JP2015108078A - Epoxy resin composition, prepreg, and fiber-reinforced composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber-reinforced composite material which has a high fracture toughness value (so-called G) in a mode I (interlayer peeling-off deformation), is optimal as a prepreg for a structural material for an aircraft, and is excellent in compression strength after impact and interlaminar shear strength.SOLUTION: An epoxy resin composition for a prepreg contains the following components (A), (B) and (C). A prepreg and a fiber-reinforced composite material use the same. The component (A): an epoxy resin represented by the following general formula (Rto Rare each independently H, halogen atom or C1-C8 alkyl group); the component (B): 4,4'-diaminodiphenyl sulfone; and the component (C): nylon 12 fine particles.

Description

  The present invention relates to a resin composition for prepreg capable of forming a fiber reinforced composite material having excellent peel strength between layers, a prepreg, and a fiber reinforced composite material.

  Fiber reinforced plastic is an anisotropic material composed of reinforced fibers and a matrix resin. For its production, a sheet-like precursor called prepreg in which reinforced fibers are impregnated with uncured resin is laminated and molded. Thereafter, a method of obtaining the target product by curing is widely used. In the following description, unless otherwise specified, the term “fiber reinforced composite material” is used to mean a fiber reinforced plastic obtained by laminating, molding and curing a prepreg.

  Since a composite material using a thermosetting resin as a matrix resin has a laminated structure, the peel strength between layers and the impact resistance characteristics are insufficient. Various methods have been proposed for the purpose of improvement, and in particular, many methods have been proposed in which a material different from the matrix resin is disposed between the layers to absorb the fracture energy.

  Patent Document 1 shows that the compressive strength after impact (CAI) of a fiber-reinforced plastic is improved by sticking a resin composition containing fine particles of a thermoplastic resin to the prepreg surface.

  In Patent Document 2, it is shown that a composite material having improved impact resistance can be obtained while maintaining tackiness by arranging long fibers made of a thermoplastic resin randomly oriented on the surface of a prepreg.

Patent Documents 1 and 2 disclose that the peeling area between layers is reduced when an impact is applied, and the CAI is improved. In general, it is known that the peeling area at the time of impact application in CAI is reduced by improving the interlaminar fracture toughness value (so-called G _IIC ) of mode II (interlaminar shear deformation) described in JIS-K7086 and the like. In Patent Documents 1 and 2, it is considered that G _IIC is improved.

On the other hand, when the peel strength between layers becomes a problem during the operation of the composite material, the low fracture toughness value (so-called G _IC ) not only in G _IIC but also in mode I (interlayer peeling deformation) becomes a problem. There are many cases, and the improvement is demanded. While it is possible to improve the G _IC by using a technique of Patent Document 1 and 2, rather than a sufficient value, a further improvement in G _IC is at present what is needed.

JP-A 63-170428 PCT publication pamphlet WO94 / 16003

  The subject of this invention is providing the shaping | molding method of the epoxy resin composition which can provide the fiber reinforced composite material which shows a high fracture toughness value with respect to the peeling deformation | transformation between layers, a prepreg, and a fiber reinforced composite material.

As a result of intensive studies to solve the above problems, the present inventors have found that the problems can be solved by using an epoxy resin composition having the following configuration. That is, the present invention is as follows.
[1] An epoxy resin composition for prepreg comprising the following components (A), (B) and (C).

Component (A): epoxy resin represented by the following general formula

(In said general formula, R < ₁ > -R < ₅ > represents a hydrogen atom, a halogen atom, or a C1-C8 alkyl group each independently.)
Component (B): 4,4′-diaminodiphenylsulfone Component (C): Nylon 12 fine particles [2] Prepreg [3] obtained by impregnating the reinforcing fiber base material with the epoxy resin composition described in [1] above A method for molding a fiber-reinforced composite material, wherein the prepreg according to [2] is used and heated and molded at a temperature rising rate of 1.8 ° C./min.

  ADVANTAGE OF THE INVENTION By this invention, the molding method of the epoxy resin composition which can provide the fiber reinforced composite material which shows a high fracture toughness value with respect to peeling peeling between layers, a prepreg, and a fiber reinforced composite material can be provided.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below, but it should be understood that the present invention is not limited to these embodiments, and various modifications can be made within the scope of the technical idea of the present invention. .

[Component (A)]
The component (A) used in the present invention is an epoxy resin represented by the following general formula. By using the epoxy resin having such a structure together with the component (B) and the component (C), a high G _IC can be expressed as a fiber-reinforced composite material.

(In said general formula, R < ₁ > -R < ₅ > represents a hydrogen atom, a halogen atom, or a C1-C8 alkyl group each independently.)
The epoxy resin represented by the above general formula can be obtained, for example, by the reaction of aniline or a substituted derivative thereof and epichlorohydrin. Specifically, N, N-diglycidyl o-toluidine, N, N-diglycidyl aniline etc. are mentioned.

It is preferable that the compounding quantity of a component (A) is 10-40 mass parts with respect to 100 mass parts of all the epoxy resin components contained in the epoxy resin composition of this invention. If the amount of component (A) is 10 parts by mass or more, the combination with the component (B) and component (C), preferably can be expected G _IC increased in an object of the present invention. More preferably, it is 20 parts by mass or more. On the other hand, it is preferable to adjust the blending amount of the component (A) to 40 parts by mass or less because the heat resistance of the cured product is hardly lowered. More preferably, it is 30 parts by mass or less.

  In addition to the epoxy resin of component (A), any epoxy resin can be used in combination, but in order to increase the heat resistance of the epoxy resin composition, an epoxy resin having at least three epoxy groups in the molecule is added. It is preferable.

  Specific examples of the epoxy resin having three or more epoxy groups in the molecule include, for example, a novolak type epoxy resin (an epoxy resin obtained by a reaction between novolak and epichlorohydrin), tetrakis (glycidyloxyphenyl) ethane, Examples thereof include a glycidyl ether type epoxy resin such as tris (glycidyloxy) methane, a glycidylamine type epoxy resin such as tetraglycidylxylylenediamine, and their halogen and alkyl substituents.

  Among these, glycidylamine type epoxy resins are preferably used because they give excellent heat resistance and elastic modulus. In particular, a trifunctional glycidylamine type epoxy resin is preferable.

  Examples of the trifunctional glycidylamine type epoxy resin include jER630 manufactured by Mitsubishi Chemical Corporation, ELM-100 manufactured by Sumitomo Chemical Co., Ltd., MY0500, MY0510, MY0600 manufactured by Huntsman, and the like. It is not a thing.

  It is preferable that the compounding quantity of the epoxy resin which has a 3 or more epoxy group in a molecule | numerator is 40-80 mass parts with respect to 100 mass parts of all the epoxy resin components contained in the epoxy resin composition of this invention. If the compounding quantity of the epoxy resin which has 3 or more epoxy groups in a molecule | numerator is 40 mass parts or more, the heat resistance and elastic modulus of an epoxy resin composition can be improved. More preferably, it is 50 parts by mass or more. On the other hand, the toughness of hardened | cured material can be improved by making the compounding quantity of the epoxy resin which has 3 or more epoxy groups in a molecule | numerator into 80 mass parts or less. More preferably, it is 70 parts by mass or less.

[Component (B)]
Component (B) used in the present invention is 4,4′-diaminodiphenylsulfone.

By using 4,4′-diaminodiphenyl sulfone as a curing agent and using this together with component (A) and component (C), high G _IC can be expressed as a fiber-reinforced composite material.

  In order to increase the curing activity, an appropriate curing aid can be combined with the component (B). Preferred examples of the curing aid include 3-phenyl-1,1-dimethylurea, 3- (3,4-dichlorophenyl) -1,1-dimethylurea (DCMU), 3- (3-chloro-4-methyl Phenyl) -1,1-dimethylurea, urea derivatives such as 2,4-bis (3,3-dimethylureido) toluene, tertiary amines, imidazole compounds, monoethylamine trifluoride, amine trichloride complexes, etc. It is done.

[Component (C)]
Component (C) used in the present invention is nylon 12 fine particles. Nylon 12 particles when used in combination with components (A) and (B), it is possible to express high G _IC as a fiber-reinforced composite material. Here, “fine particles” mean particles having an average particle diameter of 2 to 90 μm.

If the average particle size of nylon 12 is 2 μm or more, the particles (nylon 12) can be localized between the layers of the reinforcing fibers and can be localized between the layers of the prepreg laminate, and the effect of the presence of the particles can be sufficiently exhibited. _IC can be further improved. On the other hand, if the average particle diameter is 90 μm or less, the arrangement of the reinforcing fibers is disturbed, or the layers of the fiber reinforced composite material obtained by lamination are thickened more than necessary, and thus adverse effects such as lowering the physical properties. Can be reduced. The average particle size of nylon 12 is particularly preferably 5 to 40 μm, and most preferably 5 to 25 μm.

  As the average particle diameter, a median diameter that can be measured by a laser diffraction particle size distribution analyzer or the like is employed.

  Examples of commercially available nylon 12 fine particles include VESTOSINT1111, VESTOSINT2070, VESTOSINT2157, VESTOSINT2158, and VESTOSTINT2159 (manufactured by Daicel-Evonik Co., Ltd.). These fine particles are generally commercially available and are excellent in availability and cost, but are not limited to the fine particles listed here.

  The outer shape, surface or internal form of the nylon 12 fine particles may be spherical or non-spherical particles.

  Spherical particles are preferred in that they do not reduce the flow characteristics of the base resin described above, but the purpose of using nylon 12 fine particles having a specific particle size is to localize the fine particles between the layers of the laminate. Since there is to suppress the progress of delamination under impact, the external shape, surface or internal form of the nylon 12 fine particles is not particularly limited.

[Optional ingredients]
In the epoxy resin composition of the present invention, one or more resins selected from the group consisting of thermoplastic resins, thermoplastic elastomers, and elastomers can be added as additives. This additive has the role of improving the toughness of the matrix resin and changing the viscoelasticity to optimize the viscosity, storage elastic modulus and thixotropic properties. The thermoplastic resin, thermoplastic elastomer or elastomer used as the additive may be used alone or in combination of two or more.

  The thermoplastic resin includes a group consisting of a carbon-carbon bond, amide bond, imide bond, ester bond, ether bond, carbonate bond, urethane bond, urea bond, thioether bond, sulfone bond, imidazole bond and carbonyl bond in the main chain. A thermoplastic resin having a bond selected from is preferably used.

  Among them, for example, a group of thermoplastic resins belonging to engineering plastics such as polyacrylate, nylon, polyaramid, polyester, polycarbonate, polyphenylene sulfide, polybenzimidazole, polyimide, polyetherimide, polysulfone and polyethersulfone are more preferably used.

  From the viewpoint of excellent heat resistance, polyimide, polyetherimide, polysulfone, polyethersulfone and the like are particularly preferably used. Among these, polyethersulfone is more preferable because it can increase toughness while maintaining the heat resistance and elastic modulus of the cured product.

  Moreover, it is preferable that these thermoplastic resins have a functional group reactive with the thermosetting resin from the viewpoint of improving toughness and maintaining the environmental resistance of the cured resin. Particularly preferred functional groups include a carboxyl group, an amino group, and a hydroxyl group.

[Prepreg]
The prepreg of the present invention is a prepreg formed by impregnating a reinforcing fiber base material with an epoxy resin composition containing the components (A), (B) and (C).

In the prepreg, the component (C): nylon 12 fine particles are distributed in a higher concentration near the surface than in the prepreg. The surface on which the nylon 12 fine particles are distributed at a high concentration may be one surface or both surfaces of the prepreg. Since the nylon 12 fine particles are distributed at a high concentration in the vicinity of the surface, the nylon 12 fine particles are localized between the layers when a plurality of prepregs are laminated. As a result, since nylon 12 particles absorb fracture energy, improves G _IC of the fiber-reinforced composite material.

The addition amount of the nylon 12 fine particles in the vicinity of the surface of the prepreg is preferably 1 to 20 g / m ^{2 and} more preferably 7.5 to 15 g / m ² per unit area of the prepreg.

  In the present invention, “near the surface” refers to a region within a range of 0 to 30% from the surface with respect to a thickness of 100% of the prepreg. In the present invention, it is assumed that 90 mass% or more of nylon 12 fine particles are localized in this region.

  The degree of localization of the nylon 12 fine particles in the prepreg can be confirmed as follows.

  First, the prepreg is closely adhered between two smooth support plates, and is cured by gradually raising the temperature over a long period of time. What is important at this time is to make the gel as low as possible. If the temperature is raised before gelation, the resin in the prepreg flows and the nylon 12 fine particles move, making it difficult to accurately evaluate the particle distribution in the original prepreg.

  After gelation, the prepreg is cured by gradually applying temperature over time. Using the cured prepreg, the cross section is magnified 200 times or more with a microscope and a photograph of 200 mm × 200 mm or more is taken.

  First, an average prepreg thickness is obtained using the obtained cross-sectional photograph. The average thickness of one prepreg layer is measured at at least five points arbitrarily selected on the photograph, and the average is taken.

  Next, a line is drawn in parallel to both directions of the prepreg at a position 30% of the thickness of the prepreg from the surface in contact with both support plates. The cross-sectional area of nylon 12 fine particles existing between the surface in contact with the support plate and 30% parallel lines is quantified on both sides of the prepreg, and the cross-sectional area of nylon 12 fine particles existing over the entire width of the prepreg is quantified. By taking the ratio, the amount of particles existing within 30% of the thickness of the prepreg from the prepreg surface is calculated.

  The quantification of the particle cross-sectional area may be performed by an image analyzer, or may be performed by cutting out all the particle portions existing in a predetermined region from the cross-sectional photograph and weighing the mass. In order to eliminate the influence of variation in the partial distribution of nylon 12 fine particles, this evaluation is performed over the entire width of the obtained photograph, and the same evaluation is performed for five or more arbitrarily selected photographs. It is necessary to take the average.

  When it is difficult to distinguish between the nylon 12 fine particles and the base resin, one of them may be selectively dyed and observed.

  As the microscope, an optical microscope or a scanning electron microscope may be used, and it may be properly used depending on the size of the nylon 12 fine particles and the staining method.

  There is no particular limitation on the reinforcing fiber base material impregnated with the epoxy resin composition of the present invention, and carbon fiber, graphite fiber, glass fiber, organic fiber, boron fiber, steel fiber, etc., such as tow, cloth, chopped fiber, mat, etc. Can be used in form.

  Among these reinforcing fibers, carbon fibers and graphite fibers are preferable in the present invention because they have good specific elastic modulus and a great effect on weight reduction. Also, any type of carbon fiber or graphite fiber can be used depending on the application.

[Fiber-reinforced composite materials]
A fiber-reinforced composite material can be obtained by heating and curing the prepreg of the present invention. In particular, a fiber reinforced composite material showing a high fracture toughness value with respect to compressive strength after impact and delamination between layers can be easily obtained by heating at a heating rate of 1.8 ° C./min and heating. .

  As a specific method for producing the fiber-reinforced composite material, a molding method such as autoclave molding, sheet wrap molding, and press molding can be used, but it is not limited to these molding methods.

  There is no restriction | limiting in particular in the use of the fiber reinforced composite material of this invention, It can use for general industrial uses, such as a structural material for aircrafts, a motor vehicle use, a ship use, a sports use, and another windmill and a roll.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited at all by these.

Each component used for the Example and the comparative example is shown below.
JER828: bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation jER630: p-aminophenol type epoxy resin, manufactured by Mitsubishi Chemical Corporation ELM-100: p-aminocresol type epoxy resin, manufactured by Sumitomo Chemical Co., Ltd., GAN : Diglycidylaminobenzene type epoxy resin, Nippon Kayaku Co., Ltd., CY-184: Hexahydrophthalic acid diglycidyl ester type epoxy resin, Huntsman Co., Ltd. E2020P: Polyethersulfone, BASF Corp. 12 fine particles, average particle size 10 μm, manufactured by Daicel-Evonik Co., Ltd., 4,4′-DDS: 4,4′-diaminodiphenylsulfone (manufactured by Wakayama Seika Kogyo Co., Ltd., product name: Seika Cure S) using a jet mill 98% particle size is 10μm or less Which was ground to a particle size. The particle size was measured with a laser diffraction particle size distribution meter (manufactured by Nikkiso Co., Ltd., product name: AEROTRAC SPR MODEL 7340).

[Example 1 and Comparative Examples 1 to 4]
Among the compositions shown in Table 1, the epoxy resin main component and E2020P were stirred and dissolved uniformly with a planetary mixer set at 180 ° C., and cooled to 60 ° C. Subsequently, nylon 12 fine particles and a curing agent were added, and the mixture was stirred and mixed with a planetary mixer set at 60 ° C. to obtain an epoxy resin composition.

The obtained epoxy resin composition was applied on a release paper with a basis weight of 48 g / m ² to obtain a resin film. Two resin films were produced. Two films are arranged so that the coating surfaces face each other, and carbon fiber (Mitsubishi Rayon Co., Ltd., “MR50R”) is placed between the two films, and pressed with a heated press roll to epoxy the carbon fiber. Was impregnated to prepare a unidirectional primary prepreg. This primary prepreg had a carbon fiber basis weight (FAW) of 190 g / m ² and a base resin content (RC) of 34% by mass.

Using the obtained primary prepreg, it was measured G _IC in the following manner. The results are shown in Table 1.

<Measurement of Mode I Fracture Toughness Value (G _IC )>
The measurement was performed according to JIS K7086. However, the laminated structure is 20 laminated in the direction of [0 °] and is 1.8 ° C./min. In the autoclave. After the temperature was raised to 180 ° C. at a rate of temperature rise of 180 ° C., it was heated at 180 ° C. for 2 hours and cured to produce a molded plate (fiber reinforced composite material). During this time, the inside of the autoclave was pressurized to 0.7 MPa, and the inside of the bag was kept in vacuum. A test piece was cut out from the obtained molded plate with a test piece size of 330.2 mm in length and 12.7 mm in width, and the test was performed at a crosshead speed of 25.4 mm / min.

As apparent from Table 1, the prepregs obtained by the present invention are better than the G _IC as a composite material in Comparative Example.

By using the prepreg of the present invention, a fiber-reinforced composite material excellent in compressive strength after impact and interlaminar shear strength can be provided. The fiber-reinforced composite material has a high fracture toughness value (so-called G _IC ) in mode I (interlaminar peeling deformation) and is optimal for structural materials for aircraft.

Claims (3)

An epoxy resin composition for prepreg comprising the following components (A), (B) and (C).
Component (A): epoxy resin represented by the following general formula

(In said general formula, R < ₁ > -R < ₅ > represents a hydrogen atom, a halogen atom, or a C1-C8 alkyl group each independently.)
Component (B): 4,4′-diaminodiphenyl sulfone Component (C): Nylon 12 fine particles   A prepreg formed by impregnating a reinforcing fiber substrate with the epoxy resin composition according to claim 1.   A method for molding a fiber reinforced composite material, wherein the prepreg according to claim 2 is used for heating and molding at a heating rate of 1.8 ° C / min.