Flame retardant, resin composition, prepreg, resin-equipped film, resin-equipped metal foil, metal-clad laminate, and wiring board

Abstract

One aspect of the present invention relates to a flame retardant which comprises a phosphorus compound represented by formula (1).　(In formula (1), A and B each independently indicate a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide structure or a diphenylphosphine oxide structure, and X indicates a straight-chain bond which includes not less than two benzene rings and not less than two oxygen atoms.)

Description

Flame retardant, resin composition, prepreg, resin-coated film, resin-coated metal foil, metal-clad laminate, and wiring board

[0001] The present invention relates to a flame retardant, a resin composition, a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board.

[0002] As the amount of information processed increases in various electronic devices, advances in packaging technologies, such as higher integration of semiconductor devices, higher wiring density, and multi-layering, are being made. Furthermore, wiring boards used in various electronic devices are required to be high-frequency compatible, such as millimeter-wave radar boards for automotive applications. To meet this requirement, substrate materials for constituting the substrates of wiring boards used in various electronic devices are required to have excellent low-dielectric properties, such as low dielectric constants and dielectric loss tangents. Furthermore, molding materials, such as substrate materials, are required to have not only excellent low-dielectric properties but also excellent heat resistance, etc.

[0003] Examples of such substrate materials include the resin composition described in Patent Document 1. Patent Document 1 discloses a resin composition containing a modified polyphenylene ether compound and an acenaphthylene compound. Patent Document 1 discloses that by using the resin composition, it is possible to obtain a cured product that has low dielectric properties and high heat resistance, and that can favorably maintain its low dielectric properties even after a water absorption treatment.

[0004] On the other hand, wiring boards used in various electronic devices are also required to have excellent flame retardancy. A commonly known method for achieving flame retardancy is to improve flame retardancy by adding a halogen-based flame retardant, such as a bromine-based flame retardant, or a halogen-containing compound, such as a halogen-containing epoxy resin, to a resin composition used as a molding material, such as a substrate material.

[0005] However, resin compositions containing halogen-containing compounds as flame retardants contain halogens in the cured product, which may generate harmful substances such as hydrogen halides upon combustion, raising concerns that they may have adverse effects on the human body and the natural environment, etc. Against this background, molding materials such as substrate materials are being demanded to be halogen-free, i.e., halogen-free.

[0006] As halogen-free flame retardants, phosphorus compounds containing a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) structure or a diphenylphosphine oxide (DPPO) structure have been proposed because these structures are effective in imparting flame retardancy.

[0007] For example, Patent Documents 2 and 3 disclose flame retardants having at least one of a DOPO structure and a DPPO structure.

[0008] In recent years, in resin compositions used as molding materials such as substrate materials, flame retardants added to the main components as described in Patent Document 1 are required to have flame retardancy superior to that of the conventional flame retardants described in Patent Documents 2 and 3.

[0009] The present invention has been made in view of the above circumstances, and an object thereof is to provide a halogen-free flame retardant having excellent flame retardancy, and a resin composition obtainable using the flame retardant, as well as a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board obtainable using the resin composition.

[0010] International Publication No. 2020 / 017399 U.S. Patent No. 10,626,250 U.S. Patent Application Publication No. 2020 / 0208057

[0011] As a result of intensive research conducted by the present inventors to solve the above problems, they succeeded in synthesizing a novel phosphorus compound and found that this novel phosphorus compound can be used as a desired flame retardant.

[0012] A flame retardant according to one embodiment of the present invention contains a phosphorus compound represented by the following formula (1):

[0013]

[0014] In formula (1), A and B each independently represent a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide structure or a diphenylphosphine oxide structure, and X represents a linear bond containing two or more benzene atoms and two or more oxygen atoms.

[0015] A resin composition according to another aspect of the present invention includes the flame retardant and a polyfunctional vinyl aromatic copolymer.

[0016] FIG. 1 shows the phosphorus compound A obtained in Example 1. １ 2 is a MALDI-TOF-MS spectrum of phosphorus compound A obtained in Example 1. FIG. 3 is a MALDI-TOF-MS spectrum of phosphorus compound B obtained in Example 1. １ 4 is a H-NMR spectrum of the phosphorus compound C obtained in Example 2. １ 5 is a H-NMR spectrum of the phosphorus compound C obtained in Example 2. １ 6 is an enlarged view of the H-NMR spectrum of the phosphorus compound D′ obtained in Example 3. １ 7 is a H-NMR spectrum of the phosphorus compound D′ obtained in Example 3. １ 8 is an enlarged view of a H-NMR spectrum. Fig. 8 is a view showing the results of an MCC test for the plate-shaped resin compositions of Examples 1 to 3 and Comparative Examples 1 to 3.

[0017] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these.

[0018] [Flame Retardant] The flame retardant according to the present embodiment is not particularly limited as long as it contains a phosphorus compound represented by the following formula (1).

[0019]

[0020] In the formula (1), A and B each independently represent a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide structure or a diphenylphosphine oxide structure, and X represents a linear bond containing two or more benzene atoms and two or more oxygen atoms.

[0021] According to this configuration, a halogen-free flame retardant having excellent flame retardancy can be provided. Furthermore, according to the present invention, by using the flame retardant, a resin composition having excellent flame retardancy can be provided. Furthermore, according to the present invention, by using the resin composition, a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board having excellent flame retardancy can be provided.

[0022] The phosphorus compound contained in the flame retardant of this embodiment is bonded by a linear bond X in which the structures represented by A and B contain two or more benzenes and two or more oxygen atoms, as represented by formula (1), and therefore the flame retardant can exhibit excellent flame retardancy. Furthermore, the phosphorus compound has a high decomposition temperature, and therefore the chemical structure of the phosphorus compound is unlikely to change even when the flame retardant containing the phosphorus compound is used at high temperatures, which is advantageous in that it is easy to handle even at high temperatures.

[0023] In this embodiment, the decomposition temperature is measured by the TG-DTA measurement method described in the Examples below. Specifically, for example, the decomposition temperature can be measured by heating a measurement sample from 25°C to 500°C at a temperature increase rate of 10°C / min under a nitrogen flow of 200 mL / min using a differential thermal thermogravimetry analyzer (such as Thermo plus EVO2 TG-DTA8122, manufactured by Rigaku Corporation).

[0024] X in the formula (1) is explained below. X in the formula (1) represents a linear bond containing two or more benzenes and two or more oxygen atoms. In this specification, "a linear bond containing two or more benzenes and two or more oxygen atoms" means that the two or more benzenes and the two or more oxygen atoms are connected in a straight line, and that the two or more benzenes are all disubstituted and unbranched. The two or more benzenes may each be ortho-, meta-, or para-disubstituted, but are preferably para-disubstituted. The benzene and the benzene, the benzene and the oxygen atom, and the oxygen atom and the oxygen atom may be bonded directly or via a linear hydrocarbon group.

[0025] When X in the formula (1) is a linear bond containing two or more benzenes and two or more oxygen atoms, the decomposition temperature of the phosphorus compound is increased. This is thought to be due to the following reasons. For example, when the benzene in the molecule is branched, as in the flame retardant described in Patent Document 3, the presence of small molecules at the branched portion causes the molecule to decompose at low temperatures. On the other hand, because X in the formula (1) is a linear bond, small molecules do not decompose from the branched portion at low temperatures, and the decomposition temperature is higher than when the benzene in the molecule is branched. Therefore, the flame retardant containing the phosphorus compound has a high decomposition temperature and is less likely to change chemical structure even when used at high temperatures, which has the advantage of being easy to handle even at high temperatures.

[0026] In the formula (1), X is a linear bond containing two or more benzene groups and two or more oxygen atoms, which contributes significantly to stacking interactions. This has the advantage of increasing the melting point of the phosphorus compound. If the melting point of the phosphorus compound is high, the flame retardant is less likely to dissolve when added to a resin and subjected to press or reflow soldering tests.

[0027] When X in formula (1) has two or more benzenes, the decomposition temperature of the phosphorus compound increases, and the chemical structure of the phosphorus compound is less likely to change even when the flame retardant containing the phosphorus compound is used at high temperatures, which is advantageous in that the phosphorus compound is easy to handle even at high temperatures. This is thought to be because benzene has stronger bonds than aliphatic hydrocarbons.

[0028] In addition, in the formula (1), from the viewpoint of increasing the intramolecular phosphorus concentration of the phosphorus compound, the number of benzene groups in X is preferably 7 or less, and more preferably 5 or less.

[0029] Preferably, the number of the benzene atom and the number of the oxygen atom are both 2. With this configuration, the phosphorus concentration in the molecule of the phosphorus compound can be increased, and the flame retardant can more reliably obtain excellent flame retardancy.

[0030] It is preferable that at least one of A and X, and B and X in formula (1) be bonded via a P(phosphorus)-O(oxygen) bond. It is more preferable that both A and X, and B and X in formula (1) be bonded via a P(phosphorus)-O(oxygen) bond. The P(phosphorus)-O(oxygen) bond is stronger than the P(phosphorus)-C(carbon) bond present in the molecule of conventional flame retardants, as described in, for example, Patent Document 2. Therefore, when at least one of A and X, and B and X are bonded via a P(phosphorus)-O(oxygen) bond, the phosphorus compound requires more energy for decomposition, resulting in a higher decomposition temperature. Therefore, when the phosphorus compound has the P(phosphorus)-O(oxygen) bond described above in its molecule, the decomposition temperature of the flame retardant is higher, and the chemical structure of the phosphorus compound is less likely to change even when the flame retardant is used at high temperatures, making it easier to handle even at high temperatures.

[0031] In the formula (1), A and B each independently represent a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide structure or a diphenylphosphine oxide structure. The 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) structure is a molecular structure represented by the following formula (2). The diphenylphosphine oxide (DPPO) structure is a molecular structure represented by the following formula (3). In the molecular structures represented by the following formulas (2) and (3), a hydrogen atom bonded to the aromatic ring may be substituted with a functional group such as an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group.

[0032]

[0033]

[0034] In the formula (1), it is preferable that either A or B represents a functional group having a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide structure. This configuration has the advantage that the melting point of the flame retardant is high, and the flame retardant is less likely to dissolve even when added to a resin and subjected to press or reflow soldering tests. The reason for this can be explained from the perspective of structural calculations. The DOPO structure is a planar structure, while the DPPO structure is a three-dimensionally expanded structure. Therefore, compounds with a large number of DOPO structures in the molecule have a high melting point due to stacking interactions.

[0035] The phosphorus concentration in the phosphorus compound is preferably 5 to 11 parts by mass relative to 100 parts by mass of the phosphorus compound, and such a configuration can more reliably obtain excellent flame retardancy. The phosphorus concentration in the phosphorus compound is more preferably 8 to 11 parts by mass, and even more preferably 9.5 to 11 parts by mass, relative to 100 parts by mass of the phosphorus compound.

[0036] More specific examples of the phosphorus compound include phosphorus compounds represented by the following formulas (4) to (13).

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047] The phosphorus compounds may be used alone or in combination as a flame retardant.

[0048] The content of the phosphorus compound is preferably 10 to 100 parts by mass, more preferably 30 to 100 parts by mass, and even more preferably 50 to 100 parts by mass, relative to 100 parts by mass of the flame retardant. By having the content of the phosphorus compound be 10 to 100 parts by mass relative to 100 parts by mass of the flame retardant, excellent flame retardancy can be more reliably obtained.

[0049] The method for producing the phosphorus compound is not particularly limited as long as it can produce the phosphorus compound, and known methods can be used. For example, the phosphorus compound represented by formula (4) can be produced by the reactions shown in Scheme 1 and Scheme 2 below. Specifically, first, the phosphorus compound represented by formula (14) is produced by the reaction shown in Scheme 1 below. Then, the phosphorus compound represented by formula (4) can be obtained by the reaction shown in Scheme 2 below using the obtained phosphorus compound represented by formula (14). Furthermore, for example, the phosphorus compound represented by formula (5) can be produced by the reaction shown in Scheme 3 below. Furthermore, for example, the phosphorus compound represented by formula (6) can be produced by the reaction shown in Scheme 4 below. More specifically, the phosphorus compounds represented by formulas (4) to (6) can be obtained by the methods described in the Examples below.

[0050]

[0051]

[0052]

[0053]

[0054] [Resin Composition] The resin composition according to this embodiment contains the flame retardant and a polyfunctional vinyl aromatic copolymer.

[0055] By including the flame retardant in the resin composition, a resin composition having excellent flame retardancy can be obtained. Specifically, since the molecular structure of the phosphorus compound included in the flame retardant is stable, the heat of combustion (heat generation) in the combustion reaction of the flame retardant is small. Therefore, a resin composition containing the flame retardant has a low peak heat release value (Peak HRR) measured by, for example, a micro-cone calorimeter (MCC) test. In other words, the flame retardant can suppress the combustion of components other than the flame retardant in the resin composition. In this embodiment, the Peak HRR measured by the MCC test can be measured by the method described in the Examples below.

[0056] Furthermore, since the flame retardant has a high decomposition temperature as described above, a resin composition containing the flame retardant has the advantage that the chemical structure of the phosphorus compound is unlikely to change even when used at high temperatures, making it easy to handle at high temperatures.

[0057] (Polyfunctional vinyl aromatic copolymer) The polyfunctional vinyl aromatic copolymer of this embodiment is not particularly limited as long as it is a polyfunctional vinyl aromatic copolymer containing a repeating unit (a) derived from a divinyl aromatic compound.Preferably, the polyfunctional vinyl aromatic copolymer contains the repeating unit (a) derived from the divinyl aromatic compound and the repeating unit (b) derived from a monovinyl aromatic compound.

[0058] More specifically, for example, the polyfunctional vinyl aromatic polymer used in the resin composition of the present embodiment has repeating units (a) derived from a divinyl aromatic compound and repeating units (b) derived from a monovinyl aromatic compound, and when the sum of the repeating units (a) and the repeating units (b) is taken as 100 mol %, the polyfunctional vinyl aromatic polymer contains 2 mol % or more and less than 95 mol % of the repeating units (a) and 5 mol % or more and less than 98 mol % of the repeating units (b).

[0059] The polyfunctional vinyl aromatic copolymer preferably further contains a repeating unit (a1) represented by the following formula (15) as part of the repeating unit (a) derived from the divinyl aromatic compound.

[0060]

[0061] In formula (15), R １ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms.

[0062] Preferred examples of the polyfunctional vinyl aromatic copolymer include soluble polyfunctional vinyl aromatic copolymers in which the molar fraction of the repeating unit (a1) in the sum of the repeating units (a) and (b) satisfies the following formula (16): 0.02≦(a1) / [(a)+(b)]≦0.8 (16), the number average molecular weight is 300 to 100,000, the molecular weight distribution expressed as the ratio of the weight average molecular weight to the number average molecular weight is 100.0 or less, and the copolymer is soluble in toluene, xylene, tetrahydrofuran, dichloroethane, or chloroform. Hereinafter, the soluble polyfunctional vinyl aromatic copolymer will also be referred to simply as "copolymer."

[0063] The soluble polyfunctional vinyl aromatic copolymer contains 2 mol % or more but less than 95 mol % of the repeating unit (a) and 5 mol % or more but less than 98 mol % of the repeating unit (b), where the total of the repeating units (a) and (b) is taken as 100 mol %, and preferably contains 2 to 80 mol % of the repeating unit (a1).

[0064] The soluble polyfunctional vinyl aromatic copolymer preferably has a number average molecular weight Mn of 300 to 100,000, a molecular weight distribution expressed as the ratio of the weight average molecular weight Mw to the number average molecular weight Mn (Mw / Mn) of 100.0 or less, and is preferably soluble in toluene, xylene, tetrahydrofuran, dichloroethane, or chloroform.

[0065] The soluble polyfunctional vinyl aromatic copolymer is not limited, but examples thereof include copolymers containing structural units derived from a repeating unit (b) derived from the monovinyl aromatic compound represented by the following formula (17) and a repeating unit (a) derived from the divinyl aromatic compound, etc., represented by the following formulas (18) and (19): These structural units may be arranged regularly or randomly.

[0066]

[0067]

[0068]

[0069] In the formula (17), R ２ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms derived from the monovinyl aromatic compound, and in the formulas (18) and (19), R １ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms derived from the divinyl aromatic compound, and in the formulas (17) to (19), h to k each independently represent an integer of 0 to 200, provided that the total of these is 2 to 20,000.

[0070] Suitable soluble polyfunctional vinyl aromatic copolymers include, for example, those represented by the formulas (17) to (19) above, where R １ and R ２ and copolymers comprising repeating units which are aromatic hydrocarbon groups selected from the group consisting of an optionally substituted phenyl group, an optionally substituted biphenyl group, an optionally substituted naphthalene group, and an optionally substituted terphenyl group.

[0071] The soluble polyfunctional vinyl aromatic copolymer is preferably solvent-soluble. The repeating units referred to in this specification are derived from monomers and include units that are present and appear repeatedly in the main chain of the copolymer, as well as units or terminal groups present at the end or side chain. Repeating units are also referred to as structural units. The terminal groups referred to in this specification include those derived from the above-mentioned monomers as well as terminal groups derived from the chain transfer agent described below.

[0072] The structural unit (a) derived from a divinylaromatic compound is contained in an amount of 2 mol% or more but less than 95 mol% of the total of the structural units (b) derived from the divinylaromatic compound and the monovinyl aromatic compound. The structural unit (a) derived from the divinylaromatic compound can have a variety of structures, such as those in which only one of two vinyl groups has reacted or those in which two have reacted. Of these, the repeating unit represented by the formula (a1) in which only one vinyl group has reacted preferably accounts for 2 to 80 mol%, more preferably 5 to 70 mol%, even more preferably 10 to 60%, and particularly preferably 15 to 50% of the total. A content of 2 to 80 mol% is believed to result in a low dielectric loss tangent, high toughness, excellent heat resistance, and excellent compatibility with other resins. When the repeating unit (a1) represented by the formula (15) in which only one vinyl group has reacted is less than 2 mol% of the total, heat resistance tends to decrease, while when it exceeds 80 mol%, interlayer peel strength tends to decrease when the laminate is formed.

[0073] The soluble polyfunctional vinyl aromatic copolymer contains the structural unit (b) derived from the monovinyl aromatic compound in an amount of 5 mol% or more and less than 98 mol% based on the total amount. More preferably, it contains 10 mol% or more and less than 90 mol%. Even more preferably, it contains 15 mol% or more and less than 85 mol%. If the structural unit (b) derived from the monovinyl aromatic compound is less than 5 mol% based on the total amount, moldability may be insufficient, and if it exceeds 98 mol%, the heat resistance of the cured product may be insufficient.

[0074] The vinyl group present in the above formula (15) acts as a cross-linking component and contributes to the development of heat resistance of the soluble polyfunctional vinyl aromatic copolymer.On the other hand, the structural unit (b) derived from a monovinyl aromatic compound does not have a vinyl group, since it is generally believed that polymerization proceeds through a 1,2-addition reaction of the vinyl group.In other words, the structural unit (b) derived from a monovinyl aromatic compound does not act as a cross-linking component, but contributes to the development of moldability.

[0075] Styrene is a preferred example of the monovinyl aromatic compound. Furthermore, a monovinyl aromatic compound other than styrene can also be used together with styrene. In this case, when the total content of the structural unit (b1) derived from styrene and the structural unit (b2) derived from a monovinyl aromatic compound other than styrene is taken as 100 mol%, the content of the structural unit (b1) derived from styrene is preferably 99 to 20 mol%, more preferably 98 to 30 mol%. A content of (b1) within the above range is preferred because it combines thermal oxidative degradation resistance and moldability. When the structural unit (b1) is greater than 99 mol%, heat resistance tends to decrease, and when the structural unit (b2) is greater than 80 mol%, moldability tends to decrease.

[0076] The number average molecular weight of the soluble polyfunctional vinyl aromatic copolymer (number average molecular weight measured using GPC in terms of standard polystyrene) is preferably 300 to 100,000, more preferably 400 to 50,000, and even more preferably 500 to 10,000. If Mn is less than 300, the amount of monofunctional copolymer component contained in the soluble polyfunctional vinyl aromatic copolymer increases, and the heat resistance of the cured product tends to decrease. If Mn is more than 100,000, gel tends to be easily formed and the viscosity increases, and therefore molding processability tends to decrease.

[0077] The soluble polyfunctional vinyl aromatic copolymer has a molecular weight distribution (Mw / Mn) expressed as the ratio of the weight average molecular weight (weight average molecular weight measured using GPC in terms of standard polystyrene) to Mn of 100.0 or less, preferably 50.0 or less, more preferably 1.5 to 30.0, and most preferably 2.0 to 20.0. If Mw / Mn exceeds 100.0, the processability of the soluble polyfunctional vinyl aromatic copolymer tends to deteriorate and gel tends to form.

[0078] The soluble polyfunctional vinyl aromatic copolymer is soluble in toluene, xylene, tetrahydrofuran, dichloroethane or chloroform as a solvent, and is preferably soluble in any of the above-mentioned solvents.To be a solvent-soluble polyfunctional copolymer, it is necessary that a part of the vinyl group of divinylbenzene remains uncrosslinked and has an appropriate degree of crosslinking.Here, soluble in a solvent means that the soluble polyfunctional vinyl aromatic copolymer dissolves in 100g of the solvent in an amount of 5g or more, preferably 30g or more, more preferably 50g or more.

[0079] The divinyl aromatic compound serves to form a branched structure to impart multifunctionality, and also serves as a cross-linking component to impart heat resistance when the resulting soluble multifunctional vinyl aromatic copolymer is thermally cured. Examples of divinyl aromatic compounds are not limited as long as they are aromatic compounds having two vinyl groups, but preferred examples include divinylbenzene (including positional isomers or mixtures thereof), divinylnaphthalene (including positional isomers or mixtures thereof), and divinylbiphenyl (including positional isomers or mixtures thereof). These compounds may be used alone or in combination of two or more. From the viewpoint of moldability, divinylbenzene (m-isomer, p-isomer, or a mixture of positional isomers thereof) is more preferred.

[0080] Examples of the monovinyl aromatic compound include styrene and monovinyl aromatic compounds other than styrene, but it is preferable to use styrene as an essential component and to use a monovinyl aromatic compound other than styrene in combination.

[0081] Styrene, as a monomer component, serves to impart low dielectric properties and thermal oxidation resistance to the soluble polyfunctional vinyl aromatic copolymer, and also serves as a chain transfer agent to control the molecular weight of the soluble polyfunctional vinyl aromatic copolymer. In addition, the monovinyl aromatic compound other than styrene improves the solvent solubility and processability of the soluble polyfunctional vinyl aromatic copolymer.

[0082] Examples of monovinyl aromatic compounds other than styrene include, but are not limited to, aromatic compounds other than styrene having one vinyl group, such as vinyl aromatic compounds such as 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. Ethylvinylbenzene (including each positional isomer or a mixture thereof), ethylvinylbiphenyl (including each positional isomer or a mixture thereof), or ethylvinylnaphthalene (including each positional isomer or a mixture thereof) are preferred because they prevent gelation of the soluble polyfunctional vinyl aromatic copolymer, are highly effective in improving solvent solubility and processability, are low cost, and are easily available. More preferred is ethylvinylbenzene (m-isomer, p-isomer, or a mixture of these positional isomers) from the viewpoints of dielectric properties and cost.

[0083] In addition to the divinyl aromatic compound and the monovinyl aromatic compound, one or more other monomer components such as a trivinyl aromatic compound, a trivinyl aliphatic compound, a divinyl aliphatic compound, or a monovinyl aliphatic compound may be used, and structural units (c) derived from these may be introduced into the soluble polyfunctional vinyl aromatic copolymer, provided that the effects of the present invention are not impaired.

[0084] Examples of the other monomer components include 1,3,5-trivinylbenzene, 1,3,5-trivinylnaphthalene, 1,2,4-trivinylcyclohexane, ethylene glycol diacrylate, butadiene, 1,4-butanediol divinyl ether, cyclohexanedimethanol divinyl ether, diethylene glycol divinyl ether, triallyl isocyanurate, etc. These can be used alone or in combination of two or more.

[0085] The molar fraction of the other monomer component relative to the sum of all monomer components is preferably less than 30 mol %. In other words, the molar fraction of the repeating unit (c) derived from the other monomer component relative to the sum of the structural units (a), (b), and (c) derived from all monomer components constituting the copolymer is preferably less than 30 mol %.

[0086] The soluble polyfunctional vinyl aromatic copolymer can be obtained by polymerizing a monomer containing the divinyl aromatic compound and the monovinyl aromatic compound in the presence of a Lewis acid catalyst. Furthermore, a known chain transfer agent (CTR) can be added during the polymerization to control the molecular weight.

[0087] (Modified Polyphenylene Ether) The resin composition preferably further contains a modified polyphenylene ether compound terminally modified with a substituent having a carbon-carbon unsaturated double bond. By further containing the polyphenylene ether compound in the resin composition, heat resistance of the thermoset resin composition can be obtained. The modified polyphenylene ether compound is not particularly limited as long as it is a modified polyphenylene ether compound terminally modified with a substituent having a carbon-carbon unsaturated double bond.

[0088] The substituent having a carbon-carbon unsaturated double bond is not particularly limited, and examples of the substituent include a substituent represented by the following formula (20) and a substituent represented by the following formula (21).

[0089]

[0090] In formula (20), p represents an integer of 0 to 10. Ａ represents an arylene group. ３ ~R ５ are independent of each other. That is, R ３ ~R ５ may be the same group or different groups. ３ ~R ５ represents a hydrogen atom or an alkyl group.

[0091] In addition, in formula (20), when p is 0, ZＡ is directly bonded to the end of the polyphenylene ether.

[0092] The arylene group is not particularly limited. Examples of the arylene group include monocyclic aromatic groups such as a phenylene group, and polycyclic aromatic groups in which the aromatic ring is not monocyclic but is polycyclic, such as a naphthalene ring. The arylene group also includes derivatives in which a hydrogen atom bonded to the aromatic ring is substituted with a functional group such as an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group. The alkyl group is not particularly limited, and is preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

[0093]

[0094] In formula (21), R ６ represents a hydrogen atom or an alkyl group. The alkyl group is not particularly limited, and is preferably, for example, an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

[0095] Preferred specific examples of the substituent represented by formula (21) include, for example, a substituent containing a vinylbenzyl group. Examples of the substituent containing a vinylbenzyl group include, for example, a substituent represented by formula (22) below. Furthermore, examples of the substituent represented by formula (21) include an acrylate group and a methacrylate group.

[0096]

[0097] More specific examples of the substituent include vinylbenzyl groups (ethenylbenzyl groups) such as p-ethenylbenzyl and m-ethenylbenzyl groups, vinylphenyl groups, acrylate groups, and methacrylate groups.

[0098] The modified polyphenylene ether compound has a polyphenylene ether chain in the molecule, and preferably has, for example, a repeating unit represented by the following formula (23) in the molecule.

[0099]

[0100] In formula (23), t represents 1 to 50. ７ ~R １０ are independent of each other. That is, R ７ ~R １０ may be the same group or different groups. ７ ~R １０ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group, among which a hydrogen atom and an alkyl group are preferred.

[0101] R ７ ~R １０ Specific examples of the functional groups mentioned in the above include the following:

[0102] The alkyl group is not particularly limited, but is preferably an alkyl group having 1 to 18 carbon atoms, and more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

[0103] The alkenyl group is not particularly limited, but is preferably an alkenyl group having 2 to 18 carbon atoms, and more preferably an alkenyl group having 2 to 10 carbon atoms. Specific examples include a vinyl group, an allyl group, and a 3-butenyl group.

[0104] The alkynyl group is not particularly limited, but is preferably an alkynyl group having 2 to 18 carbon atoms, and more preferably an alkynyl group having 2 to 10 carbon atoms. Specific examples include an ethynyl group and a prop-2-yn-1-yl group (propargyl group).

[0105] The alkylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkyl group, but for example, an alkylcarbonyl group having 2 to 18 carbon atoms is preferred, and an alkylcarbonyl group having 2 to 10 carbon atoms is more preferred. Specific examples include an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a pivaloyl group, a hexanoyl group, an octanoyl group, and a cyclohexylcarbonyl group.

[0106] The alkenylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkenyl group, but for example, an alkenylcarbonyl group having 3 to 18 carbon atoms is preferred, and an alkenylcarbonyl group having 3 to 10 carbon atoms is more preferred. Specific examples include an acryloyl group, a methacryloyl group, and a crotonoyl group.

[0107] The alkynylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkynyl group, but for example, an alkynylcarbonyl group having 3 to 18 carbon atoms is preferred, and an alkynylcarbonyl group having 3 to 10 carbon atoms is more preferred. Specific examples include a propioloyl group.

[0108] The weight-average molecular weight (Mw) of the modified polyphenylene ether compound is not particularly limited. Specifically, it is preferably 500 to 5,000, more preferably 800 to 4,000, and even more preferably 1,000 to 3,000. The weight-average molecular weight may be measured by a general molecular weight measurement method, specifically, a value measured using gel permeation chromatography (GPC) or the like. Furthermore, when the modified polyphenylene ether compound has a repeating unit represented by the formula (23) in the molecule, t is preferably a value such that the weight-average molecular weight of the modified polyphenylene ether compound falls within this range. Specifically, t is preferably 1 to 50.

[0109] Examples of the modified polyphenylene ether compound include a modified polyphenylene ether compound represented by the following formula (24) and a modified polyphenylene ether compound represented by the following formula (25). As the modified polyphenylene ether compound, these modified polyphenylene ether compounds may be used alone, or these two types of modified polyphenylene ether compounds may be used in combination.

[0110]

[0111]

[0112] In formula (24) and formula (25), R １１ ~R １８ and R １９ ~R ２６ each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group. W １ and W ２ each independently represents a substituent having a carbon-carbon unsaturated double bond. D and E represent repeating units represented by the following formulas (26) and (27), respectively. In addition, in formula (25), Y represents a linear, branched, or cyclic hydrocarbon having 20 or less carbon atoms.

[0113]

[0114]

[0115] In the formulas (26) and (27), m and n each represent an integer of 0 to 20. ２７ ~R ３０ and R ３１ ~R ３４ each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group.

[0116] The modified polyphenylene ether compound represented by the formula (24) and the modified polyphenylene ether compound represented by the formula (25) are not particularly limited as long as they satisfy the above-mentioned constitution. Specifically, in the formula (24) and the formula (25), R １１ ~R １８ and R １９ ~R ２６ As described above, each of R is independent. １１ ~R １８ and R １９ ~R ２６ may be the same group or different groups. １１ ~R １８ and R １９ ~R ２６ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group, among which a hydrogen atom and an alkyl group are preferred.

[0117] In formula (26) and formula (27), m and n each preferably represent a value of 0 to 20, as described above. Furthermore, it is preferable that m and n represent a numerical value such that the sum of m and n is 1 to 30. Therefore, it is more preferable that m represents a value of 0 to 20, n represents a value of 0 to 20, and the sum of m and n represents a value of 1 to 30. Furthermore, R ２７ ~R ３０ and R ３１ ~R ３４ are independent of each other. That is, R ２７ ~R ３０ and R ３１ ~R ３４ may be the same group or different groups. ２７ ~R ３０ and R ３１ ~R ３４ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group, among which a hydrogen atom and an alkyl group are preferred.

[0118] R １１ ~R３４ is R in the above formula (23). ７ ~R １０ is the same as

[0119] In the formula (25), as described above, Y is a linear, branched, or cyclic hydrocarbon having 20 or less carbon atoms. Examples of Y include a group represented by the following formula (28).

[0120]

[0121] In the formula (28), R ３５ and R ３６ are each independently a hydrogen atom or an alkyl group. Examples of the alkyl group include a methyl group. Examples of the group represented by formula (28) include a methylene group, a methylmethylene group, and a dimethylmethylene group, and among these, a dimethylmethylene group is preferred.

[0122] In the formula (24) and the formula (25), W １ and W ２ are each independently a substituent having a carbon-carbon unsaturated double bond. １ and W ２ There are no particular limitations on the substituent W as long as it is a substituent having a carbon-carbon unsaturated double bond. １ and W ２ Examples of the substituent include a substituent represented by the formula (20) and a substituent represented by the formula (21). In the modified polyphenylene ether compound represented by the formula (24) and the modified polyphenylene ether compound represented by the formula (25), W １ and W ２ may be the same substituent or different substituents.

[0123] More specific examples of the modified polyphenylene ether compound represented by the formula (24) include modified polyphenylene ether compounds represented by the following formula (29).

[0124]

[0125] More specific examples of the modified polyphenylene ether compound represented by the formula (25) include a modified polyphenylene ether compound represented by the following formula (30) and a modified polyphenylene ether compound represented by the following formula (31).

[0126]

[0127]

[0128] In the formulas (29) to (31), m and n have the same meaning as m and n in the formulas (26) and (27), and are independently 0 to 20. In addition, in the formulas (29) and (30), R ３ ~R ５ , p and Z Ａ is R in the above formula (20). ３ ~R ５ , p and Z Ａ In the above formula (30) and formula (31), Y is the same as Y in the above formula (25). In the above formula (31), R ６ is R in the above formula (21). ６ is the same as

[0129] The method for synthesizing the modified polyphenylene ether compound used in the present embodiment is not particularly limited as long as it is possible to synthesize a modified polyphenylene ether compound terminally modified with a substituent having a carbon-carbon unsaturated double bond. Specific examples include a method of reacting polyphenylene ether with a compound in which a substituent having a carbon-carbon unsaturated double bond and a halogen atom are bonded.

[0130] Examples of compounds in which a substituent having a carbon-carbon unsaturated double bond is bonded to a halogen atom include compounds in which a substituent represented by the formulas (20) to (22) is bonded to a halogen atom. Specific examples of the halogen atom include a chlorine atom, a bromine atom, an iodine atom, and a fluorine atom, with a chlorine atom being preferred. More specific examples of compounds in which a substituent having a carbon-carbon unsaturated double bond is bonded to a halogen atom include p-chloromethylstyrene and m-chloromethylstyrene.

[0131] The polyphenylene ether used as a raw material is not particularly limited as long as it can ultimately synthesize a predetermined modified polyphenylene ether compound. Specific examples include polyphenylene ethers composed of 2,6-dimethylphenol and at least one of a bifunctional phenol and a trifunctional phenol, and compounds containing polyphenylene ether as a main component, such as poly(2,6-dimethyl-1,4-phenylene oxide). A bifunctional phenol is a phenolic compound having two phenolic hydroxyl groups per molecule, such as tetramethylbisphenol A. A trifunctional phenol is a phenolic compound having three phenolic hydroxyl groups per molecule.

[0132] (Curing Agent) The resin composition preferably further contains a curing agent. This configuration has the advantage of providing excellent heat resistance in the thermoset resin composition. The curing agent is not particularly limited as long as it can react with the polyfunctional vinyl aromatic copolymer to cure the resin composition containing the polyfunctional vinyl aromatic copolymer. Examples of the curing agent include curing agents having at least one functional group in the molecule that contributes to the reaction with the polyfunctional vinyl aromatic copolymer. Examples of the curing agent include styrene, styrene derivatives, compounds having an acryloyl group in the molecule, compounds having a methacryloyl group in the molecule, compounds having a vinyl group in the molecule, compounds having an allyl group in the molecule, compounds having a maleimide group in the molecule, and compounds having an acenaphthylene structure in the molecule.

[0133] Examples of the styrene derivatives include bromostyrene and dibromostyrene.

[0134] The compound having an acryloyl group in the molecule is an acrylate compound. Examples of the acrylate compound include a monofunctional acrylate compound having one acryloyl group in the molecule and a polyfunctional acrylate compound having two or more acryloyl groups in the molecule. Examples of the monofunctional acrylate compound include methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate. Examples of the polyfunctional acrylate compound include tricyclodecane dimethanol diacrylate.

[0135] The compound having a methacryloyl group in the molecule is a methacrylate compound. Examples of the methacrylate compound include a monofunctional methacrylate compound having one methacryloyl group in the molecule and a polyfunctional methacrylate compound having two or more methacryloyl groups in the molecule. Examples of the monofunctional methacrylate compound include methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate. Examples of the polyfunctional methacrylate compound include tricyclodecane dimethanol dimethacrylate.

[0136] The compound having a vinyl group in the molecule is a vinyl compound. Examples of the vinyl compound include a monofunctional vinyl compound (monovinyl compound) having one vinyl group in the molecule, and a polyfunctional vinyl compound having two or more vinyl groups in the molecule. Examples of the polyfunctional vinyl compound include divinylbenzene and polybutadiene.

[0137] The compound having an allyl group in the molecule is an allyl compound. Examples of the allyl compound include a monofunctional allyl compound having one allyl group in the molecule and a polyfunctional allyl compound having two or more allyl groups in the molecule. Examples of the polyfunctional allyl compound include diallyl phthalate (DAP).

[0138] The compound having a maleimide group in the molecule is a maleimide compound. Examples of the maleimide compound include a monofunctional maleimide compound having one maleimide group in the molecule, a polyfunctional maleimide compound having two or more maleimide groups in the molecule, and a modified maleimide compound. Examples of the modified maleimide compound include a modified maleimide compound in which a portion of the molecule is modified with an amine compound, a modified maleimide compound in which a portion of the molecule is modified with a silicone compound, and a modified maleimide compound in which a portion of the molecule is modified with an amine compound and a silicone compound.

[0139] The compound having an acenaphthylene structure in the molecule is an acenaphthylene compound. Examples of the acenaphthylene compound include acenaphthylene, alkylacenaphthylenes, halogenated acenaphthylenes, and phenylacenaphthylenes. Examples of the alkylacenaphthylenes include 1-methylacenaphthylene, 3-methylacenaphthylene, 4-methylacenaphthylene, 5-methylacenaphthylene, 1-ethylacenaphthylene, 3-ethylacenaphthylene, 4-ethylacenaphthylene, and 5-ethylacenaphthylene. Examples of the halogenated acenaphthylenes include 1-chloroacenaphthylene, 3-chloroacenaphthylene, 4-chloroacenaphthylene, 5-chloroacenaphthylene, 1-bromoacenaphthylene, 3-bromoacenaphthylene, 4-bromoacenaphthylene, and 5-bromoacenaphthylene. Examples of the phenylacenaphthylenes include 1-phenylacenaphthylene, 3-phenylacenaphthylene, 4-phenylacenaphthylene, and 5-phenylacenaphthylene. The acenaphthylene compound may be a monofunctional acenaphthylene compound having one acenaphthylene structure in the molecule, as described above, or a polyfunctional acenaphthylene compound having two or more acenaphthylene structures in the molecule.

[0140] Among the above, preferred curing agents include, for example, polyfunctional acrylate compounds having two or more acryloyl groups in the molecule, polyfunctional methacrylate compounds having two or more methacryloyl groups in the molecule, polyfunctional vinyl compounds having two or more vinyl groups in the molecule, styrene derivatives, allyl compounds having an allyl group in the molecule, maleimide compounds having a maleimide group in the molecule, and acenaphthylene compounds having an acenaphthylene structure in the molecule.

[0141] The curing agent may be used alone or in combination of two or more kinds.

[0142] (Each Content) The content of the flame retardant is preferably 10 to 100 parts by mass per 100 parts by mass of the resin component (organic component) in the resin composition. If the content of the flame retardant is within the above range, there is an advantage that sufficient flame retardancy can be imparted while maintaining the dielectric properties of the resin composition. The content of the flame retardant is more preferably 15 to 90 parts by mass, and even more preferably 20 to 80 parts by mass per 100 parts by mass of the resin component (organic component) in the resin composition. In this specification, the term "resin component" refers to the resin component (organic component) contained in the resin composition.

[0143] The content of the polyfunctional vinyl aromatic copolymer is preferably 10 to 95 parts by mass per 100 parts by mass of the resin component (organic component) in the resin composition. If the content of the polyfunctional vinyl aromatic copolymer is within this range, a resin composition having excellent dielectric properties of a cured product can be obtained. The content of the polyfunctional vinyl aromatic copolymer is more preferably 15 to 90 parts by mass, and even more preferably 20 to 90 parts by mass per 100 parts by mass of the resin component (organic component) in the resin composition.

[0144] As described above, the resin composition may contain the modified polyphenylene ether compound. When the resin composition contains the polyphenylene ether compound, for example, the total content of the polyfunctional vinyl aromatic copolymer and the modified polyphenylene ether compound is preferably 10 to 95 parts by mass per 100 parts by mass of the resin component (organic component) in the resin composition. When the content of the polyfunctional vinyl aromatic copolymer and the modified polyphenylene ether compound is within this range, a resin composition with excellent dielectric properties and moldability can be obtained. The total content of the polyfunctional vinyl aromatic copolymer and the modified polyphenylene ether compound is more preferably 15 to 90 parts by mass, and even more preferably 20 to 90 parts by mass, per 100 parts by mass of the resin component (organic component) in the resin composition.

[0145] As described above, the resin composition may contain the curing agent. When the resin composition contains the curing agent, for example, the content of the curing agent is preferably 5 to 50 parts by mass per 100 parts by mass of the resin component (organic component) in the resin composition. If the content of the curing agent is within this range, there is an advantage that a resin composition with excellent heat resistance of the cured product can be obtained. It is more preferable that the content of the curing agent is 10 to 50 parts by mass per 100 parts by mass of the resin component (organic component) in the resin composition.

[0146] (Other Components) The resin composition according to this embodiment may contain other components (other components) in addition to the components described above, as necessary, as long as the effects of the present invention are not impaired. Examples of other components contained in the resin composition according to this embodiment include additives such as a styrene-based elastomer, an inorganic filler, a reaction initiator, a reaction accelerator, a catalyst, a dispersant, a leveling agent, a silane coupling agent, an antifoaming agent, an antioxidant, a heat stabilizer, an antistatic agent, an ultraviolet absorber, a dye or pigment, and a lubricant. Furthermore, the resin composition may contain a thermosetting resin such as polyphenylene ether or an epoxy resin in addition to the modified polyphenylene ether compound, the curing agent, and the polyfunctional vinyl aromatic copolymer.

[0147] As described above, the resin composition according to this embodiment may contain a styrene-based elastomer.

[0148] The styrene-based elastomer may be, for example, a polymer obtained by polymerizing a monomer containing a styrene-based monomer, and may be a styrene-based copolymer. Examples of the styrene-based copolymer include copolymers obtained by copolymerizing one or more of the styrene-based monomers with one or more other monomers copolymerizable with the styrene-based monomer. The styrene-based polymer preferably includes a hydrogenated styrene-based copolymer obtained by hydrogenating the styrene-based copolymer.

[0149] The styrene-based monomer is not particularly limited, but examples thereof include styrene, styrene derivatives, styrene in which some of the hydrogen atoms on the benzene ring have been substituted with alkyl groups, styrene in which some of the hydrogen atoms on the vinyl group have been substituted with alkyl groups, vinyltoluene, α-methylstyrene, butylstyrene, dimethylstyrene, isopropenyltoluene, etc. These styrene-based monomers may be used alone or in combination of two or more.

[0150] The copolymerizable other monomer is not particularly limited, and examples thereof include olefins such as α-pinene, β-pinene, and dipentene, non-conjugated dienes such as 1,4-hexadiene and 3-methyl-1,4-hexadiene, conjugated dienes such as 1,3-butadiene and 2-methyl-1,3-butadiene (isoprene), etc. The copolymerizable other monomers may be used alone or in combination of two or more.

[0151] Examples of the styrene copolymer include methylstyrene (ethylene / butylene) methylstyrene copolymer, methylstyrene (ethylene-ethylene / propylene) methylstyrene copolymer, styrene-isoprene copolymer, styrene-isoprene styrene copolymer, styrene (ethylene / butylene) styrene copolymer, styrene (ethylene-ethylene / propylene) styrene copolymer, styrene-butadiene styrene copolymer, styrene (butadiene / butylene) styrene copolymer, and styrene-isobutylene styrene copolymer.

[0152] Examples of the hydrogenated styrene copolymer include hydrogenated products of the styrene copolymers. More specific examples of the hydrogenated styrene copolymer include hydrogenated methylstyrene (ethylene / butylene) methylstyrene copolymer, hydrogenated methylstyrene (ethylene-ethylene / propylene) methylstyrene copolymer, hydrogenated styrene-isoprene copolymer, hydrogenated styrene-isoprene styrene copolymer, hydrogenated styrene (ethylene / butylene) styrene copolymer, and hydrogenated styrene (ethylene-ethylene / propylene) styrene copolymer.

[0153] The styrene-based elastomers may be used alone or in combination of two or more kinds.

[0154] As the styrene-based elastomer, a commercially available product may be used, for example, "DYNARON 9901P" manufactured by JSR Corporation.

[0155] When the resin composition of this embodiment contains the styrene-based elastomer, its content is not particularly limited, but is preferably, for example, 5 to 50 parts by mass per 100 parts by mass of the resin component (organic component) in the resin composition. If the content of the styrene-based elastomer is within this range, a resin composition having superior glass transition temperature and heat resistance and further suppressed thermal degradation of dielectric properties can be obtained more reliably. The content of the styrene-based elastomer is more preferably 10 to 50 parts by mass per 100 parts by mass of the resin component (organic component) in the resin composition.

[0156] The resin composition according to this embodiment may further contain a filler such as an inorganic filler. Examples of fillers include those added to suppress thermal expansion and enhance flame retardancy of the cured resin composition, but are not particularly limited thereto. Furthermore, the inclusion of a filler can further enhance heat resistance and flame retardancy. Specific examples of fillers include fillers made of at least one material selected from the group consisting of silica (e.g., spherical silica), metal oxides (e.g., alumina, titanium oxide, and mica), metal hydroxides (e.g., aluminum hydroxide and magnesium hydroxide), talc, aluminum borate, barium sulfate, and calcium carbonate. Furthermore, the filler preferably contains at least one material selected from the group consisting of silica, mica, and talc, and more preferably contains a filler made of spherical silica. Furthermore, the fillers may be used singly or in combination of two or more types. Furthermore, the fillers may be used as they are, or may be surface-treated with the silane coupling agent.

[0157] Furthermore, when the resin composition of the present embodiment contains the filler, the content (filler content) thereof is preferably 30 to 270 parts by mass, and more preferably 50 to 250 parts by mass, per 100 parts by mass of the resin component (organic component) in the resin composition.

[0158] As described above, the flame retardant has a high decomposition temperature, and therefore, even when the flame retardant is added to a resin with a high decomposition temperature, it can impart stable flame retardancy compared to conventional flame retardants.

[0159] (Production Method) The method for producing the resin composition is not particularly limited, and examples thereof include a method of mixing the flame retardant and the polyfunctional vinyl aromatic copolymer with other components as needed. Specifically, when obtaining a varnish-like composition containing an organic solvent, it is prepared, for example, as follows. Components of the resin composition that are soluble in an organic solvent are added to the organic solvent and dissolved. Heating may be performed as needed. Subsequently, components that are insoluble in the organic solvent (e.g., inorganic fillers, etc.) are added as needed, and the mixture is dispersed using a ball mill, bead mill, planetary mixer, roll mill, or the like until a predetermined dispersion state is achieved, thereby preparing a varnish-like resin composition. The organic solvent used here is not particularly limited, as long as it dissolves the modified polyphenylene ether compound, the curing agent, etc., and does not inhibit the curing reaction. Specific examples include toluene and methyl ethyl ketone (MEK).

[0160] (Uses) Furthermore, by using the resin composition of this embodiment, prepregs, resin-coated metal foils, metal-clad laminates, resin-coated films, and wiring boards can be obtained, and the prepregs, resin-coated metal foils, metal-clad laminates, resin-coated films, and wiring boards are also included in the present invention. The prepregs, resin-coated metal foils, metal-clad laminates, resin-coated films, and wiring boards using the resin composition have low dielectric properties and excellent flame retardancy.

[0161] The wiring board will be described in more detail below as an example of the above.

[0162] [Wiring Board] The wiring board in this embodiment has an insulating layer containing a cured product of the resin composition, and wiring provided on the insulating layer.

[0163] The method for producing the wiring board is not particularly limited as long as it can produce the wiring board. Specifically, a method of producing a wiring board using a prepreg obtained using the resin composition can be mentioned. For example, this method involves first impregnating a fibrous substrate with the resin composition prepared in a varnish form, followed by drying to produce a prepreg. One or more of the obtained prepregs are stacked, and then a metal foil such as copper foil is placed on both sides or one side of the prepreg. The metal foil and the prepreg are then heated and pressurized to form an integrated laminate, thereby producing a double-sided or single-sided metal foil-clad laminate. Examples of such methods include a method of producing a wiring board in which wiring is provided as a circuit on the surface of an insulating layer by etching the metal foil on the surface of the metal-clad laminate produced in this way to form a circuit. That is, the wiring board can be obtained by partially removing the metal foil on the surface of the metal-clad laminate to form a circuit. In addition to the above methods, examples of the circuit formation method include a semi-additive process (SAP) and a modified semi-additive process (MSAP). The wiring board has an insulating layer with low dielectric properties and excellent flame retardancy. Such a wiring board is a wiring board with an insulating layer with low dielectric properties and excellent flame retardancy. The wiring board may be multi-layered or single-layered.

[0164] The fibrous base material and the metal foil may be those that are commonly used in prepregs and metal-clad laminates, and are not particularly limited.

[0165] This specification discloses various aspects of the technology as described above, but the main technologies among them are summarized below.

[0166] The flame retardant according to the first aspect of the present invention contains a phosphorus compound represented by the following formula (1):

[0167]

[0168] In formula (1), A and B each independently represent a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide structure or a diphenylphosphine oxide structure, and X represents a linear bond containing two or more benzene atoms and two or more oxygen atoms.

[0169] In a second aspect of the present invention, the flame retardant is the flame retardant of the first aspect, wherein the number of benzene groups and the number of oxygen atoms are both two.

[0170] The flame retardant according to the third aspect of the present invention is the flame retardant according to the first or second aspect, wherein A and X, and B and X in the formula (1) are both bonded via a phosphorus-oxygen bond.

[0171] A flame retardant in a fourth aspect of the present invention is the flame retardant in any one of the first to third aspects, wherein either A or B in formula (1) represents a functional group having a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide structure.

[0172] A resin composition according to a fifth aspect of the present invention comprises the flame retardant according to any one of the first to fourth aspects and a polyfunctional vinyl aromatic copolymer.

[0173] The resin composition in a sixth aspect of the present invention is the resin composition in the fifth aspect, wherein the polyfunctional vinyl aromatic copolymer contains a repeating unit (a) derived from a divinyl aromatic copolymer and a repeating unit (b) derived from a monovinyl aromatic compound.

[0174] The resin composition according to a seventh aspect of the present invention is the resin composition according to the fifth or sixth aspect, further comprising a modified polyphenylene ether compound terminally modified with a substituent having a carbon-carbon unsaturated double bond.

[0175] The resin composition according to an eighth aspect of the present invention is the resin composition according to any one of the fifth to seventh aspects, further comprising a curing agent.

[0176] A prepreg in a ninth aspect of the present invention comprises the resin composition or a semi-cured product of the resin composition in any one of the fifth to eighth aspects, and a fibrous base material.

[0177] A resin-coated film in a tenth aspect of the present invention comprises a resin layer containing the resin composition in any one of the fifth to eighth aspects or a semi-cured product of the resin composition, and a support film.

[0178] A resin-coated metal foil according to an eleventh aspect of the present invention comprises a resin layer containing the resin composition according to any one of the fifth to eighth aspects or a semi-cured product of the resin composition, and a metal foil.

[0179] A metal-clad laminate according to a twelfth aspect of the present invention comprises an insulating layer containing a cured product of the resin composition according to any one of the fifth to eighth aspects, and a metal foil.

[0180] A metal-clad laminate according to a thirteenth aspect of the present invention comprises an insulating layer containing a cured product of the prepreg according to the ninth aspect, and a metal foil.

[0181] A wiring board according to a fourteenth aspect of the present invention comprises an insulating layer containing a cured product of the resin composition according to any one of the fifth to eighth aspects, and wiring.

[0182] A wiring board according to a fifteenth aspect of the present invention comprises an insulating layer containing a cured product of the prepreg according to the ninth aspect, and wiring.

[0183] The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0184] Test Example 1 The flame retardants of Examples 1 to 3 and Comparative Examples 1 and 2 were prepared as follows, and the decomposition temperatures and melting points of the flame retardants were measured.

[0185] Example 1 As a flame retardant for Example 1, a phosphorus compound B represented by the above formula (4) was prepared as follows.

[0186] (Synthesis of Phosphorus Compound A) Before synthesizing phosphorus compound B, phosphorus compound A represented by the above formula (14) was first synthesized. First, all glassware to be used was dried at 100°C. A 500 mL three-necked flask equipped with a dropping funnel and a water bath was prepared, and the atmosphere inside the flask was purged with argon. 9.6 g of dihydroxydiphenylmethane (4,4'-dihydroxydiphenylmethane, manufactured by Tokyo Chemical Industry Co., Ltd., "B0819") and 300 mL of dehydrated dichloromethane (ultra-dehydrated dichloromethane, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., "044-31235") were placed in the 500 mL three-necked flask and dissolved.

[0187] 13.9 g of triethylamine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., "208-02643") and 1.5 g of dimethylaminopyridine (4-dimethylaminopyridine, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., "044-19211") were added in this order and stirred for 5 minutes.

[0188] 10 g of diphenylphosphinic chloride ("C1415" manufactured by Tokyo Chemical Industry Co., Ltd.) was placed in a dropping funnel and added dropwise to the reaction solution. The reaction was carried out at room temperature for 15 hours.

[0189] 100 mL of saturated aqueous ammonium chloride solution (FUJIFILM Wako Pure Chemical Industries, Ltd. "013-02992") was prepared and added to the reaction solution. Triethylamine was converted into a salt and transferred to the aqueous phase. The organic phase was separated, and the aqueous phase was extracted twice with 100 mL of dichloromethane (FUJIFILM Wako Pure Chemical Industries, Ltd. "135-02446"). MgSO ４ After drying at 400°C, the resulting 500 mL of dichloromethane solution was purified by silica gel chromatography (packing material: Merck's "1.09385.5000" silica gel, eluent: dichloromethane, ethyl acetate) to remove unreacted diphenylphosphinic chloride and dimethylaminopyridine. At this time, it is believed that residual triethylamine was also distilled off.

[0190] The resulting solid was dissolved in 300 mL of dichloromethane and purified again by silica gel chromatography (column size: 45 mm, length: 12 cm, packing: 200 g of Merck "1.09385.5000" silica gel, eluent: dichloromethane, ethyl acetate, TLC / HPLC monitoring conditions: ethyl acetate only). Specifically, the 0-substituted, 1-substituted, and 2-substituted products were separated, and the 1-substituted product was obtained.

[0191] After purification, the product was dried at 100° C. and 100 Pa for 1 hour, to obtain 5.6 g of a colorless solid phosphorus compound A in a yield of 33%.

[0192] (Identification of phosphorus compound A) １ From the results of H-NMR and MALDI-TOF MS measurements, it was confirmed that phosphorus compound A was the compound represented by formula (14) above.

[0193] ・ １ H-NMR analysis of phosphorus compound A １ The results of H-NMR (400 MHz, solvent: dichloromethane) analysis are shown in FIG. １ From the results of H-NMR analysis, signals consistent with the chemical structure of the phosphorus compound A represented by the above formula (14) were obtained.

[0194] MALDI-TOF MS The MALDI-TOF MS (JEOL) spectrum of phosphorus compound A is shown in Figure 2. The theoretical value of the molecular weight of the phosphorus compound represented by the above formula (14) is 400.41, while the measured values ​​were 400.12 (100%), 401.13 (27.0%), and 402.13 (2.7%), as shown in Figure 2, and it was confirmed that the theoretical value and the measured value were almost identical. The measurement conditions were as follows:

[0195] Measurement mode: spiral, matrix: DCTB, polarity: positive, TFANa added

[0196] (Synthesis of Phosphorus Compound B) First, all glassware to be used was dried by heating at 100° C. for 1 hour or more. A 500 mL three-neck flask equipped with a magnetic stirrer, a hot water bath, and a thermometer installed to monitor the temperature of the reaction solution was prepared.

[0197] 3.6 g of a phosphaphenanthrene derivative (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, manufactured by Tokyo Chemical Industry Co., Ltd., "D1874") and 80 mL of dehydrated toluene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., "204-17915") were added to a 500 mL three-neck flask and dissolved, and the temperature was maintained at 20°C or below. 1.3 g of trichloroisocyanuric acid (manufactured by Tokyo Chemical Industry Co., Ltd., "T0620") was added in 0.3 g portions in five batches under ice cooling. At this time, attention was paid to the reaction temperature so that it did not exceed 40°C. After addition, the mixture was stirred at room temperature for 1 hour.

[0198] Under ice cooling, 5.5 g of phosphorus compound A was added to the reaction solution at once, and the mixture was stirred at room temperature for 1 hour. Under ice cooling, 2.9 g of triethylamine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., "208-02643") was added dropwise using a dropping funnel. The mixture was then stirred at room temperature for 1 hour.

[0199] The reaction solution was transferred to a separatory funnel and washed once with water, once with a 1% aqueous phosphoric acid solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., "162-20492"), and once with saturated saline, and then the solvent was distilled off.

[0200] The product was purified twice by silica gel chromatography (packing material: Merck's "1.09385.5000" silica gel, eluent: dichloromethane, ethyl acetate (eluent determined by TLC)). Recrystallization was performed and the product was dried at 100°C and 100 Pa for 1 hour, obtaining 4.9 g of a white solid phosphorus compound B in a yield of 58%.

[0201] (Purity of phosphorus compound B) The purity of phosphorus compound B was measured using liquid chromatography. The purity value was calculated from the area of ​​the chart obtained by liquid chromatography analysis (Area %). The purity was confirmed to be 95.0%. The specific analysis conditions are as follows:

[0202] Column: ZORBAX SiL Eluent: ethyl acetate 1.0 mL / min Observation wavelength: 280 nm

[0203] (Identification of Phosphorus Compound B) In the phosphorus compound B,１ The results of H-NMR (400 MHz, solvent: dichloromethane) analysis are shown in Figure 3. １ The results of the H-NMR analysis showed signals consistent with the chemical structure of the phosphorus compound represented by the above formula (4).

[0204] Example 2 As a flame retardant of Example 2, the phosphorus compound C (C') represented by the above formula (5) was prepared as follows.

[0205] (Synthesis of Phosphorus Compounds C and C') First, all glassware to be used was dried by heating at 100°C for 1 hour or more. A 500 mL three-neck flask equipped with a magnetic stirrer, a hot water bath, and a thermometer installed so as to monitor the temperature of the reaction solution was prepared.

[0206] A 500 mL three-neck flask was charged with 24.9 g of a phosphaphenanthrene derivative (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, manufactured by Tokyo Chemical Industry Co., Ltd., "D1874") and 300 mL of dehydrated toluene (ultra-dehydrated toluene, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., "204-17915") and dissolved, and the temperature was maintained at 20°C or below.

[0207] 8.9 g of trichloroisocyanuric acid ("T0620" manufactured by Tokyo Chemical Industry Co., Ltd.) was divided into 0.89 g portions and added in 10 portions under ice cooling. At this time, attention was paid to the reaction temperature so that it did not exceed 40° C. After addition, the mixture was stirred at room temperature for 1 hour.

[0208] Under ice cooling, 9.6 g of dihydroxydiphenylmethane (4,4'-dihydroxydiphenylmethane) was added to the reaction solution all at once, and the mixture was stirred at room temperature for 1 hour.

[0209] Under ice cooling, 20.4 g of triethylamine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., "208-02643") was added dropwise using a dropping funnel, followed by stirring at room temperature for 1 hour.

[0210] The reaction solution was transferred to a separatory funnel and washed once with water, once with a 1% aqueous phosphoric acid solution ("162-20492" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and once with saturated saline, and the solvent was distilled off. Thereafter, the residue was purified by silica gel column chromatography (packing material: "1.09385.5000" silica gel manufactured by Merck, eluent: dichloromethane).

[0211] The solid was washed by suspending in acetone and dried at 100 Pa and 100° C. for 1 hour to obtain 15.4 g of a white solid phosphorus compound C in a yield of 51%.

[0212] Further, 10 g of phosphorus compound C was purified by sublimation in three separate batches to obtain 6.5 g of phosphorus compound C', which was a colorless glassy solid, with a yield of 65%. The sublimation purification conditions were 340° C., 2×10 －２ The temperature was set at 100 Pa for 3 hours. Specifically, the phosphorus compound C before the sublimation purification was melted and evaporated, and precipitated as a liquid in a low-temperature portion.

[0213] (Purity of phosphorus compounds C and C') The purity of phosphorus compound C was measured using liquid chromatography. The purity value was calculated from the area of ​​the chart obtained by liquid chromatography analysis (Area %). The purity of phosphorus compound C was confirmed to be 95.8%. The purity of phosphorus compound C' was confirmed to be 97.5%. The specific analysis conditions are as follows:

[0214] Column: ZORBAX SiL Eluent: ethyl acetate 0.5 mL / min Observation wavelength: 280 nm

[0215] (Identification of phosphorus compound C) １ The results of H-NMR (400 MHz, solvent: dichloromethane) analysis are shown in Figure 4. １ The results of H-NMR analysis showed that signals consistent with the chemical structure of the phosphorus compound represented by the above formula (5) were obtained. Also, Fig. 5 shows an enlarged view of a part of Fig. 4.

[0216] Example 3 As a flame retardant of Example 3, a phosphorus compound D (D') represented by the above formula (6) was prepared as follows.

[0217] (Synthesis of Phosphorus Compounds D and D') First, all glassware to be used was dried at 100° C. A 1 L three-necked flask equipped with a dropping funnel and a water bath was prepared, and the atmosphere inside the flask was replaced with argon.

[0218] 5.0 g of dihydroxydiphenylmethane (4,4'-dihydroxydiphenylmethane, manufactured by Tokyo Chemical Industry Co., Ltd., "B0819") and 750 mL of dehydrated dichloromethane (ultra-dehydrated dichloromethane, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., "044-31235") were placed in a 1 L three-neck flask and dissolved. 8.0 g of triethylamine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., "208-02643") and 0.9 g of dimethylaminopyridine (4-dimethylaminopyridine, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., "044-19211") were added in this order, and the mixture was stirred for 5 minutes.

[0219] 14.5 g of diphenylphosphinic chloride ("C1415" manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 20 mL of dichloromethane ("135-02446" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), placed in a dropping funnel, and added dropwise to the reaction solution. The mixture was stirred at room temperature for 6 hours to allow the reaction to proceed.

[0220] 100 mL of saturated aqueous ammonium chloride solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., "013-02992") was prepared and added to the reaction solution. Triethylamine was converted into a salt and transferred to the aqueous phase. The organic phase was separated, and the aqueous phase was extracted twice with 100 mL of dichloromethane. MgSO ４ After drying, the solution was concentrated to about 500 mL.

[0221] The resulting 500 mL of dichloromethane solution was purified by silica gel chromatography (packing material: Merck "1.09385.5000" silica gel, eluent: dichloromethane) to remove unreacted diphenylphosphinic acid chloride and dimethylaminopyridine. Furthermore, it is believed that residual triethylamine was also distilled off.

[0222] The resulting solid was dissolved in 300 mL of dichloromethane and purified again by silica gel chromatography (column size: 45 mm diameter, length: 12 cm, packing material: 200 g of silica gel manufactured by Merck "1.09385.5000", eluent: dichloromethane, TLC / HPLC monitoring conditions: ethyl acetate only).

[0223] After purification, the product was dried at 100°C and 100 Pa for 1 hour, obtaining 13.7 g (91% yield) of a white solid phosphorus compound D. Furthermore, 3.5 g of phosphorus compound D was purified by sublimation to obtain 2.1 g of a white solid phosphorus compound D'.

[0224] (Purity of Phosphorus Compounds D and D') The purity of phosphorus compounds D and D' was measured using liquid chromatography. The purity value was calculated from the area of ​​the chart obtained by liquid chromatography analysis (Area %). It was confirmed that the purity of both phosphorus compounds D and D' was 99.0% or higher. The specific analysis conditions were as follows:

[0225] Column: ZORBAX SiL Eluent: ethyl acetate 1.0 mL / min Observation wavelength: 273 nm

[0226] (Identification of Phosphorus Compound D') In the phosphorus compound D', １ The results of H-NMR (400 MHz, solvent: dichloromethane d2) analysis are shown in FIG. １ From the results of H-NMR analysis, signals consistent with the chemical structure of the phosphorus compound D' represented by the above formula (6) were obtained. Also, Fig. 7 shows an enlarged view of a part of Fig. 6.

[0227] Comparative Example 1 As a flame retardant in Comparative Example 1, a phosphorus compound E represented by the following formula (32) was prepared as follows.

[0228]

[0229] First, 2 moles (approximately 432 g) of DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), 1 mole (approximately 128 g) of 1,4-bis(chloromethyl)benzene, and 2,400 g of dichlorobenzene solvent were placed in a blender, heated to 150°C, and stirred to dissolve the solids and form a homogeneously mixed solution, which was then heated and stirred continuously for 24 hours.

[0230] The solution was then cooled to room temperature, washed with hexane, and filtered to obtain white crystals, which were then calcined at 120°C for 6 hours to obtain a white powder of phosphorus compound E (a phosphorus compound represented by the formula (32) (phosphorus concentration: 11.6 parts by mass)).

[0231] Comparative Example 2 As a flame retardant in Comparative Example 2, a phosphorus compound F represented by the following formula (33) was prepared as follows.

[0232]

[0233] First, 2 moles (432 g) of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), 1 mole (251 g) of biphenyldichlorobenzyl, and 2,400 g of toluene were added to a stirring tank, and then the mixture was stirred at a temperature of 170°C for 16 hours to react and produce a solution. After the solution was cooled to room temperature, hexane was added to the solution to rinse the reaction product, and then a white crystalline product was obtained after filtration. Subsequently, the white crystalline product was calcined at a temperature of 120°C to obtain phosphorus compound F (phosphorus compound represented by the above formula (33) (phosphorus concentration: 10.2 parts by mass)).

[0234] [TG-DTA Measurement of Flame Retardants] Phosphorus Compound B of Example 1, Phosphorus Compound C' of Example 2, Phosphorus Compound D' of Example 3, Phosphorus Compound E of Comparative Example 1, and Phosphorus Compound F of Comparative Example 2 were subjected to TG-DTA measurement using a differential thermal thermogravimetry analyzer (Thermo plus EVO2 TG-DTA8122, manufactured by Rigaku Corporation) to measure the decomposition temperature (volatilization / decomposition peak temperature) and melting point in a nitrogen atmosphere. Specifically, the TG-DTA measurement was performed by heating the measurement sample from 25°C to 500°C at a temperature increase rate of 10°C / min under a nitrogen flow of 200 mL / min. The results are shown in Table 1.

[0235]

[0236] [Discussion] The flame retardants of Examples 1 to 3 had higher decomposition temperatures (volatilization / decomposition peak temperatures) than the flame retardants of Comparative Examples 1 and 2. Therefore, it was found that the chemical structure of the flame retardants of Examples 1 to 3 is less likely to change even when used at high temperatures, and therefore they are easy to handle even at high temperatures.

[0237] Test Example 2 Plate-shaped resin compositions were prepared using the flame retardants of Examples 1 to 3 and Comparative Examples 1 and 2 prepared in Test Example 1, and the flame retardancy of the flame retardants was evaluated.

[0238] [Preparation of Plate-Like Resin Compositions] Plate-like resin compositions of Examples 1 to 3 and Comparative Examples 1 and 2 were prepared as follows using resin compositions containing, as flame retardants, phosphorus compound B of Example 1, phosphorus compound C' of Example 2, phosphorus compound D' of Example 3, phosphorus compound E of Comparative Example 1, and phosphorus compound F of Comparative Example 2. Furthermore, as a further comparative example, a plate-like resin composition of Comparative Example 3 was also prepared in the same manner as the plate-like resin compositions of Examples 1 to 3 and Comparative Examples 1 and 2, except that no flame retardant was contained.

[0239] (Preparation of Varnish) First, the components used in preparing the varnish-like resin composition used to produce the plate-shaped resin composition will be described.

[0240] Polyfunctional vinyl aromatic copolymer: A copolymer obtained by the following method was used.

[0241] 3.0 mol (390.6 g) of divinylbenzene, 1.8 mol (229.4 g) of ethylvinylbenzene, 10.2 mol (1066.3 g) of styrene, and 15.0 mol (1532.0 g) of n-propyl acetate were charged into a 5.0 L reactor, and 600 mmol of a boron trifluoride diethyl ether complex was added at 70 ° C., followed by a reaction for 4 hours. After the polymerization solution was terminated with an aqueous sodium bicarbonate solution, the oil layer was washed three times with pure water, and the mixture was subjected to devolatilization under reduced pressure at 60 ° C. to recover the copolymer. The obtained copolymer was weighed, and it was confirmed that 896.7 g of copolymer was obtained.

[0242] The copolymer obtained had an Mn of 2,980, an Mw of 41,300, and an Mw / Mn ratio of 13.9. The constituent units of the copolymer were calculated as follows: Structural unit (a): 30.4 mol % (33.1 wt %), Structural unit (b2): 12.2 mol % (14.2 wt %), Structural unit (b1): 57.4 mol % (52.7 wt %), and Structural unit (a1): 23.9 mol % (25.9 wt %).

[0243] Modified PPE: Modified PPE obtained by the following method was used.

[0244] The modified polyphenylene ether compound is a polyphenylene ether compound having a terminal vinylbenzyl group (ethenylbenzyl group) (a modified polyphenylene ether compound obtained by reacting polyphenylene ether with chloromethylstyrene). Specifically, the modified polyphenylene ether compound is obtained by the following reaction.

[0245] First, 200 g of polyphenylene ether (SA90 manufactured by SABIC Innovative Plastics, 2 terminal hydroxyl groups, weight average molecular weight Mw 1700), 30 g of a 50:50 mass ratio mixture of p-chloromethylstyrene and m-chloromethylstyrene (chloromethylstyrene: CMS manufactured by Tokyo Chemical Industry Co., Ltd.), 1.227 g of tetra-n-butylammonium bromide as a phase transfer catalyst, and 400 g of toluene were charged into a 1-liter three-neck flask equipped with a temperature controller, a stirrer, a cooling device, and a dropping funnel, and the mixture was stirred. The polyphenylene ether, chloromethylstyrene, and tetra-n-butylammonium bromide were stirred until they were dissolved in toluene. The mixture was gradually heated, and finally heated until the liquid temperature reached 75 ° C. Then, an aqueous sodium hydroxide solution (20 g sodium hydroxide / 20 g water) was added dropwise to the solution as an alkali metal hydroxide over 20 minutes. The mixture was then stirred at 75°C for an additional 4 hours. Next, the contents of the flask were neutralized with 10 parts by mass of hydrochloric acid, and a large amount of methanol was then added. This caused a precipitate to form in the liquid in the flask. That is, the product contained in the reaction solution in the flask was reprecipitated. The precipitate was then filtered, washed three times with a mixture of methanol and water in a mass ratio of 80:20, and then dried under reduced pressure at 80°C for 3 hours. A vinylbenzene-terminated PPE with a weight-average molecular weight (Mw) of 2,300 was obtained.

[0246] The obtained solid is １ H-NMR (400MHz, CDCl ３ , TMS). １ As a result of measuring H-NMR, a peak attributable to ethenylbenzyl was confirmed at 5 to 7 ppm, confirming that the obtained solid was ethenylbenzylated polyphenylene ether.

[0247] Curing agent: Acenaphthylene compound (manufactured by JFE Chemical Corporation)

[0248] Styrene-based elastomer: hydrogenated styrene (ethylene / butylene) styrene copolymer ("DYNARON 9901P" manufactured by JSR Corporation, content of styrene-derived structural units: 53 parts by mass, weight average molecular weight: 100,000)

[0249] The above components other than the flame retardant were added to toluene in the composition (parts by mass) shown in Table 2, and mixed so that the solid content was 100 parts by mass per 90 parts by mass of toluene. The mixture was stirred for 2 hours. The flame retardant was then added to the resulting liquid in the composition (parts by mass) shown in Table 2, and the mixture was mixed in a mortar to disperse the flame retardant. This resulted in a varnish-like resin composition (varnish).

[0250]

[0251] (Coating of Varnish) The varnish obtained in the manner described above was dropped onto a heat-resistant release film and spread evenly to a thickness of about 0.5 mm.

[0252] (Drying: Semi-curing Step) The varnish-coated release film obtained above was semi-cured by drying it in the air for 1 hour at 120° C. Subsequently, the semi-cured portion was peeled off from the release film and then crushed in a mortar to obtain a semi-cured mortar-pulverized product.

[0253] (Build-up of semi-cured powder) A pad paper (280 μm thick) with a square hole of 54 mm on each side and the same outer dimensions as the copper foil (FV-WS manufactured by Furukawa Electric Co., Ltd., thickness 18 μm) was placed on top of the copper foil, and 0.9 g of the semi-cured mortar-ground product described above was placed in the hole so as to have a uniform thickness. Thereafter, copper foil of the same type and shape as the copper foil was laminated on the semi-cured mortar-ground product and the pad paper to form a pressure body.

[0254] (Pressing: Curing Step) The pressure-receiving body was heated and pressurized under the following conditions: The temperature was raised from 20°C to 200°C at a rate of 3°C per minute. At the start of heating, the pressure was set so that the pressure on the semi-hardened powder was 0.45 MPa. Thereafter, when the temperature reached 130°C, the pressure was set so that the pressure on the semi-hardened powder was 0.90 MPa, and the semi-hardened powder was cured.

[0255] After curing, the copper foils on both sides of the cured resin were removed to obtain a plate-shaped resin composition measuring 54 mm long x 54 mm wide x approximately 280 μm thick.

[0256] [Evaluation] Micro-cone calorimeter (MCC) measurement was carried out on the plate-shaped resin compositions of Examples 1 to 3 and Comparative Examples 1 to 3 in accordance with ASTM D7309-21a. Specifically, the measurement sample was heated from 75°C to 850°C at a temperature increase rate of 1°C / sec in a nitrogen atmosphere. Figure 8 shows the relationship between temperature and HRR in the MCC measurement. Table 3 also shows the Peak HRR and the temperature at which HRR was maximized.

[0257]

[0258] [Discussion] As is clear from the results in Table 3, the plate-shaped resin compositions of Examples 1 to 3, which used phosphorus compound B, phosphorus compound C', and phosphorus compound D' as flame retardants, respectively, had low Peak HRRs in the MCC test and exhibited excellent flame retardancy. It is generally believed that the flame retardant has a high flame retardancy effect if the temperatures at which the HRR is maximized are close between a resin composition excluding the flame retardant and a resin composition containing the flame retardant. Looking at the measurement results for the temperatures at which the HRR is maximized, the temperatures in Examples 1 to 3 are close to the temperatures in Comparative Example 3, which used a resin composition not containing a flame retardant. Therefore, it is believed that the flame retardants used in Examples 1 to 3 exhibited excellent flame retardancy.

[0259] On the other hand, in Comparative Examples 1 and 2, the Peak HRR in the MCC test was high, and the temperature at which the HRR reached its maximum was about 60°C higher than the temperature at which the HRR reached its maximum in Comparative Example 3, which did not contain a flame retardant. These results demonstrate that the flame retardants used in Comparative Examples 1 and 2 were inferior in flame retardancy to the flame retardants used in Examples 1 to 3.

[0260] This application is based on Japanese Patent Application No. 2024-050125 filed on March 26, 2024, the contents of which are incorporated herein by reference.

[0261] In order to express the present invention, the present invention has been properly and sufficiently described above through the embodiments with reference to the drawings, but it should be recognized that those skilled in the art can easily change and / or improve the above-mentioned embodiments. Therefore, unless the changes or improvements made by those skilled in the art are at a level that causes departure from the scope of the claims described in the claims, such changes or improvements are interpreted as being included in the scope of the claims.

[0262] According to the present invention, it is possible to provide a halogen-free flame retardant having excellent flame retardancy.

Claims

1. A flame retardant containing a phosphorus compound represented by the following formula (1): (In formula (1), A and B each independently represent a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide structure or a diphenylphosphine oxide structure, and X represents a linear bond containing two or more benzene atoms and two or more oxygen atoms.) 2. The flame retardant according to claim 1, wherein the number of said benzene atoms and said oxygen atoms is two.

3. The flame retardant according to claim 1, wherein A and X, and B and X in formula (1) are bonded via a phosphorus-oxygen bond.

4. The flame retardant according to claim 1, wherein in formula (1), either A or B represents a functional group having a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide structure.

5. A resin composition comprising the flame retardant of claim 1 and a polyfunctional vinyl aromatic copolymer.

6. The resin composition according to claim 5, wherein the polyfunctional vinyl aromatic copolymer contains a repeating unit (a) derived from a divinyl aromatic copolymer and a repeating unit (b) derived from a monovinyl aromatic compound.

7. The resin composition according to claim 5, further comprising a modified polyphenylene ether compound terminally modified with a substituent having a carbon-carbon unsaturated double bond.

8. The resin composition according to claim 5, further comprising a curing agent.

9. A prepreg comprising the resin composition according to any one of claims 5 to 8 or a semi-cured product of said resin composition and a fibrous base material.

10. A resin-coated film comprising a resin layer containing the resin composition according to any one of claims 5 to 8 or a semi-cured product of said resin composition, and a support film.

11. A resin-coated metal foil comprising a resin layer containing the resin composition according to any one of claims 5 to 8 or a semi-cured product of said resin composition, and a metal foil.

12. A metal-clad laminate comprising an insulating layer containing a cured product of the resin composition according to any one of claims 5 to 8 and a metal foil.

13. A metal-clad laminate comprising an insulating layer containing a cured product of the prepreg according to claim 9 and a metal foil.

14. A wiring board comprising an insulating layer containing a cured product of the resin composition according to any one of claims 5 to 8 and wiring.

15. A wiring board comprising an insulating layer containing a cured product of the prepreg according to claim 9 and wiring.

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