JP2006265458A - Resin composition for prepregs, and prepreg - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prepreg which is a carbon fiber reinforced composite material excellent in strength and elongation and to provide a resin composition for use in such a prepregs. <P>SOLUTION: The resin composition for the prepreg comprises a tri- or higher functional epoxy resin, a monofunctional epoxy resin having a biphenyl skeleton and an aromatic amino compound. The prepreg is obtained by impregnating a carbon fiber with the resin composition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a resin composition for prepreg and a prepreg.

  A carbon fiber reinforced composite material obtained from a prepreg in which carbon fiber is impregnated with an epoxy resin has excellent mechanical properties, and is therefore used in fields such as aviation, space, sports, leisure, civil engineering, and architecture.

  Conventionally, an epoxy resin used as a matrix resin of a resin composition for a prepreg has been desired to have a low viscosity at room temperature in consideration of manufacturability of the prepreg. Examples of the low viscosity epoxy resin include a trifunctional glycidylamine type epoxy resin represented by the formula (I) and a bifunctional biphenyl type epoxy resin represented by the formula (II).

However, the present inventor has found that when such an epoxy resin is used in a large amount in a resin composition for prepreg, strength and elongation after curing are impaired.
The present inventor has also found a problem that when a monofunctional epoxy resin is used as a diluent for the matrix resin, the strength after curing is lowered.

  Then, an object of this invention is to provide the resin composition for prepregs which can be used for such a prepreg which is excellent in intensity | strength and elongation when it is set as a carbon fiber reinforced composite material.

  As a result of intensive studies on the above problems, the present inventors impregnated carbon fiber with a resin composition for prepreg containing a trifunctional or higher functional epoxy resin, a monofunctional epoxy resin having a biphenyl skeleton, and an aromatic amino compound. It was found that the prepreg that can be obtained by forming a carbon fiber reinforced composite material excellent in strength and elongation, and the present invention was completed based on this finding.

That is, the present invention provides the following (1) to (5).
(1) A resin composition for prepreg containing a trifunctional or higher functional epoxy resin, a monofunctional epoxy resin having a biphenyl skeleton, and an aromatic amino compound.
(2) The resin composition for prepreg according to (1) above, wherein the content of the monofunctional epoxy resin having the biphenyl skeleton is 3 to 35% by mass in the total amount of the epoxy resin.
(3) The resin composition for a prepreg according to the above (1) or (2), further comprising a thermoplastic resin and / or a rubber having a nitrile group.
(4) A prepreg obtainable by impregnating carbon fiber with the resin composition for prepreg according to any one of (1) to (3) above.
(5) A carbon fiber reinforced composite material obtainable by curing the prepreg as described in (4) above.

  Since the prepreg of the present invention uses the resin composition for prepreg of the present invention, it is excellent in strength and elongation when it is a carbon fiber reinforced composite material.

Hereinafter, the present invention will be described in more detail.
First, the prepreg resin composition of the present invention will be described.
The resin composition for prepreg of the present invention is a resin composition for prepreg containing a trifunctional or higher functional epoxy resin, a monofunctional epoxy resin having a biphenyl skeleton, and an aromatic amino compound.

The trifunctional or higher functional epoxy resin will be described below.
A trifunctional or higher functional epoxy resin is a compound having three or more epoxy groups in one molecule. The trifunctional or higher functional epoxy resin is not particularly limited. For example, a glycidyl ether type epoxy resin and a glycidyl amino type epoxy resin are mentioned.

  Examples of the tri- or higher functional glycidyl ether type epoxy resin include epoxy resins such as phenol novolac type, orthocresol novolac type, trishydroxyphenylmethane type, and tetraphenylolethane type.

  Examples of the tri- or higher functional glycidylamino epoxy resin include diaminodiphenylmethane type epoxy resin such as tetraglycidyldiaminodiphenylmethane (TGDDM) represented by the formula (1) and diamino such as tetraglycidyldiaminodiphenylsulfone (TGDDS). Diphenylsulfone type epoxy resin, aminophenol type represented by formula (2) such as triglycidyl-p-aminophenol, triglycidyl-m-aminophenol, tetraglycidylmetaxylenediamine (TGMXDA), tetraglycidyl 1,3 -Bisaminomethylcyclohexane (TG1,3-BAC), triglycidyl isocyanurate (TGIC), hydantoin type, novolak type having a dicyclopentadienyl skeleton.

As a commercial item of the tetraglycidyl diamino diphenylmethane (TGDDM) represented by Formula (1), ELM-434 (made by Sumitomo Chemical Co., Ltd.) and MY-721 (made by Huntsman Advanced Materials) are mentioned, for example.
As a commercial item of triglycidyl-p-aminophenol represented by the formula (2), for example, MY-0510 (manufactured by Huntsman Advanced Materials) can be mentioned.

  Among them, the tri- or higher functional epoxy resin is preferably tetraglycidyldiaminodiphenylmethane represented by the formula (1), triglycidyl-p-aminophenol or triglycidyl-m-aminophenol represented by the formula (2).

Trifunctional or higher functional epoxy resins can be used alone or in combination of two or more.
As a combination of trifunctional or higher functional epoxy resins, for example, a combination of a trifunctional epoxy resin and a tetrafunctional epoxy resin can be mentioned as one of preferred embodiments. Among these, a combination of tetraglycidyldiaminodiphenylmethane represented by the formula (1) as the tetrafunctional epoxy resin and triglycidyl-p-aminophenol represented by the formula (2) as the trifunctional epoxy resin is preferable.

The monofunctional epoxy resin having a biphenyl skeleton will be described below.
The monofunctional epoxy resin having a biphenyl skeleton is a compound having at least one biphenyl skeleton and one epoxy group in one molecule.

  The monofunctional epoxy resin having a biphenyl skeleton is not particularly limited. For example, the compound represented by following formula (3) is mentioned.

  In the formula, R represents an alkylene group having 1 to 6 carbon atoms that can be bonded to at least one of an oxygen atom, a nitrogen atom, and a sulfur atom.

Such alkylene groups, for example, methylene group, ethylene group, propylene group, trimethylene group, an alkylene group such as _{butylene; -O-CH 2 -, -} O-CH 2 CH 2 -, - O-CH An alkylene group bonded to an oxygen atom such as ₂ CH ₂ CH ₂ — is exemplified.

  Examples of the monofunctional epoxy resin having a biphenyl skeleton include o-phenylphenol glycidyl ether, m-phenylphenol glycidyl ether, and p-phenylphenol glycidyl ether represented by the following formula (4). Among these, o-phenylphenol glycidyl ether represented by the following formula (4) is preferable.

  Since o-phenylphenol glycidyl ether represented by the formula (4) has a melting point of 30 ° C., it tends to be liquid around room temperature, and can effectively reduce the viscosity of the resin composition for prepreg.

The monofunctional epoxy resins having a biphenyl skeleton can be used alone or in combination of two or more.
The monofunctional epoxy resin having a biphenyl skeleton is not particularly limited for its production. For example, it can be produced according to the method described in JP-A-7-149913.

  By containing a monofunctional epoxy resin having a biphenyl skeleton, (1) the resin composition for prepreg of the present invention has a low viscosity, and (2) the resin composition for prepreg of the present invention has strength and elongation after curing. The prepreg obtained by impregnating the carbon fiber with the resin composition for prepreg of the present invention is excellent in tack and drape, and (4) obtained from such a prepreg. The carbon fiber reinforced composite material that can be obtained is excellent in strength.

  The resin composition for a prepreg of the present invention can contain a monofunctional epoxy resin other than the above-described epoxy resin, other than a bifunctional epoxy resin and a monofunctional epoxy resin having a biphenyl skeleton.

  The bifunctional epoxy resin is not particularly limited as long as it is a compound having two epoxy groups. For example, bisphenol A type, bisphenol F type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol S type, bisphenol AF type, such as the compound represented by formula (5), represented by formula (6) Examples thereof include glycidyl ether type epoxy resins such as biphenyl type, naphthalene type, fluorene type, polyalkylene glycol type and alkylene glycol type such as compounds; glycidyl amine type epoxy resins such as hydantoin type, aniline type and toluidine type.

  A bifunctional epoxy resin can be used individually or in combination of 2 types or more, respectively.

  Examples of monofunctional epoxy resins other than monofunctional epoxy resins having a biphenyl skeleton include phenyl allyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, glycidol, and phenyl obtained by reacting monovalent phenol with epichlorohydrin. A glycidyl ether is mentioned. Such monofunctional epoxy resins can be used alone or in combination of two or more.

  The content of the monofunctional epoxy resin having a biphenyl skeleton is preferably 3 to 35% by mass and more preferably 3 to 10% by mass in the total amount of the epoxy resin contained in the resin composition for prepreg. . In such a range, the tack and drape are excellent, and the workability is excellent.

The aromatic amino compound will be described below.
The aromatic amino compound is a compound having at least one aromatic hydrocarbon group and at least two amino groups in one molecule.

  The aromatic amino compound is not particularly limited, and for example, 3,3′-diaminodiphenylsulfone (3,3′-DDS), 4,4′-diaminodiphenylsulfone (4,4) represented by the following formula (7): '-DDS), 3,3'-diaminodiphenylmethane (3,3'-DDM), 4,4'-diaminodiphenylmethane (4,4'-DDM), diaminodiphenyl ether (DADPE), bisaniline, benzyldimethylaniline It is done.

Among these, 3,3′-diaminodiphenyl sulfone and 4,4′-diaminodiphenyl sulfone represented by the following formula (7) are preferable from the viewpoint of heat resistance.
An aromatic amino compound can be used individually or in combination of 2 types or more, respectively.

  The content of the aromatic amino compound is preferably such that the ratio of the active hydrogen equivalent of the aromatic amino compound to the epoxy equivalent of the entire epoxy resin (active hydrogen equivalent / epoxy equivalent) is 0.6 to 1.2, More preferably, it is 0.7-1.0. In such a range, the heat resistance and strength are excellent.

  The resin composition for a prepreg of the present invention is further mentioned as one of preferred embodiments that further contains a thermoplastic resin and / or a rubber having a nitrile group.

  The thermoplastic resin is not particularly limited. For example, polyacetal, polyamide, polyamideimide, polyarylene oxide, polyarylate, polyimide, polyethylene terephthalate, polyethylene naphthalate, polyetherimide, polyetheretherketone, polyethersulfone, polycarbonate, polysulfone, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl formal , Polyphenylene oxide, polybutylene terephthalate, polyphenylene sulfide, polybenzimidazole, and polymethyl methacrylate.

  One preferred embodiment of the thermoplastic resin is one that is compatible with a trifunctional or higher functional epoxy resin and / or a monofunctional epoxy resin having a biphenyl skeleton contained in the prepreg resin composition of the present invention. .

  Among the thermoplastic resins, polyethersulfone is preferable from the viewpoint of high compatibility with the epoxy resin and excellent heat resistance. As polyether sulfone, the compound represented by following formula (8) is mentioned, for example.

  The number average molecular weight of the thermoplastic resin is preferably 15,000 to 30,000. In this range, the obtained cured product has excellent toughness, and the viscosity of the prepreg resin composition does not become too high. From the point which is excellent by these characteristics, 20,000-25,000 are more preferable.

  A thermoplastic resin can be used individually or in combination of 2 types or more, respectively.

  It is preferable that content of a thermoplastic resin is 5-70 mass parts with respect to a total of 100 mass parts of an epoxy resin. In such a range, the cured product of the resulting composition has excellent toughness and excellent mechanical properties. From the point which is excellent by these characteristics, 5-50 mass parts is more preferable.

The rubber having a nitrile group will be described below.
Examples of the rubber having a nitrile group include a nitrile rubber such as acrylonitrile-butadiene rubber, a carboxy group-containing nitrile rubber, a liquid carboxy group-terminated nitrile rubber (CTBN), an amino-terminated nitrile rubber (ATBN), or a mixture thereof. Can be mentioned. A commercially available nitrile rubber can be used.
Examples of the rubber having a nitrile group include a liquid rubber and a solid rubber. A solid is preferable from the viewpoint of maintaining the rigidity of the matrix resin. Solid acrylonitrile-butadiene rubber is preferable because it maintains the rigidity of the matrix resin and is excellent in compatibility with the epoxy resin.

  The number average molecular weight of the rubber having a nitrile group is preferably 100,000 to 300,000. In the case of this range, the obtained cured product has excellent toughness, and the viscosity of the prepreg resin composition does not become too high.

  The rubber | gum which has a nitrile group can be used individually or in combination of 2 or more types, respectively.

  The content of the rubber having a nitrile group is preferably 3 to 15 parts by mass and more preferably 5 to 10 parts by mass with respect to 100 parts by mass in total of the epoxy resin. In such a range, the fracture toughness and mechanical strength are excellent.

  The rubber having a nitrile group can be used as a mixture with an elastomer such as urethane rubber, styrene-butadiene rubber, or polyester elastomer.

  Further, as the rubber having a nitrile group, for example, an elastomer having a core and a shell including a rubber having a nitrile group can be used. Such a core / shell type elastomer has good dispersibility in the epoxy resin composition. Examples of the component of the shell include polyacrylate, polyacrylonitrile, polystyrene, polymethyl methacrylate, or a mixture thereof. The core / shell type elastomer is not particularly limited for its production. For example, it can be produced according to a conventionally known method.

  When the resin composition for prepreg contains a thermoplastic resin and a rubber having a nitrile group, the content of the thermoplastic resin and the rubber having a nitrile group is 3 to 20 parts by mass with respect to a total of 100 parts by mass of the epoxy resin. It is preferable that it is 5-10 mass parts. In such a range, the fracture toughness and mechanical strength are excellent.

  When the resin composition for prepreg of the present invention further contains a thermoplastic resin and / or a rubber having a nitrile group, the impact strength after curing is excellent and the crack growth rate can be slowed.

  The resin composition for a prepreg of the present invention is a filler, an anti-aging agent, an antioxidant, a pigment (dye), a plasticizer, a thixotropic agent, if necessary, within a range not impairing the object of the present invention. Various additives such as an ultraviolet absorber, a flame retardant, a solvent, a surfactant (including a leveling agent), a dispersant, a dehydrating agent, an adhesion imparting agent, and an antistatic agent can be contained.

  Examples of the filler include organic or inorganic fillers having various shapes. Specifically, for example, fumed silica, calcined silica, precipitated silica, ground silica, fused silica; diatomaceous earth; iron oxide, zinc oxide, titanium oxide, barium oxide, magnesium oxide; calcium carbonate, magnesium carbonate, zinc carbonate; Waxite clay, kaolin clay, calcined clay; carbon black; these fatty acid treated products, resin acid treated products, urethane compound treated products, and fatty acid ester treated products.

Specific examples of the anti-aging agent include hindered phenol compounds.
Specific examples of the antioxidant include butylhydroxytoluene (BHT) and butylhydroxyanisole (BHA).

  Specific examples of the plasticizer include, for example, dioctyl phthalate (DOP), dibutyl phthalate (DBP); dioctyl adipate, isodecyl succinate; diethylene glycol dibenzoate, pentaerythritol ester; butyl oleate, methyl acetylricinoleate; phosphorus Examples include tricresyl acid, trioctyl phosphate; propylene glycol adipate polyester, butylene glycol adipate polyester.

Specific examples of the thixotropic agent include aerosil (manufactured by Nippon Aerosil Co., Ltd.) and dispalon (manufactured by Enomoto Kasei Co., Ltd.).
Specific examples of the adhesion imparting agent include terpene resins, phenol resins, terpene-phenol resins, rosin resins, and xylene resins.

Specific examples of the flame retardant include chloroalkyl phosphate, dimethylmethylphosphonate, bromine atom and / or phosphorus atom-containing compound, ammonium polyphosphate, neopentyl bromide-polyether, and brominated polyether.
Examples of the antistatic agent include quaternary ammonium salts; hydrophilic compounds such as polyglycols and ethylene oxide derivatives.

  The resin composition for prepreg of the present invention is not particularly limited for its production. For example, the above-mentioned essential components and optional components are put in a reaction vessel, and the mixture is sufficiently kneaded using a stirrer such as a mixing mixer under reduced pressure.

  The resin composition for a prepreg of the present invention is a one-component prepreg containing a main component containing a trifunctional or higher functional epoxy resin and a monofunctional epoxy resin having a biphenyl skeleton, and a curing agent containing an aromatic amino compound. It can be used as a resin composition.

  The present inventor uses, as an epoxy resin, a trifunctional or higher functional epoxy resin and a monofunctional epoxy resin having a biphenyl skeleton, thereby (1) a trifunctional or higher functional epoxy resin and a monofunctional epoxy having a biphenyl skeleton. The prepreg resin composition containing the epoxy resin and the aromatic amino compound has a low viscosity. (2) Although such a prepreg resin composition contains a monofunctional epoxy resin, After curing, excellent in elastic modulus, strength and elongation, Tg is difficult to decrease, (3) prepreg obtained by impregnating carbon fiber with such a prepreg resin composition is excellent in tack and drape, (4) The carbon fiber reinforced composite material obtained from such a prepreg has excellent heat resistance and excellent tensile strength while maintaining interlayer shear force. And, it was to the completion of the present invention.

Next, the prepreg of the present invention will be described.
The prepreg of the present invention is a prepreg that can be obtained by impregnating carbon fiber with the resin composition for prepreg of the present invention.

  The resin composition for prepreg used is not particularly limited as long as it is a resin composition for prepreg of the present invention.

  The content of the resin composition for prepreg is preferably 70 to 35% by volume, and preferably 60 to 40% by volume in the entire volume of the prepreg from the viewpoint of characteristics such as strength.

The carbon fiber will be described below.
The carbon fiber used is not particularly limited. Examples thereof include polyacrylonitrile-based carbon fibers (PAN-based carbon fibers) and pitch-based carbon fibers.
Carbon fiber is not particularly limited in its form and arrangement. For example, a unidirectional material in which reinforcing fibers are aligned in one direction, a woven fabric, a non-woven fabric composed of short cut reinforcing fibers, a braid, a tow, a knit, and a mat can be used. The form and arrangement | sequence of carbon fiber can be freely selected according to the site | part to be used and a use.
The content of carbon fiber is preferably 30 to 65% by volume and more preferably 40 to 60% by volume in the volume of the entire prepreg.

  In addition to carbon fibers, the prepreg of the present invention is reinforced such as graphite fibers, aramid fibers, silicon carbide fibers, alumina fibers, boron fibers, high-strength polyethylene fibers, tungsten carbide fibers, PBO fibers, glass fibers, and metal fibers. Fibers can be included.

  The prepreg is not particularly limited as long as it is produced by impregnating the carbon fiber with the resin composition for prepreg of the present invention. For example, it can be produced according to a conventionally known method.

Examples of the impregnation method include a hot melt method and a wet method.
When the prepreg is produced by a wet method, the resin composition for prepreg of the present invention is dissolved in a solvent to prepare a varnish, and then impregnated with carbon fibers. Examples of the solvent used when preparing the varnish include ketone solvents such as methyl ethyl ketone (MEK). The amount of the solvent used is preferably 1 to 20 parts by mass with respect to 100 parts by mass of the resin composition for prepreg of the present invention because the drying process can be short.
Further, since the resin composition for prepreg of the present invention has a low viscosity, it can be impregnated into carbon fiber as it is to produce a prepreg.

  When producing a prepreg by the hot melt method, for example, after the resin composition for prepreg is first heated and melted, the resin composition is uniformly applied onto a release paper while the resin is uncured to produce a resin film, There is a method in which carbon fiber is sandwiched from both sides with a resin film, and then the resin is impregnated while being pressurized and heated.

  The heating temperature is preferably 60 to 150 ° C. When the heating temperature is 60 ° C. or higher, the carbon fiber can be sufficiently impregnated with the resin composition for prepreg, and the prepreg has an appropriate tack and excellent handleability. When the temperature is 150 ° C. or lower, the resin curing reaction does not proceed excessively during the impregnation of the carbon fiber with the resin composition for prepreg, and the prepreg drape is excellent.

  The carbon fiber fraction in the prepreg is preferably 50 to 80% by mass. When the carbon fiber fraction is 50% by mass or more, the obtained carbon fiber reinforced composite material has excellent strength characteristics such as compressive strength. When the amount is 80% by mass or less, carbon fibers are less likely to rub against each other, and the carbon fiber reinforced composite material having excellent durability and less fatigue of the fibers can be obtained.

  The prepreg that can be obtained is excellent in storage stability at room temperature. Even if it is left at room temperature for about 1 week, the change with time of tack and drape is slight, and it is very easy to handle.

  The prepreg of the present invention is excellent in tack and drape. The prepreg of the present invention can be a carbon fiber reinforced composite material having excellent strength.

Next, the carbon fiber reinforced composite material of the present invention will be described.
The carbon fiber reinforced composite material of the present invention is a fiber reinforced composite material that can be obtained by curing the prepreg of the present invention.

  The prepreg used is not particularly limited as long as it is a prepreg of the present invention.

  As a method for producing a carbon fiber reinforced composite material from a prepreg, for example, a method in which the fiber direction is changed little by little so as to have pseudo-isotropic property, and then cured by heating is preferable. It is mentioned as one of the aspects.

  As for the heating temperature here, 100-200 degreeC is preferable. When the heating temperature is 100 ° C. or higher, the curing reaction of the matrix resin is sufficient, and the resulting carbon fiber reinforced composite material is excellent in heat resistance and environmental resistance. In the case of 200 ° C. or lower, the thermal shrinkage when cooled from the molding temperature to room temperature is small, and even when the thermal shrinkage occurs, the location where the thermal shrinkage occurs is not likely to be a defective part, and the fracture resistance is excellent.

  The carbon fiber reinforced composite material is not particularly limited with respect to its molding method. For example, a conventionally known molding method can be used. Specifically, for example, open mold molding such as hand lay-up molding and spray-up molding; press molding such as autoclave molding, vacuum back molding, internal pressure molding and compression molding; resin transfer molding (RTM), filament winding (FW) ), Tape winding, roll winding, pultrusion molding, roll press continuous molding, injection mobile, reaction injection molding (RIM).

  The carbon fiber reinforced composite material of the present invention is not particularly limited with respect to its use. For example, motorcycle parts such as motorcycle frames, cowls, and fenders; doors, bonnets, tailgates, side fenders, side panels, fenders, energy absorbing members, trunk lids, hardtops, side mirror covers, spoilers, diffusers, ski carriers, engine cylinders Automotive parts such as covers, engine hoods, chassis, air spoilers, propeller shafts, etc .; vehicle outer panels such as leading vehicle noses, roofs, side panels, doors, cart covers, side skirts; railway vehicle parts such as luggage racks and seats; Aero parts such as interiors, wing inner panels, outer panels, roofs, floors, etc., mounted on cars and motorcycles, and side skirts; window frames, luggage racks, seats, floor panels, wings, props Aircraft parts such as fuselage, casings such as notebook PCs and mobile phones; medical uses such as X-ray cassettes and top boards; acoustic product uses such as flat speaker panels and speaker cones; golf heads, face plates, snowboards, surfing Sports equipment applications such as boards and protectors; general industrial applications such as leaf springs, windmill blades, elevators (籠 panels, doors).

  The carbon fiber reinforced composite material of the present invention is excellent in tensile strength while maintaining the interlayer shear force.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these.
1. Preparation of Resin Composition for Prepreg Each component shown in Table 1 below was mixed using a stirrer with the composition (parts by mass) shown in Table 1 to obtain each composition shown in Table 1.

3. Curing of resin composition for prepreg Each of the obtained resin compositions for prepreg was cured at 180 ° C. for 2 hours to obtain test pieces.

(1) Glass transition temperature (Tg)
Using a viscoelasticity measuring device (DMA) (TA Instruments, RDS-II), each test specimen obtained was obtained from room temperature at a heating rate of 5 ° C./min under conditions of a frequency of 1 Hz and a strain of 0.01%. The glass transition temperature (° C.) was measured by heating to 250 ° C. The results are shown in Table 1. The higher the glass transition temperature (Tg), the better the heat resistance.

(2) Bending elastic modulus and bending strength Using each obtained test piece, the bending elastic modulus and bending strength of each test piece were measured according to JIS K7171-1994. The results are shown in Table 1.

(3) Fracture toughness value K _IC
Each of the obtained resin compositions for prepreg was cured at 180 ° C. for 2 hours to prepare a resin plate having a thickness of 7 mm. Using this resin plate, one side was notched in accordance with the method described in ASTM D5045-96. The stress at the time of fracture was measured by a three-point bending test. The results are shown in Table 1.

4). Preparation of Prepreg Each prepreg resin composition was coated on release paper using a reverse roll coater to prepare a resin film. Next, the two resin films are overlapped so as to sandwich both surfaces of carbon fibers (Treka (registered trademark) T-700, manufactured by Toray Industries, Inc., tensile elastic modulus 230 GPa) arranged in one direction in a sheet shape. It was. Thereafter, the resin was impregnated with carbon fiber by heating and pressing to obtain a unidirectional prepreg with a basis weight of 196 ± 5 g / cm ² and a mass fraction of the matrix resin of 34%.

5. Evaluation of Prepreg (1) Tack Two obtained unidirectional prepregs were laminated to form a plate having a thickness of about 0.5 mm, and then the presence or absence of tack (adhesive strength) was evaluated by 10 levels by finger touch. Evaluation was performed at 25 ° C. The results are shown in Table 1. Details of the 10-level evaluation of tack are shown below. The higher the numerical value of the tack evaluation, the lower the viscosity of the prepreg resin composition, and the better. It is preferable on implementation that the numerical value of tack evaluation is 6-9.

The details of the 10-level evaluation of tack are as follows.
10: It is sticky and cannot be removed when bonded.
It is closer to 10 than 9: 8.
It is closer to 10 than 8: 7.
It is closer to 10 than 7: 6.
It is closer to 10 than 6: 5.
5: Tack of prepreg of Comparative Example 1.
It is closer to 1 than 4: 5.
It is closer to 1 than 3: 4.
It is closer to 1 than 2: 3.
1: It cannot be attached at all.

(2) Drape The obtained unidirectional prepreg was bent by hand, and the presence / absence of drape (the suppleness of the prepreg) was evaluated by 10 levels by finger touch. Evaluation was performed at 25 ° C. The results are shown in Table 1. The details of the 10-step evaluation of drape are shown below. The higher the numerical value of the drape evaluation, the lower the viscosity of the resin composition for prepreg, and the closer the flexibility of the carbon fiber, the better. It is preferable in practice that the numerical value of the drape evaluation is 6-9.

The details of the 10-step evaluation of drape are as follows.
10: Drape close to the original carbon fiber.
It is closer to 10 than 9: 8.
It is closer to 10 than 8: 7.
It is closer to 10 than 7: 6.
It is closer to 10 than 6: 5.
5: Drape of the prepreg of Comparative Example 1.
It is closer to 1 than 4: 5.
It is closer to 1 than 3: 4.
It is closer to 1 than 2: 3.
1: Drape that breaks the resin when bent. There is no drape.

6). Preparation of carbon fiber reinforced composite material 10 unidirectional prepregs obtained were laminated so that the directions of carbon fibers were the same to form a laminate, and the laminate was autoclaved at 180 ° C. for 2 hours, 0.6 MPa. Was formed at a rate of temperature increase of 2 ° C./min to obtain a plate-like carbon fiber reinforced composite material.

7). Evaluation of Carbon Fiber Reinforced Composite Material (1) 90 ° Tensile Strength A test piece having a length of 250 mm, a width of 25 mm, and a thickness of 2.0 mm was prepared from the obtained plate-like carbon fiber reinforced composite material, and an autograph was used. According to EN2597, a 90 ° tensile test with respect to the fiber direction was performed under the conditions of a grip length of 50 mm and a test speed of 0.5 mm / min. The obtained load at break is applied to the formula of 90 ° tensile strength (MPa) = [load at break / cross-sectional area (test piece width × test piece thickness)] to obtain 90 ° tensile strength. It was. The results are shown in Table 1. The higher the value, the better the 90 ° tensile strength.

(2) Interlaminar shear strength A test piece having a length of 20 mm, a width of 10 mm, and a thickness of 2.0 mm was prepared from the obtained plate-like carbon fiber reinforced composite material, and a span length of 10 mm according to EN2563 using an autograph. The interlaminar shear strength test was conducted by three-point bending at a test speed of 1 mm / min. The obtained load at break is applied to the formula of interlaminar shear strength (MPa) = [3/4 × load at break ÷ cross-sectional area (width of test piece × thickness of test piece)] Asked. The results are shown in Table 1. The higher the value, the better the interlaminar shear strength.

Each component in Table 1 is as follows.
Tetrafunctional epoxy resin [epoxy resin represented by formula (1)]: ELM-434, manufactured by Sumitomo Chemical Co., Ltd.

Trifunctional epoxy resin [epoxy resin represented by formula (2)]: MY-0510, manufactured by Huntsman Advanced Materials

Bifunctional epoxy resin 1 [epoxy resin represented by formula (5)]: YD-8125, manufactured by Tohto Kasei Co., Ltd.

Bifunctional epoxy resin 2 [epoxy resin represented by formula (6)]: YX-4000, manufactured by Japan Epoxy Resin Co., Ltd.

Biphenyl epoxy resin [o-phenylphenol glycidyl ether represented by formula (4)]: OPP-G, manufactured by Sanko

Phenyl glycidyl ether: epoxy resin represented by formula (9), manufactured by Tokyo Chemical Industry Co., Ltd.

・ 3,3′-DDS: 3,3′-diaminodiphenylsulfone, manufactured by Wakayama Seika Kogyo Co., Ltd. ・ PES: polyethersulfone, manufactured by Sumitomo Chemical Co., Ltd.

  As is apparent from the results shown in Table 1, the cured products obtained from the resin compositions for prepregs of the examples have higher flexural modulus, flexural strength, and fracture toughness values than the cured products of the comparative examples. Does not reduce temperature. In addition, even when a large amount of monofunctional epoxy resin having a biphenyl skeleton is added as in Examples 2 and 3, the bending elastic modulus, bending strength, and fracture toughness are excellent, and the glass transition temperature (Tg) is substantially equal to or higher. I understand that there is.

  Regarding the prepreg, since the evaluation values of the tack and drape are higher than those of the comparative example, the prepreg of the present invention has less tack and has flexibility close to that of carbon fiber, and for the prepreg of the present invention. It can be seen that the resin composition has a low viscosity. Moreover, even if the thermoplastic resin is further added to the prepreg resin composition as in Examples 4 to 5 and the ratio of the liquid material in the prepreg resin composition is reduced, the prepreg is excellent in tack and drape. .

  About a carbon fiber reinforced composite material, an Example maintains an interlayer shear strength substantially equal compared with a comparative example, and is excellent in 90 degree tensile strength.

Claims (5)

  A resin composition for prepreg containing a trifunctional or higher functional epoxy resin, a monofunctional epoxy resin having a biphenyl skeleton, and an aromatic amino compound.   2. The resin composition for prepreg according to claim 1, wherein the content of the monofunctional epoxy resin having a biphenyl skeleton is 3 to 35% by mass in the total amount of the epoxy resin.   Furthermore, the resin composition for prepregs of Claim 1 or 2 containing the rubber | gum which has a thermoplastic resin and / or a nitrile group.   A prepreg obtainable by impregnating a carbon fiber with the resin composition for prepreg according to claim 1.   A carbon fiber reinforced composite material obtainable by curing the prepreg according to claim 4.