Graphite manufacturing method

Abstract

The present invention relates to a method for producing graphite for use as high-temperature insulating material in the form of cubes, plates, or other components or as a filter. The objective is to provide a cost-effective method for producing graphite that can use particularly advantageous and renewable raw materials as starting materials, as well as waste paper. This objective is achieved by preparing a base material in the form of a mixture of carbon-based materials containing tree leaves, moss, or similar materials, such as grass, corn leaves, or at least one of sawdust, waste paper, or natural fibers, in any desired mixing ratio. The mixture is then macerated with a solvent for a relatively long period of time and shredded. A binder is then added to the mixture until a substantially homogeneous, paste-like mixture is obtained. The mixture is pressed to remove most of the solvent until a sufficiently stable, solvent-free press is obtained. The press is then dried until the residual solvent evaporates. The press is then graphitized into a block in a high-temperature furnace at temperatures above 2,000°C in an oxygen-free atmosphere under protective gas or in a vacuum.

Description

[Technical Field]

[0001] The present invention relates to a method for producing graphite for use as high temperature insulating material in the form of cubes, plates or other components or as filters. [Background technology]

[0002] In industrial production, where processes take place at high temperatures and high-temperature radiation into the environment is undesirable, because such radiation would result in unnecessary energy losses, high-temperature insulating materials are always required.Since such high-temperature insulating materials are required in large quantities, it is advantageous to use as starting materials as renewable and, in particular, inexpensive raw materials as much as possible.

[0003] Furthermore, the manufacturing process should be as simple as possible and should involve as few steps as possible, resulting in low overall costs. Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is to provide a cost-effective method for producing graphite for use as high-temperature insulating material or as a filter or building material, which method allows the use of particularly advantageous and renewable raw materials as starting materials, as well as waste paper.

[0005] According to the present invention, the above problem is solved by: - producing a base material in the form of a mixture of carbon-based materials containing leaves, moss or similar materials, such as grass, corn leaves, or at least one of sawdust, waste paper or natural fibers as raw materials, in any mixture ratio of these materials; - then macerating the mixture with a solvent for a relatively long period of time and chopping; - mixing the mixture with a binder until a substantially homogeneous paste-like mixture is formed; - removing most of the solvent by pressing the mixture until a sufficiently stable and solvent-free pressing product is produced; - drying the pressings until any residual solvent has evaporated; and - graphitizing said pressed pieces into blocks in a high-temperature furnace at temperatures above 2,000°C in an oxygen-free atmosphere under protective gas or in vacuum; This is achieved by:

[0006] In a first embodiment of the present invention, water is used as the solvent.

[0007] Alternatively, polyacrylonitrile (PAN) dissolved in dimethyl sulfoxide (DMSO) can be used as a solvent and binder at the same time, but in this case the pressed product must be immersed in water to initiate polymerization of the polyacrylonitrile, followed by drying.

[0008] The mixture can also be pressed by isostatic pressing to produce the pressed product.

[0009] In a further development of the invention, a water-soluble binder is added to the mixture during chopping in order to influence the density, with sugar in the form of syrup coming into consideration as a preferred binder.

[0010] Additionally, wheat starch can be mixed into the pasty mixture to affect the density of the final product.

[0011] In yet another aspect of the invention, the pressings are dried in an elevated temperature stabilization step prior to the high temperature treatment.

[0012] Finally, in a further processing step, the high temperature resistant graphitized block can have its surface post-processed in a mechanical processing step to produce standard parts.

[0013] Additionally, the graphitization temperature can be up to 3,000°C.

[0014] In order to make it possible to better machine blocks or plates made from graphite, for example by milling or turning, the material is impregnated to a density of 1 g / cm 3 It is advantageous to densify to a density less than 1000 MPa. For the impregnation treatment, phenolic resins, phosphates or pitch can be used.

[0015] The impregnated graphite can then be re-graphitized, and the process can be repeated multiple times.

[0016] The result is a cost-effective graphite element with improved mechanical properties suitable for use as a filter in the form of a cube, plate or other element.

[0017] The present invention will be described in more detail below with reference to examples. [Example]

[0018] To produce any shape of graphitized high temperature insulation material, filter or building material from cost-effective starting materials, a base material in the form of a mixture of carbon-based materials is first produced.

[0019] This base material should contain as raw materials at least one of leaves, moss or similar materials, such as grass, corn leaves, or sawdust, waste paper or natural fibers, and it can be produced in any mixture ratio of said materials.

[0020] The mixture is then macerated in a solvent, such as water, for a relatively long period of time and then mechanically chopped, with a binder being mixed into the mixture after chopping until a substantially homogeneous paste-like mixture is formed under stirring, chopping being possible but not necessary. Maceration of the mixture may be required for between one hour and several days, depending on the materials used.

[0021] The mixture is then pressed to remove most of the solvent until a sufficiently stable, solvent-free, and easy-to-handle pressing is produced, after which the pressing is dried in air, in a furnace, or in an oven until the residual solvent evaporates, taking great care to ensure that no solvent residue remains in the pressing that could damage the pressing by outgassing during subsequent high-temperature processing.

[0022] Finally, the pressed product is graphitized to a block in a high-temperature furnace in an oxygen-free atmosphere under protective gas or in vacuum at temperatures above 2,000°C, where the graphitization temperature can be up to 3,000°C.

[0023] As a precaution, the pressings may be dried at elevated temperatures in an additional stabilization step prior to the high temperature treatment.

[0024] The graphite block can then be broken down into the desired parts by mechanical processing.

[0025] Alternatively, polyacrylonitrile (PAN) dissolved in dimethyl sulfoxide (DMSO) can be used instead of water as a solvent and binder at the same time, but in this case the pressed product must be immersed in water to initiate polymerization of the polyacrylonitrile, followed by drying.

[0026] The mixture can also be pressed by isostatic pressing to produce the pressed product.

[0027] Furthermore, in order to influence the density, a water-soluble binder can be added to the mixture of carbon-based materials during the shredding, in which case sugar in the form of syrup comes into consideration as an advantageous binder.

[0028] Alternatively or additionally, wheat starch can be mixed into the pasty mixture to affect the density of the final product.

[0029] Finally, in a further processing step, the high temperature resistant graphitized block can have its surface post-processed in a mechanical processing step to produce standard parts.

[0030] In order to be able to process the blocks or plates made of graphite even better, for example by milling or turning, the material is impregnated with a thickness of 1 g / cm 3 It is advantageous to densify the pulp to a density less than 1000 kJ / cm, in which case phenolic resins, phosphates or pitch can be used for the impregnation treatment.

[0031] The impregnated graphite can then be re-graphitized, and the process can be repeated multiple times.

[0032] As a result, the method according to the invention can be used to produce cost-effective graphite components with improved mechanical properties suitable for use as high temperature insulating materials or as filters in the form of cubes, plates or other components.

Claims

1. 1. A method for producing graphite for use as high temperature insulating material or as a filter in the form of cubes, plates or other members, comprising: - producing a base material in the form of a mixture of carbon-based materials containing leaves, moss or similar materials as raw materials, such as grass, corn leaves, or at least one of sawdust, waste paper or natural fibers, in any mixing ratio of said raw materials; - then macerating the mixture with a solvent for a relatively long period of time and chopping; - mixing the mixture with a binder until a substantially homogeneous paste-like mixture is obtained; - removing most of the solvent by pressing the mixture until a sufficiently stable and solvent-free pressing is produced; - drying the pressings until the residual solvent has evaporated; and - graphitizing said pressed pieces to blocks in a high-temperature furnace in an oxygen-free atmosphere under protective gas or in vacuum at temperatures above 2,000°C; The method, characterized by:

2. 2. The method according to claim 1, characterized in that water is used as the solvent.

3. 2. The method according to claim 1, characterized in that polyacrylonitrile (PAN) dissolved in dimethyl sulfoxide (DMSO) is used as solvent and simultaneously binder.

4. 4. The method according to claim 3, wherein the pressed product is immersed in water to cause polymerization of the polyacrylonitrile.

5. 2. The method according to claim 1, wherein the pressing of the mixture to produce the pressed product is carried out by isostatic pressing.

6. 10. The method of claim 1, wherein a water-soluble binder is added to the mixture during shredding to affect density.

7. 7. The method according to claim 6, characterized in that sugar in the form of a syrup is used as binder.

8. 10. The method of claim 1, wherein wheat starch is mixed into the pasty mixture to influence the density of the final product.

9. 9. The method according to claim 1, wherein the pressings are dried at elevated temperature in a stabilization step before the high-temperature treatment.

10. 10. The method according to claim 1, wherein the high-temperature resistant graphitized block is subjected to a post-processing of its surface in a mechanical processing step to produce standard parts.

11. 2. The method of claim 1, wherein the graphitization temperature is up to 3,000°C.

12. 12. A method according to any one of claims 1 to 11, characterized in that the graphitized block is densified by an impregnation treatment to a density of less than 1 g / cm.

13. 13. The method according to claim 12, characterized in that for the impregnation treatment, phenolic resin, phosphate or pitch can be used.

14. 14. The method according to claim 12 or 13, characterized in that the impregnated graphite is then re-graphitized, wherein this process can be repeated multiple times.

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