JPH03197360A - Production of carbon fiber-reinforced carbon material - Google Patents

Abstract

PURPOSE:To improve uniformity, strength and resistance to oxidation by molding a prepreg comprising carbon fiber having pitches on the surface and subjecting to a carbonizing treatment and an impregnated carbonizing treatment. CONSTITUTION:Pitches having <=100mum granular diameter are suspended in a solution of pitch-adhering agent (e.g. PS) dissolved in a solvent (e.g. benzene) to obtain a suspension. Then, said suspension is adhered on the surface of carbon fiber and dried, thus the solvent is removed to obtain a prepreg. Next, said prepreg is laminated and molded with heating, then a resultant molded material is heated up to 800-1100 deg.C in an inert gas atmosphere at <=100 deg.C/hr temperature rising rate, thus carbonized by holding for about 1hr and impregnated with pitch or a resin capable of carbonizing, carbonized in an inert gas atmosphere at 800-1100 deg.C for about 1hr, and then heat-treated in an inert gas atmosphere at 1200-3000 deg.C for 30-60min, as necessary.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a carbon fiber-reinforced carbon material (hereinafter referred to as C/C composite) using pitch as a matrix-forming raw material.

[Prior Art] C/C composites, which have high specific strength and excellent heat resistance, occupy an important position as materials for aviation, space, and the like.

Conventionally, two methods are known for manufacturing C/C composites.

The first is a mixture of polyacrylonitrile (PAN)-based, pitch-based, or rayon-based carbon fibers and thermosetting resins such as phenol resins and furan resins, which are carbon matrix raw materials, or pitches, and then heated and molded. of,
This is a method in which carbon treatment is performed in an inert gas atmosphere, and if necessary, a cycle of impregnation with resin, pitch, etc., and carbonization treatment is repeated (for example, Japanese Patent Publication No. 62-212262).

The second method involves forming carbon fibers into a rough shape in advance, and then depositing carbon in the gaps between the carbon fibers using a chemical vapor deposition method to obtain a C/C composite.
bon Vol, 6. p397-403゜1968).

Currently, among the above, C/C that matrixes pitches
To manufacture a composite, pitches can be mixed with carbon fibers in their powder form and then put into a mold and press-molded, or the pitches can be heated to over 250°C to melt them and the carbon fibers can be mixed into the mixture. A method is used in which pitches are attached to carbon fibers to form a prepreg by passing the fibers through the fibers, and then the prepreg is placed in a mold and press-molded.

[The problem that the invention aims to solve! ] However, when producing a C/C composite that uses pitch as a matrix, it is difficult to mix the pitch as a powder evenly, and this method can only use a few short fibers. It is difficult to use long fibers or fabrics. Furthermore, in order to heat pitches to melt them and pass carbon fibers therein to make prepregs, a temperature of 250° C. or higher is required, which complicates equipment and safety issues.

In addition, even if pitches are simply suspended in a solvent and attached to carbon & l fibers through carbon fibers, if the pitches are dried to form a prepreg, the pitches will not be completely dissolved and will be uneven. Moreover, pitches do not have flexibility, and pitches fall off from carbon fibers during post-processing operations.

Therefore, an object of the present invention is to achieve effective production by uniformly attaching pitches to carbon fibers without using special equipment such as heating when producing a C/C composite using pitches as matrix forming raw materials. The goal is to do the following.

[! ! Means for Solving the Problem] That is, in the production of a C/C composite using pitches as a raw material for forming a matrix, the present invention involves dissolving a pitch adhesive in a solvent and suspending pitches in a solution that is applied to carbon fibers. After that, the solvent is removed to form a prepreg, and the prepreg is heated and formed, then carbonized,
Impregnation, carbonization treatment, and final heat treatment if necessaryC
/C composite manufacturing method.

In the present invention, as described above, a pitch adhesive is dissolved in a solution and a solution in which pitches are suspended is attached to the surface of carbon fibers, and then the solvent is removed to prepare a prepreg.
The prepreg is characterized by the fact that the pitch easily and uniformly adheres to the surface of the carbon fiber, and since this prepreg is used, the pitch does not fall off and the desired composition of C/C can be obtained.
It can be a composite.

The present invention will be explained in detail below.

The reinforcing carbon fiber used in the present invention may be polyacrylonitrile (PAN)-based, rayon-based, or pitch-based, and may also be in the form of carbon fiber or graphite fiber. Either short fibers or continuous fibers having a length of about 0.05 to 50 mm can be used.

The carbon fibers may also be in the form of sheet-like carbon fiber structures such as cloth, felt, or mats. It may be directed or oriented in any particular direction.

The pitches used as raw materials for forming the matrix include 30 to 70% by weight of pitch such as impregnated pitch and binder pitch, and 70 to 70% by weight of carbonaceous powder such as raw coke and carbon black.
30% by weight is mixed using a kneader or the like. At this time, if the pitch is less than 30% by weight, it is difficult to form a molded product due to the lack of binder during C/C composite molding, and if it exceeds 70% by weight, the pitch will be washed away during molding and the desired molding material will not be obtained. Can not.

At this time, as for the particle size of the pitch, if the particle size is large, it will not fit between the carbon fibers sufficiently and it will not be possible to form a high-strength C/C composite. desirable.

Such pitches are used together with a pitch adhesive that dissolves in a solvent such as polystyrene, rubber, or polyvinyl alcohol, and are suspended in a solvent to form a solution. Pitch adhesive is dissolved in a solvent, and after the solvent is removed, it acts as a binder, and when it is made into prepreg, it prevents inflexible pitches, which have weaker adhesion than the surface of carbon fibers, from falling off. It is used for the purpose of In addition, the pitch adhesive is
During carbonization, the material is gasified to create open pores of several microliters to several tens of microliters, so in the impregnation carbonization process, a large amount of impregnating agent enters the open pores and serves to increase the density. The solvent is one that dissolves the pitch adhesive, and the most suitable one can be selected depending on the pitch adhesive. For example, if the pitch adhesive is polystyrene or rubber, organic solvents such as chloroform or benzene, or polyvinyl If it is alcohol, water etc. can be used.

In addition, in the method of the present invention, when an organic solvent is used, most of the pitches are insoluble, although some of the components may be dissolved, and when water is used as a solvent, the pitches are Since they hardly dissolve, they are used in a suspended state.

Carbon fibers or carbon fiber bundles are immersed in this solution,
After impregnating the solution into the fibers, the solvent is removed by drying to obtain a prepreg. Such prepregs are laminated or cut and mixed, and then heat molded or the like is performed to form a molded body.

In the molded article, it is desirable that the carbon fiber or carbon fiber structure is contained in an amount of 20 to 60% by weight, preferably 40 to 60% by weight.If the carbon fiber is less than 20% by weight, the resultant C/C composite Because there are too few reinforcing fibers, the strength will be low. On the other hand, if it exceeds 90% by weight, the matrix content is too small, so the shear strength at the glabella decreases, and the reinforcing effect of the carbon fibers is not sufficiently exerted.

This compact is carbonized in a non-oxidizing gas atmosphere such as nitrogen or argon. At this time, if the molded body is carbonized as it is, it will cause blistering, so it is preferable to carry out the carbonization treatment as it is while being fixed using a fixing material made of a material that does not deform even at high temperatures during carbonization.

Temperature during carbonization treatment is 800℃ or higher, 1100℃
The following is used: In this case, if the temperature increase rate during carbonization is too fast, the matrix material (pitch) will shrink due to thermal decomposition and gas generation will be intense, making it easy for large cracks to occur. Therefore, it is desirable that the temperature increase rate is usually 100° C./hr or less, preferably 20° C./hr or less.

The initial intermediate thus obtained after carbonization still has high porosity and is further impregnated with pitch or carbonizable resin to obtain a high density, high strength C/C composite. After that, carbonization treatment is performed again in an atmosphere of non-oxidizing gas such as argon, and the temperature at this time is preferably aOO°C or more and 1100°C or less, and is maintained at a predetermined temperature for about 1 hour.

It is desirable to repeat the impregnation treatment and carbonization treatment until the pores of the carbon fiber-reinforced carbon material are filled and the density becomes almost constant.Then, if necessary, the final graphitization treatment is performed using nitrogen,
1200℃~30℃ in non-oxidizing gas atmosphere such as argon
The process is carried out at 00°C to form the final C/C composite. The graphitization treatment time is such that heating is performed at a predetermined temperature for 30 minutes or more, preferably 1 hour or more, in order to stabilize the properties.

Hereinafter, the present invention will be explained according to Examples.

[Example] Pitch 50% by weight with average particle size lOμm and softening point 240°C
and raw coke (volatile content 10%) with an average particle size of 10μI5
0% by weight was mixed at 210° C. using a kneader, and then the particle size of this mixture was adjusted to 100 μm or less to obtain a raw material pitch mixture.

Example 1 160 parts by weight of a raw pitch mixture and 150 parts by weight of polystyrene as a pitch adhesive were placed in xooo parts by weight of chloroform as a solvent and stirred to dissolve the polystyrene and prepare a solution in which pitches were suspended.

A PAN-based carbon fiber bundle cloth (satin weave) with 911,000 filaments was immersed in this solution, dried to remove the solvent, and made into a prepreg of 120 x 1
Cut into 20mm square pieces, stack 2S sheets in a mold, and heat at 300°C.
, press molding was carried out at a pressure of 100 kg/cm''.

Example 2 A prepreg was prepared in the same manner as in Example 1 except that polyvinyl alcohol was used instead of polystyrene as a pitch adhesive and water was used instead of chloroform as a solvent, and press molded under the same conditions.

Comparative Example 1 A prepreg was prepared in the same manner as in Example 1 without using polystyrene as a pitch adhesive, and press-molded under the same conditions.

Comparative Example 2 Raw pitch mixture powder and 120× similar to Example 1
Carbon fiber bundle crosses (satin weave) cut into 120+e+s squares were stacked alternately in a mold by hand so that the ratio of pitch powder and carbon fibers was the same as in Example 1, and pressed under the same conditions as in Example 1. Molded.

Example 3 150 parts by weight of the raw pitch mixture and 150 parts by weight of polystyrene as a pitch adhesive were placed in 1000 parts by weight of chloroform as a solvent and stirred to dissolve the polystyrene and prepare a solution in which pitches were suspended.

After immersing one PAN-based continuous carbon fiber with a number of filaments of 1200 in this solution, it was dried to remove the solvent and made into prepreg, which was cut into short fibers of 30 cm.
They were laminated in a 0x120mm square mold and press-molded at a temperature of 300°C and a pressure of 100kg/cm''.

Comparative Example 3 A prepreg was produced in the same manner as in Example 3 without using polystyrene as a pitch adhesive, and press-molded under the same conditions.

Comparative Example 4 Raw pitch mixture and PA with 12,000 filaments
Example 3 N-based continuous carbon fibers cut into short fibers of 30 haze were mixed so that the ratio of pitch and carbon fibers was the same as in Example 3, mixed in a dry blender, and put into a mold.
Press molding was carried out under the same conditions.

The results of the press molding obtained are shown in Table 1.

Table 1 Press molding results The products using polystyrene and polyvinyl alcohol (Examples 1 and 2.3) as pitch adhesives produced beautiful molded bodies, but the prepregs made without using pitch adhesives (Comparative Example 1.3) The pitch fell off and a molded product could not be formed. Furthermore, when the raw material pitch mixture powder was directly mixed with carbon fibers without preparing a prepreg (Comparative Example 2.4), a molded body with non-uniformity and low density was obtained.

In this way, a molded article can be easily manufactured by preparing a prepreg using a pitch adhesive such as polystyrene.

Example 4 The molded product of Example 1 was sandwiched between stainless steel plates and fixed using bolts.

This was heated to 600°C at a heating rate of 10°C/hr in a nitrogen atmosphere.
The matrix was carbonized by increasing the temperature to ℃.

Next, after removing the fixing material, 10℃/h in nitrogen atmosphere
The temperature was raised to 1000° C. at a heating rate of r and held for 1 hour for carbonization treatment. Furthermore, after impregnating this carbonized first intermediate with pitch for impregnation at 200°C under vacuum, this impregnated body was heated to 1000°C at a heating rate of 10°C/hr under a nitrogen atmosphere.
The impregnated pitch was completely carbonized. Subsequently, the above impregnation and carbonization steps were repeated three more times to obtain an intermediate.

The resulting intermediate was heated to 2000° C. at a heating rate of 10° C./inch in an argon atmosphere and held for 1 hour to obtain a C/C composite.

Comparative Example 5 The compact of Comparative Example 2 was carbonized under the same conditions as in Example 4 to obtain a C/C composite.

The results of the strength test of the obtained C/C composite are 342
Shown in the table.

When manufacturing a C/C composite using the test results in Table 2 as a matrix, it is possible to easily and uniformly produce a prepreg without the pitch falling off without using a heating device to melt the raw material pitch. In addition, it improves the workability of prepreg,
It has become possible to create a C/C composite that is uniform and has high strength properties.

C/C composites made from pitch have higher oxidation resistance than those made from resin, and are expected to have a wider range of applications.

The one using polystyrene (Example 4) as a pitch adhesive has better bending strength and hardness than Comparative Example 5. In this way, the prepreg made using the pitch adhesive has a uniform distribution of the matrix in the carbon fibers, resulting in a C/C composite with excellent strength.

[Effect of the invention] By using the pitch adhesive of the present invention, pitch and 4 other people

Claims (1)

[Claims] 1. In the production of carbon fiber-reinforced carbon materials using pitches as raw materials for forming a matrix, a solution in which a pitch adhesive is dissolved in a solvent and pitches are suspended is attached to the surface of carbon fibers, A method for producing a carbon fiber-reinforced carbon material, characterized in that the solvent is then removed to obtain a prepreg, and the prepreg is heated and formed, followed by carbonization, impregnation, carbonization, and final heat treatment if necessary.