JP2006233188A - Prepreg for composite material and composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prepreg providing a carbon fiber-reinforced composite material exhibiting high-degree mechanical strength not only in a room-temperature dried condition but also in a wet heat condition; and to provide a carbon fiber-reinforced composite material obtained therefrom. <P>SOLUTION: The prepreg for the composite material comprises the following constituent elements [A], [B] and [C] as essential components, and the matrix resin has a complex viscosity coefficient η* within the range of 10-100,000 Pa s in a dynamic viscoelasticity measurement at 0.5 Hz measuring frequency and 50°C measuring temperature: [A]: reinforcing fiber comprising the carbon fiber; [B] an epoxy resin; and [C] a benzoxazine compound having a structural unit represented by structural formula (I). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prepreg for obtaining a carbon fiber reinforced composite material suitable for use in aircraft applications, marine applications, sports applications, and other general industrial applications, including aircraft structural materials, and a carbon fiber reinforced composite material obtained therefrom. It is.

  Carbon fiber reinforced composite materials composed of carbon fibers and matrix resin cured products are widely used in aircraft, automobiles, and industrial applications due to 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 the matrix resin constituting such a composite material, a thermosetting resin excellent in impregnation and heat resistance is often used, and the thermosetting resin has excellent moldability, high temperature, wet environment (humid heat environment). Even so, it is necessary to develop a high mechanical strength.

  As this thermosetting resin, phenol resin, melanin resin, bismaleimide resin, unsaturated polyester resin, epoxy resin, etc. are used. Among them, epoxy resin is excellent in heat resistance and moldability, and is a carbon fiber composite material. It is widely used because high mechanical strength can be obtained.

  Conventional carbon fiber reinforced composite materials have a sufficiently high adhesion between carbon fiber and matrix resin in a normal environment at room temperature and good mechanical strength. Then, since the matrix resin is plasticized by absorbing moisture and the mechanical strength is impaired due to such a decrease in adhesiveness, improvement in heat and humidity resistance is strongly desired.

  For this reason, attempts have been made to reduce the porosity of the composite material or reduce the polarity of the resin as a measure for suppressing the ingress of moisture into the composite material.

In order to reduce the polarity of the resin, methods such as introducing a side chain such as an alkyl group into the polymer molecule constituting the resin, increasing the alkyl group of the main chain, increasing the epoxy equivalent, and reducing the curing agent are considered. It is done. (For example, see Patent Documents 1 and 2)
However, when side chains such as alkyl groups are introduced, the heat resistance decreases, and when the main alkyl chain is lengthened, the modulus of elasticity and heat resistance decrease, and when the epoxy equivalent is increased and the curing agent is decreased, carbon is reduced. There is a problem that the mechanical strength such as the compressive strength in the fiber direction, the tensile strength in the non-fiber direction, the shear strength, and the peel strength is greatly reduced in the resulting composite material due to a decrease in adhesion to the fiber.
Japanese Patent No. 3483684 US Pat. No. 6,379,799

  An object of the present invention is to provide a prepreg that provides a carbon fiber reinforced composite material that exhibits high mechanical strength not only under room temperature drying but also in a moist heat environment, and a carbon fiber reinforced composite material obtained therefrom. And

  In order to achieve the above object, the prepreg of the present invention has the following configuration. That is, a prepreg for a composite material having the following components [A], [B], and [C] as essential components, and measuring the dynamic viscoelasticity of the matrix resin at a measurement frequency of 0.5 Hz and a measurement temperature of 50 ° C. Is a composite prepreg characterized by having a complex viscosity η * in the range of 10 to 100,000 Pa · s.

[A]: Reinforcing fiber made of carbon fiber [B]: Epoxy resin [C]: Benzoxazine compound having a structural unit represented by structural formula (I)

(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 chain alkyl group having 1 to 12 carbon atoms, or phenyl substituted with halogen. A hydrogen atom bonded to at least one of the ortho and para carbon atoms to which the oxygen atom of the aromatic ring is bonded)
Moreover, it is preferable that it is a prepreg for composite materials containing as a component [D] 1 or more types chosen from a thermoplastic resin, a thermoplastic elastomer, and an elastomer.

Furthermore, the component [B] is a prepreg for a composite material using a liquid or semi-solid epoxy resin having an epoxy equivalent of less than 220 and a solid epoxy resin having an epoxy equivalent of 220 or more in combination. The liquid epoxy resin having an epoxy equivalent of less than 220 contained is preferably a composite prepreg that is 30 to 80% by weight in the entire component [B].
Furthermore, it is preferable that it is a prepreg for composite materials containing polyphenols as component [E]. The composite material of the present invention is a composite material obtained by curing these prepregs for composite materials.

  According to the present invention, as will be described below, it is possible to provide a composite material having excellent mechanical properties in a wet and heat environment while satisfying various properties required for the composite material.

  Hereinafter, an example of the best embodiment in the present invention will be described.

  The component [A] of the present invention is a reinforcing fiber made of carbon fiber. The carbon fiber is effective for causing the fiber-reinforced composite material to exhibit high heat and humidity resistance, specific strength, and specific elastic modulus.

  Examples of the carbon fiber include, but are not limited to, a long fiber aligned in one direction, a bi-directional woven fabric, a multiaxial woven fabric, a non-woven fabric, a mat, a knit, and a braid.

  As the carbon fiber, any type of carbon fiber can be used depending on the application, but so-called high-strength carbon fiber is preferable from the viewpoint of high tensile strength of the fiber and high impact resistance when used as a composite material. That is, the strand tensile strength in the strand tensile test is preferably 4.4 GPa or more, and more preferably 4.6 GPa or more. Such strand tensile strength is preferably as high as possible, but about 4.9 GPa is often sufficient. When it exceeds 10 GPa, the workability of the obtained composite material may deteriorate. Further, the tensile elongation at break is preferably 1.7% or more, and more preferably 1.8% or more. The higher the tensile elongation at break, the better. However, about 2.0% is often sufficient for the purpose of the present invention. The strand tensile test here refers to a test conducted based on JIS R7601 (1986) after impregnating a bundle of carbon fibers with a resin having the following composition and curing at 130 ° C. for 35 minutes.

* Resin composition-3,4-epoxycyclohexylmethyl-3,4-epoxy-cyclohexyl-carboxylate (for example, ERL-4221, manufactured by Union Carbide) 100 parts by weight-boron trifluoride monoethylamine (for example, Stella Chemifa Corporation) (Made by company) 3 parts by weight Acetone (for example, manufactured by Wako Pure Chemical Industries, Ltd.) 4 parts by weight The carbon fiber preferably has a tensile modulus of 200 GPa or more. The use of carbon fibers having a high tensile modulus leads to high rigidity when a composite material is used. Such tensile elastic modulus is more preferably 210 GPa or more, and further preferably 220 GPa or more. The higher the tensile elastic modulus, the better. However, if it is about 230 GPa, it is often sufficient for the purpose of the present invention. If it exceeds 700 GPa, the impact resistance of the resulting composite material may be reduced.

  Carbon fibers may also be used in combination with other reinforcing fibers. Examples of other reinforcing fibers include glass fibers, aramid fibers, boron fibers, alumina fibers, and silicon carbide fibers.

  The component [B] of the present invention is an epoxy resin, and is mainly used as a matrix resin in the present invention. Any epoxy resin can be used as long as it is a compound having at least two epoxy groups in the molecule. Specifically, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol type epoxy resin such as tetrabromobisphenol A type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, etc. Novolak type epoxy resin, tetraglycidyl diaminodiphenylmethane, triglycidylaminophenol, glycidyl aniline, glycidyl amine type epoxy resin such as glycidyl o-toluidine, isocyanate modified epoxy resin containing oxazolidone ring, biphenyl skeleton Epoxy resin containing, epoxy resin containing naphthalene skeleton, epoxy resin containing triphenylmethane skeleton, Epoxy resins containing black cyclopentadiene skeleton, an alicyclic epoxy resin, and the like.

  It is also preferable to use a combination of these epoxy resins. In a prepreg for a composite material, since drapability is required, it is essential that the matrix resin is in a liquid or semi-solid state. Therefore, it is preferable to use a liquid or semi-solid epoxy resin having an epoxy equivalent of less than 220 as the epoxy resin of the component [B]. On the other hand, since composite materials are required to have mechanical properties such as impact resistance and high tensile strength, matrix resins are required to have physical properties such as high toughness and high elongation. Therefore, in addition to a liquid or semi-solid epoxy resin having an epoxy equivalent of less than 220, an epoxy resin that is a high molecular weight polymer having an epoxy equivalent of 220 or more is used as the epoxy resin of the component [B]. Is preferred.

  About this combined use aspect, it is preferable that the compounding quantity of the epoxy resin whose epoxy equivalent is less than 220 is 30 to 80 weight% in the whole structural component [B]. When it is less than 30% by weight, the drape property is insufficient, and when it exceeds 80% by weight, mechanical properties such as impact resistance and tensile strength tend to be lowered.

  Component [C] of the present invention is a benzoxazine compound having a structural unit represented by Structural Formula (I).

(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 chain alkyl group having 1 to 12 carbon atoms, or phenyl substituted with halogen. A hydrogen atom bonded to at least one of the ortho and para carbon atoms to which the oxygen atom of the aromatic ring is bonded)
Examples of R ₁ include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, cyclopentyl group, cyclohexyl group, phenyl group, o-methylphenyl group, m-methyl. Phenyl group, p-methylphenyl group, o-ethylphenyl group, m-ethylphenyl group, p-ethylphenyl group, ot-butylphenyl group, mt-butylphenyl group, pt-butylphenyl group , O-chlorophenyl group, o-bromophenyl group and the like can be preferably exemplified. Among these, a methyl group, an ethyl group, a propyl group, a phenyl group, and an o-methylphenyl group are more preferable because they give good handleability.

  In the present invention, as the benzoxazine compound, for example, those selected from the group consisting of compounds represented by the following structural formulas (II) to (IX) are preferably used, but are not limited thereto.

  The benzoxazine compound of the constituent element [C] may be composed only of a monomer, or several molecules may be polymerized into an oligomer state, or benzoxazine compounds having different structures may be used simultaneously. . The benzoxazine compound of component [C] is mixed with the epoxy resin of component [B] to form a matrix resin.

  The benzoxazine compound of the constituent element [C] generates a phenolic hydroxyl group in the molecule by a ring-opening reaction by heat. The produced phenolic hydroxyl group reacts with the epoxy group of the epoxy resin of the constituent element [B] to produce a cured product having low water absorption and excellent heat and moisture resistance. Therefore, a compound that promotes the ring-opening reaction of the benzoxazine compound as the constituent element [C] may be used as necessary. Examples of compounds that promote the ring-opening reaction include phenolic compounds, proton acids such as carboxylic acids and sulfonic acids, Lewis acids such as boron trihalide complexes, amine compounds such as aromatic amines and imidazoles, and triphenylphosphine. Can do. These may be used alone or in combination of two or more.

  Component [D] of the present invention is an additive added to the matrix resin, and is composed of one or more selected from thermoplastic resins, thermoplastic elastomers, and elastomers. Component [D] has a role of improving the toughness of the matrix resin composition and changing the viscoelasticity to optimize the viscosity, storage elastic modulus, and thixotropy. The thermoplastic resin, thermoplastic elastomer, and elastomer used as component [D] may be used alone or in combination of two or more.

  The thermoplastic resin is selected from carbon-carbon bond, amide bond, imide bond, ester bond, ether bond, carbonate bond, urethane bond, urea bond, thioether bond, sulfone bond, imidazole bond and carbonyl bond in the main chain. A thermoplastic resin having a bond is preferably used. A group of thermoplastic resins belonging to engineering plastics such as polyacrylates, polyamides, polyaramids, polyesters, polycarbonates, polyphenylene sulfides, polybenzimidazoles, polyimides, polyetherimides, polysulfones, polyethersulfones are more preferably used. Particularly preferably, polyimide, polyetherimide, polysulfone, polyethersulfone and the like are preferably used because of their excellent heat resistance. Moreover, it is preferable that these thermoplastic resins have reactivity with the thermosetting resin from the viewpoint of improving toughness and maintaining the environmental resistance of the cured resin. Particularly preferred functional groups include a carboxyl group, an amino group, and a hydroxyl group. As commercially available products of these thermoplastic resins, polyethersulfone includes SUMIKAEXCEL (registered trademark) PES3600P, SUMIKAEXCEL (registered trademark) PES5003P, SUMIKAEXCEL (registered trademark) PES5200P, SUMIKAEXCEL (registered trademark, and above, Sumitomo Chemical Industries). As PES7200P and polyetherimide, Ultem (registered trademark) 1000, Ultem (registered trademark, above, manufactured by Nippon GE Plastics) 1010 and the like can be used.

  These thermoplastic resins may be used after being dissolved in a matrix resin, or may be used after being finely divided by a method such as pulverization or the like.

  The amount of the thermoplastic resin blended is preferably 1 to 30 parts by weight with respect to 100 parts by weight of the total epoxy group-containing compound in the matrix resin. It may have an effect of increasing the mechanical strength of the reinforced plastic.

  As the thermoplastic elastomer, a polyester-based or polyamide-based thermoplastic elastomer is preferably blended. The thermoplastic elastomer here is a block copolymer composed of a hard segment component and a soft segment component, and is a polymer having a glass transition temperature below room temperature and a melting point above room temperature. The polyester-based or polyamide-based thermoplastic elastomer has a structure in which the hard segment component is a polyester unit or a polyamide unit. As these thermoplastic elastomers, for example, those described in International Publication No. 96/02592 pamphlet can be used.

  Many commercial products can also be used. Examples of commercially available polyester-based thermoplastic elastomers include Toray Du Pont's “Hytrel” and Toyobo's “Belprene”. Polyamide thermoplastic elastomers include ATOFINA's “PEBAX” and Mitsubishi Chemical's “ NOVAMID "and the like.

  These thermoplastic elastomers may be used after being dissolved in a matrix resin, or may be used after being finely divided by a method such as pulverization or the like.

  Since the resin composition containing the thermoplastic elastomer as described above has excellent tackiness and low viscosity, it is excellent in drape and impregnation into reinforcing fibers. Further, compared to the case where such a thermoplastic elastomer is not blended, the temperature dependency of the viscoelastic function of the resin, particularly the change near room temperature is small, so the temperature dependency of the prepreg handling property is reduced, which is preferable. . Therefore, a prepreg using the same can exhibit excellent properties in tackiness, drapeability, and quality. In order to obtain such an effect, it is preferable to add 1 to 30 parts by weight of the thermoplastic elastomer to 100 parts by weight of the epoxy group-containing compound in the matrix resin.

  As the elastomer, solid rubber, liquid rubber, rubber particles, or the like can be used. In general, solid rubber has a large increase in viscosity when dissolved in the same amount in a matrix resin compared to liquid rubber, so that the heat resistance of the molded product can be maintained relatively while maintaining the resin composition in the molding process at an appropriate viscosity level. preferable. In particular, the temperature dependency of the viscoelastic function of the matrix resin is reduced, the handling property is not easily deteriorated even if the working environment temperature changes when handling the prepreg, and the change in tackiness with time due to leaving the prepreg is reduced, and the cured product It is possible to improve the surface smoothness of the molded plate. As the solid rubber, an acrylonitrile-butadiene copolymer which is a random copolymer of butadiene and acrylonitrile is preferable from the viewpoint of compatibility with the epoxy resin. The compatibility with the epoxy resin can be controlled by changing the copolymerization ratio of acrylonitrile. Further, a solid rubber having a functional group is more preferable in order to increase the adhesion with the epoxy resin. Examples of the functional group include a carboxyl group and an amino group. In particular, a solid acrylonitrile-butadiene rubber containing a carboxyl group is preferable. Hydrogenated nitrile rubber is also preferable because of its excellent weather resistance. NIPOL (registered trademark) 1072, NIPOL 1072J, NIPOL 1472, NIPOL 1472HV, NIPOL 1042, NIPOL 1043, NIPOLDN 631, NIPOL 1001, ZETPOL (registered trademark) 2020, ZETPOL 2210, ZETPOL 3110 (manufactured by ZETPOL 3110) Can be mentioned.

  As the rubber particles, crosslinked rubber particles and core-shell rubber particles obtained by graft polymerization of a different polymer on the surface of the crosslinked rubber particles are preferably used. Commercially available crosslinked rubber particles include FX601P (made by JSR) made of a crosslinked product of carboxyl-modified butadiene-acrylonitrile copolymer, CX-MN series (made by Nippon Shokubai Co., Ltd.) made of acrylic rubber fine particles, YR. -500 series (manufactured by Toto Kasei Co., Ltd.) can be used. Commercially available core-shell rubber particles include paraloid (registered trademark) EXL-2655 (manufactured by Kureha Chemical Co., Ltd.), acrylate ester / methacrylate ester copolymer comprising butadiene / alkyl methacrylate / styrene copolymer. Staphyloid (registered trademark) AC-3355, TR-2122 (manufactured by Takeda Pharmaceutical Co., Ltd.), PARALOID (registered trademark) EXL-2611, EXL-3387 (composed of butyl acrylate / methyl methacrylate copolymer) Rohm & Haas) can be used.

  These rubber components improve toughness, but easily reduce the elastic modulus and heat resistance of the resin. Therefore, when blended, the amount added is 0.1 to 20 parts by weight with respect to 100 parts by weight of the epoxy group-containing compound in the matrix resin. Preferably, the amount is 1 to 10 parts by weight.

  In this invention, you may use the compound generally called the hardening | curing agent of an epoxy resin as another component. For example, aromatic amines such as diaminodiphenylmethane and diaminodiphenylsulfone, aliphatic amines such as triethylenetetramine and isophoronediamine, carboxylic acid anhydrides such as dicyandiamide, tetramethylguanidine and methylhexahydrophthalic anhydride, adipic acid Examples thereof include carboxylic acid hydrazides such as hydrazide, carboxylic acid amides, and polyphenol compounds. Among these, it is preferable that each structural isomer of diaminodiphenylsulfone is included in order to give good heat resistance and curability.

  In the composite material prepreg of the present invention, it is preferable that the matrix resin further contains polyphenols as the constituent element [E]. Component [E] is a polyphenol and is characterized by having two or more phenolic hydroxyl groups. The component [E] is added to the matrix resin, and has an effect of improving the elastic modulus and heat-and-moisture resistance of the cured product. Therefore, it is possible to improve the compressive strength of the obtained carbon fiber composite material in a wet heat environment.

  As the polyphenols of component [E], phenol novolac resins, phenol aralkyl resins, biphenyl skeleton-containing phenol resins, naphthalene skeleton-containing phenol resins, and the like are preferably used, but are not limited thereto.

  As the commercially available component [E], H-1, H-4, DL-92, HF-1 (all phenol novolac resins: manufactured by Meiwa Kasei Co., Ltd.), MEH-7800 (phenol aralkyl resins: Meiwa) Kasei Co., Ltd.), MEH-7851 (biphenyl skeleton-containing phenol resin: Meiwa Kasei Co., Ltd.), SN-160L (naphthalene skeleton-containing phenol resin: Toto Kasei Co., Ltd.), and the like can be used.

  As addition amount of component [E], it is preferable to set it as 5-100 weight part with respect to 100 weight part of epoxy-group containing compounds, such as an epoxy resin in a matrix resin, and it is still more preferable that it is 10-50 weight part. . If the addition amount of the component [E] is too small, the effect of improving the compressive strength in a moist heat environment is not sufficient, and if it is too much, the viscosity increases and the prepreg drape tends to decrease.

  In the present invention, an inorganic additive may be further added. Inorganic additives include inorganic particles such as calcium carbonate, titanium oxide, aluminum hydroxide, aluminum silicate, particulate silica, calcium carbonate, mica, talc, montmorillonite, smectite, carbon black, silicon carbide, and alumina hydrate. Can be mentioned.

  Now, the drapability of the prepreg correlates with the viscoelasticity of the matrix resin. For measurement of the viscoelasticity of the resin, a dynamic viscoelasticity measurement method using a parallel plate is usually used. The dynamic viscoelasticity changes depending on the measurement temperature and the measurement frequency. As a representative value of the viscoelastic behavior near room temperature, the complex viscosity η under the conditions of a measurement temperature of 50 ° C. and a measurement frequency of 0.5 Hz is used. When * is in the range of 10 to 100000 Pa · s, it is preferable because a prepreg having a drape suitable for an application such as an aircraft can be obtained. Furthermore, the range of 100 to 3000 Pa · s is more preferable. If the complex viscosity η * is higher than this range, not only will the drapability be inadequate, but the prepreg tack may be insufficient and impregnation of the reinforcing fibers made of carbon fibers may be difficult. . Further, when the complex viscosity η * is less than this range, the prepreg shape retention may be deteriorated.

  Next, the manufacturing method of the prepreg of this invention is demonstrated. The prepreg of the present invention is not particularly limited as long as the matrix resin composition of the present invention is impregnated into the reinforcing fiber. For example, the matrix resin is dissolved in a solvent such as methyl ethyl ketone or methanol to lower the viscosity and impregnate. It can be produced by a wet method or a method such as a hot melt method in which the viscosity is lowered and impregnated by heating.

  In the wet method, a prepreg can be obtained by immersing reinforcing fibers in a liquid containing a matrix resin, and then pulling up and evaporating the solvent using an oven or the like.

  In the hot melt method, a method of directly impregnating a reinforcing fiber with a matrix resin whose viscosity has been reduced by heating, or a film in which a resin composition is once coated on release paper or the like is first created, and then from both sides or one side of the reinforcing fiber. A prepreg impregnated with a matrix resin can be produced by stacking the films and applying heat and pressure. The hot melt method is preferable because there is no solvent remaining in the prepreg.

  Moreover, in order to make the handleability of the prepreg of the present invention within an appropriate range, it is preferable that the maximum temperature reached by the resin composition is in the range of 60 ° C to 150 ° C in the step of impregnating the reinforcing fiber with resin. Furthermore, it is preferable that it is 80-130 degreeC. When the maximum temperature exceeds 150 ° C., the curing reaction partially proceeds in the matrix resin composition, and the Tg of the uncured resin may increase, and an appropriate drape property may not be achieved. In some cases, sufficient impregnation may be difficult.

  In the prepreg of the present invention, the matrix resin composition does not necessarily need to be impregnated to the inside of the carbon fiber bundle, and the epoxy resin composition is formed near the surface of the carbon fiber aligned in one direction in a sheet shape or the carbon fiber fabric. May be localized.

  In order to form a carbon fiber reinforced composite material using the prepreg of the present invention, a method of heat-curing the resin while applying pressure to the laminate after laminating the prepreg can be used.

  Examples of methods for heat curing the resin while applying 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 fiber-reinforced composite material according to the present invention is suitable for use in aircraft applications, marine applications, sports applications, and other general industrial applications, including aircraft structural materials. High mechanical strength can be expressed.

  Hereinafter, the present invention will be described more specifically with reference to examples. About each Example and the comparative example, preparation of a resin composition, a prepreg, a composite material, etc. and the measurement of various physical properties were performed by the method shown next.

<Preparation of resin composition>
In each example and comparative example, the following raw material resins were used, and a resin composition was prepared by kneading with a kneader according to the composition shown in Table 1.
[Epoxy resin]
MY720 (manufactured by Huntsman Advanced Materials Corp., tetraglycidyldiaminodiphenylmethane, epoxy equivalent: 125)
Epicoat 630 (Japan Epoxy Resin Co., Ltd., triglycidylaminophenol, epoxy equivalent: 97.5)
Epicoat 828 (Japan Epoxy Resin Co., Ltd., bisphenol A type epoxy resin, epoxy equivalent: 189)
Epicote 1004 (Japan Epoxy Resin Co., Ltd., bisphenol A type epoxy resin, epoxy equivalent: 975)
HP7200L (Dainippon Ink Co., Ltd., dicyclopentadiene type epoxy resin, epoxy equivalent: 245)
[Benzoxazine compounds]
-Fa type (Shikoku Kasei Kogyo Co., Ltd., bisphenol F-aniline type benzoxazine)
・ Ba type (manufactured by Shikoku Chemicals Co., Ltd., bisphenol A-aniline type benzoxazine)
[Additive]
-PES (manufactured by Sumitomo Chemical Co., Ltd., polyethersulfone, SUMIKAEXCEL PES5003P)
MEH7800SS (Maywa Kasei Co., Ltd., phenol aralkyl resin)
SN160L (manufactured by Tohto Kasei Co., Ltd., naphthalene skeleton-containing phenol resin)
[Others]
・ SumiCure S (Sumitomo Chemical Co., Ltd., 4,4'-diaminodiphenylsulfone)
・ BF3 ・ Piperidin (manufactured by Stella Chemifa Corporation)
-Dynamic viscoelasticity measurement The dynamic viscoelasticity measurement of the matrix resin was performed using a dynamic analyzer RDAII type manufactured by Rheometrics. For the measurement, a parallel plate having a radius of 25 mm was used, and the complex viscosity η * was obtained under the conditions of a measurement temperature of 50 ° C., a measurement frequency of 0.5 Hz, and a GAP of 1 mm.

2. Preparation of Prepreg The matrix resin shown in Table 1 (the numbers in the table represent parts by weight) was coated on a release paper with a basis weight of 52 g / m ² using a knife coater to prepare a resin film with a predetermined resin basis weight. This resin film was superposed on both sides of carbon fibers (weight per unit area 190 g / m ² ) aligned in one direction, and a heat roll was used to impregnate the matrix resin while heating and pressing to prepare a one-way prepreg. In addition, carbon fiber "Torayca (registered trademark)" T700G-12K (12,000 fibers, tensile strength 4.9 GPa, tensile elastic modulus 240 GPa, tensile elongation 2.1%) manufactured by Toray Industries, Inc. is used as the reinforcing fiber. It was.

3. Drapability The unidirectional prepreg prepared by the method described above is cut into a 100 mm × 100 mm square to obtain a test piece. It was confirmed whether or not it was possible to mold into a SUS double curved surface of R = 100 mm in an atmosphere of a room temperature dry state (25 ° C. ± 2 ° C., relative humidity 50%). As a judgment scale, ◯ indicates that molding is possible without wrinkles, and x indicates that wrinkles are generated.

4). 0 ° compressive strength of laminated composite material (composite material) The fiber direction of the unidirectional prepreg produced by the above-mentioned method is aligned, 4 ply layers are laminated, and the autoclave is elevated at 180 ° C for 3 hours under a pressure of 0.59 MPa. A laminated composite material was produced by molding at a temperature rate of 1.5 ° C./min. About this laminated body, 0 degree compressive strength was calculated | required according to JISK7076 (1991). The compressive strength was measured for five samples, and the average 0 ° compressive strength was determined. The measurement was performed in a high temperature moisture absorption state (after being immersed in 71 ° C. warm water for 2 weeks and in an atmosphere at 82 ° C.).

5. 0 ° tensile strength of laminated composite material (composite material) The fiber direction of the unidirectional prepreg produced by the method described above is aligned, 6 plies are laminated, and the autoclave is elevated at 180 ° C for 3 hours under a pressure of 0.59 MPa. A laminated composite material was produced by molding at a temperature rate of 1.5 ° C./min. About this laminated body, 0 degree tensile strength was calculated | required according to JISK7073 (1988). Such tensile strength was measured for five samples, and the average 0 ° tensile strength was determined. The measurement was performed in a room temperature dry state (25 ° C. ± 2 ° C., relative humidity 50%).

6). Measurement results The results are shown in Table 1. In Comparative Example 2, since the matrix resin became solid, the dynamic viscoelasticity measurement could not be performed because the sample slipped between the parallel plates. Moreover, compared with the comparative examples 1 and 2, each Example had high 0 degree compressive strength in a high temperature moisture absorption state, and was excellent in the moist heat characteristic.

Claims (6)

A prepreg for a composite material having the following components [A], [B], and [C] as essential components, and complex in dynamic viscoelasticity measurement at a measurement frequency of 0.5 Hz and a measurement temperature of 50 ° C. A prepreg for a composite material having a viscosity η * in the range of 10 to 100,000 Pa · s.
[A]: Reinforcing fiber made of carbon fiber [B]: Epoxy resin [C]: Benzoxazine compound having a structural unit represented by structural formula (I)

(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 chain alkyl group having 1 to 12 carbon atoms, or phenyl substituted with halogen. A hydrogen atom bonded to at least one of the ortho and para carbon atoms to which the oxygen atom of the aromatic ring is bonded)   2. The prepreg for a composite material according to claim 1, wherein the constituent element [D] includes one or more selected from a thermoplastic resin, a thermoplastic elastomer, and an elastomer.   The prepreg for a composite material according to claim 1 or 2, wherein the component [B] is a liquid or semi-solid epoxy resin having an epoxy equivalent of less than 220 and a solid epoxy resin having an epoxy equivalent of 220 or more.   4. The composite according to claim 3, wherein a liquid or semi-solid epoxy resin having an epoxy equivalent of less than 220 contained in the component [B] is 30 to 80 wt% in the entire component [B]. Material prepreg.   The prepreg for a composite material according to any one of claims 1 to 4, wherein the component [E] contains polyphenols.   The composite material obtained by hardening | curing the prepreg for composite materials in any one of Claims 1-5.