KR100327134B1 - Manufacturing method of exfoliated graphite - Google Patents

Abstract

The present invention relates to a method for producing expanded graphite by forming an interlayer compound present between layers of graphite using powder of lithium and paraffin without thermally expanding the graphite, and then heat-treating the same. In the method for producing expanded graphite, which forms an interlayer compound and heat-treats it to produce expanded graphite, (A) a treatment mixture obtained by mixing metallic lithium powder and paraffin in a weight ratio of 1: 1 by mixing the graphite mixture with graphite powder, and Chemical treatment step of reacting the mixture for 5 to 7 hours at a temperature range of 180 to 230 ℃, pressure of 250 to 350kg / ㎠; (B) a coarse grinding step of grinding the chemically treated mixture to 60 mesh or less; (C) a water treatment step of dipping the crudely ground mixture in water at a temperature of 70 to 80 ° C. for at least one hour and then taking it out; (D) a drying step of drying the water-treated mixture; And (e) a heat treatment step of heat treating the dried mixture at a temperature of 750 to 900 ° C.

Accordingly, while providing a manufacturing method for producing expanded graphite having a sufficiently high degree of expansion, the amount of sulfur oxides and nitrates contained in the obtained expanded graphite is greatly reduced, thereby greatly reducing the problem of corroding metal when used as a sealing material. It can be effective.

Description

Manufacturing method of expanded graphite {Manufacturing method of exfoliated graphite}

The present invention relates to a method for producing expanded graphite. More specifically, the present invention relates to a method for producing expanded graphite by forming an interlayer compound existing between layers of graphite using powder of lithium and paraffin without thermally expanding the graphite, and then heat-treating it. will be.

Expanded graphite refers to a low-density graphite powder on a fiber worm which rapidly thermally decomposes an interlayer compound of graphite or its residual compound under high temperature and expands the interlayer space of the graphite in a direction perpendicular to the layer surface by the gas pressure as the decomposition product.

The expanded graphite was in Shafhautl, B., in the middle of the 19th century. Seed. It was made by BCBrodie and the like, and it was found that a molded article of various shapes can be made without a binder. In the 1970's, it was manufactured as a sheet by UCC and grafoil. It has been manufactured and sold under the trade name, and has been used as a sealing material, a heat insulating material, etc. in various industrial fields, and the production and use of expanded graphite have been noted in Japan. Expanded graphite, which is made of natural graphite, is easy to statically plastically deform, and a compact having a maximum density of about 2.1 can be easily obtained by physical adhesion even if the powder is pressed as it is, but it can be a sheet having a relatively low density of plasticity. In the case of molding without a binder, graphite oxide, hydrofluoric acid, polycarboxyran, and the like may be used as the binder. The density can be adjusted within the range of about 0.8 to 1.5 depending on the molding conditions, it can be adjusted depending on the intended use. Representative physical properties are listed in Table 1 below.

Such expanded graphite has good plasticity and compression restorability, and has characteristics not found in conventional carbon materials. In addition, the anisotropy is large and the ventilation rate is excellent regardless of the low density. The thickness of the sheet may be usually about 0.5 mm, and may be used as it is or in a stacked form. The powder may be molded as it is, and may be freely applied in molding, such as being primarily processed onto a chip and then molded into a predetermined shape.

Conventional methods for producing expanded graphite include graphite powders such as natural graphite, pyrolytic graphite, and kishi graphite, and inorganic acids such as concentrated sulfuric acid, acetic acid and selenic acid, and strong oxidizing agents such as concentrated acetic acid, perchloric acid, permanganate, dichromate, and hydrogen peroxide. After chemical treatment to produce a graphite intercalation compound, it was washed with water, dried, and heat treated at a high temperature of about 700 ° C or higher.

For industrial mass production, the graphite powder is acid treated with 90% concentrated sulfuric acid (95 to 98%) and 10% concentrated nitric acid (specifically 1.33), and sulfuric acid-interlayer compound (H ₂ SO _4- ). GIC) is produced, washed with water, dried, and then heat-treated at a temperature of about 800 ° C., so-called 'chemical deposition method' has been known in general. However, such chemical deposition method has recently been avoided due to the pollution and the working environment due to the vapor and nitrous oxide (NO _x ) containing heavy metals generated during the rapid heat treatment, to reduce the vapor and nitrate It is being replaced by a method using an oxidizing agent such as sulfite and hydrogen perchlorate.

However, despite the replacement of oxidants, chemical deposition methods cannot (1) avoid the generation of harmful gases from oxidants, (2) require large amounts of water at the time of washing, and (3) batch processing methods. (Batch type), there was a problem that continuous manufacturing is difficult.

As one method for solving this problem, an electrolytic manufacturing method has been studied.

The electrolytic production method has been developed to produce a graphitic acid sulfate interlayer compound by electrolytic oxidation of graphite powder in sulfuric acid, and then partially decompose the compound by electrolytic reduction to form a residual compound remaining in the graphite interlayer.

This method requires (1) no oxidizing agent, (2) no water washing, (3) a relatively thin sulfuric acid solution of about 10 mol / l, and (4) an expansion rate during heat treatment. It can be controlled by electrolytic conditions, and (5) it has the advantage of being able to operate continuously. However, this electrolytic manufacturing method has to use electricity for a long time, low productivity, low productivity, low intercalation effect of sulfuric acid, it is not easy to form the interlayer compound, there may be a problem that the structure of the graphite is partially destroyed.

When expanded graphite is processed into a sealing material or the like, it is preferable that sulfur oxides and nitrates contained therein do not contain these sulfur oxides or nitrates because they cause corrosion of the counter metal. In the manufacturing method, there is a problem that it is extremely difficult to avoid the inclusion of sulfur oxides or nitrates in the expanded graphite obtained because of the presence of sulfur or nitrogen components contained in the graphite and because sulfuric acid, acetic acid, etc. are used as the oxidizing agent.

In addition, a method of preparing expanded graphite which rapidly heats the residual compound, which is a decomposition product thereof, using KC ₂₄ (THF) ₂ ternary graphite interlayer compound as a starting material has been proposed, but since tetrahydrofuran is added, There is a problem that productivity is reduced due to complexity, and potassium is also used, which is difficult to handle under atmospheric conditions because potassium easily reacts with moisture in the air, and it is not only difficult to intercalate potassium, but also to intercalation. The interlayer compound is also unstable on its own, resulting in a complicated manufacturing process.

It is an object of the present invention to provide a method for producing expanded graphite by forming an interlayer compound present between layers of graphite using powder of lithium and paraffin and then heat treating it.

It is another object of the present invention to provide an expanded graphite prepared by a method of producing expanded graphite by forming an interlayer compound present between layers of graphite using powder of lithium and paraffin and then heat treating it.

In the method for producing expanded graphite according to the present invention, in the method for producing expanded graphite in which an interlayer compound is formed in graphite and heat-treated to produce expanded graphite, (a) metal lithium powder and paraffin in a weight ratio of 1: 1. A chemical treatment step of mixing the treated mixture by mixing with graphite powder and reacting the mixture under a temperature range of 180 to 230 ° C. and a pressure of 250 to 350 kg / cm 2 for 5 to 7 hours; (B) a coarse grinding step of grinding the chemically treated mixture to 60 mesh or less; (C) a water treatment step of dipping the crudely ground mixture in water at a temperature of 70 to 80 ° C. for at least one hour and then taking it out; (D) a drying step of drying the water-treated mixture; And (e) a heat treatment step of heat-treating the dried mixture at a temperature of 750 to 900 ° C.

In the chemical treatment step of (a), the mixing ratio of the mixture: graphite powder may be in a ratio of 10 to 30% by weight: 70 to 90% by weight.

In the drying step of (d) it may consist of drying the mixture at a temperature of at least 100 ℃ or more for at least 2 hours.

Hereinafter, the present invention will be described in detail with reference to specific examples.

In the method for producing expanded graphite according to the present invention, a treatment mixture obtained by mixing metal lithium powder and paraffin in a weight ratio of 1: 1 is mixed with graphite powder, and the mixture is in a temperature range of 180 to 230 ° C., 250 to 350 kg / Chemically treated by reacting for 5 to 7 hours at a pressure of cm 2, and then heat-treating it at a temperature of 750 to 900 ° C. to easily and easily produce expanded graphite with little residual sulfur oxides and nitrates. It is characterized by.

The chemical treatment step (a) is a step for forming an interlayer compound in graphite, which is characterized by forming an interlayer compound using a mixture of lithium metal powder and paraffin, unlike conventional oxidizing agents or strong acids. The treatment mixture of this mixture of metallic lithium powder and paraffin can greatly reduce the residual sulfur oxides and nitrates in the expanded graphite obtained. In order to facilitate the formation of the interlayer compound, the reaction after mixing the treated mixture and the graphite powder may be made to react for 5 to 7 hours under a temperature range of 180 to 230 ° C. and a pressure of 250 to 350 kg / cm 2. If the reaction temperature is less than 180 ° C there may be a problem that does not occur a sufficient reaction, on the contrary exceeding 230 ° C may have a problem that the paraffin is modified and lost. If the reaction pressure is less than 250kg / ㎠ may also have a problem that a sufficient reaction does not occur, on the contrary, exceeding 350kg / ㎠ can be understood as merely an increase in unnecessary pressure. If the reaction time is less than 5 hours there may be a problem that the reaction is not completed sufficiently, it can be understood that the maintenance of the reaction conditions for more than 7 hours is only unnecessary.

The mixing ratio of the treated mixture: graphite powder in the above is preferably made in a ratio of 10 to 30% by weight: 70 to 90% by weight. When the content of the treated mixture is less than 10% by weight, there may be a problem in that the amount of the interlayer compound in the graphite is low, so that the degree of expansion is low. There may be problems that prevent you from doing so.

In the coarse grinding step (b), the chemically treated mixture is pulverized to 60 mesh or less by a conventional method and apparatus, and serves to make the particle size uniform. In the water treatment step of (c), the crudely ground mixture is immersed in water at a temperature of 70 to 80 ° C. for at least 1 hour and then taken out to serve to remove water-soluble impurities. The drying step of (d) serves to remove the water contained in the mixture in the water treatment step. These coarse grinding step, water treatment step and drying step can be understood to be the same or similar to the processes for performing grinding, water treatment and drying in the conventional method for producing expanded graphite. In particular, it is preferable that the drying step comprises drying the mixture at a temperature of at least 100 ° C. or more for at least 2 hours. The degree of expansion may vary depending on the dry state, and control of the residual amount of water in the mixture after drying may be easily adjusted according to the physical properties of the expanded graphite to be obtained.

Thereafter, the mixture dried in the heat treatment step (e) may be thermally treated at a temperature of 750 to 900 ° C., thereby obtaining expanded graphite. As the heat treatment step is an important step for determining the degree of expansion of the expanded graphite, it will be apparent to those skilled in the art that the physical properties of the expanded graphite obtained by adjusting the degree of expansion can be easily adjusted.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described.

The following examples are intended to illustrate the invention and should not be understood as limiting the scope of the invention.

Example

Treated mixture of metal lithium powder and paraffin oil in a weight ratio of 1: 1 is mixed with natural graphite according to the following Table 2, and reacted under a pressure of 200 ° C. and 300 kg / cm 2 for 6 hours to form an interlayer compound in the graphite. After coarsely pulverizing it to 60 mesh, it was immersed in water at a temperature of 75 ° C. for 1 hour and then taken out and dried at 105 ° C. for 2 hours. The dried powdery mixture was filled with twelve transparent quartz tubes having a diameter of 20 mm and a height of 100 mm by 0.1 g for each quartz tube. Then, each quartz tube was heat-treated according to the heat treatment temperature according to Table 2, and the volume expansion degree was measured. Was repeated three times. The degree of expansion is shown in Table 2 below with the average value of the volume of the final expanded graphite at 100% of the original volume.

As a result of the synthesis of the above embodiments, expanded graphite having sufficiently high degree of expansion is produced by using a mixture of metal lithium powder and paraffin in place of a conventional oxidant or strong acid as a treatment mixture for forming an interlayer compound in graphite. It could be confirmed.

Therefore, according to the present invention, there is an effect of providing a manufacturing method for producing expanded graphite having a sufficiently high degree of expansion.

In addition, according to the present invention, since there is no use of an oxidizing agent or a strong acid, the amount of sulfur oxides and nitrates contained in the expanded graphite obtained is greatly reduced, thereby greatly reducing the problem of corrosive metals when used as a sealing material. .

Although the present invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the technical scope of the present invention, and such modifications and modifications are within the scope of the appended claims.

Claims (3)

In the manufacturing method of expanded graphite to form an interlayer compound in the graphite, and to heat-treat it to produce expanded graphite, (A) The treatment mixture obtained by mixing metallic lithium powder and paraffin in a weight ratio of 1: 1 is mixed with graphite powder, and the mixture is mixed for 5 to 7 hours under a temperature range of 180 to 230 ° C. and a pressure of 250 to 350 kg / cm 2. Reacting a chemical treatment step; (B) a coarse grinding step of grinding the chemically treated mixture to 60 mesh or less; (C) a water treatment step of dipping the crudely ground mixture in water at a temperature of 70 to 80 ° C. for at least one hour and then taking it out; (D) a drying step of drying the water-treated mixture; And (E) a heat treatment step of heat-treating the dried mixture at a temperature of 750 to 900 ° C; Method for producing expanded graphite, characterized in that consisting of. The method of claim 1, Process for producing the expanded graphite characterized in that the mixing ratio of the treated mixture: graphite powder in the chemical treatment step (a) of 10 to 30% by weight: 70 to 90% by weight. The method of claim 1, The method of claim 1, wherein the drying of the mixture comprises drying the mixture at a temperature of at least 100 ° C. for at least 2 hours.