JP7488635B2 - Polyphenylene ether, curable composition, dry film, prepreg, cured product, laminate, and electronic component - Google Patents

Description

(1) The Society of Polymer Science, Japan, Abstracts of the Society of Polymer Science, Vol. 68, No. 1 [2019], published May 14, 2019 (2) Date of the conference: May 30, 2019, 68th Annual Meeting of the Society of Polymer Science

The present invention relates to polyphenylene ether, and further to a curable composition, dry film, prepreg, cured product, laminate, and electronic component that contain the polyphenylene ether.

The spread of high-capacity, high-speed communications, such as those typified by fifth-generation communications systems (5G), and millimeter-wave radar for automotive ADAS (advanced driving systems), has led to the increasing frequency of signals in communications devices.

However, when epoxy resins and other materials are used as wiring board materials, the relative dielectric constant (Dk) and dielectric loss tangent (Df) are not low enough, so as the frequency increases, the transmission loss due to dielectric loss increases, causing problems such as signal attenuation and heat generation. For this reason, polyphenylene ether, which has excellent low dielectric properties, has been used, but because polyphenylene ether is a thermoplastic resin, there are problems with heat resistance.

As a means to solve this problem, Non-Patent Document 1 proposes introducing allyl groups into the polyphenylene ether molecule to make it into a thermosetting resin.

J. Nunoshige, H. Akahoshi, Y. Shibasaki, M. Ueda, J. Polym. Sci. Part A: Polym. Chem. 2008, 46, 5278-5282.

However, polyphenylene ether is soluble in only a limited number of solvents, and the polyphenylene ether obtained by the method of Non-Patent Document 1 is soluble only in highly toxic solvents such as chloroform and toluene. This poses the problem of difficulty in handling the resin varnish and in controlling exposure to solvents during the process of forming a coating and curing it in applications such as wiring boards.

The object of the present invention is to provide a polyphenylene ether that maintains low dielectric properties while also being soluble in a variety of solvents (organic solvents other than highly toxic organic solvents, such as cyclohexanone).

As a result of intensive research aimed at achieving the above object, the inventors discovered that the above problems could be solved by using specific phenols as raw materials for polyphenylene ether, and thus completed the present invention.

According to the present invention, a phenol satisfying at least condition 1;
a polyhydric phenol having two or more phenolic hydroxyl groups in its molecular structure and having no hydrogen atom at the ortho position of the phenolic hydroxyl group;
The present invention provides a polyphenylene ether, which is characterized in that the polyphenylene ether is made from raw material phenols comprising:
(Condition 1)
Contains hydrogen atoms at the ortho and para positions

The present invention preferably comprises a phenol satisfying at least condition 1,
a polyhydric phenol having two or more phenolic hydroxyl groups in its molecular structure and having no hydrogen atom at the ortho position of the phenolic hydroxyl group;
and a slope calculated in a conformation plot of the polyphenylene ether is less than 0.6.
(Condition 1)
Contains hydrogen atoms at the ortho and para positions

The raw material phenols are
The mixture may contain a phenol (A) that satisfies at least both of the following condition 1 and the following condition 2, or a mixture of a phenol (B) that satisfies at least the following condition 1 but does not satisfy the following condition 2, and a phenol (C) that does not satisfy the following condition 1 but satisfies the following condition 2.
(Condition 1)
Having hydrogen atoms at the ortho and para positions (condition 2)
It has a hydrogen atom at the para position and a functional group containing an unsaturated carbon bond.

According to the present invention, there is provided a curable composition comprising the polyphenylene ether and a peroxide. The curable composition may also comprise a crosslinking curing agent.

According to the present invention, there is provided a dry film or prepreg obtained by coating or impregnating a substrate with the curable composition.
According to the present invention, there is provided a cured product obtained by curing the curable composition.
According to the present invention, there is provided a laminate comprising the above-mentioned cured product.
According to the present invention, there is provided an electronic component having the above-mentioned cured product.

The present invention makes it possible to provide polyphenylene ether that is soluble in various solvents while maintaining low dielectric properties.

FIG. 1 shows the results of NMR analysis of polyphenylene ether.

The method for producing polyphenylene ether of the present invention and the polyphenylene ether obtained by the method are specifically described below, but the present invention is not limited thereto.

In addition, when isomers exist in the described compounds, all possible isomers can be used in the present invention unless otherwise specified.

In addition, in the present invention, unless otherwise specified, "unsaturated carbon bond" refers to an ethylenic or acetylenic carbon-carbon multiple bond (double bond or triple bond).

In the present invention, when describing the raw material phenols, terms such as "ortho position" and "para position" are used, unless otherwise specified, the position of the phenolic hydroxyl group is taken as the reference (ipso position).

In the present invention, when it is simply expressed as "ortho position", it means "at least one of the ortho positions". Therefore, unless there is any particular contradiction, when it is simply expressed as "ortho position", it may be interpreted as meaning either one of the ortho positions, or it may be interpreted as meaning both ortho positions.

<<<Polyphenylene ether and method for producing same>>>
Hereinafter, each step of the method for producing (synthesizing) the polyphenylene ether of the present invention and the polyphenylene ether of the present invention obtained by the method will be described. As described later, the polyphenylene ether of the present invention is a polyphenylene ether having a branched structure. Therefore, the polyphenylene ether of the present invention may be expressed as a branched polyphenylene ether.

<<<<Process>>>
In the method for producing polyphenylene ether of the present invention, it is only necessary to use a specific phenol as a raw material in carrying out oxidative polymerization, and other than that, conventionally known methods for producing polyphenylene ether can be applied.

In addition, in the method for producing polyphenylene ether of the present invention, phenols that are used as raw materials and can become structural units of polyphenylene ether are collectively referred to as "raw material phenols."

The polyphenylene ether of the present invention can be produced, for example, by preparing a polymerization solution containing a specific phenol, a catalyst, and a solvent (polymerization solution preparation step), bubbling oxygen into at least the solvent (oxygen supply step), and oxidatively polymerizing the phenol in the oxygen-containing polymerization solution (polymerization step).

The polymerization solution preparation step, oxygen supply step, and polymerization step are described below. Each step may be performed continuously, or a part or all of one step may be performed simultaneously with a part or all of another step, or a step may be interrupted and another step may be performed during that time. For example, an oxygen supply step may be performed during the polymerization solution preparation step or the polymerization step. In addition, the method for producing polyphenylene ether of the present invention may include other steps as necessary. Examples of other steps include a step of extracting the polyphenylene ether obtained by the polymerization step (for example, a step of performing reprecipitation, filtration, and drying).

<<Polymerization solution preparation process>>
The polymerization solution preparation step is a step of mixing raw materials including phenols to be polymerized in the polymerization step to prepare a polymerization solution. The raw materials for the polymerization solution include raw phenols, a catalyst, and a solvent.

<Raw phenols>
In the method for producing polyphenylene ether of the present invention, the polymerization solution contains, as a raw material phenol, a phenol satisfying the following condition 1 as an essential component. Note that in the present application, when the term "phenol" is used simply, it means a phenol that is not a polyhydric phenol, i.e., a monohydric phenol.
(Condition 1)
It has hydrogen atoms at the ortho and para positions.

Phenols that satisfy condition 1 (for example, phenols (A) and (B) described below) have hydrogen atoms at the ortho position, so when they are oxidatively polymerized with phenols, ether bonds can be formed not only at the ipso and para positions but also at the ortho position, making it possible to form a branched chain structure.

Phenols that do not satisfy condition 1 (for example, phenols (C) and (D) described below) undergo oxidative polymerization, forming ether bonds at the ipso and para positions, and are polymerized into a linear chain.

In this way, a part of the structure of the specified polyphenylene ether is branched by benzene rings ether-bonded at least at the ipso, ortho, and para positions. The polyphenylene ether is considered to be, for example, a compound that is a polyphenylene ether having a branched structure in the skeleton as shown in at least formula (i).

In formula (i), R _a to R _k each represent a hydrogen atom or a hydrocarbon group having 1 to 15 carbon atoms (preferably 1 to 12 carbon atoms).

The raw material phenols may contain other phenols that do not satisfy condition 1, as long as the effects of the present invention are not impaired.

Other phenols include, for example, phenols (C) and (D) described below, and phenols that do not have a hydrogen atom at the para position. In order to increase the molecular weight of polyphenylene ether, it is preferable to further include phenols (C) and (D) as raw material phenols.

The polymerization solution also contains a specified polyhydric phenol as an essential component. The specified polyhydric phenol is a compound having at least two (preferably two) phenolic hydroxyl groups in its molecular structure and having no hydrogen atoms at the ortho positions of the at least two phenolic hydroxyl groups. The phenolic hydroxyl groups in the polyhydric phenol undergo a polymerization reaction, and polyphenylene ether chains having the above-mentioned branched structure are added and/or grow at both ends of the polyhydric phenol. As a result, a polyphenylene ether having a more complicated (highly branched) structure than conventional polyphenylene ether is formed, and the solubility in cyclohexanone, etc. is improved. In addition, since the polyphenylene ether chains exist at both ends of the polyhydric phenol, the number of terminal hydroxyl groups is increased compared to when the polyhydric phenol is not used. This is advantageous when modifying the terminal hydroxyl groups to modify the polyphenylene ether.

It is preferable that the specified polyhydric phenol does not have a hydrogen atom at the para position of the at least two phenolic hydroxyl groups. Not having a hydrogen atom at the para position makes it easier to control the reaction and makes it easier to increase the molecular weight of the resulting polyphenylene ether.

In a preferred method for producing polyphenylene ether of the present invention, the polymerization solution contains a phenol satisfying the following conditions. The polymerization solution may contain a phenol satisfying all of the following conditions, or may contain a plurality of phenols satisfying each of the conditions.
(Condition 1)
Having hydrogen atoms at the ortho and para positions (condition 2)
It has a hydrogen atom at the para position and a functional group containing an unsaturated carbon bond.

That is, a preferred method for producing polyphenylene ether of the present invention is
(Mode 1) A mode in which, as a raw material phenol, at least a phenol (A) satisfying both of the following conditions 1 and 2 is contained as an essential component, or
(Mode 2) A mode in which, as raw material phenols, at least a phenol (B) which satisfies the following condition 1 but does not satisfy condition 2 and a phenol (C) which does not satisfy condition 1 but satisfies condition 2 are included as essential components:
They are classified into two types:
(Condition 1)
Having hydrogen atoms at the ortho and para positions (condition 2)
It has a hydrogen atom at the para position and a functional group containing an unsaturated carbon bond.

The above-mentioned form 1 may be a form further including phenols (B) and/or phenols (C) as raw material phenols. Also, the above-mentioned form 2 may be a form further including phenols (A) as raw material phenols.

The method for producing polyphenylene ether of the present invention is preferably either the above-mentioned form 2 or the above-mentioned form 1 containing phenols (B) and/or phenols (C) as further essential components.

The raw material phenols may also contain other phenols as long as the effects of the present invention are not impaired.

Other phenols include, for example, phenols (D), which are phenols that have a hydrogen atom at the para position, no hydrogen atom at the ortho position, and no functional group containing an unsaturated carbon bond.

In both the above-mentioned form 1 and the above-mentioned form 2, it is preferable to further include phenol (D) as a raw material phenol in order to increase the molecular weight of the polyphenylene ether.

The method for producing polyphenylene ether of the present invention is most preferably in the above embodiment 2, further comprising phenol (D) as the raw material phenol.

Furthermore, in the above embodiment 2, from an industrial and economical point of view, it is preferable that the phenol (B) is at least one of o-cresol, 2-phenylphenol, 2-dodecylphenol, and phenol, and the phenol (C) is 2-allyl-6-methylphenol.

The phenols (A) to (D) and the specified polyhydric phenols are described in more detail below.

As described above, the phenol (A) is a phenol that satisfies both conditions 1 and 2, i.e., a phenol that has hydrogen atoms at the ortho and para positions and has a functional group that contains an unsaturated carbon bond, and is preferably a phenol (a) represented by the following formula (1).

In formula (1), R ₁ to R ₃ are hydrogen atoms or hydrocarbon groups having 1 to 15 carbon atoms. However, at least one of R ₁ to R ₃ is a hydrocarbon group having an unsaturated carbon bond. From the viewpoint of facilitating polymerization by oxidative polymerization, the hydrocarbon group preferably has 1 to 12 carbon atoms.

Examples of phenols (a) represented by formula (1) include o-vinylphenol, m-vinylphenol, o-allylphenol, m-allylphenol, 3-vinyl-6-methylphenol, 3-vinyl-6-ethylphenol, 3-vinyl-5-methylphenol, 3-vinyl-5-ethylphenol, 3-allyl-6-methylphenol, 3-allyl-6-ethylphenol, 3-allyl-5-methylphenol, and 3-allyl-5-ethylphenol. Only one type of phenol represented by formula (1) may be used, or two or more types may be used.

As described above, phenol (B) is a phenol that satisfies condition 1 but does not satisfy condition 2, i.e., a phenol that has hydrogen atoms at the ortho and para positions and does not have a functional group containing an unsaturated carbon bond, and is preferably a phenol (b) represented by the following formula (2).

In formula (2), R ₄ to R ₆ are hydrogen atoms or hydrocarbon groups having 1 to 15 carbon atoms. However, R ₄ to R ₆ do not have an unsaturated carbon bond. From the viewpoint of facilitating polymerization by oxidative polymerization, the hydrocarbon group preferably has 1 to 12 carbon atoms.

Examples of phenols (b) represented by formula (2) include phenol, o-cresol, m-cresol, o-ethylphenol, m-ethylphenol, 2,3-xylenol, 2,5-xylenol, 3,5-xylenol, o-tert-butylphenol, m-tert-butylphenol, o-phenylphenol, m-phenylphenol, and 2-dodecylphenol. Only one type of phenol represented by formula (2) may be used, or two or more types may be used.

As described above, the phenol (C) is a phenol that does not satisfy condition 1 but satisfies condition 2, i.e., a phenol that has a hydrogen atom at the para position, does not have a hydrogen atom at the ortho position, and has a functional group that contains an unsaturated carbon bond, and is preferably a phenol (c) represented by the following formula (3).

In formula (3), R ₇ and R ₁₀ are hydrocarbon groups having 1 to 15 carbon atoms, and R ₈ and R ₉ are hydrogen atoms or hydrocarbon groups having 1 to 15 carbon atoms, provided that at least one of R ₇ to R ₁₀ is a hydrocarbon group having an unsaturated carbon bond. From the viewpoint of facilitating polymerization by oxidative polymerization, the hydrocarbon group preferably has 1 to 12 carbon atoms.

Examples of phenols (c) represented by formula (3) include 2-allyl-6-methylphenol, 2-allyl-6-ethylphenol, 2-allyl-6-phenylphenol, 2-allyl-6-styrylphenol, 2,6-divinylphenol, 2,6-diallylphenol, 2,6-diisopropenylphenol, 2,6-dibutenylphenol, 2,6-diisobutenylphenol, 2,6-diisopentenylphenol, 2-methyl-6-styrylphenol, 2-vinyl-6-methylphenol, and 2-vinyl-6-ethylphenol. Only one type of phenol represented by formula (3) may be used, or two or more types may be used.

As described above, the phenol (D) is a phenol having a hydrogen atom at the para position, no hydrogen atom at the ortho position, and no functional group containing an unsaturated carbon bond, and is preferably a phenol (d) represented by the following formula (4).

In formula (4), R ₁₁ and R ₁₄ are hydrocarbon groups having 1 to 15 carbon atoms and no unsaturated carbon bonds, and R ₁₂ and R ₁₃ are hydrogen atoms or hydrocarbon groups having 1 to 15 carbon atoms and no unsaturated carbon bonds. From the viewpoint of facilitating polymerization by oxidative polymerization, the hydrocarbon group preferably has 1 to 12 carbon atoms.

Examples of phenols (d) represented by formula (4) include 2,6-dimethylphenol, 2,3,6-trimethylphenol, 2-methyl-6-ethylphenol, 2-ethyl-6-n-propylphenol, 2-methyl-6-n-butylphenol, 2-methyl-6-phenylphenol, 2,6-diphenylphenol, and 2,6-ditolylphenol. Only one type of phenol represented by formula (4) may be used, or two or more types may be used.

The specified polyhydric phenol has two or more phenolic hydroxyl groups in its molecular structure and has no hydrogen atom at the ortho position of the phenolic hydroxyl group. Preferably, it has no hydrogen atom at the para position of the phenolic hydroxyl group. For example, it is polyhydric phenol (e) represented by the following formula (9) or polyhydric phenol (f) represented by the following formula (10).

In formula (9), R1 to R5 are a hydrogen atom, a hydroxyl group, or a hydrocarbon group having 1 to 15 carbon atoms, and at least one of R1 to R5 is a hydroxyl group, and the ortho-position of the hydroxyl group is not a hydrogen atom. From the viewpoint of facilitating polymerization by oxidative polymerization, it is preferable that the hydrocarbon group has 1 to 12 carbon atoms.

Among the polyhydric phenols (e) represented by formula (9), the dihydric phenols are compounds represented by the following formulas (9-1) to (9-3).

In formula (9-1), R1 and R4 are a hydrocarbon group having 1 to 15 carbon atoms, and R2 and R3 are a hydrogen atom or a hydrocarbon group having 1 to 15 carbon atoms.
In formula (9-2), R1, R3 and R5 are hydrocarbon groups having 1 to 15 carbon atoms, and R12 is a hydrogen atom or a hydrocarbon group having 1 to 15 carbon atoms.
In formula (9-3), R1 to R5 are hydrocarbon groups having 1 to 15 carbon atoms.
From the viewpoint of facilitating polymerization into a polymer during oxidative polymerization, the hydrocarbon group preferably has 1 to 12 carbon atoms.

Examples of polyhydric phenols (e) represented by formula (9) include 3,6-dimethylcatechol, 3,6-t-butylcatechol, 3,6-diallylcatechol, 3-methyl-6-allylcatechol, 3-methyl-6-cyclohexylcatechol, 3-methyl-6-phenylcatechol, 3-methyl-6-benzylcatechol, 3,4,6-trimethylcatechol, tetramethylcatechol, 2,4,6-trimethylresorcinol, tetramethylresorcinol, tetramethylhydroquinone, 4,6-dimethylpyrogallol, trimethylphloroglucinol, trimethylhydroxyquinol, and hexahydroxybenzene. Only one type of polyhydric phenol (e) represented by formula (9) may be used, or two or more types may be used.

In formula (10), X is a single bond or a divalent organic group. Examples of the divalent organic group include a divalent hydrocarbon group (preferably an alkylene group or an alkylidene group), a phosphine atomic group (-PR _X -), an amine atomic group (-NR _X -), an amide bond (-CO-NH-), and an azo group (-N=N-). _{R X} is a hydrogen atom or a hydrocarbon group having 1 to 15 carbon atoms, preferably 1 to 6 carbon atoms. The divalent hydrocarbon group preferably has 1 to 12 carbon atoms, more preferably 1 to 3 carbon atoms.
In formula (10), R1 to R10 are a hydrogen atom, a hydroxyl group, or a hydrocarbon group having 1 to 15 carbon atoms, at least one of R1 to R5 is a hydroxyl group, at least one of R6 to R10 is a hydroxyl group, and the ortho-position of the hydroxyl group is not a hydrogen atom. From the viewpoint of facilitating polymerization into a polymer during oxidative polymerization, the hydrocarbon group preferably has 1 to 12 carbon atoms.

Among the polyhydric phenols (f) represented by formula (10), the dihydric phenols are compounds represented by the following formulas (10-1) to (10-6).

In formula (10-1), R1 to R3 and R6 to R8 are each a hydrogen atom or a hydrocarbon group having 1 to 15 carbon atoms, and R4 and R9 are each a hydrocarbon group having 1 to 15 carbon atoms.
In formula (10-2), R1 to R3 and R6 to R7 are each a hydrogen atom or a hydrocarbon group having 1 to 15 carbon atoms, and R4, R8 and R10 are each a hydrocarbon group having 1 to 15 carbon atoms.
In formula (10-3), R1 to R3, R6 and R10 are hydrogen atoms or hydrocarbon groups having 1 to 15 carbon atoms, and R4, R7 and R9 are hydrocarbon groups having 1 to 15 carbon atoms.
In formula (10-4), R1 to R2 and R6 to R7 are each a hydrogen atom or a hydrocarbon group having 1 to 15 carbon atoms, and R3, R5, R8 and R10 are each a hydrocarbon group having 1 to 15 carbon atoms.
In formula (10-5), R1 to R2, R6 and R10 are hydrogen atoms or hydrocarbon groups having 1 to 15 carbon atoms, and R3, R5, R7 and R9 are hydrocarbon groups having 1 to 15 carbon atoms.
In formula (10-6), R1, R5, R6 and R10 are hydrogen atoms or hydrocarbon groups having 1 to 15 carbon atoms, and R2, R4, R7 and R9 are hydrocarbon groups having 1 to 15 carbon atoms.
From the viewpoint of facilitating polymerization into a polymer during oxidative polymerization, the hydrocarbon group preferably has 1 to 12 carbon atoms.

The polyhydric phenol (f) represented by the formula (10) is
2,2'-dihydroxy-3,3'-dimethylbiphenyl,
2,2'-dihydroxy-3,3'-diallylbiphenyl,
2,2'-dihydroxy-3,3'-dicyclohexylbiphenyl,
2,2'-dihydroxy-3,3'-diphenylbiphenyl,
2,2'-dihydroxy-3,3',5,5'-tetramethylbiphenyl,
2,2'-dihydroxy-3,3',5,5'-tetra-t-butylbiphenyl,
4,4'-dihydroxy-3,3',5,5'-tetramethylbiphenyl,
4,4'-dihydroxy-2,2',3,3',5,5'-hexamethylbiphenyl,
4,4'-dihydroxy-2,2',3,3',5,5',6,6'-octamethylbiphenyl,
4,4'-dihydroxy-3,3',5,5'-tetraisopropylbiphenyl,
4,4'-dihydroxy-3,3',5,5'-tetra-t-butylbiphenyl,
Bis(2-hydroxy-3-methylphenyl)methane,
Bis(2-hydroxy-3,5-dimethylphenyl)methane,
Bis(2-hydroxy-3-t-butyl-5-methylphenyl)methane,
Bis(4-hydroxy-3,5-dimethylphenyl)methane,
Bis(4-hydroxy-3,5-diallylphenyl)methane,
Bis(4-hydroxy-3,5-dicyclohexylphenyl)methane,
Bis(4-hydroxy-3,5-diphenylphenyl)methane,
Bis(4-hydroxy-3,5-dimethylphenyl)phenylmethane 1,1-bis(4-hydroxy-3,5-dimethylphenyl)ethane,
1,2-bis(4-hydroxy-3,5-dimethylphenyl)ethane 1,1-bis(4-hydroxy-3,5-dimethylphenyl)-1-phenylethane 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane,
2,2-bis(4-hydroxy-3-methyl-5-ethylphenyl)propane,
2,2-bis(4-hydroxy-3-phenyl-5-ethylphenyl)propane,
2,2-bis(4-hydroxy-3,5-dimethylphenyl)butane,
1,1-bis(4-hydroxy-3,5-dimethylphenyl)cyclohexane,
1,4-bis(4-hydroxy-3,5-dimethylphenyl)benzene,
9,9-bis(4-hydroxy-3,5-dimethylphenyl)fluorene,
bis(4-hydroxy-3,5-dimethylphenyl)phosphine,
bis(4-hydroxy-3,5-dimethylphenyl)phenylphosphine,
bis(4-hydroxy-3,5-dimethylphenyl)amine,
Bis(4-hydroxy-3,5-dimethylphenyl)methylamine,
Bis(4-hydroxy-3,5-dimethylphenyl)phenylamine,
4-hydroxy-3,5-dimethyl-N-(4-hydroxy-3,5-dimethylphenyl)benzamide,
Examples include 4,4'-dihydroxy-3,3',5,5'-tetrakismethylazobenzene, etc. The polyhydric phenols (f) represented by the formula (10) may be used alone or in combination of two or more.

Here, the specified polyhydric phenol may be a polyhydric phenol other than the polyhydric phenol (e) represented by formula (9) and the polyhydric phenol (f) represented by formula (10). Examples include tris(4-hydroxy-3,5-dimethylphenyl)methane, 1,1,1-tris(4-hydroxy-3,5-dimethylphenyl)ethane, 1,1,2-tris(4-hydroxy-3,5-dimethylphenyl)ethane, tetrakis(4-hydroxy-3,5-dimethylphenyl)methane, and tris(4-hydroxy-3,5-dimethylphenyl)amine.

Here, in the present invention, examples of the hydrocarbon group include an alkyl group, a cycloalkyl group, an aryl group, an alkenyl group, and an alkynyl group, and preferably an alkyl group, an aryl group, and an alkenyl group. Examples of the hydrocarbon group having an unsaturated carbon bond include an alkenyl group and an alkynyl group. These hydrocarbon groups may be linear or branched.

Furthermore, other phenols may include phenols that do not have a hydrogen atom at the para position.

It is preferable that the ratio of phenols satisfying condition 1 to the total amount of raw material phenols is 1 to 50 mol%.

The ratio of phenols satisfying condition 2 to the total amount of raw material phenols is preferably 0.5 to 99 mol%, and more preferably 1 to 99 mol%.

<Catalyst>
The catalyst is not particularly limited, and any suitable catalyst used in the oxidative polymerization of polyphenylene ether may be used.

Catalysts include, for example, amine compounds and metal amine compounds consisting of heavy metal compounds such as copper, manganese, and cobalt and amine compounds such as tetramethylethylenediamine. In particular, to obtain a copolymer with a sufficient molecular weight, it is preferable to use a copper-amine compound in which a copper compound is coordinated to an amine compound. Only one type of catalyst may be used, or two or more types may be used.

The catalyst content is not particularly limited, but may be 0.1 to 0.6 mol % relative to the total amount of raw phenols in the polymerization solution.

Such catalysts may be dissolved in advance in a suitable solvent.

<Solvent>
The solvent is not particularly limited, and may be any suitable solvent used in the oxidative polymerization of polyphenylene ether. It is preferable to use a solvent capable of dissolving or dispersing the phenolic compound and the catalyst.

Specific examples of the solvent include aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; halogenated aromatic hydrocarbons such as chloroform, methylene chloride, chlorobenzene, dichlorobenzene, and trichlorobenzene; nitro compounds such as nitrobenzene; methyl ethyl ketone (MEK), cyclohexanone, tetrahydrofuran, ethyl acetate, N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), propylene glycol monomethyl ether acetate (PMA), and diethylene glycol monoethyl ether acetate (CA). Only one type of solvent may be used, or two or more types may be used.

The solvent may include water or a solvent that is compatible with water.

The amount of solvent in the polymerization solution is not particularly limited and may be adjusted as appropriate.

<Other ingredients>
The polymerization solution may contain other raw materials as long as the effects of the present invention are not impaired.

<<Oxygen supply process>>
The oxygen supplying step is a step of bubbling an oxygen-containing gas into the polymerization solution.

The time for which oxygen gas is passed through and the oxygen concentration in the oxygen-containing gas used can be changed as appropriate depending on the air pressure, temperature, etc.

<<Polymerization process>>
The polymerization step is a step in which phenols in a polymerization solution are oxidatively polymerized under conditions in which oxygen is supplied to the polymerization solution.

Specific polymerization conditions are not particularly limited, but for example, stirring may be performed at 25 to 100°C for 2 to 24 hours.

The polyphenylene ether of the present invention is obtained by the above-mentioned production method, in other words, it is a polyphenylene ether obtained by oxidatively polymerizing the above-mentioned raw material phenols.

<<End Modification>>
A part or all of the terminal hydroxyl groups in the polyphenylene ether thus obtained can be modified by using a modifying compound according to a conventionally known method. The type of modifying compound, reaction temperature, reaction time, presence or absence of a catalyst, and the type of catalyst can be appropriately designed. Two or more types of compounds may be used as the modifying compound. As mentioned above, the number of terminal hydroxyl groups becomes relatively large when the polyhydric phenol is used. This is advantageous when modifying the terminal hydroxyl groups to modify the polyphenylene ether.

Here, the modifying compound may be any compound capable of modifying a terminal hydroxyl group, and specifically, may be an organic compound having one or more carbon atoms that can react with a phenolic hydroxyl group in the presence or absence of a catalyst. Such an organic compound may contain an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom, a halogen atom, etc.

When a terminal hydroxyl group is modified with a modifying compound, an ether bond or an ester bond is usually formed between the terminal hydroxyl group and the modifying compound.

It is also possible to impart properties derived from the modifying compound to the terminally modified polyphenylene ether. For example, the flame retardancy of the cured product can be improved by the modifying compound containing a phosphorus atom (more specifically, the modifying compound being a halogenated organophosphorus compound). In addition, from the viewpoint of the heat resistance of the cured product, it is preferable that the modifying compound contains a heat- or light-reactive functional group. For example, the modifying compound contains an unsaturated carbon bond, a cyanate group, or an epoxy group, which can improve the reactivity of the terminally modified polyphenylene ether of the present invention.

A suitable example of a modifying compound is an organic compound represented by the following formula (A):

In formula (A), _R , _R and _R are each independently a hydrogen atom or a hydrocarbon group having 1 to 9 carbon atoms, R is a divalent hydrocarbon group having 1 to 9 carbon atoms, and _X is a group capable of reacting with a phenolic hydroxyl group, such as F, Cl, Br, I or CN.

The modification of the terminal hydroxyl groups of the polyphenylene ether can be confirmed by comparing the hydroxyl value of the polyphenylene ether with that of the terminally modified polyphenylene ether. Note that the terminally modified polyphenylene ether may have some unmodified hydroxyl groups.

Here is an example of a structural analysis of polyphenylene ether.

Figure 1 shows 13C-NMR spectra, with the upper spectrum being that of a copolymer of o-cresol and 2-allyl-6-methylphenol, and the lower spectrum being that of a copolymer of 2,6-dimethylphenol and 2-allyl-6-methylphenol. As the spectrum chart shows, it is difficult to identify peaks in polyphenylene ether (PPE) when raw material phenols that satisfy condition 1 are used. Therefore, when considering structural analysis using 13C-NMR spectra, it is preferable to identify the polyphenylene ether of the present invention using the synthetic raw materials.

Here, it is possible to identify the branching structure (degree of branching) of a given polyphenylene ether by carrying out the following analysis.

<Analysis procedure>
After preparing polyphenylene ether chloroform solutions at intervals of 0.1, 0.15, 0.2, and 0.25 mg/mL, a graph of refractive index difference and concentration is created while feeding at 0.5 mL/min, and the refractive index increment dn/dc is calculated from the slope. Next, the absolute molecular weight is measured under the following device operating conditions. With reference to the chromatogram of the RI detector and the chromatogram of the MALS detector, a regression line is obtained by the least squares method from a logarithmic graph (conformation plot) of molecular weight and radius of gyration, and the slope is calculated.

<Measurement conditions>
Device name: HLC8320GPC
Mobile phase: Chloroform Column: TOSOH TSKguard column HHR-H
+ TSKgelGMHHR-H (2 bottles)
+ TSKgel G2500HHR
Flow rate: 0.6 mL/min.
Detector: DAWN HELEOS (MALS detector)
+ Optilab rEX (RI detector, wavelength 254 nm)
Sample concentration: 0.5 mg/mL
Sample solvent: Same as mobile phase. 5 mg of sample dissolved in 10 mL of mobile phase. Injection volume: 200 μL
Filter: 0.45 μm
STD Reagent: Standard polystyrene Mw 37,900
STD concentration: 1.5 mg/mL
STD solvent: Same as mobile phase. 15 mg of sample is dissolved in 10 mL of mobile phase. Analysis time: 100 min.

For resins with the same absolute molecular weight, the more branching of the polymer chain progresses, the smaller the distance from the center of gravity to each segment (radius of gyration). Therefore, the slope of the logarithmic plot of absolute molecular weight and radius of gyration obtained by GPC-MALS indicates the degree of branching, with a smaller slope indicating a greater degree of branching. In the present invention, a smaller slope calculated from the above conformation plot indicates a greater degree of branching in the polyphenylene ether, and a larger slope indicates a lesser degree of branching in the polyphenylene ether.

In polyphenylene ether, the slope is, for example, less than 0.6, and is preferably 0.55 or less, 0.50 or less, 0.45 or less, or 0.40 or less. When the slope is within this range, the polyphenylene ether is considered to have sufficient branching. The lower limit of the slope is not particularly limited, but is, for example, 0.05 or more, 0.10 or more, 0.15 or more, or 0.20 or more.

The slope of the conformation plot can be adjusted by changing the temperature, amount of catalyst, stirring speed, reaction time, amount of oxygen supplied, and amount of solvent during the synthesis of polyphenylene ether. More specifically, by increasing the temperature, increasing the amount of catalyst, increasing the stirring speed, lengthening the reaction time, increasing the amount of oxygen supplied, and/or decreasing the amount of solvent, the slope of the conformation plot tends to become lower (the polyphenylene ether becomes more easily branched).

The polyphenylene ether of the present invention preferably has a number average molecular weight of 2,000 to 30,000. More preferably, it is 5,000 to 30,000, even more preferably 8,000 to 30,000, and particularly preferably 8,000 to 25,000. Furthermore, the polyphenylene ether of the present invention preferably has a polydispersity index (PDI: weight average molecular weight/number average molecular weight) of 1.5 to 20. The number average molecular weight and weight average molecular weight are measured by gel permeation chromatography (GPC) and converted using a calibration curve prepared using standard polystyrene.

From the viewpoint of solvent solubility, the hydroxyl value of the polyphenylene ether of the present invention is preferably 7.0 or more when the number average molecular weight (Mn) is 10,000 or more. In other words, when the number average molecular weight (Mn) is 5,000 or more, the hydroxyl value is preferably 14.0 or more, and when the number average molecular weight is 20,000 or more, the hydroxyl value is preferably 3.5 or more.

The polyphenylene ether of the present invention preferably has a solution viscosity of 250 or less (P) when the weight average molecular weight (Mw) is 130,000 or more and the concentration when dissolved in chloroform is 0.5 (g/mL). Also, it is preferable that the solution viscosity is 250 or less (P) when the weight average molecular weight (Mw) is 35,000 or more and the concentration is 0.5 (g/mL).

1 g of the polyphenylene ether of the present invention is preferably soluble in 100 g of cyclohexanone (more preferably 100 g of cyclohexanone, DMF and PMA) at 25°C. The solubility of 1 g of polyphenylene ether in 100 g of a solvent (e.g., cyclohexanone) means that no turbidity or precipitation is visually observed when 1 g of polyphenylene ether is mixed with 100 g of a solvent. It is more preferable that the polyphenylene ether of the present invention is soluble in an amount of 1 g or more in 100 g of cyclohexanone at 25°C.

<<Applications>>
The polyphenylene ether of the present invention maintains low dielectric properties and is soluble in various solvents (solvents other than highly toxic solvents), and therefore can be used in a variety of applications.

The following describes specific uses of the polyphenylene ether of the present invention, including a curable composition and a cured product obtained by curing the curable composition.

<Curable Composition>
The curable composition contains the polyphenylene ether of the present invention and a peroxide, and preferably further contains a crosslinking curing agent. The curable composition may contain other components within the range not impairing the effects of the present invention.

The polyphenylene ether of the present invention is as described above, so we will explain the peroxide, crosslinking curing agent and other components.

The peroxide has the effect of opening the unsaturated carbon bonds contained in the polyphenylene ether of the present invention and promoting the crosslinking reaction.

Peroxides include methyl ethyl ketone peroxide, methyl acetoacetate peroxide, acetylacetonate peroxide, 1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)butane, t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, di-t-butyl hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, 2,5-di Examples of peroxides include methyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-butene, acetyl peroxide, octanoyl peroxide, lauroyl peroxide, benzoyl peroxide, m-toluyl peroxide, diisopropyl peroxydicarbonate, t-butylene peroxybenzoate, di-t-butyl peroxide, t-butylperoxyisopropyl monocarbonate, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, etc. Only one type of peroxide may be used, or two or more types may be used.

Among these, peroxides with a one-minute half-life temperature of 130°C to 180°C are preferred from the standpoint of ease of handling and reactivity. Such peroxides have a relatively high reaction initiation temperature, so they are unlikely to promote curing when curing is not required, such as during drying, and do not impair the storage stability of the polyphenylene ether resin composition. In addition, they have low volatility and do not volatilize during drying or storage, providing good stability.

The amount of peroxide added is preferably 0.01 to 20 parts by mass, more preferably 0.05 to 10 parts by mass, and particularly preferably 0.1 to 10 parts by mass, per 100 parts by mass of the solid content of the curable composition in terms of the total amount of peroxide. By keeping the total amount of peroxide within this range, it is possible to prevent deterioration of the film quality when formed into a coating film while ensuring sufficient effect at low temperatures.

If necessary, it may also contain azo compounds such as azobisisobutyronitrile and azobisisovaleronitrile, or radical initiators such as dicumyl and 2,3-diphenylbutane.

Cross-linking curing agents cross-link polyphenylene ether in three dimensions.

As the crosslinking type curing agent, one having good compatibility with polyphenylene ether is used, and examples thereof include polyfunctional vinyl compounds such as divinylbenzene, divinylnaphthalene, and divinylbiphenyl; vinylbenzyl ether compounds synthesized by the reaction of phenol with vinylbenzyl chloride; allyl ether compounds synthesized by the reaction of styrene monomer, phenol with allyl chloride; and further, trialkenyl isocyanurate. As the crosslinking type curing agent, trialkenyl isocyanurate, which has particularly good compatibility with polyphenylene ether, is preferred, and specifically, triallyl isocyanurate (hereinafter, TAIC (registered trademark)) and triallyl cyanurate (hereinafter, TAC) are preferred. These exhibit low dielectric properties and can increase heat resistance. In particular, TAIC (registered trademark) is preferred because of its excellent compatibility with polyphenylene ether.

As the crosslinking curing agent, a (meth)acrylate compound (methacrylate compound and acrylate compound) may be used. In particular, it is preferable to use a trifunctional to pentafunctional (meth)acrylate compound. As the trifunctional to pentafunctional methacrylate compound, trimethylolpropane trimethacrylate or the like may be used, while as the trifunctional to pentafunctional acrylate compound, trimethylolpropane triacrylate or the like may be used. The use of these crosslinking agents can improve heat resistance. Only one type of crosslinking curing agent may be used, or two or more types may be used.

The polyphenylene ether of the present invention has a branched structure that improves solubility in various solvents, but it may be difficult to improve the dielectric properties. However, since it contains a hydrocarbon group with an unsaturated carbon bond, it is possible to obtain a cured product with excellent dielectric properties, especially when cured with TAIC (registered trademark).

The blend ratio of polyphenylene ether to crosslinking curing agent is preferably 20:80 to 90:10 by weight, and more preferably 30:70 to 90:10. If the blend amount of polyphenylene ether is 20 parts by weight or more, appropriate toughness is obtained, and if it is 90 parts by weight or less, excellent heat resistance is obtained.

The curable composition is usually provided or used in a state where the polyphenylene ether is dissolved in a solvent. The polyphenylene ether of the present invention has higher solubility in solvents than conventional polyphenylene ethers, so a wide range of solvents can be selected depending on the application of the curable composition.

Examples of solvents that can be used in the curable composition of the present invention include conventionally usable solvents such as chloroform, methylene chloride, and toluene, as well as relatively safe solvents such as N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), cyclohexanone, propylene glycol monomethyl ether acetate (PMA), diethylene glycol monoethyl ether acetate (CA), methyl ethyl ketone, and ethyl acetate. Only one type of solvent may be used, or two or more types may be used.

The amount of solvent in the curable composition is not particularly limited and can be adjusted as appropriate depending on the application of the curable composition.

The curable composition may contain known and commonly used raw materials such as resins other than the polyphenylene ether of the present invention and other additives, within the scope of not impairing the effects of the present invention.

Such a curable composition can be obtained by appropriately mixing the raw materials.

<Cured Product>
The cured product can be obtained by curing the above-mentioned curable composition.

The method for obtaining a cured product from the curable composition is not particularly limited, and can be appropriately changed depending on the composition of the curable composition. As an example, after carrying out a step of applying the curable composition to a substrate as described above (e.g., applying with an applicator, etc.), a drying step of drying the curable composition is carried out as necessary, and a thermal curing step of thermally crosslinking the polyphenylene ether by heating (e.g., heating with an inert gas oven, hot plate, vacuum oven, vacuum press, etc.) is carried out. The conditions for carrying out each step (e.g., coating thickness, drying temperature and time, heating temperature and time, etc.) can be appropriately changed depending on the composition and application of the curable composition, etc.

<Dry film, prepreg>
The dry film or prepreg of the present invention is obtained by applying the above-mentioned curable composition to a substrate.

The substrate may be a metal foil such as copper foil, a film such as polyimide film, polyester film, or polyethylene naphthalate (PEN) film, or a fiber such as glass cloth or aramid fiber.

A dry film can be obtained, for example, by applying a curable composition onto a polyethylene terephthalate film, drying it, and laminating a polypropylene film as necessary.

Prepregs are obtained, for example, by impregnating glass cloth with a curable composition and drying it.

<Laminated plate>
In the present invention, a laminate can be produced using the above-mentioned prepreg.

To explain in more detail, one or more prepregs of the present invention are layered, and then a metal foil such as copper foil is layered on both or just one of the upper and lower surfaces of the prepreg, and the layered product is heated and pressurized to produce a laminate having metal foil on both sides or just one side of the laminated product.

<Electronic Components>
Such a cured product has excellent dielectric properties and heat resistance and can be used for electronic parts, etc.

The electronic components having the cured product are not particularly limited, but preferred examples include high-capacity, high-speed communications such as the fifth generation communication system (5G) and millimeter wave radar for automotive ADAS (advanced driving systems).

The polyphenylene ether of the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited thereto.

<<<Synthesis of polyphenylene ether>>>
<<Synthesis of PPE-1 to PPE-6>>
In a 100mL two-necked eggplant flask, 0.5g of di-μ-hydroxo-bis[(N,N,N',N'-tetramethylethylenediamine)copper(II)] chloride (Cu/TMEDA) and 1mL of tetramethylethylenediamine (TMEDA) were added and dissolved thoroughly, and oxygen was supplied at 10mL/min. 0.71g (2.5mmol) of 4,4'-dihydroxy-2,2',3,3'5,5'-hexamethylbiphenyl, 1.08g (10mmol) of o-cresol, 1.48g (10mmol) of 2-allyl-6-methylphenol, and 9.76g (80mmol) of 2,6-dimethylphenol were dissolved in 50mL of toluene, and the solution was added dropwise to the flask and reacted at 40°C for 6 hours while stirring at a rotation speed of 600rpm. After the reaction was completed, the product was reprecipitated in a mixture of 200 mL of methanol and 2 mL of concentrated hydrochloric acid, filtered, and dried at 80° C. for 24 hours to obtain PPE-1. PPE-2 to PPE-6 were prepared in the same manner as PPE-1, except that the monomers in Table 1 were charged in the respective molar ratios.

<Measurement of average molecular weight>
The number average molecular weight (Mn), weight average molecular weight (Mw) and polydispersity index (PDI: Mw/Mn) of each PPE were determined by gel permeation chromatography (GPC). In GPC, Shodex K-805L was used as the column, the column temperature was 40° C., the flow rate was 1 mL/min, the eluent was chloroform, and the standard substance was polystyrene.

<Measurement of Hydroxyl Value>
The hydroxyl value of each PPE was measured by the following procedure. 2.0 g of sample (PPE) was precisely weighed into a two-neck flask, 10 mL of pyridine was added to completely dissolve it, and 5 mL of acetylating agent (a solution in which 25 g of acetic anhydride was dissolved in pyridine to a volume of 100 mL) was added exactly, and the mixture was heated at 60°C for 2 hours to acetylate the hydroxyl groups. After the reaction was completed, the reaction mother liquor was diluted with 10 mL of pyridine, and re-precipitated with 200 mL of warm water to decompose the unreacted acetic anhydride. The two-neck flask was further washed with 5 mL of ethanol. A few drops of phenolphthalein solution were added as an indicator to the warm water used for re-precipitation purification, and titrated with 0.5 mol/L potassium hydroxide ethanol solution. The end point was when the indicator's light red color continued for 30 seconds. A blank test was also performed in the same manner without adding the sample.

The hydroxyl value, hydroxyl equivalent and number of hydroxyl groups per molecule were calculated from the following formulas.
Hydroxyl value (mgKOH/g) = [{(b-a) x F x 28.05}/S] + D
S: sample amount (g)
a: Consumption of 0.5 mol/L potassium hydroxide ethanol solution (mL)
b: Blank test: Consumption of 0.5 mol/L potassium hydroxide ethanol solution (mL)
F: Factor of 0.5 mol/L potassium hydroxide ethanol solution D: Acid value (mg KOH/g)
Hydroxyl equivalent (g/eq.)=56.1/hydroxyl value×1000
Number of hydroxyl groups per molecule = Mn/hydroxyl equivalent

<Conformation plot slope>
To understand the branching structure (degree of branching) of each PPE, the slope of the conformation plot was calculated. The analytical method was as described above.

<Solubility of each PPE in solvent>
A solubility test was conducted for each PPE in chloroform, methylene chloride, toluene, methyl ethyl ketone (MEK), cyclohexanone, tetrahydrofuran (THF), ethyl acetate, N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), propylene glycol monomethyl ether acetate (PMA), and diethylene glycol monoethyl ether acetate (CA). 100 g of each solvent and each PPE were placed in a 200 mL sample bottle, a stirrer was added, and the mixture was stirred for 10 minutes, then left at 25°C for 10 minutes, and the state was visually observed and evaluated.

A solution that was clear when 1 g of PPE was dissolved was marked with a "◎", a solution that was clear when 0.01 g of PPE was dissolved was marked with a "○", a solution that was cloudy when 0.01 g of PPE was dissolved was marked with a "△", and a solution in which PPE precipitated even when 0.01 g of PPE was mixed was marked with an "X".

<<<Preparation of Composition>>>
A PPE composition (varnish) was prepared by mixing each material according to the composition shown in Table 3. The numbers in the table are in parts by mass. "Perbutyl P" in the table stands for α,α'-bis(t-butylperoxy-m-isopropyl)benzene.

<<Evaluation>>
Each PPE composition and the cured product obtained therefrom were evaluated for the items described below.

<Environmental Response>
The varnishes using cyclohexanone as the solvent were rated as "good", and the varnishes using chloroform as the solvent were rated as "bad".

<Film-forming properties>
The PPE composition was applied to the shine side of a 18 μm thick copper foil with an applicator so that the thickness of the cured product was 50 μm. Next, the composition was dried at 90° C. for 30 minutes in a hot air circulation drying oven. After that, the composition was completely filled with nitrogen using an inert oven, heated to 200° C., and cured for 60 minutes. Then, the copper foil was etched away to obtain a cured film.

Those that obtained a self-supporting film after curing were rated as "Good", and those that did not obtain a self-supporting film were rated as "Poor". Those that did not obtain a self-supporting film were not evaluated as follows.

<Dielectric properties>
The dielectric properties, that is, the relative dielectric constant Dk and the dielectric loss tangent Df, were measured according to the following method.
The cured film was obtained by the above procedure. The obtained cured film was cut into a length of 80 mm, a width of 45 mm, and a thickness of 50 μm, and this was used as a test piece to measure by the SPDR (Split Post Dielectric Resonator) resonator method. The measuring device used was a vector network analyzer E5071C manufactured by Keysight Technologies, LLC, an SPDR resonator, and a calculation program manufactured by QWED. The conditions were a frequency of 10 GHz and a measurement temperature of 25° C.

<Adhesion>
The adhesion was evaluated in accordance with the copper-clad laminate test standard JIS-C-6481. The PPE composition was applied to the rough surface of a low-roughness copper foil (FV-WS (manufactured by Furukawa Electric Co., Ltd.): Rz = 1.5 μm) so that the thickness of the cured product was 50 μm. Next, it was dried at 90 ° C for 30 minutes in a hot air circulation drying oven. Then, it was completely filled with nitrogen using an inert oven, heated to 200 ° C, and cured for 60 minutes. An epoxy adhesive (Araldite) was applied to the obtained cured film side, and a copper-clad laminate (length 150 mm, width 100 mm, thickness 1.6 mm) was placed on it and cured at 60 ° C for 1 hour in a hot air circulation drying oven. Next, a 10 mm wide and 100 mm long cut was made in the low-roughness copper foil, one end of which was peeled off and gripped with a gripper, and 90 ° peel strength was measured.
(Measurement condition)
Testing machine: Tensile testing machine EZ-SX (manufactured by Shimadzu Corporation)
Measurement temperature: 25°C
Stroke: 35mm
Stroke speed: 50 mm/min
Number of measurements: Average of 5 measurements

Those with a 90° peel strength of 5.0 N/cm or more were rated as "◎", those with a 90° peel strength of 4.0 N/cm or more but less than 5.0 N/cm were rated as "◯", and those with a 90° peel strength of less than 4.0 N/cm were rated as "X".

<<Synthesis of Modified PPE-1 to Modified PPE-6>>
In a 200 mL two-necked flask equipped with a dropping funnel, 10 g of PPE-1, 1.5 g of allyl bromide as a modifying compound, 0.22 g of benzyl tributyl ammonium bromide as a phase transfer catalyst, and 50 mL of tetrahydrofuran were added and stirred at 25°C. 8 mL of 1M NaOH aqueous solution was added dropwise to the solution over 10 minutes. Then, the solution was further stirred at 25°C for 5 hours. Next, the reaction solution was neutralized with hydrochloric acid, reprecipitated in 1 L of methanol, filtered, washed three times with a mixture of methanol and water in a mass ratio of 80:20, and dried at 80°C for 24 hours to obtain modified PPE-1. Modified PPE-2 to modified PPE-6 were synthesized in the same manner as modified PPE-1.

<Measurement of average molecular weight>
By the above-mentioned method, the number average molecular weight (Mn), weight average molecular weight (Mw) and polydispersity index (PDI: Mw/Mn) of each modified PPE were determined.

<<<Preparation of Composition>>>
A PPE composition (varnish) was prepared by mixing each material according to the composition shown in Table 5. The numbers in the table are in parts by mass. "Perbutyl P" in the table stands for α,α'-bis(t-butylperoxy-m-isopropyl)benzene.

<<Evaluation>>
Each PPE composition and the cured product obtained therefrom were evaluated for the items described below.

<Environmental Response>
The varnishes using cyclohexanone as the solvent were rated as "good", and the varnishes using chloroform as the solvent were rated as "bad".

<Film-forming properties>
The PPE composition was applied to the shine side of a 18 μm thick copper foil with an applicator so that the thickness of the cured product was 50 μm. Next, the composition was dried at 90° C. for 30 minutes in a hot air circulation drying oven. After that, the composition was completely filled with nitrogen using an inert oven, heated to 200° C., and cured for 60 minutes. Then, the copper foil was etched away to obtain a cured film.

Those that obtained a self-supporting film after curing were rated as "Good", and those that did not obtain a self-supporting film were rated as "Poor". Those that did not obtain a self-supporting film were not evaluated as follows.

<Dielectric properties>
The dielectric properties, that is, the relative dielectric constant Dk and the dielectric loss tangent Df, were measured according to the following method.
The cured film was obtained by the above procedure. The obtained cured film was cut into a length of 80 mm, a width of 45 mm, and a thickness of 50 μm, and this was used as a test piece to measure by the SPDR (Split Post Dielectric Resonator) resonator method. The measuring device used was a vector network analyzer E5071C manufactured by Keysight Technologies, LLC, an SPDR resonator, and a calculation program manufactured by QWED. The conditions were a frequency of 10 GHz and a measurement temperature of 25° C.

<Heat resistance>
A cured film was obtained by the above procedure. The obtained cured film was cut into a length of 30 mm, width of 5 mm, and thickness of 50 μm, and the glass transition temperature (Tg) was measured using a DMA7100 (Hitachi High-Tech Science Corporation). The temperature range was 30 to 280°C, the heating rate was 5°C/min, the frequency was 1 Hz, the strain amplitude was 7 μm, the minimum tension was 50 mN, and the gripper distance was 10 mm. The glass transition temperature (Tg) was defined as the temperature at which tan δ was maximized.

Glass transition temperatures (Tg) of 210°C or higher were rated as "◎", those between 190°C and 210°C were rated as "◯", and those below 190°C were rated as "X".

<Tensile properties>
The cured film was obtained by the above procedure. The obtained cured film was cut into a piece having a length of 8 cm, a width of 0.5 cm and a thickness of 50 μm, and the tensile elongation at break was measured under the following conditions.
[Measurement condition]
Testing machine: Tensile testing machine EZ-SX (manufactured by Shimadzu Corporation)
Distance between chucks: 50 mm
Test speed: 1 mm/min
Elongation calculation: (tensile travel distance/chuck distance) x 100

Tensile elongation at break of 4.0% or more was rated as "◎", 1.0% or more but less than 4.0% was rated as "◯", and less than 1.0% was rated as "X".

Claims (8)

A phenol satisfying at least condition 1;
a polyhydric phenol having two or more phenolic hydroxyl groups in its molecular structure and having no hydrogen atom at the ortho position of the phenolic hydroxyl group;
The raw material phenols include
The phenols satisfying at least the condition 1 are phenols represented by the following formula (1) or (2):
the phenol represented by the formula (2) is at least one selected from o-cresol, m-cresol, o-ethylphenol, m-ethylphenol, 2,3-xylenol, 2,5-xylenol, 3,5-xylenol, o-tert-butylphenol, m-tert- butylphenol, and 2-dodecylphenol;
A polyphenylene ether, characterized in that the polyhydric phenol having two or more phenolic hydroxyl groups in the molecular structure is a phenol represented by the following formula (9) or (10):
(Condition 1)
Contains hydrogen atoms at the ortho and para positions
(In the formula (1), R ₁ to R ₃ are a hydrogen atom or a hydrocarbon group having 1 to 15 carbon atoms, and the hydrocarbon group is an alkyl group, an alkenyl group, or an alkynyl group. However, at least one of R ₁ to R ₃ is an alkenyl group or an alkynyl group.)
(In the formula (2), R ₄ to R ₆ each represent a hydrogen atom or an alkyl group having 1 to 15 carbon atoms.)
(In formula (9), R1 to R5 each represent a hydrogen atom, a hydroxyl group, or a hydrocarbon group having 1 to 15 carbon atoms, at least one of R1 to R5 represents a hydroxyl group, and the ortho-position of the hydroxyl group is not a hydrogen atom.)
(In formula (10), X is a single bond or a divalent hydrocarbon group, a phosphine atomic group, an amine atomic group, an amide bond or an azo group ; R1 to R10 are a hydrogen atom, a hydroxyl group or a hydrocarbon group having 1 to 15 carbon atoms; at least one of R1 to R5 is a hydroxyl group, at least one of R6 to R10 is a hydroxyl group, and the ortho-position of the hydroxyl group is not a hydrogen atom.) The raw material phenols are
The polyphenylene ether according to claim 1, comprising a mixture of a phenol (A) that satisfies at least both of the following condition 1 and the following condition 2, or a phenol (B) that satisfies at least the following condition 1 but does not satisfy the following condition 2, and a phenol (C) that does not satisfy the following condition 1 but satisfies the following condition 2.
(Condition 1)
Having hydrogen atoms at the ortho and para positions (condition 2)
It has a hydrogen atom at the para position and a functional group containing an unsaturated carbon bond. A curable composition comprising the polyphenylene ether according to any one of claims 1 to 2 and a peroxide. The curable composition according to claim 3, characterized in that it contains a crosslinking curing agent. A dry film or prepreg obtained by applying or impregnating a substrate with the curable composition according to any one of claims 3 to 4. A cured product obtained by curing the curable composition according to any one of claims 3 to 4. A laminate comprising the cured product according to claim 6. An electronic component comprising the cured product according to claim 6.

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