JPH05148017A - Production of carbon fiber-reinforced carbon material for general purpose - Google Patents

Abstract

PURPOSE:To provide a production process for a high-performance but inexpensive C/C composite for general purposes through simple procedures by using, as a filler, carbon fibers of a mixture thereof with chopped fibers or milled fibers, which are randomly oriented by twisting carbon yarn. CONSTITUTION:Carbon yarn is twisted to be oriented randomly, and the yarn is impregnated with a thermosetting resin and/or a thermoplastic resin to produce prepregs, The prepregs are formed and carbonized to give a sintered product. The product is impregnated with substantially quinoline-insoluble component-free pitch of high softening point of 150 to 250 deg.C and made infusible in air at 200 to 350 deg.C, then carbonized in an inert atmosphere at 800 to 1,200 deg.C, further impregnated with the pitch of high softening point until the bulk density reaches more than 1.5g/cm<3>, and infusion and carbonization treatments are repeated, finally graphitized at 1,500 to 2,500 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a general-purpose carbon fiber reinforced carbon material, and more specifically, carbon fibers obtained by twisting carbon fiber yarns as reinforcing fibers (fillers) and randomly orienting them. The present invention relates to a method for producing a carbon fiber reinforced carbon material using a mixture of carbon fiber, chopped fiber and milled fiber.

[0002]

2. Description of the Related Art Carbon composite materials in which carbon is used as a matrix and are reinforced with carbon fibers are carbon fiber reinforced carbon materials (hereinafter referred to as
C / C-composite), and this C / C-
Composites have excellent mechanical properties, heat resistance, corrosion resistance, friction, and braking properties, and are utilized as aerospace equipment components such as rocket nozzles, space shuttle nose and leading edges, and aircraft brake discs. Has been converted. Recently, commercialization has been promoted as a first wall material for nuclear reactors and fusion reactors, and medical materials such as bones and joints and turbine materials.

Although there are various manufacturing methods for the C / C-composite having such excellent characteristics, carbon fiber tow, cloth, felt and the like are impregnated with a thermosetting resin such as a phenol resin to prepare a prepreg. To obtain a fired body by carbonizing it in an inert atmosphere, and then apply a thermosetting resin such as furan resin or tar pitch to the fired body. Densification treatment of impregnating with a different thermoplastic resin and carbonizing
It is common to repeat the process 15 to 15 times to obtain a C / C-composite.

Further, the weaving method of carbon fibers used for the production of C / C-composites is roughly classified according to the orientation direction of the fibers, and (1) one-dimensional orientation of fibers such as unidirectional laminated material,
(2) Two-dimensional orientation of fibers such as cross laminated material and cross laminated material, and (3) Three-dimensional orientation in which vertical yarns are oriented in the thickness direction of the two-dimensionally oriented laminated material. ..

[0005]

Among these, the one-dimensional and two-dimensional oriented materials have a weak point that the interlaminar strength is significantly inferior to that of the orientation direction of the fiber, and thus, in the manufacturing process of the C / C-composite. There are problems that a layered crack occurs, a good carbon material cannot be obtained, or sufficient strength is not exhibited. In the case of this one-dimensional and two-dimensional orientation, a fairly strict temperature control is required in the process of laminating the prepregs and subsequent curing, and the process itself is complicated, which requires a lot of labor and time. .. Further, in the case of three-dimensional orientation, the volume filling factor of the three-dimensional orientation material itself and the fiber becomes lower than that of the one-dimensional and two-dimensional materials, and as a result, the strength of the C / C-composite does not appear. is there. Moreover, three-dimensional alignment materials are also very expensive.

It is an object of the present invention to twist carbon fiber yarn as a filler and randomly orient it,
Or, using a mixture of the carbon fiber, chopped fiber, and milled fiber, a high-performance and inexpensive general-purpose C with a simple process
/ C-composite manufacturing method.

[0007]

In order to achieve the above object, according to a first aspect of the present invention, a carbon fiber yarn is twisted and randomly oriented, and a thermosetting resin and / or A prepreg is made by impregnating a thermoplastic resin, molded, and then carbonized to obtain a fired body, which has a high softening point pitch of 150 to 250 ° C. which does not substantially contain quinoline insoluble matter. And then infusible in air at 200 to 350 ° C., then carbonized at 800 to 1200 ° C. in an inert atmosphere, and further softened until the bulk density becomes 1.5 g / cm ³ or more. A method for producing a general-purpose carbon fiber-reinforced carbon material is provided, which comprises repeating point pitch impregnation, infusibilization, and carbonization treatment, and finally performing graphitization treatment at 1500 to 2500 ° C.

According to the second aspect of the present invention, the carbon fiber yarn is twisted and randomly oriented, and chopped fiber and / or milled fiber is mixed with this fiber to obtain a reinforcing fiber. Thermosetting resin and /
Or make a prepreg by impregnating with a thermoplastic resin,
This is molded and then carbonized to obtain a fired body, and the fired body is impregnated with a high softening point pitch having a softening point of 150 to 250 ° C. substantially free of quinoline insoluble matter, and then 200 to 350 in air. After infusibilizing at ℃, heat treatment at 800 ~ 3000 ℃ in an inert atmosphere, further impregnation, infusibilization and heat treatment of the high softening point pitch until the bulk density becomes 1.5 g / cm ³ or more. A method for producing a general-purpose carbon fiber reinforced carbon material is provided which is characterized by repeating.

The present invention will be described in more detail below. Book
Randomly blended to be used as filler in invention
Carbon fibers are polyacrylonitrile-based, rayon-based, pigment
It may be any type of switch. Also high strength yarn (pull
Strength: 200kg / mm²Above), high elasticity yarn (tensile elasticity)
Rate: 30t / mm ²Any of the above). these
The carbon fiber yarn is cut into 0.5 to 2 m length,
Carbon fiber by fixing one side and rotating the other
The yarn is twisted to obtain randomly oriented fibers.
Be done.

Further, by twisting the cut carbon fiber yarn, applying tension in the longitudinal direction, and instantaneously releasing the tension, three-dimensionally randomly oriented fibers can be obtained. These randomly oriented fibers are shown in FIGS.
For example. In the present invention, the carbon fiber yarn is not limited to these shapes as long as it is twisted and randomly oriented.

Further, chopped fibers (chopped fibers, which may be finer than milled fibers) and milled fibers (ground fibers) used in the second embodiment of the present invention are also polyacrylonitrile-based, rayon-based, and pitch-based. Any type of yarn, high strength yarn, high elasticity yarn, and general-purpose grade (tensile strength: 70 kg / mm ² ) may be used. The chopped fiber preferably has a fiber length of 0.5 to 6 mm, and the milled fiber preferably has a fiber length of 50 to 500 μm.

In the second aspect of the present invention, the carbon fiber yarn is twisted and randomly oriented, and chopped fibers and / or milled fibers are mixed to form reinforcing fibers (fillers). This mixing is (1) mixing ratio of randomly oriented fibers and chopped fibers (= random fibers: chopped fibers) = 100: 5 to 40 (weight ratio) (2) mixing of randomly oriented fibers and milled fibers Ratio (= random fiber: chopped fiber) = 10
0: 5 to 40 (weight ratio) (3) Mixing ratio of randomly oriented fibers, chopped fibers and milled fibers (= random fiber: (chopped fiber + milled fiber)) = 10
0: 5 to 40 (weight ratio), {chopped fiber: milled fiber = 100: 0 to 100 (weight ratio)}. The purpose of mixing chopped fiber and milled fiber is to intercalate these randomly oriented fibers, forming so-called bridges and filling pores in the molded product to increase the bulk density and strength of the final product. In addition, it also serves as a passage for the gas generated during the firing process, and a good product with no cracks or blisters can be obtained even at a considerably high firing rate. If the mixing ratio is other than the above, the desired effect cannot be obtained.

Further, in the first and second aspects of the present invention, the raw material of the carbon material which becomes the matrix is a thermosetting resin such as phenol, epoxy, furan, polyphenylene or polyimide, tar pitch, petroleum It may be a thermoplastic resin such as pitch.

When a thermosetting resin such as a phenol resin is used, in the first aspect of the present invention, the randomly oriented carbon fibers are used, and in the second aspect of the present invention, the mixed carbon fibers are loaded with the resin. A usual method of impregnating into a prepreg and molding it as it is may be used.

The impregnation method may be any of a vacuum impregnation method, a pressure impregnation method, a dipping impregnation method and the like. The molding method may be press molding, autoclave molding, or the like.

To cure the resin, 100 to 300 ° C.
Temperature is required, and this curing treatment is performed while holding the molded body. That is, it is necessary to prevent the spring back of the prepreg during curing by fixing the molded body from above and below and from the side by tightening it with a jig. When the curing of the resin is sufficiently completed, the jig is removed, but the temperature and time required for the curing are 100 to 300 ° C. and 30 minutes to 2 hours, and it is necessary to cure the conventional two-dimensional oriented fiber such as cloth. Curing is completed in a remarkably short time as compared with the time (200 to 400 hours).

The cured product thus obtained is subsequently carbonized at 800 to 1200 ° C. to obtain a fired product (primary fired product). The time required for this treatment may be as short as 20 to 40 hours. It is possible to obtain a non-defective primary fired body having no cracks or swelling.

When a thermoplastic resin such as pitch is used, randomly oriented carbon fibers are used in the first aspect of the present invention, and the mixed carbon fibers are put in a mold in the second aspect of the present invention. This is held and fixed by a jig, dipped in a molten pitch and impregnated to obtain a molded prepreg. As the impregnation method, any method such as an immersion impregnation method, a vacuum impregnation method, or a pressure impregnation method may be used. This molded prepreg can be subsequently carbonized at 800 to 1200 ° C to obtain a primary fired body.

In consideration of the phenomenon that the pitch melts in the carbonization process, the carbon fiber held and fixed by a jig is dipped in the molten pitch, and then the carbon fiber is dipped in the pitch at 800 to 1200 ° C. There is also a method of carbonizing. The time required for the carbonization treatment when a primary fired body is obtained using a thermoplastic resin may be 20 to 40 hours as in the case of a thermosetting resin, and is a primary product of a non-defective product with no cracks or swelling. A fired body can be obtained.

The primary fired body of the C / C-composite obtained in this way is not sufficient in bulk density and strength, and in order to obtain a high-density and high-strength C / C-composite, a conventional method is used. It is necessary to appropriately repeat the impregnation treatment and the carbonization treatment (densification treatment). As the impregnating material used for this impregnation treatment, inexpensive tar pitch and petroleum pitch are desirable.
Tar pitch is more preferable as the impregnating material. This is because tar pitch is rich in aromaticity, has a high carbonization rate, and has a large true specific gravity.

Here, the pitch contains substantially no quinoline insoluble matter, and further, the softening point is 150 to 25.
It is important to be in the range of 0 ° C. The quinoline insoluble matter in the pitch is a solid particle, and this particle closes the pores in the carbonaceous material, and therefore significantly reduces the permeation rate of the impregnating material in the impregnation operation.

Further, the softening point is preferably a high softening point pitch of 150 to 250.degree. Since the higher the softening point of the pitch, the higher the carbonization yield in carbonization,
By using a pitch with a high carbonization yield, the number of densifications can be reduced. A pitch having a softening point of less than 150 ° C. has a low carbonization yield and must be densified 8 to 15 times to obtain a C / C-composite having a predetermined density. Will be expensive. On the other hand, pitch having a softening point of more than 250 ° C. has a high viscosity at the pitch impregnation temperature, and sufficient permeability cannot be obtained.

In order to uniformly impregnate the pitch to the inside of the C / C-composite, it is necessary to select a temperature at which the pitch has a sufficiently low viscosity (0.5 poise or less, according to a flow tester). The impregnation temperature is 100 ° C. higher than the softening point of the pitch. That is, in the present invention, the impregnation temperature is preferably about 250 to 350 ° C., and at this temperature, the pitch is thermally stable and the characteristics do not change due to heat.

After this pitch impregnation treatment, 20
Infusibilization is performed at 0 to 350 ° C. This infusibilization treatment is an oxidation treatment of the impregnated pitch, and by performing this infusibilization treatment, the carbonization yield in the next carbonization treatment increases. If the infusibilization temperature is less than 200 ° C., the oxidation reaction does not proceed sufficiently and the infusibilizing effect is not recognized.

On the other hand, if the infusibilization temperature exceeds 350 ° C.,
The oxidation reaction proceeds too much and adversely affects the properties of the C / C-composite.

In the first embodiment of the present invention, the carbonization treatment is subsequently carried out, but the usual treatment temperature is 800 to 1200.
Perform at ℃. This high softening point pitch impregnation-infusibilization-carbonization treatment can be repeated 2 to 4 times to obtain a C / C-composite having a bulk density of 1.5 g / cm ³ or more.

The method for producing a C / C-composite according to the first aspect of the present invention is a method for producing a C / C-composite having a bulk density of 1.5 g / cm ³ or more, and finally adding 1
It is characterized in that it is graphitized at 500 to 2500 ° C. Here, the reason why the bulk density must be 1.5 g / cm ³ or more is that the low density C / C-composite having a bulk density of less than 1.5 g / cm ³ originally has no strength because it has many pores. Moreover, even if this is treated at 1500 to 2500 ° C., the strength does not appear. Graphitization is 1500-2
500 ° C is preferred. The graphitization provides increased strength and lubricity to the C / C-composite.

The C / C-composite thus obtained has a bulk density of 1.5 to 1.8 g / cm ³ and a bending strength of 10
〜20kg / mm ² , has a compression strength of 8-14kg / mm ² ,
It is an isotropic C / C-composite. The C / C-composite obtained in the first aspect of the present invention has isotropic characteristics, and thus is particularly suitable for application as a brake material.

In the second aspect of the present invention, the heat treatment (carbonization-graphitization treatment) is carried out subsequent to the infusibilization, but it is carried out at a normal treatment temperature of 800 to 3000 ° C.
This high softening point pitch impregnation-infusibilization-800-3000 ° C
The heat treatment of 2 to 4 times is repeated for a total bulk density of 1.5 g /
It is possible to obtain C / C-composites with values of cm ^{3 and} above.

The C / C-composite thus obtained according to the second aspect of the present invention has a bulk density of 1.5 to 1.8.
g / cm ³ , bending strength 15 to 30 kg / mm ² , compression strength 10 to 2
It is an isotropic C / C-composite having a characteristic of 0 kg / mm ² . The C / C-composite obtained in the second aspect of the present invention has isotropic characteristics, and thus is particularly suitable for application as a brake material.

[0031]

【Example】

 The present invention will be specifically described below based on examples.

(Example 1) High-strength type polyacrylonitrile-based carbon fiber (PAN-based, tensile strength 300 kg / m
m ^2, fiber diameter 8 [mu] m, 12K yarn) was cut to a length of 1 m, one fixed and rotating the other of the yarn twisted carbon fiber to obtain a fiber containing an oriented randomly.
300 g of this carbon fiber was impregnated with a phenolic resin to obtain a prepreg. This prepreg is 12 cm x 1
It was placed in a mold of 2 cm × 5 cm (length × width × height), pressure was applied from above to mold, and the resin was cured by holding it at 150 ° C. for 2 hours as it was. The molded body was taken out of the mold and treated at 1000 ° C. in a nitrogen atmosphere at a temperature rising rate of 30 ° C./hr. The obtained primary fired body had a bulk density of 1.25 g / cm ³ ,
The carbon fiber volume content (Vf) was 56%.

Next, tar pitch (softening point 200 ° C., quinoline insoluble matter trace, softening point was measured by a flow tester) was applied to this primary fired body under a pressure of 15 kg / cm ² at 330
After impregnation at 0 ° C, the molded body was held in air at 300 ° C for 2 hours for infusibilization treatment. Subsequently, carbonization treatment was performed in a nitrogen atmosphere at a temperature rising rate of 20 ° C./hr up to 1000 ° C. This high softening point pitch impregnation-infusibilization-carbonization treatment was repeated 3 times in total, and then graphitization treatment was performed at the final 2000 ° C. to obtain a bulk density of 1.58 g / cm ³ and a bending strength of 12 kg / mm ² (pressurizing direction). A C / C-composite was obtained.

The test piece in this characteristic test is 50 × 1.
It is a rectangular parallelepiped of 0 × 1.5 mm (length × width × thickness), and the bulk density was obtained from the dry weight of the test piece and the volume obtained from the dimensions. The bending strength was determined by using the 3-point bending test method, the distance between fulcrums was 40 mm, and the crosshead speed in the autograph was 1 mm / min. Knife edge standard is JISK69
The radius of curvature of the tip of the fulcrum edge is 2 mm, and the radius of curvature of the tip of the pressure wedge is 5 mm. The number of measurement tests is three.

(Example 2) 300 g of the randomly oriented carbon fiber shown in Example 1 was added to 12 cm x 12 cm x 5 cm.
It was put in a sus frame having a size of cm (length × width × height) and tightened from above to obtain a preform. This preform was placed in an impregnation tank, and tar pitch (softening point 80.5 ° C, benzene insoluble content 15.8 wt%, quinoline insoluble content 3.5 wt%) melted at 220 ° C was placed in the impregnation tank under a vacuum of 5 mmHg. It was injected and carbon fibers were impregnated with pitch. Subsequently, under normal pressure, carbon fibers were immersed in pitch in a nitrogen gas atmosphere at a heating rate of 200 ° C./hr to carbonize up to 600 ° C., and further held at this temperature for 1 hour. Next, after taking out the molded body from the impregnation tank, 300 ° C in a nitrogen gas atmosphere.
The temperature was raised to 1000 ° C. at a heating rate of / hr to obtain a primary fired body. The obtained primary fired body has a bulk density of 1.20 g / c.
It was m ^3, Vf52%.

This primary fired body was densified in the same manner as in Example 1 (high softening point pitch impregnation-infusibilization-carbonization treatment), and finally graphitized at 2000 ° C. to give a bulk density of 1.63.
A C / C-composite having g / cm ³ and bending strength of 15 kg / mm ² (pressurizing direction) was obtained. The bending strength of this C / C-composite in the direction perpendicular to the pressing direction was measured. Bending strength in the pressing direction is 15kg / mm ² and bending strength in the vertical direction is 14.5kg / mm ²
It was shown to be isotropic.

(Example 3) Pitch-based carbon fiber of high elasticity type (mesophase pitch-based, tensile elastic modulus 30 t / mm ² ,
Yarn having a fiber diameter of 15 μm and 6K) was cut into a length of 1,5 m, and one of the yarns was fixed and the other was rotated to twist the carbon fibers to obtain randomly oriented carbon fibers. 300 g of this carbon fiber was impregnated with a phenolic resin to obtain a prepreg. This prepreg is 12 cm x
It was placed in a mold of 12 cm × 5 cm (length × width × height), pressure was applied from above to mold, and the resin was cured by keeping it at 150 ° C. for 2 hours. Next, this molded body was taken out of the mold and treated at 1000 ° C. in a nitrogen atmosphere at a temperature rising rate of 50 ° C./hr. The obtained primary fired body had a bulk density of 1.31 g / cm ³ and a carbon fiber volume content (Vf) of 52%.
Met.

Next, this primary fired product was impregnated with petroleum pitch (softening point 210 ° C., quinoline insoluble matter trace) at 350 ° C. under a pressure of 20 kg / cm ² , and then infusibilized at 300 ° C. for 2 hours. Was applied. Subsequently, carbonization treatment was performed in a nitrogen atmosphere at a temperature rising rate of 25 ° C./hr up to 1000 ° C. This high softening point pitch impregnation-infusibilization-carbonization treatment was repeated 3 times in total, and then graphitization treatment was carried out at the final 2200 ° C. to give a bulk density of 1.65.
A C / C-composite having g / cm ³ and bending strength of 18 kg / mm ² (pressurizing direction) was obtained.

(Comparative Example 1) Two-dimensionally oriented fiber diameter 8 μ
A plain woven surface woven fabric of m carbon fiber (PAN type, tensile strength 300 kg / mm ² ) was impregnated with phenol type resin in the same manner as in Example 1 to obtain a prepreg. 20 sheets of this prepreg were laminated and subjected to autoclave molding. As a result of treating this molded body at 1000 ° C. at a temperature rising rate of 30 ° C./hr, peeling occurred between layers and a good product was not obtained.

Comparative Example 2 A C / C-composite was produced under the same conditions as in Example 1, except that the tar pitch, which is the impregnating material in the densification treatment, was changed. Tar pitch of quinoline insoluble matter trace was used as the impregnating material. The obtained C / C-composite had a low bulk density of 1.32 g / cm ³ and a bending strength of 2.5 kg / mm ² .

Example 4 High-strength type polyacrylonitrile-based carbon fiber (PAN-based, tensile strength 300 kg / m
m ^2, fiber diameter 8 [mu] m, 12K yarn) was cut to a length of 1 m, one fixed and rotating the other of the yarn twisted carbon fiber to obtain a fiber containing an oriented randomly.
50 g of this 3 g length chopped fiber (pitch type, tensile strength 100 kg / mm ² , fiber diameter 12 μm) is added to 250 g of this fiber.
g was added and mixed to obtain a filler. This filler was impregnated with a phenolic resin to obtain a prepreg. This prepreg is 12 cm x 12 cm x 5 cm (length x width x
(Height), and the resin was cured by keeping it at 150 ° C. for 2 hours. The molded body was taken out of the mold and treated at 1000 ° C. in a nitrogen atmosphere at a temperature rising rate of 30 ° C./hr. The obtained primary fired body had a bulk density of 1.29 g / cm ³ and a carbon fiber volume content (Vf).
It was 55%.

Then, the primary fired body was impregnated with tar pitch (softening point 200 ° C., quinoline insoluble matter trace, softening point was measured by flow tester) at 330 ° C. under a pressure of 18 kg / cm ² , and The molded body was held in air at 300 ° C. for 2 hours for infusibilization treatment. 2 in a nitrogen atmosphere
The carbonization-graphitization treatment was performed up to 2000 ° C. at a heating rate of 0 ° C./hr. This high softening point pitch impregnation-insolubilization-carbonization-graphitization treatment was repeated a total of 3 times to obtain a bulk density of 1.63 g / cm ³ ,
A C / C-composite having a bending strength of 21.0 kg / mm ² (pressurizing direction) was obtained.

The test piece in this characteristic test is 50 × 10.
It is a rectangular parallelepiped of x 1.5 mm (length x width x thickness), and the bulk density was obtained from the dry weight of the test piece and the volume obtained from the dimensions. The bending strength was determined by using the 3-point bending test method, the distance between fulcrums was 40 mm, and the crosshead speed in the autograph was 1 mm / min. Knife edge standard is JISK691
The radius of curvature of the tip of the fulcrum edge is 2
mm, the radius of curvature of the tip of the pressure wedge is 5 mm. The number of measurement tests is three.

(Example 5) 300 g of mixed carbon fibers of randomly oriented fibers and chopped fibers shown in Example 4
S of 12 cm x 12 cm x 5 cm (length x width x height)
It was put in a us-made frame and tightened from above to obtain a preform. This preform was placed in an impregnation tank and tar pitch (softening point 82.8 ° C, benzene insoluble matter 16.5 wt%, quinoline insoluble matter trace) melted at 220 ° C was 6 mmHg.
Was injected into the impregnation tank under vacuum to impregnate the carbon fibers with pitch. Subsequently, the temperature rise rate 220 under normal pressure.
The carbon fiber was carbonized to 600 ° C. while being immersed in the pitch in a nitrogen gas atmosphere at a temperature of ° C./hr, and further maintained at this temperature for 1 hour. Next, after taking out the molded body from the impregnation tank, the temperature was raised to 1000 ° C. at a temperature rising rate of 300 ° C./hr in a nitrogen gas atmosphere to obtain a primary fired body. The obtained primary fired body had a bulk density of 1.25 g / cm ³ and a carbon fiber volume content (Vf) of 53.
%Met.

This primary fired body was densified in the same manner as in Example 4 (high softening point pitch impregnation-infusibilization-carbonization-graphitization treatment) to give a bulk density of 1.65 g / cm ³ and a bending strength of 19.0 kg.
A C / C-composite of / mm ² (pressurizing direction) was obtained. The bending strength of this C / C-composite in the direction perpendicular to the pressing direction was measured. Bending strength of the pressure direction was shown to vertical bending strength 19.0 kg / mm ² is 18.5 kg / mm ² becomes isotropic.

(Example 6) Pitch-based carbon fiber of high elasticity type (mesophase pitch-based, tensile elastic modulus 40 t / mm ² ,
A yarn having a fiber diameter of 16 μm and 6K) was cut into a length of 1.7 m, and one of the yarns was fixed and the other was rotated to twist the carbon fibers to obtain randomly oriented carbon fibers. This carbon fiber (260 g) has a length of 200 μm milled fiber (pitch type, tensile strength 100 kg / mm ² , fiber diameter 12 μm
m) 40 g was mixed to obtain a reinforcing fiber. The mixed fiber was impregnated with a phenolic resin to obtain a prepreg. This prepreg is 12 cm x 12 cm x 5 cm (length x width x
(Height), and pressure was applied from above to mold, and the resin was cured by holding the pressure at 150 ° C. for 2 hours. Next, this molded body was taken out from the mold and treated at 1000 ° C. in a nitrogen atmosphere at a temperature rising rate of 100 ° C./hr. The obtained primary fired body had a bulk density of 1.33 g / cm ³ and a carbon fiber volume content (Vf) of 53%.

Next, this primary fired body was impregnated with petroleum pitch (softening point 210 ° C., quinoline insoluble matter trace) at 350 ° C. under a pressure of 20 kg / cm ² , and then infusibilized at 300 ° C. for 2 hours. Was applied.

Subsequently, carbonization was performed up to 1000 ° C. at a temperature rising rate of 25 ° C./hr in a nitrogen atmosphere. This high softening point pitch impregnation-infusibilization-carbonization treatment was repeated 3 times in total, and then graphitized at the final temperature of 2200 ° C. to give a bulk density of 1.75 g / c
A C / C-composite having m ³ and a bending strength of 22 kg / mm ² (pressurizing direction) was obtained.

Comparative Example 3 Two-dimensionally oriented fiber diameter 7 μm
A plain woven surface woven fabric of m carbon fiber (PAN type, tensile strength 360 kg / mm ² ) was impregnated with phenol resin in the same manner as in Example 4 to obtain a prepreg. 30 sheets of this prepreg were laminated and subjected to autoclave molding. As a result of subjecting this molded body to 1000 ° C. at a temperature rising rate of 40 ° C./hr, peeling occurred between layers, and a good product was not obtained.

Comparative Example 4 A C / C-composite was produced under exactly the same conditions as in Example 4, except that the tar pitch as the impregnating material in the densification treatment was changed. As the impregnating material, tar pitch having a softening point of 93 ° C. and quinoline insoluble matter trace was used. The obtained C / C-composite had a low bulk density of 1.35 g / cm ³ and a bending strength of 6.5 kg / mm ² .

Comparative Example 5 A C / C-composite was produced under exactly the same conditions as in Example 4, except that chopped fibers were not added and only randomly oriented fibers were used as reinforcing fibers. The obtained C / C-composite had a low bulk density of 1.45 g / cm ³ and a bending strength of 9.5 kg / mm ² .

[0052]

Since the present invention is constituted as described above, according to the present invention, a carbon fiber yarn as a filler is twisted and randomly oriented, or the carbon fiber, chopped fiber and milled fiber. By using the mixed fiber of (3), a high-strength, isotropic C / C-composite can be obtained by a simple process with good productivity and at low cost, so that the industrial effect of the present invention is very large.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of fibers in which a carbon fiber yarn used in the present invention is twisted and randomly oriented (radial branch shape).

FIG. 2 is a schematic view showing another example of fibers in which carbon fiber yarns used in the present invention are twisted and randomly oriented (radial branch shape).

FIG. 3 is a schematic view showing an example of fibers in which carbon fiber yarns used in the present invention are twisted and randomly oriented (nodular aggregate).

FIG. 4 is a schematic view showing an example of fibers in which carbon fiber yarns used in the present invention are twisted and randomly oriented (double-twisted fiber bundle).

[Explanation of symbols]

 1 carbon fiber 2 carbon fiber yarn 3 double-twisted fiber bundle

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location // B29B 11/16 7722-4F 15/08 7722-4F (72) Inventor Masaru Sato Chiba 1 Kawasaki-cho, Chiba City, Technical Research Division, Kawasaki Steel Co., Ltd. (72) Inventor Noriyoshi Fukuda, 1 Kawasaki-machi, Chiba City, Chiba Prefecture Technical Research Division, Kawasaki Steel Co., Ltd. (72) Inventor, Takeshi Uchika Chiba, Chiba Prefecture Ichikawasaki-cho 1 Kawasaki Steel Co., Ltd. Technical Research Division (72) Inventor Hirotoshi Nakayama 1 Kawasaki-cho, Kakamigahara-shi, Gifu Prefecture Kawasaki Heavy Industries, Ltd. Gifu factory (72) Inventor Mamoru Imuta Kawasaki-cho, Kagamihara-shi, Gifu Prefecture No. 1 Kawasaki Heavy Industries, Ltd. Gifu Factory (72) Inventor Akihito Sakai No. 1 Kawasaki-cho, Kakamigahara City, Gifu Prefecture Kawasaki Heavy Industries Ltd. Gifu Factory (72) Invention Mid-Hiroshi Tani Gifu Prefecture Kakamigahara Kawasaki-cho, address 1 Kawasaki Heavy Industries, Ltd., Gifu in the factory

Claims (2)

[Claims] 1. A carbon fiber yarn is twisted and randomly oriented, and this fiber is impregnated with a thermosetting resin and / or a thermoplastic resin to prepare a prepreg, which is molded and then carbonized to be fired. The calcined body has a softening point of 150 to 2 which is substantially free of quinoline insoluble matter.
It is impregnated with a high softening point pitch of 50 ° C., subsequently infusible at 200 to 350 ° C. in air, and then 8 in an inert atmosphere.
Carbonization treatment is carried out at 00 to 1200 ° C., and further impregnation of the high softening point pitch, infusibilization and carbonization treatment are repeated until the bulk density becomes 1.5 g / cm ³ or more, and finally 1500
A method for producing a general-purpose carbon fiber reinforced carbon material, characterized by performing graphitization at 2,500 ° C. 2. A carbon fiber yarn is twisted and randomly oriented, and chopped fibers and / or milled fibers are mixed with the fibers to form reinforcing fibers, and the reinforcing fibers are thermosetting resins and / or thermoplastic resins. To form a prepreg, which is then carbonized to obtain a fired body, and the fired body is impregnated with a high softening point pitch having a softening point of substantially 150 to 250 ° C. which does not substantially contain quinoline insoluble matter. Then, after infusibilizing in air at 200 to 350 ° C., heat treatment is performed at 800 to 3000 ° C. in an inert atmosphere, and further, the high softening point pitch is adjusted until the bulk density becomes 1.5 g / cm ³ or more. A method for producing a general-purpose carbon fiber reinforced carbon material, which comprises repeating impregnation, infusibilization and heat treatment.