JPH0647496B2 - Method for producing carbon fiber reinforced carbon composite material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a carbon fiber-reinforced carbon composite material having excellent strength, friction and sliding characteristics.

[Prior art]

Generally, carbon fiber reinforced carbon composite materials (hereinafter "c / c composite materials"
Say. Is PAN-based, pitch-based or rayon-based long-short carbon fiber impregnated with thermosetting resin such as phenol resin or furan resin, or thermoplastic resin such as pitch, or mixed and heat-molded to form an inert gas. It is obtained by firing at 600 to 1000 ° C. in a non-oxidizing atmosphere. A method for producing a c / c composite material using short fibers is, for example, for producing a porous carbon electrode as disclosed in JP-A-54-41295 or JP-A-57-129814. After mixing the solvent and carbon fiber with a mixer, matte with a screen,
A method of applying pressure is known. Further, JP-A-58-30
As seen in Japanese Patent No. 537, a method of mixing a solvent and carbon fibers having different lengths by ultrasonic vibration in a molding die has been attempted in order to mix carbon fibers having different lengths.

(Problems to be solved by the invention) However, since the c / c composite material using these short fibers is porous, or because the carbon fibers are in a bundle shape or a lump shape, pores are locally formed. However, there is a problem in that the carbon fibers have uneven distribution, and the carbon fibers are not uniform in strength, and uniform properties cannot be obtained when used as a friction material or a sliding member.

(Means for Solving the Problems) Then, the inventors of the present invention diligently studied a method for producing a c / c composite material using short fibers, and found that short fibers of carbon fibers were
The single fibers constituting the carbon fibers are uniformly dispersed by beating in a solvent to obtain a carbon fiber aggregate in which the single fibers are randomly oriented by an operation such as papermaking. We have found that the above problems can be solved by using a / c composite material, and have completed the present invention.

That is, an object of the present invention is to provide a c / c composite material in which short fibers of carbon fibers are uniformly dispersed, has excellent sliding properties, and has sufficient strength, and the object is to provide a carbon fiber aggregate. In a method for producing a carbon fiber-reinforced carbon composite material by mixing and molding a resin and a pitch with a resin or a pitch, the carbon fiber aggregate is obtained by beating a carbon fiber aggregate composed of a plurality of single fibers in a solvent. Of the carbon fiber-reinforced carbon composite material, wherein the single fibers are uniformly dispersed in a solvent, and the single fibers obtained by removing the solvent as needed are carbon fiber aggregates oriented in random directions. It is easily achieved by the manufacturing method.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail. As the carbon fiber used in the present invention, any known carbon fiber such as pitch-based, PAN-based or rayon-based carbon fiber can be used. Further, if necessary, inorganic fibers such as SiC, Al ₂ O ₃ and carbon black, and inorganic substances may be mixed and added.

The form of carbon fiber usually used is a form of a plurality of single fibers such as tow, strand, roving and yarn, and it is preferable to use short fibers obtained by cutting these. And these short fibers are formed from a bundle of a plurality of single fibers, and in the present invention, these short fibers, usually 0.3 to 100 mm, preferably 1
When a short fiber of about 50 mm is used to form a c / c composite material, it is possible to disperse the short fiber into each single fiber constituting the short fiber and to fill the matrix material between them to improve the characteristics. Is important for.

For this reason, in the present invention, the bundle of short fibers is beaten in a solvent to be fibrillated into single fibers, and the filaments are uniformly dispersed in the solvent.

Here, the beating process can be performed by using, for example, a beader or the like which is usually used for the beating process of pulp or the like.

That is, a mixture of a solvent and a short-fiber carbon fiber is supplied to a beating treatment apparatus consisting of a tank with a partition and a rotating roll with a blade and a fixed receiving blade, and between the rotating roll and the receiving blade. By passing it, a vortex is generated between the adjacent blades of the rotating roll, and the short fibrous carbon fibers are fibrillated as single fibers. Further, in order not to damage the carbon fiber, it is preferable that the distance between the rotary roll and the receiving blade is 100 μm or more, and the blade of the rotary roll and the tip of the receiving blade are covered with a rubber material or the like.

The circumferential speed of the rotating roll is 600 to obtain smooth rotation.
It is preferably m / min or less, and the treatment time varies depending on the treatment amount and the size of the apparatus, but it is necessary that the mixture of the solvent and the short fibers passes once or more between the rotary roll and the blade.

Generally, the blade attached to the rotating roll used in the beating process has a blade thickness of 1 to 15 mm and a blade number of about 60 to 114,
The receiving blade does not necessarily have to have a gear shape, but when using a gear shape, the blade thickness is 3 to 12 mm and the number of blades is 15 to
About 20 sheets are used.

As the mixture of the solvent and the short fibrous carbon fiber, water, an organic solvent such as acetone or various alcohols, and a phenol resin, a furan resin, or a matrix resin such as pitches or these resins and acetone, various alcohols, anthracene oil A mixture of such an organic solvent as described above and a mixture of about 0.01 to 10 wt% of short fiber carbon fibers is used, and the short fibers are beaten in the beating apparatus to disperse them into single fibers. At this time, a thickener such as sodium fibrin glycolate, polyvinyl alcohol, or hydroxycellulose may be added to the solvent.

The slurry in which the single fibers that have been beaten in this manner are dispersed one by one is supplied to, for example, a mold having a screen at the bottom, and the solvent is removed from the bottom if necessary, and then dried. A carbon fiber aggregate in which single fibers are randomly oriented is obtained. Here, the state in which the single fibers are randomly oriented means that the adjacent single fibers of the single fibers constituting the carbon fiber aggregate are oriented in substantially different directions, and have a regular orientation state as a whole. It is a thing.

The bulk density of the carbon fiber aggregate thus obtained is usually 0.00
1 to 0.1 g / cm ₃ is obtained.

Further, at this time, the resin impregnation step as a later step may be omitted by previously mixing the molding resin with the solvent, or the mold with the screen may be shared with the molding mold.

The carbon fiber aggregate thus obtained is mixed with or impregnated with a matrix such as a petroleum-based or coal-based pitch, and then dried. At this time, the matrix is used by dissolving it in a solvent such as alcohol, acetone or anthracene oil and adjusting the viscosity to an appropriate value.

Then, in the molded body from which this dried product is obtained, V _f = 5
It is filled in a metal mold so that the content becomes about 60%, preferably about 10 to 45%, and pressure molding is performed at a temperature of 100 to 500 ° C. Then, 1-2 in an inert gas atmosphere such as N ₂ gas
The temperature is raised to 800 to 1000 ° C. at a heating rate of 00 ° C./hr and fired to obtain a c / c composite material.

The calcined c / c composite material may be appropriately densified by, for example, the following two methods to further improve the strength.

1) Densification treatment with resin or pitch Put the above c / c composite material in a tank heated to a predetermined temperature, evacuate the inside of the tank, supply resin or molten pitch, and fire it Impregnate the voids with a matrix. After that, it is fired again at a temperature of 800 to 1000 ° C. to carbonize the impregnated pitch.

The densification treatment of the c / c composite material is performed by repeating the above steps.

2) Densification treatment by CVD The above c / c composite material placed in the reaction tube is heated by an induction heating coil or the like, and hydrocarbon vapors are supplied into the reaction tube together with H ₂ gas and Ar gas to generate heat. Impregnate voids with decomposed carbon to densify.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples unless it exceeds the gist of the present invention.

[Example 1] 10 parts by weight of Pitch-based carbon fiber in the form of a chopped strand having a length of 10 mm and a number of filaments of 4,000 was supplied as a solvent together with 1000 parts by weight of water to an oval open tank, and a large number of teeth were provided. Using a device equipped with a rotating roll and a blade directly below the rotating roll with a rubber film interposed between them at a distance of 2 mm, the rotating roll was rotated at a peripheral speed of 480 m / min for 30 seconds for beating treatment to dissolve the chow strand. After fiberization, an aqueous solution containing uniformly dispersed carbon fibers was supplied to a mold having a screen at the bottom, water was discharged from the bottom, and water was removed by drying to remove monofilaments with a bulk density of 0.03 g / cm _3. A carbon fiber aggregate oriented in a random direction was obtained.

The phenolic resin 17 is added to 31 parts by weight of this carbon fiber aggregate.
After impregnating with a resin solution in which 1 part by weight and 52 parts by weight of ethanol were mixed, it was dried overnight. Fill this into the mold, 25
Pressing was performed at a temperature of 0 ° C. to obtain a molded product having a fiber volume content (V _f ) of 40%.

This molded body was fired at 1000 ° C. in a heating furnace to obtain a c / c composite material.

Next, after impregnating the obtained c / c composite material with a liquid pitch at a temperature of about 200 ° C., it is fired at 1000 ° C. in a heating furnace, and the same impregnation-firing operation is repeated 4 times to obtain a bending strength of 12 kg / mm ²
The c / c composite material of the present invention was obtained.

This c / c composite material has an outer diameter of 80 mm, an inner diameter of 60 mm and a thickness of 10 mm.
The disc-shaped c / c composite material thus obtained was rubbed with each other to perform a wet constant-speed friction test. The results are shown in Table 1.

[Comparative Example 1] The same procedure as in Example 1 was performed except that the beating process was not performed.
A c / c composite material was obtained. The bending strength of the obtained c / c composite is 5 kg.
It was / mm ² .

The obtained c / c composite material was subjected to a wet constant speed friction test in the same manner as in Example 1. The results are shown in Table 1.

[Example 2] 10 parts by weight of Pitch-based carbon fiber in the form of a chopped strand having a length of 10 mm and 4000 filaments, and 50 parts by weight of a phenol-based resin and 950 ethanol as a solvent.
Using a mixture of parts by weight, the same treatment as in Example 1 was performed, and then the solvent was removed using a mold having a screen at the bottom to remove a small amount of phenol resin and ethanol on the carbon fiber surface. A carbon fiber aggregate having fibers oriented in random directions was obtained.

This carbon fiber aggregate was dried for a day and then treated under the same conditions as in Example 1 to obtain a c / c composite material having a bending strength of 10 kg / mm ² . Also, this c / c composite material showed good friction characteristics as in Example 1.

Claims (2)

[Claims] 1. A method for producing a carbon fiber reinforced carbon composite material by mixing and molding a carbon fiber aggregate and a resin or pitch, and producing a carbon fiber reinforced carbon composite material, wherein the carbon fiber aggregate comprises a plurality of single fibers. The single fiber obtained by beating the aggregate in a solvent to uniformly disperse the single fiber in the solvent and removing the solvent as needed is a carbon fiber aggregate oriented in random directions. And a method for producing a carbon fiber reinforced carbon composite material. 2. The method according to claim 1, wherein the carbon fiber aggregate consisting of a plurality of single fibers has a length of 0.3 to 100 mm.