JP7448409B2 - prepreg - Google Patents

Description

The present invention relates to prepregs used for manufacturing fiber reinforced composite materials.

Fiber-reinforced composite materials (hereinafter sometimes referred to as "composites") made of reinforcing fibers and resin are widely used in aircraft, sports/leisure, and general industries due to their light weight, high strength, and high modulus of elasticity. . This fiber-reinforced composite material is often manufactured via a prepreg in which reinforcing fibers and resin are integrated in advance.

A thermosetting resin or a thermoplastic resin is used as the resin constituting the prepreg. In particular, prepregs made of thermosetting resins are widely used because of their high degree of molding freedom due to their tackiness and drapability. However, since thermosetting resins generally have low toughness, there is a problem that when thermosetting resins are used as resins constituting prepregs, the impact resistance of composites made using this prepregs becomes low. Therefore, many methods of improving impact resistance are being studied.
As methods for improving impact resistance, for example, the methods described in Patent Documents 1 to 5 are conventionally known.

Patent Document 1 describes a method of imparting toughness to a thermosetting resin by dissolving a thermoplastic resin in the thermosetting resin. According to this method, a certain degree of toughness can be imparted to the thermosetting resin. However, in order to impart high toughness, a large amount of thermoplastic resin must be dissolved in the thermosetting resin. As a result, a thermosetting resin in which a large amount of thermoplastic resin is dissolved has a significantly high viscosity, making it difficult to impregnate a sufficient amount of resin into the reinforcing fiber base material made of carbon fiber. Composites made using such prepregs include defects such as voids. As a result, the compressive performance and damage tolerance of the composite structure is negatively affected.

Patent Documents 2 to 4 describe prepregs in which fine thermoplastic resin particles are localized on the surface of the prepreg. These prepregs have low initial tackiness because the particle-shaped thermoplastic resin is localized on the surface. Furthermore, since the curing reaction with the curing agent inherent in the surface layer progresses, the storage stability is poor and the tackiness and drape properties deteriorate over time. Furthermore, a composite produced using a prepreg in which such a curing reaction has proceeded has many defects such as voids, and the mechanical properties of the composite structure are significantly deteriorated.

Patent Document 5 describes a prepreg in which thermoplastic resin particles, fibers, or films are distributed near the surface layer on one or both surfaces. When particles or fibers are used as the thermoplastic resin, the tackiness may be low or the mechanical properties of the resulting composite may be reduced for the same reasons as in Patent Documents 2 to 4 mentioned above. Furthermore, when a film is used as the thermoplastic resin, the advantages of thermosetting resins, such as tackiness and drapability, are lost. In addition, drawbacks derived from thermoplastic resins, such as poor solvent resistance, are significantly reflected in the composite structure.

Japanese Unexamined Patent Publication No. 60-243113 Japanese Patent Application Publication No. 07-41575 Japanese Patent Application Publication No. 07-41576 Japanese Patent Application Publication No. 07-41577 Japanese Patent Application Publication No. 08-259713

An object of the present invention is to provide a prepreg that has excellent storage stability as a prepreg and can be used to produce a fiber-reinforced composite material that has excellent compression properties, heat and humidity resistance, interlaminar toughness, and electrical conductivity. .

That is, the present invention provides a primary prepreg consisting of a reinforcing fiber base material and an epoxy resin composition A impregnated into a reinforcing fiber layer formed by the reinforcing fiber base material, and an epoxy resin composition formed on one or both sides of the primary prepreg. The prepreg is characterized in that the epoxy resin composition A and the epoxy resin composition B each have the following formulations.
Epoxy resin composition A:
Epoxy resin composition containing an epoxy resin having an epoxy equivalent of 120 g/eq or less: Epoxy resin composition B:
An epoxy resin containing an epoxy resin represented by the following chemical formula (1) and a curing agent for the epoxy resin, in which the content of the curing agent is 150 to 300% in equivalent ratio to the total amount of epoxy resin contained in the epoxy resin composition B. Composition

(In formula (1), R ₁ to R ₄ each independently represent one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and a halogen atom, X is -CH ₂ -, -O-, -S-, -CO-, -C(=O)O-, -O-C(=O)-, -NHCO-, -CONH-, -SO ₂ - (represents one selected from)

According to the present invention, it is possible to provide a prepreg that has excellent storage stability as a prepreg and can be used to produce a fiber-reinforced composite material that has excellent compression properties, moist heat resistance properties, interlaminar toughness, and electrical conductivity. .

FIG. 1 is an explanatory diagram showing a schematic cross-section of the prepreg of the present invention. 2(a), 2(b) and 2(c) of FIG. 2 are explanatory diagrams sequentially showing the process of manufacturing the prepreg of the present invention. FIG. 3 is a conceptual diagram showing an example of the prepreg manufacturing process of the present invention.

The present invention will be explained in detail below.
(1) Structure of prepreg The prepreg of the present invention comprises a primary prepreg consisting of a reinforcing fiber base material, an epoxy resin composition A impregnated into a reinforcing fiber layer formed by the reinforcing fiber base material, and This is a prepreg that is integrated with a surface layer made of epoxy resin composition B formed on one or both sides of the prepreg.

FIG. 1 is an explanatory diagram showing a schematic cross-section of the prepreg of the present invention. In FIG. 1, 100 is a prepreg of the present invention, and 10 is a primary prepreg. The primary prepreg 10 is composed of a reinforcing fiber layer made of reinforcing fibers 11 and an epoxy resin composition A13 impregnated into this reinforcing fiber layer. On the surface of the primary prepreg 10, a resin layer made of epoxy resin composition B15 is formed integrally with the primary prepreg 10.

In the prepreg of the present invention, from the viewpoint of obtaining good tackiness and room temperature storage stability, the epoxy resin contained in the epoxy resin composition A that constitutes the primary prepreg and the epoxy resin composition B that constitutes the surface layer. The mass ratio of the epoxy resin is preferably 9:1 to 1:1.

(2) Primary Prepreg In the present invention, the primary prepreg is a layer consisting of a sheet-like fiber reinforced base material at the center of the prepreg cross section and the epoxy resin composition A impregnated into the reinforced fiber base material. The primary prepreg is represented as a primary prepreg 10 in FIGS. 2(b) and (c).

The reinforcing fiber base material used for the primary prepreg is a base material obtained by processing reinforcing fibers into various shapes. The reinforcing fiber base material is preferably in the form of a sheet. Examples of reinforcing fibers that can be used include carbon fibers, glass fibers, aramid fibers, silicon carbide fibers, polyester fibers, ceramic fibers, alumina fibers, boron fibers, metal fibers, mineral fibers, rock fibers, and slag fibers. Among these reinforcing fibers, carbon fibers, glass fibers, and aramid fibers are preferable, and carbon fibers are more preferable because they have good specific strength and specific modulus and can yield lightweight and high-strength composite materials, and have excellent tensile strength. Therefore, PAN-based carbon fibers are particularly preferred.

When the reinforcing fibers are carbon fibers, the tensile modulus of the carbon fibers is preferably 170 to 600 GPa, more preferably 220 to 450 GPa. The tensile strength of this carbon fiber is preferably 3920 MPa or more. By using carbon fibers that satisfy this condition, the mechanical properties of the composite using the prepreg of the present invention can be improved.

Examples of the sheet-like reinforcing fiber base material include a sheet-like material made of a large number of reinforcing fibers aligned in one direction, two-way fabrics such as plain weave and twill weave, multiaxial fabrics, nonwoven fabrics, mats, knits, braids, An example is paper made from reinforcing fibers. The thickness of the sheet-shaped reinforcing fiber base material is, for example, 0.01 to 3 mm, preferably 0.1 to 1.5 mm.

(3) Epoxy resin composition A
Each component used in epoxy resin composition A will be explained below.

(i) Epoxy resin The epoxy resin composition A used in the present invention contains an epoxy resin having an epoxy equivalent of 120 g/eq or less. The content of the epoxy resin having an epoxy equivalent of 120 g/eq or less in the epoxy resin composition A is 60 to 100% by mass, preferably 70 to 90% by mass, based on the total mass of the epoxy resin composition A. By including an epoxy resin with an epoxy equivalent of 120 g/eq or less within this range, high resin impregnation properties can be obtained during prepreg production, and the elastic modulus of the cured resin is improved, making it possible to improve the elasticity of the cured resin. Various physical properties of composites can be improved.

Examples of the epoxy resin having an epoxy equivalent of 120 g/eq or less include glycidylamine type epoxy such as triglycidyl aminophenol, tetraglycidyl-m-xylylene diamine, tetraglycidyl bis(aminomethyl)cyclohexane, and derivatives thereof. Among them, it is preferable to use epoxy resins containing aromatic groups such as triglycidylaminophenol and tetraglycidyl-m-xylylene diamine, and in particular, epoxy resins containing aromatic groups such as triglycidylaminophenol and its derivatives. It is preferable to use a trifunctional epoxy resin.

After curing and molding the prepreg, in order to express excellent composite physical properties, the total amount of epoxy resin contained in epoxy resin composition A and epoxy resin composition B (hereinafter also referred to as "total epoxy resin amount") , trifunctional epoxy resin is preferably contained in an amount of 30% by mass or more, more preferably 30 to 70% by mass. If the content of the trifunctional epoxy resin is less than 30% by mass, the compression properties may deteriorate, which is undesirable. If it exceeds 70% by mass, the handleability of the resulting prepreg may deteriorate, which is not preferred.

The epoxy resin crosslinks to form a network structure through a thermosetting reaction with the curing agent. By using a trifunctional epoxy resin, a composite with high crosslink density can be obtained. Examples of the trifunctional epoxy resin include N,N,O-triglycidyl-p-aminophenol and N,N,O-triglycidyl-m-aminophenol.

The epoxy resin composition A may further contain other epoxy resins as long as the content of the epoxy resin having an epoxy equivalent of 120 g/eq or less is within the above range. As other epoxy resins, conventionally known epoxy resins can be used. Specifically, the following examples can be used. Among these, epoxy resins containing an aromatic group are preferred, and epoxy resins containing either a glycidyl amine structure or a glycidyl ether structure are preferred. Furthermore, alicyclic epoxy resins can also be suitably used.

Epoxy resins containing a glycidylamine structure include tetraglycidyldiaminodiphenylmethane, N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-m-aminophenol, N,N,O- Examples include triglycidyl-3-methyl-4-aminophenol and various isomers of triglycidylaminocresol.

Examples of epoxy resins containing a glycidyl ether structure include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, phenol novolac epoxy resins, and cresol novolac epoxy resins.

Moreover, these epoxy resins may have a non-reactive substituent in the aromatic ring structure or the like, if necessary. Examples of non-reactive substituents include alkyl groups such as methyl, ethyl and isopropyl, aromatic groups such as phenyl, alkoxyl groups, aralkyl groups, and halogen groups such as chlorine and bromine.

From the viewpoint of room temperature storage stability, it is preferable that the epoxy resin composition A does not substantially contain an epoxy resin curing agent. Here, "substantially free" means that the content of the curing agent in the total mass of the composition is 40% by mass or less, preferably 10% by mass or less, and more preferably 1% by mass or less. .

(ii) Thermoplastic resin Epoxy resin composition A preferably contains an epoxy resin-soluble thermoplastic resin. Moreover, the epoxy resin composition A preferably contains an epoxy resin-insoluble thermoplastic resin. A particularly preferred embodiment is one in which the epoxy resin composition A contains both an epoxy resin-soluble thermoplastic resin and an epoxy resin-insoluble thermoplastic resin.

A part of the epoxy resin-insoluble thermoplastic resin and the epoxy resin-soluble thermoplastic resin (the epoxy resin-soluble thermoplastic resin remaining without being dissolved in the matrix resin after curing) is manufactured using the prepreg of the present invention. (hereinafter, these dispersed particles may be referred to as "interlayer particles"). These interlayer particles suppress the propagation of shocks applied to the composite. Therefore, when the epoxy resin composition A contains an epoxy resin-soluble thermoplastic resin or an epoxy resin-insoluble thermoplastic resin, the impact resistance of the composite obtained from the prepreg of the present invention can be improved.

(ii-1) Epoxy resin soluble thermoplastic resin When the epoxy resin composition A contains an epoxy resin soluble thermoplastic resin, the viscosity of the epoxy resin composition is adjusted and the impact resistance of the resulting composite is improved. .

The epoxy resin-soluble thermoplastic resin is a thermoplastic resin that can be partially or completely dissolved in the epoxy resin at a temperature at or below the temperature at which a composite is molded using the prepreg of the present invention. Here, "partially dissolved in the epoxy resin" means that when 100 parts by mass of epoxy resin is mixed with 10 parts by mass of thermoplastic resin having an average particle size of 20 to 50 μm and stirred at 190°C for 1 hour, the particles This means that the particles disappear or the particle size changes by 10% or more.

If the epoxy resin-soluble thermoplastic resin is not completely dissolved, it can be dissolved in the epoxy resin by heating during the curing process of the epoxy resin, and the viscosity of the epoxy resin composition can be increased. This can prevent the epoxy resin composition from flowing (a phenomenon in which the resin composition flows out from within the prepreg) due to a decrease in viscosity during the curing process.
The epoxy resin-soluble thermoplastic resin is preferably a resin that dissolves 80% by mass or more in the epoxy resin at 190°C.

Specific examples of the epoxy resin-soluble thermoplastic resin include polyethersulfone, polysulfone, polyetherimide, and polycarbonate. These may be used alone or in combination of two or more. The epoxy resin-soluble thermoplastic resin contained in the epoxy resin composition is particularly preferably polyethersulfone or polysulfone having a weight average molecular weight (Mw) in the range of 8,000 to 100,000 as measured by gel permeation chromatography. If the weight average molecular weight (Mw) is less than 8,000, the resulting FRP will have insufficient impact resistance, and if it is more than 100,000, the viscosity will be extremely high and the handling properties may be significantly deteriorated. It is preferable that the molecular weight distribution of the epoxy resin-soluble thermoplastic resin is uniform. In particular, the polydispersity (Mw/Mn), which is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), is preferably in the range of 1 to 10, more preferably in the range of 1.1 to 5. More preferred.

The epoxy resin-soluble thermoplastic resin preferably has a reactive group that is reactive with the epoxy resin or a functional group that forms a hydrogen bond. Such an epoxy resin-soluble thermoplastic resin can improve the dissolution stability during the curing process of the epoxy resin. Moreover, toughness, chemical resistance, heat resistance, and heat-and-moisture resistance can be imparted to the composite obtained after curing the prepreg.

As the reactive group having reactivity with the epoxy resin, a hydroxyl group, a carboxylic acid group, an imino group, an amino group, etc. are preferable. It is more preferable to use a hydroxyl-terminated polyether sulfone because the composite obtained from the prepreg has particularly excellent impact resistance, fracture toughness, and solvent resistance.

The content of the epoxy resin-soluble thermoplastic resin contained in the epoxy resin composition A can be adjusted as appropriate depending on the viscosity. From the viewpoint of processability of the prepreg, preferably 5 to 90 parts by mass, more preferably 5 to 40 parts by mass, particularly preferably 15 to 35 parts by mass, based on 100 parts by mass of epoxy resin contained in epoxy resin composition A. It is. If the amount is less than 5 parts by mass, the impact resistance of the composite obtained from the prepreg may be insufficient, which is not preferable. If the content of the epoxy resin-soluble thermoplastic resin is more than 90 parts by mass, the viscosity becomes extremely high and the handleability of the prepreg may be significantly deteriorated, which is not preferable.
The epoxy resin-soluble thermoplastic resin preferably contains a reactive aromatic oligomer (hereinafter also simply referred to as "aromatic oligomer") having an amine end group.

The epoxy resin composition A has a high molecular weight due to the curing reaction between the epoxy resin and the curing agent during heat curing. As the two-phase region expands due to the increase in molecular weight, the aromatic oligomer dissolved in the epoxy resin composition A causes reaction-induced phase separation. Through this phase separation, a two-phase resin structure in which the cured epoxy resin and the aromatic oligomer are co-continuous is formed within the matrix resin. Furthermore, since the aromatic oligomer has an amine terminal group, a reaction with the epoxy resin also occurs. Since each phase in this co-continuous two-phase structure is strongly bonded to each other, solvent resistance is also improved.

This co-continuous structure absorbs external impacts on the composite obtained from the prepreg and suppresses crack propagation. As a result, composites made with prepregs containing reactive aromatic oligomers with amine end groups have high impact resistance and fracture toughness.

As this aromatic oligomer, known polysulfones having amine end groups and polyether sulfones having amine end groups can be used. Preferably, the amine end group is a primary amine (-NH ₂ ) end group.

The aromatic oligomer blended into the epoxy resin composition A preferably has a weight average molecular weight of 8,000 to 40,000 as measured by gel permeation chromatography. If the weight average molecular weight is less than 8,000, the effect of improving the toughness of the matrix resin is undesirable. In addition, if the weight average molecular weight exceeds 40,000, the viscosity of the resin composition becomes too high, which tends to cause processing problems such as difficulty in impregnating the reinforcing fiber layer with the resin composition, which is not preferable.

As the aromatic oligomer, commercially available products such as "Virantage DAMS VW-30500 RP (registered trademark)" (manufactured by Solvay Specialty Polymers) can be preferably used.

The form of the epoxy resin-soluble thermoplastic resin is preferably particulate. By using a particulate epoxy resin-soluble thermoplastic resin, it can be uniformly blended into the resin composition, and a prepreg with high moldability can be obtained.

The average particle diameter of the epoxy resin-soluble thermoplastic resin is preferably 1 to 50 μm, more preferably 3 to 30 μm. If it is less than 1 μm, the viscosity of the epoxy resin composition increases significantly, and it may become difficult to add a sufficient amount of the epoxy resin-soluble thermoplastic resin to the epoxy resin composition, which is not preferable. On the other hand, if it exceeds 50 μm, it may be difficult to obtain a sheet with a uniform thickness when processing the epoxy resin composition into a sheet, and the rate of dissolution into the epoxy resin will be slow, making it difficult to form a composite obtained from the prepreg. This is not preferable because it becomes non-uniform.

(ii-2) Epoxy resin-insoluble thermoplastic resin Epoxy resin-insoluble thermoplastic resin refers to a thermoplastic resin that does not substantially dissolve in epoxy resin at the temperature at which a composite is molded using prepreg or at a temperature lower than that. That is, when 100 parts by mass of an epoxy resin is mixed with 10 parts by mass of a thermoplastic resin with an average particle diameter of 20 to 50 μm and stirred at 190°C for 1 hour, the heat does not change the particle size by 10% or more. Refers to plastic resin. Note that the temperature for molding the composite is generally 100 to 190°C. Further, the particle diameter is visually measured using a microscope, and the average particle diameter means the average value of the particle diameters of 100 randomly selected particles.

Examples of the epoxy resin-insoluble thermoplastic resin include polyamide, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyester, polyamideimide, polyimide, polyether ketone, polyether ether ketone, polyethylene naphthalate, polyether nitrile, and polybenzimidazole. . Among these, polyamide, polyamideimide, and polyimide are preferred because they have high toughness and heat resistance. Polyamide and polyimide are particularly effective in improving the toughness of composites. These may be used alone or in combination of two or more. Moreover, these copolymers can also be used.

In particular, amorphous polyimide, polyamide 6 (a polyamide obtained by a ring-opening polycondensation reaction of caprolactam), polyamide 11 (a polyamide obtained by a ring-opening polycondensation reaction of undecane lactam), polyamide 12 (a polyamide obtained by a ring-opening polycondensation reaction of lauryllactam), Polyamide 1010 (polyamide obtained by copolymerization of sebacic acid and 1,10-decanediamine), amorphous polyamide (also called transparent polyamide, in which polymer crystallization does not occur) The heat resistance of composites obtained from prepregs can be improved by using polyamides such as polyamides (or polyamides whose polymer crystallization rate is extremely slow).

The content of the epoxy resin-insoluble thermoplastic resin in the epoxy resin composition A is appropriately adjusted depending on the viscosity of the epoxy resin composition. From the viewpoint of processability of prepreg, preferably 5 to 50 parts by mass, more preferably 10 to 45 parts by mass, particularly preferably 20 to 40 parts by mass, per 100 parts by mass of epoxy resin contained in epoxy resin composition A. Department. If it is less than 5 parts by mass, the resulting FRP may have insufficient impact resistance, which is not preferable. If it exceeds 50 parts by mass, the impregnating properties of the epoxy resin composition and the drape properties of the obtained prepreg may be deteriorated, which is not preferable.
The preferred average particle size and morphology of the epoxy resin-insoluble thermoplastic resin are the same as those of the epoxy resin-soluble thermoplastic resin.

(iii) Other additives The epoxy resin composition A may contain conductive particles, a flame retardant, an inorganic filler, and an internal mold release agent.
Examples of the conductive particles include conductive polymer particles such as polyacetylene particles, polyaniline particles, polypyrrole particles, polythiophene particles, polyisothianaphthene particles, and polyethylenedioxythiophene particles, carbon particles, carbon fiber particles, metal particles, inorganic materials, or organic materials. Examples include particles in which a core material made of a material is coated with a conductive substance.

Examples of flame retardants include phosphorus-based flame retardants. As the phosphorus-based flame retardant, one containing a phosphorus atom in the molecule can be used, and examples thereof include organic phosphorus compounds such as phosphoric acid esters, condensed phosphoric acid esters, phosphazene compounds, polyphosphates, and red phosphorus.

Examples of inorganic fillers include aluminum borate, calcium carbonate, silicon carbonate, silicon nitride, potassium titanate, basic magnesium sulfate, zinc oxide, graphite, calcium sulfate, magnesium borate, magnesium oxide, and silicate minerals. can be mentioned. In particular, it is preferable to use silicate minerals. A commercially available silicate mineral includes THIXOTROPIC AGENT DT 5039 (manufactured by Huntsman Japan Co., Ltd.).

Examples of the internal mold release agent include metal soaps, vegetable waxes such as polyethylene wax and carbana wax, fatty acid ester mold release agents, silicone oil, animal wax, and fluorine-based nonionic surfactants. The blending amount of these internal mold release agents is preferably 0.1 to 5 parts by mass, more preferably 0.1 to 5 parts by mass, based on 100 parts by mass of epoxy resin composition A, from the viewpoint of exhibiting the mold release effect from the mold. is 0.2 to 2 parts by mass.

Commercially available internal mold release agents include "MOLD WIZ (registered trademark)" INT1846 (manufactured by AXEL PLASTICS RESEARCH LABORATORIES INC.), Licowax S, Licowax P, Licowax OP, Licowax PE190, Licowax PED (manufactured by Clariant Japan), Examples include stearyl stearate (SL-900A; manufactured by Riken Vitamin Co., Ltd.).

(4) Epoxy resin composition B
Epoxy resin composition B contains an epoxy resin represented by chemical formula (1) and a curing agent for the epoxy resin. The content of the curing agent is 150 to 300% in equivalent ratio to the total amount of epoxy resin contained in the epoxy resin composition B.
This epoxy resin composition B is a component constituting the surface layer 15a of the prepreg of the present invention in FIG. 2(c). Each component used in epoxy resin composition B will be explained below.

(i) Epoxy resin Epoxy resin composition B contains an epoxy resin represented by the following chemical formula (1).

(In formula (1), R ₁ to R ₄ each independently represent one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and a halogen atom, X is -CH ₂ -, -O-, -S-, -CO-, -C(=O)O-, -O-C(=O)-, -NHCO-, -CONH-, -SO ₂ - (represents one selected from)

When R ₁ to R ₄ are an aliphatic hydrocarbon group or an alicyclic hydrocarbon group, the number of carbon atoms thereof is 1 to 4.
It is preferable that

The epoxy resin represented by the chemical formula (1) is a tetrafunctional epoxy resin, in which an amino group having two glycidyl groups is bonded to the diaminodiphenyl skeleton at the para and meta positions, respectively. The present inventors estimate that the elastic modulus and heat resistance of the cured resin are increased due to the special three-dimensional structure of the cured resin caused by this structure.

The epoxy resin represented by the chemical formula (1) is preferably tetraglycidyl-3,4'-diaminodiphenyl ether. When R ₁ to R ₄ are hydrogen atoms, it is preferable because the formation of a special three-dimensional structure of the cured resin is less likely to be inhibited. Further, it is preferable that X is -O- because the synthesis of the compound is facilitated.

In epoxy resin composition B, the ratio of the epoxy resin represented by chemical formula (1) to the total amount of epoxy resins is preferably 20 to 95% by mass, more preferably 25 to 90% by mass, particularly preferably 30 to 85% by mass. Mass%. If it is less than 20% by mass, the heat resistance and elastic modulus of the resulting cured resin may decrease, which is not preferable. On the other hand, if it exceeds 95% by mass, the viscosity of the epoxy resin composition is high, the impregnation into the fiber-reinforced base material tends to decrease, and various physical properties of the composite obtained from the prepreg may deteriorate, which is not preferable.

(ii) Curing agent As the curing agent used in the epoxy resin composition B, a known curing agent for epoxy resins can be used. Among these, it is preferable to use an amine curing agent. Examples of the amine curing agent include dicyandiamide, various isomers of aromatic amine curing agents, and aminobenzoic acid esters.

Dicyandiamide is preferable because it has excellent storage stability of the prepreg. In addition, aromatic diamine compounds such as 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, and 4,4'-diaminodiphenylmethane and derivatives thereof having non-reactive substituents have good heat resistance. This is particularly preferable because it provides a cured product with excellent properties. Here, the non-reactive substituent is the same as the non-reactive substituent described in the description of the epoxy resin.

As the aminobenzoic acid esters, trimethylene glycol di-p-aminobenzoate and neopentyl glycol di-p-aminobenzoate are preferably used. Composite materials cured using these materials have inferior heat resistance compared to various isomers of diaminodiphenylsulfone, but have excellent tensile elongation. Therefore, the type of curing agent to be used is appropriately selected depending on the use of the composite material.

The amount of the curing agent contained in the epoxy resin composition B is 150 to 300%, preferably 200 to 280%, in terms of equivalent ratio to the total amount of epoxy resin contained in the epoxy resin composition B, from the viewpoint of curing all the epoxy resins. %. The amount of the curing agent may be appropriately adjusted within the above range depending on the type of epoxy resin and curing agent used. The amount of the curing agent is appropriately adjusted in consideration of the presence or absence of a curing agent/curing accelerator, the amount added, the stoichiometry of the chemical reaction with the epoxy resin, the curing speed of the composition, and the like.

(iii) Thermoplastic resin Epoxy resin composition B may contain a thermoplastic resin dissolved in an epoxy resin. This thermoplastic resin is the epoxy resin-soluble thermoplastic resin described above. The epoxy resin-soluble thermoplastic resin blended in epoxy resin composition B may be the same as the epoxy resin-soluble thermoplastic resin blended in epoxy resin composition A, or may be different from each other. .

When epoxy resin composition B contains an epoxy resin-soluble thermoplastic resin, it is preferably 5 to 50 parts by mass, more preferably 5 to 40 parts by mass, per 100 parts by mass of epoxy resin contained in epoxy resin composition B. . If it is less than 5 parts by mass, the resulting prepreg and composite material may have insufficient impact resistance, which is not preferable. On the other hand, if it exceeds 50 parts by mass, the viscosity may become extremely high and handling properties may be significantly deteriorated, which is not preferable.

(iv) Other additives The epoxy resin composition B may further contain the conductive particles, flame retardant, inorganic filler, and internal mold release agent described above.

(5) Method for producing epoxy resin composition Epoxy resin composition A and epoxy resin composition B can be produced by mixing the components constituting the epoxy resin of epoxy resin composition A and epoxy resin composition B. can. The order in which these are mixed does not matter. Conventionally known methods can be applied, and the mixing temperature is, for example, 40 to 120°C, preferably 50 to 100°C, more preferably 50 to 90°C. If the temperature exceeds 120°C, the curing reaction may partially proceed, impregnating into the reinforcing fiber base layer may decrease, and the storage stability of the resulting epoxy resin composition and the prepreg manufactured using it may deteriorate. It may decrease. If the temperature is less than 40°C, the viscosity of the epoxy resin composition may be high and mixing may become substantially difficult.

Conventionally known mixing machines can be used for mixing. Specific examples include a roll mill, a planetary mixer, a kneader, an extruder, a Banbury mixer, a mixing container equipped with stirring blades, and a horizontal mixing tank. Mixing of each component can be performed in the air or under an inert gas atmosphere. When mixing is performed in the atmosphere, an atmosphere with controlled temperature and humidity is preferred. For example, it is preferable to mix at a temperature controlled at a constant temperature of 30° C. or lower, or in a low humidity atmosphere with a relative humidity of 50% RH or lower.

(6) Prepreg manufacturing method The prepreg of the present invention can be manufactured using the above-mentioned epoxy resin composition A and epoxy resin composition B using a conventionally known method. It is preferable to manufacture by a dry method in which the reinforcing fiber layer is impregnated with the resin composition A whose viscosity has been reduced by heating. Such a dry method is preferable because no organic solvent remains, compared to a wet method in which the reinforcing fiber layer is impregnated with the epoxy resin composition A dissolved in an organic solvent and then the organic solvent is removed. Hereinafter, the method for manufacturing the prepreg of the present invention will be explained using a dry method.

First, a film made of epoxy resin composition A (hereinafter referred to as "resin A film") and a film made of epoxy resin composition B (hereinafter referred to as "resin B film") are manufactured. This can be done in a known manner.

Next, a resin A film is laminated on one or both sides of the reinforcing fiber layer in the thickness direction, and hot pressed using a hot roller or the like. As a result, the epoxy resin composition A of the resin A film is impregnated into the reinforcing fiber layer to obtain a primary prepreg. Thereafter, a resin B film is laminated on one or both sides of the primary prepreg in the thickness direction, and the primary prepreg and the resin B film are integrated by hot pressing with a hot roller or the like. Thereby, the prepreg of the present invention can be obtained.

FIGS. 2(a) to 2(c) are explanatory diagrams sequentially showing the process of manufacturing the prepreg of the present invention. First, the epoxy resin composition A is applied to both sides of the reinforcing fiber layer 12 made of reinforcing fibers 11 in the thickness direction.
A resin A film 13a consisting of is laminated (FIG. 2(a)). The reinforcing fiber layer 12 and the resin A film 13a are hot pressed using a hot roller or the like. Thereby, the reinforcing fiber layer 12 is impregnated with the epoxy resin composition A, and the primary prepreg 10 is obtained (FIG. 2(b)). Thereafter, a resin B film 15a made of epoxy resin composition B is laminated on one or both sides of the primary prepreg 10 in the thickness direction (FIG. 2(c)). Next, the primary prepreg 10 and the resin B film 15a are integrated by hot pressing using a hot roller or the like. Thereby, a prepreg 100 of the present invention is obtained (FIG. 1).

FIG. 3 is a conceptual diagram showing an example of the prepreg manufacturing process of the present invention. In FIG. 3, 21 is a reinforcing fiber layer in which carbon fibers are aligned in one direction, and run in the direction of arrow A. A resin A film 13a with release paper 14a is supplied from a film roll 23 to both sides of the reinforcing fiber layer 21 in the thickness direction. The reinforcing fiber layer 21 and the resin A film 13a are hot-pressed by a hot roller 40 with a release paper 14a interposed therebetween, to form the primary prepreg 10. Thereafter, the release paper 14a on one or both sides of the primary prepreg is wound around the roller 24. Next, a resin B film 15a with a release paper is supplied from the film roll 25 to one or both sides of the primary prepreg 10 on which the release paper has been wound. This primary prepreg 10 and the resin B film 15a are hot-pressed by a hot roller 41 with a release paper interposed therebetween, thereby forming the prepreg 100 of the present invention. This prepreg 100 is wound around a roller 101.

The temperature during hot pressing of the resin A film is, for example, 70 to 160°C, preferably 70 to 140°C. If the temperature during hot pressing of the resin A film is less than 70°C, the viscosity of the epoxy resin composition A constituting the resin A film will not be sufficiently reduced. As a result, it is difficult to sufficiently impregnate the epoxy resin composition A into the reinforcing fiber layer.

The linear pressure during hot pressing of the resin A film is, for example, 1 to 25 kg/cm, preferably 2 to 15 kg/cm. When the linear pressure during hot pressing of the resin A film is less than 1 kg/cm, it is difficult to sufficiently impregnate the reinforcing fiber layer with the resin composition A constituting the resin A film. If the linear pressure during hot pressing of the resin A film exceeds 25 kg/cm, the impregnation pressure cannot be increased because the reinforcing fibers themselves will be damaged.

The temperature during hot pressing of the resin B film is, for example, 50 to 130°C, preferably 60 to 120°C. If the temperature during hot pressing of the resin B film is less than 50° C., the surface tack will be too strong, and the mold releasability of the resin film will deteriorate, which may impair the process stability of prepreg production. If the temperature of the resin B film during hot pressing exceeds 130°C, it will mix with the epoxy resin composition A used in the primary prepreg, and the reaction will proceed. As a result, when stored for a long period of time, tackiness and drape properties are impaired.

The linear pressure during hot pressing of the resin B film is, for example, 0.1 to 10 kg/cm, preferably 0.5 to 6 kg/cm. If the linear pressure of the resin B film during hot pressing is less than 0.1 kg/cm, the resin B film cannot be sufficiently bonded to the primary prepreg. When the linear pressure during hot pressing exceeds 10 kg/cm, the reaction with the curing agent progresses due to sinking into the epoxy resin composition A used in the primary prepreg. As a result, when stored for a long period of time, tackiness and drape properties are impaired.

In the prepreg of the present invention manufactured by the above manufacturing method, the epoxy resin composition A13 is present in the reinforcing fiber layer as shown in FIG.
The prepreg production speed is, for example, 0.1 m/min or more, preferably 1 m/min or more, and more preferably 5 m/min or more, considering productivity and economy.

The resin A film and the resin B film can each be produced by a known method. For example, it can be produced by casting or casting onto a support such as release paper or film using a die coater, applicator, reverse roll coater, comma coater, knife coater, or the like. The resin temperature during film formation can be appropriately set depending on the resin composition and viscosity.

The thickness of the resin B film is preferably 2 to 30 μm, more preferably 5 to 20 μm. When the thickness of the resin B film is less than 2 μm, it is not preferable because the tackiness of the resulting prepreg decreases. If the thickness of the resin B film exceeds 30 μm, it is not preferable because the handleability of the obtained prepreg and the molding accuracy of the composite will deteriorate.

The prepreg of the present invention is not limited to the above manufacturing method, but can also be manufactured by, for example, sequentially laminating a resin A film and a resin B film on both sides of the reinforcing fiber layer in the thickness direction and hot pressing in one step. . In this case, it is necessary to perform hot pressing at a low temperature so that the curing agent contained in the epoxy resin composition B does not diffuse into the epoxy resin composition A.
The prepreg of the present invention may contain a stabilizer, a mold release agent, a filler, a coloring agent, etc. within a range that does not impede the effects of the present invention.

In the prepreg of the present invention, the reinforcing fiber content is preferably 40 to 80% by mass, more preferably 50 to 70% by mass. If the reinforcing fiber content is less than 40% by mass, it is not preferable because the strength etc. of the composite produced using this prepreg will be insufficient. If the reinforcing fiber content exceeds 80% by mass, the amount of resin impregnated into the reinforcing fiber layer of the prepreg will be insufficient, and as a result, voids etc. will occur in the composite made using this prepreg, so it is preferable. do not have.

In the prepreg of the present invention, the curing agent contained in the epoxy resin composition B is diffused into the epoxy resin composition A by heating while applying pressure. As a result, both epoxy resin composition A and epoxy resin composition B are cured.

(7) Fiber-reinforced composite material A fiber-reinforced composite material (composite) can be obtained by curing the prepreg of the present invention by heating and pressurizing it under specific conditions. Examples of methods for producing a composite using the prepreg of the present invention include known molding methods such as autoclave molding and press molding.

(i) Autoclave molding method When producing a composite using the prepreg of the present invention, an autoclave molding method can be preferably used. In the autoclave molding method, a prepreg and a film bag are sequentially placed in the lower mold of a mold, the prepreg is sealed between the lower mold and the film bag, and the space formed by the lower mold and the film bag is evacuated. This is a molding method that uses heat and pressure using an autoclave molding device. The conditions during molding are preferably a temperature increase rate of 1 to 50° C./min, heating and pressurization at 0.2 to 0.7 MPa and 130 to 180° C. for 10 to 300 minutes.

(ii) Press molding method As another method for manufacturing a composite using the prepreg of the present invention, a press molding method can be preferably used. The production of a fiber reinforced composite material by the press molding method is carried out by heating and pressing the prepreg of the present invention or a preform formed by laminating the prepregs of the present invention using a mold. The mold is preferably heated to a curing temperature in advance.

The temperature of the mold during press molding is preferably 150 to 210°C. Molding temperature is 150
When the temperature is above 0.degree. C., a curing reaction can be sufficiently caused, and a fiber reinforced composite material can be obtained with high productivity. Further, if the molding temperature is 210° C. or lower, the resin viscosity will not become too low, and excessive flow of the resin within the mold can be suppressed. As a result, it is possible to suppress the outflow of the resin from the mold and the meandering of the fibers, making it possible to obtain a high-quality composite.

The pressure during molding is, for example, 0.05 to 2 MPa, preferably 0.2 to 2 MPa. When the pressure is 0.05 MPa or more, appropriate flow of the resin can be obtained, and poor appearance and generation of voids can be prevented. Moreover, since the prepreg adheres well to the mold, a composite with a good appearance can be manufactured. If the pressure is 2 MPa or less, the resin will not be made to flow more than necessary, so that the resulting FRP will be less likely to have poor appearance. Furthermore, since no more load than necessary is applied to the mold, deformation of the mold is less likely to occur. The molding time is, for example, 1 to 8 hours.

Hereinafter, the present invention will be explained in more detail with reference to Examples. The components and test methods used in the Examples and Comparative Examples are described below.

〔component〕
Details of the components used are as follows.

(Epoxy resin)
- Tetraglycidyl-4,4'-diaminodiphenylmethane (Araldite MY721 manufactured by Huntsman, number of glycidyl ethers/number of aromatic rings = 0, epoxy equivalent = 112 g/eq, hereinafter abbreviated as "4,4'-TGDDM")
- Tetraglycidyl-3,4'-diaminodiphenyl ether (synthesized by the method of Synthesis Example 1 below. Represented by formula (1). Epoxy equivalent = 112 g/eq, hereinafter referred to as "3,4'-TGDDE" abbreviated)

(In formula (1), R ₁ to R ₄ each independently represent one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and a halogen atom, X is -CH ₂ -, -O-, -S-, -CO-, -C(=O)O-, -O-C(=O)-, -NHCO-, -CONH-, -SO ₂ - (represents one selected from)

・Triglycidyl-m-aminophenol (Araldite MY0600 manufactured by Huntsman, number of glycidyl ethers/number of aromatic rings = 1, epoxy equivalent = 106 g/eq, hereinafter abbreviated as "TG-mAP")
・Resorcinol diglycidyl ether (EX-201 manufactured by Nagase ChemteX, number of glycidyl ethers/number of aromatic rings = 2, epoxy equivalent = 115 g/eq, hereinafter abbreviated as "Resorcinol-DG")

(Amine curing agent)
・3,3'-diaminodiphenylsulfone (manufactured by Konishi Chemical Industry Co., Ltd., hereinafter abbreviated as "3,3'-DDS")

(Epoxy resin-insoluble thermoplastic resin)
・TR-55 (product name): (M Chemie Japan Co., Ltd. Grilamid, average particle size 5-35 μm, hereinafter abbreviated as "TR-55")
・VEST0SINT 2158 (product name): (Polyamide 12 manufactured by Daicel Evonik, average particle size 5 to 35 μm, hereinafter abbreviated as "PA12")

(Epoxy resin soluble thermoplastic resin)
・Polyether sulfone (Sumika Excel PES-5003P, manufactured by Sumitomo Chemical Co., Ltd., average particle size 20 μm, hereinafter abbreviated as "PES")

(Carbon fiber)
・Tenax (registered trademark) IMS65 E23 830tex: (carbon fiber strand, tensile strength 5.8GPa, tensile modulus 290GPa, sizing agent adhesion amount 1.2% by mass, manufactured by Teijin Ltd.)
・Tenax (registered trademark) IMS65 E22 830tex (carbon fiber strand, tensile strength 5.8GPa, tensile modulus 290GPa, sizing agent adhesion amount 0.5% by mass, manufactured by Teijin Ltd.)

(Synthesis Example 1) Synthesis of 3,4'-TGDDE 3,4'-TGDDE was synthesized by the following method. 1110.2 g (12.0 mol) of epichlorohydrin was charged into a four-necked flask equipped with a thermometer, dropping funnel, condenser, and stirrer, and the temperature was raised to 70°C while purging with nitrogen. 200.2 g (1.0 mol) of 3,4'-diaminodiphenyl ether dissolved in 1000 g was added dropwise over 4 hours. The mixture was further stirred for 6 hours to complete the addition reaction, and N,N,N',N'-tetrakis(2-hydroxy-3-chloropropyl)-3,4'-diaminodiphenyl ether was obtained. Subsequently, the temperature inside the flask was lowered to 25° C., and then 500.0 g (6.0 mol) of a 48% NaOH aqueous solution was added dropwise thereto over 2 hours, and the mixture was further stirred for 1 hour. After the cyclization reaction was completed, ethanol was distilled off, and extraction was performed with 400 g of toluene, followed by washing twice with 5% saline. Toluene and epichlorohydrin were removed from the organic layer under reduced pressure to obtain 361.7 g (yield: 85.2%) of a brown viscous liquid. The purity of the main product, 3,4'-TGDDE, was 84% (HPLC area %).

(1) Properties of prepreg (1-1) Impregnability The impregnability of the resin into the fiber base material was evaluated based on the water absorption rate of the prepreg. In this evaluation, the lower the water absorption rate of the obtained prepreg, the higher the resin impregnation property.
The prepreg was cut into a square with a side of 100 mm, and the mass (W ₁ ) was measured. Thereafter, the prepreg was submerged in water in a desiccator. The pressure inside the desiccator was reduced to 10 kPa or less to replace the air and water inside the prepreg. The prepreg was taken out of the water, the water on the surface was wiped off, and the mass (W ₂ ) of the prepreg was measured. From these measured values, the following formula: Water absorption rate (%) = [(W ₂ - W ₁ )/W ₁ ] x 100
W ₁ : Mass of prepreg (g)
W ₂ : Mass of prepreg after water absorption (g)
The water absorption rate was calculated using , and evaluated based on the following criteria.
○: Water absorption rate is less than 10%.
×: Water absorption rate is 10% or more

(1-2) Room temperature storage stability After storing the prepreg at a temperature of 26.7°C and a humidity of 65% for 10 days, the prepreg was cut and evaluated by laminating it in a mold. The evaluation criteria were as follows.
○: Even when laminated to the mold, it follows well, and the handling is almost the same as immediately after manufacturing.
△: The curing reaction of the prepreg progresses and the tack/drape properties are reduced, but there is no problem in using it even if it is laminated into a mold.
×: The curing reaction of the prepreg progresses, and the tack/drape properties are significantly reduced, making it difficult to laminate into a mold.

(2) Physical properties of prepreg processed products (2-1) Hole compressive strength (OHC)
The prepreg obtained in the above (1-2) was cut into a square with a side of 360 mm and laminated to obtain a laminate with a laminate configuration [+45/0/-45/90] _3S . Using a normal vacuum autoclave molding method, molding was carried out under a pressure of 0.59 MPa at 180° C. for 2 hours. The obtained molded product was cut into a size of 38.1 mm width x 304.8 mm length, and a hole with a diameter of 6.35 mm was punched in the center of the test piece to obtain a test piece for a perforated compressive strength (OHC) test. . The test piece and test were measured in accordance with SACMA SRM3, and the perforated compressive strength was calculated from the maximum point load.

(2-2) Hot-wet OHC
The prepreg obtained in the above (1-2) was cut into a square with a side of 360 mm and laminated to obtain a laminate with a laminate configuration [+45/0/-45/90] _3S . Using a normal vacuum autoclave molding method, molding was carried out under a pressure of 0.59 MPa at 180° C. for 2 hours. The obtained molded product was cut into a size of 38.1 mm width x 304.8 mm length, and a hole with a diameter of 6.35 mm was punched in the center of the test piece to obtain a test piece for a perforated compressive strength (OHC) test. . Using a pressure cooker (manufactured by Espec, HASTEST PC-422R8), the prepared OHC test piece was subjected to water absorption treatment at 121° C. for 72 hours.
The test was conducted in accordance with SACMA SRM3, and the perforated compressive strength was calculated from the maximum point load. Note that the measurements were performed at 104°C and 121°C.

(2-3) Interlaminar fracture toughness mode I (GIc)
The prepreg obtained in (1-2) above was cut into a square with a side of 360 mm and then laminated to produce two laminates with 10 layers laminated in the 0° direction. In order to generate initial cracks, a release sheet was sandwiched between the two laminates, and both were combined to obtain a prepreg laminate having a laminate configuration [0] ₂₀ . Using a normal vacuum autoclave molding method, molding was carried out under a pressure of 0.59 MPa at 180° C. for 2 hours. The obtained molded product was cut into a size of 25.0 mm width x 160.0 mm length to obtain a test piece with interlaminar fracture toughness mode I (GIc).

As a test method for GIc, a double cantilever beam interlayer fracture toughness test method (DCB method) is used, and after a pre-crack (initial crack) of 2 to 5 mm is generated from the tip of the release sheet, the crack is further propagated. I did it. The test was conducted in accordance with JIS K 7086, and measurements were performed with n=5.

(2-4) Volume resistivity in the thickness direction The prepreg obtained in (1-2) above was cut into a square with a side of 360 mm and laminated to form a laminate with a laminate configuration [+45/0/-45/90] _4S . Obtained. Using a normal vacuum autoclave molding method, molding was carried out under a pressure of 0.59 MPa at 180° C. for 2 hours. The obtained molded product was cut into a size of 40.0 mm width x 40.0 mm length to obtain a test piece for measuring volume resistivity in the thickness direction. Apply a voltage between the front and back surfaces of the test piece to measure the volume resistivity in the thickness direction (Ω cm)
was measured. Note that the measurement was performed using a digital ohmmeter.

[Example 1]
Thermoplastic resins (PES5003P and PA-12) were dissolved in epoxy resin (TG-mAP) at 120°C using a stirrer. Thereafter, the temperature was lowered to 80° C. and mixed for 30 minutes to prepare epoxy resin composition A. The types and amounts of the components used were as shown in Table 1.

Additionally, thermoplastic resin (PES5003P) and curing agent (3,3'-DDS) were added to epoxy resin (3,4'-TGDDE) using a stirrer and mixed for 30 minutes to prepare epoxy resin composition B. did. The types and amounts of the components used were as shown in Table 1.
Epoxy resin composition A was applied onto release paper using a reverse roll coater to prepare resin film A. Further, using a reverse roll coater, epoxy resin composition B was applied onto release paper to produce resin film B. The basis weight was 60 g/m ² for resin film A and 40 g/m ² for resin film B.

Next, the carbon fiber strands were uniformly arranged in one direction (fabric weight 190 g/m ² ) and fed between two sheets of resin A film, and the carbon fiber strands were supplied using a roller at a temperature of 70 to 140°C and a pressure of 10 kg/cm. A primary prepreg was obtained by applying pressure and heating.
Thereafter, the primary prepreg is supplied between two resin B films, and is heated and pressed at a temperature of 60 to 120°C and a pressure of 1.5 kg/cm using a roller, and wound onto a roll to obtain a prepreg. Ta.

The content of resin in the entire prepreg was 35% by mass. Table 1 shows various performances of the obtained prepreg. In Example 1, very high values of composite physical properties were obtained, and the storage stability at room temperature was also good.

[Example 2]
In Example 1, TG-mAP and 4,4'-TGDDM were used as the epoxy resins used in epoxy resin composition A in the amounts shown in Table 1, and the thermoplastic resin PES5003P was added in the amounts shown in Table 1. A prepreg was obtained in the same manner as in Example 1.

[Comparative Examples 1 to 7]
A prepreg was obtained in the same manner as in Example 1, except that the components and amounts used to obtain epoxy resin composition A and epoxy resin composition B were changed to those listed in Table 1.

In Comparative Example 1, the trifunctional glycidylamine type epoxy resin MY0600 is present at a high concentration in the impregnated layer (inner layer), and the curing agent 3,3'-DDS is present in the tack layer (surface layer), so the room temperature storage stability is poor. I was able to improve it. However, since the resin containing the tack layer (surface layer) was a tetrafunctional glycidylamine type epoxy resin 4,4'-TGDDM, the mechanical properties of the composite, Hot-wet OHC, were lowered.

In Comparative Example 2, the resin contained in both the impregnated layer (inner layer) and the tack layer (surface layer) is a tetrafunctional glycidylamine type epoxy resin 4,4'-TGDDM, and the tack layer (surface layer) contains a hardening agent 3,3'-DDS. Because of the presence of , room temperature storage stability was improved. However, the mechanical properties OHC and hot-wet OHC of the composite decreased.

In Comparative Example 3, the hardening agent 3,3'-DDS is present in the impregnated layer (inner layer), and the trifunctional glycidylamine type epoxy resin MY0600 is present in a high concentration in the tack layer (surface layer), so it can be stored at room temperature. Stability has been improved. However, the mechanical properties of composite OHC, Hot-wet
OHC decreased.

In Comparative Example 4, the hardening agent 3,3'-DDS is present in the impregnated layer (inner layer), and the trifunctional glycidylamine type epoxy resin MY0600 is present in a high concentration in the tack layer (surface layer), so it can be stored at room temperature. Stability has been improved. However, the mechanical properties of composite OHC, Hot-wet
OHC decreased.

In Comparative Example 5, the storage stability at room temperature deteriorated due to the presence of a high concentration of trifunctional glycidylamine type epoxy resin MY0600 and the curing agent 3,3'-DDS in the impregnation layer (inner layer) and tack layer (surface layer). did.

In Comparative Example 6, the storage stability at room temperature deteriorated due to the presence of a high concentration of trifunctional glycidylamine type epoxy resin MY0600 and the curing agent 3,3'-DDS in the impregnation layer (inner layer) and tack layer (surface layer). did.

In Comparative Example 7, the storage stability at room temperature deteriorated due to the presence of a high concentration of trifunctional glycidylamine type epoxy resin MY0600 and the curing agent 3,3'-DDS in the impregnation layer (inner layer) and tack layer (surface layer). did.

[Comparative Examples 8 and 9]
A prepreg was obtained in the same manner as in Example 1, except that the components and amounts used to obtain epoxy resin composition A and epoxy resin composition B were changed to those listed in Table 1.

The prepreg of the present invention can be used for producing fiber-reinforced composite materials (composites).

100... Prepreg 10... Primary prepreg 11... Carbon fiber 12... Reinforcing fiber layer 13... Epoxy resin composition A
13a... Resin A film 14a... Release paper 15... Epoxy resin composition B
15a... Resin B film 21... Reinforcing fiber layer 23... Roll of resin A film 24... Roll of release paper 25... Roll of resin B film 40, 41... Heat roller 101...Prepreg winding roll

Claims (8)

A primary prepreg consisting of a reinforcing fiber base material and an epoxy resin composition A impregnated into the reinforcing fiber layer formed by the reinforcing fiber base material, and an epoxy resin composition formed on one or both sides of the primary prepreg. A prepreg consisting of a surface layer consisting of a substance B, and an epoxy resin composition A and an epoxy resin composition B each having the formulation shown below , and the epoxy resin composition A substantially containing the curing agent of the epoxy resin. A prepreg characterized in that a trifunctional epoxy resin is contained in an amount of 30% by mass or more based on the total amount of epoxy resins contained in an epoxy resin composition A and an epoxy resin composition B.
Epoxy resin composition A:
Epoxy resin composition containing an epoxy resin having an epoxy equivalent of 120 g/eq or less: Epoxy resin composition B:
An epoxy resin containing an epoxy resin represented by the following chemical formula (1) and a curing agent for the epoxy resin, in which the content of the curing agent is 150 to 300% in equivalent ratio to the total amount of epoxy resin contained in the epoxy resin composition B. Composition

(In formula (1), R ₁ to R ₄ each independently represent one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and a halogen atom, X is -CH ₂ -, -O-, -S-, -CO-, -C(=O)O-, -O-C(=O)-, -NHCO-, -CONH-, -SO ₂ - (represents one selected from) The prepreg according to claim 1, wherein the epoxy resin composition A further contains an epoxy resin-soluble thermoplastic resin. The prepreg according to claim 2 , wherein the epoxy resin-soluble thermoplastic resin is polyethersulfone, polysulfone, polyetherimide or polycarbonate. The prepreg according to any one of claims 1 to 3 , wherein the epoxy resin composition A further contains an epoxy resin-insoluble thermoplastic resin. The prepreg according to claim 4 , wherein the epoxy resin-insoluble thermoplastic resin is amorphous polyamide, polyamide 6, polyamide 12, or amorphous polyimide. The prepreg according to any one of claims 1 to 5 , wherein the curing agent contained in the epoxy resin composition B is an aromatic diamine compound. The prepreg according to claim 6 , wherein the aromatic diamine compound is 3,3'-diaminodiphenylsulfone. The prepreg according to any one of claims 1 to 7 , wherein the reinforcing fiber base material is made of carbon fiber.