JP2008231288A - Epoxy resin composition for fiber-reinforced composite material, prepreg and fiber-reinforced composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epoxy resin composition for a fiber-reinforced composite material for forming a fiber-reinforced composite material, which is light and excellent in strength characteristics and can be produced at a low cost with less man-power; and to provide a prepreg and a fiber-reinforced composite material. <P>SOLUTION: This epoxy resin composition for a fiber-reinforced composite material comprises an epoxy resin, a curing agent and fullerene, where the fullerenes contain those having 35-80 μm maximum particle diameters. A prepreg and a fiber-reinforced composite material each using the composition are also disclosed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an epoxy resin composition useful for a fiber reinforced composite material, a prepreg as an intermediate substrate for obtaining a fiber reinforced composite material, and a fiber reinforced composite material suitable for sports use, aerospace use, general industrial use, In particular, the present invention relates to a fiber-reinforced composite material that can be suitably used for tubular body materials such as golf shafts, fishing rods, and automobile propeller shafts.

  A one-pack type epoxy resin composition consisting of an epoxy resin, which is a compound having an epoxy group in the molecule, and its curing agent has excellent mechanical strength, chemical resistance, heat resistance, and good adhesion to reinforcing fibers. Because of its properties, it is used as a matrix resin for fiber reinforced composite materials in combination with reinforcing fibers such as carbon fibers.

  Fiber reinforced composite material consisting of reinforced fiber and matrix resin is lightweight and has excellent strength characteristics, so it can be used for sports applications such as golf shafts, fishing rods, rackets such as tennis and badminton, sticks such as hockey, and aerospace applications. Although widely used in general industrial applications such as automobiles / ships, bathtubs, helmets, etc., in order to meet the demand for further weight reduction, there is a need for a technique for improving the strength characteristics of such materials.

  Moreover, in order to obtain a fiber reinforced composite material having excellent mechanical properties, an epoxy resin having an aromatic skeleton is used among epoxy resins. However, since such an epoxy resin has poor weather resistance, it is exposed to natural light for a long time. In other applications, light-shielding coating must be applied to the outer surface, and the weight increases by the amount of coating, and the light weight, which is a great merit of fiber-reinforced composite materials, cannot be fully utilized. Among them, golf shafts, fishing rods, etc. are applications that are strongly required to be lightweight, but since they are used outdoors, light-shielding coating is indispensable, and fiber-reinforced composite materials with high weather resistance are strongly demanded. ing.

In response to the demand to improve the strength characteristics of fiber reinforced composite materials using epoxy resin compositions, for example, an epoxy resin composition containing carbon short fibers is used as a matrix resin to improve the mechanical properties of unidirectional composite materials. Techniques are known. (For example, see Patent Document 1)
Also known is a technique for improving the resin bending strength by using a resin composition obtained by blending finely dispersed fullerenes having an average particle diameter of 0.001 μm or more and 30 μm or less into a curable resin (for example, patents) However, this method does not suggest an improvement in the mechanical strength or weather resistance of the tubular body of the fiber-reinforced composite material, and its effect is insufficient.

  On the other hand, in order to give weather resistance to the matrix resin, it is generally performed to add a light stabilizer to the matrix resin. However, light stabilizers are expensive, leading to increased costs. There were also problems such as a decrease in mechanical properties.

  Therefore, as a means for solving the problem of weather resistance, for example, it has been proposed to arrange a weather resistant fiber reinforced resin layer having a certain thickness on the outer surface of a fiber reinforced composite material composed of reinforced fibers and a matrix resin. (For example, refer to Patent Document 3). However, this method has a problem that processability is deteriorated because a light-resistant fiber-reinforced resin layer needs to be separately disposed.

As described above, in these known techniques, an epoxy resin composition and a fiber-reinforced composite material capable of exhibiting sufficient effects regarding the mechanical strength and weather resistance of the tubular body have not yet been obtained. Further, as represented by Patent Document 2, a technique for improving the strength of a fiber-reinforced composite material by blending fullerenes with a resin is usually a method of using fullerenes that are likely to aggregate, using an expensive disperser. Since it is necessary to disperse the resin so that it becomes nano-order, there is a problem that it takes considerable cost and labor to adjust the resin. Further, in order to improve the physical properties, fullerenes need to be added in a considerable amount, but since they are expensive, there is a problem that the cost of the final product increases in proportion thereto.
JP 2003-201388 A JP 2004-182775 A JP 2002-103500 A

  In view of the background of the above-described prior art, the present invention efficiently uses fullerenes, has a lower cost than ever, and has excellent strength characteristics without taking time and weather resistance. It aims at providing the fiber reinforced composite material which can achieve weight reduction because it is excellent in property.

The present invention employs any of the following means in order to solve the above-mentioned problems.
(1) An epoxy resin composition for a fiber-reinforced composite material comprising an epoxy resin, a curing agent, and fullerenes, and the fullerenes having a maximum particle size of 35 to 80 μm object.
(2) The epoxy resin composition according to the above (1), wherein the fullerenes contain 10 to 50% by volume of those having a maximum particle size of 35 to 80 μm.
(3) The epoxy resin composition as described in (1) or (2) above, wherein the fullerene contains 0.1 to 10% by volume having a maximum particle size of 0.1 to 1 μm.
(4) A prepreg comprising the epoxy resin composition according to any one of (1) to (3) and a reinforcing fiber.
(5) The prepreg according to (4) above, wherein the reinforcing fiber is a carbon fiber.
(6) A method for producing a prepreg, wherein the reinforcing fiber sheet is impregnated with the epoxy resin composition according to any one of (1) to (3) from at least one side thereof.
(7) A fiber-reinforced composite material configured using the prepreg according to (4) or (5).

  According to the present invention, not only can a prepreg having good handleability and excellent moldability be provided, but also a fiber-reinforced composite material having excellent mechanical properties and weather resistance can be provided.

  Furthermore, according to the present invention, it is possible to provide a fiber-reinforced composite material that is lightweight and excellent in mechanical properties such as bending strength of a cylindrical fiber-reinforced composite material.

  The present invention has been intensively studied on the above-mentioned problems, and found that the fullerenes contained in the epoxy resin composition were controlled to have a specific particle size, and as a result, the weather resistance was improved and reached the present invention. did.

  The epoxy resin composition for reinforced fiber composite material of the present invention comprises an epoxy resin, a curing agent and fullerenes.

  An epoxy resin is a compound having an average of more than one epoxy group in the molecule. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, glycidylamine type epoxy resin, aminophenol type epoxy resin, isocyanate modified epoxy resin, fat Use cyclic epoxy resin, urethane modified epoxy resin, brominated bisphenol A type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, bisphenol S type epoxy resin, fluorene type epoxy resin, etc. Can do. These epoxy resins can be used singly or in combination of two or more, and can be used from liquid to solid.

  Curing agents include aromatic amines such as diaminodiphenylmethane and diaminodiphenylsulfone, aliphatic amines, imidazole derivatives, dicyandiamide, tetramethylguanidine, thiourea addition amines, carboxylic acids such as methylhexahydrophthalic anhydride, Acid hydrazide, carboxylic acid amide, polyphenol compound, novolac resin, polymercaptan, Lewis acid complex such as boron fluoride ethylamine complex, and the like can be used. Among these, dicyandiamide is preferably included from the viewpoint of thermal stability. In addition, an adduct having curing activity obtained by reacting these curing agents with an epoxy resin can be used in place of the curing agent. Furthermore, those obtained by encapsulating these curing agents are preferably used in order to increase the storage stability of the prepreg.

  Examples of fullerenes include C60, C70, C76, C86, C116, etc., and these can be used alone or in admixture of two or more. Examples of C60 alone include Nanom Purple (registered trademark) (C60 (containing 98%)) [manufactured by Frontier Carbon Co., Ltd.] and the like. As a mixture of C60 and C70, Nanommix (registered trademark) is used. ST-F (containing C60 (60%) and C70 (25%))) [manufactured by Frontier Carbon Co., Ltd.]. In addition, functionalized and hydrogenated fullerenes may be used. Examples of hydrogenated fullerenes and hydroxylated fullerenes include Nanomuspectra (registered trademark) [manufactured by Frontier Carbon Co., Ltd.]. It is done.

  When fullerenes having a maximum particle size in the range of 35 to 80 μm are contained in the epoxy resin composition, fullerenes having a large particle size are obtained when the epoxy resin composition is impregnated from one side into a sheet of reinforcing fibers. Can be localized on one side of the prepreg, and by placing such a prepreg on the outermost layer of the fiber reinforced composite material, the surface where the large particle size fullerenes are localized is used to strengthen the fiber. It becomes difficult to enter the composite material, and deterioration of the epoxy resin can be suppressed. Since fullerenes exist in a particle state without melting in the epoxy resin composition, fullerenes having a maximum particle size in this range are reinforced fibers when the reinforcing fiber sheet is impregnated with the epoxy resin composition. It is localized in the prepreg surface layer by the filter effect between single fibers. Fullerenes having a maximum particle size of less than 35 μm tend to enter the carbon fiber bundle and do not localize in the prepreg surface layer. In addition, fullerenes having a maximum particle size of more than 80 μm have a particle size that is too large to be uniformly dispersed in the prepreg surface layer.

  Moreover, when using the epoxy resin composition of this invention for a prepreg, it is preferable that the content rate of the reinforced fiber in this prepreg is 70 to 85 weight%. When the content of reinforcing fibers is less than 70% by weight, the filter effect is reduced, and fullerenes having a large maximum particle size cannot be efficiently localized on the surface layer, whereas when the content is greater than 85% by weight. In addition, the amount of the matrix resin is too small, and an unimpregnated portion may be generated, resulting in a decrease in physical properties or a deterioration in handleability. Fullerenes having a large maximum particle size localize and impart light resistance to the prepreg surface layer. In order to sufficiently exhibit such effects, the fullerenes are added in an amount of 0.02 to 100 parts by weight based on 100 parts by weight of the epoxy resin. It is preferable to blend 10 parts by weight. If the blending amount is less than 0.02 parts by weight, the light resistance may be lowered. On the other hand, if the blending amount is more than 10 parts by weight, the handleability such as the tack may be lowered.

  The fullerenes preferably contain 0.1 to 10% by volume of those having a maximum particle size in the range of 0.1 to 1 μm. By containing a specific amount of fullerenes having a small maximum particle size, when the epoxy resin composition of the present invention is used for a prepreg, the sheet of reinforcing fiber is pressed and impregnated with the epoxy resin composition. Such fullerenes enter between the single fibers of the reinforcing fiber, and improve the Charpy impact strength of the fiber-reinforced composite material obtained by using the prepreg.

  This is because fullerene particles with a large maximum particle diameter are incorporated in the outer layer part and fullerene particles with a small maximum particle diameter are incorporated into the fiber reinforced composite material. On the other hand, when the outer layer has a large maximum particle size, the progress of the fracture is stopped, or the direction of the fracture is bent by these particles, so the concentration force acting on the crack is weakened and the fracture occurs. It becomes difficult to be done. Furthermore, because the particles having a small maximum particle diameter in the inside induce a large number of microcracks at the tip of the macroscopic destruction and disperse and weaken the force acting on the cracks, the destruction of the internal structure is prevented.

  The epoxy resin composition of the present invention includes a step of dispersing fullerenes in advance in a dispersion medium such as a liquid epoxy resin, an epoxy resin in which the fullerenes obtained are dispersed, and an epoxy resin, a curing agent, and if necessary. In addition, it can be produced by blending other components such as a curing accelerator and a thermoplastic resin.

  As a method for the dispersion treatment, a dispersion apparatus and a dispersion medium are appropriately adjusted so that fullerenes having a maximum particle size of 35 to 80 μm remain. At this time, it is preferable that 0.003 to 20 parts by weight of [C] is dispersed with respect to 100 parts by weight of the dispersion medium, more preferably 0.01 to 10 parts by weight, and 0.02 to 3 parts by weight. Most preferably. If the amount is less than 0.003 parts by weight, the amount of fullerenes may be reduced when the epoxy resin composition is used, and the effect of improving the physical properties may be small. The handleability may deteriorate. If the amount is more than 20 parts by weight, the dispersion process may take a lot of time, or the tack may be lowered when a prepreg is formed.

  The dispersion medium is preferably an epoxy resin or a compound having a functional group capable of reacting with a curing agent, and particularly preferably an epoxy resin. When the epoxy resin composition is cured, if the dispersion medium reacts with the epoxy resin or the curing agent and is not taken into the system, the physical properties may be deteriorated.

  In the resin preparation step in the present invention, it is preferable to use a kneader, a planetary mixer, or a twin screw extruder.

  The prepreg of the present invention can be produced by a prepreg forming step for producing a prepreg by impregnating a reinforcing fiber with the epoxy resin composition for fiber reinforced composite material prepared by the above production method.

  As this prepreg process, there are a wet method in which a matrix resin is dissolved in a solvent such as methyl ethyl ketone and methanol to lower the viscosity and impregnation, and a hot melt method in which the viscosity is lowered by heating and impregnated.

  The wet method is a method of obtaining a prepreg by immersing a reinforcing fiber such as carbon fiber in a liquid made of an epoxy resin composition, then pulling it up and evaporating the solvent using an oven or the like.

  The hot melt method is a method in which an epoxy resin composition whose viscosity has been reduced by heating is directly impregnated into reinforcing fibers such as carbon fibers, or a film in which an epoxy resin composition is once coated on a release paper is first prepared. This is a method for producing a prepreg impregnated with a resin by overlapping the film from both sides or one side of carbon fiber or the like and heating and pressing. The hot melt method is preferable because there is no solvent remaining in the prepreg, and in the present invention, the hot melt method is preferably used as the prepreg step.

  In this invention, it shape | molds in a fiber reinforced composite material using the above prepregs. The fiber-reinforced composite material is molded, for example, 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. 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, a prepreg is wound around a mandrel and fixed so that the prepreg does not peel off from the mandrel, or a tape-like thermoplastic resin film (wrapping tape) is provided on the outside of the prepreg in order to apply molding pressure to the prepreg. 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 obtained in the present invention preferably has a glass transition temperature of 100 to 150 ° C, more preferably 100 to 140 ° C. If it is lower than 100 ° C., heat resistance may be insufficient in sports applications. When it exceeds 150 ° C., the residual thermal stress is large, and the mechanical properties of the fiber-reinforced composite material after heat curing may be lowered.

Hereinafter, the present invention will be described more specifically with reference to examples. The details of the materials used for resin preparation in this example are as follows.
[Epoxy resin]
“Epicoat (registered trademark)” 828 (Bisphenol A type epoxy resin, bifunctional) “Epicoat (registered trademark)” 1001 (Bisphenol A type epoxy resin, bifunctional) manufactured by Japharne Epoxy Resins Co., Ltd. “Epicron (registered trademark)” N-740 (phenol novolac type epoxy resin, multifunctional) manufactured by Dainippon Ink Co., Ltd. [curing agent]
DICY7 (Dicyan Diamide) DCMH99 (3- (3,4-dichlorophenyl) -1,1-dimethylurea) manufactured by Jaffa Phenyl Resin Co., Ltd. [Fullerenes] manufactured by Hodogaya Chemical Co., Ltd.
“Nanomu Mix” Frontier Carbon Co., Ltd. [Polyvinyl formal]
“Vinilec (registered trademark)” manufactured by K Chisso Corporation In addition, the evaluation methods in the examples are as follows.

A. Particle size of fullerenes present in fiber reinforced composite material Using a scanning electron microscope (SEM), the longitudinal section of the fiber reinforced composite material was observed under the following measurement conditions. Fullerenes in one prepreg layer The localization state of was confirmed. In this example, system S-4100 manufactured by Hitachi, Ltd. was used as the SEM.

Acceleration voltage: 3 kV
Deposition: Pt-Pd approx. 4μm
Ten arbitrary longitudinal sections of the fiber reinforced composite material were selected and photographed.

  From these images, the cross section of the particle at each cross section was measured, and the major axis was defined as the particle diameter in the present invention.

  Moreover, the volume% of fullerenes was calculated | required by dividing the image which image | photographed the longitudinal cross section into fullerenes and other parts by utilizing the difference in lightness and darkness.

B. Charpy impact value A test piece is prepared according to JIS-K-7077 using a unidirectional prepreg, and a Charpy impact test is performed using an instrumented Charpy impact tester. The test piece dimensions were 6 mm thickness, 10 mm width and 60 mm length, and the span distance was 40 mm.

C. Weather resistance test The fiber reinforced composite material produced by the method described above was subjected to an accelerated weather resistance test for 1000 hours in accordance with ISO4892-4 (2004).

D. In-plane shear strength In-plane shear strength was measured according to JIS K7079 (1991). The number of tests was n = 5, and the average value was the in-plane shear strength. As a tester, a tensile tester Instron 1185 was used. The test piece was made of a unidirectional fiber reinforced composite material prepared by laminating prepregs so that the direction of carbon fibers was ± 45 ° by the above method, and the size was as follows.
Thickness: 2.0 ± 1.0mm
Width: 25.0 ± 1.0mm
Length: 237.0 ± 10.0mm
Table 1 summarizes the resin composition, prepreg characteristics, and fiber reinforced composite material characteristics of each example.

(Example 1)
0.02 part by weight of Nanomumix was blended with 15 parts by weight of “Epicoat” 828 shown in Table 1 as a dispersion medium, and dispersed with a homomixer at room temperature. Then, the remaining epoxy resin raw material and vinylec K were blended and melted by heating so as to have the composition shown in Table 1, and then DICY7 and DCMU99 were blended at 60 ° C. to obtain an epoxy resin composition.

The obtained epoxy resin composition was applied to a release paper using a reverse roll coater to prepare a resin film. Next, a resin film is stacked on both sides of carbon fiber “Torayca” (registered trademark) T800HB-12K (manufactured by Toray Industries, Inc.) arranged in one direction, and heated and pressurized (130 ° C., 0.4 MPa). Thus, the epoxy resin composition was impregnated to obtain a unidirectional prepreg having a fiber weight per unit area of 125 g / m ² and a fiber weight content of 76%. A test piece was prepared using the obtained unidirectional prepreg, and the Charpy impact value was measured.

Further, the obtained unidirectional prepreg was laminated so that the directions of the carbon fibers were the same, and cured by heating and pressing at 130 ° C. and a pressure of 290 Pa for 2 hours using an autoclave to obtain a fiber-reinforced composite material. Obtained.
Using the obtained fiber reinforced composite material, the particle size, Charpy impact value, in-plane shear strength before the weather resistance test and in-plane shear strength after the weather resistance test were measured. When the fiber-reinforced composite material obtained has a particle size of 35 to 80 μm and is disposed in the outer layer, both the weather resistance and the Charpy impact value are improved.
(Example 2)
The experiment was conducted in the same manner as in Example 1 except that the amount of nano-mix was changed from 0.02 parts by weight to 0.05 parts by weight.
(Example 3)
The experiment was conducted in the same manner as in Example 1 except that the amount of nano-mix was changed from 0.02 parts by weight to 0.1 parts by weight.
Example 4
The experiment was conducted in the same manner as in Example 1 except that the amount of nanomux mixed was changed from 0.02 parts by weight to 1 part by weight.
(Example 5)
Except for homomixer dispersion under the condition that the maximum particle size of fullerene is 42% by volume of 35-80 μm and 12% by volume of 0.1-1 μm, the same as in Example 1. The experiment was conducted.
(Comparative Example 1)
The experiment was performed in the same manner as in Example 1 except that the nano-mix was not blended.

  The properties of the obtained fiber reinforced composite material were improved in both weather resistance and Charpy impact value in Examples 1 to 5 in which the particle size of 35 to 80 μm was arranged in the outer layer. However, in Comparative Example 1 in which 35 to 80 μm was not arranged on the surface layer, both Charpy strength and weather resistance tended to be lower than those in Examples.

Claims (7)

  An epoxy resin composition for a fiber-reinforced composite material comprising an epoxy resin, a curing agent and fullerenes, and the fullerenes having a maximum particle size of 35 to 80 μm.   The epoxy resin composition according to claim 1, wherein the fullerenes contain 10 to 50% by volume of those having a maximum particle size of 35 to 80 µm.   The epoxy resin composition according to claim 1 or 2, wherein the fullerenes contain 0.1 to 10% by volume of those having a maximum particle size of 0.1 to 1 µm.   A prepreg comprising the epoxy resin composition according to claim 1 and reinforcing fibers.   The prepreg according to claim 4, wherein the reinforcing fibers are carbon fibers. The manufacturing method of the prepreg characterized by impregnating a reinforcing fiber sheet with the epoxy resin composition of Claims 1-3 from the at least single side | surface.   The fiber reinforced composite material comprised using the prepreg of Claim 4 or 5.