JP2000297141A - Epoxy resin composition for prepreg and prepreg - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-viscosity epoxy resin composition which show an excellent impregnating ability and yields a prepreg showing an excellent handleability, shelf stability and curability at low temperatures of 100 deg.C or below, and a prepreg which shows an excellent handleability, shelf stability and curability at low temperatures of 100 deg.C or below. SOLUTION: This epoxy resin composition for prepregs mainly comprises an epoxy resin and a hardener, wherein the hardener is a non-initiating, latent reactive hardener. The epoxy resin composition has a viscosity at 50 deg.C of 5 Pa.sec or smaller. A prepreg is prepared by impregnating a reinforcement with the epoxy resin composition for prepregs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a matrix resin used for a prepreg as an intermediate base material of a fiber-reinforced resin composite material, and a prepreg.

[0002]

2. Description of the Related Art Fiber reinforced composite materials (hereinafter referred to as FRP)
Is widely used from sports and leisure to aircraft. The prepreg, which is an intermediate substrate used in molding the FRP, is obtained by impregnating a reinforcing fiber aggregate with a thermosetting matrix resin mainly. FRP
Is performed by laminating the prepregs, heating and pressing. The performance required of this prepreg, of course, is that it has excellent mechanical properties after curing, but it also has excellent storage stability at room temperature, can be quickly shaped at the molding temperature, and has excellent handleability. ,
In other words, appropriate tack (stickiness) and drape (flexibility)
Is also a large required performance.

[0003] From the above requirements, thermosetting resins, particularly epoxy resin compositions, are most preferably used as the matrix resin used for the prepreg. As a method for producing a prepreg using the epoxy resin composition as a matrix resin, a hot melt method can be exemplified. With the hot melt method, an epoxy resin composition containing a curing agent is heated and melted at a temperature at which the curing reaction starts but is not completed, and is applied thinly and uniformly to a support such as a release process paper. This is a method in which the epoxy resin composition is laminated on a reinforcing fiber assembly and further heated at a temperature at which a curing reaction starts but is not completed to reduce the viscosity of the epoxy resin composition, and the epoxy resin composition is impregnated into the reinforcing fiber assembly.

As described above, prepregs are required to have appropriate tack and drape properties, and therefore, besides having excellent curability and physical properties after curing, matrix resins have a somewhat limited viscosity level. Required. That is,
If the viscosity of the matrix resin is too low, the tack becomes too tight and the prepreg becomes very difficult to handle. Conversely, if the viscosity of the matrix resin is too high, when applying the resin to the release process paper in the hot melt method, the coating speed must be considerably slowed down, or the basis weight of the coated resin may be reduced. It becomes uneven. Furthermore, the impregnation of the reinforcing fiber aggregate becomes insufficient, which adversely affects physical properties and appearance after curing.

[0005] In particular, in the case of a prepreg that cures at 100 ° C or lower, it is not possible to apply too high heat during the coating or impregnating step. This is because when heated at a high temperature, the matrix resin is cured, and the obtained prepreg loses appropriate tack and drape properties. The viscosity of the matrix resin cannot be lowered so as to sacrifice the handleability of the prepreg. Therefore, a relatively high-viscosity matrix resin is used for the production of prepreg.
Therefore, the current situation is that the productivity is inferior to the production of a normal type prepreg that cures at 120 to 130 ° C.

A so-called excellent latent curing agent is used in an epoxy resin composition for a prepreg which can be cured at a temperature of 100 ° C. or less and in a short time and can maintain stability at room temperature for a long period of time. Examples of such an epoxy resin composition include, for example, JP-A-4-31420, JP-A-4-31421, and JP-A-4-3255.
No. 18, JP-A-5-9262, JP-A-5-9
263 and JP-A-5-310892. However, the latent curing agents used in these epoxy resin compositions all have a detonating effect, and once the reaction starts, the high reactivity is maintained even when the temperature is returned to around room temperature. There is. Therefore, the application and impregnation steps of the epoxy resin composition must be performed at a temperature at which the latent curing agent does not start the curing reaction. Also, considering the handling properties of the prepreg at room temperature, the viscosity of the epoxy resin composition cannot be reduced so much. Therefore, the epoxy resin composition must be used for producing a prepreg with a high viscosity.

[0007] Japanese Patent Application Laid-Open No. 61-44919 and
JP-A-113020 discloses an epoxy resin composition using a sulfonium salt as a catalyst. However, this epoxy resin composition is basically of an amine curing type, and although its excellent latent curability is disclosed, its curing temperature is as high as 150 ° C. or higher.

[0008] JP-A-6-228283 discloses an epoxy resin composition using a sulfonium salt as a curing agent and an amine compound as a stabilizer. However, the curing temperature of this epoxy resin composition is still as high as 130 ° C. or higher.

[0009]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an epoxy resin composition having a low viscosity and excellent impregnation properties, and furthermore, handleability, storage stability and curability at a low temperature of 100 ° C. or lower. Provided is an epoxy resin composition for producing a prepreg excellent in prepreg, and a prepreg obtained by impregnating a reinforcing material with the epoxy resin composition, which is easy to handle, has storage stability, and has a low temperature of 100 ° C or less. To provide a prepreg having excellent curability.

[0010]

Means for Solving the Problems In order to solve the above problems, the epoxy resin composition for prepreg and the prepreg of the present invention have the following constitutions. That is, the epoxy resin composition for prepreg of the present invention is an epoxy resin composition containing an epoxy resin and a curing agent as main components, wherein the curing agent is a latent reaction type curing agent having no detonating effect,
The viscosity of the epoxy resin composition at 0 ° C. is 5 Pa · se
c or less.

Further, the epoxy resin composition for prepreg of the present invention preferably has a viscosity at 25 ° C. of 10 Pa · sec or less. Preferably, the curing agent is an onium salt-based curing agent. Further, the curing agent is preferably an onium salt-based curing agent containing as a main component at least one onium salt selected from the group consisting of a sulfonium salt, an ammonium salt and a phosphonium salt. The onium salt has the following general formula (1)
Is preferably a sulfonium salt represented by (Wherein, R ₁ , R ₂ and R ₃ each independently represent an alkyl group or an aryl group, and X ⁻ represents SbF ₆ ⁻ , AsF
₆ ^- or PF ₆ ^- it is. )

[0012]

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Further, the onium salt is preferably a sulfonium salt represented by the following general formula (2). (In the formula, R ₁ and R ₄ each independently represent an alkyl group or an aryl group, and S ⁺ and R ₄ form a heterocyclic structure. X ⁻ represents SbF ₆ ⁻ , AsF _6.
^- or PF ₆ ^- is. )

[0014]

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The prepreg of the present invention is characterized in that a reinforcing material is impregnated with the epoxy resin composition for prepreg. Further, in the prepreg of the present invention, it is preferable to increase the viscosity of the epoxy resin composition by a heat treatment. In addition, the prepreg of the present invention has a viscosity of 50 Pa · sec.
It is preferable that it is above.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The epoxy resin used in the present invention is not particularly limited, and any epoxy resin such as bisphenol A type, bisphenol F type, bisphenol S type, phenol novolak type, cresol novolak type, alicyclic type, etc. Can also be used. However, in the epoxy resin composition for prepreg of the present invention, since the curing reaction proceeds by cationic polymerization, an epoxy resin that captures active cationic species and causes reaction inhibition is not preferable.

The epoxy resin composition for prepreg of the present invention must have a viscosity at 50 ° C. of 5 Pa · sec or less in order to have good impregnation. The epoxy resin composition for prepreg of the present invention, when using, for example, an alicyclic epoxy resin as the epoxy resin, 60
The curing reaction starts at around ° C. Therefore, the impregnation temperature is preferably 50 ° C. or less. Further, in order to have good impregnation, the viscosity must be 5 Pa · sec or less. Therefore, the viscosity of the epoxy resin composition for prepreg of the present invention must be 5 Pa · sec or less at 50 ° C., and preferably 10 Pa · sec or less at 25 ° C.

In the present invention, the viscosity is measured by the following apparatus and conditions. Apparatus: DSR-200 manufactured by Rheometrics or equivalent Condition: Parallel plate (25 mm diameter) Strain rate 10 rad / sec Temperature 50 ° C

The curing agent used in the present invention must be a latent reaction type curing agent having no detonating effect. The detonation effect means that once the epoxy resin composition using the curing agent is heated to the temperature at which the reaction starts, the latent reactivity is impaired, and the stability before heating is obtained even if the temperature is lowered again to around room temperature. There is no action.

The curing agent used in the present invention is not particularly limited, but an onium salt-based curing agent can be suitably used because it has an excellent balance between curing characteristics at 100 ° C. or lower and stability at room temperature. . Specifically, antimony pentachloride-acetyl chloride complex, diaryliodonium salt, alkoxysilane compound, boron halide-tertiary amine adduct, benzylsulfonium salt, benzylammonium salt, pyridinium salt, benzylsulfonium salt, hydrazinium salt, etc. Can be exemplified.

As the curing agent used in the present invention, an onium salt-based curing agent containing at least one of sulfonium salts, ammonium salts and phosphonium salts as a main component can be used at 100 ° C. or lower. It is further preferable in terms of the balance between the curing characteristics and the stability at room temperature.

The curing agent used in the present invention is a sulfonium salt represented by the following general formula (1):
It is more preferable in view of the balance between the curing characteristics at 0 ° C. or lower and the stability at room temperature. (Wherein R ₁ , R ₂ and R ₃ are
Each represents an independent alkyl or aryl group,
X ^- is SbF ₆ ^-, AsF ₆ ^- or PF ₆ ^- is. )

[0023]

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The curing agent used in the present invention is a sulfonium salt represented by the following general formula (2), in terms of balance between curing characteristics at 100 ° C. or lower and stability at room temperature. More preferred. (Wherein R ₁ and R ₄
Represents an independent alkyl group or an aryl group, and S ⁺ and R ₄ form a heterocyclic structure. Further, X ^- is SbF ₆ ^-, AsF ₆ ^- or PF ₆ ^- is. Commercially available as such a curing agent is San-Aid SI manufactured by Sanshin Chemical Industry Co., Ltd.

[0025]

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A prepreg obtained by impregnating a reinforcing material with the prepreg epoxy resin composition of the present invention is also provided by the present invention. The prepreg obtained by increasing the viscosity of the epoxy resin composition impregnated in the prepreg of the present invention is more preferable because of excellent handleability. There is no particular limitation on the level of thickening, but if the thickening is not enough, the tack becomes too strong to handle. The viscosity of the epoxy resin composition after thickening is 50 Pa ·
sec or more is preferable, and 100 Pa · sec or more is more preferable because of excellent handling. Here, it is preferable to increase the viscosity by heating, but in the case of reacting with light or the like, the viscosity may be increased by irradiation with light or other electromagnetic waves.

The reinforcing material used in the present invention is not particularly limited. Examples of the material include carbon fiber,
Fibers such as glass fiber, organic fiber (polyaramid fiber, polyethylene fiber, etc.), boron fiber, steel fiber and the like can be mentioned. Also, the form is not particularly limited,
One tow, which is a unit of thousands to tens of thousands of filaments, or a so-called tow prepreg in which several tows are combined, such as a unidirectional tape prepreg in which tows are arranged in one direction and aligned. Or a cloth material such as plain weave, twill weave, satin weave or multiaxial three-dimensional fabric.

The method for preparing the prepreg of the present invention is not particularly limited. However, since the epoxy resin composition of the present invention has a very low viscosity, it is not necessary to use a conventional hot melt method or a lacquer method. For example, the epoxy resin composition of the present invention is directly impregnated into a reinforcing material by a dipping method, excess epoxy resin composition is squeezed out, adjusted to a desired RC (resin content), and heat-treated to prepare a prepreg of the present invention. An example of the method is as follows. According to this method, there is no need for a step of applying the epoxy resin composition to the release step paper unlike the hot melt method. Therefore, since the release process paper is not necessarily required, it is advantageous in terms of process and cost. Further, since the impregnating property of the epoxy resin composition is greatly improved, the line speed can be increased. In addition, since a solvent is not used unlike the lacquer method, it is also effective in environmental health.

Since the epoxy resin composition for prepreg of the present invention has a low viscosity, it is very excellent in impregnating properties and improvement in productivity can be expected. Further, since the prepreg of the present invention uses an epoxy resin composition containing a latent reaction type curing agent having no detonating effect, it has a storage stability near room temperature and a storage stability of 1%.
Not only does it have curability at a relatively low temperature of 00 ° C. or less, but even if the epoxy resin composition is thickened by heat treatment, the reaction rate is significantly reduced by lowering the temperature to around room temperature, Handleability is maintained for a long time.

[0030]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples, but it should be understood that the present invention is not limited to these Examples. Examples 1 to 8 and Comparative Examples 1 to 4 are summarized in Tables 1 and 2. The description of the abbreviations used in Table 1 and Table 2, other supplementary explanations, and details of the evaluation method are as follows.

Ep828: Liquid Bisphenol A epoxy resin “Epicoat 828” manufactured by Yuka Shell Co. Ep1001: Semisolid bisphenol A epoxy resin “Epicoat 1001” manufactured by Yuka Shell Ep152: Phenol novolak manufactured by Yuka Shell Epoxy 152 Epoxy: Epoxy Shell, Epoxy 807 liquid bisphenol F epoxy resin CY179: Ciba Geigy, alicyclic epoxy resin SI-60L: Sanshin Chemical Industries, Epoxy resin cured SunAid HX3722: Asahi Ciba, epoxy resin curing agent NOVACURE DETA: diethylenetriamine

Viscosity at 50 ° C. [Poise] The viscosity at 50 ° C. and 25 ° C. of the epoxy resin composition before impregnating the reinforcing material was measured by the above-described viscosity measurement method. The unit is Pa · sec. PP heat treatment time [min] Immediately after the epoxy resin was impregnated with the reinforcing material, it was placed in a dryer at 80 ° C and heat treated. Table 1 shows the time (unit: minutes) in the dryer at this time. 50 ° C. viscosity [Pa · sec] after thickening The epoxy resin composition before impregnating the reinforcing material is referred to as “PP
The viscosity was measured at 50 ° C. according to the above-mentioned viscosity measurement method. Unit is Pa · se
c.

PP handleability The handleability (tack) of the prepreg was 25 ° C and 35 ° C.
Evaluation was made by touch in an environment of ° C. ○ indicates that it is easy to handle at an appropriate tack level, △ indicates that the tack is at a manageable level but the tack is slightly strong, and x indicates that the tack is too strong and very difficult to handle. PP impregnating ability The prepreg was torn and examined for the presence of dry fibers. ○ indicates complete impregnation without any dry fiber, △ indicates that a little like dry fiber is observed, and X indicates that dry fiber is clearly observed and impregnation is insufficient. Curability A state of curing when 10 plies of prepreg were laminated in one direction and cured in a 90 ° C. press for 1 hour was shown. ○
Indicates that the composition was cured, and x indicates that the composition was not cured. The cured product was subjected to the cross-sectional observation described later and a 90-degree tensile test.

PP Life The life of the prepreg at 25 ° C. was evaluated by touch. 2
The prepreg was left in a room at 5 ° C. in a state where light was blocked, and the tack and drape of the prepreg were evaluated in the same room. When the prepreg hardened and hardened, the life expired, and when the life did not expire even after 20 days from the start of the evaluation, it was evaluated as ○. For those whose lives have expired before the 20th, the number of days the lives have expired is noted. Cross section of PP cured product The cross section of the cured product in the curability test was observed in a direction substantially perpendicular to the fiber direction, and the voids in the layer and between layers were evaluated. If impregnation is insufficient, voids are seen in the layer. If the tack is too strong and a void is trapped during lamination, voids are seen between the layers.は indicates that no void is seen, △ indicates that a void may be seen depending on the observation place, and x indicates that a void is seen over almost the entire area. 90 degree tensile test For those cured by a curing test, JIS-K707
A tensile test was performed in accordance with No. 3. Table 1 shows n number 6
The average intensity of the points was noted. This value decreases when a large number of voids exist between the layers or within the layers.

Example 1 A latent reaction type curing agent having no detonating effect (Sun-Aid SI-60L manufactured by Sanshin Chemical Industry Co., Ltd.) was added to 100 parts by mass of a bisphenol A type epoxy resin (Epicoat 828 manufactured by Yuka Shell Co., Ltd.). Mix parts by mass,
An epoxy resin composition for prepreg of the present invention was obtained. The viscosity at 50 ° C. of the epoxy resin composition is 0.5 Pa ·
sec. The epoxy resin composition is impregnated at 50 ° C. with a reinforcing material prepared by aligning CF (carbon fiber) TR50S-12L manufactured by Mitsubishi Rayon Co., Ltd. on a sheet in one direction,
CF basis weight 150g / m ² , RC (resin content) 3
3% by weight of the prepreg of the present invention was obtained. Next, the prepreg of the present invention is subjected to a heat treatment at 80 ° C. × 50 minutes,
I got a prepreg. A series of evaluations were performed on the epoxy resin composition and the prepreg, and all the evaluation results are shown in Table 1.

Comparative Example 1 As a comparative example, an example using a curing agent that is not a latent reaction type will be described. DE as curing agent
A resin was prepared in the same manner as in Example 1 except that TA was used in the composition shown in Table 1. Each evaluation was performed for the obtained epoxy resin composition in the same manner as in Example 1, and the results are shown in Table 1. Since the curing agent used is not a latent reaction type, it thickens before applying the heat thickening treatment, and the life is ×
Met. Other evaluations could not be performed.

Comparative Example 2 As a comparative example, an example in which a latent curing agent having an initiating action is used instead of a latent reaction type curing agent having no initiating action is shown. Resin preparation and prepreg preparation were carried out in the same manner as in Example 1 except that NOVACURE HX3722 manufactured by Asahi Ciba was used in place of SI-60L as a curing agent. However, as shown in Table 1, the heat treatment time of the prepreg is determined while observing the tack condition.
80 ° C. × 40 minutes. Table 1 also shows the evaluation results.
As for the life, it was completely out of life after 3 days. HX3722 is a microcapsule-type heat-curing catalyst for epoxy resin, but has a detonating effect, and is characterized in that once heated, the reaction does not stop even after returning to room temperature. Therefore, the reaction of the epoxy resin composition was stopped halfway at room temperature, and the B stage (appropriate tack state) could not be maintained for a long time.

Example 2 A prepreg of the present invention was prepared in the same manner as in Example 1 except that the heat treatment of the prepreg after impregnation with the epoxy resin composition was performed at 80 ° C. for 40 minutes.
The prepreg was evaluated in the same manner as in Example 1. The results are shown in Table 1. It can be seen that the prepreg is excellent in the impregnation property of the epoxy resin composition and also excellent in handleability, storage stability and curability.

Example 3 A prepreg of the present invention was prepared in the same manner as in Example 1 except that the heat treatment of the prepreg after impregnation with the epoxy resin composition was performed at 80 ° C. for 30 minutes.
The prepreg was evaluated in the same manner as in Example 1. The results are shown in Table 1. The prepreg was excellent in impregnating property of the epoxy resin composition, and the handleability at 35 ° C. was a level that could handle even though the tackiness was somewhat strong, and the handleability at 25 ° C. was very excellent. In addition, storage stability and curability were excellent.

Example 4 An epoxy resin composition of the present invention having the composition shown in Table 1 was prepared. The epoxy resin composition was impregnated into a reinforcing material in the same manner as in Example 1 and heat-treated at 80 ° C. for 40 minutes as shown in Table 1 to obtain a prepreg of the present invention.
Table 1 also shows the evaluation results of the prepreg. It can be seen that the prepreg is excellent in the impregnation property of the epoxy resin composition and also excellent in handleability, storage stability and curability.

Example 5 An epoxy resin composition of the present invention having the composition shown in Table 2 was prepared. The epoxy resin composition was impregnated into a reinforcing material in the same manner as in Example 1 and heat-treated at 80 ° C. for 20 minutes as shown in Table 2 to obtain a prepreg of the present invention.
Table 2 also shows the evaluation results of the prepreg. It can be seen that the prepreg has excellent impregnation properties, and also has excellent handling properties, storage stability, and curability.

Comparative Example 3 As a comparative example, the case where the viscosity at 50 ° C. of the epoxy resin composition exceeded 50 poise was exemplified. An epoxy resin composition having the composition shown in Table 2 was prepared, and the epoxy resin composition was impregnated into a reinforcing material in the same manner as in Example 1 and heat-treated at 80 ° C. for 30 minutes as shown in Table 2 to obtain a prepreg. . Table 2 also shows the evaluation results of the prepreg.
Shown in Because of the high viscosity of the epoxy resin composition, the prepreg had poor impregnation, and some voids were observed between layers in the cured product. Also, because of the void, 9
The 0-degree tensile strength was also low.

Comparative Example 4 As a comparative example, the case where the tack of the prepreg was proper without increasing the viscosity of the epoxy resin composition was exemplified. That is, an epoxy resin composition having the composition shown in Table 2 was prepared. 50 of the epoxy resin composition
The viscosity at ℃ is 2500 poise, and the handleability as a prepreg is at a satisfactory level without increasing the viscosity after impregnation. The epoxy resin was impregnated into a reinforcing material in the same manner as in Example 1 to obtain a prepreg. As shown in Table 2, although the epoxy resin composition had an extremely high viscosity, the impregnation was very poor and the curability was good, but the molded product contained many voids in the layer, The tensile strength was considerably low.

Example 6 The compositions shown in Table 2 were uniformly mixed to obtain an epoxy resin composition for prepreg of the present invention.
The viscosity at 25 ° C. of the epoxy resin composition is 8.8P
a · sec. The epoxy resin composition is impregnated at 25 ° C. with a reinforcing material prepared by unidirectionally arranging CF (carbon fiber) TR50S-12L on a sheet in one direction at 25 ° C., and has a CF weight of 150 g / m ² and RC (resin content). 33% by weight of the prepreg of the present invention was obtained. Then
The prepreg of the present invention was subjected to a heat treatment at 80 ° C. for 30 minutes to obtain a prepreg. A series of resin evaluations were performed on the epoxy resin composition and the prepreg. The results are shown in Table 2. Excellent performance was shown in all evaluation items.

[Examples 7 and 8] An epoxy resin composition of the present invention and a prepreg having the compositions shown in Table 2 were prepared in the same manner as in Example 6. The epoxy resin composition and the prepreg were subjected to a series of evaluations, and the results are shown in Table 2. Good performance was obtained in all evaluations.

Example 9 An epoxy resin composition of the present invention having the same composition as in Example 1 was prepared, and the epoxy resin composition was manufactured by Mitsubishi Rayon Co., Ltd.
F. One tow of TR50S-12L was impregnated with 30 wt% of RC, and then heated at 80 ° C. for 50 minutes to obtain a prepreg in a tow form of the present invention. The tow-shaped prepreg was excellent in handleability, and was sufficiently cured at 90 ° C. × 1 hour when it was formed into a pipe by filament winding. When observing the cross section of the molded product,
No voids were observed in both layers. Further, the life was 25 days or more at 25 ° C., and the storage stability was excellent.

Example 10 An epoxy resin composition of the present invention having the same composition as in Example 1 was prepared, and impregnated with Mitsubishi Rayon Co., Ltd. CF cloth, TR3110M.
Heat treatment was performed at 50 ° C. for 50 minutes to obtain a cloth-shaped prepreg of the present invention. The cloth-shaped prepreg was also excellent in handleability, and was sufficiently cured at 90 ° C. for 1 hour when 10 plies were laminated and molded in the same manner as in Example 1. When the cross section of the molded product was observed, no void was observed in both the layers and between the layers. Further, the life was 25 days or more at 25 ° C., and the storage stability was excellent.

[0048]

[Table 1]

[0049]

[Table 2]

[0050]

As described above, the epoxy resin composition for prepreg of the present invention comprises an epoxy resin and a curing agent as main components, and the curing agent is a latent reaction type curing agent having no explosive action. Since the viscosity of the epoxy resin composition at 5 ° C. is 5 Pa · sec or less, a prepreg excellent in impregnation into a reinforcing material, and further excellent in handleability, storage stability, and curability at a low temperature of 100 ° C. or less is obtained. It becomes possible. When the viscosity at 25 ° C. of the epoxy resin composition for prepreg of the present invention is 10 Pa · sec or less, the impregnating property is excellent.

When an onium salt-based curing agent is used as the curing agent, the balance between the curing characteristics at 100 ° C. or lower and the stability at room temperature is excellent. When an onium salt-based curing agent containing at least one onium salt selected from the group consisting of a sulfonium salt, an ammonium salt and a phosphonium salt as the main component is used as the curing agent, the curing property at 100 ° C. or lower is used. Excellent balance between stability at room temperature.

Further, the latent reaction type hardening agent having no detonating action is used.
As the agent, a sulfonium represented by the following general formula (1)
When a salt is used, the curing characteristics at 100 ° C or lower and the room temperature
A better balance of stability. (Where R₁ , R_Two 
And R_Three Are independent alkyl groups or all
X represents a^- Is SbF₆ ^-, AsF₆ ^-Or PF ₆ ^-
It is. )

[0053]

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When a sulfonium salt represented by the following general formula (2) is used as the latent-reaction-type curing agent having no detonating effect, the balance between the curing characteristics at 100 ° C. or less and the stability at room temperature. Is even better. (In the formula, R ₁ and R ₄ each independently represent an alkyl group or an aryl group, and S ⁺ and R ₄ form a heterocyclic structure.
Further, X ^- is SbF ₆ ^-, AsF ₆ ^- or PF ₆ ^- is. )

[0055]

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Further, since the prepreg of the present invention is obtained by impregnating a reinforcing material with the epoxy resin composition for prepreg, it is excellent in handleability, excellent in curability at a low temperature of 100 ° C. or less, and furthermore, in room temperature. Storage stability is also good.
The prepreg obtained by increasing the viscosity of the epoxy resin composition impregnated in the prepreg of the present invention by heat treatment has excellent handleability, curability at a low temperature of 100 ° C. or lower, and good storage stability at room temperature. It is. In addition, 50 after thickening
The viscosity of the epoxy resin composition at 50 ° C. is 50 Pa · s
A prepreg having an ec or more is more excellent in handleability.

Claims (9)

[Claims] 1. An epoxy resin composition comprising an epoxy resin and a curing agent as main components, wherein the curing agent is a latent reaction type curing agent having no detonating action, and the viscosity of the epoxy resin composition at 50 ° C. 5Pa ・
An epoxy resin composition for prepreg, wherein the composition is not more than sec. 2. The viscosity at 25 ° C. is 10 Pa · sec.
The epoxy resin composition for prepreg according to claim 1, wherein c is equal to or less than c. 3. The epoxy resin composition for prepreg according to claim 1, wherein the curing agent is an onium salt-based curing agent. 4. An onium salt-based curing agent containing as a main component at least one onium salt selected from the group consisting of sulfonium salts, ammonium salts and phosphonium salts. 2. The epoxy resin composition for prepreg according to 1. 5. The epoxy resin composition for prepreg according to claim 4, wherein the onium salt is a sulfonium salt represented by the following general formula (1). Embedded image (Wherein, R ₁ , R ₂ and R ₃ each independently represent an alkyl group or an aryl group, and X ⁻ represents SbF ₆ ⁻ , A
sF ₆ ^- or PF ₆ ^- is. ) 6. The epoxy resin composition for prepreg according to claim 4, wherein the onium salt is a sulfonium salt represented by the following general formula (2). Embedded image (In the formula, R ₁ and R ₄ each independently represent an alkyl group or an aryl group, and S ⁺ and R ₄ form a heterocyclic structure. X ⁻ represents SbF ₆ ⁻ , AsF ₆ ⁻ or PF ₆ ^- a is). 7. A prepreg obtained by impregnating a reinforcing material with the epoxy resin composition for prepreg according to claim 1. 8. The prepreg according to claim 7, wherein the epoxy resin composition impregnated by heat treatment is thickened. 9. The prepreg according to claim 8, wherein the viscosity of the epoxy resin composition at 50 ° C. after the thickening is 50 Pa · sec or more.