Method for producing cured product, cured product, and electronic component

Abstract

Provided is a technology pertaining to a method for producing a cured product, the method being capable of obtaining a cured product having sufficient strength when a curable composition is cured in an air atmosphere. A method for producing a cured product according to an aspect comprises a step for heating and curing, in an air atmosphere, a curable composition containing a polyphenylene ether having a structure in which a functional group represented by formula (1) is directly bonded to a benzene ring. (In formula (1), R is a C1-C8 alkyl group.)

Description

Method for producing cured product, cured product and electronic component

[0001] The present invention relates to a method for producing a cured product, 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 have become increasingly high-frequency.

[0003] However, when epoxy resins or 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] Also, as disclosed in Patent Document 1, polyphenylene ether is known which is obtained by introducing styryl groups into the molecular terminals of polyphenylene ether to form a curable resin.

[0005] International Publication No. 2022 / 009977

[0006] As described above, curable compositions containing thermosetting polyphenylene ethers have excellent low dielectric properties and are therefore widely used industrially.

[0007] Here, when such polyphenylene ether having a functional group with an unsaturated double bond such as a styryl group is cured under an atmospheric atmosphere, curing inhibition due to oxygen occurs, and sufficient strength cannot be obtained, which may result in cracks in the cured product. For this reason, such curable compositions are usually cured under a nitrogen atmosphere. However, in order to perform curing of the curable composition under a nitrogen atmosphere, dedicated equipment is required, and for the purpose of reducing the cost of introducing the equipment, there is a demand for a method for producing a cured product that can obtain a cured product having sufficient strength when cured under an atmospheric atmosphere.

[0008] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a technique relating to a method for producing a cured product, which can give a cured product having sufficient strength when a curable composition is cured under atmospheric conditions.

[0009] One aspect of the present invention is a method for producing a cured product, which includes the step of heat-curing, under atmospheric conditions, a curable composition containing a polyphenylene ether having a structure in which a functional group represented by the following formula (1) is directly bonded to a benzene ring: (In formula (1), R is an alkyl group having 1 to 8 carbon atoms.)

[0010] In the method for producing a cured product according to the above aspect, the functional group represented by formula (1) may be an allyl group. The polyphenylene ether may have a branched structure. The weight-average molecular weight Mw of the polyphenylene ether may be 4,000 to 50,000.

[0011] Another aspect of the present invention is a cured product obtained by curing, under atmospheric conditions, a curable composition containing a polyphenylene ether having a structure in which a functional group represented by the following formula (1) is directly bonded to a benzene ring: (In formula (1), R is an alkyl group having 1 to 8 carbon atoms.)

[0012] Yet another aspect of the present invention is an electronic component, the electronic component having the cured product of the above-described aspect.

[0013] According to the present invention, it is possible to provide a technique relating to a method for producing a cured product, which can give a cured product having sufficient strength when a curable composition is cured under atmospheric conditions.

[0014] Hereinafter, embodiments of the present invention will be described in detail. In this specification, the expression "a to b" in the description of a range of values ​​means that the range is from a to b, unless otherwise specified.

[0015] The number average molecular weight (Mn) and weight average molecular weight (Mw) of polyphenylene ether were 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.

[0016] The present inventors have found that the above-mentioned problems can be solved by using a curable composition containing a polyphenylene ether having a structure in which a functional group represented by formula (1) is directly bonded to a benzene ring, and have thus completed the present invention. Hereinafter, the curable composition used in the method for producing a cured product according to the embodiment and the method for producing the cured product will be described.

[0017] (Curable composition) The curable composition used in the embodiment contains the polyphenylene ether described below. The curable composition may contain other components. Each component will be described in detail below.

[0018] <Polyphenylene ether> Polyphenylene ether is a polyphenylene ether (hereinafter also referred to as curable polyphenylene ether) having a structure in which a functional group represented by the following formula (1) is directly bonded to a benzene ring. (In formula (1), R is an alkyl group having 1 to 8 carbon atoms.) The functional group represented by formula (1) is preferably an allyl group.

[0019] The curable polyphenylene ether is preferably a polyphenylene ether having a branched structure (curable branched polyphenylene ether).

[0020] The curable polyphenylene ether can be synthesized, for example, by using, as a raw material phenol, a phenol having a structure in which a functional group represented by the following formula (1) is directly bonded to a benzene ring. (In formula (1), R is an alkyl group having 1 to 8 carbon atoms.) The functional group represented by formula (1) is preferably an allyl group.

[0021] Specific examples of phenols having a structure in which the functional group represented by formula (1) is directly bonded to a benzene ring include o-allylphenol, m-allylphenol, 3-allyl-6-methylphenol, 3-allyl-6-ethylphenol, 3-allyl-5-methylphenol, 3-allyl-5-ethylphenol, 2-allyl-6-methylphenol, 2-allyl-6-ethylphenol, 2-allyl-6-phenylphenol, 2-allyl-6-styrylphenol, 2,6-diallylphenol, 2,6-dimethyl-4-allylphenol, 2,4-dimethyl-6-allylphenol, and 2-methyl-4-allylphenol.

[0022] When the curable polyphenylene ether has a branched structure, the raw material phenols include phenols that satisfy the following condition 1. (Condition 1) Have hydrogen atoms at the ortho and para positions. Phenols that satisfy condition 1 have hydrogen atoms at the ortho positions, 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 ether obtained using such phenols as raw material phenols can form a branched chain structure.

[0023] Furthermore, examples of phenols that satisfy the above condition 1 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, 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 that satisfy the condition 1, only one type may be used, or two or more types may be used.

[0024] On the other hand, by not using a phenol that satisfies condition 1 as the raw material phenol, it is possible to synthesize polyphenylene ether having a linear structure.

[0025] The raw material phenols may also contain other phenols. Examples of the other 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. Only one type of the other phenols may be used, or two or more types may be used.

[0026] Furthermore, as the other phenols, phenols having no hydrogen atoms at either the para or ortho position may be used. When a phenol having no hydrogen atoms at either the para or ortho position is used as the raw material phenol, the residue of the phenol forms the terminal moiety of the polyphenylene ether. For example, when 2,6-dimethyl-4-allylphenol is used, the 2,6-dimethyl-4-allylphenol residue forms the terminal moiety.

[0027] When a curable branched polyphenylene ether is obtained, in the synthesis of the curable polyphenylene ether, the content of phenols that satisfy at least condition 1 relative to the total amount of 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.

[0028] In the synthesis of curable polyphenylene ether, the content of phenols having a structure in which a functional group represented by formula (1) is directly bonded to a benzene ring relative to the total amount of raw material phenols is preferably 1 mol% or more, 2 mol% or more, 3 mol% or more, 4 mol% or more, or 5 mol% or more, and is also preferably 50 mol% or less, 40 mol% or less, 30 mol% or less, 20 mol% or less, or 15 mol% or less.

[0029] The other phenols may be used alone or in combination of two or more.

[0030] When other phenols are used in the synthesis of the curable polyphenylene ether, the content of the other phenols relative to the total amount of the 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.

[0031] In calculating the content of phenols relative to the total amount of raw material phenols, when phenols are used that have a structure in which the functional group represented by formula (1) is directly bonded to a benzene ring and that satisfy condition 1, the content is calculated assuming that the phenols are phenols that have a structure in which the functional group represented by formula (1) is directly bonded to a benzene ring and also satisfy condition 1.

[0032] The weight-average molecular weight of the curable polyphenylene ether is preferably 4,000 or more, 5,000 or more, or 10,000 or more, and preferably 50,000 or less, or 20,000 or less.The number-average molecular weight of the curable polyphenylene ether is preferably 1,000 or more, 2,000 or more, 4,000 or more, or 5,000 or more, and more preferably 20,000 or less, or 10,000 or less.

[0033] The curable polyphenylene ether can be produced by a known polyphenylene ether synthesis method, except that the raw material phenols and the ratio of the raw material phenols used are as described above. For example, polyphenylene ether having a branched structure can be produced by referring to the synthesis method disclosed in WO 2020 / 017570. Polyphenylene ether having a linear structure can also be produced by a similar method, except that phenols satisfying condition 1 are not used.

[0034] The content of the curable polyphenylene ether in the curable composition is preferably 40 to 98 mass %, more preferably 50 to 95 mass %, based on the total amount of non-volatile components in the curable composition (when an inorganic filler is contained, based on the total amount excluding the inorganic filler).

[0035] The curable composition of the present disclosure may further contain a polyphenylene ether that does not have a structure in which the functional group represented by formula (1) is directly bonded to a benzene ring.

[0036] <Antioxidant> The curable composition of the present disclosure can contain an antioxidant. Examples of antioxidants that can be used include conventionally known phosphorus-based antioxidants, sulfur-based antioxidants, phenol-based antioxidants, and amine-based antioxidants. In particular, it is preferable to include at least one selected from phosphorus-based antioxidants and sulfur-based antioxidants. By using a curable polyphenylene ether as the curable resin and combining it with a sulfur-based antioxidant or a phosphorus-based antioxidant, it is easy to obtain a cured product with excellent low dielectric properties, even when cured in an atmospheric environment. Furthermore, the cured product thus obtained is likely to maintain its low dielectric properties even when subjected to a heating process, such as exposure to an atmospheric environment at 200°C.

[0037] <Sulfur-Based Antioxidant> The sulfur-based antioxidant is an antioxidant containing a sulfur atom. The sulfur-based antioxidant differs from the phenol-based antioxidant described below in that it does not have a hindered phenol structure.

[0038] Examples of sulfur-based antioxidants include conventionally known sulfur-based antioxidants such as thioether-based, mercaptobenzimidazole-based, thiocarbanilide-based, dibenzyl disulfide, and zinc diallyldithiophosphate.

[0039] The sulfur-based antioxidant preferably has a structure (thiopropionic acid ester skeleton) represented by the following formula (2).

[0040]

[0041] In formula (2), * represents a binding site.

[0042] Examples of sulfur-based antioxidants having the structure represented by formula 1 include didodecyl thiodipropionate, dioctadecyl thiodipropionate, dilauryl thiodipropionate, distearyl thiodipropionate, dimyristyl thiodipropionate, dodecyl octadecyl thiodipropionate, and pentaerythritol-tetrakis[3-lauryl thiopropionate].

[0043] <Phosphorus-Based Antioxidant> The phosphorus-based antioxidant is an antioxidant containing a phosphorus atom. The phosphorus-based antioxidant differs from the phenol-based antioxidant described below in that it does not have a hindered phenol structure.

[0044] The phosphorus-based antioxidant is not particularly limited, and examples thereof include known antioxidants such as phosphoric acid-based, phosphoric ester-based, phosphorous acid-based, and phosphite-based antioxidants.

[0045] The phosphorus-based antioxidant is preferably a phosphite-based antioxidant having a structure represented by the following formula (3):

[0046]

[0047] In formula (3), R １ , R ２、 R ３ is an organic group. １ , R ２ , R ３ Two or more of may be bonded to each other to form a ring.

[0048] Examples of the phosphorus-based antioxidant represented by formula (3) include triethyl phosphite, tris(2-ethylhexyl) phosphite, tridecyl phosphite, trilauryl phosphite, trioleyl phosphite, triphenyl phosphite, tricresyl phosphite, phenyldiisodecyl phosphite, tri(nonylphenyl) phosphite, tris(2,4-di-t-butylphenyl) phosphite, diphenyl monodecyl phosphite, diphenyl mono(2-ethyl hexyl)phosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octyl phosphite, distearyl pentaerythritol diphosphite, 3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, and the like.

[0049] In the curable composition, the total content of the phosphorus-based antioxidant and the sulfur-based antioxidant is preferably at least 0.10 parts by mass, at least 0.20 parts by mass, at least 0.50 parts by mass, or at least 1.00 parts by mass, and is preferably at most 20.00 parts by mass, at most 15.00 parts by mass, at most 10.00 parts by mass, or at most 5.00 parts by mass, per 100 parts by mass of the curable polyphenylene ether. By setting the total content of the phosphorus-based antioxidant and the sulfur-based antioxidant within this range, it becomes easier to obtain a cured product that is excellent in insulation reliability, etc., while still exhibiting the effects derived from the antioxidants.

[0050] The antioxidant may contain a sulfur atom and a phosphorus atom. Thus, an antioxidant containing a sulfur atom and a phosphorus atom is treated as both a phosphorus-based antioxidant and a sulfur-based antioxidant.

[0051] <Other Components> Examples of other components include additives such as peroxides, inorganic fillers such as silica, cross-linking curing agents, 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, rust inhibitors, and adhesion imparting agents.

[0052] 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.

[0053] 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.

[0054] 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 content of the curable polyphenylene ether in the curable composition.

[0055] 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.

[0056] 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 content of the curable polyphenylene ether in the curable composition.

[0057] Preferably, the curable composition is substantially free of compounds having epoxy groups. Here, "substantially free" means that the content of compounds having epoxy groups relative to the entire curable composition is 1% by mass or less. More preferably, the content of compounds having epoxy groups relative to the entire curable composition is 0% by mass. The curable composition of the present disclosure can give a cured product having sufficient strength even when cured under atmospheric conditions, so there is no need to include epoxy groups as other curable groups. Therefore, deterioration of low dielectric properties due to curing of epoxy groups can be suppressed.

[0058] The curable composition may also be in the form of a varnish containing a solvent. As the solvent, a solvent capable of dissolving the polyphenylene ether described above is preferred, and examples thereof include chloroform, methylene chloride, toluene, N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), cyclohexanone, propylene glycol monomethyl ether acetate (PMA), diethylene glycol monoethyl ether acetate (CA), methyl ethyl ketone, ethyl acetate, etc. These may be used alone or in combination of two or more.

[0059] The curable composition may be provided in the form of a dry film or a prepreg.

[0060] The dry film has a resin layer made of the curable composition of the present disclosure on a carrier film (support film), and is used by laminating the resin layer so that it is in contact with a substrate.

[0061] 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.

[0062] The film materials for the carrier film and the cover film may be any of those known to be used for dry films.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] The prepreg can be obtained, for example, by impregnating a substrate such as glass cloth with a curable composition and drying it.

[0067] (Method for Producing Cured Product) The method for producing a cured product according to the embodiment includes a curing step of heat-curing the curable composition containing the polyphenylene ether under atmospheric conditions, and may further include a film-forming step of forming a film from the curable composition containing the polyphenylene ether, as needed.

[0068] In the film-forming step, the curable composition is applied to a substrate (for example, by application with an applicator, etc.), and then, if necessary, a drying step is carried out to dry the curable composition, thereby forming a resin layer on the substrate. Alternatively, a dry film may be laminated on the substrate to form a resin layer made of the curable composition.

[0069] When a drying step is carried out, for example, heat drying using a hot air circulation drying furnace, a hot plate, an oven, etc. can be mentioned. Conditions for the drying step include, for example, a drying temperature of 70 to 140°C and a drying time of 1 to 30 minutes. The drying step may be carried out in an air atmosphere or a nitrogen atmosphere, but is preferably carried out in an air atmosphere.

[0070] In the curing step, the polyphenylene ether is thermally crosslinked by heating in an air atmosphere using, for example, a hot air circulation drying oven, a hot plate, an oven, etc., to cure the resin layer. The conditions for the curing step are, for example, a heating temperature of 180 to 240°C and a heating time of 30 minutes to 2 hours.

[0071] The atmospheric atmosphere may be, for example, an air atmosphere or an atmosphere containing about 80 vol % nitrogen and about 20 vol % oxygen. The atmospheric atmosphere means a state in which atmospheric control such as nitrogen substitution is not substantially performed, and atmospheric changes due to changes in the surrounding environment are allowed.

[0072] The curing step is preferably carried out under atmospheric pressure, which may be a pressure of about 1013 hPa. Under atmospheric pressure means that pressure control such as pressurization, depressurization, or pressing is not substantially performed, and pressure changes due to changes in the surrounding environment, such as temperature and atmospheric pressure, are permitted.

[0073] Polyphenylene ethers containing functional groups with unsaturated double bonds primarily undergo curing through crosslinking via radical polymerization, so curing in the atmosphere can be inhibited by the deactivation of radicals by oxygen in the air. When this occurs, the crosslinking of the polyphenylene ether does not proceed sufficiently, resulting in a significant decrease in the strength of the cured product and sometimes cracks in the cured product.

[0074] In this regard, the method for producing a cured product according to the embodiment allows for the production of a cured product with sufficient strength even in an air atmosphere. The inventors have discovered that a structure in which a functional group represented by formula (1) is directly bonded to a benzene ring is oxidized by heating in an air atmosphere, and this oxidation promotes an oxidative crosslinking reaction. Although the detailed mechanism is unclear, it is presumed that a structure in which a functional group represented by formula (1) is directly bonded to a benzene ring is more susceptible to oxidative crosslinking than functional groups with other unsaturated double bonds because it has a benzyl position that is easily oxidized. Therefore, even if curing inhibition occurs, the oxidative crosslinking reaction can compensate for the crosslinking of the polyphenylene ether, and therefore it is presumed that a cured product with sufficient strength can be obtained even when cured in an air atmosphere.

[0075] The cured product according to the embodiment can be obtained by the method for producing a cured product according to the above-described aspect. In other words, the cured product according to the embodiment is obtained by curing, under atmospheric conditions, a curable composition containing a polyphenylene ether having a structure in which a functional group represented by the following formula (1) is directly bonded to a benzene ring: (In formula (1), R is an alkyl group having 1 to 8 carbon atoms.) Details of the curable composition are as described above. Although it is difficult to specify the detailed structure of the cured product according to the embodiment, it is presumed that the cured product has a crosslinked structure in which the functional group represented by formula (1) is oxidatively crosslinked.

[0076] (Electronic Component) The electronic component according to the embodiment has the above-described cured product, and can be used for various purposes as a material for forming a laminate or electronic component.

[0077] The use of the electronic component according to the embodiment is not particularly limited, but preferred examples include insulating materials in electronic components such as those used in large-capacity, high-speed communications typified by fifth-generation communication systems (5G) and millimeter-wave radars for automotive ADAS (Advanced Driver Assistance Systems).

[0078] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations can also be adopted.

[0079] EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these.

[0080] (Raw Materials) <Polyphenylene Ether (PPE)> PPE1: PPE obtained by Synthesis Example 1 below PPE2: OPE-2St manufactured by MGC PPE3: SA9000 manufactured by SABIC PPE4: PPE obtained by Synthesis Example 2 below PPE5: PPE obtained by Synthesis Example 3 below PPE6: PPE obtained by Synthesis Example 4 below PPE7: PPE obtained by Synthesis Example 5 below The number average molecular weight, weight average molecular weight, chemical formula, functional groups and structure of each PPE are shown in Table 1.

[0081]

[0082] Synthesis Example 1: 19.8 g of 2,6-dimethylphenol and 2.42 g of 2-allylphenol were added to a 500 mL separable flask, and the resulting mixture was dissolved in 261 g of toluene. Furthermore, di-μ-hydroxo-bis[(N,N,N',N'-tetramethylethylenediamine)copper(II)] chloride (Cu / TMEDA) was adjusted to 0.18 wt % and tetramethylethylenediamine (TMEDA) to 0.16 wt %, and while blowing dry air into the reaction solution at a flow rate of 75 mL / min, the mixture was stirred at a stirring speed of 200 rpm using a four-blade paddle impeller and reacted at 40°C for a predetermined time to obtain a reaction solution containing polyphenylene ether. After stopping the heating of the reaction solution and the blowing of dry air, the precipitate was removed by filtration, and the resulting mixture was diluted with 1,200 mL of methanol, 4.0 mL of concentrated hydrochloric acid, and 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 PPE1. In this way, PPE1 was synthesized. PPE1 had a number-average molecular weight of 11,100 and a weight-average molecular weight of 36,300.

[0083] Synthesis Example 2: SA90 (manufactured by MGC, PPE with hydroxyl groups at both ends, Mn=1,600, 5.00 g, 3.1 mmol) and cesium carbonate (3.03 g, 9.3 mmol) were added to a 100 mL recovery flask and the atmosphere was replaced with nitrogen. Allyl iodide (1.57 g, 9.3 mmol) and dehydrated DMF (50 mL) were then added, and the mixture was heated and stirred at 80°C for 16 hours. The reaction solution was added dropwise to a reprecipitation solvent (methanol:ion-exchanged water = 400:400 mL), yielding PPE4 (2.90 g, 55%) as a white powder.

[0084] Synthesis Example 3: 2,6-dimethylphenol and 4-allyl-2,6-dimethylphenol were used as raw material phenols. A 500 mL separable flask was used as the reaction vessel, and 46.73 g (95 mol%) of 2,6-dimethylphenol and 3.27 g (5 mol%) of 4-allyl-2,6-dimethylphenol were dissolved in 286.30 g of toluene to prepare a raw material solution. Furthermore, 1.04 g of di-μ-hydroxo-bis[(N,N,N',N'-tetramethylethylenediamine)copper(II)] chloride (Cu / TMEDA) and 1.06 g of tetramethylethylenediamine (TMEDA) were added. While blowing dry air into the reaction solution at a flow rate of 150 mL / min, the mixture was stirred at a stirring rate of 200 rpm and reacted at 40°C for 15 hours to obtain a reaction solution containing polyphenylene ether. After heating the reaction solution and stopping the blowing of dry air, the precipitate was removed by filtration, and the reaction mixture was diluted with 1,200 mL of methanol, 4.0 mL of concentrated hydrochloric acid, and 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 PPE5. PPE5 had a number average molecular weight of 5,800 and a weight average molecular weight of 9,500.

[0085] Synthesis Example 4 2,6-dimethylphenol, o-cresol, 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 39.17 g (80 mol %) of 2,6-dimethylphenol, 4.33 g (10 mol %) of o-cresol, and 6.50 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) was added, and the mixture was stirred at a stirring speed of 200 rpm while blowing dry air into the reaction solution at a flow rate of 150 mL / min, 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 the blowing of dry air, the precipitate 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 PPE6. PPE6 had a number-average molecular weight of 15,000 and a weight-average molecular weight of 30,200.

[0086] Synthesis Example 5 Diallyl isocyanurate (19.14 g, 91.49 mmol), 2,6-dimethylphenol (13.43 g, 109.9 mmol), hexamethylenetetramine (0.125 g, 0.892 mmol), paraformaldehyde (4.396 g), DMF (45.39 g), and ion-exchanged water (1.22 g) were added to a 100 mL two-neck flask, and the reaction system was placed under a nitrogen atmosphere by bubbling with nitrogen for 15 minutes, followed by heating and stirring at 120° C. for 18 hours. The reaction solution was added dropwise to a reprecipitation solvent (methanol:ion-exchanged water:35% hydrochloric acid=150:600:1.5 mL), yielding 4DT-26DMP (28.9 g, 84.2 mmol) represented by the following structural formula as a white powder.

[0087] The starting phenols were 2,6-dimethylphenol, o-cresol, and 4DT-26DMP. 2,6-dimethylphenol (87.90 g, 85 mol%), o-cresol (0.82 g, 10 mol%), and 4DT-26DMP (1.27 g, 5 mol%) were added to a 100 mL two-necked eggplant flask, and the resulting mixture was dissolved in 56.7 g of toluene. Furthermore, 0.227 g of di-μ-hydroxo-bis[(N,N,N',N'-tetramethylethylenediamine)copper(II)] chloride (Cu / TMEDA) and 0.207 g of tetramethylethylenediamine (TMEDA) were added and stirred (stir bar, 350 rpm). The reaction was carried out at 40°C for 15 hours while blowing dry air into the reaction solution at a flow rate of 30 mL / min, yielding a reaction solution containing polyphenylene ether. The resulting reaction solution was filtered through 5C filter paper, and the filtrate was added dropwise to a reprecipitation solvent of Alcosol K (0.3 L), ion-exchanged water (5 mL), and 35% hydrochloric acid (1 mL), and the precipitate was filtered to obtain PPE7. PPE7 had a number-average molecular weight of 11,200 and a weight-average molecular weight of 25,400.

[0088] <Crosslinking curing agent> TAIC (triallyl isocyanurate) manufactured by Mitsubishi Chemical Corporation <Peroxide> Perbutyl P40 manufactured by NOF Corporation

[0089] (Curable Composition) The raw materials (amount: parts by mass) shown in Table 2 were mixed and stirred to obtain curable compositions of each example and comparative example.

[0090] (Creation of cured film) <In air atmosphere> The curable composition of each Example and Comparative Example was applied to the shine side of 18 μm thick copper foil so that the film thickness after curing was 35 μm, and dried at 90°C for 5 minutes in a hot air circulation drying oven (primary heating). Next, the composition was cured in an air circulation drying oven at 200°C for 1 hour (secondary heating) to obtain a cured film on the copper foil. <In nitrogen atmosphere> The curable composition of each Example and Comparative Example was cured in the same manner as in air atmosphere, except that the secondary heating was performed using an inert oven in a nitrogen atmosphere.

[0091] (Evaluation of Strength of Cured Product) The strength of the cured films obtained under a nitrogen atmosphere and under an air atmosphere was evaluated according to the following criteria. The results are shown in Table 2. A: No cracks occurred after curing. B: Cracks occurred after curing.

[0092]

[0093] The results shown in Table 2 show that PPE having a structure in which the functional group represented by formula (1) is directly bonded to a benzene ring has sufficient strength when cured in the atmosphere.

[0094] The method for producing a cured product according to the present invention can produce a cured product having sufficient strength when cured under atmospheric conditions, and is therefore suitable for use as a method for producing insulating materials for electronic components such as millimeter-wave radar for high-capacity, high-speed communications, such as those typified by fifth-generation communication systems (5G), and for automotive ADAS (Advanced Driver Assistance Systems). CROSS-REFERENCE TO RELATED APPLICATIONS

[0095] This application claims priority based on Japanese Patent Application No. 2024-074506, filed with the Japan Patent Office on May 1, 2024, the entire disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A method for producing a cured product, comprising the step of heat-curing, in an atmospheric environment, a curable composition containing a polyphenylene ether having a structure in which a functional group represented by the following formula (1) is directly bonded to a benzene ring: (In formula (1), R is an alkyl group having 1 to 8 carbon atoms.) 2. The method for producing a cured product according to claim 1, wherein the functional group represented by formula (1) is an allyl group.

3. The method for producing a cured product according to claim 1, wherein the polyphenylene ether has a branched structure.

4. The method for producing a cured product according to claim 1, wherein the weight average molecular weight Mw of the polyphenylene ether is 4,000 to 50,000.

5. A cured product obtained by curing in an atmospheric environment a curable composition containing a polyphenylene ether having a structure in which a functional group represented by the following formula (1) is directly bonded to a benzene ring: (In formula (1), R is an alkyl group having 1 to 8 carbon atoms.) 6. An electronic component comprising the cured product according to claim 5.

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