JP4506189B2 - Epoxy resin composition, prepreg and fiber reinforced composite material - Google Patents

Description

  The present invention relates to an epoxy resin composition and a prepreg impregnated with the resin composition. More specifically, the present invention relates to an epoxy resin composition excellent in process passability during prepreg production, and a prepreg excellent in workability. It is.

  A fiber reinforced composite material composed of a reinforced fiber and a matrix resin is widely used in sports applications, aerospace applications, and general industrial applications because of its excellent lightweight performance and mechanical properties. Among them, for sports applications, golf club shafts, fishing rods, rackets such as tennis and badminton, sticks such as hockey are important applications.

  There are various methods for producing fiber reinforced composite materials. Among them, a plurality of prepregs, which are sheet-like intermediate materials in which reinforced fibers are impregnated with a matrix resin, are laminated, and then heated to form a fiber reinforced composite. A method of obtaining a material is preferably used.

  Pre-preg requires moderate tackiness (adhesiveness) between prepregs for lamination and molding, and also requires moderate drape (flexibility) because it may be wrapped around a mandrel or bonded to a curved surface. It is said.

  In recent years, a prepreg suitable for lightweight design has been demanded in particular due to further weight reduction requirements of fiber reinforced composite materials. High-modulus carbon fibers are used as the reinforcing fibers and the fiber content in the prepreg tends to be increased. is there. However, when a high elastic modulus carbon fiber is used as the reinforcing fiber, the drapeability of the prepreg tends to be lowered. When the reinforcing fiber content is increased, the tackiness is lowered and the handling property is sacrificed.

Therefore, in order to improve handling, a method of combining a liquid epoxy resin having a specific viscosity range, an epoxy resin having a softening point in a specific range, and a thermoplastic resin having a specific weight average molecular weight has been proposed. However, although the tack and drape properties can be secured to some extent, the thermal stability (pot life) of the resin is not sufficient, so that the processability is inferior. A method of combining a bifunctional epoxy resin and an epoxy resin having a specific molecular structure has also been proposed (see, for example, Patent Document 2). However, tackiness tends to decrease with time, and handling is sufficient. It could not be said.
JP 2003-2990 A JP-A-8-301982

  An object of the present invention is to solve the above-described problems and provide a resin composition suitable as a matrix resin for a prepreg. Another object of the present invention is to provide a prepreg with good handleability that contributes to weight reduction of the fiber-reinforced composite material. Furthermore, it is providing the fiber reinforced composite material which was lighter and excellent in various characteristics.

  The present invention has the following configuration in order to achieve the above-described object. That is, it is an epoxy resin composition containing at least the following components [A], [B], and [C].

[A] Dicyclopentadiene type epoxy resin having an average epoxy equivalent of 200 to 300 [B] Curing agent containing epoxy resin [C] dicyandiamide having an average epoxy equivalent of 1000 or more and 10,000 or less Further, the epoxy resin composition and the reinforcement A prepreg composed of fibers.

Furthermore, it is a fiber reinforced composite material obtained by curing such a prepreg, and a fiber reinforced composite material comprising a cured product of the epoxy resin composition and reinforcing fibers.

  The epoxy resin composition of the present invention makes it possible to provide a prepreg having excellent handleability even when a high elastic modulus reinforcing fiber is used or when the reinforcing fiber content is increased. Moreover, since the epoxy resin composition of this invention has the outstanding thermal stability, it enables it to manufacture a prepreg stably.

  Moreover, the prepreg of the present invention is excellent in tackiness and drapeability. Furthermore, since the change with time of tackiness is small, the handleability is good for a long time. Moreover, since the handleability is good and the moldability is excellent, a fiber-reinforced composite material having excellent mechanical properties can be provided.

  Furthermore, the fiber-reinforced composite material of the present invention is lightweight and has excellent mechanical properties such as torsional strength.

  The epoxy resin composition of the present invention is an epoxy resin composition containing at least the following components [A], [B], and [C].

[A] Dicyclopentadiene type epoxy resin having an average epoxy equivalent of 200 to 300 [B] Curing agent containing epoxy resin [C] dicyandiamide having an average epoxy equivalent of 1000 or more and 10000 or less In the present invention, the component [A ] and [B] it is necessary that coexist. Either one does not result in a resin composition excellent in thermal stability, but surprisingly, excellent thermal stability can be obtained by combining [A] and [B]. For example, the viscosity after holding for 2 hours at 80 ° C. relative to the initial viscosity at 80 ° C., that is, the viscosity increase ratio at 80 ° C. can be suppressed to 1.6 to 3.2 times.

As a component [A] of the present invention may, if dicyclopentadiene type epoxy resin having an average epoxy equivalent of 200 to 300, Ru can be used without particular limitation. The average epoxy equivalent is sometimes retention is deteriorated for aging of less than 200 and a tack, which may have greater than 300 and the effect of improving the initial tack is reduced.

Commercially available dicyclopentadiene type epoxy resins having an average epoxy equivalent of 200 to 300 may be used, for example, Epicron (registered trademark) HP7200L (epoxy equivalents 245 to 250, softening point 54 to 58), Epicron HP7200 (epoxy equivalents) 255-260, softening point 59-63), Epicron HP7200H (epoxy equivalent 275-280, softening point 80-85), Epicron HP7200HH (epoxy equivalent 275-280, softening point 87-92) (above, Dainippon Ink & Chemicals, Inc.) Manufactured by Co., Ltd.), XD-1000-L (epoxy equivalents 240-255, softening point 60-70), XD-1000-2L (epoxy equivalents 235-250, softening point 53-63) (Nippon Kayaku ( Co., Ltd.), Tactix (registered trademark) 556 (epoxy equivalents 215-2) 5, a softening point of 79 ° C.) (Vantico Inc Co., Ltd.) and the like.

  The component [A] is preferably contained in an amount of 5 to 55% by weight, more preferably 10 to 50% by weight, in 100% by weight of the total epoxy resin. If it is lower than 5% by weight, the effect of improving the thermal stability is small, the heat resistance is lowered and the initial tack value may be lowered. If it exceeds 55% by weight, the residual thermal stress increases, so that the physical properties of the fiber-reinforced composite material may be lowered.

  The epoxy resin of the component [B] needs to have an average epoxy equivalent of 1000 or more and 10000 or less, preferably 1200 or more and 8000 or less, and more preferably 1500 or more and 5000 or less. When the average epoxy equivalent is less than 1000, the effect of improving the thermal stability is reduced, and the tack retention may be lowered. In the prepreg manufacturing process exceeding 10,000, the impregnation property of the resin becomes insufficient, and the physical properties of the fiber reinforced composite material may be deteriorated.

  As an epoxy resin commercial item whose average epoxy equivalent of component [B] is 1000 or more, Ep1005F (made by Japan Epoxy Resin Co., Ltd., average epoxy equivalent 1000), ST-5100 (manufactured by Toto Kasei Co., Ltd., average) Epoxy equivalent 1000), ST-4100D (manufactured by Tohto Kasei Co., Ltd., epoxy equivalent 1000), Ep1005H (Japan Epoxy Resin Co., Ltd., average epoxy equivalent 1290), Ep5354 (Japan Epoxy Resin Co., Ltd., average epoxy equivalent) 1650), DER-667 (Dow Chemical Japan Co., Ltd., average epoxy equivalent 1775), EP-5700 (Asahi Denka Kogyo Co., Ltd., average epoxy equivalent 1925), Epc 7050 (Dainippon Ink Co., Ltd., average) Epoxy equivalent 1925), YD-017 (manufactured by Toto Kasei Co., Ltd., average) Poxy equivalent 1925), Ep1007 (Japan Epoxy Resin Co., Ltd., average epoxy equivalent 1950), Ep5057 (Japan Epoxy Resin Co., Ltd., average epoxy equivalent 2250), Ep4007P (Japan Epoxy Resin Co., Ltd., average epoxy equivalent) 2270), DER-668 (manufactured by Dow Chemical Japan Co., Ltd., average epoxy equivalent 2750), YD-019 (manufactured by Tohto Kasei Co., Ltd., average epoxy equivalent 2850), EP-5900 (manufactured by Asahi Denka Kogyo Co., Ltd.) Average epoxy equivalent 2850), Ep1009 (manufactured by Japan Epoxy Resin Co., Ltd., average epoxy equivalent 3300), Ep4110P (manufactured by Japan Epoxy Resin Co., Ltd., average epoxy equivalent 3800), YD-020N (manufactured by Toto Kasei Co., Ltd., average) Epoxy equivalent 3900), Ep1010 Japan Epoxy Resin, Average Epoxy Equivalent 4000), Ep4010P (Japan Epoxy Resin Co., Ltd., Average Epoxy Equivalent 4400), DER-669 (Dow Chemical Japan Co., Ltd., Average Epoxy Equivalent 4500), YD-020H (Toto Kasei) Co., Ltd., average epoxy equivalent 5250), Ep1256 (manufactured by Japan Epoxy Resin Co., Ltd., average epoxy equivalent 7700), Ep4250 (manufactured by Japan Epoxy Resin Co., Ltd., average epoxy equivalent 8500), Ep4275 (Japan Epoxy Resin Co., Ltd.) Product, average epoxy equivalent 8500), Ep5203 (manufactured by Japan Epoxy Resin Co., Ltd., average epoxy equivalent 9000), Ep4210 (manufactured by Japan Epoxy Resin Co., Ltd., average epoxy equivalent 10,000), and the like.

  Component [B] is preferably 5 to 55% by weight, more preferably 10 to 50% by weight, based on 100% by weight of the total epoxy resin. When the blending amount is less than 5% by weight, the effect of improving the thermal stability is lowered and the tack retention of the prepreg may be lowered. On the other hand, when the blending amount exceeds 55% by weight, the impregnation property of the resin to the reinforcing fiber becomes insufficient in the prepreg manufacturing process, and the physical properties of the fiber reinforced composite material may be lowered.

As a curing agent for the component [C] of the present invention, it is essential to contain dicyandiamide from the viewpoint of thermal stability .

  When producing a prepreg, even if a particle with a large particle size is impregnated with pressure, it does not enter the reinforcing fiber bundle. For this reason, when the average particle diameter of dicyandiamide is increased, the amount of the curing agent in the reinforcing fiber bundle is decreased, and the curing reaction is partially incomplete, which may cause deterioration of the mechanical properties of the composite material. For these reasons, the average particle diameter of dicyandiamide is preferably 10 μm or less, and more preferably 5 μm or less. Here, the average particle diameter means volume average.

  It is preferable to use 2 to 10 parts by weight of dicyandiamide with respect to 100 parts by weight of the epoxy resin. If it is less than 2 parts by weight, the curing reaction may be incomplete, and if it exceeds 10 parts by weight, it may cause a decrease in physical properties.

  The matrix resin used in the present invention preferably contains a urea compound as a curing aid. When dicyandiamide is used alone as a curing agent, heating at 180 ° C. for about 2 hours is necessary to obtain a sufficient curing reaction rate. Therefore, in addition to dicyandiamide, a curing agent such as aromatic amine and aliphatic amine, and a curing accelerator can be used in combination.

  Although it does not specifically limit as a hardening accelerator, An imidazole compound, a urea compound, tertiary amine, etc. can be mentioned. In order to enhance the storage stability of the resin composition, a microcapsule type curing accelerator whose surface is covered with a resin coating may be used. Among these curing accelerators, a urea compound is particularly preferably used because a sufficient accelerating effect can be obtained without substantially impairing the storage stability of the resin composition.

  It is preferable to use 1 to 10 parts by weight of the urea compound with respect to 100 parts by weight of the epoxy resin. If the amount is less than 1 part by weight, the accelerating effect is weakened. Therefore, if the resin composition is heated at 135 ° C. for about 2 hours, the resin composition may not be sufficiently cured. The storage stability of the resin composition at high temperatures may be insufficient.

  A thermoplastic resin, a thermoplastic elastomer, an elastomer, inorganic particles, etc. can be added to the epoxy resin composition in the present invention as necessary.

  The thermoplastic resin used in the present invention is preferably one that is soluble in an epoxy resin. Moreover, even if it is insoluble in the epoxy resin, it is preferably pulverized and finely divided, and can be blended.

  Specifically, polyamide, polyamideimide, polyaramide, polyarylene oxide, polyarylate, polyimide, polyethylene terephthalate, polyetherimide, polyether terephthalate, polyetherimide, polyetheretherketone, polyethersulfone, polycarbonate, polycarbonate, poly Vinyl acetate, polystyrene, polysulfone, polyvinyl acetal, polyvinyl formal, polyphenylene oxide, polyphenylene sulfide, polypropylene, polybenzimidazole, polymethyl methacrylate and the like are used.

  Of these, polyamide is particularly effective in improving toughness and impact resistance without substantially impairing the elastic modulus of the cured product. In particular, polyterimide and polyethersulfone are effective in improving the adhesion to carbon fiber without impairing the heat resistance of the cured product. Furthermore, polyvinyl acetal and polyvinyl formal are preferable because they are easily soluble with an epoxy resin by heating, improve adhesiveness with carbon fibers without impairing the heat resistance of the cured product, and can adjust the viscosity. .

It is preferable that 0.1-10 weight part of this polyvinyl acetal or polyvinyl formal is contained with respect to 100 weight part of all epoxy resins, 0.1-8 weight part, Furthermore, 0.1-5 weight part Preferably there is. If it exceeds 10 parts by weight, the impregnation property of the resin to the reinforcing fiber becomes insufficient in the prepreg manufacturing process, and the physical properties of the fiber-reinforced composite material may be lowered.

  In the epoxy resin composition of the present invention, G ′ at 30 ° C. at a measurement frequency of 0.5 Hz is preferably 3000 to 1000000 Pa. When G 'is less than 3000 Pa, the change in tack with time is large, and a problem of furnace dropping during molding may occur. When it exceeds 1,000,000, the drape property tends to be lowered.

  The reinforcing fiber used in the present invention is not particularly limited, and carbon fiber, glass fiber, aramid fiber, boron fiber, alumina fiber, silicon carbide fiber and the like can be used. Two or more of these fibers can be mixed, but it is preferable to use carbon fibers in order to obtain a lighter and more durable molded product. Among them, it is preferable to use a carbon fiber having a tensile modulus of 200 to 500 GPa, preferably 300 to 500 GPa, in order to obtain a material excellent in lightweight performance and mechanical properties.

  In the present invention, for example, prepreg reinforcing fibers may be arranged in one direction, such as woven fabric (cross), tow, mat, knit, and the like. Among them, it is preferable to adopt one that is aligned in one direction because the strength characteristics can be easily designed by the laminated structure.

  The reinforced fiber weight content of the prepreg of the present invention and the fiber-reinforced composite material is 60 to 90% by weight, more preferably 70 to 85% by weight. Thus, when making the prepreg of the area | region with a high fiber content rate, when the epoxy resin composition of this invention is used, the improvement effect of tack property and drape property will appear more clearly, and it will become excellent. In addition, by using the particularly preferable resin composition, it is possible to control the change in handling properties with time. Furthermore, the quality and performance of the fiber-reinforced composite material obtained can be made excellent.

Preferably the fiber weight per unit area of the prepreg of the present invention is 40~250g / m ^2, preferably further is 50 to 200 g / m ^2. When the fiber weight per unit area is less than 40 g / m ² , the shape retention of the prepreg is lowered and the handling becomes somewhat difficult. On the other hand, if the fiber weight per unit area exceeds 250 g / m ² , the fiber alignment inside the prepreg is likely to be disturbed, making it difficult to obtain a high-performance fiber-reinforced composite material.

  In this way, even with a prepreg with a small fiber weight per unit weight, excellent properties that cannot be obtained with conventional resins in terms of drapeability, handleability such as tack aging control, and quality and performance after curing Can be obtained.

  The fiber basis weight and fiber content mentioned here can be determined by eluting the resin from the prepreg with an organic solvent and measuring the fiber weight.

  For example, the fiber-reinforced composite material of the present invention is molded in the following manner. After laminating the pattern obtained by cutting the prepreg, the fiber reinforced composite material is obtained by heat curing the resin while applying pressure to the laminate. Examples of methods for applying heat and pressure include a press molding method, an autoclave molding method, a vacuum pressure molding method, a sheet winding method, and an internal pressure molding method. Especially for sports equipment, the sheet winding method or the internal pressure molding method is preferable. Adopted.

The sheet winding method is a method of forming a cylindrical object by winding a prepreg around a mandrel, and is suitable for producing a rod-shaped body such as a golf shaft or a fishing rod. Specifically, they wound prepreg on a mandrel, fixed or so prepreg does not peel from the mandrel, or to impart molding pressure to the prepreg, tape-like thermoplastic resin film on the outer side of the prepreg (lapping tape) Is wound and the resin is heated and cured in an oven, and then the core metal is removed to obtain a cylindrical molded product.

  In the internal pressure molding method, a preform in which a prepreg is wound around an internal pressure applying body made of a thermoplastic resin is set in a mold, high pressure air is introduced into the internal pressure applying body, and the mold is heated at the same time. This is a method for forming a fiber-reinforced composite material. This internal pressure molding method is suitably used when molding a complicated shape such as a specially shaped golf shaft or bat, particularly a racket such as tennis or badminton.

  The fiber reinforced composite material of the present invention preferably has a glass transition temperature of 100 to 140 ° C, more preferably 110 to 130 ° C. If it is less than 100, the heat resistance is insufficient in sports applications. When the temperature exceeds 140 ° C., the residual thermal stress is large, and the mechanical properties of the fiber-reinforced composite material after heat curing are lowered.

Hereinafter, the present invention will be described more specifically with reference to examples. In addition, the evaluation method in an Example is as showing below. Tables 1, 2, and 3 collectively show the resin composition, resin composition characteristics, prepreg characteristics, and fiber reinforced composite material characteristics of each example.
A. Thermal stability (thickening ratio) and resin dynamic viscoelasticity The raw materials listed in Table 1 were kneaded using a kneader to prepare a resin composition. The thermal stability of the resin composition was evaluated as a thickening factor in the examples. For measuring the viscosity, a viscoelasticity measuring apparatus ARES manufactured by Rheometrics was used. The measurement uses a parallel plate with a radius of 20 mm, the distance between the plates is 1.0 ± 0.1 mm, the measurement start temperature is 25 ° C., the heating rate is 1.9 ° C./min, and the measurement frequency is 0.5 Hz, and the temperature is 80 ° C. And then isothermal measurement was performed for 2 hours. From the complex viscosity η * (1) at 80 ° C. 30 minutes after the start of measurement and the complex viscosity η * (2) at 80 ° C. after 150 minutes, the value obtained by the following equation was used as the viscosity increase ratio. The storage elastic modulus at 30 ° C. was measured from the value at 30 ° C. after about 2 minutes and 30 seconds.
Thickening factor = η * (2) / η * (1)
B. Preparation of prepreg a. Production of Bias Material The raw materials listed in Table 1 were kneaded using a kneader to prepare a resin composition. The resin composition was applied to a release paper using a reverse roll coater to prepare a resin film. Next, resin films are stacked on both sides of carbon fiber “Treca (registered trademark) M40SC-12K (manufactured by Toray Industries, Inc.)” having a tensile elastic modulus of 392 GPa arranged in one direction, and heated and pressurized (130 ° C., 0 4 MPa), the resin was impregnated to prepare a unidirectional prepreg having a fiber weight per unit area of 100 g / m ² and a fiber weight content of 76%.
b. Production of Straight Material The raw materials listed in Table 1 were kneaded using a kneader to prepare a resin composition. The resin composition was applied to a release paper using a reverse roll coater to prepare a resin film. Next, a resin film is laminated on both sides of carbon fiber “Treca (registered trademark) T800H-12K (manufactured by Toray Industries, Inc.)” having a tensile elastic modulus of 294 GPa arranged in one direction, and heated and pressurized (130 ° C., 0.4 MPa), the resin was impregnated to prepare a unidirectional prepreg having a basis weight of 116 g / m ² and a fiber weight content of 76%.
C. Tackability of prepreg After prepregs were pressure-bonded, they were peeled off, and the peel strength T (MPa) was determined by dividing the maximum load by the sample area. Using “Instron” (registered trademark) 4201 universal material testing machine (manufactured by Instron Japan Co., Ltd.) as a measuring device, the measurement was performed under the following conditions.
・ Environment: 23 ± 2 ℃, 50 ± 5% RH
・ Sample: 50x50mm
・ Loading speed: 1 mm / min ・ Adhesive load: 0.11 MPa
・ Loading time: 5 ± 2 seconds ・ Peeling speed: 10 mm / min The tackiness test was performed by first peeling off the release paper and release film from the surface of the prepreg and measuring “initial tack T0”, release paper and release film. Was peeled off and left in the measurement environment for 1 day, and “1 day after tack T1” was measured. In addition, the change rate of tack was calculated from the following formula.
Tack variability (%) = 100 × (T0−T1) / T0
D. Drapability of prepreg Drapability evaluation in this example was performed by measuring the flexural modulus of prepreg. The measuring method of the bending elastic modulus was performed according to JIS K7074 “Bending test method of fiber reinforced plastic”. An “Instron” 4201 universal material testing machine (manufactured by Instron Japan Co., Ltd.) was used as a measuring apparatus, and measurement was performed under the following conditions.
・ Environment: 23 ± 2 ℃, 50 ± 5% RH
・ Sample: 85mm (fiber direction) x 15mm
・ Loading speed: 5 mm / min ・ Distance between fulcrums: 40 mm
・ Indenter diameter: 4mmφ
The obtained reciprocal number D (GPa ⁻¹ ) of the 0 ° bending elastic modulus was used as an index of drapeability. In the drapeability test, the drapeability immediately after the release paper and the release film were peeled off from the prepreg surface was measured.
E. Impregnation property The impregnation property of the finished prepreg was evaluated by visual and tactile sensation in four stages. In the table, “Excellent” is indicated by “Good”, “Good” is indicated by “Good”, “Slightly unimpregnated part” is indicated by “△”, and Impregnation failure is indicated by “X”.
F. The operation of making the following cylindrical fiber reinforced composite material (a) ~ (e), has a laminated structure of _{[± 45 ° 3/0 °} 3] with respect to the cylindrical axis, inner diameter 10mm cylindrical fibers A reinforced composite material was prepared. A stainless steel round bar having a diameter of 10 mm (both 1000 mm in length) was used for the mandrel.
(A) Two unidirectional prepregs were cut into a rectangle of 800 mm in length and 103 mm in width so that the fiber direction was 45 degrees with respect to the axial direction of the mandrel. The two sheets were bonded so that the fiber directions intersected with each other and shifted in the lateral direction by 16 mm (corresponding to the half circumference of the mandrel).
(B) It wound around the mandrel which carried out the mold release process of the bonded prepreg (bias material) so that the longitudinal direction of a prepreg and the axial direction of a mandrel may correspond.
(C) On top of that, a prepreg (straight material) cut into a rectangle of 800 mm in length and 112 mm in width so that the fiber direction is in the longitudinal direction so that the longitudinal direction of the prepreg and the axial direction of the mandrel coincide with each other. I wrapped it.
(D) Wrapping tape (heat-resistant film tape) was wound, and heat-molded in a curing furnace at 130 ° C. for 2 hours.
(E) After molding, the mandrel was extracted and the wrapping tape was removed to obtain a cylindrical fiber reinforced composite material.
G. Measurement of torsional strength of cylindrical fiber reinforced composite material A test piece of 400 mm length was cut out from a cylindrical fiber reinforced composite material having an inner diameter of 10 mm, and “Golf Club Shaft Certification Criteria and Standard Confirmation Method” (Product Safety Association, Trade) The torsion test was conducted according to the method described in the Minister of Industry 5th Production No. 2087 (1993). The test piece gauge length was 300 mm, and 50 mm at both ends of the test piece was held with a fixing jig. The torsional strength was obtained by the following formula.

Torsional strength (N · m · deg) = Fracture torque (N · m) × Twist angle at break (deg)
H. Glass transition temperature (Tg)
F. Using the fiber reinforced composite material prepared in step 1, the glass transition temperature was measured by a differential scanning calorimeter (DSC) according to JIS K7121. A sealed sample container having a capacity of 50 μl was packed with 15 to 20 mg of sample, heated to 30 to 200 ° C. at a heating rate of 40 ° C./min, and measured. In this case, Pyris1DSC manufactured by PerkinElmer was used as a measuring device.

  Specifically, in the portion showing the step change of the obtained DSC curve, the straight line equidistant from the extended straight line of each baseline in the vertical axis direction and the curve of the step change portion of the glass transition intersect. The temperature at the point was taken as the glass transition temperature.

Example 1
Each raw material was mixed by the compounding ratio shown in Table 1, and the epoxy resin composition was produced. The resulting resin composition had a thickening ratio of 4.7 and a stable resin composition was obtained. Using such an epoxy resin composition, a prepreg and a cylindrical fiber reinforced composite material were produced by the above-described method. The obtained prepreg was excellent in impregnation property and handleability as shown in Table 1. Moreover, the torsional strength of the cylindrical fiber reinforced composite material was as high as 2400 N · m · deg.

(Examples 2 to 7)
As shown in Table 1, an epoxy resin composition, a prepreg, and a cylindrical fiber reinforced composite material were produced in the same manner as in Example 1 except that the blending ratio of the constituent element [A] to the constituent element [B] was changed. The resulting resin composition had a thickening ratio of 1.7 to 4.3, which was a more stable resin composition than Example 1. In Examples 3, 4, and 5, particularly stable resin compositions were obtained. Using such an epoxy resin composition, a prepreg and a cylindrical fiber reinforced composite material were produced by the method described above. As shown in Table 1, the obtained prepreg was excellent in impregnation property and further excellent in tack after standing for 1 day. In addition, the torsional strength of the cylindrical reinforcing fiber composite material was as high as 2410 to 2610 N · m · deg.

(Comparative Example 1)
As shown in Table 2, an epoxy resin composition, a prepreg, and a cylindrical fiber reinforced composite material were produced in the same manner as in Example 1 except that the component [B] was not blended. The resulting epoxy resin composition had a thickening factor of 12.1 and was unstable. Further, the tack retention of the prepreg was low, and the torsional strength of the cylindrical reinforcing fiber composite material was 2100 N · m · deg, which was lower than in the examples.

(Comparative Example 2)
As shown in Table 2, an epoxy resin composition, a prepreg, and a cylindrical fiber reinforced composite material were produced in the same manner as in Example 1 except that the component [A] was not blended. The resulting epoxy resin composition had a thickening factor of 11.1 and was unstable. Further, the initial tack value of the prepreg was low, and the torsional strength of the cylindrical fiber reinforced composite material was 2250 N · m · deg, which was lower than that of the example.

(Example 8)
As shown in Table 2, an epoxy resin composition was prepared in the same manner as in Example 3 except that the constituent element [B] was changed from Ep1007 to Ep1005H to an epoxy resin having a slightly low epoxy equivalent. The resulting resin composition has a thickening ratio of 3.2, which is slightly inferior to that of Example 3. However, the resin composition is stable and has excellent prepreg handling properties and excellent torsional strength of the cylindrical fiber-reinforced composite material. Met.

(Examples 9 to 11)
As shown in Table 2, an epoxy resin composition, a prepreg, and a cylindrical fiber reinforced composite material were produced in the same manner as in Example 3 except that the component [B] was changed to an epoxy resin having a different epoxy equivalent. The viscosity increase ratio of the obtained epoxy resin composition was 1.5 to 1.7, which was more excellent. Moreover, the handleability of the prepreg and the torsional strength of the cylindrical fiber reinforced composite material were also excellent.

(Comparative Example 3)
As shown in Table 2, the epoxy resin composition, prepreg, and cylindrical fiber reinforced composite material were prepared in the same manner as in Example 3 except that the component [B] was changed to an epoxy resin having an average epoxy equivalent of 1000 or less. Produced. The resulting epoxy resin composition had a thickening factor of 10.3 and was unstable. Moreover, the tack retention of the prepreg was low, and the torsional strength of the cylindrical reinforcing fiber was 2260, which was lower than that of the example.

(Example 12)
As shown in Table 3, the epoxy resin composition, prepreg, and cylindrical fiber reinforced composite material were prepared in the same manner as in Example 4 except that 0.2 parts by weight of polyvinyl formal was blended with 100 parts by weight of the epoxy resin. Produced. The stability of the obtained epoxy resin composition, the handleability of the prepreg, and the torsional strength of the cylindrical fiber reinforced composite material were all excellent.

(Examples 13 to 17)
As shown in Table 3, an epoxy resin composition, a prepreg, and a cylindrical fiber reinforced composite material were produced in the same manner as in Example 12 except that the blending amount of polyvinyl formal was changed. The stability of the obtained epoxy resin composition, the handleability of the prepreg, and the torsional strength of the cylindrical fiber reinforced composite material are all excellent, and Examples 13 to 5 have the highest torsional strength among the examples. Indicated. On the other hand, in Examples 16 and 17 in which polyvinyl formal was 7 parts by weight and 13 parts by weight, the torsional strength tended to be slightly reduced.

(Example 18)
As shown in Table 3, an epoxy resin composition, a prepreg, and a fiber reinforced composite material were produced in the same manner as in Example 4 except that the constituent element [A] was changed to an epoxy resin having a different softening point. The stability of the obtained epoxy resin composition, the handleability of the prepreg, and the torsional strength of the cylindrical fiber reinforced composite material were all excellent.

Claims (12)

An epoxy resin composition comprising at least the following components [A], [B], and [C].
[A] Dicyclopentadiene type epoxy resin having an average epoxy equivalent of 200 to 300 [B] Curing agent containing epoxy resin [C] dicyandiamide having an average epoxy equivalent of 1000 or more and 10,000 or less The epoxy resin composition according to claim 1, wherein the component [A] is contained in an amount of 5 to 55% by weight in 100% by weight of the total epoxy resin. The epoxy resin composition according to claim 1 or 2, wherein the component [B] is contained in an amount of 5 to 55% by weight in 100% by weight of the total epoxy resin. The epoxy resin composition according to any one of claims 1 to 3 , wherein 0.1 to 10 parts by weight of polyvinyl acetal or polyvinyl formal is contained with respect to 100 parts by weight of all epoxy resins. The epoxy resin composition according to any one of claims 1 to 4 , comprising a urea compound as a curing aid. The epoxy resin composition according to any one of claims 1 to 5 storage modulus G measuring at 30 ° C. in the measurement frequency 0.5 Hz 'is 3000～100000Pa. A prepreg comprising the reinforcing fiber and the epoxy resin composition according to any one of claims 1 to 6 . The prepreg according to claim 7, wherein the reinforcing fibers include at least carbon fibers. The prepreg according to claim 7 or 8, wherein the reinforcing fiber weight content is 60 to 90%. A fiber-reinforced composite material obtained by curing the prepreg according to claim 7 or 8 . A fiber-reinforced composite material comprising a cured product of the epoxy resin composition according to any one of claims 1 to 6 and reinforcing fibers. The fiber-reinforced composite material according to claim 10 or 11 , having a glass transition temperature of 100 to 140 ° C.