JPH11130536A - Carbon material and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carbon material having small friction coefficient and suitable as a sliding component, by preparing the carbon material so as to have the ratio (fG) of the (002) peak area of the graphite component to the total area of all peaks shown in an X-ray diffraction pattern. SOLUTION: This carbon material is prepared by adjusting the FG-value to 8% or larger and can be produced by adopting processes comprising (A) compounding raw materials, (B) heating and kneading (incorporation), (C) molding, (D) calcining and (E) graphitization. It is especially preferable to conduct heat kneading at <=280 deg.C and calcining in the presence of any antioxidant measure at the same time and extremely preferable to add the selection of kinds of raw materials in combination with the above-mentioned measure. Wrapping the object to be calcined with paper or metal foil is suitable as an anti-oxidant measure. Coal pitch or coal tar is appropriate to a binder in the raw materials and artificial graphite, coal coke or petroleum coke is appropriate to aggregate in the raw materials.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a carbon material, and more particularly to a special carbon material suitable for a sliding member.

[0002]

2. Description of the Related Art One of the characteristics of carbon materials is self-lubricating properties. Utilizing this characteristic, carbon materials are used for sliding members such as bearings and vacuum pump blades. The sliding member refers to a material or part that slides in contact with a counterpart material, and includes a material that is flowing a current at this time. Since carbon materials can control the electrical conductivity to some extent, they are also used in electric brushes as a special type of the above-mentioned sliding parts.

[0003] The friction coefficient is one of the important characteristics of these sliding members. It has been empirically found that this friction coefficient decreases as the degree of graphitization increases, but it has not been clarified quantitatively. The degree of graphitization is generally determined by the method described in Michio Inagaki, “Experimental Technology for Carbon Materials I” (edited by the Society of Carbon Materials, p. 55, published by Science and Technology Corporation, 1978).
Graphite crystals of Co (002 or 004) and Lc (00
2 or 004). Further, as shown in Carbon 13, Vol. 335 (1975) by S. Otani et al., The X-ray diffraction profiles were determined for the graphite component (hereinafter referred to as G component), the turbostratic component (hereinafter referred to as T component), and the amorphous carbon component (hereinafter referred to as A). Component) has also been proposed. However, even in these methods, the relationship between the friction coefficient and the degree of graphitization has not been clarified, and as a result, there is no known method of producing a material having a small friction coefficient, which is suitable as a special carbon material, with a high yield. .

[0004]

The present invention has completed the present invention by clarifying the relationship between the coefficient of friction and the degree of graphitization and finding a method for controlling the degree of graphitization. The present invention provides a carbon material having a small coefficient of friction and suitable as a sliding member, and a method for producing the carbon material with high yield.

[0005]

That is, the present invention relates to a carbon material in which the area of a graphite component peak represented by an X-ray (002) diffraction line is 8% or more (f _G ≧ 8%) of the entire peak area. Further, the present invention provides a method for producing a carbon material including a raw material blending step, a heating kneading (kneading) step, a forming step, a firing step, and a graphitizing step.
2) The present invention relates to a method for producing a carbon material, wherein the area of a graphite component peak appearing in a diffraction line is adjusted to 8% or more (f _G ≧ 8%) of the entire peak area.

The present invention also relates to a method for producing the carbon material, wherein the heating and kneading (kneading) step is performed at a temperature of 280 ° C. or lower. The present invention also relates to a method for producing the carbon material, wherein the firing step is performed in an antioxidant atmosphere. Further, the present invention relates to a method for producing the carbon material, wherein the object to be fired is wrapped in a paper or a metal foil in an antioxidant atmosphere. Furthermore, the present invention relates to a method for producing the carbon material using a binder selected from coal-based pitch and coal-based tar and an aggregate selected from artificial graphite, coal-based coke and petroleum-based coke as raw materials.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The carbon material of the present invention is an X-ray (00
2) The area of the graphite component peak (f _G ) that appears in the diffraction line is 8% or more (f _G ≧ 8%) of the entire peak area. Here, f _G is an index indicating the degree of graphitization in the above-mentioned method of S. Otani et al., And the area intensity of the graphite component (G component) appearing on the X-ray (002) diffraction line is expressed by the total area intensity. (Hereinafter referred to as f _G ). The present inventors have found that there is a close relationship between this value and the friction coefficient of the carbon material (hereinafter referred to as μ). That procedure, as no mu is decreased to increase the f _G is f _G is less than 8%, f _G = 8% by mu ≒ 0.3
It was found that when f _G exceeds 8%, the value becomes almost constant. Therefore, in order to obtain a carbon material having a small μ suitable for a sliding part or the like, it was found that f _G ≧ 8% should be adjusted.

[0008] Here will be described in detail how to obtain the f _G of the present invention based on the S.Otani's method. FIG. 1A shows an example of an X-ray (002) diffraction pattern of a carbon material. FIG.
In (a), profile 1 is actual measurement data, and profile 2 is obtained by performing background correction on this in accordance with the Gakushin method described in the above-mentioned “Carbon Materials Experimental Technique I”. In the method of S. Otani et al., The peak at 2θ of 26.1 ° corresponds to the turbostratic structure, and the peak at 2θ of 26.4 ° corresponds to the graphite structure. And profile 2
Are composite peaks in which these coexist. Therefore, when this is divided into the respective structures based on the above correction, the turbostratic component 3 and the graphite component 4 are divided so as to have a symmetrical waveform as shown in FIGS. Then, the area intensity of the graphite component 4 and the entire area intensity, that is, the turbostratic component 3
And f _G seeking the ratio of the integrated intensity of the sum of graphite components 4 and. Here, the X-ray diffraction is measured for the powder of the carbon material to be measured, as described in the above-mentioned “Carbon Material Experimental Technique I”.

[0009] The carbon material of the present invention is prepared by the X-ray (00
2) It may be prepared so that the area of the graphite component peak appearing on the diffraction line is at least 8% (f _G ≧ 8%) of the entire peak area, and there are several methods for this. The method for producing a carbon material of the present invention employs a general method, that is, a method including a compounding step of raw materials, a heating and kneading (kneading) step, a forming step, a firing step, and a graphitizing step. be able to.

[0010] The raw material blending step is a step of blending a binder such as pitch and an aggregate such as coke. It is preferable that the mixing ratio is 7/3 to 5/5 in terms of the weight ratio of aggregate / binder. Aggregate here, beforehand, jet mill,
It is preferable that the particles are pulverized to an average particle diameter of 5 to 30 μm using a pin mill, impact type pulverizer, rod mill, ball mill or the like. One method for producing the carbon material of the present invention is to select the type of the raw material. As the raw material, coal-based pitch and coal-based tar are preferable as the binder. In the case of petroleum-based materials, it is difficult to produce the carbon material of the present invention having the above characteristics. As the aggregate, artificial graphite, coal-based coke, and petroleum-based coke (fluid coke, delayed coke) are preferable. Natural graphite has a low specific gravity after graphitization, making it difficult to produce the carbon material of the present invention.

After mixing the raw materials, they are kneaded by heating (also called kneading). As a method for producing the carbon material of the present invention, this step is preferably performed at 280 ° C. or lower, and more preferably 230 ° C. or higher from the viewpoint of reducing the heating and kneading time. When the temperature of the heat kneading exceeds 280 ° C., the f _G tends to be less than 8%. This step can be performed using a batch-type kneader such as a double-arm mixer or a ribbon mixer, or a continuous-type kneader such as a paddle type or a screw type. In the case of a batch type kneader, the heating time is preferably 2 hours to 24 hours, and in the case of a continuous type kneader, it may be about 3 seconds to 30 minutes.

After cooling, it is preferable to pulverize using a jet mill, a pin mill, an impact type pulverizer, a rod mill, a ball mill or the like, and more preferable to pulverize to an average particle diameter of 20 to 30 μm. The pulverized raw material is then formed. There is no particular limitation on the molding method, and it is possible to employ a method in which the material is filled into a mold and molded by a uniaxial press, extrusion molding, rubber press (CIP), or the like.

Next, a firing step is performed. As a method for producing the carbon material of the present invention, there is a method in which this firing step is performed in an antioxidant atmosphere. In the case of oxidizing conditions, for example, when a gas that oxidizes carbon such as oxygen, carbon dioxide, and water vapor is present in the atmosphere in the firing furnace, f _G <8% is likely to occur, and it is difficult to obtain the carbon material of the present invention. . Examples of a method for forming the atmosphere under an antioxidant atmosphere include a non-oxygen atmosphere, for example, under a gas atmosphere such as nitrogen gas, helium gas, and argon gas, under vacuum, and the like. Even if the atmosphere is an enzymatic gas, a method of wrapping the object to be fired with paper or metal foil so that the atmosphere gas does not directly touch the object to be fired is preferable. Here, it is necessary that the material to be wrapped has a shape that remains in the initial stage of firing, and an organic material such as vinyl is melted or burnt out in the initial stage of firing and has no effect.

The paper used here may be any paper as long as it is carbonized in the early stage of firing and the shape of the package does not change, and examples thereof include newsprint, kraft paper, and cardboard paper. The wrapping method is preferably such that there is no gap. In addition, as the metal, it is sufficient that the metal does not melt in the early stage of sintering.
Not only steel foil but also aluminum foil whose melting point is lower than the maximum firing temperature may be used. Also in this case, it is preferable to wrap so that there is no gap. In the present invention, the method of processing at a temperature of 280 ° C. or less in the kneading step and further performing some antioxidant measures in the firing step has a high effect of obtaining a carbon material having a low coefficient of friction with a high yield. It is particularly preferred, and very particularly preferred to combine the selection of the type of raw materials.

The calcination can be carried out using a batch type furnace, a continuous type furnace, or the like, preferably at 700 to 1000 ° C. for a total time of from half a month to one month from the start of the temperature rise. After firing,
If necessary, pitch and the like can be impregnated, and the above-mentioned firing can be performed again. After firing, graphitization is performed. Graphitization is performed using a batch type Acheson furnace, induction furnace, continuous type, etc.
It is preferable to carry out at 00 to 3000 ° C. Thus, the carbon material of the present invention can be manufactured. The obtained special carbon material is machined and polished as necessary, and used as various sliding members.

Hereinafter, the operation will be described. The generation mechanism of the graphite component in the carbon material is as follows. At the initial stage of carbonization, carbon atoms form hexagonal mesh planes, which are then polycondensed to form a plane macromolecule, which is then stacked in layers to form graphite crystals. Therefore, it can be said that the reason why the degree of graphitization decreases is that the mechanism does not proceed in any of the above mechanisms. In the production method of the present invention, when the kneading temperature is 280 ° C. or lower, oxygen in the atmosphere causes a dehydrogenation reaction and polycondensates into planar macromolecules. At this stage, since oxygen in the atmosphere undergoes an addition reaction to hexagonal mesh plane molecules and does not become planar molecules, it is presumed that they do not build up on each other and do not become graphite crystals. Similarly, in the production method of the present invention, if any anti-enzyme measures are taken in the firing step, since there is no heteroatom such as oxygen that undergoes addition reaction, it becomes a plane macromolecule in the initial reaction of carbonization, and graphite Presumed to be crystals.

[0017]

Embodiments of the present invention will be described below. Example 1 Pitch coke as an aggregate (LPC manufactured by Nippon Steel Chemical Co., Ltd.)
-A) and carbon black (lamp black) as binders using coal-based pitch (PK- manufactured by Kawasaki Steel Corporation)
E) and 25% by weight of coal tar, respectively,
Kneading at 240 ° C, B255 ° C, C270 ° C, and D280 ° C, respectively, using a double-arm kneader, then cooling, pulverizing to about 30 μm with a hammer mill, and pressing with a uniaxial press at a pressure of 600 kg / cm ^2. (300 × 150 × 110 (mm)). After that, it is baked at about 900 ° C. for 10 hours,
Graphitization was performed at 00 ° C. for 10 hours to obtain a sample. Where sought f _G in a way that shows these samples the following A: 14
%, B15%, C12%, and D10%. Further, when the friction coefficient μ was measured by a motor input difference method (a method in which a sample was pressed against a rotor of a DC motor to measure the electric power for achieving a constant number of revolutions and converted μ), A: 0.20 ,
B: 0.24, C: 0.20, D: 0.21.

Measurement method of f _G The X-ray diffractometer uses Philips PW-1700, current 20 mA, voltage 40 KV, slit 1/6 °,
A 0.15 mm, 1/6 °, copper cathode was used, and a nickel filter was used as a filter, and a (002) diffraction line of carbon was obtained. This method is based on the above-mentioned “Carbon Materials Experiment Technology I”.
According to the Gakushin method described in. The obtained diffraction diagram is obtained by correcting the diffraction line according to the Gakushin method (002) so that the profile on the low angle side is substantially symmetrical, and then the difference between the profile and the corrected profile is lowered vertically. The profile was on the high angle side. The profile at this time is symmetric. The area intensity ratio between the profile and the profile was defined as fG.

Example 2 A green compact obtained under the same conditions as in Example 1 was used.
mm thickness aluminum foil, F: copper foil of the same thickness, G: steel foil of the same thickness, H: newspaper, I: cardboard, wrapped tightly and fired at about 900 ° C., then about 2800 ° C. F _G of the sample obtained by graphitization with E: 18%, F: 1
7%, G: 15%, H: 13%, I: 13%, μ
Are E: 0.18, F: 0.18, G: 0.20, H:
0.16, I: 0.19.

Example 3 The same composition as in Example 1 was used, and after kneading at 290 ° C., Example 4
The samples fired under the same conditions as those of Examples E, F, G, H and I, and then graphitized at about 2800 ° C., J, K,
L, M and N were obtained. These f _G are J: 14%, K: 1
3%, L: 10%, M: 9%, N: 9%, and μ is 0.20, 0.22, 0.24, 0.26,
It was 0.26.

Example 4 Kneaded at 280 ° C. using 50% of self-made artificial graphite and 50% of a coal-based binder (PK-E manufactured by Kawasaki Steel Corp.) as raw materials, pulverized to about 30 μm after cooling, and 600 kg / kg after molding at a pressure of cm ^2, the sample P obtained by firing at about 900 ° C.
Had a f _G of 18% and a μ of 0.20.

[0022] In Comparative Example 1 Example 3, after firing the green compact at about 900 ° C. without antioxidant, f _G of the sample O obtained by graphitizing at about 2800 ° C. is 4%, mu is 0.40 Met.

Comparative Example 2 In Example 1, the kneading temperature was changed to Q: 285 ° C., R: 2
When the temperature was changed to 90 ° C., S: 295 ° C., and T: 300 ° C., these f _G were Q: 6%, R: 5%, S: 4%,
T: 3%, and μ are 0.48, 0.46,
0.51 and 0.58.

FIG. 2 is a graph showing the relationship between f _G and the coefficient of friction (μ) based on the above experimental results.

[0025]

The carbon material of the present invention has a low coefficient of friction,
It is suitable as a sliding member. Further, according to the method for producing a carbon material of the present invention, a carbon material having a small coefficient of friction and suitable as a sliding member can be produced with high yield.

[Brief description of the drawings]

FIG. 1 is a graph showing how to determine f _G of the present invention based on the method of S. Otani et al.

FIG. 2 is a graph showing the relationship between f _G and the coefficient of friction (μ) of the experimental results of the example.

[Explanation of symbols]

 1: Actual measurement profile 2: Background corrected profile 3: Turbulent component 4: Graphite component

Claims (6)

[Claims] 1. The area of a graphite component peak appearing on an X-ray (002) diffraction line is at least 8% of the entire peak area (f _G ≧ 8).
%) Carbon material. 2. An X-ray (002) diffraction line of a carbon material obtained in a method for producing a carbon material including a raw material blending step, a heating kneading (kneading) step, a forming step, a firing step, and a graphitizing step. A method for producing a carbon material, wherein the area of a graphite component peak is adjusted to 8% or more (f _G ≧ 8%) of the entire peak area. 3. The method for producing a carbon material according to claim 2, wherein the heating kneading (kneading) step is performed at a temperature of 280 ° C. or lower. 4. The method for producing a carbon material according to claim 2, wherein the firing step is performed in an antioxidant atmosphere. 5. The method for producing a carbon material according to claim 4, wherein the formation in the antioxidant atmosphere is performed by wrapping the object to be fired with paper or metal foil. 6. A raw material comprising a binder selected from coal-based pitch and coal-based tar, and an aggregate selected from artificial graphite, coal-based coke, and petroleum-based coke. Production method of carbon material.