JP2000169250A - Method for producing carbon fiber reinforced carbon composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a CC material having high-density and high-strength material properties by efficiently depositing and filling pyrolytic carbon into voids of the CC material and performing densification. SOLUTION: A carbon composite is impregnated with a matrix binder to form a composite, and a CC composite obtained by calcining and carbonizing in a non-oxidizing atmosphere is used as a base material.
First densification treatment in which pyrolytic carbon is deposited and filled in 75 to 90% of the pore volume of the substrate having a pore diameter of 0.5 to 30 μm by VD or pulse CVI, and then cured by impregnating with a matrix resin liquid to obtain a non-oxidizing atmosphere Firing and carbonization under the base material pore diameter 10 ~
A second densification treatment filling 60 to 70% of the pore volume of 300, and furthermore, pyrolytic carbon is deposited and deposited by vacuum CVD or pulse CVI to 80 to 95% of the pore volume of 0.5 to 30 μm of the pore diameter of the substrate. The third densification treatment is sequentially performed, and when performing the low pressure CVD or the pulse CVI in the first densification treatment and the third densification treatment, the CC substrate is subjected to a low pressure CVD or a pulse CVI reaction apparatus. A method for producing a CC material, wherein the material is set with an interval of 1 to 5 mm between the table and the table.

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 carbon fiber reinforced carbon composite material (hereinafter, also referred to as "CC material") having a dense material structure and having a high-density and high-strength material property.

[0002]

2. Description of the Related Art CC materials have excellent specific strength and specific elastic modulus due to the composite of carbon fibers, and also have the lightweight properties unique to carbon materials, and excellent heat resistance and chemical stability. -It is useful in application fields used under severe conditions at high temperatures, such as structural materials for spacecraft, dies for hot pressing, and members for high-temperature furnaces. Typical technologies for manufacturing this CC material include: (1) Laminating a carbon fiber woven fabric impregnated with a matrix binder, compressing it into a predetermined shape by pressing, etc., and then pressing the prepreg molded body in a non-oxidizing atmosphere. (2) A method of forming a carbon fiber tow immersed in a matrix binder into a predetermined shape by a filament winding method, and similarly performing a calcination treatment of the prepreg molded body. C in preform organization
Methods of depositing carbon using VD (chemical vapor deposition) are known.

In order to obtain a large CC material,
The method (1) is the most practical as an industrial means. However, when using the method (1), a considerable amount of matrix binder is pressed out during compression molding,
In the process of firing and carbonizing the prepreg molded body, a phenomenon such as the volatilization of volatile components contained in the matrix binder occurs, so that the material structure of the obtained CC material tends to have a low density and a low strength. Therefore, a secondary densification treatment is generally performed in which a binder resin such as a carbonizable phenol resin or a furan resin or a coal-based or petroleum-based pitch is forcibly impregnated into the voids of the material structure of the CC material and then fired. .

For example, JP-A-2-283666 discloses that pitch-based carbon fibers oriented two-dimensionally or three-dimensionally are impregnated with coal tar pitch and / or petroleum-based pitch, and then carbonized in the impregnated state. And then graphitize the treated material at 2000 to 3000 ° C.
Next, as a densification treatment, the graphitized material is impregnated with a coal tar pitch and / or a petroleum pitch substantially free of a quinoline-insoluble component at a softening point of 150 to 250 ° C., followed by a carbonization-graphitization treatment. A method for producing a CC material in which the application step is repeated until a desired density is obtained is disclosed in
No. 139832 discloses that a mixture with a thermosetting resin containing 10 to 60% by weight of an optically isotropic coal tar pitch having a softening point of 200 to 300 ° C. is impregnated into carbon fibers to prepare a prepreg, which is then molded. The primary fired body obtained by performing the carbonization treatment is impregnated with a high softening point pitch having a softening point substantially containing no quinoline insolubles and having a softening point of 150 to 250 ° C,
A method for producing a carbon material has been proposed in which a process of infusing at 200 to 350 ° C. in air and then performing a carbonization-graphitization treatment in an inert atmosphere is repeated until the bulk density becomes 1.6 g / cc or more. ing.

[0005] The applicant of the present invention uses carbon fibers having a residual carbon ratio of 45%.
After the composite molding with the matrix binder composed of the above thermosetting resin liquid, 1400 to 1
A carbonization treatment is performed in a temperature range of 700 ° C. to form a primary fired body having a porosity of 1% or less, and the primary fired body is impregnated and cured with a thermosetting resin liquid having a residual carbon ratio of 45% or more, and then a non-oxidizing atmosphere is prepared. A method of producing a CC material which is heat-treated in a temperature range of 2000 ° C. or higher (JP-A-5-229868) has been developed and proposed.

Further, the present applicant has proposed a method for producing a CC material having a high density and excellent strength properties, by impregnating a carbon fiber with a matrix binder, forming a composite, and then calcining and carbonizing in a non-oxidizing atmosphere. The CC composite is used as a base material, and the pitch is impregnated into the CC base material in a non-oxidizing atmosphere at 800 to 1200 ° C.
A first densification step in which the bulk density of the material is adjusted to 1.1 to 1.5 g / cc by repeating the calcining and carbonizing treatment a plurality of times, and then a thermosetting resin liquid is impregnated and cured to obtain a non-oxidizing atmosphere of 800. ~ 1
A method for producing a CC material in which a second densification step in which the bulk density of a material is increased to 1.6 g / cc or more by repeating a process of firing and carbonizing at 200 ° C. a plurality of times (Japanese Patent Laid-Open No. 8-245273) Suggested.

Further, CVD (Chemical Vapor Depositio)
n: Chemical vapor deposition (CVI) and Chemical Vapor Inf
A method has been developed in which carbon is deposited and densified by chemical vapor infiltration (e.g., chemical vapor infiltration method). For example, Japanese Patent Application Laid-Open No. 1-212277 discloses a carbon fiber molded body 10-70.
And a carbonaceous matrix composed of 5 to 80 Vol% and having a porosity of 10 to 55%. C to deposit and coat carbon by gas phase pyrolysis
Japanese Patent Laid-Open Publication No. Hei 8-2976 discloses a method for producing a C material. A mixed gas of methane and hydrogen is applied to a molded body made of carbon fiber at a temperature of 1200 to 1300 ° C. and a total pressure of a mixed gas of methane and hydrogen. 20 to 80 Torr, partial pressure of methane to 10 to 32.5
A method for producing a CC material in which pyrolytic carbon is deposited as a Torr by a gas phase infiltration method is disclosed.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a CVD or C
The method for filling and densifying the pyrolytic carbon deposited in the gas phase by the VI into the voids of the CC material was further studied, and the purpose was to develop the method. It is an object of the present invention to provide a method for producing a high-density, high-strength CC material by well-precipitating and filling and performing a densification treatment.

[0009]

In order to achieve the above object, a method for producing a carbon fiber reinforced carbon composite material according to the present invention comprises: impregnating a carbon fiber with a matrix binder to form a composite; The base material is a CC composite obtained by firing and carbonizing, and pyrolysis carbon is applied to the pores of the base material by vacuum CVD or pulse CVI in the voids of the CC base material, with a pore size of 0.5 to
The first is to deposit and fill 75 to 90% of the pore volume of 30 μm.
Densification treatment, then impregnated with a matrix resin solution, cured, calcined and carbonized in a non-oxidizing atmosphere and having a pore diameter of 10 to 10
A second densification treatment to fill 60 to 70% of the pore volume of 300 μm, and furthermore, pyrolysis carbon is deposited and deposited on the base material by 80 to 95% of the pore volume of 0.5 to 30 μm pore size by low pressure CVD or pulse CVI. The third densification treatment is performed sequentially, and when performing the low-pressure CVD or pulse CVI in the first densification treatment and the third densification treatment, the CC base material is reduced to a base material of the low-pressure CVD or pulse CVI reaction apparatus. It is characterized in that it is set with an interval of 1 to 5 mm between it and the cradle.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The carbon fibers to be used as a reinforcing material in the present invention include polyacrylonitrile, rayon, and the like.
A fibrous body, a felt, a tow or the like in which a woven fabric such as a plain weave, a satin weave, a twill weave or the like manufactured from various materials such as a pitch system is oriented in a one-dimensional or multidimensional direction is used. As the matrix binder, for example, a phenol-based or furan-based thermosetting resin liquid having a residual carbon ratio of 50% by weight or more, a coal-based or petroleum-based pitch, or the like is suitably used.

The carbon fiber is immersed or coated in the matrix binder to impregnate the carbon fiber with the matrix binder, wet the surface sufficiently with the binder, semi-cured to form a prepreg, and then laminated and applied. Press molding to produce a composite molded body. In addition, at the time of this compounding, the fiber volume content (Vf) in the case where the carbon fiber content is CC composite is 5
It is desirable to set in advance to be 0 to 70% from the viewpoint of securing strength.

After the resin component and the like are cured by heating, the composite molded body is calcined and carbonized in a carbonizing furnace maintained in a non-oxidizing atmosphere by a conventional method to obtain a CC composite. Examples of the carbonization furnace include a lead hammer furnace of a type in which carbonization is performed while being covered with a carbonaceous packing material such as coke powder, and an electric furnace in which the inside of the system is held by a non-oxidizing gas such as nitrogen or argon. The calcined carbonization is usually performed at a temperature of 800 ° C. or higher.

According to the present invention, the CC composite thus obtained is used as a substrate, and the CC substrate is 0.1 to 300 μm
And a porosity of 13 to 18%. The method is characterized in that a densification treatment of a first densification treatment, a second densification treatment and a third densification treatment is sequentially performed on the voids of the CC composite base material.

The first densification treatment is mainly performed under reduced pressure CVD (Chemical) in pores having a pore diameter of 0.5 to 30 μm in the voids of the CC base material.
This is a step of depositing and filling pyrolytic carbon by vapor deposition (chemical vapor deposition) or pulse CVI (chemical vapor infiltration).
Reduced pressure CVD is a method of performing a CVD reaction by reducing the pressure in the reaction system to several tens to several mmHg and exhausting a gas present in the voids of the CC base material, and then introducing a raw material gas. This is a method of intermittently repeatedly performing evacuation of the inside, instantaneous introduction of the source gas, and holding and decomposition of the source gas under a short-period depressurization and pressure increase. It is preferable to use easily pyrolyzable hydrocarbon gas such as methane, propane, propylene, and benzene as a raw material gas for depositing carbon by a gas phase thermal decomposition reaction.

In the CVD reaction and the CVI reaction, a CC base material is placed on a base support of a reactor, heated, and the supplied raw material gas is thermally decomposed to deposit carbon. The pyrolysis temperature varies depending on the type of raw material gas, but is generally 900 to
Heat to 1300 ° C to cause a thermal decomposition reaction. During this thermal decomposition, a temperature distribution tends to occur in the CC base material, and in particular, the surface temperature of the CC base tends to be higher than the temperature inside the base material. In such a case, carbon is easily deposited on the surface of the CC base material, and pyrolytic carbon is deposited near the entrance of the void. As a result, pyrolytic carbon is deposited at the entrance of the void before the interior of the void is filled with carbon, and it becomes difficult to efficiently deposit and fill the pyrolytic carbon into the void.

Therefore, in the present invention, the raw material gas is decomposed by low-pressure CVD or pulse CVI, and when the CC base is placed on the base support of the low-pressure CVD or pulse CVI reactor, the CC base and the base are separated. 1 to 5 between the cradle
By setting at intervals of mm, the temperature distribution inside the CC base material is alleviated and the filling speed is improved.
As a result, the temperature difference between the surface and the inside of the CC base material is reduced, the temperature distribution is equalized, the deposition of pyrolytic carbon on the surface of the CC base material can be suppressed, and the heat can be extended deep into the voids. Decomposed carbon can be deposited and filled in a short time. If the distance is less than 1 mm, the temperature distribution cannot be equalized sufficiently. On the other hand, if the distance exceeds 5 mm, the thermal efficiency is reduced and the effect of improving the temperature distribution is not recognized.

The second densification treatment is a treatment in which the matrix resin liquid is impregnated into the CC base material subjected to the first densification treatment, cured, and calcined and carbonized in a non-oxidizing atmosphere. By this treatment, the resin liquid enters the pores of the CC base material having pores of 10 to 300 μm and is carbonized.
μm pores are mainly filled. An initial condensate of a thermosetting resin such as a phenol resin, a furan resin, or an epoxy resin is used for the matrix resin liquid, and the matrix resin liquid can be impregnated by immersion or application in these matrix resin liquids. Impregnation is preferred. For example, the matrix resin liquid is impregnated with pressure at a pressure of 5 to 15 kg / cm ² to the CC base material subjected to the first densification treatment,
Next, after heat curing, the resin component is heated to a temperature of 800 ° C. or higher, preferably 800 to 2000 ° C. in a non-oxidizing atmosphere, and the resin component is calcined and carbonized.

By this second densification treatment, the matrix resin liquid that has not been filled during the first densification treatment and has penetrated into the pores of the voids and the like is carbonized, and the pores are filled and densified. However, the release of condensed water and gas occurs during the heat curing and calcining of the resin component, so that new fine voids are generated.

In the third densification treatment, the fine voids (pores having a pore diameter of 0.5 to 300 μm, having a pore diameter of 0.5 to 300 μm) are used.
(Pores of about 30 .mu.m) is efficiently densified with pyrolytic carbon. The third densification treatment can be performed in the same manner as the first densification treatment, and pyrolysis carbon is deposited and filled in the fine voids by low-pressure CVD or pulse CVI to achieve densification.

In this way, the voids of the CC base material are filled with the pyrolytic carbon, and the material structure becomes dense,
A CC material having high-strength material properties can be manufactured. The CC material thus manufactured can be subjected to a high-purification treatment using a halogen gas, and if necessary, an oxidation-resistant coating can be applied to the surface.

[0021]

Hereinafter, examples of the present invention will be described in comparison with comparative examples.

Example 1 (1) Preparation of CC base material: A polyacrylonitrile-based high-strength high-elasticity type plain woven carbon fiber woven fabric was coated with a phenolic resin precondensate as a matrix binder and sufficiently impregnated for 48 hours. The prepreg sheet was air-dried. This prepreg sheet is laminated and put into a mold, and the temperature is 1
After performing composite molding under the heat and pressure conditions of 10 ° C. and a pressure of 20 kg / cm ² , the resin component was cured by heating to a temperature of 250 ° C. Then, it is transferred into a firing furnace maintained in a nitrogen gas atmosphere, and
It was heated to 1000 ° C. at a rate of temperature rise of 1000 ° C./hr, and kept for 5 hours for calcination. Thus, 100 × 100 × 5
A mm CC substrate was prepared. The obtained CC base material has a carbon fiber volume content (Vf) of 65%, a bulk density of 1.33 g / cc, a porosity of 15.7%, and a pore volume of 0.5 to 30 μm of 19 mm ³ / g.
, And a pore volume of ^{30 to} 300 μm was 99 mm ³ / g.

(2) First densification treatment: The above-described CC is placed on a substrate support in a reaction furnace of a high-frequency induction heating type reduced pressure CVD apparatus.
The substrates were set at intervals of 2 mm. Using propane as a raw material gas, evacuating the system, and setting the furnace pressure to 50 To
The reaction was carried out at a temperature of 1050 ° C. for 20 hours under a reduced pressure of rr to deposit pyrolytic carbon and fill the voids of the C / C substrate. Pyrolytic carbon mainly fills pores of 0.5 to 30 μm, bulk density 1.41 g / cc, porosity 10.6%, 0.5 to 30 μm
The pore volume of 30 μm was 3 mm ³ / g, and the pore volume of 30 to 300 μm was 87 mm ³ / g.

(3) Second densification treatment: The above-mentioned CC base material subjected to the first densification treatment is immersed in a phenol resin precondensate, and the system is pressurized to 8 kg / cm ² at room temperature to obtain phenol. After impregnation with the resin initial condensate, the resin was cured by heating to 250 ° C. Then, it was placed in a firing furnace maintained in a nitrogen gas atmosphere, heated to a temperature of 2000 ° C. at a temperature rising rate of 5 ° C./hr, and held for 5 hours for firing carbonization. The obtained CC composite material has a pore volume of 0.5 to 30 μm of 19 mm ³ / g, 30 to 30 μm.
The pore volume of 0 μm was 28 mm ³ / g.

(4) Third densification treatment: The same treatment as the first densification treatment was performed. That is, a CC base material subjected to the second densification treatment was set at intervals of 2 mm on a base support in a reaction furnace of a high-frequency induction heating type reduced pressure CVD apparatus. Using propane as source gas, furnace pressure 50 Torr, temperature 1
The reaction was performed at 050 ° C. for 40 hours. The obtained CC composite material has a bulk density of 1.75 g / cc, a porosity of 2.5%, and 0.5 to 30 μm.
3m ³ / g pore volume, 30-300μm pore volume 1
It was 1 mm ³ / g.

Examples 2 to 5 and Comparative Examples 1 and 2 Using a CC substrate prepared in the same manner as in Example 1,
When performing the first densification treatment and the third densification treatment, the distance from the substrate pedestal is changed to set it on the substrate pedestal of the reduced pressure CVD reactor, and the densification treatment is performed by changing the thermal decomposition temperature. did.
All the second densification treatments were performed in the same manner as in Example 1.

Comparative Example 3 Using a CC base material prepared in the same manner as in Example 1,
The densification treatment was performed in the same manner as in Example 1 except that the third densification treatment was not performed.

Comparative Example 4 Using a CC substrate prepared in the same manner as in Example 1,
A densification treatment was performed in the same manner as in Example 1 except that the first densification treatment was not performed.

The bulk density, three-point bending strength and porosity of the obtained CC material were measured, and the results are shown in Table 1 in comparison with the first and third densification treatment conditions. Table 2 shows how the pore volume changes due to pore filling. The three-point bending strength is 150 mm in length and 12.5 in width.
mm, 4 mm thick test piece, distance between fulcrums 64 mm, crosshead speed 6 mm / min, other conditions are ASTM D79
Tested according to 0.

[0030]

[Table 1]

[0031]

[Table 2]

From the results shown in Table 1, the CC materials of Examples 1 to 5 manufactured by the manufacturing method of the present invention are compared with the CC materials of Comparative Examples 1 to 4 manufactured by the manufacturing method which deviates from the manufacturing requirements of the present invention. It can be seen that the three-point bending strength is high, the bulk density is high, and the porosity is low. Further, the CC material of Comparative Example 3 in which the third densification treatment was omitted in Example 1 and the CC material of Comparative Example 4 in which the densification treatment was not performed in Example 1 were also set at a distance of 2 mm from the CC base material. Nevertheless, the three-point bending strength and the bulk density are both low. Also, from the results in Table 2, the CC materials of Examples 1 to 5 manufactured by the manufacturing method of the present invention show pores having a pore diameter of 0.5 to 30 μm by the first densification process and the third densification process. Efficiently, and the pore size is 30 to 300 μm by the second densification process.
It turns out that the pores of m are efficiently filled.

[0033]

As described above, according to the present invention, the CC material is subjected to the three-stage densification treatment of the first densification treatment, the second densification treatment, and the third densification treatment under specific conditions. Can be deposited and filled with pyrolytic carbon effectively. Therefore, it is very useful as a method for producing a high-strength, high-density CC material having a dense material structure.

Claims (1)

[Claims] 1. A CC composite obtained by impregnating a carbon fiber with a matrix binder, forming a composite, and calcining and carbonizing in a non-oxidizing atmosphere as a base material.
A first densification treatment in which pyrolytic carbon is deposited and filled in 75 to 90% of the pore volume of the substrate having a pore diameter of 0.5 to 30 μm by VD or pulse CVI, and then cured by impregnating with a matrix resin liquid to obtain a non-oxidized material; Second densification treatment of firing and carbonizing in a neutral atmosphere to fill 60 to 70% of the pore volume of the substrate with a pore diameter of 10 to 300 μm, and further, reduced pressure CVD or pulse CV
I, a third densification treatment in which pyrolytic carbon is deposited and filled in 80 to 95% of the pore volume of the substrate having a pore diameter of 0.5 to 30 μm in order, and the first densification treatment and the third densification Carbon fiber, wherein a CC substrate is set at a distance of 1 to 5 mm between the substrate and a substrate support of a reduced-pressure CVD or pulse CVI reaction apparatus when performing low-pressure CVD or pulse CVI in the chemical treatment. A method for producing a reinforced carbon composite.