GB1574168A

GB1574168A - Carbon body and a method of manufacturing it

Info

Publication number: GB1574168A
Application number: GB5051877A
Authority: GB
Original assignee: C Conradty Nuernberg GmbH and Co KG
Current assignee: C Conradty Nuernberg GmbH and Co KG
Priority date: 1977-01-11
Filing date: 1977-12-09
Publication date: 1980-09-03
Also published as: SE7714070L; IN146923B; BR7708611A; DE2700866C2; DE2700866A1; JPS5388813A; FR2376831A1; AR215670A1; NL7800113A; BE862778A

Description

(54) A CARBON BODY AND A METHOD OF MANUFACTURING IT (71) We, C. CONRADTY NURNBERG G.m.b.H. & Co. KG., a Company of the Federal Republic of Germany, of Grünthal, 8505 Rothenback a.d. Pegnitz, Federal Republic of Germany, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a method of manufacturing a carbon body having high porosity, low gross density and low heat conductivity and made of single or multilayer carbon or graphite felt which is treated with a carbonaceous binder and sub sequently carbonized or graphitized by pressure and heating, and to a carbon body per se whenever made by the method.

Known carbon and graphite felt has a disadvantage in that it is not dimensionally stable or self-supporting whereas other known carbon bodies that do possess the said properties to an adequate degree are not made of carbon or graphite felt but from expanded plastics that shrinks considerably during processing and thus causes manufacturing difficulties which have not yet been eliminated.

According to the present invention we provide a method of manufacturing a carbon body having high porosity, low gross density and low heat conductivity and made of single or multi-layer carbon felt as hereinbefore defined which is treated with a carbonaceous binder and subsequently carbonized or graphitized wherein the single or multi-layer carbon felt is partially impreg nated with the binder and pressurized to obtain a carbon body of high configurational stability and a gross density of 10e 500 kg/m3.

According to a further aspect of the in- vention we provide a carbon body per se whenever made by the said method.

Herein the term carbon felt is used both in the specification and in the appended claims to include graphite felt.

Partial impregnation can be brought about in two ways. Firstly, a dilute binder solution can be used, and part of the impregnating solution can be removed by rolling, pressing, centrifuging or suspension.

After impregnation or after partial removal of the impregnating solution, the solvent is evaporated. Alternatively, an undiluted binder can be used and the undesired portion of binder can subsequently be removed by pressing, rolling or the like. Partial impregnation is brought about simply by immersing the carbon felt in the impregnating agent or solution thereof, or by the known vacuum-pressure process.

After partial impregnation e.g. with phenol formaldehyde synthetic resin, the carbon felt in one or more layers is subjected to condensation treatment. If a number of carbon felt layers are stacked, condensation is brought about by pressure on the stack, during which the individual layers are uniformly stuck together without an additional adhesive or cement being needed. The pressure applied is chosen so that the carbon felt or stack of carbon felt has plane parallel surfaces. After condensation, the carbon felt or stack of carbon felt is completely dimensionally stable. Next, it is carbonized and, if required, graphitized in known manner.

If the impregnating agent is not a synthetic resin but coal-tar pitch or a solution thereof, there is usually no need of a condensation process before carbonization. In the carbonization process, the partly impregnated single or multi-layer carbon felt is arranged in the desired geometrical shape, e.g. a large flat plate. When the carbon felt is disposed in a number of layers, the individual layers are homogeneously bonded during carbonization.

The gross density of the carbon body can be varied in dependence on the density of the initial carbon felt, the impregnating agent, the amount of agent and the process parameters such as pressure, temperature and time. Gross densities below 100 kg/m3 result in lower mechanical strength and dimensional stability, whereas at densities about 500 kg/cm3 the porosity and thermal insulation are too low.

Three examples of the method of manufacture will now be described.

EXAMPLE 1 A carbon felt rectangular prism measuring 200x200x10 mm having a gross density of 50 kg/m3 was impregnated by immersion in a 30% methanolic phenolformaldehyde resin solution. The wet carbon felt was suspended from one corner, whereupon part of the impregnating solution ran out of the carbon felt. After about thirty minutes the sheet of carbon felt, which was still damp, was placed between two stacks of paper and, as a result of slight pressure, most of the remaining impregnating agent in the carbon felt was pressed out. The carbon felt, which was then nearly dry, was subjected to the final drying process. After twenty four hours most of the solvent originally present in the carbon felt had evaporated. The carbon felt was slightly sticky.Next, it was placed between two 300x 300x20 mm graphite plates and heattreated at 1500C in a drying cabinet for three hours, thus producing a condensation of the synthetic resin used. The resulting carbon body, which had complete dimensional stability was placed in known manner in powdered carbon and heat-treated at 12000C. The resulting carbon body had the following parameters: Porosity: > 90% Gross Density: 130 kg/m3.

Electric resistivity: 2000Qmm2/m.

EXAMPLE 2 Five carbon felt discs 300 mm diameter and 5 mm thick were partially impregnated with a phenol formaldehyde resin solution as in Example 1 and stacked after drying in air. The stack was compressed to a height of 23 mm, using two graphite plates 320 mm diameter and 30 mm thick and a number of clamps. Next the stack was heat-treated at 1500C for five hours. to condense the resin.

The stack was then taken out of the clamps; it was already firm and dimensionally stable and was then heat-treated at 1 2000C as in Example 1. The resulting carbon body had the following parameters: Porosity: > 90% Cross Density: 150 kg/m3.

Electric Resistivity: l800mm2/m.

EXAMPLE 3 A carbon felt disc 200 mm diameter and 5 mm thick was impregnated by immersion in molten coal-tar pitch having a density of 1250 kg/m and the excess pitch was squeezed out by compressing the hot carbon felt between two graphite discs. After cooling, the excess pitch clinging to the edges was cut off with a knife, whereupon the body was carbonized in known manner at 8000C.

The resulting carbon body had the following parameters: Porosity: 60% Gross Density: 480 kg/m3.

Electric resistivity: 2127Qmm2/m.

WHAT WE CLAIM IS:- 1. A method of manufacturing a carbon body having high porosity, low gross density and low heat conductivity and made of single or multi-layer carbon felt as hereinbefore defined which is treated with a carbonaceous binder and subsequently carbonized or graphitized wherein the single or multilayer carbon felt is partially impregnated with the binder and pressurized to obtain a carbon body of high configurational stability and a gross density of 100--500 kg/m3.

2. The method according to claim 1, wherein a number of layers of stacked carbon felt having plane parallel surfaces are uniformly stuck together and are configuration;ally stable.

3. The method according to claim 2, wherein the surfaces of the individual carbon felt layers are stuck together by condensation of the resins of the binder.

4. The method according to claim 1, wherein the carbon body is partially impregnated with coal-tar pitch.

5. The method according to claim 1, wherein the carbon body is partially impregnated with a solution of coal-tar pitch.

6. The method according to any one of claims 1 to 3, wherein the carbon body is partially impregnated with a synthetic resign.

7. The method according to claim 6, wherein the synthetic resin is phenol formaldehyde resin.

8. The method of manufacturing a carbon body according to any of the preceding claims, wherein the carbon felt is partially impregnated with the binder and then carbonized..

9. The method according to claim 8, wherein partial impregnation is brought about with a solution of the binder, after which the solvent is removed.

10. The method according to claim 8, wherein partial impregnation is brought about with a non-diluted binder, after which the undesired portion of binder is removed.

11. The method according to any one

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

agent, the amount of agent and the process parameters such as pressure, temperature and time. Gross densities below 100 kg/m3 result in lower mechanical strength and dimensional stability, whereas at densities about 500 kg/cm3 the porosity and thermal insulation are too low.

Three examples of the method of manufacture will now be described.

EXAMPLE 1 A carbon felt rectangular prism measuring 200x200x10 mm having a gross density of 50 kg/m3 was impregnated by immersion in a 30% methanolic phenolformaldehyde resin solution. The wet carbon felt was suspended from one corner, whereupon part of the impregnating solution ran out of the carbon felt. After about thirty minutes the sheet of carbon felt, which was still damp, was placed between two stacks of paper and, as a result of slight pressure, most of the remaining impregnating agent in the carbon felt was pressed out. The carbon felt, which was then nearly dry, was subjected to the final drying process. After twenty four hours most of the solvent originally present in the carbon felt had evaporated. The carbon felt was slightly sticky.Next, it was placed between two 300x 300x20 mm graphite plates and heattreated at 1500C in a drying cabinet for three hours, thus producing a condensation of the synthetic resin used. The resulting carbon body, which had complete dimensional stability was placed in known manner in powdered carbon and heat-treated at 12000C. The resulting carbon body had the following parameters: Porosity: > 90% Gross Density: 130 kg/m3.

Electric resistivity: 2000Qmm2/m.

EXAMPLE 2 Five carbon felt discs 300 mm diameter and 5 mm thick were partially impregnated with a phenol formaldehyde resin solution as in Example 1 and stacked after drying in air. The stack was compressed to a height of 23 mm, using two graphite plates 320 mm diameter and 30 mm thick and a number of clamps. Next the stack was heat-treated at 1500C for five hours. to condense the resin.

The stack was then taken out of the clamps; it was already firm and dimensionally stable and was then heat-treated at 1 2000C as in Example 1. The resulting carbon body had the following parameters: Porosity: > 90% Cross Density: 150 kg/m3.

Electric Resistivity: l800mm2/m.

EXAMPLE 3 A carbon felt disc 200 mm diameter and 5 mm thick was impregnated by immersion in molten coal-tar pitch having a density of

1250 kg/m and the excess pitch was squeezed out by compressing the hot carbon felt between two graphite discs. After cooling, the excess pitch clinging to the edges was cut off with a knife, whereupon the body was carbonized in known manner at 8000C.

The resulting carbon body had the following parameters: Porosity: 60% Gross Density: 480 kg/m3.

Electric resistivity: 2127Qmm2/m.

WHAT WE CLAIM IS:- 1. A method of manufacturing a carbon body having high porosity, low gross density and low heat conductivity and made of single or multi-layer carbon felt as hereinbefore defined which is treated with a carbonaceous binder and subsequently carbonized or graphitized wherein the single or multilayer carbon felt is partially impregnated with the binder and pressurized to obtain a carbon body of high configurational stability and a gross density of 100--500 kg/m3.
2. The method according to claim 1, wherein a number of layers of stacked carbon felt having plane parallel surfaces are uniformly stuck together and are configuration;ally stable.
3. The method according to claim 2, wherein the surfaces of the individual carbon felt layers are stuck together by condensation of the resins of the binder.
4. The method according to claim 1, wherein the carbon body is partially impregnated with coal-tar pitch.
5. The method according to claim 1, wherein the carbon body is partially impregnated with a solution of coal-tar pitch.
6. The method according to any one of claims 1 to 3, wherein the carbon body is partially impregnated with a synthetic resign.
7. The method according to claim 6, wherein the synthetic resin is phenol formaldehyde resin.
8. The method of manufacturing a carbon body according to any of the preceding claims, wherein the carbon felt is partially impregnated with the binder and then carbonized..
9. The method according to claim 8, wherein partial impregnation is brought about with a solution of the binder, after which the solvent is removed.
10. The method according to claim 8, wherein partial impregnation is brought about with a non-diluted binder, after which the undesired portion of binder is removed.
11. The method according to any one

of claims 8 to 10, wherein the carbon felt is partially impregnated by the vacuumpressure process.
12. The method according to any one of claims 8 to 11, wherein before carbonization, the carbon felt is stabilised by condensation of the binder.
13. The method according to claim 12, wherein stacked layers of carbon felt are stuck together by condensation of the synthetic resin used as a binder.
14. A carbon body whenever made by the method of any one of claims 1 to 13.
15. A carbon body whenever made as hereinbefore described with particular reference to the Examples.