JP5252869B2 - Epoxy resin composition for fiber reinforced composite material and prepreg - Google Patents

Description

  The present invention relates to an epoxy resin composition for fiber-reinforced composite materials and a prepreg.

  A fiber-reinforced composite material (hereinafter referred to as FRP) made of a reinforcing fiber such as carbon fiber or glass fiber and an epoxy resin is excellent in lightness, corrosion resistance, durability, and other mechanical properties. Therefore, they are used in a wide range of fields such as sports and leisure applications such as golf shafts, fishing rods and bicycle frames, general industrial applications, and further applications such as aircraft and vehicles.

  As the reinforcing fiber, carbon fiber is preferably used because it is excellent in specific strength and specific elasticity. FRP is often used in a tubular shape as represented by golf shafts and fishing rods. Such a carbon fiber reinforced resin tubular body is usually excellent in terms of lightness, high rigidity, and static strength, but has poor flexibility, and the carbon fiber has a low fracture elongation. It is considered difficult to improve toughness.

  However, in recent years, there has been an increasing demand for improving the impact resistance of FRP, mainly in the sports field. This is because not only the occurrence of defects such as breakage of the product can be prevented by improving the impact resistance of the FRP, but further weight reduction can be achieved by increasing the degree of design freedom accompanying the improvement of the impact resistance.

In the case of FRP, especially carbon fiber composite material (CFRP) using carbon fiber as a reinforcing fiber, the prepreg obtained by impregnating the resin composition into the reinforcing fiber in advance is formed into a desired shape because the resulting composite material has high mechanical properties. A method of forming after cutting and heat-curing is widely used. However, the prepreg is obtained by impregnating a reinforcing fiber with a resin composition, and is used as an intermediate material when manufacturing FRP.
In general, a thermosetting resin is mainly used as a prepreg resin composition from the viewpoint of strength development. Among these, epoxy resins are widely used from the viewpoints of handleability and strength development.

In the FRP using a thermosetting resin as a resin composition or a fiber reinforced resin tubular body using the FRP, examples of improved impact resistance include the following.
(1) FRP and fiber reinforced resin tubular body in which organic fibers are added to a fiber reinforced resin layer (Patent Documents 1 to 5).
(2) FRP using a film, tape or the like made of an organic polymer together with a fiber reinforced resin layer (Patent Documents 6 to 7).
(3) A fiber-reinforced resin tubular body using a layer composed of glass fibers and a resin composition on the outside of the FRP as an outer layer (Patent Document 8).
(4) FRP in which a rubber component is added to the resin composition of the fiber reinforced resin layer (Patent Document 9).
(5) A fiber reinforced resin tubular body using a specific resin such as a bisphenol A type epoxy resin or an oxazolidone ring-containing epoxy resin as the resin composition of the fiber reinforced resin layer (Patent Document 10).

(1) and (2) improve the delamination strength of the laminate by the fiber reinforced resin layer. Specifically, for the purpose of effectively improving the peel strength between layers of the laminate, fine particles of thermoplastic resin and the like are intensively distributed between the layers. However, in this method, there is a problem that a significant decrease in tack level in the prepreg is unavoidable, and the process and quality control are complicated. It is also difficult to reduce the weight of the product.
Moreover, although the method of inserting a kind of shock absorbing layer called an interleaf is also shown (for example, patent documents 11-14), all are the fall of the fiber ratio by an interlayer becoming thick, the tack level in a prepreg There is a risk of a decrease in handleability due to a decrease in the temperature.

In (3), the glass fiber, which is a different material, is added to improve the impact resistance. However, since different materials are added as in (1) and (2), it is difficult to reduce the weight. Further, the improvement in impact resistance is not so great, and further improvement in impact resistance is desired.
In (4), a rubbery polymer such as an acrylonitrile-butadiene copolymer is added to the epoxy resin component, and the rubber layer is microphase-separated at the time of curing. In this method, the impact resistance is improved according to the amount of these components added, but the rigidity tends to be lost.
In (5), although impact resistance is improved to some extent, further improvement in impact resistance is desired.
In view of the above, there is a need for a method for obtaining FRP having excellent mechanical properties and superior impact resistance.

Further, prepregs generally used for FRP such as golf shafts and tennis rackets are usually several tens of μm on the surface of the release layer of process paper (release paper) whose surface has been released from a resin composition made of epoxy resin or the like. The reinforcing fiber is applied to the resin coating surface, and the reinforcing fiber is impregnated with the resin composition by pressing while heating. If the viscosity of the resin composition is too high in the impregnation step, not only properties such as tackiness and flexibility that are strongly required for the prepreg are significantly reduced, but also the prepreg processability is markedly reduced. Therefore, it is necessary to prevent the viscosity of the resin composition from becoming too high.
JP 51-118538 A Japanese Patent Laid-Open No. 62-164482 JP-A-8-20651 JP-A-9-176347 Japanese Patent Laid-Open No. 10-337436 Japanese Patent Laid-Open No. 9-239082 Japanese Patent Laid-Open No. 10-235767 JP-A-10-329247 Japanese Patent Laid-Open No. 2001-13962 JP 2000-24151 A U.S. Pat. No. 3,472,730 JP 51-58484 A JP-A-60-63229 JP-A-60-231738

As a result of intensive research, in order to obtain a fiber-reinforced composite material having excellent impact resistance, it is necessary that the fracture toughness value of the cured resin composition after curing is 400 J / m ² or more. I understood it.
The present invention provides an epoxy resin composition for fiber-reinforced composite materials that has high process passability and is excellent in mechanical properties and impact resistance (toughness) when FRP is used. Moreover, in this invention, the prepreg by which the said epoxy resin composition for fiber reinforced composite materials was impregnated in the reinforced fiber is provided.

The epoxy resin composition for fiber-reinforced composite material of the present invention comprises an epoxy resin (I) and a polyamide resin (II) that dissolves in an amount of 1% by mass or more in the epoxy resin (I) when heated and dissolved at 180 ° C. for 6 hours. ) And a curing agent (III) that cures the epoxy resin (I) at 100 to 160 ° C., and the epoxy resin (I) (100 parts by mass) is represented by the following formula (1): The epoxy resin (A) having an oxazolidone ring represented by 5 to 50 parts by mass and the other epoxy resin (B) 95 to 50 parts by mass, and the polyamide resin (II) is a polyamide derived from a polymerized fatty acid s and, polyoxyalkylene glycols and polyether ester amide block copolymer der obtained by copolymerization of the polyether esters derived from dicarboxylic acids The content of the polyamide resin (II) is 1.5 to 20 parts by mass with respect to 100 parts by mass of the epoxy resin (I), and the content of the curing agent (III) is the epoxy resin (I). ) 1.5 to 20 parts by mass with respect to 100 parts by mass.

（式（１）中、Ｒ^１、Ｒ^２はそれぞれ独立に水素原子又はメチル基、Ｘ^１〜Ｘ^４はそれぞれ独立にハロゲン原子、水素原子、又は炭素数１〜４のアルキル基、Ｒ^３〜Ｒ^６はそれぞれ独立に水素原子又は炭素数１〜４のアルキル基である。また、Ｑ^１は下記式（２）又は（３）である。）

(In the formula ^{(1), R 1, R} 2 each independently represent a hydrogen atom or a methyl ^group, X 1 to X ⁴ each independently represents a halogen atom, a hydrogen atom, or an alkyl group having 1 to 4 carbon ^{atoms, R} 3 ~ R ⁶ is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and Q ¹ is the following formula (2) or (3).

（式（２）中のＺ^１〜Ｚ^４はそれぞれ独立に水素原子又は炭素数１〜４のアルキル基である。）

(Z ^{1 to} Z ⁴ in the formula (2) are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

（式（３）中のＴ^１〜Ｔ^８はそれぞれ独立に水素原子又は炭素数１〜４のアルキル基である。また、Ｑ^２は単結合、−ＣＨ_２−、−Ｃ（ＣＨ_３）_２−、−ＳＯ_２−、−ＳＯ−、−Ｓ−、又は−Ｏ−である。）

(T ^{1 to} T ⁸ in Formula (3) are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Q ² is a single bond, —CH ₂ —, —C (CH ₃ ) _{2. -, - SO 2 -, -} SO -, - S-, or -O- and is).

（式（４）中、ａは１〜１０、ｂは１〜１０、ｃは１〜２０で、いずれも整数である。また、ＰＡは下記式（５）であり、ＰＥは下記式（８）である。）

(In the formula (4), a is 1 to 10, b is 1 to 10, c is 1 to 20, and both are integers. PA is the following formula (5), and PE is the following formula (8). ).)

（式（５）中、ｄは０〜２、ｅは０〜２、ｆは１〜１０で、いずれも整数である。ただし、ｄ及びｅが同時に０になることはない。また、αは２〜４０の整数である。また、ＰＡ^１及びＰＡ^２はそれぞれ独立に、下記式（６）及び／又は下記式（７）である。）

(In the formula (5), d is 0 to 2, e is 0 to 2, f is 1 to 10, and both are integers, provided that d and e are not 0 at the same time. (It is an integer of 2 to 40. In addition, PA ¹ and PA ² are each independently the following formula (6) and / or the following formula (7).)

（式（６）中、βは２〜４０、γは２〜４０で、いずれも整数である。また、Ｒ^７、Ｒ^８はそれぞれ独立に水素原子又はメチル基である。）

(In formula (6), β is 2 to 40, and γ is 2 to 40, both of which are integers. R ⁷ and R ⁸ are each independently a hydrogen atom or a methyl group.)

（式（７）中、βは２〜４０、γは２〜４０で、いずれも整数である。）

(In formula (7), β is 2 to 40, and γ is 2 to 40, both of which are integers.)

（式（８）中、ｇは３〜２０、ｈは１〜１０で、いずれも整数である。θは２〜８、φは２〜４０で、いずれも整数である。）

(In Formula (8), g is 3-20, h is 1-10, and all are integers. Θ is 2-8, φ is 2-40, and both are integers.)

  In the epoxy resin composition for fiber-reinforced composite materials of the present invention, the curing agent (III) is preferably dicyandiamide.

  In the prepreg of the present invention, the reinforcing fiber is impregnated with the epoxy resin composition for fiber-reinforced composite material.

  The resin composition for fiber-reinforced composite material of the present invention can produce FRP having high process passability and excellent mechanical properties and impact resistance (toughness). In addition, according to the present invention, it is possible to provide a prepreg in which reinforcing fibers are impregnated with the resin composition for fiber-reinforced composite materials.

The epoxy resin composition for fiber-reinforced composite material of the present invention (hereinafter referred to as a resin composition) includes an epoxy resin (I), a polyamide resin (II) soluble in the epoxy resin (I), and a curing agent. (III).
Epoxy resin (I) consists of epoxy resin (A) and other epoxy resins (B) other than epoxy resin (A).

The epoxy resin (A) has an oxazolidone ring and has a structure represented by the following formula (1).
The epoxy resin (I) can be synthesized, for example, by a method of reacting an epoxy resin and an isocyanate compound in the presence of an oxazolidone ring-forming catalyst as disclosed in JP-A-5-43655. Moreover, AER4151, AER4152, etc. by Asahi Kasei Chemicals Co., Ltd. can be used.

（式（１）中、Ｒ^１、Ｒ^２はそれぞれ独立に水素原子又はメチル基、Ｘ^１〜Ｘ^４はそれぞれ独立にハロゲン原子、水素原子、又は炭素数１〜４のアルキル基、Ｒ^３〜Ｒ^６はそれぞれ独立に水素原子又は炭素数１〜４のアルキル基である。また、Ｑ^１は下記式（２）又は（３）である。）

(In the formula ^{(1), R 1, R} 2 each independently represent a hydrogen atom or a methyl ^group, X 1 to X ⁴ each independently represents a halogen atom, a hydrogen atom, or an alkyl group having 1 to 4 carbon ^{atoms, R} 3 ~ R ⁶ is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and Q ¹ is the following formula (2) or (3).

（式（２）中のＺ^１〜Ｚ^４はそれぞれ独立に水素原子又は炭素数１〜４のアルキル基である。）

(Z ^{1 to} Z ⁴ in the formula (2) are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

（式（３）中のＴ^１〜Ｔ^８はそれぞれ独立に水素原子又は炭素数１〜４のアルキル基である。また、Ｑ^２は単結合、−ＣＨ_２−、−Ｃ（ＣＨ_３）_２−、−ＳＯ_２−、−ＳＯ−、−Ｓ−、又は−Ｏ−である。）

(T ^{1 to} T ⁸ in Formula (3) are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Q ² is a single bond, —CH ₂ —, —C (CH ₃ ) _{2. -, - SO 2 -, -} SO -, - S-, or -O- and is).

The content of the epoxy resin (A) in the epoxy resin (I) is 5 to 50 parts by mass with the total amount of the epoxy resin (I) being 100 parts by mass.
If an epoxy resin (A) is 5 mass parts or more, the resin composition excellent in impact resistance will be obtained. Moreover, when an epoxy resin (A) exceeds 50 mass parts, the improvement effect of the impact resistance with respect to the addition amount is small.

  The other epoxy resin (B) is an epoxy resin other than the epoxy resin (A) and is not particularly limited. For example, a bifunctional epoxy resin having two epoxy groups in the molecule, a polyfunctional epoxy resin having three or more epoxy resins, and the like can be mentioned. These epoxy resins may use only 1 type and may use 2 or more types together.

  Examples of the bifunctional epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, epoxy resin having an alkyl skeleton as the main chain, biphenyl type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene Type epoxy resin, fluorene type epoxy resin, aminophenol type epoxy resin, novolac type epoxy resin, aliphatic epoxy resin, alicyclic epoxy resin, etc., and those brominated epoxy resins, rubber components such as CTBN, and clayton And an epoxy resin modified with an air stoma or the like.

  Examples of the polyfunctional epoxy resin include phenol novolac type epoxy resin, cresol type epoxy resin, glycidylamine type epoxy resin such as tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol and tetraglycidylamine, tetrakis (glycidyloxyphenyl) ethane, A glycidyl ether type epoxy resin such as tris (glycidyloxymethane) can be mentioned, and a combination thereof is preferably used.

The other epoxy resin (B) is uniformly dissolved in the epoxy resin (A) and the polyamide resin (II) described later from the viewpoint of processability and stability of the resin composition, or is mixed with these components. Is preferred.
Content of the other epoxy resin (B) in epoxy resin (I) is 50-95 mass parts when the whole quantity of epoxy resin (I) is 100 mass parts. When the other epoxy resin (B) is 50 parts by mass or more, the effect of the other epoxy resin (B) can be obtained while keeping the impact resistance of the resin composition high. If other epoxy resin (B) is 95 mass parts or less, the resin composition excellent in impact resistance will be obtained.

  The polyamide resin (II) is soluble in the epoxy resin (I), and is a polyamide resin that dissolves 1% by mass or more in the epoxy resin (I) when heated and dissolved at 180 ° C. for 6 hours.

  As the polyamide resin (II), a polyesteramide copolymer is preferable. Specifically, polyamide resins derived from polymerized fatty acids mainly composed of dimer acids (dimerized fatty acids) derived from fatty acids, polyamide resins derived from the polymerized fatty acids, and polyethers Polyamide elastomers containing both in the molecular skeleton by copolymerization using one or more selected from the group consisting of polyesters, polyetheresters, ie, polyetheresteramide, polyetheresteramide block copolymer Examples thereof include a polyester and a polyesteramide copolymer. These may use only 1 type and may use 2 or more types together.

Examples of polyamide resins derived from polymerized fatty acids include PA series (PA-100, PA-100A, PA-102A, PA-105A, PA-100A) manufactured by Fuji Kasei Kogyo Co., Ltd.
Moreover, as polyamide resin (II), the polyetheresteramide (polyetheresteramide block copolymer) shown by following formula (4 ) is preferable. The polyether ester amide is a polymer obtained by reacting a polyamide component with a polyether ester component comprising polyoxyalkylene glycol and dicarboxylic acid, and having an amide bond, an ether bond and an ester bond in the molecular chain. High compatibility with epoxy resin. Therefore, a fine sea-island structure can be formed with the epoxy resin (I). As a result, the effect of improving the impact resistance while maintaining excellent mechanical properties is great.

（式（４）中、ａは１〜１０、ｂは１〜１０、ｃは１〜２０で、いずれも整数である。また、ＰＡは下記式（５）であり、ＰＥは下記式（８）である。）

(In the formula (4), a is 1 to 10, b is 1 to 10, c is 1 to 20, and both are integers. PA is the following formula (5), and PE is the following formula (8). ).)

（式（５）中、ｄは０〜２、ｅは０〜２、ｆは１〜１０で、いずれも整数である。ただし、ｄ及びｅが同時に０になることはない。また、αは２〜４０の整数である。また、ＰＡ^１及びＰＡ^２はそれぞれ独立に、下記式（６）及び／又は下記式（７）である。すなわち、ＰＡ^１、ＰＡ^２はいずれも、式（６）の構成単位単独の場合と、式（７）の構成単位単独の場合と、式（６）の構成単位と式（７）の構成単位とが混在している場合とがある。）

(In the formula (5), d is 0 to 2, e is 0 to 2, f is 1 to 10, and both are integers, provided that d and e are not 0 at the same time. It is an integer of 2 to 40. In addition, PA ¹ and PA ² are each independently the following formula (6) and / or the following formula (7), that is, both PA ¹ and PA ² are represented by the formula (6 ) In the case of a single structural unit, in the case of a single structural unit in formula (7), and in the mixed case of a structural unit in formula (6) and a structural unit in formula (7).

（式（６）中、βは２〜４０、γは２〜４０で、いずれも整数である。また、Ｒ^７、Ｒ^８はそれぞれ独立に水素原子又はメチル基である。）

(In formula (6), β is 2 to 40, and γ is 2 to 40, both of which are integers. R ⁷ and R ⁸ are each independently a hydrogen atom or a methyl group.)

（式（７）中、βは２〜４０、γは２〜４０で、いずれも整数である。）

(In formula (7), β is 2 to 40, and γ is 2 to 40, both of which are integers.)

（式（８）中、ｇは３〜２０、ｈは１〜１０で、いずれも整数である。また、θは２〜８、φは２〜４０で、いずれも整数である。）

(In Formula (8), g is 3-20, h is 1-10, and all are integers. Moreover, (theta) is 2-8, (phi) is 2-40, and all are integers.

  The method for producing the polyetheresteramide may be any method as long as a uniform and high molecular weight polymer can be obtained. For example, first, a method of synthesizing a polyamide oligomer, adding a polyoxyalkylene glycol and dicarboxylic acid to the polyamide oligomer, and heating under reduced pressure to increase the degree of polymerization can be mentioned.

Moreover, as such a polyether ester amide, a commercial item can also be used. Examples of commercially available polyether ester amides include TPAE series (TPAE12, TPAE31, TPAE32, TPAE38, TPAE8, TPAE10, TPAE100, TPAE23, TPAE63, TPAE200, TPAE201, and TPAE260) manufactured by Fuji Kasei Kogyo.
Among these, TPAE32 is a mixture of the compounds represented by the formulas (4) to (8). In the formulas (4) to (8), a = b = 1, c = 7.26, d = 0.16, e = 0.84, f = 2.23, α = 10, β = 34, γ = 2, g = 12, h = 1, θ = 4, and φ = 10. R ⁷ and R ⁸ are both hydrogen atoms. Further, in TPAE 32, both PA ¹ and PA ² are in a state in which the constituent unit of formula (6) and the constituent unit of formula (7) are mixed.

  The curing agent (III) is a curing agent capable of curing the epoxy resin by heating at 100 ° C. to 160 ° C., and is preferably dicyandiamide from the viewpoint of exhibiting high mechanical properties when made into a fiber-reinforced composite material. By using dicyandiamide as a curing agent, curing at 160 ° C. or less is facilitated, and a pot life exceeding one month can be realized at 20 ° C.

Curing agent such as diaminodiphenyl methane that allows the curing reaction at 180 ° C. is not preferable because the polyamide resin in the cured process is likely to undergo phase separation. In addition, amino compounds and imidazoles that can undergo a curing reaction at 100 ° C. or less are not preferable because there is a possibility that the bond formation between the end of the polyamide resin and the functional group in the epoxy resin may not proceed sufficiently. However, those obtained by encapsulating these curing agents may be used for enhancing the storage stability of the prepreg.

  Content of hardening | curing agent (III) is 1.5-20 mass parts with respect to 100 mass parts of epoxy resins (I). Moreover, it is preferable that content is 2-10 mass parts. When the content of the curing agent (III) is 1.5 parts by mass or more, a resin composition capable of producing a fiber-reinforced composite material in which the curing reaction of the epoxy resin (I) proceeds sufficiently and has excellent mechanical properties. can get. Moreover, if content of hardening | curing agent (III) is 20 mass parts or less, sufficient storage stability will be acquired and the physical property of the resin composition after hardening will also become favorable.

The resin composition of the present invention may contain a curing accelerator in addition to the epoxy resin (I), the polyamide resin (II), and the curing agent (III).
Examples of the curing accelerator include imidazole, imidazole derivatives, urea compounds, imidazole carboxylates and metal complexes, tertiary amine compounds, and the like.
When dicyandiamide is used as the curing agent (III), a urea accelerator such as phenyldimethylurea, 3- (3,4-dichlorophenyl) -1,1, dimethylurea (DCMU) or an imidazole derivative is used as a curing accelerator. Urea compounds, imidazoles and amines are preferably used.

  It is preferable that the addition amount of a hardening accelerator is 1-15 mass parts with respect to 100 mass parts of epoxy resins (I). Further, the addition amount is more preferably 2 to 10 parts by mass. If the addition amount of a hardening accelerator is 1 mass part or more, the function of a hardening accelerator will be fully acquired. Moreover, if the addition amount of a hardening accelerator is 15 mass parts or less, there is almost no possibility that the storage stability in 20 degreeC will fall.

Moreover, the resin composition of this invention may contain the additive for providing functionality.
As the additive, for example, a thermoplastic resin can be used for the purpose of controlling the resin viscosity and the handling property of the prepreg.
The thermoplastic resin is compatible with the epoxy resin (I) and does not adversely affect the physical properties of the fiber reinforced composite material. For this reason, polyvinyl formal resin, polyvinyl butyral resin, polyethylene oxide resin, polymethyl methacrylate resin Polyamide resin, polyester resin, polyethersulfone resin, polysulfone resin, polyetherimide resin, polyimide resin, phenoxy resin and the like are preferable. Two or more of these thermoplastic resins may be mixed and used.

  Further, the additive may include rubber particles, soluble rubber, rubber having a core-shell structure, and the like. These are at least partially dissolved in the mother resin, or exist in the form of particles without being dissolved. In the present invention, in order to obtain a prepreg of good quality, if particles are present, the particles are pulverized or dissolved in advance so that particles having a particle diameter of about 50 μm or more are not substantially included. It is preferable to keep it.

In order to impart flame retardancy, inorganic fillers such as silica, aluminum hydroxide, magnesium hydroxide, alumina, talc, and magnesium oxide, antimony compounds, and the like may be used. You may use these in mixture of 2 or more types. In addition, for the purpose of controlling the fluidity of the resin, fine silica particles, a surfactant as a wetting agent or a desiccant, a silicon-based organometallic compound, or the like can be used.
The amount of the additive used is preferably 20% by mass or less based on the total amount of the resin composition. If the additive is 20% by mass or less, there is almost no risk of impairing the impact resistance of the resulting resin composition.

  The resin composition of the present invention is a cured resin product having excellent impact resistance (toughness) due to the synergistic effect of the epoxy resin (I) containing the epoxy resin (A) having an oxazolidone ring and the polyamide resin (II). (Hardened resin composition) and fiber reinforced composite material can be manufactured. Among these, when any component is not included, excellent impact resistance (toughness) cannot be obtained.

In order to obtain a fiber-reinforced composite material having excellent impact resistance, it is necessary that the fracture toughness value of the cured resin composition on the cured plate is 400 J / m ² or more. Even toughness type resin compositions have fracture toughness values of around 300 J / m ² .
On the other hand, the resin composition of the present invention has a fracture toughness value of 400 J / m ² or more, and can produce a fiber-reinforced composite material having excellent impact resistance.

The prepreg of the present invention is obtained by impregnating reinforcing fibers with the resin composition described above.
The reinforcing fiber is not particularly limited, and examples thereof include organic fibers such as carbon fiber, polyaramid fiber, and polyethylene fiber, boron fiber, steel fiber, glass fiber, and the like in terms of specific strength, and carbon in terms of specific strength and specific elasticity. It is preferably a fiber.
There is no particular limitation on the form and arrangement of the reinforcing fibers, for example, one tow which is a unit of several thousand to several tens of thousands of filaments, or a form like a so-called tow prepreg having a shape obtained by collecting several tows, Forms such as a unidirectional tape prepreg in which tows are arranged and aligned in one direction, forms such as a cloth (woven fabric), mats, knits, and sleeves can be used.

  As a method for producing a prepreg, a conventionally known method can be used. For example, a resin composition is applied to the surface of a release layer of a process paper (release paper) whose surface has been release-treated, with a thickness of several tens of μm, A method of impregnating the reinforcing fiber with the resin composition by arranging the reinforcing fiber on the resin coated surface and pressing it while heating can be mentioned.

  In addition, although the epoxy resin composition for fiber reinforced composite materials of the present invention is particularly suitable for prepreg, it can also be suitably used as a matrix resin for compound applications, for example.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited by the following description.
The abbreviations and test methods of the compounds in the examples are as follows.

Epoxy resin (A)
AER4152: Epoxy resin having an oxazolidone ring (manufactured by Asahi Kasei Chemicals Corporation)

Other epoxy resin (B)
jER828: Bisphenol A type liquid epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd.)
jER807: Bisphenol F type liquid epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd.)
jER1001: Bisphenol A type solid epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd.)
jER1002: bisphenol A type solid epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd.)
BPA328: Acrylic rubber modified bisphenol A type epoxy resin (manufactured by Nippon Shokubai Co., Ltd.)

Polyamide resin (II)
TPAE32: Polyetheresteramide copolymer (Fuji Kasei Kogyo Co., Ltd.)

Curing agent (III)
DICY: Dicyandiamide (Product name: Dicy 7, Japan Epoxy Resin Co., Ltd.)

Curing accelerator DCMU: 3- (3,4-dichlorophenyl) -1,1-dimethylurea (Product name: DCMU99, manufactured by Hodogaya Chemical Co., Ltd.)
Thermoplastic resin PVF: Polyvinyl formal (Product name: Vinylec E, manufactured by Chisso Corporation)

The resin composition is evaluated by evaluating the processability of the resin composition, and measuring the three-point bending strength as the heat resistance, fracture toughness value (GIC), and mechanical properties of the cured resin composition (resin cured product). It was done by doing.
[Heat resistance (G'-Tg)]
A resin composition containing the curing agent (III) is molded at 130 ° C. under curing conditions for 1.5 hours to obtain a cured resin plate having a thickness of 2 mm as a resin cured product, and then this is further reduced to 60 mm. A test piece was prepared by cutting into a length × 12 mm width. Then, using a dynamic viscoelasticity measuring device (RDA-700) manufactured by Rheometric Far East Co., Ltd., the test piece was heated at 5 ° C./STEP, and 10 radians / second was applied to the test piece. A shear force was applied at a speed, and the temperature dependence of the storage rigidity of the test piece was measured. The intersection of the tangent in the glass state region and the tangent in the transition region of the temperature dependence curve of the storage rigidity was determined as the glass transition temperature.

[Fracture toughness value (GIC)]
Using the obtained cured resin plate having a thickness of 3 mm, the fracture toughness value (GIC) of the resin was evaluated in accordance with ASTM D5045-compliant SENB method.

[3-point bending strength]
Using the obtained cured resin plate having a thickness of 2 mm, bending strength, elastic modulus, and elongation were evaluated in accordance with JIS K6911.

[Process passability]
50 g of a resin composition heated to 60 ° C. was placed on a release paper coated with a silicon release agent. Next, using a simple coater heated to 60 ° C., it was evaluated whether a resin film having a thickness of 0.04 mm could be produced from the resin composition. When a resin film having a thickness of 0.04 mm can be produced at 5 m / min, it was judged that the process passability was good.

[Example 1]
Resin compositions were prepared with the compositions shown in Table 1.
AER415 2 (50 g), jER828 (100 g), jER1001 (50 g), and TPAE 3 2 (5.6 g) were sequentially added to the flask, and then dissolved in a flask adjusted to 180 ° C. until uniform. Then, after cooling to 50 ° C. to 60 ° C., DICY (10.8 g) and DCMU (7.2 g) were added, and stirred and mixed until uniform to obtain a resin composition. Next, the air in the resin composition is degassed by reducing the pressure inside the flask with a vacuum pump, and then sandwiched between two glass plates that have been subjected to a release treatment using a silicon-based release agent. The resin composition was cured by heating for 1.5 hours to obtain a cured resin plate that was a cured resin product. However, when sandwiching the resin composition, a cured resin plate having a thickness of 2 mm and a thickness of 3 mm was obtained by inserting a spacer.

[Examples 2 to 7]
A resin composition was prepared in the same manner as in Example 1 except that the type and composition of the resin and curing agent used were changed as shown in Table 1, and a cured resin plate was obtained.

[Comparative Examples 1-4]
A resin composition was prepared in the same manner as in Example 1 except that the type and composition of the resin and curing agent used were changed as shown in Table 2, and a cured resin plate was obtained.
Moreover, the evaluation result of Examples 1-7 is shown in Table 3, and the evaluation result of Comparative Examples 1-4 is shown in Table 4.

The cured resin plate of Example 1 exhibited a high fracture toughness value exceeding 400 J / m ² while maintaining excellent heat resistance exceeding 115 ° C. Further, the three-point bending strength was high strength exceeding 10 MPa, and the process passability was also good. From these results, it was confirmed that a cured resin product having excellent mechanical properties and impact resistance (toughness) was obtained, and that the resin composition had high process passability.
Similar results were obtained in Examples 2-7.

On the other hand, the cured resin plate of Comparative Example 1 had a high three-point bending strength of 13 MPa, but had a low fracture toughness value of 300 J / m ² and a low impact resistance.

  Although the cured resin plate of Comparative Example 2 has excellent three-point bending strength, fracture toughness value, etc., since the content of the epoxy resin (A) contained in the epoxy resin (I) is large, the viscosity of the resin composition is high. The resin film could not be produced under high conditions.

The cured resin plate of Comparative Example 3 had a high three-point bending strength of 12 MPa, but had a very low fracture toughness value of 232 J / m ² and a low impact resistance.

  The cured resin plate of Comparative Example 4 contained a large amount of polyamide resin (II), the viscosity of the resin composition was high, and DICY and DCMU added at 60 ° C. could not be mixed uniformly. Therefore, evaluation about a cured resin board was not able to be performed.

  According to the epoxy resin composition for fiber-reinforced composite material and the prepreg of the present invention, a fiber-reinforced composite material having both excellent mechanical properties and impact resistance can be produced. Therefore, it is useful in various fields centering on the sports field.

Claims (3)

The epoxy resin (I), the polyamide resin (II) that dissolves 1% by mass or more in the epoxy resin (I) when heated and dissolved at 180 ° C. for 6 hours, and the epoxy resin (I) at 100 to 160 ° C. A resin composition containing a curing agent (III) that cures at
The epoxy resin (I) (100 parts by mass) includes 5 to 50 parts by mass of an epoxy resin (A) having an oxazolidone ring represented by the following formula (1), and 95 to 50 parts by mass of another epoxy resin (B). Consists of
The polyamide resin (II) has a polyamides derived from polymerized fatty acid, a polyether ester amide block copolymer obtained by copolymerization of the polyether esters derived from polyoxyalkylene glycol and dicarboxylic acids,
Content of the said polyamide resin (II) is 1.5-20 mass parts with respect to 100 mass parts of said epoxy resins (I),
Content of the said hardening | curing agent (III) is an epoxy resin composition for fiber reinforced composite materials which is 1.5-20 mass parts with respect to 100 mass parts of said epoxy resins (I).

(In the formula ^{(1), R 1, R} 2 each independently represent a hydrogen atom or a methyl ^group, X 1 to X ⁴ each independently represents a halogen atom, a hydrogen atom, or an alkyl group having 1 to 4 carbon ^{atoms, R} 3 ~ R ⁶ is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and Q ¹ is the following formula (2) or (3).

(Z ^{1 to} Z ⁴ in the formula (2) are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

(T ^{1 to} T ⁸ in Formula (3) are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Q ² is a single bond, —CH ₂ —, —C (CH ₃ ) _{2. -, - SO 2 -, -} SO -, - S-, or -O- and is). The epoxy resin composition for fiber-reinforced composite materials according to claim 1, wherein the curing agent (III) is dicyandiamide. Prepregs for fiber-reinforced composite materials epoxy resin composition according impregnated into reinforcing fibers to claim 1 or 2.