JP2014009280A - Fiber-reinforced composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber-reinforced composite material that has mechanical properties of CAI and ILSS or the like at a high level, and that can improve both a mode I interlayer fracture toughness value Gand a mode II interlayer fracture toughness value Gat the same time at a high level.SOLUTION: A fiber-reinforced composite material includes: two or more reinforcement fiber inclusion layers in which two or more prepregs are laminated and cured; and a resin layer in an interlayer region of each reinforcement fiber inclusion layer, wherein the resin layer comprises a cured material of a resin composition including: a compound having a benzoxazine ring, an epoxy resin, a curing agent, a toughness improver, and a polyether sulfone particle, in the composite material, Gis at least 330 J/m, and Gis at least 1,100 J/m, and the composite material is useful for automobile use, railway vehicle use, aircraft use, ship application, a building component of a windmill or the like, and a component of other general industrial use or the like.

Description

The present invention is suitable for automotive applications, railway vehicle applications, aircraft applications, marine applications, sports applications, wind turbines, and other general industrial applications. Mode I interlaminar fracture toughness value G _IC and mode II interlaminar fracture toughness value G _The present invention relates to a fiber-reinforced composite material that can improve _IIC at a high level at the same time and that can have various mechanical strengths at a high level and can be further reduced in weight.

Fiber reinforced composite materials composed of various fibers and matrix resins are widely used for automobiles, railway vehicles, aircraft, ships, sporting goods and other general industrial applications because of their excellent mechanical properties.
In recent years, the application range of fiber reinforced composite materials has been expanded as the use results have been increased.
As such fiber-reinforced composite materials, those using a compound having a benzoxazine ring have been proposed in Patent Documents 1 and 2, for example. The compound having a benzoxazine ring has excellent moisture resistance and heat resistance, but has a problem of inferior toughness, and has been devised to compensate for the defects by blending epoxy resin and various resin fine particles.
By the way, among post-impact compressive strength (hereinafter abbreviated as CAI), interlayers at high temperature and high humidity, among the mechanical properties required for automobiles, railways, aircraft, marine applications, sports applications, windmills, and other general industrial applications. It is desired to further reduce the weight of fiber-reinforced composite materials applied to main structures and the like by simultaneously achieving shear strength (hereinafter abbreviated as ILSS) and interlaminar fracture toughness in a high dimension. In addition, the mode I interlaminar fracture toughness value G _IC and the mode II interlaminar fracture toughness value G _IIC must be simultaneously increased. However, in the example specifically described in the above patent document, it cannot be said that these can be achieved at the same time in a high dimension.
As a technique for improving the mechanical characteristics, for example, Patent Document 3 discloses a technique of blending polyamide 12 fine particles with a thermosetting resin such as an epoxy resin for the purpose of improving CAI.
A fiber reinforced composite material using such a technique can maintain CAI to some extent high, but has not yet achieved both ILSS at high temperature and high humidity.
Patent Document 4 discloses a composite having a laminate structure in which resin layers containing specific polyamide fine particles and carbon fiber-containing layers are alternately laminated as a carbon fiber composite material capable of achieving both CAI and ILSS at a high level. The materials are listed.
However, in this document, a composite material having a laminate structure using a compound having a benzoxazine ring is not specifically described, and it is difficult to obtain excellent characteristics of a compound having a benzoxazine ring.
Also, in mobile applications, delamination in fiber reinforced composite materials is likely to occur due to collisions during traveling and tool drop impact during maintenance, etc., so the above mode I interlaminar fracture toughness values G _IC and mode II interlaminar Development of a material that can simultaneously improve both the fracture toughness value G _IIC at a high level is desired.

JP 2007-16121 A JP 2010-13636 A JP 2009-286895 A JP 2009-221460 A

The object of the present invention is to provide a fiber reinforcement that has a high level of mechanical properties such as CAI and ILSS, and can simultaneously improve both the mode I interlaminar fracture toughness value G _IC and the mode II interlaminar fracture toughness value G _IIC. It is to provide a composite material.

  In order to solve the above problems, the present inventors have a composite structure having a laminate structure in which a plurality of reinforcing fiber-containing layers and a resin layer formed of a composition containing a compound having a specific benzoxazine ring are laminated. Attempted to produce material. As a result, when a compound having a specific benzoxazine ring, an epoxy resin, and nylon 12 particles are used as raw materials for the composition, it is difficult to obtain a desired laminate structure, and the desired interlaminar fracture toughness value and mechanical It was found that there was little expectation for further improvement in the strength of the machine. Thus, the present inventors have completed the present invention by finding that a laminated body structure can be obtained by variously examining the thermoplastic particles to be added and a desired effect can be achieved.

(式中、Ｒ₁は、炭素数１〜１２の鎖状アルキル基、炭素数３〜８の環状アルキル基、フェニル基、又は炭素数１〜１２の鎖状アルキル基若しくはハロゲンで置換されたフェニル基を示す。また、式中の芳香環の酸素原子が結合している炭素原子のオルト位とパラ位の少なくとも一方の炭素原子には水素原子が結合している。）
(B)エポキシ樹脂と、(C)硬化剤と、(D)靭性向上剤と、(E)ポリエーテルスルフォン粒子とを含む、樹脂組成物の硬化物からなり、繊維強化複合材料の、モードＩ層間破壊靭性値G_ICが３３０Ｊ／ｍ²以上、且つモードII層間破壊靭性値G_IICが１１００Ｊ／ｍ²以上である繊維強化複合材料が提供される。 According to the present invention, a fiber reinforced composite material comprising a plurality of reinforcing fiber-containing layers laminated and cured with a plurality of prepregs, and a resin layer in an interlayer region of each reinforcing fiber-containing layer,
The resin layer is (A) a compound having a benzoxazine ring represented by the formula (1) in the molecule;

(In the formula, R ₁ represents a chain alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group having 3 to 8 carbon atoms, a phenyl group, or a phenyl group substituted with a chain alkyl group having 1 to 12 carbon atoms or a halogen. In addition, in the formula, a hydrogen atom is bonded to at least one of the ortho-position and para-position of the carbon atom to which the oxygen atom of the aromatic ring is bonded.)
A mode I fiber reinforced composite material comprising a cured product of a resin composition comprising (B) an epoxy resin, (C) a curing agent, (D) a toughness improver, and (E) polyethersulfone particles. A fiber-reinforced composite material having an interlaminar fracture toughness value G _IC of 330 J / m ² or more and a mode II interlaminar fracture toughness value G _IIC of 1100 J / m ² or more is provided.

Since the fiber-reinforced composite material of the present invention has a laminate structure of a reinforcing fiber-containing layer and a resin layer made of a cured product of the above resin composition, it has mechanical properties such as CAI and ILSS at a high level, and Both mode I interlaminar fracture toughness value G _IC and mode II interlaminar fracture toughness value G _IIC can be improved at a high level simultaneously. Therefore, the fiber-reinforced composite material of the present invention can be suitably used for automobile applications, railway vehicle applications, aircraft applications, marine applications, sports applications, building components such as windmills, and other general industrial applications.

The present invention will be described in detail below.
The fiber reinforced composite material of the present invention (hereinafter sometimes abbreviated as the composite material of the present invention) includes a plurality of reinforcing fiber-containing layers obtained by laminating and curing a plurality of prepregs, and an interlayer region between the reinforcing fiber-containing layers. And a resin layer obtained by curing a specific resin composition, wherein the mode I interlaminar fracture toughness value G _IC and the mode II interlaminar fracture toughness value G _IIC exhibit a specific value or more.
In the composite material of the present invention, the G _IC is, 330j / m ² or more, preferably 450 J / m ² or more, particularly preferably 550j / m ² or more. The upper limit is not particularly limited, but is about 800 J / m ² . The G _IIC is 1100 J / m ² or more, preferably 1250 J / m ² or more, particularly preferably 1500 J / m ² or more. The upper limit is not particularly limited, but is about 3000 J / m ² . If one of the G _IC and the G _IIC is less than the lower limit, the delamination suppressing effect at a high level cannot be obtained, and it may be difficult to reduce the weight of the composite material. Such an interlaminar fracture toughness value is presumed to be due to the fact that the composite material of the present invention is composed of a laminate structure and the resin layer is composed of a cured product of a specific resin composition.

In the present invention, the laminated structure having the reinforcing fiber-containing layer and the resin layer can be confirmed by taking a cross-sectional photograph of the laminated body with a digital microscope.
In the composite material of the present invention, the thickness of each reinforcing fiber-containing layer is usually 90 to 140 μm, preferably 95 to 135 μm, and the thickness of each resin layer is usually 10 to 60 μm, preferably 15 to 55 μm. It is. Here, the thickness of the resin layer is the thickness of the region where no reinforcing fiber exists, and the reinforcing fiber present on the side closest to the resin layer among the reinforcing fibers in the reinforcing fiber-containing layer on both sides of the resin layer. It was set as the space | interval of the outer surfaces of a fiber.

The composite material of the present invention is, for example, a method of preparing a prepreg by a known method using a raw material containing a specific resin composition and reinforcing fibers, laminating the prepreg, and curing it under the conditions described later, etc. Can be manufactured.
The specific resin composition used in the composite material of the present invention includes (A) a compound having a benzoxazine ring represented by the above formula (1) in the molecule, (B) an epoxy resin, (C) a curing agent, D) toughness improver and (E) polyethersulfone particles.

The component (A) used in the resin composition is a compound having a benzoxazine ring represented by the above formula (1).
In the formula (1), R ₁ is substituted with a chain alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group having 3 to 8 carbon atoms, a phenyl group, or a chain alkyl group having 1 to 12 carbon atoms or a halogen. Represents a phenyl group.
Examples of the chain alkyl group having 1 to 12 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a t-butyl group.
Examples of the cyclic alkyl group having 3 to 8 carbon atoms include a cyclopentyl group and a cyclohexyl group.
Examples of the phenyl group substituted with a chain alkyl group having 1 to 12 carbon atoms or halogen include, for example, a phenyl group, an o-methylphenyl group, an m-methylphenyl group, a p-methylphenyl group, an o-ethylphenyl group, Examples include m-ethylphenyl group, p-ethylphenyl group, ot-butylphenyl group, mt-butylphenyl group, pt-butylphenyl group, o-chlorophenyl group, and o-bromophenyl group.
Among R ₁ , R ₁ is preferably a methyl group, an ethyl group, a propyl group, a phenyl group, or an o-methylphenyl group among the above examples.

  As the benzoxazine resin of component (A), for example, a monomer represented by the following formula, an oligomer obtained by polymerizing several molecules of the monomer, a compound having a benzoxazine ring having a structure different from these monomers, and at least of these monomers A reaction product with one kind is preferred.

  The component (A) is excellent in flame retardancy because the benzoxazine ring undergoes ring-opening polymerization to form the same skeleton as the phenol resin. In addition, excellent mechanical properties such as low water absorption and high elastic modulus can be obtained from the dense structure.

Component (B), which is an epoxy resin used in the resin composition, is a component that controls the viscosity of the composition and increases the curability of the composition.
As the component (B), for example, an epoxy resin having a precursor such as an amine, a phenol, a carboxylic acid, or an intramolecular unsaturated carbon is preferable.

Examples of epoxy resins having amines as precursors include tetraglycidyldiaminodiphenylmethane, glycidyl compounds of xylenediamine, triglycidylaminophenol, and glycidylanilines, their respective positional isomers, and substitution with alkyl groups or halogens. It is done.
Hereinafter, in the case of exemplifying commercially available products, in the liquid product, the complex viscoelastic modulus η * at 25 ° C. obtained by a dynamic viscoelasticity measuring device described later is described as the viscosity.

  Commercially available products of tetraglycidyldiaminodiphenylmethane include, for example, “Sumiepoxy” (registered trademark, hereinafter the same) ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), “Araldite” (registered trademark, the same hereinafter) MY720, “Araldite” MY721, “ "Araldite" MY9512, "Araldite" MY9612, "Araldite" MY9634, "Araldite" MY9663 (manufactured by Huntsman Advanced Materials), "jER" (registered trademark, hereinafter the same) 604 (manufactured by Mitsubishi Chemical Corporation) Can be mentioned.

Commercially available products of triglycidylaminophenol include, for example, “jER” 630 (viscosity: 750 mPa · s) (manufactured by Mitsubishi Chemical Corporation), “Araldite” MY0500 (viscosity: 3500 mPa · s), MY0510 (viscosity: 600 mPa · s). s) (manufactured by Huntsman Advanced Materials), ELM100 (viscosity: 16000 mPa · s) (manufactured by Sumitomo Chemical).
Examples of commercially available glycidyl anilines include GAN (viscosity: 120 mPa · s) and GOT (viscosity: 60 mPa · s) (manufactured by Nippon Kayaku Co., Ltd.).

Examples of the glycidyl ether type epoxy resin having phenol as a precursor include, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, epoxy resin having a biphenyl skeleton, phenol novolak type epoxy resin, cresol novolak type Epoxy resin, resorcinol type epoxy resin, epoxy resin having naphthalene skeleton, trisphenylmethane type epoxy resin, phenol aralkyl type epoxy resin, dicyclopentadiene type epoxy resin, diphenylfluorene type epoxy resin and various isomers and alkyl groups thereof, Examples include halogen substitution products.
Moreover, an epoxy resin obtained by modifying an epoxy resin having a phenol precursor with urethane or isocyanate is also included in this type.

Examples of commercially available liquid bisphenol A type epoxy resins include “jER” 825 (viscosity: 5000 mPa · s), “jER” 826 (viscosity: 8000 mPa · s), and “jER” 827 (viscosity: 10,000 mPa · s). , “JER” 828 (viscosity: 13000 mPa · s), (manufactured by Mitsubishi Chemical Corporation), “Epiclon” (registered trademark, the same applies hereinafter) 850 (viscosity: 13000 mPa · s) (manufactured by DIS Corporation), “ “Epototo” (registered trademark, the same applies hereinafter) YD-128 (viscosity: 13000 mPa · s) (manufactured by Nippon Steel Chemical Co., Ltd.), DER-331 (viscosity: 13000 mPa · s), DER-332 (viscosity: 5000 mPa · s) ) (Manufactured by Dow Chemical Company).
Examples of commercially available solid or semi-solid bisphenol A type epoxy resins include “jER” 834, “jER” 1001, “jER” 1002, “jER” 1003, “jER” 1004, “jER” 1004AF, and “jER”. "1007", "jER" 1009 (manufactured by Mitsubishi Chemical Corporation).

Examples of commercially available liquid bisphenol F-type epoxy resins include “jER” 806 (viscosity: 2000 mPa · s), “jER” 807 (viscosity: 3500 mPa · s), and “jER” 1750 (viscosity: 1300 mPa · s). , “JER” (manufactured by Mitsubishi Chemical Corporation), “Epiclon” 830 (viscosity: 3500 mPa · s) (manufactured by DIC Corporation), “Epototo” YD-170 (viscosity: 3500 mPa · s), “Epototo” YD-175 (viscosity: 3500 mPa · s) (manufactured by Nippon Steel Chemical Co., Ltd.).
Commercially available products of solid bisphenol F type epoxy resins include, for example, 4004P, “jER” 4007P, “jER” 4009P (manufactured by Mitsubishi Chemical Corporation), “Epototo” YDF2001, “Epototo” YDF2004 (above Nippon Steel) Chemical Co., Ltd.).

Examples of the bisphenol S type epoxy resin include EXA-1515 (manufactured by DIC Corporation).
Examples of commercially available epoxy resins having a biphenyl skeleton include “jER” YX4000H, “jER” YX4000, “jER” YL6616 (manufactured by Mitsubishi Chemical Corporation), NC-3000 (manufactured by Nippon Kayaku Co., Ltd.). ).

Examples of commercially available phenol novolac epoxy resins include “jER” 152, “jER” 154 (manufactured by Mitsubishi Chemical Corporation), “Epicron” N-740, “Epicron” N-770, “Epicron” N -775 (manufactured by DIC Corporation).
Examples of commercially available products of the cresol novolac type epoxy resin include “Epicron” N-660, “Epicron” N-665, “Epicron” N-670, “Epicron” N-673, “Epicron” N-695 (above, DIC Co., Ltd.), EOCN-1020, EOCN-102S, EOCN-104S (Nippon Kayaku Co., Ltd.).

As a commercial item of a resorcinol type epoxy resin, “Denacol” (registered trademark, the same applies hereinafter) EX-201 (viscosity: 250 mPa · s) (manufactured by Nagase ChemteX Corporation) can be mentioned.
Examples of commercially available epoxy resins having a naphthalene skeleton include “Epiclon” HP4032 (manufactured by DIC Corporation), NC-7000, and NC-7300 (manufactured by Nippon Kayaku Co., Ltd.).
Examples of commercially available trisphenylmethane type epoxy resins include TMH-574 (manufactured by Sumitomo Chemical Co., Ltd.).

Commercially available dicyclopentadiene type epoxy resins include, for example, “Epicron” HP7200, “Epicron” HP7200L, “Epicron” HP7200H (above, manufactured by DIC Corporation), “Tactix” (registered trademark) 558 (Huntsman Advanced) -Materials company make), XD-1000-1L, XD-1000-2L (above, Nippon Kayaku Co., Ltd. product) is mentioned.
Examples of commercially available urethane and isocyanate-modified epoxy resins include AER4152 (produced by Asahi Kasei E-Materials Co., Ltd.) having an oxazolidone ring.

  Examples of the epoxy resin having a carboxylic acid as a precursor include glycidyl compounds of phthalic acid, glycidyl compounds of hexahydrophthalic acid and dimer acid, and various isomers thereof.

Examples of commercially available products of diglycidyl phthalate include “Epomic” (registered trademark, the same applies hereinafter) R508 (viscosity: 4000 mPa · s) (manufactured by Mitsui Chemicals), “Denacol” EX-721 (viscosity: 980 mPas). S) (manufactured by Nagase ChemteX Corporation).
Commercially available products of hexahydrophthalic acid diglycidyl ester include, for example, “Epomic” R540 (viscosity: 350 mPa · s) (manufactured by Mitsui Chemicals), AK-601 (viscosity: 300 mPa · s) (Nippon Kayaku ( Co., Ltd.).
Examples of commercially available dimer acid diglycidyl ester include “jER” 871 (viscosity: 650 mPa · s) (manufactured by Mitsubishi Chemical Corporation), “Epototo” YD-171 (viscosity: 650 mPa · s) (Nippon Steel). Chemical Co., Ltd.).

As an epoxy resin which uses intramolecular unsaturated carbon as a precursor, an alicyclic epoxy resin is mentioned, for example.
Specifically, as a commercially available product of (3 ′, 4′-epoxycyclohexane) methyl-3,4-epoxycyclohexanecarboxylate, for example, “Celoxide” (registered trademark, the same shall apply hereinafter) 2021P (viscosity: 250 mPa · s) ) (Manufactured by Daicel Chemical Industries, Ltd.), CY179 (viscosity: 400 mPa · s) (manufactured by Huntsman Advanced Materials), (3 ′, 4′-epoxycyclohexane) octyl 3,4-epoxycyclohexanecarboxylate Examples of the product include “Celoxide” 2081 (viscosity: 100 mPa · s) (manufactured by Daicel Chemical Industries, Ltd.), 1-methyl-4- (2-methyloxiranyl) -7-oxabicyclo [4.1. .0] Commercially available heptane includes, for example, “Celoxide” 3000 (viscosity: 20 mPa · s). (Daicel Chemical Industries, Ltd.).

The lower the viscosity at 25 ° C. of the epoxy resin which is liquid at 25 ° C., the more preferable from the viewpoint of tack and draping properties, and 5 mPa · s or more and 20000 mPa · s or less, which is the lower limit obtained as a commercially available epoxy resin, is preferable. * More preferably, it is s or more and 15000 mPa * s or less. When it exceeds 20000 mPa · s, tack and drape properties may deteriorate.
As an epoxy resin solid at 25 ° C., an epoxy resin having a high aromatic content is preferable in order to increase flame retardancy. For example, an epoxy resin having a biphenyl skeleton, an epoxy resin having a naphthalene skeleton, or a phenol aralkyl type epoxy resin. Is mentioned.

  In the resin composition, the preferable content ratio of the component (A) and the component (B) is usually 65 to 78% by mass, particularly preferably 70 to 75%, so that the total of these components is 100% by mass. % By mass and usually 22 to 35% by mass of component (B), particularly preferably 25 to 30% by mass. When the content ratio of the component (A) is less than 65% by mass, that is, when the content ratio of the component (B) exceeds 35% by mass, the ILSS of the resulting reinforcing fiber composite may be lowered, and the resin is cured. There is a possibility that the glass transition temperature of the object may be lowered.

In the resin composition, as the curing agent of the component (C), for example, diethyltoluenediamine, metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, metaxylenediamine, aromatic amines such as various derivatives thereof, triethylenetetramine, Aliphatic amines such as isophoronediamine, imidazole derivatives, dicyandiamide, tetramethylguanidine, carboxylic acid anhydrides such as methylhexahydrophthalic anhydride, carboxylic acid hydrazides such as adipic hydrazide, carboxylic acid amides, monofunctional phenols and bisphenol A Such as Lewis acid complexes such as polyfunctional phenolic compounds, bis (4-hydroxyphenyl) sulfide, polyphenolic compounds, polymercaptan, carboxylates, boron trifluoride ethylamine complexes, etc. German or mixtures of two or more can be used, inter alia aromatic amines, sulfonic acid esters, polyfunctional phenolic compounds, such as monofunctional phenols and bisphenol A, alone or mixtures of two or more polyphenol compounds are preferable.
These curing agents react with a compound having a benzoxazine ring as the component (A) and an epoxy resin as the component (B) to obtain a fiber-reinforced composite material having excellent heat resistance and moisture resistance.

  In the resin composition, the content ratio of the component (C) is usually 5 to 20 parts by mass, preferably 7 to 15 parts by mass with respect to 100 parts by mass of the component (A) + the component (B). If the amount is less than 5 parts by mass, the curing reaction is slow, so that a high temperature and a long time are required to increase the degree of curing of the entire resin composition. If it exceeds 20 parts by mass, mechanical properties such as glass transition temperature of the cured product may be lowered.

The (D) toughness improver used in the resin composition is a component that dissolves in the resin composition and is selected from the group consisting of organic fine particles or organic fine particles dissolved in a liquid resin or resin monomer. There is at least one kind.
Here, dissolution means that the fine particles of component (D) are dispersed in the composition, and the fine particles and the substances constituting the composition have an affinity for each other and are in a uniform or mixed state. means.
Examples of the liquid resin or resin monomer include reactive elastomers, hiker CTBN-modified epoxy resins, hiker CTB-modified epoxy resins, urethane-modified epoxy resins, nitrile rubber-added epoxy resins, crosslinked acrylic rubber fine particle-added epoxy resins, and silicone-modified epoxy resins. A thermoplastic elastomer-added epoxy resin can be used.

As the organic fine particles, for example, thermosetting resin fine particles, thermoplastic resin fine particles, or a mixture thereof can be used.
Examples of the thermosetting resin fine particles include epoxy resin fine particles, phenol resin fine particles, melamine resin fine particles, urea resin fine particles, silicone resin fine particles, urethane resin fine particles, or a mixture thereof.

Examples of the thermoplastic resin fine particles include copolymerized polyester resin fine particles, phenoxy resin fine particles, polyimide resin fine particles, polyamide resin fine particles, acrylic fine particles, butadiene-acrylonitrile resin fine particles, styrene fine particles, olefin fine particles, nylon fine particles, butadiene. -Alkyl methacrylate / styrene copolymer, acrylic ester / methacrylic ester copolymer, or a mixture thereof.
As the acrylic fine particles, Nanostrength M22 (trade name, manufactured by Arkema Co., Ltd.), which is commercially available as a copolymer comprising methyl methacrylate / butyl acrylate / methyl methacrylate, can also be used.
As commercially available core / shell type fine particles, Staphyloid AC3355 (trade name, manufactured by Ganz Kasei Co., Ltd.), MX120 (trade name, manufactured by Kaneka Corporation) and the like can be used.

The acrylic fine particles can be produced by (1) monomer polymerization, (2) polymer chemical treatment, (3) polymer mechanical pulverization, etc., but the method (3) gives a fine product. Therefore, it is not preferable because the shape is irregular.
Examples of the polymerization method include emulsion polymerization, soap-free emulsion polymerization, dispersion polymerization, seed polymerization, suspension polymerization, or a method in which these are used in combination with each other, the particle size is fine, partially crosslinked structure, core / shell structure, Emulsion polymerization and seed polymerization are used in which fine particles having a hollow structure and a polar structure (epoxy group, carboxyl group, hydroxyl group, etc.) are obtained.
As commercially available core / shell type fine particles, Staphyloid AC3355 (trade name, manufactured by Ganz Kasei Co., Ltd.), F351 (trade name, manufactured by Nippon Zeon Co., Ltd.), Kureha Paraloid EXL-2655 (trade name, Kureha) Chemical Industry Co., Ltd.), MX120 (trade name, manufactured by Kaneka Corporation) and the like.

  In the resin composition, the content ratio of the component (D) is preferably 3 to 20 parts by mass, particularly preferably 5 to 15 parts by mass with respect to 100 parts by mass of the component (A) + the component (B). If the amount is less than 3 parts by mass, the effect of improving the toughness of the resin composition may not be obtained, and cracks may occur during curing of the resin composition. When it exceeds 20 mass parts, there exists a possibility that the heat resistance of a resin composition may fall.

The polyether sulfone particles of component (E) used in the resin composition can maintain a powder state in the composition, preferably those having a glass transition temperature of 200 ° C. or higher, particularly those having 220 to 250 ° C. Is desirable. Here, the glass transition temperature is a midpoint temperature obtained based on JIS K7121 using a differential calorimeter (DSC).
The polyether sulfone particles of component (D) are polyether sulfone particles (E1) having an average particle size of 1 μm or more and less than 15 μm, preferably 5 μm or more and less than 15 μm, or an average particle size of 15 μm or more and 60 μm or less, preferably 15 μm or more and 30 μm. The following polyether sulfone particles (E2) are preferably used separately. As described above, the reason why the (E1) component and the (E2) component are divided according to the average particle diameter is that the desired effect of the present invention can be obtained by controlling the content ratio of these components to be described later. It is because it becomes easy.
Here, the average particle diameter means the average value of the lengths of the long diameters of each particle measured with 100 particles arbitrarily selected from particles enlarged 200 to 500 times with a scanning electron microscope (SEM). To do.

As the component (E), commercially available products can be used, and examples thereof include “Sumika Excel PES5003P” (manufactured by Sumitomo Chemical Co., Ltd.) and “Ultrason E 2020 P SR micro” (manufactured by BASF).
The component (E) is preferably spherical particles from the viewpoint of not reducing the flow characteristics of the resin composition, but may be non-spherical particles.

When the component (E1) is used as the component (E), the content ratio of the component (E1) is preferably 20 to 30 parts by weight, particularly preferably 100 parts by weight of the component (A) + component (B). 20 to 25 parts by mass. If the amount is less than 20 parts by mass, the CAI may decrease, and if the amount exceeds 30 parts by mass, the ILSS may decrease.
When the component (E2) is used as the component (E), the content ratio of the component (E2) is preferably 5 parts by mass or more and less than 20 parts by mass with respect to 100 parts by mass of the component (A) + the component (B). Preferably it is 7-18 mass parts. If it is less than 5 parts by mass, CAI and toughness may be reduced, and if it is 20 parts by mass or more, ILSS may be reduced.

In the composition of the present invention, for example, nanocarbon, a flame retardant, a release agent, and the like can be blended within a range that does not impair the physical properties.
Examples of nanocarbon include carbon nanotubes, fullerenes, and derivatives thereof.
Examples of the flame retardant include phosphoric acid such as red phosphorus, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, xylenyl diphenyl phosphate, resorcinol bisphenyl phosphate, bisphenol A bisdiphenyl phosphate, etc. Examples include esters and borate esters.
Examples of the mold release agent include silicone oil, stearic acid ester, and carnauba wax.

  The kneading method of the resin composition is not particularly limited. For example, a kneader, a planetary mixer, a twin screw extruder or the like is used. Further, from the viewpoint of the dispersibility of the particle component, it is preferable that the particles are previously diffused into the liquid resin component to be blended in the benzoxazine resin composition with a homomixer, three rolls, a ball mill, a bead mill, and an ultrasonic wave. . Further, when mixing with the matrix resin or pre-diffusion of particles, heating / cooling, pressurization / depressurization may be performed as necessary. From the viewpoint of storage stability, it is preferable to store in a refrigerator / freezer immediately after kneading.

  The viscosity of the resin composition is preferably 10 to 3000 Pa · s at 50 ° C. from the viewpoint of tack and drape. More preferably, it is 10-2500 Pa.s, Most preferably, it is 100-2000 Pa.s. If it is less than 10 Pa · s, the change with time of tack due to the sinking of the resin composition may become large. On the other hand, when it exceeds 3000 Pa · s, the tack becomes weak, and the drape property may be lowered.

Preferred examples of the reinforcing fiber used for producing the composite material of the present invention include glass fiber, carbon fiber, graphite fiber, aramid fiber, boron fiber, alumina fiber, and silicon carbide fiber. Two or more kinds of these fibers may be mixed and used, but in order to obtain a molded product that is lighter and more durable, it is preferable to use carbon fiber or graphite fiber.
In the present invention, any type of carbon fiber or graphite fiber can be used depending on the application, but since a composite material having excellent impact resistance and high rigidity and mechanical strength can be obtained, The tensile elastic modulus in the strand tensile test is preferably 150 to 650 GPa, more preferably 200 to 550 GPa, and further preferably 230 to 500 GPa.
The strand tensile test refers to a test carried out based on JIS R7601 (1986) after impregnating a bundle of reinforcing fibers with a resin having the following composition and curing it at a temperature of 130 ° C. for 35 minutes.

The form of the reinforcing fiber is not particularly limited, and examples thereof include long fibers aligned in one direction, tows, woven fabrics, mats, knits, braids, and short fibers chopped to a length of less than 10 mm.
Here, the long fiber is a single fiber or a fiber bundle substantially continuous for 10 mm or more. A short fiber is a fiber bundle cut into a length of less than 10 mm. In particular, an array in which reinforcing fiber bundles are aligned in a single direction is most suitable for applications that require a high specific strength and specific elastic modulus. Arrangements are also suitable for the present invention.

The prepreg for preparing the composite material of the present invention is obtained by impregnating the reinforcing fiber with the resin composition.
Examples of the impregnation method include a wet method in which the resin composition is dissolved in a solvent such as methyl ethyl ketone and methanol to lower the viscosity and impregnated, and a hot melt method (dry method) in which the viscosity is lowered by heating and impregnated. it can.
The wet method is a method in which a reinforcing fiber is immersed in a solution of the resin composition and then lifted and the solvent is evaporated using an oven or the like. The hot melt method is a method in which a resin composition whose viscosity is reduced by heating is directly reinforced fiber Or impregnating the reinforcing fibers with resin by layering the film from both sides or one side of the reinforcing fibers and heating and pressurizing them. It is a method to make it.
The hot melt method is preferable because substantially no solvent remains in the prepreg.

The obtained prepreg preferably has a reinforcing fiber amount per unit area of 70 to 3000 g / m ² . When the amount of reinforcing fibers is less than 70 g / m ^2, it is necessary to increase the number of laminated sheets in order to obtain a predetermined thickness when the composite material of the present invention is molded, and the work may be complicated. On the other hand, when the amount of reinforcing fibers exceeds 3000 g / m ² , the prepreg drapability tends to deteriorate. If the prepreg is flat or simple, the amount of reinforcing fibers may exceed 3000 g / m ² . Moreover, the weight content rate of a reinforced fiber becomes like this. Preferably it is 30-90 mass%, More preferably, it is 35-85 mass%, More preferably, it is 40-80 mass%. When the weight content of the reinforcing fiber is less than 30% by mass, the amount of resin is too large to obtain the advantages of the composite material having excellent specific strength and specific elastic modulus. May become too large. If the weight content of the reinforcing fibers exceeds 90% by mass, resin impregnation failure occurs, and the resulting composite material may have many voids.

The prepreg can be made into the composite material of the present invention by, for example, a method of heat-curing a resin under specific conditions while applying pressure to the laminate after lamination.
The heat-curing conditions can be performed, for example, under the condition of holding at a temperature of about 180 ° C. for 1 to 5 hours.

Examples of the method for applying heat and pressure include a press molding method, an autoclave molding method, a bagging molding method, a wrapping tape method, and an internal pressure molding method.
The wrapping tape method is a method of forming a tubular body made of a composite material by winding a prepreg on a mandrel or the like, and is a suitable method for producing a rod-shaped body such as a golf shaft or a fishing rod. More specifically, a prepreg is wound around a mandrel, a wrapping tape made of a thermoplastic film is wound around the outside of the prepreg for fixing and applying pressure, and the resin is heated and cured in an oven, and then a cored bar. This is a method for extracting a tube to obtain a tubular body.

  In the internal pressure molding method, a preform obtained by winding a prepreg on an internal pressure applying body such as a tube made of a thermoplastic resin is set in a mold, and then a high pressure gas is introduced into the internal pressure applying body to apply pressure and at the same time In this method, the mold is heated and molded. This method is preferably used when molding a complicated shape such as a golf shaft, a bad, a racket such as tennis or badminton.

The composite material of the present invention can also be obtained by impregnating a resin composition directly on a reinforcing fiber substrate and curing it. For example, it can also be produced by a method of laminating a base material of reinforcing fibers and a film made of the resin composition, and heating and pressurizing the laminate.
The film made of the resin composition refers to a film obtained by applying a predetermined amount of a resin composition with a uniform thickness on a release paper or a release film in advance. Examples of the reinforcing fiber base material include long fibers arranged in one direction, two-way woven fabric, non-woven fabric, mat, knit, braided string, and the like.
Lamination includes not only simply superimposing reinforcing fiber base materials but also performing preforming by attaching to various molds and core materials.
As the core material, a foam core or a honeycomb core is preferably used. As the foam core, urethane or polyimide is preferably used. As the honeycomb core, an aluminum core, a glass core, an aramid core, or the like is preferably used.

The composite material of the present invention has a post-impact compressive strength (CAI) of usually 250 MPa or more, preferably 300 MPa or more, and an interlaminar shear strength (ILSS) of usually 50 MPa or more, preferably 60 MPa, measured under the conditions in Examples described later. above, the mode I interlaminar fracture toughness G _IC is usually 330j / m ² or more, preferably 450 J / m ² or more, the mode II interlayer fracture toughness G _II
C is usually 1100 J / m ² or more, preferably 1600 J / m ² or more.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. Various physical properties were measured by the following methods. The results are shown in Tables 1 and 2.
Examples 1-3, Comparative Examples 1-3
About each Example and the comparative example, the raw material was mixed in the ratio shown in Table 1 and Table 2, and the resin composition was obtained.
The raw materials used here are as shown below.
Component (A): benzoxazine resin Fa (bisphenol F-aniline type, manufactured by Shikoku Kasei Co., Ltd.)
Pa (phenol-aniline type, manufactured by Shikoku Kasei Co., Ltd.)
Component (B): Epoxy resin “Celoxide” (registered trademark) 2021P (manufactured by Daicel Chemical Industries, Ltd.)
Bisphenol A type diglycidyl ether (YD-128, manufactured by Nippon Steel Chemical Co., Ltd.)
Component (C): curing agent bis (4-hydroxyphenyl) sulfide (manufactured by Tokyo Chemical Industry Co., Ltd.)
Component (D): Toughness improver Nanostrength (M22, manufactured by Arkema)
Component (E): Polyethersulfone particles SUMIKAEXCEL PES5003P (manufactured by Sumitomo Chemical Co., Ltd.)
Ultrason E 2020 P SR micro (manufactured by BASF)
Polyamide 12 particles “VESTOSINT” (registered trademark) 2158 (polyamide 12 having an average particle diameter of 20 μm, manufactured by Daicel-Evonik Co., Ltd.)
“VESTOSINT” (registered trademark) 2159 (polyamide 12 having an average particle diameter of 10 μm, manufactured by Daicel Evonik Co., Ltd.)

<Prepreg tackiness test>
Using the obtained resin composition, it was applied onto release paper to obtain a resin film. The resin film was supplied from above and below carbon fibers aligned in one direction and impregnated to prepare a prepreg. The amount of carbon fiber per unit area of this prepreg was 150 g / m ² , and the amount of matrix resin was 67 g / m ² .
The tack of the obtained prepreg was determined by a tactile sensation method. Immediately after peeling the release paper from the surface of the prepreg, press the prepreg with your finger and hold it with a good tack, △ if it is slightly too strong or weak, △, if the tack is too strong and does not peel off from your finger Those that do not have a cross.

<Measurement of CAI>
The obtained prepreg was quasi-isotropically laminated with 32 plies in a [+ 45 ° / 0 ° / −45 ° / 90 °] _4s configuration, and heated in an autoclave at a temperature of 180 ° C. and a pressure of 0.6 MPa for 2 hours. Cured to obtain CFRP. With respect to this CFRP, in accordance with SACMA SRM 2R-94, a sample having a length of 150 mm × width of 100 mm was cut out, a drop weight impact of 6.7 J / mm was applied to the center of the sample, and the compressive strength after impact was obtained.

<Measurement of ILSS>
12 layers of the obtained prepreg were laminated in the 0 degree direction, and heat-cured for 2 hours at a temperature of 180 ° C. and a pressure of 0.6 MPa in an autoclave to obtain CFRP. This CFRP was cut out into a rectangle with a 0 degree direction of 13 mm and a width direction of 6.35 mm in accordance with ASTM D2402--07, and immersed in 71 ° C. warm water for 2 weeks according to ASTM D2402-07, and sufficiently absorbed. The interlaminar shear strength was measured under an environment of 82 ° C.

<Confirmation of reinforcing fiber-containing layer and resin layer>
The obtained prepreg was quasi-isotropically laminated with 32 plies in a [+ 45 ° / 0 ° / −45 ° / 90 °] _4s configuration, and heated in an autoclave at a temperature of 180 ° C. and a pressure of 0.6 MPa for 2 hours. Cured to obtain CFRP. The CFRP was cut and the cut surface was polished. The cut surface was photographed with a microscope (manufactured by Keyence Corporation). The reinforcing fiber-containing layer and the resin layer were confirmed from the photograph.

<Measurement of interlaminar fracture toughness G _IC and G _IIC >
Twenty-six layers of the obtained prepreg were laminated in the 0 degree direction, and heat-cured in an autoclave at a temperature of 180 ° C. and a pressure of 0.6 MPa for 2 hours to obtain CFRP. The CFRP was cut into rectangles having a 0 degree direction of 250 mm and a width direction of 25 mm in accordance with JIS K7086 and measured.

From Tables 1 and 2, it was found that CAI, ILSS, G _IC and G _IIC were higher when the polyether sulfone particles were added than when the polyamide 12 particles were added.

Claims (4)

A fiber-reinforced composite material comprising a plurality of reinforcing fiber-containing layers laminated and cured with a plurality of prepregs, and a resin layer in an interlayer region of each reinforcing fiber-containing layer,
The resin layer is (A) a compound having a benzoxazine ring represented by the formula (1) in the molecule;

(In the formula, R ₁ represents a chain alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group having 3 to 8 carbon atoms, a phenyl group, or a phenyl group substituted with a chain alkyl group having 1 to 12 carbon atoms or a halogen. In addition, in the formula, a hydrogen atom is bonded to at least one of the ortho-position and para-position of the carbon atom to which the oxygen atom of the aromatic ring is bonded.)
A mode I fiber reinforced composite material comprising a cured product of a resin composition comprising (B) an epoxy resin, (C) a curing agent, (D) a toughness improver, and (E) polyethersulfone particles. A fiber-reinforced composite material having an interlaminar fracture toughness value G _IC of 330 J / m ² or more and a mode II interlaminar fracture toughness value G _IIC of 1100 J / m ² or more.   (B) The epoxy resin is a cresol novolac epoxy resin, a phenol novolac epoxy resin, a biphenyl epoxy resin, a naphthalene epoxy resin, an aromatic glycidyl ester epoxy resin, an aromatic amine epoxy resin, or a resorcin epoxy resin The fiber-reinforced composite material according to claim 1, which is at least one epoxy resin selected from the group consisting of alicyclic epoxy resins.   The fiber-reinforced composite material according to claim 1 or 2, wherein (C) the curing agent is at least one selected from the group consisting of an aromatic amine, a monofunctional phenol, a polyfunctional phenol compound, or a polyphenol compound.   (D) The toughness improver is at least one selected from the group consisting of inorganic fine particles, organic fine particles, or inorganic fine particles and / or organic fine particles dispersed in a liquid resin or resin monomer. 4. The fiber-reinforced composite material according to any one of 3.