WO2024070840A1 - Alkyl silyl peroxide, heat-curable composition, resin film, prepreg, metal laminate, and printed wiring board - Google Patents

Abstract

An alkyl silyl peroxide which is at least one compound selected from the group consisting of compounds represented by general formula (1) and compounds represented by general formula (2). The alkyl silyl peroxide is a novel polymerization initiator usable in steps for curing heat-polymerizable compositions at high temperatures.

Description

Alkylsilyl peroxide, thermosetting composition, resin film, prepreg, metal laminate, and printed wiring board

The present invention relates to alkylsilyl peroxides, thermosetting compositions, resin films, prepregs, metal laminates, and printed wiring boards.

Organic peroxides generate radicals when decomposed by heat, and are used as polymerization initiators for plastics and cross-linking agents for rubber. The decomposition temperature of organic peroxides can be adjusted depending on their chemical structure, and organic peroxides are used at various processing temperatures from room temperature to around 200°C. Among these organic peroxides, dialkyl peroxides have a high decomposition temperature and are used, for example, as cross-linking agents for rubber. In this case, when the rubber is kneaded in a molten state at around 100°C, the decomposition of dialkyl peroxide is so slight that the rubber does not cross-link, but by heating to around 180°C, radicals are generated and the rubber can be cross-linked.

On the other hand, with the remarkable progress in information network technology and the expansion of services that utilize information networks, there is a demand for electronic devices that can handle larger amounts of information and faster processing speeds, and this trend is accelerating with the spread of fifth-generation mobile communication systems. For this reason, electronic circuit board materials such as printed wiring boards used in electronic devices are required to have excellent dielectric properties such as low dielectric constant and low dielectric dissipation factor, as well as high heat resistance. Due to the high heat resistance of these materials, process temperatures for curing processes and the like are becoming higher.

As the radical polymerizable compound of the thermosetting composition used in electronic circuit board materials, polyphenylene ether or maleimide having a radical polymerizable double bond at the molecular end is preferably used because of its excellent dielectric properties. Dialkyl peroxide is used as the curing agent (Patent Documents 1-3).

International Publication No. 2008/033612 JP 2021-61409 A International Publication No. 2020/158849

The alkylperoxy radicals generated by the decomposition of dialkyl peroxides generate carbon radicals through secondary decomposition. These carbon radicals add to the double bonds of radically polymerizable compounds, initiating the curing reaction. Furthermore, in dialkyl peroxides with long carbon chains such as t-amyl or t-hexyl groups, the decomposition temperature of the dialkyl peroxide is lower than in cases where the carbon chain is short such as t-butyl groups. Therefore, dialkyl peroxides with long carbon chains such as those described above decompose too quickly in the curing process at high temperatures of, for example, 190°C or higher, and therefore the curing reaction cannot be carried out sufficiently, and the heat resistance of the cured product cannot be ensured sufficiently.

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide an alkylsilyl peroxide, which is a novel polymerization initiator that can be used in the curing process of a thermally polymerizable composition at high temperatures.

That is, the present invention relates to a compound represented by the general formula (1):

(In formula (1), R ¹ and R ² are independently an alkyl group or a phenyl group having 1 to 6 carbon atoms, R ³ is an alkyl group or a phenyl group having 3 to 6 carbon atoms, and R ⁴ is an alkyl group having 2 to 5 carbon atoms), and a compound represented by general formula (2):

(in formula (2), R ⁵ and R ⁶ are independently an alkyl group having 1 to 6 carbon atoms or a phenyl group, R ⁷ is an alkyl group having 2 to 6 carbon atoms, and R ⁸ is an ethylene group or an acetylene group).

The present invention also relates to a thermosetting composition containing the alkylsilyl peroxide and a radical polymerizable compound.

The present invention also relates to a resin film formed from the thermosetting composition.

The present invention also relates to a prepreg in which the thermosetting composition is impregnated or applied to a fibrous substrate.

The present invention also relates to a metal-clad laminate in which the resin film or the prepreg is laminated with a metal foil.

The present invention also relates to a printed wiring board in which a portion of the metal foil has been removed from the metal-clad laminate.

The present invention further relates to a method for producing the alkylsilyl peroxide, which includes a step of reacting a silyl chloride compound and a hydroperoxide compound as raw materials.

The alkylsilyl peroxide of the present invention has a trialkylsilyl group, and therefore has a higher decomposition temperature than dialkyl peroxide, allowing the curing process of the thermosetting composition to be carried out efficiently at high temperatures.

In addition, in the case of dialkyl peroxides such as di-t-hexyl peroxide, there is a problem that some of the dialkyl peroxide volatilizes during the solvent drying process, which is a pretreatment process for the curing process of the thermosetting composition. However, it is expected that such volatilization can be suppressed with alkylsilyl peroxides that have a trialkylsilyl group.

The above-mentioned thermosetting composition is suitable for curing at high temperatures, which improves the heat resistance of the resulting cured product. Furthermore, when a resin such as polyphenylene ether or maleimide is used as the radical polymerizable compound contained in the thermosetting composition, low-polarity decomposition products such as ethyl radicals (carbon radicals) can be introduced to the resin terminals, improving the dielectric properties of the cured product.

<Alkylsilyl peroxide>
The alkylsilyl peroxide of the present invention is represented by the general formula (1):

(In formula (1), R ¹ and R ² are independently an alkyl group or a phenyl group having 1 to 6 carbon atoms, R ³ is an alkyl group or a phenyl group having 3 to 6 carbon atoms, and R ⁴ is an alkyl group having 2 to 5 carbon atoms), and a compound represented by general formula (2):

(In formula (2), R ⁵ and R ⁶ are independently an alkyl group having 1 to 6 carbon atoms or a phenyl group, R ⁷ is an alkyl group having 2 to 6 carbon atoms, and R ⁸ is an ethylene group or an acetylene group).

In the formula (1), examples of R ¹ and R ² include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a t-butyl group, an n-pentyl group, a neopentyl group, an n-hexyl group, and a phenyl group.

In the formula (1), examples of R ³ include an n-propyl group, an isopropyl group, an n-butyl group, a t-butyl group, an n-pentyl group, a neopentyl group, an n-hexyl group, and a phenyl group.

In the formula (1), examples of R ⁴ include an ethyl group, an n-propyl group, an n-butyl group, a t-butyl group, an n-pentyl group, and a neopentyl group.

In the formula (2), examples of ^R5 and ^R6 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a t-butyl group, an n-pentyl group, a neopentyl group, an n-hexyl group, and a phenyl group.

In the formula (2), examples of R ⁷ include an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a t-butyl group, an n-pentyl group, a neopentyl group, and an n-hexyl group.

Specific examples of the alkylsilyl peroxide of the present invention are shown below, but the present invention is not limited to these.

Preferably, the dialkyl peroxide includes compounds 1 to 18, and more preferably compounds 4, 5, 6, 12, 13, 14, 16, and 19. More preferably, the dialkyl peroxide includes a silyl group in which one of the substituents is a t-butyl group and the remaining two are methyl groups, all of the silyl group's substituents are phenyl groups, one of the silyl group's substituents is a phenyl group and the remaining two are methyl groups, or two of the silyl group's substituents are phenyl groups and the remaining one is a methyl group.

<Method for producing alkylsilyl peroxide>
The method for producing the alkylsilyl peroxide represented by the general formula (1) is not limited in any way. For example, the method for producing the alkylsilyl peroxide represented by the general formula (3):

and a hydroperoxide compound represented by general formula (4):

(hereinafter also referred to as step (X))

The method for producing the alkylsilyl peroxide represented by the general formula (2) is not limited in any way. For example, the method for producing the alkylsilyl peroxide represented by the general formula (5):

and a silyl chloride compound represented by the general formula (4) (hereinafter also referred to as step (Y)).

In the step (X) or the step (Y), the hydroperoxide compound represented by the general formula (3) or the general formula (5) and the silyl chloride compound represented by the general formula (4) can be commercially available products.

In the step (X), the hydroperoxide compound represented by the general formula (3) is preferably used in an amount of 0.8 to 5.0 moles, more preferably 1.0 to 3.0 moles, per 1.0 mole of the silyl chloride compound represented by the general formula (4), from the viewpoint of increasing the yield of the target product. In the step (Y), the hydroperoxide compound represented by the general formula (5) is preferably used in an amount of 0.4 to 10.0 moles, more preferably 0.5 to 6.0 moles, per 1.0 mole of the silyl chloride compound represented by the general formula (4), from the viewpoint of increasing the yield of the target product.

In the step (X) or the step (Y), it is preferable to use a base catalyst. The base catalyst is not particularly limited, but examples thereof include pyridine, dimethylaminopyridine, triethylamine, sodium hydroxide, potassium hydroxide, sodium carbonate, and the like. The base catalyst may be used alone or in combination of two or more kinds.

In the step (X) or the step (Y), the amount of the base catalyst used is not particularly limited, but from the viewpoint of increasing the yield of the target product, it is preferable to use 0.1 to 5.0 moles, and more preferably 1.0 to 3.0 moles, per 1.0 mole of the silyl chloride compound represented by the general formula (4).

In the step (X) or the step (Y), it is preferable to use an organic solvent. The organic solvent is not particularly limited, but is preferably an organic solvent that is inactive in the reaction system. Examples of the organic solvent include non-polar compounds such as pentane, hexane, and toluene; and polar compounds such as acetone, acetonitrile, tetrahydrofuran, and ethyl acetate. The organic solvent may be used alone or in combination of two or more kinds.

In the step (X) or the step (Y), the amount of the organic solvent used is not particularly limited, but is usually about 0.1 to 100 parts by mass per part by mass of the chloride compound represented by the general formula (4) or the general formula (6).

The reaction temperature in step (X) or step (Y) is preferably -10°C or higher, more preferably 0°C or higher, from the viewpoint of increasing the yield of the target product, and is preferably 60°C or lower, more preferably 50°C or lower, from the viewpoint of safety.

The reaction time of step (X) or step (Y) cannot be determined in general because it varies depending on the raw materials and reaction temperature, but from the viewpoint of increasing the yield of the target product, it is usually preferably 0.1 hours or more, more preferably 0.5 hours or more, and preferably 5 hours or less.

The step (X) or the step (Y) can be carried out under an air atmosphere at normal pressure, but can also be carried out under a nitrogen atmosphere or nitrogen gas flow.

After step (X) or step (Y), the alkylsilyl peroxide can be purified by washing with an aqueous electrolyte solution such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium sulfite, hydrogen chloride, sulfuric acid, or sodium chloride, or ion-exchanged water to remove excess raw materials and by-products.

The resulting alkylsilyl peroxide can be identified using gas chromatography (GC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), mass spectrometry (MS), etc.

<Thermosetting Composition>
The thermosetting composition of the present invention contains an alkylsilyl peroxide and a radical polymerizable compound. The thermosetting composition may further contain other components in appropriate combination.

<Radical Polymerizable Compound>
The radical polymerizable compound is not particularly limited as long as it can be polymerized by a thermal radical polymerization reaction, and examples thereof include compounds having an ethylenically unsaturated group such as a vinyl group, an allyl group, a methacryl group, a styryl group, a meth(acryl) group, or a maleimide group. From the viewpoint of being able to improve the dielectric properties and heat resistance of a cured product using the above-mentioned alkylsilyl peroxide, examples thereof include polyphenylene ether and maleimide.

The polyphenylene ether is not particularly limited as long as it is a polyphenylene ether having a radically polymerizable double bond at the molecular end. The polyphenylene ether having the radically polymerizable double bond can be used alone or in combination of two or more kinds.

Specific examples of the structural unit of the polyphenylene ether include poly(2,6-dimethyl-1,4-phenylene ether), poly(2-methyl-6-ethyl-1,4-phenylene ether), poly(2-methyl-6-phenyl-1,4-phenylene ether), poly(2,6-dichloro-1,4-phenylene ether), etc., and poly(2,6-dimethyl-1,4-phenylene ether) is preferred from the viewpoint of excellent dielectric properties and heat resistance. Further, specific examples of the structural unit of the polyphenylene ether include, for example, a copolymer of 2,6-dimethylphenol and other phenols (for example, 2,3,6-trimethylphenol, 2-methyl-6-butylphenol, 2-allylphenol, etc.); a polyphenylene ether copolymer obtained by coupling 2,6-dimethylphenol with biphenols or bisphenols; and a polyphenylene ether having a linear or branched structure obtained by heating poly(2,6-dimethyl-1,4-phenylene ether) or the like with a phenolic compound such as a bisphenol or trisphenol in a toluene solvent in the presence of an organic peroxide to cause a redistribution reaction. The phenylene group in the phenylene ether unit may have a substituent, and the polyphenylene ether may contain other structural units other than the phenylene ether unit within a range that does not impair the effects of the present invention.

Examples of the radically polymerizable double bond at the molecular end include (meth)acryloyl groups, styryl groups, vinylbenzyl groups, vinyl groups, allyl groups, and 1,3-butadienyl groups. Among these, (meth)acryloyl groups and vinylbenzyl groups are preferred from the viewpoints of high reactivity during heat curing and excellent dielectric constant and dielectric dissipation factor of the cured product.

The number of radically polymerizable double bonds in one molecule of the polyphenylene ether having radically polymerizable double bonds at the molecular terminal is preferably 1.5 to 6 on average, more preferably 1.6 to 4 on average, and even more preferably 1.7 to 3 on average.

The number of ethylenically unsaturated double bonds in one molecule of the polyphenylene ether having a radically polymerizable double bond at the molecular end can be measured, for example, by measuring the number of hydroxyl groups remaining in the polyphenylene ether and calculating the reduction from the number of hydroxyl groups in the polyphenylene ether before modification with a compound having an ethylenically unsaturated double bond. The method for measuring the number of hydroxyl groups remaining in the polyphenylene ether conforms to the method described in Polymer Research Papers, vol. 51, No. 7, p. 480 (1994), in which tetraethylammonium hydroxide is added to a methylene chloride solution of the polyphenylene ether and the absorbance of the mixed solution at a wavelength of 318 nm is measured.

The polyphenylene ether having a radically polymerizable double bond at the molecular end preferably has a structure represented by the following general formula (6).

(In formula (6), X is any linking group having a valence of a, Y is a radically polymerizable double bond at the molecular end, and a is an integer from 1 to 6.)

Specific examples of X in the formula (6) include divalent phenols such as bisphenol A, bisphenol F, bisphenol S, fluorene bisphenol, 4,4'-dihydroxybiphenyl, 2,2'-dihydroxybiphenyl, 4,4'-dihydroxy-3,3'5,5'-tetramethylbiphenyl, 4,4'-dihydroxy-2,2',3,3'5,5'-hexamethylbiphenyl, hydroquinone, and resorcin, and trivalent or higher phenols such as tris-(4-hydroxyphenyl)methane, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, phenol novolac, o-cresol novolac, and naphthol novolac.

The polyphenylene ether having a radically polymerizable double bond at the molecular end preferably has a number average molecular weight of 800 or more and 5000 or less, more preferably 900 or more and 4500 or less, and even more preferably 1000 or more and 3000 or less, from the viewpoint of dielectric properties and impregnation into fibrous substrates.

The number average molecular weight may be measured by a general molecular weight measurement method, such as a polystyrene equivalent value measured using gel permeation chromatography (GPC). Specifically, after preparing a measurement sample with a sample concentration of 0.2 w/vol% (solvent: chloroform), the measurement can be performed using a measurement device HLC-8220GPC (manufactured by Tosoh Corporation), column: ShodexGPC KF-405L HQ x 3 (manufactured by Showa Denko K.K.), eluent: chloroform, injection amount: 20 μL, flow rate: 0.3 mL/min, column temperature: 40°C, detector: RI.

The method for synthesizing the polyphenylene ether having a radically polymerizable double bond at the molecular end is not particularly limited, as long as it is possible to synthesize a modified polyphenylene ether modified with a radically polymerizable double bond. Specifically, a method of reacting a compound having an ethylenically unsaturated double bond and a chlorine atom with the polyphenylene ether before modification can be mentioned. Examples of the compound having an ethylenically unsaturated double bond and a chlorine atom include (meth)acryloyl chloride and vinylbenzyl chloride. In addition, the polyphenylene ether having a radically polymerizable double bond at the molecular end may be a commercially available product, such as "OPE-2St" (manufactured by Mitsubishi Gas Chemical Co., Ltd.) or "Noryl SA9000" (manufactured by SABIC Innovative Plastics).

The maleimide is not particularly limited as long as it is a compound having a maleimide group in the molecule. Examples of the maleimide include monofunctional maleimides having one maleimide group in the molecule, and polyfunctional maleimides having two or more maleimide groups in the molecule. The maleimides can be used alone or in combination of two or more kinds.

Specific examples of the maleimides include, for example, the monofunctional maleimides, such as phenylmaleimide, cyclohexylmaleimide, chlorophenylmaleimide such as o-chlorophenylmaleimide, methylphenylmaleimide such as o-methylphenylmaleimide, hydroxyphenylmaleimide such as p-hydroxyphenylmaleimide, carboxyphenylmaleimide such as p-carboxyphenylmaleimide, N-dodecylmaleimide, and phenylmethanemaleimide. Examples of the polyfunctional maleimide include phenylene bismaleimides such as 4,4'-diphenylmethane bismaleimide, polyphenylmethane maleimide, and m-phenylene bismaleimide, bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 1,6'-bismaleimide-(2,2,4-trimethyl)hexane, 4,4'-diphenyl ether bismaleimide, 4,4'-diphenylsulfone bismaleimide, 1,3-bis(3-maleimidophenoxy)benzene, and 1,3-bis(4-maleimidophenoxy)benzene. Among these, polyfunctional maleimides are preferred from the viewpoint of the glass transition temperature of the cured product, with 4,4'-diphenylmethane bismaleimide and 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide being more preferred.

The maleimide may be a commercially available product, such as those manufactured by Daiwa Kasei Kogyo Co., Ltd. under the product names "BMI-1000", "BMI-4000", and "BMI-5100", those manufactured by Designer Molecules Inc. under the product names "BMI-689", "BMI-2560", "BMI-3000", and "BMI-5000P", and those manufactured by Nippon Kayaku Co., Ltd. under the product name "MIR-3000-70MT".

The dialkyl peroxide may be used in any amount relative to the radical polymerizable compound, and is usually preferably used in an amount of 0.05 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, relative to 100 parts by mass of the radical polymerizable compound.

<Other ingredients>
The thermosetting composition of the present invention may further contain other components in appropriate combination. Examples of other components include elastomers such as polyfunctional monomers, solvents, organic peroxides, azo compounds, polyisoprene, polybutadiene, styrene-butadiene rubber, butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, styrene-butadiene-styrene block copolymers, styrene-ethylene-butylene-styrene block copolymers, ethylene-styrene-divinylbenzene copolymers, ethylene-hexene-styrene-divinylbenzene copolymers, fluororubbers, and silicone rubbers, inorganic fillers such as natural silica, fused silica, synthetic silica, amorphous silica, hollow silica, alumina, boron nitride, aluminum nitride, clay, talc, and short glass fibers, silane coupling agents such as γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-(meth)acryloxypropyltrimethoxysilane, flame retardants, polymerization inhibitors, ultraviolet absorbers, light stabilizers, metal deactivators, surfactants, lubricants, thickeners, defoamers, antistatic agents, pigments, and dyes.

The polyfunctional monomer can be blended from the viewpoint of adjusting the viscosity of the thermosetting composition and improving the heat resistance of the cured product. Examples of the polyfunctional monomer include polyfunctional (meth)acrylates such as ethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate, vinylbenzene derivatives such as 1,4-divinylbenzene and 4-vinylbenzoic acid-2-acryloylethyl ester, alkenyl isocyanurate derivatives such as triallyl isocyanurate (TAIC), and alkenyl cyanurate derivatives such as triallyl cyanurate (TAC). Among these, triallyl isocyanurate and triallyl cyanurate are preferred because of their excellent heat resistance. The polyfunctional monomers can be used alone or in combination of two or more.

The amount of the polyfunctional monomer is preferably 5 to 50 parts by mass, more preferably 7 to 40 parts by mass, and even more preferably 10 to 30 parts by mass, per 100 parts by mass of the radical polymerizable compound.

The solvent may be added from the viewpoint of improving the viscosity of the thermosetting composition, the impregnation of the glass cloth, the smoothness of the cured film, etc. The solvent is not particularly limited as long as it can dissolve or disperse the above components and is a solvent that volatilizes when dried.

From the viewpoint of solubility, the solvent is preferably an aromatic solvent such as toluene or xylene; a ketone solvent such as acetone, methyl ethyl ketone, cyclopentanone or cyclohexanone; or an amide solvent such as dimethylformamide, dimethylacetamide or N-methylpyrrolidone. These solvents may be used alone or in combination of two or more. From the viewpoint of the solubility of the thermosetting composition in the solvent and the ease of the evaporation process, the amount of the solvent used is preferably 10 to 1000 parts by mass, and more preferably 20 to 500 parts by mass, per 100 parts by mass of the solid content of the thermosetting composition.

<Method of preparing thermosetting composition>
When preparing the thermosetting composition, the alkylsilyl peroxide, the radical polymerizable compound, and other components as necessary are charged into a container, and dissolved or dispersed according to a conventional method using a ball mill, a bead mill, a planetary mixer, a roll mill, or the like. At this time, heating may be performed as necessary. When the radical polymerizable compound or the like is dissolved in a solvent by heating, unnecessary gelation can be suppressed by cooling the solution to 50° C. or less after dissolution and then blending the alkylsilyl peroxide. In addition, filtration through a mesh or membrane filter or the like may be performed as necessary.

<Resin film>
The resin film of the present invention is formed from the thermosetting composition. The resin film contains the thermosetting composition before curing, but the thermosetting composition may be partially cured. The resin film can be obtained, for example, by drying a resin varnish, which is a mixture of the thermosetting composition and the solvent, alone, or by applying the resin varnish onto a support such as a support film and then drying it. The solvent is dried and removed using a hot air dryer or the like, for example, at 20°C to 180°C. The drying temperature is preferably 20 to 150°C, more preferably 50 to 130°C.

Examples of the support for the resin film include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polyethylene, polypropylene and polyvinyl chloride, polycarbonate, polyimide, ethylene tetrafluoroethylene copolymer, metal foils such as copper foil and aluminum foil, and release paper. The resin-coated metal foil obtained by applying the thermosetting composition to a metal foil and then drying and removing the solvent with a hot air dryer or the like is also called the resin-coated metal foil. The support may have been subjected to a chemical or physical treatment such as a mud treatment, a corona treatment or a release treatment.

The resin film is suitable as an interlayer insulating sheet, adhesive film, etc. for laminates such as multilayer printed wiring boards.

<Prepreg>
The prepreg of the present invention is a composite of a fibrous substrate and the thermosetting composition. The prepreg contains a thermosetting composition before curing, but a part of the thermosetting composition may be cured. The prepreg is preferably a composite of a fibrous substrate and a thermosetting composition impregnated or applied to the fibrous substrate. Even when the thermosetting composition is applied to the surface of the fibrous substrate to form a layer, a structure in which the cured product of the thermosetting composition is impregnated into the substrate can be obtained by press molding for curing the prepreg. The prepreg can be obtained, for example, by impregnating or applying a substrate such as glass cloth with a resin varnish which is a mixture of the thermosetting composition of the present invention and a solvent, and then drying and removing the solvent. It is also possible to repeat the impregnation or application multiple times. Furthermore, the amount of impregnation can be adjusted to the desired amount by repeating the impregnation or application using multiple thermosetting compositions with different concentrations and compositions. The solvent is dried and removed using a hot air dryer or the like, for example, at 20 ° C. to 180 ° C. The drying temperature is preferably from 20 to 150°C, and more preferably from 50 to 130°C.

Examples of the fibrous substrate include glass cloth, aramid cloth, polyester cloth, glass nonwoven fabric, aramid nonwoven fabric, pulp paper, and linter paper. Among these, glass cloth is preferred because it provides excellent mechanical strength to the printed wiring board, and flattened glass cloth is even more preferred. These fibrous substrates can be used alone or in combination of two or more types. The thickness of the fibrous substrate can be, for example, 1 to 300 μm.

The proportion of the solid content of the thermosetting composition in the solid content of the prepreg is preferably 30 to 80 mass%, and more preferably 40 to 70 mass%. If the above proportion is less than 30 mass%, the insulation reliability tends to be poor when the prepreg is used for electronic boards, etc. If the above proportion is more than 80 mass%, the mechanical properties such as flexural modulus tend to be poor when used for electronic boards, etc.

<Metal-clad laminate>
The metal-clad laminate of the present invention is a laminate in which the resin film or the prepreg is laminated with a metal foil. The laminate can be produced by stacking one or more of the resin films and/or prepregs on a substrate such as a metal foil, and then curing the thermosetting composition by press molding to form an insulating layer. It is also possible to use the resin-coated metal foil instead of the metal foil. The hot molding can be carried out, for example, at a temperature of 180°C to 240°C, a heating time of 30 minutes to 300 minutes, and a surface pressure of 20 kgf/ ^cm2 to 40 kgf/ ^cm2 .

The metal foil is not particularly limited, but examples include aluminum and copper foil, and among these, copper foil is preferred because of its low electrical resistance. The thickness of the metal foil that can be used is, for example, 1 to 50 μm.

The resin film and prepreg to be combined with the metal foil may be one or more sheets, and depending on the application, the metal foil is laminated on one or both sides to be processed into a laminate. Metal-clad laminates are particularly suitable for use as printed wiring boards.

<Printed Wiring Board>
The printed wiring board of the present invention is obtained by forming a circuit on the surface of the resin film or prepreg by partially removing the metal foil on the surface of the metal-clad laminate by etching or the like and forming wiring. The printed wiring board contains the thermosetting composition, and is therefore excellent in dielectric properties such as dielectric constant and dielectric loss tangent, moldability, and heat resistance.

In addition to the above, the thermosetting composition is used for molding, lamination, adhesives, composite materials such as copper-clad laminates, etc. In particular, when an isocyanate or epoxy body is used alone or in combination, typical applications include prepregs made from semi-cured resins and laminates made from cured prepregs. Also, when an epoxy body is used, typical applications include semiconductor encapsulation materials.

The present invention will be explained in detail below with reference to examples, but the present invention is not limited to the following examples in any way.

<Synthesis of alkylsilyl peroxide>
<Production Example 1, Synthesis of Compound 5>
In a 500 mL round-bottom flask, t-butyldimethylsilyl chloride (purity 99%, 90.43 g, 0.6 mol), toluene (74.50 g), and t-hexyl hydroperoxide (purity 85.0%, 74.45 g, 0.63 mol) were added and stirred. The solution was cooled to 15° C., and pyridine (purity 99%, 94.42 g, 1.20 mol) was added dropwise. After the dropwise addition, the solution was stirred for 1 hour, and the resulting solution was reduced and washed with an aqueous sodium sulfite solution and then washed with water. Thereafter, ^the solution was dehydrated using sodium sulfate and magnesium sulfate to obtain a toluene solution of t-butyldimethyl(t-hexylperoxy)silane (203.4 g, concentration 24.2% by mass, yield 35.3% by mass) represented by the above general formula (1) in which R ¹ and R ² are methyl groups, R 3 is a t-butyl group, and R ⁴ is a propyl group.

The structure of the alkylsilyl peroxide was identified by ¹ H-NMR measurement and ¹³ C-NMR measurement using an AVANCEN NMR spectrometer (manufactured by BRUCKER) and by TOFMS (manufactured by JEOL Ltd.). The purity was calculated by the simple area method using GC (Shimadzu Corporation GC-2014 series). The analytical results of the obtained compound 5 by EI-MS and ¹ H-NMR are shown in Table 1.

<Production Example 2, Synthesis of Compound 6>
The procedure was the same as in Production Example 1, except that t-hexyl hydroperoxide was changed to 1,1,3,3-tetramethylbutyl hydroperoxide. A toluene solution of t-butyldimethyl(1,3,3-tetramethylbutylperoxy)silane (186.46 g, concentration 31.3% by mass, yield 37.3% by mass) was obtained. The analytical results of the obtained compound 6 by EI-MS and ¹ H-NMR are shown in Table 1.

<Production Example 3, Synthesis of Compound 4>
The procedure was the same as in Production Example 1, except that t-hexyl hydroperoxide was changed to t-amyl hydroperoxide. A toluene solution of t-butyldimethyl(t-amylperoxy)silane (185.35 g, concentration 25.2% by mass, yield 35.7% by mass) was obtained. The analytical results of the obtained compound 4 by EI-MS and ¹ H-NMR are shown in Table 1.

<Production Example 4, Synthesis of Compound 13>
The procedure was the same as in Production Example 1, except that t-butyldimethylsilyl chloride was changed to triphenylsilyl chloride. A toluene solution of triphenyl(t-hexylperoxy)silane (328.1 g, concentration 24.3% by mass, yield 70.5% by mass) was obtained. The analytical results of the obtained compound 13 by EI-MS and ¹ H-NMR are shown in Table 1.

<Production Example 5, Synthesis of Compound 14>
The procedure was the same as in Production Example 1, except that t-butyldimethylsilyl chloride was changed to triphenylsilyl chloride and t-hexyl hydroperoxide was changed to 1,1,3,3-tetramethylbutyl hydroperoxide. A toluene solution of triphenyl(1,3,3-tetramethylbutylperoxy)silane (386.3 g, concentration 24.0% by mass, yield 76.3% by mass) was obtained. The analytical results of the obtained compound 14 by EI-MS and ¹ H-NMR are shown in Table 1.

<Production Example 6, Synthesis of Compound 12>
The procedure was the same as in Production Example 1, except that t-butyldimethylsilyl chloride was changed to triphenylsilyl chloride and t-hexyl hydroperoxide was changed to t-amyl hydroperoxide. A toluene solution of triphenyl(t-amylperoxy)silane (316.1 g, concentration 23.6% by mass, yield 68.5% by mass) was obtained. The analytical results of the obtained compound 12 by EI-MS and ¹ H-NMR are shown in Table 1.

<Production Example 7, Synthesis of Compound 16>
Dimethylaminopyridine (purity 99%, 122.17 g, 1.0 mol), tetrahydrofuran (201.35 g), and 2,5-dimethyl-2,5-di-t-butyl hydroperoxide (purity 75.5%, 62.56 g, 0.27 mol) were added to a 500 mL round-bottom flask and stirred. The solution was cooled to 15° C., and a solution of t-butyldimethylsilyl chloride (purity 99%, 90.43 g, 0.6 mol) in tetrahydrofuran (30.0 g) was added dropwise. After the end of the dropwise addition, the solution was stirred for 3 hours, and the resulting solution was reduced and washed with an aqueous sodium sulfite solution and then washed with water. Thereafter, the mixture was dehydrated using sodium sulfate and magnesium sulfate to obtain a toluene solution of 2,2,3,3,6,6,9,9,12,12,13,13-dodecamethyl-4,5,10,11-tetraoxa-3,12-disilatetradecane represented by the above general formula (2) in which R ⁵ and R ⁶ are methyl groups, R ⁷ is a t-butyl group, and R ⁸ is an ethylene group. The mixture was then isolated by silica gel column chromatography to obtain 2,2,3,3,6,6,9,9,12,12,13,13-dodecamethyl-4,5,10,11-tetraoxa-3,12-disilatetradecane (44.5 g, purity 99.9%, yield 21.9% by mass). The analytical results of the obtained compound 16 by EI-MS and ¹ H-NMR are shown in Table 1.

<Production Example 8, Synthesis of Compound 19>
The procedure was the same as in Production Example 1, except that t-butyldimethylsilyl chloride was changed to phenyldimethylsilyl chloride. A toluene solution of phenyldimethyl(t-hexylperoxy)silane (220.4 g, concentration 58.8% by mass, yield 70.2% by mass) was obtained. The analytical results of the obtained compound 19 by EI-MS and ¹ H-NMR are shown in Table 1.

<Evaluation of decomposition starting temperature>
As a DSC (differential scanning calorimeter), a "DSC-7000X" manufactured by Hitachi High-Tech Science Corporation was used. For the measurement, about 8 mg of the synthesis sample was placed in a SUS cell, and the temperature was raised from 50°C to 300°C at a heating rate of 10°C per minute under a nitrogen atmosphere. The decomposition onset temperature was taken as the intersection point of the original baseline of the DSC and the tangent at the inflection point. The measurement results of the decomposition onset temperatures (°C) of the dialkyl peroxides synthesized in Production Examples 1 to 7 are shown in Table 1. In addition, the results of di-t-butyl peroxide, di-t-hexyl peroxide, and 2,5-dimethyl-2,5-(di-t-butylperoxy)hexane are shown as reference examples for comparison with Production Examples 1 to 7.

The alkylsilyl peroxide in the manufacturing example has a high decomposition temperature, so the curing process of the thermosetting composition can be carried out efficiently at high temperatures.

<Evaluation of Volatility>
For the analysis, a TG-DTA6200 manufactured by SII NanoTechnology, Inc. (measurement conditions: Al cell, air atmosphere, temperature rise 30° C. (90° C./min)→80 (30 min), sample amount 15 mg) was used to measure the weight loss rate (%) of the dialkyl peroxides synthesized in Production Examples 5 and 7. The results are shown in Table 2.

<Examples 1 to 13 and Comparative Examples 1 to 6>
<Production of Cured Product and Evaluation of Dielectric Properties>
Each component (parts by mass) shown in Tables 3 and 4 was diluted with toluene to a concentration of 50% by mass, and 6 g of the solvent-dissolved composition was placed in an aluminum dish and dried at 400 Pa and 60°C for 2 hours using a vacuum dryer (EYELA VACUUM OVEN VOS-3LSD), and then further dried in the solvent at 80°C for 2 hours. The obtained powder was molded at 130°C using a hand press (manufactured by Toyo Seiki Co., Ltd.) and cured at 200°C to obtain a cured product (film, 16 cm circular, 60 μm thick). The dielectric constant and dielectric loss tangent at 1 GHz of the obtained cured product were measured according to a method conforming to IPC-TM-650-2.5.5.9, and are shown in Tables 3 and 4.

<Evaluation of heat resistance>
The glass transition temperature of the cured product was measured using a DSC (differential scanning calorimeter) "DSC-7000X" manufactured by Hitachi High-Tech Science Corporation. For the measurement, about 2 mg of the synthetic sample was placed in an Al cell, and the temperature was raised from 50°C to 350°C at a heating rate of 10°C per minute under a nitrogen atmosphere. The temperature was determined as the point where a straight line equidistant in the vertical direction from the straight line extending the low-temperature side and high-temperature side baselines intersects with the curve of the stepwise change in the glass transition. The results are shown in Tables 3 and 4.

In Tables 3 and 4, OPE-2St 2200 is polyphenylene ether having an average of two ethylenically unsaturated double bonds at the molecular terminals (number average molecular weight: 2200, manufactured by Mitsubishi Gas Chemical Company, Inc.);
OPE-2St 1200 is a polyphenylene ether having an average of two ethylenically unsaturated double bonds at the molecular terminals (number average molecular weight: 1200, manufactured by Mitsubishi Gas Chemical Company, Inc.);
SA9000 is a polyphenylene ether having an average of two ethylenically unsaturated double bonds at the molecular terminals (number average molecular weight is 2756, manufactured by SABIC Innovative Plastics);
BMI-1000 is maleimide, manufactured by Tokyo Chemical Industry Co., Ltd.;
BMI-5100 is maleimide, manufactured by Tokyo Chemical Industry Co., Ltd.;
Compound 5 is t-butyldimethyl(t-hexylperoxy)silane (concentration 24.2% by mass) of Production Example 1;
Compound 6 is t-butyldimethyl(1,3,3-tetramethylbutylperoxy)silane (concentration 31.3% by mass) of Production Example 2;
Compound 4 is t-butyldimethyl(t-amylperoxy)silane (concentration 25.2% by mass) of Production Example 3;
Compound 13 is triphenyl(t-hexylperoxy)silane (concentration 24.3% by mass) of Production Example 4;
Compound 14 is triphenyl(1,3,3-tetramethylbutylperoxy)silane (concentration 24.0% by mass) of Production Example 5;
Compound 12 is triphenyl(t-amylperoxy)silane (concentration 23.6% by mass) of Production Example 6;
Compound 16 is 2,2,3,3,6,6,9,9,12,12,13,13-dodecamethyl-4,5,10,11-tetraoxa-3,12-disilatetradecane of Production Example 7;
Compound 19 is phenyldimethyl(t-hexylperoxy)silane (concentration: 58.8% by mass) of Production Example 8;
Di-t-butyl peroxide was manufactured by NOF Corporation (purity 98%);
Di-t-hexyl peroxide was manufactured by NOF Corporation (purity 90%);
2,5-Dimethyl-2,5-(di-t-butylperoxy)hexane was manufactured by NOF Corporation (purity 94%);
TAIC (Triallyl Isocyanurate) is a product of Tokyo Chemical Industry Co., Ltd. (purity 96.0%).

Compared to Examples 1-11 and Comparative Examples 1-5, and to Examples 12-13 and Comparative Examples 6-7, cured products exhibiting superior physical properties were obtained.

Claims (8)

1. General formula (1):
   

   

   (In formula (1), R ¹ and R ² are independently an alkyl group or a phenyl group having 1 to 6 carbon atoms, R ³ is an alkyl group or a phenyl group having 3 to 6 carbon atoms, and R ⁴ is an alkyl group having 2 to 5 carbon atoms), and a compound represented by general formula (2):
   

   

   (in formula (2), R ⁵ and R ⁶ are independently an alkyl group having 1 to 6 carbon atoms or a phenyl group, R ⁷ is an alkyl group having 2 to 6 carbon atoms, and R ⁸ is an ethylene group or an acetylene group).
2. A thermosetting composition comprising the alkylsilyl peroxide according to claim 1 and a radical polymerizable compound.
3. The thermosetting composition according to claim 2, characterized in that the radical polymerizable compound is polyphenylene ether or maleimide.
4. A resin film formed from the thermosetting composition according to claim 3.
5. A prepreg in which the thermosetting composition according to claim 3 is impregnated or coated on a fibrous substrate.
6. A metal-clad laminate comprising the resin film according to claim 4 or the prepreg according to claim 5 laminated with a metal foil.
7. A printed wiring board characterized in that a portion of the metal foil is removed from the metal-clad laminate described in claim 6.
8. A method for producing the alkylsilyl peroxide according to claim 1, comprising the steps of:
   A method for producing an alkylsilyl peroxide, comprising a step of reacting a silyl chloride compound with a hydroperoxide compound as raw materials.