JP2019163438A - Epoxy resin composition, prepreg, fiber-reinforced composite material, and method for producing them - Google Patents

Abstract

To provide an epoxy resin composition from which a prepreg having excellent storage stability and a fiber-reinforced composite material having excellent compression characteristics can be produced.SOLUTION: An epoxy resin composition contains the following epoxy resin [A] and an aromatic epoxy resin (number of glycidyl ether/number of aromatic rings=2) having a glycidyl ether group [B].SELECTED DRAWING: None

Description

  The present invention relates to an epoxy resin composition, a prepreg, a fiber reinforced composite material, and a method for producing them. More specifically, an epoxy resin composition capable of producing a prepreg having excellent storage stability and a fiber-reinforced composite material having excellent compression properties; a prepreg produced using the epoxy resin composition; the prepreg And a manufacturing method thereof.

  Fiber reinforced composite materials composed of reinforced fibers and resins have features such as light weight, high strength, and high elastic modulus, and are widely applied to aircraft, sports / leisure, and general industries. This fiber-reinforced composite material is often manufactured via a prepreg in which reinforcing fibers and a resin called a matrix resin are integrated in advance.

  As the resin constituting the prepreg, a thermosetting resin or a thermoplastic resin is used. In particular, a prepreg using a thermosetting resin is widely used because of its high degree of molding freedom due to its tackiness and drapeability. Since thermosetting resins generally have low toughness, when a thermosetting resin is used as the resin constituting the prepreg, there is a problem that CFRP produced using this prepreg has low impact resistance. Therefore, a method for improving the impact resistance has been studied.

As methods for improving such impact resistance, methods described in Patent Documents 1 to 4 are conventionally known.
Patent Document 1 describes a method for 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, the thermosetting resin in which a large amount of the thermoplastic resin is dissolved has a remarkably high viscosity, and it becomes difficult to impregnate a sufficient amount of the resin inside the reinforcing fiber base made of carbon fiber. A composite produced using such a prepreg has many defects such as voids. As a result, it has a negative effect on the compression performance and damage tolerance of the composite structure.
Patent Documents 2 to 4 describe prepregs in which thermoplastic resin fine particles are localized on the prepreg surface. These prepregs have low initial tackiness because the particle-shaped thermoplastic resin is localized on the surface. Moreover, since the curing reaction with the curing agent present in the surface layer proceeds, the storage stability is poor, and the tackiness and draping properties deteriorate with time. Furthermore, a composite produced using such a prepreg that has undergone a curing reaction contains many voids and other defects, and the mechanical properties of the composite structure are significantly reduced.

JP-A-60-243113 JP 07-41575 A JP 07-41576 JP 07-41577

  An object of the present invention is to solve the above-mentioned problems of the prior art and to produce an epoxy resin composition capable of producing a prepreg having excellent storage stability and a fiber-reinforced composite material having excellent compression characteristics; Another object of the present invention is to provide a prepreg produced using a product; a fiber-reinforced composite material produced using the prepreg; and a method for producing them.

  As a result of studying the above problems, the present inventors have produced a prepreg using an epoxy resin composition comprising a combination of predetermined epoxy resins, and produced a fiber-reinforced composite material using the prepreg. The present inventors have found that the above problems can be solved and have completed the present invention.

  The present invention for achieving the above object is as follows.

  [1] The following chemical formula (1)

(However, in Chemical Formula (1), R _{1 to} R ₄ each independently represents one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and a halogen atom; Is —CH ₂ —, —O—, —S—, —CO—, —C (═O) O—, —O—C (═O) —, —NHCO—, —CONH—, —SO ₂ —. Represents one selected.)
An epoxy resin [A] represented by:
An aromatic epoxy resin having a glycidyl ether group, wherein the number of glycidyl ethers / the number of aromatic rings is 2;
An epoxy resin composition comprising:

  [2] The epoxy resin composition according to [1], wherein the epoxy resin [A] is tetraglycidyl-3,4'-diaminodiphenyl ether.

  [3] The epoxy resin composition according to [1] or [2], wherein the epoxy resin [B] is resorcinol diglycidyl ether.

  The invention described in the above [1] to [3] is an epoxy resin composition characterized by using a combination of predetermined epoxy resins.

  [4] The epoxy resin composition according to any one of [1] to [3], wherein a mass ratio between the epoxy resin [A] and the epoxy resin [B] is 2: 8 to 9: 1. .

  The invention described in [4] is an epoxy resin composition in which the epoxy resin [A] and the epoxy resin [B] are mixed at a predetermined ratio. By mixing at this ratio, the handleability of the prepreg can be made particularly excellent.

[5] a reinforcing fiber substrate;
The epoxy resin composition according to any one of [1] to [4] impregnated in the reinforcing fiber base;
A prepreg characterized by comprising:

  The invention described in [5] is a prepreg produced using the epoxy resin composition described in any one of [1] to [4]. This prepreg has high handleability due to the composition of the epoxy resin composition.

  [6] The prepreg according to [5], wherein the reinforcing fiber base is a reinforcing fiber base made of carbon fiber.

  In the invention described in [6], carbon fiber is used as a material constituting the reinforcing fiber substrate.

  [7] A method for producing a prepreg, comprising impregnating a reinforcing fiber substrate with the epoxy resin composition according to any one of [1] to [4].

  The invention described in [7] is a method for producing a prepreg using the epoxy resin composition according to any one of [1] to [4], and the reinforcing fiber is caused by the composition of the epoxy resin composition. Highly impregnated into the substrate.

  [8] A method for producing a fiber-reinforced composite material, wherein the prepreg according to [5] or [6] is laminated and heated at a pressure of 0.05 to 2 MPa and a temperature of 150 to 210 ° C. for 1 to 8 hours. .

The invention described in [8] is a method for producing a fiber-reinforced composite material having high compression characteristics using the prepreg described in [5] or [6].

The epoxy resin composition of the present invention is a cured product having a specific improvement in storage stability of a prepreg at room temperature due to the number of glycidyl groups and a three-dimensional positional relationship, and a high crosslinking density after a curing reaction. Form. Therefore, even when a prepreg after storage for a long period of time is used, a fiber-reinforced composite material having a high cross-linking density and high physical properties can be produced.

  Hereinafter, the details of the epoxy resin composition, the prepreg, the fiber reinforced composite material, and the production method thereof according to the present invention will be described.

1. Epoxy resin composition The epoxy resin composition of the present invention contains at least an epoxy resin [A] and an epoxy resin [B], and an amine-based curing agent. In addition to these, the epoxy resin composition of the present invention may contain a thermoplastic resin and other additives.

  The epoxy resin composition of the present invention preferably has a viscosity at 100 ° C. of 0.1 to 500 Pa · s, and more preferably 1 to 100 Pa · s. When it is less than 0.1 Pa · s, the resin easily flows out from the prepreg. When it exceeds 500 Pa · s, an unimpregnated portion tends to occur in the prepreg. As a result, voids and the like are easily formed in the obtained fiber-reinforced composite material.

  The cured resin obtained by curing the epoxy resin composition of the present invention preferably has a glass transition temperature of 150 ° C. or higher, and more preferably 170 to 400 ° C. When it is less than 150 ° C., the heat resistance is insufficient.

  The cured resin obtained by curing the epoxy resin composition of the present invention preferably has a flexural modulus measured by the JIS K7171 method of 3.0 GPa or more, more preferably 3.5 to 30 GPa. More preferably, it is 0-20 GPa. When it is less than 3.0 GPa, the properties of the obtained fiber-reinforced composite material are likely to be deteriorated.

(1-1) Epoxy resin [A]
The epoxy resin composition of the present invention has the following chemical formula (1)

(However, in Chemical Formula (1), R _{1 to} R ₄ each independently represents one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and a halogen atom; Is —CH ₂ —, —O—, —S—, —CO—, —C (═O) O—, —O—C (═O) —, —NHCO—, —CONH—, —SO ₂ —. Represents one selected.)
The epoxy resin [A] shown by these is included. When R _{1 to} R ₄ are an aliphatic hydrocarbon group or an alicyclic hydrocarbon group, the number of carbon atoms is preferably 1 to 4.

  In the epoxy resin [A], two aromatic rings are bonded via an X group, and a diglycidyl group is bonded to each aromatic ring. Among them, in one aromatic ring, the X group and the diglycidyl group are bonded at the para position, and in the other one aromatic ring, the X group and the diglycidyl group are bonded at the meta position. The present inventors presume that due to the special three-dimensional structure of the cured resin generated by this structure, the elastic modulus and heat resistance of the cured resin are increased.

The epoxy resin [A] is preferably tetraglycidyl-3,4'-diaminodiphenyl ether. A case where R _{1 to} R ₄ are hydrogen atoms is preferable because formation of a special three-dimensional structure of the cured resin is difficult to be inhibited. In addition, X is preferably —O— because the compound can be easily synthesized.

  The ratio of the epoxy resin [A] to the total amount of the epoxy resin in the epoxy resin composition of the present invention is preferably 20 to 95% by mass, more preferably 40 to 60% by mass, and 55 to 55% by mass. More preferably, it is 90 mass%. If it is less than 20% by mass, the heat resistance and elastic modulus of the resulting cured resin may be reduced. When it exceeds 95 mass%, the viscosity of an epoxy resin composition is high, and the impregnation property to a reinforced fiber base material tends to fall. As a result, in any case, various physical properties of the obtained CFRP may deteriorate.

(1-2) Epoxy resin [B]
The epoxy resin composition of the present invention is an aromatic epoxy resin having a glycidyl ether group, and includes an epoxy resin [B] having the number of glycidyl ethers / number of aromatic rings of 2. In the present invention, a condensed ring structure such as a naphthalene ring or an anthracene ring is regarded as one aromatic ring.
The epoxy resin [B] reduces the viscosity of the epoxy resin [A], improves the resin impregnation property at the time of preparing the prepreg, and improves the elastic modulus of the cured resin. Therefore, by using the epoxy resin [A] and the epoxy resin [B] in combination, various physical properties of the FRP can be improved while maintaining heat resistance and high elastic modulus.

  The epoxy resin [B] is not particularly limited as long as the number of glycidyl ethers / the number of aromatic rings is 2, but glycidyl ether type epoxy resins such as o-hydroquinone, resorcinol, p-hydroquinone and derivatives thereof. It is preferable to use resorcinol and derivatives thereof.

  In the epoxy resin composition of the present invention, the mass ratio of the epoxy resin [A] to the epoxy resin [B] is preferably 2: 8 to 9: 1, and preferably 4: 6 to 9: 1. More preferably, it is more preferably 6: 4 to 8: 2. By mix | blending in this ratio, the epoxy resin composition which has a viscosity suitable for preparation of a prepreg can be produced, and the hardening body with a high crosslinking density can be obtained.

  The epoxy resin [B] is a viscosity reducing agent that lowers the viscosity of the epoxy resin [A]. By using the epoxy resin [B] in combination with the epoxy resin [A] and an amine-based curing agent described later, a cured product having a high crosslinking density is obtained. .

The epoxy resin composition of the present invention essentially comprises the above two types of epoxy resins, but may contain other epoxy resins.
In the epoxy resin composition of the present invention, the ratio of the epoxy resin [A] and the epoxy resin [B] to the total epoxy resin amount is preferably 50% by mass or more, and more preferably 70% by mass or more. preferable.

As other epoxy resins, conventionally known epoxy resins can be used. Specifically, those exemplified below can be used. Among these, an epoxy resin containing an aromatic group is preferable, and an epoxy resin containing either a glycidylamine structure or a glycidyl ether structure is preferable. Moreover, an alicyclic epoxy resin can also be used suitably.
Examples of the epoxy resin 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 the epoxy resin containing a glycidyl ether structure include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, and cresol novolac type epoxy resin.
Moreover, these epoxy resins may have a non-reactive substituent in aromatic ring structure etc. as needed. 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.

(1-3) Amine-based curing agent A known amine-based curing agent is used for the epoxy resin composition of the present invention. Examples of amine curing agents include dicyandiamide, various isomers of aromatic amine curing agents, and aminobenzoic acid esters.

  Dicyandiamide is preferable because of 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 having non-reactive substituents have good heat resistance. From the viewpoint of providing a cured product. 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 are inferior in heat resistance to various isomers of diaminodiphenylsulfone, but are excellent in tensile elongation. Therefore, the type of curing agent to be used is appropriately selected according to the use of the composite material.

  The amount of the curing agent contained in the epoxy resin composition is an amount suitable for at least curing the epoxy resin blended in the epoxy resin composition. What is necessary is just to adjust the quantity of a hardening | curing agent suitably according to the kind of epoxy resin and hardening | curing agent to be used. The amount of the curing agent is appropriately adjusted in consideration of the presence and addition amount of other curing agents and curing accelerators, the chemical reaction stoichiometry with the epoxy resin, the curing rate of the composition, and the like. It is preferable to mix | blend 30-100 mass parts of hardening | curing agents with respect to 100 mass parts of epoxy resins contained in a prepreg, and it is more preferable to mix | blend 30-70 mass parts.

(1-4) Thermoplastic Resin The epoxy resin composition of the present invention may contain a thermoplastic resin. Examples of the thermoplastic resin include an epoxy resin-soluble thermoplastic resin and an epoxy resin-insoluble thermoplastic resin.

(1-4-1) Epoxy resin-soluble thermoplastic resin The epoxy resin composition can also contain an epoxy resin-soluble thermoplastic resin. This epoxy resin-soluble thermoplastic resin adjusts the viscosity of the epoxy resin composition and improves the impact resistance of the resulting FRP.

The epoxy resin-soluble thermoplastic resin is a thermoplastic resin that can be partially or wholly dissolved in the epoxy resin at a temperature at which FRP is molded or at a temperature lower than that. Here, a part of the epoxy resin is dissolved when 100 parts by mass of the epoxy resin is mixed with 10 parts by mass of a thermoplastic resin having an average particle diameter of 20 to 50 μm and stirred at 190 ° C. for 1 hour. Disappears or the particle size changes by 10% or more.
On the other hand, the epoxy resin-insoluble thermoplastic resin refers to a thermoplastic resin that does not substantially dissolve in the epoxy resin at a temperature at which FRP is molded 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 having an average particle diameter of 20 to 50 μm and stirred at 190 ° C. for 1 hour, the particle size does not change by 10% or more. It refers to a plastic resin. In general, the temperature at which FRP is molded is 100 to 190 ° C. The particle diameter is measured visually with a microscope, and the average particle diameter means the average value of the particle diameters of 100 particles selected at random.

  When the epoxy resin-soluble thermoplastic resin is not completely dissolved, it is dissolved in the epoxy resin by being heated in the curing process of the epoxy resin, and the viscosity of the epoxy resin composition can be increased. Thereby, it is possible to prevent the flow of the epoxy resin composition (a phenomenon in which the resin composition flows out from the prepreg) due to a decrease in viscosity in the curing process.

  The epoxy resin-soluble thermoplastic resin is preferably a resin that dissolves in an epoxy resin at 190 ° C. by 80 mass% or more.

  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 8000 to 100,000 as measured by gel permeation chromatography. When the weight average molecular weight (Mw) is less than 8000, the impact resistance of the obtained FRP becomes insufficient, and when it is more than 100,000, the viscosity is remarkably increased and the handling property may be remarkably deteriorated. The molecular weight distribution of the epoxy resin-soluble thermoplastic resin is preferably uniform. In particular, the polydispersity (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably in the range of 1 to 10, and preferably in the range of 1.1 to 5. More preferred.

  The epoxy resin-soluble thermoplastic resin preferably has a reactive group 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 moist heat resistance can be imparted to the FRP obtained after curing.

  As the reactive group having reactivity with the epoxy resin, a hydroxyl group, a carboxylic acid group, an imino group, an amino group, and the like are preferable. Use of a hydroxyl-terminated polyethersulfone is more preferred because the resulting FRP is particularly excellent in impact resistance, fracture toughness and solvent resistance.

  Content of the epoxy resin soluble thermoplastic resin contained in an epoxy resin composition is suitably adjusted according to a viscosity. From the viewpoint of workability of the prepreg, 5 to 90 parts by mass are preferable, 5 to 40 parts by mass are more preferable, and 15 to 35 parts by mass are more preferable with respect to 100 parts by mass of the epoxy resin contained in the epoxy resin composition. . If the amount is less than 5 parts by mass, the resulting FRP may have insufficient impact resistance. When the content of the epoxy resin-soluble thermoplastic resin is high, the viscosity is remarkably increased, and the prepreg handling property may be remarkably deteriorated.

  The epoxy resin-soluble thermoplastic resin preferably contains a reactive aromatic oligomer having an amine end group (hereinafter also simply referred to as “aromatic oligomer”).

  The epoxy resin composition has a high molecular weight due to a curing reaction between the epoxy resin and the curing agent during heat curing. When the two-phase region is expanded by increasing the molecular weight, the aromatic oligomer dissolved in the epoxy resin composition causes reaction-induced phase separation. By this phase separation, a two-phase structure of a resin in which the cured epoxy resin and the aromatic oligomer are co-continuous is formed in the matrix resin. Moreover, since the aromatic oligomer has an amine terminal group, a reaction with an epoxy resin also occurs. Since the phases in this co-continuous two-phase structure are firmly bonded to each other, the solvent resistance is also improved.

  This co-continuous structure absorbs external impact on the FRP and suppresses crack propagation. As a result, FRP produced using a prepreg containing a reactive aromatic oligomer having an amine end group has high impact resistance and fracture toughness.

As this aromatic oligomer, a known polysulfone having an amine end group and a polyether sulfone having an amine end group can be used. The amine end group is preferably a primary amine (—NH ₂ ) end group.

  The aromatic oligomer blended in the epoxy resin composition preferably has a weight average molecular weight of 8000 to 40,000 as measured by gel permeation chromatography. When the weight average molecular weight is less than 8000, the effect of improving the toughness of the matrix resin is low. On the other hand, when the weight average molecular weight exceeds 40000, the viscosity of the resin composition becomes too high, and processing problems such as difficulty in impregnating the resin composition in the reinforcing fiber layer tend to occur.

  As the aromatic oligomer, a commercially available product 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 not particularly limited, but is preferably particulate. The particulate epoxy resin-soluble thermoplastic resin can be uniformly blended in the resin composition. Moreover, the moldability of the obtained prepreg is high.

  The average particle size of the epoxy resin-soluble thermoplastic resin is preferably 1 to 50 μm, and particularly preferably 3 to 30 μm. When it is less than 1 μm, the viscosity of the epoxy resin composition is remarkably increased. Therefore, it may be difficult to add a sufficient amount of the epoxy resin-soluble thermoplastic resin to the epoxy resin composition. When exceeding 50 micrometers, when processing an epoxy resin composition into a sheet form, it may become difficult to obtain a sheet of uniform thickness. Moreover, since the melt | dissolution rate to an epoxy resin becomes slow and obtained FRP becomes non-uniform | heterogenous, it is not preferable.

(1-4-2) Epoxy resin insoluble thermoplastic resin The epoxy resin composition may contain an epoxy resin insoluble thermoplastic resin in addition to the epoxy resin soluble thermoplastic resin. In the present invention, the epoxy resin composition preferably contains both an epoxy resin-soluble thermoplastic resin and an epoxy resin-insoluble thermoplastic resin.

  Part of epoxy resin-insoluble thermoplastic resin and epoxy resin-soluble thermoplastic resin (epoxy resin-soluble thermoplastic resin remaining undissolved in the cured matrix resin) is dispersed in the FRP matrix resin (Hereinafter, the dispersed particles are also referred to as “interlayer particles”). The interlayer particles suppress the propagation of the impact received by the FRP. As a result, the impact resistance of the obtained FRP is improved.

  Examples of the epoxy resin insoluble thermoplastic resin include polyamide, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyester, polyamideimide, polyimide, polyetherketone, polyetheretherketone, polyethylene naphthalate, polyethernitrile, and polybenzimidazole. . Among these, polyamide, polyamideimide, and polyimide are preferable because of high toughness and heat resistance. Polyamide and polyimide are particularly excellent in improving toughness against FRP. These may be used alone or in combination of two or more. Moreover, these copolymers can also be used.

  In particular, amorphous polyimide, nylon 6 (registered trademark) (polyamide obtained by ring-opening polycondensation reaction of caprolactam), nylon 11 (polyamide obtained by ring-opening polycondensation reaction of undecane lactam), nylon 12 (lauryl lactam) Polyamide obtained by a ring-opening polycondensation reaction), nylon 1010 (polyamide obtained by copolymerization reaction of sebacic acid and 1,10-decanediamine), amorphous nylon (also called transparent nylon, polymer crystal) The heat resistance of the resulting FRP can be particularly improved by using a polyamide such as nylon which does not cause crystallization or has a very slow polymer crystallization rate.

  Content of the epoxy resin insoluble thermoplastic resin in an epoxy resin composition is suitably adjusted according to the viscosity of an epoxy resin composition. From the viewpoint of workability of the prepreg, the amount is preferably 5 to 50 parts by mass, more preferably 10 to 45 parts by mass, with respect to 100 parts by mass of the epoxy resin contained in the epoxy resin composition. More preferably, it is 40 parts by mass. When the amount is less than 5 parts by mass, the resulting FRP may have insufficient impact resistance. When it exceeds 50 mass parts, the impregnation property of an epoxy resin composition, the drape property of the prepreg obtained, etc. may be reduced.

  The preferable average particle diameter and form of the epoxy resin-insoluble thermoplastic resin are the same as those of the epoxy resin-soluble thermoplastic resin.

(1-5) Other additives The epoxy resin composition of the present invention may contain conductive particles, a flame retardant, an inorganic filler, and an internal 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 The particle | grains which coat | covered the core material which consists of material with an electroconductive substance are illustrated.

  An example of the flame retardant is a phosphorus-based flame retardant. The phosphorus-based flame retardant is not particularly limited as long as it contains a phosphorus atom in the molecule, and examples thereof include organic phosphorus compounds such as phosphate esters, condensed phosphate esters, phosphazene compounds, and polyphosphates, and red phosphorus. It is done.

  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, silicate mineral Is mentioned. In particular, it is preferable to use a silicate mineral. As a commercial item of a silicate mineral, THIXOTROPIC AGENT DT 5039 (made by Huntsman Japan Co., Ltd.) is mentioned.

  Examples of the internal mold release agent include metal soaps, vegetable waxes such as polyethylene wax and carbana wax, fatty acid ester type mold release agents, silicone oil, animal waxes, and fluorine type nonionic surfactants. The compounding amount of these internal mold release agents is preferably 0.1 to 5 parts by mass, and more preferably 0.2 to 2 parts by mass with respect to 100 parts by mass of the epoxy resin. Within this range, the effect of releasing from the mold is suitably exhibited.

  Commercially available products of the internal mold release agent include “MOLD WIZ (registered trademark)” INT 1846 (manufactured by AXEL PLASTICS RESEARCH LABORATORIES INC.), Liowax S, Liwawax P, Liwawax OP, Liwawax PE190, Liwawax PED (manufactured by Liwawax PED) Examples include stearyl stearate (SL-900A; manufactured by Riken Vitamin Co., Ltd.).

(1-6) Method for Producing Epoxy Resin Composition The epoxy resin composition of the present invention comprises an epoxy resin [A] and an epoxy resin [B] and, if necessary, other than the epoxy resins [A] and [B]. It can be produced by mixing an epoxy resin, a curing agent, a thermoplastic resin and other components. The order of these mixing is not ask | required.

  The method for producing the epoxy resin composition is not particularly limited, and any conventionally known method may be used. As mixing temperature, the range of 40-120 degreeC can be illustrated. When the temperature exceeds 120 ° C., the curing reaction partially proceeds and the impregnation property into the reinforcing fiber base layer is lowered, or the resulting epoxy resin composition and the storage stability of the prepreg produced using the epoxy resin composition are reduced. It may decrease. When the temperature is lower than 40 ° C., the viscosity of the epoxy resin composition is high, and mixing may be substantially difficult. Preferably it is 50-100 degreeC, More preferably, it is the range of 50-90 degreeC.

A conventionally well-known thing can be used as a mixing machine apparatus. Specific examples include a roll mill, a planetary mixer, a kneader, an extruder, a Banbury mixer, a mixing container equipped with a stirring blade, a horizontal mixing tank, and the like. Mixing of each component can be performed in air | atmosphere or inert gas atmosphere. When mixing is performed in the air, an atmosphere in which temperature and humidity are controlled is preferable. Although not particularly limited, for example, it is preferable to mix in 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.

2. Prepreg The prepreg of the present invention comprises a reinforcing fiber base and the epoxy resin composition impregnated in the reinforcing fiber base.

  The prepreg of the present invention is a prepreg in which a part or the whole of the reinforcing fiber base is impregnated with the epoxy resin composition. It is preferable that the content rate of the epoxy resin composition in the whole prepreg is 15-60 mass% on the basis of the total mass of a prepreg. When the resin content is less than 15% by mass, voids or the like are generated in the obtained fiber-reinforced composite material, and the mechanical properties may be lowered. When the resin content exceeds 60% by mass, the reinforcing effect by the reinforcing fibers becomes insufficient, and the mechanical properties relative to mass may be substantially low. The resin content is preferably 20 to 55% by mass, and more preferably 25 to 50% by mass.

(2-1) Reinforcing fiber base material There is no restriction | limiting in particular as a reinforcing fiber base material used by this invention, For example, carbon fiber, glass fiber, aramid fiber, silicon carbide fiber, polyester fiber, ceramic fiber, alumina fiber, boron Examples thereof include fibers, metal fibers, mineral fibers, rock fibers, and slug fibers.

  Among these reinforcing fibers, carbon fibers, glass fibers, and aramid fibers are preferable. Carbon fiber is more preferable in that it has a good specific strength and specific elastic modulus, and a lightweight and high-strength fiber-reinforced composite material can be obtained. Polyacrylonitrile (PAN) -based carbon fibers are particularly preferable in terms of excellent tensile strength.

  When PAN-based carbon fiber is used as the reinforcing fiber, the tensile elastic modulus is preferably 100 to 600 GPa, more preferably 200 to 500 GPa, and particularly preferably 230 to 450 GPa. Further, the tensile strength is preferably 2000 to 10000 MPa, and more preferably 3000 to 8000 MPa. The diameter of the carbon fiber is preferably 4 to 20 μm, and more preferably 5 to 10 μm. By using such a carbon fiber, the mechanical properties of the obtained fiber-reinforced composite material can be improved. Moreover, in this invention, it is preferable that it is a reinforcing fiber bundle with which the sizing agent adhered 0.01 to 10 mass% with respect to the mass of the reinforcing fiber to which the sizing agent adhered, and 0.05 to 3.0 mass%. The adhesion amount is more preferable, and the adhesion amount is particularly preferably 0.1 to 2.0% by mass. There exists a tendency for the adhesiveness of a reinforced fiber and matrix resin to become strong, so that there is much adhesion amount of a sizing agent. On the other hand, the interlaminar toughness of the composite material obtained with a lower adhesion amount tends to be excellent. The most preferable amount of the sizing agent is 1.0 to 2.0% by mass from the viewpoint of adhesion between the reinforcing fiber and the matrix resin, and from the viewpoint of interlayer toughness of the resulting composite material, 0.1 to 1. 0% by mass.

  The reinforcing fiber is preferably used in the form of a sheet. As the reinforcing fiber sheet, for example, a sheet in which a large number of reinforcing fibers are aligned in one direction, bi-directional woven fabrics such as plain weave and twill weave, multiaxial woven fabric, non-woven fabric, mat, knit, braid, paper made of reinforcing fibers Can be mentioned. Among these, it is preferable to use a unidirectionally aligned sheet, a bi-directional woven fabric, or a multiaxial woven fabric base material formed in the form of a sheet of reinforcing fibers as a continuous fiber, because a fiber-reinforced composite material having more excellent mechanical properties can be obtained. The thickness of the sheet-like reinforcing fiber base is preferably 0.01 to 3 mm, and more preferably 0.1 to 1.5 mm.

(2-2) Manufacturing method of prepreg The manufacturing method of the prepreg of the present invention is not particularly limited, and any conventionally known method can be adopted. Specifically, a hot melt method or a solvent method can be suitably employed.

  In the hot melt method, a resin composition is applied to a release paper in the form of a thin film to form a resin composition film, and the resin composition film is laminated on a reinforcing fiber substrate and heated under pressure. This is a method of impregnating the reinforcing fiber base layer with the resin composition.

  The method for forming the resin composition into a resin composition film is not particularly limited, and any conventionally known method can be used. Specifically, a resin composition film is obtained by casting and casting a resin composition on a support such as release paper or film using a die extrusion, applicator, reverse roll coater, comma coater, etc. Can do. The resin temperature at the time of producing the film is appropriately determined according to the composition and viscosity of the resin composition. Specifically, the same temperature conditions as the mixing temperature in the aforementioned method for producing an epoxy resin composition are preferably used. The impregnation of the resin composition into the reinforcing fiber base layer may be performed once or may be performed in multiple steps.

  The solvent method is a method in which the epoxy resin composition is made into a varnish using an appropriate solvent, and this varnish is impregnated into the reinforcing fiber base layer.

  Among these conventional methods, the prepreg of the present invention can be suitably produced by a hot melt method that does not use a solvent.

  The impregnation temperature when the epoxy resin composition film is impregnated into the reinforcing fiber base layer by the hot melt method is preferably in the range of 50 to 150 ° C. When the impregnation temperature is less than 50 ° C., the viscosity of the epoxy resin is high and the reinforcing fiber base layer may not be sufficiently impregnated. When the impregnation temperature exceeds 140 ° C., the curing reaction of the epoxy resin composition proceeds, and the storage stability of the resulting prepreg may be reduced, or the drapeability may be reduced. The impregnation temperature is more preferably 60 to 130 ° C, and particularly preferably 70 to 120 ° C.

The impregnation pressure when impregnating the epoxy resin composition film into the reinforcing fiber base layer by the hot melt method is appropriately determined in consideration of the viscosity, resin flow, etc. of the resin composition.
The specific impregnation pressure is a linear pressure of 0.01 to 250 (N / cm), and preferably 0.1 to 200 (N / cm).

3. Fiber Reinforced Composite Material A fiber reinforced composite material (FRP) can be obtained by curing the prepreg of the present invention by heating and pressing under specific conditions. Examples of a method for producing FRP using the prepreg of the present invention include known molding methods such as autoclave molding and press molding.

(3-1) Autoclave molding method As a method for producing the FRP of the present invention, an autoclave molding method is preferably used. In the autoclave molding method, a prepreg and a film bag are sequentially laid on the lower mold of the 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. At the same time, it is a molding method in which heating and pressurization are performed by an autoclave molding apparatus. The molding conditions are preferably a heating rate of 1 to 50 ° C./min, heating and pressurizing at 0.2 to 0.7 MPa and 130 to 180 ° C. for 10 to 300 minutes.

(3-2) Press molding method As a manufacturing method of FRP of this invention, the press molding method is used preferably. The production of FRP by the press molding method is carried out by heating and pressurizing a prepreg of the present invention or a preform formed by laminating the prepreg of the present invention using a mold. The mold is preferably heated to the curing temperature in advance.

  As for the temperature of the metal mold | die at the time of press molding, 150-210 degreeC is preferable. When the molding temperature is 150 ° C. or higher, the curing reaction can be sufficiently caused, and FRP can be obtained with high productivity. Further, if the molding temperature is 210 ° C. or lower, the resin viscosity does not become too low, and the excessive flow of the resin in the mold can be suppressed. As a result, since the outflow of resin from the mold and the meandering of the fibers can be suppressed, a high quality FRP can be obtained.

The pressure during molding is 0.05 to 2 MPa, and preferably 0.2 to 2 MPa. When the pressure is 0.05 MPa or more, an appropriate flow of the resin can be obtained, and appearance defects and generation of voids can be prevented. Further, since the prepreg is sufficiently adhered to the mold, an FRP having a good appearance can be manufactured. If the pressure is 2 MPa or less, the resin does not flow more than necessary, and thus the appearance failure of the obtained FRP is unlikely to occur. Moreover, since the load more than necessary is not applied to the mold, the mold is hardly deformed.
The molding time is preferably 1 to 8 hours.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to an Example. The components and test methods used in the examples and comparative examples are described below.

〔component〕
(Epoxy resin)
Epoxy resin [A]
Tetraglycidyl-3,4′-diaminodiphenyl ether (synthesized by the method of Synthesis Example 1, hereinafter abbreviated as “3,4′-TGDDE”)
Epoxy resin [B]
Resorcinol diglycidyl ether (EX-201, manufactured by Nagase ChemteX Corp., number of glycidyl ethers / number of aromatic rings = 2, hereinafter abbreviated as “Resorcinol-DG”)
Other epoxy resins / tetraglycidyl-4,4′-diaminodiphenylmethane (Araldite MY721 manufactured by Huntsman, number of glycidyl ethers / number of aromatic rings = 0, hereinafter abbreviated as “TGDDM”)
Bisphenol A-diglycidyl ether (Mitsubishi Chemical Corporation jER825, number of glycidyl ethers / number of aromatic rings = 1, hereinafter abbreviated as “DGEBA”)
Triglycidyl-m-aminophenol (manufactured by Huntsman Araldite MY0600, number of glycidyl ethers / number of aromatic rings = 1, hereinafter abbreviated as “TG-mAP”)
(Amine-based curing agent)
3,3′-diaminodiphenyl sulfone (manufactured by Konishi Chemical Industries, Ltd., hereinafter abbreviated as “3,3′-DDS”)
(Epoxy resin insoluble thermoplastic resin)
Polyamide 12 (TR-55, manufactured by M Chemie Japan, average particle size 20 μm, hereinafter abbreviated as “PA12”)
(Epoxy resin-soluble thermoplastic resin)
Polyethersulfone (Sumitomo Chemical Co., Ltd. Sumika Excel PES-5003P, average particle size 20 μm, hereinafter abbreviated as “PES”)
(Carbon fiber)
"Tenax (registered trademark)" IMS65 E23 830tex (carbon fiber strand, tensile strength 5.8 GPa, tensile elastic modulus 290 GPa, sizing agent adhesion amount 1.2 mass%, manufactured by Teijin Ltd.)
"Tenax (registered trademark)" IMS65 E22 830tex (carbon fiber strand, tensile strength 5.8 GPa, tensile elastic modulus 290 GPa, sizing agent adhesion amount 0.5 mass%, manufactured by Teijin Ltd.)

[Synthesis Example 1] Synthesis of 3,4'-TGDDE Into a four-necked flask equipped with a thermometer, dropping funnel, condenser and stirrer was charged 1110.2 g (12.0 mol) of epichlorohydrin and purged with nitrogen. While performing, the temperature was raised to 70 ° C., and 200.2 g (1.0 mol) of 3,4'-diaminodiphenyl ether dissolved in 1000 g of ethanol was added dropwise thereto 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, after the temperature in the flask was lowered to 25 ° C., 500.0 g (6.0 mol) of a 48% NaOH aqueous solution was added dropwise thereto over 2 hours, followed by further stirring for 1 hour. After completion of the cyclization reaction, ethanol was distilled off, extracted with 400 g of toluene, and washed twice with 5% saline. When toluene and epichlorohydrin were removed from the organic layer under reduced pressure, 361.7 g (yield: 85.2%) of a brown viscous liquid was obtained. The purity of the main product, 3,4′-TGDDE, was 84% (HPLC area%).

[Evaluation methods]
(1) Physical properties of cured resin (1-1) Preparation of epoxy resin composition A soluble thermoplastic resin was dissolved in an epoxy resin at 120 ° C at a ratio described in Table 1 using a stirrer. Thereafter, the temperature was lowered to 80 ° C., a curing agent and a non-soluble thermoplastic resin were added, and mixed for 30 minutes to prepare an epoxy resin composition. In the composition shown in Table 1, the glycidyl group of the epoxy resin and the amino group of the curing agent are equivalent.

(1-2) Preparation of cured resin product After defoaming the epoxy resin composition prepared in (1-1) in a vacuum, a silicon resin product set to a thickness of 4 mm with a 4 mm thick silicon resin spacer It was poured into the mold. It was cured at a temperature of 180 ° C. for 2 hours to obtain a cured resin having a thickness of 4 mm.

(1-3) Viscosity Using a rheometer ARES-RDA manufactured by TA Instruments Inc., using a parallel plate with a diameter of 25 mm, setting the thickness of the epoxy resin composition between the parallel plates to 0.5 mm, and an angular velocity of 10 The viscosity of the epoxy resin composition adjusted at (1-1) up to 180 ° C. at a heating rate of 2 ° C./min under the condition of radians / second was measured, and the viscosity at 100 ° C. was measured from the temperature-viscosity curve.

(1-4) Resin bending strength and resin bending elastic modulus The test was carried out according to JIS K7171 method. The dimension of the resin test piece at that time was prepared as 80 mm × 10 mm × 4 mm. The distance L between fulcrums was 16 × h (thickness), a bending test was performed at a test speed of 2 m / min, and the bending strength and the bending elastic modulus were measured.

(1-5) DMA-Tg
The glass transition temperature was measured according to the SACMA 18R-94 method.
The dimension of the resin test piece was prepared as 50 mm × 6 mm × 2 mm. Using a dynamic viscoelasticity measuring device Rheogel-E400 manufactured by UBM, the distance between chucks is 30 mm under the conditions of a measurement frequency of 1 Hz, a heating rate of 5 ° C./min, and a strain of 0.0167%. The storage elastic modulus E ′ was measured up to. Log E ′ was plotted against temperature, and the temperature obtained from the intersection of the approximate straight line of the flat region of log E ′ and the approximate straight line of the region where E ′ transitions was recorded as the glass transition temperature (Tg).

(2) Handling of prepreg (2-1) Preparation of prepreg Using a reverse roll coater, the epoxy resin composition obtained in (1-1) is applied onto release paper, and a resin having a weight of 50 g / m ^2. A film was prepared. Next, the carbon fibers were aligned in one direction so that the fiber mass per unit area was 190 g / m ² to prepare a sheet-like reinforcing fiber base layer. The resin film was stacked on both surfaces of the reinforcing fiber base layer, and heated and pressurized under the conditions of a temperature of 95 ° C. and a pressure of 0.2 MPa, to prepare a unidirectional prepreg having a carbon fiber content of 65% by mass.

(2-2) Storage stability The prepreg obtained in (2-1) was stored at a temperature of 26.7 ° C. and a humidity of 65% for 10 days, and then evaluated by cutting the prepreg and laminating it on a mold. The evaluation results were expressed by the following criteria (◯ to ×).
○: Even if laminated on a mold, it follows sufficiently, and the handleability is almost the same as immediately after production.
X: The prepreg curing reaction has progressed, the tack / draping property has been remarkably lowered, and it is difficult to laminate the mold onto the mold.

(2-3) Molding Void After storing the prepreg obtained in (2-1) at a temperature of 26.7 ° C. and a humidity of 65% for 10 days, the prepreg was cut into 150 mm × 150 mm, and the laminated configuration [0] ₁₀ Lamination was performed, and the laminate was subjected to compaction treatment (storage of the laminate in a vacuum pack) and stored in an environment at a temperature of 23 ° C.
After 32 days of lamination, a normal vacuum autoclave molding method was used, and molding was performed for 2 hours under the condition of 180 ° C. under a pressure of 0.59 MPa. The test piece was cut out and subjected to cross-sectional polishing, and the presence or absence of voids was observed with a microscope.
○: No void ×: With void

(2-4) Tack property The tack property of the prepreg was measured by the following method using a tacking test apparatus TAC-II (RHESCA CO., LTD.). As a test method, the prepreg obtained in (2-1) was set on a test stage held at 27 ° C., an initial load of 100 gf was applied with a φ5 tack probe held at 27 ° C., and 10 mm / sec. The maximum load at the time of drawing at the test speed was determined.
A tack probe test was performed on the prepreg immediately after production and the prepreg stored at a temperature of 26.7 ° C. and a humidity of 65% for 10 days. The evaluation results were expressed by the following criteria (◯ to ×).
○: The load immediately after production is 200 gf or more, and the tack retention after storage for 10 days is 50% or more and less than 100%. ×: The load immediately after production is 200 gf or more and the tack retention after 10 days storage is less than 50%.

(2-5) Drapability The drapeability of the prepreg was evaluated by the following test in accordance with ASTM D1388. The prepreg obtained in (2-1) was cut in a 90 ° direction with respect to the 0 ° fiber direction, and the drapability (flexibility rigidity, mg * cm) against an inclination with an inclination angle of 41.5 ° was evaluated. This evaluation was performed immediately after manufacturing the prepreg and after storage for a predetermined period at a temperature of 26.7 ° C. and a humidity of 65%. The evaluation results were expressed by the following criteria (◯ to ×).
○: Drapability after 20 days is the same as immediately after production.
X: Drapability after 20 days has decreased by 50% or more compared to immediately after production

(3) Physical properties of CFRP (3-1) OHC
The prepreg obtained in (2-1) was cut into a square having a side of 360 mm and laminated to obtain a laminated body having a laminated structure [+ 45/0 / −45 / 90] _3S . Using a normal vacuum autoclave molding method, molding was performed for 2 hours at 180 ° C. under a pressure of 0.59 MPa. The obtained molded product was cut into a dimension of width 38.1 mm × length 304.8 mm, drilled with a diameter of 6.35 mm at the center of the test piece, and a test piece for perforated compressive strength (OHC) test was obtained. .
The test piece and the test were measured according to SACMA SRM3, and the porous compressive strength was calculated from the maximum point load.

(3-2) In-plane shear strength (IPSS) and in-plane shear modulus (IPSM)
The prepreg obtained in (2-1) was cut into a square having a side of 300 mm and laminated to obtain a laminated body having a laminated structure [+ 45 / −45] _2S .
The measurement sample was molded for 2 hours under the condition of 180 ° C. under a pressure of 0.59 MPa using a normal vacuum autoclave molding method. The obtained molded product was cut into a size of 25 mm wide × 230 mm long, measured according to SACMA SRM7, and IPS strength and elastic modulus were calculated from the maximum point load.

(3-3) Compressive strength after impact (CAI)
The prepreg obtained in (2-1) was cut into a square having a side of 360 mm and laminated to obtain a laminated body having a laminated structure [+ 45/0 / −45 / 90] _3S . Using a normal vacuum autoclave molding method, molding was performed for 2 hours at 180 ° C. under a pressure of 0.59 MPa. The obtained molded product was cut into a size of 101.6 mm width × 152.4 mm length to obtain a test piece for compressive strength after impact (CAI) test. The specimen (sample) was subjected to measurement of the dimensions of each test piece, and the impact test was performed using a falling weight impact tester (Dynatop, manufactured by Instron) and applied impact energy of 30.5 J. After the impact, the damaged area of the specimen was measured with an ultrasonic flaw detector (Scratch Kramer SDS3600, HIS3 / HF). After the impact, the strength test of the specimen was performed by applying one strain gauge to each of the left and right sides of the specimen at 25.4 mm from the top and 25.4 mm from the side. After affixing the gauge, the crosshead speed of the testing machine (manufactured by Shimadzu Corporation) was 1.27 mm / min, and a load was applied until the specimen was broken.

(3-4) Interlaminar fracture toughness mode I (GIc)
The prepreg obtained in (2-1) was cut into a square having a side of 360 mm, and then laminated to produce two laminates in which 10 layers were laminated in the 0 ° direction. In order to generate an initial crack, the release sheet was sandwiched between 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 performed for 2 hours at 180 ° C. under a pressure of 0.59 MPa. The obtained molded product (FRP) was cut into a dimension of width 12.7 mm × length 330.2 mm to obtain a test piece of interlaminar fracture toughness mode I (GIc).
As a test method of GIc, a double cantilever interlaminar fracture toughness test method (DCB method) is used, and after a 12.7 mm pre-crack (initial crack) is generated from the tip of the release sheet, a test to further develop the crack Went. The test was terminated when the crack growth length reached 127 mm from the tip of the pre-crack. The crosshead speed of the test piece tensile tester was 12.7 mm / min, and measurement was performed at n = 5.
The crack propagation length was measured from both end faces of the test piece using a microscope, and GIc was calculated by measuring the load and crack opening displacement.

(3-5) Interlaminar fracture toughness mode II (GIIc)
After the prepreg obtained in (2-1) was cut to a predetermined size, two laminates were produced by laminating and laminating 10 layers in the 0 ° direction. In order to form an initial crack, a release sheet was sandwiched between 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 performed for 2 hours at 180 ° C. under a pressure of 0.59 MPa. The obtained molded product (fiber reinforced composite material) was cut into a dimension of width 12.7 mm × length 330.2 mm to obtain a test piece of interlaminar fracture toughness mode II (GIIc). A GIIc test was performed using this test piece.
As a GIIc test method, an ENF test (end notched flexure test) in which a three-point bending load is applied was performed. The distance between fulcrums was 101.6 mm. Place the test piece so that the tip of the sheet made of PTFE sheet with a thickness of 25 μm is 38.1 mm from the fulcrum, and apply a bending load to this test piece at a speed of 2.54 mm / min to cause initial cracks. Formed.
Thereafter, the test piece was placed so that the tip of the crack was at a position 25.4 mm from the fulcrum, and the test was performed by applying a bending load at a speed of 2.54 mm / min. Similarly, three tests were performed, and GIIc of each time was calculated from the load-stroke of each bending test, and then the average value thereof was calculated.
The tip of the crack was measured from both end faces of the test piece using a microscope. The measurement of the GIIc test was performed using n = 5 test pieces.

[Examples 1-6, Comparative Examples 1-5]
The components described in Table 1 were mixed using a stirrer to obtain an epoxy resin composition. Table 1 shows various physical properties of the cured resin obtained by curing the obtained epoxy resin composition. Examples 1 to 5 showed a low viscosity of 130 Pa · s or less at 100 ° C., a high bending strength of 180 MPa or more, a high bending elastic modulus of 4.3 GPa or more, and a high Tg of 190 ° C. or more.

  A prepreg was prepared using each epoxy resin composition obtained above and IMS65 E23 830tex. Various handling properties of the obtained prepreg are shown in Table 1. Examples 1 to 6 showed good results in all evaluations of storage stability, molding voids, tackiness, and drapeability.

Table 1 shows various physical properties of CFRP prepared using the obtained prepreg. Examples 1 to 6 have a high OHC of 320 MPa or more, a high IPSS of 120 MPa or more, a high IPSM of 5.7 GPa or more, a high CAI of 310 MPa or more, a low CAI damage area of 4.0 cm ² or less, and 620 J / m ² or more. A high GIc of 2200 J / m ² or higher was exhibited.

In Comparative Examples 1 and 4, the viscosity was lowered using DGEBA without using the epoxy resin [B], but the physical properties of the resin and the CFRP were lowered.
In Comparative Example 2, the viscosity was lowered using TG-mAP without using the epoxy resin [B], but the storage stability of the prepreg was lowered.
In Comparative Examples 3 and 5, TGDDM was used without using the epoxy resin [A], but the resin physical properties of CFRP were low.
In Comparative Example 4, the viscosity was lowered using TG-mAP without using the epoxy resin [B], but the physical properties of CFRP were lowered.

[Examples 7 to 10]
The components described in Table 1 were mixed using a stirrer to obtain an epoxy resin composition. Table 1 shows various physical properties of the cured resin obtained by curing the obtained epoxy resin composition. Examples 7 to 10 exhibited a low viscosity of 130 Pa · s or less at 100 ° C., a high bending strength of 180 MPa or more, a high bending elastic modulus of 4.3 GPa or more, and a high Tg of 190 ° C. or more.

  A prepreg was prepared using each epoxy resin composition obtained above and IMS65 E22 830tex. Various handling properties of the obtained prepreg are shown in Table 1. Examples 7 to 10 showed good results in all evaluations of storage stability, molding voids, tackiness, and drapeability.

Table 1 shows various physical properties of CFRP prepared using the obtained prepreg. Examples 7 to 10 have a high OHC of 320 MPa or more, a high IPSS of 120 MPa or more, a high IPSM of 5.7 GPa or more, a high CAI of 310 MPa or more, a low CAI damage area of 4.0 cm ² or less, a 660 J / m ² or more. A high GIc of 2200 J / m ² or higher was exhibited.

Claims (8)

The following chemical formula (1)

(However, in Chemical Formula (1), R _{1 to} R ₄ each independently represents one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and a halogen atom; Is —CH ₂ —, —O—, —S—, —CO—, —C (═O) O—, —O—C (═O) —, —NHCO—, —CONH—, —SO ₂ —. Represents one selected.)
An epoxy resin [A] represented by:
An aromatic epoxy resin having a glycidyl ether group, wherein the number of glycidyl ethers / the number of aromatic rings is 2;
An epoxy resin composition comprising:   The epoxy resin composition according to claim 1, wherein the epoxy resin [A] is tetraglycidyl-3,4′-diaminodiphenyl ether.   The epoxy resin composition according to claim 1 or 2, wherein the epoxy resin [B] is diglycidyl resorcinol.   The epoxy resin composition according to any one of claims 1 to 3, wherein a mass ratio of the epoxy resin [A] and the epoxy resin [B] is 2: 8 to 9: 1. A reinforcing fiber substrate;
The epoxy resin composition according to any one of claims 1 to 4, impregnated in the reinforcing fiber substrate,
A prepreg characterized by comprising:   The prepreg according to claim 5, wherein the reinforcing fiber base is a reinforcing fiber base made of carbon fiber.   A method for producing a prepreg, comprising impregnating a reinforcing fiber substrate with the epoxy resin composition according to any one of claims 1 to 4. A method for producing a fiber-reinforced composite material, wherein the prepreg according to claim 5 or 6 is laminated and heated at a pressure of 0.05 to 2 MPa and a temperature of 150 to 210 ° C for 1 to 8 hours.