JP6771883B2 - Epoxy resin compositions, prepregs and fiber reinforced composites - Google Patents

Description

The present invention relates to an epoxy resin composition preferably used as a matrix resin for a fiber-reinforced composite material suitable for sports applications and general industrial applications, and a prepreg and a fiber-reinforced composite material using the same as a matrix resin.

Epoxy resins are widely used in various industrial fields such as paints, adhesives, electrical and electronic information materials, and advanced composite materials due to their excellent mechanical properties. In particular, epoxy resins are often used in fiber-reinforced composite materials composed of reinforcing fibers such as carbon fibers, glass fibers, and aramid fibers and matrix resins.

For the production of fiber-reinforced composite materials, prepregs in which a carbon fiber base material is pre-impregnated with an epoxy resin are widely used. After laminating or preforming, the prepreg is heated to cure the epoxy resin to give a molded product. As for the characteristics required for the prepreg, in addition to the molded product exhibiting excellent mechanical properties, in recent years, excellent productivity, that is, quick curing is required. This tendency is particularly strong in industrial applications such as automobiles where productivity is required.

In addition, current prepregs are reactive even at room temperature and usually require freezing storage. Since it is necessary to arrange refrigeration equipment and thaw before use, a prepreg that can be stored and handled at room temperature and has excellent storage stability is required.

As a technique for improving storage stability, Patent Document 1 discloses a method of coating the particle surface of an imidazole derivative having a controlled particle size with a borate ester compound, and achieves both good storage stability and curing speed. It is stated that it is possible.

Patent Document 2 describes that an epoxy resin composition having long-term storage stability can be obtained by controlling the amount of hydrolyzed chlorine in the epoxy resin within an appropriate range.

Patent Document 3 discloses a method of using a curing agent in which the time from the curing start temperature to the curing degree reaching a certain level is controlled and the particle size and the curing temperature are limited, and storage stability and quick curing are improved. It is stated that they are compatible.

Japanese Unexamined Patent Publication No. 9-157498 Japanese Unexamined Patent Publication No. 2003-301029 Japanese Unexamined Patent Publication No. 2004-75914

However, since the method described in Patent Document 1 uses a highly active imidazole derivative, long-term storage stability may be lost due to the heat history during resin preparation, prepreg preparation, and prepreg storage / transportation. It was.

Further, although Patent Documents 2 and 3 show resin compositions having relatively high storage stability, it cannot be said that the storage stability is sufficient. In addition, there was no mention of the elastic modulus and bending of the cured resin, which are important for the mechanical properties of the carbon fiber composite material.

Therefore, the present invention provides an epoxy resin composition and a prepreg that are stable against the heat history during the manufacturing process and storage / transportation and have a high level of storage stability, and have excellent mechanical properties as a fiber-reinforced composite material. It is an object of the present invention to provide an epoxy resin composition showing the above.

As a result of diligent studies to solve the above problems, the present inventors have found an epoxy resin composition having the following constitution, and have completed the present invention. That is, the epoxy resin composition of the present invention has the following constitution.

An epoxy resin composition containing the following components [A], [B], [C], and [D], and satisfying the following conditions [a] and [b].
[A]: Epoxy resin [B]: Dicyandiamide [C]: Aromatic urea [D]: Borate ester [a]: Analyzing the epoxy resin composition with a differential scanning calorimeter at an isothermal temperature of 100 ° C. under a nitrogen stream. When the epoxy resin composition is analyzed by a differential scanning calorimetry at an isothermal temperature of 60 ° C. under a nitrogen stream, the time from reaching 100 ° C. to the peak top of the heat flow is 60 minutes or less [b]. It takes more than 25 hours from reaching 60 ° C to the peak heat flow.

The prepreg of the present invention is a prepreg composed of the epoxy resin composition and carbon fibers.

Further, the fiber-reinforced composite material of the present invention is a fiber-reinforced composite material obtained by curing the prepreg.

According to the present invention, an epoxy resin composition that is stable against the heat history during the manufacturing process and storage / transportation, has extremely excellent storage stability, and the fiber-reinforced composite material obtained by molding a prepreg has high mechanical properties. , And prepregs and fiber-reinforced composite materials using the epoxy resin composition can be provided.

The epoxy resin composition of the present invention contains component [A]: epoxy resin, component [B]: dicyandiamide, component [C]: aromatic urea compound, and component [D] boric acid ester as essential components. First, these components will be described.

(Component [A])
The component [A] in the present invention is an epoxy resin. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, novolac type epoxy resin, epoxy resin having a fluorene skeleton, both phenol compound and dicyclopentadiene. Epoxy resin made from polymer, diglycidyl resorcinol, tetrakis (glycidyloxyphenyl) ethane, glycidyl ether type epoxy resin such as tris (glycidyloxyphenyl) methane, tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, triglycidylamino Examples thereof include glycidylamine type epoxy resins such as cresol and tetraglycidylxylene diamine. As the epoxy resin, these may be used alone or a plurality of types may be combined.

The component [A] preferably contains a trifunctional or higher functional epoxy resin. By containing a trifunctional or higher functional epoxy resin, an epoxy resin composition having extremely high storage stability and a good curing rate can be obtained.

The trifunctional or higher functional epoxy resin is represented by the following formula (I) and / or the following formula (II) of the component [A1] from the viewpoint of the balance between the curing rate, the storage stability, and the mechanical properties of the cured product. It is preferably an epoxy resin. The component [A1] is generally known as a phenol novolac type epoxy resin, a cresol novolac type epoxy resin, or a dicyclopentadiene type epoxy resin, and is commercially available as a mixture of bifunctional or higher functional polyfunctional epoxy resins. ..

The component [A1] is preferably contained in an amount of 10 parts by mass to 50 parts by mass out of 100 parts by mass of the total epoxy resin contained in the epoxy resin composition from the viewpoint of balance between storage stability and curing rate. Further, from the viewpoint of curing speed, it is preferable that the proportion of the trifunctional or higher functional epoxy resin in the component [A1] is large, and from that viewpoint, the average number of epoxy groups of the component [A1] is 3.0 or more. Is preferable.

(In the formula, R ₁ , R ₂ , and R ₃ represent a hydrogen atom or a methyl group, and n represents an integer of 1 or more.)

(N represents an integer of 1 or more).

Commercially available products of component [A1] include "jER (registered trademark)" 152, 154, 180S (all manufactured by Mitsubishi Chemical Corporation), "Epiclon (registered trademark)" N-740, N-770, N- 775, N-660, N-665, N-680, N-695, HP7200L, HP7200, HP7200H, HP7200HH, HP7200HHH (all manufactured by DIC Corporation), PY307, EPN1179, EPN1180, ECN9511, ECN1273, ECN1280, ECN128 , ECN1299 (above, manufactured by Huntsman Advanced Material), YDPN638, YDPN638P, YDCN-701, YDCN-702, YDCN-703, YDCN-704 (above, manufactured by Toto Kasei Co., Ltd.), DEN431, DEN438, DEN439 (above) As mentioned above, manufactured by Dow Chemical Corporation).

Further, as the trifunctional or higher functional epoxy resin, it is preferable to include a glycidylamine type epoxy resin having the component [A2] trifunctional or higher.

Specific examples of the component [A2] include tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, triglycidylaminocresol, tetraglycidylxylylenediamine and the like.

Commercially available products of component [A2] include "Sumiepoxy (registered trademark)" ELM434 (manufactured by Sumitomo Chemical Corporation), YH434L (manufactured by Toto Kasei Co., Ltd.) and "jER (registered trademark)" as tetraglycidyldiaminodiphenylmethane. "604 (manufactured by Mitsubishi Chemical Corporation)," Araldite (registered trademark) "MY720, MY721 (manufactured by Huntsman Advanced Materials) and the like can be used. Examples of triglycidylaminophenol or triglycidylaminocresol include "Sumiepoxy (registered trademark)" ELM100, ELM120 (manufactured by Sumitomo Chemical Corporation), "Araldite (registered trademark)" MY0500, MY0510, MY0600 (Huntsman Advanced Materials). , "JER (registered trademark)" 630 (manufactured by Mitsubishi Chemical Corporation), etc. can be used. As tetraglycidylxylylenediamine and its hydrogenated product, "TETRAD (registered trademark)" -X, "TETRAD (registered trademark)" -C (manufactured by Mitsubishi Gas Chemical Company, Inc.) and the like can be used.

It is preferable that the component [A2] is contained in an amount of 10 to 50 parts by mass out of 100 parts by mass of the total epoxy resin from the viewpoint of the balance between storage stability and curing rate.

It is also preferable to include the component [A3] bisphenol F type epoxy resin as the component [A] from the viewpoint of the balance between the storage stability and the elastic modulus of the cured resin product. The component [A3] preferably contains 20 parts by mass to 90 parts by mass out of 100 parts by mass of the total epoxy resin.

Commercially available products of the component [A3] include, for example, "jER (registered trademark)" 806, 807, 4002P, 4004P, 4007P, 4009P (all manufactured by Mitsubishi Chemical Corporation), "Epototo (registered trademark)" YDF-2001, Examples include YDF-2004 (all manufactured by Toto Kasei Co., Ltd.).

(Component [B])
The component [B] in the present invention is dicyandiamide. Dicyandiamide is a compound represented by the chemical formula (H ₂ N) ₂ C = N-CN. Dicyandiamide is excellent in giving a cured resin product high mechanical properties and heat resistance, and is widely used as a curing agent for epoxy resins. Examples of commercially available products of such dicyandiamide include DICY7 and DICY15 (all manufactured by Mitsubishi Chemical Corporation).

It is preferable to add dicyandiamide [B] as a powder to the epoxy resin composition from the viewpoint of storage stability at room temperature and viscosity stability during prepreg production. Further, it is preferable to disperse dicyandiamide [B] in advance in a part of the epoxy resin of the component [A] by using a triple roll or the like in order to make the epoxy resin composition uniform and improve the physical properties of the cured product. ..

When dicyandiamide is blended as a powder in a resin, its average particle size is preferably 10 μm or less, more preferably 7 μm or less. For example, when the reinforcing fiber bundle is impregnated with the epoxy resin composition by heating and pressurizing in the prepreg manufacturing step, if the average particle size is 10 μm or less, the resin impregnation property inside the fiber bundle is good.

The total amount of dicyandiamide [B] is 0.3 to 1.2 equivalents of active hydrogen groups and 0.3 to 0.7 equivalents of the epoxy groups of all the epoxy resin components contained in the epoxy resin composition. The amount is preferably in the range. When the amount of active hydrogen groups is in this range, a cured resin product having an excellent balance between heat resistance and mechanical properties can be obtained.

When dicyandiamide [B] is used in combination with the component [C] described later, the curing temperature of the resin composition can be lowered as compared with the case where the component [B] is blended alone. In the present invention, it is necessary to use the component [B] and the component [C] in combination in order to obtain a good curing rate.

(Component [C])
The epoxy resin composition of the present invention needs to contain an aromatic urea compound as a component [C]. The component [C] acts as a curing accelerator, and a good curing rate can be obtained when used in combination with the component [B].

Specific examples of the aromatic urea compound in the component [C] include 3- (3,4-dichlorophenyl) -1,1-dimethylurea, 3- (4-chlorophenyl) -1,1-dimethylurea, and phenyldimethylurea. , Toluene bisdimethylurea and the like. As commercially available aromatic urea compounds, DCMU-99 (manufactured by Hodogaya Chemical Industry Co., Ltd.), "Omicure (registered trademark)" 24 (manufactured by PTI Japan Co., Ltd.), etc. are used. be able to.

The blending amount of the aromatic urea compound in the component [C] is preferably 1 to 8 parts by mass, more preferably 1.5 to 6 parts by mass, based on 100 parts by mass of the epoxy resin of the component [A]. More preferably, it is 2 to 4 parts by mass. By blending the component [C] in this range, an epoxy resin composition having an excellent balance between storage stability and curing rate and giving a cured resin product having good physical properties can be obtained.

Although component [C] is known as a curing accelerator having relatively high storage stability, long-term storage stability was not always sufficient because the reaction with the epoxy resin proceeded slowly even at room temperature. There are various theories about the reaction mechanism between the epoxy resin and the component [C], but a mechanism has been proposed in which the amine compound liberated by the decomposition of the urea group reacts with the epoxy resin. The inventors of the present application considered the reason why long-term stability could not be obtained at room temperature as follows. That is, since the dissociation reaction of the urea group is a reversible reaction, it is considered that a trace amount of amine compound is liberated and contained in the epoxy resin composition containing the component [C]. On the other hand, the nucleophilic reaction between the amine compound and the epoxy resin is an irreversible reaction. Most of the liberated amine compounds return to urea by a reversible reaction, but if they react with some epoxy groups, the cross-linking reaction proceeds irreversibly. It was thought that the long-term stability of the resin composition would be impaired by repeating this. Therefore, in order to obtain extremely high storage stability, it is necessary to use it in combination with the component [D] described later.

(Component [D])
The epoxy resin composition of the present invention needs to contain a boric acid ester as the component [D]. By using the component [C] and the component [D] in combination, the reaction between the component [C] and the epoxy resin at the storage temperature is suppressed, so that the storage stability of the prepreg is significantly improved. The mechanism is not clear, but since the component [D] has Lewis acidity, the amine compound liberated from the component [C] and the component [D] may interact with each other to reduce the reactivity of the amine compound. I'm wondering if there is one.

Further, by using the component [C] and the component [D] in combination, a resin composition having excellent stability to the thermal history can be obtained. Stabilization of amine compounds using component [D] has been known so far (for example, described in Patent Document 1), but this technique stabilizes amine compounds having high reactivity with epoxy resins. It was something that turned into. In the step of blending the resin composition and the step of impregnating the reinforcing fiber in the case of forming a prepreg together with the reinforcing fiber, heat may be applied to the resin composition, but the highly reactive amine compound and component [D] In combination with, the stability to the heat history at that time was not sufficient. On the other hand, when the component [C] and the component [D] are used in combination as in the present application, the amount of the amine compound liberated from the component [C] is limited, so that the component [C] is used alone. Better stability to thermal history is obtained than if it were. From this viewpoint as well, it is necessary to use the component [C] and the component [D] together.

Specific examples of the borate ester of the component [D] include trimethylborate, triethylborate, tributylborate, tri-n-octylborate, tri (triethylene glycol methyl ether) borate, tricyclohexylborate, and trimentylborate. Aromatic borates such as alkylborate, trio-cresylborate, trim-cresylborate, trip-cresylborate, triphenylborate, tri (1,3-butanediol) viborate, tri (2) -Methyl-2,4-pentanediol) Vivorate, trioctylene glycol diborate and the like.

Further, as the boric acid ester, a cyclic boric acid ester having a cyclic structure in the molecule can also be used. Examples of the cyclic borate include tris-o-phenylene bisbolate, bis-o-phenylene pyrobolate, bis-2,3-dimethylethylenephenylene pyrobolate, bis-2,2-dimethyltrimethylene pyroborate and the like. ..

Examples of products containing such borate esters include "Cure Duct (registered trademark)" L-01B (Shikoku Chemicals Corporation) and "Cure Duct (registered trademark)" L-07N (Shikoku Chemicals Corporation). ).

The blending amount of the component [D] is preferably 0.1 to 8 parts by mass, more preferably 0.15 to 5 parts by mass, still more preferably, with respect to 100 parts by mass of the epoxy resin of the component [A]. Is 0.2 to 4 parts by mass. By blending the component [D] in this range, an epoxy resin composition having an excellent balance between storage stability and curing rate and giving a cured resin product having good physical properties can be obtained.

(Analysis of Epoxy Resin Composition Using Differential Scanning Calorimetry)
In the present invention, for measuring the curing rate of the epoxy resin composition, for example, thermal analysis using a differential scanning calorimeter is used.

The heat generated by the differential scanning calorimetry is caused by the reaction of the epoxy resin composition. Therefore, in the isothermal measurement, the time until heat generation appears is related to the reaction rate of the epoxy resin composition. The peak top of heat generation in the isothermal measurement represents the time when the reaction is most active at that temperature, and can be used as an index of reactivity.

(100 ° C isothermal measurement of epoxy resin composition using differential scanning calorimeter)
In the epoxy resin composition of the present invention, when isothermal measurement at 100 ° C. is performed with a differential scanning calorimeter, the time from when the temperature reaches 100 ° C. until the heat flow rate reaches the top of the exothermic peak is T (100). , T (100) is 60 minutes or less, more preferably 45 minutes or less, and even more preferably 30 minutes or less. By using the epoxy resin composition having T (100) of 60 minutes or less as the matrix resin, it is possible to provide a curing rate within a range that does not impair productivity. A prepreg using an epoxy resin composition having a T (100) of more than 60 minutes as a matrix resin has an insufficient curing rate.

(60 ° C isothermal measurement of epoxy resin composition using differential scanning calorimetry)
Further, the epoxy resin composition of the present invention is T (60) when the time from reaching 60 ° C. to the heat flow rate reaching the top of the exothermic peak is T (60) when the isothermal measurement is performed at 60 ° C. ) Is 25 hours or more, and more preferably 28 hours or more. By using the epoxy resin composition having T (60) of 25 hours or more as the matrix resin, the prepreg can be provided with long-term storage stability. A prepreg using an epoxy resin composition for less than 25 hours as a matrix resin has insufficient storage stability at room temperature.

(Ingredient [E])
The epoxy resin composition of the present invention may contain a thermoplastic resin as the component [E] as long as the effects of the present invention are not lost. The thermoplastic resin is not an essential component in the present invention, but by blending it in the epoxy resin composition, it is possible to control the viscoelasticity and impart toughness to the cured product.

Examples of such a thermoplastic resin include at least selected from polymethyl methacrylate, polyvinylformal, polyvinylbutyral, polyvinylacetal, polyvinylpyrrolidone, aromatic vinyl monomer, vinyl cyanide monomer, and rubbery polymer. Examples thereof include polymers containing two types of constituents, polyamides, polyesters, polycarbonates, polyarylene oxides, polysulfones, polyethersulfones, and polyimides. Examples of polymers containing at least two types selected from aromatic vinyl monomers, vinyl cyanide monomers, and rubbery polymers as constituents include acrylonitrile-butadiene-styrene copolymer (ABS resin) and acrylonitrile. -Styrene copolymer (AS resin) and the like can be mentioned. Polysulfone and polyimide may have an ether bond or an amide bond in the main chain.

Polymethylmethacrylate, polyvinylformal, polyvinylbutyral, and polyvinylpyrrolidone have good compatibility with many types of epoxy resins such as bisphenol A type epoxy resin and novolak type epoxy resin, and control the fluidity of the epoxy resin composition. Is preferable in that the effect of the above is large, and polyvinyl formal is particularly preferable. Examples of commercially available products of these thermoplastic resins are "Denka Butyral (registered trademark)", "Denkaformal (registered trademark)" (manufactured by Denki Kagaku Kogyo Co., Ltd.), and "Vinirec (registered trademark)" (JNC Co., Ltd.). ) Made) and so on.

In addition, the resins themselves of polysulfone, polyethersulfone, and polyimide have excellent heat resistance, and tetraglycidyldiaminodiphenylmethane and triglycidylamino, which are epoxy resins often used for applications requiring heat resistance, such as structural members of aircraft. There are polymers with a resin skeleton that have appropriate compatibility with glycidylamine-type epoxy resins such as phenol, triglycidylaminocresol, and tetraglycidylxylene diamine, and the use of these polymers has the effect of controlling the fluidity of the epoxy resin composition. In addition to being large, it is preferable because it has the effect of increasing the impact resistance of the fiber-reinforced resin composite material. Examples of such polymers include "Radel (registered trademark)" A (manufactured by Solvay Advanced Polymers) and "Sumika Excel (registered trademark)" PES (manufactured by Sumitomo Chemical Co., Ltd.) for polysulfone. Examples thereof include "Ultem (registered trademark)" (manufactured by GE Plastics) and "Polymid (registered trademark)" 5218 (manufactured by Huntsman).

When the epoxy resin composition of the present invention contains a thermoplastic resin, it is preferably contained in an amount of 1 to 60 parts by mass with respect to 100 parts by mass of the epoxy resin contained in the epoxy resin composition.

(Mixing of particles)
The epoxy resin composition of the present invention is a coupling agent, thermosetting resin particles, conductive particles such as carbon black, carbon particles, metal-plated organic particles, or silica gel, as long as the effects of the present invention are not impaired. , Clay and other inorganic fillers can be blended. These additions have an effect of increasing the viscosity of the epoxy resin composition and reducing the resin flow, an effect of improving the elastic modulus of the cured resin product, an effect of improving heat resistance, and an effect of improving wear resistance.

(Preparation method of epoxy resin composition)
The epoxy resin composition of the present invention may be kneaded using a machine such as a kneader, a planetary mixer, a three-roll or twin-screw extruder, or with a beaker if uniform kneading is possible. You may mix it by hand using a spatula or the like.

(Bending characteristics of cured epoxy resin)
The flexural modulus of the cured resin product when the epoxy resin composition of the present invention is cured at 130 ° C. for 2 hours is preferably 3.5 GPa or more, and more preferably 3.7 GPa or more. When the elastic modulus is 3.5 GPa or more, a fiber-reinforced composite material having excellent static strength can be obtained. The upper limit of the flexural modulus is generally 5.0 GPa or less.

Here, the method for measuring the flexural modulus and the bending deflection amount of the cured resin product is as follows. A cured resin product having a thickness of 2 mm is obtained by curing at a temperature of 130 ° C. for 2 hours in a mold set to have a thickness of 2 mm by a spacer. A test piece having a width of 10 mm and a length of 60 mm was cut out from this cured resin product, and an Instron universal testing machine (manufactured by Instron) was used to set the span length to 32 mm and the crosshead speed to 2.5 mm / min, and JIS. By carrying out a three-point bending test in accordance with K7171 (1994), the flexural modulus and the amount of bending flexure can be measured.

The curing temperature and curing time for obtaining the cured resin product are not particularly limited, and the optimum conditions vary depending on the shape and thickness of the molded product. Therefore, it is arbitrarily selected by the user, but a runaway reaction may occur. From the viewpoint of molding in a short time while suppressing the temperature, it is preferable to cure at a temperature of 130 ° C. to 150 ° C. for 90 minutes to 2 hours.

(Fiber reinforced composite material)
Next, the fiber-reinforced composite material will be described. By composite-integrating the epoxy resin composition of the present invention with reinforcing fibers and then curing the epoxy resin composition, a fiber-reinforced composite material containing the cured product of the epoxy resin composition of the present invention as a matrix resin can be obtained.

The reinforcing fiber used in the present invention is not particularly limited, and glass fiber, carbon fiber, aramid fiber, boron fiber, alumina fiber, silicon carbide fiber and the like are used. Two or more of these fibers may be mixed and used. Among these, it is preferable to use carbon fiber which can obtain a lightweight and highly rigid fiber-reinforced composite material.

(Prepreg)
In order to obtain a fiber-reinforced composite material, it is preferable to prepare a prepreg composed of an epoxy resin composition and reinforcing fibers in advance. It is a material form in which the arrangement of prepreg fibers and the ratio of resin can be precisely controlled, and the characteristics of the composite material can be maximized. The prepreg can be obtained by impregnating the reinforcing fiber base material with the epoxy resin composition of the present invention. Examples of the impregnation method include known methods such as a hot melt method (dry method).

In the hot melt method, the reinforcing fibers are directly impregnated with the epoxy resin composition whose viscosity has been reduced by heating, or a film coated with the epoxy resin composition on a release paper or the like is prepared, and then both sides of the reinforcing fibers are prepared. Alternatively, it is a method in which the films are laminated from one side and the reinforcing fibers are impregnated with the resin by heating and pressurizing.

In the prepreg laminated molding method, as a method of applying heat and pressure, a press molding method, an autoclave molding method, a bagging molding method, a lapping tape method, an internal pressure molding method and the like can be appropriately used.

The cured product of the epoxy resin composition of the present invention and the fiber-reinforced composite material containing reinforcing fibers are preferably used for sports applications, general industrial applications and aerospace applications. More specifically, in sports applications, it is preferably used for golf shafts, fishing rods, rackets for tennis and badminton, sticks for hockey, ski poles, and the like. In addition, for general industrial applications, structural materials for moving objects such as automobiles, bicycles, ships and railroad vehicles, drive shafts, leaf springs, wind turbine blades, pressure vessels, flywheels, papermaking rollers, roofing materials, cables, and repair reinforcement materials. It is preferably used for such purposes.

Examples are shown below, and the present invention will be described in more detail, but the present invention is not limited to the description of these examples.

The components used in this embodiment are as follows.

<Material used>
-Epoxy resin [A]
[A1] -1 "jER (registered trademark)" 154 (phenol novolac type epoxy resin, epoxy equivalent: 178, average number of functional groups: 3.0 / molecule, manufactured by Mitsubishi Chemical Corporation)
[A1] -2 "Epiclon (registered trademark)" N-775 (phenol novolac type epoxy resin, epoxy equivalent: 190, average number of functional groups: 6.5 / molecule, manufactured by DIC Corporation)
[A1] -3 "Epiclon (registered trademark)" HP-7200H (dicyclopentadiene type epoxy resin, epoxy equivalent: 279, average number of functional groups: 3.0 / molecule, manufactured by DIC Corporation)
[A1] -4 "jER (registered trademark)" 152 (phenol novolac type epoxy resin, epoxy equivalent: 177, average number of functional groups: 2.2 / molecule, manufactured by Mitsubishi Chemical Corporation)
[A2] -1 "Sumiepoxy (registered trademark)" ELM434 (tetraglycidyldiaminodiphenylmethane, epoxy equivalent: 125, manufactured by Sumitomo Chemical Co., Ltd.)
[A2] -2 "Araldite (registered trademark)" MY0600 (triglycidyl m-aminophenol, epoxy equivalent: 118, manufactured by Huntsman Advanced Materials)
[A3] -1 "Epiclon (registered trademark)" 830 (liquid bisphenol F type epoxy resin, epoxy equivalent: 168, manufactured by DIC Corporation)
[A3] -2 "Epototo (registered trademark)" YDF-2001 (solid bisphenol F type epoxy resin, epoxy equivalent: 475, manufactured by Toto Kasei Co., Ltd.)
[A] -1 "jER (registered trademark)" 828 (liquid bisphenol A type epoxy resin, epoxy equivalent: 189, manufactured by Mitsubishi Chemical Corporation)
[A] -2 "jER (registered trademark)" 1001 (solid bisphenol A type epoxy resin, epoxy equivalent: 475, manufactured by Mitsubishi Chemical Corporation).

・ Disyandiamide [B]
[B] -1 DICY7 (dicyandiamide, manufactured by Mitsubishi Chemical Corporation).

-Aromatic urea compound [C]
[C] -1 DCMU99 (3- (3,4-dichlorophenyl) -1,1-dimethylurea, manufactured by Hodogaya Chemical Co., Ltd.)
[C] -2 "Omicure (registered trademark)" 24 ( toluene bisdimethylurea , manufactured by PTI Japan Co., Ltd.).

-Curing accelerators other than aromatic urea compounds [C']
[C'] -1 "Curesol (registered trademark)" 2PHZ-PW (2-phenyl-4,5-dihydroxymethylimidazole, manufactured by Shikoku Chemicals Corporation)
[C'] -2 "Curesol (registered trademark)" 2P4MHZ-PW (2-phenyl-4-methyl-5-hydroxymethylimidazole, manufactured by Shikoku Chemicals Corporation)
[C'] -3 "Cure Duct (registered trademark)" P-0505 (Epoxy-imidazole adduct, manufactured by Shikoku Chemicals Corporation).

-Mixture containing boric acid ester [D]
[D] -1 "Cure Duct (registered trademark)" L-07N (composition containing 5 parts by mass of a boric acid ester compound, manufactured by Shikoku Chemicals Corporation).

-Thermoplastic resin [E]
[E] -1 "Vinirec (registered trademark)" K (polyvinyl formal, manufactured by JNC Co., Ltd.).

-Other compounds Bisphenol S (bis (hydroxyphenyl) sulfone manufactured by Tokyo Chemical Industry Co., Ltd., crushed with a hammer mill and then classified by sieving. Average particle size: 14.8 μm).

<Preparation method of epoxy resin composition>
(1) Method for producing curing accelerator master and curing agent master Liquid resin [A3] -1 ("Epoxylon (registered trademark)" 830) or [A] -1 ("jER (registered trademark)" 828) 10 To a mass part (10 parts by mass out of 100 parts by mass of the epoxy resin [A]), the aromatic urea compound [C] or the curing accelerator [C'] and the mixture [D] containing the borate ester are added. Then, it was kneaded at room temperature using a kneader. The mixture was passed twice between the rolls using three rolls to prepare a curing accelerator master. When dicyandiamide [B] and bisphenol S are contained in the curing accelerator master, bisphenol S is added, kneaded at room temperature using a kneader, and then passed twice between the rolls using three rolls to pass the curing agent master. Made.

(2) Method for Producing Epoxy Resin Composition Among the epoxy resins [A], [A3] -1 ("Epiclon (registered trademark)" 830) or [A] -1 ( "JER (registered trademark)" 828) Add 90 parts by mass of epoxy resin [A] and thermoplastic resin [E] excluding 10 parts by mass, raise the temperature to 150 ° C while kneading, and knead at 150 ° C for 1 hour. As a result, a transparent viscous liquid was obtained. After lowering the temperature of the viscous liquid while kneading it to 60 ° C., the curing agent master prepared in (1) above was blended and kneaded at 60 ° C. for 30 minutes to obtain an epoxy resin composition.

The component compounding ratios of each Example and Comparative Example are shown in Tables 1 to 5.

<Evaluation method of resin composition characteristics>
(1) T (100)
Weigh 3 mg of the epoxy resin composition into a sample pan, and use a differential scanning calorimeter (Q-2000: manufactured by TA Instruments) to heat the temperature from 30 ° C to 100 ° C / min to 100 ° C for 8 hours. Isothermal measurements were taken. The isothermal measurement start time was 42 seconds after the temperature rise start time, and the time from the isothermal measurement start time to the heat flow reaching the exothermic peak top was measured and acquired as the time to the peak top during the isothermal measurement at 100 ° C. .. The measurement was performed by 3 samples per level, and the average value was adopted. Hereinafter, the average value obtained in this measurement is referred to as T (100) (however, the unit of T (100) is [minute]).

(2) T (60)
Weigh 3 mg of the epoxy resin composition into a sample pan, and use a differential scanning calorimeter (Q-2000: manufactured by TA Instruments) to raise the temperature from 30 ° C to 100 ° C / min to 60 ° C for 48 hours. Isothermal measurements were taken. Eighteen seconds after the start time of temperature rise was set as the isothermal measurement start time, and the time from the start time of isothermal measurement until the heat flow reached the top of the exothermic peak was measured and acquired as the time to the peak top of the isothermal measurement at 60 ° C. .. The measurement was performed by 3 samples per level, and the average value was adopted. Hereinafter, the average value obtained in this measurement is referred to as T (60) (however, the unit of T (60) is [time]). If the peak top did not appear even after 48 hours, the value of T (60) was set to "48 or more".

<Method of producing and evaluating cured resin>
(1) Elastic modulus and deflection of the cured resin product After defoaming the epoxy resin composition in vacuum, 130 in a mold set to a thickness of 2 mm with a 2 mm thick "Teflon" (registered trademark) spacer. It was cured at a temperature of ° C. for 90 minutes to obtain a plate-shaped resin cured product having a thickness of 2 mm. A test piece having a width of 10 mm and a length of 60 mm was cut out from this cured resin product, and using an Instron universal testing machine (manufactured by Instron), the span was 32 mm and the crosshead speed was 100 mm / min. JIS K7171 (1994) The three-point bending was carried out according to the above, and the elastic modulus and the deflection were measured. The average value of the values measured when the number of samples n = 5 was taken as the elastic modulus and the deflection value.

<Prepreg manufacturing method and evaluation method>
(1) Method for producing prepreg The epoxy resin composition produced according to the above <Method for producing an epoxy resin composition> was applied onto a paper pattern using a film coater to prepare a resin film having a grain size of 74 g / m ² . ..

This resin film is set in a prepreg device and heated and pressed from both sides of the carbon fiber "Treca" (registered trademark) T700S (manufactured by Toray Industries, Inc., with a grain of 150 g / m ² ) that is made into a sheet that is aligned in one direction. It was impregnated to obtain a prepreg having a resin content of 33% by mass.

(2) Evaluation method of curing rate of prepreg The curing rate of prepreg is the handling when the prepreg is cut into 20 cm squares, sandwiched between 150 μm-thick "Teflon (registered trademark)" sheets, pressed at 130 ° C, and then taken out. Judged by gender. The handleability was judged according to the following criteria, and A to C were accepted.
A: The prepreg was not deformed when it was taken out after 20 minutes.
B: The prepreg was deformed when it was taken out after 20 minutes, but it was not deformed when it was taken out after 30 minutes.
C: The prepreg was deformed when it was taken out after 30 minutes, but it was not deformed when it was taken out after 40 minutes.
D: The curing rate was insufficient and the prepreg was deformed when taken out after 40 minutes.

(3) Method for evaluating storage stability of prepreg The storage stability of prepreg was determined by the amount of increase in the glass transition temperature when the prepreg was cut into 10 cm squares and left at 40 ° C. for 60 days. The glass transition temperature was raised from -50 ° C to 50 ° C at 10 ° C / min using a differential scanning calorimeter (Q-2000: manufactured by TA Instruments) after measuring 8 mg of prepreg after storage on a sample pan. It was warmed and measured. The midpoint of the inflection point of the obtained heat generation curve was acquired as Tg.

(4) Evaluation method of storage stability of prepreg after heat treatment at 80 ° C. for 1 hour As an index of storage stability when heat history was added, the storage stability of prepreg after heat treatment at 80 ° C. for 1 hour was evaluated. .. The prepreg was cut into 10 cm squares, and the prepreg was allowed to stand on the surface of a press machine prepared at 80 ° C. for 1 hour, and then rapidly cooled on an aluminum plate at room temperature to prepare a prepreg sample to which a heat history was added. The storage stability of the obtained sample was evaluated by measuring the amount of increase in the glass transition temperature when the sample was left at 40 ° C. for 60 days in the same manner as in (3).

<Characteristic evaluation method for carbon fiber composite material (CFRP)>
(1) Method for producing CFRP unidirectional laminate The unidirectional laminate used for evaluating the characteristics of CFRP was produced by the following method. The fiber directions of the unidirectional prepregs produced according to the above <Method for producing prepregs> were aligned, and 13 ply lamination was performed. The laminated prepreg was covered with a nylon film so as not to have a gap, and this was heated and pressed in an autoclave at 130 ° C. and an internal pressure of 0.3 MPa for 2 hours to cure, thereby producing a unidirectional laminated plate.

(2) Evaluation Method of 0 ° Bending Strength of CFRP The unidirectional laminated board produced according to the above was cut out so as to have a thickness of 2 mm, a width of 15 mm, and a length of 100 mm. Three-point bending was performed according to JIS K7074 (1988) using an Instron universal testing machine (manufactured by Instron). The measurement was performed with a span of 80 mm, a crosshead speed of 5.0 mm / min, a thickness diameter of 10 mm, and a fulcrum diameter of 4.0 mm, and a 0 ° bending strength was measured. The average value of the values measured when the number of samples n = 6 was taken as the value of 0 ° bending strength.

(3) Method for evaluating 90 ° bending strength of CFRP A unidirectional laminated board produced according to the above was cut out so as to have a thickness of 2 mm, a width of 15 mm, and a length of 60 mm. Three-point bending was performed according to JIS K7074 (1988) using an Instron universal testing machine (manufactured by Instron). The measurement was performed with a span of 40 mm, a crosshead speed of 1.0 mm / min, a thickness diameter of 10 mm, and a fulcrum diameter of 4.0 mm, and a 90 ° bending strength was measured. The average value of the values measured with the number of samples n = 6 was taken as the value of the 90 ° bending strength.

(Example 1)
[A] 30 parts by mass of "jER (registered trademark)" 154, 40 parts by mass of "jER (registered trademark)" 828, 30 parts by mass of "jER (registered trademark)" 1001 as an epoxy resin, and [B] DICY7 as a dicyandiamide. 5.3 parts by mass, and 3.0 parts by mass of DCMU99 as a [C] aromatic urea compound, and 3.0 parts by mass of "Cureduct (registered trademark)" L-07N as a mixture containing [D] borate ester. An epoxy resin composition was prepared according to the above <Method for producing an epoxy resin composition> using 3.0 parts by mass of "Vinirec (registered trademark)" K as a part and a thermoplastic resin. That is, it is a liquid resin [A]. -1 ("jER®" 828) 10 parts by mass (10 parts by mass out of 100 parts by mass of epoxy resin [A]), 3.0 parts by mass of DCMU99, and "Cureduct (registered trademark)""3.0 parts by mass of L-07N was added and kneaded at room temperature using a kneader. Using three rolls, the mixture was passed twice between the rolls to prepare a curing accelerator master. DICY7 was used as the curing accelerator master. Was added in an amount of 5.3 parts by mass and kneaded at room temperature using a kneader, and then passed twice between the rolls using three rolls to prepare a curing agent master.

In the kneader, as 90 parts by mass of the remaining epoxy resin [A], 30 parts by mass of "jER (registered trademark)" 154, 30 parts by mass of "jER (registered trademark)" 828, and "jER (registered trademark)" 1001. 30 parts by mass was added, and 3.0 parts by mass of "Vinirec (registered trademark)" K was added. The temperature was raised to 150 ° C. while kneading, and the mixture was kneaded at 150 ° C. for 1 hour to obtain a transparent viscous liquid. The obtained viscous liquid was cooled to 60 ° C. while kneading, and then the curing agent master prepared above was added and kneaded at 60 ° C. for 30 minutes to obtain an epoxy resin composition.

When T (100) and T (60) were measured for this epoxy resin composition, T (100) was 43 minutes and T (60) was 29 hours.

Further, the epoxy resin composition was cured by the method described in the above <Method for producing and evaluating a cured resin product> to prepare a cured resin product, and the three-point bending test described above was performed. As a result, the elastic modulus was 3. The mechanical properties of the cured resin product were also good, with a flexural modulus of 10.2 mm and 3 GPa.

Further, from the obtained epoxy resin composition, a prepreg was prepared by the method described in <Method for producing and evaluating prepreg>. The obtained prepreg had sufficient tackiness and drapeability. When the curing rate and storage stability described above were evaluated for the obtained prepreg, the prepreg was cured to the extent that the prepreg was not deformed within 30 minutes at 130 ° C., and Tg was obtained after storage at 40 ° C. for 60 days. Only at an increase of 2 ° C., the prepreg had sufficient curing rate and storage stability. Furthermore, regarding the stability to the thermal history, when the storage stability of the prepreg after heat treatment at 80 ° C. for 1 hour was evaluated, Tg remained at an increase of 3 ° C. after storage at 40 ° C. for 60 days, and before heat treatment at 80 ° C. It had almost the same storage stability as.

As a result of laminating and curing to prepare a one-way laminated plate by the method described in <Evaluation method of carbon fiber composite material (CFRP)> and performing a three-point bending test, 0 ° bending strength is 1420 MPa and 90 ° bending strength. Was 105 MPa, and the mechanical properties of CFRP were also good.

(Examples 2 to 16)
An epoxy resin composition, a cured resin product, and a prepreg were prepared in the same manner as in Example 1 except that the resin compositions were changed as shown in Tables 1 to 3. The obtained prepregs all showed sufficient tackiness and drapeability as in Example 1.

For the epoxy resin compositions of each example, T (100) and T (60) are as shown in Tables 1 to 3, respectively.

As a result of the same evaluation as in Example 1 regarding the curing rate and storage stability of the prepreg and the stability in the thermal history, sufficient curing rate, storage stability, and stability in the thermal history were obtained at all levels. Indicated.

In addition, the elastic modulus and the deflection value of the cured resin product were both good, and the mechanical properties of CFRP were also good.

(Comparative Example 1)
With respect to the resin compositions shown in Table 4, an epoxy resin composition, a prepreg, and a cured resin product were prepared in the same manner as in Example 1. The properties of the resin composition and the evaluation results are shown in Table 4. The value of T (60) of the epoxy resin composition was less than 23 hours and 25 hours, and the storage stability of the prepreg was insufficient. Moreover, when the storage stability of the prepreg after heat treatment at 80 ° C. for 1 hour was evaluated, the Tg increased significantly to 44 ° C., probably because it contained bisphenol S, and stability in the thermal history could not be obtained.

(Comparative Example 2)
With respect to the resin compositions shown in Table 4, an epoxy resin composition, a prepreg, and a cured resin product were prepared in the same manner as in Example 1. This composition corresponds to the composition obtained by removing bisphenol S from Comparative Example 1. The properties of the resin composition and the evaluation results are shown in Table 4. The storage stability and cured product properties of the prepreg were good and stable to the thermal history, but the value of T (100) of the epoxy resin composition was longer than 70 minutes and 60 minutes, and the obtained prepreg The curing rate was insufficient.

(Comparative Example 3)
An epoxy resin composition, a prepreg, and a cured resin product were prepared in the same manner as in Example 4 except that the component [D] was not added. The properties of the resin composition and the evaluation results are shown in Table 4. The value of T (60) of the epoxy resin composition was 19 hours and less than 25 hours, and the storage stability of the prepreg was insufficient. Moreover, when the storage stability of the prepreg after heat treatment at 80 ° C. for 1 hour was evaluated, the Tg increased significantly to 43 ° C., and stability in the thermal history could not be obtained.

(Comparative Example 4)
The epoxy resin composition and prepreg were prepared in the same manner as in Example 2 except that the curing accelerator was changed to "Curesol (registered trademark)" 2PHZ-PW (1.0 part by mass) and the component [D] was not added. , And a cured resin product were prepared. The properties of the resin composition and the evaluation results are shown in Table 4. The storage stability and cured product properties of the prepreg were good, and the prepreg was also stable in the thermal history, but the value of T (100) of the epoxy resin composition was extremely longer than 300 minutes and 60 minutes, and the obtained prepreg was obtained. The curing rate was insufficient.

(Comparative Example 5)
The epoxy resin composition and prepreg were prepared in the same manner as in Example 2 except that the curing accelerator was changed to "Curesol (registered trademark)" 2P4MHZ-PW (1.0 part by mass) and the component [D] was not added. , And a cured resin product were prepared. The properties of the resin composition and the evaluation results are shown in Table 4. The value of T (60) of the epoxy resin composition was less than 24 hours and 25 hours, and the storage stability of the prepreg was insufficient. Moreover, when the storage stability of the prepreg after heat treatment at 80 ° C. for 1 hour was evaluated, the Tg increased significantly to 44 ° C., and stability in the thermal history could not be obtained.

(Comparative Example 6)
An epoxy resin composition, a prepreg, and a cured resin were prepared in the same manner as in Example 1 except that the resin compositions were changed as shown in Table 5. The properties of the resin composition and the evaluation results are shown in Table 5. The value of T (60) of the epoxy resin composition was less than 15 hours and less than 25 hours, and the storage stability of the prepreg was insufficient. Moreover, when the storage stability of the prepreg after the heat treatment at 80 ° C. for 1 hour was evaluated, the Tg increased significantly to 42 ° C., and the stability in the thermal history could not be obtained. Further, the balance between the elastic modulus and the bending of the cured resin product was deteriorated, and the 90 ° bending strength of CFRP was as low as 83 MPa.

(Comparative Example 7)
An epoxy resin composition, a prepreg, and a cured resin were prepared in the same manner as in Example 1 except that the resin compositions were changed as shown in Table 5. The properties of the resin composition and the evaluation results are shown in Table 5. The storage stability and cured product properties of the prepreg were good, and the prepreg was also stable in the thermal history, but the value of T (100) of the epoxy resin composition was much longer than 70 minutes and 60 minutes, and the obtained prepreg was obtained. The curing rate was insufficient.

(Comparative Example 8)
An epoxy resin composition, a prepreg, and a cured resin were prepared in the same manner as in Example 1 except that the resin compositions were changed as shown in Table 5. The properties of the resin composition and the evaluation results are shown in Table 5. The value of T (60) of the epoxy resin composition was less than 24 hours and 25 hours, and the storage stability of the prepreg was insufficient.

(Comparative Example 9)
An epoxy resin composition, a prepreg, and a cured resin were prepared in the same manner as in Example 1 except that the resin compositions were changed as shown in Table 5. The properties of the resin composition and the evaluation results are shown in Table 5. The storage stability and cured product properties of the prepreg were good, and the prepreg was also stable in the thermal history, but the value of T (100) of the epoxy resin composition was much longer than 65 minutes and 60 minutes, and the obtained prepreg was obtained. The curing rate was insufficient.

(Comparative Example 10)
An epoxy resin composition, a prepreg, and a cured resin were prepared in the same manner as in Example 1 except that the resin compositions were changed as shown in Table 5. The properties of the resin composition and the evaluation results are shown in Table 5. The value of T (60) of the epoxy resin composition was 22 hours and less than 25 hours, and the storage stability of the prepreg was insufficient.

(Comparative Example 11)
An epoxy resin composition, a prepreg, and a cured resin were prepared in the same manner as in Example 1 except that the resin compositions were changed as shown in Table 5. The properties of the resin composition and the evaluation results are shown in Table 5. The value of T (60) of the epoxy resin composition was 13 hours and less than 25 hours, and the storage stability of the prepreg was insufficient. Moreover, when the storage stability of the prepreg after heat treatment at 80 ° C. for 1 hour was evaluated, the Tg increased significantly to 43 ° C., and stability in the thermal history could not be obtained. Further, the balance between the elastic modulus and the bending of the cured resin product was deteriorated, and the 90 ° bending strength of CFRP was as low as 73 MPa.

Since the epoxy resin composition of the present invention has extremely excellent storage stability and excellent mechanical properties when cured, it is suitably used as a matrix resin for a fiber-reinforced composite material. In addition, the prepreg and fiber reinforced composite material of the present invention are preferably used for sports applications, general industrial applications and aerospace applications.

Claims (6)

The following components [A], [B], [C], [D] wherein the following conditions [a] and meets [b], the epoxy resin of component [A] is [A1] or [A2] An epoxy resin composition comprising 10 parts by mass to 50 parts by mass in 100 parts by mass of all epoxy resins .
[A]: Epoxy resin [B]: Dicyandiamide [C]: Aromatic urea [D]: Borate ester [a]: Analyzing the epoxy resin composition with a differential scanning calorimeter at an isothermal temperature of 100 ° C. under a nitrogen stream. When the epoxy resin composition is analyzed by a differential scanning calorimetry at an isothermal temperature of 60 ° C. under a nitrogen stream, the time from reaching 100 ° C. to the peak top of the heat flow is 60 minutes or less [b]. , The time from reaching 60 ° C to the peak top of the heat flow is 25 hours or more.
[A1] Epoxy resin represented by formula (I) and / or formula (II)

(In the formula, R ₁ , R ₂ , and R ₃ represent a hydrogen atom or a methyl group, and n represents an integer of 1 or more.)

(N represents an integer of 1 or more.)
[A2] Trifunctional or higher functional glycidylamine type epoxy resin [A1] The epoxy resin composition according to claim 1 , wherein the average number of functional groups of the epoxy groups of the epoxy resin represented by the formula (I) and / or the formula (II) is 3.0 elements / molecule or more. The epoxy resin composition according to claim 1 or 2 , wherein the component [A] contains [A3] bisphenol F-type epoxy resin in an amount of 20 to 90 parts by mass based on 100 parts by mass of the total epoxy resin. The epoxy resin composition according to any one of claims 1 to 3 , wherein the cured resin composition cured by heating at 130 ° C. for 2 hours has a flexural modulus of 3.5 GPa or more. A prepreg comprising the epoxy resin composition according to any one of claims 1 to 4 and carbon fibers. A fiber-reinforced composite material obtained by curing the prepreg according to claim 5 .