JPH0832765B2 - Epoxy resin composition, prepreg, cured product thereof, and composite material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides an epoxy resin cured product having high toughness, high elastic modulus, heat resistance, thermal decomposition resistance, low water absorption and solvent resistance. The present invention relates to a resin composition, a prepreg using the resin as a matrix resin, a cured product thereof, and a fiber reinforced plastic.

[Prior Art] Epoxy resins are widely used in various industrial fields such as molding, lamination, adhesives, and sealants by taking advantage of their excellent mechanical properties and chemical resistance. In particular, epoxy resins are often used for reinforcing fibers and fiber-reinforced composite materials containing matrix resin as an essential component. On the other hand, however, the epoxy resin has a drawback that it is brittle and has a problem that the cured product has poor impact resistance. Particularly when used for structural materials such as aircraft and automobiles, poor impact resistance is a major problem.

Various attempts have been made to improve the drawbacks of these epoxy resins, especially the brittleness.

As described in Diamant et al., P.422-436 of the 29th National Sampe Symposium (1984), a rubber-like polymer having a terminal functional group (for example, a carboxyl group-terminated butadiene / acrylonitrile rubber) is used as an epoxy resin. Addition improves the resin toughness. But,
It has a drawback that the elastic modulus (particularly at high temperature) is greatly reduced.

In addition, the improvement of toughness by adding this rubber is effective only for epoxy resins having a low crosslink density, and cannot be applied to epoxy resins having a high crosslink density (see “Elastomer-modified epoxy resin toughness mechanism, second report”). Proven in NASA Contractor Report 3852p.20 (1984).

Thermoplastic resins have been added to epoxy resin compositions in an attempt to increase the toughness of high crosslink density epoxy resins. In Polymer Vol.30p.213 (1989), CB Backnal et al. Are studying polyetherimide as a modifier. The cured resin has a microphase-separated structure, and as the amount of polyetherimide added increases, the morphology in which polyetherimide forms a domain changes from the morphology in which polyetherimide forms a continuous phase, and as the amount added increases. It states that the toughness of the cured resin is improved. However, as described that the phase of polyetherimide is easily dissolved by methylene chloride, it has a drawback of poor solvent resistance. In addition, there is also a drawback that the viscosity of the composition becomes extremely high because of the addition of the high molecular weight thermoplastic resin, and the workability is greatly reduced.

Attempts have also been made to use a thermoplastic resin having a functional group capable of reacting with epoxy at the terminal and having a molecular weight in the oligomer region as a modifier so that a large amount can be added. For example, in U.S. Pat. No. 4,656,208 and JP-A-61-228016, studies have been made on adding a polysulfone oligomer having an epoxy-reactive functional group at the end to an epoxy resin composition. It is stated that the cured resin has a microphase-separated structure (sea-island structure), and polypyrsulfone exists in a high concentration in the continuous phase, and exhibits high toughness. Similar review
J. at the Annual Sampe Symposium P.580 (1986)
-It has been announced by E. McGrath and others. It is stated that the resin toughness increases as the molecular weight of polysulfone increases or the amount of polysulfone increases, but the viscosity of the system increases and workability decreases. In European Patent Publication No. 0311349 (1989), it is also considered to add an amine-terminated polyallylsulfone to an epoxy resin composition. Although the morphology of the cured resin is unclear because the photograph is unclear, one with a uniform structure due to the skeleton structure of polyallylsulfone, one having a continuous structure with both polyallylsulfone phase and epoxy resin phase separated, and a continuous phase It is said that the island phase of polyallylsulfone will change to the epoxy phase. Then, it is stated that the toughness is highest when both the polyallylsulfone phase and the epoxy resin phase have a continuous structure.

However, when a polylsulfone-based modifier is used, the heat resistance of the epoxy resin cannot be improved, and the heat resistance will be reduced depending on the epoxy resin selected.

An attempt has been made to improve the toughness of an epoxy resin while simultaneously improving the glass transition temperature (Tg) in a wet state.
-622. If a polyamide, imide or amide imide oligomer having a reactive terminal is used as the toughness modifier, the Tg of the oligomer is equal to or higher than the Tg of the epoxy resin, so not only the toughness but also the Tg in the wet state is improved. Is. Aromatic polyimide is generally difficult to dissolve in a solvent, but it is well known that the solubility of the polyimide is improved by introducing a bulky substituent into the benzene ring of the aromatic diamine. Also in the case of JP-A-2-622, a polyimide synthesized by using a diamine having a substituent on the benzene ring such as p-bis (4-isopropylidene-2,6-dimethylaniline) benzene shown in the examples. Is said to be soluble in epoxy resins below about 80 ° C. It is a polyimide that is easily dissolved in a solvent as it is dissolved in acetone and methyl ethyl ketone. The toughness value of the cured epoxy resin prepared by adding 30 wt% of the imide oligomer is at most However, it is not sufficient (assuming an elastic modulus of 3.6 GPa.
G _IC = 630 J / m ² ).

[Problems to be Solved by the Invention] The present inventors have excellent high toughness, and at the same time, have high elastic modulus, low water absorption, high heat resistance, high thermal decomposition resistance, and high solvent resistance, and As a result of intensive studies on an epoxy resin composition giving a cured product having high stability of physical properties, a prepreg using the same as a matrix resin, a cured product thereof and a fiber reinforced plastic, the following invention was reached.

[Means for Solving the Problems] In order to achieve the above object, the present invention employs the following configurations.

That is, the epoxy resin composition of the present invention essentially includes the following constituent elements [A] and [B].

[A]: Epoxy resin [B]: A polyimide having an amino group terminal as an essential component having the structure of formula I The present invention also provides a prepreg containing the above resin as a matrix resin, a cured product thereof, and a fiber reinforced plastic.

 Hereinafter, description will be added for each component.

The element used as the constituent element [A] in the present invention is an epoxy resin. An epoxy resin is a resin having an average of two or more epoxy groups per molecule. In particular, an epoxy resin using an amine, a phenol, or a compound having a carbon-carbon double bond as a precursor is preferable.

Specifically, as an epoxy resin having an amine as a precursor, tetraglycidyldiaminodiphenylmethane,
Triglycidyl-p-aminophenol, triglycidyl-m-aminophenol, various isomers of triglycidylaminocresol, and epoxy resins containing phenols as precursors include bisphenol A type epoxy resins,
Bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin,
Examples of the cresol novolac type epoxy resin, the resorcinol type epoxy resin, and the epoxy resin having a compound having a carbon-carbon double bond as a precursor include an alicyclic epoxy resin.

Brominated epoxy resins obtained by bromizing these epoxy resins are also used.

These epoxy resins may be used as a mixture of two or more kinds, and may contain a monoepoxy compound.

For example, a composition obtained by combining a glycidyl amine type epoxy resin and a glycidyl ether type epoxy resin is preferable because it has both heat resistance, water resistance and good workability.
In particular, a combination of glycidyl amine type epoxy resins such as triglycidyl-p-aminophenol and triglycidyl-m-aminophenol derivatives and glycidyl ether type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin and resorcinol type epoxy resin. Gives a resin composition excellent in workability due to the low viscosity of each resin.

Usually, epoxy resin is used in combination with a curing agent. As the curing agent, any compound having an active group capable of reacting with an epoxy group can be used. Preferably,
A compound having an amino group, an acid anhydride group, an azido group or a hydroxyl group is suitable. Examples thereof include, but are not limited to, dicyandiamide, various isomers of diaminodiphenyl sulfone, aminobenzoic acid esters, various acid anhydrides, phenol novolac resins, and cresol novolac resins.

Dicyandiamide is preferred because it is excellent in storage stability of prepreg. When an aromatic diamine is used as a curing agent, an epoxy resin cured product having good heat resistance can be obtained. In particular, various isomers of diaminodiphenyl sulfone are most suitable for the present invention because they give cured products having good heat resistance. As the aminobenzoic acid esters, trimethylene glycol di-p-aminobenzoate and neopentyl glycol di-p-aminobenzoate are preferably used. Compared with diaminodiphenyl sulfone, the heat resistance is inferior, but the tensile elongation, Since it has excellent toughness, it is selected and used according to the application.

When an acid anhydride represented by methylhexahydrophthalic anhydride is used as a curing agent, a cured product having high heat resistance is provided, and an epoxy resin composition having low viscosity and excellent workability is obtained.

It is preferable to use a phenol novolac resin or a cresol novolac resin as a curing agent because an ether bond having excellent hydrolysis resistance is introduced into the molecular chain to improve the moisture resistance of the cured product.

Further, various curing catalysts can be used together. A typical example thereof is a monoethylamine complex of boron trifluoride.

A cyanate resin (triazine resin) is also preferably used in combination with an epoxy resin. In this case, cyanate undergoes a curing reaction with epoxy to give a resin cured product having a low water absorption.

As the constituent element [B], an aromatic poiliimide oligomer is used in order to further improve the heat resistance of the epoxy resin and not impair the high elastic modulus and high solvent resistance. Generally, polyimide has excellent heat resistance and solvent resistance among aromatic thermoplastic resins. If it is turned over that it has excellent solvent resistance, it means that it is not easily dissolved in the epoxy resin monomer.

However, the present inventors have found that the polyimide having the skeleton of the above formula I is insoluble in general-purpose solvents such as acetone, methyl ethyl ketone, and methylene chloride but can be dissolved in epoxy resin monomers. Then, by using this as a modifier, the inventors invented an epoxy resin composition having particularly high toughness, high heat resistance, low water absorption and high solvent resistance.

In the case of the above-mentioned known example JP-A-2-622, p-bis (4-isopropylidene-2,6) was used as an aromatic amine used in the synthesis of epoxy-modified polyimide oligomers in the examples.
-Diamine of specific structure such as dimethylaniline) benzene is used. This aims at improving the solubility by having a substituent on the aromatic ring, but when an imide oligomer having such a structure is used, the toughness-improving curing of the epoxy cured product was insufficient.

Further, in the description of the imide oligomer in Japanese Patent Laid-Open No. 2-622, which is a known example, an example in which an amine component is copolymerized is not shown.

However, the present inventors have obtained a polyimide having high toughness, high heat resistance, and low water absorption by using a polyimide oligomer having a skeleton of the formula I, which does not have a substituent on the aromatic ring of the main chain. However, they have found that they are epoxy-soluble and have succeeded in dramatically improving the toughness of epoxy resins.

Further, the constituent element [B] is preferably a copolymer of the structure of formula I and another diamine monomer represented by the structure of formulas II and III.

Particularly, in the formulas II and III, X is -O-, -SO.
_{2 -, - C (CH 3} ) 2 - it is bound is particularly preferable in enhancing the resin toughness.

As the acid dianhydride used in the synthesis, in formula IV, Y is —O— or —CO— or n is 0 to improve the epoxy solubility and to improve the toughness of the cured resin. Is particularly preferable. If a particularly preferred copolymerized polyimide is used, G of the epoxy resin modified by the
_IC exceeds 1000 J / m ² .

X is _{-CO -, - SO 2 -,} - O -, - S-, or -C
(M) _2- (M is hydrogen, alkyl, allyl or haloalkyl), and n is 0 or 1.

Y is _{-CO -, - SO 2 -,} - O -, - S-, or -C
(M) _2- (M is hydrogen, alkyl, or haloalkyl), and n is 0 or 1.

The copolymerization ratio (molar ratio) of the diamine structure of formula I and the diamine structure of formula II and / or formula III in the constituent element [B] is preferably 0.5: 9.5 to 10: 0.

From the viewpoint of viscosity when the constituent element [B] is dissolved in the epoxy resin monomer, the above-mentioned copolymerization ratio is 1: 9 to 5: 5.
Is preferred, and 1: 9 to 3: 7 is particularly preferred. From the viewpoint of toughness of the cured resin, 1: 9 to 3: 7 is preferable. Further, from the viewpoint of heat resistance, 2: 8 to 9: 1 is preferable.

Examples of preferred diamines and acid dianhydrides for oligomer synthesis are given below, but the present invention is not limited thereto.

When used as the aromatic polyimide constituent element [B], a microphase-separated structure in which a phase mainly composed of at least the constituent element [B] becomes a three-dimensionally continuous structure is formed in the cured product, which is conventionally obtained. It becomes a cured product with high toughness that was not available. An example of a fracture surface of a cured product provided by the resin composition of the present invention is shown in FIG. This is a photograph of the fracture surface of the cured epoxy resin product of Example 1, taken with a scanning electron microscope. It can be seen that due to the existence of two phases having different compositions, the energy required for fracture takes a large amount in the form of fracture with severe irregularities.

The phase separation structure period is preferably about 0.01 to 50 microns. If it is 0.01 micron or less, the unevenness of the fracture surface is shallow and it is difficult to exhibit high toughness. On the contrary, even if it exceeds 50 microns, the toughening effect is diminished. The thickness is more preferably about 0.1 to 10 microns, further preferably about 0.5 to 3 microns.

Since the polyimide having the phase-separated structure and the skeleton of the formula I has a low water absorption compared with the epoxy resin, the water absorption of the cured product becomes significantly smaller than that of the original epoxy resin. Furthermore, the polyimide oligomers made epoxy soluble by the structure of Formula I are not themselves soluble in general-purpose solvents such as acetone, methyl ethyl ketone and methylene chloride. In addition, since it has a functional group that reacts with the epoxy resin, it is incorporated into a crosslinked structure, and as a result, the solvent resistance of the cured product becomes excellent. Regarding the heat resistance of the polyimide oligomer, the glass transition temperature can be arbitrarily set within a considerably large range by changing the type of the copolymerization monomer, but the polyimide having the structure of the formula I has extremely high heat resistance and has the above low water absorption. Along with the efficiency, it improves the heat resistance of the epoxy resin in a wet state.

Having a functional group capable of reacting with the constituent element [A] in the structure of the constituent element [B] is preferable also from the viewpoint of solvent resistance and resin toughness. Most preferred is when an amino group is present at the terminus of component [B]. At the time of oligomer synthesis, it is easy to terminate the amino group by using a 1 mol excess of diamine with respect to the acid dianhydride. Further, the polyimide oligomer suitable for the present invention does not necessarily require a 100% imidization ratio, and may have a partial amic acid state, and in some cases from the viewpoint of phase interface adhesiveness Is preferred.

The amount of the constituent element [B] is preferably 10 to 50% by weight in the resin composition. If it is less than this range, the effect of improving toughness is small, and if it is more than this range, the workability is significantly reduced. It is more preferably 15 to 40% by weight.

The molecular weight of component [B] is about 2000 in terms of number average molecular weight.
A range of ~ 20,000 is preferred. When the molecular weight is smaller than this, the effect of improving toughness is small, and when the molecular weight is larger than this, the resin viscosity increases remarkably. As a result, it becomes difficult to coat the resin or impregnate the fibers with the resin during the production of the prepreg, and the tackiness and drapeability of the prepreg are impaired, resulting in a marked decrease in workability. More preferably about
It is in the range of 2000 to 10000, more preferably in the range of about 3000 to 6000.

The present invention provides a fiber reinforced plastic having high toughness and high strength, which comprises an epoxy resin composition comprising the constituent elements [A] and [B] and a reinforcing fiber [C], and a prepreg for providing the same. The reinforcing fiber used at that time is a fiber generally used as an advanced composite material and having good heat resistance and tensile strength. For example, the reinforcing fibers include carbon fibers,
Examples thereof include graphite fiber, aramid fiber, silicon carbide fiber, alumina fiber, boron fiber, tungsten carbide fiber, and glass fiber. Among them, carbon fibers and graphite fibers, which have a good specific strength and specific elastic modulus and greatly contribute to weight reduction, are most preferable in the present invention. It is possible to use all kinds of carbon and graphite fibers for carbon fiber and graphite fiber depending on the application, but high strength and high elongation carbon fiber with a tensile strength of 450 kgl / mm ² and a tensile elongation of 1.7% or more is the most suitable. Is suitable. Carbon fibers and graphite fibers may be used in combination with other reinforcing fibers. The shape and arrangement of the reinforcing fibers are not limited, and the reinforcing fibers may be used in a single direction, a random direction, a sheet shape, a mat shape, a woven shape, or a braided shape. In addition, an array in which reinforcing fibers are aligned in a single direction is most suitable for applications that require high specific strength and high elastic modulus, but a cloth (fabric) array that is easy to handle. Are also suitable for the present invention.

The resin in the fiber reinforced plastic has the microphase separation structure described above. The optimum range of the phase separation structure period is smaller than the distance between the fibers. Therefore, its optimum range is affected by the fiber content, but it is about 0.
It is in the range of 01 to 10 microns, more preferably about 0.1 to 3 microns. In the fiber reinforced plastic, when the phase mainly composed of the constituent element [B] exists separately from the phase mainly composed of the constituent element [A], the phase mainly composed of the constituent element [A] is reinforced fiber [C ] It is preferable that it is unevenly distributed around [] from the viewpoint of adhesion between the fiber and the resin.

The fracture strain energy release rate G _IC of the cured resin produced by the composition of the present invention is measured by the double torsion (DT) method. The outline of the measuring method is shown in FIG. For more information on the DT method, Journal of Materials Science
20 (1985) p.77-84. G _IC is calculated crack load P, the slope [Delta] C / .DELTA.a _i and crack growth of the sample thickness t for crack extension distance a _i compliance C by the following equation.

G _IC = P ² (ΔC / Δa _i ) / 2t (However, the compliance C is defined by the crosshead displacement amount δ when the crack occurs and the cracking load P. C = δ / P) The crosshead that applies the load The speed was 1 mm / min.

[Operation] In the present invention, the addition of the constituent element [B] forms a microphase-separated structure having good phase interface adhesion in the cured epoxy resin. It is characterized in that at least the phase mainly composed of the constituent element [B] forms a three-dimensionally continuous structure, and the phase separation structure period is about 0.01 to 50 microns. By forming such a microphase-separated structure, an epoxy resin having significantly improved burst toughness is provided. Further, the addition of the constituent element [B] has a remarkable effect of improving the heat resistance of the epoxy resin and decreasing the water absorption. Moreover, the addition of the constituent element [B] maintains the original high elastic modulus and high solvent resistance of the thermosetting resin.

The following examples are for explaining the present invention in more detail, and are not limited to the contents thereof.

Example 1 Part A In a 3000 ml separable flask equipped with a nitrogen inlet, a thermometer, a stirrer and a dehydration trap, 415 g (1.01 mol) of 2,2-bis [4- ( 4-Aminophenoxy) phenyl] propane (BAPP), 39.1 g (0.1
12 mol) of 9,9-bis (4-aminophenyl) fluorene (FDA) [manufactured by Wakayama Seika Kogyo Co., Ltd.] was dissolved in 2000 ml of N-methyl-2-pyrrolidone (NMP) with stirring. Therefore, solid biphenyltetracarboxylic dianhydride (S-BP
DA) [Mitsubishi Kasei Co., Ltd.] 300g (1.02mol) was added little by little, and after stirring at room temperature for 4 hours, triethylamine 100m
Approximately 37 ml by adding l and toluene 100 ml and azeotropic dehydration at 160 ℃
Of water was obtained. After cooling the reaction mixture,
Diluted with NMP and slowly poured into 301 acetone to precipitate the amine-terminated polyimide oligomer as a solid product. Then, the precipitate was vacuum dried at 180 ° C. When the number average molecular weight (Mn) of this oligomer was measured by gel permeation chromatography (GPC) using a dimethylformamide (DMF) solvent, it was 5200 in terms of polyethylene glycol (PEG). The glass transition point was 248 ° C according to the differential thermal analyzer (DSC). Further, it was found from the NMR spectrum that the imidization proceeded almost completely and the amine terminal ratio was about 95%.

Part B In a beaker, 36 g of the polyimide oligomer of Part A above and resorcinol diglycidyl ether (HELOXY WC-6
9) 57 g of [Wilmington Chemical Co.] was added. It was heated and dissolved at 150 ° C. for 1 hour, and then 27 g of Sumicure S (4,4′-DDS) [Sumitomo Chemical Co., Ltd.] was added and dissolved for 10 minutes.

After a vacuum pump was connected to the container and the contents were degassed under vacuum, the contents were poured into a mold (vacant space: 120 × 120 × 3 mm) that had been subjected to a release treatment that had been preheated to 120 ° C. in advance. A curing reaction was performed at 180 ° C. for 2 hours in an oven to prepare a resin cured plate having a thickness of 3 mm.

Tg of the obtained cured resin is 178 ℃ and 231 ℃ by DSC measurement.
Met. When the sample was cut out from this and the fracture strain energy release rate G _IC was measured, it was 1200 j / m ² , and the flexural modulus E was 370 kg / mm ² . From here, calculating the resin toughness K _IC by the following equation Became.

K _Ic = (G _IC · E) ^{1/2 When} a resin plate of 60 × 10 × 2 mm was boiled for 20 hours, its water absorption rate was 2.8%.

The result of observing the fracture surface of the cured resin with a scanning electron microscope is shown in FIG. It can be seen that the rugged fracture pattern that reflects the microphase-separated structure is significant, and that the energy consumed for fracture is large. The size of the structural period was about 1 to 5 μm.

Part C A prepreg was prepared as follows.

A resin having the above composition was prepared with a kneader and coated with a constant thickness on a release paper thinly coated with a silicon release agent. Using a carbon fiber trading card T800H (manufactured by Toray Industries, Inc.), carbon fibers were aligned in one direction between two sheets of the resin-coated paper prepared above and then pressure-bonded to obtain a prepreg. At this time, the weight fraction of resin in the prepreg is 35.
%, And the basis weight of the carbon fiber was 145 g / m ² . This prepreg has a pseudo isotropic structure ((+ 45 ° / 90 ° / −45 ° / 0
°) _4s ) was laminated in 32 layers, and heating was performed at 180 ° C for 2 hours under a pressure of 6 kg / cm ² by using an ordinary vacuum bag autoclave molding method to obtain a cured plate. The fiber volume was 56 ± 2%. Cut out a 4 ″ × 6 ″ test piece, 1500 in ・ lb / in
After applying the impact energy of, a compression test was performed. As a result, it showed a residual compressive strength of 52 ksi. Further, 16 pieces of the above prepregs were laminated in a single direction, and a 90 ° C. tensile elongation was measured using a cured plate similarly formed, and it was 1.4%. When 8 prepregs were laminated in a single direction and a 0 ° tensile strength was measured using a similarly shaped cured plate, it was 443 ksi.
Met.

In addition, a tensile test was performed using a cured plate that was laminated in 10 layers with a composition of (± 25 / ± 25.90) _s , and was similarly molded, and the strength at which plate edge peeling occurred first was measured and found to be 48.4 ksi. .

Example 2 Part A As diamine, 286 g (0.697 mol) of 2,2-bis [4-
(4-Aminophenoxy) phenyl] propane (BAPP)
And 162 g (0.465 mol) of 9,9-bis (4-aminophenyl) fluorene (FDA) [manufactured by Wakayama Seika Kogyo Co., Ltd.],
Tetracarboxylic acid dianhydride as acid dianhydride (S-BPD
A) A polyimide oligomer was synthesized in the same manner as in Example 1 except that 300 g (1.02 mol) of [Mitsubishi Kasei Co., Ltd.] was used.

The number average molecular weight (Mn) of this oligo was 5000 in terms of polyethylene glycol (PEG). The glass transition point was 310 ° C according to a differential thermal analyzer (DSC). Further, it was found from the NMR spectrum that the imidization ratio was about 94% and the amine terminal ratio was about 90%.

Part B In a beaker, 36 g of the polyimide oligomer of Part A above and resorcinol diglycidyl ether (HELOXY WC-6
9) 57 g of [Wilmington Chemical Co.] was added. Dissolve it by heating at 150 ° C for 1 hour, and then use 27g of Sumikyua-
S (4,4'-DDS) [Sumitomo Chemical Co., Ltd.] was added and dissolved for 10 minutes.

After a vacuum pump was connected to the container and the contents were degassed under vacuum, the contents were poured into a mold (vacant space: 120 × 120 × 3 mm) that had been subjected to a release treatment that had been preheated to 120 ° C. in advance. A curing reaction was performed at 180 ° C. for 2 hours in an oven to prepare a resin cured plate having a thickness of 3 mm.

The Tg of the obtained cured resin had the first endotherm at 180 ° C by DSC measurement, and the endotherm on the high temperature side corresponding to the oligomer rich phase was not clear. Cut out the sample from here,
Breaking strain energy release rate GlC measured 1200 J / m ²
And the flexural modulus was 380 kg / mm ² . from here,
Calculate resin toughness K _IC Became. Also, when a 60 × 10 × 2 mm resin plate was boiled for 20 hours, its water absorption rate was 2.7%.

On the fracture surface of the cured resin, a severely rugged fracture pattern reflecting the microphase-separated structure was observed. The size of the structural period was about 1 to 4 μm.

Example 3 Part A 401.8 g (1.153 mol) of 9,9-bis (4 as diamine
-Aminophenyl) fluorene (FDA) [manufactured by Wakayama Seika Kogyo Co., Ltd.], tetracarboxylic acid dianhydride (S-BPDA) [manufactured by Mitsubishi Kasei Co., Ltd.] as acid dianhydride 300 g (1.02mo
A polyimide oligomer was synthesized in the same manner as in Example 1 except that l) was used.

The number average molecular weight (Mn) of this oligomer was 6200 in terms of polyethylene glycol (PEG). The glass transition point was about 400 ° C according to the differential thermal analyzer (DSC). Further, it was found from the NMR spectrum that the imidization proceeded almost completely and the amine terminal ratio was about 93%.

Part B In a beaker, 25 g of the polyimide oligomer of Part A and 20 g of triglycidyl-p-aminophenol (MY0510) [manufactured by Ciba Geigy] and 20 g of bisphenol F type epoxy resin (Epc830) [manufactured by Dainippon Ink and Chemicals, Inc.] added. Dissolve it by heating at 150 ℃ for 1 hour, then 18.5g
Sumicure-S (4,4'-DDS) [Sumitomo Chemical Co., Ltd.
Manufactured] was added and dissolved in 10 minutes. After a vacuum pump was connected to the container and the contents were degassed under vacuum, the contents were poured into a mold (vacant space: 120 × 120 × 3 mm) that had been subjected to a release treatment that had been preheated to 120 ° C. in advance. 180 ℃ 2 in the oven
The resin was cured for 3 hours to prepare a 3 mm thick resin cured plate.

The Tg of the obtained cured resin had the first endotherm at 205 ° C by DSC measurement, and the endotherm on the high temperature side corresponding to the oligomer rich phase was not clear. Cut out the sample from here,
The breaking strain energy release rate G _IC was measured to be 900 J / m ² , and the flexural modulus was 380 kg / mm ² . From here, calculating the resin toughness K _IC Became. When a 60 × 10 × 2 mm resin plate was boiled for 20 hours, its water absorption rate was 2.4%.

Example 4 Part A 416.5 g (0.963 mol) of 2,2-bis [4 as diamine
-(3-Aminophenoxy) phenyl] sulfone (BAPS
-M) and 83.6 g (0.240 mol) of 9,9-bis (4-aminophenyl) fluorene (FDA) [Wakayama Seika Kogyo Co., Ltd.
Manufactured] and biphenyltetracarboxylic dianhydride (S-BPDA) [manufactured by Mitsubishi Kasei Co., Ltd.] as an acid dianhydride, 300 g (1.
A polyimide oligomer was synthesized by the same procedure as in Example 1 except that 02 mol) was used as a raw material monomer.

The number average molecular weight (Mn) of this oligomer was 5,200 in terms of polyethylene glycol (PEG). The glass transition point was 318 ° C according to a differential thermal analyzer (DSC).
Further, it was found from the NMR spectrum that the imidization proceeded almost completely and the amine terminal ratio was about 95%.

Part B Into a beaker, 28.6 g of the above-mentioned polyimide oligomer of Part A and 50 g of bisphenol A type epoxy resin (Ep825) (produced by Yuka Shell Epoxy Co., Ltd.) were added and dissolved by heating at 150 ° C. for 1 hr, and then 16.8 g of Sumicure S (4 , 4'-DDS)
[Sumitomo Chemical Co., Ltd.] was added and dissolved in 10 minutes.

A vacuum pump was connected to the container to perform vacuum defoaming, and then the contents were poured into a mold which had been preheated to 130 ° C. and which had been subjected to a mold release treatment. A curing reaction was performed at 180 ° C. for 2 hours in an oven to prepare a resin cured plate having a thickness of 3 mm. Otherwise, the same procedure as in Example 1 was repeated. Of the obtained cured resin
Tg had the first endotherm at 205 ℃ in DSC measurement, and the endotherm on the high temperature side corresponding to the oligomer-rich phase was not clear. Also,
The fracture strain energy release rate G _IC was 1400 J / m ² , and the flexural modulus was 370 kg / mm ² . Calculate the resin toughness K _IC from here Met. When a 60 × 10 × 2 mm resin plate was boiled for 20 hours, its water absorption rate was 1.4%.

Comparative Example 1 Part A In a 3000 ml separable flask equipped with a nitrogen inlet, a thermometer, a stirrer and a dehydration trap, 280 g (0.68 mol) of 2,2-bis [4- ( 4-aminophenoxy) phenyl] propane (BAPP) with 1200 ml of N
Dissolved in methyl-2-pyrrolidone (NMP) with stirring. Therefore, solid biphenyltetracarboxylic dianhydride (BP
DA-S) [Mitsubishi Kasei Co., Ltd.] 180 g (0.61 mol) was added little by little, and the mixture was stirred at room temperature for 3 hours and then heated to 120 ° C. to 1
Stir for hours. Bring the flask back to room temperature and use triethylamine.
After adding 50 ml and 50 ml of toluene, the temperature was raised again and azeotropic dehydration was carried out at 160 ° C. to obtain about 20 ml of water. In this process, polyimide oligomer was deposited and became a precipitate. The reaction mixture was cooled, poured into 201 of acetone and washed. 1 more
It was transferred to water of 01, washed by boiling, and then vacuum dried at 180 ° C. The glass transition point of this oligomer is determined by a differential thermal analyzer (DS
According to C), it was 240 ° C.

Part B In a beaker, 36 g of the polyimide oligomer of Part A above and resorcinol diglycidyl ether (HELOXY WC-6
9) 57 g of [Wilmington Chemical Co.] was added. It was heated at 150 ° C. for 2 hours, but the oligomer did not dissolve in the epoxy.

[Comparative Example 2] An epoxy resin plate was prepared by repeating the same procedure as in Example 1 without adding the imide oligomer as the constituent element [B]. The Tg of the obtained cured resin was 172 ° C. When the breaking strain energy release rate G _IC was measured, it was 150 J / m ² and the flexural modulus was 385 kg / mm ² . The water absorption rate after boiling for 20 hours was 4.0%.

The compressive strength after impact and the tensile elongation in the 90 ° direction of the composite using a unidirectional prepreg with the same resin composition as a matrix were measured. Prepreg is Example 1
Was prepared in the same manner as.

At this time, the weight fraction of the resin in the prepreg was 35%, and the weight per area of the prepreg was 145 g / m ² . This prepreg has a pseudo isotropic structure ((+ 45 ° / 90 ° /
-45 ° / 0 °) _4s ) to be laminated in 32 layers, and 180 ° C x 6kg / cm ² under pressure using ordinary vacuum bag autoclave molding method
A cured plate was obtained by heating for 2 hours. Its fiber volume is 56 ±
It was 2%. Cut out a 4 "x 6" test piece and 1500in
-A compression test was performed after applying an impact energy of lb / in. As a result, the residual compressive strength was 21.5 ksi. Further, 16 sheets of the above prepreg were laminated in a single direction, and 90 ° tensile elongation was measured using a cured plate similarly formed.
It was 7%. When 8 prepregs were laminated in a single direction and a 0 ° tensile strength was measured using a similarly formed cured plate, it was 402 ksi.

In addition, a tensile test was conducted using 10 cured layers of (± 25 / ± 25/90) _s , and a similarly formed cured plate was used. there were.

Comparative Example 3 An epoxy resin plate was prepared by repeating the same procedure as in Example 3 without adding the imide oligomer as the constituent element [B]. The Tg of the obtained cured resin was 202 ° C. When the fracture strain energy release rate G _IC was measured, it was 120 J / m ² , and the flexural modulus was 385 kg / mm ² . The water absorption rate after boiling for 20 hours was 3.6%.

[Comparative Example 4] A resin plate was prepared by repeating the same procedure as in Example 4 without adding the imide oligomer as the constituent element [B]. The Tg of the obtained cured resin was 207 ° C. When the fracture strain energy release rate G _IC was measured, it was 150 J / m ² , and the flexural modulus was 365 kg / mm ² . The water absorption rate after boiling for 20 hours was 2.2%.

EFFECTS OF THE INVENTION The thermosetting resin composition according to the present invention has good workability, excellent toughness, high elastic modulus, high heat resistance, low water absorption, high solvent resistance, and various physical properties. A cured resin product having high stability is provided. Furthermore, the prepreg using this as a matrix resin has good tackiness and drape, and the fiber-reinforced composite material that is a cured product has high toughness, high impact resistance, high strength, high elongation, and high heat resistance, It has low water absorption and high solvent resistance. The carbon fiber reinforced composite material using the resin composition of the present invention as a matrix resin also has an effect that the tensile strength is extremely high. Generally, the tensile strength in the fiber direction of the fiber-reinforced composite material is largely due to the tensile strength of the reinforcing fiber itself, but the tensile strength of the composite material is lower than the calculated value estimated from the tensile strength of the fiber itself. Stay in. However, it has been found that by using the resin of the present invention as a matrix, the fiber strength can be sufficiently drawn out and the strength of the composite material can be improved as compared with the case where a conventional resin is used.

It was also found that the tensile strength in the non-fiber direction also improves because the resin is less likely to crack, reflecting the high toughness of the resin. In addition, cracking is suppressed when fatigue such as a thermal cycle is applied.

Furthermore, it has been found that the reduction of the thin profit between the laminated layers, which tends to occur when the cross laminated plate is stretched or when the impact energy is applied, is significantly suppressed. As a result, the residual compressive strength after applying impact energy was significantly improved.

As described above, since the resin of the present invention has high toughness, it is particularly useful when used as a matrix resin of a fiber-reinforced composite material and gives a high-performance composite material.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing a microstructure-separated particle structure of the fracture surface of the cured resin obtained in Example 1. FIG. 2 is an illustration of the double torsion (DT) method for measuring the fracture strain energy release rate G _IC of the cured resin.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C08L 79/08 LRC // C08L 63:00

Claims (10)

[Claims] 1. An epoxy resin composition comprising the following constituent elements [A] and [B] as essential components. [A]: Epoxy resin [B]: A polyimide having an amino group terminal as an essential component having the structure of formula I 2. The epoxy resin composition according to claim 1, wherein the constituent element [B] contains a structure of formula II or formula III. X is _{-CO -, - SO 2 -,} - O -, - S-, or -C
(M) _2- (M is hydrogen, alkyl, allyl or haloalkyl), and n is 0 or 1. 3. The copolymerization ratio (molar ratio) of formula I to formula II and / or formula III in the constituent [B] is 0.5: 9.5 to 10: 0.
The epoxy resin composition according to claim 2, wherein 4. The epoxy resin composition according to claim 3, wherein the component [B] contains a structure of the formula IV. Y is _{-CO -, - SO 2 -,} - O -, - S-, or -C
(M) _2- (M is hydrogen, alkyl, or haloalkyl), and n is 0 or 1. 5. The epoxy resin composition according to claim 4, wherein the amount of the constituent [B] is 10 to 45% by weight based on the total weight of the constituents [A] and [B]. 6. The component [B] has a number average molecular weight of 2000 to 10
The epoxy resin composition according to claim 4, which is 000. 7. A prepreg comprising the epoxy resin composition according to claim 1 and a reinforcing fiber [C]. 8. A fiber reinforced plastic obtained by curing the prepreg according to claim 7. 9. The prepreg according to claim 7, further characterized in that the reinforcing fiber [C] is a carbon (graphite) fiber. 10. A fiber reinforced plastic obtained by curing the prepreg according to claim 9.