JPH0776647A - Epoxy resin composition and prepreg - Google Patents

Abstract

PURPOSE:To provide an epoxy resin composition composed of an epoxy resin, an organic thixotropic agent and an amine-based hardener, having excellent moldability and resin-flowability in curing and useful as a prepreg for fiber- reinforced composite material. CONSTITUTION:This epoxy resin composition is produced by compounding (A) 100 pts.wt. of an epoxy resin (preferably a mixture of a phenolic novolak epoxy resin or a cresol novolak epoxy resin and a bisphenol A epoxy resin) with (B) 0.1-10 pts.wt. (preferably 1-5 pts.wt.) of an organic thixotropic agent (preferably dibenzylidene sorbitol and its derivative or tribenzylidene sorbitol and its derivative) and (C) 1-10 pts.wt. (preferably 2.5-6 pts.wt.) of an amine- based hardener (preferably dicyandiamide or diaminodiphenylsulfone. A prepreg can be produced by impregnating the composition in reinforcing fibers.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to epoxy resin compositions and prepregs for fiber reinforced composite materials. More specifically, the present invention relates to an epoxy resin composition having excellent moldability, in particular, a resin flow property upon curing, and a prepreg obtained by impregnating the composition with a reinforcing fiber.

[0002]

2. Description of the Related Art In recent years, a fiber-reinforced composite material comprising a reinforcing fiber such as carbon fiber, glass fiber and aramid fiber and a matrix mainly composed of a resin has been widely used as a metal product by taking advantage of its lightness and design. Has been used in. In particular, a carbon fiber reinforced composite material (hereinafter abbreviated as CFRP) makes use of its excellent mechanical properties, including sports and leisure fields represented by golf club shafts, fishing rods, and tennis rackets.
It is widely used in industrial fields such as rolls and rotating bodies, and aerospace fields such as primary and secondary structural materials for aircraft.

As a resin composition for prepreg used for producing such a fiber reinforced plastic,
Conventionally, for example, Japanese Patent Publication No. 60-58420 and Japanese Patent Publication No. 5420
No. 8-167625, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine, which is a glycidyl ether type epoxy resin. Mixtures of type epoxy resins and the like are known.

As curing agents for these thermosetting epoxy resins, amines, acid anhydrides, polyamide resins, imidazoles, etc. are known, and they are used by appropriately adding an appropriate amount to the above-mentioned epoxy resin mixture. ing. CFR molded using these resin compositions as a matrix
If P has appropriate molding conditions, a very good molded product in which physical properties such as strength, elastic modulus and heat resistance are balanced can be obtained.

However, if the molding method for obtaining these CFRPs is poor, the defective rate is high, the productivity is not increased, and the cost is increased, and the physical properties of the molded article are reduced depending on the conditions taken to avoid them. It is often the case that it drops and destroys well-balanced characteristics. First, there is a problem of resin flow such as resin flow and protrusion during curing. The conventional epoxy resin for prepreg has a remarkable decrease in viscosity with an increase in temperature during curing and molding, and under high temperature and high pressure, the resin is in an extremely easy-to-flow state. For this reason, the phenomenon that the reinforcing fibers are disturbed during the molding process or the weight of the molded product falls below the set value due to the resin squeezing out, leading to variations in products and an increase in defective rate.

To solve this problem, various methods have heretofore been taken. For example, as one of them, JP-A-62-62
No. 127317, a method of changing the resin composition by increasing the proportion of a high molecular weight solid epoxy resin can be mentioned. However, in these cases, the tack and drape of the prepreg are changed, impairing moldability and handleability, and conversely increasing the defective rate of the molded product. In addition, the ease of molding the prepreg is an important issue even if no special measures are taken.
That is, if the tack is too weak, even if the prepregs are overlapped and pressed down, they are immediately peeled off and cannot be laminated. Therefore, it becomes necessary to raise the working environment temperature until proper tackiness is obtained. On the other hand, if the tack is too high, for example, if the prepregs are accidentally overlaid, it cannot be redone and the working environment temperature must be lowered.

Similarly, when the drape of the prepreg is too hard or too soft, it becomes difficult to form the prepreg, which often causes disorder of the reinforcing fibers and voids in the formed product, resulting in an increase in the defective rate of the product. It will be. As a measure for this, there is an appropriate work environment temperature, but since the tack changes at the same time due to this change in work environment temperature, it is difficult to choose a work environment temperature that balances the two. It was

In addition to the above-mentioned method, a method has been adopted in which the flow-through during curing of the resin is reduced by adding an additive to the epoxy resin composition. As examples of these, an elastomer such as CTBN or a thermoplastic resin such as polyvinyl formal (Japanese Patent Laid-Open No. 62-169829) is used by being added to an epoxy resin. However, these results in the fact that the heat resistance (Tg) of the molded product and the rigidity of the molded product are actually lowered, and none of these are satisfactory matrix resin systems.

Furthermore, as one of the methods for adding an additive to an epoxy resin composition, there is addition of inorganic particles which are often used for paints and sealing. In particular, silicon dioxide having a small particle size (famous as Aerosil as a commercial product), hectorite, and the like, which are useful for preventing dripping, are used as an inorganic thixotropic agent and exert their effects. However, these inorganic thixotropy imparting agents also agglomerate particles when mixed with the base epoxy resin, so-called, in this state, it is difficult to obtain a uniform mixture, or a thin film To form
Due to these aggregates, a uniform and flat film could not be obtained, leading to the occurrence of a defective rate.

[0010]

Therefore, in the present invention, an improved epoxy resin composition capable of eliminating the flowability of resin at the time of molding and obtaining a prepreg having an appropriate tack drape and the composition for strengthening the composition. The present invention provides a prepreg obtained by impregnating fibers for use.

[0011]

That is, the present invention provides an epoxy resin composition comprising the following components (a), (b) and (c) and a prepreg obtained by impregnating a reinforcing fiber with the epoxy resin composition. Is. (A) Epoxy resin (b) Organic thixotropic agent (c) Amine curing agent Here, the epoxy resin is not particularly limited as long as it is an epoxy resin generally used for prepreg. Specific examples include bisphenol A type epoxy resin, bisphenol F type epoxy resin,
Phenol novolac type epoxy resin, cresol novolac type epoxy resin, glycidyl amine type epoxy resin, glycidyl ester type epoxy resin, alicyclic epoxy resin, urethane modified bisphenol A type epoxy resin, etc. may be used alone or in combination. I can.

However, the preferred embodiment is a phenol novolac type epoxy resin or a mixture of a cresol novolac type epoxy resin and a bisphenol A type epoxy resin. Examples of such a phenol novolac type epoxy resin include Epicoat 152, 154 (produced by Yuka Shell Epoxy Co., Ltd.), DEN 431, 438, 43.
9,485 (manufactured by Dow Chemical Co.), EPN138, 11
39, (manufactured by Ciba Geigy), N730, 738, 74
0, 770, 775, 865, 870, 510 (manufactured by Dainippon Ink and Chemicals, Inc.), EPPN201 (manufactured by Nippon Kayaku Co., Ltd.), YDPN601, 602 (manufactured by Toto Kasei Co., Ltd.), and others. If it is an equivalent product, it can be appropriately selected and used.

As the cresol novolac type epoxy resin, ECN273, 280, 299 (manufactured by Asahi Kasei Kogyo Co., Ltd.), EP180 (manufactured by Yuka Shell Epoxy Co., Ltd.), N66
5, 670, 673, 680, 690, 695 (manufactured by Dainippon Ink and Chemicals, Inc.), EOCN102, 103, 10
4 (manufactured by Nippon Kayaku Co., Ltd.), ECN701, 702, 703,
704 (manufactured by Tohto Kasei Co., Ltd.) and the like, and other equivalent products of these products can be appropriately selected and used.

As the bisphenol A type epoxy resin, AER330, 331, 337, 661, 664,
667, 669 (manufactured by Asahi Kasei Corporation), EP 827, 82
8, 834, 1001, 1002, 1004, 100
7,1009 (made by Yuka Shell Epoxy Co., Ltd.), DER33
1,332,662,663u (manufactured by Dow Chemical Co.),
CY205, 230, 232, 221, 257, 25
2, 255, 250, 260, 280 (manufactured by Ciba Geigy), Epicron 840, 850, 855, 860, 1
050, 3050, 4050, 7050 (manufactured by Dainippon Ink and Chemicals), YD115, 1115CA, 117, 121,
127, 128, 128CA, 128S, 134, 00
1Z, 011, 012, 014, 014ES, 017,
019, 020, 002 (manufactured by Tohto Kasei Co., Ltd.) and the like, and if they are equivalent products of these products, they can be appropriately selected and used.

Here, when the characteristics of these epoxy resins are examined in the present invention, the use of a mixture of a phenol novolac type epoxy resin or a cresol novolac type epoxy resin and a bisphenol A type epoxy resin is a preferable embodiment. Considering the characteristics of the resin, such as the temperature dependence of the viscosity before curing, the heat resistance and the elastic modulus after curing of these resins, etc., there are preferable weight mixing ratios for the respective amounts used.

That is, the novolac type epoxy resin has a high cross-linking density of the cured molded product, and as a result, exhibits high heat resistance and a high elastic modulus of the resin cured product, but has a low elongation and is brittle. Indicates. On the other hand, since the bisphenol A type epoxy resin has various epoxy equivalents, the elongation and toughness of the resin cured product can be controlled by appropriately mixing them. Further, considering the ease of molding of the prepreg, that is, tackiness and drapeability, it is desirable to mix an appropriate amount of a liquid epoxy resin and a solid epoxy resin at room temperature, that is, a softening point of 5
85% to 50% of solid epoxy resin (combined bisphenol A type epoxy resin and novolac type epoxy resin) at 0 ° C. (duran mercury method) or more with respect to all epoxy resins,
Preferably, 80% to 60% is blended, while the epoxy resin which is liquid at room temperature corresponds to the rest. From this viewpoint, the compounding amount of the novolak type epoxy resin is 10 to 70 parts by weight, preferably 20 to 50 parts by weight, based on 100 parts by weight of the total epoxy resin, while the bisphenol A type epoxy resin is the novolac. This corresponds to the total amount excluding the compounding amount of the type epoxy resin. Also,
The liquid epoxy resin is preferably 15 to 50 parts by weight, and more preferably 100 to 100 parts by weight of the epoxy resin.
It will be 20 to 40 parts by weight.

The organic thixotropy-imparting agent used in the present invention may be any organic compound capable of imparting thixotropy to the above resin, but is compatible with the above epoxy resin system from the viewpoint of uniformity of mixing. Those are preferable. Specific examples include dibenzylidene sorbitol and its derivatives, tribenzylidene sorbitol and its derivatives, carboxymethyl cellulose and its derivatives, alginic acid and its derivatives, chitin and its derivatives, chitosan and its derivatives, and the like.

Among these, the most preferable embodiment is dibenzylidene sorbitol and its derivative and tribenzylidene sorbitol and its derivative. Examples of commercially available products thereof include gelol (manufactured by Shin Nippon Rika Co., Ltd.) and EC-1.
(Made by EC Chemical). In the present invention, in order to uniformly dissolve the above-mentioned organic thixotropy-imparting agent in the epoxy resin, it is useful to add a small amount of a reactive diluent for epoxy unless the physical properties of the epoxy resin are deteriorated. is there.

The amount of the organic thixotropic agent used in the present invention is 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of the total amount of the epoxy resin. Is desirable. When the blending amount of the thixotropy imparting agent is small, the thixotropy of the epoxy resin composition is low and the effect of improving the resin flow property during curing is low. On the other hand, if the blending amount is too large, the physical properties of the molded product may deteriorate. In these senses, the amount of the organic thixotropy-imparting agent added to the epoxy resin is preferably an appropriate weight ratio.

In the present invention, the method of mixing the organic thixotropic agent and the epoxy resin is not particularly limited. For example, it is possible to easily mix in a molten state at room temperature or, if necessary, in an atmosphere of 100 ° C. or higher. It is also possible to mix them via a solvent in which both are soluble. Further, it is also possible to use a polymer, an elastomer, particles or the like (for example, polyvinyl formal, polybutadiene-modified resin, anhydrous silica particles or the like) as a known modifier together with these resin compositions. .

The curing agent for the epoxy resin composition used in the present invention is an amine type curing agent. Generally, for sports and leisure and industrial use, curing at around 130 ° C. is the mainstream, and in consideration of storage stability, dicyandiamide is preferable among amines. For aircraft and structural members that require heat resistance, curing at around 180 ° C is the mainstream, and at this time diaminodiphenyl sulfone is desirable.

In the present invention, when these curing agents are used, the use of a curing accelerator is also an effective means in view of moldability and productivity. For example, as a curing accelerator, 3- (3,4-dichlorophenyl) -1,1-N
Examples thereof include urea compounds such as dimethylurea and 3-phenyl-1,1-N-dimethylurea, imidazole derivatives, and boron trifluoride amine derivatives.

In such a combination of the curing agent and the curing accelerator, the curing agent is added in an amount of 1 to 10 parts by weight (preferably 2.5 to 6 parts by weight) per 100 parts by weight of the epoxy resin. The agent is 1 to 10 parts by weight (preferably 2.
5 to 6 parts by weight) is preferable. The reinforcing fibers used in the present invention include carbon fibers, glass fibers, organic fibers such as aramid fibers, silicon carbide fibers,
Inorganic fibers such as alumina fibers and boron fibers, and high strength and high elastic modulus fibers such as metal fibers. Further, the form thereof may be continuous fibers or long fibers, and the fibers are arranged in parallel in one direction and / or aligned in a sheet shape, or the above-mentioned array is laminated so as to intersect in the fiber direction. It can be used in the form of a cloth, such as a mat or a woven fabric of the above-mentioned reinforcing fiber.

In the present invention, the method of integrating the resin composition and the reinforcing fiber into a prepreg is not particularly limited, and a known method may be used. Examples of these methods include a hot melt method and a wet method using a solvent. The hot melt method is a method of forming a prepreg without a solvent, and the reinforcing fibers are aligned in parallel at a constant interval on a film-shaped resin coated on a release paper with a constant thickness, and the temperature is 60 ° C to 100 ° C. Heat to about ℃ and impregnate with resin to make a prepreg.

In the wet method, a resin is dissolved in a solvent, the resin is put in an impregnation tank, the reinforcing fibers are passed through the impregnation tank to impregnate the resin, and then the solvent is removed to form a prepreg. At this time, as the solvent, various solvents such as methyl ethyl ketone, methylene chloride, methyl cellosolve, acetone, methanol, dimethylformamide, and N-methylpyrrolidone may be used alone or in combination.

The content of the reinforcing fibers of the prepreg thus produced is generally 50 to 75 wt% with respect to the total weight of the prepreg in which the reinforcing fibers and the resin are combined,
It is preferably 55 to 70 wt%.

[0027]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. However, these examples do not limit the scope of the present invention. The evaluation methods in Examples and Comparative Examples are as follows. (1) Resin flow amount measuring method According to the method described in JIS K-7071-1988 "Testing method for prepreg consisting of carbon fiber and epoxy resin".

(2) Tack measurement method Two tape-shaped prepregs are laminated and the 90 ° peel strength between the prepregs is evaluated. Temperature / humidity conditions: 27 ° C., 55% RH (Samples are left for 4 hours before being laminated.) Lamination method: Two prepregs at a linear pressure of 1 kg / c
m, 1 m / sec. Laminated test piece; width 1 cm, test stroke length 10 cm, 90 ° peeling speed; 500 mm / sec. (3) Drape measurement method A prepreg is laminated and the initial storage elastic modulus of dynamic viscoelasticity by this three-point bending method is examined.

Evaluation equipment: RSA-2 manufactured by Rheometric Co.
Dynamic viscoelastic device Evaluation conditions: 27 ° C, 55% RH, 3-point bending method, frequency 1
Hz test piece; width 12 mm, pitch 48 mm, thickness about 2 mm

[0030]

Example 1 EPPN as a novolac type epoxy resin
45 parts by weight of 201 (manufactured by Nippon Kayaku Co., Ltd.), 30 parts by weight of AER331R (manufactured by Asahi Chemical Industry Co., Ltd.) as a bisphenol A type epoxy resin, 25 parts by weight of AER661 (manufactured by Asahi Kasei Corporation), and 100 parts by weight of epoxy resin. 3 parts by weight of gelol DH (manufactured by Shin Nippon Rika Co., Ltd.) as an organic thixotropy-imparting agent are put into a stirrer, and 1
After dissolving and mixing at 40 ° C., the temperature is lowered and dicyandiamide (hereinafter referred to as DIC) is added to 100 parts by weight of the epoxy resin.
5 parts by weight of Y) and 4 parts by weight of 3- (3,4-dichlorophenyl) -1,1-N dimethylurea (hereinafter referred to as DCMU), and mixed by stirring at 60 ° C. For use as an epoxy resin composition.

Next, commercially available high-strength carbon fiber (tensile strength 400 kg / mm ² , tensile elastic modulus 23.5 t / m 2
m ² ; manufactured by Asahi Kasei Carbon Fiber Co., Ltd.) was impregnated with the above resin composition by the hot melt method, and the resin content was 37.
A unidirectional carbon fiber prepreg with a wt% of carbon fiber basis weight of 125 g / m ² was obtained. The resin flow of the obtained prepreg was 5.2% as measured by the above method. Also,
When a golf shaft was molded using the obtained prepreg, the moldability was good, there was no resin ejection, and the defective rate of molding was very low. Table 1 summarizes these results.

[0032]

Example 2 E as an organic thixotropic agent
After using C-1 (manufactured by E.C. Chemical Co., Ltd.) to prepare a resin composition in the same manner as in Example 1 except that, a carbon fiber prepreg was prepared and evaluated in the same manner. The resin flow amount of the obtained prepreg was 5.7%, and the moldability as a shaft was good. In addition, the defective rate of shaft molding was very low, and all were good without voids or scratches.

[0033]

Comparative Example 1 A resin composition was prepared in the same manner as the epoxy resin of Example 1 except that an organic thixotropic agent was not added. Using this resin, a carbon fiber prepreg was prepared by the same method as in Example 1 and evaluated by the same method. The amount of resin flow in the experiment is 16.3
%, The shaft made from the obtained prepreg had a high resin flow and a high failure rate.

[0034]

Comparative Example 2 Instead of an organic thixotropic agent, polyvinyl formal (Denka formal # 20;
A resin composition was prepared in the same manner as in Example 1 except that 5 parts by weight of Denki Kagaku Kogyo Co., Ltd.) was added and mixed. Using this, a carbon fiber prepreg was prepared in the same manner as in Example 1 and evaluated in the same manner. The amount of resin flow is 10.2%,
The shaft made from the obtained prepreg had a high failure rate.

[0035]

Comparative Example 3 The same as Example 1 except that 5 parts by weight of a carboxyl group-terminated butadiene-acrylonitrile copolymer elastomer (CTBN1300-13; Ube Industries, Ltd.) was added and mixed instead of the organic thixotropic agent. To prepare a resin composition. Using this, a carbon fiber prepreg was prepared in the same manner as in Example 1 and evaluated in the same manner. The resin flow of this prepreg is 14.5.
%, The shaft made from the resulting prepreg had a high failure rate.

[0036]

[Table 1]

[0037]

The prepreg using the epoxy resin composition for a prepreg of the present invention is a well-balanced one having a very low resin flow property and an appropriate tack and drape property. For this reason, when a molded product is produced using the prepreg, workability is improved, the ejection of the resin at the time of curing and molding is reduced, and as a result, the defective molding rate is reduced, and an inexpensive non-defective product can be produced.

Claims (2)

[Claims] 1. An epoxy resin composition comprising the following components (a), (b) and (c). (A) Epoxy resin (b) Organic thixotropic agent (c) Amine curing agent 2. A prepreg obtained by impregnating reinforcing fiber with the epoxy resin composition according to claim 1.