Method for producing carbonized or graphitized molded parts

Abstract

The present invention relates to a method for producing carbonized or graphitized molded parts. It is an object of the present invention to provide a method for producing carbonized or graphitized molded parts, which is particularly easy to realize and also allows the production of complex molded parts without mechanical post-processing. This is achieved by preparing a liquid and as homogenized as possible castable polymer mixture consisting of carbon granules, pitch, carbon black or graphite powder and polyacrylonitrile dissolved in an organic solvent, filling the liquid polymer mixture into a mold and immersing the filled mold in water for a defined time until the polymer mixture is sufficiently hardened and dimensionally stable, after which the mold is opened and the prefabricated hardened molded part is uniformly heated in an oven in air at a defined temperature for stabilization and for degassing volatile components, and the molded part is subjected to a high-temperature treatment in an oven under protective gas for carbonization or graphitization.

Description

[Technical Field]

[0001] The present invention relates to a method for producing carbonized or graphitized molded parts. [Background technology]

[0002] Such carbonized or graphitized molded parts, which are also suitable for use at high temperatures, can be any three-dimensional part, such as a lining for a furnace, a building element or any hollow body, vessel or crucible.

[0003] These molded parts cannot be produced by simply molding and then sintering carbon black or graphite, so it is generally necessary to prepare a suitable carbon-containing, moldable composition. For this purpose, carbon black, coke, or graphite is usually mixed in the form of granules with a suitable binder, such as a thermoplastic binder. Pitches based on coal tar or petroleum pitch, or synthetic resins, are also considered as binders.

[0004] These mixtures are then pressed into green molded parts and carbonized in a furnace at about 3,000°C, where the binder is decomposed into volatile components, leaving behind carbon and binder coke as the binder residue in the form of a porous structure.

[0005] Alternatively, the green molded part can be placed between electrodes in a furnace as a resistive element and heated by an electric current. Summary of the Invention [Problem to be solved by the invention]

[0006] The invention is based on the object of providing a method for producing carbonized or graphitized molded parts which is particularly easy to implement and which also makes it possible to produce complex molded parts without mechanical post-processing. [Means for solving the problem]

[0007] This is achieved by preparing a liquid and as homogenized as possible polymer mixture consisting of carbon granules, pitch, carbon black or graphite powder and fibrous material, pulp, starch and polyacrylonitrile dissolved in an organic solvent, filling a moldable polymer mixture with the polymer mixture, and immersing the filled mold in water for a predetermined time until the polymer mixture hardens into a molded part and becomes dimensionally stable, after which the mold is opened and the pre-fabricated hardened molded part is heated to a predetermined temperature in an air atmosphere in an oven for stabilization and to degas volatile components from the molded part, and then treating the molded part at a high temperature in an oven under protective gas or vacuum to carbonize or graphitize the molded part.

[0008] Natural fibers such as bamboo fibers or graphite fibers can be mixed as fiber material into the polymer mixture in order to influence the strength or porosity of the carbonized or graphitized molded part to be produced.

[0009] The polymer mixture is homogenized at room temperature, and in this case, the polymer mixture is homogenized at about 160°C, and if the mixture contains a high temperature pitch having a melting point of 120°C, it is homogenized until it melts.

[0010] In a further aspect of the invention, the mold filled with the polymer mixture is immersed in water for several hours or days to harden and form the molded part, after which it can be opened and removed from the mold.

[0011] Thereafter, the prefabricated hardened molded part is stabilized and Gas release The process is carried out in air at a stabilization temperature of 140° C. up to a maximum of 450° C., with a temperature of 250° C. being preferred.

[0012] Stabilization of prefabricated hardened molded parts and Gas release This can occur during heating of the furnace to the stabilization temperature.

[0013] In a further step, the prefabricated shaped part is carbonized at a constant temperature of about 1,000° C. until pure carbon with various crystalline structures is produced.

[0014] In another development of the invention, the prefabricated molded part is graphitized at a temperature above 2,000°C.

[0015] The prefabricated molded part can then be fully graphitized at temperatures in excess of 2,500°C.

[0016] It is understood that the carbonization, graphitization and full graphitization are each carried out under protective gas, suitably argon or helium. Preferably, the graphitization is carried out at a heating rate of 1° C. / min until the target temperature is reached, followed by annealing for about 30 minutes, although annealing for several hours is also possible.

[0017] In principle, it is also possible to mix the polymer mixture with metal or silicon powder and heat treat it under protective gas at temperatures above 1,000° C. to form metal carbide or silicon carbide.

[0018] Polyacrylo Nitrile Dimethyl sulfoxide is preferably used as the solvent for this because of its relatively low health risk, but dimethylformamide or N-methyl-2-pyrrolidone are also in principle suitable as solvents.

[0019] The present invention will be described in more detail below with reference to examples. [Example]

[0020] The basic idea of ​​the present invention is to first prepare a pourable liquid which is easy to handle and which can be poured into a mold.

[0021] For this purpose, a polymer mixture is prepared consisting of polyacrylonitrile dissolved in a solvent such as dimethyl sulfoxide, and then pitch and / or carbon black and / or graphite powder, as well as fibrous materials, pulp, etc., are mixed in until the mixture has a pourable consistency.

[0022] The mixture is then homogenized at room temperature, or, if the mixture contains pitch, at about 160° C. to melt the pitch.

[0023] The homogenized mixture is then filled into a mold, which is then completely immersed in water until the mixture is sufficiently hardened and shape-stable. This process can last for several hours or days, depending on the mixing ratio of the mixture.

[0024] The mold can then be opened and the prefabricated hardened molded part is allowed to settle.

[0025] This is done in air at a stabilization temperature of 140°C up to 450°C, with a temperature of 250°C being preferred, whereby stabilization of the prefabricated molded part can also occur in an oven up to the stabilization temperature.

[0026] The prefabricated molded parts are then carbonized at a constant temperature of about 1,000° C. until pure carbon with various crystalline structures is produced.

[0027] The prefabricated molded part can then be graphitized at a temperature above 2,000°C or can be fully graphitized at temperatures above 2,500°C.

[0028] To avoid thermal stress, the graphitization is preferably carried out at a heating rate of 1° C. / min until the target temperature is reached, followed by annealing for about 30 minutes.

[0029] The result of the process according to the invention is essentially three products, namely, molded parts each consisting of carbon, graphite of various structures, or pure graphite of pure structure.

[0030] Alternatively, the polymer mixture can be mixed with metal or silicon powder to form metal carbide or silicon carbide upon high temperature treatment of the prefabricated molded part at >1,000°C, which allows for further production of yet another product.

[0031] The advantages of the method of the present invention are the ease of handling and the ability to produce complex shaped parts without mechanical post-processing. While this application is directed to the invention set forth in the claims, the disclosure of this application also includes: 1. A method for producing a carbonized or graphitized molded part, comprising: preparing a homogenized castable polymer mixture consisting of carbon granules, pitch, carbon black or graphite powder, and fibrous material, pulp, starch and polyacrylonitrile dissolved in an organic solvent; filling said pourable polymer mixture into a mold; immersing the filled mold in water for a predetermined time until the polymer mixture hardens into a molded part and becomes shape stable; Thereafter, opening the mold and stabilizing the pre-fabricated hardened molded part by heating it in an oven in an air atmosphere to a predetermined temperature in order to stabilize it and to degas volatile components from it; carrying out a high-temperature treatment in an oven under protective gas or vacuum in order to carbonize or graphitize the molded part; The method characterized by: 2. The method according to claim 1, wherein natural fibers such as bamboo fibers or graphite fibers are mixed into the polymer mixture as a fiber material. 3. The method according to claim 1 or 2, wherein the homogenization of the polymer mixture is carried out at room temperature, and in this case, if pitch is mixed in, the homogenization of the polymer mixture is carried out at 160°C until the pitch melts. 4. The method according to any one of the above 1. to 3., wherein the mold filled with the polymer mixture is immersed in water for several hours or days to harden and form the molded part. 5. A method according to any one of the preceding paragraphs 1 to 4, characterized in that the prefabricated hardened molded part is stabilized and homogenized at a temperature of from 140°C up to 450°C, preferably at 250°C. 6. The method according to claim 5, wherein the stabilization and homogenization of the prefabricated hardened molded part occurs during heating of the furnace to the stabilization temperature. 7. The method according to any one of 1. to 6. above, characterized in that the prefabricated molded part is carbonized at a constant temperature of 1,000°C until pure carbon with various crystalline structures is produced. 8. The method according to any one of 1. to 6. above, wherein the prefabricated molded part is graphitized at a constant temperature of 2,000°C or higher. 9. The method according to any one of 1. to 6., wherein the prefabricated molded part is fully graphitized at a temperature exceeding 2,500°C. 10. The method according to claim 8 or 9, wherein the graphitization is carried out at a heating rate of 1°C / min until the target temperature is reached, and then annealed for more than 30 minutes. 11. The method according to claim 1, wherein dimethyl sulfoxide, dimethylformamide or N-methyl-2-pyrrolidone is used as the solvent.

Claims

1. 1. A method for producing a carbonized or graphitized molded part, comprising: preparing a homogenized, pourable polymer mixture by mixing carbon granules, pitch, carbon black and / or graphite powder and fibrous material and / or starch with polyacrylonitrile dissolved in an organic solvent until the resulting mixture has a pourable consistency; mixing metal powder or silicon powder into said homogenized castable polymer mixture; homogenizing the pourable mixture at room temperature or at 160°C if the pourable mixture contains pitch; filling the homogenized castable polymer mixture into a mold; completely immersing the mold filled with the polymer mixture in water for a predetermined time ranging from several hours to several days until the polymer mixture hardens into a molded part in the mold and becomes shape stable; Thereafter, opening the mold and stabilizing the cured molded part by heating in an oven in an air atmosphere to a temperature of 140°C to 450°C to stabilize and degas volatile components from the molded part; and carrying out a high-temperature treatment in a furnace under protective gas or vacuum in order to carbonize the molded part at a temperature above 1,000°C or to graphitize it at a temperature above 2,000°C, with the formation of metal carbide or silicon carbide; A method characterized by:

2. 2. The method of claim 1, wherein natural fibers are mixed as fibrous material with the polymer mixture.

3. 3. The method according to claim 1 or 2, characterized in that the cured molded part is stabilized and degassed at 250°C.

4. 10. The method of claim 1, wherein stabilization and degassing of the cured molded part occurs during furnace heating to the stabilization temperature.

5. 2. The method of claim 1, wherein the molded part is fully graphitized at a temperature above 2,500°C with the formation of metal carbide or silicon carbide.

6. 6. The method of claim 1 or 5, wherein the graphitization is carried out at a heating rate of 1° C. / min until the target temperature is reached, followed by annealing for more than 30 minutes.

7. 3. The process according to claim 1, wherein dimethyl sulfoxide, dimethylformamide or N-methyl-2-pyrrolidone is used as the solvent.

8. 2. The method according to claim 1, characterized in that bamboo fibers or graphite fibers are mixed as fibrous materials.

9. The method according to claim 1, characterized in that pulp is mixed as the fibrous material.