Title of Invention

A PROCESS FOR THE MANUFACTURE OF HIGH DENSITY SOLID CARBON"

Abstract Abstract : A process for the manufacture of high density solid carbon for use in highly electrically conducting and high tensile and compressive strength product comprising subjecting the raw/ green coke obtained from petroleum or coal tar pitch base to conventional mechanical treatment and grinding to obtain material of particle size 1-5 micron, subjecting the said particle sized material to a mounding pressure in a hydraulic press, sintering the said pressed material to a temperature of 800°C -1200°C in an insert atmosphere at a temperature of 2000°C -2700°C to remove any remaining volatile material and nitrogen, thus resulting in the formation of solid carbon having high density.
Full Text The present invention relates to a process for the manufacture of high density solid carbon. All the processes known so far for the preparation of the solid carbon result in the preparation of solid carbon possessing very low density upto 1.8 g/cm3. But the present invention relates to an improved process for the preparation of the solid carbon having relatively higher density (from 1.8 to 2.1 g/cm ) than all the known compounds prepared so far from the previously known processes.
BACKGROUND OF THE INVENTION
Carbon and graphite possess unique combination of mechanical, thermal and electrical properties not exhibited by any other single material. Therefore these materials are preferred for various mechanical and electrical applications especially at high temperatures under non oxidizing atmosphere.
Carbon materials are widely used for engineering materials: electrodes in the metallurgical industries, moderator and structural materials in the nuclear industry and the like. Recently the use of the said carbon and carbon particles has extended to rocket nozzles and high temperature heat exchangers. Conventional carbon and graphite materials are normally made using a calcined filler coke and binder, such as coal tar or petroleum pitch, through carbonization and graphitization
processes.These filler binder routes however suffer decomposition and molecular rearrangement of binder phase during carbonization and subsequent high temperature heating result in the formation of pores and voids. Therefore it is known to be difficult to fabricate a dense and strong carbon and graphite body for structural application by the conventional means of synthesizing the said carbon. The carbon products containing these pores and voids lack the required strength and the required ability to withstand stress.Though these pores and voids can be partially filled in during subsequent impregnations but the process is quite lengthy and at times costly. Moreover , secondary impregnations may not result in the formation of uniformly dense strong products,necessary for the mechanical and structural applications.
Therefore , in order to make a high density carbon , various techniques have been used in the fabrication , such as repeated impregnation with pitch and heat treatment in an autoclave, use of high yield pitch, or the filling up of pores with a deposition of pyrolytic carbon. Various , alternative methods like carbon mesobeads ,self sinterable carbon and the like are being explored to fabricate dense carbon products .
STATEMENT OF INVENTION
According to the present invention there is provided for a process for the manufacture of high density solid carbon for use in highly electrically conducting and high tensile and compressive strength product comprising subjecting the raw/ green coke obtained from petroleum or coal tar pitch base to conventional mechanical treatment and grinding to obtain material of particle size 1-5 micron, subjecting the said particle sized material to a moulding pressure in a hydraulic press, sintering the said pressed material to a temperature of 800°C - 1200°C in an inert atmosphere to remove the volatile contents, subjecting the said sintered solid mass to further heating in a second inert atmosphere at a temperature of 2000°C -2700 C to remove any remaining volatile material and nitrogen, thus resulting in the formation of solid carbon having high density.
SUMMARY OF THE INVENTION
The present invention relates to a process for the
preparation of the solid carbon possessing relatively higher density as compared to the carbon prepared from the conventional methods.The main embodiment of the present invention is that the process for the preparation of the solid carbon does not involve the use of the binders thereby eliminating the chances of decomposition of the product at higher temperatures which is the root cause for the pores and voids in the solid carbon formed by any of the conventional processes.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a process for the preparation of the solid carbon. The said process relates to the formation of the solid carbon through a solid phase sintering method without the use of any of the binders at any stage of the process.
The carbon powder is known to be non sinterable , the carbon products are therefore generally fabricated through pitch binder phase. The conventional method for preparing the solid carbon involves mixing of the calcined coke with pitch binder which is then heat treated for carbonization and graphitization. However the pitch binder phase decomposes during the process of heat treatment which results in the formation of pores inside the material so formed. The subsequent impregnations if done repeatedly do improve the
density of the solid carbon but it does not result in the formation of uniformly dense carbon.Therefore the carbon formed by repeated impregnations though might be in possession of a better density but as the density is not uniform therefore the carbon thus formed is not very strong , thus this carbon can not be used for the mechanical and structural applications.
The present invention relates to formation of solid carbon by a self sinterable process. The said process comprises of subjecting the raw coke ;also known as green coke obtained from the petroleum or from coal tar pitch base to a mechanical treatment and grinding in a ball mill for a period ranging from a period of 60 -80 hours so as to obtain material of a particle size of about 1-5 micron. This mechanical treatment leads to decrease in the size of the carbon particles which also lead to change in the volatile content with time. The carbon thus formed is more reactive as the decrease in size lead to increase in the surface area.This along with the change in volatile contents helps in making the carbon sinterable. These grinded and very fine
particle sized materials thus obtained are further subjected
2 to a moulding pressure ranging from 350 kg/cm to a pressure
2 of 900 Kg/cm in a hydraulic press. The pressing results in
the formation of a green solid material which has volatile
content ranging from 6% to 10% The green solid material is
o o now sintered at a temperature of 800 -1200 Celsius in an
inert atmosphere of nitrogen to remove any volatile contents
possessed by the said particles.The sintering in an inert
o o atmosphere of nitrogen at a temperature range of 800-1200 C
not only removes all the volatile content contained in the green solid material but it also removes the undesirable organic molecules mainly consisting of Hydrogen and carbon .During this stage the green carbon solids undergo a volume
shrinkage of about 20-30 %. The specified temperature of
o o about 800-1200 Celsius is comparatively lower as compared to
the temperature conditions that generally prevail in the conventional methods known so far for the preparation of the solid carbon .The said sintered solid mass so formed is subjected to a further heating again in an inert atmosphere
but not of nitrogen but that of Argon, at a temperature of
o o 2000-2700 celsius . This step ensures the removal of the any
left out volatile material and also the removal of Nitrogen.This leaves behind a harder solid carbon having high uniform density with no volatile content and no Nitrogen.
The present invention relates to a process for the preparation of solid carbon for use in highly electrically conducting and high tensile and compressive strength product comprising subjecting the raw/green coke obtained from petroleum or coal tar pitch base to a mechanical treatment and grinding to obtain material of particle size 1-5 micron, subjecting the said particle sized material to a
moulding pressure in a hydraulic press , sintering the said
o o pressed material to a temperature of 800 -1200 C in an inert
temperature to remove the volatile contents ,subjecting the
said sintered mass to further heating in a second inert
o o atmosphere at a temperature of 2000-2700 C to remove any
remaining volatile material and nitrogen, thus resulting in the formation of solid carbon having high density.
The following examples are presented herewith as an illustration of this invention and are not in any way intended to act as an undue limitation on the generally broad scope of the invention.
EXAMPLE 1
Raw / green coke from petroleum or from coal tar pitch base is subjected to mechanical treatment and grinding in ball mills for 50 hours till material of fine particle size 3 micron size is obtained.The material in the form of fine
particle size is subjected to moulding in a hydraulic press
2 450 Kg/cm to obtain the green solid material. The green
solid material having volatile contents 6-10% is further
sintered in an inert atmosphere of Nitrogen and heated to
o 1000 celsius to remove the volatile content and organic
molecules consisting of hydrogen and carbon.The sintered solid mass thus obtained has nitrogen and some left over volatile substance.lt is further heated in an inert
atmosphere of Argon at a temperature of 2200 Celsius, thus all the volatile substance and Nitrogen is removed leaving behind a harder solid carbon having a high density, no volatile content and no Nitrogen.
EXAMPLE 2
Raw / green coke from petroleum or coal tar pitch base is subjected to a mechanical treatment and grinding in ball mills for about 55 hours till material of fine particle size 4 micron is obtained.This material in the form of a fine
particle size is subjected to moulding in a hydraulic press
2 at a pressure of 500 Kg /cm to obtain green solid material.
The green solid material having volatile substance 6-10% is
further sintered in an inert atmosphere of Nitrogen and
o heated upto 1100 celsius to remove the volatile content and
organic molecules consisting of hydrogen and carbon. The sintered solid mass thus obtained still has some volatile
content and also Nitrogen. It is therefore heated again now
o in an inert atmosphere of Argon and at a temperature of 2400
celsius , thus all the volatile substances and Nitrogen are removed thereby leaving behind a harder solid carbon having a high density with no trace of nitrogen or any volatile content.





WE CLAIM:
1. A process for the manufacture of high density solid carbon
for use in highly electrically conducting and high tensile and
compressive strength product comprising subjecting the raw/ green
coke obtained from petroleum or coal tar pitch base to
conventional mechanical treatment and grinding to obtain
material of particle size 1-5 micron, subjecting the said
particle sized material to a mounding pressure in a hydraulic
press, sintering the said pressed material to a temperature of
800°C - 1200°C in an inert atmosphere to remove the volatile
contents, subjecting the said sintered solid mass to further
heating in a second inert atmosphere at a temperature of 2000 C -
2700 C to remove any remaining volatile material and nitrogen,
thus resulting in the formation of solid carbon having high
density.
2. A process for the manufacture of solid carbon as claimed in
claim 1, wherein the said raw/green coke is subjected to a
mechanical treatment and grinding in a ball mill for a period
ranging from a 60 - 80 hours to obtain said particle sized
material.
3. A process for the manufacture of solid carbon coke as
claimed in claim 1, wherein the said particle sized material is
subjected to a mounding pressure in a hydraulic press at a
Pressure of 350-900 kg/cm2.
4. A process for the manufacture of solid carbon coke as
claimed in claim 1, wherein the said inert atmosphere is of
nitrogen.
5. A process for the manufacture of solid carbon coke as
claimed in claim I, wherein the said second inert atmosphere is
of argon.
6. A process for the manufacture of high density solid carbon
for use in highly electrically conducting and high tensile and
compressive strength product, substantially as hereinbefore
described with reference to the foregoing Examples.

Documents:

105-del-1996-abstract.pdf

105-del-1996-claims.pdf

105-del-1996-correspondence-others.pdf

105-del-1996-correspondence-po.pdf

105-del-1996-description (complete).pdf

105-del-1996-form-1.pdf

105-del-1996-form-2.pdf

105-del-1996-form-3.pdf

105-del-1996-gpa.pdf

105-del-1996-petition-138.pdf


Patent Number 214550
Indian Patent Application Number 0105/DEL/1996
PG Journal Number 08/2008
Publication Date 22-Feb-2008
Grant Date 12-Feb-2008
Date of Filing 17-Jan-1996
Name of Patentee DEPARTMENT OF SCIENCE AND TECHNOLOGY
Applicant Address TECHNOLOGY BHAVAN, NEW MEHRAULI ROAD, NEW DELHI 110016, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 LALIT MOHAN MANOCHA INSTITUTE OF MATERIALS SCIENCE, SARDAR PATEL UNIVERSITY, VALLABH VIDYANAGAR- 388120, GUJRAT, INDIA.
PCT International Classification Number C01B 31/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA