Title of Invention	AN IMPROVED PROCESS FOR THE HYDROTHERMAL SYNTHESIS OF BOEHMITE, α-ALUMINA OR THEIR MIXTURES IN DOPED FORM.
Abstract	This invention relates to an improved process for the hydrothermal synthesis of boehmite, a-alumina or their mixtures in doped form. In the present process fine crystalline powders of doped boehmite, a-alumina or their mixtures from commercial aluminium metal stock in a single step are obtained by hydrothermal synthesis. The boehmite, a alumina oe their mixture in doped forms are obtained by taking dopants like chromium(for ruby or pink alumina) , manganese (brown alumina), magnesium (for spinel) in the form of water soluble salt or aluminium alloys containing the dopant (Al-Mg alloys) along with initial reactants and conducting hydrothermal reaction.

Title of Invention

AN IMPROVED PROCESS FOR THE HYDROTHERMAL SYNTHESIS OF BOEHMITE, α-ALUMINA OR THEIR MIXTURES IN DOPED FORM.

Abstract

This invention relates to an improved process for the hydrothermal synthesis of boehmite, a-alumina or their mixtures in doped form. In the present process fine crystalline powders of doped boehmite, a-alumina or their mixtures from commercial aluminium metal stock in a single step are obtained by hydrothermal synthesis. The boehmite, a alumina oe their mixture in doped forms are obtained by taking dopants like chromium(for ruby or pink alumina) , manganese (brown alumina), magnesium (for spinel) in the form of water soluble salt or aluminium alloys containing the dopant (Al-Mg alloys) along with initial reactants and conducting hydrothermal reaction.

Full Text	This invention relates to an improved process for the hydrothermal synthesis of boehmite, α-alumina or their mixtures in the doped form. The invention particularly relates to an improved hydrothermal process for obtaining fine crystalline powders of doped boehmite, a-alumina or their mixtures from commercial aluminium metal stock in a single step. The boehmite, alumina or their mixtures produced by the process of this invention are useful as ceramic raw materials for the ceramic industry. The powders prepared by the process of this invention would also be used in the manufacture of structural and electronic ceramic components. They are used in these applications as resistors, insulators, electron tube elements, lamp envelopes as well as in the preparation of alumina matrix based composite products, as alumina based plasma coating or spray coating powders, in alumina refractories, in alumina abrasives, in alumina-silicon carbide (whisker) based composite cutting tool materials and the like. The strength and toughness of the component developed is dependent on the grain size of the fine powders of alumina or boehmite synthesized. The hitherto known process for the preparation of boehmite and a-alumina utilises bauxite ore or trihydroxides of aluminium. This process involves several steps of chemical reaction, purification and heating (calcination) to high temperatures. Alumina is produced by the now well-known and classical hydrothermal Bayer's process which involves the following steps: Bauxite ore is crushed, mixed with caustic soda to form soluble sodium aluminates; these are further seeded with alumina trihydrate and hydrolysed for several hours at moderate temperatures to obtain gibbsite, A1(OH)3. This product is settled and filtered to separate from spent liquor and is finally calcined at 1200°C to transform gibbsite into a-alumina. For comprehensive details of the above said process reference may be made to the publication "Alumina as a Ceramic Material" ed., Walter H Gitzen, American Ceramic Society (1970). Though boehmite is known to occur naturally in European bauxite, its extraction and crystallisation are quite challenging. It is prepared synthetically by careful ageing of aluminium hydroxide gels followed by the thermal treatment between 170-550°C. The product is sharply dependent on conditions of treatment and is often contaminated by mixtures of several other phases. Alternatively, hydrothermal treatment of Bayer's alumina trihydrate in water or alkaline solution is carried out for long hours. While Bloch and Bugosh describe processes for the preparation of boehmite comprising of heating finely divided metallic aluminium and aluminohydrates hydrothermally at 250-375°C. (Bloch.H.S, U.S.Pat, 2,758,011, 8th July 1956: Bogosh J U.S.Pat, 2,915,475, 12th Jan. 1959), hydrothermal methods describing the synthesis of α-alumina starting from solid aluminium metal are not known. The conventional Bayer's process for a-alumina synthesis as stated above requires a hydrothermal synthesis of purified bauxite ore followed by thermal treatment at 1200°C of the product (gibbsite) obtained. The calcination step coarsens the grains of a-alumina. The hydrothermal reaction of alumina trihydrates or of aluminium powders were carried out in sealed gold capsules in very small quantities with external pressurisation and this method is not suited to large scale synthesis of boehmite and a-alumina. The contamination from starting materials in case of incomplete reactions in another problem to be overcome. This involves multiple steps of aluminium leaching followed by the treatment of products to free them from leaching media etc. An easy method of removal of unreacted materials is therefore required in any process that would be improvised for the synthesis of the two products, namely, boehmite and a-alumina. The main object of the present invention is to provide an improved process for the production of bohemite and a-alumina by a hydrothermal route which enables easy separation of unreacted raw materials from the products of the reaction. Another object of the present invention is to provide an improved process for the preparation of boehmite, a-alumina or their mixtures in doped forms (with other specific impurities e.g. Cr3+ , Mg2+ , Mn2+ etc.). The process of the present invention is based on our finding that the above products could be obtained by a hydrothermal reaction at low temperatures (300-550°C) and at low pressures (15-120 MPa) in open reactors placed inside high pressure autoclaves in a single step. The pressure is preferably generated autogeneously inside the autoclaves by a combination of the pressure of water vapor reaching the superheated or supercritical state and the pressure of hydrogen gas liberated by the reaction of aluminium and water (in the superheated / supercritical state.). The invention uses commercially available aluminium rod stock along with demineralised water (with dissolved salts or aluminium alloys containing the doping element depending on whether a doped product is required or not) placed in open reactors inside the autoclaves for achieving the conversion. The use of aluminium as a rod stock enables reaction to be terminated at any stage and aids the easy (physical) separation of the unreacted rod stock left from the products of the reaction. This is made possible since the reaction between the metal rod stocks and water proceeds layer wise from the outside of the rod stocks and equally from all sides. The product after it builds up a sufficient thickness separated out as a layer. Continuos reaction over a period of time would build up successive loose layers of products. These can be therefore physically separated from the main reactant rod stock. The yield of the product as well as the kinetics of the reactions could be controlled easily by the ratio of the quantity of water to the metal stock taken as well as by the temperature of the reaction. It is possible to obtain boehmite, α-alumina or their mixtures in doped forms as well, by taking the dopants e.g., chromium (for ruby or pink alumina) manganese (brown alumina) magnesium (for spinel) etc. in the form of water soluble salt (in requisite quantities) or aluminium alloys containing the dopant (e.g. Al-Mg alloys) element along with the initial reactants and conducting the hydrothermal reaction described before. Since solid blocks of aluminium are used the reaction rates could be slow down (as compared to the case where fine metal powders are used) and the products could also be doped more uniformly and extensively by this process due to the slowness of the reaction. Accordingly, the present invention provides an improved process for the hydrothermal synthesis of boehmite, a-alumina or their mixtures in doped form which comprises; oxidizing aluminum metal blocks with water in the ratio of 1:2.20 to 2.52 to 1 -.4:4.5 to 4.79 by wt. in presence of aqueous solution salts Cr2O3 for chromium doping, MnCO3 for manganese doping and magnesium in the presence of magnesium format or acetate salts or in the form of Al - Mg alloy for Mg doping in the range from 1-30 wt.% of alumina in an autoclave at temperatures in the range of 300-550°C, pressure in the range of 15-120 MPa, cooling an autoclave to room temperature, separating the unreacted solid from the product powders by removing physically, washing and drying the said powders in air or in vacuum to obtain free flowing powders of boehmite, ,, a alumina or their mixtures; heating the said free flowing powders in the temperature range of 1250-1450°C for 2 to 4 hrs. for homogeneous distribution of dopants to obtain desired products, the said products are characterized by X-ray diffraction for phase analysis in case of Cr and Mn salt finished doped product is obtained whereas in case of Mg salts or Al - Mg alloy, finished doped product is magnesium spinal. EXAMPLES The examples 1-14 given in the following table 1 indicates the conditions of experiments conducted by following a general procedure described here in under to obtain a-alumina and boehmite or their mixtures, in doped form. SYNTHESIS OF UNDOPED PRODUCTS A small commercial aluminum metal block weighing approximately 10 grams is taken in an alumina container which can be introduced into an open reactor vessel inside a hvdrothermal autoclave and 25-50 ml of demineralised water is added to it. The autoclave is closed and heated at 2-10°C/min to a temperature between 300-500°C. After reaching the required temperature, the autoclave and contents are held up to 3 hours at the same final temperature while the pressure reaches values ranging from 15-120 MPa depending upon the volume loading and the final temperature reached in the autoclave. The autoclave is then cooled naturally to room temperature and opened after release of pressure. After separation of unreacted aluminium block physically (as one block) the products are washed and air/vacuum dried. The phases in the product are characterised by XRD. The product is boehmite (B) if the temperature used is in the range of 300-350°C, a-alumina (A) if the temperature is in the range of 450-550°C and a mixture of the two in the intermediate temperature range of 350-450°C. The size of product powders fall typically in the size range of-325 mesh (ASTM). TABLE-I (Table Removed) A= α-alumina : B= Boehmite * = Mass reacted for one hour only SYNTHESIS OF DOPED PRODUCTS The examples 1-3 given in the following table II summarise some of the experiments conducted by following a general procedures described here in under to obtain Cr, Mn and Mg (MgA12O4 - Magnesium spinel) doped products. If the product is to be doped with ions of elements like Cr, Mn, Mg etc. the latter are taken along with aluminium block in the form of water soluble salts (e.g.,CrO3 for Cr doping, MnCO3 for Mn doping and magnesium in the form of magnesium formate or acetate salts or in the form of Al-Mg alloys for Mg doping). The reaction after the addition of dopant salts or alloys to demineralised water is carried out as described earlier for synthesis of undoped products. The products from hydrothermal reaction are recovered, washed with water to free it from unreacted dopant materials and characterised by XRD for phase identification. Subsequently the products are heated in the temperature range of 1250-1450°C for 2-4 hours to achieve homogeneous distribution of the dopant in the a-alumina product powder. These final heat-treated products are again characterised by XRD for phase analysis. Mn and Cr doped samples have XRD patterns identical to a-alumina with no other additional picks thereby indicating that both Mn and Cr can be doped substitutionally into the a-alumina structure. In the case of magnesium salts or Al-Mg alloy, however, magnesium spinel is formed besides a-alumina in appropriate amounts (XRD analysis). Thus alumina -spinel mixtures can also be obtained by this process. The quantitative analysis of the products could be done by SEM-EDAX, Electron microprobe analysis or by quantitative XRD methods. The results (e.g., table II) indicate that doping small quantities of other metal oxides like MnO, CraOs and MgO-spinel into a-alumina is indeed possible. Some typical results are summarised in table II. The process could be extended to doping other element oxides into a-alumina by going through similar hydrothermal synthetic route followed by the heat treatment schedules described above. TABLE-II (Table Removed) A = α-Alumina Sp = Magnesium aluminate Mg-Al2O4 spinel * By SEM-EDAX method X by XRD quantitative analysis We Claim: 1. An improved process for the hydrothermal synthesis of boehmite, a-alumina or their mixtures in doped form which comprises; oxidizing aluminum metal blocks with water in the ratio of 1:2.20 to 2.52 to 1:4:4.5 to 4.79 by wt. in presence of aqueous solution salts Cr2O3 for chromium doping, MnCO3 for manganese doping and magnesium in the presence of magnesium format or acetate salts or in the form of Al - Mg alloy for Mg doping in the range from 1-30 wt.% of alumina in an autoclave at temperatures in the range of 300-550°C, pressure in the range of 15-120 MPa, cooling an autoclave to room temperature, separating the unreacted solid from the product powders by removing physically, washing and drying the said powders in air or in vacuum to obtain free flowing powders of boehmite,, a alumina or their mixtures; heating the said free flowing powders in the temperature range of 1250-1450°C for 2 to 4 hrs. for homogeneous distribution of dopants to obtain desired products, the said products are characterized by X-ray diffraction for phase analysis in case of Cr and Mn salt finished doped product is obtained whereas in case of Mg salts or Al - Mg alloy, finished doped product is magnesium spinal. 2 An improved process as claimed in claim 1, wherein the temperature is in the range of 300-350°C for boehmite, temperature is in the range of 450-550°C for a alumina and if the temperature is in the range of 350-450°C for a mixture of boehmite and alumina. 3 An improved process as claimed in claims 1-2 wherein for Mg doping the % of aluminum - Magnesium alloy used is 5 and 10%. 4. An improved process for the hydrothermal synthesis of boehmite, a-alumina or their mixtures in the doped form substantially as herein described with reference to the examples.

Full Text

This invention relates to an improved process for the hydrothermal synthesis of boehmite, α-alumina or their mixtures in the doped form. The invention particularly relates to an improved hydrothermal process for obtaining fine crystalline powders of doped boehmite, a-alumina or their mixtures from commercial aluminium metal stock in a single step. The boehmite, alumina or their mixtures produced by the process of this invention are useful as ceramic raw materials for the ceramic industry. The powders prepared by the process of this invention would also be used in the manufacture of structural and electronic ceramic components. They are used in these applications as resistors, insulators, electron tube elements, lamp envelopes as well as in the preparation of alumina matrix based composite products, as alumina based plasma coating or spray coating powders, in alumina refractories, in alumina abrasives, in alumina-silicon carbide (whisker) based composite cutting tool materials and the like. The strength and toughness of the component developed is dependent on the grain size of the fine powders of alumina or boehmite synthesized.
The hitherto known process for the preparation of boehmite and a-alumina utilises bauxite ore or trihydroxides of aluminium. This process involves several steps of chemical reaction, purification and heating (calcination) to high temperatures. Alumina is produced by the now well-known and classical hydrothermal Bayer's process which involves the following steps: Bauxite ore is crushed, mixed with caustic soda to form soluble sodium aluminates; these are further seeded with alumina trihydrate and hydrolysed for several hours at moderate temperatures to obtain gibbsite, A1(OH)3. This product is settled and filtered to separate from spent liquor and is finally calcined at 1200°C to transform gibbsite into a-alumina. For comprehensive details of the above said process reference may be made to the publication "Alumina as a Ceramic Material" ed., Walter H Gitzen, American Ceramic Society (1970).
Though boehmite is known to occur naturally in European bauxite, its extraction and crystallisation are quite challenging. It is prepared synthetically by careful ageing of

aluminium hydroxide gels followed by the thermal treatment between 170-550°C. The product is sharply dependent on conditions of treatment and is often contaminated by mixtures of several other phases. Alternatively, hydrothermal treatment of Bayer's alumina trihydrate in water or alkaline solution is carried out for long hours. While Bloch and Bugosh describe processes for the preparation of boehmite comprising of heating finely divided metallic aluminium and aluminohydrates hydrothermally at 250-375°C. (Bloch.H.S, U.S.Pat, 2,758,011, 8th July 1956: Bogosh J U.S.Pat, 2,915,475, 12th Jan. 1959), hydrothermal methods describing the synthesis of α-alumina starting from solid aluminium metal are not known.
The conventional Bayer's process for a-alumina synthesis as stated above requires a hydrothermal synthesis of purified bauxite ore followed by thermal treatment at 1200°C of the product (gibbsite) obtained. The calcination step coarsens the grains of a-alumina. The hydrothermal reaction of alumina trihydrates or of aluminium powders were carried out in sealed gold capsules in very small quantities with external pressurisation and this method is not suited to large scale synthesis of boehmite and a-alumina. The contamination from starting materials in case of incomplete reactions in another problem to be overcome. This involves multiple steps of aluminium leaching followed by the treatment of products to free them from leaching media etc. An easy method of removal of unreacted materials is therefore required in any process that would be improvised for the synthesis of the two products, namely, boehmite and a-alumina.
The main object of the present invention is to provide an improved process for the production of bohemite and a-alumina by a hydrothermal route which enables easy separation of unreacted raw materials from the products of the reaction.
Another object of the present invention is to provide an improved process for the preparation of boehmite, a-alumina or their mixtures in doped forms (with other specific impurities e.g. Cr3+ , Mg2+ , Mn2+ etc.).

The process of the present invention is based on our finding that the above products could be obtained by a hydrothermal reaction at low temperatures (300-550°C) and at low pressures (15-120 MPa) in open reactors placed inside high pressure autoclaves in a single step. The pressure is preferably generated autogeneously inside the autoclaves by a combination of the pressure of water vapor reaching the superheated or supercritical state and the pressure of hydrogen gas liberated by the reaction of aluminium and water (in the superheated / supercritical state.). The invention uses commercially available aluminium rod stock along with demineralised water (with dissolved salts or aluminium alloys containing the doping element depending on whether a doped product is required or not) placed in open reactors inside the autoclaves for achieving the conversion. The use of aluminium as a rod stock enables reaction to be terminated at any stage and aids the easy (physical) separation of the unreacted rod stock left from the products of the reaction. This is made possible since the reaction between the metal rod stocks and water proceeds layer wise from the outside of the rod stocks and equally from all sides. The product after it builds up a sufficient thickness separated out as a layer. Continuos reaction over a period of time would build up successive loose layers of products. These can be therefore physically separated from the main reactant rod stock. The yield of the product as well as the kinetics of the reactions could be controlled easily by the ratio of the quantity of water to the metal stock taken as well as by the temperature of the reaction.
It is possible to obtain boehmite, α-alumina or their mixtures in doped forms as well, by taking the dopants e.g., chromium (for ruby or pink alumina) manganese (brown alumina) magnesium (for spinel) etc. in the form of water soluble salt (in requisite quantities) or aluminium alloys containing the dopant (e.g. Al-Mg alloys) element along with the initial reactants and conducting the hydrothermal reaction described before. Since solid blocks of aluminium are used the reaction rates could be slow down (as compared to the case where fine metal powders are used) and the products could also be doped more uniformly and extensively by this process due to the slowness of the reaction.

Accordingly, the present invention provides an improved process for the hydrothermal synthesis of boehmite, a-alumina or their mixtures in doped form which comprises; oxidizing aluminum metal blocks with water in the ratio of 1:2.20 to 2.52 to 1 -.4:4.5 to 4.79 by wt. in presence of aqueous solution salts Cr2O3 for chromium doping, MnCO3 for manganese doping and magnesium in the presence of magnesium format or acetate salts or in the form of Al - Mg alloy for Mg doping in the range from 1-30 wt.% of alumina in an autoclave at temperatures in the range of 300-550°C, pressure in the range of 15-120 MPa, cooling an autoclave to room temperature, separating the unreacted solid from the product powders by removing physically, washing and drying the said powders in air or in vacuum to obtain free flowing powders of boehmite, ,, a alumina or their mixtures; heating the said free flowing powders in the temperature range of 1250-1450°C for 2 to 4 hrs. for homogeneous distribution of dopants to obtain desired products, the said products are characterized by X-ray diffraction for phase analysis in case of Cr and Mn salt finished doped product is obtained whereas in case of Mg salts or Al - Mg alloy, finished doped product is magnesium spinal.
EXAMPLES
The examples 1-14 given in the following table 1 indicates the conditions of experiments conducted by following a general procedure described here in under to obtain a-alumina and boehmite or their mixtures, in doped form.
SYNTHESIS OF UNDOPED PRODUCTS
A small commercial aluminum metal block weighing approximately 10 grams is taken in an alumina container which can be introduced into an open reactor vessel inside a hvdrothermal autoclave and 25-50 ml of demineralised water is added to it. The autoclave

is closed and heated at 2-10°C/min to a temperature between 300-500°C. After reaching the required temperature, the autoclave and contents are held up to 3 hours at the same final temperature while the pressure reaches values ranging from 15-120 MPa depending upon the volume loading and the final temperature reached in the autoclave.
The autoclave is then cooled naturally to room temperature and opened after release of pressure. After separation of unreacted aluminium block physically (as one block) the products are washed and air/vacuum dried. The phases in the product are characterised by XRD. The product is boehmite (B) if the temperature used is in the range of 300-350°C, a-alumina (A) if the temperature is in the range of 450-550°C and a mixture of the two in the intermediate temperature range of 350-450°C. The size of product powders fall typically in the size range of-325 mesh (ASTM).
TABLE-I
(Table Removed)

*A= α-alumina : B= Boehmite
** = Mass reacted for one hour only
SYNTHESIS OF DOPED PRODUCTS
The examples 1-3 given in the following table II summarise some of the experiments conducted by following a general procedures described here in under to obtain Cr, Mn and Mg (MgA12O4 - Magnesium spinel) doped products.
If the product is to be doped with ions of elements like Cr, Mn, Mg etc. the latter are taken along with aluminium block in the form of water soluble salts (e.g.,CrO3 for Cr doping, MnCO3 for Mn doping and magnesium in the form of magnesium formate or acetate salts or in the form of Al-Mg alloys for Mg doping). The reaction after the addition of dopant salts or alloys to demineralised water is carried out as described earlier for synthesis of undoped products. The products from hydrothermal reaction are recovered, washed with water to free it from unreacted dopant materials and characterised by XRD for phase identification.
Subsequently the products are heated in the temperature range of 1250-1450°C for 2-4 hours to achieve homogeneous distribution of the dopant in the a-alumina product powder. These final heat-treated products are again characterised by XRD for phase analysis. Mn and Cr doped samples have XRD patterns identical to a-alumina with no other additional picks thereby indicating that both Mn and Cr can be doped substitutionally into the a-alumina structure. In the case of magnesium salts or Al-Mg alloy, however, magnesium spinel is formed besides a-alumina in appropriate amounts (XRD analysis). Thus alumina -spinel mixtures can also be obtained by this process. The quantitative analysis of the products could be done by SEM-EDAX, Electron microprobe analysis or by quantitative XRD methods. The results (e.g., table II) indicate that doping small quantities of other metal oxides like MnO, CraOs and MgO-spinel into a-alumina is indeed possible.

Some typical results are summarised in table II. The process could be extended to doping other element oxides into a-alumina by going through similar hydrothermal synthetic route followed by the heat treatment schedules described above.
TABLE-II
(Table Removed)

A = α-Alumina
Sp = Magnesium aluminate Mg-Al2O4 spinel
* By SEM-EDAX method
X by XRD quantitative analysis

We Claim:
1. An improved process for the hydrothermal synthesis of boehmite, a-alumina or their mixtures in doped form which comprises; oxidizing aluminum metal blocks with water in the ratio of 1:2.20 to 2.52 to 1:4:4.5 to 4.79 by wt. in presence of aqueous solution salts Cr2O3 for chromium doping, MnCO3 for manganese doping and magnesium in the presence of magnesium format or acetate salts or in the form of Al - Mg alloy for Mg doping in the range from 1-30 wt.% of alumina in an autoclave at temperatures in the range of 300-550°C, pressure in the range of 15-120 MPa, cooling an autoclave to room temperature, separating the unreacted solid from the product powders by removing physically, washing and drying the said powders in air or in vacuum to obtain free flowing powders of boehmite,, a alumina or their mixtures; heating the said free flowing powders in the temperature range of 1250-1450°C for 2 to 4 hrs. for homogeneous distribution of dopants to obtain desired products, the said products are characterized by X-ray diffraction for phase analysis in case of Cr and Mn salt finished doped product is obtained whereas in case of Mg salts or Al - Mg alloy, finished doped product is magnesium spinal.
2 An improved process as claimed in claim 1, wherein the temperature is in the range of
300-350°C for boehmite, temperature is in the range of 450-550°C for a alumina and if
the temperature is in the range of 350-450°C for a mixture of boehmite and alumina.
3 An improved process as claimed in claims 1-2 wherein for Mg doping the % of
aluminum - Magnesium alloy used is 5 and 10%.
4. An improved process for the hydrothermal synthesis of boehmite, a-alumina or their mixtures in the doped form substantially as herein described with reference to the examples.

Documents:

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90-del-2003-claims.pdf

90-del-2003-correspondence-others.pdf

90-del-2003-correspondence-po.pdf

90-del-2003-description (complete).pdf

90-del-2003-form-1.pdf

90-del-2003-form-19.pdf

90-del-2003-form-2.pdf

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Patent Number

217563

Indian Patent Application Number

90/DEL/2003

PG Journal Number

37/2008

Publication Date

12-Sep-2008

Grant Date

27-Mar-2008

Date of Filing

04-Feb-2003

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	THANDALI SRINIVASAN KANNAN	NAL, BANGLORE,INDIA.
2	PRASANTA KUMAR PANDA	NAL, BANGLORE
3	VELLORE ABDUL JABEL	NAL, BANGLORE

PCT International Classification Number

A04F 7/02

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA