JP3345963B2 - Epoxy resin composition for yarn prepreg and yarn prepreg - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an epoxy resin composition suitable as a matrix resin for yarn prepreg, which provides excellent mechanical properties such as high elasticity, high strength and high toughness in addition to excellent handling properties and moldability. It is about.

[0002]

2. Description of the Related Art Fiber-reinforced composite materials comprising a reinforcing fiber and a matrix resin are used for various structural materials. Among them, composite materials having high specific strength and specific rigidity have come to be widely used for aircraft requiring light weight.

As an example, composite materials are applied to rotor blades (rotor blades) such as helicopters, and rotor blades such as windmills in addition to aircraft. Such a rotor blade is required to have characteristics such as a need for fatigue strength to withstand variable loads such as large tensile force, lift force and bending torsion, and a composite material has a high tensile specific strength and good fatigue characteristics.
It is suitable for this application because it has features such as a free airfoil distribution.

The above-mentioned composite rotor is usually manufactured from a so-called yarn prepreg in which an epoxy resin is impregnated into a bundle of reinforcing fibers such as glass fibers. This yarn prepreg is required to be excellent in handling properties and moldability, as well as excellent in mechanical properties such as interlayer shear strength and toughness.

[0005] Regarding the handling property, it is important that the prepreg has an appropriate tack and drape property in order to facilitate the laminating operation.

[0006] In particular, yarn prepregs need to have good unwinding properties from bobbins, and therefore require a higher level of tack and drape, which is different from that of ordinary one-way prepregs.

With respect to moldability, it is important to control the flow of the matrix resin in order to achieve a desired resin content and not to generate defects such as voids.

Regarding mechanical properties such as interlaminar shear strength and toughness, the obtained rotor blades must have excellent physical properties in order to sufficiently withstand variable loads such as large tensile force, lift and bending torsion. is necessary.

[0009]

DISCLOSURE OF THE INVENTION The present invention has good handling properties such as tack and drape properties of a prepreg, has few defects such as voids in a molded product, and has good mechanical properties such as interlayer shear strength and toughness. Provided is a yarn prepreg and an epoxy resin composition suitable for it, which are capable of sufficiently withstanding variable loads such as large tensile force, lift and bending torsion when molding rotor blades of an aircraft or a windmill, etc. The task is to

[0010]

In order to solve the above problems, the epoxy resin composition for yarn prepreg of the present invention has the following constitution. That is, an epoxy resin composition comprising an epoxy resin, a solid nitrile rubber, and an aromatic amine-based curing agent, wherein the epoxy resin contains a solid bisphenol A type epoxy resin at room temperature in an epoxy resin.
An epoxy resin composition for yarn prepreg, wherein the epoxy resin composition contains 2 to 8% by weight of a solid nitrile rubber in the epoxy resin composition.

Further, the yarn prepreg of the present invention has the following constitution. That is, it is a yarn prepreg using the epoxy resin composition for yarn prepreg as a matrix.

First, the epoxy resin used in the present invention will be described in detail.

The epoxy resin composition for yarn prepreg of the present invention contains 20 to 50% by weight of a bisphenol A type epoxy resin which is solid at room temperature in the epoxy resin. If the amount of the bisphenol A type epoxy resin solid at room temperature is less than 20% by weight, the tack of the prepreg becomes excessive and the bobbin unwinding property of the yarn prepreg deteriorates. On the other hand, if it exceeds 50 wt%, the tackiness of the prepreg becomes too low, the adhesive strength between the prepregs is lost, or the drapability of the prepreg is impaired, so that the laminating work becomes difficult. Also,
The heat resistance of the composite material is also reduced.

As the epoxy resin suitable for the present invention other than the above-mentioned bisphenol A type epoxy resin which is solid at room temperature, in particular, an epoxy resin having an amine, a phenol, or a compound having a carbon-carbon double bond as a precursor is used. preferable.

Specifically, epoxy resins having amines as precursors include various isomers of tetraglycidyldiaminodiphenylmethane, triglycidyl-p-aminophenol, triglycidyl-m-aminophenol, and triglycidylaminocresol. Body. Tetraglycidyldiaminodiphenylmethane is preferable because of its excellent heat resistance as a resin for composite materials as an aircraft structural material.

Examples of the epoxy resin having a phenol as a precursor include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, and resorcinol type epoxy resin. Can be

A liquid bisphenol A type epoxy resin,
Since the bisphenol F type epoxy resin has a low viscosity, it is preferable to mix it with other epoxy resins and additives. However, if a large amount of this liquid epoxy resin is used, the tack of the prepreg becomes excessive and the yarn prepreg unwinds the bobbin.

Examples of the epoxy resin using a compound having a carbon-carbon double bond as a precursor include an alicyclic epoxy resin.

Also, brominated epoxy resins obtained by brominating these epoxy resins are preferably used from the viewpoint of reducing the water absorption of the resin and improving the environmental resistance.

These epoxy resins may be used alone, or may be used by being appropriately compounded. A combination of a glycidylamine-type epoxy resin and a glycidylether-type epoxy resin is particularly preferable because it has both heat resistance, water resistance and workability.

From the viewpoint of balancing heat resistance, water resistance and workability, the following combinations of epoxy resins are particularly preferred. That is, the compositions of the various epoxy resins are selected from the following ranges.

Tetraglycidyl diaminodiphenylmethane 10 to 50% Liquid bisphenol A type epoxy 1 to 10% Liquid bisphenol F type epoxy 5 to 25% Solid bisphenol A type epoxy 10 to 50% Brominated bisphenol A type epoxy 5 to 30% Wherein an aromatic diamine is used as an epoxy resin curing agent. With other epoxy resin curing agents, it is not possible to improve the heat resistance of the obtained resin effect material. Examples of the aromatic diamine curing agent include various isomers of diaminodiphenyl sulfone, aminobenzoic acid esters, various isomers of diaminodiphenylmethane, and the like. In particular, various isomers of diaminodiphenyl sulfone are most suitable for the present invention because they give cured products having good heat resistance. The addition amount is preferably from 0.7 to 1.2 equivalents to the epoxy based on the stoichiometry of the epoxy group of the epoxy resin and the active hydrogen of diaminodiphenylsulfone from the viewpoint of improving heat resistance.

In the present invention, in addition to the above-mentioned curing agent, various additive catalysts can be used in combination for the purpose of improving the curability of the resin. A typical example is a monoethylamine complex of boron trifluoride.

The epoxy resin composition for yarn prepreg of the present invention uses a solid nitrile rubber as another essential component. In the present invention, the solid rubber refers to a rubber having substantially no fluidity at room temperature. The addition of the solid rubber has the effect of imparting tackiness and softness to the resin, and improves the tack and drape property which is an important property as a prepreg. Further, by adding solid rubber, the resin flow during molding is controlled, and a dense composite material free from defects such as voids can be obtained.

Moreover, the resin composition containing the solid rubber has a high thixotropy despite having a high viscosity, so that the apparent viscosity of the resin decreases in a shearing field such as a prepreg process. This has the advantage that the resin impregnation becomes easier than expected. Further, when a resin composition containing a solid rubber is used, the toughness of the composite material is improved, while the inherent high elastic modulus, high heat resistance, and high solvent resistance of the thermosetting resin are small.

As such a solid rubber, a so-called nitrile rubber obtained by copolymerizing acrylonitrile and butadiene is preferably used from the viewpoint of improving the affinity with the epoxy resin. The acrylonitrile copolymerization amount of the nitrile rubber is 15 from the viewpoint that the compatibility between the solid rubber and the epoxy resin is not deteriorated, while the elastic property of the rubber is impaired and the tack and drape properties of the prepreg are deteriorated.
~ 45% is preferred. Further, from the viewpoint of improving the solvent resistance and mechanical properties of the cured resin, the resin preferably has a carboxyl group capable of reacting with an epoxy resin or a curing agent in the molecule.

In the present invention, the compounding amount of the solid rubber is 2 to 8 wt% in the resin composition. If the compounding amount of the solid rubber is less than 2 wt%, the flexibility of the obtained prepreg is poor and the handling property is deteriorated, the resin flow at the time of molding is increased, the resin content is reduced, and resin deficient portions are observed. And other problems occur. On the other hand, when the compounding amount of the solid rubber exceeds 8 wt%, the resin viscosity becomes too high, so that it becomes difficult to produce a prepreg having good impregnation properties, and the heat resistance and the elastic modulus of the obtained molded body are increased. And solvent resistance will fall.

The yarn prepreg of the present invention comprises the above-described epoxy resin composition and reinforcing fibers. As the reinforcing fiber used in the yarn prepreg of the present invention, generally, a fiber having excellent heat resistance and tensile strength used as an advanced composite material is used. Specifically, for example,
Carbon fiber, graphite fiber, aramid fiber, silicon carbide fiber,
Alumina fiber, boron fiber, tungsten carbide fiber, glass fiber and the like can be mentioned.

In the yarn prepreg of the present invention, in addition to the epoxy resin composition and the reinforcing fibers, granules such as calcium carbonate, talc, mica, silica, carbon black, silicon carbide, alumina hydrate and the like are further epoxied. Mixing with the resin composition is also effective and preferable for adjusting the viscosity of the resin to an appropriate value and improving the physical properties of the obtained composite material, such as compressive strength and toughness.

The yarn prepreg of the present invention can be obtained by impregnating the above-mentioned reinforcing fiber with the above-mentioned epoxy resin composition by a conventional method.

Hereinafter, the present invention will be described in more detail by way of examples.

[0032]

The evaluation methods used in the examples and comparative examples are as follows.

The resin cured plate for measuring mechanical properties was prepared by removing the solvent, pouring the resin composition degassed under reduced pressure into a mold having a thickness of 2 mm, and heating and curing at 180 ° C. for 2 hours. The obtained hardened plate is cut out to a predetermined size, and JIS K69
The flexural modulus was determined according to 11. The water absorption test piece for bending measurement was prepared by immersing a cured resin piece in hot water at 71 ° C. for 2 weeks.

The glass transition temperature of the cured resin is determined according to JIS K
Determined by the DSC method according to 7121.

The prepreg is made of glass fiber as a reinforcing fiber.
Using a strand , the ME
After impregnation with the K solution, the solvent was volatilized so that the volume content (Vf) of the glass fibers became 57%.

[Examples 1 and 2, Comparative Examples 1 to 4] The resin composition was as shown in Table 1, and the resin was prepared according to the following procedure. That is, 20% of solid rubber
After the epoxy resin was added to the MEK solution while stirring at room temperature and uniformly dissolved, a 20% MEK solution of diaminodiphenyl sulfone was gradually added while stirring at room temperature to obtain a uniform epoxy resin composition solution.

[0037]

[Table 1] Table 2 shows the evaluation results of the resin cured product and the yarn prepreg obtained from this.

[Table 2] In Example 1 and Example 2, the Tg of the cured resin, the flexural modulus under water absorption, and the fracture toughness exhibited good values. Further, the tack and drape properties of the prepreg were satisfactory.

However, when the content of the solid rubber is less than 2% (Comparative Example 1), since the minimum viscosity of the resin is low, the resin flow becomes large and the thickness of the obtained fiber-reinforced composite material becomes uneven. Disadvantages arose.

Conversely, when the content of the solid rubber is more than 8% (Comparative Example 3), the resin viscosity becomes too high, impairing the prepreg impregnating property and reducing the resin flow. The defect that many voids generate | occur | produced in the fiber reinforced composite material was observed. Further, the flexural modulus at high temperature under water absorption was significantly reduced.

On the other hand, when the content of the solid epoxy resin EP1001 was less than 20% (Comparative Example 1), the tackiness of the prepreg was excessive, and the handling property was impaired. In addition, the content of EP1001 which is a solid epoxy resin is 5%.
If it is more than 0% (Comparative Example 4), the tack of the prepreg hardly disappears, and the drape property is impaired.

[0041]

As described above, the prepreg has good handleability such as tackiness and drapability, has few defects such as voids in a molded product, and has excellent mechanical properties such as interlayer shear strength and toughness. It is possible to provide a yarn prepreg capable of sufficiently withstanding a variable load such as a large tensile force, a lift and a bending torsion when a rotary blade or the like is formed, and an epoxy resin composition suitable for the yarn prepreg.

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Claims (3)

(57) [Claims] 1. An epoxy resin composition comprising an epoxy resin, a solid nitrile rubber and an aromatic amine-based curing agent, wherein the epoxy resin is a bisphenol A type epoxy resin which is solid at room temperature and is 20 to 50 wt% in the epoxy resin. An epoxy resin composition for yarn prepreg, wherein the epoxy resin composition contains 2 to 8% by weight of a solid nitrile rubber. 2. The method according to claim 1, wherein the aromatic amine curing agent is 4,4'-diaminodiphenyl sulfone.
1 Symbol placing yarn prepreg epoxy resin composition. 3. A yarn prepreg comprising the epoxy resin composition for yarn prepreg according to claim 1 as a matrix.