JPH0639519B2 - Epoxy resin composition and prepreg - Google Patents

Description

TECHNICAL FIELD The present invention relates to an epoxy resin composition which can be cured at a relatively low temperature and is excellent in storage stability, and carbon fiber impregnated with the epoxy resin composition. It is about prepreg. The prepreg of the present invention in which carbon fiber is impregnated with the resin composition of the present invention is excellent in drape property and tackiness, and is easy to handle. Further, since the molded product obtained from the prepreg has excellent heat resistance and mechanical properties, the obtained carbon fiber reinforced resin composite material (CFRP composite) well reflects the high strength and high elastic modulus of the carbon fiber, and particularly, It provides a composite (composite material) having excellent bending strength and also has excellent fracture toughness (impact characteristics).

[Prior art]

The fiber-reinforced resin composite material has high specific strength and specific elastic modulus, and as a lightweight and high-strength material, it is compounded with reinforced fibers of long fiber and short fiber and various matrix resins, aerospace, ship, It is widely used as a high-performance product in transportation equipment such as vehicles, functional members in advanced industrial fields such as automation equipment, and sports and leisure products such as fishing rods and golf shafts. As a matrix resin for such a fiber-reinforced resin composite material, long-fiber-shaped reinforcing fibers are used, and thermosetting resins such as unsaturated polyester resins, epoxy resins, and polyimide resins have been conventionally used.

When manufacturing a composite, make a prepreg in which carbon fiber is impregnated with the thermosetting resin as an intermediate product,
A general method is to stack these in predetermined dimensions and angles and cure by heating and pressing to obtain a molded product.

Even in the production of composite materials for sports and leisure such as fishing rods and golf shafts, it is often composited through the form of prepreg, and as a matrix resin, it is relatively low of 120 to 130 ° C among various thermosetting resins. Epoxy resins, which can be molded at temperature and have good mechanical properties, are often used.

[Problems in the prior art]

The epoxy resin composition of a type that can be molded at a relatively low temperature is mainly a composition in which an epoxy resin and a dicyandiamide / urea compound-based curing accelerator are combined, as described in JP-B-58-5925. . In this case, the type of the main component epoxy resin is a combination of a phenol novolac type epoxy resin and a bisphenol A type epoxy resin, so that there is a problem that the crosslink density of the cured resin is low and the elastic modulus is slightly inferior. When used as a matrix resin for the composite, the apparent 0 ° bending strength of the flat plate was low and the performance of the composite could not be sufficiently obtained.

In JP-A-60-58422, a combination of tetraglycidyldiaminodiphenylmethane / novolac type epoxy resin / dicyandiamide / urea compound type curing accelerator has high heat resistance, low temperature fast curing property, and storage stability. Of good composition. In this case, it is described that a small amount of diaminodiphenylsulfone may be prepolymerized for the purpose of adjusting the viscosity of the resin composition, but this does not sufficiently improve the mechanical properties of the molded product. .
Also, in this case, since the rigidity of the matrix resin is high,
Although it has excellent mechanical properties such as 0 ° bending strength of a flat plate,
Since the resin is hard and brittle, it has a drawback that the composite has poor impact properties.

Further, JP-A-62-129308 discloses a combination of epoxy resin / polyallyl ether sulfone / dicyandiamide / urea compound type curing accelerator. Also in this case, by mixing polyallyl ether sulfone into the epoxy resin, the viscosity of the resin composition was adjusted, flow control during molding was performed, and the moldability was improved without lowering the mechanical properties. It is a thing. However, in this case, by increasing the crosslink density of the cured resin,
It is not for the purpose of improving the rigidity of the matrix resin and for enhancing the mechanical properties of the composite, and in fact, it is not of a composition suitable for obtaining the excellent fiber performance of high-strength and high-elasticity carbon fibers. It was

[Object of the Invention]

The present invention overcomes the above-mentioned drawbacks, can be cured at a relatively low temperature, is excellent in storage stability, and well reflects the high strength and high elastic modulus of the carbon fiber used, and particularly flexural strength and impact. An object of the present invention is to provide a resin composition and a prepreg that give a composite having properties.

[Structure and Effect of Invention]

 The present invention is as follows.

(1) Melt viscosity at 80 ° C including the following [A] to [E]
An epoxy resin composition which is 100 to 10,000 poise and is curable at 90 to 130 ° C.

[A] 100 parts by weight of an epoxy resin containing at least 50 parts by weight or more of a glycidyl amine type epoxy resin [B] at least 1 selected from polyamide, polysulfone, polyether sulfone and polyether imide
Thermoplastic resin of 10 to 30 parts by weight [C] Dicyandiamide 2 to 10 parts by weight [D] Urea compound represented by the following formula 2 to 5 parts by weight (However, X and Y are the same or different and are H, Cl, OCH ₃
Represents ) [E] 15-30 parts by weight of diaminodiphenyl sulfone (2) A prepreg obtained by impregnating carbon fiber with the epoxy resin composition according to claim 1.

The epoxy resin composition of the present invention is prepared by uniformly dissolving the component [B] in the component [A] in advance without using a solvent, and then mixing it with the components [C], [D] and [E]. At this time, it is possible to provide a relatively uniform matrix resin composition for hot melt in which the mixing ratio of the thermoplastic resin component is particularly high. When the thermoplastic resin component is added to the matrix resin, the viscosity of the entire resin composition tends to increase. Therefore, the epoxy resin [A] component used contains 50 parts by weight or more of a resin having a viscosity of 100 poise or less at 50 ° C. It is preferable.

Prepreg obtained from the composition of the present invention, excellent mechanical properties of the epoxy resin component, without impairing the heat resistance,
Composites with improved toughness and associated impact properties can be provided.

The carbon fiber used in the present invention has excellent tensile strength in order to exhibit excellent mechanical properties as a composite.
A carbon fiber having a modulus of 300 kgf / mm ² or more and an elastic modulus of 20 Ton / mm ² or more is desirable. Further, the resin composition of the present invention well reflects the high strength and high elastic modulus of carbon fiber, and has a tensile elastic modulus.
Even for highly elastic carbon fibers of 40 to 60 Ton / mm ² , a bending elastic modulus that retains a contribution of 80% or more of the calculated elastic modulus assuming the additivity is given to provide high strength and high elastic carbon. It can be said that the resin composition is suitable for fibers.

Among the matrix resin compositions used in the present invention, as the glycidylamine type epoxy resin of the component (A), Araldite MY720 (manufactured by Ciba Geigy),
Epotote YH434, YDM 120 (Toto Kasei Co., Ltd.), E
LM-120, ELM-100, ELM-434 (Sumitomo Chemical Co., Ltd.), Epicoat 604 (Shell Chemical Co., Ltd.) and the like.

It is necessary to use 50 parts by weight or more of the glycidyl amine type epoxy resin among the epoxy resins of the component (A).
If it is less than 50 parts by weight, the cross-linking density of the cured resin will not be sufficiently high as expected, the glass transition temperature will be low, and both heat resistance and mechanical strength will decrease.

The epoxy resin as the component [A] is, in addition, bisphenol A type epoxy resin, Epicoat 815, Epicoat 828, Epicoat 834, Epicoat 1001, Epicoat 1002 (manufactured by Shell Chemical Co.), and phenol / novolak type epoxy resin, Epicoat 152, Epicoat 154 (manufactured by Shell Chemical Co., Ltd.), Dow epoxy DEN 43
1, DEN 438, DEN 439 (Dow Chemical Company),
EPPN 201 (Nippon Kayaku Co., Ltd.), Epiclon N 740
Ardite ECN 1235, ECN 127 as cresol novolac type epoxy resin (manufactured by DIC)
3, ECN 1280 (Ciba Geigy), EOCN 1
02, EOCN 103, EOCN 104 (manufactured by Nippon Kayaku Co., Ltd.) and the like can also be used.

Further, as an alicyclic epoxy resin, Araldite CY-
179, CY-178, CY-182, CY-183 (manufactured by Ciba-Geigy) or the like can also be used.

When about 10 parts by weight of urethane modified bisphenol A type epoxy resin Adeka Resin EPU-6, EPU-10, EPU-15 (manufactured by Asahi Denka Co., Ltd.) is used, it is excellent in flexibility and has good adhesion to the reinforcing fiber. A resin composition can be provided.

An epoxy resin-based reactive diluent such as polypropylene glycol diglycidyl ether, diglycidyl ether, butanediol glycidyl is added in such an amount that the heat resistance of the resin cured product is not lowered in order to adjust the viscosity of the entire resin composition. It is also possible to use ether, 2-glycidyl phenyl glycidyl ether, resorcinol diglycidyl ether, alkylphenol glycidyl ether, phenyl glycidyl ether, butyl glycidyl ether, cresol glycidyl ether, styrene oxide and the like in combination. In this case, the blending amount of these is 10
It is preferably not more than parts by weight.

The thermoplastic resin as the component (B) includes, as a polyamide resin, a thermoplastic polyamide having a melting point of 150 ° C or higher, Elvamide (manufactured by DuPont), and a polysulfone resin having a glass transition temperature of 190 ° C or higher, Udel Polysulfone P-1700 (Union). -Carbide), Victrex PES, a polyethersulfone resin with a glass transition temperature of 220 ° C or higher
(Manufactured by ICI) and ULTEM (manufactured by GE), which is a polyetherimide resin having a glass transition temperature of 210 ° C. or higher, these thermoplastic resins have a particle size of 400 μm or less, particularly 100 μm or less from the viewpoint of resin preparation. It is preferably in powder form.

Further, in consideration of heat resistance, it is preferable to use a thermoplastic resin having a glass transition temperature of 200 ° C. or higher. In particular, Victrex PES (I
CI make) and polyetherimide resin ULTEM
The use of a single system (commercially available from GE) or a combined system improves the toughness and accompanying impact properties without impairing the excellent mechanical properties and heat resistance of the resin composition, resulting in a good composite. It is possible to obtain moldings that give performance.

It is necessary to use 10 to 30 parts by weight of these thermoplastic resins with respect to 100 parts by weight of the epoxy resin. When the amount is less than 10 parts by weight, the mechanical strength is good, but the resin tends to be brittle and the impact properties tend to be poor. If it is more than 30 parts by weight, the viscosity of the entire resin composition will be high, which will hinder the workability during prepreg production, and the prepreg itself's handleability such as tackiness and drape will deteriorate, resulting in composite performance. It is also not preferable because it adversely affects

As the dicyandiamide as the component [C], a commercially available product is used, but in consideration of reactivity and moldability, a fine powder having a particle diameter of 10 μm or less is preferable.

By using the dicyandiamide as the component [C] and the urea compound as the component [D] in combination, a temperature of 90 to 130 ° C.
It is possible to provide a resin composition and a prepreg that can be completely cured in a curing time of a minute and have a pot life of 1 month or more at room temperature.

The amount of the component [C] used is 2 to 10 parts by weight. If it is less than 2 parts by weight, it will not function as a curing agent, and if it is more than 10 parts by weight, those not involved in the reaction will remain in the resin composition, adversely affecting the moldability and mechanical properties of the composite. .

The urea compound as the component [D] is required to be 2 to 5 parts by weight. If it is less than 2 parts by weight, it will not function as a curing accelerator, and if it is more than 5 parts by weight, the reactivity will be too strong and the reaction will proceed at a relatively low temperature. Will become severe and workability will be hindered, and the pot life of the prepreg itself will become short.

The mixing ratio of the component [C] and the component [D] can be arbitrarily determined in consideration of the purpose of use, the molding method, the molding conditions and the like.

As the diaminodiphenyl sulfone as the component [E], a commercially available product may be used. The amount used is 15 to 30 parts by weight. In the resin system of the present invention, the [C] component and [D] component are used.
The purpose of using the component [E] is to add the component [E] to this system, knowing that the amine component will be in excess, even though the use of the component alone is sufficient for complete curing. Therefore, the mechanical strength of the composite is further improved. Especially when using highly elastic carbon fiber,
The high elastic modulus of carbon fiber can be efficiently reflected in the composite.

That is, the combined use of the [C] component / [D] component / [E] component enables complete curing at a temperature of 90 to 130 ° C. in a curing time of 30 to 120 minutes and high strength of the carbon fiber used. ,
It was possible to give a composite that reflected the high elastic modulus well and was particularly excellent in bending strength. In this case, [A]
The glycidylamine type epoxy resin used as a component in an amount of 50 parts by weight or more is also important in combination with the component [E], and has the role of further improving the elastic modulus of the cured resin and enhancing the mechanical properties of the composite. In particular, the effect is further exerted when the preliminary reaction described later is performed.

As the compounding amount of the component [E], 15 to 30 parts by weight are used,
If the amount is less than 15 parts by weight, the effect of the compounding is insufficient, and if the amount is more than 30 parts by weight, the hygroscopic property of the molded article deteriorates, which is not preferable.

A small amount of the [E] component may be taken out from 15 to 30 parts by weight of the [E] component and pre-reacted with a part or the whole of the [A] component. In this case, the preliminary reaction conditions are:
The temperature is preferably 120 to 140 ° C. for 60 to 120 minutes, and the amount of the component [E] is preferably 15 parts by weight or less with respect to 100 parts by weight of the component [A].

Also, as a curing accelerator for epoxy resin, a very small amount of
BF ₃ monoethylamine, BF ₃ benzylamine, 2-ethyl-4 methylimidazole, 2-ethylimidazole, 2,
4-dimethylimidazole, 2-phenylimidazole, C
It is also possible to use o [III] acetylacetonate or the like together.

In the present invention, the component (B) may not be uniformly mixed with the epoxy resin and may have an appropriate phase separation structure, but rather it tends to improve the impact properties of the composite and is thus preferred.

Among the resin composition for prepreg used in the present invention,
In addition to the above essential components, a small amount of rubber component that does not deteriorate heat resistance (for example, a carboxyl group-terminated butadiene-acrylonitrile copolymer, nitrile rubber, epoxy-modified polybutadiene rubber, etc.) and prepreg handleability are not deteriorated. A filler (for example, silica powder), a flame retardant such as antimony trioxide, a coloring agent, or the like may be added.

The resin composition for prepreg of the present invention can be prepared, for example, by the following method.

That is, each component is supplied to a kneading device, and preferably kneaded by heating under an inert gas atmosphere. The heating temperature at this time is lower than the curing start temperature of the epoxy resin. Alternatively, after dissolving the component [B] in the component [A], the components [C] [D] [E] may be added and kneaded. Usually, the component [B] is dissolved in the component [A] at a temperature of 20 to 200 ° C, particularly preferably a temperature of 100 to 150 ° C. In this case, from the viewpoint of resin preparation, the component [B] is preferably in the form of fine powder having a particle size of 100 μm or less in order to accelerate dissolution.

By this operation, it becomes possible to prepare an epoxy resin composition in which the thermoplastic resin is highly blended up to 30 parts by weight, but blending the thermoplastic resin in an amount of 30 parts by weight or more makes the viscosity of the composition very high. This is not preferable because it becomes high and kneading becomes difficult. It also adversely affects the mechanical properties of the resulting composite.

When the carbon fiber is impregnated with the resin composition for prepreg of the present invention to form a prepreg, the so-called hot melt method which is already known can be used.

Since the resin composition of the present invention dissolves the thermoplastic resin of the component (B) in the epoxy resin of the component (A),
It is possible to produce a prepreg by a melt method, and further, there is provided an excellent resin composition for a prepreg which has the excellent heat resistance of an epoxy resin and the toughness / impact strength of a thermoplastic resin without being affected by a residual solvent. .

Further, due to the problem of solubility, the component [B] may break out in a phase of 50 μm or less, but even in that case, there is no hindrance to the preparation of the prepreg by the hot melt method.

The unidirectional or woven prepreg obtained by such an operation has good quality.

[Examples and Comparative Examples]

Examples 1 to 6 and Comparative Examples 1 to 7 The main components [A] and [B] were weighed and placed in a beaker so that the types and blending ratios shown in Table 1 were obtained. This was heated with stirring at 130 ° C. for 1 hour to obtain a uniform resin mixture. Next, in the roll mill mixing, [C], [D] and [E] components having the compounding ratios shown in Table 1 were added,
Mixing was performed at 30 ° C for 30 minutes to obtain a resin composition for prepreg, and the gel time of the resin composition at 130 ° C and the viscosity at 80 ° C were measured.

A resin film was prepared from this composition using a film coater, and carbon fiber (CF) Vesphite HMS-46X (manufactured by Toho Rayon Co., tensile strength) was formed on the resin film.
380kgf / mm ^2, an elastic modulus 46T / mm ²⁾ arranged, heating, impregnated, to obtain a CF basis weight 140 g / m ^2, resin content of 34 wt% of the unidirectional prepreg. The pot life of the prepreg was set as the time until it was left in a temperature-controlled room at 23 ° C until the drape property of the prepreg disappeared.

From this prepreg, a predetermined number of prepregs were cut and laminated, and a test piece was cut out from a molded plate that had been heat-cured by autoclave molding under the molding conditions of a heating rate of 2 ° C / min and 130 ° C for 90 minutes, and glass transition. The temperature, 0 ° interlaminar shear strength, 0 ° bending strength, and ± 45 ° Charpy impact value were measured. Further, the contribution rate (Er / Ec × 100) of the actually measured flexural modulus Er to the flexural modulus Ec of the composite calculated from the elastic modulus of the carbon fiber assuming the additivity was calculated. The results are shown in Table 1.

Further, as comparative examples, among the components [A], a system containing less than 50 parts by weight of a glycidylamine type epoxy resin, a system containing less [B] component, a system containing more [B] component, a system containing less [C] component,
With respect to the system containing little [D] component and the system containing no [E] component, prepregs were produced and molded under the same conditions as in the examples, and the physical properties were measured. The results obtained are shown in Table 2.

From the above results, it was revealed that Examples 1 to 6 can be cured at a relatively low temperature and have excellent composite performance as compared with Comparative Examples.

Example 7 The components [A] and [B], which are the main components, were weighed and placed in a beaker so that the types and blending ratios shown in Table 1 were obtained. This was heated with stirring at 130 ° C. for 1 hour to obtain a uniform resin mixture. Next, add 10 parts by weight of the component [E],
Preliminary reaction was performed at 120 ° C for 120 minutes. Next, in the roll mill mixing, 10 parts by weight of the components [C], [D] and [E] having the compounding ratios shown in Table 1 were added and mixed at 80 ° C. for 30 minutes to obtain a resin composition for prepreg. The gel time at 130 ° C. and the viscosity at 80 ° C. of the composition were measured.

After that, a prepreg was made in the same manner as in Examples 1 to 6. Molded plates were prepared in the same manner as in Examples 1 to 6 and their composite characteristics were measured. As shown in Table 1, these were composites having excellent mechanical properties.

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Claims (2)

[Claims] 1. An epoxy resin composition containing the following [A] to [E], having a melt viscosity at 80 ° C. of 100 to 10,000 poise, and curable at 90 to 130 ° C. [A] 100 parts by weight of an epoxy resin containing at least 50 parts by weight or more of a glycidyl amine type epoxy resin [B] at least 1 selected from polyamide, polysulfone, polyether sulfone and polyether imide
Thermoplastic resin of 10 to 30 parts by weight [C] Dicyandiamide 2 to 10 parts by weight [D] Urea compound represented by the following formula 2 to 5 parts by weight (However, X and Y are the same or different and are H, Cl, OCH ₃
Represents ) [E] Diaminodiphenyl sulfone 15 to 30 parts by weight 2. A prepreg obtained by impregnating carbon fiber with the epoxy resin composition according to claim 1.