KR100824430B1 - Graphite with high density and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a high-density graphite comprising a filler and a binder in which the volatile content is controlled by heat-treating the pitch at a constant temperature and time conditions, and a method of manufacturing the same. In the present invention, the filler prepared using the pitch had a higher volatile content than the conventional filler, and the graphite prepared through carbonization and graphitization using the filler had high density and high hardness. In addition, the graphite produced in the present invention was self-lubricating and densified to almost no pores. Therefore, graphite produced according to the method of the present invention can be used for mechanical parts or mechanical seals as high density graphite.

Graphite, Fillers, Binders, Volatiles

Description

Graphite having high density and its manufacturing method {GRAPHITE WITH HIGH DENSITY AND MANUFACTURING METHOD THEREOF}

1 is a schematic representation of an apparatus for producing high density graphite in accordance with the present invention.

Figure 2 is a graph showing the volatilization amount of the filler prepared in Example 1 and Example 2 of the present invention and the filler prepared in Comparative Example 1.

3 is a graph showing the volatilization amount of the binder prepared in Example 1 and Comparative Example 2 of the present invention.

Figure 4a is a graph showing the friction coefficient for each load according to the moving distance of the specimen after the carbonization process in Example 1 of the present invention.

Figure 4b is a graph showing the friction coefficient for each load according to the moving distance of the specimen after the graphitization process in Example 1 of the present invention.

Figure 5a is a photograph of the specimen surface prepared after carbonization and graphitization in Example 1 of the present invention by optical microscope.

Figure 5b is a photograph of observation of the specimen surface prepared after carbonization and graphitization in Example 2 of the present invention with an optical microscope.

Figure 5c is a photo observation of the specimen surface prepared after carbonization and graphitization in Comparative Example 1 of the present invention with an optical microscope.

5d is a photograph of the specimen surface prepared after carbonization and graphitization in Comparative Example 2 of the present invention with an optical microscope.

* Explanation of symbols for the main parts of the drawings *

1: Furnace 2: SUS beaker

3: motor 4: nitrogen gas injection site

5: outgassing area 6: thermocouple

7: PID controller

The present invention relates to a high density graphite and a method for manufacturing the same, and more particularly, to a high density graphite comprising a filler and a binder prepared by adjusting the volatile content by heat treatment at a constant temperature and time conditions pitch and a method for producing the same will be.

Graphite has a single carbon element and is chemically very stable, and has excellent corrosion resistance. In addition, graphite is an anisotropic structure having a van der waals bond in the c-axis direction and a covalent bond in the a- and b-axis directions, and is widely used as a material for mechanical structures because of its unique characteristics.

In particular, they are very suitable materials for mechanical seals due to their self-lubricating properties and chemical durability, excellent thermal conductivity and processability. Graphite seals for mechanical seals must be dense to maintain airtightness. In general, the characteristics of the final graphite vary depending on the characteristics such as the orientation and density of the coke, so the control of the coke is very important. The coke has an amorphous structure with an orientation when the pitch is heat treated at 500 ° C. or higher in an inert atmosphere. The coke is controlled to have almost no volatiles at 500 ° C. or higher to have a more developed orientation to increase the carbon yield. However, coke with little volatile content produced in this way has no formability and no sintering ability, so that pitch binders are mixed and used at a constant ratio.

Therefore, in order to produce high density and airtight graphite, a method of controlling the volatilization of coke as a raw material to a certain level is required. However, studies on controlling the volatilization of coke for high density graphite have not been made. Was not.

That is, Korean Patent Application No. 2003-7011696 discloses a method for manufacturing a graphite material for use in a lithium secondary battery negative electrode, but a method of manufacturing graphite using a general process of pulverizing and carbonizing coke and then graphitizing it. The density of the finished graphite was not high.

In addition, Korean Patent Application No. 2002-7006684 discloses a method for producing a graphite powder having an increased density, but a method of increasing the density by surface treatment of the graphite powder.

The inventor of the present invention, while studying to produce a high-density graphite that can be effectively used for mechanical seals, etc., the heat treatment at a constant temperature and time to prepare a filler and a binder with a controlled volatile content, coke and binder of a certain ratio After forming a mixed powder of, the graphite was prepared by heating in an inert atmosphere, and the present invention was completed by confirming that the graphite thus prepared was excellent graphite having high density.

The technical problem to be achieved by the present invention is to provide a method for producing graphite having high density and excellent properties.

In order to achieve the above technical problem, the present invention provides a high-density graphite comprising a filler having a volatile content of 3 to 7% by weight and a binder having a volatile content of 58 to 60% by weight.

In addition, the present invention, the step of heat-treating the pitch at 490 ~ 500 ℃ for 0.5 to 4 hours to prepare a filler having a volatile content of 3 to 7% by weight; Heat-treating the pitch at 200 to 240 ° C. for 1 to 6 hours to prepare a binder having a volatile content of 58 to 60 wt%; Adjusting the particle size of the filler and binder to 325 mesh or less; And it provides a method for producing high density graphite comprising the step of mixing the filler and the binder.

As used herein, the term 'filler' refers to coke having graphite crystals as a raw material for producing graphite. In addition, a "volatile content" means the hydrocarbon compound which is a free radical in an aromatic compound, or is responsible for one axis of a hexagonal ring.

Hereinafter, the present invention will be described in detail.

The high-density graphite according to the present invention comprises the steps of heat-treating the pitch at 490-500 ° C. for 0.5-4 hours to prepare a filler having a volatile content of 3-7 wt%; Heat-treating the pitch at 200 to 240 ° C. for 1 to 6 hours to prepare a binder having a volatile content of 58 to 60 wt%; Adjusting the particle size of the filler and binder to 325 mesh or less; And it is prepared using a method comprising the step of mixing the filler and the binder.

In the above-mentioned pitch (pitch) is a residue from the pyrolysis of organic matter or distillation of tar, in the present invention, it is preferable to use coal or petroleum pitch, specifically, it is most preferable to use coal pitch.

In order to manufacture high-density graphite, the volatilization amount of the filler and the binder, which are raw materials used in the manufacture of graphite, plays an important role. In the present invention, the filler and the binder produce high-density graphite by effectively controlling the temperature and time during the manufacture of the filler and the binder. It was adjusted to include the amount of volatile in the range possible.

In the present invention, the filler is preferably prepared by heat treatment at a pitch of 490 ~ 500 ℃ for 0.5 to 4 hours, when the temperature is less than 490 ℃, the decrease in volatile content is small and the polycondensation of the aromatic compound is slow and the molecular weight is small When carbonized and graphitized, the porosity increases in the internal structure, and the density decreases and the mechanical strength decreases.When the temperature exceeds 500 ° C, the entire amount of volatile CH compounds, that is, methyl and ethyl groups, is removed. This does not occur at all, and there is no decomposition of methyl and ethyl groups during carbonization, that is, there is no dehydrogenation reaction, so that the self-sintering of the coke as a filler does not occur, resulting in no increase in density and strength. In addition, the heat treatment in the above is preferably made for 0.5 to 4 hours, if the heat treatment time is less than 0.5 hours, the retention time is short, the desired amount of volatile control can not be achieved, if it exceeds 4 hours, the amount of reduction of volatile content is large and aromatic compounds This is because the polycondensation reaction of the polymer is excessively excessive, resulting in the rapid deterioration of self sintering during carbonization and graphitization, resulting in a problem in that high density graphite cannot be produced. Fillers prepared under the conditions of temperature and time in the above range include a volatilization amount of 3 to 7% by weight, which is most suitable for the production of high density graphite.

In the present invention, the binder is preferably prepared by heat treatment at 200 to 240 ℃ pitch for 1 to 6 hours. When the molecules in the pitch are rearranged linearly, graphite crystallization occurs easily during carbonization and graphitization. If the temperature is less than 200 ° C. during the manufacture of the binder, molecules of a complex structure are linearly reorganized by decomposition of methyl and ethyl groups in the pitch. The problem arises that no arrays occur. In addition, when the temperature exceeds 240 ° C, decomposition of methyl and ethyl groups, which are CH compounds, occurs in earnest, and volatile matters decrease, polycondensation reactions begin to occur, thereby improving molecular weight. Therefore, a problem arises in that the viscosity is sharply improved so that it does not contribute to the improvement of moldability, which is a role of the binder. In addition, the heat treatment in the above is preferably made for 1 to 6 hours, if the heat treatment time is less than 1 hour, the pitch of the liquid phase is not uniformly heated, the problem that the pitch molecule rearrangement does not occur uniformly, exceeds 6 hours This is because the rearrangement of molecules and uniform heat treatment are no longer enhanced, which causes a problem that the effect is no longer improved in proportion to time. The binder prepared under the conditions of the temperature and time of the said range is 58-60 weight% of volatile matters, and is suitable for high density graphite manufacture.

On the other hand, in the method for producing high density graphite according to the present invention, when preparing the filler and binder, it is stirred at a speed of 80 ~ 120rpm under an inert atmosphere in order to induce effective discharge of volatiles and uniform polycondensation reaction during heat treatment. It is important. In order to linearly rearrange molecules of the pitch, decomposition of CH compounds, such as methyl and ethyl groups, must occur. The stirring process helps these functional groups to be effectively decomposed. If the stirring speed is less than 80rpm, the process speed becomes ineffective, and if it exceeds 120rpm, the molten pitch overflows out of the reaction vessel, making it difficult to operate. Therefore, it is preferable to stir in the above range. The inert atmosphere may be nitrogen atmosphere or argon atmosphere.

In addition, the filler and binder prepared by the heat treatment is then performed by a ball mill to adjust the particle size to 325 mesh (44㎛) or less. In the above, the ball mill rotation speed varies depending on the size of the container and the amount of material. In addition, when the particle size of the filler and the binder is 325 mesh or less, it can be made of high density graphite. Pitch decomposes the methyl and ethyl groups, which are CH compounds, by heat treatment, and rearrangements occur at the same time as polymerization proceeds by polycondensation. In this process, a small amount of volatile matter is left, and self-sintering occurs due to dehydrogenation reaction during imparting moldability and carbonization and graphitization, thereby increasing density. The self-crystallization crystallization proceeds by leading the bonding with neighboring fillers by dehydrogenation reaction. When the particle size is less than 325 mesh, the self-crystallization crystallization takes place actively because of high surface energy. The organization has the advantage of being compact.

On the other hand, in the present invention, after molding the filler and the binder with the volatile content controlled through the heat treatment as described above, the carbonization by heat treatment for 2 to 4 hours at 1100 ~ 1250 ℃, heat treatment for 1 to 3 hours at 2200 ~ 3000 ℃ Finally, the graphite according to the present invention is produced.

As such, the graphite prepared according to the method of the present invention includes a filler having a volatile content of 3 to 7 wt% and a binder having a volatile content of 58 to 60 wt%, and a density of 1.6 to 1.8 g / cm. ³ , Shore hardness is 100-110 and has the outstanding characteristic.

Hereinafter, the present invention will be described in detail by way of examples.

However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited to the following examples.

Example 1 Preparation of High Density Graphite 1

Coal and pitch binders were prepared using graphite-based pitch (Dongyang Steel Chemical Co., Ltd.) having the characteristics shown in Table 1 as raw materials.

Solubility (%) S.P. (℃) Coalization Value (%) Specific gravity (g / cm ² ) BI TI pitch 10-15 30-35 100-120 50 1.2

  BI: Benzene insoluble TI: Toluene insoluble S. P .: Softening point

First, in order to prepare a coke as a filler, the coal-based pitch was charged into an SUS container and charged into the reactor (see FIG. 1), and heat-treated with stirring at 80 rpm for 60 minutes at 490 ° C. at a temperature increase rate of 5 ° C./min.

Thereafter, in order to prepare a binder, the coal-based pitch was loaded into the reactor (see FIG. 1) in a SUS container, and heat-treated while stirring at 80 rpm for 5 hours at 240 ° C. at a temperature increase rate of 5 ° C./min.

The heat treatment apparatus was controlled to ± 1 ℃ using a PID temperature controller (SCR unit). Nitrogen gas was injected to maintain the inert atmosphere so that the pitch did not react with air and oxidized during the heat treatment.

The heat-treated filler and the binder were each wet ball milled at a speed of 250 rpm for 12 hours to collect only powders having a particle size of 325 mesh (<44 μm) or less. Specimen molding for performance test was to quantify the powder mixed with coke and binder at 80:20, and then to produce a circular specimen with a diameter of 110mm at a molding pressure of 0.1kg / mm ² , and finally put it in 2000 bar after putting into CIP . The molded specimen was carbonized by maintaining the temperature at 1 ° C./min under argon atmosphere at 1100 ° C. for 2 hours. The carbonized specimen was graphitized again by maintaining the mixture at 2200 ° C. for 1 hour at 5 ° C./min under argon atmosphere to produce final graphite.

Example 2 Preparation of High Density Graphite 2

 Graphite was manufactured using the same method as in Example 1 except that the coke was heat-treated at 500 ° C.

Comparative Example 1

Graphite was manufactured using the same method as in Example 1, except that the coke was heat-treated at 510 ° C.

Comparative Example 2

Except that the binder was heat-treated at 400 ℃ to produce a graphite using the same method as in Example 1.

Test Example 1 Measurement of Volatile Content of Filler and Binder

7 mg each of the fillers and binders prepared in Examples 1 and 2 and Comparative Examples 1 and 2, respectively, were heated at a rate of 10 ° C./min from 25 ° C. to 1200 ° C. under argon atmosphere, while TGA / The volatilization amount was measured using an SDTA851 Thermal Analysis System, and the results are shown in FIGS. 2 and 3.

According to FIG. 2, the coke produced at the heat treatment temperature of 510 ° C. in Comparative Example 1 had a volatilization amount of 0.7 wt%. On the other hand, coke produced at the heat treatment temperatures of 490 ° C and 500 ° C in Example 1 and Example 2, respectively, was 6.8% by weight and 3.1% by weight.

In addition, according to FIG. 3, the binder prepared at the heat treatment temperature of 400 ° C. in Comparative Example 2 had a volatile content of 36.1 wt%. On the other hand, in Example 1, the binder prepared at a heat treatment temperature of 240 ° C. had a volatile content of 58.2 wt%.

That is, the volatilization amount of the coke and the binder prepared under the temperature and time conditions according to the present invention was higher than the coke or binder prepared in the comparative example, it could be confirmed that it can be used as an excellent raw material for producing high density graphite.

Test Example 2 Comparative Property Test of Graphite

 The graphite, prepared in Examples 1 and 2 and Comparative Examples 1 and 2, was tested for measuring density, shrinkage, and Shore hardness.

Density was measured by the Archimedes method by KS L 3114, the results are shown in Table 2 below.

Shrinkage was measured by measuring the length of the test piece before carbonization and graphitization and the length of the test piece after carbonization and graphitization was calculated as a percentage by dividing the shrinkage length by the initial length, the results are shown in Table 2 below.

Shore Hardness was measured using a Shore Hardness Tester manufactured by SATO, Japan, and the average value was determined after measuring three times for each side of the specimen. Table 2 shows.

After molding After carbonization After graphitization Density (g / cm ³ ) Density (g / cm ³ ) Shrinkage (%) Shoa hardness Density (g / cm ³ ) Shrinkage (%) Shoa hardness Example 1 1.30 1.56 12.4 110 1.75 4.4 102 Example 2 1.31 1.51 10.3 105 1.63 3.3 100 Comparative Example 1 1.36 1.18 0 53 1.15 0 51 Comparative Example 2 1.31 1.54 11.8 105 1.74 4.3 95

As shown in Table 2, in Examples 1 and 2 and Comparative Examples 1 and 2, the density after simply molding by mixing the filler and the binder was similar. However, the density after carbonization was higher than those in Examples 1 and 2, and the specimen heat treated in Example 1 after graphitization was the highest at 1.75 g / cm ³ . This is thought to be because densification of coke with a large amount of volatilization occurred due to the thermal condensation reaction during the carbonization process.

In the case of the Shore hardness value was also the highest as 110 in Example 1 it was confirmed that the thermal polycondensation reaction was active to increase the binding force. On the other hand, in Comparative Example 1, the Shore hardness value was very low, which means that the coke had the least amount of volatilization, so that the thermal polycondensation reaction did not occur in the carbonization process, so that it was not densified.

In the case of the shrinkage rate, the largest shrinkage occurred at 12.4% in Example 1. This means that the CH compound that is a volatile component, that is, methyl group, ethyl group, etc., is thermally condensed with an aromatic compound due to dehydrogenation reaction and sintered to increase the shrinkage rate. On the other hand, in Comparative Example 1, the smallest volatile content of coke occurred, and dehydrogenation reaction hardly occurred. Therefore, the thermal polycondensation reaction of the aromatic compound by dehydrogenation was not accompanied, so that no shrinkage occurred and consequently, no densification.

As a result, the coke prepared at a temperature of 490 ~ 500 ℃ and the binder prepared at 200 ~ 240 ℃ high volatilization amount, after which the graphite produced through carbonization and graphitization process as a raw material has a high density and high hardness I could confirm it.

[Test Example 3] Tribological Properties of Graphite Prepared by Carbonization and Graphitization

In order to observe the frictional wear characteristics of the specimens prepared by carbonization and graphitization in Example 1, a frictional test of pin-on-disc type was performed.

In the friction wear test, the specimen holder was subjected to a vertical load on the specimen, and the counterpart was a S45C steel disc with a diameter of 200 mm and a hardness of 85. Friction wear specimens were polished with abrasive cloths 400 and 1200, and the ends of the specimens were polished roundly so as to be consistent with the counterpart. The coefficient of friction was calculated by placing the specimen in dry contact on a steel disk rotating at 600 rpm and measuring the force applied to the specimen when a load of 1 to 5 kg was placed on it, and the result is illustrated in FIG. After) and FIG. 4B (after graphitization).

As shown in Figure 4a, it can be seen that the friction coefficient of the specimen after carbonization increases the friction coefficient as the wear increases. Also, as the load increased, the friction coefficient increased more clearly. After carbonization, the specimens are amorphous and do not develop graphite crystals, so slippage does not occur during friction.

On the other hand, as shown in Figure 4b, the friction coefficient of the specimen after graphitization shows a low and stable friction behavior. Even if the load is increased, it shows stable friction behavior without increasing the friction coefficient. After graphitization, the specimen develops graphite crystals in which the hexagonal plates are superimposed, and thus easily slips to the a and b planes. Therefore, when the friction is started, the self-lubrication of the graphite is expressed to show a low coefficient of friction and stable friction behavior even with increasing load.

That is, the graphite produced through the final graphitization in the present invention was confirmed that the self-lubrication.

Test Example 4 Surface Observation After Friction

 For graphite prepared in Examples 1 and 2 and Comparative Examples 1 and 2, the surface after friction was measured using an American OLYMPUS BX51 optical microscope (OLYMPUS, USA), and the results are shown in FIGS. 5A to 5D. Shown in

After carbonization, the specimen using the coke having a heat treatment temperature of 510 ° C. on the polishing surface (Comparative Example 1) showed no coking between the coke and the binder, and the coke was separated from the coke as a filler (FIG. 5c). . Specimens using coke heat treated at 500 ° C. (Example 2) were found to be coke and binder, coke and coke after carbonization (Fig. 5b). Specimens using coke heat-treated at 490 ° C. (Example 1), although the coke and the binder, coke and coke was made, it can be seen that a significant amount of fine pores are present (Fig. 5a). This is due to the difference in the amount of volatilized coke, which is believed to be due to the formation of pores in the tissue as the hydrocarbon compounds undergo decomposition and polycondensation. In addition, the pore formation difference in the tissues due to the 240 ° C. heat treatment binder and the 400 ° C. heat treatment binder (Comparative Example 2, FIG. 5D) having different carbon yields was not large. Therefore, the hydrocarbon compound included in the binder was no larger than the hydrocarbon compound present in the coke for contributing to the promotion of polycondensation. Therefore, the role of the binder is believed to contribute to uniform molding rather than densification of the tissue.

After graphitization, the specimen using the coke heat-treated at 510 ° C. (Comparative Example 1) showed that the bond between the coke and the binder, the coke and the coke did not get better than after the carbonization (FIG. 5C). Specimens (Examples 1 and 2) using coke heat treated at 490 ° C. and 500 ° C. showed significant disappearance of pores in the tissue (FIGS. 5A and 5B). This is because the hydrocarbon compound present in the specimen after carbonization promotes the polycondensation reaction in the graphitization process, and thus, the tissue is densified. In addition, the difference in the microstructure between the binders having different heat treatment temperatures is not so great that it is considered that the hydrocarbon compound of coke contributes to the densification of the tissue during the graphitization process.

As described above, in the present invention, the filler and the binder prepared by using the pitch had a high volatilization amount, and the graphite finally manufactured through the carbonization and graphitization process using the filler and the binder had a high density and hardness. Was also high. In addition, the graphite produced in the present invention was highly self-lubricating and dense pores. Therefore, graphite produced according to the method of the present invention can be used for mechanical parts or mechanical seals as high density graphite.

Claims (9)

A high density graphite comprising a filler in which the volatile content is adjusted to 3 to 7% by weight by heat-treating the pitch and a binder in which the volatile content is adjusted to 58 to 60% by weight by heat-treating the pitch. The method of claim 1, The filler is characterized in that the volatile content is controlled by heat treatment the pitch at 490 ~ 500 ℃ for 0.5 to 4 hours High density graphite. The method of claim 1, The binder is heat-treated for 1 to 6 hours at 200 ~ 240 ℃ characterized in that the volatile content is controlled High density graphite. The method of claim 1, The filler is characterized in that the coke High density graphite. The method of claim 2 or 3, The heat treatment is made while stirring the pitch at a rotational speed of 80 ~ 120rpm in an inert atmosphere High density graphite. Heat-treating the pitch at 490 to 500 ° C. for 0.5 to 4 hours to prepare a filler having a volatile content of 3 to 7 wt%; Heat-treating the pitch at 200 to 240 ° C. for 1 to 6 hours to prepare a binder having a volatile content of 58 to 60 wt%; Adjusting the particle size of the filler and binder to 325 mesh or less; And Mixing the filler and binder Method for producing high density graphite comprising a. The method of claim 6, The filler is characterized in that the coke Method for producing high density graphite. The method of claim 6, The heat treatment is made while stirring the pitch at a rotational speed of 80 ~ 120rpm in an inert atmosphere Method for producing high density graphite. The method of claim 6, After molding the mixed filler and binder, the first heat treatment for 1 to 3 hours at 1250 ~ 1250 carbonization, and the heat treatment for 1 to 3 hours at 2200 ~ 3000 ℃ further comprises the step of graphitizing Method for producing high density graphite.

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