JPH0347295B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-resistant molding material in which reinforcing fibers are impregnated with a specific formulation and B-staged to form a flexible prepreg.

In recent years, with the development of the space and aviation industries, there has been a strong desire to develop lightweight materials that can withstand the harsh environments at high altitudes or in space.

Particularly in the aircraft industry, reducing fuel costs is a major factor influencing the profits of air transport companies.

Furthermore, in space development, there has been a strong desire to increase the amount of objects launched by reducing the weight of launch materials, and various materials have been developed.

In view of this situation, the present inventors focused on polyimide, which is lightweight and has excellent heat resistance, and aimed to improve the biggest problems of current polyimide, such as processability and gas generation in vacuum. The present invention was achieved through research aimed at achieving this goal.

That is, the present invention impregnates reinforcing fibers with a compound consisting of a polyimide resin, a reactive group-containing polymer oligomer selected from epoxy groups and vinyl groups, a reactive vinyl group-containing monomer, and a solvent, and B-stages the reinforcing fibers. The present invention provides a heat-resistant molding material that can be used as a flexible prepreg.

Examples of the polyimide resin according to the present invention include kelimide resin, bismaleimide resin, and bismaleimide triazine resin, and the type thereof is not particularly limited. However, it is essential for the polyimide resin in the present invention to be dissolved in a solvent or to be uniformly dispersed by stirring, and preferably to be dissolved in a solvent.

Examples of the reactive group-containing polymer oligomers selected from epoxy groups and vinyl groups (hereinafter simply referred to as reactive group-containing polymer oligomers) that characterize the present invention include epoxy resins, vinyl ester resins, and low polymers thereof. (polymerized 2 to 10 molecules of epoxy resin or vinyl ester resin). This molecular weight is about 200 to 100,000.

These reactive group-containing high molecular weight oligomers are
It partially reacts with the polyimide resin and reactive vinyl group-containing monomer contained in the system, imparting fluidity necessary during curing, and at the same time imparting appropriate flexibility to the prepreg. Further, it is necessary that the amount added does not significantly lower the heat resistance of the polyimide resin, and the optimum amount is 10 to 70% by weight, preferably 20 to 50% by weight.

Examples of these reactive group-containing polymer oligomers include epoxy resins commercially available under the trade name "Epiclon" manufactured by Dainippon Ink Chemical Co., Ltd. and vinyl esters under the trade name "Deitskrite". , these can be used alone or in a form containing the following reactive vinyl group-containing monomers.

Next, the reactive vinyl group-containing monomer in the present invention reduces the viscosity of the system, makes it easier to impregnate the reinforcing fibers, gives flexibility and adhesion to the prepreg, and further impregnates the reinforcing fibers. After that, a portion of the reactive vinyl group-containing monomer is heated to evaporate the solvent and achieve B-staging, that is, a semi-cured state where the reaction has progressed to a certain extent and is no longer soluble in the solvent, but the reaction progresses further when heated. Or most of it evaporates, ensuring that the solvent scatters. Therefore, the monomer must not be below the boiling point of the solvent nor above 180°C.

Also, at least a portion of the monomer remains in the prepreg, but it polymerizes during curing and does not cause gas generation in vacuum. This addition amount is
10 to 100 parts by weight per 100 parts by weight of polyimide resin, per 100 parts by weight of solvent and polyimide resin
10 to 200 parts by weight.

Although one type of reactive vinyl group-containing monomer may be used, it is more preferable to use several types of monomers, and as the monomers are successively scattered during B-staging, the concentration of the remaining solvent becomes thinner. Furthermore, similar scattering of monomers and residual solvent occurs during press molding.

Also, of course, when using several types of monomers, the higher the boiling point of the monomer, the better the heat resistance when the molecular weight is increased, and it is desirable that the scattering of monomers occur in order from the one with the worse heat resistance. .

Examples of the reactive vinyl group-containing monomers include styrenes such as styrene, methylstyrene, and divinylbenzene; acrylic acid, methacrylic acid, and their esters; and allyl group-containing monomers such as triallyl isocyanurate and triallyl cyanurate. included. Furthermore, a vinyl group polymerization catalyst such as benzoyl peroxide can be added to the system as required.

It is desirable that the solvent used in the present invention uniformizes the composition impregnated into the reinforcing fibers, lowers the viscosity, facilitates impregnation, and further evaporates during heating during B-staging.

Also, it is particularly desirable to have a material that dissolves the compound into a homogeneous solution.

As a solvent for dissolving polyimide resin, N
- A high boiling point solvent such as methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide or the like having a boiling point of 140° C. or higher is used.

When these high boiling point solvents are used in the present invention, the amount used is reduced as much as possible and the insufficient amount is replaced with a low boiling point solvent such as acetone, methanol, methyllene chloride, ethyl acetate, etc. to facilitate solvent volatilization. things are desirable.

The use of a solvent in the present invention involves uniformly dispersing and preferably dissolving the polyimide resin by selecting the one with the lowest boiling point, and then adding a low boiling point solvent to the solvent to obtain the required amount of solvent. . The solvent to be added to obtain the required amount of solvent must be selected from a solvent that will not uniformly disperse or condense the polyimide resin once dissolved or uniformly dispersed.

The reinforcing fibers according to the present invention include carbon fibers,
Includes organic fibers such as aramid fibers and silicon carbide fibers, and inorganic fibers such as glass fibers, silica fibers, alumina fibers, and ceramic fibers that can be used up to 400℃.

Further, the forms of these used fibers include woven fabric, unidirectionally aligned fibers, pine, etc., but the shape is not particularly limited.

The molding material of the present invention is produced by impregnating reinforcing fibers with a blend consisting of polyimide resins, reactive group-containing polymer oligomers, one to several kinds of reactive vinyl group-containing monomers, a high boiling point solvent, and a low boiling point solvent. ~
It is dried at a temperature of 200°C for several minutes to several tens of minutes to form a B-stage and is made into a prepreg. after that,
FRP boards can be made by stacking the required number of sheets and press forming.

One of the important features of the present invention is that this press forming can be performed at low pressure. In other words, heat-resistant polyimide resins conventionally need to be molded at fairly high pressures of 50 to 150 Kg/cm ² , and for this reason, the pressure of 3 to 15 Kg/cm ² normally used in the aircraft and space industries has to be molded. It was not possible to obtain a good molded product using standard autoclave molding. However, in the present invention, it is possible to perform molding at a lower pressure of 6 to 8 kg/cm ² and autoclave molding is possible.

Since the molding material of the present invention can be used in autoclave molding, heat-resistant FRP molded products can be easily produced, and it is useful in that it can be widely used in the aviation and space industries. It is particularly suitable for interior materials in this field.

Examples will be explained below, but "parts" and "%" in the text are based on weight.

Example 1 Kelimide (manufactured by Mitsui Petrochemicals) as a compound
60 parts, Deitskrite UE8200 (manufactured by Dainippon Ink and Chemicals Co., Ltd.) 20 parts, triallyl isocyanurate (manufactured by Nippon Kasei Co., Ltd.) 10 parts, styrene monomer (1st class reagent) 10 parts, dimethylformamide (1st class reagent)
Mix 30 parts of acetone and 50 parts of acetone (first class reagent) to make a uniform solution.

60 parts g of Torayca Cloth 614Z (manufactured by Toray Industries, Inc.) was impregnated with 80 g of the mixture and heated at 100°C for 20 minutes, then at 150°C.
The material was dried for 5 minutes, turned into a B-stage, and made into a prepreg. This prepreg was flexible and had surface adhesiveness.

Laminated 15 plies of this prepreg and heated at 180℃ for 8
It was molded under pressure of Kg/cm ² to obtain an FRP board.

The bending strength of this FRP board is 67Kg/mm ² at room temperature and 250℃.
The strength retention rate was 49Kg/mm ² and 73%.

Also, the interlaminar shear strength is 4.5Kg/mm ² at room temperature and 250℃.
The strength retention rate was 3.4Kg/mm ² 2 and 76%.

The weight loss of this FRP board after 15 minutes at 350℃ is 0.5%.
It was hot.

Example 2 Bismaleimide (manufactured by Mitsui Toatsu) as a compound
50 copies, Epicron 850 (Dainippon Ink Chemical Co., Ltd.)
(manufactured by Yukuraku), 8.5 parts of diaminodiphenylsulfone (manufactured by Yukuraku), 10 parts of styrene monomer, and 80 parts of acetone were mixed and stirred uniformly.

120g of this compound was impregnated into 100g of glass cloth SLS-213B (manufactured by Asahi Fiberglass Co., Ltd.),
Drying was performed at 100°C for 10 minutes and at 120°C for 5 minutes to obtain a prepreg with flexibility and surface tackiness.

Laminated 15 sheets of the prepreg and heated at 180℃, 7kg/
An FRP board was obtained by press molding under pressure of mm ² .

The bending strength of this FRP board is 65Kg/mm ² at room temperature and 250℃.
The strength retention rate is 72 ^{%, and the interlaminar shear strength is 4.7Kg/mm 2 at} room temperature and 3.4Kg/mm ² at 250℃.
The strength retention rate was 72%.

Claims (1)

[Claims] 1. A reinforcing fiber is impregnated with a compound consisting of a polyimide resin, a reactive group-containing polymer oligomer selected from epoxy groups and vinyl groups, a reactive vinyl group-containing monomer, and a solvent, and B-staged to form a flexible prepreg. Heat-resistant molding material.