JP5252711B2 - Epoxy resin composition - Google Patents

Description

  The present invention relates to an epoxy resin composition, a prepreg obtained by using the epoxy resin composition, and a fiber-reinforced composite material.

  Epoxy resins have excellent performance in terms of mechanical properties, electrical properties, thermal properties, chemical resistance, adhesiveness, etc., so that paints, insulating materials for electrical and electronic products, adhesives, etc. It is used for a wide range of applications. Recently, there is a demand for higher functionality such as further strengthening, heat resistance, and weight reduction of epoxy resins.

Patent Document 1 discloses a tolylene diisocyanate-modified epoxy resin of bisphenol A type epoxy resin as an epoxy resin that can achieve both heat resistance and flexibility.
As a resin modified with a compound other than tolylene diisocyanate, Patent Document 2 discloses an epoxy resin obtained by modifying a bisphenol A type epoxy resin using polymethylene isocyanate.
Patent Document 3 discloses glycidyl ether of 4,4′-bis-3,3 ′, 5,5′-tetramethylbiphenyl as a resin having improved heat resistance.
In Patent Document 4, as a resin with further improvements, 4,4′-bis-3,3 ′, 5,5′-tetramethylbiphenyl glycidyl ether was modified with polyhydric phenol to lower the softening point. A resin is disclosed.

JP-A-5-222160 Japanese National Patent Publication No. 4-506678 JP 58-39677 A JP-A-3-14816

When the resin disclosed in Patent Documents 1 and 2 is intended to increase heat resistance, it simultaneously increases in viscosity and cannot achieve both heat resistance and low viscosity.
Although the resin disclosed in Patent Document 3 has high heat resistance, it has a high softening point and has a sharp viscosity drop, so it is not suitable for composite materials.
The resin disclosed in Patent Document 4 shows no improvement in heat resistance, and the resulting resin is brittle.

  In view of the above circumstances, the problem to be solved by the present invention is to provide an epoxy resin composition excellent in handleability capable of obtaining a cured product excellent in balance between heat resistance and mechanical properties.

  As a result of intensive studies in order to solve the above problems, the present inventor has obtained an isocyanate-modified epoxy resin (A) containing a specific structure having a biphenyl skeleton and an oxazolidone ring, and an epoxy resin (B) other than (A). And the epoxy resin composition containing a hardening | curing agent (C) discovered that the said subject could be solved, and completed this invention.

That is, the present invention is as follows.
[1]
An isocyanate-modified epoxy resin (A) having a structure represented by the following general formula (1);
An epoxy resin (B) other than (A),
A curing agent (C);
An epoxy resin composition comprising:

(In the formula, R _{1 to} R ₈ and R _{10 to} R ₁₇ are each independently a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, or an alkoxy which may have a substituent. A group, an aryl group which may have a substituent, an amino group which may have a substituent, a nitro group or a carboxyl group, wherein R ₉ is a divalent or higher valent which may have a substituent; Indicates a functional group.)
[2]
The epoxy resin composition according to the above [1], further comprising a plasticizer (D).
[3]
The epoxy resin composition according to the above [1] or [2], wherein R ₉ comprises one or more skeletons selected from isophorone, benzene, toluene, diphenylmethane, naphthalene, polymethylene polyphenylene polyphenyl, and hexamethylene.
[4]
In the above [1] to [3], the proportion of the component (A) in the epoxy resin composition is 0.1 to 0.95 in a mass ratio of (A) / (A) + (B). Any one of the epoxy resin compositions.
[5]
A prepreg obtained by a production method including a step of impregnating a fiber base material with the epoxy resin composition according to any one of the above [1] to [4] by coating and / or dipping.
[6]
A fiber-reinforced composite material obtained by a production method including the steps of laminating the prepreg according to the above [5] and heating and pressing.

  The cured product obtained from the epoxy resin composition of the present invention has an excellent balance between heat resistance and mechanical properties, and can be suitably used as a material for a prepreg or a fiber-reinforced composite material.

  Hereinafter, the best mode for carrying out the present invention (hereinafter, this embodiment) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

The epoxy resin composition of this embodiment is
An isocyanate-modified epoxy resin (A) having a structure represented by the following general formula (1);
An epoxy resin (B) other than (A),
A curing agent (C).

(In the formula, R _{1 to} R ₈ and R _{10 to} R ₁₇ are each independently a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, or an alkoxy which may have a substituent. A group, an aryl group which may have a substituent, an amino group which may have a substituent, a nitro group or a carboxyl group, wherein R ₉ is a divalent or higher valent which may have a substituent; Indicates a functional group.)

  The isocyanate-modified epoxy resin (A) is a resin having a structure represented by the above general formula (1), and the viscosity of the epoxy resin composition is lowered by having the structure, and the cured product is heat resistant. And fracture toughness is very excellent.

Hereinafter, each symbol in the present embodiment will be described.
In the general formula (1), examples of the halogen atom represented by R _{1 to} R ₈ and R _{10 to} R ₁₇ include a fluorine atom, a chlorine atom, and a bromine atom.

In the general formula (1), the “alkyl group” of the optionally substituted alkyl group represented by R _{1 to} R ₈ and R _{10 to} R ₁₇ has 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms. Represents a linear or branched alkyl group, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, etc. Is mentioned. Among these, since the branched chain tends to have higher heat resistance than the straight chain, it is preferably an isopropyl group, an isobutyl group, or a tert-butyl group, and more preferably a tert-butyl group.

In the general formula (1), the “alkoxy group” of the optionally substituted alkoxy group represented by R _{1 to} R ₈ and R _{10 to} R ₁₇ has 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms. Represents a linear or branched alkoxy group, for example, methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, hexyloxy group, etc. And preferably a methoxy group or an ethoxy group.

In the general formula (1), examples of the “aryl group” of the optionally substituted aryl group represented by R _{1 to} R ₈ and R _{10 to} R ₁₇ include a phenyl group and a naphthyl group. Is a phenyl group.

The alkyl group, aryl group, alkoxy group and amino group represented by R _{1 to} R ₈ and R _{10 to} R ₁₇ may be substituted with one or more substituents at substitutable positions. Examples of such a substituent include a halogen atom (for example, fluorine atom, chlorine atom, bromine atom), an alkyl group having 1 to 6 carbon atoms (for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl). Group, sec-butyl group, tert-butyl group, pentyl group, hexyl group), aryl group (for example, phenyl group, naphthyl group), aralkyl group (for example, benzyl group, phenethyl group), alkoxy group (for example, methoxy group) Ethoxy group) and the like.

Examples of the divalent or higher functional group represented by R ₉ include a single bond, an optionally substituted alkylene group, and an optionally substituted arylene group.

  “Alkylene group” means a divalent group derived by further removing one hydrogen atom at any position from the above-defined “alkyl group”. For example, methylene group, ethylene group, methylethylene group, ethyl And ethylene group, 1,1-dimethylethylene group, 1,2-dimethylethylene group, trimethylene group, 1-methyltrimethylene group, 2-methyltrimethylene group, tetramethylene group, etc., preferably methylene group, Examples include an ethylene group, a methylethylene group, a 1,1-dimethylethylene group, and a trimethylene group.

The “arylene group” of the optionally substituted arylene group represented by R ₉ means a divalent group derived from the “aryl group” by further removing one hydrogen atom at an arbitrary position. .

The optionally substituted alkylene group and arylene group represented by R ₉ may be substituted with one or more substituents at substitutable positions. Examples of the substituent include a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom), an alkyl group having 1 to 6 carbon atoms (for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group), aryl group (for example, phenyl group, naphthyl group), aralkyl group (for example, benzyl group, phenethyl group), alkoxy group (for example, methoxy group, ethoxy group) Group) and the like.

  The isocyanate-modified epoxy resin of the present embodiment is selected from biphenyl, bisphenol A, bisphenol F, bisphenol AF, bisphenol AC, bisphenol S, phenol novolac, and cresol novolac in addition to the structure represented by the general formula (1). One or more skeletons may be included.

  The weight average molecular weight of the isocyanate-modified epoxy resin of this embodiment is preferably 800 or more, more preferably 900 or more, and still more preferably 1000 or more. When the weight average molecular weight is less than 800, the heat resistance of the cured product tends to be low, and at the same time, the toughness tends to decrease and become brittle. Here, the weight average molecular weight refers to a value measured by gel permeation chromatography in terms of polystyrene.

  The epoxy equivalent of the isocyanate-modified epoxy resin of the present embodiment is preferably 250 or more, more preferably 350 or more, and still more preferably 400 or more. When the epoxy equivalent is larger than 250, the toughness tends to increase. Here, an epoxy equivalent means the value measured by the potentiometric titration method by JIS-K-7236.

The method for producing the isocyanate-modified epoxy resin of the present embodiment is not particularly limited. For example, by reacting an isocyanate compound and a glycidyl compound having a biphenyl skeleton in the presence of an oxazolidone ring-forming catalyst, it is almost the theoretical amount. Can be obtained. The isocyanate compound and the glycidyl compound are preferably reacted in an equivalent ratio of 1: 2 to 1:10. When the ratio of the two is in the above range, the heat resistance and water resistance of the cured epoxy resin are better. There is a tendency.

  In this embodiment, you may use together glycidyl compounds other than the glycidyl compound which has a biphenyl skeleton as a raw material for obtaining an isocyanate modified epoxy resin. Specific examples thereof include dihydric phenols such as bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetramethyl bisphenol A, tetramethyl bisphenol F, tetramethyl bisphenol AD, tetramethyl bisphenol S, and tetrabromobisphenol A. 1,1,1-tris (4-hydroxyphenyl) methane, 1,1,1- (4-hydroxyphenyl) ethane, 4,4- [1- [4- [1- (4 Compounds obtained by glycidylating tris (glycidyloxyphenyl) alkanes such as -hydroxyphenyl) -1-methylethyl] phenyl] ethylidene] bisphenol; and novolacs such as phenol novolak, cresol novolak, and bisphenol A novolak Rishijiru of the compounds, and the like, but not particularly limited thereto.

Specific examples of the isocyanate compound used as the raw material include, for example, methane diisocyanate, butane-1,1-diisocyanate, ethane-1,2-diisocyanate, butane-1,2-diisocyanate, transvinylene diisocyanate, propane-1,3- Diisocyanate, butane-1,4-diisocyanate, 2-butene-1,4-diisocyanate, 2-methylbutene-1,4-diisocyanate, 2-methylbutane-1,4-diisocyanate, pentane-1,5-diisocyanate, 2, 2-dimethylpentane-1,5-diisocyanate, hexane-1,6-diisocyanate, heptane-1,7-diisocyanate, octane-1,8-diisocyanate, nonane-1,9-diisocyanate, decane-1,10- Isocyanate, dimethylsilane diisocyanate, diphenylsilane diisocyanate, ω, ω′-1,3-dimethylbenzene diisocyanate, ω, ω′-1,4-dimethylbenzene diisocyanate, ω, ω′-1,3-dimethylcyclohexane diisocyanate, ω , Ω′-1,4-dimethylcyclohexane diisocyanate, ω, ω′-1,4-dimethylnaphthalene diisocyanate, ω, ω′-1,5-dimethylnaphthalene diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1, 4-diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 1-methylbenzene-2,4-diisocyanate, 1-methylbenzene 2,5-diisocyanate, 1-methylbenzene-2,6-diisocyanate, 1-methylbenzene-3,5-diisocyanate, diphenyl ether-4,4′-diisocyanate, diphenyl ether-2,4′-diisocyanate, naphthalene-1, 4-diisocyanate, naphthalene-1,5-diisocyanate, biphenyl-4,4′-diisocyanate, 3,3′-dimethylbiphenyl-4,4′-diisocyanate, 2,3′-dimethoxybisphenyl-4,4′- Diisocyanate, diphenylmethane-4,4′-diisocyanate, 3,3′-dimethoxydiphenylmethane-4,4′-diisocyanate, 4,4′-dimethoxydiphenylmethane-3,3′-diisocyanate, diphenylsulfite-4,4′- Diisocyanate, di Bifunctional isocyanate compounds such as Enirusurufon-4,4'-diisocyanate;
Polyfunctional isocyanate compounds such as polymethylene polyphenyl isocyanate, triphenylmethane triisocyanate, tris (4-phenylisocyanate thiophosphate) -3,3 ′, 4,4′-diphenylmethane tetraisocyanate;
Examples include, but are not limited to, multimers such as dimers and trimers of the isocyanate compounds, blocked isocyanates masked with alcohol and phenol, and bisurethane compounds. Two or more of these isocyanate compounds may be used in combination.

  Among the above isocyanate compounds, the heat resistance tends to be improved, so that it is preferably a bifunctional or trifunctional isocyanate compound, more preferably a bifunctional isocyanate compound, more preferably isophorone, benzene, toluene, diphenylmethane, naphthalene, poly It is a bifunctional isocyanate compound having a skeleton selected from methylene polyphenylene polyphenyl and hexamethylene. When the number of functional groups of the isocyanate compound is too large, the storage stability tends to decrease, and when it is too small, the heat resistance tends to decrease.

[catalyst]
The catalyst used in the present embodiment is not particularly limited as long as it is used for oxazolidone ring formation, but may be a catalyst that selectively generates an oxazolidone ring in the reaction of a glycidyl compound and an isocyanate compound. preferable.

The catalyst for selectively producing such an oxazolidone ring is not particularly limited, and examples thereof include lithium compounds such as lithium chloride and butoxy lithium, and complex salts such as boron trifluoride;
Quaternary ammonium salts such as tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, tetrabutylammonium bromide;
Tertiary amines such as dimethylaminoethanol, triethylamine, tributylamine, benzyldimethylamine, N-methylmorpholine;
Phosphines such as triphenylphosphine;
Allyltriphenylphosphonium bromide, diallyldiphenylphosphonium bromide, ethyltriphenylphosphonium chloride, ethyltriphenylphosphonium iodide, tetrabutylphosphonium acetate / acetic acid complex, tetrabutylphosphonium acetate, tetrabutylphosphonium chloride, tetrabutylphosphonium bromide, tetrabutylphosphonium Phosphonium compounds such as iodide;
A combination of triphenylantimony and iodine;
Imidazoles such as 2-phenylimidazole and 2-methylimidazole;
Etc. These catalysts can be used individually by 1 type or in combination of 2 or more types.

  The amount of the oxazolidone ring-forming catalyst is not particularly limited, and is usually used in the range of about 5 ppm to 2% by mass, preferably 10 ppm to 1% by mass with respect to the total amount of the glycidyl compound and isocyanate compound as raw materials. %, More preferably 20 to 5000 ppm, still more preferably 20 to 1000 ppm. When the amount of the catalyst used is 2% by mass or less, a decrease in moisture resistance tends to be suppressed. On the other hand, when the amount is 5 ppm or more, production efficiency tends to be improved.

  The epoxy resin composition of this embodiment contains the isocyanate-modified epoxy resin (A) described above, an epoxy resin (B) other than (A), and a curing agent (C).

[Epoxy resin (B)]
The epoxy resin (B) is not particularly limited, and various known resins can be appropriately selected and used. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hindered-in type epoxy resin, biphenyl type epoxy resin, alicyclic epoxy resin, triphenylmethane type epoxy resin, phenol novolac type epoxy resin, cresol Novolak type epoxy resin, naphthol novolak type epoxy resin, bis A novolak type epoxy resin, dicyclopentadiene / phenol epoxy resin, alicyclic amine epoxy resin, aliphatic amine epoxy resin, and epoxy resins halogenated from these Can be mentioned. These can be used alone or in combination of two or more.

The ratio of the isocyanate-modified epoxy resin (A) component in the epoxy resin composition is preferably 0.1 to 0.95 in terms of a mass ratio of (A) / (A) + (B). More preferably 0.2 to 0.8, more preferably from 0.25 to 0.7. When the proportion of the component (A) is in the above range, the balance between fracture toughness and the temperature at which the elastic modulus starts to decrease tends to be good.

[Curing agent (C)]
The curing agent (C) is not particularly limited, and various known materials can be appropriately selected and used. From the viewpoint of the reaction rate at the time of curing, a guanidine derivative, an aromatic amine compound, and a novolak type. It is preferably at least one selected from the group consisting of phenol resins. These guanidine derivatives, aromatic amine compounds, and novolac type phenol resins can be used singly or in combination of two or more.

  Specific examples of guanidine derivatives include dicyandiamide derivatives such as dicyandiamide, dicyandiamide-aniline adduct, dicyandiamide-methylaniline adduct, dicyandiamide-diaminodiphenylmethane adduct, dicyandiamide-diaminodiphenyl ether adduct, guanidine nitrate, guanidine carbonate, phosphorus Guanidine salts such as guanidine acid, guanidine sulfamate, aminoguanidine bicarbonate, acetylguanidine, diacetylguanidine, propionylguanidine, dipropionylguanidine, cyanoacetylguanidine, guanidine succinate, diethylcyanoacetylguanidine, dicyandiamidine, N-oxymethyl -N'-cyanoguanidine, N, N'-dicarboethoxyguanidine, etc. It is not particularly limited to these.

  Specific examples of the aromatic amine compound include, for example, metaphenylenediamine, paraphenylenediamine, 3,3′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylmethane, and 4,4 ′. -Diamino diphenyl ether etc. are mentioned, However, It does not specifically limit to these.

  Specific examples of the novolak type phenol resin include, but are not limited to, phenol novolak, bisphenol A novolak, cresol novolak, naphthol novolak, and the like.

  The blending amount of the curing agent (C) is not particularly limited and is appropriately set according to the desired design. When the curing agent (C) is a guanidine derivative, the isocyanate-modified epoxy resin (A) It is preferable that it is 1-9 mass% with respect to the total amount, and when a hardening | curing agent (C) is an aromatic amine compound, it is 10-50 mass% with respect to the total amount of an isocyanate modified epoxy resin (A). Preferably, when the curing agent (C) is a novolak type phenol resin, the content is preferably 20 to 60% by mass with respect to the total amount of the isocyanate-modified epoxy resin (A). Setting the blending amount of the curing agent (C) in the above range is preferable from the viewpoint of suppressing the decrease in the crosslinking density and the decrease in Tg of the cured product and ensuring the moisture resistance.

[Plasticizer (D)]
The epoxy resin composition of this embodiment may further contain a plasticizer (D). Examples of the plasticizer (D) include thermoplastic elastomers and crosslinked rubbers.

  Examples of thermoplastic elastomers include polyester-based thermoplastic elastomers and polyamide-based thermoplastic elastomers, but the latter tends to be superior in physical properties such as compression strength and interlayer shear strength of fiber-reinforced composite materials. preferable.

  Examples of the crosslinked rubber include acrylonitrile-butadiene copolymer, styrene-butadiene copolymer, and the like. The former is preferable because the compatibility with the epoxy resin tends to be good.

  Content of a plasticizer (D) becomes like this. Preferably it is 1-30 mass% with respect to the whole epoxy resin composition, More preferably, it is 2-20 mass%. Setting the content of the plasticizer (D) to 30% by mass or less is preferable from the viewpoint of preventing the resin viscosity from increasing and impairing the resin into the prepreg. On the other hand, the content of 1% by mass or more is preferable from the viewpoint of maintaining good prepreg tackiness and suppressing molding defects.

[Filler (E)]
The epoxy resin composition of this embodiment may further contain a filler (E). The inclusion of the filler (E) is preferable because of rheology control, that is, thickening and thixotropy imparting effects.

  Examples of the filler (E) include talc, aluminum silicate, finely divided silica, calcium carbonate, mica, alumina hydrate, zinc powder, carbon black, silicon carbide and the like, and fine particles from the viewpoint of imparting thixotropic properties. Silica is preferred.

  Content of a filler (E) becomes like this. Preferably it is 1-10 mass% with respect to the whole epoxy resin composition, More preferably, it is 1-5 mass%. Setting the filler (E) content to 10% by mass or less is preferable from the viewpoint of preventing the resin viscosity from being too high and impregnating the resin into the prepreg and preventing the adhesive strength between the prepregs from decreasing. It is. On the other hand, the content of 1% by mass or more is preferable from the viewpoint of suppressing the occurrence of resin fading on the surface of the molded product.

[Curing Accelerator] It is also possible to adjust the curing rate of the epoxy resin composition by further blending the epoxy resin composition with a curing accelerator. Various known accelerators can be used without particular limitation, and examples thereof include urea compounds, imidazoles, tertiary amines, phosphines, aminotriazoles and the like. Moreover, you may use combining the said epoxy resin and a well-known hardening accelerator.

[Epoxy resin varnish] The above-mentioned epoxy resin composition is preferably used as an epoxy resin varnish uniformly dissolved or dispersed in a solvent. The solvent to be used is not particularly limited as long as it can dissolve or disperse the above epoxy resin composition. For example, acetone, methyl ethyl ketone, methyl cellosolve, methyl isobutyl ketone, dimethylformamide, propylene glycol monomethyl ether, toluene, xylene And mixed solvents thereof.

[Prepreg production method]
A prepreg can be produced using the epoxy resin varnish. The prepreg of the present embodiment can be obtained, for example, by a production method including a step of impregnating the above epoxy resin composition into a fiber base material by applying and / or dipping. Moreover, as another method for obtaining the prepreg of this embodiment, the manufacturing method including the process of adding an organic and / or inorganic short fiber to the epoxy resin composition of this embodiment is mentioned.

  The prepreg of the present embodiment includes a step of impregnating a fiber base material with the above epoxy resin composition or a step of adding short fibers to the epoxy resin composition, and a step of drying the fiber base material or short fibers containing the epoxy resin. It is preferable.

  The prepreg obtained by using the epoxy resin composition of the present embodiment has improved mechanical strength, improved dimensional stability, and excellent stability.

  As the fiber base material, various known materials can be appropriately selected and used, and are not particularly limited. Examples thereof include various glass cloths such as roving cloth, cloth, chopped mat, and surfacing mat, asbestos cloth, and metal fiber cloth. , And other synthetic or natural inorganic fiber cloth; woven or non-woven fabric obtained from synthetic fibers such as polyvinyl alcohol fiber, polyester fiber, acrylic fiber, wholly aromatic polyamide fiber, polytetrafluoroethylene fiber; cotton cloth, linen cloth, felt, etc. Natural fiber cloth; carbon fiber cloth; natural cellulosic cloth such as kraft paper, cotton paper, paper-glass mixed paper, and the like. Among these, a carbon fiber cloth is preferable because of its low specific gravity and excellent specific strength and specific elastic modulus. Moreover, these fiber base materials can be used individually by 1 type or in combination of 2 or more types.

  The thickness of the fiber substrate may be appropriately set according to the thickness of the prepreg, desired mechanical strength and dimensional stability, and is usually about 0.05 to 0.30 mm, but is particularly limited. It is not a thing.

  The proportion of the fiber base in the prepreg is appropriately set according to the desired performance of the prepreg and is not particularly limited, but is preferably 30 to 90% by mass with respect to the total amount of the prepreg, 40 More preferably, it is -80 mass%, and it is further more preferable that it is 50-70 mass%. Setting the fiber substrate to 30% by mass or more is preferable from the viewpoint of obtaining a cured product having more excellent dimensional stability and strength. On the other hand, setting the fiber substrate to 90% by mass or less is preferable from the viewpoint of obtaining a cured product having better adhesion. In addition, when the ratio of a fiber base material is 30-90 mass% with respect to the total amount of a prepreg, it can be judged that an impregnation property is favorable.

  The impregnation of the epoxy resin composition into the fiber base material can be carried out, for example, by applying the epoxy resin composition to the base material or immersing (dipping) the fiber base material in the epoxy resin composition. This impregnation treatment can be repeated a plurality of times as necessary, and the impregnation is repeatedly performed using a plurality of epoxy resin compositions having different compositions and concentrations at that time to obtain a desired resin composition and resin. It is also possible to adjust the amount.

  Furthermore, when the prepreg is dried, it is preferable to adjust the degree of heating to a semi-cured state of the epoxy resin composition, that is, a so-called B-stage state. The drying conditions of the prepreg are appropriately set according to the desired material, thickness, etc. of the prepreg, and are usually conditions of a drying temperature of 100 to 200 ° C. and a drying time of about 1 to 30 minutes.

[Method for producing fiber-reinforced composite material]
The fiber reinforced composite material can be manufactured by laminating the above-described prepreg and heating and pressing. The heating and pressing may be performed according to a conventional method, for example, a temperature of 80 to 300 ° C., a pressure of 0.01 to 100 MPa, and a time of 1 minute to 10 hours, more preferably a temperature of 120 to 250 ° C. and a pressure. It is performed under the conditions of 0.1 to 10 MPa, time 1 minute to 5 hours.

Next, the present embodiment will be described more specifically with reference to examples and comparative examples. However, the present embodiment is not limited to the following examples without departing from the gist thereof.
The physical properties in the examples were measured by the following methods.

(1) Fracture toughness test (K _IC ) The cured product of the epoxy resin composition was measured according to an elastoplastic fracture toughness test method (JSME S 001-1981). As a test method, a test piece of length 20 mm × width 4 mm × thickness 2 mm with a crack of about 2.5 mm in the center of the test piece was measured at an indenter moving speed of 0.5 mm / min and a distance between fulcrums of 17.6 mm. Measurement was performed by a three-point bending test.

(2) Glass transition temperature About a carbon fiber reinforced composite material impregnated with an epoxy resin composition and cured, using a dynamic viscoelasticity measuring device DDV-25FP (manufactured by Orientec Co., Ltd.), length 20 mm × width 4 mm X A test piece having a thickness of 2 mm was heated at a rate of 2 ° C / min, and the temperature at which the elastic modulus E 'decreased was determined.

(3) Compressive strength The compressive strength was measured based on SACMA-SRM-2R-94 for the carbon fiber reinforced composite material impregnated with the epoxy resin composition and cured.

(4) Infrared absorption spectrum (IR)
Using JASCO Corporation FT / IR-6100, measurements were performed in the range of 600 to 4000 cm ⁻¹ .

[Synthesis Example 1]
In the reactor, 100 parts by mass of a biphenol type epoxy resin (trade name: YX4000, manufactured by Japan Epoxy Resin Co., Ltd., epoxy equivalent 185 g / eq) as a raw material glycidyl compound, and tetrabutylammonium bromide (trade name: tetrabromide bromide) 0.04 parts by mass of -n-butylammonium (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the mixture was stirred and heated to adjust the internal temperature to 175 ° C. Furthermore, 11.8 parts by mass of tolylene diisocyanate (trade name: Coronate T80 (trademark), manufactured by Nippon Polyurethane Co., Ltd.) as a raw material isocyanate compound was charged into the reactor over 90 minutes. After completion of the addition, the reaction temperature was kept at 175 ° C. and the mixture was stirred for 8 hours to obtain an isocyanate-modified epoxy resin (A-1). When the obtained resin was subjected to IR measurement, peaks were observed at 1750 cm ⁻¹ and 910 cm ⁻¹ , and it was confirmed that the resin contained an oxazolidone ring and an epoxy group.

[Synthesis Example 2]
In the reactor, 100 parts by mass of biphenol type epoxy resin (trade name: YX4000H, manufactured by Japan Epoxy Resin Co., Ltd., epoxy equivalent 185 g / eq) and hexamethylene diisocyanate (trade name: Duranate 50M, Asahi Kasei Chemicals (as a raw material glycidyl compound) 8.9 parts by mass) was mixed and heated and melted at 100 ° C. Next, 0.04 part by mass of tetrabutylammonium bromide was added as a catalyst, and after stirring until uniform, the temperature was raised and the internal temperature was 175 ° C. The reaction temperature was kept at 175 ° C., and the mixture was stirred for 8 hours to obtain an isocyanate-modified epoxy resin (A-2). When the obtained resin was subjected to IR measurement, peaks were observed at 1750 cm ⁻¹ and 910 cm ⁻¹ , and it was confirmed that the resin contained an oxazolidone ring and an epoxy group.

[Synthesis Example 3]
Modification was performed in the same manner as in Example 1 except that the raw material isocyanate compound was changed to 6.0 parts by mass of isophorone diisocyanate (trade name: Desmodur I (trademark), manufactured by Sumika Bayer Urethane Kogyo Co., Ltd.). The isocyanate-modified epoxy resin (A-3) was obtained. When the obtained resin was subjected to IR measurement, peaks were observed at 1750 cm ⁻¹ and 910 cm ⁻¹ , and it was confirmed that the resin contained an oxazolidone ring and an epoxy group.

[Comparative Synthesis Example 1]
As a raw material glycidyl compound, 90 parts by mass of a bisphenol A type epoxy resin (trade name: AER260, manufactured by Asahi Kasei Chemicals Corporation, epoxy equivalent 186 g / eq) was heated to 150 ° C. and filled with nitrogen. Thereto was added 0.03 part by mass of 2-methylimidazole (manufactured by Wako Pure Chemical Industries, Ltd.), and the mixture was stirred and heated to an internal temperature of 160 ° C. Furthermore, 10 parts by mass of 4,4′-methylenebis (phenylisocyanate) (trade name: Millionate MT (trademark), manufactured by Nippon Polyurethane Co., Ltd.) as a raw material isocyanate compound was charged into the reactor over 30 minutes. After completion of the addition, the reaction temperature was kept at 160 ° C. and the mixture was stirred for 15 minutes to obtain an isocyanate-modified epoxy resin (A-4). When the obtained resin was subjected to IR measurement, peaks were observed at 1750 cm ⁻¹ and 910 cm ⁻¹ , and it was confirmed that the resin contained an oxazolidone ring and an epoxy group.

[Comparative Synthesis Example 2]
This was carried out in the same manner as in Epoxy Resin Production Example A described in JP-A 63-30520. That is, 100 parts by mass of glycidyl ether of 4,4′-bis-3, 3 ′, 5,5′-tetramethylbiphenyl and 54 parts by mass of tetrabromobisphenol A were added 0.03 parts by mass of tetramethylammonium iodide as a catalyst. The resultant was added and reacted at 170 ° C. for 3 hours to obtain a solid epoxy resin (B-1) (epoxy equivalent 460) at room temperature.

[Examples 1-6 and Comparative Examples 1-3]
Using the obtained isocyanate-modified epoxy resins (A-1) to (A-4), the epoxy resin (B-1) and YX4000, an epoxy resin composition was prepared according to the formulation shown in Table 1.

[Manufacture of prepreg and carbon fiber reinforced composite materials]
Carbon fiber cloth (trade name: TORAYCA CROSS CO6343, manufactured by Toray Industries, Inc.) is immersed in the epoxy resin compositions obtained in Examples 1 to 6 and Comparative Examples 1 to 5 for 5 minutes, and the epoxy resin composition is incorporated into the carbon fibers. After impregnating the material, the glass cloth was heated in an oven at 170 ° C. for 2 minutes to obtain a prepreg.
The obtained prepreg was cut into a 10 cm square, 7 sheets were stacked, and pressed with a hot plate press at 40 kgf / cm ² and 180 ° C. for 60 minutes to obtain a carbon fiber reinforced composite material. The obtained carbon fiber reinforced composite material was measured for glass transition temperature (starting temperature of decrease in elastic modulus E ′), fracture toughness (K _IC ), and compressive strength, and the results are shown in Table 1.

  As is clear from the results in Table 1, the fiber reinforced composite materials obtained using the epoxy resin compositions of the present embodiment (Examples 1 to 6) are excellent in balance between heat resistance and mechanical properties. there were.

  The cured product obtained by curing the isocyanate-modified epoxy resin of the present invention has an excellent balance between heat resistance and mechanical properties, and can be used industrially for a wide range of applications such as paints, insulating materials for electric and electronic materials, and adhesives. Have sex.

Claims (5)

An isocyanate-modified epoxy resin (A) having a structure represented by the following general formula (1);
An epoxy resin (B) other than (A),
A curing agent (C);
A plasticizer (D);
An epoxy resin composition comprising:

(In the formula, R _{1 to} R ₈ and R _{10 to} R ₁₇ are each independently a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, or an alkoxy which may have a substituent. A group, an aryl group which may have a substituent, an amino group which may have a substituent, a nitro group or a carboxyl group, wherein R ₉ is a divalent or higher valent which may have a substituent; Indicates a functional group.) The epoxy resin composition according to claim 1, wherein R ₉ contains one or more skeletons selected from isophorone, benzene, toluene, diphenylmethane, naphthalene, polymethylene polyphenylene polyphenyl, and hexamethylene. The epoxy of Claim 1 or 2 whose ratio of the said (A) component in the said epoxy resin composition is 0.1-0.95 by mass ratio of (A) / (A) + (B). Resin composition. The prepreg obtained by the manufacturing method including the process of impregnating the epoxy resin composition of any one of Claims 1-3 to the fiber base material by application | coating and / or immersion. A fiber-reinforced composite material obtained by a production method including the steps of laminating the prepreg according to claim 4 and heating and pressing.