Method for the production of graphite

Abstract

The invention relates to a method for producing graphite for use as a high-temperature insulation material or as a filter in the form of cubes, sheets or other components. The aim is to create a low-cost method for producing graphite in which particularly favourable and renewable raw materials as well as waste paper can be used as starting materials. Said aim is achieved by: producing a base material in the form of a mixture of carbon-based materials containing, in any mixing ratio, at least one raw material selected from foliage, moss or similar materials, such as grass, corn leaves or even sawdust, waste paper or natural fibres; soaking the mixture in a solvent over an extended period of time and comminuting it; adding a binder to the mixture until a largely homogeneous paste-like mixture is obtained; largely removing the solvent by pressing the mixture until a sufficiently stable and low-solvent pressed article is obtained; drying the pressed article until the remaining solvent has evaporated; and graphitising the pressed article to produce a block in a high-temperature furnace in an oxygen-free atmosphere, under inert gas, or in a vacuum at a temperature of > 2,000°C.

Description

[0001] Process for producing graphite

[0002] The invention relates to a process for producing graphite for use as a high-temperature insulation material or as a filter in the form of cubes, plates or other components.

[0003] High-temperature insulation materials are required in industrial manufacturing wherever processes take place at high temperatures and where high temperature radiation into the environment is undesirable, as it leads to unnecessary energy losses. Since such high-temperature insulation materials are required in large quantities, it is advantageous to use renewable and particularly inexpensive raw materials as the starting material.

[0004] In addition, the manufacturing process should be as simple as possible and involve as few steps as possible so that the overall costs are low.

[0005] The object of the invention is to create a cost-effective process for the production of graphite for use as a high-temperature insulation material or as a filter or building material, in which particularly inexpensive and renewable raw materials as well as waste paper can be used as starting material.

[0006] According to the invention this is achieved by

[0007] - that a base material in the form of a mixture of carbon-based materials, containing at least one of the raw materials leaves, moss or similar materials, such as grass, corn leaves or sawdust, waste paper or natural fibers, which is produced in any mixing ratio of the materials,

[0008] - that the mixture is then soaked in a solvent over a longer period of time and crushed,

[0009] - that a binding agent is added to the mixture until a largely homogeneous paste-like mixture is formed,

[0010] - that the solvent is largely removed by pressing the mixture until a sufficiently stable and low-solvent compact is obtained,

[0011] - that the pellet is dried until the residual solvent has evaporated, and

[0012] - that the compact is graphitized into a block in a high-temperature furnace in an oxygen-free atmosphere under protective gas or in a vacuum at a temperature of > 2,000 ° C.

[0013] In a first embodiment of the invention, water is used as the solvent.

[0014] Alternatively, polyacrylonitrile (PAN) dissolved in dimethyl sulfoxide (DMSO) can be used as a solvent and binder. In this case, however, it is necessary to immerse the compressed pellet in water to polymerize the polyacrylonitrile and then dry it.

[0015] The pressing of the mixture to produce the pellet can also be done by isostatic pressing.

[0016] In a further development of the invention, a water-soluble binding agent is added to the mixture during comminution in order to influence the density, the most suitable binding agent being sugar in the form of syrup.

[0017] It is also possible to add wheat starch to the paste-like mixture to influence the density of the final product.

[0018] In a further embodiment of the invention, the compact is dried at elevated temperature in a stabilization step before the high-temperature treatment.

[0019] Finally, in a further processing step, it is possible to rework the surface of the high-temperature-resistant graphitized block in a mechanical processing step in order to produce standard components.

[0020] Furthermore, the graphitization temperature can reach up to 3,000 ° C.

[0021] In order to be able to process the manufactured graphite blocks or plates more effectively, e.g. by milling or turning, it is advisable to reduce the material to a density of < 1 g / cm 3 to be compacted by impregnation. Phenolic resin, phosphate or pitch can be used for impregnation.

[0022] The impregnated graphite can then be re-graphitized, and this process can be repeated several times.

[0023] The result is cost-effective graphite components with improved mechanical properties that are suitable for use as filters in the form of cubes, plates or other components.

[0024] The invention is explained in more detail below using an exemplary embodiment.

[0025] In order to produce graphitized high-temperature insulation material, filters or even building materials of any shape from cost-effective starting materials, a base material in the form of a mixture of carbon-based materials is first produced.

[0026] This basic material should contain at least one of the raw materials leaves, moss or similar materials, such as grass, corn leaves or even sawdust, waste paper or natural fibers, which is produced in any mixture ratio of these materials.

[0027] The mixture is then soaked in a solvent, such as water, for an extended period and then mechanically ground. A binding agent is added to the mixture after grinding until a largely homogeneous, pasty mixture forms upon stirring. Grinding is possible but not always necessary. Soaking the mixture may take between 1 hour and several days, depending on the materials used.

[0028] The solvent is then largely removed by pressing the mixture until a sufficiently stable, low-solvent compact is formed that is easy to handle. The compact is then dried in air, an oven, or a dryer until the remaining solvent has evaporated. It is essential to ensure that no solvent residue remains in the compact, as this could cause damage to the compact through outgassing during the subsequent high-temperature treatment.

[0029] Finally, the compact is graphitized into a block in a high-temperature furnace in an oxygen-free atmosphere under protective gas or in vacuum at a temperature of > 2,000 ° C, whereby the graphitization temperature can be up to 3,000 ° C.

[0030] As a precaution, the pellet can be dried at an elevated temperature in an additional stabilization step before the high-temperature treatment.

[0031] The graphite block can then be broken down into the desired components by mechanical processing.

[0032] Alternatively, instead of water, polyacrylonitrile (PAN) dissolved in dimethyl sulfoxide (DMSO) can be used as a solvent and binder. In this case, however, it is necessary to immerse the compressed pellet in water to polymerize the polyacrylonitrile and then dry it.

[0033] The pressing of the mixture to produce the pellet can also be done by isostatic pressing.

[0034] Furthermore, it is possible to add a water-soluble binder to the mixture of carbon-based materials during comminution in order to influence the density, with sugar in the form of syrup being the most suitable binder.

[0035] Alternatively or additionally, wheat starch can be added to the paste-like mixture to influence the density of the final product.

[0036] Finally, in a further processing step, it is possible to rework the surface of the high-temperature-resistant graphitized block in a mechanical processing step in order to produce standard components.

[0037] In order to be able to process the manufactured graphite blocks or plates more effectively, such as by milling or turning, it is advisable to impregnate the material to a density of < 1 g / cm 3 to compact, whereby phenolic resin, phosphate or pitch can be used for impregnation.

[0038] The impregnated graphite can then be re-graphitized, and this process can be repeated several times.

[0039] As a result, the process according to the invention can be used to produce cost-effective graphite components with improved mechanical properties, which are suitable for use as high-temperature insulation material or as filters in the form of cubes, plates or other components.

Claims

Process for producing graphite Patent claims 1. A process for the production of graphite for use as a high-temperature insulation material or as a filter in the form of cubes, plates or other components, characterized in that a base material in the form of a mixture of carbon-based materials, containing at least one of the raw materials leaves, moss or similar materials, such as grass, corn leaves or sawdust, waste paper or natural fibers, is produced in any desired mixing ratio of the raw materials, - that the mixture is then soaked in a solvent over a longer period of time and crushed, - that a binding agent is added to the mixture until a largely homogeneous paste-like mixture is formed, - that the solvent is largely removed by pressing the mixture until a sufficiently stable and low-solvent compact is obtained, - that the pellet is dried until the residual solvent has evaporated, and - that the compact is graphitized into a block in a high-temperature furnace in an oxygen-free atmosphere under protective gas or in a vacuum at a temperature of > 2,000 ° C.

2. Process according to claim 1, characterized in that water is used as solvent.

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

4. A method according to claim 3, characterized in that the compact produced by pressing is immersed in water to cause polymerization of the polyacrylonitrile.

5. A method according to claim 1, characterized in that the pressing of the mixture to produce the compact is carried out by isostatic pressing.

6. A method according to claim 1, characterized in that a water-soluble binder is added to the mixture during comminution to influence the density.

7. A process according to claim 6, characterized in that sugar in the form of syrup is used as the binding agent.

8. A method according to claim 1, characterized in that wheat starch is added to the paste-like mixture to influence the density of the final product.

9. Method according to one of claims 1 to 8, characterized in that the compact is dried at elevated temperature in a stabilization step before the high-temperature treatment. 10 . Method according to one of claims 1 to 9 , characterized in that the high-temperature-resistant graphitized block in a mechanical processing step superficially reworked to produce standard components.

11. The process according to claim 1, characterized in that the graphitization temperature is up to 3,000°C.

12. The process according to any one of claims 1 to 11, characterized in that the graphitized block is compacted by impregnation to a density of < 1 g / cm3.

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

14. A method according to claim 12 and 13, characterized in that the impregnated graphite is subsequently re-graphitized, whereby this process can be repeated several times.