JP3097259B2 - Epoxy resin composition and prepreg - Google Patents

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, particularly to an epoxy resin composition suitable for a matrix resin for a fiber-reinforced composite material. In detail, together with good molding processability, improve the brittleness of thermosetting resin-based fiber reinforced composite materials,
An object of the present invention is to provide an epoxy matrix resin which provides a fiber reinforced composite material having excellent impact resistance.

[0002]

2. Description of the Related Art Epoxy resins are widely used in the industrial field because of their excellent moldability and good mechanical properties of cured products. In particular, it is widely used as a matrix resin in the field of fiber-reinforced composite materials using carbon fiber, glass fiber, aramid fiber or the like as a reinforcing material.

[0003]

However, as the field of application of these composite materials has expanded, new characteristics have been required for matrix resins. One of them is improvement of moldability. When epoxy resin becomes hot, viscosity decreases and it becomes easy to impregnate between fibers.However, when viscosity decreases too much, resin flows too much and fiber is disturbed, and problems such as deterioration of dimensional accuracy of molded products occur. I do. However, when an attempt is made to increase the viscosity at a high temperature, the viscosity near room temperature increases, so-called tack and drape become small, and a prepreg having poor molding workability is obtained.

[0004] Further, since the epoxy matrix resin is a thermosetting resin, its cured product has essentially poor impact resistance. When a composite material is applied to a structural member such as an aircraft and a civil engineering building, improvement of the composite material is desired. In order to improve the moldability due to such viscosity characteristics and the impact resistance of the cured product, it is generally known to add a high molecular weight polymer. However, the compatibility between epoxy resin and high molecular weight polymer is not always good, not all polymers improve the viscosity characteristics of epoxy resin, and all polymers with good compatibility improve the impact resistance of cured epoxy resin Nothing to do.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a polyvinyl acetal resin having a specific structure has excellent compatibility with an epoxy resin, and that the polyvinyl acetal resin has a specific structure. The present inventors have found that addition is effective in solving these problems, and have reached the present invention.

That is, in the epoxy resin composition containing (A) an epoxy compound and (B) a curing agent, (C) a polyvinyl acetal resin mainly composed of a repeating unit represented by the following general formula (I) is added. By
It has been found that an epoxy matrix resin having excellent moldability and impact resistance can be obtained. This effect is added (I)
This is considered to be due to the improvement in compatibility due to the substituent R of the polyvinyl acetal of the formula.

[0007]

Embedded image

Wherein R represents an aryl group, an aralkyl group or an aryl group-containing vinyl group which may have a substituent, R ′ represents H or an alkyl group having C = 1 to 10, and a, b , C, d represent the percentage of each structural unit in the formula, 5 ≦ a ≦ 85, 0 ≦ b ≦ 80, 10 ≦ c ≦ 5
0, 0 ≦ d ≦ 30) Note that the general formula (I) and similar structural formulas described in the present specification are simply formulas for expressing the quantitative ratio of each structural element of the resin, It does not specify the arrangement (for example, block structure or the like). The polyvinyl acetal-based resin represented by the general formula (I) may contain other components as long as the object of the present invention is not impaired.

Hereinafter, the present invention will be described. Various epoxy compounds such as bisphenol type epoxy, phenol novolak type epoxy, cresol novolak type epoxy, glycidylamine type epoxy, alicyclic epoxy and glycidyl ester type epoxy are used as the epoxy compound (A) used in the present invention. it can. Examples of suitable bisphenol A type epoxy include "Epicoat" 828, 1001, 1004, 1009 (manufactured by Yuka Shell Epoxy), and "Araldite" GY25.
0, "Araldite" 6071, 6072, 6097,
6099 (Ciba-Geigy), "Dow Epoxy" D
ER331, 661, 664, 669 (manufactured by Dow Chemical Company) or the like can be used.

Suitable phenol novolak epoxies are, for example, "Epicoat" 15, 154 (manufactured by Yuka Shell Epoxy) and "Araldite" EPN113.
8, 1139 (manufactured by Ciba-Geigy), "Dow Epoxy" DEN431, 438, 485 (manufactured by Dow Chemical) can be used. Suitable gresol novolaks are specifically "Araldite" ECN 1235,12
73, 1299 (manufactured by Ciba Geigy), "EOCN"
102 (manufactured by Nippon Kayaku Co., Ltd.) and the like can be used. Preferable examples of the glycidylamine type epoxy include “Araldite” MY720 (manufactured by Ciba-Geigy), “Sumiepoxy” ELM100, 120, 434 (manufactured by Sumitomo Chemical). Suitable alicyclic epoxies are specifically “Araldite” CY175, 177, 179
(Manufactured by Ciba-Geigy) or the like can be used. Preferably, as the glycidyl ester type epoxy, specifically, "Epicoat" 190P, 191P (manufactured by Yuka Shell Epoxy) and "Araldite" CY184, 192 (manufactured by Ciba Geigy) can be used. Other "Araldite" X
Bisphenol F type epoxy such as PY306 (manufactured by Ciba-Geigy) and brominated epoxy such as "Epicoat" 5050, 5051 (manufactured by Yuka Shell Epoxy) can also be used.

The curing agent for the epoxy compound (B) used in the present invention includes aromatic polyamine, acid anhydride,
Usual epoxy curing agents such as dicyandiamide and BF ₃ .amine complex are used. Dicyandiamide and aromatic diamine are preferably used for the composite material. In order to control the curing reaction, N- (3,4-dichlorophenyl)
A urea compound having a specific structure such as -N ', N'-dimethylurea and a curing accelerator such as a BF ₃ .amine complex can be used in combination.

The component (C) used in the present invention, which is a polyvinyl acetal resin mainly composed of a repeating unit represented by the general formula (I), is obtained by converting polyvinyl alcohol to an aldehyde represented by the following general formula (II) or (III). And acetalization by a known method.

[0013]

Embedded image R-CHO (II)

[0014]

R'-CHO (III) (wherein R and R 'are R and R' in the general formula (I) shown above)
Synonymous with Examples of the aldehyde represented by the general formula (II) include benzaldehydes, naphthaldehydes, cinnamaldehydes, and alkyl aldehydes having a phenyl group or a naphthyl group.
In these aldehydes, those having an alkyne, an alkoxy group, an amino group, an alkylamino group, an acylamino group, a carboxyl group, a carboxylic acid ester group, a hydroxyl group, or a halogen atom as a substituent on the benzene ring and the naphthalene ring can also be used. Each of these aldehydes contains an aromatic ring. It is considered that the introduction of the aromatic ring improves the solubility of the polyvinyl acetal resin in the epoxy resin, and improves the viscosity characteristics of the resin composition and the impact resistance of the cured product. Specific examples of these aldehydes include benzaldehyde, 1-naphthaldehyde, phenylacetaldehyde, o-tolualdehyde, p-tolualdehyde, o-anthaldehyde, m-
-Anthaldehyde, p-anthaldehyde, p-ethylbenzaldehyde, o-chlorobenzaldehyde, p
-Chlorobenzaldehyde, cinnamic aldehyde and the like.

As the aldehyde represented by the general formula (III), formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, capronaldehyde,
Capryl aldehyde, capry aldehyde and the like can be mentioned. The degree of acetalization of the polyvinyl acetal resin is suitably in the range of 50 to 85 mol%.
Further, R in the structural unit acetal is preferably at least 10 mol%. If this is small, the compatibility with the epoxy resin is reduced, and it is difficult to obtain the improvement effect. It is appropriate that the raw material polyvinyl alcohol has a degree of polymerization of 100 to 3000 and may partially contain unsaponified acetyl groups, but the amount must be 30 mol% or less.

(C) The amount of the polyvinyl acetal resin used depends on the purpose, but if the amount of the polyvinyl acetal added is small, the effect of improving the impact resistance is small.
When the viscosity is increased, the viscosity, especially at high temperature, becomes too high, and it becomes difficult to mix without a solvent, the fluidity of the resin at the time of molding is reduced, and defects are likely to occur in the cured product. 0.1 to 30 parts by weight with respect to parts by weight,
It is preferably 0.5 to 20 parts by weight, and as a particularly remarkable range of the effect, 1 to 10 parts by weight.

The epoxy resin composition of the present invention can be mixed with a solvent and impregnated into reinforcing fibers by a so-called wet method to form a prepreg as an intermediate material, or mixed with no solvent under heating, and then mixed. The reinforcing fibers can also be impregnated using a hot melt method. As the reinforcing fibers, carbon fibers, glass fibers, aramid fibers, alumina fibers, polyethylene fibers and the like are used. These reinforcing fibers are used in the prepreg in an amount of 30 to 75% by weight.

Although the epoxy resin composition of the present invention is suitable for a fiber-reinforced composite material, it can be used in other fields utilizing properties such as impact resistance, adhesives, paints, linings, electric insulating materials, and civil engineering building materials. It is also possible to apply to such as.

[0019]

【Example】

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto without departing from the scope of the appended claims. Incidentally, the impact test in the examples was performed using ASTM-D.
Notched Izod impact test according to 256,
An impact was applied from a thickness direction to a flat test piece having a width of 10 mm and a thickness of 2 mm. (Example 1) 20 parts by weight of "Epicoat" 828 (manufactured by Yuka Shell Epoxy), 46 parts by weight of "Epicoat" E1001 (manufactured by Yuka Shell Epoxy), 34 parts by weight of DEN438 (manufactured by Dow Chemical Company), and 4 parts by weight of dicyandiamide (manufactured by Yuka Shell Co., DICY7) as a curing agent,
N- (3,4-dichlorophenyl)-as a curing accelerator
N ', N'-dimethylurea (manufactured by Hodogaya Chemical Co., Ltd., DC
MU99) A polyvinyl acetal resin 5 represented by the following structural formula (IV) obtained by acetalizing polyvinyl alcohol with benzaldehyde to 4 parts by weight of an epoxy resin composition
A part by weight was uniformly dissolved in a mixed solvent of tetrahydrofuran (THF) / methanol to prepare a solution of the resin composition of the present invention.

[0021]

Embedded image

This resin solution was converted to carbon fiber (T3, manufactured by Toray Industries, Inc.).
00) and continuously wound on a drum, width 0.5
m, a sheet having a length of 3 m was prepared and vacuum-dried at 40 ° C. for 24 hours. The obtained prepreg having a resin content of 35% was laminated and cured at 120 ° C. for 2 hours to obtain a unidirectional laminate having a thickness of 2 mm. A test piece having a width of 10 mm and a length of 70 mm was cut out from the laminate and subjected to an impact test. Impact strength is 11
It was 8 kJ / m ² .

(Example 2) "Epicoat" 828 (manufactured by Yuka Shell Epoxy) 18 parts by weight, "Epicoat" E1
001 (made by Yuka Shell Epoxy) 48 parts by weight, DEN
438 (manufactured by Dow Chemical Company) and 2 parts by weight of a polyvinyl acetal resin represented by the following structural formula (V) obtained by acetalizing polyvinyl alcohol with phenylacetylaldehyde and butyraldehyde were mixed with heating. Then, 4 parts by weight of dicyandiamide (manufactured by Yuka Shell Co., DICY7) as a curing agent, and N as a curing accelerator
4 parts by weight of-(3,4-dichlorophenyl) -N ', N'-dimethylurea (manufactured by Hodogaya Chemical Co., Ltd., DCMU99) were added to prepare a resin composition of the present invention.

[0024]

Embedded image

The obtained resin composition was applied to release paper to form a resin film. Next, a unidirectional prepreg having a resin content of 35% was obtained by sandwiching unidirectionally aligned carbon fibers (manufactured by Toray Industries, Inc., T300) between the resin films and continuously applying pressure with a hot roll. Using this prepreg, a laminate was prepared in the same manner as in Example 1, and an impact test was performed. The impact strength was 107 kJ / m ² .

(Embodiment 3) "Araldite" MY720
100 parts by weight (manufactured by Ciba-Geigy), 42 parts by weight of 4,4'-diaminodiphenylsulfone, 0.5 part by weight of BF ₃ .ethylamine complex and 7.5 parts by weight of the polyvinyl acetal resin used in Example 2 were THF. To prepare a solution of the resin composition of the present invention. Using this solution, prepreg was formed in the same manner as in Example 1, and then cured at 180 ° C. for 2 hours to obtain a laminate. The impact strength of this laminate is 112 kJ
/ M ² . (Comparative Example 1) In order to confirm the effect of the polyvinyl acetal resin, the composition containing no polyvinyl acetal was evaluated. In the composition of Example 1, the same resin composition was used except that the polyvinyl acetal resin was not included.
Dissolved in HF / methanol. Using this solution, prepreg was formed in the same manner as in Example 1, and then cured at 120 ° C. for 2 hours to obtain a laminate. The impact strength of this laminate is 84 kJ
/ M ² . Further, the prepreg had a high adhesiveness and a poor workability.

Comparative Example 2 In order to confirm the effect of the polyvinyl acetal of the present invention, a composition using polyvinyl butyral instead of the polyvinyl acetal was evaluated. A resin solution was prepared using 5 phr of a polyvinyl butyral resin (“S-LEC” BL-S, manufactured by Sekisui Chemical Co., Ltd.) instead of the polyvinyl acetal resin in the composition of Example 1. Using this solution, a prepreg was prepared in the same manner as in Example 1, but the polyvinyl butyral resin had poor solubility in epoxy, so that the resin was precipitated during drying, and had a strong tackiness and poor workability. there were.

[0028]

According to the present invention, there can be obtained an epoxy resin composition having improved moldability and capable of obtaining a molded article having excellent impact resistance. In particular, it can be suitably used as a matrix resin of a fiber-reinforced composite material.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-9262 (JP, A) JP-A-63-37137 (JP, A) JP-A-63-37136 (JP, A) JP-A-62 169829 (JP, A) JP-A-61-225268 (JP, A) JP-A-55-27342 (JP, A) JP-A-63-37135 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) C08L 63/00-63/10 C08L 29/14 C08J 5/24

Claims (2)

(57) [Claims] 1. An epoxy resin composition containing (A) an epoxy compound and (B) a curing agent, wherein (C) a polyvinyl acetal-based resin mainly composed of a repeating unit represented by the following general formula (I) is added. An epoxy resin composition comprising: Embedded image (Wherein R is an aryl group which may have a substituent,
An aralkyl group or an aryl group-containing vinyl group,
R ′ represents H or an alkyl group of C = 1 to 10, a,
b, c, and d represent the percentage of each structural unit in the formula and 5
≦ a ≦ 85, 0 ≦ b ≦ 80, 10 ≦ c ≦ 50, 0 ≦ d ≦
30) 2. A prepreg obtained by impregnating a reinforcing fiber with the epoxy resin composition according to claim 1.