JP3073083B2 - Fibrous polyimide resin molding for reinforcing composite materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fibrous polyimide resin for reinforcing a composite material used to impart excellent toughness and crack resistance to a composite material obtained from a thermosetting matrix resin and a reinforcing fiber. About the body.

[0002]

2. Description of the Related Art Composite materials using high-strength and high-elasticity fibers such as carbon fibers as reinforcing fibers have the advantage of being superior in specific strength and specific elasticity.
It has been widely used for applications. Usually, epoxy resins used as matrix resins, thermosetting resins such as bismaleimide resins have various features, but have the drawback of poor toughness, so their use has been considerably restricted. Was. A method of adding a rubber component or a thermoplastic resin to improve the disadvantages of the thermosetting resin is generally used. However, in order to achieve a sufficient effect of improving toughness, it is necessary to add a large amount of the resin. As a result, the solvent property and the handling property are reduced.

There is also a proposal for a method called an interleaf for improving the toughness of a molded product by inserting a film of an adhesive or a thermoplastic resin between laminations of a prepreg in which a thermosetting resin is impregnated into a reinforcing fiber. Has been done,
It has not been put to practical use because the fiber content cannot be increased and workability is poor.

As an alternative method, for example, a method has been proposed in which fine particles of a thermoplastic resin are localized on the surface of a prepreg to provide an effect similar to that of an interleaf (Japanese Patent Laid-Open No. 1-110537). In this case, even in this case, not only is it inevitable that the tack of the prepreg is greatly reduced, but also problems such as complication of the process and complication of quality control occur.

[0005] Further, the resin-based composite material has a problem that cracks occur due to thermal stress during molding or thermal cycle based on the difference in thermal expansion coefficient between the resin and the reinforcing fiber (carbon fiber). For these materials, attempts have been made to increase the elongation of the resin. However, satisfactory results have not been obtained as higher reinforced fiber structures such as current three-dimensional fabrics are obtained.

On the other hand, the present inventors use a specific fibrous thermoplastic resin molded article in combination with a composite material composed of reinforcing fibers, and thereby 1) easily dispose an appropriate amount on the surface and inside of the prepreg. be able to.

2) Tack level control of the prepreg is easy.

3) There is no need to handle high-viscosity materials, and the conventional prepreg manufacturing process can be used as it is.

4) The crack resistance of the molded product is improved.

It has been found that various effective features can be obtained.

An object of the present invention is to impart excellent toughness and crack resistance without impairing the excellent thermal and mechanical properties of a composite material obtained from a thermosetting matrix resin and reinforcing fibers. It is.

[0012]

The gist of the present invention is to provide 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride as a main component of an aromatic dianhydride and 5' as a main component of a diamine. (6) Polyimide resin produced from -amino-1- (4'-aminophenyl) -1,3,3-trimethylindane is dissolved in a solvent, and this solution is extruded into a fibrous form, and the solvent is evaporated and dried. This is a fibrous polyimide resin molded product for reinforcing a composite material obtained by the above method.

The polyimide resin used in the present invention comprises 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride as a main component of an aromatic dianhydride and 5 (6) -amino acid as a main component of a diamine. It is produced by a known condensation reaction using -1- (4'-aminophenyl) -1,3,3-trimethylindane.

The reaction can be carried out in the molten state at a temperature above the melting point of at least one of the components or in a suitable solvent. By carefully adjusting the molar amounts of the aromatic dianhydride and the diamine, it is possible to adjust the molecular weight of the resulting polyimide resin in a fairly wide range. By using pyridine or the like as a catalyst, the formation of a polyimide resin can be promoted.

The aromatic dianhydride used is 3,3 ',
4,4'-benzophenonetetracarboxylic dianhydride as a main component, that is, 3,3 ',
It contains 4,4′-benzophenonetetracarboxylic dianhydride in an amount of 90 mol% or more, and other aromatic dianhydrides include, for example, pyromellitic dianhydride 3,
3'-bisphthalyl ether dianhydride and the like can be mentioned.

As the diamine, 5 (6) -amino-1
-(4'-aminophenyl) -1,3,3-trimethylindane as a main component, that is, 5
(6) -amino-1- (4'-aminophenyl) -1,
It contains 3,3-trimethylindane in an amount of 90 mol% or more.
Examples thereof include 6-hexanediamine, 2,2,4-trimethylhexane-1,6-diamine-1,6-bis [4-aminophenyl] hexane, and 4,4′-methylenedianiline.

3,3 ', 4,4'- in aromatic dianhydride
When the amount of 5 (6) -amino-1- (4'-aminophenyl) -1,3,3-trimethylindane in benzophenonetetracarboxylic dianhydride and diamine is less than the above molar number, dissolution in a solvent described below. This is not preferred because the properties may decrease.

The polyimide resin used in the present invention has a repeating unit having the following main structure.

[0019]

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The obtained polyimide resin is in a solid state and in a powder state. As the average molecular weight of the polyimide resin, any of the number average molecular weight, mass average molecular weight, and Z average molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC) is 10,000 or more, more preferably 20,000 or more. If the molecular weight is lower than this, problems such as yarn breakage occur during spinning, and even if the yarn is formed, it is not preferable because it cannot withstand subsequent use in terms of strength.

As the solvent to be used, a solvent capable of uniformly dissolving the polyimide resin and capable of producing a solution having a viscosity of 10 ² to 10 ⁵ poise (25 ° C.) measured by a B-type rotational viscometer is used. For example, dichloromethane, dichloroethane, chloroform, tetrachloroethane, tetrahydrofuran, dioxane, acetophenone, cyclohexanone, m-cresol, γ-butyrolactone, dimethylformamide, dimethylacetamide, N
-Methylpyrrolidone, a mixture thereof, a mixture of these solvents with another solvent, and the like. Preferably, dichloromethane, dichloroethane, chloroform, tetrachloroethane and the like are used. Further, a solvent obtained by mixing methanol with dichloromethane is preferable from the viewpoint of easy evaporation of the solvent, easy adjustment of the solution viscosity, and little change in the solution viscosity. The mixing ratio is particularly preferably dichloromethane / methanol = 99-80 / 1-20 weight ratio.
As a method for dissolving a polyimide resin in a solvent,
It can be performed by a known method such as dark mixing. In order to suppress the rise in solution temperature due to the generation of heat of dissolution, it is preferable to carry out the reaction while cooling the vessel, and attention should be paid to the increase in viscosity due to evaporation of the solvent.

The viscosity of the solution at room temperature (25 ° C.) as measured by a B-type rotational viscosity measurement should be in the order of 10 ² to 10 ⁵ poise, preferably 10 ³ poise. Depending on the molecular weight of the polyimide resin used, in a mixed solvent of dichloromethane / methanol = 99 to 80/1 to 20% by weight, the solution concentration of the polyimide resin should be 15 to 30% by weight for the stability of spinning. Is most preferable as a (spinning) solution.

The thus prepared solution is extruded into a fibrous form, and the solvent is evaporated and dried to obtain a fibrous polyimide resin molded article for reinforcing a composite material of the present invention. -A drying furnace whose temperature is controlled to be higher than the boiling point of the solvent, after being sent into a cylinder whose temperature is controlled by a filter, filtered by a filter to remove foreign matter, and then continuously extruded from a spinning nozzle into an atmosphere whose temperature is controlled. It is obtained by passing through the inside, evaporating the solvent, drying, and winding at a constant speed by a roller.
An appropriate oil agent may be applied to prevent troubles during winding and to prevent static electricity, but it is preferable that no oil agent be adhered in order to avoid adverse effects in later compounding. Also, the interface (confounding) processing is a preferable method for improving the handling. The form can be changed by a spinning nozzle or the like such as a monofilament or a bundle thereof. The cross-sectional shape of the fibrous polyimide resin molded product for a composite material thus obtained is 3
It has a non-circular and non-elliptical cross-sectional shape whose main shape is an amber shape having one or more branches. For example, it is an irregular cross-sectional shape having a main shape as shown in FIGS.

Since the cross-sectional shape is so high, the fibrous polyimide resin molding for reinforcing the composite material of the present invention is uniformly dispersed and mixed in a bundle of reinforcing fibers, for example, carbon fibers, and then the composite is formed by injecting and impregnating a second resin. The fibrous polyimide resin molded product for material reinforcement is prevented from becoming rigid with the movement of the second resin, and the dispersibility becomes very good. Also, due to the irregular cross-section, a space through which the second resin can penetrate is sufficient, and the polyimide resin molded article for reinforcing a composite material and the second resin are well mixed.

Further, since it has a large specific surface area, it has characteristics such that it is easily compatible with the matrix resin, has improved solubility, and is hardly penetrated when placed on the prepreg surface. Further, it is preferable to be solid, but even if it is hollow or porous, it can be used without any problem when molding conditions and subsequent selection of a matrix resin do not cause inconvenience such as molding failure due to selection of a matrix resin. it can.

The fiber diameter may be set according to the spinning nozzle diameter and the manufacturing conditions according to the application. In addition, a stretching treatment is also effective.

[0027]

By using the fibrous polyimide resin molded article for reinforcing a composite material of the present invention, excellent toughness and excellent toughness can be obtained without impairing the excellent thermal and mechanical properties of the thermosetting matrix resin. Crack resistance can be imparted. In particular, it is suitably used as an aircraft structural material.

[0028]

The present invention will be described in more detail with reference to the following examples.

Examples 1 to 3, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride and 5 (6) -amino-1- (4'-aminophenyl) -1,3,3-trimethyl A yellow powdery polyimide resin was obtained from Indan based on US Pat. No. 3,856,752.

The molecular weight of the obtained polyimide resin was measured by gel permeation chromatography (GPC). As a result, the number average molecular weight was 29000 and the mass average molecular weight was 6500.
0, and the Z average molecular weight was 110000. The obtained polyimide resin was mixed with a dichloromethane / methanol (91/9 weight ratio) mixed solvent at a concentration of 23 wt% of the polyimide resin, and the mixture was thoroughly stirred and dissolved at room temperature to prepare a uniform solution.

When the viscosity of this solution was measured by a B-type rotational viscometer, it was 1250 poise. This solution was easily filtered through a non-woven fabric filter, and then heated to about 60 ° C.
The mixture was discharged from a φ × 26 Hole spinning nozzle at a rate of 9.34 cc / min, the solvent was evaporated and dried in an atmosphere at 40 ° C. to 90 ° C., and the film was taken up at 250 m / min.
Thus, a fibrous polyimide resin molded product for reinforcing a composite material was obtained.

The obtained fibrous polyimide resin molding for reinforcing a composite material had 26 filaments, an average fineness of 96.4 denier, a maximum tensile strength of 102 g / denier, a maximum tensile elongation of 106%, and a yield strength of 72 g / denier. It was denier.

As a result of observation of the cross section with an electron microscope, it was found that the main shape was an amber shape having three or more branches, and a cross-sectional shape other than an ellipse other than a circle was shown.

The following examination was carried out using the fibrous polyimide resin molding for reinforcing a composite material of the present invention. A unidirectional prepreg was produced from a high-strength medium-elastic carbon fiber (manufactured by Mitsubishi Rayon Co., Ltd., MR-50K, tensile strength 5600 MPa elastic modulus 300 GPa) and a resin composition shown in Table 1 by a hot melt method. The prepreg had a basis weight of 145 g / m ² resin content of 31% by weight.

The prepreg is coated with the fibrous polyimide resin molded product for reinforcing a composite material of the present invention on both surfaces of the prepreg in the same direction as CF by a filament winding method so that the fiber weight per side is 8 g / m ^2. The interval (1.
(4 mm interval) and lightly embedded in the prepreg.

From the prepreg, small pieces of a predetermined size are cut out (+ 45 ° / 0 ° / -45 ° / 90 °), laminated on _4S, and then subjected to autoclave molding to form a test piece for measuring the compressive strength after impact. Molded.

Using this test piece, SACMA (Suppli
ers of Advanced Composites Materials Association) R
270 according to ecommended Method SRM2-88
The compressive strength after the lb-in impact was measured, and the results shown in Table 1 were obtained.

[0038]

[Table 1]

Comparative Examples 1 to 3 The resin content of the prepreg was adjusted to 36% by weight.
Unidirectional prepregs were produced in the same manner as in Examples 1 to 3. The evaluation was performed without adhering the polyimide fiber molded article for reinforcing a composite material of the present invention. Table 1 shows the results.

As is apparent from the above results, the fiber-reinforced composite molded article obtained by using the fibrous polyimide molded article for reinforcing a composite material of the present invention has a higher compressive strength after impact than the comparative example and has excellent resistance to impact. It turns out that it shows an impact property.

Example 4 The fibrous polyimide molding for reinforcing a composite material obtained in Example 1 was converted to a high-strength medium-elastic carbon fiber (Mitsubishi Rayon Co., Ltd .;
R-50K, tensile strength 5600MPa, elastic modulus 300G
Pa), and the filaments were loosened and uniformly dispersed in a bundle of carbon fibers and wound up. The mixing ratio was polyimide / carbon fiber = 5 bundle / 1 bundle (polyimide / carbon fiber = 9.6 / 100 weight ratio). Further, a prepreg was produced from the mixed fiber thus obtained and the resin composition of Example 1 (resin film weight: 60 g / m ² ) by a hot melt method.

When the cross section of the prepreg was observed with a microscope after impregnation with the resin, the fibrous polyimide resin molded product for reinforcing the composite material showed excellent dispersibility.

Further, a fibrous polyimide resin molded product for reinforcing a composite material was wound at an equal interval by a filament winding method so as to be 5 g / m ² per side to obtain a prepreg. A small piece having a predetermined size was cut out from the obtained prepreg, and a test piece for measuring compressive strength after impact was formed and evaluated in the same manner as in Example 1. Compressive strength after impact of 265 MPa was obtained.

Further, for the thermal cycle test, (+
45 / -45 / 0/90) _2SLaminated and molded
Was. The test piece was cooled to -52 ° C (10 minutes) → 132 ° C (10 minutes).
1 minute 40 minutes, a total of 10 cycles of thermal shock
Was. After that, the cross section is polished and cracks occur with an optical microscope
Was evaluated. No cracks observed
Was.

Comparative Example 4 A test piece for a thermal cycle was prepared from the prepreg of Comparative Example 1 and evaluated in the same manner as in Example 4. After the thermal shock, cracks were observed.

[Brief description of the drawings]

FIG. 1 is a typical cross-sectional shape of a fibrous polyimide resin molding for reinforcing a composite material of the present invention. FIG. 2 is a typical cross-sectional shape of a fibrous polyimide resin molding for reinforcing a composite material according to the present invention. FIG. 3 is a typical cross-sectional shape of a fibrous polyimide resin molding for reinforcing a composite material of the present invention. FIG. 4 is a typical cross-sectional shape of a fibrous polyimide resin molded product for reinforcing a composite material of the present invention. FIG. 5 is a typical cross-sectional shape of a fibrous polyimide resin molded product for reinforcing a composite material according to the present invention.

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ Identification code FI B29K 105: 08 (72) Inventor Masayuki Fukumoto 4-160 Sunadabashi, Higashi-ku, Nagoya-shi, Aichi Japan Mitsubishi Rayon Co., Ltd. Government Yoko Nakajima (58) Field surveyed (Int. Cl. ⁷ , DB name) D01F 6/74 C08J 5/04

Claims (4)

(57) [Claims] 1. The method according to claim 1, wherein the main component of the aromatic dianhydride is 3,
5 (6) -amino-1 as a main component of 3 ', 4,4'-benzophenonetetracarboxylic dianhydride and diamine
-Reinforcement of a composite material obtained by dissolving a polyimide resin formed from (4'-aminophenyl) -1,3,3-trimethylindane in a solvent, extruding this solution into a fiber form, evaporating the solvent and drying the solvent. Fibrous polyimide resin molded article. 2. The polyimide resin having an average molecular weight of 100
2. The fibrous polyimide resin molded article for reinforcing a composite material according to claim 1, wherein the number is 00 or more. 3. A mixed solvent of dichloromethane and methanol (dichloromethane / methanol = 99-80 / 1).
-20% by weight) and the polyimide resin concentration is 15-3.
The fibrous polyimide resin molding for reinforcing a composite material according to claim 1, wherein a solution of 0% by weight is used. 4. The composite material according to claim 1, wherein the cross-sectional shape is a modified cross-sectional shape other than a circle and an elliptical shape, the main shape being an amber shape having three or more branches. Fibrous polyimide resin molding for reinforcement.