JP2021109945A - Polyphenylene ether, curable composition containing polyphenylene ether, dry film, prepreg, cured product, laminate, and electronic component - Google Patents

Abstract

To provide a polyphenylene ether having both of low dielectric properties and excellent insulation reliability.SOLUTION: A polyphenylene ether is obtained from a raw material phenol containing a phenol satisfying at least condition 1 and has an inclination of less than 0.6 calculated by a conformation plot, in which the copper concentration is less than 100 ppm and the chlorine concentration is less than 500 ppm. (Condition 1) It has hydrogen atoms at ortho position and para position.There is also provided a curable composition comprising the polyphenylene ether.SELECTED DRAWING: None

Description

The present invention relates to a polyphenylene ether, a curable composition containing the polyphenylene ether, and a dry film, a prepreg, a cured product, a laminated board, and an electronic component using the curable composition containing the polyphenylene ether.

With the widespread use of large-capacity high-speed communications represented by the 5th generation communication system (5G) and millimeter-wave radars for ADAS (advanced driver assistance systems) of automobiles, the frequency of signals of communication devices is increasing.

However, when an epoxy resin or the like is used as the wiring board material, for example, the relative permittivity (Dk) and the dielectric loss tangent (Df) are not sufficiently low, so that the higher the frequency, the larger the transmission loss due to the dielectric loss occurs. , There were problems such as signal attenuation and heat generation. Therefore, various materials such as polyphenylene ether having excellent low dielectric properties have been proposed and used for applications in such a high frequency region.

For example, Non-Patent Document 1 proposes a polyphenylene ether having further improved heat resistance by introducing an allyl group into the molecule of the polyphenylene ether to form a thermosetting resin.

J. Nunoshige, H. Akahoshi, Y. Shibasaki, M. Ueda, J. Polym. Sci. Part A: Polym. Chem. 2008, 46, 5278-3223.

On the other hand, in order to realize excellent insulation reliability in the resin component used for the insulating film such as a wiring board, impurities such as copper catalyst and chlorine used for synthesizing the resin component are reduced and purified to high purity. Resin is required. However, conventional polyphenylene ethers are limited in soluble solvents, and the polyphenylene ethers obtained by the method of Non-Patent Document 1 are also soluble only in highly toxic solvents such as chloroform and toluene. Therefore, there is a problem that it is difficult to remove impurities by purifying the resin.

Therefore, an object of the present invention is to provide a curable composition containing a polyphenylene ether purified to high purity and the polyphenylene ether, which has both low dielectric properties and excellent insulation reliability.

As a result of diligent studies toward the realization of the above object, the present inventors have improved the solubility in a solvent and enabled purification to reduce impurities such as copper catalyst and chlorine according to the polyphenylene ether having a branched structure. They have found that they can provide highly purified polyphenylene ethers, and have completed the present invention. That is, the present invention is as follows.

The present invention (1)
A polyphenylene ether obtained from a raw material phenol containing at least a phenol satisfying condition 1 and having a slope of less than 0.6 calculated by a conformation plot.
Chlorine concentration is less than 500ppm
It is a polyphenylene ether characterized by a copper concentration of less than 100 ppm.

The present invention (2)
It is a curable composition containing the polyphenylene ether of the invention (1).

The present invention (3)
A dry film or prepreg obtained by applying or impregnating the curable composition of the invention (2) onto a substrate.

The present invention (4)
It is a cured product obtained by curing the curable composition of the invention (2).

The present invention (5)
It is a laminated board characterized by containing the cured product of the invention (4).

The present invention (6)
It is an electronic component characterized by having a cured product of the invention (4).

According to the present invention, it is possible to provide a curable composition containing a highly purified polyphenylene ether and the polyphenylene ether, which has both low dielectric properties and excellent insulation reliability.

Hereinafter, the curable composition containing the polyphenylene ether of the present invention and the polyphenylene ether will be described, but the present invention is not limited to the following.

If isomers are present in the described compounds, all possible isomers can be used in the present invention unless otherwise noted.

In the present invention, phenols used as a raw material for polyphenylene ether (PPE) and which can be a constituent unit of polyphenylene ether are collectively referred to as "raw material phenols".

In the present invention, when the raw material phenols are described as "ortho-position" or "para-position", the position of the phenolic hydroxyl group is used as a reference (ipso-position) unless otherwise specified.

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

In the present invention, a polyphenylene ether in which some or all functional groups (for example, hydroxyl groups) of the polyphenylene ether are modified may be simply referred to as "polyphenylene ether". Therefore, the term "polyphenylene ether" includes both unmodified polyphenylene ethers and modified polyphenylene ethers, unless otherwise inconsistent.

Although monovalent phenols are mainly disclosed as raw material phenols in the present specification, polyvalent phenols may be used as raw material phenols as long as the effects of the present invention are not impaired.

In the present specification, "resin composition" may be used to mean "curable composition".

In the present specification, when the upper limit value and the lower limit value of the numerical range are described separately, it is assumed that substantially all combinations of each lower limit value and each upper limit value are described within a consistent range. do.

<<<<< Polyphenylene ether >>>>>
The polyphenylene ether of the present invention is a polyphenylene ether having a branched structure, which is obtained from raw material phenols including phenols satisfying at least condition 1. Such a polyphenylene ether is referred to as a predetermined polyphenylene ether.
(Condition 1)
Has hydrogen atoms at the ortho and para positions

Phenols satisfying condition 1 {for example, phenols (A) and phenols (B) described later} have a hydrogen atom at the ortho position, and therefore, when oxidatively polymerized with phenols, only the ipso position and the para position are present. In addition, since an ether bond can be formed even at the ortho position, it is possible to form a branched chain-like structure.

As described above, a polyphenylene ether having a branched structure may be expressed as a branched polyphenylene ether.

As described above, a part of the structure of the predetermined polyphenylene ether is branched by the benzene ring in which at least three positions of the ipso position, the ortho position and the para position are ether-bonded. The predetermined polyphenylene ether is considered to be, for example, a polyphenylene ether compound having a branched structure represented by at least the formula (i) in the skeleton.

In formula (i), R _{a to} R _k are hydrogen atoms or hydrocarbon groups having 1 to 15 carbon atoms (preferably 1 to 12 carbon atoms).

Here, the raw material phenols constituting the predetermined polyphenylene ether may contain other phenols that do not satisfy the condition 1 as long as the effects of the present invention are not impaired.

Examples of such other phenols include phenols (C) and phenols (D) described later, and phenols having no hydrogen atom at the para position. In particular, when phenols (C) and phenols (D), which will be described later, are oxidatively polymerized, ether bonds are formed at the ipso and para positions, and they are polymerized linearly. Therefore, in order to increase the molecular weight of the polyphenylene ether, it is preferable to further contain phenols (C) and phenols (D) as raw material phenols.

Here, the predetermined polyphenylene ether preferably has a functional group containing an unsaturated carbon bond. The method for incorporating a functional group containing an unsaturated carbon bond in the polyphenylene ether is not particularly limited, but the following [Method 1] or [Method 2] is preferable.

[Method 1]
Method 1 is
As raw material phenols
Phenols (A) that satisfy at least both the following condition 1 and the following condition 2 are included (form 1), or
This is a method (form 2) in which a mixture of phenols (B) that satisfy at least the following condition 1 and do not satisfy the following condition 2 and phenols (C) that do not satisfy the following condition 1 and satisfy the following condition 2 is contained.
(Condition 1)
It has hydrogen atoms at the ortho and para positions (Condition 2)
It has a hydrogen atom at the para position and has a functional group containing an unsaturated carbon bond.

According to Method 1, a predetermined polyphenylene ether having a functional group containing an unsaturated carbon bond derived from a raw material phenol can be obtained.

[Method 2]
Method 2 is
This is a method in which the terminal hydroxyl group of a branched polyphenylene ether is modified to a functional group containing an unsaturated carbon bond to obtain a terminal-modified polyphenylene ether.

According to the method 2, even when the raw material phenols do not have a functional group containing an unsaturated carbon bond, a predetermined polyphenylene ether having a functional group containing an unsaturated carbon bond introduced can be obtained.

[Method 1] and [Method 2] may be carried out at the same time.

<< Predetermined polyphenylene ether obtained by method 1 >>

Since the predetermined polyphenylene ether obtained by Method 1 uses at least phenols satisfying Condition 2 {for example, any of phenols (A) and phenols (C)} as a phenol raw material, at least unsaturated carbon bonds are formed. It will have cross-linking property due to the containing hydrocarbon group. When the predetermined polyphenylene ether has a hydrocarbon group containing such an unsaturated carbon bond, modification such as epoxidation is carried out using a compound that reacts with the hydrocarbon group and has a reactive functional group such as an epoxy group. It is also possible to do.

That is, the predetermined polyphenylene ether obtained by Method 1 is, for example, a polyphenylene ether having a branched structure as represented by the formula (i) in the skeleton, and has a hydrocarbon group containing at least one unsaturated carbon bond. It is considered to be a compound having a functional group. Specifically, it is considered that _{at least one of Ra to} R _{k in} the above formula (i) is a compound which is a hydrocarbon group having an unsaturated carbon bond.

In particular, in the above form 2, from an industrial and economic point of view, the phenols (B) are at least one of o-cresol, 2-phenylphenol, 2-dodecylphenol and phenol, and the phenols ( C) is preferably 2-allyl-6-methylphenol.

Hereinafter, the phenols (A) to (D) will be described in more detail.

As described above, the phenols (A) are phenols that satisfy both conditions 1 and 2, that is, phenols having hydrogen atoms at the ortho and para positions and having a functional group containing an unsaturated carbon bond. It is preferably the phenols (a) represented by the following formula (1).

In the 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. The hydrocarbon group preferably has 1 to 12 carbon atoms from the viewpoint of facilitating polymerization during oxidative polymerization.

Examples of the phenols (a) represented by the formula (1) include o-vinylphenol, m-vinylphenol, o-allylphenol, m-allylphenol, 3-vinyl-6-methylphenol, and 3-vinyl-6-. Ethylphenol, 3-vinyl-5-methylphenol, 3-vinyl-5-ethylphenol, 3-allyl-6-methylphenol, 3-allyl-6-ethylphenol, 3-allyl-5-methylphenol, 3- Examples thereof include allyl-5-ethylphenol. As the phenols represented by the formula (1), only one kind may be used, or two or more kinds may be used.

As described above, the phenols (B) have a hydrogen atom at the ortho-position and a para-position and do not have a functional group containing an unsaturated carbon bond, that is, a phenol that satisfies the condition 1 and does not satisfy the condition 2. It is a phenol, preferably a phenol (b) represented by the following formula (2).

In the 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 unsaturated carbon bonds. The hydrocarbon group preferably has 1 to 12 carbon atoms from the viewpoint of facilitating polymerization during oxidative polymerization.

Examples of the phenols (b) represented by the formula (2) include phenol, o-cresol, m-cresol, o-ethylphenol, m-ethylphenol, 2,3-xylenol, 2,5-xylenol, 3,5. Examples thereof include -xylenol, o-tert-butylphenol, m-tert-butylphenol, o-phenylphenol, m-phenylphenol, 2-dodecylphenol, and the like. As the phenols represented by the formula (2), only one kind may be used, or two or more kinds may be used.

As described above, the phenols (C) are phenols that do not satisfy condition 1 and satisfy condition 2, that is, they have a hydrogen atom at the para position, do not have a hydrogen atom at the ortho position, and have an unsaturated carbon bond. It is a phenol having a functional group containing, and is preferably a phenol (c) represented by the following formula (3).

In the 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. However, _{at least one of R 7 to} R ₁₀ is a hydrocarbon group having an unsaturated carbon bond. The hydrocarbon group preferably has 1 to 12 carbon atoms from the viewpoint of facilitating polymerization during oxidative polymerization.

Examples of the phenols (c) represented by the formula (3) include 2-allyl-6-methylphenol, 2-allyl-6-ethylphenol, 2-allyl-6-phenylphenol, and 2-allyl-6-styrylphenol. , 2,6-divinylphenol, 2,6-diallylphenol, 2,6-diisopropenylphenol, 2,6-dibutenylphenol, 2,6-diisobutenylphenol, 2,6-diisopentenylphenol, 2, Examples thereof include -methyl-6-styrylphenol, 2-vinyl-6-methylphenol, 2-vinyl-6-ethylphenol and the like. As the phenols represented by the formula (3), only one kind may be used, or two or more kinds may be used.

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

In formula (4), R ₁₁ and R ₁₄ are hydrocarbon groups having 1 to 15 carbon atoms having no unsaturated carbon bond, and R ₁₂ and R ₁₃ have no hydrogen atom or unsaturated carbon bond. It is a hydrocarbon group having 1 to 15 carbon atoms. The hydrocarbon group preferably has 1 to 12 carbon atoms from the viewpoint of facilitating polymerization during oxidative polymerization.

Examples of the phenols (d) represented by the formula (4) include 2,6-dimethylphenol, 2,3,6-trimethylphenol, 2-methyl-6-ethylphenol, and 2-ethyl-6-n-propylphenol. , 2-Methyl-6-n-butylphenol, 2-methyl-6-phenylphenol, 2,6-diphenylphenol, 2,6-ditolylphenol and the like can be exemplified. As the phenols represented by the formula (4), only one kind may be used, or two or more kinds may be used.

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 an alkyl group, an aryl group and an alkenyl group are preferable. Examples of the hydrocarbon group having an unsaturated carbon bond include an alkenyl group and an alkynyl group. In addition, these hydrocarbon groups may be linear or branched chain.

<< Predetermined polyphenylene ether obtained by method 2 >>
The predetermined polyphenylene ether obtained by Method 2 is a terminally denatured branched polyphenylene ether.

Since such a terminally modified branched polyphenylene ether has a branched structure and the terminal hydroxyl group is modified, a cured product having a low dielectric property further reduced while being soluble in various solvents can be obtained. Further, the terminal-modified branched polyphenylene ether has extremely good reactivity as a result of arranging unsaturated carbon bonds at the terminal positions, and the resulting cured product has better performance.

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

Here, the modification compound is not particularly limited as long as it contains a functional group having an unsaturated carbon bond and can react with a phenolic hydroxyl group in the presence or absence of a catalyst.

Preferable examples of the modification compound include an organic compound represented by the following formula (11).

Wherein _{(11), R A, R} B, R C are each independently hydrogen or a hydrocarbon group having 1 to 9 carbon atoms, _{R D} is a hydrocarbon group having 1 to 9 carbon atoms Yes, X is a group capable of reacting with phenolic hydroxyl groups such as F, Cl, Br, I or CN.

From another viewpoint, a preferable example of the modification compound is an organic compound represented by the following formula (11-1).

In formula (11-1), R is a vinyl group, an allyl group, or a (meth) acrylic loyl group, and X is a group capable of reacting with phenolic hydroxyl groups such as F, Cl, Br, and I. ..

The modification of the terminal hydroxyl group of the branched polyphenylene ether can be confirmed by comparing the hydroxyl values of the branched polyphenylene ether and the terminal modified branched polyphenylene ether. The terminal-modified branched polyphenylene ether may remain partially unmodified hydroxyl groups.

The reaction temperature, reaction time, presence / absence of catalyst, type of catalyst, etc. at the time of denaturation can be appropriately designed. Two or more kinds of compounds may be used as a modification compound.

When the predetermined polyphenylene ether is obtained by the method 2, the branched polyphenylene ether before modification may be a branched polyphenylene ether containing an unsaturated carbon bond (the predetermined polyphenylene ether obtained by the above-mentioned method 1) or an unsaturated carbon bond. It may be a branched polyphenylene ether that does not contain it.

The branched polyphenylene ether containing no unsaturated carbon bond may be a polyphenylene ether obtained from a raw material phenol containing at least phenols satisfying the following condition 1 and not containing phenols satisfying the following condition Z.
(Condition 1)
It has hydrogen atoms at the ortho and para positions (condition Z).
Contains functional groups with unsaturated carbon bonds

As described above, the branched polyphenylene ether containing no unsaturated carbon bond contains phenols {for example, phenols (B)} that satisfy condition 1 and do not satisfy condition Z as essential components.

The branched polyphenylene ether containing no unsaturated carbon bond may contain other phenols that do not satisfy the condition Z as additional raw material phenols.

Other phenols that do not satisfy the condition Z include, for example, phenols that have a hydrogen atom at the para position, do not have a hydrogen atom at the ortho position, and do not have a functional group containing an unsaturated carbon bond. (D), phenols and the like which do not have a hydrogen atom at the para position and do not have a functional group containing an unsaturated carbon bond can be mentioned.

In order to increase the molecular weight of the polyphenylene ether, it is preferable to further contain phenols (D) as raw material phenols in the predetermined polyphenylene ether containing no unsaturated carbon bond.

When a branched polyphenylene ether containing no unsaturated carbon bond is used as a raw material, an unsaturated carbon bond is not introduced into the side chain because the raw material phenol does not contain phenols satisfying the above condition Z. Curability is imparted by modifying a part or all of the terminal hydroxyl groups of the polyphenylene ether obtained by oxidative polymerization of the raw material phenols to a functional group having an unsaturated carbon bond. As a result, deterioration of low dielectric properties, light resistance, and environmental resistance due to the terminal hydroxyl group is suppressed, and the unsaturated carbon bond at the terminal site has excellent reactivity, so that it can be cured with a cross-linking type curing agent described later. As a product, high strength and excellent crack resistance can be obtained.

When the branched polyphenylene ether does not contain unsaturated carbon bonds, the proportion of phenols satisfying condition 1 and not satisfying condition Z with respect to the total amount of raw material phenols is, for example, 10 mol% or more.

Here, examples of the hydrocarbon group having an unsaturated carbon bond and not containing a functional group include an alkyl group, a cycloalkyl group, and an aryl group. In addition, these hydrocarbon groups may be linear or branched chain.

In such methods 1 and 2, the ratio of phenols satisfying condition 1 to the total amount of raw material phenols used in the synthesis of the predetermined polyphenylene ether is preferably 1 to 50 mol%.

Further, it is not necessary to use phenols satisfying the above condition 2, but when they are used, the ratio of phenols satisfying condition 2 to the total amount of raw material phenols may be 0.5 to 99 mol%. It is preferably 1 to 99 mol%, more preferably 1 to 99 mol%.

The predetermined polyphenylene ether obtained by the methods 1 and 2 as described above has a branched structure, so that the solubility and compatibility with various solvents are improved. From this, the predetermined polyphenylene ether is dissolved in a hydrophilic solvent after synthesis, and at the same time, water is mixed and mixed, so that the copper catalyst used for synthesis is eluted in water without remaining in the resin. Furthermore, chlorine remaining due to hydrochloric acid can be reduced, and purification can be performed with high purity. When the obtained high-purity purified predetermined polyphenylene ether of the present invention is used as a constituent component of a curable composition described later, the components in the composition are uniformly dissolved or dispersed to obtain a uniform cured product. It becomes possible. As a result, this cured product has excellent mechanical properties in addition to low dielectric properties and excellent insulation reliability.

The physical characteristics and properties of the predetermined polyphenylene ether of the present invention purified to high purity will be described below.
<< Physical characteristics and properties of predetermined polyphenylene ether >>
<Degree of branching of predetermined polyphenylene ether>
The branched structure (degree of branching) of the predetermined polyphenylene ether can be confirmed based on the following analysis procedure.

(Analysis procedure)
After preparing a chloroform solution of polyphenylene ether at intervals of 0.1, 0.15, 0.2, 0.25 mg / mL, create a graph of the difference in refractive index and concentration while sending the solution at 0.5 mL / min. , The index of refraction 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, the regression line by the least squares method is obtained from the log-log graph (conformation plot) of the molecular weight and the radius of gyration, and the slope is calculated.

(Measurement condition)
Device name: HLC8320GPC
Mobile phase: Chloroform column: TOSOH TSKgradcolumnHHR-H
+ TSKgelGMHHR-H (2)
+ TSKgelG2500HHR
Flow velocity: 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. Dissolve 5 mg of sample 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. Dissolve 15 mg of sample in 10 mL of mobile phase Analysis time: 100 min

In resins having the same absolute molecular weight, the distance (radius of gyration) from the center of gravity to each segment becomes smaller as the branching of the polymer chain progresses. Therefore, the slope of the logarithmic plot of the absolute molecular weight and the radius of gyration obtained by GPC-MALS indicates the degree of branching, and the smaller the slope, the more the branching progresses. In the present invention, the smaller the slope calculated in the conformation plot, the more polyphenylene ether branches, and the larger the slope, the less polyphenylene ether branches.

In the predetermined polyphenylene ether of the present invention, the inclination is less than 0.6, preferably 0.55 or less, 0.50 or less, 0.45 or less, 0.40 or less, or 0.35 or less. .. When the above slope is in this range, it is considered that the polyphenylene ether has sufficient branching. The lower limit of the inclination 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 inclination of the conformation plot can be adjusted by changing the temperature, the amount of catalyst, the stirring speed, the reaction time, the amount of oxygen supplied, and the amount of solvent in the synthesis of polyphenylene ether. More specifically, by increasing the temperature, increasing the amount of catalyst, increasing the stirring speed, increasing the reaction time, increasing the amount of oxygen supply, and / or decreasing the amount of solvent, the slope of the conformation plot is tilted. It tends to be low (polyphenylene ether is more likely to branch).

<Molecular weight of predetermined polyphenylene ether>
The predetermined polyphenylene ether of the present invention preferably has a number average molecular weight of 2,000 to 30,000, more preferably 5,000 to 30,000, and preferably 8,000 to 30,000. It is more preferably 8,000 to 25,000, and particularly preferably 8,000 to 25,000. By setting the molecular weight in such a range, it is possible to improve the film-forming property of the curable resin composition while maintaining the solubility in a solvent. Further, the predetermined polyphenylene ether constituting the curable composition of the present invention preferably has a polydispersity index (PDI: weight average molecular weight / number average molecular weight) of 1.5 to 20.

In the present invention, the number average molecular weight and the weight average molecular weight are measured by gel permeation chromatography (GPC) and converted by a calibration curve prepared using standard polystyrene.

<Hydroxyl group value of predetermined polyphenylene ether>
The hydroxyl value of the predetermined polyphenylene ether of the present invention is preferably 15.0 or less, more preferably 2 or more and 10 or less, still more preferably 2 or more, and more preferably 2 or more and 10 or less in the range of the number average molecular weight (Mn) of 2,000 to 30,000. It is 3 or more and 8 or less.

In addition, when the predetermined polyphenylene ether is the predetermined polyphenylene ether obtained by the method 2, the hydroxyl value may be lower than the above-mentioned numerical value.

<Solvent solubility of predetermined polyphenylene ether>
1 g of the given polyphenylene ether is soluble at 25 ° C., preferably with respect to 100 g of cyclohexanone (more preferably with respect to 100 g of cyclohexanone, DMF and PMA). The fact that 1 g of polyphenylene ether is soluble in 100 g of a solvent (for example, cyclohexanone) means that when 1 g of polyphenylene ether and 100 g of solvent are mixed, turbidity and precipitation cannot be visually confirmed. It is more preferable that the predetermined polyphenylene ether is soluble in 1 g or more with respect to 100 g of cyclohexanone at 25 ° C.

<Copper concentration and chlorine concentration>
The predetermined polyphenylene ether of the present invention has a copper concentration of less than 100 ppm, preferably less than 20 ppm.

The copper concentration of polyphenylene ether is determined by weighing the sample polyphenylene ether in a platinum crucible and heating it at 600 ° C. for 1 hour in an electric furnace to volatilize and burn the resin component, and then dissolve the residue with nitrate to 100 ml. It is obtained by constant volume and measurement by ICP emission spectrometry (device: ICP emission spectroscope Varian 720-ES).

The predetermined polyphenylene ether of the present invention has a chlorine concentration of less than 500 ppm, preferably less than 70 ppm.

The chlorine concentration of the polyphenylene ether is such that the sample polyphenylene ether is burned under an oxygen stream and the generated gas is absorbed by a 0.3% hydrogen peroxide solution. Then, the chloride ion in the absorption liquid is measured by an ion chromatograph method (instrument: Integration manufactured by Thermo Fisher Scientific Co., Ltd.).

The predetermined polyphenylene ether of the present invention having such a copper concentration and a chlorine concentration can be obtained by carrying out a purification step described later.

Hereinafter, a method for producing the predetermined polyphenylene ether of the present invention purified to high purity will be described.
<< Production method of predetermined polyphenylene ether >>
The predetermined polyphenylene ether purified to high purity of the present invention uses conventionally known methods for synthesizing polyphenylene ethers (polymerization conditions, presence / absence of catalyst, type of catalyst, etc.) except that specific ones are used as raw material phenols. It can be applied and manufactured.

Next, an example of the method for producing the predetermined polyphenylene ether will be described.

The predetermined polyphenylene ether is, for example, preparing a polymerization solution containing a specific phenol, a copper catalyst and a solvent (polymerization solution preparation step), aerating oxygen through at least the solvent (oxygen supply step), and containing oxygen. It can be produced by oxidatively polymerizing phenols in a polymerization solution (polymerization step) and reducing the content of copper concentration (copper concentration derived from a copper catalyst) contained in a predetermined polyphenylene ether (purification step). ..

Hereinafter, the polymerization solution preparation step, the oxygen supply step, the polymerization step and the purification step will be described. It should be noted that each step may be carried out continuously, a part or all of a certain step and a part or all of another step may be carried out at the same time, or a certain step may be interrupted and during that time. Another step may be carried out. For example, the oxygen supply step may be carried out 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, if necessary. Examples of other steps include a step of extracting the polyphenylene ether obtained by the polymerization step (for example, a step of reprecipitation, filtration and drying), a modification step described above, and the like.

<Polymerization solution preparation process>
The polymerization solution preparation step is a step of preparing a polymerization solution by mixing each raw material containing phenols to be polymerized in the polymerization step described later. Examples of the raw material of the polymerization solution include raw material phenols, a copper catalyst, and a solvent.

(Copper catalyst)
The copper catalyst is not particularly limited, and an appropriate copper catalyst used in the oxidative polymerization of polyphenylene ether may be used.

Examples of the copper catalyst include a metal amine compound composed of copper and an amine compound such as tetramethylethylenediamine. In particular, in order to obtain a copolymer having a sufficient molecular weight, the amine compound is coordinated with the copper compound. It is preferable to use a copper-amine compound. Only one type of copper catalyst may be used, or two or more types may be used.

The content of the copper catalyst is not particularly limited, but may be 0.1 to 0.6 mol% or the like with respect to the total amount of the raw material phenols in the polymerization solution.

Such a copper catalyst may be previously dissolved in an appropriate solvent.

(solvent)
The solvent is not particularly limited, and an appropriate solvent used in the oxidative polymerization of polyphenylene ether may be used. As the solvent, 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, and nitro compounds such as nitrobenzene. Methyl ethyl ketone (MEK), cyclohexanone, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), ethyl acetate, N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF), propylene glycol monomethyl ether Examples thereof include acetate (PMA), diethylene glycol monoethyl ether acetate (CA), 1,4-dioxane, and acetonitrile. Of these, toluene is preferable because it does not inhibit the synthetic reaction and can carry out the reaction in a stable manner. Only one type of solvent may be used, or two or more types may be used.

The solvent may include water, a solvent compatible with water, and the like.

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

(Other raw materials)
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 supply step is a step of aerating an oxygen-containing gas in the polymerization solution.

The ventilation time of the oxygen gas and the oxygen concentration in the oxygen-containing gas used can be appropriately changed according to the atmospheric pressure, the air temperature, and the like.

<Polymerization process>
The polymerization step is a step of oxidatively polymerizing phenols in the polymerization solution under the condition that oxygen is supplied to the polymerization solution.

The specific polymerization conditions are not particularly limited, but for example, stirring may be performed under the conditions of 25 to 100 ° C. for 2 to 24 hours.

In the polymerization of the predetermined polyphenylene ether through the steps described above, by referring to the above-mentioned methods 1 and 2, a specific method for introducing a branched polyphenylene ether and a functional group containing an unsaturated carbon bond is specified. I can understand the method. That is, a predetermined polyphenylene ether having a functional group containing an unsaturated carbon bond is provided by specifying the type of the raw material phenols or by further providing a step (modification step) of modifying the terminal hydroxyl group after the polymerization step. (Polymer solution) can be obtained.

<Refining process>
The purification process is, for example,
A solution containing a predetermined polyphenylene ether (polymer solution) obtained in the polymerization step and a good solvent in which the predetermined polyphenylene ether is a soluble organic solvent is brought into contact with a poor solvent containing an aqueous solvent and hydrochloric acid, and the polymer is reprecipitated. In the primary purification step of obtaining a predetermined polyphenylene ether for primary purification by precipitating
A drying step of drying the primary purification predetermined polyphenylene ether obtained in the primary purification step, and a drying step of drying the predetermined polyphenylene ether.
Primary purification A solution containing a predetermined polyphenylene ether and a predetermined polyphenylene ether in which the predetermined polyphenylene ether is soluble, preferably a good solvent which is hydrophilic, and a poor solvent containing an aqueous solvent (however, the chlorine concentration is less than 500 ppm). , And the polymer is precipitated by reprecipitation to obtain a predetermined polyphenylene ether for secondary purification.
including.

Each step may be carried out while adjusting the pressure and temperature within a range that does not impair the effects of the present invention.

In the purification step, filtration may be carried out at any timing (for example, before the primary purification step). Further, the filtration may be performed a plurality of times.

(Primary purification process)
The primary purification step can be carried out according to a conventionally known method. The primary purification step can be carried out, for example, as follows.
A solution obtained by adding a good solvent to a predetermined polyphenylene ether (polymer solution), if necessary, is added dropwise to a poor solvent containing an aqueous solvent and hydrochloric acid to reprecipitate the predetermined polyphenylene ether (polymer solution).
Further, in the primary purification step, by stirring, the efficiency of moving the copper catalyst to the poor solvent by reacting the copper catalyst contained in the predetermined polyphenylene ether (polymer solution) with hydrochloric acid can be improved. In the primary purification step, hydrochloric acid functions as a complexing agent for the copper catalyst.
Then, the primary purified predetermined polyphenylene ether is taken out by filtration.
Further, the primary purification predetermined polyphenylene ether may be washed with a solvent or the like.

The good solvent is not particularly limited, and is an aromatic hydrocarbon such as benzene, toluene, xylene and ethylbenzene, a halogenated aromatic hydrocarbon such as chloroform, methylene chloride, chlorobenzene, dichlorobenzene and trichlorobenzene, and a nitro compound such as nitrobenzene. , Methyl ethyl ketone (MEK), cyclohexanone, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTH F), ethyl acetate, N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF), propylene glycol monomethyl Examples thereof include ether acetate (PMA), diethylene glycol monoethyl ether acetate (CA), 1,4-dioxane, and acetonitrile. Of these, a good solvent having an affinity with the good solvent used in the polymerization step is preferable.

The poor solvent is a solvent in which the solubility of the predetermined polyphenylene ether is relatively lower than that of the good solvent.
The poor solvent is not particularly limited as long as it is an aqueous solvent. The aqueous solvent may contain only water, or may be a mixture of water and an aqueous solvent (for example, methanol, ethanol, isopropanol, acetone, etc.). Above all, an aqueous solvent in which water and methanol are combined is preferable because the work efficiency of the subsequent filtration step is excellent.

The conditions for dropping, stirring, and filtering are not particularly limited, and known conditions carried out by a reprecipitation method or the like may be adopted.

The concentration of hydrochloric acid used is not particularly limited, and may be a concentration sufficient to react with the copper catalyst.

The solvent may contain a known chelating agent (for example, ethylenediamineacetic acid, disodium ethylenediamineacetate, diethylenetriaminepentaacetic acid, etc.).

(Drying process)
The drying in the drying step may be carried out according to a known method depending on the solvent used and the like. As an example, the drying step can be carried out by heating at −80 to 130 ° C. for 1 to 6 hours.

By performing the drying, the hydrochloric acid contained in the predetermined polyphenylene ether for the primary purification can be removed, and the filtration time in the secondary purification step can be shortened.

(Secondary purification process)
The secondary purification step can be carried out according to a conventionally known method. The secondary purification step can be carried out, for example, as follows.
A solution containing a high concentration of the primary purification predetermined polyphenylene ether (polymer solution) in a good solvent is added dropwise to a poor solvent containing an aqueous solvent to reprecipitate the predetermined polyphenylene ether.
Further, in the secondary purification step, the efficiency of transferring chlorine contained in the predetermined polyphenylene ether (polymer solution) to the poor solvent can be improved by performing stirring.
Then, the secondary purification predetermined polyphenylene ether is taken out by filtration or the like.
Secondary purification The predetermined polyphenylene ether may be further washed with a solvent or the like.

The good solvent is not particularly limited, and is an aromatic hydrocarbon such as benzene, toluene, xylene and ethylbenzene, a halogenated aromatic hydrocarbon such as chloroform, methylene chloride, chlorobenzene, dichlorobenzene and trichlorobenzene, and a nitro compound such as nitrobenzene. , Methyl ethyl ketone (MEK), cyclohexanone, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTH F), ethyl acetate, N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF), propylene glycol monomethyl Examples thereof include ether acetate (PMA), diethylene glycol monoethyl ether acetate (CA), 1,4-dioxane, and acetonitrile. Among them, it is preferable that the solvent has an affinity with a poor solvent (aqueous solvent) (hydrophilicity), and examples thereof include N-methyl-2-pyrrolidone, tetrahydrofuran, 1,4-dioxane, and acetonitrile. In particular, tetrahydrofuran and NMP are more preferable because they are excellent in the solubility of the predetermined polyphenylene ether and are excellent in the affinity with the poor solvent.

The solvent may contain a known chelating agent. Examples of the chelating agent include ethylenediaminetetraacetic acid, diethylenetriamine pentaacetic acid, hydroxylethylenediamine trivinegar, and salts thereof. By using a chelating agent in the secondary purification step, it is possible to remove the copper catalyst that was not removed in the primary purification step without causing residual chlorine.

The poor solvent is a solvent in which the solubility of the predetermined polyphenylene ether is relatively lower than that of the good solvent.
The poor solvent is not particularly limited as long as it is an aqueous solvent. The aqueous solvent may contain only water, or may be a mixture of water and an aqueous solvent (for example, methanol, ethanol, isopropanol, acetone, etc.).
The chlorine concentration of the poor solvent is less than 500 ppm, preferably less than 100 ppm, more preferably less than 50 ppm, still more preferably less than 10 ppm, and particularly preferably 0 ppm (although unavoidable chlorine content is acceptable). To do.).

The conditions for dropping, stirring, and filtering are not particularly limited, and conditions implemented by a known reprecipitation method or the like may be adopted.

After the secondary purification step, a further drying step may be carried out, which can be carried out under the same conditions as the drying step after the primary purification step.

<<<< Curable composition >>>>>
The curable composition of the present invention contains a predetermined polyphenylene ether purified to a high purity having a copper concentration of less than 100 ppm and a chlorine concentration of less than 500 ppm.
The predetermined polyphenylene ether may be used alone or in combination of two or more.
Here, in the present invention, curing is any one of a self-crosslinking reaction of a predetermined polyphenylene ether in a curable composition, a cross-linking reaction between the predetermined polyphenylene ether and other components, and a cross-linking reaction of other components other than the predetermined polyphenylene ether. Refers to one or more reactions. In addition, the curable composition may contain other components as long as the effects of the present invention are not impaired. Hereinafter, each component will be described.

<< Predetermined polyphenylene ether >>
The predetermined polyphenylene ethers constituting the curable composition of the present invention are as described above.

The content of the predetermined polyphenylene ether in the curable composition of the present invention is typically 5 to 30% by mass or 10 to 20% by mass based on the total solid content of the composition. From another viewpoint, the content of the predetermined polyphenylene ether in the curable composition is 20 to 60% by mass based on the total solid content of the composition.

The solid content in the curable composition means a component other than a solvent (particularly an organic solvent), or a mass or volume thereof.

<< Other ingredients >>
Other components include known components such as fillers (inorganic fillers as well as organic fillers such as PTFE powder), flame retardant improvers (phosphorus compounds, etc.), cellulose nanofibers, cyanate ester resins, epoxy resins, etc. It may contain components such as a phenol novolac resin, an elastomer, a dispersant, a curing accelerator, a cross-linking type curing agent (cross-linking agent), a polymerization initiator, an adhesion imparting agent, and a solvent.

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

Here, examples of the base material include metal foils such as copper foils, polyimide films, polyester films, films such as polyethylene naphthalate (PEN) films, and fibers such as glass cloth and aramid fibers.

The dry film can be obtained, for example, by applying a curable composition on a polyethylene terephthalate film, drying it, and laminating a polypropylene film as needed.

The prepreg is obtained, for example, by impregnating a glass cloth with a curable composition and drying it.

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

The method for obtaining the 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 performing a step of applying a curable composition on a substrate as described above (for example, coating with an applicator or the like), a drying step of drying the curable composition is carried out if necessary. Then, a thermosetting step of thermally cross-linking the polyphenylene ether by heating (for example, heating by an inert gas oven, a hot plate, a vacuum oven, a vacuum press, etc.) may be carried out. The conditions of implementation in each step (for example, coating thickness, drying temperature and time, heating temperature and time, etc.) may be appropriately changed according to the composition, application, and the like of the curable composition.

<<<<<< Laminated board >>>>>
The laminated board of the present invention contains the cured product of the present invention described above, and can be produced, for example, by using the above-mentioned prepreg.

More specifically, one or a plurality of prepregs of the present invention are laminated, and metal foils such as copper foil are laminated on both upper and lower surfaces or one side thereof, and the laminate is heat-press molded to be laminated and integrated. A laminated plate having a metal foil on both sides or a metal foil on one side can be produced.

<<<<< Electronic components >>>>>
The electronic component of the present invention has the above-mentioned cured product of the present invention, and has excellent dielectric properties and heat resistance, so that it can be used for various purposes.

The application is not particularly limited, but preferably, a large-capacity high-speed communication represented by a 5th generation communication system (5G), a millimeter-wave radar for ADAS (advanced driver assistance system) of an automobile, and the like can be mentioned.

Next, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

<<< Synthesis and Purification of PPE Resin of Example 1 >>>
Di-μ-hydroxobis [(N, N, N', N'-tetramethylethylenediamine) copper (II)] chloride (Cu / TMEDA) in a 1 L two-necked eggplant flask equipped with a reflux tube and a stir bar. ) 0.5 g and 0.6 mL of tetramethylethylenediamine (TMEDA) were added, and the mixture was stirred at 700 rpm. A raw material solution was prepared by dissolving 19.8 g of 2,6-dimethylphenol and 2.42 g of 2-allylphenol, which are raw material phenols, in 0.3 L of toluene. This raw material solution was added to the flask, and the mixture was heated and stirred at 700 rpm for 6 hours at 40 ° C. while bubbling oxygen gas.
After completion of the reaction, the reaction solution from which the Cu catalyst had been removed by suction filtration was added dropwise to a mixed solution of methanol 1.2 L: water 27 ml: hydrochloric acid 4 mL, stirred at room temperature for 12 hours at 900 rpm, and polyphenylene ether was recovered by suction filtration. (Primary purification step).
The polyphenylene ether obtained in the primary purification step was dried under reduced pressure at 80 ° C. for 4 hours (drying step).
The solid polyphenylene ether obtained in the drying step was dissolved in 200 ml of NMP, added dropwise to a mixed solution of 0.6 L of methanol: 75 ml of water: 0.9 g of EDTA-4Na, and the mixture was stirred at room temperature for 12 hours at 900 rpm. Then, the polyphenylene ether was recovered by suction filtration (secondary purification step).
The polyphenylene ether obtained in the secondary purification step was dried under reduced pressure at 100 ° C. for 6 hours to obtain a branched PPE.
The number average molecular weight of the branched PPE was 15,000, and the weight average molecular weight was 55,000. The slope of the conformation plot of the branched PPE was 0.33.

<<< Synthesis and Purification of PPE Resins of Examples 2-4 and Comparative Examples 1-4 >>
The type of poor solvent used in the primary purification step was changed, the drying step was changed, and the types of good solvent and poor solvent used in the secondary purification step were changed so as to meet the conditions shown in the table. Except for the above, the PPE resins of Examples 2-4 and Comparative Examples 1-4 were synthesized and purified in the same manner as in Example 1.

The time required for filtration in the primary purification step and the secondary purification step is shown in the table.

<<< Evaluation >>>
<< Impurity Concentration >>
The copper concentration and chlorine concentration contained in each PPE resin were measured by the method described above. The copper concentration and chlorine concentration of each PPE resin are shown in the table.

When the copper concentration was less than 20 ppm, it was evaluated as “⊚”, when it was 20 ppm or more and less than 100 ppm, it was evaluated as “◯”, and when it was 100 ppm or more, it was evaluated as “x”.

When the chlorine concentration was less than 70 ppm, it was evaluated as “⊚”, when it was 70 ppm or more and less than 500 ppm, it was evaluated as “◯”, and when it was 500 ppm or more, it was evaluated as “x”.

<< Filtration time >>
In the filtration of the secondary purification step, those having a filtration time of less than 40 minutes were evaluated as "⊚", those having a filtration time of 40 minutes or more and less than 10 minutes were evaluated as "◯", and those having a filtration time of 100 minutes or more were evaluated as "x".

<Preparation of curable composition>
13.25 parts by mass of PPE resin of Example 1, 13.25 parts by mass of TAIC (manufactured by Mitsubishi Chemical Co., Ltd.) as a cross-linking type curing agent, and 6.2 parts by mass of Tough Tech H1051 (manufactured by Asahi Kasei Co., Ltd.) as an adhesion imparting agent. , Cyclohexanone (100 parts by mass) was added and stirred, and 58.4 parts by mass of spherical silica (manufactured by Admatex Co., Ltd .: trade name "SC2500-SVJ") was further added as an inorganic filler, and after stirring, a three-roll mill was used. It was evenly dispersed.
Finally, 0.53 parts by mass of α, α'-bis (t-butylperoxy-m-isopropyl) benzene (manufactured by Nippon Oil & Fats Co., Ltd .: trade name "Perbutyl P"), which is a peroxide, is mixed and stirred. By doing so, a curable composition containing the PPE resin of Example 1 was prepared.

In the curable composition containing the PPE resin of Example 1, a curable composition containing the PPE resin of Comparative Example 3 was prepared by the same procedure except that the PPE resin of Example 1 was used as the PPE resin of Comparative Example 3. did.

<< Dielectric characteristics >>
A cured product was prepared using the PPE resin of Example 1 and the PPE resin of Comparative Example 3, and the relative permittivity Dk and the dielectric loss tangent Df, which are the dielectric properties, were measured according to the following methods.

Each curable composition containing the PPE resin of Example 1 or Comparative Example 3 was applied to the shine surface of a copper foil having a thickness of 18 μm with an applicator so that the thickness of the cured product was 50 μm, and a hot air circulation type drying oven was used. It was dried at 90 ° C. for 30 minutes. Then, after curing at 200 ° C. for 1 hour in an inert oven, the copper foil was etched to obtain a cured product (cured film) composed of each composition.

Relative permittivity Dk and dielectric loss tangent Df were measured by the SPDR (Split Post Dielectric Resonator) resonator method using the prepared cured film cut into a length of 80 mm, a width of 45 mm, and a thickness of 50 μm as a test piece. A vector network analyzer E5071C manufactured by Keysight Technologies, Inc., an SPDR resonator, and a calculation program manufactured by QWED were used as measuring instruments. The conditions were a frequency of 10 GHz and a measurement temperature of 25 ° C.

<Test result of dielectric property>
Cured product using PPE resin of Example 1 Dk: 3.0, Df: 0.0015
Cured product using PPE resin of Comparative Example 3 Dk: 3.0, Df: 0.0016

<< Insulation reliability >>
A substrate for HAST was prepared using the PPE resin of Example 1 and the PPE resin of Comparative Example 3, and the insulation reliability was evaluated by HAST (High Accelerated Life Test / High Accelerated Stress Test) for 500 hours.

<Manufacturing of HAST substrate>
Each curable composition containing the PPE resin of Example 1 or Comparative Example 3 was applied to a roughened copper-clad BT (bismaleimide triazine) substrate with an applicator so as to have a dry film thickness of 60 μm, and a hot air circulation type was applied. It was dried at 90 ° C. for 30 minutes in a drying oven. Next, FV-WS (HVLP foil) manufactured by Furukawa Electric Co., Ltd. was installed as a copper foil on the dry film of each composition so that the roughened surfaces were in contact with each other, and a vacuum laminator (hot plate temperature: 100 ° C., vacuum drawing: 30 s) was installed. , Pressurization: 30 s (0.5 MPa)). Then, it was cured at 200 ° C. for 1 hour in an inert oven to obtain a laminated board having a cured product layer made of each composition and a copper foil on a copper-clad BT substrate. Then, the copper foil on the surface layer was etched into a circle having a diameter of 10 mm using an etching solution for a printed circuit board manufactured by Sanhayato to prepare a substrate for HAST.

<Test conditions for insulation resistance>
In each HAST substrate, the surface layer (circular with a diameter of 10 mm) copper foil is used as the anode, and the copper foil surface of the copper-clad BT substrate is used as the cathode, and the HAST device (MIGRATION TESTER MODEL MIG-8600B manufactured by IMV) and chamber (manufactured by Hirayama) are used. The test was carried out using HASTEST (registered trademark) MODEL PC-R8D) under the conditions: 110 ° C./85% RH / 50V / 500h.

<Test result of insulation resistance value>
The resistance value when the voltage was applied for 500 hours was as follows.
Substrate with a cured product using the PPE resin of Example 1 1.5 × 10 ¹¹ (Ω)
Substrate 1.5 × 10 ⁹ having a cured product using the PPE resin of Comparative Example 3 (Omega)

As described above, it was confirmed that the cured product using the PPE resin of Example 1 has both low dielectric properties and excellent insulation reliability as compared with the cured product using the PPE resin of Comparative Example 3. ..

Claims (6)

A polyphenylene ether obtained from a raw material phenol containing at least a phenol satisfying condition 1 and having a slope calculated by a conformation plot of less than 0.6.
The copper concentration is less than 100 ppm
A polyphenylene ether characterized by a chlorine concentration of less than 500 ppm.
(Condition 1)
Has hydrogen atoms at the ortho and para positions A curable composition comprising the polyphenylene ether according to claim 1. A dry film or prepreg obtained by coating or impregnating a substrate with the curable composition according to claim 2. A cured product obtained by curing the curable composition according to claim 2. A laminated board comprising the cured product according to claim 4. An electronic component having the cured product according to claim 4.