JPH08157272A - Production of carbon fiber reinforced carbon composite material - Google Patents

Abstract

PURPOSE: To unnecessitate facilities for preventing explosion and equipment for treating waste gas and to safely produce a composite material having physical properties comparable to those of a conventional carbon fiber composite material at a very low cost. CONSTITUTION: A suspension prepd. by dispersing 15-70 pts.wt. thermosetting resin selected from among phenolic resin, furan resin and a mixture of them and 30-85 pts.wt. carbonaceous powder in 150-700 pts.wt. aq. soln. so prepd. as to regulate the concn. of a water-soluble polymer to 0.3-5wt.% is impregnated into carbon fibers and the fibers contg. the impregnated material are dried, compacted and fired to produce the objective carbon fiber reinforced carbon composite material.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a method for producing a carbon fiber reinforced carbon composite material. More specifically, the present invention uses an impregnating material (matrix precursor) containing water as a dispersion medium, does not use an organic solvent that is high in manufacturing cost and dangerous in handling, and is extremely safe and inexpensive in the manufacturing process. The present invention relates to a method for manufacturing a fiber reinforced carbon composite material.

[0002]

2. Description of the Related Art Carbon fiber reinforced carbon composite materials (hereinafter sometimes simply referred to as C / C composite materials, C / C materials, etc.) are lightweight materials having high thermal conductivity, heat resistance and thermal shock resistance. hand,
Highly heat-conductive materials such as heat sinks, heat-resistant materials for space openers, heat-resistant parts such as fusion reactor furnace wall materials, and heat-resistant sliding materials that are extremely useful as brake materials under severe operating conditions such as aircraft and race cars. Is.

Conventional C / C composite material manufacturing methods are roughly classified into three types. One is a method of precipitating carbon between carbon fibers as a matrix of a C / C composite material by vapor phase growth. A molded product in which a bundle of carbon fibers is assembled into a predetermined shape is put in a furnace and is heated at a high temperature. This is a method (so-called CVD method) of heating and then causing a hydrocarbon-based gas to pass through a furnace for thermal decomposition to deposit and solidify carbon into a carbon fiber compact. However, this method has the drawbacks that it is difficult to deposit carbon evenly inside the carbon fiber bundle, it contains many defects such as cracks and voids, and its production requires a lot of time and cost. .

Another method is to use a thermosetting resin as a matrix precursor. In this method, since the carbonization yield of the thermosetting resin is as low as about 50%, C
Cracks and voids occur as in the VD method. In this method, the process of re-impregnating carbonaceous pitch by a method called re-impregnation and firing is repeated several times (usually 5 to 10).
There is also a method of reducing defects such as cracks and voids that have occurred, but this has a drawback that it takes a lot of time, and at the same time, even if the defects are reduced, the strength cannot be sufficiently increased. Further, there is a method in which carbonaceous pitch is melted as a matrix precursor and impregnated and then carbonized. The carbonaceous pitch used in this method needs to have a low softening point (usually 350 ° C. or lower) to the extent that it can be impregnated, and therefore the carbonization yield is low. As a result, this method also causes cracks and voids during firing as in the two methods described above.

Therefore, in order to improve such a point,
The present inventors have used a method in which raw coke powder having a high carbon yield is used as the carbonaceous pitch, and furfural or the like having a strong dissolving power is used as an organic solvent for the thermosetting resin (JP-A-3-247563). , A method of using a high boiling point solvent as an organic solvent and drying under reduced pressure (Japanese Patent Laid-Open No. 5-51
No. 257) and the like. However, the method of using an organic solvent as a solvent for such a thermosetting resin is expensive in terms of safety because the manufacturing equipment must have an explosion-proof structure and exhaust gas treatment is required for environmental protection. It has a disadvantage that it is not easy to handle.

On the other hand, carbon fiber short fibers (hereinafter sometimes referred to as CF short fibers) are replaced with polyvinyl alcohol (hereinafter
A method for producing a C / C material in which papermaking is performed with an aqueous solution, impregnated with a thermosetting resin, and firing is performed (JP-A-1-
160867 gazette), a carbon fiber spherical body, a CF short fiber, and a binder such as PVA are wet mixed, molded, impregnated with a thermosetting resin, and fired (Japanese Patent Publication No. 6-5511). Gazette) or a method for producing a C / C material in which a sheet obtained by paper-making carbon whiskers and pitch particles is pressure-molded and then fired (JP-A-3-174359).
Is proposed. However, when water is used as the dispersion medium in this way, although it is possible to obtain an isotropic C / C material by making CF short fibers as reinforcing fibers, unidirectional C using continuous long fibers of carbon fibers is used. In the case of the / C material, it was impossible to produce a good C / C material because there was no entanglement between the carbon fibers.

[0007]

Therefore, an object of the present invention is to use a carbonaceous powder suspension for impregnation using water as a dispersion medium, thereby avoiding the use of an organic solvent which is high in manufacturing cost and dangerous in handling. Another object of the present invention is to provide a method for manufacturing a carbon fiber reinforced carbon composite material which is extremely safe and inexpensive in the manufacturing process.

[0008]

According to the present invention, a phenol resin is added to 150 to 700 parts by weight of an aqueous solution prepared so that the concentration of the water-soluble polymer is 0.3 to 5% by weight.
A carbon fiber is impregnated with a suspension in which 15 to 70 parts by weight of a thermosetting resin selected from a furan resin and a mixture thereof and 30 to 85 parts by weight of a carbonaceous powder are impregnated, and then the obtained impregnating material is contained. Provided is a method for producing a carbon fiber-reinforced carbon composite material, which comprises drying, shaping, and then firing the carbon fiber.

Further, according to the present invention, as a preferred embodiment, there is provided a method for producing a carbon fiber reinforced carbon composite material, wherein the water-soluble polymer is polyvinyl alcohol, carboxymethyl cellulose, polyethylene oxide or a mixture thereof. Provided is a method for producing a unidirectional carbon fiber-reinforced carbon composite material, in which the carbon fiber is fired at a temperature of 500 ° C. or higher.

The method for producing a C / C composite material of the present invention is a method in which a suspension obtained by dispersing a specific amount of a phenol resin and / or furan resin and a carbonaceous powder in an aqueous solution of a water-soluble polymer of a specific concentration is used as a carbon material. After impregnating the fiber, the carbon fiber containing the impregnating material was dried, molded, and then fired.According to this manufacturing method, no explosion-proof equipment or exhaust gas treatment equipment is required because no organic solvent is used. In addition, the production cost can be kept low, the water-soluble polymer acts as a binder after drying, and since the amount is appropriate, the formation of voids in the firing step is avoided and conventional organic solvents are used. A material having the same or higher physical properties as the manufactured C / C composite material can be manufactured extremely safely and inexpensively.

The present invention will be described in detail below. In the present invention, a mixture of a thermosetting resin selected from a phenol resin, a furan resin and a mixture thereof and a carbonaceous powder in a specific ratio is used as a matrix precursor for impregnating carbon fibers. The greatest feature is that an aqueous solution containing a water-soluble polymer in an amount of 0.3 to 5% by weight is used as a medium (dispersion medium) for dispersing and preparing an impregnating material.

In the present invention, the water-soluble polymer not only serves as a dispersant for the carbonaceous powder and the thermosetting resin, but also remains at the interface between the carbon fiber and the matrix after the water is dried and removed. Acting as a binder. Therefore, the concentration of the water-soluble polymer must be equal to or higher than the specific concentration having a binder action. On the other hand, in the process of firing, these water-soluble polymers are decomposed by heat and form voids inside the C / C material.
Performance of material C deteriorates. From these results, in the present invention, an aqueous solution in which the concentration of the water-soluble polymer is 0.3 to 5% by weight (preferably 0.5 to 3% by weight) is used.

In this case, various natural or synthetic polymers are used as the water-soluble polymer. Specific examples thereof include polyvinyl alcohol, carboxymethyl cellulose, polyethylene oxide, methyl cellulose, water-soluble acrylic resin and the like. Any water-soluble polymer may be used as long as the molecular weight and the degree of polymerization are water-soluble and the binder effect is recognized. Among these, polyvinyl alcohol, carboxymethyl cellulose and polyethylene oxide are preferable from the viewpoint of the binder effect.

As described above, in the present invention, as the matrix precursor to be impregnated into the carbon fiber, the carbonaceous powder is mixed in the thermosetting resin selected from the phenol resin, the furan resin and the mixture thereof in the specific ratio. Use one. That is, the above aqueous solution polymer-containing aqueous solution 150 to 7
15 to 70 parts by weight of the thermosetting resin and 30 to 85 parts by weight of carbon powder are added to 00 parts by weight. If the proportion of the aqueous solution is less than 150 parts by weight, the viscosity of the suspension of the thermosetting resin and the carbonaceous powder becomes high, and the impregnation into the carbon fiber becomes insufficient. If the ratio of the aqueous solution exceeds 700 parts by weight, a dense C / C material cannot be obtained. The amount of thermosetting resin added is less than 15 parts by weight and the amount of carbonaceous powder added is 85
If it exceeds the weight part, moldability is poor and a dense C / C material cannot be obtained. Further, if the amount of the thermosetting resin added is more than 70 parts by weight and if the amount of the carbonaceous powder added is less than 30 parts by weight, the volatile component during firing of the matrix precursor is increased, resulting in large cracks and voids during firing. Therefore, a good C / C material cannot be obtained.

In the present invention, as the thermosetting resin,
Phenolic resins, furan resins or mixtures thereof with high carbonization yield are used. Phenolic resins include resol type obtained by reaction of phenols and aldehydes in the presence of alkali, and novolac type obtained from phenols and aldehydes by acidic catalyst. There is something. The novolac type is preferably a self-curing type containing a curing agent such as hexamethylenediamine. Further, various phenol resins can be mixed and used.

As the furan resin, a furan resin initial condensate can be used. The precondensate includes those consisting of furfuryl alcohol or a furfuryl alcohol / furfural mixture. Further, a phenol resin initial reaction product or a mixture of a pre-cured resin and a furan resin initial reaction product can be used. Here, the initial reaction product means a liquid resin.

In the present invention, as the carbonaceous powder, C /
Petroleum-based, coal-based, compound-based pitch, raw coke, coke, calcined coke, carbon black, artificial graphite having an H (atomic ratio) of 1.8 or more, a softening point of 400 ° C. or more, and a volatile content of 20 wt% or less, Natural graphite or the like is used. The average particle size of these is 0.5 to 5 μm. The particle size distribution is 2 μm or more and 35% by weight or more, 1-2 μm.
20% by weight or more and 1 μm or more and 30% by weight or more are preferable.

In the preparation of the matrix precursor-containing solution for impregnation, the concentration of the water-soluble polymer is 0.3-5% by weight.
A predetermined amount of thermosetting resin and carbonaceous powder are added and dispersed in the aqueous solution prepared so that The procedure for adding and mixing the aqueous solution (dispersion medium), the resin and the carbonaceous powder is not particularly limited. As the dispersion method, a ball mill,
Any method such as a method using ultrasonic waves can be adopted.

The carbon fiber used in the present invention is PAN.
System, mesophase pitch system, isotropic pitch system and other long fibers generally called carbon fiber fired at 500 ° C. or higher. Needless to say, it may be graphite fiber fired at a high temperature.

Impregnation of the matrix precursor-containing solution into the carbon fibers is usually carried out at room temperature, but it may be carried out under heating within a temperature range in which the curing reaction of the resin does not substantially proceed. The impregnation method can be adapted to the shape of the carbon fiber. For example, in the case of continuous yarn, the yarn can be impregnated by continuously passing the yarn through a solution containing a matrix precursor and winding the yarn around a drum or a frame. The impregnation can also be performed under reduced pressure.

After impregnation, the matrix precursor containing carbon fibers are dried prior to forming. Drying is generally carried out at room temperature and normal pressure, but may be carried out under heating or under reduced pressure in order to shorten the drying time. It is desirable that the drying is performed within a temperature range from the temperature at which the resin softens to the temperature at which the curing reaction of the resin does not proceed substantially. For example, it is in the range of 50 to 100 ° C.

The carbon fiber content of the obtained matrix precursor-containing carbon fiber, that is, the carbon fiber volume content (Vf), is appropriate to be 40 to 80% after firing, and particularly 50 to 50%. 75% is preferable.

The dried sheet-form carbon fiber containing the matrix precursor is usually used in an amount of 5 to 25 MP after stacking the sheets.
It is molded under the pressure of a. The molding utilizes the curing reaction of the resin. The molding temperature range is 8 for phenol resin.
0 to 200 ° C., and in the case of furan resin, for example, 70 to
160 ° C., in the case of a mixture thereof, for example 70 to 200
° C. However, it is not limited to this range. The heating time is generally 10 minutes to 10 hours or longer. It is desirable to gradually increase the temperature stepwise or continuously in this temperature range. Pressurization is usually performed in the range of 5 to 25 MPa, but 10 to 20 MP is particularly preferable.
a. The obtained molded product is carbonized by firing according to a known method at a temperature of 2,000 ° C. or higher, preferably at a temperature of 2,500 ° C. or higher, in an inert atmosphere, at atmospheric pressure or under pressure, and carbonized. In addition, it is graphitized.

In order to densify the C / C composite material and improve its strength, a step of re-impregnating a thermosetting resin, a carbonaceous powder, etc. and re-baking the re-impregnated material, a step of repeating the steps. It can also be added by a known method.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the technical scope of the present invention is not limited thereto. All parts shown below are based on weight.

Example 1 Coke powder 7 having 25 parts of a phenol resin, a softening point of 550 ° C., a volatile content of 0.5% by weight, and an average particle diameter of 1.0 μm with respect to 375 parts of a 0.5% by weight polyvinyl alcohol aqueous solution.
The total amount of matrix was dispersed in 5 parts to obtain a suspension for impregnation. A carbon fiber bundle was impregnated with this suspension, water was removed by drying, and the carbon fibers were molded and cured so that the carbon fibers were oriented in one direction.
Then, carbonization was carried out under atmospheric pressure in an argon stream to obtain a C / C composite material of the present invention. The C / C composite material obtained had a carbon fiber volume content (Vf) of 55% and a bulk density (ρ) of 1.
It was 62 g / cm ³ , had no cracks and few voids, and the porosity of this sample was measured to be 20% by volume, which was a very good property as a C / C material without re-impregnation. .

Example 2 In Example 1, 4.0% by weight of polyvinyl alcohol
35 parts of phenol resin and 65 parts of coke powder in an aqueous solution of
A C / C composite material of the present invention was obtained in the same manner as in Example 1 except that the parts were dispersed. The obtained C / C composite material had Vf = 55%, ρ = 1.65 g / cm ³ , no cracks and few voids, and the porosity of this sample was 18% by volume, which is extremely good. It had various properties.

Comparative Example 1 Impregnation, drying and molding were carried out in the same manner as in Example 2 except that an aqueous solution containing 0.05% by weight of polyvinyl alcohol was used, but the amount of polyvinyl alcohol was too small. Sheet shape cannot be maintained in the drying process due to C /
A C molded body could not be obtained.

Comparative Example 2 In Example 2, 7.0% by weight of polyvinyl alcohol
A C / C composite material for comparison was obtained in the same manner as in Example 2 except that the aqueous solution of 1 was used. The obtained C / C composite material had Vf = 55% and ρ = 1.45 g / cm ³ , and many voids were generated. The porosity of this sample was measured and found to be 29% by volume, indicating that the sample had more porosity.

Comparative Example 3 A comparative C / C composite material was obtained in the same manner as in Example 2 except that the addition amount was 75 parts of phenol resin and 25 parts of coke powder. The obtained C / C composite material had Vf = 62% and ρ = 1.55 g / cm ³ . The porosity of this sample was measured and found to be 24% by volume, and although it had the same physical properties as in Example 1, large cracks occurred with the shrinkage of the thermosetting resin.

Comparative Example 4 A comparative C / C composite material was obtained in the same manner as in Example 2 except that the addition amount was 12 parts of phenol resin and 88 parts of coke powder. Although it was difficult to maintain the sheet shape during the drying process, the C / C composite material obtained had Vf = 45% and ρ = 1.35 g / cm ³ .
The porosity of this sample was measured and found to be 34% by volume, indicating that cracking had occurred.

[0032]

The method for producing a carbon fiber reinforced carbon composite material according to the present invention comprises the steps of adding 150 to 700 parts by weight of an aqueous solution prepared so that the concentration of the water-soluble polymer is 0.3 to 5% by weight.
15 to 70 parts by weight of a thermosetting resin selected from a phenol resin, a furan resin and a mixture thereof, and a carbonaceous powder 3
Since the carbon fiber is impregnated with a suspension in which 0 to 85 parts by weight are dispersed, according to the present manufacturing method,
Since safe and easy-to-use water is used as a dispersion medium for carbonaceous powder and thermosetting resin, explosion-proof equipment and exhaust gas treatment equipment are not required and production costs can be kept low. A C / C composite material having the same physical properties as the C composite material can be manufactured extremely inexpensively and safely. Therefore, the present method is useful as an industrial method for producing a C / C composite material which is useful as a material for precision processing.

Claims (1)

[Claims] 1. The concentration of the water-soluble polymer is 0.3 to 5% by weight.
15 to 70 parts by weight of a thermosetting resin selected from a phenol resin, a furan resin and a mixture thereof and 30 to 85 parts by weight of a carbonaceous powder are dispersed in 150 to 700 parts by weight of an aqueous solution prepared so that A method for producing a carbon fiber-reinforced carbon composite material, comprising: impregnating the carbon fiber with the suspension, drying the obtained impregnating material-containing carbon fiber, shaping the carbon fiber, and then firing the carbon fiber.