JP2009215481A - Prepreg and fiber-reinforced composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prepreg having excellent workability such as tackiness and drapeability and to provide a fiber-reinforced composite material obtained by curing the prepreg and having excellent mechanical properties such as tensile strength and compression strength. <P>SOLUTION: Provided are a prepreg at least including the following constituent components (A) to (E), wherein the amount of the component (B) in the constituent components is 25-45 pts.wt. based on 100 pts.wt. of total epoxy resin of the component (A) and the component (B), and a fiber-reinforced composite material produced by curing the prepreg. (A) An epoxy resin containing ≥3 glycidyl groups in the molecule; (B) at least one of epoxy resin selected from glycidyl aniline, glycidyl o-toluidine, diglycidyl aniline and diglycidyl o-toluidine; (C) a thermoplastic resin having a functional group reactive with glycidyl group; (D) an epoxy resin hardener; and (E) a carbon fiber having essentially true round cross-section. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to prepregs and fiber reinforced composite materials. More specifically, the present invention relates to a fiber reinforced composite material that is a prepreg excellent in workability such as tack / drape and excellent in mechanical properties such as tensile strength and compressive strength.

In recent years, fiber reinforced composite materials using carbon fibers, aramid fibers, etc. as reinforcing fibers have utilized their high specific strength and specific modulus to make structural materials such as aircraft and automobiles, tennis rackets, golf shafts, fishing rods, etc. It is used for general industrial purposes and is expanding year by year.
In recent years, as the number of use cases increases, the required characteristics for this fiber-reinforced composite material have become stricter. In particular, there is a strong demand for higher strength accompanying the weight reduction of fiber reinforced composite materials. In addition, since the fiber reinforced composite material may have a reduced rigidity when it is thinned with a reduction in weight, there is an increasing demand for a high elastic modulus.

  In addition, with the increase in size of members in which fiber reinforced composite materials are used, conventional fiber reinforced composite materials may generate thermal stress, internal heat generation, increase in assembly man-hours, and the like. On the other hand, increasing the compressive strength of the fiber-reinforced composite material leads to a reduction in the thickness of the fiber-reinforced composite material, and thus is expected to have effects such as reduction of thermal stress, reduction of internal heat generation, and reduction of assembly man-hours. As a result, high rigidity is required and the fiber-reinforced composite material layer is thick, so it can be easily applied to the molding of large structural materials such as aircraft main wings and windmill blades, which were difficult to manufacture. Is done.

In order to obtain a fiber reinforced composite material having high compressive strength, a combination of specific epoxy resins is disclosed as a matrix resin to be combined, but no combination with specific fibers is suggested as in the present invention. (For example, Patent Documents 1 and 2)
In addition, as an intermediate base material for obtaining such a fiber-reinforced composite material, a prepreg made into a sheet form by impregnating an epoxy resin into a reinforcing fiber is used, and the prepreg has an appropriate tack / drape property. Is also important at the same time.

  Tackiness is the tackiness of the prepreg, and drapeability is the suppleness of the prepreg. If the tackiness is too small, the prepreg that has been pressed down in the prepreg laminating process will be peeled off immediately, thereby hindering the laminating workability. On the other hand, if the tackiness of the prepreg is too great, the prepreg will stick due to its own weight, and for example, it will be difficult to peel off later for correction. Also, if the prepreg drape is poor, the prepreg is stiff and the laminating workability is significantly reduced, and the laminated prepreg does not accurately conform to the curved surface shape of the mold, it becomes wrinkled, the reinforcing fibers break, and molding Problems that cause defects in the products are likely to occur.

As described above, an appropriate matrix resin is used to obtain a fiber-reinforced composite material that is formed by a prepreg excellent in workability such as tack / draping property and excellent in tensile strength and compression strength. No specific reinforcing fiber combination has been previously known.
JP2003-026768A JP 2003-238657 A

  In view of the background of such prior art, the present invention provides a prepreg excellent in workability such as tack and drape, and further, when cured, a fiber excellent in mechanical properties such as tensile strength and compressive strength. It is intended to provide reinforced composite materials.

  The present invention employs the following means in order to solve such problems.

  That is, the prepreg of the present invention is configured to include at least the following constituents [A] to [E], and the [B] component of the constituents includes the [A] component and the [B] component. 25 to 45 parts by weight are contained in 100 parts by weight of the total epoxy resin.

[A] Epoxy resin having 3 or more glycidyl groups in the molecule [B] At least one epoxy resin selected from glycidyl aniline, glycidyl o-toluidine, diglycidyl aniline, diglycidyl o-toluidine [C] Reaction with glycidyl group [D] Epoxy resin curing agent [E] Carbon fiber having a substantially circular cross section The preferred embodiment of such a prepreg is:
(1) The component [C] component is contained in 10 parts by weight or more and 20 parts by weight or less in a total of 100 parts by weight of the components [A] to [D].
(2) The component [C] component is polyethersulfone,
(3) The component [B] is diglycidylaniline or diglycidyl o-toluidine.

  The fiber-reinforced composite material of the present invention is characterized by being formed by curing such a prepreg.

  According to the present invention, it is possible to provide a prepreg excellent in workability such as tack / drape, and a fiber-reinforced composite material made of such a prepreg is a high-strength fiber-reinforced composite material that could not be achieved so far. The fiber reinforced composite material obtained by this method has excellent mechanical properties such as tensile strength and compressive strength, so that it has been difficult to apply to aircraft main wings and windmill blades. It can use suitably for the large sized structural member which receives distributed loads, such as.

  The present invention has intensively studied the above problems, that is, a prepreg excellent in workability such as tack and drape, and a fiber reinforced composite material excellent in mechanical properties such as tensile strength and compressive strength. As a result of trying to contain a specific epoxy resin component in a specific range, it was found that such problems could be solved at once, and the present invention was achieved.

  Hereinafter, the prepreg of the present invention will be described in detail. The prepreg of the present invention comprises a matrix resin composed of an epoxy resin composition essentially comprising the components [A] to [D] and a reinforcing fiber as the component [E]. Here, the matrix resin is an essential component of the fiber-reinforced composite material, and is a resin constituting a matrix that fills the gap between the reinforcing fiber and the reinforcing fiber.

  The epoxy resin component used for the [A] component of the epoxy resin that is a constituent component of the prepreg of the present invention is a component necessary for the development of heat resistance and mechanical properties, and has three or more glycidyl groups in the molecule. It is an epoxy resin. Here, the epoxy resin refers to a thermosetting resin obtained by introducing a glycidyl group into a molecule by reacting an epihalohydrin such as epichlorohydrin with an amino group or a hydroxyl group in the molecule. When the number of glycidyl groups in one molecule is one, the function is 1 (or monofunctional), the number of glycidyl groups is 2, and the number of glycidyl groups is n. Moreover, when n is 3 or more, it may be called polyfunctionality. Examples of glycidylamine type epoxy resins having amines as precursors include four glycidyl groups in the molecule, that is, tetrafunctional tetraglycidyldiaminodiphenylmethane, glycidyl compound of tetrafunctional xylenediamine, and trifunctional triglycidylaminophenol. These include positional isomers different from the position of each amino group, and substituted products in which aromatic hydrogen is substituted with an alkyl group or halogen. Among these, tetraglycidyldiaminodiphenylmethane and its positional isomers, alkyls, and halogen-substituted products are preferable as matrix resins for composite materials as aircraft structural materials because of their excellent heat resistance.

  Commercially available products of the above-mentioned tetraglycidyldiaminodiphenylmethane include Sumiepoxy ELM434 (manufactured by Sumitomo Chemical), Araldite MY720, Araldite MY721, Araldite MY9512, Araldite MY9612, Araldite MY9634, Araldite MY9663 (manufactured by Huntsman Advanced j) (Registered trademark) "604 (manufactured by Japan Epoxy Resin Co., Ltd.), EPR497, EPR494 (manufactured by Bakelite AG), and the like.

  Examples of commercially available glycidyl compounds of xylenediamine include TETRAD-X (manufactured by Mitsubishi Gas Chemical Company).

  Commercially available products of triglycidylaminophenol include “jER (registered trademark)” 630 (manufactured by Japan Epoxy Resin Co., Ltd.), Araldite MY0500, MY0510 (manufactured by Huntsman Advanced Materials), ELM100 (manufactured by Sumitomo Chemical Co., Ltd.), and the like. .

  The epoxy resin component used as the component [B] of the prepreg component of the present invention is an essential component for giving the matrix resin a high elastic modulus even under wet heat and an optimum viscosity for use as a matrix resin. is there. As such an epoxy resin component, an epoxy resin obtained by reacting aniline or toluidine having a methyl group introduced into the aromatic ring of aniline and an epihalohydrin such as epichlorohydrin is used. More specifically, monofunctional monoglycidyl aniline, monofunctional monoglycidyl toluidine, difunctional diglycidyl aniline and diglycidyl o-toluidine. Among these, diglycidyl aniline or diglycidyl o-toluidine toluidine is preferably used from the viewpoint of having two reactive groups in the molecule and being incorporated into the crosslinked structure of the epoxy resin and causing little reduction in heat resistance.

  Examples of commercially available diglycidylaniline include GAN (manufactured by Nippon Kayaku Co., Ltd.) and EPR493 (manufactured by Bakerite AG).

  GOT (made by Nippon Kayaku Co., Ltd.) is mentioned as a commercial item of diglycidyl o-toluidine.

  The blending amount of the component [B] of the prepreg of the present invention is 25 to 45 parts by weight with respect to 100 parts by weight of the epoxy resin in which the [A] and [B] components are combined. If the amount is less than 25 parts by weight, the mechanical properties such as compressive strength may not be sufficiently improved when the fiber reinforced composite material is used. If the amount exceeds 45 parts by weight, the heat resistance of the matrix resin or the fiber reinforced composite material decreases. There are things to do.

  [C] component of the constituent component of the prepreg of the present invention is a thermoplastic resin having a functional group having reactivity with a glycidyl group. By having a functional group reactive with the glycidyl group, at least a part of the functional group reactive with the glycidyl group reacts when the epoxy resin is cured. By this reaction, in the cured matrix resin, the thermoplastic resin is compatible with the cured epoxy resin phase, or when the thermoplastic resin phase is not compatible, the cured epoxy resin phase and the thermoplastic resin phase are separated. The effect is that the interface is firmly bonded.

  Further, the adhesion between the [C] component and the [E] component constituting the prepreg of the present invention increases, so that the interfacial adhesive strength is improved. For example, when used as a unidirectional fiber reinforced composite material, the fiber direction 90 ° direction (hereinafter, as described in JIS K7017 (1999), the fiber direction of the unidirectional fiber-reinforced composite material is defined as the axial direction, and the axial direction defined as the 0 ° axis is 90 °. In addition, the prepreg, which is an intermediate for obtaining a fiber-reinforced composite material, is also defined in the same manner). An effect is obtained.

  Specific examples of the functional group that reacts with the glycidyl group in the [C] component include a hydroxyl group, a carboxyl group, an amino group, and an acid anhydride. Of these, a hydroxyl group is preferably used from the viewpoint of storage stability.

Further, as the skeleton of the thermoplastic resin of the [C] component, those having at least a phenyl ether group or a phenyl thioether group in the main skeleton are preferable from the viewpoint of high heat resistance. Specific examples include polyethersulfone, polyetherimide, polyetherethersulfone, polyphenylene ether, and polysulfone. Among these, polyetherimide and polyethersulfone, which are easily dissolved in uncured epoxy resin, are preferably used. Is done.
From the above viewpoint, as a specific example of a commercially available product of the component [C] preferably used in the present invention, Sumika Excel PES5003P (manufactured by Sumitomo Chemical Co., Ltd.) is used as a polyethersulfone having a hydroxyl group at the terminal, and an acid anhydride is used at the terminal. And polyetherimide having an amino group include Ultem 1000, Ultem 1010, Ultem 1040 (manufactured by GE Plastics Co., Ltd.) and the like.
The blending amount of the [C] component of the prepreg of the present invention depends on how to select the [A] component and the [B] component, but a total of 100 weights including the [A] to [D] components. It is preferable that it is 3-33 weight part in a part, and the range of 10 weight part or more and 20 weight part or less is more preferable. If the amount is less than 3 parts by weight, the viscosity of the resin composition containing the [A] component to [D] component, which is a matrix resin, becomes too low, and the carbon fiber bundle, which is a reinforcing fiber, is impregnated with a carbon fiber bundle. During storage, the matrix resin is likely to sink, and the prepreg tack may change over time. On the other hand, when the amount exceeds 33 parts by weight, the viscosity of the matrix resin becomes too high, and it may be difficult to impregnate the carbon fiber with the matrix resin.

  [D] component of the prepreg component of the present invention is an epoxy resin curing agent, which is an essential component for reacting with [A] and [B] to form a crosslinked structure and to give mechanical properties such as heat resistance. It is.

As the epoxy resin curing agent of the component [D], any compound having an active group capable of reacting with an epoxy resin can be used. As the compound having such an active group, a compound having an amino group, an acid anhydride group, or an azide group can be preferably used. Specific examples of the compound having such an active group include dicyandiamide, alicyclic amine, aliphatic amine, aromatic amine, aminobenzoic acid ester, various acid anhydrides, phenol novolak resin, cresol novolak resin, Examples include imidazole derivatives, Lewis acid complexes such as boron trifluoride complexes and boron trichloride complexes.
In particular, an aromatic amine curing agent or an amine having an aromatic in the molecule is preferably used in terms of providing a cured product having excellent mechanical properties. Among these, aromatic polyamines are preferable from the viewpoint of heat resistance. Specific examples of the aromatic polyamines and amines having an aromatic group include metaphenylenediamine, diaminodiphenylmethane and diaminodiphenylsulfone as aromatic amines, and metaxylenediamine as an amine having aromatic groups in the molecule. And various derivatives such as these positional isomers and alkyl-substituted products. These curing agents can be used alone or in combination of two or more. Of these, diaminodiphenylmethane, diaminodiphenylsulfone, its positional isomers, and alkyl-substituted products are desirable from the viewpoint of imparting heat resistance to the composition.

  The [D] component preferably reacts with the [C] component. The [D] component reacts with the [C] component to improve the compatibility between the [C] component and the epoxy resin. In the cured epoxy resin, the [C] component becomes compatible with the epoxy resin phase. Even when the phases are separated, it is preferable because the interface between the phase mainly composed of the epoxy resin and the phase mainly composed of the [C] component is firmly bonded.

The optimum value of the added amount of the [D] component depends on the types and amounts of the [A] to [C] components and the type of the curing agent. For example, in an amine curing agent such as an aromatic amine curing agent, the stoichiometric equivalent ratio is between 0.5 and 1.4 with respect to the total glycidyl groups contained in the epoxy resin composition of the present invention. Is preferred. Most preferably, it is 0.6-1.4. When the amount is less than 0.5, the curing reaction may not occur sufficiently and poor curing may occur, or the curing may take a long time. When more than 1.4, the hardening | curing agent which was not consumed at the time of hardening may become a defect, and a mechanical physical property may fall.
These curing agents may be used alone or in combination. Moreover, you may use together with a hardening accelerator. For example, combinations of aromatic polyamines and Lewis acid complexes, combinations of dicyandiamide and imidazole derivatives, combinations of dicyandiamide and urea compounds, and combinations such as aromatic polyamines, dicyandiamide and urea compounds are cured at relatively low temperatures. In order to obtain high heat and water resistance, it is preferably used. In the case of the above combinations, Lewis acid complexes and urea compounds are used as curing accelerators, so that they are used in the range of 0.05 to 10 parts by weight in 100 parts by weight of [A] to [D]. Is preferred. When the amount is less than 0.05 parts by weight, the effect of promoting the curing may not be obtained. When the amount exceeds 10 parts by weight, the curing becomes too fast, and the surface is uneven when finally made into a fiber reinforced composite material. The surface quality may deteriorate.

  In the matrix resin forming the prepreg of the present invention, components other than the components [A] to [D] may be used as additives. Specifically, components that can be used as additives include epoxy resins that do not fall under [A] component and [B] component, thermoplastic resin components that do not have a reaction point with epoxy resin in the molecule, rubber components, inorganic And particles.

  As epoxy resins other than the above-mentioned [A] component and [B] component, bifunctional bisphenol type epoxy resins, epoxy resins having a biphenyl skeleton, urethane and isocyanate modified epoxy resins, fluorene type epoxy resins, naphthalene type epoxy resins Etc. Examples of the bisphenol type epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin. Commercially available bisphenol A type epoxy resins include “EPON (registered trademark)” 825, “jER (registered trademark)” 826, “jER (registered trademark)” 827, “jER (registered trademark)” 828, “jER ( Registered trademark) 834, jER (registered trademark) 1001, jER (registered trademark) 1002, jER (registered trademark) 1003, jER (registered trademark) 1004, jER (registered trademark) 1004AF , “JER (registered trademark)” 1007, “jER (registered trademark)” 1009 (manufactured by Japan Epoxy Resin Co., Ltd.), “Epicron (registered trademark)” 850 (manufactured by Dainippon Ink Industries, Ltd.), “Epototo (Registered trademark) “YD-128 (manufactured by Toto Kasei Co., Ltd.), DER-331, DER-332 (manufactured by Dow Chemical Co., Ltd.), and the like. Examples of the brominated bisphenol A type epoxy resin include “jER (registered trademark)” 5050, “jER (registered trademark)” 5054, “jER (registered trademark)” 5057 (manufactured by Japan Epoxy Resins Co., Ltd.) and the like. . Commercially available bisphenol F type epoxy resins include “jER (registered trademark)” 806, “jER (registered trademark)” 807, “jER (registered trademark)” 1750, “jER (registered trademark)” 4002, “jER”. (Registered trademark) "4004P", "jER (registered trademark)" 4007P, "jER (registered trademark)" 4009P (manufactured by Japan Epoxy Resin Co., Ltd.), "Epiclon (registered trademark)" 830 (Dainippon Ink Chemical Co., Ltd.) "Epototo (registered trademark)" YD-170, "Epototo (registered trademark)" YD-175, "Epototo (registered trademark)" YDF2001, "Epototo (registered trademark)" YDF2004 (above Toto Kasei Co., Ltd.) ))). Examples of the tetramethylbisphenol F type epoxy resin include YSLV-80XY (manufactured by Nippon Steel Chemical Co., Ltd.). Examples of the bisphenol S type epoxy resin include “Epiclon (registered trademark)” EXA-1514 (manufactured by Dainippon Ink & Chemicals, Inc.). Commercially available epoxy resins having a biphenyl skeleton include “jER (registered trademark)” YX4000H, “jER (registered trademark)” YX4000, “jER (registered trademark)” YL6616 (above, manufactured by Japan Epoxy Resins Co., Ltd.). ) And NC-3000 (manufactured by Nippon Kayaku Co., Ltd.). Examples of commercially available urethane and isocyanate-modified epoxy resins include AER4152 (produced by Asahi Kasei Epoxy Co., Ltd.) having an oxazolidone ring and ACR1348 (produced by Asahi Denka Co., Ltd.). In addition, examples of the fluorene type epoxy resin include (manufactured by Nagase ChemteX), and examples of the naphthalene type epoxy resin include “Epiclon (registered trademark)” HP4032 (manufactured by Dainippon Ink & Chemicals, Inc.).

  The epoxy resin not corresponding to these [A] component and [B] component is preferably 0 to 50 parts by weight, more preferably 0 to 30 parts by weight, in a total of 100 parts by weight of the epoxy resin component contained in the matrix resin. It may be included. When the amount of the epoxy resin not corresponding to the [A] component and the [B] component is 50 parts by weight or more, the elastic modulus of the matrix resin may be significantly lowered, which is not preferable. In addition, it is preferable to blend a solid epoxy resin at room temperature because the viscosity of the resin composition can be easily controlled and the tack / drape property of the prepreg can be appropriately given. The epoxy resin solid at room temperature here is an epoxy resin having a glass transition temperature or a melting point of 30 ° C. or higher. These glass transition temperatures and melting points can be determined by the method described in JIS K7121 (1987) using a differential calorimeter (DSC). The glass transition temperature was the midpoint temperature.

  Examples of the thermoplastic resin component having no reaction point with the epoxy resin in the molecule include polypropylene, polybutyl terephthalate, ABS, polyamide, polyethylene terephthalate, polymethacrylic acid ester, polyvinyl acetal resin, polyacetal, polycarbonate, and polyamideimide. It is done. This may be dissolved in the matrix resin, or may be insoluble in the matrix or added in the form of particles or fibers. In order not to increase the viscosity of the matrix resin, it is preferably in the form of particles, particularly preferably spherical particles. When used as fibers or particles, any fiber diameter, fiber length, and particle diameter may be selected, but it should be noted that the orientation of the reinforcing fibers is not disturbed. Specifically, from the viewpoint of not disturbing the orientation of the reinforcing fibers, the fiber diameter is preferably 50 nm or more and 100 μm or less, and the particle diameter is preferably 50 nm or more and 100 μm or less. In particular, polyamide particles and polyimide particles are preferably used, and as a commercially available product of polyamide particles, SP-500 manufactured by Toray Industries, Inc., “Orgasol” manufactured by Arkema Co., Ltd., and the like can be used. When the thermoplastic resin component having no reaction point with the epoxy resin in the molecule is used after being dissolved in the matrix resin, it is set to 10 parts by weight or less in 100 parts by weight of the total matrix resin from the viewpoint of tack and draping properties. It is preferable. When blended in the form of insoluble particles or fibers in the matrix resin, 0 to 20 parts by weight may be blended in 100 parts by weight of the total matrix resin. If it is added in an amount of more than 20% by weight, the heat resistance of the epoxy resin may be impaired, and the tackiness when used as a prepreg may be lowered.

  As the rubber component, carboxy-terminated butadiene rubber, amino-terminated butadiene rubber, silicon rubber, and the like are preferably used in terms of improving the toughness of the matrix resin. In particular, when the terminal functional group is capable of reacting with the epoxy resin that is the main component of the matrix resin composition, an addition amount of 10 parts by weight or less with respect to 100 parts by weight of the total epoxy resin contained in the composition. Further improvement in toughness and fatigue properties can be expected. More preferably, it is 1 part by weight or more and 10 parts by weight or less. Specifically, a rubber having a terminal functional group having a carboxyl group or an amino group is preferably used in terms of good affinity with an epoxy resin. The rubber component may be dissolved in the matrix resin or may be dispersed in the form of particles. In the case where the rubber component is used in the form of particles, those obtained by granulating rubber alone or those obtained by forming a core shell with an acrylic resin or the like are preferably used. These rubber particles having a particle size of 1 μm or less, preferably 500 nm or less, improve toughness even with a smaller amount and have a small decrease in heat resistance.

  As the viscosity of the uncured product of the matrix resin used in the prepreg of the present invention, those having a viscosity at 50 ° C. of 100 to 10,000 Pa · s are preferably used from the viewpoint of tackiness of the obtained prepreg. Viscosity can be adjusted according to the type of the [A] component, how to select the skeleton of the [C] component, its molecular weight, blending amount, and the like. As will be described later, the viscosity at 50 ° C. is defined as a complex viscoelastic modulus η * obtained when the temperature is simply raised using a rheometer. There is a tendency that the tackiness tends to be weaker as the viscosity is higher, and the change with time of the tack becomes larger as the viscosity is lower. However, it is greatly affected by the relative amount with the [E] component, the form of the [E] component, and the method for producing the prepreg. When tackiness is too strong, when stacking multiple prepregs (referred to as lamination), there is a decrease in workability such as incorrect lamination cannot be corrected, and when tackiness is too weak, prepreg may be peeled off or misaligned during lamination. Workability may be reduced. Tack quality is often judged by the operator's tactile sensation.

  The method for kneading the matrix resin used in the prepreg of the present invention may be any method generally used for preparing an epoxy resin composition. For example, a kneader or a planetary mixer is used. At the time of kneading, a solvent may or may not be used as necessary. Moreover, you may perform a heating and pressure increase / decrease as needed. When kneading the curing agent, kneading at a temperature of 100 ° C. or less and for a short time such as within 1 hour is preferable from the viewpoint of storage stability of the kneaded matrix resin or prepreg.

  The carbon fiber that is the [E] component of the prepreg component of the present invention is an essential element for developing tensile strength when a fiber-reinforced composite material is used, and is a carbon fiber having a perfect cross section.

  Here, a perfect circle means that 20 or more carbon fiber sections are observed at random, the radius of the circumscribed circle centering on the centroid of the section is the major axis, and the radius of the inscribed circle is the minor axis. It means that the average of the / minor axis ratio is between 1.00 and 1.20. Preferably, it is between 1.00-1.10, More preferably, it is 1.00-1.05. When the major axis / minor axis ratio is higher than 1.20, it may be difficult to uniformly impregnate the carbon fiber bundle with the resin. In the case of a perfect circle, the impregnation of the resin into the fiber bundle is improved, and as a result, a stable fiber-reinforced composite material is obtained.

  As the form of such carbon fiber, there are used long fibers aligned in one direction, tows, woven fabrics, mats, knits, braids, short fibers cut to a length of less than 10 mm, and the like. As used herein, long fibers refer to single fibers or fiber bundles that are substantially continuous for 10 mm or more. A short fiber is a fiber bundle cut to 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. Sequences are also preferably used in the present invention.

  As the perfect circular carbon fiber, those having a strand strength of 5000 MPa to 9500 MPa and an elastic modulus of 270 GPa to 400 GPa in a strand tensile test are preferably used.

  The strand tensile test here refers to a test performed based on JIS R7601 (1986) after impregnating a bundle of carbon fibers with a resin having the following composition and curing it at a temperature of 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, manufactured by Stella Chemifa Corporation) ): 3 parts by weight / acetone (for example, manufactured by Wako Pure Chemical Industries, Ltd.): 4 parts by weight The carbon fiber as the [E] component used in the present invention includes carbons such as polyacrylonitrile, rayon and pitch. Although fibers are mentioned, it is preferable to use polyacrylonitrile as a precursor in that it is easy to obtain a high-strength material necessary for the present invention. In addition, as a method for spinning polyacrylonitrile, wet, dry or dry wet methods can be employed. However, wet or dry wet spinning is preferable because high-strength carbon fibers can be easily obtained. The spun precursor fiber is made into carbon fiber by flameproofing and carbonization. Performing surface oxidation treatment such as electrolytic surface treatment on the obtained carbon fiber as necessary increases the strength of the carbon fiber by removing the fragile portion on the surface of the carbon fiber or increases the adhesion to the matrix resin. It is preferably used from the viewpoint of improving the quality. The number of carbon fiber filaments used is preferably 1000 to 100,000, more preferably 3000 to 50000.

A sizing agent is used to bundle the carbon fibers as the component [E] as a fiber bundle. As the carbon fiber sizing agent, a sizing agent having at least one functional group selected from the group consisting of glycidyl group, hydroxyl group, acrylate group, methacrylate group, carboxyl group and carboxylic anhydride group is preferably used. This is because an interaction such as a chemical bond or a hydrogen bond occurs between the functional group on the surface of the carbon fiber and the functional group in the polymer network of the resin cured product, thereby enhancing the adhesion between the carbon fiber and the resin cured product. . Examples of the sizing agent include polyethylene glycol, a reaction product of polyethylene glycol and bisphenol A type epoxy resin, a reaction product of polyethylene glycol and bisphenol F type epoxy resin, polyethylene glycol diglycidyl ether, a glycidyl compound of polyglycerol, polypropylene The glycidyl compound, bisphenol A type epoxy, bisphenol F type epoxy, biphenyl type epoxy, dimer acid diglycidyl ester, dimer acid modified bisphenol type epoxy and the like are preferably used.
The adhesion amount of the sizing agent varies depending on the matrix resin to be combined, but 0.01 to 5.00% by weight is preferably used with respect to the total weight of the carbon fiber and the sizing component as the [E] component. When the adhesion amount is less than 0.01% by weight, the function as a sizing agent is often not obtained, and when the adhesion amount exceeds 5.00% by weight, mechanical properties such as heat resistance of the matrix resin are impaired. Sometimes.

  In order to attach such a sizing agent to the carbon fiber bundle (filament), a method of using a sizing solution in which the sizing agent is dissolved or dispersed in a solvent, applying the sizing solution to the carbon fiber filament, and then drying the solvent is preferably used. It is done.

  As the solvent used in the sizing solution, water or an organic solvent such as DMF or MEK can be used, but water is preferably used as the solvent from the viewpoint of handleability and safety. When using a sizing agent that is sparingly soluble in water, it is preferable to use an organic solvent because it is not necessary to use a dispersant such as a surfactant.

  As a means for imparting the sizing agent to the carbon fiber bundle, a roller sizing method, a roller dipping method and a spray method can be used. Among these, a roller sizing method is preferably used because a sizing agent can be uniformly attached to carbon fibers having a large number of filaments per bundle. The liquid temperature of the sizing agent is preferably in the range of 10 to 50 ° C. in order to suppress fluctuations in the concentration of the sizing agent due to solvent evaporation. The conditions for removing the solvent by drying are from 120 to 120 in order to prevent thermal decomposition of the sizing agent, or to react the sizing agent with the functional group on the carbon fiber surface simultaneously with the solvent removal, or to promote the curing of the sizing agent. A range of 10 seconds to 10 minutes at a temperature of 300 ° C. is preferable, and a range of 30 seconds to 4 minutes is more preferable.

  The amount of adhesion of the sizing agent to the carbon fiber bundle which is the [E] component of the constituent component is an electric furnace set at a temperature of 450 ° C. in a nitrogen stream of 50 liters / minute after weighing the carbon fiber bundle (W1). For 15 minutes to completely pyrolyze the sizing agent. Then, the carbon fiber bundle after being transferred to a container in a dry nitrogen stream at 20 liters / minute and cooled for 15 minutes is weighed (W2), and the sizing agent adhesion amount is obtained by the following equation.

Sizing adhesion amount (%) = [W1-W2] / W1 × 100
The prepreg of the present invention can be produced by a wet method, a hot melt method, or the like.
The wet method is a method in which a reinforcing fiber is immersed in a solution made of a matrix resin and an organic solvent such as methyl ethyl ketone, toluene, styrene, etc., and then the solvent is lifted and evaporated using an oven. The hot melt method is performed by heating. A method in which the reinforcing fiber is impregnated directly with the low-viscosity matrix resin, or a film in which the matrix resin is once coated on a release paper or the like is prepared, and then the film is stacked on both sides or one side of the reinforcing fiber and heated. This is a method of impregnating a reinforcing fiber with a resin by pressing. The hot melt method is preferable because substantially no solvent remains in the prepreg.

The prepreg preferably has a reinforcing fiber amount of 70 to 1000 g / m ² per unit area. More preferably, it is 70-500 g / m < ² >. When the amount of the reinforcing fiber is less than 70 g / m ^2, it is necessary to increase the number of laminated layers in order to obtain a predetermined thickness when forming the fiber reinforced composite material, and the work may be complicated. On the other hand, when the amount of reinforcing fibers exceeds 2000 g / m ² , the prepreg drapability tends to deteriorate. The fiber weight content is preferably 30 to 90% by weight, more preferably 35 to 85% by weight, and still more preferably 40 to 80% by weight.

  When the fiber weight content is less than 30% by weight, the amount of the resin is too large to obtain the advantages of the fiber reinforced composite material having excellent specific strength and specific elastic modulus, and when the fiber reinforced composite material is molded, The amount of heat generated may be too high. On the other hand, if the fiber weight content exceeds 90% by weight, poor resin impregnation may occur, and the resulting composite material may have many voids.

  The drapeability referred to here is the flexibility of deformation of the prepreg, and is a characteristic that affects the shapeability of the mold during lamination. There are various evaluations as an index. For example, the prepared prepreg is cut to 300 mm in the 0 ° direction and 25 mm in the 90 ° direction, and is attached to the corner of the crossing base 100 mm, and further fixed with tape. There is a method of standing still and measuring the bending angle θ of the prepreg.

  The bending angle θ is an angle between a portion where the prepreg is not fixed and the side surface of the gantry, and θ takes a value from 0 to 90. For the bending angle θ, the distance from the side surface of the gantry and the height from the surface of the prepreg fixed to the gantry to the end where the prepreg is not fixed are measured, and the bending angle θ is calculated from the value of this tangent. The higher the bending angle θ, the lower the drapability. If the drapeability is low, it is difficult to form a curved surface, and if the drapeability is too high, wrinkles are likely to be close, so there is a range in which the handleability is good. A preferable bending angle θ is 30 to 65 °.

  After laminating the obtained prepreg, the composite material according to the present invention is produced by a method of heat-curing the resin while applying pressure to the laminate.

  As a method for applying heat and pressure, a press molding method, an autoclave molding method, a bagging molding method, a wrapping tape method, an internal pressure molding method, or the like is employed.

The wrapping tape method is a method of forming a tubular body made of a fiber-reinforced composite material by winding a prepreg on a mandrel or other core metal, and is a method suitable for producing a rod-shaped body such as a golf shaft or fishing rod. is there. 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.
Also, the internal pressure molding method is to set a preform in which a prepreg is wound on an internal pressure applying body such as a tube made of a thermoplastic resin in a mold, and then introduce a high pressure gas into the internal pressure applying body to apply pressure. At the same time, 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 curing temperature and time when the fiber-reinforced composite material of the present invention is molded in an autoclave or an oven vary depending on the type and amount of the selected curing agent and curing catalyst, but the heat resistance is 130 ° C. or higher. For applications that require high properties, it is preferable to cure at a temperature of 120 to 220 ° C. for 0.5 to 8 hours. A temperature increase rate of 0.1 to 10 ° C./min is preferably used. When the rate of temperature increase is less than 0.1 ° C./min, the time required to reach the target curing temperature becomes very long and workability may be reduced. On the other hand, if the rate of temperature rise exceeds 10 ° C./min, a temperature difference occurs in various portions of the reinforcing fibers, so that a uniform cured product may not be obtained.

  When molding the fiber-reinforced composite material of the present invention, pressure is not essential, but pressure may be increased or decreased as necessary. By increasing or decreasing the pressure, effects such as improvement of surface quality, suppression of internal voids, improvement of adhesion to metal or plastic to be bonded at the time of curing, or parts made of fiber reinforced composite material may be obtained.

  Since the fiber-reinforced composite material of the present invention has high tensile strength and adhesive strength, it can be widely used in general work applications such as windmills, automobiles, and bicycles, as well as aerospace applications that require high mechanical properties.

Hereinafter, the present invention will be described in more detail with reference to examples. Various physical properties were measured by the following methods. These physical properties were measured in an environment at a temperature of 23 ° C. and a relative humidity of 50% unless otherwise specified.
(1) Preparation of matrix resin In the kneader, the epoxy resin of [A] component, the thermoplastic resin of [C] component, the epoxy resin other than [A] component and [B] component are kneaded and the temperature rises to 150 ° C. Warmed and kneaded at 150 ° C. for 2 hours to obtain a transparent viscous liquid. This liquid is lowered to 100 ° C., the component [B] is added and kneaded for 1 hour, and then the temperature is lowered while kneading to 80 ° C., a predetermined amount of a curing agent and a curing accelerator are added, and the epoxy resin composition is kneaded for 30 minutes. Obtained. The component blend ratios of the examples and comparative examples are as shown in Table 1.
(2) Viscosity measurement of uncured resin The viscosity of the uncured product of the matrix resin was measured using a dynamic viscoelasticity measuring device (Rheometer RDA2: manufactured by Rheometric Co., Ltd.), a parallel plate with a diameter of 40 mm, and a temperature increase rate of 2 The temperature was simply raised at 0 ° C./min, and measurement was performed at a frequency of 0.5 Hz and a gap of 1 mm. The viscosity was raised from room temperature (25 ° C.), and the complex viscoelastic modulus η * at 50 ° C. was recorded as the viscosity. The number of measurements n was 1.
(3) Bending test of cured resin product After defoaming the uncured resin composition in a vacuum, 130 ° C. in a mold set to a thickness of 2 mm with a 2 mm thick “Teflon (registered trademark)” spacer. The resin was cured at a temperature of 2 hours for 2 hours to obtain a cured resin having a thickness of 2 mm. The cured resin was cut to a width of 10 ± 0.1 mm and a length of 60 ± 1 mm to obtain a test piece. Using an Instron universal testing machine (manufactured by Instron), three-point bending with a span of 32 mm was measured according to JIS-K7171, and the elastic modulus was determined. The number of measurements was n = 5, and the average value was obtained.
Moreover, in order to perform a bending test in a humid heat environment, after being immersed in boiling water for 48 hours, the bending test was performed at an atmospheric temperature of 83 ° C. to obtain a flexural modulus in a humid heat environment. The number of measurement n was set to 5, and the average value was obtained.
(4) Glass transition temperature of resin cured product About the measurement of the glass transition temperature of the resin cured product obtained by the method of (3) above, based on JIS K7121 (1987) using a differential calorimeter (DSC). The measured midpoint temperature was taken as the glass transition temperature. The number of measurements n was 3, and the average value was obtained.
(5) Production of prepreg The prepreg was produced as follows. The uncured resin composition was formed into a film on a release paper with a basis weight of 52 g / m ² using a knife coater to obtain a resin film. Using this resin film, carbon fiber (weighing 190 g / m ² ) aligned in one direction was heated and pressure impregnated to obtain a unidirectional prepreg. The carbon fiber is “Treka (registered trademark)” T800G-12K-31E (Toray Industries, Inc.) having a strand strength of 5800 MPa, a strand elastic modulus of 29.4 GPa, and a long diameter / short diameter ratio of 1.05 and 12,000 filaments. Using. In Comparative Example 2, a carbon fiber bundle having an elliptical cross-sectional shape of 12,000 filaments having a strand strength of 5800 MPa, a strand elastic modulus of 29.4 GPa, a specific gravity of 1.8, and a major axis / minor axis ratio of 1.50 was used.
(6) Compression test of fiber reinforced composite material The unidirectional prepreg obtained by the method of (5) above is cut into a predetermined size and laminated in six directions, then a vacuum bag is used, and an autoclave is used. And cured at a temperature of 180 ° C. and a pressure of 6 kg / cm ² for 2 hours to produce two unidirectional reinforcing materials (fiber reinforced composite materials).
Four plates in which one fiber-reinforced composite material was cut to 35 × 100 mm in the fiber direction were produced.
These four sheets were used as a tab material, and the other unidirectional reinforcing material was placed so that the distance between the tabs was 8 mm and the distance between the tabs was in the same position, and was adhered with an adhesive. A test piece for Method A described in JIS K7076 (1991) was produced. According to JIS K7076 (1991), this test piece was subjected to a compression test at a crosshead speed of 1.0 mm / min using an Instron universal testing machine (Instron). The number n of the test pieces was 5.

The ambient temperature was 23 ° C. and 50% relative humidity under normal conditions. Moreover, in the test in a humid heat environment, after immersing the above-mentioned test piece in boiling water for 48 hours, it was set as atmospheric temperature 83 degreeC, the test piece was introduce | transduced into the thermostat, and it measured after reaching 83 degreeC. In addition, n number of the test piece was performed by five.
(7) 90 ° bending test The unidirectional prepreg obtained by the method of (5) above is cut into a predetermined size, and 10 sheets are laminated in one direction, and then a vacuum bag is formed, and the temperature is set to 180 using an autoclave. It was cured at 4 ° C. under a pressure of 6 kg / cm ² to obtain a unidirectional reinforcing material (fiber reinforced composite material).

  The unidirectional reinforcing material was cut in a length direction of 90 °, a width of 15 mm, and a length of 60 mm to obtain a test piece. In accordance with JIS K7017 (1999), this specimen was subjected to a three-point bending test using an Instron universal testing machine (Instron) at a crosshead speed of 1.0 mm / min and a fulcrum of 40 mm. The number n of the test pieces was 5.

  From comparison between Examples 1, 2, and 5 and Comparative Example 1, it can be seen that the H / W compressive strength and the adhesion are lowered depending on the presence or absence of Component B. From the comparison between Example 3 and Comparative Example 2, it can be seen that the compression characteristics are lowered due to the shape of the fiber cross section. A comparison between Example 4 and Comparative Example 3 shows that the compressive strength of the fiber-reinforced composite material is lowered depending on the presence or absence of Component C. From the comparison between Examples 1 and 2 and Comparative Example 4, it can be seen that the heat resistance of the resin and the compressive properties of the fiber-reinforced composite material in the wet and heat environment are impaired depending on the presence or absence of Component A.

  The prepreg of the present invention is a prepreg that provides a high-strength fiber-reinforced composite material that could not be achieved before, and the fiber-reinforced composite material obtained thereby is a main wing or windmill for aircraft use that has been difficult to apply until now. It is suitably used for a large-sized structural member that receives a distributed load such as a blade of the above.

Claims (5)

100 parts by weight of an epoxy resin comprising at least the following components [A] to [E], and the component [B] being the sum of the components [A] and [B] A prepreg characterized by being contained in an amount of 25 to 45 parts by weight.
[A] Epoxy resin having 3 or more glycidyl groups in the molecule [B] At least one epoxy resin selected from glycidyl aniline, glycidyl o-toluidine, diglycidyl aniline, diglycidyl o-toluidine [C] Reaction with glycidyl group Thermoplastic resin having functional group [D] epoxy resin curing agent [E] carbon fiber having a substantially circular cross section 2. The prepreg according to claim 1, wherein the component [C] component is contained in an amount of 3 to 33 parts by weight in a total of 100 parts by weight of the components [A] to [D]. The prepreg according to claim 1 or 2, wherein the component [C] is polyethersulfone. The prepreg according to claim 1, wherein the component [B] is diglycidylaniline or diglycidyl o-toluidine. The fiber reinforced composite material comprised by hardening | curing the prepreg in any one of Claims 1-4.