Title of Invention	AN IMPROVED PROCESS FOR THE PREPARATION OF HIGH QUALITY IMPREGNATING GRADE PITCH
Abstract	The present invention provides an improved process for the preparation of high quality impregnating grade pitch. More particularly, the present invention provides an improved process for the preparation of coal tar pitch having low contents of quinoline insolubles (Ql) and toluene insolubles (Tl) and high content of coking value. It is used for densification of carbon-carbon composites made in various forms as aircraft brakes, nose cones, heat shields, high temperature dies, bone plates and hip joints etc. The same pitch can also be used to impregnate the graphite electrodes for use in steel industry.

Title of Invention

AN IMPROVED PROCESS FOR THE PREPARATION OF HIGH QUALITY IMPREGNATING GRADE PITCH

Abstract

The present invention provides an improved process for the preparation of high quality impregnating grade pitch. More particularly, the present invention provides an improved process for the preparation of coal tar pitch having low contents of quinoline insolubles (Ql) and toluene insolubles (Tl) and high content of coking value. It is used for densification of carbon-carbon composites made in various forms as aircraft brakes, nose cones, heat shields, high temperature dies, bone plates and hip joints etc. The same pitch can also be used to impregnate the graphite electrodes for use in steel industry.

Full Text	Field of the invention The present invention relates to an improved process for the preparation of high quality impregnating grade pitch. More particularly, the present invention relates to an improved process for the preparation of coal tar pitch having low contents of quinoline insolubles (Ql) and toluene insolubles (Tl) and high content of coking value. It is used for densification of carbon-carbon composites made in various forms as aircraft brakes, nose cones, heat shields, high temperature dies, bone plates and hip joints etc. The same pitch can also be used to impregnate the graphite electrodes for use in steel industry. Background of the invention The commercially available coal tars are obtained from the destructive distillation of metallurgical coals by the steel industry. The coal tars, so obtained, invariably contain soot-like fine particles formed by the thermal cracking of tar vapours and entrained fine particles of coal and coke. Since coal tar pitches are residues obtained in the distillation of such coal tars, these very Ql particles are also found in these pitches. The commercially available coal tars and coal tar pitches normally contain Ql in range of 4-15% which make them unsuitable for the impregnation purpose. In the prior art, three methods employing, separately, filtration, solvent extraction and centrifugation are known for removing Ql from coal tars and coal tar pitches. The filtration method involves the filtration of molten coal tar precursor heated to about 250°C through filters of various types to get low Ql tar or pitch. The method of solvent extraction, on the other hand employs the use of solvents to extract the solvent-soluble portion of coal tars or coal tar pitches which are low in Ql. The solvent is then removed from the soluble portion by the conventional distillation technique. The centrifugation method involves the removal of Ql from the molten coal tar precursor using industrial centrifugal machines. These known processes for the removal of Ql have certain drawbacks which make them cumbersome as well as expensive. To obviate the above mentioned drawbacks, we in our earlier patent No. 186256 (2002) have provided the process for the producing the low QI/QI free impregnating pitches which have been obtained by heat treating commercial coal tar pitches with the mixture of special industrial solvents to cause coagulation of Ql particles as Ql mass in the pitch solvent mixtures. The major pitch solvent portion containing no or low Ql can be distilled to remove the solvent and obtain the impregnating pitch. The characteristics of low Ql / Ql-free impregnating grade coal tar pitch obtainable with the above processes are Softening point 80 - 120°C Quinoline insoluble 0.0 - 3.0% Toluene insoluble 16-24% Coking value 42 - 46 % Specific gravity 1.26 - 1.28 Ash content 0.05 % (Max.) All the methods mentioned above produce impregnating grade of pitches of low coking value (42-46%) besides having low contents of Ql (0-3%) . Therefore, a large number of impregnations followed by carbonization cycles are required to improve the bulk density of the carbon-carbon composites and graphite electrodes. As a result, the process of producing carbon-carbon composites and graphite electrodes through large number of impregnation and carbonization cycles is tedious, cumbersome, time consuming and expensive. Objectives of the invention The main object of the present invention is to provide a process for the preparation of impregnating grade pitch with a high content of coking value (50-65%). Yet another objective of the present invention is to provide an improved process for the preparation of impregnating grade pitch, which is useful for making carbon-carbon composites, graphite electrodes etc. Still another object of the invention is to provide an improved process for the preparation of impregnating grade pitch , which possesses Ql in the range of 0-3%. Summary of the invention Accordingly the present invention provides an improved process for the preparation of high quality impregnating grade pitch having high coking value and containing low Quinoline insolubles, and the said process comprising the steps of: a) heat treating the coal tar pitch or a mixture of coal tar pitch and petroleum pitch, at temperatures in the range of 300-450°C, in an inert atmosphere or under reduced pressure of 4-40 cmHg, for a period of 0.2-2.Ohr to obtain the precursor pitch, b) mixing the resulting precursor pitch containing Quinoline insolubles with an organic solvent in the proportion of 2-10, c) heating the above said resultant mixture to a temperature in the range of 120- 250°C, in an inert atmosphere, for a period in the range of 2 to 24 hours, d) separating the above said heated mixture into two parts by simple separation device or decantation or process of filtration and obtaining the one major part containing low Ql and the other part containing High Ql, and e) distilling the major part under vacuum at a temperature upto 400°C to obtain the desired product. In an embodiment of the present invention the organic solvent used is selected from light or medium creosote oil, wash oil and heavy oil. In yet another embodiment the ratio of solvent-to-coal tar pitch is preferably in the range of 2 to 5. In yet another embodiment the heat treatment is carried out, preferably at a temperature in the range of 130-180°C. In yet another embodiment the heat treatment is carried out, preferably for a period in the range of 4-10 hours. In yet another embodiment the distillation is carried out at a temperature eferably in the range of 300-330°C . In yet another embodiment the distillation is carried out at a pressure, preferably in the range of 4-40 cm Hg for period of 10-15 minutes. In still another embodiment the high quality coal tar pitch obtained has high coking value of 50-65% and low quinoline-insoluble contents of 0-3%. Detail description of the invention The present invention provides a process for the preparation of novel impregnating grade pitch which is useful for making carbon-carbon composites, graphite electrodes and the like, which comprises (i) Heating of a commercial coal tar pitch or a mixture of commercial coal tar pitch and petroleum pitch at a temperature in the range of 300-450 °C in inert atmosphere or under reduced pressure to obtain a pitch of high softening point (150 - 350°C) and with higher value of Ql (5-50%), Tl (30-70%) and coking value (70-80%). (ii) Heating the resulting pitch in the presence of suitable inexpensive aromatic solvent, such as tar oil, wash oil, toluene, etc respectively, in requisite proportions, at a temperature around 80-170°C, to cause the dissolution of the pitch in the solvent. (iii) The Ql containing mass is then separated from the pitch-solvent mixture by a simple separating device or a decantation process or a filtration process, (iv) The pitch-solvents mixture is then distilled at temperatures upto 360°C to recover the solvents in inert atmosphere or under reduced pressure and obtain the novel impregnating-grade pitch. The novel feature of the present invention are the use of the precursor pitch material obtained by heat-treatment of a coal tar pitch or mixture of coal tar pitch and petroleum pitch which is then treated with a suitable aromatic solvent to extract the solvent soluble portion low in Ql or free of Ql which is then distilled to remove the solvent and obtain the high quality impregnating grade coal tar pitch. The following examples are given by the way of illustration and therefore should not be construed to limit the scope of the invention. Example 1 Equal quantities of Ql free coal tar pitches and petroleum pitches are heated to 430°C under reduced pressure of 6cm Hg to obtain pitches of softening point of 195°C, Ql and Tl content of 1.0 and 36.5 respectively, coking value of 72.5 and SG of 1.29 The resulting pitch is dissolved in toluene in the ratio (1:6 by wt.) at a temperature of 90-100°C and solution is filtered and distilled to recover the solvent and obtain the novel impregnating pitch with a yield of 33%. The pitch possess a SP of 120°C, Ql of 1.2%, Tl of 7.5%, CV of 63.3% and SG of 1.28. Example 2 The above experiment is repeated and heat treated pitch is dissolved in a commercial inexpensive industrial solvent toluene and the solvent soluble portion is distilled to get pitch of SP of 115°C, Ql of 2.2%, Tl of 23.2% and CV of 62.2%. Example 3 A commercial low Ql coal tar pitch is heat treated upto 430°C under a reduced pressure of 12 cm to produce a pitch of S.P. of 213°C, Ql of 22%, Tl of 58.6, CV of 75.8% and S.G. of 1.34. The resulting pitch is heat treated in presence of coal tar oil (1:6) and soluble portion is distilled to recover the solvent and obtain the impregnating pitch. The final pitch possesses a S.P. of 83°C, Ql of 0.2%, Tl of 3.7% and CV of 52.6%. Example 4 A commercial low Ql coal tar pitch is heat treated upto 380°C for 1.25 hrs under partial vacuum of 4 cm Hg to produce a pitch of S.P. of 192°C, Ql of 5.6%, Tl of 60.8, CV of 68% and S.G. of 1.33. The resulting pitch is heat treated with toluene and the solvent portion is distilled to recover the solvent and obtain the impregnating pitch possess a SP of 81 °C, Ql of 1.3%, Tl of 4.4% and CV of 54.3% and SG of 1.29. Example 5 A low Ql coal tar pitches is heated upto 380°C for 1.25hr under reduced pressure to obtain a pitch of softening point of more than 300°C, Ql of 15.2%, Tl of 66.8% and CV of 78.8%. The treated pitch is heated in presence of coal tar oil and soluble portion is distilled to recover the solvent and obtain impregnating pitch with a yield of 36%. The pitch possesses a SP of 87°C, Ql of 0.1%, Tl of 3.5%, CV of 53.4% and SG of 1.27. Example 6 A low Ql coal tar pitch is heated upto 405°C for 15min under reduced pressure (4 cm Hg) to obtain a pitch of softening point of more than 210°C, Ql of 15%, Tl of 57.5% and CV of 73.5% and SG of 1.33. The treated pitch is heated in presence of suitable solvent and soluble portion is distilled to recover the solvent and obtain impregnating pitch. The pitch possesses a SP of 120°C, Ql of 0.9%, Tl of 7.6%, CV of 58.2% and SG of 1.29. Advantages: The main advantage of the present invention is the simplicity of the process coupled with the enhanced efficient impregnation of the special pitch to obtain dense carbon-carbon composite and graphite electrodes with fewer impregnation cycles. Besides this, as mentioned already, this process can also lead to a variety of other pitches suitable for several other applications. We ciaim 2. An improved process for the preparation of high quality impregnating grade pitch having high coking value and containing low Quinoline insolubles, and the said process comprising the steps of: a) heat treating the coal tar pitch or a mixture of coal tar pitch and petroleum pitch, at temperatures in the range of 300-450°C, in an inert atmosphere or under reduced pressure of 4-40 cmHg, for a period of 0.2-2.Ohr to obtain the precursor pitch, b) mixing the resulting precursor pitch containing Quinoline insolubles with an organic solvent in the proportion of 2-10, c) heating the above said resultant mixture to a temperature in the range of 120- 250°C, in an inert atmosphere, for a period in the range of 2 to 24 hours, d) separating the above said heated mixture into two parts by simple separation device or decantation or process of filtration and obtaining the one major part containing low Ql and the other part containing High Ql, and e) distilling the major part under vacuum at a temperature upto 400°C to obtain the desired product. 2. An improved process as claimed in claim 1 wherein the organic solvent used is selected from light or medium creosote oil, wash oil, heavy oil. 3. An improved process as claimed in claims 1 and 2 wherein the ratio of solvent-to-coal tar pitch is preferably in the range of 2 to 5. 4. An improved process as claimed in claims 1-3 wherein the heat treatment is carried out, preferably at a temperature in the range of 130-180°C. 5. An improved process as claimed in claims 1-4 wherein the heat treatment is carried out, preferably for a period in the range of 4-10 hours. 6. An improved process as claimed in the claims 1-5, wherein the distillation is carried out at a temperature preferably in the range of 300-330°C . 7. An improved process as claimed in claims 1-6, wherein the distillation is carried out at a pressure, preferably in the range of 4-40 cm Hg for period of 10-15 minutes. 8. An improved process as claimed in claims 1-6, wherein the high quality coal tar pitch obtained has high coking value of 50-65% and low quinoline- insoluble contents of 0-3%. 9. An improved process for the preparation of high quality coal tar pitch, substantially as herein described with reference to the examples.

Full Text

Field of the invention
The present invention relates to an improved process for the preparation of high quality impregnating grade pitch. More particularly, the present invention relates to an improved process for the preparation of coal tar pitch having low contents of quinoline insolubles (Ql) and toluene insolubles (Tl) and high content of coking value. It is used for densification of carbon-carbon composites made in various forms as aircraft brakes, nose cones, heat shields, high temperature dies, bone plates and hip joints etc. The same pitch can also be used to impregnate the graphite electrodes for use in steel industry.
Background of the invention
The commercially available coal tars are obtained from the destructive distillation of metallurgical coals by the steel industry. The coal tars, so obtained, invariably contain soot-like fine particles formed by the thermal cracking of tar vapours and entrained fine particles of coal and coke. Since coal tar pitches are residues obtained in the distillation of such coal tars, these very Ql particles are also found in these pitches. The commercially available coal tars and coal tar pitches normally contain Ql in range of 4-15% which make them unsuitable for the impregnation purpose.
In the prior art, three methods employing, separately, filtration, solvent extraction and centrifugation are known for removing Ql from coal tars and coal tar pitches. The filtration method involves the filtration of molten coal tar precursor heated to about 250°C through filters of various types to get low Ql tar or pitch. The method of solvent extraction, on the other hand employs the use of solvents to extract the solvent-soluble portion of coal tars or coal tar pitches which are low in Ql. The solvent is then removed from the soluble portion by the conventional distillation technique. The centrifugation method involves the removal of Ql from the molten coal tar precursor using industrial centrifugal machines. These known processes for the removal of Ql have certain drawbacks which make them cumbersome as well as expensive. To obviate the above mentioned drawbacks, we in our earlier patent No. 186256 (2002) have provided the process for the
producing the low QI/QI free impregnating pitches which have been obtained by heat treating commercial coal tar pitches with the mixture of special industrial solvents to cause coagulation of Ql particles as Ql mass in the pitch solvent mixtures. The major pitch solvent portion containing no or low Ql can be distilled to remove the solvent and obtain the impregnating pitch.
The characteristics of low Ql / Ql-free impregnating grade coal tar pitch obtainable with the above processes are
Softening point 80 - 120°C
Quinoline insoluble 0.0 - 3.0%
Toluene insoluble 16-24%
Coking value 42 - 46 %
Specific gravity 1.26 - 1.28
Ash content 0.05 % (Max.)
All the methods mentioned above produce impregnating grade of pitches of low coking value (42-46%) besides having low contents of Ql (0-3%) . Therefore, a large number of impregnations followed by carbonization cycles are required to improve the bulk density of the carbon-carbon composites and graphite electrodes. As a result, the process of producing carbon-carbon composites and graphite electrodes through large number of impregnation and carbonization cycles is tedious, cumbersome, time consuming and expensive.
Objectives of the invention
The main object of the present invention is to provide a process for the preparation of impregnating grade pitch with a high content of coking value (50-65%).
Yet another objective of the present invention is to provide an improved process for the preparation of impregnating grade pitch, which is useful for making carbon-carbon composites, graphite electrodes etc.
Still another object of the invention is to provide an improved process for
the preparation of impregnating grade pitch , which possesses Ql in the range of 0-3%.
Summary of the invention
Accordingly the present invention provides an improved process for the preparation of high quality impregnating grade pitch having high coking value and containing low Quinoline insolubles, and the said process comprising the steps of:
a) heat treating the coal tar pitch or a mixture of coal tar pitch and
petroleum pitch, at temperatures in the range of 300-450°C, in an
inert atmosphere or under reduced pressure of 4-40 cmHg, for a
period of 0.2-2.Ohr to obtain the precursor pitch,
b) mixing the resulting precursor pitch containing Quinoline insolubles
with an organic solvent in the proportion of 2-10,
c) heating the above said resultant mixture to a temperature in the
range of 120- 250°C, in an inert atmosphere, for a period in the
range of 2 to 24 hours,
d) separating the above said heated mixture into two parts by simple
separation device or decantation or process of filtration and obtaining
the one major part containing low Ql and the other part containing
High Ql, and
e) distilling the major part under vacuum at a temperature upto 400°C
to obtain the desired product.
In an embodiment of the present invention the organic solvent used is selected from light or medium creosote oil, wash oil and heavy oil.
In yet another embodiment the ratio of solvent-to-coal tar pitch is preferably in the range of 2 to 5.
In yet another embodiment the heat treatment is carried out, preferably at a temperature in the range of 130-180°C.
In yet another embodiment the heat treatment is carried out, preferably for a period in the range of 4-10 hours.
In yet another embodiment the distillation is carried out at a temperature eferably in the range of 300-330°C .
In yet another embodiment the distillation is carried out at a pressure, preferably in the range of 4-40 cm Hg for period of 10-15 minutes.
In still another embodiment the high quality coal tar pitch obtained has high coking value of 50-65% and low quinoline-insoluble contents of 0-3%.
Detail description of the invention
The present invention provides a process for the preparation of novel impregnating grade pitch which is useful for making carbon-carbon composites, graphite electrodes and the like, which comprises
(i) Heating of a commercial coal tar pitch or a mixture of commercial coal tar pitch and petroleum pitch at a temperature in the range of 300-450 °C in inert atmosphere or under reduced pressure to obtain a pitch of high softening point (150 - 350°C) and with higher value of Ql (5-50%), Tl (30-70%) and coking value (70-80%).
(ii) Heating the resulting pitch in the presence of suitable inexpensive aromatic solvent, such as tar oil, wash oil, toluene, etc respectively, in requisite proportions, at a temperature around 80-170°C, to cause the dissolution of the pitch in the solvent.
(iii) The Ql containing mass is then separated from the pitch-solvent mixture by a simple separating device or a decantation process or a filtration process, (iv) The pitch-solvents mixture is then distilled at temperatures upto 360°C to recover the solvents in inert atmosphere or under reduced pressure and obtain the novel impregnating-grade pitch.
The novel feature of the present invention are the use of the precursor pitch material obtained by heat-treatment of a coal tar pitch or mixture of coal tar pitch and petroleum pitch which is then treated with a suitable aromatic solvent to extract the solvent soluble portion low in Ql or free of Ql which is then distilled to remove the solvent and obtain the high quality impregnating grade coal tar pitch.
The following examples are given by the way of illustration and therefore should not be construed to limit the scope of the invention.
Example 1
Equal quantities of Ql free coal tar pitches and petroleum pitches are heated to 430°C under reduced pressure of 6cm Hg to obtain pitches of softening point of 195°C, Ql and Tl content of 1.0 and 36.5 respectively, coking value of 72.5 and SG of 1.29 The resulting pitch is dissolved in toluene in the ratio (1:6 by wt.) at a temperature of 90-100°C and solution is filtered and distilled to recover the solvent and obtain the novel impregnating pitch with a yield of 33%. The pitch possess a SP of 120°C, Ql of 1.2%, Tl of 7.5%, CV of 63.3% and SG of 1.28.
Example 2
The above experiment is repeated and heat treated pitch is dissolved in a commercial inexpensive industrial solvent toluene and the solvent soluble portion is distilled to get pitch of SP of 115°C, Ql of 2.2%, Tl of 23.2% and CV of 62.2%.
Example 3
A commercial low Ql coal tar pitch is heat treated upto 430°C under a reduced pressure of 12 cm to produce a pitch of S.P. of 213°C, Ql of 22%, Tl of 58.6, CV of 75.8% and S.G. of 1.34. The resulting pitch is heat treated in presence of coal tar oil (1:6) and soluble portion is distilled to recover the solvent and obtain the impregnating pitch. The final pitch possesses a S.P. of 83°C, Ql of 0.2%, Tl of 3.7% and CV of 52.6%.
Example 4
A commercial low Ql coal tar pitch is heat treated upto 380°C for 1.25 hrs under partial vacuum of 4 cm Hg to produce a pitch of S.P. of 192°C, Ql of 5.6%, Tl of 60.8, CV of 68% and S.G. of 1.33. The resulting pitch is heat treated with toluene and the solvent portion is distilled to recover the solvent and obtain the
impregnating pitch possess a SP of 81 °C, Ql of 1.3%, Tl of 4.4% and CV of 54.3% and SG of 1.29.
Example 5
A low Ql coal tar pitches is heated upto 380°C for 1.25hr under reduced pressure to obtain a pitch of softening point of more than 300°C, Ql of 15.2%, Tl of 66.8% and CV of 78.8%. The treated pitch is heated in presence of coal tar oil and soluble portion is distilled to recover the solvent and obtain impregnating pitch with a yield of 36%. The pitch possesses a SP of 87°C, Ql of 0.1%, Tl of 3.5%, CV of 53.4% and SG of 1.27.
Example 6
A low Ql coal tar pitch is heated upto 405°C for 15min under reduced pressure (4 cm Hg) to obtain a pitch of softening point of more than 210°C, Ql of 15%, Tl of 57.5% and CV of 73.5% and SG of 1.33. The treated pitch is heated in presence of suitable solvent and soluble portion is distilled to recover the solvent and obtain impregnating pitch. The pitch possesses a SP of 120°C, Ql of 0.9%, Tl of 7.6%, CV of 58.2% and SG of 1.29.
Advantages:
The main advantage of the present invention is the simplicity of the process coupled with the enhanced efficient impregnation of the special pitch to obtain dense carbon-carbon composite and graphite electrodes with fewer impregnation cycles. Besides this, as mentioned already, this process can also lead to a variety of other pitches suitable for several other applications.

We ciaim
2. An improved process for the preparation of high quality impregnating grade pitch having high coking value and containing low Quinoline insolubles, and the said process comprising the steps of:
a) heat treating the coal tar pitch or a mixture of coal tar pitch and
petroleum pitch, at temperatures in the range of 300-450°C, in an
inert atmosphere or under reduced pressure of 4-40 cmHg, for a
period of 0.2-2.Ohr to obtain the precursor pitch,
b) mixing the resulting precursor pitch containing Quinoline insolubles
with an organic solvent in the proportion of 2-10,
c) heating the above said resultant mixture to a temperature in the
range of 120- 250°C, in an inert atmosphere, for a period in the
range of 2 to 24 hours,
d) separating the above said heated mixture into two parts by simple
separation device or decantation or process of filtration and obtaining
the one major part containing low Ql and the other part containing
High Ql, and
e) distilling the major part under vacuum at a temperature upto 400°C
to obtain the desired product.

2. An improved process as claimed in claim 1 wherein the organic solvent
used is selected from light or medium creosote oil, wash oil, heavy oil.
3. An improved process as claimed in claims 1 and 2 wherein the ratio of
solvent-to-coal tar pitch is preferably in the range of 2 to 5.
4. An improved process as claimed in claims 1-3 wherein the heat treatment is
carried out, preferably at a temperature in the range of 130-180°C.
5. An improved process as claimed in claims 1-4 wherein the heat treatment
is carried out, preferably for a period in the range of 4-10 hours.
6. An improved process as claimed in the claims 1-5, wherein the distillation is
carried out at a temperature preferably in the range of 300-330°C .
7. An improved process as claimed in claims 1-6, wherein the distillation is
carried out at a pressure, preferably in the range of 4-40 cm Hg for period of
10-15 minutes.
8. An improved process as claimed in claims 1-6, wherein the high quality
coal tar pitch obtained has high coking value of 50-65% and low quinoline-
insoluble contents of 0-3%.
9. An improved process for the preparation of high quality coal tar pitch,
substantially as herein described with reference to the examples.

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Patent Number

271369

Indian Patent Application Number

531/DEL/2008

PG Journal Number

08/2016

Publication Date

19-Feb-2016

Grant Date

18-Feb-2016

Date of Filing

05-Mar-2008

Name of Patentee

COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH

Applicant Address

ANUSANDHAN BHAWAN, RAFI MARG, NEW DELHI-110 001,INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	BHATIA GOPAL	NATIONAL PHYSICAL LABORATORY DR. K.S.KRISHNAN MARG, NEW DELHI 110 012
2	ARCHANA	NATIONAL PHYSICAL LABORATORY DR. K.S.KRISHNAN MARG, NEW DELHI 110 012
3	BISHT RAJENDRA SINGH	NATIONAL PHYSICAL LABORATORY DR. K.S.KRISHNAN MARG, NEW DELHI 110 012
4	RAMAN VASANTHA	NATIONAL PHYSICAL LABORATORY DR. K.S.KRISHNAN MARG, NEW DELHI 110 012
5	SENGUPTA PINAKI RANJAN	NATIONAL PHYSICAL LABORATORY DR. K.S.KRISHNAN MARG, NEW DELHI 110 012
6	NEGI TRILOK SINGH	NATIONAL PHYSICAL LABORATORY DR. K.S.KRISHNAN MARG, NEW DELHI 110 012

PCT International Classification Number

C04B 35/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA