JP3342925B2 - Composite material of vapor grown carbon fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long fiber composite material,
More specifically, the present invention relates to improvement of a long fiber composite material based on a vapor grown carbon fiber and a resin matrix.

[0002]

2. Description of the Related Art Conventionally, long fibers, for example, plastics,
Long fiber composite materials dispersed as a filler in a matrix of metal, rubber, cement, or the like have been used or developed in various fields. Long fiber composite materials are known as FRP, FRM, FRR, FRC, etc.
It is also known that their mechanical strength, heat resistance, wear resistance and the like are extremely excellent.

[0003] The applicant of the present invention has previously filed a patent application for fine carbon fibers produced by the gas phase method as Japanese Patent Application Laid-Open No. 61-70014. Moreover, since the fine carbon fibers created according to JP-A-61-70014 have a very small diameter of 0.01 to 1.0 μm, a composite material using this as a filler is used as a continuous fiber having a large diameter. On the other hand, it was found that a composite material having a high strength could be obtained by forming a composite as a base material, and a patent application was filed as Japanese Patent Publication No. Hei 4-30972.

[0004]

It is said that the newly created fine carbon fiber obtained in Japanese Patent Publication No. Hei 4-30972, which was previously developed by the present applicant, preferably has an aspect ratio of 2-200. Since these fibers include extremely long fibers, when these fibers are mixed and used in a resin of a long fiber composite material as in the present invention, there is a problem that the mechanical properties of the composite material are adversely affected.

[0005] The inventors of the present invention have conducted intensive studies, and as a result, have found that a small amount of vapor-grown carbon fiber having a diameter of 0.01 to 3.0 µm is pulverized to a length that can be uniformly mixed. It has been found that the phase-grown carbon fiber can exert an excellent effect as a composite material. Furthermore, if the composite material using the vapor-grown carbon fiber as a filler is composited with a long fiber as a base material, since the base material is already reinforced, the 90 ° bending strength, impact strength, interlayer The shear strength was also found to be significantly improved.

Accordingly, it is an object of the present invention to provide a long fiber composite material having extremely excellent mechanical strength such as 90 ° bending strength, impact strength, and interlaminar shear strength.

[0007]

In order to achieve the above object, the long fiber reinforced composite material of the present invention has a diameter of 0.01 to 0.01 mm.
A mother of a resin composite material obtained by filling a resin matrix with 1 to 10% by weight of a vapor-grown carbon fiber having a thickness of 3.0 μm, an average aspect ratio of 2 to 100 and substantially not having an aspect ratio of 200 or more. And a long fiber.

In this case, carbon fibers can be suitably used as the long fibers.

[0009]

In the composite material of vapor-grown carbon fiber of the present invention, the composite amount of vapor-grown carbon fiber is 1 to 10% by weight, preferably 1 to 7% by weight, and most preferably 3 to 5% by weight. . When the composite amount is 10% by weight or more, the bending strength in the 90 ° direction decreases, and when it is 1% or less, the effect of the vapor-grown carbon fiber composite does not appear.

The crystal structure of the vapor grown carbon fiber is different depending on the heat treatment temperature, and a 002 plane spacing of 0.335 nm to 0.355 nm can be obtained, and any of them can be used. From the viewpoint of adhesiveness to the resin, those having a surface spacing of 0.345 nm to 0.355 nm are preferable.

In the present invention, the long fibers include carbon,
Any material such as glass, alumina, silicon carbide, and boron may be used, and among them, carbon fiber is particularly preferable. As the carbon fiber, either a PAN type or a pitch type may be used. The fiber diameter, strength, elastic modulus, and elongation are not limited.

In the present invention, the production of vapor-grown carbon fiber used as a filler for a composite material is described in
This can be performed in the same manner as in JP-A-70014.

[0013] When the aspect ratio is large, the fibers tend to agglomerate with each other, forming many flocs and making it difficult to uniformly disperse the fibers. Therefore, it is known that the vapor grown carbon fiber should be cut in advance before mixing the vapor grown carbon fiber with the resin. However, in the composite material of long fiber, resin, and vapor grown carbon fiber,
If the vapor grown carbon fiber is used as it is, the 0 ° direction tensile strength, 90 ° direction tensile strength and 0 ° bending strength can be improved, but the 90 ° direction bending strength, interlaminar shear strength, compression strength, impact strength, etc. It is surprising that they are not improved but are improved by pulverizing the vapor-grown carbon fibers in advance and adding a small amount thereof, and the reason is unknown.

These properties are important items for structural materials, and it is expected that the present invention will have remarkable applications in such applications of CFRP.

Considering the difficulty of dispersion, the vapor grown carbon fiber has a diameter of 0.01 to 3 μm, an average aspect ratio of 2 to 100, preferably 0.1 to 2 μm, and an average aspect ratio of 3 to 100 μm. 50, more preferably 0.1 diameter
It is preferable that the average aspect ratio is 5 to 20 .mu.m. Although the aspect ratio shown here is an average value, it is not preferable that even a small amount of vapor grown carbon fiber having an aspect ratio exceeding 200 is contained.

In order to obtain a vapor grown carbon fiber having a small variation in the aspect ratio, it is necessary to pulverize the newly produced fine carbon fiber obtained by the method disclosed in Japanese Patent Publication No. 62-49363 by a suitable pulverizing means. preferable. Although there is no limitation on the pulverizing means, there may be used an Aquamizer (registered trademark), a ball mill, and a jet mill, which are stirred together with small spheres.
A high impact treatment is preferred, in which the vapor-grown carbon fiber alone is loaded into a hybridizer (registered trademark) that vigorously stirs in an air stream to collide and crush the fibers with the stirring blades and walls, and between the fibers, thereby treating the fibers. The length of the fiber can be adjusted without breaking the fiber diameter direction by the residence time of the vapor-grown carbon fiber in the hybridizer and the number of revolutions of the stirring blade, so that the hybridizer is particularly preferable. In addition,
The hybridizer has a peripheral speed of 120 to 60 m / s,
Preferably, it is in the range of 90 to 70 m / s.

In the case where pulverization is not carried out, even if the average aspect ratio is reduced under fiber production conditions, the fibers contain a considerably large aspect ratio, and the effects of the present invention cannot be obtained.

In the present invention, as a base material for filling the vapor grown carbon fiber, an epoxy resin can be particularly mentioned. The epoxy resin may be modified in various ways, or may be added with additives for modification (substances other than vapor-grown carbon fiber: rubber-like particles, thermoplastic resin particles, carbon black, etc.). In addition to the epoxy resin, it is of course possible to use a thermosetting resin similar to the epoxy resin such as a phenol resin or a polyimide resin, or a thermoplastic resin such as Nylon, PPS, or PEEK.

According to the present invention, a 90 ° bending strength, an interlaminar shear strength, an impact strength, and the like are improved by mixing a vapor-grown carbon fiber in a matrix in advance in a composite material using continuous fibers. It is possible. Further, it is possible to reduce the heat conduction to half of the conventional one. In addition, the 90 ° bending strength described herein is generally a bending strength of a fiber axis in a 90 ° direction with respect to the orientation direction of long fibers. On the other hand, the direction in which the long fibers are oriented is called a 0 ° direction.

Such an effect is particularly remarkable when the prepreg is not a textile prepreg but a unidirectional prepreg.

[0021]

Next, embodiments of the present invention will be described.

Production of vapor-grown carbon fiber Benzene and ferrocene are heated and gasified in separate vessels, respectively, and gases are led out of a hydrogen cylinder and a nitrogen cylinder, respectively, to obtain a hydrogen: nitrogen: benzene: ferrocene ratio. 82.7: 7.5: 8.6: 1.2, and the total flow rate was 665 ml / min (0 ° C., 1 atm conversion),
This mixed gas was heated to a soaking part 3 having an inner diameter of 52 mm and a temperature of 1070 ° C.
It was continuously passed through a 00 mm cylindrical reaction tube. As a result, a carbon fiber having a diameter of 0.8 μm and an average length of 180 μm was obtained.

The above-obtained vapor-grown carbon fiber is pulverized with a hybridizer at 8000 rpm for 2 minutes to provide the present invention having an average diameter of 0.8 μm and an average length of 12 μm (aspect ratio 15). A vapor-grown carbon fiber was obtained.

In addition, vapor-grown carbon fibers having different average aspect ratios were prepared by changing the number of revolutions of the hybridizer. Table 1 shows the relationship between the hybridizer conditions and the average aspect ratio at that time.

Production of Composite Material Example 1 Epoxy resin containing a reaction equivalent of dicyandiamide as a curing agent (equivalent to Epicoat 828 manufactured by Shell Chemical Co., Ltd.)
In addition, the diameter 0.8 μm obtained above and the average length 12 μm
m of vapor-grown carbon fiber was added at 5% by weight, and kneaded while defoaming in vacuum. The resin containing the vapor-grown carbon fiber is 7 μm in diameter, 350 kg / mm ² in strength, and the elastic modulus is 24 ton.
/ Mm ² of PAN-based carbon fiber was applied to a sheet arranged in one direction to prepare a unidirectional prepreg. This prepreg is laminated in one direction, and in an autoclave, 130 ° C.
And molded at 3kg / cm ^{2, 2} hours, thickness 3.0mm
Was made. Table 2 shows the results of a 90 ° bending strength test performed on the flat plate. Table 3 shows the results of measuring the impact strength and interlayer shear force of the flat plate.

COMPARATIVE EXAMPLE 1 A molded article was prepared in exactly the same manner as described above using the untreated vapor-grown carbon fibers of the hybridizer shown in Table 1.
The bending strength in the 90 ° direction measured in the same manner as described above is as shown in Table 2.

Example 2 Molding was performed in exactly the same manner as described above, using a vapor grown carbon fiber having a diameter of 0.8 μm, a length of 15 μm, and an average aspect ratio of 19, which was hybridized under the conditions of 6000 rpm and 2 minutes shown in Table 1. A body was prepared and measured as above 9
The bending strength in the 0 ° direction was 10.1 kg / mm ² .

Example 3 Molding was performed in exactly the same manner as described above, using vapor-grown carbon fibers having a diameter of 0.8 μm, a length of 20 μm, and an average aspect ratio of 25, which were hybridized under the conditions of 5000 rpm and 2 min shown in Table 1. A body was prepared and measured as above 9
The bending strength in the 0 ° direction was 10.0 kg / mm ² .

Example 4 Epoxy resin containing a reaction equivalent of dicyandiamide as a curing agent (equivalent to Epicoat 828 manufactured by Shell Chemical Co., Ltd.)
In addition, the diameter 0.8 μm obtained above and the average length 12 μm
m of vapor grown carbon fiber was added by 3% by weight, and kneaded while vacuum degassing. The resin containing the vapor-grown carbon fiber is 7 μm in diameter, 350 kg / mm ² in strength, and the elastic modulus is 24 ton.
/ Mm ² of PAN-based carbon fiber to prepare a unidirectional prepreg. The prepregs were laminated in one direction, and molded in an autoclave at 130 ° C., 3 kg / cm ² for 2 hours to prepare a flat plate having a thickness of 3.0 mm. Table 2 shows the results of a 90 ° bending strength test performed on this flat plate. Table 3 shows the results of measuring the impact strength and the interlayer shear force of the flat plate.

Comparative Example 2 From the carbon fiber prepreg containing no vapor-grown carbon fiber, a molded article was prepared in exactly the same manner as above, and the bending strength in the 90 ° direction measured in the same manner as above was obtained. And the results of measuring the impact strength and the interlaminar shear force are as shown in Table 3.

Comparative Example 3 Epoxy resin containing a reaction equivalent of dicyandiamide as a curing agent (equivalent to Epicoat 828 manufactured by Shell Chemical Co., Ltd.)
In addition, the diameter 0.8 μm obtained above and the average length 12 μm
m of vapor grown carbon fiber was added by 20% by weight, and kneaded while vacuum degassing. This vapor-grown carbon fiber-containing resin is 7 μm in diameter, 350 kg / mm ² in strength, and elasticity is 24 to.
It was applied to PAN-based carbon fiber of n / mm ² to prepare a unidirectional prepreg. The prepregs were laminated in one direction, and molded in an autoclave at 130 ° C., 3 kg / cm ² for 2 hours to prepare a flat plate having a thickness of 3.0 mm. The result of conducting a 90 ° bending strength test on this flat plate is as follows:
It is as shown in Table 2. Table 3 shows the results of measuring the impact strength and the interlayer shear force of the flat plate.

Example 5 A newly prepared fine carbon fiber having a diameter of 0.8 μm and a length of 130 μm was pulverized with a hybridizer under the conditions of 5000 rpm and 2 min to obtain a vapor-grown carbon fiber having an average aspect ratio of 25. Next, 95% by weight of a bismaleimide resin (F650, manufactured by HEXCEL, USA) mixed with a reactive diluent
And 5% by weight of the vapor grown carbon fiber prepared above were mixed to prepare a base resin. Example 1 using this base resin
A one-way prepreg was created as in. This prepreg was laminated, and the conditions were set at 177 ° C. and 6 kg / cm ^{2 for} 6 hours.
An r curing reaction was caused to obtain a composite material. 90 at that time
The bending strength in the ° direction was 12.6 kg / mm ² , and the interlaminar shear strength was 11.9 kg / mm ² . For comparison, a compact was prepared in the same manner as described above from a carbon fiber prepreg containing no vapor-grown carbon fiber, and the measurement was similarly performed. The bending strength in the 90 ° direction at that time is 11.6 kg.
/ Mm ² , and the interlayer shear strength was 10.5 kg / mm ² .

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments.
It will be appreciated that various design changes may be made within the spirit and scope of the invention, such as being adaptable to other matrix materials known in the art.

[0037]

According to the present invention, a base material of a resin composite material obtained by filling a vapor-grown carbon fiber containing no large aspect ratio fiber into a resin base material, and a long fiber is compounded with the base material. Accordingly, a long fiber reinforced composite material having improved properties such as 90 ° bending strength, interlayer shear strength, and impact strength can be obtained.

For a long-fiber reinforced composite material in which long fibers are arranged in one direction, the improvement in 90 ° bending strength is a surprising effect, and is expected for future applications.

Claims (3)

(57) [Claims] A vapor-grown carbon fiber having a diameter of 0.01 to 3.0 μm, an average aspect ratio of 2 to 100 and substantially no aspect ratio of 200 or more is contained in a resin matrix in an amount of 1 to 10%. A base material of a resin composite material filled by weight%,
A long fiber reinforced composite material comprising a long fiber. 2. The composite material according to claim 1, wherein the long fibers are carbon fibers. 3. The composite material according to claim 1, wherein the long fibers are arranged in one direction.