JP4821163B2 - 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, and more particularly to an epoxy resin composition for carbon fiber reinforced composite materials having excellent heat resistance and toughness.

  Epoxy resin compositions are widely used as matrix resins for fiber reinforced composite materials. In particular, carbon fiber reinforced plastic (CFRP), which uses carbon fiber as a reinforced base material, has high specific strength and specific elastic modulus. Therefore, it is used as a structural material to reduce the weight of aircraft in commercial aircraft by taking advantage of its characteristics. ing. The CFRP matrix resin includes an epoxy resin mainly composed of polyfunctional glycidylamine represented by N, N, N ′, N′-tetraglycidyldiaminodiphenylmethane, and an epoxy resin containing diaminodiphenylsulfone as a curing agent. There are many examples using the composition.

  However, a cured resin obtained by curing an epoxy resin composition containing a polyfunctional glycidylamine type epoxy resin as a main component is characterized by high modulus of elasticity and heat resistance, but has a problem of low elongation, hardness and brittleness. It was. In general, epoxy resin compositions tend to have low toughness for those with excellent heat resistance, and inferior heat resistance to those with high toughness, so it is difficult to find an epoxy resin composition with both characteristics It is in.

For this reason, Patent Document 1 proposes improving the balance between toughness and rigidity by adding a 1-2 functional epoxy resin or a thermoplastic resin to a polyfunctional epoxy resin such as tetraglycidylaminodiphenylmethane. However, although the improvement of elongation and toughness can be seen by the combination of low-functional epoxy resin and thermoplastic resin, it is not yet sufficient level, and because of thermoplastic resin, prepreg workability such as tackiness and draping property is A problem that significantly decreases occurs.
Japanese Patent Laid-Open No. 2004-277481

  An object of the present invention is to provide an epoxy resin composition for a fiber-reinforced composite material that has both high heat resistance and toughness as a matrix resin of a fiber-reinforced composite material and improves prepreg workability.

The epoxy resin composition for fiber-reinforced composite material of the present invention that achieves the above object comprises 75 to 85% by weight of a polyfunctional epoxy resin (A) having at least three epoxy groups in one molecule, and a bisphenol F type. 40 to 60 parts by weight of the thermoplastic resin (C) soluble in the epoxy resin component and 100 parts by weight of the epoxy resin component composed of 15 to 25% by weight of the epoxy resin (B), and a curing agent An epoxy resin composition containing (D), wherein the polyfunctional epoxy resin (A) contains a low-viscosity triglycidylaminophenol having a viscosity at a temperature of 25 ° C. of 1000 mPa · s or less in a weight ratio of 3 / 5 and contain more state, and are viscosity 5000 mPa · s or less at a temperature 25 ° C. of the bisphenol F type the epoxy resin (B), the said thermoplastic resin ( ) Polyether sulfone resin, polyether imide, and wherein polyimide, polyamide, to be selected from polyamideimide.

  The epoxy resin composition for fiber-reinforced composite material of the present invention is compatible with a high level of heat resistance and toughness of a cured resin by blending an epoxy resin component having a specific viscosity and a thermoplastic resin with a specific composition. However, the deterioration of the prepreg workability associated with the addition of the thermoplastic resin can be improved.

  In the epoxy resin composition for fiber-reinforced composite material of the present invention, the polyfunctional epoxy resin (A) having at least 3 epoxy groups in one molecule is useful for increasing the heat resistance and rigidity of the cured resin. It is more preferable to have 3 to 4 epoxy groups in one molecule. When the number of epoxy groups in one molecule is less than 3, it is not preferable because the heat resistance and rigidity of the resin cured product cannot be increased.

In the present invention, the polyfunctional epoxy resin (A) is a low-viscosity triglycidylaminophenol having a viscosity at a temperature of 25 ° C. of 1000 mPa · s or less of 3/5 or more, preferably 7/10 to 9/10. It contains by weight. The weight ratio of the low-viscosity triglycidylaminophenol may be 3/5 or more, and the total amount of the polyfunctional epoxy resin (A) may be low-viscosity triglycidylaminophenol .

The low-viscosity triglycidylaminophenol having a viscosity at a temperature of 25 ° C. of 1000 mPa · s or less is liquid at a temperature of 25 ° C. to ensure fluidity and maintain sufficient tackiness and draping properties of the prepreg. Useful.

In the low-viscosity triglycidylaminophenol, the viscosity at a temperature of 25 ° C. is 1000 mPa · s or less, preferably 850 mPa · s or less, more preferably 550 to 700 mPa · s. If the viscosity of the low-viscosity triglycidylaminophenol at 25 ° C. exceeds the above range, the viscosity of the epoxy resin composition increases, and work such as tackiness and draping properties of the prepreg using the epoxy resin composition as a matrix There is a risk that the performance will be reduced. Further, when the viscosity is less than 550 mPa · s, when curing the epoxy resin composition, the volatile becomes high, there is a possibility that it becomes difficult cured resin having sufficient heat resistance and rigidity is obtained.

In the present invention, the polyfunctional epoxy resin (A) is a polyfunctional epoxy resin having at least three epoxy groups in one molecule in addition to the low-viscosity triglycidylaminophenol , and the weight ratio is less than 2/5. It may contain. That is, the polyfunctional epoxy resin (A) may contain a high-viscosity polyfunctional epoxy resin having a viscosity at a temperature of 25 ° C. exceeding 1000 mPa · s, but it may not be contained. When the polyfunctional epoxy resin (A) contains a polyfunctional epoxy resin having a high viscosity, the weight ratio of the polyfunctional epoxy resin having a high viscosity is less than 2/5, preferably 1/6 or more and less than 2/5. It is. When the weight ratio of the polyfunctional epoxy resin having a high viscosity exceeds 2/5, the fluidity and workability of the prepreg are deteriorated, which is not preferable. When the weight ratio is less than 1/6 or more 2/5, without impairing the flow properties and the prepreg workability, Ru can improve the heat resistance and mechanical strength of the cured resin, or to maintain.

The polyfunctional epoxy resin (A) is preferably a glycidylamine type epoxy resin, a phenol novolac type epoxy resin, a cresol novolac type epoxy resin, or a glycidyl ether type epoxy resin, and a glycidylamine type epoxy resin is particularly preferable. Among the glycidylamine type epoxy resins, tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, triglycidylaminocresol, tetraglycidyl m-xylylenediamine, N, N-diglycidylaniline and the like are preferable, and particularly low viscosity triglycidyl. as aminophenol, N, N, O-triglycidyl -p- aminophenol resins are preferred, as high viscosity polyfunctional epoxy resins, N because of its high heat resistance, N, N ', N'- tetraglycidyl diaminodiphenylmethane Is preferred.

  The compounding quantity of the polyfunctional epoxy resin (A) used for the resin composition of this invention is 75 to 85 weight%, Preferably it is 75 to 80 weight%, More preferably, it is 75 weight% or more and less than 80 weight%. If the blending amount of the polyfunctional epoxy resin (A) is less than the above, the heat resistance and rigidity of the cured resin may be reduced, and if it exceeds the above range, the strength, elongation and toughness of the cured resin will be reduced. There is a fear.

  The bisphenol F type epoxy resin (B) used for the epoxy resin composition for fiber-reinforced composite materials of the present invention plays a role of improving elongation and toughness.

  In the present invention, the bisphenol F type epoxy resin (B) is liquid at a temperature of 25 ° C., and the liquid state is useful for ensuring fluidity and maintaining sufficient tackiness and draping properties of the prepreg. It is.

  The viscosity of the bisphenol F-type epoxy resin (B) at a temperature of 25 ° C. is 5000 mPa · s or less, preferably 4000 mPa · s or less, more preferably 1000 to 3000 mPa · s. When the above range is exceeded, the viscosity of the epoxy resin composition becomes high, and workability such as tackiness and draping property of the prepreg using the epoxy resin composition as a matrix may be lowered. Moreover, there exists a possibility that elongation and toughness of a resin cured material may fall that a viscosity is less than 1000 mPa * s.

  The viscosity of the polyfunctional epoxy resin (A) and the bisphenol F type epoxy resin (B) is a viscosity measurement value using a BH type rotational viscometer. It is a value obtained by placing it in a constant temperature bath at 25 ° C. and making a scale with a stable load of the BH type rotational viscometer as a measured value. In addition, when measuring an epoxy resin with a high viscosity, it is set as the value of the measurement temperature of 50 degreeC as the temperature of a thermostat 50 degreeC, for example.

  The blending amount of the bisphenol F type epoxy resin (B) is 15 to 25% by weight, preferably 20 to 25% by weight, more preferably more than 20% by weight and 25% by weight or less. If the blending amount of the bisphenol F-type epoxy resin (B) is less than the above, the elongation and toughness of the cured resin may be reduced, and if it exceeds the above range, the heat resistance and rigidity of the cured resin may be reduced. is there.

  In the epoxy resin composition of the present invention, the total of the epoxy resin components composed of the epoxy resins (A) and (B) is 100% by weight, and the thermoplastic resin (C) is 100% by weight of the epoxy resin component. The amount of each compound is regulated by weight with respect to parts.

Thermoplastic resins for use in fiber-reinforced composite material epoxy resin composition of the present invention (C) has a high compatibility or affinity with the epoxy resin component, Ri thermoplastic resin der that soluble in the epoxy resin component, It is selected from polyethersulfone resin (PES), polyetherimide (PEI), polyimide, polyamide, and polyamideimide . In particular, polyethersulfone resin (PES) is preferable because it is soluble in the epoxy resin component and can improve physical properties such as toughness and elongation while maintaining the heat resistance of the cured resin at a high level.

  The method for dissolving the thermoplastic resin (C) in the epoxy resin component is not particularly limited, but preferably, until the epoxy resin component is made into a uniform solution using a planetary mixer set at a temperature of 120 to 130 ° C. After stirring and mixing, the thermoplastic resin (C) is added to this solution and stirred and mixed for about 1 to 3 hours until the powder of the thermoplastic resin (C) is uniformly dissolved.

  The thermoplastic resin (C) used in the present invention is preferably fine particles. By making the thermoplastic resin (C) fine particles, when solubilized in the epoxy resin component, it can be dissolved uniformly, so that the rigidity and toughness of the cured resin can be compatible at a high level, preferable. The fine particle size of the thermoplastic resin (C) is not particularly limited as long as it can be uniformly solubilized in the epoxy resin component, but the average particle size is preferably 200 μm or less, more preferably 10 to 200 μm, still more preferably. Is 30-100 μm. If the average particle diameter exceeds the above range, the thermoplastic resin (C) particles may not be uniformly dissolved in the epoxy resin component, which is not preferable.

  In the resin composition of the present invention, the blending amount of the thermoplastic resin (C) is 40 to 60 parts by weight, preferably 43 to 57 parts by weight with respect to 100 parts by weight of the epoxy resin component (A) and (B). Parts, more preferably 46 to 54 parts by weight. If the blending amount of the thermoplastic resin (C) is less than the above range, there is a possibility that a sufficient effect of improving the elongation and toughness of the cured resin product may not be obtained. In addition, since the viscosity of the epoxy resin composition is further increased, workability such as tackiness and draping properties in a prepreg produced using the epoxy resin composition tends to decrease, which is not preferable.

  In the present invention, the curing agent (D) is not particularly limited as long as it is a compound having an active group capable of reacting with an epoxy group, but is not limited to aromatic amines such as diaminodiphenylmethane and diaminodiphenylsulfone, and aliphatic groups. Preferred are amines, imidazole derivatives, dicyandiamide, tetramethylguanidine, thiourea-added amines, carboxylic acid anhydrides such as methylhexahydrophthalic anhydride, carboxylic acid hydrazides, carboxylic acid amides, polyphenol compounds, novolak resins, polymercaptans, etc. Can be mentioned. In particular, diaminodiphenyl sulfone is preferably used from the viewpoint of improving the heat resistance of the cured resin. Specifically, 3,3′diaminodiphenylsulfone (3,3′-DDS) and / or 4,4′diaminodiphenylsulfone (4,4′-DDS) are preferable. As the curing agent (D), either one of 3,3′-DDS and 4,4′-DDS may be used, or both may be used together.

  In the resin composition of the present invention, the amount of the curing agent (D) is preferably the ratio of the active hydrogen equivalent of the curing agent to the epoxy equivalent of the epoxy resin components (A) and (B) above. 0.7 equivalent or more, more preferably 0.7 to 0.9 equivalent, and still more preferably 0.75 to 0.85 equivalent. If the blending amount of the curing agent (D) is less than the above range, sufficient heat resistance of the resin cured product may not be obtained, and if it exceeds the above range, the number of crosslinking points of the epoxy resin increases, but the crosslinking density Decreases, and the rigidity and heat resistance of the resin cured product tend to decrease, which is not preferable.

  The epoxy resin composition for fiber-reinforced composite material of the present invention is compatible with a high level of heat resistance and toughness of a cured resin by blending an epoxy resin component having a specific viscosity and a thermoplastic resin with a specific composition. However, the deterioration of the prepreg workability associated with the addition of the thermoplastic resin can be greatly improved.

  The epoxy resin composition for a fiber-reinforced composite material of the present invention essentially comprises the above components (A) to (D), but the above (A) is necessary as long as the effects of the present invention are not impaired. Various additives such as known curing agents, thermosetting resins, fillers, stabilizers, flame retardants, and pigments other than the component (D) may be contained.

  The prepreg of the present invention can be obtained by impregnating the reinforcing fiber base material with the epoxy resin composition of the present invention. Preferred examples of the reinforcing fiber base include carbon fiber, graphite fiber, aramid fiber, and glass fiber. Of these reinforcing fibers, it is particularly preferable to use carbon fibers for the reinforcing fiber substrate.

  The ratio of the epoxy resin composition in the prepreg is preferably 30 to 50% by mass, more preferably 32 to 42% by mass. When the ratio of the epoxy resin composition is within this range, the heat resistance and toughness of the carbon fiber reinforced composite material obtained by thermosetting the prepreg can be compatible at a high level.

  The method for producing the prepreg of the present invention is by placing so-called resin films in which the epoxy resin composition of the present invention is applied on a release paper in a thin film form above and below the reinforcing fiber base, and heating and pressing. A hot melt method in which the reinforcing fiber base material is impregnated with the epoxy resin composition can be preferably exemplified. Since the prepreg of the present invention uses the specific epoxy resin composition, the prepreg is excellent in tackiness and draping property, and has good prepreg workability, so that the production efficiency of the prepreg can be improved.

  A fiber-reinforced composite material can be produced by subjecting the prepreg of the present invention to thermosetting molding such as ordinary autoclave molding or hot press molding. The fiber-reinforced composite material obtained in this way has excellent characteristics that achieve both high heat resistance and toughness.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

  Production method of unidirectional prepreg and unidirectional fiber reinforced molding plate shown in Examples and Comparative Examples and evaluation of workability of prepreg, measurement of glass transition temperature of carbon fiber reinforced composite material, interlaminar shear strength, 0 ° tensile strength, The in-plane shear strength was measured as follows.

[Production method of unidirectional prepreg]
A resin film is formed on a release paper using an epoxy resin composition, and this film is heated and pressurized to unidirectionally arranged carbon fibers (IM-600 manufactured by Toho Tenax Co., Ltd.) so that the resin content is 35% by weight. And unidirectional prepreg having a resin basis weight of 190 g / m ² was obtained.

[Production Method of Unidirectional Fiber Reinforced Molded Plate]
10 sheets of the obtained unidirectional prepregs were laminated in the direction of [0 °], and a vacuum pack was applied to the laminate and heated in an autoclave at a temperature of 180 ° C. for 2 hours to be cured and unidirectional fiber reinforced molding. A plate was made. During this time, the inside of the autoclave was pressurized to 0.32 MPa with compressed air.

[Method of measuring viscosity of epoxy resin]
The can containing the epoxy resin was placed in a thermostatic bath at a temperature of 25 ° C., and the viscosity of the epoxy resin was measured by the above-described method using a BH type rotational viscometer. When measuring a highly viscous epoxy resin, the measurement temperature was 50 ° C.

[Glass transition temperature of carbon fiber reinforced composite material (CFRP)]
The obtained unidirectional fiber reinforced molded plate was processed into a size of 3 mm × 3 mm, and the glass transition temperature immediately after the test piece was processed with a thermomechanical analyzer (TMA apparatus) under conditions of a heating rate of 10 ° C./min. It was measured.

[Evaluation of workability of prepreg-tack and drape]
Each of the prepregs was evaluated with ten levels of tackiness and drapeability by using tentacles. The scoring method was determined by a relative evaluation in which a prepreg having standard tackiness and draping properties was separately prepared and the score was 5. A high score was given to the tackiness of a highly tacky prepreg, and a high score was given to the drapeability of a highly flexible prepreg.

[90 ° tensile strength]
The obtained unidirectional fiber reinforced molded plate was processed into a predetermined size, and the 90 ° tensile strength was measured according to EN-2597.

[Interlaminar shear strength]
The obtained unidirectional fiber-reinforced molded plate was processed into a predetermined size, and the interlayer shear strength was measured according to EN-2563.

[In-plane shear strength of CFRP]
Sixteen prepregs are laminated mirror-symmetrically in the direction of [+ 45 ° / −45 °], a vacuum pack is applied to this laminate, and it is heated in an autoclave at a temperature of 180 ° C. for 2 hours and cured to form a molded plate Was made. During this time, the inside of the autoclave was pressurized to 0.32 MPa with compressed air. The obtained molded plate was processed into a predetermined dimension, and the in-plane shear strength was measured according to ASTM D-3518.

In Examples 1 to 7 and Comparative Examples 1 to 4, the raw materials shown below were used.
・ Polyfunctional epoxy resin (A)
Resin A-1: N, N, O-triglycidyl-p-aminophenol resin (MY-0510 manufactured by Huntsman Advanced Materials) Viscosity of 550 to 850 mPa · s at a temperature of 25 ° C.
Resin A-2: N, N, N ′, N′-tetraglycidyldiaminodiphenylmethane resin (MY-721 manufactured by Huntsman Advanced Materials) Viscosity of 3600 to 5000 mPa · s at a temperature of 50 ° C.
・ Bisphenol type epoxy resin (B)
Resin B-1: Bisphenol F type epoxy resin (room temperature liquid type, YDF-170 manufactured by Tohto Kasei Co., Ltd.) Viscosity of 2000 to 5000 mPa · s at a temperature of 25 ° C.
Resin B-2: Bisphenol A type epoxy resin (room temperature liquid type, YD-8125 manufactured by Tohto Kasei Co., Ltd.) Viscosity of 4000 to 5000 mPa · s at a temperature of 25 ° C.
・ Thermoplastic resin (C)
Resin C-1: Polyether sulfone resin (Sumitomo Chemical Co., Ltd., SUMIKAEXCEL PES5003P) is a fine particle product having an average particle diameter of 45 μm by impact pulverization.
・ Curing agent (D)
Curing agent D-1: 3,3′-diaminodiphenyl sulfone (3,3′-DAS manufactured by Konishi Chemical Industry Co., Ltd.)

Examples 1-7
The total amount of the epoxy resins (A) and (B) having the composition shown in Table 1 was stirred and mixed using a planetary mixer set at a temperature of 125 ° C. until a uniform solution was obtained. Next, the entire amount of the thermoplastic resin (C) was added to this solution, and the mixture was stirred and mixed for about 2 hours until the powder of the resin (C) was uniformly dissolved. Thereafter, the temperature of the planetary mixer was set to 95 ° C. When the resin temperature became uniform, the curing agent (D) was added, and the epoxy resin composition was prepared by stirring and mixing for about 1 hour.

  In addition, the unit of the epoxy resin component of (A) and (B) is weight%, and these sum total is 100 weight%. The blending of the component (C) was expressed by parts by weight with respect to 100 parts by weight of the epoxy resin components (A) and (B). Moreover, the blending of the component (D) was expressed by the equivalent of the curing agent with respect to the epoxy group equivalent of the epoxy resin component.

  Using the obtained epoxy resin composition, a prepreg and a fiber reinforced molded plate were prepared. Further, the glass transition temperature, the interlaminar shear strength, the 0 ° tensile strength, the in-plane shear strength, the tack property and draping property of the prepreg were measured by the above methods. The measurement results are shown in Table 1.

Comparative Examples 1-4
Except having changed the epoxy resin composition as shown in Table 2, it was prepared in the same manner as in the Examples, and various evaluations were performed. The measurement results are shown in Table 2.

  The epoxy resin composition (Examples 1 to 7) of the present invention has a high level of heat resistance and toughness of the cured resin by blending an epoxy resin component having a specific viscosity and a thermoplastic resin with a specific composition. While achieving both, it was confirmed that the prepreg workability of the tack property and the drape property was excellent and its practical value was high. On the other hand, in the comparative example not satisfying any of the requirements of the present invention, it was confirmed that the effect of improving the elongation and toughness was insufficient or the prepreg workability was poor.

  Therefore, by using the epoxy resin composition of the present invention, it was recognized that the heat resistance and toughness of the cured resin product can be compatible at a high level, and that a prepreg with good workability can be obtained.

Claims (5)

An epoxy resin component composed of 75 to 85% by weight of polyfunctional epoxy resin (A) having at least three epoxy groups in one molecule and 15 to 25% by weight of bisphenol F type epoxy resin (B) An epoxy resin composition comprising 40 to 60 parts by weight of a thermoplastic resin (C) soluble in the epoxy resin component and 100 parts by weight of a curing agent (D), the polyfunctional epoxy The resin (A) contains 3/5 or more by weight of low-viscosity triglycidylaminophenol having a viscosity at a temperature of 25 ° C. of 1000 mPa · s or less, and the temperature of the bisphenol F-type epoxy resin (B) Ri der viscosity of 5000 mPa · s or less at 25 ° C., the thermoplastic resin (C) is polyether sulfone resin, polyether imide, polyimide, Po Amides, fiber-reinforced composite-body epoxy resin composition you wherein a is selected from polyamideimide.   The epoxy resin composition for fiber reinforcement according to claim 1, wherein the thermoplastic resin (C) is fine particles having an average particle diameter of 200 μm or less.   The epoxy resin composition for fiber reinforcement according to claim 1 or 2, wherein the thermoplastic resin (C) is a polyethersulfone resin.   The curing agent (D) is 3,3 ′ diaminodiphenyl sulfone and / or 4,4 ′ diaminodiphenyl sulfone, and the blending amount of the curing agent is 0.7 equivalent or more with respect to the epoxy group of the epoxy resin component. The epoxy resin composition for fiber reinforcement according to any one of claims 1 to 3. The carbon fiber prepreg which uses the epoxy resin composition in any one of Claims 1-4.