WO2024070886A1 - Phosphorus-containing phenol compound, curable resin composition containing said phosphorus-containing phenol compound, cured product, and method for producing said phosphorus-containing phenol compound - Google Patents

Abstract

Provided is a phosphorus-containing phenol compound, a cured product of which has excellent flame retardancy, heat resistance, and dielectric properties, a low moisture absorption rate, and little change in dielectric properties after moisture absorption.　A phosphorus-containing phenol compound represented by general formula (1). In general formula (1), Ar is an optionally substituted C6-30 aromatic ring group, R1 each independently are a hydrogen or a substituent represented by general formula (2), and at least one R1 contains a substituent represented by general formula (2). m is an integer of 3 to 6.

Description

Phosphorus-containing phenolic compound, curable resin composition containing said phosphorus-containing phenolic compound, cured product, and method for producing said phosphorus-containing phenolic compound

The present invention relates to a reactive phosphorus compound, in particular a phosphorus-containing phenolic compound, which is useful as a flame retardant for thermosetting resins such as epoxy resins. The present invention also relates to a curable resin composition containing the phosphorus-containing phenolic compound and a curable resin composition, and a method for producing the phosphorus-containing phenolic compound.

Plastic materials have excellent mechanical properties and moldability, making them suitable for a wide range of applications, from building materials to electrical and electronic equipment. However, most plastic materials are flammable, so flame retardancy is essential for their use in applications such as electrical and electronic products, office automation equipment, and communications equipment, to ensure safety against heat generation and ignition.

Additive flame retardants such as halogen-based flame retardants, inorganic flame retardants, and phosphorus-based flame retardants are commonly used as flame retardant technology for plastic materials, regardless of the type of resin or application. However, it has been pointed out that halogen-based flame retardants, mainly bromine-based, may be a source of highly carcinogenic dioxins, and there is a trend to restrict their use in response to the recent movement to reduce environmentally hazardous substances. In addition, inorganic flame retardants such as magnesium hydroxide and aluminum hydroxide have a flame retardant effect due to endothermic heat, but they must be added in large quantities to achieve sufficient flame retardancy, which causes a decrease in various properties of plastic molded products. For this reason, phosphorus-based flame retardants are widely used, which do not generate harmful substances and can be flame retarded with the addition of relatively small amounts, but they still have unavoidable effects on properties, such as a decrease in processability due to bleed-out, a decrease in glass transition temperature, etc.

In order to solve the problems of these additive flame retardants, reactive flame retardants that contain phosphorus atoms, a flame retardant component, and have reactive groups have been developed and widely used. As reactive flame retardants that can be applied to epoxy resin compositions that are widely used in the electronics and electrical fields, for example, Patent Document 1 discloses a phosphorus-containing epoxy resin obtained by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (hereinafter abbreviated as "DOPO") with quinones and then reacting with an epoxy resin. Patent Document 2 discloses a phenolic resin obtained by reacting bisphenol A with formaldehyde as a curing agent for epoxy resins, to obtain hydroxymethylbisphenol A, and then reacting with DOPO, and Patent Document 3 discloses a phenolic resin to which phosphorus atoms have been introduced by reacting DOPO with anisaldehyde and then reacting with a triazine skeleton-containing phenolic resin. These resins solve the problems of processability such as bleed-out of flame retardants, and do not show any deterioration in thermal properties such as heat resistance.

However, in recent years, in the field of electronic and electrical materials where flame retardancy is essential, the rapid evolution of electronic devices such as smartphones has led to a change in the properties required of flame retardants. In particular, in the field of information and communications, the increase in the amount of information processed has led to an increase in the frequency of signals, and a strong demand for flame retardant materials with low dielectric constants and low dielectric tangents is being placed on them to reduce transmission loss. In addition, there are a wide variety of requirements, such as low moisture absorption, stable properties against environmental changes, and heat resistance. As a flame retardant that can be applied to epoxy resin compositions exhibiting low dielectric properties, Patent Document 4 discloses that phosphorus-containing active esters that have been introduced with a DOPO skeleton exhibit flame retardancy and low dielectric properties. In this way, epoxy resins and phosphorus-containing curing agents that can be imparted with flame retardancy without reducing general properties such as heat resistance by introducing DOPO into the structure are widely known, but there is a problem that the DOPO skeleton is easily hydrolyzed, and the hydroxyl groups generated by hydrolysis cause a large change in dielectric properties after moisture absorption and water absorption. To address this issue, Patent Document 5 discloses a phosphate ester-type phenolic compound that exhibits minimal change in dielectric properties after absorbing water, but the dielectric properties and heat resistance are insufficient, and there are still no flame retardants that are sufficient to meet high-level requirements.

Patent No. 3533973 Patent No. 5678109 Patent No. 5516980 Patent No. 5637418 WO2021/256351

The problem that the present invention aims to solve is to provide a phosphorus-containing phenolic compound that has excellent flame retardancy, heat resistance, and dielectric properties in the cured product, has a small water absorption rate, and exhibits little change in dielectric properties after absorbing water, a curable resin composition that contains the phosphorus-containing phenolic compound and a curable resin, an epoxy resin composition that uses the compound as a curing agent, a cured product thereof, and a method for producing the phosphorus-containing phenolic compound.

As a result of extensive research into the above-mentioned problems, the inventors discovered that a phosphorus-containing phenolic compound with a specific structure has excellent heat resistance and dielectric properties, and undergoes little change in dielectric properties after absorbing water, which led to the invention.

That is, the present invention relates to a phosphorus-containing phenol compound represented by the following formula (1).

In general formula (1), Ar is an aromatic ring group having 6 to 30 carbon atoms which may have a substituent, and R1 is independently hydrogen or a substituent represented by the following general formula (2), with at least one R1 containing a substituent represented by general formula (2). m is an integer of 3 to 6.

In general formula (2), R2 and R3 each independently represent a linear or branched alkyl group having 1 to 5 carbon atoms, and n2 and n3 each independently represent an integer of 0 to 5.

In the present invention, phosphorus-containing phenol compounds in which Ar is an aromatic ring group selected from the group consisting of a benzene skeleton, a naphthalene skeleton, a biphenyl skeleton, and an anthracene skeleton are preferred, and phosphorus-containing phenol compounds in which Ar is a benzene skeleton are more preferred.

In the present invention, a phosphorus-containing phenolic compound in which m is 3 is more preferred. Particularly preferred are phosphorus-containing phenolic compounds in which m is 3 and, for three OR1 groups in general formula (1), the compounds contain 10 to 80 mol % of a compound in which two R1s are hydrogen and one R1 is a substituent represented by general formula (2) (monosubstitution), 5 to 50 mol % of a compound in which one R1 is hydrogen and two R1s are substituents represented by general formula (2) (disubstitution), and 1 to 50 mol % of a compound in which three R1s are substituents represented by general formula (2) (trisubstitution).

The present invention is a method for producing a phosphorus-containing phenol compound, which comprises reacting 0.1 to 0.9 moles of a compound represented by general formula (4) with 1 mole of a hydroxyl group of a compound represented by general formula (3).

In formula (3), Ar and m are the same as those in formula (1).

In formula (4), X represents a halogen atom, and R2, R3, n2, and n3 are each defined as in formula (2).

The present invention is a curable resin composition containing the above-mentioned phosphorus-containing phenolic compound and a curable resin. A cured product is obtained by curing the above-mentioned curable resin composition.

The phosphorus-containing phenolic compound of the present invention exhibits minimal change in dielectric properties after absorbing water, making it extremely useful as a flame-retardant material for reducing transmission loss at higher frequencies associated with the increased amount of information processed by electronic devices.

1 shows a GPC chart of the phosphorus-containing phenol compound obtained in Example 2. (The dotted line is the raw material, and the solid line is the product.)

The present invention will be described in detail below.
The phosphorus-containing phenol compound of the present invention is represented by the following general formula (1).

In the general formula (1), Ar is an aromatic ring group having 6 to 30 carbon atoms which may have a substituent. The aromatic ring group is not particularly limited, and examples thereof include monocyclic aromatic compounds such as benzene, furan, pyrrole, thiophene, imidazole, pyrazole, oxazole, isoxazole, thiazole, isothiazole, pyridine, pyrimidine, pyridazine, pyrazine, and triazine from which m hydrogen atoms have been removed; and condensed aromatic compounds such as naphthalene, anthracene, phenalene, phenanthrene, quinoline, isoquinoline, quinazoline, phthalazine, pteridine, coumarin, indole, benzimidazole, benzofuran, and acridine from which m hydrogen atoms have been removed. In addition, the aromatic ring group may be a combination of a plurality of these aromatic compounds, and examples thereof include ring-assembled aromatic compounds such as biphenyl, binaphthalene, bipyridine, bithiophene, phenylpyridine, phenylthiophene, terphenyl, diphenylthiophene, and quaterphenyl from which m hydrogen atoms have been removed. Preferred are benzene, naphthalene, biphenyl and anthracene, and more preferred is benzene.

The aromatic ring represented by Ar may contain a substituent other than -OR1. Examples of the substituent include an alkyl group having 1 to 10 carbon atoms and an alkoxy group having 1 to 10 carbon atoms, preferably an alkyl group having 1 to 10 carbon atoms.

The alkyl group having 1 to 10 carbon atoms is not particularly limited, but includes methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, neopentyl, 1,2-dimethylpropyl, n-hexyl, isohexyl, n-nonyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and cyclononyl groups, of which methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl groups are preferred, and methyl and ethyl groups are even more preferred.

Alkoxy groups having 1 to 10 carbon atoms are not particularly limited, but examples include methoxy groups, ethoxy groups, propoxy groups, isopropoxy groups, butoxy groups, pentyloxy groups, hexyloxy groups, 2-ethylhexyloxy groups, octyloxy groups, and nonyloxy groups. These substituents may be used alone or in combination of two or more types.

In formula (1), m is an integer of 3 to 6, preferably 3 or 4, and more preferably 3. Each R1 is independently hydrogen or a substituent represented by the following formula (2).

In general formula (2), R2 and R3 each independently represent a linear or branched alkyl group having 1 to 5 carbon atoms.

Specific examples of alkyl groups having 1 to 5 carbon atoms include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, etc. Among these, methyl, ethyl, propyl, and isopropyl are preferred from the viewpoint of reactivity in production and ease of availability, with the methyl group being particularly preferred.

n2 and n3 are each independently an integer of 0 to 5, preferably 0 or an integer of 2 or more, and more preferably 2. When n2 and n3 are 1 or more, the substitution positions of R2 and R3 on the benzene ring are not particularly limited, but it is preferable that each is independently present at the ortho or meta position with respect to the phosphate ester bond. The presence of an alkyl group at the ortho position hydrophobically blocks the phosphate ester, reducing water absorption and suppressing hydrolysis, thereby further improving the properties of the phosphorus-containing phenol compound of the present invention. For this reason, it is particularly preferable that alkyl groups are substituted at two ortho positions with respect to the phosphate ester bond, and n2 and n3 are preferably 2 or more.

The ratio of hydrogen in R1 and the substituent represented by general formula (2) in the phosphorus-containing phenol compound of the present invention is not particularly limited, but at least one R1 contains a substituent represented by general formula (2). By containing the structure of general formula (2), the phosphorus-containing phenol compound of the present invention can exhibit excellent flame retardancy. In the phosphorus-containing phenol compound (mixture) of the present invention, the ratio of the substituent represented by general formula (2) in R1 as a compound (mixture) is preferably 10 mol % or more, more preferably 30 mol % or more, and even more preferably 50 mol % or more.
Examples of phosphorus-containing phenolic compounds of the present invention include, but are not limited to, compounds of the following structures and mixtures thereof:

The phosphorus-containing phenol compound of the present invention does not need to be used as a single compound, but may be a mixture containing multiple compounds with different numbers of substituents represented by general formula (2). The more the number of substituents represented by general formula (2) increases, the more the flame retardancy and dielectric properties improve, and the fewer the structures of general formula (2), the more reactive hydroxyl groups there are, which improves heat resistance and prevents the bleed-out of the flame retardant. Therefore, by containing multiple compounds with different numbers of substituents represented by general formula (2), well-balanced properties can be achieved.

The manufacturing method is described in detail below, but the phosphorus-containing phenol compound of the present invention can be obtained by reacting a polyhydric phenol compound represented by the general formula (3) described below with a phosphorus compound represented by the general formula (4). Since the raw material polyhydric phenol compound does not contain phosphorus, the introduction of the substituent represented by the general formula (2) can be determined by measuring the phosphorus content of the compound after the reaction.

The introduction of the substituent represented by the general formula (2) can be judged by the phosphorus content. If the phosphorus content is not 0, the introduction of the substituent represented by the general formula (2) can be judged, but if the phosphorus content is low, flame retardancy is not expressed, and from the viewpoint of flame retardancy, the higher the phosphorus content, the better. However, as the phosphorus content increases, the number of hydroxyl groups decreases, and heat resistance may be insufficient or bleed-out may occur. Therefore, the phosphorus content of the phosphorus-containing phenolic compound is preferably 1.5 to 15.0 mass%, more preferably 3.0 to 12.0 mass%, and even more preferably 5.0 to 10.0 mass%.
The hydroxyl equivalent of the phosphorus-containing phenol compound is in the range of 50 to 1000 g/eq, preferably 80 to 800 g/eq, and more preferably 100 to 600 g/eq.

In terms of availability of raw materials, the phosphorus-containing phenol compound of the present invention is preferably a mixture of the following general formulas (5), (6), and (7). More preferably, the compound contains 10 to 80 mol% of a compound (monosubstitution) represented by the following general formula (5) in which two R1s are hydrogen and one R1 is a substituent represented by general formula (2), 5 to 50 mol% of a compound (disubstitution) represented by the following general formula (6) in which one R1 is hydrogen and two R1s are substituents represented by general formula (2), and 1 to 50 mol% of a compound (trisubstitution) represented by the following general formula (7) in which three R1s are substituents represented by general formula (2), thereby obtaining a cured product with excellent balance of flame retardancy, heat resistance, and dielectric properties. More preferably, the monosubstitution is 20 to 70 mol%, the disubstitution is 10 to 40 mol%, and the trisubstitution is 2 to 40 mol%. It is acceptable for unreacted raw material phenols to remain, but it is desirable that the amount is less than 30 mol%.

In the above general formulae (5), (6), and (7), R2, R3, n2, and n3 are defined as in general formula (2).

The compositions of the above general formulas (5), (6), and (7) can be confirmed by liquid chromatography, size exclusion chromatography, etc.

Next, a method for producing the phosphorus-containing phenolic compound of the present invention will be described. The phosphorus-containing phenolic compound of the present invention is an aromatic phosphate ester having one or more phenolic hydroxyl groups, and its production method conforms to a general method for producing an aromatic phosphate ester. That is, one example of the reaction form is an esterification reaction using phosphorus oxyhalide (phosphoryl halide) and phenols as raw materials, and the corresponding phosphate ester can be obtained by a dehydrohalogenation reaction.

In order to prevent a hydrolysis reaction catalyzed by the by-product hydrogen halide and to efficiently obtain the product, this esterification reaction is carried out using a catalyst and/or removing the released hydrogen halide from the reaction system.
The released hydrogen halide (e.g., hydrogen chloride) is a gas, and since its volume increases when it is gasified, it is easily released outside the reaction system in the case of a highly reactive raw material, but in the case of a less reactive raw material, the amount of hydrogen halide released is small and it tends to remain in the system, which may cause a hydrolysis reaction. In such cases, it is effective to capture the generated hydrogen halide to prevent the hydrolysis reaction from occurring, and amines are sometimes used as hydrogen halide scavengers.

Since the phosphorus-containing phenol compound of the present invention is a compound represented by the above general formula (1), it is necessary to react a polyhydric hydroxy compound represented by the following general formula (3) corresponding to the general formula (1) as a raw material with a phenol and a phosphorus oxyhalide, which are raw materials for the phosphorus halide compound represented by the following general formula (4) corresponding to the above general formula (2).

In formula (3), Ar and m are the same as those in formula (1).

However, when a polyhydric hydroxy compound having multiple hydroxyl groups and represented by general formula (3), which is an essential raw material for the phosphorus-containing phenolic compound of the present invention, is reacted with phosphorus oxyhalide, a side reaction occurs in which multiple hydroxyl groups react with phosphorus oxyhalide, so it is necessary to appropriately adjust the reaction order, raw material charging ratio, reaction conditions, etc., to efficiently obtain the target compound.

Therefore, instead of reacting the three raw materials of the polyhydric hydroxy compound represented by the general formula (3), the phenols which are the raw materials of the halogenated phosphorus compound represented by the general formula (4), and the phosphorus oxyhalide at once, the phosphorus oxyhalide, for example, phosphorus oxychloride (POCl3) is reacted with the phenols first to obtain the halogenated phosphorus compound represented by the following general formula (4), and then the obtained halogenated phosphorus compound represented by the general formula (4) is reacted with the polyhydric hydroxy compound represented by the general formula (3), thereby making it possible to efficiently obtain the target compound. In this case, in the first reaction, the phenols are mixed in a ratio of 2 moles per mole of the phosphorus oxyhalide. The phenols are preferably in the range of 1.8 to 2.2 moles, more preferably 1.9 to 2.1 moles.

In the compound represented by formula (4), R2, R3, n2, and n3 are the same as those in formula (2), and X represents a halogen atom.

The phosphorus-containing phenol compound of the present invention can be obtained by reacting the hydroxyl groups of a polyhydric hydroxy compound represented by general formula (3) with a halogenated phosphorus compound represented by general formula (4). Therefore, by adjusting the molar ratio of the halogenated phosphorus compound of general formula (4) to the hydroxyl groups, it is possible to control the hydroxyl group equivalent and phosphorus content.

The molar ratio of the reaction is preferably 0.1 to 0.9 moles, more preferably 0.2 to 0.8 moles, and even more preferably 0.3 to 0.7 moles of the halogenated phosphorus compound represented by general formula (4) per mole of hydroxyl groups of the polyhydric hydroxy compound represented by general formula (3). A ratio of 0.1 moles or less is not preferred because the phosphorus content decreases and flame retardancy is insufficient, while a ratio of 0.9 moles or more is not preferred because the number of hydroxyl groups, which are reactive groups, decreases and heat resistance is insufficient.

The curable flame-retardant resin composition of the present invention contains the above-mentioned phosphorus-containing phenolic compound as an essential component, and can be obtained by mixing a curable resin with a phosphorus-containing phenolic compound. There are no limitations on the curable resin, so long as it reacts with the hydroxyl group of the phosphorus-containing phenolic compound of the present invention, and examples of the curable resin include epoxy resins and maleimide resins.

Epoxy resins that can be used in the present curable resin composition are not particularly limited, but include, for example, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol AF type epoxy resins, phenol novolac type epoxy resins, naphthol novolac type epoxy resins, dicyclopentadiene type epoxy resins, phenol aralkyl type epoxy resins, naphthol type epoxy resins, naphthol aralkyl type epoxy resins, naphthalene type epoxy resins, glycidylamine type epoxy resins, cresol novolac type epoxy resins, biphenyl type epoxy resins, tetramethylbiphenyl type epoxy resins, linear aliphatic epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexane dimethanol type epoxy resins, trimethylol type epoxy resins, halogenated epoxy resins, triphenylmethane type epoxy resins, tetraphenylethane type epoxy resins, etc. These epoxy resins may be used alone or in a mixture of two or more.

The amounts of the phosphorus-containing phenolic compound and the epoxy resin are determined based on the phosphorus content of the resin composition. The phosphorus content in the resin composition is preferably 0.5 to 5.0% by mass, and more preferably 1.0 to 4.0% by mass. If the phosphorus content is 0.5% by mass or less, flame retardancy is not exhibited, and if it is 5.0% by mass or more, the amount of phosphorus-containing phenolic compound is high, resulting in an excess of hydroxyl groups relative to epoxy groups, which is not preferred as it results in insufficient crosslinking and a brittle cured product. In addition, when an epoxy resin is used as a curable resin, it may contain a curing agent other than the phosphorus-containing phenolic compound of the present invention.

Examples of hardeners that can be used in combination with phosphorus-containing phenolic compounds include phenolic hardeners, amine compounds, amide compounds, acid anhydride compounds, naphthol hardeners, active ester hardeners, benzoxazine hardeners, cyanate ester hardeners, and acid anhydride hardeners. These may be used alone or in combination of two or more.

The amount of hardener other than the phosphorus-containing phenolic compound of the present invention is preferably such that the phosphorus content of the resin composition of the present invention is 0.5 to 5.0 mass %, and the molar ratio (Nh/Ne) of the total number of moles (Nh) of reaction points between the phosphorus-containing phenolic compound and the epoxy groups of the other hardener to the number of moles (Ne) of the epoxy groups is 0.7 to 1.3, preferably 0.9 to 1.1. Molar ratios outside this range are not preferred because they result in insufficient crosslinking and a brittle cured product.

The resin composition of the present invention may also contain a curable resin other than an epoxy resin. Examples of curable resins other than an epoxy resin include vinyl ester resins, polyvinylbenzyl resins, unsaturated polyester resins, curable vinyl resins, radical polymerizable resins such as maleimide resins, and cyanate resins.

The curable resin composition of the present invention may contain a curing accelerator as necessary. Examples of the curing accelerator used here include phosphorus-based compounds, tertiary amines, imidazoles, organic acid metal salts, Lewis acids, and amine complex salts. The amount of the curing accelerator added is preferably 0.1 to 10.0 parts by mass per 100 parts by mass of the total of the phosphorus-containing phenolic compound, the curable resin, and other curing agents.

In addition to the components described above, the resin composition of the present invention can contain other components, such as thermosetting resins, thermoplastic resins, organic fillers, inorganic fillers, organic solvents, thickeners, defoamers, adhesion promoters, colorants, and additives, as appropriate.

Examples of thermoplastic resins include polystyrene, polyphenylene ether resin, polyetherimide resin, polyethersulfone resin, PPS resin, polycyclopentadiene resin, polycycloolefin resin, etc., known thermoplastic elastomers such as styrene-ethylene-propylene copolymer, styrene-ethylene-butylene copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, hydrogenated styrene-butadiene copolymer, hydrogenated styrene-isoprene copolymer, etc., and rubbers such as polybutadiene and polyisoprene. Preferred examples include polyphenylene ether resin (unmodified) and hydrogenated styrene-butadiene copolymer.

A filler can be blended into the curable resin composition of the present invention. Examples of fillers include those added to enhance the heat resistance and flame retardancy of the cured product of the curable resin composition, and known fillers can be used, but are not particularly limited. In addition, by including a filler, the heat resistance, dimensional stability, flame retardancy, etc. can be further improved. Specific examples include silica such as spherical silica, metal oxides such as alumina, titanium oxide, and mica, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, talc, aluminum borate, barium sulfate, and calcium carbonate. When metal hydroxides such as aluminum hydroxide and magnesium hydroxide are used, they act as flame retardant assistants, and flame retardancy can be ensured even with a low phosphorus content. Among these, silica, mica, and talc are preferred, and spherical silica is more preferred. In addition, one of these may be used alone, or two or more may be used in combination.

The filler may be used as is, or may be surface-treated with a silane coupling agent such as a vinyl silane type, methacryloxy silane type, acryloxy silane type, or styryl silane type, or an epoxy silane type, amino silane type, or cationic silane type. This increases the adhesive strength with the metal foil and the interlayer adhesive strength between resins. Also, instead of surface-treating the filler in advance, the above silane coupling agent may be added using the integral blend method.

The amount of filler is preferably 10 to 200 parts by mass, and more preferably 30 to 150 parts by mass, per 100 parts by mass of the total solids excluding the filler (including organic components such as monomers and flame retardants, but excluding solvents).

The curable resin composition of the present invention may further contain additives other than those mentioned above. Examples of additives include defoamers such as silicone-based defoamers and acrylic acid ester-based defoamers, heat stabilizers, antistatic agents, UV absorbers, dyes and pigments, lubricants, dispersants such as wetting dispersants, etc.

The cured product obtained by curing the curable resin composition of the present invention can be used as a molded product, laminate, cast product, adhesive, coating, or film. For example, a cured product of a semiconductor encapsulation material is a cast product or molded product, and a method for obtaining a cured product for such applications is to cast the curable resin composition or mold it using a transfer molding machine or injection molding machine, and then heat it at 80 to 230°C for 0.5 to 10 hours to obtain a cured product.

The curable resin composition of the present invention can also be used as a prepreg. When producing a prepreg, the composition can be prepared in a varnish form to be used as a resin varnish for the purpose of impregnating a substrate (fibrous substrate) for forming a prepreg or for the purpose of using the composition as a circuit board material for forming a circuit board.
This resin varnish is suitable for circuit boards and can be used as a varnish for circuit board materials. Specific applications of the circuit board materials referred to here include printed wiring boards, printed circuit boards, flexible printed wiring boards, build-up wiring boards, etc.

The above resin varnish is prepared, for example, as follows.
First, each component that can be dissolved in an organic solvent, such as the phosphorus-containing phenol compound of the present invention and the epoxy resin component, is put into an organic solvent and dissolved. At this time, heating may be performed as necessary. Then, as necessary, a component that is not dissolved in an organic solvent, such as an inorganic filler, is added, and dispersed using a ball mill, a bead mill, a planetary mixer, a roll mill, or the like, to prepare a varnish-like curable resin composition. The organic solvent used here is not particularly limited as long as it dissolves the resin component used in the epoxy resin composition of the present invention and does not inhibit the curing reaction. For example, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; esters such as ethyl acetate, propyl acetate, and butyl acetate; polar solvents such as dimethylacetamide and dimethylformamide; aromatic hydrocarbon solvents such as toluene and xylene, and the like can be used alone or in combination of two or more of them.

When preparing a resin varnish, the amount of organic solvent used is preferably 5 to 900% by mass, more preferably 10 to 700% by mass, and particularly preferably 20 to 500% by mass, relative to 100% by mass of the curable resin composition of the present invention.

　Known materials are used as the substrates used to create prepregs, and examples of such substrates include glass fiber, carbon fiber, polyester fiber, polyamide fiber, alumina fiber, and paper, which may be used alone or in combination of two or more. If necessary, coupling agents may be used with these substrates to improve adhesion at the interface between the resin and the substrate. Common coupling agents include silane coupling agents, titanate coupling agents, aluminum-based coupling agents, and zircoaluminate coupling agents.

The prepreg of the present invention can be obtained by impregnating a substrate with the resin varnish and then drying it. Impregnation is performed by dipping, coating, etc. Impregnation can be repeated multiple times as necessary, and in this case, it is also possible to repeat impregnation using multiple solutions with different compositions and concentrations to adjust to the final desired resin composition and resin amount. After impregnation, the substrate can be heated and dried at 100 to 180°C for 1 to 30 minutes to obtain a prepreg. Here, the amount of resin in the prepreg is preferably 30 to 80% by mass.

The curable resin composition of the present invention can also be used as a laminate. When a laminate is formed using prepregs, one or more prepregs are laminated, metal foil is placed on one or both sides to form a laminate, and the laminate is heated and pressed to laminate and integrate it. Here, the metal foil can be a single metal foil, an alloy metal foil, or a composite metal foil such as copper, aluminum, brass, or nickel. The conditions for heating and pressing the laminate can be appropriately adjusted to the conditions under which the curable resin composition is cured, but if the pressure is too low, air bubbles may remain inside the obtained laminate and the electrical properties may deteriorate, so it is preferable to pressurize under conditions that satisfy the moldability. For example, the temperature can be set to 180 to 230°C, the pressure to 49.0 to 490.3 N/cm2 (5 to 50 kgf/cm2), and the heating and pressing time to 40 to 240 minutes. Furthermore, a multilayer board can be produced by using the single-layer laminate obtained in this way as an inner layer material. In this case, a circuit is first formed on the laminate using an additive or subtractive method, and the surface of the formed circuit is then treated with an acid solution for blackening to obtain an inner layer material. An insulating layer is formed on one or both circuit-forming surfaces of this inner layer material using a resin sheet, metal foil with resin, or prepreg, and a conductor layer is formed on the surface of the insulating layer to form a multilayer board.

A method for producing a build-up film from the curable composition of the present invention includes, for example, applying the above-mentioned resin varnish onto a support film and drying it to form a film-like insulating layer. The film-like insulating layer thus formed can be used as a build-up film for multilayer printed wiring boards.

The drying step is preferably carried out so that the organic solvent content in the build-up film resin composition layer is 10% by mass or less, and preferably 5% by mass or less. Drying conditions vary depending on the type of organic solvent in the varnish and the amount of organic solvent, but drying can be carried out at 50 to 160°C for about 3 to 20 minutes.

The thickness of the build-up film formed on the support is usually equal to or greater than the thickness of the conductor layer. Since the thickness of the conductor layer of a circuit board is usually in the range of 5 to 70 μm, it is preferable that the thickness of the resin composition layer is 10 to 100 μm.

In addition, it is preferable that the build-up film of the present invention is protected by a protective film, since this can prevent the adhesion of dirt and the like to the surface and prevent scratches.

The above-mentioned support film and protective film may be made of polyolefins such as polyethylene, polypropylene, and polyvinyl chloride; polyesters such as polyethylene terephthalate and polyethylene naphthalate; polycarbonate; polyimide; and even release paper and metal foils such as copper foil and aluminum foil. The support film and protective film may be subjected to a mud treatment, corona treatment, or release treatment.

The thickness of the support film is not particularly limited, but is usually in the range of 10 to 150 μm, and preferably in the range of 25 to 50 μm. The thickness of the protective film is preferably 1 to 40 μm.

The support film described above is peeled off after laminating it onto the circuit board, or after forming an insulating layer by heat curing. Peeling off the support film after the adhesive film has been heat cured can prevent curing inhibition caused by oxygen during the curing process, and can also prevent the adhesion of dirt, etc. When peeling off after curing, the support film is usually subjected to a release treatment beforehand.

The present invention will now be described with reference to examples, but is not limited to these. In each example, all parts are by weight.
The physical properties of each cured sample in the examples were measured by the methods described below.

(1) Molecular weight and molecular weight distribution of polymer: The molecular weight and molecular weight distribution of the phosphorus-containing phenol compound were measured using GPC (Tosoh Corporation, HLC-8120GPC) with tetrahydrofuran as a solvent, a flow rate of 1.0 ml/min, a column temperature of 38° C., and a calibration curve based on monodisperse polystyrene.
(2) Hydroxyl equivalent: Approximately 6 mg/eq of sample was weighed out into a 100 mL stoppered flask, 3 mL of a mixed reagent of acetic anhydride/pyridine = 3/1 (volume ratio) was added, a cooling tube was attached, the mixture was heated to reflux on a hot plate for 5 minutes, and after cooling for 5 minutes, 1 mL of water was added. The solution was titrated potentiometrically with a 0.5 mol/L KOH/MeOH solution to calculate the hydroxyl equivalent.
(3) Phosphorus content: Sulfuric acid, hydrochloric acid, and perchloric acid were added to the sample, which was then heated and wet-ashed to convert all phosphorus atoms into orthophosphate. Metavanadate and molybdate were reacted in the sulfuric acid acid solution, and the absorbance at 420 nm of the resulting phosphorus vanadate molybdate complex was measured. The phosphorus atom content was expressed in mass% based on a calibration curve previously prepared using potassium dihydrogen phosphate.
(4) Glass transition temperature: Measured from the baseline shift using a differential scanning calorimeter manufactured by Hitachi High-Tech Science Corporation at a heating rate of 10° C./min.
(5) Dielectric constant and dielectric loss tangent: The dielectric constant (Dk) and dielectric loss tangent (Df) at a frequency of 1 GHz were determined by a capacitance method in an environment of 25° C. and humidity of 60% using a material analyzer (manufactured by AGILENT Technologies) in accordance with the IPC-TM-6502.5.5.9 standard.
(6) Flame retardancy: Evaluated by the vertical method using five test pieces in accordance with UL 94. The evaluation was recorded as V-0, V-1, or V-2.
(7) Water absorption: In accordance with JIS K 7209, a cured sample was immersed in water at 23° C. and the saturated water content was determined.
(8) Rate of change in dielectric properties after water absorption: The rate of change was calculated from the measured value (A1) of the cured sample before the water absorption test and the measured value (A2) after water absorption according to the following formula.
Dielectric property change rate (%) = (A2 - A1) / A1 x 100

In the synthesis examples, the following compounds were used as raw materials.
Phosphorus oxychloride (Tokyo Chemical Industry Co., Ltd.)
・2,6-Dimethylphenol (Tokyo Chemical Industry Co., Ltd.)
・Phloroglucinol (Tokyo Chemical Industry Co., Ltd.)

Synthesis Example 1 Synthesis of di-2,6-xylyl phosphorochloridate (DXPC) Into a 2 L four-neck flask equipped with a stirrer, a thermometer, and a hydrochloric acid recovery device (a condenser connected to a water scrubber), 767 g (5 mol) of phosphorus oxychloride (structural formula below),

2,6-dimethylphenol (structural formula below) 1200 g (9.8 mol),

140 g of xylene as a solvent and 6.2 g (0.065 mol) of magnesium chloride as a catalyst were charged. The resulting mixed solution was gradually heated to a temperature of 160°C over about 3 hours while stirring to react, and the generated hydrogen chloride gas was collected with a water scrubber. Thereafter, the pressure in the flask was gradually reduced to 20 kPa at the same temperature, and xylene, unreacted phosphorus oxychloride and 2,6-dimethylphenol, and by-product hydrogen chloride were removed to obtain 1700 g of a reaction product mainly composed of di-2,6-xylyl phosphorochloridate (DXPC: structural formula below). The chlorine content of the reaction mixture was 10.9% by mass.

Example 1 Synthesis of Phosphorus-Containing Phenol (Compound A) Into a 200 mL four-neck flask equipped with a stirrer, a thermometer, and a hydrochloric acid recovery device (a condenser connected to a water scrubber), 51.6 g of mesitylene, 12.6 g (0.1 mol) of phloroglucinol (structural formula below),

21.8 g (0.06 mol) of di-2,6-xylyl phosphorochloridate obtained in Synthesis Example 1 and 0.4 g (0.004 mol) of anhydrous magnesium chloride as a catalyst were charged. The resulting mixed solution was gradually heated to 155°C while stirring, and after reaching 155°C, the reaction was carried out for 18 hours and the generated hydrogen chloride was collected. After cooling to 60°C, 35 g of ethyl acetate was added, and the mixture was washed with acid, neutralized, washed twice with water, and the solvent was removed to obtain 26.1 g of compound A.
Compound A had a hydroxyl equivalent of 125 g/eq and a phosphorus content of 6.4% by mass. Furthermore, it was confirmed by GPC that the compound contained 68 mol % of a compound in which one hydroxyl group of phloroglucinol had reacted with di-2,6-xylyl phosphorochloridate (monosubstitution, structural formula below), 10 mol % of a compound in which two hydroxyl groups had reacted (disubstitution, structural formula below), 2 mol % of a compound in which three hydroxyl groups had reacted (trisubstitution, structural formula below), and 20 mol % of phloroglucinol.

(Example 2) Synthesis of phosphorus-containing phenol (compound B) 110.9 g of mesitylene, 12.6 g (0.1 mol) of phloroglucinol, 54.5 g (0.15 mol) of di-2,6-xylyl phosphorochloridate, and 0.8 g (0.008 mol) of anhydrous magnesium chloride as a catalyst were charged into a 200 mL four-neck flask equipped with a stirrer, a thermometer, and a hydrochloric acid recovery device (a condenser connected to a water scrubber). The resulting mixed solution was gradually heated to 155°C while stirring, and after reaching 155°C, the mixture was reacted for 18 hours and the generated hydrogen chloride was collected. After cooling to 60°C, 60 g of ethyl acetate was added, and the mixture was subjected to acid washing, neutralization, and two water washings, and the solvent was removed to obtain 51.2 g of compound B.
Compound B had a hydroxyl equivalent of 412 g/eq and a phosphorus content of 8.4% by mass. Furthermore, it was confirmed by GPC that the compound contained 39.5 mol % of a compound in which one hydroxyl group of phloroglucinol had reacted with di-2,6-xylyl phosphorochloridate (monosubstitution product), 34.0 mol % of a compound in which two hydroxyl groups had reacted (disubstitution product), 25.0 mol % of a compound in which three hydroxyl groups had reacted (trisubstitution product), and 1.5 mol % of phloroglucinol.

(Example 3) Synthesis of phosphorus-containing phenol (compound C) 249.5 g of mesitylene, 12.6 g (0.1 mol) of phloroglucinol, 87.2 g (0.24 mol) of di-2,6-xylyl phosphorochloridate, and 1.2 g (0.012 mol) of anhydrous magnesium chloride as a catalyst were charged into a 300 mL four-neck flask equipped with a stirrer, a thermometer, and a hydrochloric acid recovery device (a condenser connected to a water scrubber). The resulting mixed solution was gradually heated to 155°C while stirring, and after reaching 155°C, the mixture was reacted for 18 hours and the generated hydrogen chloride was collected. After cooling to 60°C, 60 g of ethyl acetate was added, and the mixture was subjected to acid washing, neutralization, and two water washings, and the solvent was removed to obtain 51.2 g of compound C.
Compound C had a hydroxyl equivalent of 587 g/eq and a phosphorus content of 9.0% by mass. Furthermore, it was confirmed by GPC that the compound contained 25 mol % of a compound in which one hydroxyl group of phloroglucinol had reacted with di-2,6-xylyl phosphorochloridate (mono-substitution product), 35 mol % of a compound in which two hydroxyl groups had reacted (di-substitution product), and 40 mol % of a compound in which three hydroxyl groups had reacted (tri-substitution product).

(Comparative Example 1) Synthesis of phosphorus-containing phenol (compound D) It was synthesized according to the method described in International Publication WO2021/256351. Specifically, 1500 g of phosphorus oxychloride, 611 g of 2,6-dimethylphenol, and 1.2 g of magnesium chloride as a catalyst were charged into a 2-liter four-neck flask equipped with a stirrer, a thermometer, and a hydrochloric acid recovery device (a condenser connected to a water scrubber).
The resulting mixed solution was gradually heated to 110°C over about 3 hours while stirring to react, and the generated hydrogen chloride (hydrochloric acid gas) was collected with a water scrubber. Thereafter, the pressure in the flask was gradually reduced to 12 kPa at 120°C to remove unreacted phosphorus oxychloride and phenol, and by-product hydrogen chloride, yielding 1,200 g of mono-2,6-dimethylphenylphosphorodichloridate.
A 2-liter four-neck flask equipped with a stirrer, a thermometer, a dropping funnel, and a condenser was charged with 320 g of 2,3,5-trimethylhydroquinone, 135 g of pyridine as a hydrogen chloride scavenger, and 200 g of toluene as a solvent. The dropping funnel was charged with 203 g of the mono-2,6-dimethylphenylphosphorodichloridate.
The mixed solution in the four-neck flask was heated to a temperature of 20° C. while stirring, and while maintaining the same temperature (20° C.), mono 2,6-dimethylphenyl phosphorodichloridate in the dropping funnel was dropped over 2 hours. After the dropwise addition was completed, the mixture was heated to 65° C. and stirred for 5 hours to obtain a reaction product. The obtained reaction product was washed with dilute hydrochloric acid and water, heated to a temperature of 150° C., reduced pressure to 2 kPa to distill off water, toluene, and low boiling points, and cooled to room temperature to obtain 330 g of a black-brown solid (compound D) having the following structure.

Examples 4 to 8, Comparative Examples 2 to 10
<Preparation of Curable Resin Composition and Preparation of Cured Product>
A varnish was prepared by mixing the various components in the ratios shown in Table 1, and was then applied to a PET film and dried in an oven at 130°C for 5 minutes to prepare a film of the resin composition. The film was then pulverized to obtain a powder of the resin composition. The powder was then sandwiched between a stainless steel mirror plate and a spacer, molded in a vacuum oven at 190°C for 90 minutes, and cured at 200°C for 5 hours to obtain a cured sample. The glass transition temperature and dielectric properties were evaluated using the cured sample.
<Preparation of flame retardant test specimens>
A varnish was prepared by mixing the various components in the ratios shown in Table 1. This resin varnish was impregnated into a glass cloth (manufactured by Nitto Boseki Co., Ltd.; 7628 type; product number H258), which was then dried by heating at 130° C. for 5 minutes to obtain a prepreg.
Eight sheets of the obtained prepreg were laminated with copper foil (3EC-III, thickness 35 μm, manufactured by Mitsui Mining & Smelting Co., Ltd.) on top and bottom, and vacuum pressed at 2 MPa under temperature conditions of 130°C x 15 minutes + 190°C x 80 minutes to obtain a laminated board with a thickness of 1.6 mm. The copper foil was etched and cut to obtain a flame retardant test piece. The flame retardant test piece was used to evaluate the flame retardancy.

The formulations and results are shown in Table 1. The abbreviations in the table represent the following compounds.
ESN-475V: Naphthalene type epoxy resin (epoxy equivalent: 325 g/eq) manufactured by Nippon Steel Chemical & Material Co., Ltd.
SN-485: Naphthol resin (hydroxyl equivalent: 210 g/eq) manufactured by Nippon Steel Chemical & Material Co., Ltd.
TPP: Triphenyl phosphate (phosphorus content 9.5% by mass) manufactured by Daihachi Chemical Industry Co., Ltd.
PX-200: Aromatic condensed phosphate ester (phosphorus content 9.02% by mass) manufactured by Daihachi Chemical Industry Co., Ltd.
LC-950PM60: DOPO-BPA manufactured by Shin A Co., Ltd. (hydroxyl equivalent: 570 g/eq, phosphorus content: 10.9% by mass, solid content: 60% by mass)
2E4MZ: 2-ethyl-4-methylimidazole manufactured by Shikoku Kasei Co., Ltd.

 

INDUSTRIAL APPLICABILITY The phosphorus-containing phenol compound of the present invention is useful for imparting flame retardancy to plastic materials, for example, thermosetting resins such as epoxy resins, used in electric and electronic products, office automation equipment, communication equipment, building materials, etc., and is particularly useful as a flame-retardant material for reducing transmission loss at higher frequencies associated with increased information processing volume in electronic devices.

Claims (8)

1. A phosphorus-containing phenol compound represented by general formula (1):
   

   

   In general formula (1), Ar is an aromatic ring group having 6 to 30 carbon atoms which may have a substituent, and R1 is independently hydrogen or a substituent represented by the following general formula (2), with at least one R1 containing a substituent represented by general formula (2). m is an integer of 3 to 6.
   

   

   In general formula (2), R2 and R3 each independently represent a linear or branched alkyl group having 1 to 5 carbon atoms, and n2 and n3 each independently represent an integer of 0 to 5.
2. The phosphorus-containing phenol compound according to claim 1, wherein Ar is an aromatic ring group selected from the group consisting of a benzene skeleton, a naphthalene skeleton, a biphenyl skeleton, and an anthracene skeleton.
3. The phosphorus-containing phenol compound according to claim 2, wherein Ar is a benzene ring.
4. The phosphorus-containing phenolic compound according to claim 3, wherein m is 3.
5. The phosphorus-containing phenol compound according to claim 4, characterized in that it contains 10 to 80 mol % of compounds in which two R1s are hydrogen and one R1 is a substituent represented by general formula (2), 5 to 50 mol % of compounds in which one R1 is hydrogen and two R1s are substituents represented by general formula (2), and 1 to 50 mol % of compounds in which three R1s are substituents represented by general formula (2), for three OR1 groups in general formula (1).
6. The method for producing a phosphorus-containing phenol compound according to any one of claims 1 to 5, characterized in that 0.1 to 0.9 moles of a compound represented by general formula (4) are reacted with 1 mole of a hydroxyl group of a compound represented by general formula (3).
   

   

   In formula (3), Ar and m are the same as those in formula (1).
   

   

   In formula (4), X represents a halogen atom, and R2, R3, n2, and n3 are each defined as in formula (2).
7. A curable resin composition comprising the phosphorus-containing phenolic compound according to any one of claims 1 to 5 and a curable resin.
8. A cured product obtained by curing the curable resin composition according to claim 7.
   

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