KR102511052B1 - Separating Method of Carbon From Waste-matrial Contained Carbon and Manufacturing Method of Expanded or Expandable Graphite Using the Separated Carbon - Google Patents

Abstract

The present invention relates to a method for separating, floating, and recovering carbon particles from carbon-containing waste resources such as battery anode materials, mag carbon, and coke, and using the recovered carbon to manufacture expanded graphite. According to the present invention, the method for separating, floating, and recovering carbon particles from carbon-containing waste resources comprises: a first step of inputting carbon-containing waste resources in water and separating and floating carbon particles through ultrasonic processing; and a second step of filtering and separating the carbon particles separated and floated through the first step, wherein the first step can be performed by adding additional a foaming agent, and more preferably, can be performed by inputting 20 to 50 parts by weight of carbon-containing waste resources and 0.05 to 0.01 parts by weight of a foaming agent prepared with anhydrous ethanol with respect to 100 parts by weight of water at 20 to 55℃.

Description

Separating Method of Carbon From Waste-matrial Contained Carbon and Manufacturing Method of Expanded or Expandable Graphite Using the Separated Carbon}

The present invention relates to a method for manufacturing expanded graphite by separating and recovering carbon particles from carbon-containing waste resources such as battery negative electrode material, mag carbon, and coke, and using the recovered carbon.

In steel mills, converters, electric furnaces, ladles, etc. are built with highly refractory refractory bricks on the inside, and at this time, the refractory bricks are usually made of magnesium carbon (MgO-C)-based refractories with excellent fire resistance. However, when a converter or the like is used for a certain period of time, slag and foreign substances are attached to the inner refractory bricks, thereby deteriorating the fire resistance function. Accordingly, after a certain period of time, the existing refractory bricks are replaced with new refractory bricks, and the existing refractory bricks are waste mag-carbon-based refractories, and a plan for utilizing them is required. Among waste magnesium refractory materials, materials whose main component is MgO are recycled to a large extent, but magcarbon (MgO-C) is hardly recycled due to its characteristics such as color.

On the other hand, most of the waste batteries for mobile phones recover expensive metal components such as Ni, Co, Mn, Cu, and Al through pre- and post-treatment processes, but graphite, the main component of the anode material, is discarded after recovery. . In the case of waste batteries for vehicles, they are reused as ESS (Energy Storage System) after recovery, and for non-reusable waste batteries, graphite is discarded after recovering metal components similar to the treatment of cell phone batteries.

As the disposal of waste resources increases, interest in the utilization of waste resources is increasing. As a representative method of utilizing carbon-containing waste resources, there is a carbon recovery method through strong acid solution treatment. However, this method has disadvantages in that a large amount of strong acid waste solution is generated after carbon recovery, so a process to process it again is required, and it is limited due to special working environments and requirements that allow the use of strong acid solution. In particular, in the case of waste mag carbon, there is a limit in that it is difficult to separate and purify carbon through a simple strong acid solution treatment method.

KR 10-0605711 B1 KR 10-0908852 B1 KR 10-2021-0073045 A KR 10-2104562 B1

The present invention was developed to improve the problems associated with the use of strong acid solutions in conventional methods of utilizing carbon-containing waste resources, and is a new method capable of separating and recovering carbon from carbon-containing waste resources without using strong acid solutions in a water solvent condition. There is a technical challenge in providing a method capable of minimizing the generation of waste after separation and recovery of carbon by using ultrasonic treatment and a small amount of foaming agent.

In addition, the present invention is to provide a method for producing expanded graphite while preferably using carbon separated and recovered from carbon-containing waste resources.

In order to solve the above technical problem, the present invention, a first step of separating and floating carbon particles by introducing carbon-containing waste resources into water and treating them with ultrasonic waves; A second step of filtering and separating the carbon particles separated and floated through the first step; provides a method for recovering carbon separated and floated from carbon-containing waste resources, characterized in that it comprises a. Here, the first step may be carried out while further adding a foaming agent, more preferably, 20 to 50 parts by weight of carbon-containing waste resources and 0.05 to 0.01 parts by weight of a foaming agent prepared with anhydrous ethanol are added to 100 parts by weight of water, and the water temperature is 20 It can be carried out while sonicating while maintaining ~55 ℃.

In addition, the present invention is a method for producing expanded graphite using carbon recovered from carbon-containing waste resources, in which an aqueous solution of sulfuric acid is added to carbon recovered from carbon-containing waste resources, and potassium permanganate (KMnO ₄ ), water, and hydrogen peroxide are added to obtain A first step of stirring; Provides a method for producing expanded graphite, characterized in that it comprises: a second step of filtering the agitated material of the first step, drying at 100 to 120 ° C or heat-treating at 300 to 350 ° C or higher. More preferably, in the first step, 10 to 50 parts by weight of an aqueous sulfuric acid solution having a concentration of 40 to 50% by weight is added to 1 part by weight of carbon recovered from carbon-containing waste resources, 1 to 5 parts by weight of potassium permanganate (KMnO ₄ ), water 100 to 200 parts by weight, hydrogen peroxide (H ₂ O ₂ ) 100 to 200 parts by weight may be added and stirred.

According to the present invention, the following effects can be expected.

First, high-purity carbon can be separated and recovered from carbon-containing waste resources such as battery anode material, mag carbon, and coke, and the separated and recovered carbon can be used to manufacture expanded graphite. As a result, it can contribute to high value-added waste resources while replacing natural graphite, which was dependent on imports.

Second, since water is used as a solvent unlike the prior art that uses a strong and weak acid as a solvent, the generation of wastewater is extremely small compared to the conventional strong and weak acid solution, which is environmentally friendly.

1 is a comparative SEM image of an existing commercial product and expanded graphite prepared according to the present invention.

The present invention relates to a method for separating and recovering carbon from carbon-containing waste resources such as battery negative electrode material, mag carbon, and coke, and a method for producing expanded graphite using the separated and recovered carbon. In the present invention, expanded graphite encompasses expandable graphite and expanded graphite.

1. Separation and recovery of carbon

The present invention relates to a method for separating and recovering carbon from carbon-containing waste resources such as battery anode material, mag carbon, and coke, and recovering carbon after separating and floating carbon from carbon-containing waste resources through sonication in an aqueous state. It has technical features. Unlike the prior art that uses a strong and weak acid as a solvent, water is used as a solvent and carbon is separated and floated through ultrasonic treatment to recover it.

Specifically, the method for recovering carbon separation and flotation from carbon-containing waste resources according to the present invention includes a first step of separating and floating carbon particles by introducing carbon-containing waste resources into water and treating them with ultrasonic waves; and a second step of filtering and separating the carbon particles separated and floated through the first step.

The first step is a process of separating and flotating carbon by ultrasonicating carbon-containing waste resources in an aqueous state. Bubbles are induced/expanded/destroyed by ultrasonic waves in the liquid phase, and a large amount of energy is generated during the bubble destruction process to separate, pulverize, and remove particles in the liquid phase to separate carbon particles, and some of the generated bubbles are not destroyed. The air bubbles float on the surface layer of the liquid phase or inside the liquid phase together with the separated carbon particles. Destructive energy due to ultrasonic waves affects the particles in the liquid phase, enabling separation and dispersion treatment between particles without damaging the particles. In particular, energy is generated during the bubble breaking process, which is accompanied by a temperature increase, and the temperature rise contributes to improving the separation effect of the carbon particles by providing an atmosphere favorable for bubble breaking. The separated carbon particles remain in the water due to the inherent hydrophobicity of carbon. The carbon particles remaining in the water are attached to the carbon particles generated by ultrasonic waves and float on the water or the surface of the water due to the floating characteristics of the bubbles. do.

The first step may be performed by further introducing a foaming agent, and the foaming agent improves the effect of generating bubbles by ultrasonic waves, thereby enabling stable formation of bubbles. In other words, since the surface tension of water is lowered by the foaming agent and fine bubbles are stably formed, it helps to separate carbon through the creation/destruction of bubbles. As the foaming agent, high-purity (99.5%) anhydrous ethanol having a hydrophobic hydrocarbon group can be preferably used.

In the first step, 20 to 50 parts by weight of carbon-containing waste resources and 0.05 to 0.01 parts by weight of a foaming agent made of high-purity anhydrous ethanol are added to 100 parts by weight of water, and the water temperature is maintained at 20 to 55 ° C. It is preferable to carry out ultrasonic treatment for about an hour. At this time, if the water temperature is less than 20 ℃, the carbon separation performance is lowered due to the large thermal energy loss due to the low temperature, and if the water temperature exceeds 55 ℃, the bubble generation is reduced due to the high temperature, resulting in a decrease in the carbon separation performance as well as floating of the separated carbon. Characteristics are also a deteriorating factor. Carbon-containing waste resources are used in an amount of 20 to 50 parts by weight per 100 parts by weight of water. If it is less than 20 parts by weight, the separation and recovery rate per carbon separation treatment process (the amount of carbon samples recovered by separation and treatment) is lowered, which is not suitable in terms of process efficiency. , If it exceeds 50 parts by weight, it is difficult to secure carbon separation efficiency due to the input amount of excessive carbon-containing waste resources compared to the water solvent, and it is difficult to secure the floating characteristics of carbon particles. The foaming agent is high-purity anhydrous ethanol, and it is preferable to use 0.05 to 0.01 parts by weight based on 100 parts by weight of water. If it is less than 0.05 parts by weight, it is difficult to secure properties as a foaming agent, and if it exceeds 0.01 parts by weight, excessive surface tension lowering characteristics due to excessive mixing There is a risk of reducing the recovery rate of carbon by degrading the separation and flotation characteristics of the separated carbon particles by causing a problem in bubble generation during ultrasonic treatment.

The second step is a process of recovering the carbon particles, and the carbon particles separated and floated through the first step are filtered and separated. Since the carbon particles are separated and floated through the first step, only the carbon particles can be separated by simply filtering the upper layer. Since the first step was carried out in a water solvent, the separated carbon particles are washed with water, and thereby become purified without going through a separate washing process. As a result, it is possible to recover carbon particles separated and refined from carbon-containing waste resources such as battery negative electrode material, mag carbon, and coke.

2. Manufacturing method of expanded graphite

The present invention proposes a method for producing expanded graphite using carbon recovered from carbon-containing waste resources. A method for producing expanded graphite according to the present invention includes a first step of adding an aqueous solution of sulfuric acid to carbon recovered from carbon-containing waste resources, adding potassium permanganate (KMnO4), water, and hydrogen peroxide to stirring; After filtering the agitated material of the first step, a second step of drying at 100 ~ 120 ℃ or heat treatment at 300 ~ 350 ℃ or more; is configured to include.

The first step is a process of oxidizing carbon, which weakens the interaction force between the carbon structures of carbon and infiltrates the acidic material into the weakened interlayer bonds. In the first step, 10 to 50 parts by weight of an aqueous solution of sulfuric acid at a concentration of 40 to 50% by weight is added to 1 part by weight of carbon recovered from carbon-containing waste resources, 1 to 5 parts by weight of potassium permanganate (KMnO ₄ ), and 100 to 200 parts by weight of water It is preferable to add 100 to 200 parts by weight of hydrogen peroxide (H ₂ O ₂ ) and carry out stirring at normal pressure and room temperature (15 to 30° C.) for 1 hr or more.

In the first step, the sulfuric acid aqueous solution is a source of hydrogen sulfate ions (HSO ₄ ^- ), and is preferably used at a concentration of 40 to 50% by weight for usability. It is preferable to use 10 to 50 parts by weight of the sulfuric acid aqueous solution at a concentration of 40 to 50% by weight based on 1 part by weight of carbon. If the sulfuric acid aqueous solution is less than 10 parts by weight, the permeability of hydrogen sulfate ions, which must be penetrated between the carbon particle structure layers, is lowered, resulting in insufficient expansion properties of carbon when manufacturing expanded graphite. It is uneconomical compared to improved penetration performance.

In the first step, potassium permanganate (KMnO ₄ ) reacts with sulfuric ^acid in a water solvent as an oxidizing agent to form hydrogen sulfate ions to be inserted into the carbon interlayer structure _. It oxidizes and plays a role in facilitating entry of hydrogen sulfate ions into the carbon interlayer structure. Potassium permanganate is used in an amount of 1 to 5 parts by weight based on 1 part by weight of carbon. If it is less than 1 part by weight, the production of hydrogen sulfate ions that must enter between the carbon interlayer structures is not sufficient, resulting in insufficient production of expanded graphite. If it exceeds 5 parts by weight, KMnO ₄ is a highly exothermic process due to the nature of KMnO 4. The reason why excessive KMnO ₄ causes process inconvenience is that potassium and manganese ions must be removed in the final process, so the use of excessive KMnO ₄ is unnecessary, and above all, expensive As a material, it is economically burdensome.

Water is used as a solvent to control the risk of excessive temperature rise since the reaction between KMnO ₄ and sulfuric acid is an exothermic reaction, and to facilitate removal through filtration and washing by ionizing potassium and manganese after the reaction of KMnO ₄ . It is preferable to use 100 to 200 parts by weight of water based on 1 part by weight of carbon. If it is less than 100 parts by weight, it is insufficient to suppress excessive heat generated in the reaction of sulfuric acid and potassium permanganate, and if it exceeds 200 parts by weight, excessive dilution of sulfuric acid As a result, the reaction with potassium permanganate is insufficient, so that the generation of hydrogen sulfate ions is inhibited, resulting in a problem unsuitable for treatment of expanded graphite.

Hydrogen peroxide (H ₂ O ₂ ) becomes a material for removing the remaining permanganic acid (MnO ₄ ). KMnO ₄ is ionized into MnO ₄ ^- by the input reaction, and the ionized MnO ₄ ^- participates in the oxidation reaction, and the remaining MnO ₄ ^- reacts with water to exist in the solvent in the form of MnO _{4 .} O ₂ ) ionizes MnO ₄ to Mn ²⁺ so that it can be separated and removed from carbon during the carbon filtration process. It is preferable to use 100 to 200 parts by weight of hydrogen peroxide based on 1 part by weight of carbon. If it is less than 100 parts by weight, the amount of hydrogen peroxide required for the reaction to remove MnO ₄ is insufficient, making it difficult to remove sufficient MnO ₄ , thereby affecting the purity of carbon. If it exceeds 200 parts by weight, unnecessary material consumption is caused by excessive mixing. .

The second step is a step of expanding graphite, which may be dried at 100 to 120 ° C to produce expandable graphite or heat-treated at 300 to 350 ° C for 12 hr or more to produce expanded graphite.

[Test Example 1] Separation efficiency of carbon according to ultrasonic treatment

1. Treatment of Magcarbon

Mag carbon (particle size up to 1±0.1mm, 0.6mm or more 16-19% by weight, less than 0.6mm, 0.3mm or more 41-52% by weight, less than 0.3mm 32-40% by weight, carbon content 15-25% by weight) was treated under the same conditions as in [Table 1] below to perform carbon separation. In [Table 1] below, ultrasonic treatment was applied for 30 minutes at an intensity of 2000 W.

Treatment of Magcarbon division Comparative Example 1 Comparative Example 2 Example 1 Example 2 Applied process Air injection injury treatment O O X X sonication X X O O Injection of foaming agent X O X O Composition (g) Mag carbon (MgO-C) 30 30 40 40 water 100 100 100 100 foaming agent - 0.03 - 0.04 Sonication time (min) - - 30 30 Water temperature change range (℃) 26~31 27-30 28~36 24-38

2. Recovery of carbon

After carbon separation was performed by applying the input amount and treatment conditions as shown in [Table 1], the separated carbon floating matter was filtered and dried in a cake state (drying at 110 ± 5 ° C for 12 hr for moisture drying), and then the carbon recovery rate (MgO -The amount of recovered carbon compared to the input amount of C) was confirmed. The confirmation results are shown in [Table 2] below.

carbon recovery rate division Comparative Example 1 Comparative Example 2 Example 1 Example 2 carbon recovery rate
(% by weight compared to MgO-C input) 0.71 0.91 8.3 18.9 carbon purity 25.5 26.0 94.3 more than 98%

As shown in [Table 2], Comparative Example 1 to which only air injection flotation treatment was applied showed an extremely low carbon recovery rate of 0.71%, and from this, it is difficult to separate and recover carbon from mag carbon through simple air injection flotation separation. can know that Comparative Example 2 was carried out by applying a foaming agent during the air injection floating separation treatment. Example 1 is a case where ultrasonic affinity treatment is applied. As can be seen, the recovery rate of carbon is 8.3%, which is significantly higher than that of Comparative Examples 1 and 2, but the recovery rate compared to the carbon contained in mag carbon is slightly lower. Example 2 is a case in which a foaming agent was applied to the ultrasonic treatment process, and the carbon recovery rate was 18.9%, which showed a high recovery rate comparable to the carbon content contained in mag carbon.

[Test Example 2] Separation efficiency of carbon according to the input amount of mag carbon

1. Treatment of Magcarbon

Mag carbon (particle size up to 1±0.1mm, 0.6mm or more 16-19% by weight, less than 0.6mm, 0.3mm or more 41-52% by weight, less than 0.3mm 32-40% by weight, carbon content 15-25% by weight) was treated under the same conditions as in [Table 3] below to perform carbon separation.

Treatment of Magcarbon division Example 3 Comparative Example 3 Comparative Example 4 Applied process sonication Sonication (2000W, 30min) Composition (g) Mag carbon (MgO-C) 40 60 80 water 100 100 100 foaming agent 0.04 Water temperature change range (℃) 24-38 34~37 56~61

2. Recovery of carbon

After carbon separation was performed by applying the treatment conditions as shown in [Table 3], the separated carbon floating matter was filtered and dried in a cake state (110 ± 5 ° C for 12 hr drying for moisture drying), and then the carbon recovery rate (MgO-C The amount of recovered carbon relative to the input amount) was confirmed. The confirmation results are shown in [Table 4] below.

carbon recovery rate division Example 3 Comparative Example 3 Comparative Example 4 carbon recovery rate
(% by weight compared to MgO-C input) 18.9 24.4 29.1 Carbon purity (%) 98 or higher 81.4 68.8

As a result of comparing the carbon recovery rate and the purity of the recovered carbon according to the input amount of mag carbon, the recovery rate increased as the input amount increased, but the purity of the recovered carbon decreased. From these results, it can be seen that when the input amount of mag-carbon is excessive, the fine mag-carbon (MgO-C) particles that are not separated along with the carbon particles separated and floated through ultrasonic treatment are also floated, resulting in an increase in the overall recovery rate (weight). Since an excessive amount of magnesium carbon (MgO-C) input affects the purity of the carbon recovered sample, it can be said that an input amount of 60 parts by weight or more is not suitable.

[Test Example 3] Separation efficiency of carbon according to the amount of foaming agent

1. Treatment of Magcarbon

Mag carbon (particle size up to 1±0.1mm, 0.6mm or more 16-19% by weight, less than 0.6mm, 0.3mm or more 41-52% by weight, less than 0.3mm 32-40% by weight, carbon content 15-25% by weight) was treated under the same conditions as in [Table 5] below to perform carbon separation.

Treatment of Magcarbon division Example 4 Comparative Example 5 Comparative Example 6 Composition sonication Sonication (2000W, 30min) input configuration
(g) MgO-C 40 40 40 water 100 100 100 foaming agent 0.04 0.005 0.4

2. Recovery of carbon

After carbon separation was performed by applying the treatment conditions as shown in [Table 5], the separated carbon floating matter was filtered in a cake state and dried (110 ± 5 ° C for 12 hr drying for moisture drying), and then the carbon recovery rate (MgO-C The amount of recovered carbon relative to the input amount) was confirmed. The confirmation results are shown in [Table 6] below.

carbon recovery rate division Example 4 Comparative Example 5 Comparative Example 6 carbon recovery rate
(% by weight compared to MgO-C input) 18.9 11.2 10.7 Carbon purity (%) 98 or higher 98 or higher 79.3

The effect of the foaming agent for carbon recovery can be confirmed through the result (Comparative Example 5) that the carbon recovery rate is lowered when the amount of the foaming agent is insufficient. In the case of an excessive amount of foaming agent, the carbon recovery rate and purity were also low.

[Test Example 4] Separation efficiency of carbon according to sonication conditions

1. Treatment of Magcarbon

Mag carbon (particle size up to 1±0.1mm, 0.6mm or more 16-19% by weight, less than 0.6mm, 0.3mm or more 41-52% by weight, less than 0.3mm 32-40% by weight, carbon content 15-25% by weight) Carbon separation was performed by treating the same under the conditions shown in Table 7 below.

Treatment of Magcarbon division Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Example 5 Example 6 input configuration
(g) MgO-C 40 40 40 40 40 40 water 100 100 100 100 100 100 foaming agent 0.04 0.04 0.04 0.04 0.04 0.04 Application conditions
(ultrasonic treatment) Century (W) 750 2,000 Processing time (min) 10 30 60 10 30 60

2. Recovery of carbon

After carbon separation was performed by applying the treatment conditions as shown in [Table 7], the separated carbon floating matter was filtered and dried in a cake state (110 ± 5 ° C for 12 hr drying for moisture drying), and then the carbon recovery rate (MgO-C The amount of recovered carbon relative to the input amount) was confirmed. The confirmation results are shown in [Table 8] below.

carbon recovery rate division Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Example 5 Example 6 Carbon recovery rate
(% by weight compared to MgO-C input) less than 1 less than 1 2.7 6.6 18.9 19.0 Carbon purity (%) 98 or higher 98 or higher 98 or higher 98 or higher 98 or higher 98 or higher

As a result of comparing the characteristics according to the intensity/time of ultrasonic treatment, it was difficult to secure a carbon recovery rate through a short treatment time of less than 1 hour through ultrasonic treatment at an intensity of 750 W (Comparative Examples 7, 8, and 9), and process efficiency was improved. For this, it was confirmed that the application of an ultrasonic treatment process of 2,000 W and 30 minutes or more was necessary.

[Manufacture Example] Manufacture of expanded graphite

Expanded graphite was prepared using the separated and recovered carbon according to Example 2 of [Test Example 1] above. Based on 1 part by weight of separated and recovered carbon, 40 parts by weight of sulfuric acid, 3.2 parts by weight of potassium permanganate, 140 parts by weight of water, and 125 parts by weight of hydrogen peroxide were added, stirred, maintained at room temperature and normal pressure for 12 hr, and filtered and dried to obtain expandable graphite ((expandable graphite) was prepared, and expanded graphite was prepared by heat-treating the expandable graphite for 4 hr at a high temperature of 300 to 330 ° C. When comparing the expandable graphite and expanded black silver prepared in this way with commercial products, the following [Table 9] and Figure 1 showed the same results.

Characteristics of expanded graphite division Commercial Products the present invention Expandable graphite
bulk density 0.58
(spec 0.56~0.60) 0.55 Expansion rate of expanded graphite spec 250~350 300~340

As shown in [Table 9], the bulk density of the expandable graphite prepared according to the present invention was confirmed to have similar characteristics to commercial products. In addition, as a result of confirming the SEM image of the expanded graphite, it was found that the degree of expansion between the carbon layers was similar to that of commercial products, as shown in FIG. It became. Thus, it can be said that the expanded graphite prepared according to the present invention has properties similar to those of commercial products.

Claims (5)

A first step of separating and floating carbon particles by introducing carbon-containing waste resources into water and treating them with ultrasonic waves; A second step of filtering and separating the carbon particles separated and floated through the first step; including,
The first step is a method for recovering carbon separated floating phase from carbon-containing waste resources, characterized in that carried out while further introducing a foaming agent. delete In paragraph 1,
In the first step, 20 to 50 parts by weight of carbon-containing waste resources and 0.05 to 0.01 parts by weight of a foaming agent prepared with anhydrous ethanol are added to 100 parts by weight of water, and ultrasonic treatment is performed while maintaining the water temperature at 20 to 55 ° C. A method for recovering carbon separation and flotation from carbon-containing waste resources. A method for producing expanded graphite using carbon recovered from carbon-containing waste resources according to claim 1 or 3,
A first step of adding sulfuric acid aqueous solution to carbon recovered from carbon-containing waste resources, adding potassium permanganate (KMnO4), water, and hydrogen peroxide to stirring; After filtering the agitated material of the first step, a second step of drying at 100 ~ 120 ℃ or heat treatment at 300 ~ 350 ℃ or more; expanded graphite manufacturing method characterized in that it comprises a. In paragraph 4,
In the first step, 10 to 50 parts by weight of an aqueous solution of sulfuric acid having a concentration of 40 to 50% by weight is added to 1 part by weight of carbon recovered from carbon-containing waste resources, 1 to 5 parts by weight of potassium permanganate (KMnO ₄ ), 100 to 100 parts by weight of water 200 parts by weight, hydrogen peroxide (H ₂ O ₂ ) 100 to 200 parts by weight of expanded graphite manufacturing method, characterized in that carried out while stirring.

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