JPH069802A - Prepreg - Google Patents

Abstract

PURPOSE:To obtain a prepreg for a fiber reinforced composite material excellent in storage stability at room temperature, capable of molding at relatively low temperature and excellent also in handling property. CONSTITUTION:In the prepreg for the fiber reinforced composite material consisting of (A) a reinforcing fiber having >=50GPa modulus and (B) an epoxy resin composition consisting of (1) 100 pts.wt. epoxy resin, (2) l-30 pts.wt. thermoplastic resin soluble in the epoxy resin and (3) 10-50 pts.wt. thermal curing type latent curing agent activated at nearly 80 deg.C, the objective prepreg is characterized in that the ratio of the component (A) to the component (B) is (40/60) to (75/25).

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention uses an epoxy resin composition that cures at a relatively low temperature as a matrix, has excellent storage stability at room temperature, can be molded at a relatively low temperature, and has excellent handleability. The present invention relates to a prepreg for a fiber reinforced composite material.

[0002]

BACKGROUND OF THE INVENTION Epoxy resins are suitable for use as matrix resins for fiber-reinforced composite materials because of their excellent mechanical properties and heat resistance after curing. They are used for structural materials such as aircraft, automobiles and ships, tennis rackets, Widely used for general-purpose sports such as fishing rods and golf club shafts.

The properties required of such a prepreg for a fiber-reinforced composite material using an epoxy resin as a matrix are not only excellent in mechanical properties of a molded product (component) after curing but also long-term stability at room temperature, Handleability [moderate tack (adhesiveness), drapeability (flexibility), etc.]
Is required, and the resin flow during molding is small. Further, there is an increasing demand for low temperature curing or short time curing in order to shorten the molding cycle and reduce the energy cost.

In response to such demands, inventions relating to prepregs which are excellent in storage stability at room temperature and which can be molded at a relatively low temperature, or epoxy resin compositions for prepregs have been reported. For example, Japanese Patent Application Laid-Open No. 61-40317 discloses an invention relating to the production of a prepreg by a hot melt method, but the condition is that the viscosity of the entire system is 500 to 50,000 poise, and the viscosity is mainly that of an epoxy resin. Adjusted by viscosity. That is, the usable epoxy resin is limited to some extent by the viscosity, and the molding temperature is 9
0 ° C or higher is required.

Japanese Patent Laid-Open No. 1-110526 discloses an invention of epoxy resin for prepreg, but there is no special control method for tackiness, drape property, or resin flow at the time of molding, and the curing temperature is 100 ° C. The above is necessary.

In other words, there was a demand for a low-temperature curing prepreg capable of controlling tack level and drape according to its specifications and stable in storage at room temperature. However, conventional techniques have been developed to satisfy all of them. Didn't.

[0007]

DISCLOSURE OF THE INVENTION The present invention has a stability of 20 days or more at room temperature, which is sufficient for practical use.
Cured at a temperature near ℃ until it has practically sufficient characteristics,
Further, it is an object of the present invention to provide a prepreg in which the resin flow during molding is suppressed and appropriate tack and drape control can be freely performed according to requirements.

[0008]

In order to achieve the above object, the present invention has the following constitution.

That is, the present invention comprises: (A) a reinforcing fiber having an elastic modulus of 50 GPa or more, and (B) an epoxy resin composition consisting of the following 1, 2 and 3: 1: epoxy resin 100 parts by weight 2: soluble in an epoxy resin Thermoplastic resin 1-30
Parts by weight 3: a heat-curable latent curing agent that is activated near 80 ° C. 10 to 50 parts by weight in a prepreg for a fiber-reinforced composite material,
The ratio (A) / (B) of (A) and (B) is 40 / 60-
It is a prepreg characterized by being 75/25.

The prepreg of the present invention is used at 80 ° C. for 1 hour,
Curing to a practically sufficient degree within 120 minutes at 120 to 140 ° C., and sufficient storage stability with a 25 ° C. prepreg life of 20 days or more.

The epoxy resin of component (B) -1 used in the present invention is not particularly limited, and is a bisphenol A type epoxy resin, a phenol novolac type epoxy resin, a cresol novolac type epoxy resin, or a glycidyl amine type epoxy resin. Is mentioned. Among these, it is preferable to use a bisphenol A type epoxy resin that is well balanced in terms of handleability, CFRP characteristics to be obtained, and economy. Also, of course, in order to have various properties, it is possible to mix and use several kinds of epoxy resins, and use a product obtained by reacting the epoxy resin with an amine compound or an acid anhydride within a range not gelling. Is also a more preferred embodiment of the present invention.

The thermoplastic resin which is soluble in epoxy as the component (B) -2 plays a role of controlling the handling property in the present invention. That is, by not affecting the curing characteristics so much, by adjusting the viscosity of the epoxy resin composition,
It is possible to suppress the flow and to impart appropriate tackiness and drape property when formed into a sheet. However, the addition amount is preferably 1 to 30 parts. 3 such additives
If added in an amount exceeding 0 part, the reactivity is lowered, and when it is cured at a low temperature, the curing becomes insufficient, and it is very difficult to obtain a molded product having mechanical strength and the like, and it is expected to be less than 1 part. The effect of adjusting viscosity is not obtained.

Examples of the thermoplastic resin which can be dissolved in the epoxy resin as the component (B) -2 include polyvinyl butyral, polyvinyl formal, polyether sulfone, polysulfone, polyarylate, and the like, but of course are not limited thereto. However, among these, polyvinyl butyral, polyvinyl formal, and polyether sulfone are highly effective and particularly desirable.

Examples of the thermosetting latent curing agent which is activated at about 80 ° C. of the component (B) -3 include amine adduct type curing agents (commercially available from Ajinomoto Co., Inc. under the trademark "Amicure"). There are microcapsule type curing agents (commercially available from Asahi Kasei Kogyo Co., Ltd. under the trademark "Nova Cure"),
Even if these curing agents are mixed with the epoxy resin, they are at room temperature to 5%.
It is relatively stable near 0 ° C and hardly reacts, but 80
It is a so-called thermosetting latent curing agent that activates and starts the reaction at around ℃. The amount of the latent curing agent added is suitably 10 to 50 parts, and if it is less than 10 parts, the curing will be insufficient, and if added in excess of 50 parts, the physical properties will be extremely lowered and the room temperature stability will be lowered. It is not preferable.

There are no particular restrictions on the method for preparing the epoxy resin of the component (B) used in the prepreg of the present invention, but since the component (B) -3 is activated at a relatively low temperature and the reaction begins,
It is not advisable to mix them all at once. The reason is that the thermoplastic resin of the component (B) -2 is generally the component (B)-
It is difficult to dissolve in the epoxy resin of No. 1 and must be dissolved at a high temperature for a long time with stirring or by adding a solvent, which causes a decrease in storage stability due to heat history and a component (B)-
This is because the influence of 3 itself can be considered. Therefore, it is preferable that the component (B) -2 is first uniformly dissolved in the component (B) -1. At that time, when it is heated, it is sufficiently cooled before adding the component (B) -3, and when a solvent is added, it is completely desolvated.

Elastic modulus of component (A) used in the present invention is 50 G
As the reinforcing fiber having Pa or more, carbon fiber which is excellent in mechanical strength of the molded product is preferably used, but it is not limited to this, and glass fiber, boron fiber, aramid fiber and the like are also used. Further, since the matrix resin used in the present invention can be cured at a relatively low temperature,
As the reinforcing fiber, it is possible to use a low-melting organic fiber which could not be used because of its heat resistance. Among them, the polyethylene fiber having a high elasticity and a high strength can be used for the mechanical properties of the molded component after molding. Since it is excellent, it is preferably used. However, since polyethylene fibers have poor adhesion to the matrix, surface treatment is required before impregnation.

The application of the prepreg according to the present invention is not particularly limited, and it can be used anywhere as long as the characteristics of the prepreg can be utilized. However, since it can be molded at a particularly low temperature, for example, urethane or acrylic heat-resistant materials can be used. It is suitable for integral molding with a foam having low properties, integral molding with a material having a relatively high moisture content such as wood, or molding with a resin mold.

[0018]

The present invention will be described in more detail with reference to the following examples.

The abbreviations of the compounds in the examples and the test methods are as follows.

Ep828: Bisphenol A type epoxy resin (made by Yuka Shell Co., Ltd.) PVF: Polyvinyl Formal Denka Formal #
200 (manufactured by Denka) PVB: Polyvinyl butyral Denka butyral # 4
000-1 (manufactured by Denka Corporation) PES: VICTREX PES 5003P (ICI
MY-24: Amine adduct type latent hardener Amicure (manufactured by Ajinomoto Co.) PN-23: 〃 HX-37211: Microcapsule type latent hardener Novacure (manufactured by Asahi Kasei) <Bending test (3-point bending) > Device: Orientec Tensilon Sample shape: length 120 mm, width 10 mm, thickness 2 mm Span length: 80 mm Indenter tip radius: 3.2 mm CROSS HEAD SPEED: 1 mm / min Physical properties were calculated by the following formulas.

FS (flexural strength) = 3 PL / 2 wt ² (kg
/ Mm ² ) FM (flexural modulus) = P'L ³ / 4wt ³ a (kg / m
m ² ) However, P: Maximum load (kg) L: Span length (mm) w: Sample width (mm) t: Sample thickness (mm) a: Initial deflection (crosshead displacement) (mm) P ': at a Load (kg) <ILSS (interlaminar shear strength)> Sample shape: length 15 mm, width 5 mm, thickness 2 mm Span length: 8 mm Indenter tip radius: 1.6 mm Other conditions are the same as the bending test, and the physical properties are as follows. It was calculated by the formula.

ILSS = 3P / 4 wt (kg / mm ² ) <Example 1> In the composition shown in Table 1, first, Ep828 of component (B) -1 and PVF of component (B) -2 were heated at 160 ° C. for 3 hours. And then cooled to room temperature and then at room temperature, the component (B) -3
MY-24 was added and mixed uniformly. The resin composition thus obtained and high-strength medium-elastic carbon fiber (manufactured by Mitsubishi Rayon Co.,
A unidirectional prepreg was produced from the MR60P and the elastic modulus of 310 GPa) by the hot melt method to obtain the prepreg of the present invention. CF basis weight of prepreg is 190 g / m ² , V
_f (reinforcing fiber volume fraction) was 60%. This prepreg was laminated in one direction to a thickness of about 2 mm and molded by an autoclave. Bending of the obtained unidirectional component at 0 ° and 90 °,
An ILSS test was performed and the results are shown together in Table 1.
The tack and drape of the prepreg immediately after production were very good, and there was almost no resin flow during molding. The tack and drape of the prepreg after 20 days were compared with those of the initial one, but there was almost no change.

<Examples 2 and 3> PVF of component (B) -2
Resin was prepared in the same manner as in Example 1 except that the amount was changed as shown in Table 1, prepreg was formed in the same manner, and molding was carried out for evaluation.
The results are also shown in Table 1.

<Example 4> PVF of component (B) -2 was added to P
Same as Example 1 except that VB is changed, and the preparation method is also the same as the above, except that the component (B) -2 is first added to the component (B) -1 at 160 ° C.
Dissolve in 3 hours, cool to room temperature and then at room temperature component (B)
-3 was added and uniformly mixed. The obtained resin composition was prepregized, molded and evaluated in the same manner as in Example 1.
The results are also shown in Table 1.

<Example 5> PVF of component (B) -2 was added to P
Except for changing to ES5 part, the same procedure as in Example 1 was repeated, and the component (B) -2 was first converted into the component (B) -1 in the same manner as in the preparation method.
The mixture was melted at 3 ° C. for 3 hours, cooled to room temperature, then added with the component (B) -3 at room temperature and mixed uniformly. The obtained resin composition was prepregized, molded and evaluated in the same manner as in Example 1. The results are also shown in Table 1.

<Examples 6 and 7> The procedure of Example 1 was repeated except that the component (B) -3 was changed as shown in Table 1, and the preparation method was also the same as that of the component (B) -2. -1 to 160 ° C,
Dissolve in 3 hours, cool to room temperature and then at room temperature component (B)
-3 was added and uniformly mixed. The obtained resin composition was prepregized, molded and evaluated in the same manner as in Example 1.
The results are also shown in Table 1.

<Comparative Example 1> The procedure of Example 1 was repeated except that the component (B) -2 was not used.
1, the component (B) -3 were uniformly mixed. The obtained resin composition was prepregized, molded and evaluated in the same manner as in Example 1. The results are also shown in Table 1. Compared to Example 1, the component characteristics were comparable, but the prepreg had too much tack (large stickiness) and the resin flow during molding was considerably large.

<Comparative Example 2> A resin was prepared in the same manner as in Example 1 except that the component (B) -3 was changed as shown in Table 1, and the same test was conducted. The results are also shown in Table 1. The physical properties of the cured product were extremely lower than those of Example 1.

Comparative Example 3 A resin was prepared in the same manner as in Example 1 except that the component (B) -3 was changed as shown in Table 1, and the same test was conducted. The results are also shown in Table 1. The strength at 90 ° was extremely low as compared with Example 1, and the prepreg after 20 days was hard without tack and had a short life.

As is clear from Table 1, the prepreg of the present invention exhibits excellent physical properties when cured at low temperatures, has excellent stability at room temperature, has no resin flow during molding, and has suitable tack and drape properties. .

<Examples 8 to 10> The same prepreg as in Example 1 was used and cured under the curing conditions shown in Table 2, and the cured products obtained were evaluated. The results are shown together in Table 2. As is clear from Table 2, the epoxy resin composition used in the present invention was sufficiently cured at 80 ° C. × 1 hr,
It can be seen that at 20 to 140 ° C., it is sufficiently cured in 20 minutes or less.

<Example 11> High strength as component (A),
The same procedure as in Example 1 was carried out except that high-elasticity polyethylene fiber (Mitsui Petrochemical Co., Ltd., Techmilon: elastic modulus 80 GPa) was used. However, the polyethylene fiber was surface-treated with nitric acid before resin impregnation. The fiber weight of the obtained prepreg was 100 g / mm ² , and V _f was 60%. This prepreg was laminated, molded and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

EFFECT OF THE INVENTION The prepreg of the present invention is cured at a low temperature of about 80 ° C. for 1 hour to a practically sufficient degree, and further 120
At a temperature of 140 ° C, it cures in a short time of 20 minutes or less. Moreover, it has a life of 20 days or more at room temperature, has a small resin flow at the time of molding, and can freely control tack and drape according to requirements, and is extremely excellent in terms of production, economy, or work environment. It is a thing.
Therefore, it is expected to be used in fields that have not been used so far due to problems of curing conditions, room temperature stability, or working environment.

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B29K 105: 08 C08L 63:00 8830-4J

Claims (8)

[Claims] 1. An epoxy resin composition comprising (A) a reinforcing fiber having an elastic modulus of 50 GPa or more and (B) the following 1, 2, and 3: 1: epoxy resin 100 parts by weight 2: a thermoplastic resin soluble in an epoxy resin 1-30
Parts by weight 3: a heat-curable latent curing agent that is activated near 80 ° C. 10 to 50 parts by weight in a prepreg for a fiber-reinforced composite material,
The ratio (A) / (B) of (A) and (B) is 40 / 60-
A prepreg characterized by being 75/25. 2. The prepreg according to claim 1, wherein the thermoplastic resin as the component (B) -2 is polyvinyl formal. 3. The prepreg according to claim 1, wherein the thermoplastic resin of the component B-2 is polyvinyl butyral. 4. The prepreg according to claim 1, wherein the thermoplastic resin of the component B-2 is polyether sulfone. 5. The prepreg according to claim 1, wherein the latent curing agent as the component B-3 is an amine adduct type latent curing agent. 6. The prepreg according to claim 1, wherein the latent curing agent as the component B-3 is a microcapsule type latent curing agent. 7. The prepreg according to claim 1, wherein the reinforcing fiber of the component (A) is a carbon fiber. 8. The prepreg according to claim 1, wherein the reinforcing fiber of the component (A) is a high strength and high elasticity polyethylene fiber.