JP3442851B2 - Epoxy resin composition for CFRP - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matrix epoxy resin composition for CFRP (carbon fiber reinforced composite material).

[0002]

2. Description of the Related Art Epoxy resins are used in a wide range 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 composite materials because of its excellent mechanical properties and heat resistance, and in particular, carbon fiber (CF) is used as a reinforcing material for general applications such as from aircraft to fishing rods and golf club shafts. Widely used.

As a method for molding these CFRP, in addition to a method using a prepreg (a precursor for a composite material in which a matrix resin and a reinforcing fiber are combined), a hand layup method, a filament winding (FW) method, a resin transfer molding method are used. (RTM) method, injection method, etc., among which FW or RTM
As a resin used in the method, it is preferable that the resin has excellent physical properties after curing, and also has low viscosity and excellent viscosity stability in consideration of impregnation property in the molding process.

As such a resin, an epoxy resin composition in which an epoxy resin, an acid anhydride type curing agent and an imidazole type catalyst are combined is preferably used. However, regarding the epoxy resin of such a resin composition, it is described in JP-A-3-17118 that the elongation of the cured resin becomes small when the molecular weight thereof is small. According to the description of the publication, the molecular weight of the epoxy resin must be 400 to 490 in view of the balance between tensile elongation and heat resistance of the cured resin. However, the higher the molecular weight is, the higher the viscosity is, which is not preferable for the impregnation property.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a CFR which has a low viscosity, excellent curability, and excellent viscosity stability, and which has a good balance between elongation and heat resistance as cured resin properties.
An object is to provide an epoxy resin composition for P.

[0006]

According to the present invention, (a) a bisphenol A type epoxy resin having a molecular weight of 400 or less: 100 parts by weight (b) a liquid acid anhydride-based curing agent: an epoxy resin as a component (a) 50-120% of stoichiometric amount (c) Imidazole catalyst: 0.1-5 parts by weight (d) Salt of at least one compound selected from carboxylic acids or esters having a -COO- structure: 0 The epoxy resin composition for CFRP composed of 2 to 3 parts by weight solves the above problems.

The epoxy resin which is the component (a) used in the present invention must be a bisphenol A type epoxy resin having a molecular weight of 400 or less, and when the molecular weight exceeds 400, the viscosity becomes high and the impregnation property deteriorates. Not suitable.

The acid anhydride type curing agent of component (b) is not particularly limited as long as it is liquid at room temperature, but methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride and methylnadic acid anhydride are preferably used. . The addition amount of the component (b) must be 50 to 120% of the stoichiometric amount with respect to the epoxy resin of the component (a), and if it exceeds this range, the heat resistance of the cured product decreases, which is not preferable. A more preferable range is 70 to 110%.

The imidazole-based catalyst of component (c) is preferably liquid at room temperature, and 2-ethyl-4-methylimidazole is preferably used. The amount added is 0.1 to 100 parts by weight of the epoxy resin of component (a).
It should be 5 parts by weight, and if it is less than 0.1 parts by weight, the curing rate will be remarkably slowed, and if it exceeds 5 parts by weight, the stability of the viscosity will be significantly impaired. A more preferable range is 0.5 to 3 parts by weight.

The compound having a --COO-- structure as the component (d) is a salt of at least one compound selected from carboxylic acids or esters. Specific examples of such compounds include fatty acids such as stearic acid and oleic acid, salts of N-acyl amino acids or alkyl ether carboxylic acids, and dialkylsulfosuccinic acid ester salts. The addition amount thereof is 0.2 to 3 with respect to 100 parts by weight of the epoxy resin of the component (a).
It is not preferable because if it is less than 0.2 parts by weight, the addition effect does not appear, and if it is more than 3 parts by weight, the heat resistance of the cured product decreases. A more preferable range is 0.5
~ 2 parts by weight.

The role of the component (d) in the present invention is very large. This is because normally, if only the components (a), (b), and (c) are excellent in heat resistance and the like, the tensile elongation of the cured resin is low, and in some cases, the tensile elongation of CF is lower than that of the unidirectional component. The resin destruction becomes rate-limiting in the tension in the ° direction, and the effect of reinforcement by CF cannot be fully exerted, but the addition of the component (d) increases the elongation of the cured resin without sacrificing other properties. This is because it can be greatly improved.

[0012]

EXAMPLES The present invention will be described in more detail below with reference to Examples. Abbreviations of compounds in Examples and Comparative Examples and test methods are as follows. Ep828: Bisphenol A type epoxy resin (Molecular weight: about 380, manufactured by Yuka Shell Co., Ltd.) Ep834: Bisphenol A type epoxy resin (Molecular weight: about 470, manufactured by Yuka Shell Co., Ltd.) MNA: MethPA anhydrous methyltetrahydrophthalic anhydride 2E4MZ: 2-Ethyl-4-methylimidazole DASS: Dialkylsulfosuccinate ester salt

[0013]

[Chemical 1]

<Bending test (3-point bending)> Device: Orientec Tensilon sample shape, L / D (= distance between fulcrums / thickness): Resin plate 60 mm ¹ × 8 mm ^w × 2 mm ^t L / D = 16: Component 0 ° 120 mm ¹ × 10 mm ^w × 2 mm ^t L / D = 40: 90 ° 60 mm ¹ × 10 mm ^w × 2 mm ^t L / D = 16 Indenter tip radius: 3.2 mm Cross head speed: 2 mm / min <TMA Tg measurement> Equipment: TA Instruments 943TMA mode: Expansion load: 1g Temperature rising rate: 10 ° C / min

(Examples 1 to 10) The compositions shown in Table 1 (numerical values are parts by weight) were poured between two glass plates sandwiching a 2 mm spacer and placed in a drier at 140 ° C. for 60 minutes for curing. It was Table 2 shows the results obtained by cutting a test piece from the obtained resin plate and performing a bending test and TMA Tg measurement. From the table, it can be seen that the balance of physical properties such as elongation and heat resistance is very good. Further, these resins were placed in a bath at 40 ° C., a unidirectional flat plate was wound by the FW method using CF of carbon fiber TR-30G manufactured by Mitsubishi Rayon Co., Ltd., and cured by a press. Molding condition is press pressure 5k
140 ° C. × 60 minutes at g / cm ² , volume content of CF is 6
It was 0%. Table 2 shows the results of the 0 ° and 90 ° bending tests of the obtained component. It can be seen that the component properties are also very good.

Comparative Examples 1 and 2 Evaluations were made in the same manner as in Examples except that the composition was changed as shown in Table 1. The evaluation results are shown in Table 2. When the amount of the curing agent was too small, the elastic modulus of the resin was extremely low, the heat resistance was low, and the component properties were poor. Further, even if the amount of the curing agent was too large, the heat resistance was low and the 90 ° bending strength was not so good.

Comparative Examples 3 and 4 Evaluations were made in the same manner as in Examples except that the composition was changed as shown in Table 1. The evaluation results are shown in Table 2. If the amount of catalyst is too small, the reactivity will decrease and the temperature will be 140 ° C x 6
It seemed that the curing was insufficient at 0 minutes. Further, when the amount of the catalyst was too large, the resin in the bath was considerably thickened, which is probably due to the effect, but the bending strength at 90 ° was not so good because the impregnation property was lowered.

Comparative Examples 5 to 7 Evaluations were made in the same manner as in Examples except that the composition was changed as shown in Table 1. The evaluation results are shown in Table 2. In the system where DASS is not added or the amount added is small, the bending elongation of the resin is not good and
Especially, the 90 ° bending strength was not so good. In addition, when the addition amount was too large, the elastic modulus and Tg of the resin physical properties decreased.

(Comparative Example 8) Evaluation was made in the same manner as in Example except that the composition was changed as shown in Table 1. The evaluation results are shown in Table 2. Again, since the viscosity was slightly high, impregnation was poor, and the 90 ° bending strength of the component was slightly lower than when the resin of the present invention was used.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

The CFR of the present invention configured as described above.
Since the epoxy resin composition for P has a low viscosity at room temperature, it has an excellent impregnation property into the reinforcing fiber and an excellent balance of curability and viscosity stability. Furthermore, the cured resin has an excellent balance between elongation and heat resistance, and the component obtained using the resin composition of the present invention exhibits very good physical properties. Further, since the epoxy resin composition of the present invention has excellent stability in the process, it is suitable for FW, RTM molding and the like.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI // C08J 5/04 CFC C08J 5/04 CFC (56) References JP-A-7-268067 (JP, A) JP-A-3 -17118 (JP, A) JP 59-6442 (JP, A) JP 59-6441 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08G 59/00- 59/72 C08L 63/00-63/10 C08J 5/04-5/10

Claims (3)

(57) [Claims] 1. A bisphenol A type epoxy resin having a molecular weight of 400 or less: 100 parts by weight (b) a liquid acid anhydride curing agent: 50 to 120% of a stoichiometric amount based on the epoxy resin of component (a). (C) Imidazole-based catalyst: 0.1 to 5 parts by weight (d) Salt of at least one compound selected from carboxylic acids or esters having a -COO- structure: 0.2 to 3 parts by weight Epoxy resin composition for CFRP 2. The epoxy resin composition for CFRP according to claim 1, wherein the component (b) is methyltetrahydrophthalic anhydride. Wherein component (d) according to claim 1 or 2 one term CFRP epoxy resin composition described dialkyl sulfosuccinate.