JPH02216274A - Production of composite material - Google Patents

Abstract

PURPOSE:To obtain a composite material, excellent in heat resistance and having sufficient toughness by treating carbon fiber with a solution containing a specific silane coupling agent and then compounding the resultant treated carbon fiber with a bismaleimide-based resin composition. CONSTITUTION:Carbon fiber is subjected to dipping treatment with a solution containing one silane coupling agent selected from aminosilane, epoxysilane and vinylsilane, then treated and compounded with a resin composition containing a polyfunctional bismaleimide (e.g. 1,2-bismaleimideoethane) and a reactive compound, e.g. alkenylphenol (e.g. O,O'-diallylbisphenol A), copolymerizable with the above-mentioned imide compound to afford a composite material. The aforementioned composite material is excellent in heat and impact resistance and useful as an aeronautical heat-resistant material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a carbon fiber composite material having excellent toughness, heat resistance, water resistance, etc.

[Conventional technology]

Currently, the mainstream carbon fiber composite materials are those that use epoxy resin as the matrix resin, but epoxy resin does not have sufficient heat resistance (the demand for heat-resistant materials is increasing mainly for aerospace applications). I am no longer able to satisfy myself.

On the other hand, although polyimide, which is known as a heat-resistant resin, has excellent heat resistance, it has problems in terms of moldability and is still hardly put into practical use. Under these circumstances, bismaleimide resin materials with an excellent balance of heat resistance and moldability are attracting attention as matrix resins for carbon fiber composite materials. Bismaleimide resins have the disadvantage of poor toughness, and improving toughness is said to be the most important point for practical use.

Methods to improve the toughness of carbon fiber composite materials using bismaleimide resin as a matrix resin have been proposed, such as blending a rubber component or copolymerizing with other monomers, but the heat resistance, etc. A satisfactory method has not been found, such as cases in which the improvement in toughness is not sufficient despite the large decrease in physical properties of carbon fibers, or the improvement in toughness as a carbon fiber composite material is not sufficient even if the fracture toughness of the resin alone is improved. do not have.

[Problem 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 resin composite material.

[Means to solve the problem]

As a result of studies to solve the above problems, the present inventors found that
The present invention was completed based on the discovery that the toughness of the resulting composite material can be significantly improved by treating carbon fiber with a specific silane coupling agent solution and then combining it with a bismaleimide resin composition.

The present invention involves treating carbon fibers with a solution of at least one silane coupling agent selected from aminosilane, epoxysilane, and vinylsilane, and then compounding the carbon fibers with a resin composition containing polyfunctional bismaleimide as a main component. This is a method for manufacturing composite materials.

When carbon fibers are treated with a dilute solution of an aminosilane coupling agent (coupling agent concentration 2.0% by weight or less), the main component is polyfunctional bismaleimide and a reactive compound copolymerizable with this compound, such as alkenylphenol. It is preferable to form a composite with a resin composition.

The term "carbon fiber" used in the present invention refers to both carbon fiber and graphite fiber, and carbon fiber is usually referred to as "carbon fiber".
It is produced by carbonizing a fibrous material called a "precursor" such as polyacrylonitrile or pitch or heating it to a graphitization temperature.

A feature of the present invention is that, prior to compounding with a resin composition, carbon fibers are treated with a solution of at least one silane coupling agent selected from aminosilane, epoxysilane/and nylsilane, and then used. However, by treating carbon fiber with a specific silane coupling agent before use, it is possible to obtain satisfactory toughness as a carbon fiber composite material. Even when combined with a resin composition having high toughness, the toughness as a composite material is not sufficiently exhibited.

Examples of the silane coupling agent used in the present invention include the following compounds. Vinylsilanes such as vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, vinyltriacetoxysilane, etc., aminosilanes such as r-7minopropyltrimethoxysilane, r
-aminopropyltriethoxysilane, r-aminopropyltriethoxysilane, γ-aminofloyl-methyl-jethoxysilane, r-ureidoglobiltriethoxysilane, r-(2-aminoethyl)aminopropyltrimethoxysilane, epoxy Silanes such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxyglobiltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, r-methacryloxyglobiltrimethoxysilane, and the like. Particularly preferred are compounds whose functional group is an amine group. Partial feeds of these 7-run coupling agents can also be used.

As a method for treating carbon fibers with a silane coupling agent, any commonly used treatment method may be used, but
Particularly preferred is a method in which the material is passed through a low concentration solution of a silane coupling agent. In this case, if the concentration of the silane coupling agent in the solution is high, the carbon fibers will aggregate too strongly and a uniform composite material will not be obtained (and the toughness of the composite material will decrease, so It is important to use a solution with a concentration of 2.0% by weight or less, especially 0.00%.
1 to 2.0% by weight is preferred.

The solvent for the low concentration solution of the silane coupling agent used in the present invention may be any solvent as long as it dissolves the silane coupling agent and is substantially inert to the silane coupling agent. When considering the drying process after treatment, organic solvents with high boiling points are not preferred.

When using an aminosilane coupling agent as the silane coupling agent, particularly preferred solvents include lower alcohols such as ethyl alcohol, mixed solvents of lower alcohols and water, and water/alcohol mixed solvents containing acid components such as acetic acid. .

The carbon fibers treated with these silane coupling agent solutions are air-dried and/or heated to remove volatile components such as solvents, and then composited with a resin composition containing polyfunctional bismaleimide as a main component.

The resin composition containing polyfunctional bismaleimide as a main component used in the present invention is a resin composition in which the compound having two or more maleimide groups in the molecule accounts for 30% by weight or more, preferably 40% by weight or more. , a monofunctional maleimide compound or other copolymerizable reactive compounds may be included within a range that does not reduce physical properties such as heat resistance and toughness.

The following compounds are used as the polyfunctional bismaleimide.

= 1.2-bismaleimidoethane, 1,6-bismaleimidehexane, 1,12-bismaleimidododecane, 1.6-bismaleimido-(2,2,4-trimethyl)hexane, 1
, 6-bismaleimido-(2,4,4-trimethyl)hexane, 1,3- or 1,4-bismaleimidobenzene, 4.4'-or ha5.3'-1:'sumaleimidodiphenylmethane, 2 .4- 2.6- or 3,4-bismaleimidotoluene, 3.3'-bismaleimidodiphenyl sulfone, 4.4'-bismaleimidodiphenyl ether, 4.4'-bismaleimidodicyclohexylmethane, 4.4'- Bismaleimide diphenylcyclohexane, 4.4'-1:' Sumaleimitocyphenylsulfide, N, N' -m- or p-xylylene bismaleimide, N, -m-phenylene bis-citraconimide, N, N'-4,4'-diphenylenebis-citraconimide and mixtures thereof. Particular preference is given to 4,4'-bismaleimidodiphenylmethane, a eutectic mixture of this compound with 1,6-bismaleimidoT(2,2,4-)limethyl)hexane and 2,4-bismaleimidotoluene.

Examples of reactive compounds copolymerizable with the polyfunctional bismaleimide compound include O9σ-diallylbisphenol A, O. Examples include σ-diallyl bisphenol F,) realyl isocyanate, divinylbenzene, N-vinylpyrrolidone, and hyethylene glycol dimethacrylate.

These copolymerizable reactive compounds may be used alone or in combination in an amount of 70% by weight or less, preferably 50% by weight, in the resin composition.
Used in the following ranges. Among these copolymerizable compounds, 0. ○′-diallylbisphenol A, 0. σ
-Alkenylphenols such as diallylbisphenol F are effective in improving the toughness and processability of resin compositions,
It is preferably used in an amount of 10 to 50% by weight in the resin composition.

The resin composition containing polyfunctional bismaleimide as a main component used in the present invention can be easily cured by heat, but it is difficult to cure the resin composition for the purpose of imparting desired properties to the cured product or adjusting the curing properties. A catalyst may also be added. As polymerization catalysts, ionic catalysts such as organophosphines, organophosphonium salts or complexes thereof, imidazoles, 6th amines, quaternary ammonium salts, boron trifluoride amine salts, organic peroxides, azobis Radical polymerization catalysts such as isobutyronitrile can be used. The amount of catalyst to be added may be determined depending on the purpose, but from the viewpoint of stability of the resin composition, it should be 0.05 to 0.05 to
5% by weight is preferred.

In the resin composition containing bismaleimide as a main component in the present invention, as long as the physical properties such as heat resistance and toughness are not deteriorated,
Carboxyl-terminated butadiene-terminated butadiene/acrylonitrile copolymers and other reactive nitrogen epoxy resins, unsaturated polyester resins, phenolic resins, silyl-r
- thermosetting resins such as resins, triazine resins, polyethersulfones, polyetherimides, polyetherketones, thermoplastic polyimides, polyesters, polyamides,
Thermoplastic resins such as polyamideimide may also be added.

The amount of these resin components added is preferably 60% by weight or less.

In carrying out the present invention, carbon fibers are first treated with a solution of the silane coupling agent described above. As a treatment method, a dipping method is preferred. Next, the carbon fiber is composited with a resin composition to obtain the desired composite material.

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

〔Effect of the invention〕

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

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 fibers (Pyrofil T-3 manufactured by Mitsubishi Rayon Co., Ltd.) were immersed in this solution and passed through it. After air drying, it was dried with hot air at 120° C. for 2 minutes and rolled up.

It was further dried at 100° C. for 5 hours under a reduced pressure of 15 m×Hg to remove residual solvent. The treated carbon fibers had a similar appearance to the untreated ones. - 54 parts by weight of 4.4'-bismaleimidiphenylmethane and 0. 46 parts by weight of σ-diallylbisphenol A were stirred and mixed at 130°C until uniform, to obtain a prepolymer. This prepolymer was stretched into a thin film on release paper at 80° C., and the treated carbon fibers were wound on a drum and impregnated with resin. One-way Gripreg (
Thread weight: 14,597 m'', resin content: 33% by weight) was obtained.This prepreg was prepared by [0°)
°/-45°/90°] for 4 seconds, cured at 182°C for 6 hours, and then slowly cured 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. The results are shown in Table 1.

"Heat resistance" refers to the 0016 layer laminated material composite.
177℃, 262℃ according to TMD-2344
The determination was made by measuring the interlaminar shear strength (LSS).

"Impact resistance" is based on NASA RP 1092, in which a board with dimensions of 4 x 6 x 0.25 inches is fixed on a stand with a 3 x 5 inch hole, and a 1/2 inch radius nose is placed in the center of the board. A 4.9 kg weight with a weight attached to it is dropped,
It was determined by applying an impact of 15,001 bins per inch of plate thickness and then subjecting the plate to a compression test.

Comparative Example 1 A composite material was obtained in the same manner as in Example 1 using carbon fibers that were not treated with an aminosilane coupling agent. The evaluation results are shown in Table 1.

Reference Example γ-Aminoglobiltriethoxysilane was mixed with a water-ethanol (water/ethanol = 1/9 weight-JL ratio) mixed solvent to prepare a 5.0% by weight solution.

Carbon fibers were treated in the same manner as in Example 1. The treated carbon fibers were bonded together and bundled.

A prepreg was created in the same manner as in Example 1 using the treated carbon fibers. The fibers did not spread well and the resin impregnation state was also poor. The post-impact compressive strength of the resulting composite material was 12.
The weight was 7 kg/M112, which was significantly lower than that of Example 1.

Example 2 r-Ureidoprobyltriethoxysilane was dissolved in a mixed solvent of water and ethanol (1/9 weight ratio) to prepare a 0.05% by weight solution, and carbon was prepared in the same manner as in Example 1. The fibers were further processed to obtain a composite material. The evaluation results are shown in Table 1.

Table 1 Example 6 3-Glycidoxyprobyl-trimethoxysilane in water
A 1.0% by weight solution was prepared by mixing a solvent with a small amount of acetic acid added to ethanol (179 weight ratio), and otherwise the carbon fiber was treated in the same manner as in Example 1 to obtain a composite material. . The evaluation results of heat resistance and impact resistance are shown in Table 2.

Example 4 Vinyltriethoxysilane was dissolved in a mixed solvent containing 2.0 g of water and 2 drops of acetic acid per 100 g of acetone.
．． A 2% by weight solution was prepared and used, and carbon fibers were otherwise treated in the same manner as in Example 1 to obtain a composite material. The evaluation results are shown in Table 2.

Example 5 Bismaleimide eutectic mixture (4,4'
- 49% by weight of bismaleimidocyphenylmethane, 2.
63% by weight of 4-bismaleimidotoluene and 1 part of 1,6-bismaleimido-(2,2,4-trimethyl)hexane
A composite material was obtained in the same manner as in Example 1, except that a mixture of 72 parts by weight (8% by weight) and 28 parts by weight of 0.0'-diallylbisphenol A was used. The evaluation results are shown in Table 2.

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.

Part 2 table

Claims (1)

[Claims] 1. Carbon fibers are treated with a solution of at least one silane coupling agent selected from aminosilane, epoxysilane, and vinylsilane, and then composited with a resin composition containing polyfunctional bismaleimide as a main component. A method for manufacturing a composite material, characterized by: 2. After treating carbon fibers with a dilute solution of an aminosilane coupling agent (coupling agent concentration 2.0% by weight or less), composite the carbon fibers with a resin composition containing polyfunctional bismaleimide and alkenylphenol as main components. A method for manufacturing a composite material, characterized by: