JPS62212262A - Manufacture of carbon fiber reinforced carbon material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing carbon fiber-reinforced carbon materials.

BACKGROUND ART A carbon fiber reinforced carbon material (hereinafter referred to as a C/C composite) is a composite material that uses carbon fiber as a reinforcing material and carbon as a matrix. Because C/C composites are reinforced with carbon fiber, they have superior mechanical properties at room and high temperatures compared to conventional carbon materials, and also have superior mechanical properties, thermal conductivity, electrical conductivity, and corrosion resistance. This makes it an essential material for spacecraft components such as rocket nozzles and aircraft brake discs. Currently, there are two main systems of manufacturing methods for C/C composites, which have a wide range of applications.

One is to simply mold carbon fiber tow, cloth, felt, etc. obtained by carbonizing polyacrylonitrile, rayon, or pitch-based fibers, and then put it in a furnace to create a
This is a method of heating to 500° C., introducing hydrocarbon gas thereto, causing decomposition and carbonization, and depositing carbon on the surface of the carbon fibers to form a C/C composite (hereinafter, this method will be referred to as the CVD method).

The CVD method has low productivity and takes a long time to obtain a predetermined density, and requires quite advanced technology to obtain a uniform carbon material with few pores (for example, carbon
vol, BP, 397-403, 1988)
.

The other type is prepreg, which is made by impregnating five-component fiber tow, cloth, felt, etc. (obtained by carbonizing polyacrylonitrile, rayon, or pitch-based fibers) with a thermosetting resin made of carbon material such as phenol resin. After laminating and heating under pressure to form a hardened molded body, carbonization treatment is performed in a non-oxidizing atmosphere, and if necessary, impregnation treatment and carbonization treatment are repeated to form a C/C composite. (referred to as the Char method).

The resin-char method has fewer restrictions than the CVD method and is industrially advantageous, but in order to obtain a predetermined density, it is necessary to repeat impregnation and carbonization several times. In addition, the carbonizable resin used for impregnation has a carbonization yield of about 55% at most.
Even if the number of times of carbonization is increased, the increase in bulk density follows the power law of the number of times of impregnation, and the impregnation efficiency becomes extremely poor.

Problems to be Solved by the Invention An object of the present invention is to reduce the number of times of impregnation and carbonization in the resin-char method, efficiently perform densification, and produce a C/C composite.

Means for Solving the Problems The method of the present invention involves impregnating pitch or thermosetting 46111ti and carbonizing a molded body made of a carbon material raw material reinforced with carbon fibers once after an initial carbonization treatment. After that, a graphitization treatment is performed, followed by an impregnation treatment and a carbonization treatment.

action Next, the content of the present invention will be explained in more detail.

The C/C composite which is the final product obtained by the present invention is hereinafter referred to as C/C composite (product), and the C/C composite which is an intermediate product in the middle of the manufacturing process is hereinafter referred to as C/C composite (product).
It is called C/C composite (intermediate).

The reinforcing carbon fiber used in the present invention may be polyacrylonitrile-based, rayon-based, or pitch-based, and may also be carbonaceous or graphite.)2
As for the form of the mis, either short fibers having a length of about 0.05 to 50 fibers or continuous fibers can be used. Further, the carbon fibers may be in the form of a sheet such as cloth, felt, or mat, and may be oriented in completely random directions in the matrix as they are or in a defibrated state. They may be arranged in any particular direction.

In addition, the carbon material raw material that becomes the matrix may be any of thermosetting resins such as phenol resin, furan resin, and polyimide resin, thermoplastic resins such as vinyl chloride resin, and pitches such as impregnated pitch and binder pitch. good.

After combining such carbon fibers or carbon fiber structures and a carbon material raw material to form a molding material, press molding or the like is performed to obtain a molded body, which is then carbonized and fired in a non-oxidizing atmosphere to form a C/C. Obtain composite (intermediate).

In the molding material, it is desirable that the carbon fiber or carbon fiber structure is contained in an amount of 20 to 80% by weight, preferably 40 to 80% by weight.

If the carbon fiber content is less than 20% by weight, the resulting C/C composite (product) will have too few reinforcing fibers, resulting in low strength. On the other hand, if it exceeds 90% by weight, the matrix content is too small, so the shear strength between the layers decreases, and the reinforcing effect of the carbon fibers is not fully exhibited.

As the molding method of the molded article in the present invention, known molding methods for fiber-reinforced plastics can be widely applied. For example, press molding method,
Filament winding method, hand layup method,
There are vacuum bag methods, etc.

The obtained molded body is heated at 800°C or higher, preferably at 1000°C or higher at 1500°C in a non-oxidizing atmosphere such as nitrogen or argon.
A C/C composite (intermediate) is obtained by carbonization firing at a temperature of 0.degree. C. or lower. In this case, if the temperature increase rate during carbonization is too fast, the resin will shrink due to thermal decomposition and gas generation will be intense, making it easy for large cracks to occur. Therefore, the heating rate is usually 1
After reaching a predetermined carbonization temperature, which is desirably 00° C./hr or less, preferably 20° C./hr or less, a holding time of 5 hr is usually sufficient for carbonization.

The C/C composite (intermediate) obtained in this way still has a fairly large porosity, and in order to obtain a high-density, high-strength C/C composite (product), this C/C composite (intermediate) The pores must be impregnated with pitch or a carbonizable thermosetting liquid resin, and then carbonized and fired again in a non-oxidizing atmosphere to make it dense.

In the impregnation process, the C/C composite (intermediate) is placed in a closed container, the pressure inside the container is reduced to several tens of mmHg or less, the gas remaining inside is expelled, and then the pitch or carbonizable material is placed in the container. A thermosetting liquid resin is poured into the container, and the pressure in the container is increased to 5 to 1000 kg'/crn' to impregnate the C/Cm7 body (middle) with the substance.

As the impregnating material, pitch is usually used, or liquid thermosetting resin such as phenol resin or furan resin is used.

Further, in this case, the above substance may be heated or diluted with a solvent in order to adjust the viscosity.

However, the pitch or resin used in this impregnation step has a carbonization yield of about 55%, and if impregnation and carbonization are simply repeated, the efficiency of densification will be extremely poor.

In the present invention, as a result of studying the impregnation and carbonization processes, by incorporating a graphitization process into the impregnation and carbonization processes,
It has been found that the impregnation efficiency is significantly improved, and more specifically, the subsequent impregnation efficiency is improved best when the graphitization treatment is performed after the first impregnation treatment and carbonization treatment.

That is, in the present invention, in order to densify the C/C composite, graphitization treatment is always performed after the first impregnation and carbonization process, and then impregnation treatment and carbonization treatment are performed, thereby improving efficiency. Good densification is achieved to obtain a high-density, high-strength C/C composite.

In the present invention, the graphitization treatment is carried out in a non-oxidizing atmosphere such as argon at a temperature of usually 1600 to 3000°C, preferably 2°C.
It is necessary to carry out the process at a temperature of 000 to 3000°C. The holding time after reaching a predetermined graphitization temperature is usually 1 to 10 hours.

Further, the graphitization treatment should be performed after the first impregnation and carbonization treatment, and if it is performed after two or more consecutive impregnation and carbonization treatments, the effect will be reduced. In some cases, if the C/C composite (intermediate) is graphitized after being impregnated and carbonized twice or more, the C/C composite (intermediate) will have fine racks and expand in volume, and even if it is impregnated and carbonized more than once, it will not have the same strength. Improvement may be hindered.

This is considered to be due to the fact that the C/C composite (intermediate) is composed of a ternary system of carbon fiber, matrix, and impregnated material, and the graphitizability of each component is different when graphitized. In other words, when three types of graphitizable substances are simultaneously graphitized, internal stress occurs in the C/C composite (intermediate) due to differences in volume shrinkage rate during graphitization, cracks occur, and volumetric expansion occurs. That's probably why.

In the case of the present invention, since graphitization is performed after the first impregnation and carbonization treatment, the ratio of the impregnated material is low;
Such volume expansion does not occur.

After the graphitization treatment, impregnation treatment and carbonization treatment are subsequently performed. This impregnation treatment can be performed in the same manner as the impregnation treatment of the above-mentioned C/C combo dift C). Further, the carbonization treatment can be performed in the same manner as the carbonization treatment of the molded body described above.

Furthermore, at the end of the manufacturing process of the C/C composite in the present invention, graphitization treatment may be further performed as necessary, thereby improving the heat resistance and oxidation resistance of the C/C composite (product) obtained. do.

Hereinafter, the present invention will be explained according to Examples.

Examples Example 1 A polyacrylonitrile carbon fiber bundle (12000 filaments) was coated with phenol resin (AV Light RM-21
It was impregnated with a 30% by weight methyl ethyl ketone solution of 0), dried, and cut into 301 pieces to obtain a prepreg.

This prepreg was laminated randomly in a mold, and the temperature was 150.
A molded body was obtained by press molding at a temperature of 50 kg/crn'. The carbon fiber content of the molded body obtained at this time was 65% by weight.

Next, this molded body was heated to 1100°C at a heating rate of 3°C/hr in a nitrogen atmosphere, and then gradually cooled to carbonize the matrix and obtain a C/C composite (intermediate). Ta.

Furthermore, Furan tree 1 is added to this C/C composite (middle).
'1l (AV;
After the temperature was raised to 0° C., it was immediately cooled slowly to completely carbonize the impregnated furan resin. Subsequently, this C/C composite (intermediate) was heated to 2000° C. in an argon atmosphere and maintained at 1 hr to graphitize it. This graphitized C
A furan resin was used for the C/C composite (intermediate) in the same manner as described above, and the impregnation and carbonization steps were repeated one more time to obtain a C/C composite (product).

Comparative Example 1 A molded body was produced under the same conditions as in Example 1, and this was carbonized to obtain a C/C composite (intermediate). Next, this C/C composite (intermediate) was produced under the same conditions as in Example 1. Impregnated with furan resin, hardened and carbonized. The above impregnation and carbonization steps are repeated one more time on this C/C composite (intermediate),
After densification, the temperature was raised to 2000°C in an argon atmosphere and maintained for 1 hour to graphitize the C/C composite (
product) was obtained.

Comparative Example 2 A molded body was produced under the same conditions as in Example 1, and this was carbonized to obtain a C/C composite (intermediate). Next, this C/C composite (intermediate) was produced under the same conditions as in Example 1. Impregnated with furan resin, hardened and carbonized. The above impregnation and carbonization steps were repeated two more times on this C/C composite (intermediate),
After densification, the temperature was raised to 2000°C in an argon atmosphere and maintained for 1 hour to graphitize the C/C composite (
product) was obtained.

The dimensions and weight of the obtained C/C composite (product) were measured, and the bulk density was determined. Each result is shown below.

Example 11.38 2 1 1.4
7 Comparative Example 11.38 2 1 1.
41 Comparative Example 21.38 3 1 1
．． 43 Example 2 Phenol resin (AV Light RM-21
It was impregnated with a 30% by weight methyl ethyl ketone solution of 0), dried, and cut into 5-axis layers to obtain a prepreg.

This prepreg was laminated randomly in a mold, and the temperature was 150.
℃ and a pressure of 50 kg/cm'' to obtain a molded body.The carbon fiber content of the molded body obtained at this time was 88% by weight.

Next, this molded body was heated to ttoo°C at a heating rate of 3°C/hr in a nitrogen atmosphere, and then immediately slowly cooled to carbonize the matrix and obtain a C/C composite (intermediate). .

Furthermore, after immersing this C/C composite (intermediate) in impregnated pitch and defoaming under reduced pressure, the pressure cuff kg/am'',
Impregnation was carried out at 200°C. After heating this compact to 850°C at a temperature increase rate of lθ°C/hr in a nitrogen atmosphere,
Immediately, it was slowly cooled to completely carbonize the impregnated pitch. Subsequently, this C/C composite (intermediate) was heated to 2000° C. in an argon atmosphere and maintained for 1 hour to graphitize it. This graphitized C/C composite (
Using impregnated pitch in the same manner as above, the impregnation and carbonization steps are repeated one more time to form a C/C composite (product).
I got it.

Comparative Example 3 A molded body was produced under the same conditions as Example 2, and this was carbonized to obtain a C/C composite (intermediate). Next, this C/C composite (intermediate) was produced under the same conditions as Example 2. Impregnated pitch was impregnated and carbonized. The above impregnation and carbonization steps were repeated one more time on this C/C composite (intermediate) to densify it, and then the temperature was raised to 2000°C in an argon atmosphere.
Graphitization was performed while maintaining lhr to obtain a C/C composite (product).

Comparative Example 4 A molded body was produced under the same conditions as in Example 2, and this was carbonized to obtain a C/C composite (intermediate). Next, this C/C composite (intermediate) was produced under the same conditions as in Example 2. Impregnated pitch was impregnated and carbonized. This C/C composite (intermediate) was subjected to the above impregnation and carbonization steps two more times to make it densified, and then heated to 2000°C in an argon atmosphere.
C/C composite (product) after graphitization with hr retention
I got it.

The dimensions and weight of the obtained C/C composite (product) were measured, and the bulk density was determined. Each result is shown below.

Example 21.39 2 1 1.5
8 Comparative Example 31.39 2 1 1.
52 Comparative Example 41.39 3 1 1
．． 5111 Example 3 Phenol resin (AV Light RM-2
It was impregnated with 30% by weight methyl ethyl ketone solution of 10), dried, and cut into 20 m thick pieces to obtain prepregs.

This prepreg was laminated randomly in a mold, and the temperature was 150.
A molded body was obtained by press molding at a temperature of 50 kg/ctn'. The carbon fiber content of the molded article obtained at this time was 68% by weight.

Next, this molded body was heated at 10°C/h in a nitrogen atmosphere.
After raising the temperature to 850°C at a heating rate of r, immediately cool slowly to carbonize the matrix and create a C/C composite (intermediate)
I got it.

Furthermore, this C/C composite (intermediate) was impregnated with furan resin (AV Light RM-1000F) under reduced pressure, and after dry explosion and curing at 170°C, this molded body was heated at 10°C/10°C in a nitrogen atmosphere. After the temperature was raised to 850° C. at a temperature increase rate of hr, it was immediately slowly cooled to completely carbonize the impregnated furan resin. Subsequently, this C/C composite (intermediate) was heated to 2000° C. in an argon atmosphere and maintained for 1 hr to graphitize it. This graphitized C/C composite (intermediate) was subjected to the impregnation and carbonization steps two more times using furan resin in the same manner as described above, and then graphitized at 2000°C in the same manner as described above to form a C/C composite ( product) was obtained.

Comparative Example 5 A molded body was produced under the same conditions as in Example 3, and this was carbonized to obtain a C/C composite (intermediate). Next, this C/C composite (intermediate) was produced under the same conditions as in Example 3. Impregnated with furan resin, hardened and carbonized. The above impregnation and carbonization steps are repeated one more time on this C/C composite (intermediate),
After densification, the temperature was raised to 2000°C in an argon atmosphere and maintained for 1 hour to graphitize the C/C composite (
intermediate) was obtained. This graphitized C/C composite (intermediate) was subjected to the impregnation and carbonization steps two more times using furan resin in the same manner as above, and then heated to 2000°C in the same manner as above.
Graphitization was performed to obtain a C/C composite (product).

The bulk density of the obtained C/C composite (product) was determined by δ11, and a three-point bending test was conducted at room temperature. The results of each measurement are shown below.

(Left below) Initial mixture Graphitization Bulk density Bending reinforcement density Times
Number of times (g/cc) (kg/mm'Example 3 1
．． 32 3 2 1.48 7.72 Comparative Example 5 1.32 4 2 1.48 5.
15 Effects of the Invention As described above, according to the method of the present invention, the efficiency of impregnation treatment and carbonization treatment is significantly improved in the manufacturing method of C/C composite compared to the conventional technology. Therefore, there are few
A C/C composite with high density and high strength can be manufactured by repeating impregnation and carbonization.

Furthermore, the method of the present invention can shorten the manufacturing process, is advantageous in terms of energy saving, and can manufacture C/C composites at low cost.

Representative Patent Attorney Masao Inoue Procedural amendment April 7, 1986

Claims (1)

[Claims] A molded body made of carbon material reinforced with carbon fibers is first carbonized, then impregnated with pitch or thermosetting liquid resin, carbonized once, graphitized, and then impregnated. A method for producing a carbon fiber-reinforced carbon material, the method comprising carbonization treatment.