JP2000212307A - Prepreg and fiber-reinforced composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject prepreg capable of curing at a lower temperature than that of a conventional one, excellent in tack and drapeability and useful for a structural material, etc., for aircraft by impregnating reinforcing fibers with a specific epoxy resin composition. SOLUTION: This prepreg is obtained by impregnating (B) reinforcing fibers (preferably carbon fibers) with (A) an epoxy resin composition containing (i) an epoxy resin formulation containing an epoxy resin having a naphthalene skeleton in the molecule and 200-400 epoxy equivalents and coumpunded therein, (ii) dicyandiamide and (iii) a urea compound. Furthermore, the amount of the compounded epoxy resin having the naphthalene skeleton in the molecule in the component (i) is preferably 40-80 pts.wt. based on 100 pts.wt. of the component A and the component (i) preferably contains at least one kind of epoxy resin selected from the group consisting of a bisphenol A type epoxy resin, a bisphenol F type epoxy resin and a bisphenol S type epoxy resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention provides excellent strength properties,
A prepreg suitable for producing a fiber-reinforced composite material having heat resistance and environmental resistance, and a fiber-reinforced composite material formed by laminating and curing the prepreg by heating and particularly applicable to structural materials for aircraft It is about.

[0002]

2. Description of the Related Art Carbon fiber reinforced composite materials using carbon fiber having excellent specific strength and specific elastic modulus as a reinforcing fiber and an epoxy resin having good wettability and adhesion with the carbon fiber as a matrix resin have excellent mechanical properties. Due to its properties, it is used for a wide range of applications in the fields of aerospace, sports and leisure, civil engineering and construction, etc. Compositions have been devised, and a number of useful prepregs, intermediates, and composites have been produced by combining them with carbon fibers. Above all, for aircraft applications
High levels of performance are often required of composite materials used as structural materials.

[0003] In applying a fiber-reinforced composite material to an aircraft structural material, it is necessary to consider in particular the enhancement of compressive strength in strength properties, and at the same time, properties such as heat resistance, water resistance and impact resistance. Also need to be increased.
As a means for this, first, in the case of reinforcing fibers, it is necessary to use reinforcing fibers having high compressive strength and tensile strength.On the other hand, in the case of matrix resin, the matrix resin itself has high rigidity and moderate toughness. It is necessary to secure. Furthermore, by increasing the adhesion between the reinforcing fiber and the matrix resin as much as possible and by cooperating the properties of the materials used, properties such as heat resistance, water resistance, impact resistance, as well as mechanical strength such as compressive strength, etc. It is necessary to be effectively expressed.

[0004] Matrix resins of composite materials applied to structural materials for aircraft include polyfunctional amine type epoxy resins such as tetraglycidyldiaminodiphenylmethane (hereinafter abbreviated as TGDDM) and diaminodiphenylsulfone (hereinafter abbreviated as DDS). In general, an aromatic amine-based curing agent such as the above is used.

[0005] However, a composite material using TGDDM as a matrix resin has a drawback that, although excellent in heat resistance, it is inferior in water resistance. On the other hand, a composite material using DDS as a matrix resin has excellent mechanical strength, but does not sufficiently cure unless heated to about 200 ° C.
Further, there is a problem that a large amount of cost is required for molding.

For this reason, it has excellent heat resistance and water resistance, and
There is a strong demand for a matrix resin for composite materials that can be sufficiently cured at about 120 ° C. during molding.

As an attempt to meet such a demand, Japanese Patent Laid-Open No.
JP-A-506536 discloses an example in which an imidazole derivative is used as a curing agent in a resin composition for a composite material. When an imidazole derivative is used, it is sufficiently cured by heating at 100 ° C. for about 2 hours during molding.
There is a problem that the mechanical strength of the composite material is insufficient in a high temperature state after water absorption. Further, JP-A-6-206860 discloses an example in which a diaminodiphenylsulfone derivative is used as a curing agent. When a diaminodiphenyl sulfone derivative is used, a composite material having excellent mechanical strength can be obtained in a high temperature state after water absorption, but it is difficult to sufficiently cure the material by heating at 120 ° C. for about 2 hours. Further, JP-A-4-239536 and JP-A-5-15-1
JP-A-70874 and JP-A-5-271386, for example, use an epoxy resin having a naphthalene skeleton in the molecule. However, all of these require a heating temperature of 170 ° C. or more for curing during molding, and the low-temperature curability is insufficient.

[0008] It is possible to sufficiently cure at the time of molding at a low temperature of about 120 ° C, greatly reduce the cost required for molding a composite material, and is excellent in heat resistance, water resistance, and impact resistance. Composite material resin compositions that can be suitably used in applications where the quality required characteristics represented by structural materials are severe include:
At present, no satisfactory product has been found so far.

[0009]

SUMMARY OF THE INVENTION The present invention provides a prepreg which can be cured at a lower temperature than before and has excellent tackiness and drapability. The prepreg is laminated, cured by heating and molded. Fiber reinforced composite material becomes excellent in heat resistance, water resistance, impact resistance,
Particularly, it is an object of the present invention to provide a prepreg which can be preferably applied to structural materials for aircraft.

[0010]

To solve the above problems, the present invention has the following arrangement. That is, it is a prepreg obtained by impregnating a reinforcing fiber with an epoxy resin composition containing the following components [A], [B], and [C]. [A] an epoxy resin compound comprising an epoxy resin having a naphthalene skeleton in the molecule and having an epoxy equivalent of 200 to 400 [B] dicyandiamide [C] urea compound In order to solve the above problems The present invention has the following configuration. That is, it is a fiber reinforced composite material obtained by laminating the above prepregs and curing and molding by heating.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have realized that the prepreg impregnated with an epoxy resin having a naphthalene skeleton in a molecule and an epoxy resin composition comprising a combined system of dicyandiamide and a urea compound has significantly lower consumption than before. The present invention has found that a fiber-reinforced composite material can be obtained by molding with energy, and that this fiber-reinforced composite material can be applied to aircraft structural materials that require heat resistance, water resistance, and impact resistance without any problem. It has been reached.

Component [A] of the present invention is an epoxy resin compound. Such an epoxy resin formulation contains an epoxy resin having a naphthalene skeleton in the molecule. When such an epoxy resin is used, the obtained composite material has particularly excellent water resistance. The epoxy resin needs to have an epoxy equivalent of 200 to 400, preferably 220 to 380, and more preferably 240 to 36.
0 is more preferred. If the epoxy equivalent is less than 200, the water resistance and impact resistance of the obtained composite material may be impaired, and if the epoxy equivalent exceeds 400, the heat resistance of the obtained composite material may be impaired.

The amount of the epoxy resin having a naphthalene skeleton in the molecule is preferably 40 to 80 parts by weight, more preferably 50 to 70 parts by weight, based on 100 parts by weight of the epoxy resin compound of the component [A] of the present invention. Parts, more preferably 55
~ 65 parts by weight is good. If the amount is less than 40 parts by weight, the heat resistance and water resistance of the obtained composite material may be impaired, and if the amount exceeds 80 parts by weight, the tackiness and drape property of the prepreg may be impaired. . Specific examples of the epoxy resin having a naphthalene skeleton in the molecule include an epoxy compound obtained by a reaction between naphthols and epichlorohydrin. Examples of commercially available epoxy resins include NC-7300L (manufactured by Nippon Kayaku Co., Ltd.) and ESN-170 (manufactured by Nippon Steel Chemical Co., Ltd.).

In the component [A] of the present invention, specific examples of the epoxy resin which can be blended in addition to the epoxy resin having a naphthalene skeleton in the molecule include a bisphenol A type epoxy resin (an epoxy resin having bisphenol A as a precursor). Bisphenol F type epoxy resin (epoxy resin having bisphenol F as a precursor), bisphenol S type (epoxy resin having bisphenol S as a precursor), phenol novolak type epoxy resin (epoxy resin having phenol novolac as a precursor), Cresol novolak type epoxy resin (cresol novolak as a precursor), resorcinol type epoxy resin (resorcinol as a precursor), biphenyl type epoxy resin (epoxy with dihydroxybiphenyl as a precursor) Resin), fluorene type epoxy resin (epoxy resin with bishydroxyphenylfluorene as a precursor), triglycidyl ether type epoxy resin (epoxy resin with triphenol as a precursor), tetraglycidyl ether type epoxy resin (tetraphenol Examples thereof include an epoxy resin as a precursor), a triglycidylaminophenol type epoxy resin (an epoxy resin having an aminophenol as a precursor), and a tetraglycidylamine type epoxy resin (an epoxy resin having a diamine as a precursor). Among these epoxy resins, bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, and bisphenol S-type epoxy resin can appropriately adjust the tackiness and drape of the prepreg without impairing the heat resistance and water resistance of the composite material. Therefore, it is preferably used. Commercially available epoxy resins other than the epoxy resin having a naphthalene skeleton in the molecule include YD-128 (manufactured by Toto Kasei Co., Ltd.) and Ep
c830 (Dai Nippon Ink Co., Ltd.), Ep-154, E
p180S65 (above, Yuka Shell Epoxy Co., Ltd.)
ELM100 (Sumitomo Chemical Co., Ltd.), ELM
434 (manufactured by Sumitomo Chemical Co., Ltd.) or the like can be used.

The component [B] of the present invention is dicyandiamide. Dicyandiamide (hereinafter abbreviated as DICY) is usually a powdery compound and belongs to an amine-based curing agent. Although it is difficult to dissolve in an epoxy resin at 25 ° C., it is a curing agent having the potential to dissolve when heated to 100 ° C. or more and react with the epoxy resin.
For this reason, a prepreg containing an epoxy resin composition containing DICY as a component is excellent in storage stability. DI
The compounding amount of CY is preferably 3 to 10 parts by weight, preferably 3 to 10 parts by weight, based on 100 parts by weight of the epoxy resin compound of the component [A].
5 parts by weight is more preferred. If the amount is less than 3 parts by weight, the heat resistance of the composite material may be impaired, and if the amount exceeds 10 parts by weight, the water resistance of the obtained composite material may be impaired. As a commercial product of DICY, DI
CY-7 (manufactured by Yuka Shell Epoxy Co., Ltd.) or the like can be used.

In the epoxy resin composition of the present invention, diaminodiphenyl sulfone (hereinafter abbreviated as DDS) may be blended as a curing agent. When DICY and DDS are used together, the adhesion between the reinforcing fiber and the matrix resin, that is, the cured resin (hereinafter simply referred to as “adhesion”) becomes strong, and in the obtained composite material, particularly in the direction parallel to the fiber direction. Compressive strength, that is, 0 degree compressive strength is preferable because it is improved. In this case, the amount of DDS is preferably 5 to 15 parts by weight, more preferably 5 to 12 parts by weight, based on 100 parts by weight of the epoxy resin compound of the component [A]. If the amount is less than 5 parts by weight, the adhesion may not be sufficiently improved,
If the amount exceeds 15 parts by weight, the heat resistance and water resistance of the resulting composite material may be impaired. DDS
As commercially available products, SUMICURE-S (manufactured by Sumitomo Chemical Co., Ltd.) can be used.

Further, the epoxy resin composition of the present invention comprises:
As a curing accelerator, a tertiary amine compound, an imidazole compound, a urea compound, or the like can be blended. When a curing agent such as DICY or DDS is used alone without using such a curing accelerator, it is necessary to cure at a high temperature of about 180 ° C. when a composite material is obtained by molding. When used, curing can be performed at a low temperature of about 120 ° C.

Among them, when a urea compound is used, a cured resin having excellent adhesion can be obtained without impairing the heat resistance and water resistance of an epoxy resin having a naphthalene skeleton in the molecule. A urea compound is used as the element [C]. As a result, a composite material exhibiting excellent 0-degree compressive strength even in a high temperature state after water absorption can be obtained despite being cured at a lower temperature than before.

The amount of the urea compound of the component [C] is preferably 2 to 8 parts by weight based on 100 parts by weight of the epoxy resin compound of the component [A]. If the amount is less than 2 parts by weight, the effect of accelerating the curing may decrease. If the amount is more than 8 parts by weight, the effect of accelerating the curing becomes excessive, so that the storage stability may be impaired. Specific examples of the urea compound include 3- (3,4-dichlorophenyl) -1,1-dimethylurea, 3- (4-chlorophenyl) -1,1-dimethylurea, phenyldimethylurea, and toluenebisdimethylurea. No.
Commercially available urea compounds include DCMU-99.
(Hodogaya Chemical Industry Co., Ltd.) can be used.

The epoxy resin composition of the present invention contains a thermosetting resin for improving the rheology of the uncured resin composition, improving the toughness of the cured resin, controlling the tackiness and drape of the prepreg, and improving the adhesiveness. A plastic resin, a thermoplastic elastomer, an elastomer, inorganic particles, a diluent, and the like can be appropriately compounded.

Specific examples of the thermoplastic resin include polyamide, polyamide imide, polyarylene oxide, polyarylate, polyimide, polyethylene terephthalate, polyether imide, polyether ether ketone, polyether sulfone, polycarbonate, polyvinyl acetate, polystyrene, and the like. Examples thereof include polysulfone, polyvinyl acetal, polyvinyl alcohol, polyvinyl formal, polyphenylene oxide, polyphenylene sulfide, polypropylene, polybenzimidazole, and polymethyl methacrylate. These thermoplastic resins can be used alone or in combination of two or more. Among such thermoplastic resins, polyetherimide,
Polyethersulfone is effective for enhancing the adhesiveness without impairing the heat resistance and water resistance of the obtained composite material. As a result, the 0-degree compressive strength of the composite material is improved.

Specific examples of the thermoplastic elastomer include:
Styrene-based, olefin-based, PVC-based, urethane-based, ester-based, and amide-based elastomers can be used, and these can be used alone or in combination of two or more.

Specific examples of the elastomer include acrylonitrile-butadiene rubber, urethane rubber, styrene-
Butadiene rubber and the like can be mentioned, and these can be used alone or in combination of two or more.

The compounding amount of the thermoplastic elastomer and the elastomer, or the compounding amount of the mixture thereof, is based on 100 parts by weight of the epoxy resin compound of the component [A].
The amount is preferably 1 to 5 parts by weight, more preferably 2 to 3 parts by weight. If the amount is less than 1 part by weight, the effects of the present invention will not be sufficiently exhibited, and if the amount exceeds 5 parts by weight, the heat resistance and water resistance of the obtained composite material will be impaired.

Specific examples of the inorganic particles include alumina, carbon black, kaolin clay, graphite, aluminum silicate, tin oxide, titanium oxide, antimony trioxide, molybdenum trioxide, silica, zirconia, aluminum hydroxide, and magnesium hydroxide. , Smectite, sericite, talc, calcium carbonate, magnesium carbonate, ferrite, mica, montmorillonite, and particles made of a material selected from molybdenum sulfide,
These can be used alone or in combination of two or more. Among them, silica particles are preferable because they effectively provide so-called thixotropic properties to the epoxy resin composition.

The silica particles are of a hydrophilic type in which silicon dioxide is a basic skeleton and the surface of the particles is covered with a silanol group, and the silica particles are hydrophobic in which hydrogen of the silanol group is substituted with an alkyl group, a silyl group or the like. Although the latter type is preferred, the latter is preferably used because it can impart high water resistance to the obtained composite material. The mixing amount of these inorganic particles is preferably 1 to 10 polymer parts, more preferably 2 to 10 parts by weight per 100 parts by weight of the epoxy resin compound of the component [A].
~ 8 parts by weight is good. If the amount is less than 1 part by weight, the effects of the present invention will not be sufficiently exerted. If the amount exceeds 10 parts by weight, the drape property of the prepreg will be easily impaired.

Specific examples of the reinforcing fibers used in the prepreg and the fiber-reinforced composite material of the present invention include aramid fibers, glass fibers, carbon fibers and the like. Among them,
Carbon fibers are preferable because they have high strength, high elastic modulus, and are lightweight. In particular, when carbon fibers having a tensile strength of 4000 MPa or more are used, a composite material having sufficient mechanical strength as an aircraft structural material, that is, a tensile strength, a tensile modulus, a compressive strength, and the like is obtained, which is preferable.

As the form and arrangement of the reinforcing fibers, long fibers,
Short fibers, woven fabrics, braids, tows, knits, mats and the like can be applied. The content of the reinforcing fibers is preferably 50 to 80% by weight based on the whole prepreg or composite material. If the content of the reinforcing fiber is less than 50% by weight, the mechanical strength of the composite material may be insufficient, and if it exceeds 80% by weight, the durability of the obtained composite material is inferior due to the rubbing of single fibers of the fiber. It may be.

In the present invention, as a method for producing a prepreg, a resin film is prepared by uniformly applying an uncured resin composition on release paper, and the resin film is laminated on both sides of the reinforcing fiber, and heated. -A method of applying pressure and impregnating the reinforcing fibers can be adopted. At this time, the temperature for impregnating the resin film is preferably 90 to 150 ° C. If the temperature is less than 90 ° C., the impregnation becomes insufficient, the tackiness of the prepreg becomes excessive, and the handleability may deteriorate,
If the temperature exceeds 150 ° C., the curing proceeds during the impregnation, and the drapability of the prepreg may be impaired.

The prepreg thus obtained has excellent storage stability at room temperature. Even if it is left at room temperature for about one week, its tackiness and drape properties change little with time, and it is extremely easy to handle. It is.

As a method for producing a composite material from a prepreg, a method is preferably employed in which the direction of the fibers is changed little by little, the fibers are laminated so as to have a pseudo isotropic property, and then cured by heating. You. The heating temperature here is preferably from 100 to 140C. Heating temperature is 100 ℃
If it is less than 1, the curing of the matrix resin becomes incomplete, and the heat resistance and water resistance of the obtained composite material may be impaired.If it exceeds 140 ° C., the heat shrinkage when cooled from the molding temperature to room temperature is ignored. In some cases, the heat-shrinked portions may become defective portions in the composite material. Furthermore, the resulting composite material is likely to be inferior in fracture resistance to excessive stress on local areas, such as primary structural materials such as aircraft wings, tail wings, fuselage, front wheel doors,
It becomes difficult to apply to large-scale structural materials represented by directional snakes and spoilers. In addition, the energy required for heating during molding also increases.

[0032]

The present invention will be described more specifically with reference to the following examples. (Examples 1 to 7, Comparative Examples 1 to 7) The following commercially available products were used as raw materials. <Epoxy resin> Epoxy resin NC-7300L having a naphthalene skeleton in the molecule (Nippon Kayaku Co., Ltd., epoxy equivalent: 210). The chemical structural formula is as shown below.

[0033]

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Epoxy resin ESN-170 having a naphthalene skeleton in the molecule (Nippon Steel Chemical Co., Ltd., epoxy equivalent: 258). The chemical structural formula is as shown below.

[0035]

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Epoxy resin HP-4032 having a naphthalene skeleton in the molecule (Deppo Nippon Ink Co., Ltd., epoxy equivalent: 150). The chemical structural formula is as shown below.

[0037]

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Bisphenol A type epoxy resin YD-
128 (manufactured by Toto Kasei Co., Ltd., epoxy equivalent: 189).
The chemical structural formula is as shown below.

[0039]

Embedded image

Bisphenol F type epoxy resin Epc
830 (Dai Nippon Ink Co., Ltd., epoxy equivalent: 18)
0). The chemical structural formula is as shown below.

[0041]

Embedded image

Tetraglycidylamine type epoxy resin
ELM434 (manufactured by Sumitomo Chemical Co., Ltd., epoxy equivalent;
120). The chemical structural formula is as shown below.

[0043]

Embedded image

In the above chemical structural formula, G is a glycidyl group (the chemical structural formula is shown below).

[0045]

Embedded image

<Curing Agent> Dicyandiamide (abbreviation: DICY), DICY-7
(Manufactured by Yuka Shell Epoxy Co., Ltd.) 4,4′-diaminodiphenyl sulfone (abbreviation: DD)
S), SUMICURE-S (manufactured by Sumitomo Chemical Co., Ltd.) <Curing accelerator> Urea compound: 3- (3,4-dichlorophenyl)-
1,1-dimethylurea (abbreviation: DCMU), DCMU
-99 (manufactured by Hodogaya Chemical Industry Co., Ltd.) Imidazole compound: 2-phenyl-4-methylimidazole (abbreviation: PMIZ), Cureazole 2P4MZ
(Manufactured by Shikoku Kasei Co., Ltd.) <Thermosetting resin> Polyetherimide (abbreviation: PEI), “Ultem”
Grade 1000 (General Electric Co., Ltd.)
Polyethersulfone (abbreviation: PES), "Victr
ex "grade 5003P (manufactured by Sumitomo Chemical Co., Ltd.) <Carbon fiber>" Treca "T700S-12K-50C (Toray Industries, Inc.)
"Treca" T800H-12K-40B (Toray Industries, Inc.)
The raw materials having the composition ratios shown in Tables 1 and 2 are kneaded in a kneader,
An epoxy resin composition was prepared. The resin composition was heated and melted, and then uniformly applied on release paper by a coater to prepare a resin film (basis weight: 52 g / m ² ).

Next, carbon fibers (basis weight: 190 g / m ² ) were aligned in the same direction, sandwiched between both sides with this resin film, and heated and pressed to impregnate the fibers with the resin to obtain a prepreg. The obtained prepreg had good tackiness and drapability, and was excellent in handleability.

After laminating the prepregs in the same fiber direction in a six-layer configuration, they were heated and cured in an autoclave at a temperature of 120 ° C. and a pressure of 0.294 MPa for 2 hours to obtain a fiber-reinforced composite material.

A test piece was cut out from the obtained fiber-reinforced composite material, immersed in hot water at 71 ° C. for 2 weeks, and then measured for 0 ° compressive strength in a thermostatic chamber adjusted to 82 ° C. in accordance with JIS K7076. Under such test conditions, the fact that the 0-degree compressive strength of the composite material in a high temperature state after water absorption is 1000 MPa or more is an index of suitability as a structural material for aircraft. From the examples and comparative examples shown in Tables 1 and 2, from the fact that the epoxy equivalent of the epoxy resin having a naphthalene skeleton in the molecule is not in the range of 200 to 400, the 0-degree compressive strength of the composite material in a high temperature state after water absorption is increased. It turns out that there is a big shortage. In addition, it can be seen that DICY is required as a hardening agent and a urea compound is required as a hardening accelerator in order to ensure sufficient 0 ° compression strength.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

According to the present invention, it is possible to obtain a prepreg which can be cured at a lower temperature than conventional and has excellent handleability such as tackiness and drapability. The prepregs are laminated, cured by heating and molded. As a result, a carbon fiber reinforced composite material having excellent 0 ° compressive strength even in a high temperature state after water absorption and suitable for use in aircraft structural materials can be obtained.

Claims (7)

[Claims] 1. The following components [A], [B] and [C]
A prepreg obtained by impregnating a reinforcing fiber with an epoxy resin composition containing: [A] An epoxy resin compound comprising an epoxy resin having a naphthalene skeleton in the molecule and having an epoxy equivalent of 200 to 400 [B] dicyandiamide [C] urea compound 2. The amount of the epoxy resin having a naphthalene skeleton in the molecule in the component [A] is 40 to 100 parts by weight of the epoxy resin compound in the component [A].
The prepreg according to claim 1, wherein the amount is from 80 to 80 parts by weight. 3. The epoxy resin composition of the component [A] contains at least one epoxy resin selected from the group consisting of bisphenol A epoxy resin, bisphenol F epoxy resin, and bisphenol S epoxy resin. The prepreg according to claim 1 or 2, wherein 4. The prepreg according to claim 1, wherein the epoxy resin composition contains diaminodiphenyl sulfone. 5. The prepreg according to claim 1, wherein the epoxy resin composition contains a thermoplastic resin. 6. The method according to claim 1, wherein the reinforcing fibers are carbon fibers.
5. The prepreg according to any one of 5. 7. A fiber-reinforced composite material obtained by laminating the prepreg according to any one of claims 1 to 6 and curing and molding by heating.