JP2017110194A - Internal pressure molding prepreg and method for producing fiber reinforced composite material - Google Patents

Abstract

Provided is a prepreg for internal pressure molding excellent in molding cycle, heat resistance and resin fluidity. A prepreg for internal pressure molding is a prepreg for internal pressure molding in which a reinforcing fiber is impregnated with an epoxy resin composition containing components (A), (B), (C), (D) and (E). (A) N, N, N ′, N′-tetraglycidyldiaminodiphenylmethane, (B) novolak type epoxy resin represented by formula 1, (C) urea compound, (D) dicyandiamide, (E) thermoplastic resin Figure] None

Description

  The present invention relates to a prepreg for internal pressure molding and a method for producing a fiber-reinforced composite material.

  Fiber reinforced composite materials using carbon fibers, aramid fibers, and the like as reinforcing fibers are widely used for general industrial applications by utilizing their high specific strength and specific elastic modulus. Specific applications include structural materials such as aircraft and automobiles, tennis rackets, golf shafts, fishing rods, bicycles, sports equipment such as bicycles, and the like. The fiber reinforced composite material manufacturing method includes a method in which a plurality of prepregs, which are sheet-like intermediate materials in which reinforcing fibers are impregnated with an uncured matrix resin, are stacked and then heat-cured. For example, a resin transfer molding method in which the above resin is poured and cured by heating is used. Among these production methods, the method using a prepreg has an advantage that it is easy to obtain a high-performance fiber-reinforced composite material because the orientation of the reinforcing fibers can be strictly controlled and the design freedom of the laminated structure is high. As the matrix resin used for the prepreg, a thermosetting resin is mainly used from the viewpoint of heat resistance and productivity, and an epoxy resin is preferably used from the viewpoint of mechanical properties such as adhesion to reinforcing fibers.

  In recent years, fiber reinforced composite materials have come to be used for bicycle applications (that is, bicycle structures) and bicycle components that require weight reduction. Among bicycle parts, bicycle wheels are generally made of metal such as steel, aluminum, and aluminum alloy. However, the wheel for competition is required to be lighter, and the fiber reinforced composite material mainly made of carbon fiber is progressing. The disc wheel is bonded to the center of the fiber reinforced composite material plate with an aluminum honeycomb sandwiched between them. Developed are ones that are integrally molded with a fiber-reinforced composite material in which spokes have a constant cross-sectional shape. These wheels can be made lighter and have a structure that cannot be realized with conventional aluminum ones, and this increases the number of users mainly in competition applications.

  As a method for forming a hollow molded article having a complicated shape such as a bicycle wheel, an internal pressure molding method is often used. With the internal pressure molding method, a preform in which a prepreg is wound on an internal pressure applying body such as a tube made of a thermoplastic resin is set in a mold, and then a high pressure gas is introduced into the internal pressure applying body to apply pressure. In this method, the mold is heated and molded.

  In general, in the internal pressure molding method, a prepreg is wound around an internal pressure imparting body such as a tube made of a thermoplastic resin in a press machine that has been heated to a resin curing temperature in advance for the purpose of simplifying and improving the efficiency of the manufacturing process. A mold set with a preform or a prepreg is set, the prepreg is heated at a high speed, and a fiber-reinforced composite material is formed in a short time. For this reason, it is very important to control the fast curability and fluidity of the resin. If the resin does not flow sufficiently when cured, voids remain inside the molded product, resulting in insufficient strength of the molded product, or the resin does not reach the entire molded product, resulting in deterioration of the appearance due to resin defects. There's a problem.

  In addition, if the resin flows too much, the toughness of the molded product decreases due to a decrease in the resin content of the molded product, the strength decreases due to the disorder of the orientation of the reinforcing fibers, the surface appearance deteriorates, and the reinforcing fibers on the surface of the molded product emerge. Deterioration of the surface appearance such as generation of voids on the surface of the molded product due to the occurrence of this, deterioration of the strength of the molded product due to void generation inside the molded product due to insufficient resin in the molded product, and variation in product weight increases There is a problem.

  In recent years, bicycle rim materials and the like have been made into fiber-reinforced composite materials, and high heat resistance is required for these applications. For example, a bicycle rim generates heat due to friction with a brake shoe during braking, and the temperature of the rim becomes 170 ° C. or higher. Therefore, a fiber reinforced composite material having a glass transition temperature of 150 ° C. or higher is required.

  Furthermore, in order to obtain a fiber-reinforced composite material having high heat resistance, it is necessary to mold the fiber-reinforced composite material at a high molding temperature. When the heat resistance of the fiber reinforced composite material is increased by the internal pressure molding method described above, the temperature of the press machine increases, so the rate of temperature increase increases, the minimum viscosity of the resin becomes too low, and the fluidity of the resin increases. It tends to be too much.

  Therefore, a prepreg for internal pressure molding in which the resin fluidity is controlled and the glass transition temperature is 170 to 180 ° C. has been proposed (Patent Documents 1 and 2).

  Moreover, a prepreg having a relatively low curing temperature of 80 to 120 ° C. and a glass transition temperature after secondary curing of 180 to 300 ° C. has been proposed (Patent Documents 3 and 4).

JP 2012-196921 A JP 2013-166117 A JP 2003-73456 A International Publication No. 2011-040602

  However, the curing temperatures of the resins of Patent Documents 1 and 2 are as high as 150 to 180 ° C. For this reason, after the curing is completed, the cooling time until the mold is removed from the mold becomes long, and the molding cycle property is inferior. Moreover, as a tube made of a thermoplastic resin used for internal pressure molding, a tube made of an expensive material that can be used even at a high curing temperature is required, and the molding cost is high.

  Moreover, when producing a prepreg using resin of patent document 3 and 4, it has the problem that time of primary hardening is long and resin flows too much.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for producing a prepreg for internal pressure molding and a fiber-reinforced composite material that are excellent in molding cycle, heat resistance, and resin fluidity during internal pressure molding. To do.

  In order to solve the above-mentioned problems, the present inventors have intensively studied, and as a result, have reached the following present invention.

That is, the prepreg for internal pressure molding according to the present invention is obtained by impregnating reinforcing fibers with an epoxy resin composition containing the following components (A), (B), (C), (D) and (E).
(A) N, N, N ′, N′-tetraglycidyldiaminodiphenylmethane (B) novolak type epoxy resin represented by the following chemical formula 1

(C) Urea compound (D) Dicyandiamide (E) Thermoplastic resin.

Moreover, the manufacturing method of the fiber reinforced composite material which concerns on this invention impregnates the reinforced fiber with the epoxy resin composition containing the following component (A), (B), (C), (D) and (E). Heating the prepreg for internal pressure molding under heat curing conditions of 110 ° C. or higher and 140 ° C. or lower for 20 minutes or longer and 40 minutes or shorter, and secondary curing of 170 ° C. or higher and 200 ° C. or lower for 90 minutes or longer and 120 minutes or shorter. A step of curing.
(A) N, N, N ′, N′-tetraglycidyldiaminodiphenylmethane (B) novolac type epoxy resin represented by the above chemical formula (C) urea compound (D) dicyandiamide (E) thermoplastic resin.

  According to this invention, there exists an effect that it is excellent in the molding cycle, heat resistance, and resin fluidity at the time of internal pressure molding.

It is a schematic graph explaining the measuring method of glass transition temperature.

  Hereinafter, the present invention will be described in detail.

<Internal pressure forming prepreg>
The prepreg for internal pressure molding according to the present invention is impregnated in a reinforcing fiber with an epoxy resin composition containing the following components (A), (B), (C), (D) and (E).
(A) N, N, N ′, N′-tetraglycidyldiaminodiphenylmethane (B) novolac type epoxy resin represented by the above chemical formula (C) urea compound (D) dicyandiamide (E) thermoplastic resin.

  The epoxy resin composition of the prepreg for internal pressure molding which concerns on this invention is excellent in heat resistance by containing a component (A), (B) and (D). Moreover, since the epoxy resin composition contains the component (C), the internal pressure molding prepreg according to the present invention is excellent in molding cycleability because the epoxy resin composition can be cured at a low temperature and in a short time. Moreover, since the prepreg for internal pressure molding which concerns on this invention can adjust the fluidity | liquidity of resin at the time of thermoforming because an epoxy resin composition contains a component (E), it is excellent in resin fluidity | liquidity.

  Hereinafter, each component will be described.

<Component (A)>
Component (A) is N, N, N ′, N′-tetraglycidyldiaminodiphenylmethane. By using a component (A), the heat resistance of an epoxy resin composition can be made high. Therefore, the internal pressure molding prepreg having heat resistance is obtained by impregnating the fiber reinforcing material with the epoxy resin composition containing the component (A).

  A commercial item can be used as a component (A). Examples of commercially available components (A) include “Sumiepoxy (registered trademark)” ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), YH434L (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.), and “jER (registered trademark)” 604 (Mitsubishi). Chemical Co., Ltd.), “Araldite (registered trademark)” MY720, Araldite MY721 (manufactured by Huntsman Advanced Materials Co., Ltd.), and the like.

<Component (B)>
The component (B) is a novolac type epoxy resin represented by the above chemical formula 1.

  Among these, the component (B) is more preferably a triphenylmethane type epoxy resin (n = 0). If it is a triphenylmethane type epoxy resin, high toughness can be provided, maintaining the heat resistance of an epoxy resin composition.

  A commercial item can be used as a component (B). Examples of commercially available components (B) include jER1031 and jER1032H60 (manufactured by Mitsubishi Chemical Corporation), and “EPPN (registered trademark)”-501H, EPPN-502H and EPPN-503H (manufactured by Nippon Kayaku Co., Ltd.). Examples of the triphenylmethane type epoxy resin include “Tactix (registered trademark)” 742 (manufactured by Huntsman Advanced Materials Co., Ltd.) and the like.

  The epoxy resin composition may contain only the component (A) and the component (B) as the epoxy resin component, or in addition to the component (A) and the component (B), the component (A) and the component (described later) Epoxy resins other than B) may be contained. When an epoxy resin composition contains epoxy resins other than a component (A) and a component (B), content of a component (A) is the sum total of content of all the epoxy resins contained in an epoxy resin composition ( Hereinafter, it is referred to as “total amount of epoxy resin”.) In 100% by mass, 10% by mass or more is more preferable, 15% by mass or more is more preferable, 60% by mass or less is more preferable, and 50% by mass or less is more preferable. If content of a component (A) is in this range, since the heat resistance of an epoxy resin composition is excellent, the prepreg for internal pressure molding more excellent in heat resistance is obtained.

  Further, the content of the component (B) is more preferably 10% by mass or more, more preferably 15% by mass or more, more preferably 70% by mass or less, and more preferably 60% by mass or less in the total amount of epoxy resin of 100% by mass. Further preferred. If content of a component (B) is in this range, since the heat resistance of an epoxy resin composition is excellent, the prepreg for internal pressure molding more excellent in heat resistance is obtained.

<Ingredient (C)>
Component (C) is a urea compound. Component (C) serves as a curing agent or curing accelerator for the epoxy resin. Due to the component (C), the epoxy resin composition can be cured at a low temperature and in a short time, so that the molding cycle property is excellent.

  Examples of the component (C) include 3-phenyl-1,1-dimethylurea, 3- (3,4-dichlorophenyl) -1,1-dimethylurea (DCMU), 3- (3-chloro-4-methyl). Phenyl) -1,1-dimethylurea, 2,4-bis (3,3-dimethylureido) toluene (TBDMU), phenyldimethylurea (PDMU), 4,4′-methylenebis (phenyldimethylurea) (MDMU), etc. Is mentioned. Among them, 2,4-bis (3,3-dimethylureido) toluene (TBDMU), phenyldimethylurea (PDMU), or 4,4′-methylenebis (phenyldimethylurea) can be obtained because both molding cycle property and heat resistance can be achieved. (MDMU) is preferred.

  A commercial item can be used as a component (C). For example, 2,4-bis (3,3-dimethylureido) toluene (TBDMU) is industrially available as “Omicure (registered trademark)” 24 (manufactured by PTI Japan) and phenyldimethylurea (PDMU) is industrially available as Omicure 94 (manufactured by PTI Japan), and 4,4'-methylenebis (phenyldimethylurea) (MDMU) is Omicure 52 and Omicure 54 (above, It is industrially available as PTI Japan Ltd., and 3- (3,4-dichlorophenyl) -1,1-dimethylurea is industrially available as DCMU99 (Hodogaya Chemical Co., Ltd.). .

  The content of the component (C) is preferably 0.4 parts by mass or more, more preferably 0.5 parts by mass or more, and 6 parts by mass or less with respect to 100 parts by mass of the total amount of epoxy resin. Preferably, it is 5 parts by mass or less, more preferably 3 parts by mass or less. If the content of the component (C) is 0.4 parts by mass or more, the epoxy resin composition can be cured at a low temperature and in a short time, so that the molding cycle property of the resulting prepreg is further improved, and 0.5 parts by mass or more. If so, the epoxy resin composition can be cured at a lower temperature and in a shorter time. As the content of the component (C) increases, the curing time tends to be shortened. However, when the content of the component (C) is too large, the heat resistance of the molded product produced using the prepreg tends to decrease. Therefore, from the viewpoint of maintaining good heat resistance of the molded product, the content of the component (C) is preferably 6 parts by mass or less.

<Component (D)>
Component (D) is dicyandiamide. Component (D) serves as a curing agent or curing accelerator for the epoxy resin.

  A commercial item can be used as a component (D). As a commercial item of a component (D), "jER cure (trademark)" DICY7 and jER cure DICY15 (above, the Mitsubishi Chemical Corporation make), and DICY-F and DICY-M (above, PiT. I Japan Co., Ltd.).

  The content of the component (D) is more preferably 4 parts by mass or more, further preferably 5 parts by mass or more, and 8 parts by mass or less with respect to 100 parts by mass of the total epoxy resin. Is more preferably 7 parts by mass or less. If content of a component (D) is 4 mass parts or more, an epoxy resin composition is excellent in heat resistance, and the heat resistance of the obtained prepreg increases more. Moreover, if content of a component (D) is 4 mass parts or more, it will play the role which adjusts the fluidity | liquidity of resin at the time of heat molding. As the content of component (D) increases, the heat resistance tends to improve. However, if the content of component (D) is too large, the surface of a molded product produced using prepreg is whitened and there is a problem in appearance. Arise. Therefore, from the viewpoint of favorably maintaining the surface appearance of the molded product, the content of the component (D) is preferably 8 parts by mass or less.

<Ingredient (E)>
Component (E) is a thermoplastic resin. A component (E) plays the role which adjusts the fluidity | liquidity of resin at the time of thermoforming. Moreover, a component (E) plays the role which provides toughness.

  Examples of the component (E) include polyvinyl formal, phenoxy resin, polyamide resin, polyimide, polysulfone, polyvinyl pyrrolidone, and polyether sulfone. From the viewpoint of heat resistance, polyvinyl formal or polyether sulfone is preferred. More preferred is polyethersulfone.

  A commercial item can be used as a component (E). Examples of commercially available components (E) include polyvinyl formal, Denkabutyral (manufactured by Denki Kagaku Kogyo Co., Ltd.) and “Vinylec (registered trademark)” E (manufactured by JNC Co., Ltd.), and phenoxy resin, “UCAR ( (Registered trademark) “PKHP (manufactured by Union Carbide Co., Ltd.)”, “Macromelt (registered trademark)” (manufactured by Henkel Hakusui Co., Ltd.) and “Amilan (registered trademark)” (manufactured by Toray Industries, Inc.) as polyamide resin, and “Ultem as polyimide” (Registered trademark) "(manufactured by General Electric Co., Ltd.) and" Matrimid (registered trademark) "5218 (manufactured by Ciba Co., Ltd.)," Sumika Excel (registered trademark) "(manufactured by Sumitomo Chemical Co., Ltd.), UDEL (polysulfone) Registered trademark) "and" RADEL (registered trademark) "(Solvay Advan Toporimazu Co., Ltd.), as polyvinylpyrrolidone, can be mentioned "Luviskol (registered trademark)" (manufactured by BASF Japan Ltd.).

<Component (F)>
Component (F) is an isocyanate-modified epoxy resin. By including a component (F) in an epoxy resin composition, toughness can be improved, without reducing heat resistance.

  A commercial item can be used as a component (F). As a commercial item of a component (F), "AER (trademark)" 4151 and AER4152 (made by Asahi Kasei E-materials Co., Ltd.) and ACR1348 (made by ADEKA Co., Ltd.) etc. which have an oxazolidone ring are mentioned, for example.

  The content of component (F) is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and 45 parts by mass or less with respect to 100 parts by mass of the total amount of epoxy resin. The amount is preferably 40 parts by mass or less, and more preferably 15 parts by mass or less. If content of a component (F) is 5 mass parts or more, an epoxy resin composition is excellent in heat resistance, and the heat resistance of the obtained prepreg increases more. Since the heat resistance tends to decrease as the content of the component (F) is increased, the content of the component (F) is more preferably 40 parts by mass or less from the viewpoint of suitably maintaining the heat resistance. .

<Other epoxy resins>
The epoxy resin composition in the prepreg for internal pressure molding according to the present invention may contain an epoxy resin other than the above-described epoxy resin (hereinafter referred to as “other epoxy resin”). Since the viscosity of the epoxy resin composition can be appropriately adjusted by using components (A) to (F) in combination with other epoxy resins, the prepreg tack and drape properties are easily adjusted to a level suitable for handling. be able to. In addition, mechanical properties such as heat resistance and toughness of the reinforced fiber plastic (FRP) including a cured product of the prepreg can be improved.

  As other epoxy resins, for example, a glycidyl ether type epoxy resin obtained from a compound having a hydroxyl group in the molecule and epichlorohydrin, a glycidylamine type obtained from a compound having an amino group in the molecule and epichlorohydrin Epoxy resin, glycidyl ester type epoxy resin obtained from compound having carboxyl group in molecule and epichlorohydrin, alicyclic epoxy resin obtained by oxidizing compound having double bond in molecule, heterocyclic ring An epoxy resin having a structure and an epoxy resin in which two or more types of groups selected from these are mixed in the molecule are used. Another epoxy resin may be used individually by 1 type, and may use 2 or more types together.

(Glycidyl ether type epoxy resin)
Specific examples of the glycidyl ether type epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, resorcinol type epoxy resin, phenol novolac type epoxy resin, trisphenol novolak type epoxy resin, cresol novolak type. Examples include epoxy resins, polyethylene glycol-type epoxy resins, polypropylene glycol-type epoxy resins, naphthalene-type epoxy resins, dicyclopentadiene-type epoxy resins, anthracene-type epoxy resins, and their positional isomers or substituted groups with alkyl groups or halogens. It is done.

  Commercially available products of bisphenol A type epoxy resins include, for example, “EPON (registered trademark)” 825, jER826, jER827, jER828, jER834 and jER1001 (manufactured by Mitsubishi Chemical Corporation), “Epiclon (registered trademark)” 850 (DIC). Co., Ltd.), “Epototo (registered trademark)” YD-128 (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.), “DER (registered trademark)”-331 and DER-332 (manufactured by Dow Chemical Japan Co., Ltd.) And “Bakelite (registered trademark)” EPR154, Bakelite EPR162, Bakelite EPR172, Bakelite EPR173, and Bakelite EPR174 (above, manufactured by Bakerite AG).

  Examples of commercially available products of bisphenol F type epoxy resin include jER806, jER807 and jER1750 (manufactured by Mitsubishi Chemical Corporation), Epicron 830 (manufactured by DIC Corporation), Epototo YD-170 and Epototo YD-175 (above, Nippon Steel). And the like, and Bakelite EPR169 (manufactured by Bakerite AG), GY281, GY282, and GY285 (manufactured by Huntsman Advanced Material).

  As a commercial item of a bisphenol S type epoxy resin, Epicron EXA-1514 (made by DIC Corporation) etc. are mentioned, for example.

  As a commercial item of a resorcinol type epoxy resin, "Denacol (trademark)" EX-201 (made by Nagase ChemteX Corporation) etc. is mentioned, for example.

  Examples of commercially available phenol novolac epoxy resins include jER152 and jER154 (manufactured by Mitsubishi Chemical Corporation), Epicron 740 (manufactured by DIC Corporation), EPN179 and EPN180 (manufactured by Huntsman Advanced Materials), and the like. .

  Examples of the cresol novolac type epoxy resin include N695 (manufactured by DIC Corporation).

  As a commercial item of a naphthalene type epoxy resin, HP-4032 and HP-4700 (made by DIC Corporation), NC-7300 (made by Nippon Kayaku Co., Ltd.), etc. are mentioned, for example.

  Examples of commercially available dicyclopentadiene type epoxy resins include XD-100 (manufactured by Nippon Kayaku Co., Ltd.) and HP7200 (manufactured by DIC Corporation).

  As a commercial item of anthracene type epoxy resin, YL7172YX-8800 (made by Mitsubishi Chemical Corporation) etc. are mentioned, for example.

(Glycidylamine type epoxy resin)
Specific examples of the glycidylamine type epoxy resin include glycidyl compounds of aminophenol, glycidyl compounds of aminocresol, glycidylanilines, and glycidyl compounds of xylenediamine.

  Commercially available products of aminophenol glycidyl compound and aminocresol glycidyl compound include, for example, jER630 (manufactured by Mitsubishi Chemical Corporation), Araldite MY0500, Araldite MY0510 and Araldite MY0600 (manufactured by Huntsman Advanced Materials), and Sumiepoxy. ELM120, Sumiepoxy ELM100 (above, manufactured by Sumitomo Chemical Co., Ltd.) and the like.

  Examples of commercially available glycidyl anilines include GAN and GOT (manufactured by Nippon Kayaku Co., Ltd.), Bakelite EPR493 (manufactured by Bakelite AG), and the like.

  Examples of the glycidyl compound of xylenediamine include TETRAD-X (manufactured by Mitsubishi Gas Chemical Company, Inc.).

(Glycidyl ester type epoxy resin)
Specific examples of the glycidyl ester type epoxy resin include phthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, dimer acid diglycidyl ester, and isomers thereof.

  Examples of commercially available products of diglycidyl phthalate include “Epomic (registered trademark)” R508 (manufactured by Mitsui Chemicals) and Denacol EX-721 (manufactured by Nagase ChemteX Corporation).

  Examples of commercially available products of hexahydrophthalic acid diglycidyl ester include Epomic R540 (manufactured by Mitsui Chemicals) and AK-601 (manufactured by Nippon Kayaku Co., Ltd.).

  Examples of commercially available dimer acid diglycidyl ester include jER871 (manufactured by Mitsubishi Chemical Corporation) and Epototo YD-171 (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.).

(Alicyclic epoxy resin)
Specific examples of the alicyclic epoxy resin include compounds having a 1,2-epoxycyclohexane ring as a partial structure.

  Examples of commercially available compounds having a 1,2-epoxycyclohexane ring as a partial structure include, for example, “Celoxide (registered trademark)” 2021P, Celoxide 2081 and Celoxide 3000 (manufactured by Daicel Corporation), and CY179 (Huntsman Advanced Material Co., Ltd.).

(Curing agent, curing accelerator)
The epoxy resin composition in the prepreg for internal pressure molding according to the present invention may contain a curing agent and a curing accelerator. The curing agent and curing accelerator can be contained in the epoxy resin composition to such an extent that the heat resistance, toughness, storage stability and fluidity of the epoxy resin composition are not impaired.

  The curing agent is not particularly limited, but amines such as aromatic amines and alicyclic amines, phenol resins, dicyandiamide or derivatives thereof, acid anhydrides, polyaminoamides, organic acid hydrazides, and isocyanates are used. May be.

  Examples of the curing accelerator include urea compounds, tertiary amines and salts thereof, imidazoles and salts thereof, triphenylphosphine and derivatives thereof, carboxylic acid metal salts, Lewis acids, Bronsted acids and salts thereof, and the like.

(Optional component)
The epoxy resin composition may contain an optional component other than the components described above as long as the effects of the present invention are not impaired.

  Optional components include rubber particles, silica powder, silicon dioxide, microballoons, antimony trioxide, alumina, titanium oxide, magnesium oxide, aluminum oxide and other inorganic particles, phosphorus compounds, magnesium hydroxide, aluminum hydroxide and other flame retardants And carbon particles such as carbon black and activated carbon, and additives such as antifoaming agents, wetting agents and internal mold release agents. These additives are blended in the epoxy resin composition depending on the purpose.

(Viscosity at 30 ° C)
The viscosity at 30 ° C. of the epoxy resin composition is more preferably 2,500 Pa · s or more, further preferably 3,000 Pa · s or more, and more preferably 20,000 Pa · s or less. Preferably, it is 15,000 Pa · s or less. When the viscosity at 30 ° C. is 2,500 Pa · s or more, the prepreg is excellent in handleability and can be easily shaped into a mold. If the viscosity at 30 ° C. is 20,000 Pa · s or less, the prepreg is not too hard and shaping into a mold is facilitated.

(Minimum viscosity)
The minimum viscosity at 100 ° C. or higher and 130 ° C. or lower of the epoxy resin composition at the time of heat molding is preferably 1 Pa · s or higher and 10 Pa · s or lower. If the minimum viscosity is 1 Pa · s or more, strength deterioration due to disorder of the orientation of the reinforcing fiber and deterioration of the surface appearance, the surface of the molded article is raised, the surface appearance such as void generation on the surface of the molded article, and It is possible to suppress a decrease in strength of the molded product due to generation of voids inside the molded product due to insufficient resin in the molded product. If the minimum viscosity is 10 Pa · s or less, voids do not remain in the molded product, the strength of the molded product is not insufficient, and the resin is sufficiently distributed throughout the molded product, so that the appearance is not deteriorated due to the lack of the resin.

(Reinforced fiber)
As the reinforcing fibers, fibers usually used as reinforcing materials for reinforcing fiber plastics (FRP) can be used, and examples thereof include carbon fibers, glass fibers, aramid fibers, polyester fibers, and mineral fibers (for example, basalt fibers). Among these, carbon fiber is preferable because it is lightweight, has high strength, has a high elastic modulus, and is excellent in heat resistance and chemical resistance.

  Examples of the carbon fiber include pitch type, polyacrylonitrile (PAN type), rayon type and the like, and any carbon fiber may be used, but the use of the PAN type carbon fiber is preferable from the viewpoint of carbon fiber productivity. More preferred. Examples of the form of the fiber reinforcing material include forms such as a milled fiber, a chopped fiber, a continuous fiber, and various woven fabrics.

<Method for producing fiber-reinforced composite material>
The method for producing a fiber-reinforced composite material according to the present invention is formed by first curing the above-mentioned prepreg for internal pressure molding under heat curing conditions of 110 ° C. or higher, 140 ° C. or lower, 20 minutes or longer, and 40 minutes or shorter by internal pressure molding. After cooling and cooling, the cured product of the prepreg for internal pressure molding is removed from the mold, and secondarily cured in a free-standing state under heat curing conditions of 170 ° C. or higher, 200 ° C. or lower, 90 minutes or longer, and 120 minutes or shorter. It is a manufacturing method of the fiber reinforced composite material including a process.

  Since the temperature of primary curing at the time of internal pressure molding is a relatively low temperature of 110 ° C. or higher and 140 ° C. or lower, viscosity reduction due to heating of the epoxy resin composition is suppressed, and the fluidity of the resin during molding can be controlled. . Further, since the cooling time is shortened, the molding cycle is improved. Since an inexpensive thermoplastic tube with low heat resistance can be used, the manufacturing cost can be reduced and the productivity is excellent.

  Moreover, the fiber reinforced composite material which has high heat resistance is obtained by secondary-curing at 170 degreeC or more and 200 degrees C or less.

(Fiber reinforced composite material)
In this specification, the fiber reinforced composite material refers to various materials obtained by curing reinforcing fibers. By the method for producing a fiber reinforced material according to the present invention, a fiber reinforced material having high heat resistance and excellent quality can be produced with high productivity. Examples of products obtained from the fiber reinforced material include structural materials such as aircraft and automobiles, sports equipment such as tennis rackets, golf shafts, fishing rods, bicycles, and housings.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

  The raw material of the epoxy resin composition used in each Example and Comparative Example and various measurement methods are shown below.

<Raw material>
<Component (A)>
N, N, N ′, N′-tetraglycidyldiaminodiphenylmethane (manufactured by Mitsubishi Chemical Corporation, “jER604”, epoxy equivalent: 120 g / eq).

<Component (B)>
A novolac type epoxy resin represented by the above chemical formula 1 (n = 0), which is a triphenylmethane type epoxy resin (manufactured by Huntsman Advanced Materials, “Tactix 742”, epoxy equivalent: 160 g / eq)
A novolac type epoxy resin represented by the above chemical formula 1 (manufactured by Mitsubishi Chemical Corporation, “jER1032H60”, epoxy equivalent: 169 g / eq).

<Ingredient (C)>
Phenyldimethylurea (manufactured by PTI Japan, “Omure 94”) (PDMU)
4,4'-methylenebis (phenyldimethylurea) (Phi-T Japan Co., Ltd., "Omicure 54") (MDMU).

<Component (D)>
Dicyandiamide (Mitsubishi Chemical Corporation, “jER Cure DICY15”, active hydrogen equivalent: 21 g / eq).

<Ingredient (E)>
Polyvinyl formal (manufactured by JNC Corporation, “Vinylec E”, Mn: 126000).

<Component (F)>
Isocyanate-modified epoxy resin (manufactured by Asahi Kasei E-material Co., Ltd., “AER4152”, epoxy equivalent: 169 g / eq).

<Other ingredients>
Bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, “jER828”, epoxy equivalent: 189 g / eq)
Bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, “jER1001”, epoxy equivalent: 475 g / eq)
Cresol novolac type epoxy resin (manufactured by DIC Corporation, “N695”, epoxy equivalent: 214 g / eq).

<Resin preparation>
(Examples 1-11, Comparative Examples 1-2)
10 parts by mass of jER828, a component (D) of parts by mass described in Tables 1 and 2 (jER cure DICY15), and each component (C) of parts by mass of Tables 1 and 2, A master batch was obtained by uniformly dispersing using a three-roll mill. The remaining components listed in Tables 1 and 2 and the component (E) were blended and stirred at 160 ° C., and the base resin was obtained after confirming that uniform dissolution was completed. The master batch and the base resin were blended and stirred at 65 ° C. to obtain a uniformly dispersed epoxy resin composition.

<Curing cured resin plate>
(Examples 1-11, Comparative Examples 1-2)
Each obtained epoxy resin composition was defoamed at 65 ° C. using a vacuum pump, and each epoxy resin composition was poured into a glass plate in which spacers of 2 mm thickness and 3 mm thickness were bitten, and both surfaces were made of glass. Cast with a plate. Each epoxy resin composition was heated from room temperature at a heating rate of 2 ° C./min using an oven, and held at 135 ° C. for 35 minutes for primary curing. After cooling to room temperature, the glass plate was removed, and the primary cured resin plate was heated at a rate of temperature rise of 2 ° C./min in an oven and kept at 180 ° C. for 120 minutes. Next curing was performed to obtain a cured resin plate.

<Measurement method>
(Viscosity at 30 ° C, minimum viscosity)
By using a viscometer ARG2 manufactured by TA Instrument, the minimum viscosity of the epoxy resin composition was measured under the conditions of a frequency of 10 radians / second, a measurement temperature range of 30 to 150 ° C., and a heating rate of 2 ° C./minute using a parallel plate. It was measured. Tables 1 and 2 show the results of the viscosity at 30 ° C. and the minimum viscosity at 100 ° C. or higher and 130 ° C. or lower.

(Glass transition temperature (Tg))
A cured resin plate obtained by secondary curing was cut with a wet diamond cutter into a length of 55 mm and a width of 12.7 mm to prepare a test piece. A DMA ARES-RDA manufactured by TA Instrument was used, the heating rate was 5 ° C./min, Freq. The storage elastic modulus (G ′) was measured under the conditions of 1 Hz and 0.05% strain. Log G ′ is plotted against temperature, and the temperature obtained from the intersection of the approximate straight line of log G ′ in the flat region before transition to glass and the approximate straight line of log G ′ in the region transition to glass is the glass transition temperature (Tg). ) (See FIG. 1).

(Fracture toughness value (G1c))
The fracture toughness value (G1c) was determined by a measurement method based on ASTM D5045. The results are shown in Tables 1 and 2.

  The internal pressure molding prepreg according to the present invention and the method for producing a fiber reinforced composite material using the prepreg have high heat resistance, and can produce excellent quality molded products with high productivity. It can be suitably used for the production of reinforced fiber plastics for applications such as parts.

Claims (7)

A prepreg for internal pressure molding in which a reinforcing fiber is impregnated with an epoxy resin composition containing the following components (A), (B), (C), (D) and (E).
(A) N, N, N ′, N′-tetraglycidyldiaminodiphenylmethane (B) novolac type epoxy resin represented by the following chemical formula 1

(C) Urea compound (D) Dicyandiamide (E) Thermoplastic resin The viscosity of the epoxy resin composition at 30 ° C. is 2,500 Pa · s or more and 20,000 Pa · s or less,
The prepreg for internal pressure molding according to claim 1, wherein a minimum viscosity of the epoxy resin composition at 100 ° C or higher and 130 ° C or lower is 1 Pa · s or higher and 10 Pa · s or lower.   The prepreg for internal pressure molding according to claim 1 or 2, wherein the component (B) is a triphenylmethane type epoxy resin.   The component (C) is at least one of phenyldimethylurea, 4,4'-methylenebis (phenyldimethylurea) and 2,4-bis (3,3-dimethylureido) toluene. The prepreg for internal pressure molding according to any one of the above.   The prepreg for internal pressure molding according to any one of claims 1 to 4, wherein the component (E) is at least one of polyvinyl formal and polyether sulfone.   The prepreg for internal pressure molding according to any one of claims 1 to 5, further comprising an isocyanate-modified epoxy resin as a component (F). An internal pressure molding prepreg in which a reinforcing fiber is impregnated with an epoxy resin composition containing the following components (A), (B), (C), (D) and (E) has a primary curing of 110 ° C. or higher and 140 ° C. The manufacturing method of the fiber reinforced composite material including the process of heat-hardening on the heat-hardening conditions below for 20 minutes or more and 40 minutes or less, and secondary hardening 170 degreeC or more and 200 degreeC or less for 90 minutes or more and 120 minutes or less.
(A) N, N, N ′, N′-tetraglycidyldiaminodiphenylmethane (B) novolac type epoxy resin represented by the following chemical formula 1

(C) Urea compound (D) Dicyandiamide (E) Thermoplastic resin

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