JP2707294B2 - Manufacturing method of composite material - Google Patents

Description

The present invention relates to a method for producing a carbon fiber composite material having excellent toughness, heat resistance, water resistance and the like.

[Conventional technology]

At present, the mainstream carbon fiber composite materials are those that use epoxy resin as matrix resin.However, epoxy resin does not have sufficient heat resistance, and the demand for heat-resistant material, which is increasing mainly in aerospace applications, has been increasing. I am not satisfied.

On the other hand, polyimide, which is known as a heat-resistant resin,
Although excellent in heat resistance, there is a problem in moldability, and it has not been practically used yet. Under these circumstances, bismaleimide-based resin materials having an excellent balance between heat resistance and moldability have been attracting attention as matrix resins for carbon fiber composite materials. Bismaleimide-based resins have the disadvantage of poor toughness, and improvement in toughness is said to be the greatest point of practical use.

As a method for improving the toughness of a carbon fiber composite material using a bismaleimide-based resin as a matrix resin, methods such as a method of blending a rubber component and a method of copolymerizing with another monomer have been proposed. Satisfactory methods have been found, such as that the toughness is not sufficiently improved despite the large decrease in the physical properties of the resin, and the toughness of the carbon fiber composite material is not sufficiently improved even if the fracture toughness of the resin alone is improved. Absent.

[Problems to be solved by the invention]

The present invention provides an advantageous method for producing a composite material having sufficient toughness without impairing the excellent heat resistance of the carbon fiber / bismaleimide-based resin composite material.

[Means for solving the problem]

The present inventors have studied to solve the above problems, and as a result, after treating with a carbon fiber and a specific silane coupling agent solution, and then compounding with a bismaleimide-based resin composition, a composite material obtained is obtained. The inventors have found that the toughness is remarkably improved and completed the present invention.

The present invention provides that after treating a carbon fiber with a solution of at least one silane coupling agent selected from amino silane, epoxy silane and vinyl silane, it is combined with a resin composition containing a polyfunctional bismaleimide as a main component. A method for producing a composite material, the method being characterized.

When a carbon fiber is treated with a dilute solution of an aminosilane coupling agent (coupling agent concentration of 2.0% by weight or less), a resin composition mainly composed of a polyfunctional bismaleimide and a reactive compound copolymerizable with the compound, for example, alkenylphenol It is preferable to combine with a substance.

The term "carbon fiber" used in the present invention means both carbon fiber and graphite fiber, and carbon fiber is obtained by carbonizing a fibrous material such as polyacrylonitrile, pitch and the like usually referred to as "precursor". It is produced by heating to the graphiting temperature.

A feature of the present invention resides in that prior to compounding with a resin composition, the carbon fiber is treated with at least one silane coupling agent solution selected from aminosilane, epoxysilane and vinylsilane before use. By treating the carbon fiber with a specific silane coupling agent before use, a satisfactory toughness as a carbon fiber composite material can be obtained.If untreated carbon fiber is used as it is, Even when combined with a resin composition having high toughness, the toughness as a composite material is not sufficiently exhibited.

As the silane coupling agent used in the present invention,
The following compounds are mentioned. Vinylsilanes such as vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, and vinyltriacetoxysilane; aminosilanes such as γ-aminopropyltrimethoxysilane;
γ-aminopropyltriethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyl-methyl-diethoxysilane, γ-ureidopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, epoxy Silanes such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane and the like. Compounds in which the functional group is an amino group are particularly preferred. Further, a partial condensate of these silane coupling agents can be used.

The method of treating the carbon fiber with the silane coupling agent may be any of the commonly used treatment methods, but a method of treating the carbon fiber by passing it through a low-concentration solution of the silane coupling agent is particularly preferred. In this case, if the concentration of the silane coupling agent in the solution is high, the convergence of the carbon fibers becomes too strong to obtain a uniform composite material, and the toughness of the composite material is reduced. This is very important. Solution concentration is less than 2.0% by weight, especially 0.001 ~
2.0% by weight is preferred.

As the solvent for the low-concentration solution of the silane coupling agent used in the present invention, any solvent may be used as long as the solvent dissolves the silane coupling agent and is substantially inert to the silane coupling agent. Considering a drying step after the treatment, an organic solvent having a high boiling point is not preferred.

As a solvent when using an aminosilane-based coupling agent as a silane coupling agent, a lower alcohol such as ethyl alcohol, a mixed solvent of lower alcohol and water,
A water / alcohol mixed solvent containing an acid component such as acetic acid is particularly preferred.

After removing volatile components such as a solvent by air drying and / or heat treatment, the carbon fiber treated with the silane coupling agent solution is composited with a resin composition containing a polyfunctional bismaleimide as a main component.

The polyfunctional bismaleimide-based resin composition used in the present invention is a resin composition in which a compound having two or more maleimide groups in a molecule accounts for 30% by weight, preferably 40% by weight or more. It may contain a monofunctional maleimide compound or another copolymerizable reactive compound as long as physical properties such as heat resistance and toughness are not reduced.

The following compounds are used as the polyfunctional bismaleimide. 1,2-bismaleimide ethane, 1,6-bismaleimide hexane, 1,12-bismaleimide dodecane, 1,6-
Bismaleimide- (2,2,4-trimethyl) hexane, 1,6
-Bismaleimide- (2,4,4-trimethyl) hexane,
1,3- or 1,4-bismaleimidobenzene, 4,4'- or
3,3'-bismaleimidodiphenylmethane, 2,4-, 2,6
-Or 3,4-bismaleimidotoluene, 3,3'-bismaleimidodiphenylsulfone, 4,4'-bismaleimidodiphenylether, 4,4'-bismaleimidodicyclohexylmethane, 4,4'-bismaleimidediph Enylcyclohexane, 4,4'-bismaleimidodiphenyl sulfide, N, N'-m- or p-xylylenebismaleimide, N, Nm-phenylenebis-citraconimide, N,
N'-4,4'-diphenylenebis-citraconimide and the like, and mixtures thereof. 4,4'-bismaleimidodiphenylmethane, this compound and 1,6-bismaleimide- (2,
Eutectic mixtures of 2,4-trimethyl) hexane and 2,4-bismaleimidotoluene are particularly preferred.

Examples of the reactive compound copolymerizable with the polyfunctional bismaleimide compound include, for example, O, O'-diallylbisphenol A, O, O'-diallylbisphenol F, triallyl isocyanate, divinylbenzene, N-vinylpyrrolidone and Ethylene glycol dimethacrylate and the like. These copolymerizable reactive compounds are used alone or as a mixture in an amount of 70% by weight or less, preferably 50% by weight or less in the resin composition. Of these copolymerizable compounds, O, O'-diallylbisphenol A, O, O '
Alkenyl phenols such as diallyl bisphenol F are also effective in improving the toughness and processability of the resin composition,
It is preferable to use 10 to 50% by weight of the resin composition.

The resin composition containing a polyfunctional bismaleimide as a main component used in the present invention can be easily cured by heat, but for the purpose of imparting desired properties to the cured product or adjusting the curing properties. A catalyst may be added. Examples of the polymerization catalyst include organophosphines, organophosphonium salts or complexes thereof, imidazoles,
Ion catalysts such as quaternary amines, quaternary ammonium salts, and boron trifluoride amine salts, and radical polymerization catalysts such as organic peroxides and azobisisobutyronitrile can be used. The amount of catalyst to be added may be determined according to the purpose,
From the viewpoint of the stability of the resin composition, 0.05 to 5 with respect to all resin components.
% By weight is preferred.

In the resin composition containing bismaleimide as the main component in the present invention, a carboxyl group-terminated butadiene / acrylonitrile copolymer, a carboxyl group-terminated polybutadiene, an acryloyloxy group-terminated butadiene / Reactive elastomers such as acrylonitrile copolymers, epoxy resins, unsaturated polyester resins, phenolic resins, silicone resins, thermosetting resins such as triazine resins, polyethersulfone, polyetherimide, polyetherketone, thermoplastic polyimide, polyester And a thermoplastic resin such as polyamide, polyamide-imide or the like. It is preferable that the addition amount of these resin components is 30% by weight or less.

In practicing the present invention, carbon fibers are first treated with a solution of the silane coupling agent. As a treatment method, a dipping method is preferable. Next, when the carbon fiber is composited with the resin composition, a target composite material is obtained.

A composite material comprising a carbon fiber treated with a silane coupling agent and a resin composition containing a polyfunctional bismaleimide as a main component can be produced by a known method. For example, first, a resin composition is formed into a film by a hot melt method or a solvent method, and then a pre-impregnated material (so-called prepreg) of a carbon fiber and a resin composition is produced by a heat impregnation method, and this is cured by a vacuum backing / autoclave method. Can be used.

〔The invention's effect〕

The composite material obtained by the method of the present invention has excellent heat resistance, impact resistance and mechanical properties, and is useful as a molding material, particularly as a heat resistant material for aerospace.

Example 1 γ-aminopropyltriethoxysilane was mixed with a water-ethanol (water / ethanol = 1/9 weight ratio) mixed solvent to prepare a 0.01% by weight solution. Carbon fiber (Pyrofil T-3 manufactured by Mitsubishi Rayon Co., Ltd.) was immersed and passed through this solution. After air-drying, it was dried with hot air at 120 ° C. for 2 minutes and wound up. Further, it was dried at 100 ° C. for 5 hours under reduced pressure of 15 mmHg,
The residual solvent was removed. The treated carbon fiber had the same appearance as the untreated carbon fiber. On the other hand, 54 parts by weight of 4,4'-bismaleimidodiphenylmethane and 46 parts by weight of O, O'-diallylbisphenol A are stirred and mixed at 130 ° C until uniform,
A prepolymer was obtained. Place this prepolymer on release paper for 80
The film was stretched on a thin film at ℃, and the treated carbon fiber was wound on a drum and impregnated with a resin. Then, it was cut open to obtain a unidirectional prepreg (having a grain weight of 145 g / m ² and a resin content of 33% by weight). This prepreg is laminated on [0 °] ₁₆ and [+ 45 ° / 0 ° / -45 ° / 90 °] _4S , and
After curing for an hour, curing was further performed at 243 ° C. for 6 hours to obtain a composite material.

The heat resistance and impact resistance of the obtained composite material were evaluated by the following methods. Table 1 shows the results.

"Heat resistance" is based on ASTM using a 0 ° 16-layer laminated composite.
According to D-2344, the interlaminar shear strength at 177 ° C and 232 ° C (I
LSS) was measured.

“Impact resistance” is 4 × 6 according to NASA RP 1092
Fix a 0.25 inch board on a 3 x 5 inch perforated table, drop a 4.9 kg weight with a 1/2 inch R nose at the center, and apply a shock of 15001 bin per inch of board thickness. After addition, the plate was determined by a compression test.

Comparative Example 1 A composite material was obtained in the same manner as in Example 1, except that carbon fibers not treated with the aminosilane coupling agent were used. Table 1 shows the evaluation results.

Reference Example γ-aminopropyltriethoxysilane was mixed with a water-ethanol (water / ethanol = 1/9 weight ratio) mixed solvent to prepare a 5.0% by weight solution. The carbon fiber was treated in the same manner as in Example 1. The treated carbon fibers adhered and bundled together. A prepreg was prepared in the same manner as in Example 1 using the treated carbon fiber. The spread of fibers is poor,
The impregnation state of the resin was also poor. The resulting composite had a compressive strength after impact of 12.7 kg / mm ² , which was significantly lower than that of Example 1.

Example 2 γ-ureidopropyltriethoxysilane was dissolved in a water / ethanol (1/9 weight ratio) mixed solvent to prepare a 0.05% by weight solution, and the carbon fiber was treated in the same manner as in Example 1 except for the above. Then, a composite material was obtained. Table 1 shows the evaluation results.

Example 3 A solvent prepared by adding a small amount of acetic acid to water-ethanol (1/9 weight ratio) of 3-glycidoxypropyl-trimethoxysilane was mixed to prepare a 1.0% by weight solution and used. The carbon fiber was treated in the same manner as described above to obtain a composite material. Table 2 shows the evaluation results of the heat resistance and the impact resistance.

Example 4 Vinyl triethoxysilane was added to 100 g of acetone with water
Dissolved in a mixed solvent containing 2.0 g and 2 drops of acetic acid to prepare and use a 0.2% by weight solution, and otherwise treated the carbon fiber in the same manner as in Example 1 to obtain a composite material. Table 2 shows the evaluation results.

Example 5 A bismaleimide eutectic mixture (4,4 ′) was used as a resin composition.
-Bismaleimidodiphenylmethane 49% by weight, 2,4-Bismaleimidetoluene 33% by weight and 1,6-Bismaleimide- (2,2,4-trimethyl) hexane 18% by weight) 72 parts by weight and O, O ' A composite material was obtained in the same manner as in Example 1 except that a mixture of 28 parts by weight of diallyl bisphenol A was used.
Table 2 shows the evaluation results.

From these results, it is known that the composite material obtained by the method of the present invention has excellent heat resistance and impact resistance.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinobu Fujie 4-160 Sunadabashi, Higashi-ku, Nagoya City, Aichi Prefecture Inside Mitsubishi Rayon Co., Ltd. (56) References JP-A-58-69747 (JP, A) JP-A Sho 60-32831 (JP, A)

Claims (2)

(57) [Claims] Claims: 1. A method comprising treating a carbon fiber with a solution of at least one silane coupling agent selected from aminosilane, epoxysilane and vinylsilane, and then forming a composite with a resin composition containing a polyfunctional bismaleimide as a main component. A method for producing a composite material, comprising: 2. A method comprising treating a carbon fiber with a dilute solution of an aminosilane coupling agent (coupling agent concentration of 2.0% by weight or less) and then complexing the carbon fiber with a resin composition containing polyfunctional bismaleimide and alkenylphenol as main components. A method for producing a composite material, comprising: