JP2009096874A - Thermosetting resin composition, cured product thereof and fiber-reinforced composite material - Google Patents

Abstract

[PROBLEMS] To prevent generation of volatile substances such as water and ammonia gas during the curing reaction, to have viscosity characteristics suitable for various molding methods for producing a fiber-reinforced composite material, and to obtain a cured product having heat resistance and Provided is a novel dihydrobenzoxazine-based thermosetting resin composition having an excellent residual carbon ratio.
A thermosetting resin composition comprising a compound having at least one dihydrobenzoxazine ring and a compound having at least one cyanate group.
[Selection figure] None

Description

  The present invention relates to a thermosetting resin composition, particularly various moldings of fiber reinforced composite materials such as resin transfer molding (hereinafter referred to as RTM) which does not generate volatiles such as water and ammonia gas in the course of curing reaction. The present invention relates to a dihydrobenzoxazine-based thermosetting resin composition having viscosity characteristics suitable for the method and excellent in the heat resistance and residual carbon ratio of the resulting cured product. Here, the viscosity characteristic suitable for various molding methods of fiber reinforced composite materials such as RTM is that the melt viscosity at a certain temperature is 10 (Pa · s) or less, and the melt viscosity does not exceed 2 hours even at that temperature. Maintains a low viscosity of 100 (Pa · s) or less (low viscosity and small change in viscosity so that the fiber can be impregnated for a long time), but immediately when the temperature is higher (curing temperature) It means to harden.

  Fiber reinforced composite materials composed of glass fibers, carbon fibers, aramid fibers, and other reinforcing fibers and matrix resins are lightweight and have excellent mechanical properties such as strength, rigidity, impact resistance, and fatigue resistance, and heat resistance. In recent years, it has been widely used in many fields such as fields such as space / aviation, automobiles, railway vehicles / ships, sporting goods, and general industrial fields.

  As the matrix resin, both a thermosetting resin and a thermoplastic resin are used. As the thermosetting resin, epoxy resin, unsaturated polyester resin, vinyl ester resin, phenol resin, maleimide resin, cyanate resin and the like are used. In particular, phenolic resins are often used in fields that require heat resistance and flame retardancy, particularly in the space and aviation fields (see, for example, Patent Document 1 or 2).

JP 2006-111682 A JP 2002-178425 A

  Methods such as a prepreg method, a hand layup method, a filament winding method, and an RTM method are applied to the production of the fiber reinforced composite material. Among these, the RTM method is a method of impregnating a liquid thermosetting resin composition into a reinforcing fiber base disposed in a mold and heat-curing, and can form a fiber-reinforced composite material having a large and complicated shape. Has features.

  The properties required for the resin used in the RTM method include a low viscosity for facilitating the impregnation of the reinforcing fiber base material and a small change in viscosity during the resin impregnation. Furthermore, after the resin is impregnated, the resin is cured in the mold, but it is also important that volatiles are not generated in the curing reaction process, and that the resin is cured as soon as the temperature is raised to a curing temperature (for example, 200 ° C.). is there. Therefore, many epoxy resins and unsaturated polyester resins are used as resins suitable for the RTM method (see, for example, Patent Documents 3 to 6).

JP 2002-120315 A JP-A-6-287270 Japanese Patent Laid-Open No. 6-136099 Japanese Patent Laid-Open No. 5-117346

  However, in fields that require heat resistance and flame retardancy such as space and aviation, epoxy resin and unsaturated polyester resin cannot provide the necessary flame retardancy and residual charcoal rate. Therefore, it is optimal to use a phenol resin as a resin excellent in these properties (flame retardancy and residual carbon ratio). When an attempt is made to apply a phenol resin to an RTM, the phenol resin is a condensation reaction, so that volatile substances such as water and ammonia gas are generated in the process. In addition, the viscosity of the resin is high, the resin does not sufficiently impregnate the reinforcing fibers when molding using RTM, defects such as voids occur, and there is a problem that a molded product with excellent quality cannot be obtained, It was difficult to apply a phenol resin to RTM (see, for example, Non-Patent Documents 7 to 9).

Polymer Composites, 23, 2, 141-152 (2002). Polymer Composites, 20, 6, 780-788 (2002). Polymer Composites, 20, 5, 675-682 (2002).

  Therefore, when performing RTM molding in fields where heat resistance and flame retardancy are required, as a substitute for conventional phenolic resins, by-products are not generated during curing and a low viscosity that can be injected into fabrics is long. It is essential to develop new materials that maintain time. Furthermore, it is also required to have various performances (for example, high heat resistance and residual carbon ratio) similar to phenol resins.

  By the way, unlike a conventional phenol resin, a dihydrobenzoxazine compound is known as a thermosetting resin that does not generate volatile substances in the curing reaction process and has low viscosity and excellent moldability (for example, Patent Document 10 or Non-patent document 11).

JP 49-47378 A Journal of Polymer Science, Polymer Physics, 32, 921 (1994).

  Dihydrobenzoxazine-based thermosetting resin compositions are mainly used for electrical and electronic components such as printed circuit boards and semiconductor encapsulating materials by utilizing their characteristics such as heat resistance, flame retardancy, electrical insulation, and low dielectric properties. Many applications have been made as materials (see, for example, Patent Documents 12 to 14).

Japanese Patent Laid-Open No. 11-60898 Japanese Patent Laid-Open No. 9-238776 Japanese Patent Laid-Open No. 6-321221

  However, a dihydrobenzoxazine-based thermosetting resin composition having viscosity characteristics suitable for RTM molding capable of molding a fiber reinforced composite material having a large and complex shape, and excellent in heat resistance and residual carbon ratio of the resulting cured product There are no reports that mention the development of products.

  Therefore, unlike the conventional phenol resin, the present invention does not generate volatiles such as water and ammonia gas in the curing reaction process, and has a viscosity characteristic suitable for various molding methods of fiber reinforced composite materials such as RTM. The present invention provides a dihydrobenzoxazine-based thermosetting resin composition having excellent heat resistance and residual carbon ratio of the obtained cured product, the cured product, and a fiber-reinforced composite material.

  As a result of intensive studies to achieve the above object, the present inventors have obtained a conventional phenol resin by adding (b) a compound having a cyanate group to a compound having a dihydrobenzoxazine ring. Compared to RTM, the dihydrobenzoxazine-based new thermosetting resin has viscosity characteristics suitable for various molding methods of fiber reinforced composite materials such as RTM, and the cured product is excellent in heat resistance and residual carbon ratio. As a result, the present invention has been completed.

That is, this invention which achieves the said subject is the following thermosetting resin composition of Claims 1-8, its hardened | cured material, and a fiber reinforced composite material.
The thermosetting resin composition according to claim 1 comprises (a) a compound having a dihydrobenzoxazine ring and (b) a compound having a cyanate group.
Moreover, the thermosetting resin composition which concerns on Claim 2 is a thermosetting resin composition of Claim 1, (a) The compound which has a dihydrobenzoxazine ring, and (b) The compound which has a cyanate group. It is formed by melt mixing or solution mixing.
The thermosetting resin composition according to claim 3 is the thermosetting resin composition according to claim 1 or 2, wherein (a) a compound having a dihydrobenzoxazine ring is 5-95 mol%, and (b) It consists of 95 to 5 mol% of a compound having a cyanate group.
Furthermore, in the thermosetting resin composition according to any one of claims 1 to 3, the thermosetting resin composition according to claim 4 has an initial viscosity of 10 (Pa · s) or less at an arbitrary temperature, And the viscosity when it hold | maintains at the same temperature for 2 hours is 100 (Pa * s) or less.

（式中、Ｒ^１は置換基を有していてもよいアルキル基、同じくアリール基、同じくアルケニル基、同じくアルキニル基、または同じくアラルキル基を示す。）
請求項６に係る熱硬化性樹脂組成物は、請求項１〜３のいずれかに記載の熱硬化性樹脂組成物において、（ｂ）シアネート基を有する化合物が、一般式（２）で表される官能基を１個以上有する化合物である。

（式中、ｎは１以上の整数、Ｒ^２はｎ価の有機基を示す。） Furthermore, the thermosetting resin composition according to claim 5 is the thermosetting resin composition according to any one of claims 1 to 3, wherein the compound (a) having a dihydrobenzoxazine ring is represented by the general formula ( It is a compound having one or more functional groups represented by 1).

(Wherein R ¹ represents an optionally substituted alkyl group, also an aryl group, also an alkenyl group, also an alkynyl group, or also an aralkyl group.)
The thermosetting resin composition according to claim 6 is the thermosetting resin composition according to any one of claims 1 to 3, wherein the compound (b) having a cyanate group is represented by the general formula (2). A compound having one or more functional groups.

(In the formula, n represents an integer of 1 or more, and R ² represents an n-valent organic group.)

The invention according to claim 7 is a cured product obtained by curing the thermosetting resin composition according to any one of claims 1 to 6.
The invention according to claim 8 is a fiber-reinforced composite material comprising the thermosetting resin composition according to any one of claims 1 to 6 and a reinforcing fiber base material.

  According to this invention, a thermosetting resin composition having viscosity characteristics suitable for various molding methods for producing a fiber-reinforced composite material such as RTM can be obtained. That is, the thermosetting resin composition of the present invention does not proceed with a curing reaction when a resin melted from the outside is poured into a fiber fabric set in a mold, and is sufficiently low to impregnate the fiber fabric. Has viscosity. However, when the temperature is raised above the melting temperature of the resin, the curing reaction proceeds rapidly. In addition, the thermosetting resin composition of the present invention can produce a dense molded product because no by-product is generated in the curing reaction process as in the case of conventional phenol resins, and the resulting cured product has a residual carbon ratio. Therefore, it can be suitably used not only as a composite material for aerospace, but also for automobile members, railway vehicle members, marine members, building members, etc., and is extremely useful.

  The thermosetting resin composition of the present invention is a resin comprising (a) a compound having 5 to 95 mol% having a dihydrobenzoxazine ring and (b) a compound having 95 to 5 mol% having a cyanate group for each functional group. Consists of ingredients. In addition, mol% shows the ratio of the functional group (a) or (b) contained in the composition.

（式中、Ｒ^１は置換基を有していてもよいアルキル基、同じくアリール基、同じくアルケニル基、同じくアルキニル基、または同じくアラルキル基を示す。）で表されるジヒドロベンゾオキサジン環を含む官能基を１個以上有し、その開環反応によってフェノール性水酸基を生成するものであれば特に限定されるものではない。このジヒドロベンゾオキサジン環を含む官能基を１個以上有する化合物は、たとえば、フェノール性水酸基を１個以上有する化合物、アミノ基を１個以上有する化合物、およびホルムアルデヒド化合物を、溶媒中もしくは無溶媒中で反応させることにより調製される。これらは単独で用いてもよく、２種以上を併用してもよい。 The compound (a) having a dihydrobenzoxazine ring is at least the general formula (1) in the molecule:

(Wherein R ¹ represents an optionally substituted alkyl group, also an aryl group, also an alkenyl group, also an alkynyl group, or also an aralkyl group) and a functional group containing a dihydrobenzoxazine ring represented by The group is not particularly limited as long as it has one or more groups and generates a phenolic hydroxyl group by the ring-opening reaction. The compound having at least one functional group containing a dihydrobenzoxazine ring is, for example, a compound having at least one phenolic hydroxyl group, a compound having at least one amino group, and a formaldehyde compound in a solvent or without a solvent. It is prepared by reacting. These may be used alone or in combination of two or more.

  The compound having one or more phenolic hydroxyl groups is not particularly limited as long as it is a compound in which at least one ortho position of the phenol nucleus is vacant (unsubstituted). For example, phenol, o-, m-, or p- Alkyl such as cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 4-n-nonylphenol, 4-n-octylphenol, 2,3,5-trimethylphenol, 4-n-hexylphenol In addition to ruphenols, compounds having one phenolic hydroxyl group such as p-cyclohexylphenol, p-cumylphenol, p-phenylylphenol, p-allylphenol, α- or β-naphthol can also be used. Examples of the compound having two or more phenolic hydroxyl groups include catechol, hydroquinone, resorcinol, 1,5-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,2′-dihydroxybiphenyl, 4,4′-dihydroxy. Biphenyl, 4,4′-oxybisphenol, 4,4′-dihydroxybenzophenone, bisphenol A, bisphenol E, bisphenol F, bisphenol S, difluorobisphenol A, 4,4 ′-[2,2,2-trifluoro-1 -(Trifluoromethyl) ethylidene] bisphenol, 4,4'-cyclopentylidene bisphenol, 4,4 '-(dimethylsilylene) bisphenol, 4,4'-cyclohexylidene bisphenol, terpene diphenol, 1,3-bis ( - hydroxyphenyl) adamantane, 1,3,5-trihydroxybenzene, 4,4 ', 4' '- such as methylidene tris phenol. Furthermore, as an oligomer obtained by reacting the phenol compound with formalin by a known method, for example, a phenol novolac type phenol resin, a cresol novolac type phenol resin, a bisphenol A novolac type phenol resin, or a resol type phenol resin can be used. In addition, various modified phenolic resins such as xylylene-modified phenolic resin, melamine-modified phenolic resin, benzoguanamine-modified phenolic resin, maleimide-modified phenolic resin, silicone-modified phenolic resin, butadiene-modified phenolic resin, poly (p-vinylphenol) and their co-polymers. Other oligomers and polymers having a phenolic hydroxyl group such as a polymer can also be used. These compounds having one or more phenolic hydroxyl groups are not limited to single use alone, and two or more types can be used in combination.

  Examples of the compound having at least one amino group include methylamine, ethylamine, n-propylamine, n-butylamine, n-dodecylamine, n-nonylamine, cyclopentylamine, cyclohexylamine, allylamine, and other alkyl monoamines and alkenyls. Examples include monoamines, aromatic monoamines such as aniline, methylaniline, ethylaniline, diethylaniline, benzylamine, o-toluidine, m-toluidine, p-toluidine, α-naphthylamine, β-naphthylamine and the like. Furthermore, 2-amino-benzylamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,10-diaminodecane, 2,7-diaminofluorene, 1,4-diaminocyclohexane, 9,10-diaminophenanthrene 1,4-diaminopiperazine, 1,4-methylenedianiline, 1,4-diaminobenzophenone, 4,4-diaminodiphenylsulfone, methylenedianiline, fluorenediamine, 4,4-oxydianiline, fluorenetetraamine, Tetraamine diphenyl ether, melamine, etc. can also be used.

  Furthermore, as the formaldehyde compound, formalin that is an aqueous formaldehyde solution, or trioxane or paraformaldehyde that is a polymer thereof can be used.

  As the reaction solvent, solvents such as toluene, xylene, 1,4-dioxane, tetrahydrofuran, 1-propanol, 1-butanol and methanol can be used.

  When all of the phenolic hydroxyl groups are reacted, it is preferable to use 1 mol of amino group and 2 mols of formaldehyde with respect to 1 mol of phenolic hydroxyl group. The reaction temperature is preferably 80 ° C to 100 ° C. When the reaction temperature is less than 80 ° C., the reaction hardly proceeds. When the reaction temperature exceeds 100 ° C., a side reaction in which the once generated dihydrobenzoxazine ring is opened and oligomerized is promoted. Although the reaction time depends on the reaction temperature, the reaction is completed in 1 to 6 hours.

  After completion of the reaction, the solvent is distilled off, and if necessary, a purification operation such as water washing or alkali washing is performed to remove unreacted phenolic hydroxyl group-containing compounds, amines, and formaldehyde compounds, thereby obtaining dihydrobenzoic acid. A compound having an oxazine ring is obtained.

  Examples of the compound having a dihydrobenzoxazine ring obtained as described above include compounds represented by the following general formulas (3) to (6).

一般式（３）中、Ｒ^１は、置換基を有していてもよいアルキル基、同じくアリール基、同じくアルケニル基、同じくアルキニル基、または同じくアラルキル基を示す。Ｒ^３は水素原子、または置換基を有していてもよいアルキル基、同じくアリール基、同じくアルコキシ基、同じくアルケニル基、同じくアルキニル基、同じくアラルキル基、もしくはハロゲン原子、ニトロ基、シアノ基、アルコキシカルボニル基、水酸基、アルキル（アリール）スルホニル基などが１置換、２置換、３置換、または４置換したものを示す。

In general formula (3), R ¹ represents an optionally substituted alkyl group, also an aryl group, also an alkenyl group, also an alkynyl group, or also an aralkyl group. R ³ is a hydrogen atom or an optionally substituted alkyl group, also an aryl group, also an alkoxy group, also an alkenyl group, also an alkynyl group, also an aralkyl group, or a halogen atom, nitro group, cyano group, alkoxy A carbonyl group, a hydroxyl group, an alkyl (aryl) sulfonyl group or the like is monosubstituted, disubstituted, trisubstituted or tetrasubstituted.

一般式（４）中、Ｒ^１は、置換基を有していてもよいアルキル基、同じくアリール基、同じくアルケニル基、同じくアルキニル基、または同じくアラルキル基を示す。Ｒ^４は単結合、または置換基を有していてもよいアルキレン基、同じくアリーレン基、同じくアルケニレン基、同じくアルキニレン基、同じくアラルキレン基、またはカルボニル基、エーテル基、チオエーテル基、シリレン基、シロキサン基、メチレンエーテル基、エステル基、スルホニル基などを示す。Ｒ^５及びＲ^６は同一または異なって水素原子、または置換基を有していてもよいアルキル基、同じくアリール基、同じくアルコキシ基、同じくアルケニル基、同じくアルキニル基、同じくアラルキル基、もしくはハロゲン原子、ニトロ基、シアノ基、アルコキシカルボニル基、水酸基、アルキル（アリール）スルホニル基などが１置換、２置換、または３置換したものを示す。なお、Ｒ^４の例を以下に示す

In general formula (4), R ¹ represents an optionally substituted alkyl group, also an aryl group, also an alkenyl group, also an alkynyl group, or also an aralkyl group. R ⁴ is a single bond or an optionally substituted alkylene group, also an arylene group, also an alkenylene group, also an alkynylene group, also an aralkylene group, or a carbonyl group, an ether group, a thioether group, a silylene group, or a siloxane group. , Methylene ether group, ester group, sulfonyl group and the like. R ⁵ and R ⁶ may be the same or different and each may be a hydrogen atom or an optionally substituted alkyl group, also an aryl group, also an alkoxy group, also an alkenyl group, also an alkynyl group, also an aralkyl group, or a halogen atom, A nitro group, a cyano group, an alkoxycarbonyl group, a hydroxyl group, an alkyl (aryl) sulfonyl group and the like are monosubstituted, disubstituted, or trisubstituted. An example of R ⁴ is shown below.

一般式（５）中、Ｒ^１は、置換基を有していてもよいアルキル基、同じくアリール基、同じくアルケニル基、同じくアルキニル基、または同じくアラルキル基を示す。Ｒ^３は水素原子、または置換基を有していてもよいアルキル基、同じくアリール基、同じくアルコキシ基、同じくアルケニル基、同じくアルキニル基、同じくアラルキル基、もしくはハロゲン原子、ニトロ基、シアノ基、アルコキシカルボニル基、水酸基、アルキル（アリール）スルホニル基などを示す。ｎは２〜２００の整数である。

In general formula (5), R ¹ represents an alkyl group which may have a substituent, also an aryl group, a alkenyl group, a alkynyl group, or a aralkyl group. R ³ represents a hydrogen atom or an optionally substituted alkyl group, an aryl group, an alkoxy group, an alkenyl group, an alkynyl group, an aralkyl group, a halogen atom, a nitro group, a cyano group, an alkoxy group. A carbonyl group, a hydroxyl group, an alkyl (aryl) sulfonyl group, etc. are shown. n is an integer of 2 to 200.

一般式（６）中、Ｒ^１は、置換基を有していてもよいアルキル基、同じくアリール基、同じくアルケニル基、同じくアルキニル基、または同じくアラルキル基を示す。Ｒ^３は水素原子、または置換基を有していてもよいアルキル基、同じくアリール基、同じくアルコキシ基、同じくアルケニル基、同じくアルキニル基、同じくアラルキル基、もしくはハロゲン原子、ニトロ基、シアノ基、アルコキシカルボニル基、水酸基、アルキル（アリール）スルホニル基などを示す。ｍは０〜１００の整数である。

In the general formula (6), R ¹ represents an alkyl group which may have a substituent, also an aryl group, a alkenyl group, a alkynyl group, or a aralkyl group. R ³ represents a hydrogen atom or an optionally substituted alkyl group, an aryl group, an alkoxy group, an alkenyl group, an alkynyl group, an aralkyl group, a halogen atom, a nitro group, a cyano group, an alkoxy group. A carbonyl group, a hydroxyl group, an alkyl (aryl) sulfonyl group, etc. are shown. m is an integer of 0-100.

  Among the above compounds, compounds represented by the general formula (3), (4) or (6) are preferable.

（式中、ｎは１以上の整数、Ｒ^２はｎ価の有機基を示す。）で表されるシアネート基を含む官能基を１個以上有する化合物であれば特に限定されるものではない。シアネート基を有する化合物は硬化反応によってトリアジン環を形成し、その剛直な骨格構造により耐熱性や残炭率に優れ、また熱時の体積変化が小さく機械的強度に優れることが特長である。 The compound having a cyanate group (b) is represented by the general formula (2) in the molecule:

(In the formula, n is an integer of 1 or more, and R ² represents an n-valent organic group.) The compound is not particularly limited as long as it has one or more functional groups including a cyanate group. A compound having a cyanate group forms a triazine ring by a curing reaction, and is characterized by excellent heat resistance and residual carbon ratio due to its rigid skeleton structure, small volume change during heating, and excellent mechanical strength.

  Specific examples of the compound having a cyanate group used in the present invention include, for example, polyfunctional phenol type cyanate resins such as phenol novolak type cyanate resin, o-cresol novolak type cyanate resin, bisphenol A novolak type cyanate resin, and bisphenol. Examples include A-type cyanate resins, bisphenol E-type cyanate resins, bisphenol F-type cyanate resins, and bisphenol-type cyanate resins such as bisphenol S-type cyanate resins. In addition, bis (3-methyl-4-cyanatephenyl) methane, bis (3-ethyl-4-cyanatephenyl) methane, bis (3,5-dimethyl-4-cyanatephenyl) methane, 1,1-bis (4 -Cyanatephenyl) ethane, bis (4-cyanatephenyl) methane, 2,2-bis (4-cyanatephenyl) -1,1,1, -3,3,3,3-hexafluoropropane, di (4-cyanate) Phenyl) ether, di (4-cyanatephenyl) thioether, 4,4-dicyanate-diphenyl, and the like. These are used alone or as a mixture of two or more.

  Further, various thermoforming resin compositions comprising (a) a compound having a dihydrobenzoxazine ring and (b) a compound having a cyanate group are subjected to various molding methods for producing a fiber reinforced composite material such as RTM. You may add a curing catalyst and a hardening | curing agent in the range which does not impair the suitable viscosity characteristic.

  Preparation of the thermosetting resin composition of the present invention comprises (a) 5 to 95 mol% of a compound having a dihydrobenzoxazine ring and (b) 95 to 5 mol% of a compound having a cyanate group for each functional group. It is preferable to obtain a resin liquid by melt mixing or solution mixing. In this case, the melt mixing temperature is preferably 50 to 150 ° C, more preferably 60 to 120 ° C. Solvents used for mixing the solution are not limited as long as they are compatible with the compounds (a) and (b). Alcohol solvents such as methanol and ethanol, ether solvents such as diethyl ether, methyl ethyl ketone, acetone , Ketone solvents such as methyl isobutyl ketone, ester solvents such as ethyl acetate, aromatic hydrocarbon solvents such as toluene and xylene, nitrile solvents such as acetonitrile, and chlorine solvents such as dichloromethane and chloroform. preferable. Moreover, as for the compounding quantity, (b) component 95-5 mol% is more preferable with respect to (a) component 5-95 mol%. Particularly preferably, (a) component is 20 to 80 mol%, and (b) component is 80 to 20 mol%. In addition, mol% shows the percentage on the basis of the functional group of (a) component and (b) component here.

  Thus, the thermosetting resin composition obtained from (a) and (b) has viscosity characteristics suitable for various molding methods for producing a fiber-reinforced composite material. That is, the melt viscosity at a certain temperature is 10 (Pa · s) or less, and a low viscosity of 100 (Pa · s) or less is maintained even after 2 hours at that temperature (the viscosity change is low at low viscosity). Since it is small, the impregnation property into the fiber is excellent for a long time), but it cures quickly when the temperature becomes higher (curing temperature, for example, 200 ° C. or higher). Specifically, the melt viscosity at room temperature to 100 ° C. is 0.01 to 10 (Pa · s), and the melt viscosity after 2 hours at the same temperature is 0.01 to 100 (Pa · s). Is preferred.

  For example, when RTM is used as a molding method, when a resin melted from the outside is injected into a fiber fabric set in a mold, the curing reaction does not proceed and the viscosity is low enough to impregnate the fiber fabric. ing. However, in the thermosetting resin of the present invention, after the resin is injected into the mold, if the temperature is raised above the melting temperature of the resin, the curing reaction proceeds rapidly, and by-products are produced during the curing reaction process as in the case of conventional phenol resins Therefore, a dense molded product can be produced.

  The thermosetting resin composition of the present invention is cured by heating, but the curability varies depending on the type and amount of the curing agent used, the heating temperature, the method of heating, etc., and can be cured in a short time. It can also be cured very slowly. In either case, complete curing can be achieved while adjusting the temperature and time. The curing temperature is usually 80 to 250 ° C, preferably 120 to 220 ° C. The curing time is usually 0.5 minutes to 8 hours, preferably 1 minute to 7 hours.

  Thus, although the thermosetting resin composition of this invention is especially suitable for RTM, it can be used suitably also for shaping | molding methods other than RTM method. For example, as other production methods, known methods such as a hand lay-up method, a prepreg method, a pultrusion method, a filament winding method, and a spray-up method can be preferably applied.

  Examples of the reinforcing fiber substrate that can be used in the present invention include paper, glass fiber, carbon fiber, aramid fiber, polyester fiber, boron fiber, alumina fiber, nylon fiber, and silicon carbide fiber. In order to obtain higher mechanical properties, glass fibers and carbon fibers are preferably used, and carbon fibers are more preferably used. These reinforcing fiber base materials are nonwoven fabrics such as long fiber mats, overlay mats, chopped strand mats, woven fabrics such as roving cloths, plain weave cloths, woven cloth cloths, woven cloths, or filaments, strands, chopped strands, Although there are various forms such as yarn and roving, since the thermosetting resin composition of the present invention has a low viscosity, it can be satisfactorily impregnated in any form of the reinforcing fiber base. The content of the reinforcing fiber substrate can be selected as appropriate, but is preferably 5 to 500 parts by weight, more preferably 10 to 300% by weight, for example, with respect to 100 parts by weight of the resin.

  As described above, the thermosetting resin composition of the present invention is optimal as a resin composition for fiber-reinforced composite materials, but other than that, electrical / electronic materials such as semiconductor sealing materials and printed circuit boards, or general It can also be applied to molded products. In addition, it can also be applied to the fields of ships, railway vehicles, automobiles, civil engineering and architecture. Therefore, if necessary, it can be filled with various fillers to produce a molding material and cured to form a molded product. Examples of the filler include organic powders such as wood powder, pulp powder, various pulverized fabrics, and thermosetting resin cured products, or silica, aluminum hydroxide, talc, clay, mica, calcium carbonate, alumina, and silica sand. Inorganic powders such as carbon and glass and granular materials, metal powders such as aluminum powder, iron powder, and copper powder. Although the compounding quantity of a filler can be selected suitably, for example, 5-1000 weight part is preferable with respect to 100 weight part of resin, and 10-500 weight part is more preferable.

  The method for producing the molding material from the thermosetting resin composition of the present invention is not particularly limited, and can be carried out using a known method. For example, a molding material can be produced by melt-kneading the resin composition and the filler.

  A known method can be used as a molding method when a molding material using the thermosetting resin composition of the present invention is reacted by heating to obtain a molded product. For example, a melt casting method, a compression molding method that heats and presses with a press, a transfer molding method in which a molding material plasticized with a preheater is pressed into a heated mold cavity, and a preform is impregnated with a resin. Examples thereof include a matched die molding method for compression molding, an SMC method, a BMC method, and a foam molding method in which a foam is obtained by foaming and curing with a foaming agent.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these.

The raw materials used in the present invention are as follows.
As reagents used for the synthesis of benzoxazine compounds, commercially available reagents were used for bisphenol A, bisphenol F, phenol, aniline, diaminodiphenylmethane, and formaldehyde aqueous solution. Further, cyanate resins are bisphenol A type cyanate resin (hereinafter abbreviated as BADCy), bisphenol E type cyanate resin (hereinafter abbreviated as LECy) and phenol novolac type cyanate resin (hereinafter abbreviated as PT15) manufactured by Lonza Japan Co., Ltd. Was used.

  As a sample used for the comparative example, a phenol resin # 200 manufactured by Lignite Co., Ltd. was used as a general phenol resin.

Evaluation of the characteristics in Examples and Comparative Examples was performed according to the following test standards and conditions.
1. Exothermic behavior by differential scanning calorimeter: The resin composition was heated at a heating rate of 10 ° C./min in a nitrogen atmosphere, and the exothermic start temperature and the exothermic peak temperature at that time were measured.
2. Gel time: Time until gelation according to JIS K 6910 stroke curing method (method in which a resin composition is placed on a heated hot plate and stirred at a constant speed using a metal spatula) (minutes) Was measured.
3. Thermogravimetric analysis: The resin composition was heated at a heating rate of 10 ° C./min in a nitrogen atmosphere, and the thermal decomposition temperature at which the weight decreased by 1%, 5% and 10% and the residual carbon ratio at 600 ° C. were measured. .
4). Melt viscosity: Measured from the temperature at which the resin melts at a temperature rise rate of 4 ° C./min to 300 ° C. using a parallel plate method of 25 mmφ at a strain of 0.1% and a frequency of 1 Hz. The temperature having viscosity and the curing temperature range were determined. Furthermore, the change with time in viscosity was measured for 2 hours at the temperature at which the viscosity of the resin in each sample was around 1 to 10 (Pa · s) or at the temperature at which the viscosity of the comparative phenol resin was reduced to the maximum.
5). Mechanical strength: According to JIS K6911, the bending strength and the bending elastic modulus were measured at a crosshead speed of 3 mm / min and a span of 100 mm. Further, according to ASTM D5045, a fracture toughness test was performed by a three-point bending method. The measurement was performed at a fulcrum distance of about 55 mm and a load speed of 1 mm / min, and a critical stress intensity factor K _IC (MPa · m ^1/2 ) was calculated.

[Synthesis Example 1]
To the flask, 1,4-dioxane and 4 mol of 37% formaldehyde aqueous solution were added, and the liquid temperature was kept at 5 ° C. or lower, and 2 mol of aniline (1,4-dioxane solution) was added dropwise with stirring. Further, 1 mol of bisphenol A (1,4-dioxane solution) was added dropwise in the same manner. After completion of the dropwise addition, the temperature was raised to the reflux temperature and the reaction was continued for 6 hours. Thereafter, the solvent is distilled off, and the high molecular weight component is removed by washing with an aqueous alkaline solution, which corresponds to the compound represented by the general formula (4). Abbreviated).

[Synthesis Example 2]
To the flask, 1,4-dioxane and 4 mol of 37% formaldehyde aqueous solution were added, and the liquid temperature was kept at 5 ° C. or lower, and 2 mol of aniline (1,4-dioxane solution) was added dropwise with stirring. Further, 1 mol of bisphenol F (1,4-dioxane solution) was added dropwise in the same manner. After completion of the addition, the temperature was raised to the reflux temperature and the reaction was continued for 6 hours. Thereafter, the solvent is distilled off, and the high molecular weight component is removed by washing with an aqueous alkali solution, which corresponds to the compound represented by the general formula (4). Abbreviated).

[Synthesis Example 3]
1,4-dioxane and 4 mol of 37% formaldehyde aqueous solution were added to the flask, and the temperature of the solution was kept at 5 ° C. or lower, and 1 mol of diaminodiphenylmethane (1,4-dioxane solution) was added dropwise with stirring. Furthermore, 2 mol of phenol (1,4-dioxane solution) was added dropwise in the same manner. After completion of the addition, the temperature was raised to the reflux temperature and the reaction was continued for 6 hours. Thereafter, the solvent is distilled off, and the diaminodiphenylmethane type benzoxazine compound monomer (corresponding to the compound represented by the above general formula (3) from which the high molecular weight component is removed by washing with an alkaline aqueous solution. Hereinafter, Pd and Abbreviated).

[Examples 1 to 13]
Ba-, Fa- and P-d as dihydrobenzoxazine compounds and BADCy and LECy as cyanate resins were melt-mixed in proportions as shown in Tables 1 to 3. Table 1 shows the results of differential scanning calorimetry (DSC) measurement and gel time measurement of the obtained resin composition, Table 2 shows the results of melt viscosity measurement, and Table 3 shows the results of thermogravimetric analysis. Shown in

[Comparative Example 1]
Table 1 shows the results of differential scanning calorimetry (DSC) measurement and gel time measurement of # 200 as a general phenol resin, Table 2 shows the results of viscosity measurement, and Table 3 shows the results of thermogravimetric analysis. Shown in

[Examples 14 to 17]
Ba and Fa as dihydrobenzoxazine compounds and BADCy and LECy as cyanate resins were blended in the proportions shown in Table 4 and melt mixed. The obtained resin composition was cast into a silicone rubber mold and cured at 180 ° C./1 hour + 200 ° C./2 hours + 220 ° C./2 hours to produce a cured product. Table 4 shows the measurement results of the mechanical strength.

[Comparative Example 2]
As a general phenol resin, # 200 was molded by transfer molding at 170 ° C. for 5 minutes, and then cured by 180 ° C./1 hour + 200 ° C./2 hours + 220 ° C./2 hours to produce a cured product. Table 4 shows the measurement results of the mechanical strength.

  From the results of the DSC measurement shown in Table 1, in all of the examples of the present invention, the DSC exothermic start temperature and the exothermic peak temperature are on the high temperature side as compared with the comparative example. Moreover, from the measurement result of gel time, it turns out that hardening reaction does not advance in the vicinity of 50-100 degreeC, and is comparatively stable. On the other hand, it can be seen that the general phenol resin of the comparative example has poor stability because gelation proceeds even at 120 ° C. in 2 minutes and is not suitable for a molding method such as RTM.

  Moreover, from the result of the viscosity measurement of Table 2, it can be seen that the conventional phenol resin of the comparative example is cured at 150 to 200 ° C. and has a very high melt viscosity. Further, after 2 hours, no fluidity is exhibited, so that a molding method such as RTM is impossible. On the other hand, in the thermosetting resin composition of the present invention, the curing reaction proceeds near 200 ° C. and not only the melt viscosity is very low, but also the low value can be maintained even after 2 hours. It is clear that it is suitable for molding such as RTM.

  Further, as a result of thermogravimetric analysis shown in Table 3, it is understood that by-product gas is generated in the curing reaction process of a general phenol resin, so that a weight loss of about 5% occurs even near the curing temperature of 200 ° C. On the other hand, it can be seen that the thermosetting resin of the present invention can obtain a dense molded product because there is almost no weight loss at 230 ° C. or lower at which the curing reaction occurs. Further, since the residual carbon ratio is at the same level as that of phenol resin, it is clear that it is useful as a composite material for aerospace, for example.

  Furthermore, from Table 4, it was found that the obtained cured product was excellent in mechanical strength.

  Since the thermosetting resin composition of the present invention is excellent in mechanical properties and heat resistance, it is most suitable as a resin composition for fiber-reinforced composite materials for space and aircraft, etc. It can also be applied to materials, electrical / electronic materials such as printed circuit boards, and general molded products. In addition, it can also be applied to the fields of ships, railway vehicles, automobiles, civil engineering and architecture. Therefore, if necessary, it can be filled with various fillers to produce a molding material and cured to form a molded product.

Claims (8)

  A thermosetting resin composition comprising (a) a compound having a dihydrobenzoxazine ring and (b) a compound having a cyanate group.   The thermosetting resin composition according to claim 1, wherein (a) a compound having a dihydrobenzoxazine ring and (b) a compound having a cyanate group are melt-mixed or solution-mixed.   The thermosetting resin composition according to claim 1 or 2, comprising (a) 5 to 95 mol% of a compound having a dihydrobenzoxazine ring and (b) 95 to 5 mol% of a compound having a cyanate group.   The thermosetting according to any one of claims 1 to 3, wherein the initial viscosity at an arbitrary temperature is 10 (Pa · s) or less and the viscosity when held at the same temperature for 2 hours is 100 (Pa · s) or less. Resin composition. (A) the compound having a dihydrobenzoxazine ring is represented by the general formula (1);

(Wherein R ¹ represents an optionally substituted alkyl group, also an aryl group, also an alkenyl group, also an alkynyl group, or also an aralkyl group) and has one or more functional groups. It is a compound, The thermosetting resin composition in any one of Claims 1-4. (B) the compound having a cyanate group is represented by the general formula (2);

(Wherein, n represents an integer of 1 or more, R ² is. Showing an n-valent organic group) thermoset according to claim 1 which is a compound having at least one functional group represented by Resin composition.   Hardened | cured material formed by hardening the thermosetting resin composition in any one of Claims 1-6.   A fiber-reinforced composite material comprising the thermosetting resin composition according to any one of claims 1 to 6 and a reinforcing fiber substrate.