JP5100001B2 - Epoxy resin composition for fiber reinforced composite materials - Google Patents

Description

  The present invention relates to an epoxy resin composition for fiber-reinforced composite materials that can be suitably used for sports applications, aerospace applications, and general industrial applications.

BACKGROUND ART Fiber reinforced composite materials composed of reinforced fibers and epoxy resin compositions are widely used for sports applications, aerospace applications, and general industrial applications. In recent years, high-strength carbon fibers with an elongation of 1.5% or more have also been developed, but this is combined with an epoxy resin composition in which the cured product exhibits high elongation, thereby reinforcing the fiber reinforced with high fracture elongation. Development of composite materials is also expected.
However, epoxy resin compositions generally have disadvantages that their cured products are brittle and have low toughness, and even when such epoxy resin compositions are used, the characteristics of high elongation carbon fibers cannot be fully utilized.

As a method of improving the fracture elongation of the cured product of the epoxy resin composition,
1) reduce the crosslink density in the cured product,
2) A method of blending a thermoplastic resin and imparting flexibility is known. However, each of the methods 1) and 2) has a drawback that the heat resistance of the cured product is lowered.

  Therefore, as an attempt to achieve both the elongation and heat resistance of the cured product of the epoxy resin composition, there is a method of dispersing a rubbery polymer such as acrylic rubber, butadiene rubber, or silicone rubber in the thermosetting resin composition. It has been studied (for example, Patent Document 1).

In the method of dispersing such a rubbery polymer in the epoxy resin composition, it is desirable that the rubbery polymer is dispersed in the epoxy resin composition with a uniform size, but generally high. The epoxy resin composition exhibiting heat resistance needs to be cured at a relatively high temperature close to the required heat resistance temperature. At that time, the rubber polymers are fused and aggregated with each other, and the epoxy resin composition It was difficult to obtain a uniformly dispersed state in the cured product.
JP-A-9-227693

  An object of the present invention is to provide an epoxy resin composition for a fiber-reinforced composite material capable of obtaining a cured product having high heat resistance and toughness, particularly high elongation at break.

The first gist of the present invention resides in an epoxy resin composition for fiber-reinforced composite material comprising the following (A1), (B) and (C).
(A1) Graft copolymer obtained by graft polymerization of an alkyl (meth) acrylate monomer and a vinyl polymerizable monomer having a functional group capable of reacting with an epoxy group onto a rubber polymer (B) Epoxy resin (C) Aromatic polyamine curing agent

Moreover, the 2nd summary of this invention exists in the epoxy resin composition for fiber reinforced composite materials formed by containing the following (A2), (B), and (C).
(A2) Graft copolymer obtained by graft polymerization of an alkyl (meth) acrylate monomer and a vinyl polymerizable monomer having two or more vinyl polymerizable functional groups onto a rubbery polymer (B) Epoxy resin (C) Aromatic polyamine curing agent

  ADVANTAGE OF THE INVENTION According to this invention, the epoxy resin composition for fiber reinforced composite materials which can obtain the hardened | cured material which has high heat resistance and toughness, especially high breaking elongation can be provided.

"Rubber polymer"
Examples of the rubbery polymer contained in any of the graft copolymers (A1), (A2), and (A3) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, ethoxyethoxyethyl (meth) acrylate, methoxytripropylene glycol (meth) acrylate, 4-hydroxybutyl (meth) acrylate, Examples include lauryl (meth) acrylate and stearyl (meth) acrylate. N-butyl acrylate and ethyl acrylate are preferred. The monomer may include a monomer having two or more vinyl polymerizable functional groups. Although not particularly limited, allyl methacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, divinylbenzene and the like can be mentioned. Allyl methacrylate is preferred.

“A1”
In the present invention, a graft copolymer obtained by graft-polymerizing an alkyl (meth) acrylate monomer and a vinyl polymerizable monomer having a functional group capable of reacting with an epoxy group onto a rubbery polymer is used as A1.

  Examples of the alkyl (meth) acrylate monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, and the like. Preferred are methyl methacrylate and ethyl acrylate.

  Since a vinyl polymerizable monomer having a functional group capable of reacting with an epoxy group is graft-polymerized, when the epoxy resin composition of the present invention is heat-cured, the graft copolymer reacts with the epoxy resin, Therefore, the graft copolymers do not contact and fuse with each other.

Examples of the functional group capable of reacting with an epoxy group include an epoxy group, a hydroxyl group, an amide group, an imide group, an amine group, an imine group, a carboxylic acid group, and a carboxylic anhydride group. Examples of the vinyl polymerizable monomer include glycidyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylic acid, (meth) acrylamide and the like. Glycidyl methacrylate is preferred.
The vinyl polymerizable monomer having a functional group capable of reacting with an epoxy group is preferably 30 parts by mass or less, more preferably 10 parts by mass or less in 100 parts by mass of the graft copolymer. When using glycidyl methacrylate, it is preferably 3 parts by mass or less.

“A2”
In the present invention, a graft copolymer obtained by graft-polymerizing an alkyl (meth) acrylate monomer and a vinyl polymerizable monomer having two or more vinyl polymerizable functional groups onto a rubbery polymer is used as A2.
The alkyl (meth) acrylate monomer is as described in “A1”.
As the vinyl polymerizable monomer having two or more vinyl polymerizable functional groups, the rubber is heated in a state where the shell is heated to the glass transition point or higher when the matrix resin is heated and cured by increasing the degree of crosslinking of the shell component. It is added for the purpose of not fusing even if the fine particles come into contact with each other. These types are not particularly limited, but include allyl methacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, divinylbenzene, and the like. Allyl methacrylate is preferred.

“A3”
In the present invention, a graft copolymer obtained by graft-polymerizing an alkyl (meth) acrylate monomer and a vinyl polymerizable monomer having two or more vinyl polymerizable functional groups onto a rubbery polymer is used as A3.
The alkyl (meth) acrylate monomer and the vinyl polymerizable monomer having two or more vinyl polymerizable functional groups are the same as described above.

“Manufacturing method of A1 to A3”
The polymerization method and polymerization conditions for obtaining the graft copolymer A1 to A3 are not particularly limited, but those produced by a known method such as emulsion polymerization, preferably soap-free emulsion polymerization, can be used.

“Average particle size of A1 to A3”
The average particle diameter of the graft copolymers A1 to A3 is preferably 0.1 to 1 μm. When the average particle size is 0.1 μm or more, the impact resistance can be improved sufficiently and the reinforcing fiber is impregnated with the epoxy resin composition for fiber-reinforced composite material of the present invention. The re-aggregation of the graft copolymer that occurs in the above can be suppressed, and an increase in the viscosity of the epoxy resin composition for fiber-reinforced composite materials can be avoided. On the other hand, when the average particle size is 1 μm or less, when the reinforcing fiber is impregnated with the epoxy resin composition for a fiber-reinforced composite material of the present invention, it can pass through the gap between the single fibers constituting the reinforcing fiber. As a result, the graft copolymer is uniformly distributed in the fiber-reinforced composite material. The average particle diameter of the graft copolymers A1 to A3 is more preferably 0.6 to 0.8 μm.

“Measuring method of average particle diameter of A1 to A3”
In the present invention, the average particle sizes of the graft copolymers A1 to A3 were measured by diluting the latex with distilled water and using a laser diffraction / scattering particle size distribution analyzer (LA-910, manufactured by Horiba, Ltd.). % Volume average particle diameter.

"Epoxy resin"
As the epoxy resin used as (B) in the present invention, various known resins can be used, and the molecular structure, molecular weight and the like are not particularly limited as long as they have at least two epoxy groups in the molecule. For example, various epoxy resins such as bisphenol type, phenol novolak type, cresol novolak type, dicyclopentadiene type, biphenyl type, and oxazolidone ring system can be used alone or in combination of two or more.

"Aromatic polyamine"
Specific examples of the aromatic polyamine used as (C) in the present invention include diaminophenylmethane, metaphenyldiamine, and diaminodiphenylsulfone. Diaminophenyl sulfone is preferred from the heat resistance of the cured product. This aromatic polyamine curing agent may be used in combination with other curing agents. For example, phenolic hardeners such as phenol novolac resin and cresol novolac resin, amine hardeners such as dicyandiamide and imidazoles, aliphatic or aromatic polyamines, acid hardeners such as organic acids, inorganic acids and acid anhydrides, etc. Is mentioned. These usage amounts are not particularly limited.

"Resin viscosity"
The viscosity of the epoxy resin composition for fiber-reinforced composite material of the present invention is not particularly limited, but is preferably in the range of 1 to 1000000 poise at 30 ° C. In resin infusion molding, 1-1000 poise is preferable, and 1-50 poise is more preferable. In the case of using a prepreg or a resin film, 10,000 to 1,000,000 poise is preferable, and 50,000 to 500,000 poise is more preferable.

"Thermoplastic resin"
A thermoplastic resin can be added to the epoxy resin composition for fiber-reinforced composite materials of the present invention. These types are not particularly limited, but polyamide, polyester, polycarbonate, polyether sulfone, polyphenylene ether, polyphenylene sulfide, polyether ether ketone, polyimide, polytetrafluoroethylene, polyether, polyolefin, liquid crystal polymer, polyarylate, polysulfone , Polyacrylonitrile styrene, polystyrene, polyacrylonitrile, polymethacrylate, ABS, AES, ASA, polyvinyl chloride and the like. Polyether sulfone is preferred from the heat resistance of the cured product.

"Additive"
The epoxy resin composition for fiber reinforced composite material of the present invention can be used in combination with various known additives as required. For example, various curing accelerators, silicone oils, natural waxes, synthetic waxes, metal salts of linear fatty acids, acid amides, esters, paraffins and other mold release agents, crystalline silica, fused silica, calcium silicate , Powders such as alumina, calcium carbonate, talc, barium sulfate, inorganic fillers such as glass fiber and carbon fiber, flame retardants such as chlorinated paraffin, bromotoluene, hexabromobenzene, antimony trioxide, carbon black, bengara, etc. Coloring agents, silane coupling agents, and the like can be used.

"Preparation method"
The preparation method of the epoxy resin composition for fiber-reinforced composite material of the present invention is not particularly limited, and a known technique such as a mixing roll or a kneader can be used.

"Reinforcing fiber"
As the reinforcing fiber constituting the fiber reinforced composite material together with the epoxy resin composition for fiber reinforced composite material of the present invention, various inorganic fibers or organic fibers such as glass fiber, carbon fiber, metal fiber, and aramid fiber can be used. In view of the strength of the fiber-reinforced composite material, glass fibers and / or carbon fibers are preferred. Among these, it is more preferable to use carbon fibers from which a fiber-reinforced composite material having excellent specific strength and specific modulus can be obtained. As a method of impregnating the fiber base material with the epoxy resin composition for fiber-reinforced composite material of the present invention, a known method can be used.

"Molding method"
The fiber reinforced composite material using the epoxy resin composition for fiber reinforced composite material of the present invention can be molded by a known method. Examples include, but are not limited to, autoclave molding, oven molding, vacuum back molding, hand layup molding, resin transfer molding (RTM), resin infusion molding such as vacuum assist RTM, and press molding. It is not something. A molding method via a prepreg is preferred. Particularly preferred are autoclave molding, oven molding, and vacuum back molding.

Hereinafter, the present invention will be described more specifically with reference to examples. Abbreviations of substance names and evaluation methods in Examples and Comparative Examples are as follows.
"Abbreviation of substance name"
"Epoxy resin"
YH434L (trade name): tetrafunctional epoxy resin manufactured by Toto Kasei Co., Ltd. ELM-100 (trade name): trifunctional epoxy resin manufactured by Sumitomo Chemical Co., Ltd. Epicoat 828 (trade name): bisphenol A type manufactured by Japan Epoxy Resin Co., Ltd. Epoxy resin BPA328 (trade name): Nippon Shokubai Co., Ltd. acrylic rubber dispersed bisphenol A type epoxy resin "Aromatic polyamine curing agent"
DDS: Diaminodiphenyl sulfone "thermoplastic resin"
PES: Polyethersulfone

“Measurement of rupture elongation (ε) of cured resin”
A 2 mm thick cured resin plate is cut into 60 mm × 8 mm, and the crosshead speed is 2 mm / min, the curvature of the support and nose indenter is R = 3.2, and the ratio of the specimen thickness to the support span is L / D = 16. A test was conducted. The breaking elongation ε was calculated according to the following equation, where D was the crosshead displacement when the test piece broke, d was the test piece thickness before the test, and L was the support span.
ε = 6 Dd / L ²

“Measurement of fracture toughness value (G _IC ) of cured resin”
In accordance with ASTM D5045 (SENB method), a cured resin plate having a thickness of 3 mm is cut into a predetermined size, and the mode I critical energy release rate G _IC of a test piece having a notch formed by applying a cutter blade to the cut portion is obtained. It was.

"Measurement of glass transition temperature ( _Tg ) of cured resin"
Using a rheometer (RDA-700, manufactured by Rheometric), the temperature was raised stepwise from 30 ° C. by 5 ° C., the loss tangent Tan δ at each temperature was plotted against the temperature, and the temperature at which Tan δ was maximized was measured. and the glass transition temperature _{T g.}

"Production example of graft copolymer"
(Production Example 1) Graft copolymer (M-1)
A 5 liter flask was charged with 88 parts of pure water, 5 parts of butyl acrylate, and 0.125 part of allyl methacrylate, and heated to 80 ° C. with stirring at 250 rpm in a nitrogen atmosphere. Next, a pre-prepared solution of 0.10 parts of potassium persulfate and 5.2 parts of pure water was added all at once and held for 60 minutes to perform the first stage soap-free emulsion polymerization. Next, 65 parts of butyl acrylate, 1.625 parts of allyl methacrylate, 0.6 parts of sodium di (2-ethylhexyl) sulfosuccinate (manufactured by Kao Corporation; trade name: Perex OT-P), 34.0 parts of pure water Was added dropwise over 180 minutes and held for 1 hour, and emulsion polymerization of the second stage was performed to obtain an acrylic rubber polymerized latex (rubber polymer R-1).
In the obtained R-1, 28.4 parts of methyl methacrylate, 0.6 part of ethyl acrylate, 1 part of glycidyl methacrylate, 0.4 part of sodium di (2-ethylhexyl) sulfosuccinate, and 15.6 parts of pure water Was added dropwise over 100 minutes, and after 1 hour, the emulsion polymerization was terminated to obtain a graft copolymer latex. The obtained graft copolymer latex was sprayed in the form of fine droplets by a pressure nozzle method using a spray dryer, dried at a hot air inlet temperature of 180 ° C., and a modifying agent (M-1 )

(Production Example 2) Graft copolymer (M-2)
To R-1 obtained in Production Example 1, 28.4 parts of methyl methacrylate, 0.6 part of ethyl acrylate, 0.75 part of allyl methacrylate, 1 part of glycidyl methacrylate, sodium di (2-ethylhexyl) sulfosuccinate 0.4 A mixture of 15.6 parts of pure water and 15.6 parts of pure water was added dropwise over 100 minutes, and after holding for 1 hour, the emulsion polymerization was terminated to obtain a graft copolymer latex. The obtained graft copolymer latex was sprayed in the form of fine droplets with a pressure dryer using a spray dryer, dried at a hot air inlet temperature of 180 ° C., and a modifier having an average latex particle size of 610 nm (M-2 )

(Production Example 3) Graft copolymer (M-3)
To R-1 obtained in Production Example 1, 28.4 parts of methyl methacrylate, 0.6 part of ethyl acrylate, 0.75 part of allyl methacrylate, 0.4 part of sodium di (2-ethylhexyl) sulfosuccinate, 15 pure water .6 parts of the mixed solution was dropped over 100 minutes, and after 1 hour, the emulsion polymerization was terminated to obtain a graft copolymer latex. The obtained graft copolymer latex was sprayed in the form of fine droplets by a pressure nozzle method using a spray dryer, dried at a hot air inlet temperature of 180 ° C., and a modifier having an average particle diameter of 600 nm (M-3 )

(Production Example 4) Graft copolymer (M-4)
A mixture of 29.4 parts of methyl methacrylate, 0.6 part of ethyl acrylate, 0.4 part of sodium di (2-ethylhexyl) sulfosuccinate, and 15.6 parts of pure water was added to the latex R-1 obtained in Production Example 1. Was added dropwise over 100 minutes, and after 1 hour, the emulsion polymerization was terminated to obtain a graft copolymer latex. The latex average particle size was 600 nm. The obtained graft copolymer latex was sprayed in the form of fine droplets by a pressure nozzle method using a spray dryer, dried at a hot air inlet temperature of 180 ° C., and a modifier having an average particle diameter of 600 nm (M-4 )

Example 1
In the composition ratio shown in Table 1, PES was dissolved in YH434L by heating at 170 ° C. for 3 hours in the flask. To this, ELM-100 and Epicoat 828 were mixed in a flask using a three-one motor stirring bar, and 10 parts by weight of the graft copolymer (M-1) was further added and mixed. DDS was added to the mixture and mixed until uniformly dispersed to obtain an epoxy resin composition (NR-1). The epoxy resin composition is cast between glass plates sandwiching a 2 or 3 mm spacer, and is cured by heating at 180 ° C. for 2 hours in a hot air drier to cure a cured resin (CR 2 or 3 mm thick) -1) was obtained. The color tone of the cured resin (CR-1) showed homogeneity, and the rubber component was uniformly dispersed. The cured toughness value G _IC , breaking elongation ε, and glass transition temperature T _g of the cured resin (CR-1) all showed high values. The measurement results are shown in Table 2.

(Example 2)
A resin composition (NR-2) and a cured resin (CR-2) were obtained in the same manner as in Example 1 except that the graft copolymer (M-2) was used instead of the graft copolymer (M-1). ) The color tone of the cured resin (CR-2) showed homogeneity as in (CR-1), and the rubber component was uniformly dispersed. These fracture toughness values G _IC , elongation at break ε, and glass transition temperature T _g all showed high values. The measurement results are shown in Table 2.

(Example 3)
A resin composition (NR-3) and a cured resin (CR-3) were obtained in the same manner as in Example 1 except that the graft copolymer (M-3) was used instead of the graft copolymer (M-1). ) The color tone of the cured resin (CR-3) showed homogeneity as in (CR-1), and the rubber component was uniformly dispersed. These fracture toughness values G _IC , elongation at break ε, and glass transition temperature T _g all showed high values. The measurement results are shown in Table 2.

(Comparative Example 1)
A resin composition (NR-4) and a cured resin (CR-4) were obtained in the same manner as in Example 1 except that the graft copolymer (M-4) was used instead of the graft copolymer (M-1). ) In this cured resin (CR-4), it was observed with the naked eye that the transparent phase and the opaque white turbid phase were phase-separated, and the rubber component was not uniformly dispersed. Although the fracture toughness value G _IC and the glass transition temperature T _g of the cured resin (CR-4) showed high values, the elongation at break ε was low. The results are shown in Table 2.

(Comparative Example 2)
A resin composition (NR-5) and a cured resin product (CR-5) were obtained in the same manner as in Example 1 except that the graft copolymer (M-1) was not added. The cured resin (CR-5) had a transparent and uniform appearance because it did not contain any rubber component. Although elongation at break ε and a glass transition temperature T _g of the cured resin (CR-5) showed a high value, fracture toughness G _IC was low. The results are shown in Table 2.

(Comparative Example 3)
A resin composition (NR-6) and a cured resin product (CR-6) were obtained in the same manner as in Comparative Example 2 except that BPA328 was used instead of Epicoat 828. In the cured resin (CR-6), it was observed with the naked eye that the transparent phase and the opaque white turbid phase were separated, and the rubber component was not uniformly dispersed. Although the glass transition temperature T _g of the cured resin (CR-6) showed a high value, breaking elongation ε and fracture toughness G _IC is a value inferior to the Examples 1-3. The results are shown in Table 2.

Claims (1)

An epoxy resin composition for fiber-reinforced composite material comprising the following (A2), (B) and (C).
(A2) an alkyl (meth) acrylate monomer ;
A vinyl polymerizable monomer having two or more vinyl polymerizable functional groups selected from allyl methacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, and divinylbenzene. With a mass ,
A graft copolymer (B) epoxy resin (C) aromatic polyamine curing agent having an average particle size of 0.6 to 0.8 μm obtained by graft polymerization of a rubber polymer