Polyphenylene ether, curable composition containing polyphenylene ether, dry film, prepeg, cured product, and electronic component

Abstract

[Problem] Provided is a polyphenylene ether having a branch structure, the polyphenylene ether having low dielectric properties and excellent solubility in solvents, an easily controllable molecular weight, and being suitable for mass production. [Solution] An embodiment of the present invention is a polyphenylene ether. The polyphenylene ether is obtained from feedstock phenols that include phenols that satisfy at least condition 1 and phenols (X) represented by formula (1). Condition 1: Having a hydrogen atom at the ortho position and the para position.

Description

Polyphenylene ether, curable composition containing polyphenylene ether, dry film, prepreg, cured product, and electronic component

[0001] The present invention relates to a polyphenylene ether, a curable composition containing the polyphenylene ether, a dry film, a cured product, and an electronic component.

[0002] With the spread of high-capacity, high-speed communications, such as those typified by fifth-generation communications systems (5G), and millimeter-wave radar for automobile ADAS (Advanced Driver Assistance Systems), signals from communications equipment are becoming increasingly high-frequency.

[0003] However, when epoxy resins and other materials are used as wiring board materials, the dielectric constant (Dk) and dielectric loss tangent (Df) are not sufficiently low, so as the frequency increases, 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.

[0004] Furthermore, Non-Patent Document 1 proposes polyphenylene ether with improved heat resistance, which is made into a thermosetting resin by introducing an allyl group into the molecule of polyphenylene ether.

[0005] However, polyphenylene ether is soluble in only limited 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. Therefore, there are problems in that it is difficult to handle the resin varnish and to control solvent exposure in the process of forming a coating film and curing it for use in wiring boards.

[0006] J. Nunoshige, H. Akahoshi, Y. Shibasaki, M. Ueda, J. Polym. Sci. Part A: Polym. Chem. 2008, 46, 5278-5282.

[0007] Under these circumstances, the present inventors have discovered that polyphenylene ether having a branched structure synthesized using a specific phenol as a raw material has high solvent solubility (JP 2020-015909 A).

[0008] However, in the course of further research, the present inventors have newly discovered that polyphenylene ether having this branched structure has a problem in that it has more polymer ends having polymerization reactivity than polyphenylene ether having a linear structure, and therefore the grown polymers further polymerize with each other (so-called coupling), resulting in a rapid increase in molecular weight. Therefore, in order to control the molecular weight of the obtained polyphenylene ether within a desired range, careful adjustment of raw material selection and production conditions, etc., is required, which may make it unsuitable for mass production.

[0009] Furthermore, the present inventors have newly discovered that low molecular weight polyphenylene ethers synthesized by controlling the molecular weight may have reduced film properties such as mechanical strength when cured due to their low molecular weight.

[0010] Therefore, an object of the present invention is to provide a polyphenylene ether having a branched structure that allows easy control of the molecular weight, suppresses an increase in molecular weight, and provides a cured product with excellent mechanical strength.

[0011] The present inventors have conducted extensive research and found that the above-mentioned problems can be solved by a polyphenylene ether obtained from a raw material phenol containing a phenol having a specific structure.

[0012] One embodiment of the present invention is a polyphenylene ether. The polyphenylene ether is obtained from raw material phenols, and the raw material phenols contain phenols that satisfy at least the following condition 1 and a phenol (X) represented by the following formula (1): (Condition 1) A phenol (X) having hydrogen atoms at the ortho and para positions (In formula (1), R Ａ , R Ｃ , R Ｅ are each independently a functional group having 1 to 10 carbon atoms, and R Ｂ , R Ｄ are each independently hydrogen or a functional group having 1 to 10 carbon atoms, and R Ａ ~R Ｅ One or more of is a functional group containing an unsaturated carbon bond.

[0013] The phenol (X) is preferably a compound represented by the following formula (2) or (3):

[0014] Another aspect of the present invention is a curable composition comprising the polyphenylene ether.

[0015] Yet another embodiment of the present invention is a dry film or prepreg obtained by applying or impregnating a substrate with the curable composition.

[0016] Yet another aspect of the present invention is a cured product obtained by curing the curable composition.

[0017] Yet another aspect of the present invention is a laminate comprising the cured product.

[0018] Yet another aspect of the present invention is an electronic component having the cured product.

[0019] According to the present invention, it is possible to provide a polyphenylene ether having a branched structure that allows easy control of the molecular weight, suppresses an increase in molecular weight, and provides a cured product with excellent mechanical strength.

[0020] FIG. 1 shows the polyphenylene ether of Example 1. １ H-NMR (CDCl ３ 2 shows the spectrum of the polyphenylene ether of Example 2. １ H-NMR (CDCl ３ , room temperature) spectrum.

[0021] When the compounds described have isomers, all possible isomers can be used in the present invention unless otherwise specified.

[0022] In this specification, unless otherwise specified, the term "unsaturated carbon bond" refers to an ethylenic or acetylenic carbon-carbon multiple bond (double bond or triple bond).

[0023] In this specification, the functional group containing an unsaturated carbon bond is not particularly limited, but may include an alkenyl group (e.g., a vinyl group, an allyl group), an alkynyl group (e.g., an ethynyl group), or a (meth)acryloyl group. From the viewpoint of excellent curability, a vinyl group, an allyl group, or a (meth)acryloyl group can be selected. Among these, from the viewpoint of excellent low dielectric properties, an allyl group is preferred. Note that the number of carbon atoms in these functional groups containing an unsaturated carbon bond may be, for example, 15 or less, 10 or less, 8 or less, 5 or less, 3 or less, etc.

[0024] In this specification, the term "hydrocarbon group" refers to a group consisting of only carbon atoms and hydrogen atoms, but is not particularly limited to such a group, and examples thereof include alkyl groups, alkenyl groups, alkynyl groups, aryl groups, and cycloalkyl groups.

[0025] In this specification, phenols that are used as raw materials for polyphenylene ether (PPE) and can become structural units of polyphenylene ether are collectively referred to as "raw material phenols."

[0026] In this specification, when describing raw material phenols, expressions such as "ortho position" and "para position" refer to the position of the phenolic hydroxyl group as the reference (ipso position) unless otherwise specified.

[0027] In this specification, when simply expressed as "ortho position" or the like, it means "at least one of the ortho positions", etc. Therefore, unless a particular contradiction occurs, when simply expressed as "ortho position", it may be interpreted as indicating either one of the ortho positions or as indicating both ortho positions.

[0028] In this specification, the number average molecular weight (Mn) and weight average molecular weight (Mw) of polyphenylene ether are determined by gel permeation chromatography (GPC), using a Shodex K-805L column at a column temperature of 40°C, a flow rate of 1 mL / min, chloroform as the eluent, and polystyrene as the standard.

[0029] In this specification, when the upper and lower limits of a numerical range are separately stated, all combinations of each lower limit and each upper limit are considered to be substantially stated within a consistent range.

[0030] Hereinafter, polyphenylene ether, a curable composition containing the polyphenylene ether, and a dry film, a cured product, and an electronic component obtained using the curable composition will be described.

[0031] <<<Polyphenylene Ether>>> <<Raw Material Phenols>> The raw material phenols for the polyphenylene ether according to this embodiment include a phenol that satisfies at least the following condition 1 and a predetermined phenol (X): (Condition 1) A phenol having hydrogen atoms at the ortho and para positions

[0032] The raw material phenols may also contain other phenols.

[0033] Each phenol will be described below.

[0034] Although monohydric phenols are mainly disclosed as the raw material phenols shown below, polyhydric phenols may also be used as the raw material phenols as long as they do not impair the effects of the present disclosure.

[0035] <Phenols Satisfying at Least Requirement 1> Phenols satisfying at least Requirement 1 have hydrogen atoms at the ortho and para positions.

[0036] Furthermore, the phenols satisfying at least the condition 1 may further satisfy the following condition 2: (Condition 2) The phenols have a hydrogen atom at the para position and a functional group containing an unsaturated carbon bond.

[0037] That is, the phenols satisfying at least condition 1 may be either (1) phenols that satisfy only condition 1 but not condition 2, or (2) phenols that satisfy both conditions 1 and 2, and the raw material phenols may contain both of these phenols.

[0038] Phenols satisfying condition 1 have a hydrogen atom at the ortho position, and therefore, when oxidatively polymerized with other phenols, ether bonds can be formed not only at the ipso and para positions but also at the ortho position. Therefore, polyphenylene ethers obtained using such phenols as raw phenols can form a branched-chain structure. More specifically, polyphenylene ethers obtained from raw phenols containing phenols satisfying condition 1 have a structure in which a portion of the structure is branched by ether-bonded benzene rings at at least three positions: the ipso, ortho, and para positions. Thus, polyphenylene ethers having a branched structure within the skeleton are sometimes referred to as branched polyphenylene ethers. Branched polyphenylene ethers exhibit excellent solubility in organic solvents.

[0039] Furthermore, since phenols satisfying condition 2 have a functional group containing an unsaturated carbon bond, polyphenylene ether obtained by using such phenols as raw material phenols has a functional group containing an ethylenic or acetylenic carbon-carbon multiple bond. More specifically, polyphenylene ether obtained from raw material phenols containing phenols satisfying condition 2 has, as part of its structure, a functional group containing an unsaturated carbon bond at least at the meta position or one of two ortho positions of the benzene ring.

[0040] Examples of phenols that satisfy only condition 1 but not condition 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, 2-dodecylphenol, etc. As phenols that satisfy condition 1, only one type may be used, or two or more types may be used.

[0041] Examples of phenols satisfying both conditions 1 and 2 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, 3-allyl-5-ethylphenol, etc. As phenols satisfying conditions 1 and 2, only one type may be used, or two or more types may be used.

[0042] In the synthesis of polyphenylene ether, the content of the phenol (A) that satisfies at least condition 1 relative to the total amount of the raw material phenols is preferably 1 mol% or more, 2 mol% or more, 3 mol% or more, or 5 mol% or more, and is preferably 50 mol% or less, 40 mol% or less, 30 mol% or less, 20 mol% or less, or 15 mol% or less.

[0043] <Phenol (X)> The phenol (X) has a structure represented by the following formula (1).

[0044] In formula (1), R Ａ , R Ｃ , R Ｅ are each independently a functional group having 1 to 10 carbon atoms, and R Ｂ , R Ｄ are each independently hydrogen or a functional group having 1 to 10 carbon atoms, and R Ａ ~R Ｅ One or more of is a functional group containing an unsaturated carbon bond.

[0045] The phenol compound (X) may have only one functional group containing an unsaturated carbon bond, or may have two or more functional groups containing an unsaturated carbon bond.

[0046] As described above, the polyphenylene ether according to this embodiment has a branched structure by containing a phenol satisfying condition 1 as a raw material phenol. Compared to polyphenylene ether having a linear structure, polyphenylene ether having a branched structure has more polymer ends that are reactive for polymerization. Therefore, the grown polymers may further polymerize with each other (i.e., coupling), resulting in a rapid increase in molecular weight, making it difficult to control the reaction. Based on this finding, in this embodiment, in addition to the phenols satisfying condition 1, a phenol (X) is further combined as a raw material phenol. Because the phenol (X) does not have hydrogen atoms at the highly reactive ortho and para positions, the polymerization reaction terminates at the end of the polyphenylene ether molecular chain where the phenol (X) has reacted. Therefore, when a moderate amount of phenol (X) constitutes the end portion of the polyphenylene ether, a rapid increase in molecular weight (coupling reaction) that occurs during the synthesis of polyphenylene ether having a branched structure can be suppressed. The polyphenylene ether obtained in this manner is likely to have excellent storage stability because unintended molecular weight increase is suppressed.

[0047] Furthermore, as disclosed in U.S. Pat. No. 3,440,217, a method for controlling the molecular weight of a polyphenylene ether having a linear structure is known, using trisubstituted phenols such as 2,6-dimethylphenol and 2,4,6-trimethylphenol as raw material phenols. However, in linear polyphenylene ethers, the polymerization reaction proceeds only at one end of the polyphenylene ether molecular chain, and the polymerization reaction terminates when the trisubstituted phenol reacts. Therefore, the present inventors have found that when a linear polyphenylene ether is molecular weight-controlled using a trisubstituted phenol, the molecular weight of the polyphenylene ether is extremely low, and the mechanical strength may be significantly reduced. In this regard, the present embodiment has found that by using a phenol (X) as the raw material phenol for a polyphenylene ether having a branched structure, it is possible to obtain a polyphenylene ether having a desired molecular weight range without excessively suppressing molecular weight increase. In the case of polyphenylene ether having a branched structure, polymerization proceeds at two or more reactive terminals. Therefore, even if the phenol (X) reacts, polymerization can be carried out at another reactive terminal. This prevents excessive suppression of an increase in molecular weight, and it is therefore presumed that polyphenylene ether having a desired molecular weight range can be obtained.

[0048] As a result, the reaction can be easily controlled, and polyphenylene ethers having a desired molecular weight range (particularly polyphenylene ethers having an industrially useful weight-average molecular weight of 5,000 to 300,000) can be efficiently produced while maintaining the excellent performance (low dielectric properties, excellent solvent solubility) derived from the branched structure. Such polyphenylene ethers have excellent mechanical strength in the cured product while the molecular weight is controlled.

[0049] In addition, the phenol (X) has a functional group containing at least an unsaturated carbon bond. In other words, the polyphenylene ether having a branched structure obtained using the phenol (X) has a functional group containing at least an unsaturated carbon bond (derived from the phenol (X)), and exhibits crosslinkability. In addition, as described above, since the phenol (X) moderately constitutes the terminal portion of the polyphenylene ether, the polyphenylene ether having a branched structure obtained exhibits crosslinkability at the terminal portion of the branched structure, and while maintaining excellent solvent solubility, the crosslinking reactivity of the polyphenylene ether is easily improved (or the mechanical strength of the obtained cured product is easily improved). It is presumed that the synergistic effect of each component according to this embodiment makes it possible to obtain a polyphenylene ether having excellent mechanical strength of the cured product while controlling the molecular weight.

[0050] Furthermore, the functional group containing an unsaturated carbon bond contained in the phenol (X) is preferably a functional group containing an unsaturated double bond and having 3 or more carbon atoms. When the functional group containing an unsaturated double bond has 3 or more carbon atoms, ease of production and storage stability are excellent.

[0051] From the viewpoint of further enhancing the effects of the present disclosure, the phenol (X) is preferably as follows.

[0052] In formula (1), the functional group containing an unsaturated carbon bond is preferably a hydrocarbon group. When the functional group containing an unsaturated carbon bond is a hydrocarbon group, it preferably has 3 to 10 carbon atoms, 3 to 5 carbon atoms, or 3 carbon atoms. More specifically, the hydrocarbon group containing an unsaturated carbon bond is a group such as [—(CH ２ ) ｎ -CH=CH ２ ] (n is an integer of 1 to 8). The n is more preferably an integer of 1 to 3, and particularly preferably 1.

[0053] In formula (1), R Ａ , R Ｃ , R Ｅ are each preferably independently a hydrocarbon group having 10 or less carbon atoms, 5 or less carbon atoms, or 3 or less carbon atoms.

[0054] In formula (1), R Ａ , R Ｃ , R Ｅ More specifically, in formula (1), it is preferable that one or more of R Ａ , R Ｃ , R Ｅ It is preferable that one of the above is a functional group containing an unsaturated carbon bond, and the other is a functional group not containing an unsaturated carbon bond.

[0055] In formula (1), at least R Ｃ is a functional group containing an unsaturated carbon bond, from the viewpoint of obtaining a cured product having particularly excellent elongation at break. A functional group containing an unsaturated carbon bond at the para position has higher crosslinking reactivity than a functional group containing an unsaturated carbon bond at the ortho position or a meta position, and therefore it is presumed that a polyphenylene ether having particularly excellent mechanical strength in a cured product can be obtained. Ａ , R Ｅ It is particularly preferred that one of the groups is a functional group containing an unsaturated carbon bond, from the viewpoint of obtaining a cured product having a high elastic modulus.

[0056] In formula (1), R Ｂ , R Ｄ are each independently hydrogen or a hydrocarbon group having 10 or less carbon atoms, hydrogen or a hydrocarbon group having 5 or less carbon atoms, hydrogen or a hydrocarbon group having 3 or less carbon atoms, hydrogen or a hydrocarbon group having 1 carbon atom, or hydrogen.

[0057] In formula (1), R Ｂ , R Ｄ When is a hydrocarbon group, it is preferably a hydrocarbon group that does not contain an unsaturated carbon bond.

[0058] In formula (1), as described above, R Ａ ~R Ｅ is a functional group containing an unsaturated carbon bond. Ａ ~R Ｅ In the formula (I), the substituent other than hydrogen that does not fall under the category of a functional group containing an unsaturated carbon bond is preferably a hydrocarbon group having 1 to 10, 1 to 5, or 1 to 3 carbon atoms.

[0059] Specific examples of the phenol (X) include a compound represented by the following formula (2) (4-allyl-2,6-dimethylphenol) or a compound represented by the following formula (3) (2-allyl-4,6-dimethylphenol). The phenol (X) can be produced using known methods, such as the synthesis method described in WO2021 / 070714.

[0060]

[0061]

[0062] In the synthesis of polyphenylene ether, the content of the phenol (X) relative to the total amount of the raw material phenols is preferably 1 mol% or more, 2 mol% or more, 3 mol% or more, or 5 mol% or more, and is preferably 50 mol% or less, 40 mol% or less, 30 mol% or less, 20 mol% or less, or 15 mol% or less.

[0063] The ratio (mol %) of the content of phenols (X) to the content (mol %) of phenols satisfying condition 1, based on the total amount of raw material phenols (phenols (X) / phenols satisfying condition 1), is preferably 0.1 to 10.0, 0.2 to 5.0, or 0.5 to 2.0.

[0064] <Other Phenols> Other phenols are phenols that do not satisfy condition 1 and do not fall under the category of phenols (X).

[0065] Examples of other phenols include (1) phenols that do not satisfy condition 1, satisfy condition 2, and do not fall under phenols (X), and (2) phenols that do not satisfy either condition 1 or condition 2, and do not fall under phenols (X).

[0066] Phenols that do not satisfy condition 1 but satisfy condition 2 and do not fall under the category of phenols (X) are, for example, phenols that have a hydrogen atom at the para position and hydrocarbon groups at both ortho positions, at least one of which has an unsaturated carbon bond. Examples of such phenols 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.

[0067] Phenols that do not satisfy either condition 1 or condition 2 and do not fall under the category of phenol (X) are, for example, phenols that have a hydrogen atom at the para position and a functional group that does not contain an unsaturated carbon bond at either ortho position. Examples of such phenols 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.

[0068] In this way, when a phenol having a hydrogen atom at the para position is used as the other phenol, ether bonds are formed at the ipso and para positions of the benzene ring, resulting in linear polymerization, which is useful for adjusting the proportion of branched structures and also makes it easier to adjust the molecular weight of the polyphenylene ether.

[0069] Furthermore, examples of phenols that do not satisfy either condition 1 or condition 2 and do not fall under the category of phenols (X) include phenols that have no hydrogen atoms at the para- and ortho-positions and have no functional group containing an unsaturated carbon bond. When a phenol that has no hydrogen atoms at either the para- or ortho-position is used as the other phenol, the polymerization reaction of polyphenylene ether is suppressed, making it easier to adjust the molecular weight of the polyphenylene ether.

[0070] The other phenols may be used alone or in combination of two or more.

[0071] When other phenols are used in the synthesis of polyphenylene ether, the content of the other phenols relative to the total amount of raw material phenols is, for example, 10 mol % or more, 20 mol % or more, 30 mol % or more, 40 mol % or more, or 50 mol % or more.

[0072] <<Method for Producing Polyphenylene Ether>> The polyphenylene ether of the present disclosure can be produced by a known method for synthesizing polyphenylene ether, except that the raw material phenols and the ratio of the raw material phenols used are as described above. For example, it can be produced by the synthesis method disclosed in International Publication WO 2020 / 017570.

[0073] <<Physical Properties / Characteristics of Polyphenylene Ether>> The weight average molecular weight of the polyphenylene ether is preferably 5,000 to 40,000, more preferably 8,000 to 30,000, and even more preferably 10,000 to 25,000. The number average molecular weight of the polyphenylene ether is preferably 5,000 to 20,000, and even more preferably 5,000 to 10,000.

[0074] The molecular weight of polyphenylene ether depends on the type of raw material phenol used, but can be adjusted by changing the reaction temperature, reaction time, etc. during synthesis. Furthermore, by increasing the proportion of phenol (X) among the raw material phenols or the proportion of other phenols that do not have hydrogen atoms at the para- and ortho-positions, the polymerization reaction is suppressed, the rate of molecular weight increase is slowed, and it becomes easy to control the molecular weight of polyphenylene ether.

[0075] <<<Curable Composition>>> The curable composition contains the polyphenylene ether according to this embodiment. The curable composition may also contain other components.

[0076] The content of polyphenylene ether in the curable composition is preferably 40 to 90 mass %, more preferably 50 to 80 mass %, based on the total amount excluding volatile components and inorganic fillers in the curable composition.

[0077] Examples of other components include inorganic fillers such as silica, peroxides, crosslinking curing agents, polyphenylene ethers other than the polyphenylene ether according to the present embodiment, polymerization initiators, resin and polymer components such as maleimide resins and styrene-based elastomers, sensitizers, adhesion aids, surfactants, leveling agents, plasticizers, adhesion agents, colorants, fibers, silane coupling agents, flame retardants, cellulose nanofibers, dispersants, thermosetting catalysts, thickeners, antifoaming agents, antioxidants, rust inhibitors, and adhesion promoters.

[0078] Other components may be appropriately selected depending on the application, etc. For example, when the curable composition contains a peroxide, the crosslinking reaction of the curable composition is accelerated, and various physical properties of the cured product are likely to be improved. Furthermore, when the curable composition contains a crosslinking curing agent, the low dielectric properties, heat resistance, etc. of the cured product are likely to be improved.

[0079] Examples of peroxides include methyl ethyl ketone peroxide, methyl acetoacetate peroxide, acetylacetonperoxide, 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.

[0080] The content of the peroxide in the curable composition is preferably 0.1 to 10 parts by mass, and more preferably 1 to 5 parts by mass, relative to 100 parts by mass of the polyphenylene ether content in the curable composition.

[0081] Examples of crosslinking curing agents include polyfunctional vinyl compounds such as divinylbenzene, divinylnaphthalene, and divinylbiphenyl; vinylbenzyl ether compounds synthesized by the reaction of phenol and vinylbenzyl chloride; styrene monomers such as diallyl phthalate and diallyl isophthalate, allyl ether compounds synthesized by the reaction of phenol and allyl chloride; and trialkenyl isocyanurates such as triallyl isocyanurate (hereinafter referred to as TAIC (registered trademark)) and triallyl cyanurate. Among these, triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, and diallyl isophthalate are preferred, as they have particularly good compatibility with polyphenylene ether. Only one type of crosslinking curing agent may be used, or two or more types may be used.

[0082] The content of the cross-linking curing agent in the curable composition is preferably 1 to 100 parts by mass, and more preferably 10 to 80 parts by mass, relative to 100 parts by mass of the polyphenylene ether content in the curable composition.

[0083] The curable composition may also be in the form of a varnish containing a solvent. The solvent is preferably one capable of dissolving the polyphenylene ether described above. Examples of the solvent include conventionally usable solvents such as chloroform, methylene chloride, and toluene, as well as 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. These may be used alone or in combination of two or more.

[0084] <<<Dry Film, Prepreg>>> The dry film has a resin layer made of the curable composition of the present disclosure on a carrier film (support film). The dry film is used by laminating the resin layer so that it is in contact with a substrate.

[0085] The dry film can be produced by uniformly applying the curable composition onto a carrier film by an appropriate method such as a blade coater, lip coater, comma coater, or film coater, drying the composition to form the resin layer described above, and preferably laminating a cover film (protective film) thereon. The cover film and the carrier film may be made of the same film material or different films.

[0086] The film materials for the carrier film and the cover film may be any of those known to be used for dry films.

[0087] As the carrier film, for example, a thermoplastic film such as a polyester film made of polyethylene terephthalate or the like having a thickness of 2 to 150 μm is used.

[0088] The cover film may be a polyethylene film, a polypropylene film, or the like, but it is preferable that the adhesive strength with the resin layer is weaker than that of the carrier film.

[0089] The thickness of the resin layer on the dry film is preferably 100 μm or less, more preferably in the range of 5 to 50 μm.

[0090] The prepreg can be obtained, for example, by impregnating a substrate such as glass cloth with a curable composition and drying it.

[0091] <<<Cured Product>>> A cured product can be produced using the curable composition or a dry film having a resin layer made of the curable composition.

[0092] 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.

[0093] For example, a cured product can be formed by the following method. After applying the curable composition to a substrate as described above (for example, by applying using an applicator, etc.), a drying step is carried out to dry the curable composition as needed, thereby forming a resin layer on the substrate. Alternatively, a dry film is laminated onto the substrate, and a resin layer made of the curable composition is transferred. Next, a thermal curing step is carried out to thermally crosslink the polyphenylene ether by heating (for example, by heating using an inert gas oven, a hot plate, a vacuum oven, a vacuum press, etc.), thereby curing the resin layer.

[0094] The conditions for carrying out each step (for example, coating thickness, drying temperature and time, heating temperature and time, etc.) may be appropriately changed depending on the composition and application of the curable composition.

[0095] <<<Electronic Components>>> Electronic components have the cured product of the present disclosure described above. The cured product of the present disclosure has excellent dielectric properties, heat resistance, and mechanical strength, and therefore can be used for various applications as a material for forming laminates and electronic components.

[0096] There are no particular limitations on the use of the material, but preferred examples include insulating materials in electronic components such as large-capacity, high-speed communications typified by fifth-generation communication systems (5G) and millimeter-wave radars for automotive ADAS (Advanced Driving Systems).

[0097] <<Synthesis of Polyphenylene Ether>> <Example 1> 2,6-dimethylphenol, 2-allylphenol, and 4-allyl-2,6-dimethylphenol were used as raw material phenols. A 500 mL separable flask was used as a reaction vessel, and a raw material solution was prepared by dissolving 34.51 g (80 mol %) of 2,6-dimethylphenol, 4.71 g (10 mol %) of 2-allylphenol, and 5.70 g (10 mol %) of 4-allyl-2,6-dimethylphenol in 286.30 g of toluene. Further, di-μ-hydroxo-bis[(N,N,N',N'-tetramethylethylenediamine)copper(II)]chloride (Cu / TMEDA) 1.04 g, tetramethylethylenediamine (TMEDA) 1.06 g were adjusted, and while blowing dry air into the reaction solution at a flow rate of 150 mL / min, the mixture was stirred at a stirring speed of 200 rpm and reacted at 40 ° C for 15 hours to obtain a reaction solution containing polyphenylene ether. After stopping the heating of the reaction solution and blowing dry air, di-μ-hydroxo-bis[(N,N,N',N'-tetramethylethylenediamine)copper(II)]chloride (Cu / TMEDA) was removed by filtration, and the mixture was diluted with 1,200 mL of methanol, 4.0 mL of concentrated hydrochloric acid, H ２ The precipitate was reprecipitated in 27.0 mL of the mixed solution, filtered under reduced pressure, washed with methanol, and dried at 80° C. for 24 hours to obtain the polyphenylene ether according to Example 1. １ H-NMR (CDCl ３ , room temperature) spectrum is shown.

[0098] Example 2 Polyphenylene ether according to Example 2 was obtained in the same manner as in Example 1, except that 2,6-dimethylphenol, 2-allylphenol, and 2-allyl-4,6-dimethylphenol were used as raw material phenols and the production conditions shown in Table 1 were used. １ H-NMR (CDCl ３ , room temperature) spectrum is shown.

[0099] Comparative Example 1 A polyphenylene ether according to Comparative Example 1 was obtained in the same manner as in Example 1, except that 2,6-dimethylphenol, 2-allylphenol, and 2,4,6-trimethylphenol were used as raw material phenols and the production conditions shown in Table 1 were used.

[0100] Reference Example 1 A polyphenylene ether according to Reference Example 1 was obtained in the same manner as in Example 1, except that 2,6-dimethylphenol and 2-allylphenol were used as raw material phenols and the production conditions shown in Table 1 were used.

[0101] <Molecular Weight> The weight average molecular weight and number average molecular weight were measured for the polyphenylene ethers of Example 1, Example 2, Comparative Example 1, and Reference Example 1. The measurement results are shown in Table 1.

[0102] <Number of terminal reactive groups per number average molecular weight> First, for each sample, １ The polymerization ratio of each raw material phenol is calculated from the results of H-NMR measurement, and the theoretical value of functional group equivalent is calculated from the polymerization ratio X of the repeating unit derived from each raw material phenol when the unit derived from phenol compound X is set to 1, using the following formula. Here, X ｉ is the polymerization ratio of raw material phenol i, W ｉ and σ respectively represent the molecular weight of the repeating unit structure derived from the raw material phenol i. The number of terminal reactive groups per number average molecular weight was calculated by dividing the number average molecular weight obtained by GPC measurement by the functional group equivalent obtained by the above formula. The number of terminal reactive groups per number average molecular weight is shown in Table 1. Note that, since Comparative Example 1 and Reference Example 1 did not have a terminal structure derived from phenol compound X, the number of terminal reactive groups per number average molecular weight was not calculated.

[0103] As shown in Table 1, by using a phenol (X) having predetermined functional groups at least at the para- and ortho-positions, as represented by formula (1), as a raw material phenol for polyphenylene ether having a branched structure, it is possible to obtain polyphenylene ether with a lower molecular weight, and it was shown that an increase in molecular weight is suppressed. On the other hand, the polyphenylene ether of Reference Example 1 was a polyphenylene ether with a higher molecular weight than the polyphenylene ethers of Examples 1 and 2, despite the same reaction time. Furthermore, as shown in Table 1, according to Examples 1 and 2, it is possible to introduce many reactive groups (allyl groups) into the terminals. Note that, in Comparative Example 1 and Reference Example 1, the number of terminal reactive groups per number average molecular weight was not calculated because phenol compound X was not used.

[0104]

[0105] <<Evaluation>> The polyphenylene ethers according to Examples 1 and 2 and the polyphenylene ether according to Comparative Example 1 were evaluated.

[0106] <Production of Cured Film> 100 parts by weight of each polyphenylene ether, 50 parts by weight of a cross-linking curing agent (product name "TAIC", manufactured by Mitsubishi Chemical Corporation), 5 parts by weight of peroxide (product name "Perbutyl P40", manufactured by NOF Corporation), and 350 parts by weight of cyclohexanone (solvent) were mixed to prepare a resin composition. Each resin composition was applied to the shine side of 18 μm thick copper foil so that the film thickness after drying was approximately 20 μm, and dried at 90 °C for 30 minutes in a hot air circulation drying oven. Next, the composition was cured in an inert oven at 200 °C for 1 hour, and then the copper foil was etched to obtain a single cured film (measurement sample). Comparative Example 1 is a polyphenylene ether that can suppress molecular weight increase to the same extent as Examples 1 and 2, but after curing, numerous cracks occurred in the cured product, and a single cured film could not be obtained. On the other hand, in Examples 1 and 2, no cracks occurred in the cured products and a single cured film was obtained, confirming that the mechanical strength of the cured products was improved compared to Comparative Example 1. Note that, in Comparative Example 1, a single cured film could not be obtained, so the following evaluations were not performed.

[0107] <Dielectric Constant> (Measurement Method) The measurement sample was cut into a length of 80 mm and a width of 45 mm to serve as a test piece, and the relative dielectric constant Dk was measured by the SPDR (Split Post Dielectric Resonator) resonator method. The measuring equipment used was a vector network analyzer E5071C manufactured by Keysight Technologies, Inc., 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.

[0108] (Measurement Results) The Dk of the cured product obtained using the polyphenylene ether of Example 1 was 2.4. The Dk of the cured product obtained using the polyphenylene ether of Example 2 was 2.7. The above results demonstrate that excellent low dielectric properties can be achieved even when the phenol compound (X) (a phenol having predetermined functional groups at least at the para- and ortho-positions) is used as a raw material phenol for polyphenylene ether having a branched structure.

[0109] <Tensile Properties> (Measurement Method) A measurement sample was cut into a length of 8 cm and a width of 0.5 cm, and the elongation at break (tensile elongation at break) was measured under the following conditions. The elastic modulus was determined from the slope of the strain at a stress of 5 MPa to 10 MPa in the obtained stress-strain curve. [Measurement Conditions] Testing machine: Tensile testing machine EZ-SX (manufactured by Shimadzu Corporation) Chuck distance: 50 mm Test speed: 1 mm / min Elongation calculation: (tensile travel distance / chuck distance) x 100

[0110] (Measurement Results) The cured product obtained using the polyphenylene ether of Example 1 had a modulus of elasticity of 2.4 GPa and a breaking elongation of 3.4%. The cured product obtained using the polyphenylene ether of Example 2 had a modulus of elasticity of 3.9 GPa and a breaking elongation of 1.4%. The above results demonstrate that by using phenol compound (X) (a phenol having predetermined functional groups at least at the para- and ortho-positions) as a raw material phenol for polyphenylene ether having a branched structure, excellent mechanical strength can be achieved while controlling the molecular weight. In particular, the use of a phenol having a predetermined hydrocarbon group at the para-position resulted in excellent breaking elongation, and the use of a phenol having a predetermined hydrocarbon group at the ortho-position resulted in excellent elastic modulus.

[0111] The polyphenylene ether according to the present invention has low dielectric properties, excellent solvent solubility, and easy molecular weight control, and is suitable for mass production. Therefore, the polyphenylene ether according to the present invention is preferably used for producing cured products constituting insulating materials in electronic components such as those used in high-capacity, high-speed communications typified by fifth-generation communication systems (5G) and millimeter-wave radars for automotive advanced driver assistance systems (ADAS). CROSS-REFERENCE TO RELATED APPLICATIONS

[0112] This application claims priority based on Japanese Patent Application No. 2023-107451, filed with the Japan Patent Office on June 29, 2023, the entire disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A polyphenylene ether obtained from raw phenols, characterized in that the raw phenols contain at least a phenol satisfying the following condition 1 and a phenol (X) represented by the following formula (1): (Condition 1) having hydrogen atoms at the ortho and para positions (In formula (1), R Ａ , R Ｃ , R Ｅ are each independently a functional group having 1 to 10 carbon atoms; R Ｂ , R Ｄ are each independently a hydrogen atom or a functional group having 1 to 10 carbon atoms; R Ａ ~R Ｅ At least one of is a functional group containing an unsaturated carbon bond.

2. The polyphenylene ether according to claim 1, wherein the phenol (X) is a compound represented by the following formula (2) or (3):

3. A curable composition comprising the polyphenylene ether according to claim 1 or 2.

4. A dry film or prepreg obtained by coating or impregnating a substrate with the curable composition according to claim 3.

5. A cured product obtained by curing the curable composition according to claim 3.

6. A laminate comprising the cured product according to claim 5.

7. An electronic part comprising the cured product according to claim 5.

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