JPH05310890A - Epoxy resin composition and prepreg for composite material prepared therefrom - Google Patents

Abstract

PURPOSE:To obtain an epoxy resin compsn. which cures at a low temp. and has an excellent storage stability at room temp. by compounding an epoxy resin with specified amts. of a bisphenol compd., a specific cure acclerator, and a curative. CONSTITUTION:100 pts.wt. epoxy resin (e.g. bisphenol A epoxy resin) is compounded with 5-100 pts.wt. bisphenol compd. (e.g. bisphenol A) or mixture thereof with a monoglycidyl ether of the bisphenol compd., 2-20 pts.wt. epoxy resin cure accelerator of the formula (wherein X1 and X2 are each H, Cl, or Br) (e.g. monochlorophenyl-N,N-dimethylurea), and 2-30 pts.wt. curative of an amine adduct type having an active hydrogen site and a catalytically functional site in the molecule, thereby giving an epoxy resin compsn., which is suitable for producing a prepreg for a fiber-reinforced composite 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 which cures at a low temperature and a prepreg for a fiber reinforced composite material which is a combination of the epoxy resin composition and a reinforcing fiber.

[0002]

2. Description of the Related Art Epoxy resins are used in a wide variety of fields because they have excellent mechanical and electrical properties after curing. For example, it is widely used as a sealant for electronic materials, paints / paving materials, and adhesives. Further, in recent years, it has come to be used as a matrix resin for fiber-reinforced composite materials because of its excellent mechanical properties and heat resistance, and is widely used for various purposes such as aircrafts, fishing rods and golf club shafts.

Among these, the matrix resin for a prepreg (a precursor for a composite material in which a matrix resin and a reinforcing fiber are combined) which is used for general purposes is excellent in mechanical properties after curing, and the prepreg at room temperature. It is required to have excellent stability and handleability. Further, in order to shorten the molding cycle and reduce the energy cost, there is an increasing demand for low-temperature curing or short-time curing matrix resins. 80 to 90 from room temperature
Some resins are already known which cure at low temperatures of ° C.
However, most of these are so-called hand layup resin compositions in which a main agent and a curing agent are mixed immediately before curing, and their stability at room temperature is poor, and their pot life is on the order of minutes to hours. In addition, the resin viscosity immediately after mixing is low and the handling and working environment are poor. The advent of a matrix resin which has improved these drawbacks and which can be cured at a low temperature and which can be prepregized by a hot melt film method like the existing 120 ° C. curable matrix resin is expected to solve all of the above problems. ..

Several inventions have been made to meet these needs. Japanese Patent Application Laid-Open No. 61-43616 discloses a combination of an epoxy resin, a dibasic acid dihydrazide compound, a urea compound and an alcohol-based or phenol-based compound having a melting point of 50 ° C. or higher. The epoxy resin compound used here has stability at 30 ° C. for 14 days or longer, but requires high temperature and long time curing conditions of 100 ° C. for 2 hours, and curing at 90 ° C. or lower causes poor curing. It cannot be used in practice.

Japanese Unexamined Patent Publication No. 1-129084 discloses a resin adhesive comprising an epoxy resin, a reaction product of bisphenol A and a monoglycidyl ether of bisphenol A, and an imidazole compound which is a curing agent and a curing accelerator. There is. This resin composition also requires a high temperature of 96 ° C. for 2 hours and a long time, and the CFRP property of using this resin composition as a matrix resin is one-way CFR.
Bending strength in P0 ° direction FS //=1.17 GPa, ILS
S = 76 MPa and CFRP characteristics FS // = 1.76 GPa, I currently used for general-purpose curing at 120 ° C.
Extremely low compared to LSS = 98 GPa. Further, the resin composition has a large increase in viscosity during resin preparation, and it is difficult to form a hot melt film.

In addition to these, a resin composition using P-hydroxystyrene (Japanese Patent Publication No. 32-18551,
US Pat. No. 3,884,992) or a resin composition using a boron trifluoride complex (European Patent Publication No. 1)
No. 65,230), but none of them satisfy the requirements sufficiently because they have poor stability at room temperature or require a high temperature for a long time for curing.

[0007]

In view of the above, the present invention has a stability at room temperature of 20 days or more, and 70
At a temperature of ~ 90 ° C, it cures until it has practically sufficient characteristics, and the curing temperature of the current general-purpose CFRP prepreg is 120 ~.
The purpose is a resin composition that cures within 30 minutes at 130 ° C.

[0008]

The present invention comprises (a) 100 parts by weight of an epoxy resin, (b) 5 to 100 parts by weight of a bisphenol compound, or a reaction product of a bisphenol compound and a monoglycidyl ether of a bisphenol compound,
(C) Epoxy resin curing accelerator 2 represented by the following general formula
~ 20 parts by weight

[Chemical 3] (D) Epoxy resin composition comprising 2 to 30 parts by weight of an amine adduct type curing agent having an active hydrogen site in the molecule and a catalytic function site, and a prepreg for fiber reinforced composite material in which the epoxy resin composition is combined with a reinforcing fiber It is in.

The epoxy resin which is the component (a) constituting the resin composition of 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. An epoxy resin can be used.
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.

Further, from the viewpoint of handleability, a liquid epoxy resin and a solid epoxy resin are mixed to obtain the optimum viscosity for use. A mixture of a liquid epoxy resin having an epoxy equivalent of 100 to 200 and a solid epoxy resin having an epoxy equivalent of 400 to 4,000 is suitable for this. Further, it is a more preferable embodiment of the present invention to use a product obtained by reacting the epoxy resin with an amine compound or an acid anhydride within a range not gelling.

The bisphenol compound as the component (b) means bisphenol A, bisphenol F and bisphenol S, and these may be used alone or in combination. Further, it is more preferable to use a reaction product of the bisphenol compound and a monoglycidyl ether of the bisphenol compound. This reaction product can be easily synthesized by mixing the raw material compounds and heating at 100 ° C. for 1 hour using a catalyst such as triphenylphosphine. Also, a reaction product of bisphenol A and bisphenol A monoglycidyl ether is marketed as DEH-85 by Dow Chemical Company. In the present invention, these compounds are used in the range of 5 to 100 parts by weight. When the amount added is 5 parts by weight or less, the elongation of the obtained cured resin is low and the CFRP characteristics obtained are also adversely affected. If the amount is 100 parts by weight or more, the curing performance of the resin composition at low temperature is deteriorated, which is not preferable.

The urea compound which is the curing accelerator of the component (c) is used in the range of 2 to 20 parts by weight. If it is 2 parts by weight or less, the resin curability is deteriorated, and if it is 20 parts by weight or more, the room temperature stability of the resin composition is deteriorated, which is not preferable. The range of 4 to 10 parts by weight is more preferable.

The amine adduct type curing agent / curing accelerator represented by the component (d) is a compound obtained by reacting a commercially available epoxy resin with an amine compound, and is a resin composition obtained by using the amine compound alone. The stability of the object is significantly improved. The amount of this amine adduct added is in the range of 2 to 30 parts by weight. Further, the range of 2 to 10 parts by weight is more preferable. If the addition amount is 2 parts by weight or less, the curability is poor, and if it is 30 parts by weight or more, the room temperature stability of the obtained resin composition is poor, which is not preferable.

An example of a compound which meets such an object is a bisphenol A type epoxy resin such as Ep8.
28 and compounds having an active hydrogen site, eg 2,
A reaction product obtained by heating 4,6-tris (dimethylaminomethyl) phenol at 100 ° C. for 1 hour can be mentioned. In this case, the ratio of the epoxy resin to be reacted with the compound having an active hydrogen site is such that the compound having an active hydrogen site is 0.1 to 1.5 mol per mol of the epoxy resin. If this amount is 0.1 mol or less, the curability of the resulting resin composition will be poor, and if it is 1.5 mol or more, the stability of the uncured resin will be poor, such being undesirable.

As the epoxy resin, the same epoxy resin as the above-mentioned component (a) can be used. Also,
Examples of the compound having an active hydrogen site include 2,4,
In addition to 6-tris (dimethylaminomethyl) phenol, 2- (dimethylaminomethyl) phenol, 2-dimethylaminoethanol, and other compounds having -OH and a tertiary amine, or 2-phenyl-1-cyanoethylimidazole, 2- Examples include imidazoles such as methyl-3-cyanoethylimidazole. Further, it is commercially available from Ajinomoto Co., Inc. as Amicure MY-24, PN-23.

The curing agents represented by (b) to (d) have already been used alone, and a resin composition having a performance corresponding thereto has been obtained. However, a resin composition which is the object of the present invention and which is cured at a low temperature and has excellent storage stability at room temperature has not been obtained. These objects can be achieved only by using the three curing agents shown in the present invention, and the selection and combination of the curing agent and the curing accelerator are the features of the present invention.

The resin composition described above is combined with reinforcing fibers to give a prepreg for a fiber-reinforced composite material.
Examples of the reinforcing fiber to be combined with the epoxy resin composition include carbon fiber, glass fiber, and aramid fiber,
It is not particularly limited.

Since the epoxy resin composition of the present invention has excellent stability as described above, a so-called hot melt film in which the resin is heated to form a thin film of the resin on the release paper can be stably prepared. For this reason, it becomes possible to manufacture a prepreg which is a precursor for CFRP by the hot melt method, which is impossible with the conventional low temperature curable resin. This makes it possible to produce a prepreg that does not require the hand lay-up method or the lacquer method using a solvent, which has been common in low-temperature curable resins up to now, which is very advantageous in terms of economy and working environment. .. Further, the room temperature stability of the prepreg obtained by using the resin composition of the present invention is 20 days or longer, and the CFRP characteristics using this prepreg have the same value as the current 120 ° C. cured product.

The epoxy resin composition of the present invention contains 70 to 9
It cures to a practically sufficient degree at a low temperature of 0 ° C. in 2 to 6 hours, and at a temperature of 120 to 140 ° C. in an extremely short time of 30 minutes or less to a practically sufficient degree. In addition, the CF obtained by the hot melt film method using the resin composition of the present invention
The prepreg for RP has sufficient storage stability of 20 days or more at room temperature, and the obtained CFRP property is 1
The same performance as the 20 ° C cured product can be obtained.

As described above, the resin composition of the present invention has a great feature as compared with the conventional low temperature curing epoxy resin composition even in the problems of production, economy, and working environment which have been particularly problematic in recent years. Have Therefore, it is expected to be used in fields that have not been used so far in curing conditions, room temperature stability of prepreg, or working environment.

[0021]

The present invention will be described in more detail with reference to the following examples. The symbol of the compound in an Example is as follows. Ep. 1001; Bisphenol A type solid epoxy resin (manufactured by Yuka Shell Co., Ltd.) Ep. 828; Bisphenol A type liquid epoxy resin (made by Yuka Shell Co., Ltd.) Ep. 152; Bisphenol novolac type epoxy resin (produced by Yuka Shell Co., Ltd.) LCB-100; Ep. Reaction product of 828 and diaminodiphenyl sulfone (DDS) ELM-120; m-aminophenol triglycidyl derivative (Sumitomo Chemical Co., Ltd.) DEH-85; Reaction product of bisphenol A and bisphenol A monoglycidyl ether (Dow Chemical Co., Ltd. Manufactured) DCMU; 3,4-dichlorophenyl-N, N-dimethylurea MCMU; monochlorophenyl-N, N-dimethylurea PMU; phenyl-N, N-dimethylurea MY-24, PN-23; amine adduct ( (Ajinomoto Co.)

The methods of measuring physical properties in Examples and Comparative Examples are as follows. (1) Cured resin three-point bending test Length 600 mm, width 8 mm, cured under prescribed curing conditions
Using a plate-shaped test piece with a thickness of 2 mm, press the center of the test piece placed on a fulcrum with a span interval of 32 mm (tip radius 3.2 mm) with an indenter with a tip radius 3.2 mm, and cross head speed 2
A 3-point bending test was performed at mm / min, and each characteristic was calculated by the following formula. Bending strength FS = 3PL / 2WT ² (kg / mm ² ) Bending elastic modulus FM = L ³ P ³ / 4WT ³ a (kg / m
m ² ) Flexural elongation ε = 6Tl (CHS) × 100 / L ² (CS)
(%) The abbreviations in the formula are the values shown below. P: Maximum load at break (kg) L: Span length (mm) W: Specimen width (mm) T: Specimen thickness (mm) a: Certain strain (mm) P ': Load at strain a (kg) l Reading of chart until breakage (mm) (CS); chart speed (mm / min) (CHS); crosshead speed (mm / min)

(2) Cured Resin Viscoelastic Property A resin viscoelastic property was measured under the following conditions using a plate test piece having a length of 60 mm, a width of 10 mm and a thickness of 2 mm. Model: RD-7700 (manufactured by Rheometrics) Measuring conditions: Heating Rate: 2 ° C / min. Strain: 0.5% Rate: 1 Hz Measurement temperature range: 50 ° C. to (3) CFRP interlaminar shear strength (ILSS) CFRP having a thickness of 2 mm and cured under predetermined conditions has a length of 15
mm, width 10 mm, the test was carried out in the same manner as the resin bending test except that the span interval was 8 mm, and ILSS was calculated by the following formula. ILSS = 3P / 4WT (kg / mm ² ) (4) CFRP 0 ° bending strength (FS //) CFRP having a thickness of 2 mm and cured under predetermined conditions has a length of 10
The test was carried out in the same manner as in the resin bending test except that the test piece was cut into 0 m and a width of 10 mm, and the span interval was set to 80 mm, and FS // was calculated by the following formula. FS // = 3PL / 2WT ² (kg / mm ² ) (5) CFRP 90 ° bending strength (FS⊥) A 2 mm thick CFRP cured under prescribed conditions to a length of 60
mm and width 10 mm, the test was carried out in the same manner as the resin bending test except that the span interval was 32 mm, and SF⊥ was calculated by the following formula. SF⊥ = 3PL / 2WT ² (kg / mm ² )

Example 1 Epoxy resin Ep. 1001
30 parts by weight, Ep. 70 parts by weight of 828 and 60 parts by weight of a phenolic curing agent DEH-85 were put into a kneader heated to 90 ° C. and uniformly mixed. After cooling the kneader heating temperature to 55 ° C. and confirming that the resin temperature was also lowered, 10 parts by weight of DCMU and 5 parts by weight of MY-24 were added and mixed to obtain a uniform resin composition. This resin composition was poured into a glass cell having a Teflon plate having a thickness of 2 mm as a spacer and heat-cured at a predetermined temperature for a period of time to obtain a transparent cured resin. Using this resin plate, a three-point bending test and viscoelasticity measurement were carried out. The results are shown in Table 1.

[0025]

[Table 1]

Example 2 The resin composition prepared in Example 1 was heated and softened at 50 to 55 ° C. to form a thin film on a release paper to prepare a hot melt film. This film was wound around a drum, and carbon fibers (Pyrofil TR-40, manufactured by Mitsubishi Rayon Co., Ltd.) aligned in one direction were heat impregnated at 70 ° C. for about 20 seconds to prepare a prepreg. The obtained prepreg has suitable tackiness and hardness,
Even after storage for 1 month, there was little change in tackiness and hardness and it had good storage stability. The adhesiveness and hardness were evaluated by wrapping the prepreg around a pencil with a diameter of 8 mm and confirming that the prepreg was not cracked or rewound.
I made a pass / fail judgment.

Further, the prepregs are laminated in one direction,
After the carbon fiber content after molding was adjusted to 60% by volume, it was heated at 80 ° C. for 5 hours using a vacuum molding method to obtain CFRP. The bending characteristics and the interlaminar shear strength of the obtained CFRP were measured and found to be FS // = 179 kg / mm.
² , ILSS = 8.9 kg / mm ² , and FS⊥ = 1
It was 3.9 kg / mm ² .

[Example 3] [Comparative Example 1] A resin composition was prepared and cured in the same manner as in Example 1 and Example 2 except that the amount of DEH-85 was changed as shown in Table 2. , And CFRP were created. Each mechanical property of the resin CFRP was evaluated. The obtained results are also shown in Table 2. All curing conditions were 80 ° C. for 5 hours. As is clear from the table, when the composition of the present invention is used, the cured resin, CFR
It can be seen that P exhibits high physical properties.

[0029]

[Table 2]

[Example 4] DEH-8 which is the component (b)
A resin composition was prepared and cured in the same manner as in Examples 1 and 2 except that the amount of 5 was kept constant at 60 parts by weight and the resin components were changed as shown in Table 3, to prepare a cured resin and CFRP. The cured resin and CFRP were cut and a bending test was carried out according to the above method. The obtained results are also shown in Tables 3 and 4. All curing conditions were 80 ° C. for 5 hours. All the prepregs using the resin compositions in the table had room temperature storage stability of 1 month or more. Further, as can be seen from the table, when the resin composition of the present invention is used, it is sufficiently cured at 80 ° C., and the physical properties of the resin and CFRP obtained are the same as those using the current 120 ° C. cured resin.

[0031]

[Table 3]

[0032]

[Table 4]

Comparative Example 2 From the resin composition of Example 1, M
A resin composition excluding Y-24 was prepared. The stability of the resin was high and the work went smoothly. However, it did not cure at 100 ° C. or lower and was gradually cured by heating at 130 ° C. for 1 hour. The mechanical properties of the obtained resin were equivalent to those of the resin composition of the present invention, but they were inferior in curing conditions and were clearly disadvantageous both in terms of productivity and economy.

Comparative Example 3 A resin composition was prepared in the same manner as in Example 1 except that DCMU was not used. This resin composition did not cure at 70 to 90 ° C., or the cured resin had an extremely low flexural elongation even when cured, which was a problem in practice. Further, 25 parts by weight or more of MY-24 is required for curing, which is not preferable because the resin stability is deteriorated.

Example 5 2,4,6-Tris (dimethylaminomethyl) phenol, 1 mol (265 g) and epoxy resin Ep. 828 1 mol (380 g) was reacted at 100 ° C. for 2 hours to obtain a reaction product (d-
1). In place of MY-24 of Example 1, this d-1 was replaced by 5
A resin having a thickness of 2 mm was obtained in the same manner as in Example 1 except that parts by weight were added. The resin cured at 80 ° C. for 5 hours was subjected to a 3-point bending test, and FS = 15.8 kg / mm ² and FM = 3.
70 kg / mm ² , ε = 7.1% was obtained. In addition, a unidirectional CFRP prepared by curing the resin composition in the same manner as in Example 2 at 80 ° C. for 5 hours was FS // = 17.
2 kg / mm ^2, and had a ILSS = 8.8kg / mm ² and FS⊥ = excellent value of 12.9 kg / mm ^2.

[Embodiment 6] In the same manner as in Embodiment 5,
(Dimethylaminomethyl) phenol 1 mol, epoxy resin Ep. 1 mol of 828 is reacted to give a reaction product d
-2 was obtained. 2 m in the same manner except that 4 parts by weight of this reaction product d-2 was added instead of MY-24 of Example 1.
An m-thick resin plate was obtained. 3 of resin cured at 80 ℃ for 5 hours
A point bending test was carried out, and FS = 16.1 kg / mm ² , F
M = 366 kg / mm ² and ε = 7.3% were obtained.

A prepreg containing the resin composition as a matrix resin was prepared in the same manner as in Example 2. 80
CFRP cured at ℃ × 5 hours, FS // 178k
g / mm ² , ILSS = 8.9 kg / mm ² , and F
It had an excellent value of S⊥ = 13.1 kg / mm ² .

[Example 7] DEH-8 which is the component (b)
A resin composition was prepared and cured in the same manner as in Examples 1 and 2 except that the amount of 5 was kept constant at 60 parts by weight and the resin components were changed as shown in Table 5, to prepare a cured resin and CFRP. The cured resin and CFRP were cut, and a bending test was performed by the method described above. The obtained results are shown in Table 5. All curing was performed by heating at 80 ° C. for 3 hours.

[0039]

[Table 5]

The resin compositions shown in Table 5 have a practically sufficient stability of 3 weeks at room temperature. Further, as can be seen from Table 5, the mechanical properties of the cured product of the present resin composition and CFRP using the present resin are equivalent to those of the current 120 ° C. cured resin.

[0041]

EFFECTS OF THE INVENTION The resin composition of the present invention cures at a low temperature of 70 ° C. to 90 ° C., and the prepreg using the resin composition of the present invention has a sufficient stability of 20 days or more at room temperature. have. Further, the obtained CFRP characteristics are the same as those of the CFRP using the current 120 ° C. curable resin.

For this reason, it becomes possible to use low heat-resistant and strong fibers such as high-strength polyester fibers which could not be used because of high curing temperature. Further, it can be used in a wide range of fields such as the field molded by the hand lay-up method, the repair of CFRP molded products, and the mold material. Especially in the field of molding by the hand lay-up method, the working environment can be improved, which is very advantageous.

Claims (5)

[Claims] 1. (a) 100 parts by weight of an epoxy resin,
(B) 5-100 parts by weight of a reaction product of a bisphenol compound or a monoglycidyl ether of a bisphenol compound and a bisphenol compound, (c) 2-20 parts by weight of an epoxy resin curing accelerator represented by the following general formula: (D) An epoxy resin composition comprising 2 to 30 parts by weight of an amine adduct type curing agent having an active hydrogen site in the molecule and a catalytic function site. 2. The epoxy resin has an epoxy equivalent of 100 to 2.
Liquid epoxy resin having 00 and an epoxy equivalent of 400
The epoxy resin composition according to claim 1, which is a mixture with a solid epoxy resin having ˜4000. 3. The curing agent as component (b) is bisphenol A.
The epoxy resin composition according to claim 1, which is a reaction product of bisphenol A and a monoglycidyl ether of bisphenol A. 4. (a) 100 parts by weight of epoxy resin,
(B) 5 to 100 parts by weight of a bisphenol compound or a reaction product of a bisphenol compound and a monoglycidyl ether of a bisphenol compound, (c) 2 to 20 parts by weight of an epoxy resin curing accelerator represented by the following general formula, ] A prepreg for a composite material comprising (d) 2 to 30 parts by weight of an amine adduct type curing agent having an active hydrogen site in the molecule and a catalytic function site, and (e) a reinforcing fiber. 5. The prepreg according to claim 4, wherein the reinforcing fiber is carbon fiber.