JPH03247565A - Production of carbon fiber-reinforced carbon material - Google Patents

Abstract

PURPOSE:To obtain the carbon-carbon composite material having high density and strength by impregnating the carbon fiber with a dispersion of a specified thermosetting resin, carbon powder and mesophase pitch powder in furfural or furfuryl alcohol, molding the fiber under pressure and burning the formed body. CONSTITUTION:The carbon fiber heat-treated at >=500 deg.C is impregnated with a dispersion of the soln. of a phenolic resin having tackiness or fluidity at ordinary temp., a furan resin or their mixture in furfural, furfuryl alcohol or their mixture as the solvent, carbon powder and mesophase pitch powder. The solvent is volatilized, the obtained carbon fiber contg. the precursor of base material is molded under pressure, and the formed body is burned under pressure to produce the desired carbon material. Graphite and/or coke are used for the carbon powder. Crude coke is excellently bonded to mesophase pitch, and consequently preferably used for the carbon powder.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention involves molding and firing carbon fiber containing mesophase pitch powder and carbon powder coated with a thermosetting resin that exhibits fluidity or stickiness at room temperature. The present invention relates to a method for producing a carbon fiber reinforced carbon material (carbon-carbon composite material).

[Prior art and problems to be solved] Carbon-carbon composite materials are lightweight materials with excellent heat resistance and thermal shock resistance.
It is extremely useful for heat-resistant sliding materials for aerospace equipment, nuclear fusion reactors, etc., high-temperature insulation materials, etc. Conventionally, such carbon-carbon composite materials include phenol resin,
A base material precursor impregnation method in which a carbon fiber molded body impregnated with a thermosetting resin such as furan resin or pitch is fired, carbonized and graphitized, and the impregnation and firing operations are repeated, and fibers of carbon fiber aggregates are used. A common method is to fill the gap with carbon by chemical vapor deposition using hydrocarbon or the like. However, these methods require many days to manufacture carbon-carbon composites.

Therefore, as an alternative to the matrix precursor impregnation method described above, a carbon fiber intermediate material containing a matrix precursor with a higher carbonization yield and sintering ability (base material precursor-containing carbon fiber) is laminated and formed. A method has been proposed for producing a relatively high quality carbon-charcoal S composite material by carrying out carbonization and then firing, without repeating the impregnation and carbonization treatment of the base material precursor. In this technology, carbon powder such as coke or graphite and mesophase pitch powder are mixed or contained in carbon fibers, laminated and formed, and then fired (Japanese Patent Laid-Open Nos. 62-148366 and 63-40764). , 63-
112463) 0 However, in these methods, carbon powder and pitch powder are simply mixed or laminated into basic fibers and pressure molded, or carbon powder, pitch powder, and carbon fiber are mixed into a sleeve of thermoplastic resin. Because the shape of the powder is laminated and pressure-molded and then fired and carbonized, the powder particles tend to move during the molding operation, and as a result,
It is difficult to manufacture a carbon-carbon composite material in which the base material is uniformly present in all the carbon fiber gaps, and there have been problems such as difficulty in obtaining a composite material with sufficiently high strength. Furthermore, since the sleeve is made of thermoplastic resin, it decomposes in the early stages of firing, generating a large amount of gas, and complicating the molding and firing steps.

[Means to solve the problem]

As an intermediate material for obtaining high-quality carbon-carbon composites with higher strength, a matrix precursor powder with high carbonization yield and carbonization bonding properties is present in all parts between carbon fibers and is uniformly distributed. It is desirable that the precursor powder adheres to the carbon fibers and that the distribution is not biased when handling the intermediate material. In order to attach carbon powder to carbon fibers, it is desirable to coat carbon powder particles with a sticky carbonizable substance. Suitable materials include thermosetting resin initial reaction products, that is, thermosetting resins that are tacky or fluid at room temperature.

Further, in order to uniformly incorporate carbon powder into carbon fibers, a method using a dispersion liquid of carbon powder may be considered. In this case, it is necessary to use a solvent that dissolves the thermosetting resin initial reactant but does not dissolve the pitch powder at all, and that thoroughly wets and disperses the carbon powder, pitch powder, and carbon fibers. However, although the solvents conventionally used in such cases are methanol, ethanol, etc., these solvents do not fully satisfy the Kamikita condition.

As a result of intensive studies from the above viewpoint, the present inventors found that furfural, furfuryl alcohol, or a mixture thereof is a solvent that satisfies the above conditions. By coating pitch powder with a thermosetting resin that is fluid or sticky at room temperature and incorporating this into carbon fiber, an intermediate material with good handling properties can be obtained, and this intermediate material is molded and then A carbon-carbon composite material exhibiting high density and high strength can be obtained by firing, and furthermore, this intermediate material is a solution in which a fluid thermosetting resin is dissolved in furfural, furfuryl alcohol, or a mixture thereof. The present inventors have discovered that carbon fibers can be obtained by dispersing mesophase pitch powder, impregnating carbon fibers with the resulting dispersion, and drying the resulting dispersion, leading to the present invention. That is, the present invention obtains carbon fibers impregnated with carbon powder coated with phenol, furan, or a mixture thereof, which is fluid or viscous at room temperature, and mesophase pitch powder as a base material precursor, and then molded and fired to produce high quality carbon.
This is a method for manufacturing carbon composite materials.

The present invention will be explained in detail below.

The carbon fibers used in the present invention are PAN-based, mesophase pitch-based, isotropic pitch-based, and all other types that are generally called carbon fibers. However, a heat treatment temperature of 500° C. or higher is used. Fibers treated at lower heat treatment temperatures may be brittle and generate a large amount of decomposition gas during firing, making them unsuitable as reinforcing materials. The single fiber diameter is generally 5 to 15 μm, but those thinner or thicker than this can also be used. The shape is, for example, 1.000~
It is an aggregate of 30,000 single fibers. This includes, for example, thread or tow. Also,
Staple carbon fibers may also be used. Carbon fibers are generally sized, but in this case it is desirable to remove this before use.

Graphite and/or coke may be used as the carbon powder. Natural graphite powder from which ash has been removed can be used as graphite, but coke may be mixed with coke by a known method, for example,
Artificial graphite powder obtained by graphitization heat treatment at a temperature of ~3,000°C is preferred. Coke is petroleum-based and coal-based.
It is obtained by heat treatment at a temperature of 50°C or higher. Therefore, this also includes raw coke. Further, the coke includes raw coke and deflagration coke further heat-treated. Raw coke is particularly preferred as carbon powder because it has good carbonization bonding properties with mesophase pitch.

The average particle size of the carbon powder is preferably 1-15 μm. The mesophase pitch used is one that has an optically anisotropic phase of 98% or more or substantially 100% and exhibits softening properties or fluidity when pressed during heating. Softening point is 270
The temperature is preferably 430°C or higher, for example, 430°C.

Such pitch has a high carbonization yield and is highly useful as a binder for carbon powder and carbon fibers.

Mesophase pitch can be produced by a known method of heat treating various petroleum-based, coal-based heavy oils or pitch at a temperature of 300 to 500°C. Further, compound pitch can be produced by heat treatment of an aromatic compound having a main structure of a condensed benzene ring such as naphthalene, anthracene, phenanthrene, or the like, or by heat treatment in the presence of a catalyst. The production of these pitches involves distillation, vacuum degassing, and
Removal of low molecular weight substances by heating ventilation etc., solvent extraction treatment,
A separation and removal process of isotropic phase pitch such as sedimentation separation can be added. Pitch is used in powder form, and its average particle size is preferably 1 to 30 μm, more preferably 2 to 15 μm. It is desirable that the volatile content is 30% or less, and 2
More preferably, it is 5% or less. Note that the volatile content referred to here is the weight loss rate when the temperature is raised from 100°C to 1000°C in an inert atmosphere at 20°C per minute.

As the thermosetting resin that exhibits fluidity or adhesiveness at room temperature, a phenol resin, a furan resin, or a mixture thereof is used. For example, as a phenolic resin,
A phenolic resin initial reaction product is used. This includes resol type resins obtained by the reaction of phenols and aldehydes in the presence of an alkali catalyst. Further, a novolac type solid powder or liquid resin produced by the reaction of phenols and aldehydes under an acidic catalyst can be mixed into and dissolved in the resol type fluid resin. In this case, hardening agents such as hexamethylenetetramine can be added. As raw material phenols, for example, phenol, resorcinol, cresol, xylenol, etc. can be used, and as aldehydes, for example, formalin, putty formaldehyde, furfural, etc. can be used. Also, mixtures thereof may be used. Commercially available products can be used as such phenol resins. As the furan resin, a condensate of furfuryl alcohol or a co-condensate of furfuryl alcohol and furfural can be used. These are made by adding an acidic catalyst to furfuryl alcohol or a mixture of furfuryl alcohol and furfural, heating it to a suitable viscosity, and then cooling it. Furthermore, the catalyst activity can be eliminated by volatilization, neutralization, or other methods before use. Commercially available products can also be used as the furan resin. It is also possible to use a phenol-furan resin which is a mixture of a phenolic resin initial reaction product and a furan resin initial reaction product.

In manufacturing the intermediate material, the thermosetting resin is dissolved in the solvent to a predetermined concentration. In the case of phenol-furan resin, it is also possible to adopt a method in which the phenol resin and furan resin are dissolved at the same time.

Carbon powder and mesophase pitch powder are dispersed in the obtained solution. There are no particular limitations on the procedures for adding and mixing the solvent, resin, and powder. For dispersion, shaking or ultrasonic dispersion can also be applied. These operations are also effective for sufficiently mixing the carbon powder and mesophase pitch powder.

The optimum mixing ratio of carbon powder, mesophase pitch powder, and thermosetting resin varies depending on the average particle diameter of carbon powder and mesophase pitch powder, carbonization yield, viscosity of dispersion, etc., but is 20 to 60.60 to 20, respectively. .30 to 10 parts by weight is preferred. If the resin is less than 10 parts by weight, adhesion of carbon powder and mesophase pitch powder to carbon fibers will be insufficient, and if it is more than 30 parts by weight, the carbonization yield of the base material will decrease.

Furthermore, if the mesophase pitch is less than 20 parts by weight, the sintering ability of the base material will be reduced, and if it is more than 60 parts by weight, the mixing ratio of resin and carbon powder will be excessively low. The carbon powder is preferably mixed in an amount of 60 to 20 parts by weight in order to increase the carbonization yield. Also,
The ratio of the solvent to 100 parts by weight of the base material precursor is, for example, 50 to 250 parts by weight.

Next, carbon fibers are impregnated with the above dispersion. in this case,
Continuous carbon fiber yarn, tow or multiple strands thereof,
Alternatively, it is convenient to immerse an aggregate of staple carbon fibers in a dispersion liquid. Since the solvent used in the present invention wets the carbon fibers well, the fibers can be opened well in the dispersion.

Ultrasound can also be used to make impregnation easier. Furthermore, it is also possible to use a method in which the carbon fibers to which the dispersion liquid is attached are moved along the outer periphery of a roller so as to open the fibers.

The carbon fibers impregnated with the dispersion liquid are taken out from the dispersion liquid tank, and then passed through a slit whose width and gap (thickness) are adjusted in advance to adjust the amount of impregnation into the carbon fibers. The impregnated carbon fibers taken out are heated below the curing temperature of the thermosetting resin or heated under reduced pressure in order to volatilize the solvent.

The heating temperature is 70℃ or less for phenolic resin, 60℃ or less for furan resin, and 60℃ or less for a mixture thereof.
It is desirable that the temperature is below 0°C. The upper limit of the drying temperature may vary depending on the amount of catalyst in the thermosetting resin or its presence or absence.

In carbon fibers incorporating an intermediate material, i.e., a matrix precursor consisting of carbon powder, mesophase pitch powder, and thermosetting resin, the amount of matrix precursor based on 100 parts by weight of carbon fiber is determined to achieve the expected carbon-carbon composite. The amount varies depending on the carbon fiber content of the material, the heat treatment temperature of the carbon fibers, the heat treatment temperature of the carbon powder, the distribution ratio of the constituent components of the base material end member, and others, but is, for example, 70 to 270 parts by weight.

The obtained intermediate material is accumulated, pressurized, heat-formed, then fired, carbonized, and optionally graphitized.

In molding, the resin is heated to its curing temperature under pressure. The temperature is 80 to 200 for phenolic resin.
In the case of furan resin, the temperature is preferably 70 to 160°C, but is not limited to this temperature range. Heating is performed by raising the temperature stepwise or continuously. The pressurization at this time is 1 to 300 kg f/ci! is preferable,
More preferably 2 to 150 kgf/cd. If the pressure is too high, the carbon fibers are likely to be damaged. Generally, heat forming is 1
It is carried out from 0 minutes to 10 hours. It may be heated for an even longer period of time.

During firing, the temperature range is from the temperature at which mesophase pitch softens and flows to the temperature at which thermal decomposition progresses significantly, e.g.
Pressure is applied at a temperature of 50°C, in particular between 350 and 600°C. In this process, the voids between the carbon fibers and the carbon powder are filled with pitch, the filled pitch is turned into coke, and the carbon fibers and the carbon powder are bonded together, and appropriate pressure is required. The pressure is preferably 20-1500
kgf/CI [l, more preferably 50 to 800 kg
f/cm. The temperature increase rate during firing is desirably slowed down as the size and thickness of the molded body increases, and it is particularly desirable to slow down the rate of temperature rise during firing in a temperature range where thermal decomposition or carbonization of the resin and pitch progresses significantly. The temperature increase rate in the range of 400 to 600°C is preferably 5°C or less, and 40°C or less, for example.
The average temperature in the range of 0 to 600°C is 0.5 to b. It is also possible to make it slower or faster depending on the convenience of pressurization or the firing temperature.

At 600° C. or higher, the heating rate can be increased along with the firing temperature. Pressure heating can also be performed by making a firing process follow the molding process of the resin curing process. Furthermore, the molded body can also be fired under isostatic pressure. The molded body fired under pressure is further heated in an inert atmosphere to a high temperature, for example to a temperature between 800°C and 3000°C.

〔Effect of the invention〕

In the base material precursor material of the present invention, individual particles of carbon powder and mesophase pitch powder that have been sufficiently mixed are coated with a viscous resin, and the viscous resin is coated on the carbon fiber surface or anywhere between the carbon fibers. Adhesive, distributed,
Easy to handle during molding. Furthermore, according to the present invention, when pressurizing and heating in the pitch softening temperature range,
In addition to the fact that pitch can sufficiently fill the gap between carbon fiber and carbon powder, the carbonization yield of carbon powder and mesophase pitch powder is high, and the carbonization yield of resin is also relatively high. It has the advantage that a high-quality carbon-carbon composite material can be produced in a relatively short period of time without repeating the impregnation and sintering steps by sintering and carbonizing the molded body under appropriate pressure.

(Example) The present invention will be described in detail below, but this is not intended to limit the technical scope of the present invention.

Example 1 35.53 parts by weight of each of petroleum-based sintered coke powder (average particle size 4.8 μm) and petroleum-based 100% mesophase pitch powder (average particle size 5.1 m) were mixed with 12 parts by weight of resol-based phenol. The resin liquid was added to a solution of 100 parts by weight of furfuryl alcohol and dispersed. Fifty PAN-based high-strength type 6,000 filament carbon fiber yarns were immersed in this dispersion and pulled up to form a sheet with a uniform thickness.

This was dried at 60° C. under reduced pressure to obtain a unidirectionally reinforced intermediate material having a thickness of 0.4 mrn, a width of 13 mrn, and an impregnated amount of 49% by weight in the tip member of the base material. The obtained intermediate material was heated at 90°C for 1 hour, then cut, stacked in a mold with a circular bottom surface of 50 m in diameter, and heated from 100°C to 13° C. under a surface pressure of 1 kg/cm2.
The mixture was heated to 0°C for 30 minutes at 10°C increments. Then 20
20°C every 10°C under a surface pressure of 30 kg/cffI up to 0°C.
It was heated for a minute. Thereafter, the temperature was raised to 350°C at a rate of 1°C per minute under a surface pressure of 45 kg/cut, and then the temperature was increased to 300°C to 600°C.
The temperature was raised at 1° C. per minute under a surface pressure of kg/crl. The compact was released from the mold and heated from 600°C to 1000°C at 2°C per minute in coke powder in an argon stream, and then at 3°C per minute.
was heated to 1200°C. Bulk density 1.79 g/
cn (, bending strength 84 kg/+nm2, thickness 3.1
A wholesale unidirectionally reinforced carbon-carbon composite was obtained.

Example 2 23 parts by weight of petroleum-based smoked coke powder with an average particle size of 5.1 μm and 23 parts by weight of petroleum-based smoked coke powder with an average particle size of 5.1 μm were added to a solution in which 6 parts by weight of resol type resin liquid and 9 parts by weight of furan resin liquid were dissolved in 114 parts by weight of furfural. 14 parts by weight of petroleum-based artificial graphite powder of .4 μm and 49 parts by weight of petroleum-based 100% mesophase pitch powder having an average particle size of 4.9 μm were dispersed. Ten 3,000 filament threads of petroleum-based high modulus continuous carbon fiber were dipped in this to impregnate it. The impregnated carbon fibers formed into a tape were dried at 55° C. under reduced pressure. A disk with a diameter of 50 mm was cut from the obtained unidirectionally reinforced intermediate material tape. This is 80
℃, 90℃, and 100℃ for 30 minutes each, 40 layers were laminated in a mold with the same dimensions as used in Example 1, and 3
1 from 100℃ to 200℃ under surface pressure of kg/cM
Heating was performed for 20 minutes at each 0°C, and for 30 minutes at each 20°C up to 360°C. Then, the temperature was raised to 600°C at a rate of 2°C per minute under a surface pressure of 400 kg/cut. The molded product released from the mold was heated at 1200°C at a rate of 3°C per minute in an argon stream.
Heated to ℃. Bulk density 1.77 g/ca! A carbon-carbon composite material having a bending strength of 79 kg/2 and a thickness of 2.8 mm was obtained.

Example 3 61 parts by weight of petroleum-based raw coke powder (average particle size 4.9 μm), 100% Tsume phase pitch powder (average particle size 3.5
(μm) and 14 parts by weight of the furan resin liquid were dispersed in 98 parts by weight of a furfural-furfuryl alcohol mixed solvent. The obtained dispersion was coated with PAN-based high modulus carbon fiber 1.
Five 2.000 filament threads were impregnated and dried. The obtained intermediate material sheet was fired to 1200°C under the same conditions as in Example 1, and then heated to 2000°C in Alcon.
heated to. High quality carbon-carbon composite discs were obtained.

Claims (7)

[Claims] (1) In a solvent of furfural, furfuryl alcohol, or a mixture thereof, a phenolic resin, furan resin, or a mixture thereof, which is sticky or fluid at room temperature, is dissolved, and carbon powder and mesophase pitch powder are dispersed. The dispersion liquid is impregnated into carbon fibers heated at a heat treatment temperature of 500° C. or higher, the solvent is volatilized, and the carbon fibers containing the base material precursor thus obtained are then molded under pressure, and the molded body is molded under pressure. A method for producing a carbon fiber-reinforced carbon material, which comprises firing. (2) The manufacturing method according to claim (1), wherein the carbon powder is one, two or three of raw coke, coke and graphite powder. (3) The manufacturing method according to claim (1) or (2), wherein the mesophase pitch powder has a volatile content of 25% or less. (4) In carbon fiber containing matrix precursor material, carbon powder, mesophase pitch powder, and resin each contain 20 to 60%
The manufacturing method according to any one of claims (1) to (3), wherein the amount is 60 to 20 parts by weight, or 30 to 10 parts by weight. (5) When molding under pressure is performed at a temperature within the curing progress temperature range of the resin below the softening point of mesophase pitch, 2 to 15
Claims (1)-(
4) The manufacturing method according to any one of 4). (6) The manufacturing method according to any one of claims (1) to (4), wherein the firing under pressure is performed at a temperature between 450 and 650°C and under a pressure of 50 to 800 kgf/cm^2. (7) Claim (1) in which the firing under pressure is performed under isostatic pressure.
The manufacturing method according to any one of -(6).