Polyfunctional vinyl aromatic copolymer, copolymer composition, cured product, and production method

Abstract

Provided are: a polyfunctional vinyl aromatic copolymer that has an excellent dielectric loss tangent, which is also less likely to deteriorate after thermal degradation, and that further has excellent heat resistance; and a composition thereof.　The polyfunctional vinyl aromatic copolymer is characterized by: containing 2-80 mol% of a repeating unit having an unsaturated group represented by formula (a1) relative to the total amount of a divinyl aromatic compound (a), a monovinyl aromatic compound (b), and a structural unit (c) that is derived from an α,α-disubstituted olefin compound; the structural unit represented by formula (c2) being 50.0 mol% or less relative to the entire amount of the structural unit (c) derived from the α,α-disubstituted olefin compound; the structural unit represented by formula (c3) being 10.0-40.0 mol %; the number average molecular weight Mn being 300-50,000; and the molecular weight distribution (Mw / Mn) represented by the ratio of the weight average molecular weight Mw to the number average molecular weight Mn being 7.0 or less.

Description

Polyfunctional vinyl aromatic copolymer, copolymer composition, cured product, and method of production

[0001] The present invention relates to a novel polyfunctional vinyl aromatic copolymer with excellent dielectric properties and flame retardancy, a method for producing the same, a curable resin composition containing the copolymer, a film made from the curable resin composition, a cured body obtained by curing the curable resin composition, a prepreg made from the curable resin composition and a substrate, a metal-clad laminate, and a printed circuit board.

[0002] With the recent increase in information and communication traffic, high-frequency information communication has become widespread, and there is a demand for electrical insulating materials with low dielectric constant and low dielectric loss tangent to improve electrical properties, particularly to reduce transmission loss in high-frequency bands. Furthermore, since printed circuit boards and electronic components using these electrical insulating materials are exposed to high-temperature solder reflow during mounting, materials with high heat resistance, i.e., those exhibiting a high glass transition temperature, are desired. In particular, recently, due to environmental concerns, lead-free solder with a high melting point is used, which has increased the demand for electrical insulating materials with even higher heat resistance. Moreover, since printed circuit boards and electronic components are exposed to high-temperature solder reflow during mounting, it is also required that the dielectric loss tangent does not deteriorate easily after high-temperature exposure.

[0003] Patent Document 1 discloses copolymers of divinyl aromatic compounds, monovinyl aromatic compounds, cycloolefin compounds, and α,α-disubstituted olefin compounds. The materials obtained in this document exhibit low dielectric loss tangent, but their dielectric loss tangent deteriorates after thermal degradation. Patent Document 2 discloses olefin-aromatic vinyl compound-diene copolymers. The materials obtained in this document exhibit low dielectric loss tangent, but have low heat resistance. Patent Documents 3, 4, and 5 disclose methods for producing isobutylene copolymers under specific conditions. However, the dielectric properties of the polymers are not examined.

[0004] International Publication No. 2020 / 067336, Japanese Patent Publication No. 2002-241449, Japanese Patent Publication No. Hei 11-349648, Japanese Patent Publication No. 2000-17020, Japanese Patent Publication No. 2022-163691

[0005] An object of the present invention is to provide a polyfunctional vinyl aromatic copolymer and a composition thereof that are not only excellent in dielectric loss tangent, but also have a dielectric loss tangent that is unlikely to deteriorate after thermal degradation and are also excellent in heat resistance.

[0006] The present invention provides a polymer and a composition thereof, as well as a production method thereof, which solve the problems of the prior art and satisfy both dielectric loss tangent with high resistance to thermal degradation and heat resistance. That is, the present invention is characterized in that, based on the total sum of structural units derived from a divinyl aromatic compound (a), a monovinyl aromatic compound (b) and an α,α-disubstituted olefin compound (c), the copolymer contains 2 to 80 mol% of a repeating unit having an unsaturated group represented by the following formula (a1), the structural unit (c) derived from the α,α-disubstituted olefin compound includes structural units represented by the following formulas (c2) and (c3), with respect to the total amount of the structural unit (c), the content of the structural unit represented by (c2) is 50.0 mol% or less, and the content of the structural unit represented by (c3) is 10.0 to 40.0 mol%, the number average molecular weight (Mn) of the polyfunctional vinyl aromatic copolymer is 300 to 50,000, and the molecular weight distribution (Mw / Mn) represented by the ratio of the weight average molecular weight Mw to the number average molecular weight Mn is 7.0 or less, which is a polyfunctional vinyl aromatic copolymer. (In the formula, R １ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms.) (R ２ , R ３ , R ４ each represent a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a linear or branched alkenyl group having 2 to 8 carbon atoms, or a linear or branched alkynyl group having 2 to 8 carbon atoms. R ５ , R ６ each represent a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 30 carbon atoms, provided that at least one of R ５ , R ６ is an aromatic hydrocarbon group.) (R ６ , R ７ each represent a linear or branched alkyl group having 1 to 8 carbon atoms, a linear or branched alkenyl group having 2 to 8 carbon atoms, or a linear or branched alkynyl group having 2 to 8 carbon atoms. R ８ , R ９ , R１０ , R １１ R is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 30 carbon atoms. ８ , R ９ At least one of the following, and R １０ , R １１ At least one of them is an aromatic hydrocarbon group.

[0007] The present invention relates to a method for producing a polyfunctional vinyl aromatic compound by polymerizing a divinyl aromatic compound (a), a monovinyl aromatic compound (b), and an α,α-disubstituted olefin compound (c) in the presence of a Lewis acid catalyst, characterized in that the polymerization is carried out at a low temperature of 0 to -50°C.

[0008] The present invention relates to a curable resin composition containing a polyfunctional vinyl aromatic copolymer and a radical polymerization initiator, a curable resin composition containing a polyfunctional vinyl aromatic copolymer and a curable reactive resin or thermoplastic resin, a cured product obtained by curing such curable resin compositions, a curable composite material comprising a curable resin composition and a substrate, a cured composite material obtained by curing a curable composite material, a laminate having a layer of cured composite material and a metal foil layer, a resin-coated metal foil having a film formed from a curable resin composition on one side of the metal foil, and a varnish for circuit board materials obtained by dissolving a curable resin composition in an organic solvent.

[0009] The polyfunctional vinyl aromatic copolymer of the present invention yields a cured product with excellent dielectric loss tangent, less deterioration of the dielectric loss tangent after thermal degradation, and excellent heat resistance.

[0010] This is the NMR chart of the copolymer obtained in Example 1A. This is the NMR chart of the copolymer obtained in Example 1B.

[0011] The present invention will be described in detail below. The polyfunctional vinyl aromatic copolymer of the present invention is a copolymer composed of units derived from monomers of a divinyl aromatic compound (a), a monovinyl aromatic compound (b), and an α,α-disubstituted olefin copolymer (c).

[0012] The polyfunctional vinyl aromatic copolymer preferably contains, with respect to the total sum of structural units (a) derived from divinyl aromatic compounds, monovinyl aromatic compounds, and α,α-disubstituted olefin compounds, 0.5 mol% to 75 mol% of structural units (a) derived from divinyl aromatic compounds, 5.0 mol% to 75 mol% of structural units (b) derived from monovinyl aromatic compounds, and 5.0 mol% to 75 mol% of structural units (c) derived from α,α-disubstituted olefin compounds. The amount of structural unit (a) is preferably 5.0 to 40 mol%, more preferably 10 to 30 mol%, the amount of structural unit (b) is preferably 20 to 60 mol%, more preferably 30 to 50 mol%, and the amount of structural unit (c) is 20 to 60 mol%, more preferably 30 to 50 mol%.

[0013] The polyfunctional vinyl aromatic copolymer may contain structural units derived from monomer compounds other than (a), (b), and (c), but the amount of these units is less than 50 mol%, preferably less than 20 mol%, and more preferably less than 10 mol%, based on 100 mol% of the total sum of structural units.

[0014] The polyfunctional vinyl aromatic copolymer contains 2 to 80 mol% of repeating units having an unsaturated group represented by the following formula (a1), preferably 5 to 50 mol%, and more preferably 10 to 30 mol%. In the formula, R １The symbol represents an aromatic hydrocarbon group having 6 to 30 carbon atoms. Examples of aromatic hydrocarbon groups having 6 to 30 carbon atoms include monocyclic aromatic compounds such as benzene, furan, pyrrole, thiophene, imidazole, pyrazole, oxazole, isoxazole, thiazole, isothiazole, pyridine, pyrimidine, pyridazine, pyrazine, and triazine; fused ring aromatic compounds such as naphthalene, anthracene, phenalene, phenanthrene, quinoline, isoquinoline, quinazoline, phthalazine, pteridine, coumarin, indole, benzimidazole, benzofuran, and acridine; and ring-aggregated aromatic compounds such as biphenyl, binaphthalene, bipyridine, bithiophene, phenylpyridine, phenylthiophene, terphenyl, diphenylthiophene, and quaterphenyl. Preferably, it is benzene, naphthalene, biphenyl, or anthracene. Particularly preferred is benzene. The aromatic hydrocarbon group may be substituted with an alkyl group.

[0015] The polyfunctional vinyl aromatic copolymer contains structural units (c) derived from α,α-disubstituted olefin compounds, represented by the following formulas (c2) and (c3). In the first embodiment, the structural units represented by (c2) are 30.0 mol% or less and the structural units represented by (c3) are 10.0 to 40.0 mol% of the total amount of constituent units of (c). In the second embodiment, the structural units represented by (c2) are 30.0 to 50.0 mol% or less and the structural units represented by (c3) are 10.0 to 40.0 mol% of the total amount of constituent units of (c). The structural units represented by formulas (c2) and (c3) are understood to be introduced into the main chain or side chain in the copolymer. R ２ , R ３ , R ４ R is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a linear or branched alkenyl group having 2 to 8 carbon atoms, or a linear or branched alkynyl group having 2 to 8 carbon atoms. ５ , R ６ R is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 30 carbon atoms. ５ , R ６At least one of them is an aromatic hydrocarbon group. R ６ , R ７ R is a linear or branched alkyl group having 1 to 8 carbon atoms, a linear or branched alkenyl group having 2 to 8 carbon atoms, or a linear or branched alkynyl group having 2 to 8 carbon atoms. ８ , R ９ , R １０ , R １１ R is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 30 carbon atoms. ８ , R ９ At least one of the following, and R １０ , R １１ At least one of them is an aromatic hydrocarbon group. Here, R in formula (c2) ２ ~R ４ , R in equation (c3) ５ ~R １１ In this regard, aromatic hydrocarbon groups having 6 to 30 carbon atoms are specifically R １ Examples of groups similar to those described above include alkyl groups such as methyl, ethyl, propyl, hexyl, or decyl groups. Examples of alkenyl groups include vinyl, allyl, or 3-butenyl groups. Examples of alkynyl groups include ethynyl or propa-2-in-1-yl (propargyl) groups.

[0016] Polyfunctional vinyl aromatic copolymers are used for quantification of peak area. １３ C-NMR (quantitative １３13C-NMR) allows for estimating the ratio of each structural unit. The ratio is obtained by (c2):(c3):others = (integral of 53-54 ppm):(integral of 55-56 ppm):((integral of 48-50 ppm)+(integral of 18-33 ppm - integral of 55-56 ppm)) / 5. In the first embodiment, based on the total amount of structural units of structural unit (c), the content of the structural unit represented by (c2) is 30.0 mol% or less, preferably 25 mol% or less, more preferably 20 mol% or less. The lower limit of the structural unit (c2) is preferably 5 mol% or more, more preferably 10 mol% or more, and still more preferably 15 mol% or more. In the second embodiment, based on the total amount of structural units of structural unit (c), the content of the structural unit represented by (c2) is 30.0 to 50.0 mol% or less. The upper limit is preferably 45 mol% or less, and the lower limit is preferably 35 mol% or more, more preferably 40 mol% or more. Exceeding the upper limit for the structural unit represented by (c2) leads to deterioration of ΔDf. The content of the structural unit represented by (c3) is 10.0 to 40.0 mol%, preferably 10 to 30 mol%, more preferably 10 to 25 mol%. When the content of the structural unit represented by (c3) is below the lower limit, it leads to deterioration of ΔDf and Tg, while when it exceeds the upper limit, it leads to deterioration of Tg.

[0017] As the divinyl aromatic compound, divinylbenzene (including each isomer), divinylnaphthalene (including each isomer), and divinylbiphenyl (including each isomer) are preferably used, but the divinyl aromatic compound is not limited to these. Further, these can be used alone or in combination of two or more. From the viewpoint of moldability, divinylbenzene (m-isomer, p-isomer or a mixture of these isomers) is more preferred.

[0018] Monovinyl aromatic compounds include, but are not limited to, vinyl aromatic compounds such as styrene, vinylnaphthalene, and vinylbiphenyl; and nuclear alkyl-substituted vinyl aromatic compounds such as o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, o-ethylvinylbenzene, m-ethylvinylbenzene, and p-ethylvinylbenzene. To prevent gelation of copolymers and improve solubility, compatibility, and processability in solvents, styrene, ethylvinylbenzene (including all isomers), ethylvinylbiphenyl (including all isomers), and ethylvinylnaphthalene (including all isomers) are particularly preferred from the viewpoint of cost and availability. From the viewpoint of compatibility and cost, styrene and ethylvinylbenzene (m-isomer, p-isomer, or mixtures thereof) are more preferred. Compounds without substituents at the α-position are preferred.

[0019] α,α-disubstituted olefin compounds include, but are not limited to, one or more monomers selected from the group consisting of isobutylene, diisobutylene, 2-methyl-1-butene, 2-methyl-1-pentene, 1-methyl-1-cyclopentene, 2-methyl-1-hexene, 1-methyl-1-cyclohexene, 2-methyl-1-heptene, 2-methyl-1-octene, 2-methyl-1-nonene, 2-methyl-1-decene, 2-methyl-1-dodecene, 2-methyl-1-tetradecene, 2-methyl-1-hexadecene, 2-methyl-1-octadecene, 2-methyl-1-eicosene, 2-methyl-1-docosene, and 2-methyl-1-tetracosene. To control the molecular weight and molecular weight distribution of the copolymer, prevent gel formation, and improve solubility, compatibility, and processability in solvents, α,α-disubstituted olefin compounds substituted with aliphatic groups, such as isobutylene, diisobutylene, 2-methyl-1-pentene, 2-methyl-1-hexene, and isoprene, can be preferably used from the viewpoint of cost and availability. From the viewpoint of ease of production and cost, isobutylene and diisobutylene are more preferable.

[0020] In the method for producing the copolymer of the present invention, a copolymer can be produced by polymerizing a monomer essentially containing a divinyl aromatic compound (a), a monovinyl aromatic compound (b) and an α,α-disubstituted olefin compound (c), and optionally further containing other monomers, in the presence of a Lewis acid catalyst at a low temperature of 0 to -50°C. The temperature is preferably -10 to -40°C. When the temperature exceeds the upper limit, the amount of the structural unit represented by (c3) decreases. When the temperature is lower than the lower limit, the molecular weight becomes too high to obtain an oligomer, the reaction slows down, and productivity deteriorates. The reaction time may be appropriately selected within the range of 30 minutes to 2 hours in the first embodiment, and within the range of 30 minutes to 8 hours in the second embodiment.

[0021] As the Lewis acid catalyst, any compound that is composed of a metal ion (acid) and a ligand (base) and can accept an electron pair can be used without particular limitation. Among Lewis acid catalysts, from the viewpoint of the thermal decomposition resistance of the obtained copolymer, metal fluorides or complexes thereof are preferable, and divalent to hexavalent metal fluorides or complexes thereof of particularly B, Al, Ga, In, Si, Ge, Sn, Pb, Sb, Bi, Ti, W, Zn, Fe, V and the like are particularly preferable. These catalysts can be used alone or in combination of two or more. From the viewpoints of controlling the molecular weight and molecular weight distribution of the obtained copolymer and polymerization activity, an ether complex of boron trifluoride is most preferably used. Examples of the ether in the ether complex include diethyl ether, dimethyl ether and the like.

[0022] The Lewis acid catalyst is preferably used in an amount within the range of 0.001 to 100 moles relative to 100 moles of the total of all monomer components. More preferably, it is 0.01 to 50 moles, and still more preferably 0.1 to 10 moles. If the upper limit is exceeded, the polymerization rate becomes too high, which makes it difficult to control the molecular weight distribution. On the other hand, if the lower limit is not reached, the polymerization rate becomes too slow, which leads to increased cost and makes it unsuitable for industrial implementation.

[0023] In the copolymer production method of the present invention, one or more Lewis base compounds can be used as co-catalysts if desired. Specific examples of Lewis base compounds include ester compounds such as propyl acetate, thioester compounds such as methyl mercaptopropionic acid, ketone compounds such as methyl ethyl ketone, amine compounds such as methylamine, ether compounds such as diethyl ether, thioether compounds such as diethyl sulfide, or phosphine compounds such as tripropyl phosphine. Among these, ester compounds and ketone compounds are preferably used because they synergistically act with the Lewis acid catalyst to easily control the polymerization rate and the molecular weight distribution of the polymer. One or more of these Lewis base compounds can be used.

[0024] The Lewis base compound used as a co-catalyst can be used in an amount ranging from 0.005 to 500 moles per 100 moles of total monomers. Preferably, it is 0.01 to 100 moles, and more preferably 0.1 to 50 moles. Within this range, the polymerization rate is appropriately maintained, the selectivity of the reaction between monomers is improved, resulting in a copolymer with excellent productivity, while excessive increases or decreases in molecular weight are suppressed, and excellent moldability is obtained.

[0025] In the first embodiment, the polymerization reaction is preferably carried out by cationic copolymerization in a homogeneous solvent, which is obtained by dissolving a polymerization raw material containing a mixture of monomers and a Lewis acid catalyst in a solvent having a dielectric constant of 2.0 to 15.0. The solvent is preferably an organic solvent that does not essentially inhibit cationic polymerization and dissolves the catalyst, polymerization additive, co-catalyst, monomers and the resulting vinyl aromatic copolymer to form a homogeneous solution, with a dielectric constant in the range of 2.0 to 15.0, and can be used alone or in combination of two or more. If the dielectric constant of the solvent is less than 2.0, the molecular weight distribution becomes broad, which is undesirable, and if it exceeds 15.0, the polymerization rate decreases. From the viewpoint of balancing polymerization activity and solubility, toluene, xylene, n-hexane, cyclohexane, methylcyclohexane, or ethylcyclohexane are particularly preferred as organic solvents.

[0026] In the second embodiment, the polymerization reaction is preferably carried out by cationic copolymerization in a homogeneous solvent obtained by dissolving the polymerization raw material, which includes the above monomer mixture and a Lewis acid catalyst, in a solvent having a dielectric constant of 1.0 to 2.9. The solvent is a compound that does not essentially inhibit cationic polymerization and dissolves the catalyst, polymerization additive, co-catalyst, monomers, and the resulting vinyl aromatic copolymer to form a homogeneous solution. Organic solvents with a dielectric constant of less than 2.9 are preferred and can be used alone or in combination of two or more. If the dielectric constant of the solvent exceeds 2.9, the proportion of structure (c2) increases and the proportion of structure (c3) decreases, resulting in deterioration of ΔDf and no improvement in heat resistance. The dielectric constant of the solvent is preferably in the range of 1.00 to 2.20, more preferably 1.00 to 2.10. The dielectric constant of the components other than monomers, i.e., the total components including the solvent and additives, is preferably less than 2.70. Preferably, it is in the range of 1.00 to 2.50. As a solvent, n-hexane, cyclohexane, methylcyclohexane, or ethylcyclohexane are particularly preferred from the viewpoint of balancing polymerization activity and solubility.

[0027] The amount of solvent used is determined considering the viscosity of the resulting polymerization solution and the ease of heat removal, such that the copolymer concentration in the polymerization solution at the end of polymerization is 1 to 90 wt%, preferably 10 to 80 wt%, and particularly preferably 20 to 70 wt%. If this concentration is less than 1 wt%, it leads to increased costs due to low polymerization efficiency, and if it exceeds 90 wt%, the molecular weight and molecular weight distribution increase, leading to a decrease in moldability.

[0028] The Mn (number-average molecular weight in terms of standard polystyrene, measured using gel permeation chromatography) of the polyfunctional vinyl aromatic copolymer of the present invention is 300 to 50,000. Preferably, Mn is 500 to 10,000, more preferably 1,000 to 5,000. The molecular weight distribution (Mw / Mn) is 7.0 or less. In the first embodiment, Mw / Mn is preferably 1.0 to 5.0, more preferably 2.0 to 3.0. In the second embodiment, Mw / Mn is preferably 1.0 to 6.0, more preferably 5.5 to 3.0.

[0029] Next, the curable resin composition of the present invention will be described. The curable resin composition preferably contains a polyfunctional vinyl aromatic copolymer and a radical polymerization initiator (also called a radical polymerization catalyst). The polyfunctional vinyl aromatic copolymer hardens by crosslinking reaction by means such as heating, but the radical polymerization initiator can lower the reaction temperature or promote the crosslinking reaction of unsaturated groups.

[0030] Examples of known radical polymerization initiators include benzoyl peroxide, cumene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexine-3, di-t-butylperoxide, t-butylcumyl peroxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane. Examples include peroxides such as dicumyl peroxide, di-t-butyl peroxyisophthalate, t-butyl peroxybenzoate, 2,2-bis(t-butyl peroxy)butane, 2,2-bis(t-butyl peroxy)octane, 2,5-dimethyl-2,5-di(benzoyl peroxy)hexane, di(trimethylsilyl) peroxide, trimethylsilyltriphenylsilyl peroxide, and 2,3-dimethyl-2,3-diphenylbutane. Among these, α,α'-bis(t-butyl peroxy-m-isopropyl)benzene is preferably used. Radical polymerization initiators can be used alone or in combination of two or more.

[0031] The amount of radical polymerization initiator added is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 8 parts by weight, per 100 parts by weight of polyfunctional vinyl aromatic copolymer. Within this range, the reaction proceeds well without inhibiting the curing reaction.

[0032] The curable resin composition may contain known curable reactive resins or thermoplastic resins. Examples of curable reactive resins include thermosetting resins, as well as resins or compounds that yield curable resins when copolymerized with polyfunctional vinyl aromatic copolymers. Examples include vinyl ester resins, polyvinyl benzyl resins, unsaturated polyester resins, curable vinyl resins, curable polyphenylene ether resins, maleimide resins, epoxy resins, polycyanate resins, phenolic resins, and one or more vinyl compounds having one or more polymerizable unsaturated hydrocarbon groups in their molecules. Examples of thermoplastic resins include polystyrene, polyphenylene ether resin, polyetherimide resin, polyethersulfone resin, PPS resin, polycyclopentazine resin, polycycloolefin resin, etc., as well as known thermoplastic elastomers such as styrene-ethylene-propylene copolymer, styrene-ethylene-butylene copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, hydrogenated styrene-butadiene copolymer, hydrogenated styrene-isoprene copolymer, etc., or rubbers such as polybutadiene and polyisoprene.

[0033] The amount of curable reactive resin or thermoplastic resin blended can be, for example, in the range of 10 to 100 parts by weight per 100 parts by weight of polyfunctional vinyl aromatic copolymer. Preferably, it is less than 50 parts by weight, more preferably less than 30 parts by weight, and even more preferably less than 10 parts by weight.

[0034] The curable resin composition may contain known flame retardants. Examples of flame retardants include halogenated flame retardants such as brominated flame retardants, halogen-free phosphate ester flame retardants, phosphazene flame retardants, or phosphinate flame retardants, which can be used individually or in combination of two or more.

[0035] The curable resin composition may contain known fillers. Examples of fillers include metal oxides such as silica, alumina, titanium oxide, and mica; metal hydroxides such as aluminum hydroxide and magnesium hydroxide; talc, aluminum borate, barium sulfate, and calcium carbonate, which can be used individually or in combination of two or more. The fillers may be used as is, or they may be surface-treated with a silane coupling agent. The silane coupling agent may also be added using the integral blend method. The filler content is preferably 10 to 200 parts by mass, more preferably 30 to 150 parts by mass, per 100 parts by mass of the resin components such as monomers.

[0036] The curable resin composition may further contain other additives. Examples of additives include defoamers such as silicone-based defoamers and acrylic acid ester-based defoamers, heat stabilizers, antistatic agents, ultraviolet absorbers, dyes and pigments, lubricants, and dispersants such as wetting and dispersing agents.

[0037] The curable resin composition of the present invention can be prepared in a varnish form to be used as a resin varnish for the purpose of impregnating a substrate (fibrous substrate) for forming a prepreg during the production of a prepreg, or for use as a circuit board material for forming a circuit board. The resin varnish is suitable for circuit boards and can be used as a varnish for circuit board materials. Specifically, examples include printed wiring boards, printed circuit boards, flexible printed wiring boards, and build-up wiring boards.

[0038] Resin varnishes are prepared, for example, as follows: Each component that can be dissolved in an organic solvent is added to the organic solvent and dissolved. Then, components that cannot be dissolved in the organic solvent, such as fillers, are added and mixed using a ball mill, bead mill, planetary mixer, roll mill, etc. Examples of organic solvents include ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; esters such as ethyl acetate, propyl acetate, and butyl acetate; polar solvents such as dimethylacetamide and dimethylformamide; and aromatic hydrocarbon solvents such as toluene and xylene. These can be used individually or in combination of two or more. From the viewpoint of dielectric properties, aromatic hydrocarbons such as benzene, toluene, and xylene are preferred.

[0039] The amount of organic solvent used is preferably 5 to 900% by weight, more preferably 10 to 700 parts by weight, and particularly preferably 20 to 500 parts by weight, per 100 parts by weight of the curable resin composition.

[0040] The cured products obtained by curing the curable resin composition of the present invention can be used as molded products, laminates, cast products, adhesives, coatings, and films. For example, the cured product of semiconductor encapsulating material is a cast product or molded product. A method for obtaining a cured product for such applications is to mold the curable resin composition using a casting or transfer molding machine, injection molding machine, etc., and then heat it at 80 to 230°C for 0.5 to 10 hours to obtain the cured product. The cured product of varnish for circuit boards is a laminate. A method for obtaining this cured product is to impregnate a substrate such as glass fiber, carbon fiber, polyester fiber, polyamide fiber, alumina fiber, or paper with varnish for circuit boards, heat and dry it to obtain a prepreg, and then laminate these prepregs together or with metal foil such as copper foil and heat press mold them. By incorporating inorganic high dielectric powder such as barium titanate, or inorganic magnetic material such as ferrite, into the curable resin composition or resin varnish, it becomes a superior material for electronic components, especially high-frequency electronic components.

[0041] The curable resin composition of the present invention is also useful as a curable composite material. A substrate is added to the curable composite material made from the curable resin composition of the present invention to increase mechanical strength and dimensional stability.

[0042] Known materials can be used as such substrates. Examples include various glass cloths such as roving cloth, cloth, chopped mat, and surfacing mat; asbestos cloth; metal fiber cloth and other synthetic or natural inorganic fiber cloths; woven or nonwoven fabrics obtained from liquid crystal fibers such as all-aromatic polyamide fibers, all-aromatic polyester fibers, and polybenzozal fibers; woven or nonwoven fabrics obtained from synthetic fibers such as polyvinyl alcohol fibers, polyester fibers, and acrylic fibers; natural fiber cloths such as cotton cloth, linen cloth, and felt; carbon fiber cloth; and natural cellulose-based cloths such as kraft paper, cotton paper, and paper-glass fiber blend paper. These can be used individually or in combination of two or more types.

[0043] The proportion of the base material in the curable composite material is preferably 5 to 90% by weight, more preferably 10 to 80% by weight, and even more preferably 20 to 70% by weight.

[0044] Curable composite materials may contain coupling agents to improve adhesion at the interface between the resin and the substrate, as needed. Common coupling agents include silane coupling agents, titanate coupling agents, aluminum-based coupling agents, and zircoaluminate coupling agents.

[0045] One method for producing curable composite materials is to uniformly dissolve or disperse a curable resin composition and other components as needed in an organic solvent, impregnate a substrate with the mixture, and then dry it. Impregnation can be carried out by dipping, coating, etc. Impregnation can be repeated multiple times as needed, and it is also possible to adjust the desired resin composition and amount by repeatedly impregnating with multiple solutions of different compositions and concentrations.

[0046] A cured composite material can be obtained by curing a curable composite material by methods such as heating. For example, one curing method involves stacking multiple layers of curable composite material, bonding the layers together under heat and pressure, and simultaneously performing thermal curing to obtain a cured composite material of the desired thickness. It is also possible to obtain a cured composite material with a new layer structure by combining a cured composite material that has already been bonded and cured with a curable composite material. Lamination and curing are usually performed simultaneously using methods such as hot pressing, but they may also be performed independently. That is, an uncured or semi-cured composite material obtained by lamination can be cured by heat treatment or other methods.

[0047] The curing conditions can be, for example, a temperature of 80 to 300°C, a pressure of 0.1 to 1000 kg / cm², and a time of 1 minute to 10 hours, more preferably a temperature of 150 to 250°C, a pressure of 1 to 500 kg / cm², and a time of 1 minute to 5 hours.

[0048] The curable resin composition of the present invention can also be used in laminates. Specifically, it consists of a layer of the curable composite material and a layer of metal foil. Examples of metal foils include copper foil, stainless steel foil, titanium foil, and aluminum foil. The thickness is not particularly limited, but is in the range of 3 to 200 μm, more preferably 3 to 105 μm.

[0049] One method for manufacturing a laminate is to laminate a curable composite material obtained from a curable resin composition and a substrate with metal foil in a layer configuration appropriate to the purpose, and then bond the layers together under heat and pressure while simultaneously thermally curing them. In the laminate, the curable composite material and metal foil are laminated in any layer configuration. The metal foil can be used as both a surface layer and an intermediate layer. It is also possible to create multiple layers by repeating the lamination and curing process multiple times.

[0050] Adhesives can also be used to bond the metal foil. Examples of adhesives include epoxy, acrylic, phenolic, and cyanoacrylate-based adhesives. Lamination and curing can be carried out under the same conditions as for the manufacture of cured composite materials.

[0051] The curable resin composition of the present invention can be formed into a film by molding it into a film shape. Its thickness is preferably in the range of 3 to 200 μm, and more preferably in the range of 5 to 100 μm.

[0052] One method for manufacturing the film is to uniformly dissolve or disperse a curable resin composition in an organic solvent, apply it to a resin film such as a PET film, and then dry it. The application can be repeated multiple times as needed, and it is also possible to adjust the desired resin composition and amount by repeatedly applying multiple solutions with different compositions and concentrations.

[0053] Resin-coated metal foil is composed of a curable resin composition and metal foil. The metal foils described above can be used in the laminate.

[0054] One method for manufacturing resin-coated metal foil is to uniformly dissolve or disperse a curable resin composition in an organic solvent, apply it to the metal foil, and then dry it. The application can be repeated multiple times as needed, and it is also possible to adjust the desired resin composition and amount by repeatedly applying multiple solutions with different compositions and concentrations.

[0055] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples. The copolymers obtained in each example and comparative example were analyzed by the following means.

[0056] <Structural Analysis by NMR Spectrum> NMR spectra were measured using a JEOL JNM-ECZ400R / S analyzer, with deuterated chloroform solvent and a chloroform concentration of 77 ppm as the reference. For the measurement, the polymer was dissolved in the solvent at a concentration of 10% by mass / volume. １ H-NMR pulses were used with a pulse width of 45° and a repetition time of 5 seconds. In addition, DEPT measurement, QUAT analysis, and 2D NMR HSQC, COSY, and HMBC measurements were performed to assign peaks. Quantitative analysis was conducted. １３For 13C-NMR spectroscopy, the polymer was dissolved in a solvent at a concentration of 10% by mass / vol., and 1% by mass / vol., with chromium(III) acetylacetonate. Quantitative 13C-NMR spectroscopy was performed using a proton gate decoupling method with NOE elimination, using a pulse width of 30° and a standard repetition time of 3 seconds. NMR measurement data were processed using the Delta analysis software included with the instrument. Structures (a1), (c2), and (c3) were identified and peaks assigned using DEPT and 2D-NMR. １ 1H-NMR and quantitative analysis １３ The respective contents were calculated using C-NMR.

[0057] <Molecular Weight and Molecular Weight Distribution of Polymers> The molecular weight and molecular weight distribution of polymers were measured using a Tosoh HLC-8320GPC, with tetrahydrofuran as the solvent, a flow rate of 1.0 ml / min, a column temperature of 40°C, and a calibration curve using monodisperse polystyrene.

[0058] <Tg of cured material> Tg was determined by reading the maximum value of the loss tangent tanδ. A dynamic viscoelasticity analyzer (DMA7100, Hitachi High-Tech Science Corporation) was used, and measurements were taken at a frequency of 1 Hz, a heating rate of 2°C / min, and a temperature range of 25°C to 250°C (the measurement temperature range was slightly changed depending on the sample characteristics). The sample was prepared by hot pressing (10 mm × 50 mm × 2 mm thick).

[0059] <Dielectric Properties of Cured Materials> The dielectric properties were evaluated using cured materials obtained from the examples. The measurement apparatus consisted of a Keysight Technologies network analyzer (E8363C) and split post dielectric resonators (SPDR). Dielectric constant (Dk) and dielectric loss tangent (Df) were measured at 23°C and 50% humidity. For the measure of Df deterioration due to thermal degradation (ΔDf), Df was measured after thermal exposure at 130°C for 1 week, and evaluated by the difference from the initial Df before thermal exposure.

[0060] An example of the first embodiment will be described. <Synthesis of copolymer> Example 1A 500 mL separable flask contains 51.74 mL of toluene and 56.82 mL of styrene, DVB630 (a mixture of divinylbenzene and ethylvinylbenzene, divinylbenzene:ethylvinylbenzene = 0.63:0.37, manufactured by Nippon Steel Chemical & Material Co., Ltd.) 49.60 mL DIB (Diisobutylene, manufactured by Tokyo Chemical Industry Co., Ltd.) 80.42 mL The mixture was prepared and cooled and stirred until the internal temperature reached -30°C. Next, the boron trifluoride diethyl ether complex (BF ３ ・Et ２ 3.81 mL of (O) was added and polymerization was started. After 30 minutes, MeOH was added to stop the reaction, and the mixture was allowed to return to room temperature. Sodium bicarbonate solution was added to neutralize the catalyst, and the mixture was washed with water three times to obtain the target copolymer varnish. The NMR chart of the obtained copolymer is shown in Figure 1. In Figure 1, from top to bottom, are the C13-NMR data, DEPT data, and QUAT data. Based on these analytical data, the copolymer is understood to have the following structure.

[0061] Using the obtained copolymer varnish, cured products were prepared and subjected to DMA analysis and dielectric property analysis. The cured product was prepared by mixing 0.5 parts by weight of perbutyl P and 0.2 parts by weight of AO-600 with 100 parts by weight of copolymer varnish, and press molding was performed in a vacuum press at 150°C for 15 minutes and 200°C for 90 minutes to obtain the cured product.

[0062] Example 2A Polymerization was carried out under the same conditions as in Example 1A, except that the internal temperature was set to -10°C, to obtain a copolymer varnish. Using the obtained copolymer varnish, a cured product was obtained under the same conditions as in Example 1A, and its physical properties were evaluated.

[0063] Example 3A Polymerization was carried out under the same conditions as in Example 1A, except that 4-methylstyrene was used instead of styrene, to obtain a copolymer varnish. Using the obtained copolymer varnish, a cured product was obtained under the same conditions as in Example 1A, and its physical properties were evaluated.

[0064] Comparative Example 1A: Polymerization was carried out under the same conditions as Example 1A, except that the internal temperature was set to 40°C. However, gelation occurred in 0.5 hours, and the target product could not be obtained.

[0065] Comparative Example 2A Polymerization was carried out under the same conditions as in Example 1A, except that the internal temperature was set to 40°C, the amount of catalyst (BF3・Et2O) was set to 0.667 mol, and 3.85 mol of propyl acetate (AcOPr) was added as a chain transfer agent for reaction control, to obtain a copolymer varnish. Using the obtained copolymer varnish, a cured product was obtained under the same conditions as in Example 1A, and its physical properties were evaluated.

[0066] Comparative Example 3A Polymerization was carried out under the same conditions as in Example 1A, except that the internal temperature was set to 40°C, the amount of catalyst (BF3・Et2O) was set to 0.667 mol, 3.85 mol of propyl acetate (AcOPr) was added as a chain transfer agent for reaction control, and 4-methylstyrene was used instead of styrene, to obtain a copolymer varnish. Using the obtained copolymer varnish, a cured product was obtained under the same conditions as in Example 1A, and its physical properties were evaluated.

[0067] Comparative Example 4A Polymerization was carried out under the same conditions as in Example 1A, except that the internal temperature was set to -70°C, to obtain a copolymer varnish. Using the obtained copolymer varnish, a cured product was obtained under the same conditions as in Example 1A, and its physical properties were evaluated.

[0068] Table 1A summarizes the synthesis conditions and physical property test results for the copolymers in Examples 1A to 3A and Comparative Examples 1A to 4A.

[0069]

[0070] An example of the second embodiment will be described. <Synthesis of copolymer> Example 1B 51.84 g of methylcyclohexane, 6.49 g of n-propyl acetate, and 56.82 g of styrene are placed in a 500 mL separable flask. DVB630 (a mixture of divinylbenzene and ethylvinylbenzene, divinylbenzene:ethylvinylbenzene = 0.63:0.37, manufactured by Nippon Steel Chemical & Material Co., Ltd.) 49.60g DIB (Diisobutylene, manufactured by Tokyo Chemical Industry Co., Ltd.) 80.42g The mixture was prepared and heated and stirred to an internal temperature of 40°C. Next, 1.27 mL of boron trifluoride diethyl ether complex was added and polymerization was started. After 5 hours, sodium bicarbonate solution was added to stop the reaction, and the mixture was returned to room temperature. After that, the mixture was washed with water three times to obtain the desired copolymer varnish. The NMR chart of the obtained copolymer is shown in Figure 2. In Figure 2, from top to bottom, are the C13-NMR data, DEPT data, and QUAT data. Based on these analytical data, the copolymer is understood to have the following structure.

[0071] Using the obtained copolymer varnish, cured products were prepared and subjected to DMA analysis and dielectric property analysis. The cured product was prepared by mixing 0.5 parts by weight of perbutyl P and 0.2 parts by weight of AO-600 with 100 parts by weight of copolymer varnish, and press molding was performed in a vacuum press at 150°C for 15 minutes and 200°C for 90 minutes to obtain the cured product.

[0072] In Example 2B, polymerization was carried out under the same conditions as in Example 1B, except that the amount of n-propyl acetate added was 3.37 g, to obtain a copolymer varnish. Using the obtained copolymer varnish, a cured product was obtained under the same conditions as in Example 1B, and its physical properties were evaluated.

[0073] Comparative Example 1B: Polymerization was carried out under the same conditions as in Example 1B, except that toluene was used as the solvent, to obtain a copolymer varnish. Using the obtained copolymer varnish, a cured product was obtained under the same conditions as in Example 1B, and its physical properties were evaluated.

[0074] Comparative Example 2B Polymerization was carried out under the same conditions as in Example 1B, except that the solvent was toluene and the amount of n-propyl acetate added was 10.11 g, to obtain a copolymer varnish. Using the obtained copolymer varnish, a cured product was obtained under the same conditions as in Example 1B, and its physical properties were evaluated.

[0075] Table 1B summarizes the synthesis conditions and physical property test results for the copolymers in Examples 1B-2B and Comparative Examples 1B-2B.

[0076]

Claims

1. A polyfunctional vinyl aromatic copolymer, which comprises 2 to 80 mol% of a repeating unit having an unsaturated group represented by the following formula (a1), based on the total sum of structural units derived from a divinyl aromatic compound (a), a monovinyl aromatic compound (b) and an α,α-disubstituted olefin compound (c), wherein the structural unit (c) derived from the α,α-disubstituted olefin compound comprises structural units represented by the following formulas (c2) and (c3), based on the total amount of the structural unit (c), the content of the structural unit represented by (c2) is 50.0 mol% or less, the content of the structural unit represented by (c3) is 10.0 to 40.0 mol%, the number average molecular weight (Mn) is 300 to 50,000, and the molecular weight distribution (Mw / Mn) expressed as the ratio of the weight average molecular weight Mw to the number average molecular weight Mn is 7.0 or less. (wherein R １ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms.) (R ２ , R ３ , R ４ each represents a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a linear or branched alkenyl group having 2 to 8 carbon atoms, or a linear or branched alkynyl group having 2 to 8 carbon atoms. R ５ , R ６ each represents a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 30 carbon atoms, provided that at least one of R ５ , R ６ is an aromatic hydrocarbon group.) (R ６ , R ７ each represents a linear or branched alkyl group having 1 to 8 carbon atoms, a linear or branched alkenyl group having 2 to 8 carbon atoms, or a linear or branched alkynyl group having 2 to 8 carbon atoms. R ８ , R ９ , R １０ , R １１ each represents a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, or an aromatic hydrocarbon group having 6 to 30 carbon atoms, provided that at least one of R ８ , R ９ , and at least one of R １０ , R １１ is an aromatic hydrocarbon group.) 2. The polyfunctional vinyl aromatic copolymer according to claim 1, wherein the α,α-disubstituted olefin compound (c) is one or more monomers selected from the group consisting of isobutylene, diisobutylene, 2-methyl-1-butene, 2-methyl-1-pentene, 1-methyl-1-cyclopentene, 2-methyl-1-hexene, 1-methyl-1-cyclohexene, 2-methyl-1-heptene, 2-methyl-1-octene, 2-methyl-1-nonene, 2-methyl-1-decene, 2-methyl-1-dodecene, 2-methyl-1-tetradecene, 2-methyl-1-hexadecene, 2-methyl-1-octadecene, 2-methyl-1-eicosene, 2-methyl-1-docosene, and 2-methyl-1-tetracosene.

3. The polyfunctional vinyl aromatic copolymer according to claim 1, wherein the monovinyl aromatic compound (b) is one or more monomers selected from the group consisting of styrene, vinylnaphthalene, vinylbiphenyl, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, m-ethylvinylbenzene, and p-ethylvinylbenzene.

4. A method for producing a polyfunctional vinyl aromatic copolymer according to claim 1, comprising polymerizing a divinyl aromatic compound (a), a monovinyl aromatic compound (b), and an α,α-disubstituted olefin compound (c) in the presence of a Lewis acid catalyst, characterized in that the polymerization is carried out at a low temperature of 0 to -50°C.

5. The method for producing a polyfunctional vinyl aromatic copolymer according to claim 4, wherein the Lewis acid catalyst is a metal fluoride or a complex thereof.

6. A curable resin composition characterized by containing the polyfunctional vinyl aromatic copolymer described in claim 1 and a radical polymerization initiator.

7. A curable resin composition characterized by containing the soluble polyfunctional vinyl aromatic copolymer described in claim 1 and a curable reactive resin or thermoplastic resin.

8. A cured product obtained by curing the curable resin composition according to claim 6.

9. A curable composite material comprising the curable resin composition described in claim 6 and a substrate, characterized in that the substrate is contained in a proportion of 5 to 90% by weight.

10. A cured composite material obtained by curing the curable composite material described in claim 9.

11. A laminate characterized by having a layer of the cured composite material described in claim 10 and a metal foil layer.

12. A resin-coated metal foil characterized by having a film formed from the curable resin composition described in claim 6 on one side of the metal foil.

13. A varnish for circuit board materials obtained by dissolving the curable resin composition according to claim 6 in an organic solvent.

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