JPH0288460A - Production of carbon fiber-reinforced carbon material - Google Patents

Abstract

PURPOSE:To obtain the title carbon fiber-reinforced carbon material consisting of a high-density C/C composite material having a low content of pores by impregnating the material with low-softeningpoint pitch and then with high- softening-point pitch, and then carbonizing the product. CONSTITUTION:Carbon fibers are previously mixed, impregnated, or coated with a matrix precursor such as resin and pitch, and the product is formed by compression molding, etc., and then carbonized to prepare a material to be impregnated. The material is impregnated one or more times with the low- softening-point pitch having <=150 deg.C, or preferably <=120 deg.C, softening point. The impregnated material is further impregnated one or more times with the high-softening-point pitch having >=160 deg.C softening point at <=420 deg.C. The impregnated material is carbonized, or carbonized and then graphitized by the same method as the conventional method to obtain the desired carbon fiber-reinforced carbon material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a carbon material reinforced with carbon fibers.

[Prior Art] Carbon materials reinforced with carbon fibers, that is, carbon fiber-reinforced carbon materials (C/C composite materials), are lightweight (specific gravity 1.5-2.
09/i>, has high mechanical strength and excellent heat resistance (heat resistance temperature 2,500 to 3,000℃), and has excellent thermal properties such as mechanical properties at high temperatures, heat shock resistance, and dimensional stability. It has excellent stability, is chemically stable except for oxidation resistance, and has various excellent properties such as mechanical strength and electrical and thermal conductivity that can be controlled to a certain extent. Therefore, this C/C composite material is particularly useful as a material for parts and products exposed to high temperatures.For example, as a heat-resistant material, it can be used for space shuttle nose cones and leading edges, rocket nozzles, reentry parts, turbines, etc. It is used as a hot mold material such as hot press molds, it is used as a friction material in disc brakes and clutches for aircraft and high-speed vehicles, it is used as a corrosion-resistant and conductive material in reaction devices, electrodes, etc., and it is used as an artificial biomaterial. Bone,
It has been applied to joints, tooth roots, etc., and its applications are expected to further expand in the future.

This C/C composite material is made by impregnating or coating carbon fibers with an organic matrix precursor such as resin or pitch in advance, molding them by means such as injection molding, and then carbonizing them. Alternatively, there are resin impregnation methods in which carbon fibers are woven in advance into a shape similar to the final product (skeleton), which is impregnated with an impregnating material, and then carbonized and graphitized. Direct thermal decomposition between the fibers of carbon fiber fabrics It is manufactured by methods such as chemical vapor deposition (CVD) that deposits carbon (Carbon 1983 (NO, 115), p196
-208).

However, the CVD method can produce a uniform and dense structure, and is a necessary manufacturing method for the production of medical materials, for example, but the CVD method can produce only the required amount of C between the fibers of carbon fiber fabric.
It takes a long time to deposit the VDrA element, making it unsuitable for manufacturing large-sized C/C composites.

In addition, in the resin impregnation method described above, a C/C composite material is produced by impregnating the material to be impregnated with the matrix precursor of the impregnating material, and carbonizing and graphitizing the material, so it is relatively easy to produce a relatively large shape. It can be manufactured in
The carbonization rate of commonly used impregnating materials is low, and there are many components that volatilize during the carbonization process of carbonization or graphitization, resulting in the formation of many pores in the product. It is difficult to obtain a high-density, high-strength product by graphitization treatment alone, and for this reason, after carbonization treatment consisting of carbonization treatment or subsequent carbonization treatment including graphitization treatment, impregnation material is impregnated again. The impregnation and carbonization treatment process, in which the carbonization treatment is performed again, is repeated several times until a predetermined density and strength are achieved. Impregnating materials used for this purpose include pitches, other thermoplastic resins, phenolic resins, furan resins, and other thermosetting resins, and these are usually impregnated in order to adjust their viscosity. It is used by heating it or diluting it with an appropriate solvent.

Among these impregnating materials, pitches are often used from the viewpoint of economy and orientation, but since pitches are thermoplastic, if they are used as impregnating materials, they will deteriorate due to heating during the carbonization process. The viscosity of the pitches decreases, the pitch flows out of the impregnated material, and large pores of 10x or more remain after carbonization. The lower the softening point, the greater the amount of pitch flowing out, and pitches with low softening points generally have a low carbonization rate, so a single impregnation carbonization treatment cannot produce a sufficient effect of impregnation carbonization. . On the other hand, pitches with a high softening point have a relatively high carbonization rate and have the advantage of flowing out during the carbonization process after impregnation, but they cannot sufficiently penetrate into pores smaller than 10 mm. First, even after impregnation and carbonization, pores smaller than 10 remain. Moreover, even if the number of repetitions of this impregnation carbonization treatment is increased, the density will increase according to the 172nd power law of the number of impregnation carbonization treatments, and if the number of impregnation carbonization treatments is repeated beyond a certain level, the number of closed pores in the material to be impregnated will increase. density improvement is reduced. For this reason, in the past, one-time impregnation carbonization treatment was not expected to have the effect of impregnation carbonization on pores of 10 Im or more, and impregnation carbonization treatment was performed several times using a low softening point pitch with a softening point of 70 to 90°C. The reality is that it is repeated.

Therefore, in order to increase the effect of re-impregnation and carbonization treatment, methods such as high-pressure impregnation in an autoclave and carbonization treatment under pressure in an autoclave have been proposed. However, all of these methods require high-pressure treatment in an autoclave, so there is a problem in that the impregnation carbonization treatment cannot be performed manually.

Moreover, the carbonization process, which includes carbonization and graphitization, usually takes a long time of 10 to 30 days, so the key to reducing the number of impregnation carbonization treatments is to reduce energy costs and reduce manufacturing time. This is extremely important from the perspective of shortening the

[Problems to be Solved by the Invention] The present invention was devised in view of this point of view, and its purpose is to provide a high-density C/C with a low pore content.
The object of the present invention is to provide a method that allows a composite material to have %A>a-5J.

Another object of the present invention is to provide a method that can improve the efficiency of impregnation carbonization treatment and produce a high-density C/C composite material with a low pore content with a small number of treatments.

In general, another object of the present invention is to achieve high-density C/C equivalent to or higher than that of the conventional method with fewer impregnation and carbonization treatments.
The object of the present invention is to provide a method by which composite materials can be manufactured.

[Means for Solving the Problems] That is, the present invention provides a method for producing a carbon fiber-reinforced carbon material that includes an impregnating carbonization step consisting of a pitch impregnation treatment and a subsequent carbonization treatment, in which the pitch impregnation treatment is performed at least once. The pitch with a softening point of 150℃ or less is 42
Pitch impregnation treatment using a low softening point pitch that is impregnated at a temperature of 0°C or lower, and pitch impregnation treatment using a high softening point pitch that involves impregnating pitch with a softening point of 160°C or higher at a temperature of 420°C or lower at least once. A method for producing a carbon fiber-reinforced carbon material, or a method for producing a carbon fiber-reinforced carbon material including an impregnation carbonization step consisting of a pitch impregnation treatment and a subsequent carbonization treatment, wherein the pitch impregnation treatment includes at least one or more Pitch impregnation treatment in which pitch is impregnated into pores of 10p or more measured with a mercury porosimeter, and pitch impregnation treatment is performed in which pitch is impregnated into pores of less than 10x measured with a mercury porosimeter at least once. A method for producing a carbon fiber reinforced carbon material.

In the present invention, the material to be impregnated to be subjected to the impregnation carbonization treatment is manufactured using a normal manufacturing method, that is, carbon fibers are mixed, impregnated, or coated with a matrix precursor such as resin or pitch in advance, and then compression molding, index molding, etc. After molding and curing by means of - carbonization, or
This can be roughly graphitized (warped) or carbonized by impregnating a woven fabric (skeleton) woven with carbon fibers in a shape similar to the final product with an impregnating material. Alternatively, in addition to those obtained by roughly graphitizing this, if necessary, the process up to carbonization can be repeated multiple times, and the process up to graphitization can be repeated multiple times. This includes what is obtained.

The pitch impregnation treatment includes at least one pitch impregnation treatment with a pitch with a low softening point of 150°C or less, preferably 120°C or less, and at least one time with a high softening point pitch with a softening point of 160°C or more. Pitch impregnation treatment is carried out, but the pitch impregnation treatment with the former low softening point pitch impregnates the pitch into the measured pores of less than 10 rhinoceros measured with a mercury porosimeter, preferably pores of 1151 or less. In addition, pitch is impregnated into pores with a size of 10 or more as measured by a mercury porosimeter by a pitch impregnation treatment with a pitch having a high softening point. The pitch impregnation treatment using the 12 low softening point pitch and the pitch impregnation treatment using the high softening point pitch may be performed in one impregnation carbonization treatment step, or may be performed in different impregnation carbonization treatment steps. When performing pitch impregnation treatment using the above-mentioned low softening point pitch and pitch impregnation treatment using high softening point pitch in one impregnation carbonization treatment process, the pitch impregnation treatment using the former low softening point pitch is performed first, and then 100℃ below the softening point of the low softening point pitch used as a post-impregnation material
It is preferable to heat the material to a higher temperature than above, to flow out the low softening point pitch impregnated into relatively large pores (10p or more) in advance, and then to perform pitch impregnation treatment with the high softening point pitch.

This pitch impregnation treatment is carried out at 420°C or below, preferably at 36°C.
It is best to carry out the process at a temperature of 0°C or lower, and this impregnation temperature is 4°C.
If the temperature exceeds 20°C, a condensation reaction of the pitch occurs, and the viscosity of the pitch increases during the pitch impregnation treatment, and sometimes it solidifies, making it impossible to obtain a sufficient effect of the impregnation carbonization treatment. This pitch impregnation treatment may be performed under pressure, and in particular, pitch impregnation treatment with a low softening point pitch is effective in impregnating pitch with pitch of less than 10 U as measured by a mercury porosimeter. Impregnation treatment is effective.

The material to be impregnated which has been subjected to the pitch impregnation treatment in this manner is subjected to a carbonization treatment consisting of carbonization or carbonization followed by graphitization, in the same manner as in a normal manufacturing method. At this time, carbonization is carried out under a non-oxidizing atmosphere at 450 to 1,10
Graphitization is carried out by gradual heating in the temperature range of 0 °C, and graphitization is carried out as necessary in an inert atmosphere at temperatures ranging from 1.800 °C to 0 °C.
It is carried out by gradual heating in a temperature range of 2,800°C.

This impregnation carbonization treatment may be performed one or more times, and since the effect of this impregnation carbonization decreases as the number of times increases, it is usually sufficient to perform the impregnation carbonization treatment four times or less. By applying the method of the present invention, even large pores can be filled with one impregnation carbonization treatment, so when performing multiple impregnation carbonization treatments, at least one of them is performed by the method of the present invention, and the other may be performed using conventional methods.

The method of the present invention can be applied to all C/C composite manufacturing methods including an impregnation carbonization treatment step.

In the manufacturing method that is used to manufacture aircraft brakes, automobile brakes, heating elements, hot press molds, etc., in which carbon IN and matrix precursor are mixed and then molded, the initial carbonization has been completed. The method of the present invention may be applied to at least one of the subsequent impregnation and carbonization steps. In a method using a woven fabric (skeleton) having a shape close to that of the final product, the method of the present invention may be applied to the culm in at least one of the subsequent impregnation and carbonization treatment steps.

When the impregnation carbonization treatment according to the method of the present invention is performed, the effect of filling the pores of the material to be impregnated is large, and the bulk density is greatly increased. In the conventional method, this impregnation carbonization treatment was repeated 10 times or more to reach a bulk density of about 1.7 to 1.89/ctA, but according to the method of the present invention, the bulk density can be reduced to 2.0/ctA.
In addition to being able to increase the amount to about 100 g/-, it is also possible to reduce the number of impregnation carbonization treatments.

[Function] Pitch with a high softening point has a large carbonization rate, and also has a small viscosity drop during carbonization, and the amount of outflow from large pores is small, but the viscosity cannot be lowered during impregnation Ii4,
Difficult to penetrate into small pores. On the other hand, pitch with a low softening point can lower the viscosity during impregnation and can penetrate into small pores.
The viscosity decreases greatly during carbonization, the amount flowing out from large pores increases, and the carbonization rate is small, so the effect of increasing density after carbonization is small.

The method of the present invention uses both pitches with a low softening point and pitches with a high softening point as impregnating materials, and impregnates small pores with the pitch with a low softening point, while impregnating large pores with the pitch with a low softening point. It is believed that by impregnating the pitch with high points, the pitch was efficiently impregnated into each pore of the material to be impregnated, and the efficiency of one-time impregnation carbonization was able to be significantly improved.

[Examples] Hereinafter, the method of the present invention will be specifically explained based on Examples and Comparative Examples.

Example 1)) A made from N-based carbon fiber and resol type phenolic resin, has a disk-like shape, and has a bulk density of 1.29.
A C/C composite material with 99/cd and an open porosity of 51.6% was prepared and used as a material to be impregnated.

This impregnated material was impregnated with tar pitch having a softening point of 86°C at 200°C and 15 kg/Cl1I-G.
Heat to 0°C to remove the escaping tar pitch, then to 380°C, 'I5! Softening point 24 under J/ci-G conditions
The material was impregnated with pitch at 0°C, placed in an electric furnace, and heated to 1,100°C in a nitrogen gas atmosphere for 110 hours to carbonize the pitch impregnated into the impregnated material.

The bulk density and open porosity of the obtained C/C composite material were measured using a mercury porosimeter (≧10II!It porosity and 10p porosity), and the porosity decreased before and after impregnation carbonization treatment (≧ The difference between the porosity before impregnation (the sum of the porosity of 10p and the porosity of <10p) is the difference between the porosity of 10p and the porosity of <
The pore filling rate was determined by dividing the total porosity by the total porosity of 104. The results are shown in Table 1.

Comparative Example 1 The same material to be impregnated as in Example 1 was used, and the same pitch with a softening point of 86°C as used in Example 1 was used.
Similarly, pitch with a softening point of 86°C was impregnated at 200°C and 15Kg/Cl1tG, and carbonized in the same manner as in Example 1 without performing heat flow treatment and impregnation treatment with high softening point pitch. The bulk density and open porosity of the C/C composite material obtained were measured, and the pore filling rate was determined. The results are shown in Table 1.

Table 1 As is clear from Table 1, the bulk density and pore filling rate of the obtained C/C composite material were higher when the impregnation carbonization treatment was performed by the method of Example 1.

Example 2 The same material to be impregnated as in Example 1 was used, and pitch with a softening point of 240°C was used for the first impregnation carbonization treatment, and pitch with a softening point of 86°C was used for the second impregnation carbonization treatment. , Example 1
Impregnation and carbonization treatment was carried out in the same manner as above.

) Regarding the C/C composite material prepared in Example 1,
The bulk density and open porosity were measured to determine the pore filling rate. The results are shown in Table 2.

Example 3 Impregnation carbonization treatment was carried out in the same manner as in Example 2, using pitch with a softening point of 86 ° C. for the first impregnation carbonization treatment and using pitch with a softening point of 240 ° C. for the second impregnation carbonization treatment. Ta.

Regarding the obtained C/C composite material, its bulk density and open porosity were measured in the same manner as in Example 1, and the pore filling rate was determined.

The results are shown in Table 2.

Comparative Example 2 Impregnation carbonization treatment was performed in the same manner as in Comparative Example 1 above, except that pitch with a softening point of 86° C. was used and the impregnation carbonization treatment was repeated twice.

As in Example 1, for the C/C composite material which was warped by 1.
The bulk density and open porosity were measured to determine the pore filling rate. The results are shown in Table 2.

Second surface carbonization treatment is sufficient, which can significantly reduce the energy cost during the production of C/C composite materials, and
A: The construction period can be shortened.

Claims (2)

[Claims] (1) In a method for manufacturing a carbon fiber-reinforced carbon material including an impregnation carbonization step consisting of a pitch impregnation treatment and a subsequent carbonization treatment, as the pitch impregnation treatment, pitch with a softening point of 150°C or less is heated to 420°C at least once. Pitch impregnation treatment with low softening point pitch impregnated at the following temperature,
4 pitches with a softening point of 160℃ or more at least once
A method for producing a carbon fiber-reinforced carbon material, which comprises performing a pitch impregnation treatment using a high softening point pitch impregnated at a temperature of 20° C. or lower. (2) In a method for producing a carbon fiber-reinforced carbon material including an impregnation carbonization step consisting of a pitch impregnation treatment and a subsequent carbonization treatment, the pitch impregnation treatment involves impregnating pitch into pores of 10 μm or more as measured by a mercury porosimeter. A method for producing a carbon fiber-reinforced carbon material, characterized in that pitch impregnation treatment and pitch impregnation treatment in which pitch is impregnated into pores of less than 10 μm measured with a mercury porosimeter are each performed at least once or more.