to 5 carbon atoms.

[0041] Examples of copper compounds for the catalyst components described herein are listed below. Suitable copper compounds include cuprous compounds, cupric compounds, and 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 metal compounds are cuprous chloride, cupric chloride, cuprous bromide, and cupric bromide. These copper salts may also be synthesized immediately upon use from an oxide (e.g., cuprous oxide), carbonate, hydroxide, or the like and the corresponding halogen or acid. A frequently used method is to mix the cuprous oxide exemplified above with a hydrogen halide (or a solution of a hydrogen halide).

[0042] 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 compounds can be used as aqueous solutions or solutions using appropriate solvents. These halogen compounds can be used alone or in combination of two or more. Preferred halogen compounds are aqueous solutions of hydrogen chloride and hydrogen bromide.

[0043] The amount of these compounds used is not particularly limited, but is preferably 2 to 20 times the molar amount of halogen atoms relative to the molar amount of copper atoms, and the preferred amount of copper atoms used is in the range of 0.02 to 0.6 moles per 100 moles of the phenol compound added to the polymerization reaction.

[0044] Examples of the diamine compound as a catalyst component are listed below: 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, amine, N,N'-n-butylethylenediamine, Ni-butylethylenediamine, N,N'-i-butylethylenediamine, Nt-butylethylenediamine, N,N'-t-butylethylenediamine, N,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. A preferred diamine compound for this embodiment is one in which the number of carbon atoms in the alkylene group connecting the two nitrogen atoms is 2 or 3. The amount of these diamine compounds used is not particularly limited, but is preferably in the range of 0.01 mol to 10 mol per 100 mol of the phenol compound added to the polymerization reaction.

[0045] In this embodiment, the polymerization catalyst may contain a primary amine and a secondary monoamine as components thereof. Examples of the secondary monoamine include, but are not limited to, 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.

[0046] A tertiary monoamine compound may also be included as a constituent of the polymerization catalyst in this embodiment. The tertiary monoamine compound is an aliphatic tertiary amine, including an alicyclic tertiary amine. Examples include trimethylamine, triethylamine, tripropylamine, tributylamine, triisobutylamine, dimethylethylamine, dimethylpropylamine, allyldiethylamine, dimethyl-n-butylamine, diethylisopropylamine, and N-methylcyclohexylamine. These tertiary monoamines may be used alone or in combination of two or more. The amount of these compounds used is not particularly limited, but is preferably 15 moles or less per 100 moles of the phenol compound added to the polymerization reaction.

[0047] In this embodiment, there is no limitation on adding a surfactant that has been known to have the effect of improving polymerization activity. Examples of such surfactants include trioctylmethylammonium chloride, known under the trade names Aliquat 336 and Capriquat. The amount of surfactant used is preferably within a range not exceeding 0.1% by mass relative to the total amount (100% by mass) of the polymerization reaction mixture.

[0048] As the oxygen-containing gas in the polymerization of this embodiment, in addition to pure oxygen, a mixture of oxygen and an inert gas such as nitrogen in any ratio, air, or a mixture of air and an inert gas such as nitrogen in any ratio can be used. Normal pressure is sufficient for the pressure in the system during the polymerization reaction, but either reduced or increased pressure can be used as necessary.

[0049] 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 gel may be formed, so it is in the range of 0 to 60°C, preferably 10 to 40°C.

[0050] In the method for producing polyphenylene ether, the polymerization can also be carried out in a poor solvent such as alcohol.

[0051] (Copper extraction and by-product removal process) In this embodiment, there are no particular limitations 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, or the like is added to the reaction solution to deactivate the catalyst. Furthermore, a conventionally known method can be used to remove the dihydric phenol by-products generated by the polymerization of polyphenylene ether. As described above, if the metal ions serving as the catalyst are substantially deactivated, the mixture can be decolorized simply by heating. Alternatively, a method of adding a required amount of a known reducing agent is also possible. Examples of known reducing agents include hydroquinone and sodium dithionite.

[0052] (Liquid-liquid separation process) In the method for producing polyphenylene ether, water may be added to extract the compound that has deactivated the copper catalyst, and then liquid-liquid separation into an organic phase and an aqueous phase may be performed, followed by removing the aqueous phase to remove the copper catalyst from the organic phase. This liquid-liquid separation step is not particularly limited, and examples thereof include static separation and separation using a centrifuge. In order to promote the liquid-liquid separation, a known surfactant or the like may be used.

[0053] (concentration / drying process) Subsequently, in the method for producing polyphenylene ether of the present embodiment, the organic phase containing the polyphenylene ether after liquid-liquid separation may be concentrated and dried by volatilizing the solvent.

[0054] The method for volatilizing the solvent contained in the organic phase is not particularly limited, but examples include a method of transferring the organic phase to a high-temperature concentration tank and concentrating it by distilling off the solvent, and a method of concentrating it by distilling off toluene using equipment such as a rotary evaporator.

[0055] The temperature for the drying treatment in the drying step is preferably at least 60° C. or higher, more preferably 80° C. or higher, even more preferably 120° C. or higher, and most preferably 140° C. or higher. When the polyphenylene ether is dried at a temperature of 60° C. or higher, the content of high-boiling-point volatile components in the polyphenylene ether powder can be efficiently reduced.

[0056] In order to obtain polyphenylene ether with high efficiency, a method of increasing the drying temperature, a method of increasing the degree of vacuum in the drying atmosphere, a method of stirring during drying, and the like are effective, but a method of increasing the drying temperature is particularly preferred from the viewpoint of production efficiency. In the drying step, it is preferable to use a dryer equipped with a mixing function. Examples of the mixing function include a stirring type dryer and a tumbling type dryer. This allows the processing amount to be increased and productivity to be maintained at a high level.

[0057] The polyphenylene ether of this embodiment can also be produced by a redistribution reaction in which a polyphenylene ether derived from a phenol of formula (1) is equilibrated with a phenol compound of formula (2) in the presence of an oxidizing agent. Redistribution reactions are known in the art and are described, for example, in U.S. Patent No. 3,496,236 to Cooper et al. and U.S. Patent No. 5,880,221 to Liska et al.

[0058] (Modification reaction step) There are no limitations on the method for introducing functional groups into the hydroxyl groups of unmodified polyphenylene ether. For example, it can be obtained by forming an ester bond between the hydroxyl groups of unmodified polyphenylene ether and a carboxylic acid (hereinafter referred to as carboxylic acid) having a carbon-carbon double bond. Various known methods can be used to form the ester bond. Examples include: a. reaction of a carboxylic acid halide with a hydroxyl group at the polymer terminal; b. formation of an ester bond by reaction with a carboxylic acid anhydride; c. direct reaction with a carboxylic acid; and d. transesterification. The reaction with a carboxylic acid halide (a) is one of the most common methods. Chlorides and bromides are commonly used as carboxylic acid halides, but other halogens may also be used. The reaction may be either a direct reaction with a hydroxyl group or a reaction with an alkali metal salt of a hydroxyl group. Since the direct reaction between a carboxylic acid halide and a hydroxyl group generates an acid such as hydrogen halide, a weak base such as an amine may be present to trap the acid. In the reaction with a carboxylic acid anhydride (b) or the direct reaction with a carboxylic acid (c), compounds such as carbodiimides or dimethylaminopyridine may be present to activate the reaction sites and promote the reaction. In the transesterification reaction (d), it is desirable to remove the produced alcohols as needed. Furthermore, known metal catalysts may be present to promote the reaction. After the reaction, the product may be washed with water, an acidic, or alkaline aqueous solution to remove by-products such as amine salts, or the target product may be recovered by dropping the polymer solution into a poor solvent such as an alcohol and reprecipitation. After washing the polymer solution, the solvent may be distilled off under reduced pressure to recover the polymer.

[0059] The method for producing the modified polyphenylene ether of the present embodiment is not limited to the method for producing the polyfunctional modified polyphenylene ether of the present embodiment described above, and the order and number of times of the oxidative polymerization step, copper extraction and by-product removal step, liquid-liquid separation step, and concentration and drying step described above may be adjusted as appropriate.

[0060] (Polyphenylene ether solution) The polyphenylene ether solution of the present embodiment contains at least the polyphenylene ether of the present embodiment and a ketone-based solvent, and may further contain other components. Furthermore, the solution may contain a solvent other than the ketone-based solvent. Examples of the ketone solvent 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 solvent to 100% by mass of the 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 mass ratio of the polyphenylene ether to 100% by mass of the polyphenylene ether solution is preferably 1 to 40% by mass, and the mass ratio of the ketone solvent to 100% by mass of the polyphenylene ether solution is preferably 60 to 99% by mass. The polyphenylene ether solution can be produced, for example, by mixing the polyphenylene ether, the ketone solvent, and any other components, other solvents, and the like.

[0061] <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 may further contain a thermoplastic resin, a flame retardant, other additives, a silica filler, a solvent, etc., as desired. The components of the thermosetting composition of this embodiment are described below.

[0062] (Polyphenylene ether) As described above, the polyphenylene ether of the present embodiment may be used as a sole resin in the thermosetting composition, or may be used in combination with polyphenylene ethers having other structures, or may be used in combination with various known additives. When used in combination with other components, the content of polyphenylene ether in the thermosetting composition is preferably 0.5 to 95 mass %, more preferably 20 to 93 mass %, and even more preferably 40 to 90 mass %.

[0063] (Crosslinking agent) Any crosslinking agent capable of initiating or facilitating a crosslinking reaction can be used in the thermosetting composition of the present embodiments. The crosslinking agent preferably has a number average molecular weight of not more than 4,000. When the number average molecular weight of the crosslinking agent is not more than 4,000, an increase in viscosity of the thermosetting composition can be suppressed, and good resin fluidity can be obtained during thermoforming. The number average molecular weight may be a value measured by a general molecular weight measurement method, and specifically, a value measured using GPC may be mentioned.

[0064] From the viewpoint of the crosslinking reaction, the crosslinking agent preferably has an average of two or more carbon-carbon unsaturated double bonds per molecule. The crosslinking agent may be composed of one type of compound or two or more types of compounds. In this specification, the term "carbon-carbon unsaturated double bond" refers to a double bond located at the end branched from the main chain when the crosslinking agent is a polymer or oligomer. An example of the carbon-carbon unsaturated double bond is a 1,2-vinyl bond in polybutadiene.

[0065] When the number-average molecular weight of the crosslinking agent is less than 600, the number (average) of carbon-carbon unsaturated double bonds per molecule of the crosslinking agent is preferably 2 to 4. When the number-average molecular weight of the crosslinking agent is 600 or more but less than 1,500, the number (average) of carbon-carbon unsaturated double bonds per molecule of the crosslinking agent is preferably 4 to 26. When the number-average molecular weight of the crosslinking agent is 1,500 or more but less than 4,000, the number (average) of carbon-carbon unsaturated double bonds per molecule of the crosslinking agent is preferably 26 to 60. When the number-average molecular weight of the crosslinking agent is within the above range, the number of carbon-carbon unsaturated double bonds being equal to or greater than the above specific value further enhances the reactivity of the crosslinking agent in the thermosetting composition of this embodiment, further improving the crosslink density of the cured product of the thermosetting composition, and as a result, imparting even better heat resistance. On the other hand, when the number-average molecular weight of the crosslinking agent is within the above range, the number of carbon-carbon unsaturated double bonds being equal to or less than the above specific value further imparts even better resin fluidity during thermoforming.

[0066] Examples of crosslinking agents include trialkenyl isocyanurate compounds such as triallyl isocyanurate (TAIC), trialkenyl 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, vinylbenzyl compounds such as divinylbenzene having vinylbenzyl groups in the molecule, and polyfunctional maleimide compounds having two or more maleimide groups in the molecule such as 4,4'-bismaleimide diphenylmethane. These crosslinking agents may be used alone or in combination of two or more. Among these, the crosslinking agent preferably contains at least one compound selected from the group consisting of triallyl cyanurate, triallyl isocyanurate, and polybutadiene. When the crosslinking agent contains at least one of the compounds described above, the thermosetting composition has better compatibility between the crosslinking agent and the polyphenylene ether, better coatability, and tends to have better board properties when mounted on an electronic circuit board.

[0067] The mass ratio of polyphenylene ether to crosslinking agent (polyphenylene ether:crosslinking agent) is preferably 25:75 to 95:5, more preferably 32:68 to 85:15, from the viewpoints of improving the compatibility between the crosslinking agent and the modified polyphenylene ether, the coatability of the thermosetting composition, and the properties of the mounted electronic circuit board.

[0068] (organic peroxide) In this embodiment, any organic peroxide capable of promoting the polymerization reaction of the thermosetting composition containing the polyphenylene ether and the 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)hexyne-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. 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)hexyne-3, di(2-t-butylperoxyisopropyl)benzene, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane are preferred, as they provide cured products with excellent heat resistance and mechanical properties and a low dielectric dissipation factor (and preferably a low dielectric constant).

[0069] The one-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. When the one-minute half-life temperature of the organic peroxide is within the range of 155 to 185° C., the compatibility of the organic peroxide with the modified PPE, the coatability of the thermosetting composition, and the properties of the mounted electronic circuit board tend to be even better. In this specification, the one-minute half-life temperature is the temperature at which the organic peroxide decomposes and the amount of active oxygen is reduced to half in one minute. The one-minute half-life temperature is determined by dissolving the organic peroxide in a solvent inert to radicals, such as benzene, to a concentration of 0.05 to 0.1 mol / L, and then thermally decomposing the organic peroxide solution in a nitrogen atmosphere.

[0070] Examples of organic peroxides with a one-minute half-life temperature in the range of 155 to 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), 2,5-dimethyl-2,5-di(benzoylperoxy)hexane (158.2°C), ), t-butyl peroxyacetate (159.9°C), 2,2-di-(t-butylperoxy)butane (159.9°C), t-butyl peroxybenzoate (166.8°C), n-butyl 4,4-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).

[0071] 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 still 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 improving the compatibility between the organic peroxide and the modified PPE and improving the coatability of the thermosetting composition; and is preferably 5 parts by mass or less, more preferably 4.5 parts by mass or less, from the viewpoint of improving the board properties when the thermosetting composition is mounted on an electronic circuit board.

[0072] (thermoplastic resin) The thermoplastic resin is preferably at least one selected from the group consisting of a block copolymer of a vinyl aromatic compound and an olefinic alkene compound and a hydrogenated product thereof (a hydrogenated block copolymer obtained by hydrogenating a block copolymer of a vinyl aromatic compound and an olefinic alkene compound), and a homopolymer of a vinyl aromatic compound. The weight average molecular weight of the thermoplastic resin is preferably more than 50,000 and not more than 780,000, more preferably 60,000 to 750,000, and even more preferably 70,000 to 700,000, from the viewpoint of achieving better compatibility with polyphenylene ether, resin fluidity, coatability of the thermosetting composition, and heat resistance during curing. When the thermosetting composition contains polyphenylene ether, a crosslinking agent, an organic peroxide, and a thermoplastic resin of the type and weight-average molecular weight described above, the compatibility of the modified PPE with the other components and the coatability to substrates tend to be good, and this in turn can result in excellent board properties when the composition is incorporated into an electronic circuit board. The weight average molecular weight can be determined by the method described in the examples below.

[0073] 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, or 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, or 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, compatibility with modified polyphenylene ether and / or adhesion strength to metal foil tends to be further improved.

[0074] The vinyl aromatic compound may be any compound having an aromatic ring and a vinyl group in the molecule, and examples thereof include styrene. The olefinic alkene compound may be any alkene having a linear or branched structure in the molecule, and examples thereof include ethylene, propylene, butylene, isobutylene, butadiene, and isoprene. From the viewpoint of achieving even better compatibility with polyphenylene ether, the thermoplastic resin is preferably at least one selected from the group consisting of styrene-butadiene block copolymers, styrene-ethylene-butadiene block copolymers, styrene-ethylene-butylene block copolymers, styrene-butadiene-butylene block copolymers, styrene-isoprene block copolymers, styrene-ethylene-propylene block copolymers, styrene-isobutylene block copolymers, hydrogenated styrene-butadiene block copolymers, hydrogenated styrene-ethylene-butadiene block copolymers, hydrogenated styrene-butadiene-butylene block copolymers, hydrogenated styrene-isoprene block copolymers, and styrene homopolymers (polystyrene), and more preferably at least one selected from the group consisting of styrene-butadiene block copolymers, hydrogenated styrene-butadiene block copolymers, and polystyrene.

[0075] The hydrogenation rate of the hydrogenated product is not particularly limited, and some carbon-carbon unsaturated double bonds derived from the olefinic alkene compound may remain.

[0076] 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 the content is within the above range, the thermosetting composition of the present embodiment tends to have better compatibility between the thermoplastic resin and the modified polyphenylene ether and better coatability, and when mounted on an electronic circuit board, the board properties tend to be better.

[0077] The thermosetting composition of the present embodiment may also contain a thermoplastic resin other than the thermoplastic resins of the type and weight average molecular weight described above.

[0078] (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 contained 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-dibromobiphenyl, and ethylene bistetrabromophthalimide; and phosphorus-based flame retardants such as resorcinol bis-diphenyl phosphate and resorcinol bis-dixylenyl phosphate. These flame retardants may be used alone or in combination of two or more. Among these, decabromodiphenylethane is preferred from the viewpoints of compatibility between the flame retardant and the modified PPE, coatability of the thermosetting composition, and superior properties of the electronic circuit boards on which the composition is mounted.

[0079] The content of the flame retardant is not particularly limited, but from the viewpoint of maintaining flame retardancy at 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 and the crosslinking agent. Furthermore, from the viewpoint of maintaining a low dielectric loss tangent of the obtained cured product (and preferably also a low dielectric constant), the content of the 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.

[0080] (Silica filler) The thermosetting composition of this embodiment may contain a silica filler, such as natural silica, fused silica, synthetic silica, amorphous silica, aerosil, and hollow silica. The content of the silica filler may be 10 to 100 parts by mass relative to 100 parts by mass of the total of the polyphenylene ether and the crosslinking agent. The silica filler may be surface-treated with a silane coupling agent or the like.

[0081] The thermosetting composition of the present embodiment may further contain additives such as a heat stabilizer, an antioxidant, a UV absorber, a surfactant, a lubricant, a solvent, etc., in addition to the flame retardant and the silica filler. When the thermosetting composition of the present embodiment contains a solvent, it 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 the present embodiment.

[0082] (solvent) From the viewpoint of solubility, the solvent is preferably an aromatic compound such as toluene or xylene, methyl ethyl ketone (MEK), cyclopentanone, cyclohexanone, chloroform, etc. These solvents may be used alone or in combination of two or more.

[0083] <Prepreg> The prepreg of this embodiment includes a substrate and the thermosetting composition of this embodiment described above, and is preferably a composite including the substrate and the thermosetting composition of this embodiment impregnated into or coated on the substrate. The prepreg can be obtained, for example, by impregnating a substrate such as glass cloth with a varnish of the thermosetting composition and then drying and removing the solvent using a hot air dryer or the like.

[0084] 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 wholly aromatic polyamide fiber, wholly aromatic polyester fiber, and polybenzoxazole fiber; 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 fabrics obtained from paper-glass blended fiber yarns; and polytetrafluoroethylene porous films. Among these, glass cloth is preferred. These substrates may be used alone or in combination of two or more.

[0085] The proportion of the solid content of the thermosetting composition of this embodiment in the prepreg (components of the thermosetting composition other than the solvent) is preferably 30 to 80 mass %, more preferably 40 to 70 mass %. Having this proportion of 30 mass % or more tends to provide better insulation reliability when the prepreg is used for electronic substrates, etc. Having this proportion of 80 mass % or less tends to provide better mechanical properties, such as flexural modulus, when used for electronic substrates, etc.

[0086] <Laminate> The laminate of this embodiment includes the cured product of the prepreg of this embodiment and a metal foil, and is preferably 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 configuration in which the cured product of the prepreg (hereinafter also referred to as a "cured product composite") and the metal foil are laminated and adhered to each other, 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 to be combined with the metal foil may be one sheet or multiple sheets, and depending on the application, the composite may be processed into a laminate by overlaying metal foil on one or both sides thereof.

[0087] Examples of methods for producing a metal-clad laminate include forming a composite (e.g., the above-mentioned prepreg) consisting of a thermosetting composition and a substrate, overlaying this with metal foil, and then curing the thermosetting composition to obtain a laminate in which the cured laminate and metal foil are laminated together. One particularly preferred application of the metal-clad laminate is a printed wiring board, which is preferably a metal-clad laminate from which at least a portion of the metal foil has been removed.

[0088] <Printed wiring board> A printed wiring board can be obtained by removing at least a portion of the metal foil from the metal-clad laminate. The printed wiring board can typically be formed by a method of pressurizing and hot molding using the prepreg of the present embodiment described above. Examples of the substrate include those similar to those described above for the prepreg. The printed wiring board contains the thermosetting composition of the present embodiment, and thus has excellent heat resistance and electrical properties (low dielectric tangent and / or low dielectric constant), can suppress fluctuations in electrical properties due to environmental changes, and has excellent insulation reliability and mechanical properties. [Example]

[0089] Hereinafter, the present embodiment will be described in more detail based on examples, but the present embodiment is not limited to the following examples.

[0090] First, the measurement methods and evaluation criteria for each physical property will be described below.

[0091] (1) The molar ratio 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) contained in the 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. 1H-NMR measurements (JEOL, 500 MHz) were performed. Before the measurements, the polyphenylene ether was heated at 140°C and 1 mmHg for 8 hours to remove volatile components such as toluene and water, and the measurements were performed as dry, unmodified polyphenylene ether. The signals of the units derived from phenol in formula (1) and formula (2) were identified, and their respective proportions were calculated. For example, in the unmodified polyphenylene ethers obtained in the Examples and Comparative Examples, the signal derived from the repeating unit derived from phenol of formula (1), i.e., the 2,6-dimethylphenol-derived structure (2,6-dimethylphenylene unit), and the signal derived from the repeating unit derived from phenol of formula (2), i.e., the 2-tert-butyl-5-methylphenol-derived structure (2-tert-butyl-5-methylphenylene unit), were assigned as follows: The peaks of the repeating units derived from each phenol appear in the following regions. Peaks derived from hydrogen atoms of the methyl groups of the 2,6-dimethylphenylene unit and the 2-tert-butyl-5-methylphenylene unit (6H and 3H, respectively): 1.60 to 2.50 ppm (excluding peaks derived from hydrogen atoms of the methyl group of toluene) Peaks (9H) derived from the hydrogen atoms of the tert-butyl group of the 2-tert-butyl-5-methylphenylene unit: 1.00 to 1.52 ppm (excluding peaks derived from the hydrogen atoms of water) The integral value of the above signal is examined, and the integral value per proton of the peak derived from the hydrogen atom of the methyl group of the 2,6-dimethylphenylene unit can be calculated using the following mathematical formula (1). E = {C - 3 × (D / 9)} / 6 Formula (1) C: Integration value of the peaks derived from the methyl groups of the 2,6-dimethylphenylene unit and the 2-tert-butyl-5-methylphenylene unit D: Integration value of the peak derived from the tert-butyl of the 2-tert-butyl-5-methylphenylene unit E: integral per proton of the peak derived from the methyl of the 2,6-dimethylphenylene unit Furthermore, the proportion (mol %) of repeating units derived from phenol of formula (1) or formula (2) can be calculated using the following formulas (2) and (3). The proportion of repeating units derived from phenol in formula (1) (mol%) = E / {(D / 9) + E} × 100 Equation (2) The proportion of repeating units derived from phenol in formula (2) (mol%) = (D / 9) / {(D / 9) + E} × 100 Equation (3)

[0092] (2) The molar ratio of the repeating units derived from impurity A to the total of the repeating units derived from phenol of formula (1), the repeating units derived from phenol of formula (2), and the repeating units derived from impurity A contained in the 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 H-NMR measurements (JEOL, 500 MHz) were performed. Prior to the measurements, the polyphenylene ether was kept at 140°C and 1 mmHg for 8 hours to remove volatile components such as toluene and water, and the measurement was performed as dry, unmodified polyphenylene ether. The signals of the units derived from phenol in formula (1), formula (2), and impurity A were identified, and their respective proportions were calculated. For example, in the unmodified polyphenylene ether obtained in the examples and comparative examples, the repeating unit derived from the phenol of formula (1), i.e., a signal derived from a 2,6-dimethylphenol-derived structure (2,6-dimethylphenylene unit), the repeating unit derived from the phenol of formula (2), i.e., a signal derived from a 2-tert-butyl-5-methylphenol-derived structure (2-tert-butyl-5-methylphenylene unit), and the repeating unit derived from impurity A, i.e., R 11 = methyl group, R 12 The signal assignment method for the repeating units where z = hydrogen atom and z = 0 was analyzed as follows. The peaks for the repeating units derived from each phenol appear in the following regions. 2,6-dimethylphenylene unit, 2-tert-butyl-5-methylphenylene unit and R in formula (11) 11 = methyl group, R 12 = hydrogen atom, and peaks derived from the hydrogen atoms of the methyl groups of the signals derived from the repeating unit where z = 0 (6H, 3H, and 12H, respectively): 1.60 to 2.50 ppm (excluding peaks derived from the hydrogen atoms of the methyl groups of toluene) Peaks (9H) derived from the hydrogen atoms of the tert-butyl group of the 2-tert-butyl-5-methylphenylene unit: 1.00 to 1.52 ppm (excluding peaks derived from the hydrogen atoms of water) R in equation (11) 11 = methyl group, R 12 = hydrogen atom, peak due to hydrogen atom of methyl group of repeating unit where z = 0 (4H): 7.35 ppm The integral value of the above signal is examined, and the integral value per proton of the peak derived from the hydrogen atom of the methyl group of the 2,6-dimethylphenylene unit can be calculated using the following mathematical formula (4). E = {C - 3 × (D / 9) - 12 × (F / 4)} / 6 Formula (4) C: Integration value of the peaks derived from the methyl groups of the 2,6-dimethylphenylene unit and the 2-tert-butyl-5-methylphenylene unit D: Integration value of the peak derived from the tert-butyl of the 2-tert-butyl-5-methylphenylene unit F: R in formula (11) 11 = methyl group, R 12 = hydrogen atom, integral value of the peaks derived from hydrogen atoms of the benzene ring of the repeating unit where z=0 E: integral per proton of the peak derived from the methyl of the 2,6-dimethylphenylene unit Furthermore, by the following formula (5), R in formula (11) 11 = methyl group, R 12 = hydrogen atom, z=0. R in equation (11) 11 = methyl group, R 12= hydrogen atoms, proportion of repeating units with z=0 (mol%) = (F / 4) / {(D / 9)+E+(F / 4)}×100 Formula (5)

[0093] (3) The molar ratio of repeating units derived from a monohydric phenol having at least one unsaturated hydrocarbon group on a carbon atom in the ortho position relative to the carbon atom to which the hydroxyl group of the phenol is bonded to the sum of repeating units derived from the phenol of formula (1) contained in the unmodified polyphenylene ether and repeating units derived from the monohydric phenol having at least one unsaturated hydrocarbon group on a carbon atom in the ortho position relative to the carbon atom to which the hydroxyl group of the phenol is bonded. 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 H-NMR measurements (JEOL, 500 MHz) were performed. Prior to the measurements, the polyphenylene ether was kept at 140°C and 1 mmHg for 8 hours to remove volatile components such as toluene and water, and the measurements were performed as dry, unmodified polyphenylene ether. The signals of the repeating unit derived from phenol of formula (1), the repeating unit derived from phenol of formula (2), and the repeating unit derived from a monohydric phenol having at least one unsaturated hydrocarbon group on the carbon atom ortho to the carbon atom to which the hydroxyl group of the phenol is bonded were identified, and the respective proportions were calculated. For example, in the unmodified polyphenylene ethers obtained in the examples and comparative examples, a signal derived from a repeating unit derived from a phenol of formula (1), i.e., a 2,6-dimethylphenol-derived structure (2,6-dimethylphenylene unit), a signal derived from a repeating unit derived from a phenol of formula (2), i.e., a 2-tert-butyl-5-methylphenol-derived structure (2-tert-butyl-5-methylphenylene unit), and a signal derived from a repeating unit derived from a monohydric phenol having at least one unsaturated hydrocarbon group on the carbon atom ortho to the carbon atom to which the phenol hydroxyl group is bonded, i.e., a 2-allylphenol-derived structure (2-allylphenylene unit), appear in the following regions: Peaks derived from hydrogen atoms of the methyl groups of the 2,6-dimethylphenylene unit and the 2-tert-butyl-5-methylphenylene unit (6H and 3H, respectively): 1.60 to 2.50 ppm (excluding peaks derived from hydrogen atoms of the methyl group of toluene) Peaks (9H) derived from the hydrogen atoms of the tert-butyl group of the 2-tert-butyl-5-methylphenylene unit: 1.00 to 1.52 ppm (excluding peaks derived from the hydrogen atoms of water) Peak due to hydrogen atoms of methylene groups of 2-allylphenylene units (2H): 3.40 ppm The integral value of the above signal is examined, and the integral value per proton of the peak derived from the hydrogen atom of the methyl group of the 2,6-dimethylphenylene unit can be calculated using the following mathematical formula (6). E = {C - 3 × (D / 9)} / 6 Formula (6) C: Integration value of the peaks derived from the methyl groups of the 2,6-dimethylphenylene unit and the 2-tert-butyl-5-methylphenylene unit D: Integration value of the peak derived from the tert-butyl of the 2-tert-butyl-5-methylphenylene unit E: integral per proton of the peak derived from the methyl of the 2,6-dimethylphenylene unit Furthermore, the proportion (mol %) of 2-allylphenylene units can be calculated using the following formula (7). Percentage of 2-allylphenylene units (mol%) = (G / 2) / {E+(G / 2)} × 100 Formula (7) G: integral per proton of the peak derived from the methylene group of the 2-allylphenylene unit

[0094] (4) The molar ratio 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) contained in the modified polyphenylene ether. The modified polyphenylene ether was prepared as follows. The modified polyphenylene ether obtained in the examples and comparative examples was dissolved in a measurement solvent (deuterated chloroform to which one drop of heavy water was added to eliminate the hydroxyl group), and tetramethylsilane was used as an internal standard. 1 H-NMR measurements (JEOL, 500 MHz) were performed. Before the measurements, the polyphenylene ether was kept at 80°C and 1 mmHg for 8 hours to remove volatile components such as toluene and water, and the measurements were performed as a dry modified polyphenylene ether. The signals of the units derived from phenol in formula (1) and formula (2) were identified, and their respective proportions were calculated. For example, in the modified polyphenylene ethers obtained in the examples and comparative examples, the signals derived from the repeating unit derived from phenol of formula (1), i.e., the 2,6-dimethylphenol-derived structure (2,6-dimethylphenylene unit), the signals derived from the repeating unit derived from phenol of formula (2), i.e., the 2-tert-butyl-5-methylphenol-derived structure (2-tert-butyl-5-methylphenylene unit), and the signals derived from a partial structure selected from the group consisting of formula (4), formula (5), formula (6), and formula (7), i.e., the signals derived from a methacryl group-derived structure, were analyzed as follows. The peaks of the repeating units derived from each phenol appear in the following regions. Peaks derived from hydrogen atoms of the 2,6-dimethylphenylene unit, 2-tert-butyl-5-methylphenylene unit, and methyl group of the methacryl group (6H, 3H, and 3H, respectively): 1.60 to 2.50 ppm (excluding peaks derived from hydrogen atoms of the methyl group of toluene) Peaks (9H) derived from the hydrogen atoms of the tert-butyl group of the 2-tert-butyl-5-methylphenylene unit: 1.00 to 1.52 ppm (excluding peaks derived from the hydrogen atoms of water) Peak due to one hydrogen atom of the methylene group of the methacryl group (1H): 4.4 to 5.8 ppm The integral value of the above signal is examined, and the integral value per proton of the peak derived from the hydrogen atom of the methyl group of the 2,6-dimethylphenylene unit can be calculated using the following mathematical formula (8). E = {C - 3 × (D / 9) - 3 × (H / 1)} / 6 Formula (8) C: Integration value of the peaks derived from the methyl groups of the 2,6-dimethylphenylene unit and the 2-tert-butyl-5-methylphenylene unit D: Integration value of the peak derived from the tert-butyl of the 2-tert-butyl-5-methylphenylene unit E: integral per proton of the peak derived from the methyl of the 2,6-dimethylphenylene unit H: Integral value of the peak derived from one hydrogen atom of the methylene group of the methacryl group Furthermore, the proportion (mol %) of repeating units derived from phenol of formula (1) or formula (2) can be calculated using the following formulas (9) and (10). The proportion of repeating units derived from phenol in formula (1) (mol%) = E / {(D / 9) + E} × 100 Equation (9) The proportion of repeating units derived from phenol in formula (2) (mol%) = (D / 9) / {(D / 9) + E} × 100 Equation (10)

[0095] (5) The molar ratio of the repeating units derived from impurity A to the total of the repeating units derived from phenol of formula (1), the repeating units derived from phenol of formula (2), and the repeating units derived from impurity A contained in the modified polyphenylene ether. The unmodified polyphenylene ether obtained in the examples and comparative examples was dissolved in a measurement solvent (deuterated chloroform to which one drop of heavy water was added to eliminate the hydroxyl group), and tetramethylsilane was used as an internal standard. 1 H-NMR measurements (JEOL, 500 MHz) were performed. Prior to the measurements, the polyphenylene ether was kept at 80°C and 1 mmHg for 8 hours to remove volatile components such as toluene and water, and the measurement was performed as dry, unmodified polyphenylene ether. The signals of the units derived from phenol in formula (1), formula (2), and impurity A were identified, and their respective proportions were calculated. For example, in the unmodified polyphenylene ether obtained in the examples and comparative examples, a signal derived from a repeating unit derived from phenol of formula (1), i.e., a 2,6-dimethylphenol-derived structure (2,6-dimethylphenylene unit), a signal derived from a repeating unit derived from phenol of formula (2), i.e., a 2-tert-butyl-5-methylphenol-derived structure (2-tert-butyl-5-methylphenylene unit), a signal derived from a partial structure selected from the group consisting of formula (4), formula (5), formula (6), or formula (7), i.e., a signal derived from a methacryl group-derived structure, and a signal derived from a repeating unit derived from impurity A, i.e., R in formula (11) 11 = methyl group, R 12 The signal assignment method for the repeating units where z = hydrogen atom and z = 0 was analyzed as follows. The peaks for the repeating units derived from each phenol appear in the following regions. 2,6-dimethylphenylene unit, 2-tert-butyl-5-methylphenylene unit, R in formula (11) 11 = methyl group, R 12 = hydrogen atom, repeating unit where z = 0, peaks derived from the hydrogen atoms of the methyl group of the signal derived from the methacryl group (6H, 3H, 12H, and 3H, respectively): 1.60 to 2.50 ppm (excluding peaks derived from the hydrogen atoms of the methyl group of toluene) Peaks (9H) derived from the hydrogen atoms of the tert-butyl group of the 2-tert-butyl-5-methylphenylene unit: 1.00 to 1.52 ppm (excluding peaks derived from the hydrogen atoms of water) R in equation (11) 11 = methyl group, R 12 = hydrogen atom, peak due to hydrogen atom of methyl group of repeating unit where z = 0 (4H): 7.35 ppm Peak due to one hydrogen atom of the methylene group of the methacryl group (1H): 4.4 to 5.8 ppm The integral value of the above signal is examined, and the integral value per proton of the peak derived from the hydrogen atom of the methyl group of the 2,6-dimethylphenylene unit can be calculated using the following formula (11). E = {C - 3 × (D / 9) - 12 × (F / 4) - 3 × (H / 1)} / 6 Formula (11) C: Integration value of the peaks derived from the methyl groups of the 2,6-dimethylphenylene unit and the 2-tert-butyl-5-methylphenylene unit D: Integration value of the peak derived from the tert-butyl of the 2-tert-butyl-5-methylphenylene unit F: R in formula (11) 11 = methyl group, R 12 = hydrogen atom, integral value of the peaks derived from hydrogen atoms of the benzene ring of the repeating unit where z=0 E: integral per proton of the peak derived from the methyl of the 2,6-dimethylphenylene unit H: Integral value of the peak derived from one hydrogen atom of the methylene group of the methacryl group Furthermore, by the following formula (12), R in formula (11) 11 = methyl group, R 12 = hydrogen atom, z=0. R in equation (11) 11 = methyl group, R 12 = hydrogen atoms, proportion of repeating units with z=0 (mol%) = (F / 4) / {(D / 9)+E+(F / 4)}×100 Formula (12)

[0096] (6) Reduced viscosity (ηsp / c) A 0.5 g / dL chloroform solution of polyphenylene ether was prepared, and the reduced viscosity (ηsp / c) (dL / g) at 30° C. was determined using an Ubbelohde viscosity tube.

[0097] (7) Average number of hydroxyl groups in polyphenylene ether 5.0 mg of polyphenylene ether was weighed out. This weighed polyphenylene ether was then dissolved in 25 mL of methylene chloride. 150 μL of a 2 mass % tetraethylammonium hydroxide (TEAH) ethanol solution was added to 2.0 mL of the prepared solution, and the absorbance (Abs) at 318 nm was measured using a UV spectrophotometer (Hitachi, Ltd.: U-3210 model) (using an absorbance measurement cell with a cell length of 1 cm). Based on the measurement results, the hydroxyl group equivalent obtained from the absorbance was calculated using the following mathematical formula (13). The average number of hydroxyl groups per polyphenylene ether molecule was also calculated using the number average molecular weight (details of which are described in (8) below) determined by gel permeation chromatography. Hydroxyl equivalent (g / mol) obtained from absorbance = [(ε × 5) / (25 × Abs)] Equation (13) (where ε is the extinction coefficient, 4700 L / mol cm.) Average number of hydroxyl groups per molecule of polyphenylene ether (number / molecule) = (number average molecular weight determined by gel permeation chromatography) / (hydroxyl equivalent weight determined from absorbance) Equation (14)

[0098] (8) Number average molecular weight (Mn) The number-average molecular weight (Mn) of the modified polyphenylene ether was measured using a gel permeation chromatography system (System 21) manufactured by Showa Denko K.K. A calibration curve was prepared using standard polystyrenes and ethylbenzene. The 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. Two Showa Denko K-805L columns connected in series were used. 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 modified polyphenylene ether was prepared and used as the measurement sample. The UV wavelength of the detector was 254 nm for standard polystyrene and 283 nm for polyphenylene ether. The number average molecular weight (Mn) (g / mol) was calculated from the ratio of peak areas based on the curve showing the molecular weight distribution obtained by GPC based on the above measurement data.

[0099] (9) Long-term solubility in methyl ethyl ketone (MEK solubility) 1.5 g of polyphenylene ether and 8.5 g of methyl ethyl ketone were weighed into a transparent glass screw tube. They were mixed at 20°C using a stirring bar and a magnetic stirrer. After one day, the solution was rated as "Good" if it maintained its transparency, "Poor" if it was clearly not dissolved or contained a large amount of insoluble matter, and "Average" if some residue remained (slight turbidity).

[0100] (10) Long-term solubility in toluene (TL solubility) 2 g of polyphenylene ether and 8 g of toluene were weighed into a transparent glass screw tube. They were mixed at 20°C using a stirring bar and a magnetic stirrer. After one day, if the solution maintained its transparency, it was rated as "Good." If it was clearly not dissolved or if a large amount of insoluble matter was present, it was rated as "Poor." If some of the solution remained undissolved (if it was slightly turbid), it was rated as "Average."

[0101] (11) Dielectric loss tangent of the cured product of the thermosetting composition The dielectric loss tangents at 10 GHz of the laminates manufactured in the examples and comparative examples were measured using a cavity resonance method. A network analyzer (N5230A, manufactured by Agilent Technologies) and a cavity resonator (Cavity Resonator CP series, manufactured by Kanto Electronics Application Development Co., Ltd.) were used as measurement devices. The laminates were cut into strips approximately 2 mm wide, 50 mm long, and 0.5 mm thick, with the glass cloth warp yarns facing the long side. The strips were then placed in an oven at 105°C ± 2°C and dried for 2 hours, after which they were left to stand in an environment of 23°C and 50±5% relative humidity for 24±5 hours. The dielectric loss tangents were then measured using the above measurement device in an environment of 23°C and 50±5% relative humidity.

[0102] The methods for producing polyphenylene ethers in the examples and comparative examples will be described below.

[0103] Example 1 A 40-liter jacketed polymerization vessel equipped with a sparger, stirring turbine blades, and baffles for introducing oxygen-containing gas at the bottom of the vessel and a reflux condenser on the vent gas line at the top of the vessel was charged with 2.4 g of cupric oxide, 18.1 g of 47% by weight aqueous hydrogen bromide solution, 5.8 g of di-t-butylethylenediamine, 28.1 g of di-n-butylamine, 85.6 g of butyldimethylamine, 17.9 kg of toluene, 1497 g of 2,6-dimethylphenol, and 503 g of 2-tert-butyl-5-methylphenol while nitrogen gas was blown in at a flow rate of 17.1 L / min to form a homogeneous solution. Next, dry air was introduced into the polymerization vessel via the sparger at a rate of 10.5 L / min to initiate polymerization. Dry air was sparged for 120 minutes to obtain a polymerization mixture. The internal temperature was controlled to 20°C during polymerization. The polymerization mixture (polymerization liquid) was in a homogeneous solution state at the end of the polymerization. The dry air flow was stopped, and 25.9 g of ethylenediaminetetraacetic acid tetrasodium salt (Dojindo Chemical Industries, Ltd.) was added to the polymerization mixture as an aqueous solution in 2 kg of water. The polymerization mixture was stirred at 70°C for 150 minutes, then allowed to stand for 20 minutes, and the organic and aqueous phases were separated by liquid-liquid separation. The organic phase was concentrated using a rotary evaporator until the polymer concentration reached 25% by mass. The above solution was mixed with methanol such that the ratio of methanol to polymer solution was 6, and the polymer was precipitated. Wet polyphenylene ether was obtained by filtration under reduced pressure using a glass filter. The wet polyphenylene ether was further washed with an amount of methanol such that the ratio of methanol to wet polyphenylene ether was 3. The above washing operation was repeated three times. Next, the wet polyphenylene ether was kept at 140°C and 1 mmHg for 120 minutes, and dry polyphenylene ether was obtained. The polyphenylene ether thus obtained was subjected to the respective measurements by the methods described above. The analytical results are shown in Table 1.

[0104] Example 2 The same procedure as in Example 1 was repeated except that the phenol raw materials were 1269 g of 2,6-dimethylphenol and 731 g of 2-tert-butyl-5-methylphenol. The results of each analysis are shown in Table 1.

[0105] Example 3 The same procedure as in Example 1 was repeated except that the phenol raw materials were 853 g of 2,6-dimethylphenol and 1147 g of 2-tert-butyl-5-methylphenol. The results of each analysis are shown in Table 1.

[0106] Example 4 The same procedure as in Example 1 was repeated except that the phenol raw materials were 454 g of 2,6-dimethylphenol and 1517 g of 2-tert-butyl-5-methylphenol. The results of each analysis are shown in Table 1.

[0107] Example 5 The same procedure as in Example 1 was repeated except that the phenol raw materials were 765 g of 2,6-dimethylphenol, 1142 g of 2-tert-butyl-5-methylphenol, and 93 g of 2-allylphenol. The results of each analysis are shown in Table 1.

[0108] Example 6 The same procedure as in Example 1 was repeated except that the phenol raw materials were 503 g of 2,6-dimethylphenol, 1128 g of 2-tert-butyl-5-methylphenol, and 369 g of 2-allylphenol. The results of each analysis are shown in Table 1.

[0109] Example 7 Oxidative polymerization, copper extraction, liquid-liquid separation, and concentration by a rotary evaporator were carried out in the same manner as in Example 3, and a polymer solution with a polymer concentration of 25% by mass was used as a stock solution for the modification reaction. A 500 mL three-neck flask equipped with a nitrogen gas inlet line at the top of the reactor and a reflux condenser on the vent gas line at the top of the reactor was charged with 200 g of unmodified polyphenylene ether solution and 0.64 g of 4-dimethylaminopyridine after nitrogen purge. 21 mL of triethylamine was added using a syringe while stirring. 10.9 mL of methacryloyl chloride was then transferred to the syringe and added dropwise to the system at room temperature. After the dropwise addition, the flask was heated in an oil bath for 1 hour, and stirring was continued at 90°C. The reaction was then continued under reflux conditions. Heating was stopped 4 hours after the start of reflux, and after the temperature returned to room temperature, 8 g of methanol was added to terminate the reaction. The reaction solution was then filtered using a glass filter to remove the by-product triethylammonium salt. The above solution was mixed with methanol in a ratio of 10:1 to polymer solution, allowing the polymer to precipitate. Wet polyphenylene ether was obtained by vacuum filtration using a glass filter. The wet polyphenylene ether was further washed with an amount of methanol such that the ratio of methanol to wet polyphenylene ether was 2.5. The above washing operation was repeated three times. The wet polyphenylene ether was then maintained at 100°C and 1 mmHg for 8 hours to obtain dry polyphenylene ether. The average number of hydroxyl groups in the polyphenylene ether was measured by the above-mentioned method, and it was confirmed that the average number of hydroxyl groups derived from the polyphenylene ether was less than 0.2 per molecule. 1 H NMR measurement was performed and the proton peaks derived from the olefin of the methacryl group were confirmed, indicating that the hydroxyl groups had been modified to methacryl groups. The analytical results are shown in Table 2.

[0110] Example 8 Oxidative polymerization, copper extraction, liquid-liquid separation, and concentration by a rotary evaporator were carried out in the same manner as in Example 3, and a polymer solution with a polymer concentration of 25% by mass was used as a stock solution for the modification reaction. A 500 mL three-neck flask equipped with a temperature controller, a stirrer, a cooling device, and a dropping funnel was charged with 200 g of the unmodified polyphenylene ether solution, 24 g of chloromethylstyrene (50 / 50 ratio of p-chloromethylstyrene and m-chloromethylstyrene, manufactured by Tokyo Chemical Industry Co., Ltd.), and 1.0 g of tetra-n-butylammonium bromide. The mixture was then stirred to dissolve, and the liquid temperature was raised to 85°C. A sodium hydroxide aqueous solution (4.2 g of sodium hydroxide / 104 g of water) was added dropwise to the mixture over 1 hour, and stirring was continued at 85°C for an additional 5 hours. Next, the resulting aqueous layer was removed using a separatory funnel, and a toluene layer containing the polymer (polymer solution) was obtained. The polymer was mixed with methanol such that the ratio of methanol to polymer solution was 10, allowing precipitation of the polymer. Wet polyphenylene ether was obtained by filtration under reduced pressure using a glass filter. The wet polyphenylene ether was further washed with a cleaning solvent (methanol:water=80:20) in an amount such that the ratio of the cleaning solvent (methanol:water=80:20) to the wet polyphenylene ether was 2.5. After the above-mentioned washing operation with the methanol-water mixed solvent was repeated three times, the wet polyphenylene ether was washed with an amount of methanol such that the ratio of methanol to the wet polyphenylene ether was 2.5. After the above-mentioned washing operation with methanol was repeated twice, the wet polyphenylene ether was kept at 100°C and 1 mmHg for 8 hours to obtain a dry polyphenylene ether. The average number of hydroxyl groups in the polyphenylene ether was measured using the method described above, and it was confirmed that the average number of hydroxyl groups derived from the polyphenylene ether was less than 0.2 per molecule. 1 H NMR measurement confirmed the presence of proton peaks at 5-7 ppm derived from styryl groups, indicating that the hydroxyl groups had been modified with styryl groups. The analytical results are shown in Table 2.

[0111] Example 9 The resulting mixture was subjected to oxidative polymerization, copper extraction, liquid-liquid separation, and rotary evaporator concentration in the same manner as in Example 3, and then maintained at 100°C and 1 mmHg for 2 hours to obtain a dry polyphenylene ether. The dry polyphenylene ether was used as a raw material for the modification reaction. Into a 500 mL three-neck flask equipped with a temperature controller, a stirrer, a cooling device, and a dropping funnel, 50 g of unmodified polyphenylene ether, 150 g of tetrahydrofuran, 12.6 g of allyl bromide, and 0.8 g of benzyltributylammonium bromide were placed and stirred at a liquid temperature of 25° C. A sodium hydroxide aqueous solution (4.2 g of sodium hydroxide / 100 mL of water) was added dropwise to the mixed liquid over 60 minutes, and stirring was continued at 25° C. for an additional 12 hours. Next, the contents of the flask were neutralized with a 10% aqueous hydrochloric acid solution and then mixed with methanol such that the ratio of methanol to polymer solution was 10, thereby precipitating the polymer. Wet polyphenylene ether was obtained by vacuum filtration using a glass filter. Furthermore, the wet polyphenylene ether was washed with a washing solvent (methanol:water=80:20) in an amount such that the ratio of washing solvent (methanol:water=80:20) to wet polyphenylene ether was 2.5. After performing the above-mentioned washing operation with the methanol-water mixed solvent three times, the wet polyphenylene ether was washed with an amount of methanol such that the ratio of methanol to wet polyphenylene ether was 2.5. After performing the above-mentioned washing operation with methanol twice, the wet polyphenylene ether was then maintained at 100°C and 1 mmHg for 8 hours, thereby obtaining dry polyphenylene ether. The average number of hydroxyl groups in the polyphenylene ether was measured using the method described above, and it was confirmed that the average number of hydroxyl groups derived from the polyphenylene ether was less than 0.2 per molecule. 1 H NMR measurement confirmed the presence of proton peaks at 3.5 to 6.5 ppm, which indicated that the hydroxyl groups had been modified to allyl groups. The analytical results are shown in Table 2.

[0112] Example 10 As in Example 5, oxidative polymerization, copper extraction, liquid-liquid separation, and concentration using a rotary evaporator were performed, followed by holding at 100°C and 1 mmHg for 2 hours to obtain dry polyphenylene ether. Methacrylic modification was performed in the same manner as in Example 7, except that the dry polyphenylene ether was used as the raw material for the modification reaction. The average number of hydroxyl groups in the polyphenylene ether was measured by the method described above, and it was confirmed that the average number of hydroxyl groups derived from the polyphenylene ether was less than 0.2 per molecule. Also 1 H NMR measurement was performed and the proton peaks derived from the olefin of the methacryl group were confirmed, indicating that the hydroxyl groups had been modified to methacryl groups. The analytical results are shown in Table 2.

[0113] Example 11 To 79 parts by weight of the polyphenylene ether described in Example 7, 20 parts by weight of TAIC (manufactured by Nippon Kasei Co., Ltd.) and 1 part by weight of organic peroxide (Perbutyl P, manufactured by NOF Corporation) were added to toluene, stirred, and dissolved to obtain a varnish (solids concentration 58% by weight). L-glass cloth (manufactured by Asahi Schwebel Co., Ltd., style: 2116) was impregnated with this varnish, passed through a specified slit to remove excess varnish, and dried in a drying oven at 105°C for a specified time to remove the toluene, yielding a prepreg. This prepreg was cut to a specified size, and the solids content of the thermosetting composition in the prepreg was calculated by comparing the mass of the prepreg with the mass of a glass cloth of the same size, which was found to be 52% by weight. A predetermined number of these prepregs were stacked, and copper foil (35 μm thick, GTS-MP foil, manufactured by Furukawa Electric Co., Ltd.) was placed on both sides of the stacked prepregs, followed by vacuum pressing to obtain a copper-clad laminate. In this vacuum pressing process, the prepreg was first heated from room temperature at a temperature increase rate of 2°C / min while applying a pressure of 40 kg / cm. 2 After the temperature reached 200°C, the pressure was increased to 40 kg / cm while maintaining the temperature at 200°C. 2 The conditions adopted were a time of 60 minutes. Next, the copper foil was removed from the copper-clad laminate by etching to obtain a laminate (thickness: about 0.5 mm). The results of each analysis are shown in Table 3.

[0114] Example 12 A laminate was obtained in the same manner as in Example 11, except that the polyphenylene ether described in Example 10 was used as the raw material. The results of each analysis are shown in Table 3.

[0115] (Comparative Example 1) A 1.5-liter jacketed reactor equipped with a sparger at the bottom for introducing oxygen-containing gas, stirring turbine blades and baffles, and a reflux condenser on the vent gas line at the top of the reactor was charged with a pre-conditioned mixture of 0.15 g of cuprous oxide and 1.12 g of 47% hydrogen bromide, 0.36 g of N,N'-di-t-butylethylenediamine, 5.31 g of dimethyl-n-butylamine, 1.74 g of di-n-butylamine, and 491.3 g of toluene. Next, with vigorous stirring, air was introduced into the reactor via the sparger at a rate of 1.05 L / min, and simultaneously oxygen was introduced. A mixed solution of 98.7 g of 2,6-dimethylphenol, 1.34 g of 2-tert-butyl-5-methylphenol, and 400.0 g of toluene was added to the solution over 60 minutes. The polymerization temperature was maintained at 40 °C by passing a heat medium through the jacket. 130 minutes after the start of air introduction, the air flow was stopped, and the reactor was purged with nitrogen gas. A 20% methanol solution containing 1.03 g of hydroquinone (a reagent manufactured by Wako Pure Chemical Industries, Ltd.) was then added in small portions. Thirty minutes after the addition of the hydroquinone methanol solution, 1.61 g of ethylenediaminetetraacetic acid tetrasodium salt tetrahydrate (a reagent manufactured by Dojindo Laboratories) was added in 200 g of water. The mixture was heated to 70°C, and copper extraction was carried out at 70°C for 2 hours. The mixture was then separated into an unmodified polyphenylene ether solution (organic phase) and an aqueous phase containing the catalyst metal by static separation. The solution was mixed with methanol at a ratio of 10:1 to the polymer solution, allowing the polymer to precipitate. Wet polyphenylene ether was obtained by vacuum filtration using a glass filter. The wet polyphenylene ether was then 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. The wet polyphenylene ether was then kept at 140° C. and 1 mmHg for 120 minutes to obtain dry polyphenylene ether. The polyphenylene ether thus obtained was subjected to the respective measurements by the methods described above. The analytical results are shown in Table 1.

[0116] (Comparative Example 2) The same procedure as in Example 1 was repeated except that the phenol raw materials were 1973 g of 2,6-dimethylphenol and 26.8 g of 2-tert-butyl-5-methylphenol. The results of each analysis are shown in Table 1.

[0117] (Comparative Example 3) The same procedure as in Example 1 was repeated except that the phenol raw materials were 1740 g of 2,6-dimethylphenol and 260 g of 2-tert-butyl-5-methylphenol. The results of each analysis are shown in Table 1.

[0118] Comparative Example 4 A 40-liter jacketed polymerization vessel equipped with a sparger, stirring turbine blades, and baffles for introducing oxygen-containing gas at the bottom of the polymerization vessel and a reflux condenser on the vent gas line at the top of the polymerization vessel was charged with 4.57 g of cupric oxide, 24.18 g of a 47% by weight aqueous hydrogen bromide solution, 11.00 g of di-t-butylethylenediamine, 62.72 g of di-n-butylamine, 149.92 g of butyldimethylamine, 20.65 kg of toluene, and 3.12 kg of 2,6-dimethylphenol while blowing nitrogen gas at a flow rate of 0.5 L / min. The mixture was stirred until a homogeneous solution was obtained and the internal temperature of the polymerization vessel reached 25°C. Next, dry air was introduced into the polymerization vessel via the sparger at a rate of 32.8 L / min to initiate polymerization. Dry air was sparged for 140 minutes to obtain a polymerization mixture. The internal temperature was controlled to 40°C during polymerization. At the end of the polymerization, the polymerization mixture (polymerization liquid) was in a homogeneous solution state. The dry air flow was stopped, and 10 kg of a 2.5% by mass aqueous solution of ethylenediaminetetraacetic acid tetrasodium salt (a reagent manufactured by Dojindo Laboratories) was added to the polymerization mixture. The polymerization mixture was stirred at 70°C for 150 minutes, then allowed to stand for 20 minutes, and the organic phase and aqueous phase were separated by liquid-liquid separation. The separated organic phase was a toluene solution containing 13.1% by mass of polyphenylene ether. The solution was placed in a jacketed stirring vessel, and a heat medium at 120°C was passed through the jacket to heat it. The vapor generated, mainly composed of toluene, was cooled in a condenser, and the toluene was removed from the system. The polymer concentration in the stirring vessel was concentrated to 30% by mass. Next, methanol was added to the polymer solution so that the ratio of methanol to polymer was 1.0, allowing the polymer to precipitate. Wet polyphenylene ether was obtained by filtration under reduced pressure using a glass filter. The wet polyphenylene ether was then washed with an amount of methanol so that the ratio of methanol to wet polyphenylene ether was 2.5. This washing procedure was repeated three times. The wet polyphenylene ether was then maintained at 140°C and 1 mmHg for 120 minutes, yielding dry polyphenylene ether. The polyphenylene ether obtained was subjected to the measurements by the methods described above. The measurement results are shown in Table 1.

[0119] (Comparative Example 5) A 40-liter jacketed polymerization vessel equipped with a sparger, stirring turbine blades, and baffles for introducing an oxygen-containing gas at the bottom of the vessel and a reflux condenser on the vent gas line at the top of the vessel was charged with 4.02 g of cupric oxide, 29.876 g of a 47% by mass aqueous hydrogen bromide solution, 9.684 g of di-t-butylethylenediamine, 46.88 g of di-n-butylamine, 122.28 g of butyldimethylamine, 17.53 kg of toluene, and 1.5 kg of 2,6-dimethylphenol while blowing nitrogen gas at a flow rate of 0.5 L / min, and stirred until a homogeneous solution was obtained and the internal temperature of the polymerization vessel reached 25° C. Next, dry air was introduced into the polymerization vessel via the sparger at a rate of 32.8 NL / min, and simultaneously a solution consisting of 1.62 kg of 2,6-dimethylphenol and 3.12 kg of toluene was added to the polymerization vessel over 30 minutes via a plunger pump. Dry air was passed through for 86 minutes to obtain a polymerization mixture. The internal temperature was controlled to 40°C during the polymerization. The polymerization mixture (polymerization liquid) was in a homogeneous solution state at the end of the polymerization. The same operation as in Comparative Example 1 was carried out. The results of each analysis are shown in Table 1.

[0120] (Comparative Example 6) The same procedure as in Example 1 was carried out except that the phenol raw material was 2 kg of 2,6-dimethylphenol and the air introduction was stopped 117 minutes after the start of the air introduction. The results of each analysis are shown in Table 1.

[0121] (Comparative Example 7) A 4.1-liter jacketed reactor equipped with a sparger at the bottom for introducing oxygen-containing gas, stirring turbine blades and baffles, and a reflux condenser on the vent gas line at the top of the reactor was charged with 0.88 g of cupric chloride dihydrate, 3.76 g of 35% hydrochloric acid, 33.57 g of N,N,N',N'-tetramethylpropanediamine, 850 g of n-butanol, 1982 g of methanol, and 630 g of 2,6-dimethylphenol. The solvent composition (weight ratio) used was n-butanol:methanol = 30:70. Next, oxygen was introduced into the reactor via the sparger at a rate of 410 mL / min with vigorous stirring. At the same time, a heat transfer medium was passed through the jacket to maintain the polymerization temperature at 40°C. The polymerization solution gradually took on the appearance of a slurry. 200 minutes after the start of oxygen introduction, the oxygen-containing gas aeration was stopped, and a 50% aqueous solution of 4.56 g of ethylenediaminetetraacetic acid tripotassium salt (reagent, Dojindo Laboratories) was added to the polymerization mixture, followed by the addition of 8.52 g of a 20% methanol solution of hydroquinone (reagent, Wako Pure Chemical Industries, Ltd.). The resulting polymerization mixture was transferred to a 4.1-liter jacketed reactor equipped with a stirring turbine blade, baffles, and a reflux condenser on the vent gas line at the top of the reactor, and the reaction was carried out at 60°C for 3 hours. After the reaction was completed, the mixture was filtered and washed three times with methanol washing solution (b) in an amount such that the mass ratio (b / a) of the washed polyphenylene ether (a) to the washing solution (b) was 4, yielding wet polyphenylene ether. The mixture was then vacuum-dried at 120°C for 4 hours to yield dried polyphenylene ether. The analytical results of the resulting polyphenylene ether are shown in Table 1.

[0122] (Comparative Example 8) The same procedure as in Example 1 was carried out except that the phenol raw material was 2 kg of 2-tert-butyl-5-methylphenol. The results of each analysis are shown in Table 1.

[0123] (Production Example 1) A 1.5-liter jacketed reactor equipped with a sparger at the bottom for introducing an oxygen-containing gas, stirring turbine blades and baffles, and a reflux condenser on the vent gas line at the top of the reactor was charged with a pre-conditioned mixture of 0.092 g of cuprous oxide and 0.69 g of 47% hydrogen bromide, 0.22 g of N,N'-di-t-butylethylenediamine, 3.27 g of dimethyl-n-butylamine, 1.07 g of di-n-butylamine, 714.65 g of toluene, 65.03 g of 2,6-dimethylphenol, and 14.97 g of 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane. Next, air was introduced into the reactor through the sparger at a rate of 0.84 L / min with vigorous stirring, and a heat medium was passed through the jacket to maintain the polymerization temperature at 20°C. 150 minutes after the start of air introduction, the air flow was stopped and the reactor was purged with nitrogen gas. Then, 0.99 g of ethylenediaminetetraacetic acid tetrasodium salt tetrahydrate (a reagent manufactured by Dojindo Laboratories) was added to the polymerization mixture as an aqueous solution in 160 g of water. The mixture was then heated to 70°C, and copper extraction was carried out at 70°C for 2 hours. The mixture was then allowed to stand to separate into an unmodified polyphenylene ether solution (organic phase) and an aqueous phase containing the catalyst metal. The unmodified polyphenylene ether was used to obtain a modified polyphenylene ether in the same manner as in Example 7. The results of each analysis are shown in Table 2.

[0124] (Comparative Example 10) A laminate was obtained in the same manner as in Example 11, except that the polyphenylene ether described in Production Example 1 was used as the raw material. The results of each analysis are shown in Table 3.

[0125] (Reference example 9) A 1.5-liter jacketed reactor equipped with a sparger at the bottom for introducing oxygen-containing gas, stirring turbine blades and baffles, and a reflux condenser on the vent gas line at the top of the reactor was charged with a pre-prepared mixture of 0.15 g of cuprous oxide and 1.12 g of 47% hydrogen bromide, 0.36 g of N,N'-di-t-butylethylenediamine, 5.31 g of dimethyl-n-butylamine, 1.74 g of di-n-butylamine, 891.3 g of toluene, 50.0 g of 2,6-dimethylphenol, and 50.0 g of 2,5-dimethylphenol. Air was then introduced into the reactor through the sparger at a rate of 1.05 L / min with vigorous stirring. The polymerization temperature was maintained at 40°C by introducing a heat medium through the jacket. 120 minutes after the air introduction began, the entire solution became highly viscous and gel formed.

[0126] [Table 1]

[0127] [Table 2]

[0128] [Table 3]

[0129] As shown in Tables 1 and 2, by comparing with the comparative examples, it was possible to obtain polyphenylene ethers of various reduced viscosities with improved solvent solubility in methyl ethyl ketone by using the polyphenylene ethers of the examples. [Industrial Applicability]

[0130] The polyphenylene ether of the present invention has excellent solvent solubility and is therefore industrially useful as an electronic material and a modifier.

Claims

1. The repeating units derived from phenol of the following formula (1) comprise 5 to 85 mol % of repeating units derived from phenol of the following formula (1) and 15 to 95 mol % of repeating units derived from phenol of the following formula (2), relative to 100 mol % in total of repeating units derived from phenol of the following formula (1) and repeating units derived from phenol of the following formula (2) (excluding the case where 85 mol % of repeating units derived from 2,6-dimethylphenol and 15 mol % of repeating units derived from 3-methyl-6-tert-butylphenol are contained), The reduced viscosity (ηsp / c) measured in a chloroform solution having a concentration of 0.5 g / dL at 30°C is 0.03 to 0.30 dL / g. A polyphenylene ether characterized by: 【Chemical 1】 (In formula (1), R １１ are 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; R １２ are each independently a 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. 【Chemistry 2】 In formula (2), R ２２ are each 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; ２２ are not both hydrogen atoms, and R ２１ is a partial structure represented by the following formula (3). 【Chemistry 3】 In formula (3), R ３１ are each independently an optionally substituted linear alkyl group having 1 to 8 carbon atoms, or two R ３１ is a cyclic alkyl structure having 1 to 8 carbon atoms to which R ３２ are each independently an optionally substituted alkylene group having 1 to 8 carbon atoms, each b is independently 0 or 1, and R ３３ is a hydrogen atom, an optionally substituted alkyl group having 1 to 8 carbon atoms, or an optionally substituted phenyl group.

2. The polyphenylene ether according to claim 1, wherein the partial structure represented by formula (3) is a t-butyl group.

3. 3. The polyphenylene ether according to claim 1, wherein the average number of hydroxyl groups per molecule is less than 2.

5.

4. The polyphenylene ether according to any one of claims 1 to 3, having an average number of hydroxyl groups of less than 0.2 per molecule.

5. The polyphenylene ether according to any one of claims 1 to 4, having at least one partial structure selected from the group consisting of the following formulas (4), (5), (6), and (7), and having an average number of hydroxyl groups per molecule of less than 0.2: 【Chemistry 4】 【Chemistry 5】 【Chemistry 6】 (In formula (6), R ６ 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 a substituent as long as the condition of having 1 to 10 carbon atoms is satisfied. 【Chemistry 7】 (In formula (7), R ７ is a saturated or unsaturated divalent hydrocarbon group having 1 to 10 carbon atoms, and the saturated or unsaturated divalent hydrocarbon may have a substituent within the range that satisfies the condition of having 1 to 10 carbon atoms; R ８ 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 a substituent as long as the condition of having 1 to 10 carbon atoms is satisfied.

6. The polyphenylene ether according to any one of claims 1 to 5, comprising a repeating unit derived from a monohydric phenol having at least one unsaturated hydrocarbon group on a carbon atom in the ortho position relative to a carbon atom to which a phenolic hydroxyl group is bonded.

7. 7. The polyphenylene ether according to claim 6, wherein the monohydric phenol is 2-allylphenol or 2-methyl-6-allylphenol.

8. The method for producing the polyphenylene ether according to any one of claims 1 to 7, comprising a step of oxidatively polymerizing the phenol of the formula (1) and the phenol of the formula (2).

9. 2. The polyphenylene ether according to claim 1, wherein the proportion of the repeating units derived from the phenol of the formula (2) is 30 to 95 mol % relative to 100 mol % in total of the repeating units derived from the phenol of the formula (1) and the repeating units derived from the phenol of the formula (2).

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