JP2014156582A - Prepreg and fiber-reinforced composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber-reinforced composite material which can provide interlaminar toughness without blending a large quantity of thermoplastic resin which may lead to deterioration of processability when preparing a prepreg, and to provide a prepreg suitable for obtaining the same.SOLUTION: Provided is a prepreg comprising at least the following [A], [B], [C], and [D]: [A] an epoxy resin; [B] a polyether imide containing a specific sulfonyl group; [C] a curing agent; and [D] reinforcing fibers.

Description

  The present invention relates to a fiber-reinforced composite material that combines excellent interlaminar toughness and excellent processability in producing a prepreg, and a prepreg suitably used for the same.

  Fiber reinforced composite materials consisting of glass fibers, carbon fibers, aramid fibers, etc., and matrix resins are lightweight compared to competing metals, etc., but have excellent mechanical properties such as strength and elastic modulus. It is used in many fields such as spacecraft members, automobile members, ship members, civil engineering and building materials, and sports equipment. In particular, in applications that require high performance such as aircraft members, carbon fibers having excellent specific strength and specific elastic modulus are often used as reinforcing fibers. On the other hand, unsaturated polyester resins, vinyl ester resins, epoxy resins, phenol resins, cyanate ester resins, bismaleimide resins, etc. are often used as matrix resins, and among them, many epoxy resins have excellent adhesion to reinforced fibers. It is used.

  A matrix resin made of an epoxy resin exhibits excellent heat resistance and good mechanical properties, but has low elongation and toughness, so a sheet-like intermediate group called a prepreg in which a reinforcing fiber is impregnated with a resin film made of an epoxy resin When materials are laminated and molded, and then cured to obtain a fiber-reinforced composite material, the interlaminar toughness may be lowered, and improvement is required.

  Conventionally, as a method for improving the toughness of an epoxy resin, a method of blending rubber or thermoplastic resin having excellent toughness with an epoxy resin has been tried. For example, a study of blending a rubber such as carboxyl-terminated acrylonitrile-butadiene rubber with an epoxy resin has been made since the 1970s and is generally well known (for example, see Patent Document 1). However, since the mechanical properties such as elastic modulus and heat resistance of rubber are much lower than those of epoxy resin, when rubber is compounded with epoxy resin, which is a matrix resin, the elastic modulus and heat resistance are reduced and the toughness is improved. It was difficult to balance the elastic modulus and heat resistance. In addition, in order to improve this defect, there is a case where rubber that is granulated like core-shell rubber is blended with epoxy resin that is matrix resin, but if the blending amount is increased in order to sufficiently improve toughness, elasticity is increased. The rate and heat resistance may be reduced (see, for example, Patent Document 2). In addition, since the matrix resin used for the fiber reinforced composite material constituting the aircraft member has a high viscosity, when the core shell rubber particles are blended with this, the core shell rubber particles may aggregate in the epoxy resin, and the epoxy resin In some cases, the resin film made of the above cannot be produced, the epoxy resin cannot be sufficiently impregnated between the reinforcing fibers, or the processability when producing the prepreg may be problematic.

  Another method for improving the toughness of the epoxy resin is to dissolve a thermoplastic resin such as polyethersulfone, polysulfone and polyetherimide in the epoxy resin, or blend it in a fine powder. It is known that the toughness is improved without impairing the mechanical properties of the epoxy resin by uniformly dispersing the thermoplastic resin (see, for example, Patent Document 3). However, in this method, it is necessary to add a large amount of thermoplastic resin, the viscosity of the epoxy resin is significantly increased, and when the prepreg is produced, the epoxy resin cannot be sufficiently impregnated between the reinforcing fibers. It may not be possible to produce a resin film made of or a problem may occur in processability when producing a prepreg.

JP-A-1-118565 JP 2009-280669 A Japanese Examined Patent Publication No. 6-43508

  The present invention has been made in view of the above, and provides a fiber-reinforced composite material that combines excellent interlayer toughness and excellent processability when producing a prepreg, and a prepreg suitably used for the same. For the purpose.

The present invention has the following configuration in order to achieve the above object. That is,
(1) A prepreg including at least the following [A], [B], [C], and [D].
[A] Epoxy resin [B] At least one polyetherimide [C] curing agent [D] reinforced fiber selected from the group consisting of the following (a), (b) and (c) (a) A polyetherimide having a sulfonyl group, having the repeating unit represented by [1].

(B) A polyetherimide having a sulfonyl group having a repeating unit represented by the following formula [2].

  In the formula, X is a group of —O— or —O—Z—O—, and the divalent linking group of the group of —O— or —O—Z—O— is the 3,3′-position, In the 4′-position, 4,3′-position, or 4,4′-position, Z is selected from the group consisting of divalent linking groups of the following formula [3].

In the formula, R is selected from the group consisting of —CO—, —SO ₂ —, —CH ₂ —, —O—, —S—, —CH (CH ₃ ) —, —C (CH ₃ ) ₂ —. Represents a divalent linking group. Y is selected from the group consisting of the divalent linking group of the above formula [3]. However, at least one sulfonyl group is contained in one or both of X and Y.
(C) A polyetherimide having a repeating unit represented by the following formula [4] and having a sulfonyl group.

  In the formula, X is a group of —O— or —O—Z—O—, and the divalent linking group of the group of —O— or —O—Z—O— is the 3,3′-position, In the 4′-position, 4,3′-position, or 4,4′-position, Z is selected from the group consisting of divalent linking groups of the following formula [3].

In the formula, R is selected from the group consisting of —CO—, —SO ₂ —, —CH ₂ —, —O—, —S—, —CH (CH ₃ ) —, —C (CH ₃ ) ₂ —. Represents a divalent linking group.

  (2) The prepreg according to (1), wherein the component [B] has a weight average molecular weight of 70000 g / mol or less.

  (3) The prepreg according to (2), wherein the component [B] has a weight average molecular weight of 35,000 to 60000 g / mol.

  (4) The prepreg according to any one of (1) to (3), wherein the component [B] has an end group that does not react with the component [A].

  (5) In 100 parts by mass of the total epoxy resin composition composed of the component [A], the component [B], and the component [C], the component [B] is included in an amount of 5 to 25 parts by mass (1) to ( The prepreg according to any one of 4).

  (6) The prepreg according to any one of (1) to (5), wherein the constituent element [C] is an aromatic polyamine represented by the following formula [5].

  (7) The prepreg according to any one of (1) to (6), including 30 parts by mass or more of an epoxy resin having a trifunctional or higher functional epoxy group in 100 parts by mass of the component [A].

  (8) The prepreg according to (7), wherein the epoxy resin having a tri- or higher functional epoxy group is a glycidylamine type epoxy resin.

  (9) The prepreg according to (8), wherein the glycidylamine type epoxy resin is an epoxy resin represented by the following formula [6].

In the formula, Q is selected from the group consisting of —CO—, —SO ₂ —, —CH ₂ —, —O—, —S—, —CH (CH ₃ ) —, —C (CH ₃ ) ₂ —. Represents a divalent linking group.

  (10) The prepreg according to any one of (1) to (9), including 5 to 40 parts by mass of a bisphenol F-type epoxy resin in 100 parts by mass of the component [A].

  (11) The prepreg according to (10), including 30 parts by mass or more of an epoxy resin represented by the following formula [6] in 100 parts by mass of the component [A].

In the formula, Q is selected from the group consisting of —CO—, —SO ₂ —, —CH ₂ —, —O—, —S—, —CH (CH ₃ ) —, —C (CH ₃ ) ₂ —. Represents a divalent linking group.

  (12) An epoxy resin cured product obtained by curing an epoxy resin composition comprising the constituent elements [A], [B], and [C] has an epoxy resin rich phase and a polyetherimide rich phase having a sulfonyl group. The prepreg according to any one of (1) to (11), which has a sea-island-structured phase separation structure and has an island phase diameter of less than 0.1 μm.

  (13) The prepreg according to any one of (1) to (12), further including thermoplastic resin particles [E].

  (14) The particle layer in which the thermoplastic resin particles [E] are localized is 20% or less in the thickness direction starting from the surface of the prepreg with respect to the thickness of the prepreg of 100%. The prepreg according to (13), which has a structure existing in a depth range.

  (15) The prepreg according to any one of (1) to (14), further including core-shell rubber particles [F].

  (16) The prepreg according to (15), comprising 1 to 12 parts by mass of the constituent element [F] in 100 parts by mass of the total epoxy resin composition.

  (17) The prepreg according to (15) or (16), wherein the component [F] has a terminal group capable of reacting with the component [A] or [C] in the shell portion.

  (18) The prepreg according to any one of (15) to (17), wherein the constituent element [F] has an epoxy group in a shell portion.

  (19) The prepreg according to any one of (15) to (18), wherein the volume average particle diameter of the constituent element [F] is 0.3 μm or less.

  (20) The cured epoxy resin obtained by curing the epoxy resin composition comprising the constituent elements [A], [B], [C], and [F] has an epoxy resin rich phase and a core shell rubber rich phase. The prepreg according to any one of (15) to (19), which has a sea-island-structured phase separation structure having a diameter of 0.1 to 3 μm.

  (21) The epoxy resin composition comprising the constituent elements [A], [B], [C], and [F] has a viscosity at 80 ° C. of 1 to 1000 Pa · s, (15) to (20) The prepreg according to any one of the above.

  (22) The prepreg according to any one of (1) to (21), wherein the constituent element [D] is a carbon fiber.

  (23) A fiber-reinforced composite material obtained by curing the prepreg according to any one of (1) to (22).

  According to the present invention, since it has the same skeleton as the epoxy resin that is the matrix resin in the molecule, the use of polyetherimide that is highly compatible with the epoxy resin that is the matrix resin provides excellent interlayer toughness and prepreg. It is possible to obtain a fiber-reinforced composite material that has excellent processability when produced, and a suitable prepreg for obtaining the same. Since the prepreg of the present invention does not require a large amount of polyetherimide, which is a thermoplastic resin, it can suppress an increase in viscosity of the epoxy resin composition, which is a matrix resin, and is excellent in processability when producing a prepreg. By using the prepreg of the present invention, a fiber reinforced composite material exhibiting excellent interlayer toughness can be obtained, and therefore it can be suitably used as a structural material for aircraft, space use, automobiles, ships, windmills and the like.

  Hereinafter, the prepreg and fiber-reinforced composite material of the present invention will be described in detail.

  A prepreg is a sheet-like intermediate molding base material in which a reinforcing fiber is impregnated with a matrix resin. In the present invention, the prepreg is an epoxy containing the above-mentioned [A], [B], and [C] in the reinforcing fiber [D]. It is a sheet-like molded intermediate substrate impregnated with a resin composition.

  As the reinforcing fiber [D] used in the prepreg of the present invention, carbon fiber, glass fiber, aramid fiber, boron fiber, PBO fiber, high strength polyethylene fiber, alumina fiber, silicon carbide fiber, and the like can be used. Two or more kinds of these fibers may be mixed and used. The form and arrangement of the reinforcing fibers [D] are not limited, and for example, fiber structures such as long fibers aligned in one direction, a single tow, a woven fabric, a knit, a nonwoven fabric, a mat, and a braid are used.

  In particular, in applications where there is a high demand for weight reduction and high strength of materials, carbon fibers can be suitably used because of their excellent specific modulus and specific strength.

  The carbon fiber preferably used in the present invention can be any type of carbon fiber depending on the application, but the strand strength of the obtained carbon fiber bundle is preferably 3.5 GPa or more, more Preferably it is 4 GPa or more, More preferably, it is 5 GPa or more. Moreover, it is preferable that the strand elastic modulus of the obtained carbon fiber bundle is 220 GPa or more, More preferably, it is 240 GPa or more, More preferably, it is 280 GPa or more. By setting the strand strength and the strand elastic modulus within the above ranges, a fiber-reinforced composite material having high mechanical properties can be obtained.

  Commercially available carbon fibers include “Torayca (registered trademark)” T800H-12K, “Torayca (registered trademark)” T800G-24K, “Torayca (registered trademark)” T800S-24K, and “Torayca (registered trademark)” T700G- 24K, "Torayca (registered trademark)" T300-3K, and "Torayca (registered trademark)" T700S-12K (above, manufactured by Toray Industries, Inc.).

  In the present invention, the total fineness of the carbon fibers is preferably 40 to 3000 g / 1000 m. When it is less than 40 g / 1000 m, damage to the carbon fiber bundle due to contact with the guide roller may easily occur during twisting, and similar damage may also occur in the impregnation treatment step of the epoxy resin composition. When it exceeds 3000 g / 1000 m, the carbon fiber bundle may not be sufficiently impregnated with the epoxy resin composition, and as a result, fatigue resistance may be reduced.

  The number of filaments in one fiber bundle is preferably in the range of 1,000 to 100,000, more preferably 3000 to 50,000, in the carbon fiber preferably used in the present invention. When the number of filaments is less than 3,000, the fiber arrangement tends to meander and may cause a decrease in strength. On the other hand, if the number of filaments exceeds 50,000, it may be difficult to impregnate the resin during prepreg production or molding. The number of filaments is more preferably in the range of 3000 to 40000.

  As the epoxy resin [A] used in the present invention, those having an excellent balance of heat resistance, mechanical properties and adhesiveness with the reinforcing fiber [D] are preferably used. In the present invention, the epoxy resin [A] is a compound having one or more epoxy groups in the molecule. An epoxy resin having N epoxy groups in a molecule is called an N-functional epoxy resin. The epoxy resin [A] in the present invention preferably contains a trifunctional or higher functional epoxy resin from the viewpoint of improving heat resistance and elastic modulus.

  The trifunctional or higher functional epoxy resin is preferably selected from glycidylamine type epoxy resins and glycidyl ether type epoxy resins. Examples of the tri- or higher functional glycidylamine type epoxy resin include diaminodiphenylmethane type, diaminodiphenyl ether type, diaminodiphenylsulfone type, and glycidylamine type epoxy resin represented by the following formula [6].

In the formula, Q is selected from the group consisting of —CO—, —SO ₂ —, —CH ₂ —, —O—, —S—, —CH (CH ₃ ) —, —C (CH ₃ ) ₂ —. Represents a divalent linking group.

  Examples of tri- or higher functional glycidylamine type epoxy resins other than the above include aminophenol type, metaxylenediamine type, 1,3-bisaminomethylcyclohexane type, and isocyanurate type epoxy resins. Among them, diaminodiphenylmethane type, diaminodiphenylsulfone type, and aminophenol type epoxy resins are particularly preferably used because of a good balance between processability when producing the prepreg and mechanical properties such as heat resistance and elastic modulus.

  Specifically, tetraglycidyldiaminodiphenylmethane is exemplified as the diaminodiphenylmethane type epoxy resin, and tetraglycidyldiaminodiphenylsulfone is exemplified as the diaminodiphenylsulfone type epoxy resin. Tetraglycidyldiaminodiphenylmethane is preferably used because of its excellent heat resistance and adhesion to reinforcing fibers. Tetraglycidyldiaminodiphenylsulfone has a sulfone skeleton in the molecule and is a polyether having a sulfonyl group, which will be described later. Since it is excellent in compatibility with imide [B], it is particularly preferably used. Examples of the aminophenol type epoxy resin include various isomers of triglycidyl-p-aminophenol, triglycidyl-m-aminophenol, and triglycidylaminocresol.

  Examples of the tri- or higher functional glycidyl ether type epoxy resin include epoxy resins such as phenol novolac type, orthocresol novolak type, phenol aralkyl type, trishydroxyphenylmethane type, and tetraphenylolethane type, and a binaphthalene skeleton. And epoxy resin. Among them, phenol novolac type epoxy resins and orthocresol novolac type epoxy resins have high heat resistance and low water absorption, so that the heat resistance and water resistance of the cured epoxy resin can be improved, and the prepreg tackiness and drape properties, etc. The processability when producing a prepreg can be adjusted.

  Other epoxy resins [A] include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, urethane modified epoxy resin, hydantoin type epoxy resin, resorcinol. Type epoxy resin, epoxy resin having a bisarylfluorene skeleton, and glycidyl aniline type epoxy resin. Among them, the bisphenol S type epoxy resin is particularly preferable because it has a sulfonyl group in the skeleton and is excellent in compatibility with a polyetherimide [B] having a sulfonyl group described later. Bisphenol F-type epoxy resins are particularly preferred because they have low viscosity, are excellent in processability when producing prepregs, and can impart high interlayer toughness to the fiber-reinforced composite material obtained.

  In addition, blending with glycidyl aniline type epoxy resin controls the viscoelasticity and fluidity of epoxy resin [A], and also gives mechanical properties such as the elastic modulus of cured epoxy resin and the tensile strength of fiber reinforced composite materials. Since the effect to improve is acquired, it is preferable. Examples of the glycidyl aniline type epoxy resin include diglycidyl aniline, monoglycidyl aniline, and derivatives having a substituent at one or more carbons selected from the 2, 3, 4, 5, 6 positions of the benzene ring. Examples of the substituent include an aryl group such as an alkyl group, a phenyl group, and a naphthyl group, an alkyl ether group such as a methoxy group, and an aryl ether group such as a phenoxy group.

  Examples of commercially available glycidyl aniline type epoxy resins include GAN, GOT (manufactured by Nippon Kayaku Co., Ltd.), PxGAN (diglycidyl-p-phenoxy aniline, manufactured by Toray Fine Chemical Co., Ltd.), and the like.

  Since the liquid bisphenol A type epoxy resin, bisphenol F type epoxy resin and resorcinol type epoxy resin have low viscosity, it is preferable to use them in combination with other epoxy resins.

  In addition, since the bisphenol A type epoxy resin solid at room temperature (about 25 ° C.) gives a structure of a cured epoxy resin having a low crosslinking density as compared with a liquid bisphenol A type epoxy resin at room temperature (about 25 ° C.), Heat resistance is reduced, but toughness is higher. For this reason, it is preferably used in combination with a glycidylamine type epoxy resin, a liquid bisphenol A type epoxy resin or a bisphenol F type epoxy resin.

  The epoxy resin having a naphthalene skeleton gives a cured product of an epoxy resin having a low water absorption and high heat resistance. Biphenyl type epoxy resins, dicyclopentadiene type epoxy resins, phenol aralkyl type epoxy resins and diphenyl fluorene type epoxy resins are also preferably used because they give a cured product of an epoxy resin having a low water absorption. Urethane-modified epoxy resins and isocyanate-modified epoxy resins are preferably used because they give a cured epoxy resin product having high fracture toughness and high elongation.

  Below, the example of the commercial item of an epoxy resin [A] is given.

  Commercially available diaminodiphenylmethane type epoxy resins include ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), “Araldite (registered trademark)” MY720, “Araldite (registered trademark)” MY721, “Araldite (registered trademark)” MY725, “Araldite” (Registered trademark) "MY9512", "Araldite (registered trademark)" MY9663 (manufactured by Huntsman Advanced Materials), "Epototo (registered trademark)" YH-434 (manufactured by Toto Kasei Co., Ltd.) and the like It is done.

  As a commercial product of a metaxylenediamine type epoxy resin, TETRAD-X (manufactured by Mitsubishi Gas Chemical Co., Ltd.) can be mentioned.

  Examples of commercially available 1,3-bisaminomethylcyclohexane type epoxy resins include TETRAD-C (manufactured by Mitsubishi Gas Chemical Co., Inc.).

  As a commercial product of an isocyanurate type epoxy resin, TEPIC-P (manufactured by Nissan Chemical Industries, Ltd.) can be mentioned.

  Commercially available products of aminophenol type epoxy resins include ELM120 and ELM100 (above, manufactured by Sumitomo Chemical Co., Ltd.), “jER (registered trademark)” 630 (manufactured by Mitsubishi Chemical Corporation), and “Araldite (registered trademark)”. MY0600, “Araldite (registered trademark)” MY0610, “Araldite (registered trademark)” MY0500, “Araldite (registered trademark)” MY0510 (manufactured by Huntsman Advanced Materials).

  As a commercially available product of the trishydroxyphenylmethane type epoxy resin, Tactix 742 (manufactured by Huntsman Advanced Materials) may be mentioned.

  As a commercial product of the tetraphenylolethane type epoxy resin, “jER (registered trademark)” 1031S (manufactured by Mitsubishi Chemical Corporation) can be mentioned.

  Examples of commercially available polyfunctional epoxy resins having a binaphthalene skeleton include “Epiclon (registered trademark)” HP4700 (manufactured by DIC Corporation).

  Commercially available polyfunctional epoxy resins containing a naphthalene skeleton include NC-7300 (manufactured by Nippon Kayaku Co., Ltd.), “Epototo (registered trademark)” ESN-175, “Epototo (registered trademark)” ESN-375 ( Examples include Toto Kasei Co., Ltd.).

  Examples of commercially available dicyclopentadiene type epoxy resins include “Epiclon (registered trademark)” HP7200 (manufactured by DIC Corporation).

  Examples of commercially available phenol novolac epoxy resins include DEN431 and DEN438 (manufactured by Dow Chemical Co., Ltd.) and “jER (registered trademark)” 152 (manufactured by Mitsubishi Chemical Corporation).

  Examples of commercially available ortho-cresol novolak epoxy resins include EOCN-1020 (manufactured by Nippon Kayaku Co., Ltd.) and “Epiclon (registered trademark)” N-660 (manufactured by DIC Corporation).

  Commercially available products of bisphenol A type epoxy resins include “EPON (registered trademark)” 825 (manufactured by Mitsubishi Chemical Corporation), “jER (registered trademark)” 828 (manufactured by Mitsubishi Chemical Corporation), and “Epicron (registered trademark)”. ) “850 (manufactured by DIC Corporation)”, “Epototo (registered trademark)” YD-128 (manufactured by Tohto Kasei Co., Ltd.), DER-331 and DER-332 (above, manufactured by Dow Chemical Company), etc. .

  As commercial products of solid bisphenol A type epoxy resin, “jER (registered trademark)” 1001, “jER (registered trademark)” 1002, “jER (registered trademark)” 1003, “jER (registered trademark)” 1004AF “jER” (Registered trademark) “1055”, “jER (registered trademark)” 1007, “jER (registered trademark)” 1009, and “jER (registered trademark)” 1010 (manufactured by Mitsubishi Chemical Corporation).

  Commercially available products of bisphenol F type epoxy resin include “jER (registered trademark)” 806, “jER (registered trademark)” 807 and “jER (registered trademark)” 1750 (above, manufactured by Mitsubishi Chemical Corporation), “Epiclon”. (Registered Trademark) “830 (manufactured by DIC Corporation)” and “Epototo (Registered Trademark)” YD-170 (manufactured by Toto Kasei Co., Ltd.).

  Commercially available products of solid bisphenol F type epoxy resin include “jER (registered trademark)” 4002, “jER (registered trademark)” 4004P, “jER (registered trademark)” 4005P, “jER (registered trademark)” 4007P and “ jER (registered trademark) "4010P (above, manufactured by Mitsubishi Chemical Corporation)," Epototo (registered trademark) "YDF2001 (manufactured by Toto Kasei Co., Ltd.), and the like.

  Examples of commercially available bisphenol S-type epoxy resins include “Epiclon (registered trademark)” EXA-154 (manufactured by DIC Corporation).

  Examples of commercially available resorcinol type epoxy resins include “Denacol (registered trademark)” EX-201 (manufactured by Nagase ChemteX Corporation).

  Examples of commercially available biphenyl type epoxy resins include “jER (registered trademark)” YX4000 and “jER (registered trademark)” YL6677 (manufactured by Mitsubishi Chemical Corporation).

  AER4152 (Asahi Kasei Epoxy Co., Ltd. product) etc. are mentioned as a commercial item of a urethane-modified epoxy resin.

  A commercial product of a hydantoin type epoxy resin includes AY238 (manufactured by Huntsman Advanced Materials).

  Commercially available epoxy resins having a bisarylfluorene skeleton include “Ogsol (registered trademark)” PG, “Ogsol (registered trademark)” PG-100, “Ogsol (registered trademark)” EG (Osaka Gas Chemical Co., Ltd.) )) And the like.

  In addition to the above, the epoxy resin [A] used in the present invention is a copolymer of the above-described epoxy resin [A] and other epoxy resin [A], a modified product, and a resin obtained by blending two or more of these. A composition or the like can also be used.

  As said epoxy resin [A] used by copolymerizing with epoxy resin [A], for example, unsaturated polyester resin, vinyl ester resin, epoxy resin, benzoxazine resin, phenol resin, urea resin, melamine resin and polyimide Examples thereof include resins. The epoxy resin [A] used by copolymerizing with the epoxy resin [A] may be used singly or in combination of two or more.

  The epoxy resin [A], the copolymer of the epoxy resin [A] and another epoxy resin [A], or the modified epoxy resin [A] may be used alone or in appropriate combination of two or more. May be. Various characteristics can be provided by using a combination of a plurality of epoxy resins [A].

  For the purpose of improving the heat resistance and elastic modulus of the cured epoxy resin obtained by curing the epoxy resin composition comprising [A], [B], and [C] of the present invention, the above-described trifunctional or higher functional group is used. Epoxy resins are preferably used. When using a trifunctional or higher functional epoxy resin, the blending amount is preferably 30 parts by mass or more, more preferably 35 parts by mass or more, and further preferably 40 parts by mass in 100 parts by mass of the epoxy resin [A]. That's it. When the blending amount of the tri- or higher functional epoxy resin is 30 parts by mass or more, the cured epoxy resin obtained by curing is preferable because it has high heat resistance and elastic modulus.

  For the purpose of improving the toughness of the cured epoxy resin obtained by curing the epoxy resin composition comprising [A], [B], and [C] of the present invention, a bisphenol F type epoxy resin is preferably used. When the bisphenol F type epoxy resin is used, the blending amount thereof is preferably 5 to 40 parts by mass, more preferably 5 to 30 parts by mass, and further preferably 10 to 10 parts by mass in 100 parts by mass of the epoxy resin [A]. 30 parts by mass. When the blending amount of the bisphenol F-type epoxy resin is within such a range, a cured epoxy resin obtained by curing while suppressing an increase in viscosity of the epoxy resin composition is preferable because it has high toughness.

  In the epoxy resin [A] of the present invention, combining a tri- or higher functional epoxy resin that gives high heat resistance and elastic modulus to a cured epoxy resin and a bisphenol F-type epoxy resin that gives high toughness to a cured epoxy resin , [A], [B], and [C] are preferable because the cured epoxy resin has high heat resistance, elastic modulus, and toughness. In particular, the combination of the diaminodiphenylmethane type epoxy resin represented by the following formula [6] and the bisphenol F type epoxy resin can impart high interlayer toughness to the fiber reinforced composite material while maintaining heat resistance and toughness. This is a preferred embodiment.

  When using a combination of a tri- or higher functional epoxy resin that gives high heat resistance and elastic modulus to the cured epoxy resin and a bisphenol F type epoxy resin that gives high toughness to the cured epoxy resin, [A], [B] From the balance between the heat resistance and toughness of the cured epoxy resin obtained by curing the epoxy resin composition comprising [C], the blending amount is trifunctional or more in 100 parts by mass of the epoxy resin [A]. The epoxy resin is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, and still more preferably 50 parts by mass or more. The bisphenol F type epoxy resin is preferably 5 to 40 parts by mass, more preferably 5 to 30 parts by mass, and still more preferably 10 to 30 parts by mass.

  In the epoxy resin [A] of the present invention, a bisphenol F type epoxy resin having an epoxy equivalent of 100 to 250 g / eq is preferably used, more preferably 120 to 230 g / eq, still more preferably 140 to 200 g / eq. is there. When the epoxy equivalent of the bisphenol F-type epoxy resin is within such a range, it is preferable because it is excellent in processability when producing a prepreg and can impart high interlayer toughness to the fiber-reinforced composite material to be obtained.

  The curing agent [C] of the epoxy resin [A] used in the present invention is a compound having an active group that can react with the epoxy group of the epoxy resin [A]. The epoxy resin curing agent makes the crosslinking density appropriate when the epoxy resin composition is cured, and provides sufficient elastic modulus and heat resistance. The curing agent [C] is not particularly limited as long as it has a functional group having reactivity with an epoxy group. More specifically, for example, dicyandiamide, aromatic polyamine, aminobenzoic acid esters, various kinds Acid anhydride, phenolic compound, phenol novolac resin, cresol novolac resin, polyphenol compound, imidazole derivative, aliphatic amine, tetramethylguanidine, thiourea addition amine, carboxylic acid anhydride such as methylhexahydrophthalic anhydride, And Lewis acid complexes such as acid hydrazide, carboxylic acid amide, polymercaptan and boron trifluoride ethylamine complex.

  When an aromatic polyamine is used as the curing agent [C] of the epoxy resin [A], an epoxy resin cured product having good heat resistance and toughness is obtained, which is preferable. In particular, among aromatic polyamines, various isomers of diaminodiphenyl sulfone represented by the following formula [5] are the most preferable curing agents for obtaining a cured epoxy resin product having good heat resistance and toughness.

  Furthermore, since various isomers of diaminodiphenyl sulfone represented by the above formula [5] have the same sulfone skeleton in the molecule as polyetherimide [B] having a sulfonyl group described later, the resulting cured epoxy resin product This is the most preferable curing agent because of improved compatibility and development of good heat resistance and toughness. It is known that when the compatibility between each component is improved, a uniform cured epoxy resin having a single glass transition temperature is obtained, and its impact resistance, elastic modulus and toughness are improved. As a result, the interlaminar toughness of the fiber-reinforced composite material obtained by curing the epoxy resin composition is improved without adding a large amount of thermoplastic resin to the epoxy resin. Here, the epoxy resin cured product obtained by curing the epoxy resin composition containing the constituent elements [A], [B], and [C] has good compatibility means that an epoxy resin added with a thermoplastic resin. In the sea-island structure seen when a cross-section of the cured epoxy resin obtained by curing the composition is observed with a transmission electron microscope, the diameter of the island phase made of thermoplastic resin is less than 0.1 μm. Say. When the compatibility is high, the cured epoxy resin has high transparency.

  The optimum value of the addition amount of the curing agent [C] for the epoxy resin varies depending on the types of the epoxy resin and the curing agent. For example, in the case of an aromatic polyamine, it is preferable to add it in a stoichiometric equivalent, but the ratio of the amount of active hydrogen of the aromatic polyamine to the amount of epoxy groups of the epoxy resin is about 0.7 to 0.9. By doing this, an epoxy resin cured product having a higher elastic modulus than that obtained when it is added so as to be stoichiometrically equivalent may be obtained, which is also a preferable mode.

  Specific examples of the aromatic polyamine include diaminodiphenylsulfone, diaminodiphenylmethane, phenylenediamine, and various derivatives and positional isomers thereof. Commercially available aromatic polyamines include, for example, “Seika Cure (registered trademark)” S, 4,4′-DDE (Wakayama Seika Kogyo Co., Ltd.), MDA-220 (Mitsui Chemicals, Inc.). , “JER Cure (registered trademark)” W (manufactured by Mitsubishi Chemical Corporation), 3,3′-DAS (manufactured by Mitsui Chemicals), “Lonza Cure (registered trademark)” M-DIPA, “Lonza Cure ( Registered trademark) "M-MIPA (above, manufactured by Lonza), TG4DAS, TG3DAS (above, made by Mitsui Chemicals Fine).

  Specific examples of the acid anhydride curing agent include methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride, methyldihydronaphthic anhydride, methylnadic anhydride, cyclopentanetetra Examples thereof include carboxylic acid dianhydride, nadic anhydride, methyl nadic anhydride, bicyclo (2.2.2) oct-7-2,3,5,6-tetracarboxylic dianhydride. A commercially available product of methyltetrahydrophthalic anhydride is “Licacid (registered trademark)” MT500 (manufactured by Shin Nippon Rika Co., Ltd.). Commercially available products of hexahydrophthalic anhydride include “Licacid (registered trademark)” HH (manufactured by Shin Nippon Rika Co., Ltd.) and HHPA (manufactured by Maruzen Petrochemical Co., Ltd.). Commercial products of methylhexahydrophthalic anhydride include “EPICLON (registered trademark)” B-570, “EPICLON (registered trademark)” B-650 (manufactured by DIC Corporation), and the like. As a commercial product of a mixture of hexahydrophthalic anhydride and methylhexahydrophthalic acid, “Rikacid (registered trademark)” MH700 (Shin Nippon Rika Co., Ltd.) formulated with methylhexahydrophthalic anhydride: hexahydrophthalic anhydride = 70: 30 Co., Ltd.). A commercially available product of methyl nadic anhydride is “Kayahard (registered trademark)” MCD (manufactured by Nippon Kayaku Co., Ltd.). Examples of commercially available trialkyltetrahydrophthalic anhydride include “jER Cure (registered trademark)” YH-306 (manufactured by Mitsubishi Chemical Corporation).

  As the curing agent [C] of the epoxy resin [A] used in the present invention, in addition to the above, a latent material of these curing agents [C], for example, an amine adduct or a microencapsulated one is used. You can also. When such a latent curing agent [C] is used, the storage stability of the prepreg, in particular, tackiness and drape properties are not easily changed even when left at room temperature, and thus, for example, a large structure having a long lamination time A product suitable for manufacturing a body is obtained.

  Moreover, a hardening accelerator can also be mix | blended with an epoxy resin [A] for the purpose of accelerating hardening. Examples of the curing accelerator include urea compounds, tertiary amines and salts thereof, imidazoles and salts thereof, triphenylphosphine or derivatives thereof, carboxylic acid metal salts, Lewis acids, Bronsted acids and salts thereof, and the like. Among these, a urea compound is preferably used from the balance between the storage stability of the prepreg and the catalytic ability. In particular, a combination of a urea compound and dicyandiamide is preferably used.

  Examples of the urea compound include N, N-dimethyl-N ′-(3,4-dichlorophenyl) urea, toluenebis (dimethylurea), 4,4′-methylenebis (phenyldimethylurea), 3-phenyl-1, 1-dimethylurea or the like can be used. Examples of commercially available urea compounds include DCMU99 (manufactured by Hodogaya Chemical Co., Ltd.), “Omicure (registered trademark)” 24, 52, 94 (manufactured by Emerald Performance Materials, LLC).

  It is preferable that the compounding quantity of a urea compound shall be 1-8 mass parts in 100 mass parts of epoxy resins [A]. When the compounding quantity of this urea compound is less than 1 mass part, reaction does not fully advance and the elasticity modulus and heat resistance of epoxy resin hardened | cured material may be insufficient. Moreover, when the compounding quantity of this urea compound exceeds 8 mass parts, since the self-polymerization reaction of an epoxy compound inhibits reaction with an epoxy compound and a hardening | curing agent, the toughness and elastic modulus of epoxy resin hardened | cured material fall. There is a case.

  Moreover, the epoxy resin [A] and the curing agent [C], or a product obtained by pre-reacting a part thereof can be blended in the epoxy resin composition. This method may be effective for adjusting the viscosity of the epoxy resin composition and improving the storage stability of the prepreg.

  The curing agent [C] of these epoxy resins [A] and the curing agent [C] that has made them latent may be used singly or in appropriate combination of two or more. Along with the above aromatic polyamines, secondary amines in which the amino group of the aromatic polyamine is partially alkylated or arylated, secondary amines such as diphenylphenylenediamine, aniline derivatives, aminobiphenyl, aminoanthraquinone, phenylphenol By using a combination of amino compounds having various ring structures such as phenols and phenols, the mechanical properties such as tensile strength of the fiber reinforced composite material and the elastic modulus and toughness of the cured epoxy resin may be effectively improved. . Moreover, you may use combining the compound used as a curing catalyst according to a use and the objective.

  The prepreg of the present invention is a polyetherimide having a sulfonyl group as a thermoplastic resin in an epoxy resin composition in order to combine the excellent interfacial toughness with the fiber-reinforced composite material obtained and the processability when producing the prepreg. It is essential to include [B]. When the polyetherimide [B] having a sulfonyl group is dissolved in the epoxy resin [A] and used, the brittleness of the epoxy resin [A] is covered with the toughness of the polyetherimide [B] having a sulfonyl group, In addition, since the difficulty of molding of the polyetherimide [B] having a sulfonyl group can be covered with the epoxy resin [A], a well-balanced base resin can be obtained as compared with the case where these are used alone. Furthermore, when polyetherimide [B] having a sulfonyl group is used, the blending amount is smaller than that of polyethersulfone generally used as a thermoplastic resin, without impairing processability when producing a prepreg, This is preferable because a fiber-reinforced composite material having high interlayer toughness can be obtained. The blending ratio of the polyetherimide [B] having a sulfonyl group with respect to 100 parts by mass of the total epoxy resin composition is preferably 5 to 25 parts by mass, more preferably 8 to 20 parts by mass, and still more preferably. Is in the range of 8-15 parts by mass. Here, the total epoxy resin composition refers to an epoxy resin composition comprising an epoxy resin [A], a polyetherimide [B] having a sulfonyl group, and a curing agent [C]. If the amount of the polyetherimide [B] having a sulfonyl group is too large, the viscosity of the epoxy resin composition increases, and the processability in producing the epoxy resin composition and prepreg may be impaired. On the other hand, if the amount of the polyetherimide [B] having a sulfonyl group is too small, the toughness of the cured epoxy resin is insufficient, and the interlayer toughness of the fiber reinforced composite material obtained by curing the prepreg may be insufficient. .

Here, the polyetherimide [B] having a sulfonyl group used in the present invention is at least one polyetherimide selected from the group consisting of the following (a), (b) and (c).
(A) A polyetherimide having a sulfonyl group having a repeating unit represented by the following formula [1].

(B) A polyetherimide having a sulfonyl group having a repeating unit represented by the following formula [2].

  In the formula, X is a group of —O— or —O—Z—O—, and the divalent linking group of the group of —O— or —O—Z—O— is the 3,3′-position, In the 4′-position, 4,3′-position, or 4,4′-position, Z is selected from the group consisting of divalent linking groups of the following formula [3].

In the formula, R is selected from the group consisting of —CO—, —SO ₂ —, —CH ₂ —, —O—, —S—, —CH (CH ₃ ) —, —C (CH ₃ ) ₂ —. Represents a divalent linking group. Y is selected from the group consisting of the divalent linking group of the above formula [3]. However, at least one sulfonyl group is contained in one or both of X and Y.
(C) A polyetherimide having a repeating unit represented by the following formula [4] and having a sulfonyl group.

  In the formula, X is a group of —O— or —O—Z—O—, and the divalent linking group of the group of —O— or —O—Z—O— is the 3,3′-position, In the 4′-position, 4,3′-position, or 4,4′-position, Z is selected from the group consisting of divalent linking groups of the following formula [3].

In the formula, R is selected from the group consisting of —CO—, —SO ₂ —, —CH ₂ —, —O—, —S—, —CH (CH ₃ ) —, —C (CH ₃ ) ₂ —. Represents a divalent linking group.

  The polyetherimide [B] having a sulfonyl group (a) is, for example, from 4,4 ′-(4,4′-isopropylidenediphenoxy) bis (phthalic anhydride) and 4,4′-diaminodiphenylmethane. It can be produced according to a known method.

  The polyetherimide [B] having a sulfonyl group (b) is, for example, a known method from an aromatic bis (ether anhydride) represented by the following formula [7] and a diamine represented by the following formula [8]. It can be manufactured according to

(In the formula, X and Y have the same meanings as described above.)
The polyetherimide [B] having a sulfonyl group (c) conforms to a known method from, for example, an aromatic bis (ether anhydride) represented by the above formula [7] and 4,4′-diaminodiphenylmethane. Can be manufactured.

  The polyetherimide [B] having a sulfonyl group used in the present invention can be produced by using a raw material as described above according to a known method, but a commercially available polyetherimide [B] having a sulfonyl group is used. You may do it. As a commercially available product, for example, “ULTEM (registered trademark)” XH6050 (manufactured by SABIC Innovative Plastics Japan LLC) is preferably used.

  In the present invention, polyetherimide [B] having a sulfonyl group having a weight average molecular weight of 70000 g / mol or less is preferably used, more preferably a weight average molecular weight is 10,000 to 60000 g / mol, and still more preferably a weight average molecular weight. Is 35,000 to 60000 g / mol. When the weight average molecular weight of the polyetherimide [B] having a sulfonyl group is within such a range, the epoxy resin cured by curing the epoxy resin composition comprising [A], [B] and [C] of the present invention The product has high toughness, and a fiber-reinforced composite material obtained by curing a prepreg comprising such an epoxy resin composition is preferred because it has high interlaminar toughness. When the weight average molecular weight of the polyetherimide [B] having a sulfonyl group is within such a range, the epoxy resin composition comprising [A], [B], and [C] of the present invention produces a prepreg. This is preferable because of excellent processability. Among these, when the weight average molecular weight of the polyetherimide [B] having a sulfonyl group is 35,000 to 60000 g / mol, the polyetherimide [B] having a large amount of sulfonyl groups [] without lowering the processability when producing the prepreg [ B] can be dissolved in the epoxy resin [A], so that an epoxy resin cured product having higher toughness can be obtained, and high fiber toughness can be imparted to the resulting fiber-reinforced composite material, which is particularly preferable. . Moreover, since the solubility with respect to the epoxy resin [A] of polyetherimide [B] which has a sulfonyl group falls when the weight average molecular weight of polyetherimide [B] which has a sulfonyl group exceeds 70000 g / mol, an epoxy resin In some cases, the process time for preparing the composition becomes long, and the processability may deteriorate.

  Since the polyetherimide [B] having a sulfonyl group used in the present invention has a small weight average molecular weight, the density of the sulfonyl group contained in the epoxy resin composition is small. Therefore, [A], [B] , [C] and the intermolecular interaction between the sulfonyl group in the polyetherimide is reduced, and increase in viscosity of the epoxy resin composition can be suppressed, so that it is preferably used. Furthermore, the polyether imide [B] having a sulfonyl group having a large weight average molecular weight compared to the polyether imide [B] having a sulfonyl group having a small weight average molecular weight is a cured epoxy resin having a high toughness in a small amount. It is preferably used because it can impart high interlaminar toughness to the resulting fiber-reinforced composite material. From the viewpoint of the balance between the viscosity of the epoxy resin composition and the interlaminar toughness of the fiber reinforced composite material, the preferred weight average molecular weight is 45,000 to 70000 g / mol, more preferably 50,000 to 60000 g / mol.

  The polyetherimide [B] having a sulfonyl group preferably has a terminal group that does not react with the epoxy group that is the terminal group of the epoxy resin [A]. As the terminal group of the polyetherimide [B] having a sulfonyl group, for example, any terminal functional group such as an aromatic ring, an amino group, a hydroxyl group, and chlorine can be used, and among them, it reacts with the epoxy group of the epoxy resin [A]. Especially preferred are aromatic rings, chlorine ends. When the end group of the polyetherimide [B] having a sulfonyl group reacts with the epoxy resin [A], the core-shell rubber particles [F] described later may be aggregated, and [A], [B], It becomes difficult to produce a resin film comprising an epoxy resin composition comprising [C] and [F], causing problems in processability when producing a prepreg, and the interlaminar toughness of the fiber-reinforced composite material obtained. It may decrease.

  Here, the cured epoxy resin obtained by curing the epoxy resin composition containing [A], [B], and [C] has a sea-island structure having [A] rich phase and [B] rich phase. May have. In the present invention, the sea-island structure refers to a structure in which a phase mainly composed of different components is phase-separated into a sea phase and an island phase and has a specific structural period. On the other hand, as a preferable embodiment of the cured epoxy resin of the present invention, there is a cured epoxy resin having no [A] rich phase and [B] rich phase. That the cured epoxy resin has no [A] rich phase and [B] rich phase means that the compatibility of the epoxy resin composition is good. Good compatibility means that the thermoplastic resin in the sea-island structure seen when the cross section of the cured epoxy resin obtained by curing the epoxy resin composition to which the thermoplastic resin is added is observed with a transmission electron microscope. The diameter of the island phase consisting of is less than 0.1 μm. Here, the diameter of the island phase indicates the size of the island phase in the sea-island structure, and is a number average value in a predetermined region. When the island phase is elliptical, the major axis is taken, and when it is indefinite, the diameter of the circumscribed circle is used. When the island phase is a circle or ellipse having two or more layers, the diameter of the outermost layer circle or the major axis of the ellipse is used. In the case of a sea-island structure, the major axis of all island phases existing in a predetermined region is measured, and the number average value thereof is taken as the island phase diameter. The diameter of the [B] rich phase island phase in the present invention is preferably less than 0.1 μm. When the island phase diameter is 0.1 μm or more, the obtained fiber-reinforced composite material may not exhibit a sufficient toughness improving effect.

  The polyetherimide [B] having a sulfonyl group may be used in combination with the following commercially available polyetherimide. Some specific examples of such polyetherimides include “ULTEM (registered trademark)” 1000 (number average molecular weight (Mn) 21000 g / mol, Mw 54000 g / mol, polydispersity 2.5), “ULTEM (registered trademark)”. "1010 (Mn 19000 g / mol, Mw 47000 g / mol, polydispersity 2.5)", "ULTEM (registered trademark)" 1040 (Mn 12000 g / mol, Mw 34000 g / mol, polydispersity 2.9), "ULTEM (registered trademark)" “XH6050 (Mn 24000 g / mol, Mw 55000 g / mol, polydispersity 2.2) (all manufactured by SABIC Innovative Plastics Japan G.K.), or a mixture containing one or more of these, is not limited thereto.

  In the present invention, in addition to the polyetherimide [B] having a sulfonyl group, the polyetherimide [B] having a sulfonyl group may be added to the epoxy resin [A] within a range not deteriorating the properties of the epoxy resin [A]. In addition, other thermoplastic resins may be dissolved and used. Such a thermoplastic resin generally has a bond selected from a carbon-carbon bond, amide bond, imide bond, ester bond, ether bond, carbonate bond, urethane bond, thioether bond, sulfone bond and carbonyl bond as the main chain. However, it may have a partially crosslinked structure, and may be crystalline or amorphous. Specifically, polyamide, polycarbonate, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyarylate, polyester, polyamide imide, polyimide, polyether imide, polyimide having phenyltrimethylindane structure, polysulfone, polyether sulfone, polyether ketone, poly Examples include ether ether ketone, polyaramid, polyether nitrile, and polybenzimidazole. As these thermoplastic resins, commercially available polymers may be used, or so-called oligomers having a molecular weight lower than that of commercially available polymers may be used.

  In the epoxy resin composition used as the matrix resin of the prepreg of the present invention, the viscoelasticity is controlled to improve the tack and drape characteristics of the prepreg, or to improve the mechanical properties such as the interlayer toughness of the fiber reinforced composite material. Organic particles such as rubber particles or thermoplastic resin particles [E], inorganic particles, or the like can be blended with the epoxy resin [A].

  In the prepreg of the present invention, among the rubber particles, core-shell rubber particles [F] can be blended for improving the toughness of the fiber-reinforced composite material. Here, the core-shell rubber particle [F] means a part of or the whole surface of the core by a method such as graft polymerization of a particulate core part mainly composed of a polymer such as a crosslinked rubber and a polymer different from the core part. Means coated particles.

  By blending the core-shell rubber particles [F], a fine sea-island structure having an [A] -rich phase and an [F] -rich phase may be formed in the epoxy matrix phase after curing. As a result, the plane strain state generated when the mode I stress is applied to the cured epoxy resin can be eliminated by fracture void formation (cavitation) of the sea-island structure, and plastic deformation of the epoxy matrix phase is induced. As a result, large energy absorption is caused and the interlaminar toughness of the fiber reinforced composite material is improved.

  In the present invention, the phase separation structure refers to a structure in which a phase mainly composed of different components is phase-separated into a sea phase and an island phase and has a specific structural period. Whether or not a phase separation structure is exhibited can be determined by a transmission electron microscope.

  As a preferred embodiment of the cured epoxy resin of the present invention, an epoxy having a sea-island structure having an [A] rich phase and a [F] rich phase, and an island phase diameter of 0.1 to 3 μm. Resin hardened material is mentioned. Here, the diameter of the island phase indicates the size of the island phase in the sea-island structure, and is a number average value in a predetermined region. When the island phase is elliptical, the major axis is taken, and when it is indefinite, the diameter of the circumscribed circle is used. When the island phase is a circle or ellipse having two or more layers, the diameter of the outermost layer circle or the major axis of the ellipse is used. In the case of a sea-island structure, the major axis of all island phases existing in a predetermined region is measured, and the number average value thereof is taken as the island phase diameter.

  The structural period and the diameter of the island phase are preferably in the range of 0.1 to 3 μm, more preferably in the range of 0.1 to 2 μm, and particularly preferably 0.1 to 1 μm. If the structural period is less than 0.1 μm, the toughness of the epoxy resin cured product may be insufficient, and if the structural period exceeds 3 μm, a cavitation effect cannot be obtained in the fiber-reinforced composite material. May not exhibit a sufficient interlayer toughness improving effect.

  The polyetherimide [B] having a sulfonyl group has good compatibility with the epoxy resin [A] used in the present invention. In particular, the polyetherimide [B] having a sulfonyl group having an unreactive terminal is a core-shell rubber. This is preferable because the affinity between the particles [F] and the epoxy resin [A] is further increased. As a result, the core-shell rubber particles [F] are well dispersed in the epoxy resin [A], and the plastic deformation of the epoxy matrix phase becomes large when the mode I stress is applied to the cured epoxy resin, and the interlayer toughness of the resulting fiber reinforced composite material Will improve.

  As the core portion of the core-shell rubber particle [F], a polymer polymerized from one or more selected from a conjugated diene monomer, an acrylate monomer, and a methacrylate ester monomer, or a silicone resin may be used. it can. Specific examples include butadiene, isoprene, and chloroprene, and a cross-linked polymer composed of these alone or in a plurality of types is preferable. In particular, since the properties of the obtained polymer are good and the polymerization is easy, butadiene is used as the conjugated diene monomer, that is, the polymer is polymerized from a monomer containing butadiene as the core component. preferable. In order to effectively improve the interlayer toughness of the fiber reinforced composite material in the present invention, the glass transition temperature of the core portion of the core-shell rubber particles [F] to be blended in the epoxy resin composition is more preferably −50 ° C. or lower. preferable.

  The shell component constituting the core-shell rubber particle [F] is preferably graft-polymerized to the above-described core component and chemically bonded to the polymer particle constituting the core component. The component constituting such a shell component is a polymer polymerized from one or more selected from, for example, methacrylic acid esters and aromatic vinyl compounds. In addition, in order to stabilize the dispersion state of the core-shell rubber particles [F], a functional group that reacts with the component contained in the epoxy resin composition of the present invention or the curing agent [C] component is introduced into the shell component. It is preferable. When such a functional group is introduced, the affinity with the epoxy resin [A] is improved, and finally it can react with the epoxy resin composition and be incorporated into the cured epoxy resin. Therefore, good dispersibility of the core-shell rubber particles [F] can be achieved. As a result, even if a small amount of the core-shell rubber particles [F] is blended, a sufficient toughness improving effect can be obtained, and the toughness of the cured epoxy resin can be improved while maintaining heat resistance and elastic modulus. Examples of such a functional group include a hydroxyl group, a carboxyl group, and an epoxy group, and among these, an epoxy group is particularly preferable from the viewpoint of improving the affinity with the epoxy resin [A]. As a method for introducing such a functional group into the shell portion, one or more components such as acrylic acid esters and methacrylic acid esters containing such a functional group are used as part of the monomer on the core surface. Examples thereof include a graft polymerization method.

  The core-shell rubber particles [F] preferably have a volume average particle diameter in the range of 0.3 μm. In particular, the thickness is preferably 0.05 to 0.3 μm, and more preferably 0.05 to 0.15 μm. The volume average particle diameter can be measured using a nanotrack particle size distribution measuring apparatus (manufactured by Nikkiso Co., Ltd., dynamic light scattering method). Alternatively, a thin section of a cured epoxy resin produced with a microtome can be observed with a transmission electron microscope, and the volume average particle diameter can be measured using image processing software from the obtained transmission electron microscope image. In this case, it is necessary to use an average value of at least 100 particles. When the volume average particle diameter of the core-shell rubber particles [F] is 0.05 μm or more, the specific surface area of the core-shell rubber particles [F] is moderately small and advantageous in terms of energy, so that aggregation does not easily occur and the toughness of the cured epoxy resin product The improvement effect is high and preferable. On the other hand, when the volume average particle diameter of the core-shell rubber particles [F] is 0.3 μm or less, the distance between the core-shell rubber particles [F] is suitably reduced, and the effect of improving the toughness of the cured epoxy resin is preferable.

  There is no restriction | limiting in particular about the manufacturing method of core-shell rubber particle [F], The thing manufactured by the well-known method can be used. Commercially available core-shell rubber particles [F] include, for example, “Paraloid (registered trademark)” EXL-2655 (Rohm & Haas Co.) made of butadiene / alkyl methacrylate / styrene copolymer, acrylic ester / methacrylate ester "STAPHYLOID (registered trademark)" AC-3355 made of a polymer, TR-2122 (manufactured by Ganz Kasei Co., Ltd.), "PARALOID (registered trademark) made of butyl acrylate / methyl methacrylate copolymer" ) "EXL-2611, EXL-3387 (manufactured by Rohm & Haas), etc. can be used. Further, a glassy polymer core layer having a glass transition temperature of room temperature or higher, such as Staphyloid IM-601, IM-602 (manufactured by Gantz Kasei Co., Ltd.), is an intermediate layer of a rubbery polymer having a low glass transition temperature. A core-shell rubber particle [F] having a three-layer structure, which is covered with a shell layer around it, can also be used.

  Usually, these core-shell rubber particles [F] are crushed and treated as a powder by pulverizing them, and the powdered core-shell rubber is often dispersed again in the epoxy resin composition. However, this method has a problem that it is difficult to stably disperse particles in a state without aggregation, that is, in a state of primary particles. In order to solve this problem, the core-shell rubber particles [F] were not removed in a lump from the production process, but finally dispersed as primary particles in one component of the epoxy resin [A], for example, the epoxy resin [A]. A preferable dispersion state can be obtained by using a material that can be handled in the state of a master batch. The core-shell rubber particles [F] that can be handled in such a masterbatch state can be produced, for example, by the method described in JP-A-2004-315572. In this production method, first, a suspension in which the core-shell rubber particles [F] are dispersed is obtained by a method of polymerizing the core-shell rubber in an aqueous medium represented by emulsion polymerization, dispersion polymerization, and suspension polymerization. Next, an organic solvent having partial solubility with water, such as a ketone solvent such as acetone or methyl ethyl ketone, or an ether solvent such as tetrahydrofuran or dioxane, is mixed into the suspension, and then a water-soluble electrolyte such as sodium chloride or chloride. Potassium is contacted, the organic solvent layer and the aqueous layer are phase-separated, and the aqueous layer is separated and removed to obtain an organic solvent in which the core-shell rubber particles [F] are dispersed. Thereafter, after mixing the epoxy resin [A], the organic solvent is removed by evaporation to obtain a master batch in which the core-shell rubber particles [F] are dispersed in the state of primary particles in the epoxy resin [A]. As the core-shell rubber particles [F] -dispersed epoxy masterbatch produced by such a method, “Kane Ace (registered trademark)” commercially available from Kaneka Corporation can be used.

  The compounding amount of the core-shell rubber particles [F] in the epoxy resin composition is 1 to 12 parts by mass out of 100 parts by mass of the total epoxy resin composition from the viewpoint of mechanical properties and processability when producing the prepreg. It is preferably 1-10 parts by mass, more preferably 2-8 parts by mass. When the blending amount is less than 1 part by mass, the toughness and plastic deformation ability of the cured epoxy resin may be lowered, and the interlaminar toughness of the resulting fiber-reinforced composite material may be lowered. On the other hand, when the blending amount exceeds 12 parts by mass, the core-shell rubber particles [F] are agglomerated with each other, so that the elastic modulus of the cured epoxy resin is significantly reduced, and the compression strength of the resulting fiber-reinforced composite material is reduced. In addition, the flow of the epoxy resin composition at the molding temperature may be insufficient, and the resulting fiber reinforced composite material may contain voids.

  As a method of mixing the core-shell rubber particles [F] in the epoxy resin [A], a commonly used dispersion method can be used. Examples thereof include a method using a three-roll, ball mill, bead mill, jet mill, homogenizer, rotation / revolution mixer, and the like. Moreover, the method of mixing the above-mentioned core shell rubber particle [F] dispersion | distribution epoxy masterbatch can also be used preferably. However, even if the core-shell rubber particles [F] are dispersed in the form of primary particles, re-aggregation may occur due to excessive heating or a decrease in viscosity. Therefore, when the core-shell rubber particles [F] are dispersed, blended, and mixed and kneaded with other components after the dispersion, it is preferably performed within a temperature and viscosity range in which re-aggregation of the core-shell rubber particles [F] does not occur. Specifically, although it varies depending on the composition, for example, when kneaded at a temperature of 150 ° C. or higher, the viscosity of the epoxy resin composition may decrease and the core-shell rubber particles [F] may be aggregated. It is preferable to knead. However, in the case where the temperature reaches 150 ° C. or higher during the curing process, re-aggregation of the core-shell rubber particles [F] is hindered with the gelation of the epoxy resin composition at the time of temperature rise, and thus can exceed 150 ° C.

  The viscosity at 80 ° C. of the epoxy resin composition comprising [A], [B], [C], and [F] of the present invention is preferably 1 to 1000 Pa · s. When the viscosity at 80 ° C. of such an epoxy resin composition is less than 1 Pa · s, it may be difficult to produce a resin film because the viscosity is too low, which may cause problems in processability when producing a prepreg, or may be produced. The prepreg thus obtained is difficult to maintain its shape, and the prepreg may be cracked. Moreover, when the viscosity at 80 ° C. of such an epoxy resin composition exceeds 1000 Pa · s, it may be difficult to produce a resin film because the viscosity is too high, and there may be a problem in processability when producing a prepreg, When producing a prepreg, the epoxy resin composition applied between the reinforcing fibers [D] may not be sufficiently impregnated. For this reason, a void is produced in the obtained fiber reinforced composite material, and the interlayer toughness of the fiber reinforced composite material may be lowered. The viscosity at 80 ° C. of the epoxy resin composition comprising [A], [B], [C], and [F] of the present invention is such that a resin film can be easily produced in the prepreg manufacturing process, and the reinforcing fiber. In order to produce a prepreg in which the resin is easily impregnated between [D], it is more preferably in the range of 5 to 300 Pa · s, and still more preferably in the range of 5 to 200 Pa · s.

  The thermoplastic resin particles [E] preferably used in the present invention are the same as the various thermoplastic resins exemplified above, and a thermoplastic resin that can be used by mixing with an epoxy resin composition is used. it can. Of these, polyamide is most preferable. Among polyamides, nylon 12, nylon 6, nylon 66, nylon 11, nylon 6/12 copolymer, and epoxy compound described in Example 1 of JP-A-01-104624 and semi-IPN ( Nylon (semi-IPN nylon) or the like having a polymer interpenetrating network structure gives particularly good adhesive strength with the epoxy resin [A]. The shape of the thermoplastic resin particles [E] may be spherical particles, non-spherical particles, or porous particles, but the spherical shape is superior in viscoelasticity because it does not deteriorate the flow characteristics of the epoxy resin composition. This is a preferred embodiment in that there is no starting point of stress concentration and high impact resistance is imparted to the resulting fiber-reinforced composite material. Examples of commercially available polyamide particles include SP-500, SP-10, TR-1, TR-2, 842P-48, 842P-80, “Trepearl (registered trademark)” TN (above, manufactured by Toray Industries, Inc.), “Orgasol (registered trademark)” 1002D, 2001UD, 2001EXD, 2002D, 3202D, 3501D, 3502D (manufactured by Arkema Co., Ltd.) and the like can be used.

  The thermoplastic resin particles [E] preferably used in the present invention are blended in an amount of 5 to 40 parts by mass with respect to 100 parts by mass of the total epoxy resin composition from the viewpoint of achieving both the elastic modulus and toughness of the resulting cured epoxy resin. More preferably, it is 10-35 mass parts, More preferably, 15-30 mass parts can be mix | blended.

  Furthermore, a layer rich in thermoplastic resin particles [E], that is, a layer where the state in which the thermoplastic resin particles [E] are present locally can be clearly observed when the cross section thereof is observed (hereinafter, It may be abbreviated as a particle layer.) Is preferably a structure formed in the vicinity of the surface of the prepreg.

  By adopting such a structure, when a prepreg is laminated and an epoxy resin is cured to form a fiber reinforced composite material, a resin layer is easily formed between the prepreg layers, that is, the composite material layers, and thereby the composite Adhesion and adhesion between the material layers are enhanced, and the resulting fiber-reinforced composite material exhibits high impact resistance.

  From such a viewpoint, the particle layer is preferably 20% deep, more preferably 10% deep from the surface of the prepreg in the thickness direction starting from the surface with respect to 100% of the thickness of the prepreg. It is preferable that it exists in the range. Further, the particle layer may be present only on one side, but care must be taken because the prepreg can be front and back. If the prepreg stacking is mistaken and there are layers with and without particles, a composite material that is vulnerable to impacts will result. In order to eliminate the distinction between front and back and facilitate lamination, the particle layer should be present on both the front and back sides of the prepreg.

  Furthermore, the ratio of the thermoplastic resin particles [E] present in the particle layer is preferably 90 to 100 parts by mass, more preferably 100 parts by mass with respect to the total amount of the thermoplastic resin particles [E] in the prepreg. Is 95 to 100 parts by mass.

  The abundance of the thermoplastic resin particles [E] can be evaluated by, for example, the following method. That is, the prepreg is sandwiched between two smooth polytetrafluoroethylene resin plates with a smooth surface, and the temperature is gradually raised to the curing temperature over 7 days to gel and cure to cure the plate-like prepreg. Make a thing. Two lines parallel to the surface of the prepreg are drawn on both surfaces of the prepreg cured product from the surface of the prepreg cured product at a depth of 20% of the thickness. Next, the total area of the thermoplastic resin particles [E] existing between the surface of the prepreg and the above line and the total area of the thermoplastic resin particles [E] existing over the thickness of the prepreg are obtained, and the prepreg The abundance ratio of the thermoplastic resin particles [E] existing in a range of 20% depth from the surface of the prepreg is calculated with respect to the thickness of 100%. Here, the total area of the thermoplastic resin particles [E] is obtained by cutting out the thermoplastic resin particle [E] portion from the cross-sectional photograph and converting from the mass. In the case where it is difficult to discriminate the thermoplastic resin particles [E] dispersed in the resin after photography, a means for dyeing the thermoplastic resin particles [E] can also be employed.

  In addition, the epoxy resin [A] of the present invention is blended with inorganic particles such as silica gel, carbon particles, clay, carbon nanotubes, carbon black, and metal powder, inorganic filler, and the like within a range that does not interfere with the effects of the present invention. Can do. Examples of carbon black include channel black, thermal black, furnace black, and ketjen black.

  In order to obtain the epoxy resin composition of the prepreg of the present invention, components other than the curing agent [C] are uniformly heated and kneaded at about 150 ° C., cooled to a temperature at which the curing reaction does not proceed easily, and then the curing agent [C]. However, the method of blending each component is not particularly limited to this method.

  In addition, the epoxy resin cured product obtained by curing the epoxy resin composition in the present invention is preferably one cured at a curing temperature of 120 to 200 ° C. for a curing time of 1 to 12 hours. It is preferable that the temperature of the epoxy resin at the time of curing falls within this temperature range, and the temperature is increased and the heat removal method is appropriately set for curing. In addition, it is preferable that the hardening degree of the obtained epoxy resin hardened | cured material exceeds 80%. Here, the degree of curing means that the calorific values of the cured epoxy resin and the uncured epoxy resin composition are evaluated by differential scanning calorimetry at a heating rate of 10 ° C./min in an inert gas atmosphere, and 100 The area of the peak appearing at ℃ to 300 ℃ was calculated as the respective calorific value of the resin composition, and {(calorific value of the uncured epoxy resin composition) − (caloric value of the cured epoxy resin)} / (uncured value) The calorific value of the epoxy resin composition) is a value calculated according to the formula of 100%. The amount of heat generated by the cured epoxy resin when the degree of cure exceeds 80% depends on the amount of heat generated by the uncured resin, but when it contains a trifunctional or higher amine type epoxy resin, the cured epoxy resin It is a standard that the calorific value (which may be expressed as the residual calorific value) is 70 J / g or less.

  As a method for dissolving the polyetherimide [B] having a sulfonyl group in the epoxy resin [A], in addition to the method for dissolving by heating as described above, the polyetherimide [B] having a sulfonyl group may be dissolved in acetone or methyl ethyl ketone. Alternatively, a method in which a solvent dissolved in a solvent such as toluene is mixed with the epoxy resin [A] to make it uniform and then the solvent is distilled off can be used. However, the blending method of each component is not particularly limited to these methods.

  The kneading method of the epoxy resin composition used for the prepreg of the present invention may be any method generally used for preparing an epoxy resin composition. For example, a kneader, a planetary mixer, a three roll or the like is used.

  Moreover, the fiber reinforced composite material of this invention can be manufactured by the method of heat-hardening an epoxy resin composition etc., providing a heat | fever and a pressure to the obtained laminated body after laminating | stacking a single or several prepreg.

  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, and the like are used. In particular, an autoclave molding method is preferably used for aircraft member molding, and a wrapping tape method and an internal pressure molding method are preferably used for sports equipment molding.

  The conditions for molding the prepreg of the present invention using an autoclave are appropriately set according to the viscoelasticity of the prepreg, the number of laminated layers, the size, etc., and the heat resistance of the fiber-reinforced composite material after curing. A pressure range of 0.1 to 1 MPa and a curing temperature of 120 to 200 ° C. are preferably used. In particular, a pressure range of 0.3 to 0.7 MPa and a curing temperature of 170 to 190 ° C. are more preferably used. When raising the temperature from room temperature to the curing temperature, the temperature may be increased to a curing temperature at a constant rate, or may be maintained for a certain period of time at an intermediate temperature, and then increased to the curing temperature (hereinafter referred to as this). A curing method using a stepwise temperature rising method is sometimes referred to as step cure). When molding a large structure, even if the temperature is set at a constant speed, uneven temperature rise occurs in the large autoclave, or the epoxy resin cured product is accumulated by heat buildup inside the structure at the time of temperature rise. Unexpected mechanical property changes and runaway reactions occur, and the flow time of the epoxy resin composition becomes insufficient with respect to the size of the structure, so that the epoxy resin composition has a gap between the reinforcing fibers [D]. Impregnation failure may occur. In order to solve such problems, step cure as described above may be used effectively. In order to improve the impregnation between the reinforcing fibers [D] of the epoxy resin composition, a partially impregnated prepreg as described above can also be used. When the pressure at the time of molding is too low, many voids are generated in the fiber-reinforced composite material after molding and the mechanical properties may be lowered. Therefore, it is preferable to set appropriate conditions according to the prepreg to be used. In addition, it is necessary to appropriately select materials that can withstand the molding conditions to be applied as materials used for autoclave molding.

  The fiber-reinforced composite material of the present invention is used for aircraft structural members, windmill blades, automobile outer panels, IC trays, notebook PC casings (housings) and other computer applications, building materials, and golf shafts and tennis rackets and other sports applications. Can be preferably used.

  Hereinafter, the prepreg and the fiber-reinforced composite material of the present invention will be described more specifically with reference to examples. The production methods and evaluation methods of the resin raw materials, prepregs and fiber reinforced composite materials used in the examples are shown below. The production environment and evaluation of the prepregs of the examples are performed in an atmosphere at a temperature of 25 ° C. ± 2 ° C. and a relative humidity of 50% unless otherwise specified.

<Epoxy resin [A]>
ELM434 (tetraglycidyldiaminodiphenylmethane, epoxy equivalent: 120, manufactured by Sumitomo Chemical Co., Ltd.)
"Araldite (registered trademark)" MY721 (tetraglycidyldiaminodiphenylmethane, epoxy equivalent: 113, manufactured by Huntsman Advanced Materials (hereinafter referred to as Huntsman))
"Araldite (registered trademark)" MY0600 (triglycidyl-m-aminophenol, epoxy equivalent: 118, manufactured by Huntsman)
JER806 (Bisphenol F type epoxy resin, epoxy equivalent: 165, manufactured by Mitsubishi Chemical Corporation)
GAN (N, N-diglycidylaniline, epoxy equivalent: 125, manufactured by Nippon Kayaku Co., Ltd.).

<Curing agent [C]>
"Seika Cure" (registered trademark) -S (4,4'-diaminodiphenyl sulfone, manufactured by Wakayama Seika Co., Ltd.)
・ 3,3′-DAS (3,3′-diaminodiphenylsulfone, manufactured by Mitsui Chemicals Fine Co., Ltd.)
-4,4'-DDE (4,4'-diaminodiphenyl ether, manufactured by Wakayama Seika Co., Ltd.).

<Carbon fiber (reinforced fiber [D])>
"Torayca (registered trademark)" T800G-24K-31E (carbon fiber with 24,000 filaments, tensile strength 5.9 GPa, tensile elastic modulus 294 GPa, tensile elongation 2.0%, manufactured by Toray Industries, Inc.).

<Thermoplastic resin particles [E]>
-Semi-IPN nylon particles A obtained by the following production method
90 parts by mass of transparent polyamide (trade name “Grillamide (registered trademark)”-TR55, manufactured by Emschem Japan Co., Ltd.), epoxy resin (trade name “jER (registered trademark)” 828 (manufactured by Mitsubishi Chemical Corporation)) 7 0.5 part by mass and a curing agent (trade name “Tomide (registered trademark)” # 296, manufactured by Fuji Kasei Kogyo Co., Ltd.) in a mixed solvent of 300 parts by mass of chloroform and 100 parts by mass of methanol Addition to obtain a homogeneous solution. Next, the obtained uniform solution was atomized using a spray gun for coating, well stirred, and sprayed toward the liquid surface of 3000 parts by mass of n-hexane to precipitate a solute. The precipitated solid was separated by filtration and washed well with n-hexane, followed by vacuum drying at a temperature of 100 ° C. for 24 hours to obtain spherical semi-IPN nylon particles A having a volume average particle diameter of 13.0 μm.

<Core shell rubber particles [F]>
"Kane Ace (registered trademark)" MX416 (manufactured by Huntsman Tetraglycidyldiaminodiphenylmethane ("Araldite (registered trademark)" MY721): 75% by mass / core shell rubber particles (volume average particle size: 0.1 μm, core part: crosslinked polybutadiene) [Glass transition temperature: −70 ° C.] Shell portion: methyl methacrylate / glycidyl methacrylate / styrene copolymer): 25% by mass master batch, epoxy equivalent: 150, manufactured by Kaneka Corporation)
“Kane Ace (registered trademark)” MX136 (bisphenol F type epoxy resin (“Araldite (registered trademark)” GY285) manufactured by Huntsman Co., Ltd.): 75% by mass / core shell rubber particles (volume average particle size: 0.1 μm, core portion: crosslinked) Polybutadiene [glass transition temperature: −70 ° C.], shell portion: methyl methacrylate / glycidyl methacrylate / styrene copolymer): 25% by mass master batch, epoxy equivalent: 220, manufactured by Kaneka Corporation).

<Thermoplastic resin [B]>
-Polyetherimide having a sulfonyl group [B1]
“Ultem (registered trademark)” XH6050 (polyetherimide, manufactured by SABIC Innovative Plastics), weight average molecular weight (Mw) 55000 g / mol).

  -Polyetherimide [B2] synthesized by the following method

(Preparation of polyamic acid stock solution)
Tetrahydrofuran (THF, 200 ml) was added to a 3-neck 1 liter round bottom flask fitted with a Dean-Stark apparatus under an inert argon gas atmosphere. THF was heated to reflux at 76 ° C. 4,4 ′-(4,4′-isopropylidenediphenoxy) bis (phthalic anhydride) (BPADA) (67.5 g, 129.8 mmol, manufactured by SABIC Innovative Plastics) over 10 minutes Of refluxing THF. After decomposition of 4,4 ′-(4,4′-isopropylidenediphenoxy) bis (phthalic anhydride), 4,4′-diaminodiphenylsulfone (32.2 g, 129.5 mmol, Wakayama Seika Co., Ltd.) in 100 ml of THF ) Was dissolved in the flask under reflux over 10 minutes. After maintaining the reaction mixture under reflux for a further 80 minutes, 100 ml of distillate was distilled. Thereafter, while continuing the distillation, triethylamine (26.3 g) and deionized (DI) water (400 ml) were simultaneously added to the flask over 25 minutes. The total amount of distillate collected was 280 ml. Thereafter, the flask was cooled to room temperature (25 ° C.) to obtain an aqueous solution of triethylamine salt of polyamic acid.

(Determination of polyamic acid concentration in polyamic acid stock solution)
A sample (2 to 3 g) weighed from the polyamic acid stock solution prepared above was heated in a vial at 250 ° C. for 15 minutes to obtain a solid oligomer polyimide. The solid content was weighed to determine the mass% in the polyamic acid stock solution. The solid mass% corresponds to the polyamic acid concentration in the polyamic acid stock solution. As described above, the solid content needs to be applied to the polyamic acid in a solvent removal step that also serves as an imidization reaction, and then the amount of the obtained polyetherimide was measured. The solid content mass% was 15.5%.

(Molecular weight of polyetherimide formed from polyamic acid)
A small amount of polyamic acid stock solution was heated in an open container at 250 ° C. for 15 minutes. This achieved two removals of solvent and conversion (curing) of the polyamic acid to the corresponding polyimide. The resulting solid polyetherimide was dissolved in chloroform and its molar weight was measured by gel permeation chromatography. The weight average molecular weight (Mw) of the obtained polyetherimide was 35000 g / mol.

  -Polyetherimide [B3] synthesized by the following method

(Preparation of polyamic acid stock solution)
Tetrahydrofuran (THF, 200 ml) was added to a 3-neck 1 liter round bottom flask fitted with a Dean-Stark apparatus under an inert argon gas atmosphere. THF was heated to reflux at 76 ° C. 4,4′-oxydiphthalic anhydride (40.3 g, 129.8 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.) was added to the refluxing THF over 10 minutes. After decomposition of 4,4′-oxydiphthalic anhydride, a solution in which 4,4′-diaminodiphenyl sulfone (32.2 g, 129.5 mmol, manufactured by Wakayama Seika Co., Ltd.) was dissolved in 100 ml of THF for 10 minutes or more. To the flask under reflux. After maintaining the reaction mixture under reflux for a further 80 minutes, 100 ml of distillate was distilled. Thereafter, while continuing the distillation, triethylamine (26.3 g) and deionized (DI) water (400 ml) were simultaneously added to the flask over 25 minutes. The total amount of distillate collected was 280 ml. Thereafter, the flask was cooled to room temperature (25 ° C.) to obtain an aqueous solution of triethylamine salt of polyamic acid.

(Determination of polyamic acid concentration in polyamic acid stock solution)
A sample (2 to 3 g) weighed from the polyamic acid stock solution prepared above was heated in a vial at 250 ° C. for 15 minutes to obtain a solid oligomer polyimide. The solid content was weighed to determine the mass% in the polyamic acid stock solution. The solid mass% corresponds to the polyamic acid concentration in the polyamic acid stock solution. As described above, the solid content needs to be applied to the polyamic acid in a solvent removal step that also serves as an imidization reaction, and then the amount of the obtained polyetherimide was measured. The solid content mass% was 15.5%.

(Molecular weight of polyetherimide formed from polyamic acid)
A small amount of polyamic acid stock solution was heated in an open container at 250 ° C. for 15 minutes. This achieved two removals of solvent and conversion (curing) of the polyamic acid to the corresponding polyimide. The resulting solid polyetherimide was dissolved in chloroform and its molar weight was measured by gel permeation chromatography. The weight average molecular weight (Mw) of the obtained polyetherimide was 35000 g / mol.

<Other polyetherimides>
“Ultem (registered trademark)” 1040 (manufactured by SABIC Innovative Plastics, Inc., weight average molecular weight (Mw) 35000 g / mol).

<Polyethersulfone>
"Sumika Excel (registered trademark)" PES5003P (manufactured by Sumitomo Chemical Co., Ltd., weight average molecular weight (Mw) 42000 g / mol).

(1) Preparation of epoxy resin composition [Examples 1 to 19] [Comparative Examples 1 to 7]
A predetermined amount of components other than the curing agent and the thermoplastic resin particles were added to the kneader, kneaded, heated and mixed at 150 ° C. to uniformly dissolve, and then kneaded at 150 ° C. for 1 hour. After the temperature was lowered to 80 ° C. while kneading, thermoplastic resin particles were added and kneaded, and then a curing agent was added and kneaded to prepare epoxy resin compositions having the compositions shown in Tables 1 and 3. In addition, the value of the epoxy resin composition in Tables 1 and 3 indicates parts by mass.

[Examples 20 to 42] [Comparative Examples 8 to 10]
In a kneader, a predetermined amount of epoxy resin, a master batch of core-shell rubber particles, and a polyetherimide having a sulfonyl group were added, kneaded, heated and mixed at 150 ° C. to uniformly dissolve, and then kneaded at 150 ° C. for 1 hour. . After the temperature was lowered to 80 ° C. while kneading, thermoplastic resin particles were added and kneaded, and then a curing agent was added and kneaded to prepare epoxy resin compositions having the compositions shown in Tables 2 and 4. In addition, the value of the epoxy resin composition in Tables 2 and 4 indicates parts by mass.

(2) Viscosity measurement of epoxy resin composition Except for not adding thermoplastic resin particles, the viscosity of the epoxy resin composition prepared by the method of (1) above is a dynamic viscoelasticity measuring device ARES (manufactured by TA Instruments). It measured using. Using a parallel plate with a diameter of 40 mm, the temperature is simply raised at a rate of temperature rise of 2 ° C./min, and the value at 80 ° C. of the complex viscosity (η ^* ) obtained under the measurement conditions of frequency 0.5 Hz and Gap 1 mm It was adopted as the viscosity of the composition.

(3) Morphology After defoaming the epoxy resin composition prepared in (1) in a vacuum, in a mold set to a thickness of 2 mm with a 2 mm thick “Teflon (registered trademark)” spacer, 180 ° C. Was cured at a temperature of 2 mm for 2 hours to obtain a cured epoxy resin having a thickness of 2 mm. This epoxy resin cured product was destroyed by applying a razor blade to a test piece cut to a size of 10 mm × 60 mm and applying an impact with a hammer, and a transmission electron microscope (TEM, trade name: M-800 type, Hitachi Ltd., the same applies hereinafter).

  In the case of the morphology of the cured epoxy resin composed of [A], [B], and [C], a structure having a sea-island structure of [A] rich phase and [B] rich phase and an island phase diameter of less than 0.1 μm One having a period was designated as “◯”, and one having an island-island structure period of 0.1 μm or more was designated as “x”.

  In the case of the morphology of the cured epoxy resin comprising [A], [B], [C], and [F], it has a sea-island structure of [A] rich phase and [F] rich phase, and the diameter of the island phase Having a range of 0.1 to 1 μm is “◎”, those having a range of more than 1 μm and 3 μm or less are “◯”, and those having a range of more than 3 μm are “x”.

  In addition, the diameter of an island phase shows the magnitude | size of the island phase in a sea island structure, and is a number average value in a predetermined area | region. When the island phase is elliptical, the major axis is taken, and when it is indefinite, the diameter of the circumscribed circle is used. When the island phase is a circle or ellipse having two or more layers, the diameter of the outermost layer circle or the major axis of the ellipse was used. In the case of a sea-island structure, the major axis of all island phases existing in a predetermined region was measured, and the number average value of these was used as the island phase diameter.

(4) Preparation of prepreg The epoxy resin composition prepared in (1) was applied onto release paper using a knife coater to prepare a resin film. Next, two resin films are stacked on both sides of the carbon fiber on a carbon fiber “Treca” (registered trademark) T800G-24K-31E manufactured by Toray Industries, Ltd., which is arranged in one direction in a sheet shape, and heated and pressed. The resin was impregnated with carbon fiber to obtain a unidirectional prepreg having a carbon fiber basis weight of 190 g / m ² and a matrix resin weight fraction of 35.5%.

(5) Measurement of Interlaminar Toughness (Mode I Interlaminar Toughness) of Fiber Reinforced Composite Material Preparation of Composite Plate for Mode I Interlaminar Toughness (G _IC ) Test and G _IC Measurement According to JIS K7086, to prepare a composite material made flat for G _IC test by the operation of the f).
(A) The unidirectional prepreg produced in (4) was laminated in 20 ply with the fiber direction aligned. However, a resin film having a width of 40 mm was sandwiched between the laminated central surfaces (between the 10th and 11th ply) and perpendicular to the fiber arrangement direction.
(B) The laminated prepreg was covered with a nylon film so that there was no gap, and cured by heating and pressing at 180 ° C. and an internal pressure of 0.6 MPa for 2 hours in an autoclave to form a unidirectional fiber-reinforced composite material.
(C) The unidirectional fiber reinforced composite material obtained in (b) was cut into a width of 20 mm and a length of 195 mm. The fiber direction was cut so as to be parallel to the length side of the sample.
(D) In accordance with JIS K7086, a pin load block (length: 25 mm, made of aluminum) was bonded to the end of the test piece (side of the film).
(E) The film insertion part was opened with a sharp blade such as a knife, and a pre-crack of 2 mm to 5 mm was introduced.
(F) A white paint was applied to both sides of the test piece in order to make it easier to observe the crack propagation.
· Fabricated using a composite material made of a flat plate, the following procedures were performed G _IC measurement.

In accordance with JIS K7086 (2006), a test was performed using an Instron universal testing machine (Instron). The crosshead speed was 0.5 mm / min until the crack growth reached 20 mm, and 1 mm / min after reaching 20 mm. Load, displacement, and, from the crack length _was calculated _{G IC.}

Example 1
In a kneading apparatus, 40 parts by mass of GAN, 60 parts by mass of ELM434 (epoxy resin [A]) and 10 parts by mass of “Ultem (registered trademark)” XH6050 (polyetherimide having a sulfonyl group [B]) were kneaded. Thereafter, 25 parts by mass of semi-IPN nylon particles A, which are thermoplastic resin particles [E], and 42 parts by mass of “Seica Cure (registered trademark)” S, which is a curing agent [C], are kneaded and used for a fiber-reinforced composite material. An epoxy resin composition was prepared. Table 1 shows the composition and ratio (in Table 1, the numbers represent parts by mass). About the obtained epoxy resin composition, the viscosity was measured according to said (2). Moreover, the obtained epoxy resin composition was coated on a release paper with a resin basis weight of 52 g / m ² using a knife coater to prepare a resin film. This resin film is superposed on both sides of carbon fiber (weight per unit area 190 g / m ² ) aligned in one direction, and a heat roll is used to heat and press the epoxy resin composition at a temperature of 100 ° C. and 0.1 MPa. To obtain a prepreg. The obtained prepreg was carried out as described in Preparation and G _IC measurement of the above (5) Mode I Interlaminar toughness (G _IC) test composite made flat, to produce a fiber-reinforced composite material, the G _IC It was measured.

(Examples 2 to 42, Comparative Examples 1 to 10)
An epoxy resin composition and a prepreg were produced in the same manner as in Example 1 except that the types and blending amounts of the epoxy resin and the curing agent were changed as shown in Tables 1 to 4. About the obtained epoxy resin composition, the viscosity was measured according to said (2). Further, the obtained prepreg, and performed as described in Preparation and G _IC measurement of the above (5) Mode I Interlaminar toughness (G _IC) test composite made flat, to produce a fiber-reinforced composite material, G _IC was measured. The results are shown in Tables 1-4.

From the comparison between Examples 1 to 19 and Comparative Examples 1 to 7, it can be seen that the fiber-reinforced composite material using the epoxy resin composition of the present invention has excellent mode I interlayer toughness (G _IC ).

Further, in comparison with Comparative Examples 1 and 2 with Examples 1-5, when using thermoplastic resin not having a sulfonyl group, it can be seen that adequate mode I interlayer toughness (G _IC) can not be obtained.

Further, by comparing Example 6 with Comparative Example 6, the mode I interlayer toughness (G _IC ) when the blending amount of the polyetherimide having a sulfonyl group is 5 parts by mass is a thermoplastic resin having no sulfonyl group. It can be seen that this is superior to the mode I interlaminar toughness (G _IC ) when the blending amount is 20 parts by mass.

  Moreover, by contrast with Examples 1-19 and the comparative example 3, even if the component [A] and [C] are mix | blended with predetermined amount, when the component [B] is not mix | blended together, It can be seen that the viscosity of the epoxy resin composition is too low to produce a resin film, and there is a problem in processability when producing a prepreg.

From the comparison between Examples 20 to 42 and Comparative Examples 8 to 10, it is found that sufficient mode I interlayer toughness (G _IC ) cannot be obtained when a thermoplastic resin having no sulfonyl group is used. Since the thermoplastic resin does not have a sulfonyl group, the affinity between the core-shell rubber particles and the epoxy resin becomes insufficient, causing the core-shell rubber particles to aggregate with each other, and the plane generated when the mode I stress is applied to the cured epoxy resin This is probably because the distorted state cannot be eliminated by cavitation.

According to the comparison between Example 26 and Comparative Example 10, even when the core-shell rubber particles are contained, the mode I interlayer toughness (G _IC ) when the blending amount of the polyetherimide having a sulfonyl group is 5 parts by mass is It turns out that the compounding quantity of the thermoplastic resin which does not have a sulfonyl group is superior to the case where it is 20 mass parts.

  According to the present invention, since a fiber-reinforced composite material having excellent processability when producing a prepreg and having excellent interlayer toughness can be obtained, it can be widely applied to aircraft structural members, windmill blades, automobile outer plates, and the like. Can and is useful.

Claims (23)

A prepreg comprising at least the following [A], [B], [C], and [D].
[A] Epoxy resin [B] At least one polyetherimide selected from the group consisting of the following (a), (b) and (c) [C] Curing agent [D] Reinforcing fiber (a) A polyetherimide having a sulfonyl group, having the repeating unit represented by [1].

(B) A polyetherimide having a sulfonyl group having a repeating unit represented by the following formula [2].

In the formula, X is a group of —O— or —O—Z—O—, and the divalent linking group of the group of —O— or —O—Z—O— is the 3,3′-position, In the 4′-position, 4,3′-position, or 4,4′-position, Z is selected from the group consisting of divalent linking groups of the following formula [3].

In the formula, R is selected from the group consisting of —CO—, —SO ₂ —, —CH ₂ —, —O—, —S—, —CH (CH ₃ ) —, —C (CH ₃ ) ₂ —. Represents a divalent linking group. Y is selected from the group consisting of the divalent linking group of the above formula [3]. However, at least one sulfonyl group is contained in one or both of X and Y.
(C) A polyetherimide having a repeating unit represented by the following formula [4] and having a sulfonyl group.

In the formula, X is a group of —O— or —O—Z—O—, and the divalent linking group of the group of —O— or —O—Z—O— is the 3,3′-position, In the 4′-position, 4,3′-position, or 4,4′-position, Z is selected from the group consisting of divalent linking groups of the following formula [3].

In the formula, R is selected from the group consisting of —CO—, —SO ₂ —, —CH ₂ —, —O—, —S—, —CH (CH ₃ ) —, —C (CH ₃ ) ₂ —. Represents a divalent linking group. The prepreg according to claim 1, wherein the component [B] has a weight average molecular weight of 70000 g / mol or less. The prepreg according to claim 2, wherein the component [B] has a weight average molecular weight of 35,000 to 60000 g / mol. The prepreg according to any one of claims 1 to 3, wherein the constituent element [B] has a terminal group that does not react with the constituent element [A]. Any one of Claims 1-4 which contain 5-25 mass parts of constituent elements [B] in 100 mass parts of all the epoxy resin compositions which consist of a constituent element [A], a constituent element [B], and a constituent element [C]. The prepreg described in 1. The prepreg according to any one of claims 1 to 5, wherein the constituent element [C] is an aromatic polyamine represented by the following formula [5].

The prepreg according to any one of claims 1 to 6, comprising 30 parts by mass or more of an epoxy resin having a tri- or higher functional epoxy group in 100 parts by mass of the constituent element [A]. The prepreg according to claim 7, wherein the epoxy resin having a tri- or higher functional epoxy group is a glycidylamine type epoxy resin. The prepreg according to claim 8, wherein the glycidylamine type epoxy resin is an epoxy resin represented by the following formula [6].

In the formula, Q is selected from the group consisting of —CO—, —SO ₂ —, —CH ₂ —, —O—, —S—, —CH (CH ₃ ) —, —C (CH ₃ ) ₂ —. Represents a divalent linking group. The prepreg in any one of Claims 1-9 containing 5-40 mass parts of bisphenol F type epoxy resins in 100 mass parts of component [A]. The prepreg of Claim 10 which contains 30 mass parts or more of epoxy resins represented by following formula [6] in 100 mass parts of component [A].

In the formula, Q is selected from the group consisting of —CO—, —SO ₂ —, —CH ₂ —, —O—, —S—, —CH (CH ₃ ) —, —C (CH ₃ ) ₂ —. Represents a divalent linking group. An epoxy resin cured product obtained by curing an epoxy resin composition comprising the constituent elements [A], [B], and [C] is a sea island having an epoxy resin rich phase and a polyetherimide rich phase having a sulfonyl group The prepreg according to any one of claims 1 to 11, which has a phase separation structure and has an island phase diameter of less than 0.1 µm. Furthermore, the prepreg in any one of Claims 1-12 containing a thermoplastic resin particle [E]. The particle layer in which the thermoplastic resin particles [E] are present locally has a depth of 20% or less from the surface of the prepreg to the thickness direction starting from the surface with respect to the thickness of the prepreg of 100%. 14. A prepreg according to claim 13 having a structure present in the range. The prepreg according to any one of claims 1 to 14, further comprising core-shell rubber particles [F]. The prepreg of Claim 15 which contains 1-12 mass parts of component [F] in 100 mass parts of all the epoxy resin compositions. The prepreg according to claim 15 or 16, wherein the component [F] has a terminal group capable of reacting with the component [A] or [C] in the shell portion. The prepreg according to any one of claims 15 to 17, wherein the component [F] has an epoxy group in a shell portion. The prepreg according to any one of claims 15 to 18, wherein the volume average particle diameter of the constituent element [F] is 0.3 µm or less. An epoxy resin cured product obtained by curing an epoxy resin composition comprising components [A], [B], [C], and [F] is a sea island having an epoxy resin-rich phase and a core-shell rubber-rich phase. The prepreg according to any one of claims 15 to 19, which has a phase separation structure and has an island phase diameter of 0.1 to 3 µm. 21. The viscosity at 80 ° C. of the epoxy resin composition comprising the components [A], [B], [C], and [F] is 1 to 1000 Pa · s. Prepreg. The prepreg according to any one of claims 1 to 21, wherein the component [D] is a carbon fiber. A fiber-reinforced composite material obtained by curing the prepreg according to any one of claims 1 to 22.