JPH0370741A - Fiber-reinforced composite material - Google Patents

Abstract

PURPOSE:To provide the subject material having excellent mechanical strength and interlaminar shearing strength, not lowering its strength even at high temperature and humidity and especially suitable as the structural material for airplanes by comprising a specific epoxy resin, a curing agent and reinforcing fibers. CONSTITUTION:The objective material comprises (A) an epoxy resin of formula I (R is H or methyl), (B) a curing agent (preferably an aromatic amine such as 3,3'-diaminodiphenyl sulfone or dicyandiamide) and (C) reinforcing fibers (e.g. carbon fibers). The compound of formula I is prepared by reacting a phenolic compound of formula II with an epihalohydrin of formula III (X is halogen) in the presence of an alkaline compound.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a fiber-reinforced composite material using an epoxy resin composition as a matrix.

<Prior Art> Fiber-reinforced composite materials are materials consisting of reinforcing fibers and matrix resin.

The matrix resin plays an important role in expressing the mechanical performance of the structure of fiber reinforced composite materials, and the physical properties such as various mechanical performances, water resistance, heat resistance, and solvent resistance are determined by the matrix resin. In order to significantly reflect the physical properties of these materials, attempts have been made to improve these properties by improving matrix resins.

Fiber-reinforced composite materials using epoxy resin compositions consisting of various epoxy resins and curing agents as matrix resins have been proposed. For example, Japanese Patent Publication No. 55-25217 discloses an epoxy resin composition using tetraglycidyldiaminodiphenylmethane as an epoxy resin and diaminodiphenylsulfone as a curing agent.
No. 83340 discloses an epoxy resin composition using triglycidylaminocresol as an epoxy resin and diaminodiphenylsulfone as a curing agent.

<Problems to be Solved by the Invention> As the field of application of composite materials expands, there is a demand for materials with even higher mechanical performance than ever before.

Among these, primary structural materials for aircraft are increasingly required to have mechanical strength, heat resistance, and low moisture absorption under high temperature and high humidity conditions.

The object shown in the above publication is aimed at increasing the mechanical strength in the O0 direction and the interlaminar shear strength (hereinafter referred to as ILSS), but in view of the above actual circumstances, it is necessary to further improve these physical properties. .

Furthermore, mechanical strength under high temperature and high humidity conditions is not necessarily sufficient.

Means for Solving the Problems> The present invention comprises an epoxy resin having a structure represented by (I) (wherein R represents a hydrogen atom or a methyl group), a curing agent, and reinforcing fibers. The present invention provides a fiber-reinforced composite material characterized by the following.

The present invention will be explained in detail below.

The epoxy resin represented by (I) above used in the present invention is produced, for example, by the method described in Japanese Patent Publication No. 1648/1983. That is, a phenol compound represented by the following, and the following -hydrogen () (in the formula, R represents a hydrogen atom or a methyl group, and X represents a \rogen atom). ) It is produced by reacting epihalohydrin shown in the following in the presence of an alkaline compound.

The phenol compound represented by the above-mentioned compound (II) is a condensation reaction between dihydric phenols such as resorcinol, hydroquinone, catechol, etc. and bis(α-methyl-αhydroxyethyl)benzenes, or the above-mentioned dihydric phenols. For example, 1,3-bis[α-(2,4-dihydroxyphenyl)-α- methylethyl]benzene, l
.

4-bis[α-(2,4-dihydroxyphenyl)-α
-Methylethyl]benzene, l,3-bis[α-(3,
Examples include 4-dihydroxyphenyl)-α-methylethyl]benzene, 1,4-bis[α-(3,4-dihydroxyphenyl)-α-methylethyl]benzene, and especially l, 3- Bis[α-(2,4-dihydroxyphenyl)-α-methylethyl]benzene is preferred.

Examples of the epihalohydrin to be used include epichlorohydrin, β-methylepichlorohydrin, epibromhydrin, β-methylepibromhydrin, and mixtures thereof, and epichlorohydrin is particularly preferably used.

Further, as another manufacturing method, the method described in Japanese Patent Application Laid-Open No. 63-254121 may be employed.

In the present invention, as the epoxy resin, the above-mentioned
), other well-known epoxy resins may be used depending on the purpose, such as imparting toughness or improving workability.
They may be mixed and used in a weight percent or less.

Examples of the curing agent for the epoxy resin used in the present invention include 3,3'-diaminodiphenylsulfone, 4.4'
-diaminodiphenyl sulfone, 4,4-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane,
4,4°-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,4-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1.3-bis(4- aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)
Benzene, 2.2-bis(4-aminophenoxyphenyl)propane, bis(4-aminophenoxyphenyl)
Aromatic aminos such as sulfone; phenols such as bisphenol A1, titrabromobisphenol A1, bisphenol S; dicyandiamide; tetramethylguanadine; phenol novolac resin, cresol novolak resin: aliphatic amine: imidazole derivative; acid anhydride; Boron trifluoride complex; carboxylic acid metal salt-amine complex etc. 1
Two or more species can be mentioned.

Especially 3,3'-diaminodiphenylsulfone, 4゜4'
Suitable are aromatic amines such as -diamino diphenyl sulfone, 3,4'-diaminodiphenyl ether, and 1,3 bis(3-aminophenoxy)benzene, and dicyandiamide.

The amount of these curing agents is usually 0.5 to 1.2 times, preferably 0.5 to 1.2 times (equivalent) to the epoxy equivalent of the epoxy resin.

Furthermore, if necessary, a tertiary amine known as a curing accelerator,
Phenol compounds, imidazoles, Lewis acids, urea derivatives, etc. may be added.

In order to impart toughness to the epoxy resin used in the present invention, well-known thermoplastic resins such as polysulfone, polyethersulfone, polyarylate, and polyetherimide, and well-known rubbers such as butadiene-acrylonitrile copolymer having a carboxyl group at the end are used. The components can be used by appropriately mixing them.

Furthermore, epoxy resins include silica, kaolin, clay talc, feldspar powder, mica, alumina, potassium titanate, metal oxides such as iron oxide and magnesium oxide, carbonates such as basic magnesium carbonate and calcium carbonate, barium sulfate, and calcium sulfate. By properly containing well-known inorganic fillers such as sulfates such as sulfates, hydroxides such as aluminum hydroxide and magnesium hydroxide, aluminum powder, copper powder, etc., the elastic modulus of cured products can be improved, and the elastic modulus of fiber-reinforced composite materials can be improved. I
LSS and 0° bending strength can be improved.

Known fibers can be used as reinforcing fibers for the fiber-reinforced composite material of the present invention.

Examples include carbon fiber, graphite fiber, glass fiber, silicon carbide fiber, alumina fiber, titania fiber, boron nitride fiber, aromatic polyamide fiber, aromatic polyester fiber, polybenzimidazole fiber, and the like.

Also, depending on the purpose of use, two or more types of fibers can be used in combination.

The proportion of reinforcing fibers in the fiber-reinforced composite material is the same as in fiber-reinforced composite materials using known epoxy resin compositions as a matrix, and may be poured as appropriate depending on the application.
It is usually in the range of 20 to 80% by volume.

The above-mentioned reinforcing fibers are used in the same aggregated form as the well-known long fibers used as fiber-reinforced composite materials. That is, the long fibers are straightly aligned in one direction, the fibers are aligned in one direction and then stacked in a different direction, and the fibers are woven into a cloth shape. In the present invention, a well-known method can be used to form a composite of the epoxy resin composition and reinforcing fibers and mold the composite. For example, an epoxy resin composition is semi-cured into a sheet, and a large number of reinforcing fibers are arranged in parallel, or a semi-molten sheet of the epoxy resin composition is layered on a woven fabric and compressed to impregnate it. or by impregnating it with an epoxy resin composition solution to form a prepreg (intermediate base material), and then forming this prepreg into a predetermined shape by a pressing method, an autoclave method, a dry filament winding method, etc. Open mold molding represented by hand lay-up method and spray-up method, blue torsion method, wet filament winding method, etc. are used.

<Effects of the Invention> A fiber-reinforced composite material using the epoxy resin composition of the present invention as a matrix has excellent mechanical strength and ILS
Furthermore, their strength does not decrease even under high temperature and humidity, making them particularly suitable as structural materials for aircraft.

<Examples> Examples are shown below to specifically explain the present invention, but the present invention is not limited thereto.

Synthesis Examples 1 to 3 [Manufacture of epoxy resin] Dimethyl sulfoxide was added as a solvent to a reactor equipped with a thermometer, a stirrer, a dropping funnel, and a reaction water recovery device.
The phenol compound and epichlorohydrin shown in Table 1 were charged in amounts shown in Table 1 and reacted. The reaction was carried out at 45° C. under reduced pressure of 40 Torr while continuously adding 175 parts by weight of a 48% aqueous sodium hydroxide solution over 5 hours. During the reaction, water was removed from the system. After completion of the reaction, unreacted epichlorohydrin was removed by vacuum distillation, the epoxy resin containing the by-product salt and dimethyl sulfoxide obtained at this time was dissolved in methyl isobutyl ketone, and the by-product salt and dimethyl sulfoxide were removed by washing with water.

Furthermore, methyl isobutyl ketone was removed by vacuum distillation to obtain a pale yellow epoxy resin. The epoxy equivalent weight and number average molecular weight of each of these resins are shown in Table 2.

Table 1 Examples 1 to 5 and Comparative Examples 1 to 3 The epoxy resins shown in Table 3 were charged in the amounts shown in the table into a universal mixer, and heated under reduced pressure at 120 to 150°C for 30 to 1 hour while degassing. Kneaded. Next, the temperature was lowered to 60 to 80'C, and then the compound listed in Table 3 was added as a curing agent, and the mixture was kneaded at 60 to 80C for 30 minutes while degassing under reduced pressure to form an epoxy resin composition for the matrix. Obtained.

The contents of each component shown in Table 3 will be explained below.

ELM-434 Nidiaminodiphenylmethane tetraglycidyl (Sumitomo Chemical ■ Sumiepoxy [F] B
LM-434) ELM-100: triglycidyl para-aminometacresol (manufactured by Sumitomo Chemical Co., Ltd. Sumiepoxy ■ELM-1
00) 3,3'-DDS: 3.3'-s diaminodiphenylsulfone 4.4°-DDS: 4.4°diaminodiphenylsulfone 3.4°-DDE: 3.4
'-Diamino diphenyl ether TPE: 1,3-bis(3-aminophenoxy)benzene Each of the matrix resin compositions obtained by the above method was molded by a casting method to prepare specimens for measuring physical properties. All curing conditions are 1.
80'C 12 hours. The water absorption rate was expressed as a percentage increase in weight after immersing the sample in boiling water for 48 hours under atmospheric pressure.

The elastic modulus was evaluated by bending properties (measured according to ASTM D-790).

Table 3 shows the physical properties of the carbon fiber reinforced molded product. A prepreg, which is a precursor of the molded body, was produced using a prepreg manufacturing machine in the following manner. That is, surface-treated carbon fibers (Magnamite IM7, manufactured by Vercules) were continuously pulled out from a bobbin, arranged in a width of 50 cm, and a release paper was coated with the above-mentioned matrix resin in a thin film, and then rolled using a roll. Crimp. The basis weight of the carbon fibers impregnated with matrix resin in this way is 150g.
/ rri' unidirectionally aligned fiber prepreg was obtained.

The obtained prepreg sheet was cut and laminated so that the reinforcing fibers were oriented in the same direction, and the sheets were inserted between hot plates of a hydraulic press heated to 180°C and gradually pressurized until the reinforcing fiber content was 6.
Look while reducing the amount of resin so that it becomes 0% by volume.
/c♂G, cured in 1 hour.

Next, the molded body was further post-cured at 180° C. for 1 hour in a hot air oven to obtain a fiber-reinforced resin cured plate having a thickness of about 2111 ff+.

0° bending strength of the obtained cured plate (ASTM-0790
) was measured.

Next, the obtained composite material cured plate was immersed in boiling water for 48 hours.
After absorbing water, the cured composite board was heated to 82°C and 121°C.
The 0° bending strength at °C was measured in the same manner.

The results are shown in Table 3.

The results in Table 3 are explained below. Comparative Examples 1 and 2 are comparisons using the same curing agent as in Example 2. The blending ratio of the curing agent depends on the epoxy equivalent of the epoxy resin that is the main ingredient. Compared to Example 2, the epoxy resin of Comparative Example 1.2 has a smaller epoxy equivalent (the number of moles of epoxy groups per unit weight is about twice) and the amount of curing agent blended is about twice as much.

Although there was no significant difference in mechanical strength before water absorption, Example 2 was significantly superior in performance at high temperatures after water absorption. Similarly, comparative example 3
is a comparison with Example 4, and in this case as well, Example 4 was superior in performance at high temperatures after water absorption. In other Examples as well, it was confirmed that when the epoxy resin used in the present invention was used as a matrix, it had excellent mechanical strength at high temperatures after water absorption.

Claims (1)

[Claims] General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R represents a hydrogen atom or a methyl group.) Epoxy resin, curing agent, and reinforcing fiber having the structure A fiber-reinforced composite material characterized by comprising: