JP3349556B2 - 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 which cures at a relatively low temperature and a prepreg for a fiber-reinforced composite material obtained by combining the epoxy resin composition with a reinforcing fiber.

[0002]

2. Description of the Related Art Epoxy resins have been used in a wide range of fields because of their excellent mechanical and electrical properties after curing. For example, there are a wide variety of materials such as sealants for electronic materials, paints / paving materials, and adhesives. Furthermore, in recent years, it has been used as a matrix resin for composite materials due to its excellent mechanical properties and heat resistance, and has been widely used from aircraft to general-purpose applications such as fishing rods and golf club shafts.

Among these, matrix resins for prepregs (precursors for composite materials in which a matrix resin and a reinforcing fiber are combined) used for general-purpose applications are, of course, excellent in mechanical properties after curing and of course, at room temperature of prepregs. Excellent stability and handleability are required. Further, there is an increasing demand for a matrix resin which is cured at a low temperature or cured for a short time in order to shorten the molding cycle and reduce the energy cost. From room temperature to 80
Some resin already cures at low temperatures of の 90 ° C. However, most of them are so-called hand lay-up resin compositions in which a main agent and a curing agent are mixed immediately before curing, and have poor stability at room temperature, and their pot life is on the order of minutes to hours. In addition, the viscosity of the resin immediately after mixing is low, and the handling properties and working environment are poor. The emergence of a matrix resin that can be cured at a low temperature with these disadvantages improved and that can be prepregged by the hot melt film method like the current 130 ° C. cured matrix resin is expected to solve all of the above problems. I have.

As a means for meeting these demands, Japanese Patent Application Laid-Open No. 61-43616 discloses an epoxy resin, a dibasic acid dihydrazide compound, a urea compound and an alcohol or phenol compound having a melting point of 50 ° C. or more. Are disclosed. These epoxy resin compounds have a stability at 30 ° C. of 14 days or more, but cannot be used practically at a curing temperature of 90 ° C. or less due to poor curing.

Japanese Patent Application Laid-Open No. 1-129084 discloses a resin adhesive comprising an epoxy resin, a reaction product of bisphenol A and monoglycidyl ether of bisphenol A, and an imidazole compound which is both a curing agent and a curing accelerator. Have been. However, the carbon fiber reinforced resin (CFRP) using this resin composition as a matrix resin has a unidirectional CFRP 0 ° bending strength FS // = 1.27G.
Pa, ILSS = 76 MPa, CFRP characteristic FS // = 1.76 which is currently used for general purpose curing at 130 ° C.
GPa and ILSS are extremely lower than 98 GPa.
Further, this resin composition has a large increase in viscosity during resin preparation, and it is difficult to form a hot melt film.

Other than 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. 165, 2
No. 30) and the like, but none of them has sufficient stability at room temperature or requires a high temperature and a long time for curing, and no resin composition sufficiently satisfies the requirements.

[0007] Recently, excellent latent curing agents for epoxy resins have been marketed. If these latent curing agents are used, they are excellent in stability at room temperature and are one-pack type curable at 80 ° C. It is possible to prepare an epoxy resin composition. However, when these resin compositions are used as a matrix resin for a prepreg, it is important that the prepreg has excellent handleability (tack and drape properties) instead of simply being one liquid. As a method for adjusting the viscosity, a method of adjusting the viscosity of the resin is generally used. However, in the case of a material that cures in a relatively low temperature range around 80 ° C, simply introducing a high-molecular-weight solid epoxy resin reduces the reactivity of epoxy molecules at the curing temperature, resulting in a decrease in reactivity and curing. Failure may occur.

[0008] Even if a sufficient amount of a curing agent is added so as not to cause curing failure, the composite material molded from the obtained prepreg can be compared with a composite material molded from a general-purpose 130 ° C cured prepreg. In addition, mechanical properties, particularly the strength in the 90 ° direction and the interlaminar shear strength were low, and there was great anxiety when used as a structural material.

[0009]

SUMMARY OF THE INVENTION The inventor of the present invention has at least 20 days at which the stability at room temperature is practically sufficient, and cures at 80 ° C. until it has practically sufficient characteristics;
When used as a matrix resin for prepreg, it is an object to provide a resin composition in which a composite material has mechanical properties equivalent to those of a general-purpose 130 ° C. curing type at a molding temperature of 80 ° C.

[0010]

The present invention employs the following means in order to solve the above-mentioned problems. That is, the present invention
(A) epoxy resin: 100 parts by weight, (b) bisphenol compound, or reaction product of bisphenol compound and monoglycidyl ether of bisphenol compound:
5 to 100 parts by weight, (c) urea epoxy resin curing agent,
(D) An epoxy resin composition comprising a heat-curable microcapsule-type latent curing agent that starts a reaction at around 80 ° C., and a prepreg for a fiber-reinforced composite material obtained by combining the epoxy resin composition with a reinforcing fiber. The resin composition of the present invention can be cured at 80 ° C., and has sufficient storage stability such that the prepreg life at 25 ° C. is 20 days or more. The CFRP obtained by curing the obtained prepreg has properties equivalent to those of the current general-purpose CFRP cured at 130 ° C.

The epoxy resin used as the component (a) in the present invention is not particularly limited, and includes bisphenol A type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, and glycidylamine type epoxy resin. No. Of these, it is preferable to use a bisphenol A type epoxy resin which is balanced in terms of handleability, obtained CFRP characteristics, or economy. In addition, the liquid epoxy resin and the solid epoxy resin should be mixed and used at an optimum viscosity in use from the viewpoint of handleability, or a product obtained by reacting the epoxy resin with an amine compound or the like to the extent that the epoxy resin does not gel is used. It is a more preferred embodiment of the invention.

The bisphenol compound as the component (b) is bisphenol A, bisphenol F or bisphenol S, and these can be used alone or in combination. It is more preferable to use a reaction product of these bisphenol compounds and a monoglycidyl ether of the bisphenol compound. This reaction product can be easily synthesized. A reaction product of bisphenol A and bisphenol A monoglycidyl ether is commercially available from Dow Chemical Company as DEH-85. In the present invention, these compounds are
Used in the range of 100 parts by weight. If the additive exceeds 5 parts by weight, the resulting cured resin will have a low elongation, which will also adversely affect the CFRP properties obtained. If the amount is less than 100 parts by weight, the curing performance of the resin composition at a low temperature is unpreferably reduced.

The urea epoxy resin curing agent of the component (c) is not particularly limited, but a compound represented by the following general formula is preferably used.

[0014]

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Further, compounds represented by the following general formula are also preferably used.

[0016]

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There is no particular limitation on the amount of component (c) to be added, but if the amount is too small, the effect of adding component (c) is not observed, and if it is too large, the life is adversely affected. The preferred range is 2 to 20 parts by weight.

The microcapsule-type latent curing agent of the component (d) must be capable of initiating a reaction at around 80 ° C., and has a core composed of a highly reactive curing agent and at least the core. The shell is made of a material that does not react with the epoxy resin until the curing agent reacts. Examples of the curing agent that can be used as a core component of such a microcapsule-type latent curing agent include amines, polyamides, imidazoles, ureas, hydrazides, and the like, and epoxy adducts of these compounds, and in particular, imidazole. Are preferred because of the excellent heat resistance of the cured resin. As the shell component, high-molecular-weight epoxy resin or polyurethane resin, polyethylene, polypropylene,
Examples include polystyrene, nylon, polyester, polyvinyl chloride, and polyvinylidene chloride. Commercially available as such a microcapsule-type latent curing agent, Novacure HX3721 and HX37 available from Asahi Kasei Corporation.
22, HX3891 and HX3891.

The amount of component (d) added is not particularly limited, but is preferably 2 to 30 parts by weight. If the amount is less than 2 parts by weight, the effect of adding the component (d) may not be obtained, and if it exceeds 30 parts by weight, the stability of the obtained resin composition may be reduced. Whether or not the component (d) starts the reaction at around 80 ° C. can be determined, for example, by using a sample obtained by mixing the component (d) with an appropriate amount of a bisphenol A type epoxy resin (such as Ep828 manufactured by Yuka Shell Co., Ltd.) as a sample, Analysis (DSC)
The determination is made based on whether or not there is a reaction exotherm in the 80 ° C. isothermal measurement.

The curing agents (b) to (d) have already been used alone, and a resin composition having a certain performance has been obtained. However, a resin composition which cures at a low temperature and exhibits excellent cured physical properties and has excellent storage stability at room temperature, which is the object of the present invention, has not been obtained. These objects can be achieved for the first time by using the above three curing agents as in the present invention, and when used as a resin for prepreg, an appropriate tack and drape property can be exhibited. The selection and combination of such a curing agent and a curing accelerator are the gist of the present invention.

In order to improve the flowability and tackiness during molding, a thermoplastic resin may be added to the resin composition of the present invention to such an extent that the curability and storage stability are not affected. The addition form may be either dissolution or dispersion. Examples of such a thermoplastic resin include polyvinyl formal, polyether sulfone, polysulfone, polyarylate, polyamide, polyparabanic acid, and phenoxy resin.

Examples of reinforcing fibers for obtaining a prepreg for a fiber-reinforced composite material in combination with the above-described resin composition of the present invention include carbon fibers, glass fibers, and aramid fibers, but are not particularly limited. is not. Since the epoxy resin composition of the present invention has excellent stability as described above, a so-called hot melt film, which forms a thin film of resin on release paper by heating the resin, can be stably adjusted. For this reason, it becomes possible to manufacture a prepreg by a hot melt method, which is impossible with a conventional low-temperature curing resin. This makes it possible to manufacture prepregs that are not based on the hand lay-up method or the lacquer method using a solvent, which has been common in conventional low-temperature curing resins, which is very advantageous both economically and in terms of working environment. .

[0023]

The present invention will be described in more detail with reference to the following examples. Abbreviations of compounds in the examples and test methods are as follows. The curing molding conditions were all 80 ° C. × 5 hours unless otherwise specified. Ep828: Bisphenol A type epoxy resin (manufactured by Yuka Shell) Ep1001: Bisphenol A type epoxy resin (manufactured by Yuka Shell) DEH-85: Bisphenol A modified curing agent (manufactured by Dow Chemical Company) DCMU: 3,4-di Chlorphenyl-N, N-
Dimethylurea Omicure 94: 3-phenyl-1, 1-dimethylurea (manufactured by ACI Japan)

[0024]

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Omicure 24: 1, 1'-4 (methyl-
m-phenylene) bis (3,3′dimethylurea)
(Manufactured by ACI Japan)

[0026]

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HX3722: microcapsule type latent curing agent (manufactured by Asahi Kasei Corporation) m-PDA: meta-phenylenediamine XDA: xylenediamine PA: phthalic anhydride PMMA: polymethyl methacrylate

<Cured resin bending test (3-point bending)> Apparatus: Orientec Tensilon sample shape, L / D (= distance between supports / thickness): resin plate 60 mm long, 8 mm wide, 2 mm thick, L / D
D = 16: CFRP 0 ° length 120mm, width 10mm, thickness 2mm, L /
D = 40: CFRP 90 ° 60mm in length, 10mm in width, 2mm in thickness, L /
D = 16 ILSS Length 30mm, Width 10mm, Thickness 4mm, L / D = 4 Indenter tip radius: 3.2mm CROSS HEAD SPEED: 2mm / min

<Curing resin viscoelastic properties> Apparatus: RDA-700 manufactured by Rheometrics Sample shape: length 60 mm, width 12 mm, thickness 2 mm Heating condition: 1 ° C / min Deformation rate: 6.28 rad / sec (= 1 Hz)

<Measurement of Exothermic Curing> Apparatus: 910-DSC made by DuPont Measurement conditions: Isothermal measurement

[Preparation 1] m-PDA as a core component
And PMMA was microencapsulated as a shell component. This microcapsule type curing agent is designated as d-1.

[Preliminary Reaction 2] XDA was used as a core component, and PMMA was microencapsulated as a shell component. This microcapsule type curing agent is referred to as d-2.

[Preliminary Reaction 3] PA was used as a core component, and PMMA was microencapsulated as a shell component. This microcapsule type curing agent is referred to as d-3.

Example 1 Epoxy resin Ep1001:
30 parts by weight, 70 parts by weight of Ep828, and 60 parts by weight of a phenolic curing agent DEH-85 were charged 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 also dropped, 10 parts by weight of Omicure 94 and 5 parts by weight of HX3722 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 molded under the curing conditions shown in Table 1 to obtain a transparent cured resin. Using this resin plate, a bending test and a viscoelasticity measurement were performed. The results are shown in Table 1.
Further, in order to confirm the curability of HX3722 at 80 ° C., 30 parts by weight of a composition was prepared with respect to 100 parts by weight of Ep828, and the curing heat generation at 80 ° C. was measured.
It was confirmed that HX3722 was cured at 80 ° C. due to heat generation during curing.

[0035]

[Table 1]

Example 2 A unidirectional prepreg was produced from the resin composition (before curing) obtained in Example 1 and carbon fibers (Pyrofil TR-40 manufactured by Mitsubishi Rayon Co., Ltd.) by a hot melt method. The film formation temperature was 50 ° C., and the impregnation into the carbon fiber was 70 ° C. This prepreg had appropriate tack and drape properties, and showed little change in tack and drape properties even after storage at 25 ° C. for one month, and had good storage stability. The evaluation of tackiness and drapability was performed by wrapping a prepreg around a pencil having a diameter of 8 mm, confirming that the prepreg did not crack or unwound, and evaluated the quality. This prepreg is about 2mm in one direction
It was laminated to a thickness and formed by vacuum forming. Vf (volume content of CF) of the obtained one-way CFRP is 60%,
As a result of performing a 0 ° and 90 ° bending and ILSS test,
° direction: FS // = 184 kg / mm ² , 90 ° direction: F
S⊥ = 10.4 kg / mm ² , ILSS = 8.9 kg /
mm ² .

[0037]

[Table 2]

Example 3, Comparative Example 1 A resin composition was prepared and cured in the same manner as in Examples 1 and 2 except that the amount of DEH-85 was changed as shown in Table 2, and a cured resin, and one-way CF
RP was created. The mechanical properties of the resin and CFRP were evaluated, and the obtained results are shown in Table 2.

[Examples 4 and 5] 94:10 parts by weight of Omicure of the component (c) of Examples 1 and 2 were added to DCMU:
10 parts by weight (Example 4), and Omicure 24:10
A resin composition was prepared and cured in the same manner as in Examples 1 and 2 except that the amount was changed to parts by weight (Example 5) to form a cured resin and a one-way CFRP. Table 3 shows the obtained results.

[Examples 6 and 7, Comparative Example 2] d-1 in which 5 parts by weight of HX3722 of the component (d) of Examples 1 and 2 were obtained by preliminary reactions 1 to 3, respectively (Example 6) , D-2
(Example 7), d-3 (Comparative Example 2): A resin composition was prepared and cured in the same manner as in Examples 1 and 2 except that each was changed to 5 parts by weight, and a cured resin and one-way CFRP was formed. Table 3 shows the obtained results. Also, d-1, d-
In order to confirm the curability at 80 ° C. of each of d and d-3, 30 parts by weight of a composition was prepared with respect to 100 parts by weight of Ep828, and the exothermic curing at 80 ° C. was measured. 1, d-2 was cured at 80 ° C., but d-3 was not cured.

[0041]

[Table 3]

[0042]

When the resin composition of the present invention is used, a temperature of 80.degree.
Cures to a practically sufficient degree. Further, the prepreg for CFRP by the hot melt film method using the resin of the present invention has practically sufficient stability of 20 days or more at room temperature, and has an appropriate tack and drape property.
The mechanical properties of FRP also show the same performance as the current 130 ° C cured product. Furthermore, the resin composition of the present invention is economical in production,
Alternatively, it has a great feature in comparison with the conventional low-temperature-curable epoxy resin composition even in the problem of the working environment, which has become a particular problem in recent years. For this reason, it is expected to be used in fields that have not been used in curing conditions, room temperature stability of prepreg, or work environment.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-325518 (JP, A) JP-A-62-174221 (JP, A) JP-A-6-322068 (JP, A) JP-A 61-174 43616 (JP, A) JP-A-1-129084 (JP, A) JP-A-6-9758 (JP, A) JP-A-5-310890 (JP, A) JP-A-2-292325 (JP, A) JP-A-53-125475 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 59/40-59/62 C08J 5/24

Claims (5)

(57) [Claims] (A) epoxy resin: 100 parts by weight (b) bisphenol compound or reaction product of bisphenol compound and monoglycidyl ether of bisphenol compound: 5 to 100 parts by weight (c) urea-based epoxy resin curing agent (D) An epoxy resin composition comprising a heat-curable microcapsule-type latent curing agent which starts a reaction at around 80 ° C. 2. An epoxy resin having an epoxy equivalent of 170 to 2
The epoxy resin composition according to claim 1, wherein the epoxy resin composition is a mixture of a liquid bisphenol-type epoxy resin having a molecular weight of 00 and a solid bisphenol-type epoxy resin having an epoxy equivalent of 400 to 4000. 3. The curing agent of component (b) is bisphenol A
The epoxy resin composition according to claim 1, wherein the epoxy resin composition is a reaction product of bisphenol A and a monoglycidyl ether of bisphenol A. 4. A prepreg obtained by impregnating (e) a reinforcing fiber with the epoxy resin composition according to claim 1. 5. The prepreg according to claim 4, wherein a carbon fiber is used as the reinforcing fiber of the component (e).