JP2002020457A - Epoxy resin composition and prepreg therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an epoxy resin composition which has good stability at a room temperature, good reactivity at a low temperature and excellent properties for preparing a cured product while the composition needs no increased amount of a curing agent to add; and a prepreg which is excellent in stability at a room temperature, reactivity at a low temperature and properties for preparing a cured product, has moderate tack and drape, and is good in workability. SOLUTION: The epoxy resin composition comprises an epoxy resin and a curing agent for curing the epoxy resin, wherein the epoxy resin contains an epoxy resin compound having a molecular weight of 500 and less at 50% by mass and more; and the composition has a viscosity of 5 Pa.sec or more and 5000 Pa.sec or less at 60 deg.C. The prepreg is prepared by impregnating the composition in a reinforcing material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin composition used as a matrix resin of a prepreg, which is an intermediate substrate of a fiber-reinforced resin composite material, and a prepreg using the same.

[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 base material of the FRP, is obtained by impregnating a reinforcing fiber aggregate with a thermosetting matrix resin mainly. When the FRP is molded, the prepregs are laminated, heated and pressed.

[0003] The performance required of this prepreg is, of course, excellent in mechanical properties after curing, but it is also excellent in handleability, that is, appropriate tack (adhesiveness) and drape (flexibility). Is to have.
Further, it is required that the composition has excellent storage stability at room temperature and can be rapidly shaped at a molding temperature. Further, recently, there has been a demand for lowering the molding temperature due to demands for shortening the molding cycle and reducing the energy cost which leads to preservation of the global environment.

[0004] Ordinary prepregs are molded at around 120 ° C, but a number of prepregs that can be molded at 100 ° C or less have been invented in response to the above requirements. Recently, many techniques have been disclosed in JP-A-7-70410, JP-A-7-196679, and the like. In each of these techniques, a latent reaction type curing agent which has excellent stability at room temperature and reacts at a relatively low temperature of 100 ° C. or less is used. In other words, in the case of a low-temperature curing prepreg having a molding temperature of 100 ° C. or lower, in order to combine the contradictory properties of room-temperature storage stability and low-temperature reaction characteristics, it is essential to use a latent reaction-type curing agent, a so-called latent curing agent. is there.

A typical example of such a latent curing agent is Amicour PN-23 of Ajinomoto Co., Inc., and NOVACURE HX3721 and HX372 of Asahi Kasei Corporation.
2. Fujicure FXE-1000 of Fuji Chemical Industry Co., Ltd.
And so on. According to the catalog and technical data of the latent curing agent, it is specified that the resin composition comprising the liquid bisphenol A epoxy resin and each latent curing agent can be cured at 80 ° C. However, when these resin compositions are cured at 80 ° C., it is necessary to add about 10 to 30 parts by mass of a latent curing agent to 100 parts by mass of the epoxy resin.

For example, in all of the above-mentioned prior art examples, 20 parts or more of a latent curing agent is used. That is, in the above-mentioned prior art, the handleability required for the prepreg and various characteristics required for the cured product are imposed on the epoxy resin, and the low-temperature curing characteristics are imposed on the latent curing agent. As the amount of the latent curing agent added increases, the reaction rate increases, and curing can be performed at 100 ° C. or less, for example, even at 80 ° C.

[0007]

However, these latent curing agents are all expensive, and the curability at a low temperature is improved by increasing the amount of the latent curing agent, but the cost of the resin composition and the prepreg is increased. , It has been used only for special purposes. In addition, most latent curing agents act as catalysts for ring-opening polymerization of epoxy resins. As the amount of added latent curing agent increases, the overall reaction speed increases, but the number of starting species becomes too large and overall There is a problem in that the physical properties of the cured product are adversely affected, such as adversely affecting the crosslinked structure of the cured product and making the cured product brittle. That is, by means of increasing the amount of the latent curing agent to improve the low-temperature curability, a resin suitable for use as the matrix resin of the composite material could not be obtained.

An object of the present invention is to provide an epoxy resin composition which can be cured at a low temperature without increasing the amount of a curing agent in the epoxy resin composition. It is an object. That is, an object of the present invention is to provide an epoxy resin composition having room temperature stability and low-temperature reactivity, and having excellent cured physical properties. It is still another object of the present invention to provide a prepreg which is not only excellent in room temperature stability, low-temperature reactivity and cured physical properties but also has good tack and drape and good handleability.

[0009]

The epoxy resin composition of the present invention is an epoxy resin composition containing an epoxy resin and a curing agent for curing the epoxy resin, wherein the epoxy resin has a molecular weight of 500 or less in the epoxy resin. The epoxy resin composition has a viscosity at 60 ° C. of 5 Pa · sec or more and 5000 mass% or more.
Pa · sec or less was taken as the solution. In addition, a solution is that a curing agent that cures an epoxy resin at 100 ° C. or lower is a latent curing agent. Further, the addition amount of the curing agent is preferably 5 parts by mass or less, particularly preferably 3 parts by mass or less based on 100 parts by mass of the epoxy resin, and the content of the low-molecular-weight epoxy resin in the epoxy resin is 60% by mass or more. Is preferred. The prepreg of the present invention is characterized in that a reinforcing material is impregnated with the epoxy resin composition.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. There is no particular limitation on the epoxy resin used in the present invention, and bisphenol A type, bisphenol F type,
Bisphenol type epoxy resin such as bisphenol S type, novolak type epoxy resin such as phenol novolak type and cresol novolak type, trifunctional epoxy resin such as aminophenol type and aminocresol type, and tetrafunctional epoxy resin such as tetraglycidyl dimethyldiphenylmethane , Other polyfunctional epoxy resins are used,
A bisphenol-type epoxy resin is preferable from the balance of reactivity, storage stability, and physical properties of a cured product, and a bisphenol A-type epoxy resin is particularly preferable in consideration of cost.

The epoxy resin composition of the present invention has a molecular weight of 5
Epoxy compound molecules of less than or equal to 50
It must be contained by mass% or more. The curability of such an epoxy resin composition is significantly improved, and the curability is not impaired even when the amount of the curing agent added is reduced. Molecular weight 5
When the content of the epoxy compound molecule of 00 or less is less than 50% by mass of the total epoxy resin, it is necessary to increase the curing property by increasing the curing agent, which not only increases the cost of the epoxy resin composition, but also increases the curing obtained. The material becomes brittle and becomes unsuitable as a matrix for the composite material. When the content of the epoxy compound molecule having a molecular weight of 500 or less is increased, the curability is improved. Therefore, the content is preferably 60% by mass or more. This is because the balance of the molecular weight of the epoxy compound molecules in the resin composition greatly contributes to the reactivity of the resin composition, and this characteristic is more remarkable in the case of curing at a low temperature of 100 ° C. or lower. It is. Here, as the molecular weight in the present invention, a number average molecular weight calculated in terms of polystyrene using gel permeation chromatography (GPC) is adopted. In addition, molecular weight 500
The mass ratio (% by mass) of the following epoxy compound molecules to the total epoxy resin is determined from the ratio of components having a number average molecular weight of 500 or less in terms of polystyrene by GPC.

The epoxy resin composition of the present invention has a viscosity at 60 ° C. of 5 Pa.s. more than 5000sec
c or less. If it is lower than 5 Pa · sec, the tack becomes too tight, which is not preferable. 500
If it exceeds 0 Pa · sec, the drape of the prepreg becomes considerably hard or impregnation is impaired. Tack is good at 50 Pa · sec or more, and 50
0 Pa · sec or less is more preferable because drape property and impregnation property of the prepreg become good.

Here, the viscosity in the present invention is a viscosity measured by the following method. Rheometrics DSR-200 or equivalent was used as the device, and the mode was:
Temp. Ramp, heating rate 2 ° C / min, shear rate 1
Under the condition of 0 radians / second, two disk plates having a diameter of 25 mm were used, and the disk plate interval was 0.5 mm.
Measure the viscosity of the resin composition at 50 to 70 ° C. between,
Determine the value at 60 ° C. If the data at 60 ° C. cannot be obtained, the value at 60 ° C. is obtained by first-order interpolation from the two data points closest to 60 ° C.

As the curing agent of the present invention, a latent curing agent capable of curing an epoxy resin at 100 ° C. or lower is preferable. Examples of such a latent curing agent include Amicour PN23 manufactured by Ajinomoto Co., Ltd., and Novacure HX3 manufactured by Asahi Ciba Co., Ltd.
721, HX3722, FXE- of Fuji Chemical Industry Co., Ltd.
1000, San-Aid SI-60 of Sanshin Chemical Industry Co., Ltd.
L, Hardener X-400 of AC R Co., Ltd.
3S, H-3293S, H-3615S, H-3731
S, H-4070S and the like, but are not limited thereto.

Whether curing is possible at 100 ° C. or lower is determined by the following method. After uniformly mixing the epoxy resin and the curing agent, the exothermic curing is measured by DSC. When the temperature at which the curing starts at that time, that is, the temperature at which the resin starts to rise from the baseline (exothermic start temperature) is 100 ° C. or less, curing can be performed at 100 ° C. or less. When the curing start temperature is 90 ° C. or lower, the curability of the epoxy resin composition is good, and it is particularly preferable. Specifically, 20 parts by mass of a curing agent is uniformly mixed with 100 parts by mass of a liquid bisphenol A type epoxy resin, for example, Epicoat 828 manufactured by Yuka Shell Co., Ltd. It measures the temperature and measures the exothermic onset temperature at that time.

The latent curing agent in the present invention is a curing agent which has high reactivity but hardly reacts around room temperature and is stable. Specifically, the viscosity at 60 ° C. after holding the same resin composition at 100 ° C. for 30 days at 30 ° C. is twice as high as that immediately after adjusting the resin composition. A curing agent that is as follows, and a curing agent that is 1.5 times or less is more preferable because of further excellent stability.

The amount of the curing agent to be added is as follows: epoxy resin 10
The amount is preferably 5 parts by mass or less with respect to 0 parts by mass in view of the balance between curability and physical properties, and more preferably 3 parts by mass or less. In the case of a hardener such as a master batch type in which an epoxy resin and a hardener are mixed in advance to form a paste, only the active ingredient is regarded as a substantial hardener and used in the paste. The epoxy resin is considered as the epoxy resin to be cured.

It is preferable to add a urea compound as a curing co-catalyst, since the curability at low temperatures is further improved without impairing the stability at room temperature. The urea-based compound is not particularly limited, and examples thereof include phenyldimethylurea, monochlorophenyldimethylurea, dichlorophenyldimethylurea, chloromethylphenyldimethylurea, toluenebisdimethylurea, and methylenediphenylbisdimethylurea.

In the epoxy resin composition of the present invention, it is possible to add a thermoplastic resin in a dissolved or powdered form, or to add inorganic or organic fine particles. In that case,
The addition amount of 10 parts by mass or less with respect to 100 parts by mass of the epoxy resin is appropriate. This is because if added in excess of 10 parts by mass, curability and physical properties of the cured product may be adversely affected. 5 parts by mass or less is more preferable.

A prepreg obtained by impregnating a reinforcing material with the epoxy resin composition of the present invention is also included in the present invention. The reinforcing material used in the prepreg of the present invention is not particularly limited, and examples of the material include fibers such as carbon fiber, glass fiber, organic fiber (such as polyaramid fiber and polyethylene fiber), boron fiber, and steel fiber. Among them, carbon fiber is preferably used because of its high strength, high elasticity and excellent performance. Glass fibers are also suitable because of their excellent balance of strength, handleability and cost.

There is no particular limitation on the form of these reinforcing materials, and there is no limitation on the form of a single tow, which is a unit of thousands to tens of thousands of filaments, or a so-called tow prepreg formed by integrating several tows. It may be in the form of 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, chopped fiber,
Alternatively, it may be a mat to which it is fixed, or a milled fiber.

The method for preparing the prepreg of the present invention is not particularly limited, but a hot melt method is preferred. The adjustment of the prepreg by the hot melt method is performed, for example, as follows. First, an epoxy resin composition of the present invention is uniformly coated on a release step paper or the like with a thickness calculated from the resin content of a target prepreg to prepare a hot melt film. At this time, coating is performed by increasing the temperature to lower the viscosity of the epoxy resin composition. However, if the temperature is too high, the epoxy resin composition starts a reaction, and the life of the prepreg is shortened, which is not preferable. on the other hand,
When the temperature is low, the coating pressure is increased and productivity is deteriorated, and the release paper is undesirably damaged. Since the preferable temperature range depends on the resin composition, it is necessary to set the coating conditions suitable for the resin composition.

Next, the reinforcing material is impregnated with the epoxy resin composition coated on the release step paper or the like. The impregnation method may be a double film method in which a hot melt film is supplied from above and below the reinforcing material, or a single film method in which a hot melt film is supplied from one of the upper and lower sides. When impregnating the reinforcing material, the hot melt film is heated to impregnate the epoxy resin composition by lowering its viscosity. This temperature condition also differs depending on the resin composition. If the temperature is too high, the resin composition starts to react and shortens the life of the prepreg.If the temperature is too low, the viscosity of the resin does not become sufficiently low and impregnation becomes poor, or the line speed is increased due to impregnation. Is not preferable because productivity is deteriorated due to dropping. It is necessary to set impregnation conditions suitable for the resin composition.

Although the use of the epoxy resin composition of the present invention is not particularly limited, it is particularly suitable as a matrix resin for prepreg. Also, the use of the prepreg of the present invention is not particularly limited, and it can be used for a use where a general-purpose 120 ° C. curing type is currently used, and the productivity can be greatly improved. The application of the prepreg of the present invention includes sports and leisure related such as golf shafts, fishing rods, tennis rackets, badminton rackets, table tennis rackets, snowboards, skateboards, skateboards, kickboards, etc., and industrial related products such as rolls, pipes and shafts. Applications are exemplified. Since the prepreg of the present invention can be cured at a low temperature, the residual stress is small, the warpage of the molded article can be suppressed, and since the residual stress is small, particularly the strength of the matrix between the layers is maintained. Can be expected.

As described above, in the epoxy resin composition of the present invention, the curability of the epoxy resin composition is improved by setting the content of the epoxy compound molecule having a molecular weight of 500 or less in the epoxy resin to 50% by mass or more. . Thereby, the amount of the latent curing agent added to the epoxy resin composition can be reduced. Therefore, an epoxy resin composition that can be cured at a low temperature of 100 ° C. or less and has excellent mechanical properties when cured can be obtained. Further, since such an epoxy resin composition is impregnated into a reinforcing material, molding at a low temperature is possible, and a prepreg excellent in mechanical properties after molding can be obtained.

[0026]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. The molecular weight measurement in each Example and each Comparative Example is G
The measurement was performed using PC (polystyrene conversion). The details of the abbreviations in each table are as follows.

Ep828: Epicoat 8 manufactured by Yuka Shell Co.
28 Ep1001: Yuka Shell Co., Ltd. Epicoat 1001 Ep1009: Yuka Shell Co., Ltd. Epicoat 1009 Ep1010: Yuka Shell Co., Ltd. Epicoat 1010 N740: Dainippon Ink Co., Ltd. Epicron N740 FXE1000: Fuji Kasei Fujicure FXE100
0 HX3722: NOVACURE HX3722 manufactured by Asahi Kasei Corporation PDMU: Phenyldimethylurea DCMU: Dichlorophenyldimethylurea TBDMU: Toluenebisdimethylurea Vinylek E: Polyvinyl Formal manufactured by Chisso YP-50: Phenoxy resin manufactured by Toto Kasei Aerosil: Aerosil manufactured by Nippon Aerosil # 380

Example 1 An epoxy resin composition of the present invention having the composition shown in Table 1 was prepared. Specifically, first, the respective epoxy resins are uniformly mixed at 120 ° C. to dissolve the solid components, and then cooled to 50 ° C. or lower, a curing agent is added thereto, and the mixture is uniformly mixed. A composition was prepared. The curing agent FXE1000 used in this example had an exothermic onset temperature of 100 ° C. or less (69 ° C.) in the above-mentioned DSC. When the viscosity at 60 ° C. of the epoxy resin composition was determined by the method described above, the value was 120 Pa · sec.
c. The mass ratio (mass%) of the epoxy compound molecule having a molecular weight of 500 or less to the total epoxy resin is represented by G
It was 64% by mass when the number average molecular weight in terms of CP and polystyrene was determined by the mass ratio of epoxy compound molecules having a molecular weight of 500 or less.

The thus obtained epoxy resin composition was defoamed and cast at 50 ° C., and then cured at 80 ° C. for 2 hours to obtain a cured resin plate. About this resin plate
A bending test was performed according to SK-7171. The results are shown in Table 1. It was found that the epoxy resin composition of Example 1 exhibited good physical properties even when molded at a temperature of 80 ° C. Further, after giving a heat history of 30 ° C. × 30 days to the resin composition before curing, the viscosity at 60 ° C. was determined again and compared with the viscosity before giving the heat history to determine the life. The life was indicated by how many times the viscosity at 60 ° C. after the heat history was higher than that before the heat history. The epoxy resin composition of Example 1 comprises:
It was found that there was almost no change in viscosity and the composition was stable around room temperature.

Example 2 Example 1 was prepared using the composition shown in Table 1.
And an epoxy resin composition of the present invention was obtained. The obtained epoxy resin composition was molded and evaluated in the same manner as in Example 1, and the results are shown in Table 1.
It was found that the epoxy resin composition of Example 2 had very good cured material properties and life.

Example 3 Example 1 was prepared using the composition shown in Table 1.
And an epoxy resin composition of the present invention was obtained. The curing agent HX3722 used had an exothermic onset temperature of 100 ° C. or less (80 ° C.) in the above-mentioned DSC. The HX3722 was a master batch type curing agent, in which a curing agent component and a liquid bisphenol A type epoxy resin were previously mixed, and the curing agent component was one third of the whole. Therefore, although 15 parts by mass of HX3722 was added, the substantial curing agent component was 5 parts by mass, and the rest was handled as an epoxy resin. The obtained epoxy resin composition was molded in the same manner as in Example 1,
The results were evaluated and the results are shown in Table 1. It was found that the epoxy resin composition of Example 3 had very good cured physical properties and life.

Examples 4 to 8 Epoxy resin compositions of the present invention were prepared in the same manner as in Example 1 with the compositions shown in Table 1. The curing agent used had an exothermic onset temperature of 1 as measured by DSC.
It was below 00 ° C. In addition, the co-catalyst is 5
The mixture was uniformly mixed at 0 ° C. or less. The obtained epoxy resin composition was molded and evaluated in the same manner as in Example 1, and the results are shown in Table 1. It was found that the epoxy resin compositions of Examples 4 to 8 had very good cured product properties and life.

Example 9 Example 1 was prepared using the composition shown in Table 2.
And an epoxy resin composition of the present invention was obtained. The obtained epoxy resin composition was molded and evaluated in the same manner as in Example 1, and the results are shown in Table 2.
Although the bending strength was slightly lower than that of Example 1, the elongation was high, and it was found that the physical properties were still good.

[Comparative Example 1] The case where the proportion of epoxy compound molecules having a molecular weight of 500 or less is less than the range of the present invention will be exemplified. An epoxy resin composition was prepared in the same manner as in Example 1 with the composition shown in Table 2, and the obtained epoxy resin composition was molded and evaluated in the same manner as in Example 1, and the results are shown in Table 2. Was. Both the bending strength and the elongation were quite low, and the proportion of molecules having a molecular weight of 500 or less was small, indicating that the curability was poor.

Examples 10 to 11 The epoxy resin compositions of the present invention having the compositions shown in Table 2 were prepared. Specifically, first, an epoxy resin and a thermoplastic resin as an additive
After homogeneously mixing and dissolving at a temperature of ° C, a curing agent was mixed and prepared in the same manner as in Example 1. With respect to the obtained epoxy resin composition, a resin plate was molded and evaluated in the same manner as in Example 1. The results are shown in Table 2. It was found that even a system in which a thermoplastic resin was dissolved and added exhibited good curability and physical properties of a cured product.

Example 12 An epoxy resin composition of the present invention was prepared using the composition shown in Table 2 in the same manner as in Example 1. The obtained epoxy resin composition was molded and evaluated in the same manner as in Example 1, and the results are shown in Table 2. It was found that even the system to which the additive was added exhibited good curability and cured material properties.

[0037]

[Table 1]

[0038]

[Table 2]

Example 13 The epoxy resin composition of the present invention obtained in Example 1 was impregnated into a carbon fiber (hereinafter abbreviated as CF) TR50S-12L manufactured by Mitsubishi Rayon Co., Ltd., which was unidirectionally aligned. Thus, a prepreg of the present invention was obtained. The prepreg was prepared by a hot melt film type double film method. The prepreg had a basis weight of 125 g / m ² and a resin content of 30% by mass. The tack drape of this prepreg was evaluated by touch, and the results are shown in Table 3. In the table, ◎ in the tack column indicates that the tack is moderate and very easy to handle, and ○ indicates that the tack is slightly strong (sticky) or slightly weak (dry) but does not hinder handling. The symbol x indicates that the tack is too tight or too weak to handle. Further, in the column of drape, ◎ indicates that the drape is moderately soft and easy to handle, ○ indicates that the drape is slightly hard but does not hinder handling, and x indicates that the drape is too hard and difficult to handle. As shown in Table 3, the obtained prepreg was ◎ in both tack and drape.

The life of this prepreg was evaluated by evaluating tack and drape after 30 ° C. × 30 days. As a result, this prepreg had the same tack and drape even after 30 ° C. × 30 days, and the prepreg had a good life. Table 3 shows, for the evaluation of the life, those having good handling immediately after preparation of the prepreg, at 30 ° C. × 3.
Those that can be used in the evaluation of tack and drape after 0 day are indicated by ◎, and those that are difficult to handle are indicated by x.

This prepreg is laminated in one direction and
× 2 hours press molding, Vf about 60%, thickness about 2m
m unidirectional carbon fiber reinforced composite material (hereinafter abbreviated as CFRP)
Was prepared. The impregnation state of the obtained CFRP was evaluated by observing a cross section perpendicular to CF with a microscope.
◎: good impregnation with no voids in the layer,
The symbol “○” indicates that some voids in the layer were observed depending on the visual field to be observed, but there was no problem. The symbol “X” indicates that voids in the layer were observed in any visual field and impregnation was insufficient. As shown in Table 3, the obtained CFRP did not show any voids in the layer and the impregnation was good. AST this CFRP
A 0 °, 90 ° bending test was performed according to MD790. FS0 (0 ° bending strength) is obtained by comparing the obtained result with the actual V
f was calculated in proportion to 60% Vf. The results are summarized in Table 3. Very good component properties.

Example 14 An epoxy resin composition and a prepreg of the present invention having the compositions shown in Table 3 were prepared in the same manner as in Example 13. Further, the CFR was obtained in the same manner as in Example 13.
P was prepared and evaluated. The results are all shown in Table 3. The tack of the prepreg was slightly strong but at a level that would not interfere with handling, drape, life, impregnation,
The component strengths were all good.

Comparative Example 2 The case where the viscosity of the epoxy resin composition is lower than the lower limit of the present invention will be exemplified. An epoxy resin composition having the composition shown in Table 3 was prepared. The viscosity at 60 ° C. was 4 Pa · sec. Using this resin composition,
A prepreg was prepared as in Example 13. The prepreg had a very strong tack and was difficult to handle.

Example 15 An epoxy resin composition and a prepreg of the present invention having the compositions shown in Table 3 were prepared in the same manner as in Example 13. Further, in the same manner as in Example 13, C
FRP was prepared and evaluated. The results are all shown in Table 3. The tack of the prepreg was good. The drape was slightly hard but at a level that would not hinder handling. Life was good. Although some impregnation was observed in the layer depending on the visual field observed with a microscope, the impregnating property was at a level without any problem, and the component strength was very good.

Comparative Example 3 A case where the viscosity of the epoxy resin composition exceeds the upper limit of the present invention will be exemplified. An epoxy resin composition having the composition shown in Table 3 was prepared. The viscosity at 60 ° C. was 5,300 Pa · sec. Next, a prepreg was prepared in the same manner as in Example 13 using this resin composition. This prepreg had a fairly low tack and was manageable, but the drape was too hard to handle. Further, in the same manner as in Example 13, C
FRP was created. When the cross section was observed, many voids were found in the layer and impregnation was poor. A bending test was performed in the same manner as in Example 13. The results are shown in Table 3. Although it is considered to be due to the effect of voids in the layer, FS90 was low.

Comparative Example 4 The case where the ratio of the epoxy compound molecule having a molecular weight of 500 or less is lower than the range of the present invention will be exemplified. An epoxy resin composition having the composition shown in Table 3 was prepared. The proportion of molecules having a molecular weight of 500 or less was 45% by mass. Using this resin composition, a prepreg was prepared in the same manner as in Example 13. This prepreg had good tack and drape, and had a good life of one month or more.
Further, a CFRP was prepared in the same manner as in Example 13. When the cross section was observed, the impregnation was good without any voids in the layer. A bending test was performed in the same manner as in Example 13. The results are shown in Table 3. Poor curability and insufficient curing, especially FS90 was quite low.

Example 16 A prepreg of the present invention was obtained by impregnating the epoxy resin composition of Example 1 with R380H103DX, a glass roving cloth manufactured by Unitika Fiberglass Co., Ltd. The tack and drape of this prepreg were good, and the evaluation result was ◎. Further, in the same manner as in Example 13, a glass fiber reinforced composite material (hereinafter referred to as GFR)
(Abbreviated as P), and the impregnation status was evaluated. As a result, no voids were observed, the impregnation status was good, and the evaluation result was ◎. This GFRP bending test was performed in the same manner as in Example 13. FS0 is 0.80 GPa, FS90 is 0.7
It was very good at 5 MPa.

[0048]

[Table 3]

[0049]

As described above, the epoxy resin composition of the present invention is an epoxy resin composition containing an epoxy resin and a curing agent for curing the epoxy resin, wherein the epoxy resin has a molecular weight of 500 or less. The epoxy resin composition has a viscosity at 60 ° C. of 5 Pa · sec or more,
Since it is 5000 Pa · sec or less, it is possible to cure at a low temperature of 100 ° C. or less without deteriorating the stability at room temperature. Further, since it is possible to lower the concentration of the curing agent in the resin composition, it becomes an epoxy resin composition having excellent mechanical properties after curing, and the production cost can be reduced. As can be widely used.

Further, since the prepreg of the present invention is obtained by impregnating such an epoxy resin composition into a reinforcing material, it is excellent in low-temperature molding characteristics at 100 ° C. or lower, room temperature stability and mechanical properties, It greatly contributes to the reduction of energy costs. In addition to having good cured product characteristics, it also has excellent handling characteristics with appropriate tack and drape.

Claims (6)

[Claims] 1. An epoxy resin composition containing an epoxy resin and a curing agent for curing the epoxy resin, wherein the epoxy resin contains 50% by mass or more of epoxy compound molecules having a molecular weight of 500 or less, and the epoxy resin The viscosity at 60 ° C. of the resin composition is 5 Pa · sec or more,
An epoxy resin composition having a viscosity of 5,000 Pa · sec or less. 2. The epoxy resin composition according to claim 1, wherein the curing agent is a latent curing agent that cures the epoxy resin at 100 ° C. or lower. 3. The method according to claim 1, wherein the amount of the curing agent is 100% or less.
The epoxy resin composition according to claim 1, wherein the amount is 5 parts by mass or less based on parts by mass. 4. The method according to claim 1, wherein the amount of the curing agent is 100% or less.
The epoxy resin composition according to claim 1, wherein the amount is 3 parts by mass or less based on parts by mass. 5. The epoxy resin composition according to claim 1, wherein the content of the epoxy compound molecule in the epoxy resin is 60% by mass or more. 6. A prepreg obtained by impregnating a reinforcing material with the epoxy resin composition according to claim 1.