JP7190258B2 - Epoxy resin composition, prepreg, and fiber reinforced composite - Google Patents

Description

The present invention relates to epoxy resin compositions, prepregs, and fiber-reinforced composites. In more detail, an epoxy resin composition having high heat resistance and elastic modulus as well as high handleability as a cured resin composition; a prepreg produced using the epoxy resin composition; a fiber-reinforced composite produced using the prepreg Regarding materials.

Fiber-reinforced composite materials, which consist of reinforcing fibers and resins, have features such as light weight, high strength, and high elastic modulus, and are widely used in 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 matrix resin are integrated in advance.

A thermosetting resin or a thermoplastic resin is used as the resin constituting the prepreg. In particular, prepregs using thermosetting resins are widely used because of their high degree of freedom in molding due to their tackiness and drapeability. Since thermosetting resins generally have low toughness, when thermosetting resins are used as resins constituting prepregs, there is a problem that CFRPs produced using these prepregs have low impact resistance. Therefore, methods for improving impact resistance have been investigated.

Methods described in Patent Documents 1 to 4 are conventionally known as methods for improving such impact resistance.
Patent Literature 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 thermosetting resin. As a result, the thermosetting resin in which a large amount of thermoplastic resin is dissolved has a significantly high viscosity, making it difficult to impregnate the inside of the fiber-reinforced base material made of carbon fibers with a sufficient amount of resin. Composites produced using such prepregs contain many defects such as voids. As a result, the compressive performance and damage tolerance of the composite structure are negatively impacted.
Patent Documents 2 to 4 describe prepregs in which thermoplastic resin fine particles are localized on the prepreg surface. These prepregs have a low initial tackiness due to localized particle-shaped thermoplastic resin on the surface. In addition, since the curing reaction proceeds with the curing agent present in the surface layer, the storage stability is poor, and the tackiness and drape properties deteriorate over time. Furthermore, a composite produced using such a prepreg in which the curing reaction has progressed contains many defects such as voids, and the mechanical properties of the composite structure are remarkably deteriorated.

Japanese Patent Laid-Open No. 60-243113 Japanese Patent Laid-Open No. 07-41575 Japanese Patent Laid-Open No. 07-41576 Japanese Patent Laid-Open No. 07-41577

An object of the present invention is to solve the above-mentioned problems of the prior art, and to produce a resin cured product having high heat resistance and elastic modulus, and to improve the impregnation property of the fiber reinforced base material and to handle the epoxy resin. An object of the present invention is to provide a resin composition. A further object of the present invention is to provide a prepreg and a fiber-reinforced composite material (hereinafter sometimes abbreviated as "FRP") produced using this epoxy resin composition, in particular, the fiber-reinforced base material is carbon fiber. (which may be abbreviated as “CFRP” in some cases).

As a result of investigations aimed at solving the above problems, the present inventors have found that the above problems can be solved by using an epoxy resin composition composed of a predetermined combination of epoxy resins, and have completed the present invention.

The present invention for achieving the above objects is described below.

[1] the following chemical formula (1)

(wherein 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-, -OC(=O)-, -NHCO-, -CONH-, -SO ₂ - represents one selected from.)
An epoxy resin [A] represented by
an epoxy resin [B] having an epoxy equivalent of 110 g/eq or less;
An epoxy resin composition comprising:

The invention described in [1] above is an epoxy resin composition obtained by mixing epoxy resin [A] and epoxy resin [B].

[2] The epoxy resin composition according to [1], wherein the epoxy resin [B] is a trifunctional epoxy resin.

The invention described in [2] above is characterized in that the epoxy resin [B] is a trifunctional epoxy resin. By using a trifunctional epoxy resin, the viscosity of the obtained resin composition can be kept low. Furthermore, the impregnating property and handleability of the resulting epoxy resin composition into the fiber-reinforced base material can be sufficiently enhanced.

[3] The epoxy resin composition according to [1], wherein the epoxy resin [B] is a triglycidylaminophenol derivative.

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

[5] The content of the epoxy resin [A] is 20 to 95% by mass based on the total amount of the epoxy resin, and the content of the epoxy resin [B] is 5 to 80% by mass based on the total amount of the epoxy resin. The epoxy resin composition according to any one of [1] to [4].

In the invention described in [5] above, the contents of the epoxy resin [A] and the epoxy resin [B] are within a predetermined range. By containing it in this ratio, it is possible to sufficiently improve the impregnability and handleability of the epoxy resin composition with respect to the fiber-reinforced base material while maintaining high heat resistance and elastic modulus of the resulting cured resin.

[6] a fiber-reinforced base material;
the epoxy resin composition according to any one of [1] to [5] impregnated in the fiber-reinforced base material;
A prepreg characterized by comprising:

The invention described in [6] above is a prepreg obtained by impregnating a fiber-reinforced base material with the epoxy resin composition described in any one of [1] to [5].

[7] A fiber-reinforced composite material comprising a cured resin obtained by curing the epoxy resin composition according to any one of [1] to [5], and a fiber-reinforced base material.

[8] A fiber-reinforced composite material obtained by curing the prepreg of [6].

The inventions described in [7] and [8] above are fiber-reinforced resins obtained by combining the cured resin of the epoxy resin composition described in any one of [1] to [5] and a fiber-reinforced base material. Composite material.

The epoxy resin composition of the present invention can produce a cured resin having high heat resistance and elastic modulus. In addition, since the epoxy resin composition of the present invention has high impregnating properties and handleability with respect to fiber-reinforced substrates, FRP having excellent properties can be produced.

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 below.

1. Epoxy Resin Composition The epoxy resin composition of the present invention comprises at least epoxy resin [A] and epoxy resin [B]. In addition to these, the epoxy resin composition of the present invention may contain a thermoplastic resin, a curing agent, 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, more preferably 1 to 100 Pa·s. If it is less than 0.1 Pa·s, the resin tends to flow out from the prepreg. If it exceeds 500 Pa·s, the prepreg tends to have non-impregnated portions. As a result, voids and the like are likely to be formed in the resulting 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, more preferably 170°C to 400°C. If the temperature is less than 150°C, the heat resistance is insufficient. As a result, voids and the like are likely to be formed in the resulting fiber-reinforced composite material.

The cured resin obtained by curing the epoxy resin composition of the present invention preferably has a flexural modulus of 3.0 GPa or more, more preferably 3.5 GPa to 30 GPa, as measured by the JIS K7171 method. 0 GPa to 20 GPa is more preferred. If it is less than 3.0 GPa, the properties of the resulting fiber-reinforced composite material tend to deteriorate.

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

(wherein 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-, -OC(=O)-, -NHCO-, -CONH-, -SO ₂ - represents one selected from.)
Contains epoxy resin [A] represented by. When R ₁ to R ₄ are aliphatic hydrocarbon groups or alicyclic hydrocarbon groups, they preferably have 1 to 4 carbon atoms.

Epoxy resin [A] is a tetrafunctional epoxy resin, and amino groups having two glycidyl groups are bonded to a diaminodiphenyl skeleton at the para- and meta-positions, respectively. The present inventors presume that the elastic modulus and heat resistance of the cured resin increase due to the special three-dimensional structure of the cured resin produced by this structure.

The epoxy resin [A] is preferably tetraglycidyl-3,4'-diaminodiphenyl ether. When R ₁ to R ₄ are hydrogen atoms, the formation of a special steric structure of the cured resin is less likely to be inhibited, which is preferable. In addition, it is preferable that X is -O- because the synthesis of the compound is facilitated.

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 95% by mass, and 55 to 95% by mass. More preferably, it is 90% by mass. If it is less than 20% by mass, the heat resistance and elastic modulus of the resulting cured resin may be lowered. If it exceeds 95% by mass, the viscosity of the epoxy resin composition is high, and the impregnation of the fiber-reinforced base material tends to deteriorate. As a result, in any case, various physical properties of the resulting CFRP may deteriorate.

(1-2) Epoxy resin [B]
The epoxy resin composition of the present invention contains an epoxy resin [B] having an epoxy equivalent of 110 g/eq or less.
The epoxy resin [B] lowers the viscosity of the epoxy resin [A], improves the resin impregnating properties during prepreg production, and improves the elastic modulus of the cured resin. Therefore, by using epoxy resin [A] and epoxy resin [B] in combination, it is possible to improve various physical properties of FRP while maintaining heat resistance and high elastic modulus.

The epoxy resin [B] is not particularly limited as long as it has an epoxy equivalent of 110 g/eq or less, but triglycidylaminophenol, tetraglycidyl-m-xylylenediamine, tetraglycidylbis(aminomethyl)cyclohexane, and It is preferable to use glycidylamine type epoxy resins such as these derivatives, and it is more preferable to use epoxy resins containing aromatic groups such as triglycidylaminophenol and tetraglycidyl-m-xylylenediamine. It is preferred to use trifunctional epoxy resins such as glycidylaminophenol and its derivatives.

The ratio of the epoxy resin [B] to the total amount of the epoxy resin in the epoxy resin composition of the present invention is preferably 5 to 80% by mass, more preferably 5 to 60% by mass, and 10 to 80% by mass. More preferably, it is 45% by mass. If it is less than 5% by mass, the viscosity of the epoxy resin composition is high, and the impregnation of the fiber-reinforced base material tends to deteriorate. If it exceeds 80% by mass, the heat resistance and elastic modulus of the resulting cured resin may decrease. As a result, in any case, various physical properties of the resulting CFRP may deteriorate.

The mass ratio of the epoxy resin [A] to the epoxy resin [B] in the epoxy resin composition of the present invention is preferably 20:80 to 98:2, more preferably 50:50 to 95:5. More preferably, it is 60:40 to 80:20. By blending in this ratio, it is possible to produce an epoxy resin composition having a viscosity suitable for producing a prepreg, and to obtain a cured product having good prepreg handleability, heat resistance, and high elastic modulus. Moreover, the more epoxy B, the better the handleability of the prepreg.

The epoxy resin composition of the present invention essentially contains the two types of epoxy resins described above, but may contain other epoxy resins.

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 preferred, and an epoxy resin containing either a glycidylamine structure or a glycidyl ether structure is preferred. Alicyclic epoxy resins can also be suitably used.
Examples of 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-type epoxy resins, bisphenol F-type epoxy resins, bisphenol S-type epoxy resins, phenol novolac-type epoxy resins, and cresol novolak-type epoxy resins.
In addition, these epoxy resins may optionally have a non-reactive substituent on the aromatic ring structure or the like. 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) Curing Agent The epoxy resin [A] and epoxy resin [B] contained in the epoxy resin composition of the present invention are cured with a curing agent. The epoxy resin composition of the present invention may or may not contain this curing agent in advance. An epoxy resin composition that does not contain a curing agent is in a state that can be mixed with a curing agent before or during curing.

The curing agent used in the present invention is a known curing agent for curing epoxy resins. As the curing agent, any substance that cures the epoxy resin [A] and the epoxy resin [B] may be used, and is appropriately selected according to the purpose of use.
Specific examples include dicyandiamide, various isomers of aromatic amine curing agents, and aminobenzoic acid esters. Dicyandiamide is preferable because it is excellent in storage stability of the prepreg. In addition, aromatic diamine compounds such as 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylmethane and their derivatives having non-reactive substituents have high heat resistance. It is particularly preferred because a cured product can be obtained. Furthermore, 3,3′-diaminodiphenyl sulfone is most preferable because the heat resistance and elastic modulus of the cured resin obtained are high. 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.

Preferred aminobenzoic acid esters include trimethylene glycol di-p-aminobenzoate and neopentyl glycol di-p-aminobenzoate. Composites cured with these curing agents have lower heat resistance but higher tensile elongation than composites cured with various isomers of diaminodiphenylsulfone. Therefore, the curing agent is appropriately selected depending on the application of the composite material.

The amount of the curing agent contained in the epoxy resin composition is an amount suitable for curing all the epoxy resins contained in the epoxy resin composition, and is appropriately selected according to the type of epoxy resin and curing agent used. adjusted. For example, when an aromatic diamine compound is used as a curing agent, it is preferably used in an amount of 25 to 65 parts by mass, more preferably 35 to 55 parts by mass, based on 100 parts by mass of the total epoxy resin.

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

(1-4-1) Epoxy resin-soluble thermoplastic resin The epoxy resin composition may 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 obtained FRP.

An epoxy resin-soluble thermoplastic resin is a thermoplastic resin that can partially or wholly dissolve in an epoxy resin at a temperature at which FRP is molded or at a temperature lower than that. Here, the term “partially dissolved in the epoxy resin” means that 10 parts by mass of a thermoplastic resin having an average particle size of 20 to 50 μm is mixed with 100 parts by mass of the epoxy resin, and when the mixture is stirred at 190° C. for 1 hour, the particles disappears or the particle size changes by 10% or more.
On the other hand, the term “epoxy resin-insoluble thermoplastic resin” refers to a thermoplastic resin that does not substantially dissolve in epoxy resin at temperatures at or below the FRP molding temperature. That is, when 10 parts by mass of a thermoplastic resin having an average particle size of 20 to 50 μm is mixed with 100 parts by mass of an epoxy resin and stirred at 190° C. for 1 hour, the particle size does not change by 10% or more. Refers to plastic resin. The temperature for molding FRP is generally 100 to 190°C. Moreover, the particle size is visually measured with a microscope, and the average particle size means the average value of the particle sizes of 100 randomly selected particles.

When the epoxy resin-soluble thermoplastic resin is not completely dissolved, it is 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 makes it possible to prevent the epoxy resin composition from flowing (phenomenon in which the resin composition flows out of the prepreg) due to a decrease in viscosity during the curing process.

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

Specific examples of epoxy resin-soluble thermoplastic resins include polyethersulfone, polysulfone, polyetherimide, polycarbonate and the like. 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) measured by gel permeation chromatography in the range of 8,000 to 100,000. 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 handleability will be significantly deteriorated. The epoxy resin-soluble thermoplastic resin preferably has a uniform molecular weight distribution. 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, more 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 forming a hydrogen bond. Such an epoxy resin-soluble thermoplastic resin can improve the dissolution stability during the curing process of the epoxy resin. In addition, toughness, chemical resistance, heat resistance and resistance to moist heat can be imparted to the FRP obtained after curing.

A hydroxyl group, a carboxylic acid group, an imino group, an amino group and the like are preferable as the reactive group having reactivity with the epoxy resin. The use of hydroxyl-terminated polyethersulfone is more preferable because the resulting FRP 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 is appropriately adjusted according to the viscosity. From the viewpoint of workability of the prepreg, it is preferably 5 to 90 parts by mass, more preferably 5 to 40 parts by mass, and even more preferably 15 to 35 parts by mass with respect to 100 parts by mass of the epoxy resin contained in the epoxy resin composition. . If it 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 becomes high, the viscosity becomes extremely high, and the handleability of the prepreg may be significantly 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. The expansion of the two-phase region due to the increase in the molecular weight causes the aromatic oligomer dissolved in the epoxy resin composition to undergo reaction-induced phase separation. Due to this phase separation, a two-phase resin structure in which the cured epoxy resin and the aromatic oligomer are co-continuous is formed in the matrix resin. Also, since aromatic oligomers have amine end groups, they also react with epoxy resins. 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 an external impact on the FRP and suppresses crack propagation. As a result, FRPs made using prepregs containing reactive aromatic oligomers with amine end groups have high impact resistance and fracture toughness.

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

The aromatic oligomer blended in the epoxy resin composition 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 8000, the effect of improving the toughness of the matrix resin is low. On the other hand, when the weight average molecular weight exceeds 40,000, the viscosity of the resin composition becomes too high, and processing problems such as difficulty in impregnating the reinforcing fiber layer with the resin composition tend to occur.

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.

Although the form of the epoxy resin-soluble thermoplastic resin is not particularly limited, it is preferably particulate. The particulate epoxy resin-soluble thermoplastic resin can be uniformly blended in the resin composition. In addition, the prepreg to be obtained has high moldability.

The average particle size of the epoxy resin-soluble thermoplastic resin is preferably 1 to 50 μm, particularly preferably 3 to 30 μm. If it is less than 1 μm, the viscosity of the epoxy resin composition is significantly increased. Therefore, it may be difficult to add a sufficient amount of epoxy resin-soluble thermoplastic resin to the epoxy resin composition. 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. Moreover, the rate of dissolution in the epoxy resin becomes slow, and the obtained FRP becomes uneven, which 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 the epoxy resin-insoluble thermoplastic resin and epoxy resin-soluble thermoplastic resin (the epoxy resin-soluble thermoplastic resin that remains undissolved in the matrix resin after curing) is in a state where the particles are dispersed in the FRP matrix resin. (The dispersed particles are hereinafter also referred to as “interlayer particles”). This interlayer particle suppresses the propagation of the impact received by the FRP. As a result, the impact resistance of the obtained FRP is improved.

Examples of epoxy resin-insoluble thermoplastic resins include polyamide, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyester, polyamideimide, polyimide, polyetherketone, polyetheretherketone, polyethylene naphthalate, polyethernitrile, and polybenzimidazole. . Among these, polyamide, polyamideimide, and polyimide are preferred because of their high toughness and heat resistance. Polyamide and polyimide are particularly excellent in improving the toughness of FRP. These may be used alone or in combination of two or more. Copolymers of these 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 the ring-opening polycondensation reaction), Nylon 1010 (polyamide obtained by the copolymerization reaction of sebacic acid and 1,10-decanediamine), amorphous nylon (also called transparent nylon, polymer crystals The heat resistance of the resulting FRP can be particularly improved by using a polyamide such as nylon, which does not undergo quenching or has a very slow crystallization rate of the polymer.

The content of the epoxy resin-insoluble thermoplastic resin in the epoxy resin composition is appropriately adjusted according to the viscosity of the epoxy resin composition. From the viewpoint of workability of the prepreg, it is preferably 5 to 50 parts by mass, more preferably 10 to 45 parts by mass, more preferably 20 to 50 parts by mass with respect to 100 parts by mass of the epoxy resin contained in the epoxy resin composition. It is more preferably 40 parts by mass. If it is less than 5 parts by mass, the resulting FRP may have insufficient impact resistance. If it exceeds 50 parts by mass, the impregnability of the epoxy resin composition and the drapeability of the obtained prepreg may be deteriorated.

The preferred average particle size and shape 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, flame retardants, inorganic fillers, and internal release agents.

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; Particles in which a core material made of an inorganic material or an organic material is coated with a conductive substance are exemplified.

Examples of flame retardants include phosphorus-based flame retardants. The phosphorus-based flame retardant is not particularly limited as long as it contains a phosphorus atom in the molecule. be 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, and silicate minerals. is mentioned. In particular, it is preferable to use silicate minerals. Commercially available silicate minerals include THIXOTROPIC AGENT DT 5039 (manufactured by Huntsman Japan KK).

Examples of internal release agents include metal soaps, vegetable waxes such as polyethylene wax and carnauba wax, fatty acid ester release agents, silicone oils, animal waxes, and fluorine-based nonionic surfactants. The content of these internal release agents is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 2 parts by mass, per 100 parts by mass of the epoxy resin. Within this range, the release effect from the mold is favorably exhibited.

Commercially available internal 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), 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], an epoxy resin [B], and optionally a thermoplastic resin, a curing agent, and other components. , can be produced by mixing. The order of these mixtures does not matter.

The method for producing the epoxy resin composition is not particularly limited, and any conventionally known method may be used. As the mixing temperature, a range of 40 to 120°C can be exemplified. If the temperature exceeds 120° C., the curing reaction partially progresses and impregnation into the fiber-reinforced base material layer is lowered, or the storage stability of the obtained epoxy resin composition and the prepreg produced using the same is deteriorated. It may decline. If the temperature is less than 40°C, the viscosity of the epoxy resin composition is high, and mixing may be substantially difficult. It is preferably in the range of 50 to 100°C, more preferably in the range of 50 to 90°C.

A conventionally known machine can be used as the mixing machine. Specific examples include roll mills, planetary mixers, kneaders, extruders, Banbury mixers, mixing vessels equipped with stirring blades, and horizontal mixing tanks. Mixing of each component can be performed in air or under an inert gas atmosphere. When mixing is performed in air, an atmosphere in which temperature and humidity are controlled is preferable. Although not particularly limited, for example, it is preferable to mix at a temperature controlled at a constant temperature of 30° C. or less or in a low-humidity atmosphere with a relative humidity of 50% RH or less.

2. Prepreg The prepreg of the present invention comprises a fiber-reinforced base material and the above-described epoxy resin composition of the present invention impregnated in the fiber-reinforced base material (hereinafter also referred to as "present epoxy resin composition").

The prepreg of the present invention is a prepreg in which a fiber-reinforced base material is partially or wholly impregnated with the epoxy resin composition. The content of the present epoxy resin composition in the entire prepreg is preferably 15 to 60% by mass based on the total mass of the prepreg. If the resin content is less than 15% by mass, voids and the like may occur in the resulting fiber-reinforced composite material, degrading mechanical properties. If the resin content exceeds 60% by mass, the reinforcing effect of the reinforcing fibers may be insufficient, resulting in substantially low mechanical properties relative to mass. The resin content is preferably 20 to 55% by mass, more preferably 25 to 50% by mass.

(2-1) Fiber-reinforced base material The fiber-reinforced base material used in the present invention is not particularly limited, and examples thereof include carbon fiber, glass fiber, aramid fiber, silicon carbide fiber, polyester fiber, ceramic fiber, alumina fiber, and boron. Fibers, metal fibers, mineral fibers, rock fibers, slag fibers and the like.

Among these reinforcing fibers, carbon fibers, glass fibers, and aramid fibers are preferred. Carbon fiber is more preferable because it has good specific strength and specific modulus, and provides a lightweight and high-strength fiber-reinforced composite material. Polyacrylonitrile (PAN)-based carbon fibers are particularly preferred because of their excellent tensile strength.

When PAN-based carbon fiber is used as the reinforcing fiber, its tensile modulus is preferably 100 to 600 GPa, more preferably 200 to 500 GPa, and particularly preferably 230 to 450 GPa. Also, the tensile strength is preferably 2000 MPa to 10000 MPa, more preferably 3000 to 8000 MPa. The diameter of the carbon fiber is preferably 4-20 μm, more preferably 5-10 μm. By using such carbon fibers, the mechanical properties of the resulting fiber-reinforced composite material can be improved.

It is preferable to form the reinforcing fiber into a sheet for use. Examples of reinforcing fiber sheets include sheets in which a large number of reinforcing fibers are aligned in one direction, bidirectional woven fabrics such as plain weaves and twill weaves, multiaxial woven fabrics, nonwoven fabrics, mats, knits, braids, and paper made from reinforced fibers. can be mentioned. Among these, it is preferable to use a unidirectional aligning sheet, a bidirectional woven fabric, or a multiaxial woven fabric base material in which reinforcing fibers are formed into a sheet form as continuous fibers, since a fiber-reinforced composite material with more excellent mechanical properties can be obtained. The thickness of the sheet-like fiber-reinforced base material is preferably 0.01 to 3 mm, more preferably 0.1 to 1.5 mm.

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

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

A method for forming a resin composition film from a resin composition is not particularly limited, and any conventionally known method can be used. Specifically, using a die extrusion, an applicator, a reverse roll coater, a comma coater, etc., a resin composition film is obtained by casting the resin composition onto a support such as a release paper or a film. can be done. The resin temperature when 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 method for producing the epoxy resin composition described above are preferably used. The impregnation of the resin composition into the fiber-reinforced base material layer may be performed in one step or in multiple steps.

The solvent method is a method in which the epoxy resin composition is made into a varnish using a suitable solvent, and the fiber-reinforced base material layer is impregnated with this varnish.

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.

When the epoxy resin composition film is impregnated into the fiber-reinforced substrate layer by a hot-melt method, the impregnation temperature is preferably in the range of 50 to 120°C. If the impregnation temperature is lower than 50° C., the epoxy resin has a high viscosity and may not be sufficiently impregnated into the fiber-reinforced base material layer. When the impregnation temperature exceeds 120° C., the curing reaction of the epoxy resin composition proceeds, and the resulting prepreg may have reduced storage stability and drape properties. The impregnation temperature is more preferably 60 to 110°C, particularly preferably 70 to 100°C.

The impregnation pressure when the epoxy resin composition film is impregnated into the fiber-reinforced substrate layer by the hot-melt method is appropriately determined in consideration of the viscosity and resin flow of the resin composition.
A specific impregnation pressure is 0.01 to 250 (N/cm), preferably 0.1 to 200 (N/cm).

3. Fiber-reinforced composite material A fiber-reinforced composite material (FRP ) can be obtained. Moreover, a fiber reinforced composite material (FRP) can be obtained by curing the prepreg of the present invention by heating and pressurizing it under specific conditions. Methods 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 An autoclave molding method is preferably used as the method for producing the FRP of the present invention. In the autoclave molding method, a prepreg and a film bag are sequentially laid in 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. In addition, it is a molding method in which heat and pressure are applied in an autoclave molding device. As for the molding conditions, it is preferable that the heating rate is 1 to 50° C./min, and heating and pressing are performed at 0.2 to 0.7 MPa and 130 to 180° C. for 10 to 30 minutes.

(3-2) Press molding method A press molding method is preferably used as the method for manufacturing the FRP of the present invention. The FRP is manufactured by the press molding method by heating and pressurizing 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 preheated to the curing temperature.

The temperature of the mold during press molding is preferably 150 to 210°C. If the molding temperature is 150° C. or higher, a sufficient curing reaction can occur, and FRP can be obtained with high productivity. Moreover, if the molding temperature is 210° C. or lower, the resin viscosity does not become too low, and excessive flow of the resin in the mold can be suppressed. As a result, the outflow of the resin from the mold and meandering of the fibers can be suppressed, so that a high-quality FRP can be obtained.

The pressure during molding is 0.05 to 2 MPa, preferably 0.2 to 2 MPa. When the pressure is 0.05 MPa or more, the resin can be appropriately flowed, and appearance defects and voids can be prevented. In addition, since the prepreg is sufficiently adhered to the mold, FRP with a good appearance can be manufactured. If the pressure is 2 MPa or less, the resin is not caused to flow more than necessary, so that the resulting FRP is less likely to have poor appearance. In addition, since no excessive load is applied to the mold, deformation of the mold is less likely to occur.
The molding time is preferably 1 to 8 hours.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the examples. Components and test methods used in 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]
・ Triglycidyl-p-aminophenol (Araldite MY0510 manufactured by Huntsman, epoxy equivalent = 97 g / eq, hereinafter abbreviated as “TG-pAP”)
・ Triglycidyl-m-aminophenol (Araldite MY0600 manufactured by Huntsman, epoxy equivalent = 106 g / eq, hereinafter abbreviated as “TG-mAP”)
Other epoxy resins Tetraglycidyl-4,4'-diaminodiphenylmethane (Araldite MY721 manufactured by Huntsman, epoxy equivalent = 112 g/eq, hereinafter abbreviated as "TGDDM")
- Tetraglycidyl-4,4'-diaminodiphenyl ether (synthesized by the method of Synthesis Example 2, epoxy equivalent = 112 g/eq, hereinafter abbreviated as "4,4'-TGDDE")
- Bisphenol A-diglycidyl ether (manufactured by Mitsubishi Chemical Corporation jER825, epoxy equivalent = 176 g / eq, hereinafter abbreviated as "DGEBA")
(curing agent)
- 3,3'-diaminodiphenyl sulfone (manufactured by Konishi Chemical Industry Co., 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”)
(Thermoplastic resin soluble in epoxy resin)
・ Polyethersulfone (Sumitomo Chemical Co., Ltd. Sumika Excel PES-5003P, average particle size 20 μm, hereinafter abbreviated as “PES”)
(carbon fiber strand)
・ “Tenax (registered trademark)” IMS65 E23 830tex (carbon fiber strand, tensile strength 5.8 GPa, tensile modulus 290 GPa, manufactured by Toho Tenax Co., Ltd.)

[Synthesis Example 1] (Synthesis of 3,4′-TGDDE)
A four-necked flask equipped with a thermometer, dropping funnel, condenser and stirrer was charged with 1110.2 g (12.0 mol) of epichlorohydrin, 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. After further stirring for 6 hours, the addition reaction was completed to give N,N,N',N'-tetrakis(2-hydroxy-3-chloropropyl)-3,4'-diaminodiphenyl ether. Subsequently, after the temperature in the flask was lowered to 25° C., 500.0 g (6.0 mol) of 48% NaOH aqueous solution was added dropwise over 2 hours, and the mixture was further stirred for 1 hour. After completion of the cyclization reaction, ethanol was distilled off, extraction was performed with 400 g of toluene, and washing was performed twice with 5% saline. When toluene and epichlorohydrin were removed from the organic layer under reduced pressure, 361.7 g (85.2% yield) of brown viscous liquid was obtained. The purity of 3,4'-TGDDE, which is the main product, was 84% (HPLC area %).

[Synthesis Example 2] (Synthesis of 4,4'-TGDDE)
A four-necked flask equipped with a thermometer, dropping funnel, condenser and stirrer was charged with 1110.2 g (12.0 mol) of epichlorohydrin, and the temperature was raised to 70°C while purging with nitrogen. 1000 g was dissolved. 200.2 g (1.0 mol) of 4,4'-diaminodiphenyl ether was added dropwise over 4 hours. After further stirring for 6 hours, the addition reaction was completed to give N,N,N',N'-tetrakis(2-hydroxy-3-chloropropyl)-4,4'-diaminodiphenyl ether. Subsequently, after the temperature in the flask was lowered to 25° C., 500.0 g (6.0 mol) of 48% NaOH aqueous solution was added dropwise over 2 hours, and the mixture was further stirred for 1 hour. After completion of the cyclization reaction, ethanol was distilled off, extraction was performed with 400 g of toluene, and washing was performed twice with 5% saline. When toluene and epichlorohydrin were removed from the organic layer under reduced pressure, 377.8 g (89.0% yield) of brown viscous liquid was obtained. The purity of the main product, 4,4'-TGDDE, was 87% (HPLC area %).

[Evaluation method]
(1) Physical properties of resin cured product (1-1) Preparation of epoxy resin composition A curing agent is added to the epoxy resin in the proportion shown in Table 1, and mixed with a stirrer at 40 ° C. for 30 minutes to obtain the epoxy resin. A composition was prepared. In addition, in the composition shown in Table 1, the glycidyl groups of the epoxy resin and the amino groups of the curing agent are equivalent.

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

(1-3) Flexural modulus A test was carried out according to JIS K7171 method. At that time, a resin test piece was prepared with dimensions of 80 mm×10 mm×h4 mm. A bending test was performed at a distance L between fulcrums of 16×h (thickness) and a test speed of 2 mm/min to measure the bending elastic modulus.

(1-4) DMA-Tg
The glass transition temperature was measured according to the SACMA 18R-94 method. The dimensions of the resin test piece were 50 mm x 6 mm x 2 mm. Using a dynamic viscoelasticity measuring device Rheogel-E400 manufactured by UBM, the measurement frequency is 1 Hz, the temperature increase rate is 5 ° C./min, and the strain is 0.0167%. The storage 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 transition region of E′ was recorded as the glass transition temperature (Tg).

(2) CFRP Physical Properties (2-1) Preparation of Epoxy Resin Composition An epoxy resin-soluble thermoplastic resin was dissolved in an epoxy resin at 120° C. using a stirrer in the proportions shown in Table 2. Thereafter, the temperature was lowered to 80° C., a curing agent and an epoxy resin-insoluble thermoplastic resin were added, and the mixture was mixed for 30 minutes to prepare an epoxy resin composition.

(2-2) Production of Prepreg Using a reverse roll coater, the epoxy resin composition obtained in (2-1) was applied onto release paper to produce a resin film with a basis weight of 50 g/m ² . Next, 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 fiber-reinforced base material layer. The resin films were laminated on both sides of the fiber-reinforced base material layer, and heated and pressed under conditions of a temperature of 95° C. and a pressure of 0.2 MPa to produce a unidirectional prepreg having a carbon fiber content of 65% by mass.

(2-3) Compressive strength after impact (CAI)
The prepreg obtained in (2-2) was cut into a square with a side of 360 mm and laminated to obtain a laminate having a laminate structure of [+45/0/-45/90] _3S . Molding was carried out for 2 hours at 180° C. under a pressure of 0.59 MPa using a normal vacuum autoclave molding method. The resulting molding was cut into a size of 101.6 mm wide by 152.4 mm long to obtain a specimen for compressive strength after impact (CAI) test. After measuring the dimensions of each test piece, the specimen (sample) was subjected to an impact test using a falling weight type impact tester (Dynatup manufactured by Instron) to give an impact energy of 30.5 J. After the impact, the damaged area of the test piece was measured with an ultrasonic flaw detector (SDS3600, HIS3/HF manufactured by Kraut Kramer). After the impact, the strength test of the specimen was performed by attaching strain gauges on each side of the specimen at a position of 25.4 mm from the top and 25.4 mm from the side. After attaching the gauge, the crosshead speed of the testing machine (Autograph manufactured by Shimadzu Corporation) was set to 1.27 mm/min, and a load was applied until the specimen fractured.

(2-4) Interlaminar fracture toughness mode I (GIc)
The prepreg obtained in (2-2) was cut into a square with a side of 360 mm, and then laminated to prepare two laminates each having 10 layers laminated in the direction of 0°. In order to generate initial cracks, a release sheet was sandwiched between the two laminates, and the two were combined to obtain a prepreg laminate having a laminate structure of [0] ₂₀ . Molding was carried out for 2 hours at 180° C. under a pressure of 0.59 MPa using a normal vacuum autoclave molding method. The obtained molding was cut into a size of 12.7 mm wide×330.2 mm long to obtain a test piece of interlaminar fracture toughness mode I (GIc).
As a test method for GIc, a double cantilever beam interlaminar fracture toughness test method (DCB method) is used, and a precrack (initial crack) of 12.7 mm is generated from the tip of the release sheet, and then the crack is further propagated. did 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 the measurement was performed with n=5.
The crack growth length was measured from both end surfaces of the test piece using a microscope, and GIc was calculated by measuring the load and crack opening displacement.

(2-5) Interlaminar fracture toughness mode II (GIIc)
After cutting the prepreg obtained in (2-2) into a predetermined size, the prepreg was laminated to prepare two laminates each having 10 layers laminated in the direction of 0°. In order to form initial cracks, a release sheet was sandwiched between two laminates, and the two were combined to obtain a prepreg laminate having a laminate configuration of [0] ₂₀ . Molding was carried out for 2 hours at 180° C. under a pressure of 0.59 MPa using a normal vacuum autoclave molding method. The obtained molding was cut into a size of 12.7 mm wide×330.2 mm long 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 (end notched flexure test) test in which a three-point bending load is applied was performed. The distance between fulcrums was 101.6 mm. A test piece was placed so that the tip of the sheet made of a PTFE sheet with a thickness of 25 μm was 38.1 mm from the fulcrum, and a bending load was applied to the test piece at a speed of 2.54 mm / min to cause initial cracks. formed.
After that, the test piece was placed so that the tip of the crack was at a position of 25.4 mm from the fulcrum, and a bending load was applied at a rate of 2.54 mm/min to conduct the test. Similarly, three tests were conducted, and the 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 surfaces of the test piece using a microscope. The measurement of the GIIc test was performed using n=5 test pieces.

(2-6) OHC
The prepreg obtained in (2-2) was cut into a square with a side of 360 mm and laminated to obtain a laminate having a laminate structure of [+45/0/-45/90] _2S . Molding was carried out for 2 hours at 180° C. under a pressure of 0.59 MPa using a normal vacuum autoclave molding method. The obtained molding was cut into a size of 38.1 mm in width and 304.8 mm in length, and a hole with a diameter of 6.35 mm was drilled in the center of the test piece to obtain a test piece for an open-hole compressive strength (OHC) test. .
The test was carried out according to SACMA SRM3, and the perforated compressive strength was calculated from the maximum point load.

(3) Handling of prepreg (3-1) Impregnation The ability to impregnate the fiber base material with the resin was evaluated from the water absorption rate of the prepreg. The lower the water absorption of the obtained prepreg, the higher the impregnability of the resin.
The prepreg obtained in (2-2) was cut into a square with a side of 100 mm, and the mass (W1) was measured. After that, 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 surface water was wiped off, and the mass (W2) of the prepreg was measured. From these measured values, the following formula Water absorption (%) = [(W2-W1) / W1] × 100
W1: Mass of prepreg (g)
W2: Mass (g) of prepreg after water absorption
was used to calculate the water absorption. The evaluation results are represented by the following criteria (○ to ×).
○: Water absorption rate is less than 10%.
×: Water absorption rate is 10% or more

[Examples 1 to 4, Comparative Examples 1 to 3]
The components shown 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 4 exhibited a high Tg of 210° C. or higher and a high elastic modulus of 4.3 GPa or higher.

[Examples 5 to 8, Comparative Examples 4 to 7]
The components shown in Table 2 were mixed using a stirrer to obtain an epoxy resin composition. A prepreg was produced using each of the obtained epoxy resin compositions. Table 2 shows various physical properties of CFRP produced using the obtained prepreg. Examples 5 to 8 exhibited a high CAI of 330 MPa or more, a high G1c of 550 J/m ² or more, a high G2c of 2100 J/m ² or more, and a high OHC of 335 MPa or more. Also, in Example 6, the prepreg was easy to handle. Compared with Examples 6 and 7, Example 5 had less epoxy resin [B], so although there was no problem, it was inferior in handleability.

In Comparative Examples 1 and 4, epoxy resin compositions were produced using DGEBA without using the epoxy resin [B], but various physical properties were lowered.
In Comparative Examples 2 and 3 and Comparative Examples 5 and 6, epoxy resin compositions were prepared using TGDDM and 4,4'-TGDDE, respectively, without using epoxy resin [A], but various physical properties were lowered. .
In Comparative Example 7, an epoxy resin composition was produced without using the epoxy resin [B], but the resin impregnability was low.

Claims (5)

Chemical formula (1) below

(wherein 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 represents -O-.)
55 to 90 % by mass of the epoxy resin [A] represented by the total amount of the epoxy resin,
10 to 45 % by mass of the epoxy resin [B], which is a triglycidylaminophenol derivative and has an epoxy equivalent of 110 g/eq or less, relative to the total amount of the epoxy resin;
comprising
An epoxy resin composition, wherein the mass ratio of the epoxy resin [A] to the epoxy resin [B] is 50:50 to 95:5 . 2. The epoxy resin composition according to claim 1, wherein the epoxy resin [A] is tetraglycidyl-3,4'-diaminodiphenyl ether. a fiber reinforced substrate;
The epoxy resin composition according to claim 1 or 2 impregnated in the fiber-reinforced base material;
A prepreg characterized by comprising: A fiber-reinforced composite material comprising a cured resin obtained by curing the epoxy resin composition according to claim 1 or 2, and a fiber-reinforced base material. A fiber-reinforced composite material obtained by curing the prepreg according to claim 3.