Title of Invention

A METHOD OF INERTISING THE IMPURITIES IN PHOSPHOGYPSUM

Abstract The invention pertains to a method of inertising free soluble impurities of phosphates and / or fluoride ions, in phosphogypsum, to make it a suitable substitute for gypsum in commercial and industrial applications. The Phosphogypsum is pre-treated individually or treated along with standard constituents during the process of manufacture, with alkyl, alkenyl and/or alkanol derivatives of ammonia, either individually or in combination with one another, to form stable intermediary phosphates and / or fluoride salts of alkyl, alkenyl and/or alkanol derivatives of ammonia
Full Text FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION: "A method of inertising the impurities in
Phosphogypsum. "
2. APPLICANT(S):
NAME: ACC Limited
NATIONALITY: Indian Company registered under The Companies
Act, 1913
ADDRESS: Cement House, 121 Maharshi Karve Road,
Mumbai 400 020, Maharashtra, India.
PREAMBLE TO THE DESCRIPTION: The following specification particularly describes the invention and the manner in which it is to be performed
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Field of invention:
The invention relates to a method of inertising soluble impurities of phosphates and fluorides and / or fluoride ions, in phosphogypsum, to make it a suitable substitute for gypsum in commercial and industrial applications, by pre-treatment or in-process treatment of the phosphogypsum
BACKGROUND OF INVENTION: Gypsum, which is essentially CaS04.2H20, is an important and essential component of cement and constitutes 4-5 % of cement. It is added to regulate the extreme setting reaction of cement, which occur in the presence of water. The scarce availability together with the cost of mineral gypsum, has made it necessary to seek and use the less expensive alternatives such as phosphogypsum. This is particularly important in the cement industry, where margins are low, cost of materials is very crucial. Phosphogypsum is a cheap byproduct from the phosphoric acid industry. It's cost is about half to one third of the cost of gypsum Phosphogypsum is essentially CaSO4 2H2O.lt is unsuitable for the manufacture of cement and several other commercial and industrial applications because of the presence of soluble impurities like Phosphates and Fluorides and other organic matter which may be present. These impurities when it exceeds minimal levels, severely restrict the use of phosphogypsum in commercial and industrial application especially in the manufacture of cement, since it retards the setting of cement when exposed to water, through the body of the cement. The soluble Phosphates reacts with calcium ions in the cement clinker and form insoluble calcium phosphate, which deposits on the surface of the hydrating grains of cement, thus hindering the penetration of water through the body of the cement grain and its reaction with water.
Similarly the Fluorides present in phosphogypsum precipitate as calcium fluoride in the lime rich region of the hydrating cement grains, preventing the setting of cement in the presence of water.
Several methods have been used to reduce the impurities in phosphogypsum and to make it equivalent to marine or mineral gypsum. The most popular process is by washing and leaching. Washing and leaching processes are cumbersome, since it involves handling of the slurry, and washing and drying the filtered cake. Another known method of treating phosphogypsum is with milk of lime [Ca(QH)2], which
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converts the soluble impurities into insoluble calcium phosphate and calcium fluorides.
In patent Application number 1335/MUM/2003, the applicants have described a process of inertisation of the impurities in Phophogypsum by Thermochemical processing route, wherein a homogenous mixture of Phosphogypsum and reactive mineral elements capable of forming insoluble phosphates and volatile fluorides are prepared on a wet /dry basis, in the ratio of 1:100 to 50:100 by weight. The mixture is pyroprocessed in a furnace at a temperature of 150°C to 800°C for a period of 5-10 seconds to 50-60 mins., depending upon the type of pyro-processing technique used, to form processed phosphogypsum (1). The Reactive mineral elements such as, aluminum, Manganese, Magnesium, Silica, Strontium, iron and barium were used. Reactive minerals such as alum, Aluminium Sulphates, Gibbisite, a-allumina, High Alumina Cements, Alumino-silicate glasses, Bauxite, and alumina bearing clays were preferred. However, this is an energy intensive process.
The present invention describes the use of chemicals namely alkyl, alkenyl and alkanol substituted derivatives of ammonia, including those occurring as industrial waste, to inertise the impurities in phosphogypsum and to make it a suitable substitute of gypsum.
Technical grade Alkanol substituted derivatives of ammonia have been used in percentages ranging from 0.02% to 0.04% of 95 - 98% purity, along with Gypsum in cement manufacture, in order to reduce energy consumption while attaining desired grain size of cement grains. The addition of higher percentage weight of these substituted derivatives of ammonia is not cost effective, since the energy benefit obtained does not offset the high cost of technical grade compounds. The invention describes for the first time the use of alkyl, alkenyl and alkanol substituted derivatives of ammonia including those occurring as industrial wastes, to treat phosphogypsum to make it suitable substitute for gypsum in many industrial and commercial applications especially cement manufacture.
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The use of treated phosphogypsum is of particular relevance in Cement Industry. Chemically treated Phosphogypsum, whether pretreated with the chemical additives or treated during the process of manufacture with these chemical additives during the Cement manufacture by intergrinding / interblending process, the performance of phosphogypsum in multigrade cement, is made equivalent or even better than with use of mineral and marine especially in terms of setting characteristics and compressive strength developments of the Cements in cement sand Mortars and Concrete.
SUMMARY:
In its main aspect, the invention relates to a method of inertising free soluble impurities of phosphates and / or fluorides ions, in phosphogypsum, to make it a suitable substitute for natural gypsums in commercial and industrial applications. The phosphogypsum is pre-treated individually or treated along with standard constituents for the industrial applications , with alkyl, alkenyl and alkanol substituted ammonia derivatives , either individually or in combination with one another to form stable intermediary phosphates and / or fluoride salts of alkyl, alkenyl and / or alkanol substituted derivatives of ammonia.
In another aspect of this invention the alkyl, alkenyl and alkanol substituted derivatives of ammonia are added in the proportion of 0.08% to 5% by weight of phosphogypsum. The molar weight of the alkyl, alkenyl and / or alkanol substituted derivatives of ammonia are one among C2H7NO, C4H11NO2, C6H15NO3, C2H8N2, C4H13N3, C6H18N4, C8H23N5, C6H15NO, C4nNO, C5H13N02, C3H9NO, C9H21NO3. In a more important aspect of the invention, industrial wastes containing the alkyl, alkenyl and alkanol substituted derivatives of ammonia is used.
In a further aspect of this invention, the industrial application for which treated phosphogypsum is to be used in manufacture of multigrade cement, which includes Ordinary Portland Cement, Portland Pozzolana Cement and Portland Slag Cement. The in - process treatment of phosphogypsum consists of addition of alkyl, alkenyl and alkanol substituted derivatives of ammonia while intergrinding / interblending
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phosphogypsum with standard constituents, during the Cement manufacture, to form the stable intermediary phosphates and fluoride salts of the alkyl, alkenyl and alkanol substituted derivatives of ammonia The standard constituents, for cement manufacture are among the group of clinker minerals and supplementary cementitious materials like slag, fly ash, limestone, metakaolin etc.
In the final aspect of this invention, the cement manufactured using phophogypsum treated by the process revealed in this invention has compressive strengths of 15 to 75 MPa at hydration ages of 1 to 28 days. Simultaneously the cement so manufactured also has an initial setting time of 70 to 150 minutes and a final setting time of 150 to 250 minutes.
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DESCRIPTION: The following is a brief description of working of this invention. In its main embodiment, the invention relates to a method of inertising the soluble impurities of phosphates and/ or fluorides ions in phosphogypsum. Phospho-gypsum which is a byproduct of the phosphoric acid industry, can be used as an inexpensive raw material in place of marine or mineral gypsum, in industry, especially in cement manufacture. The phosphate and fluorides impurities are inertised either by the pretreatment of phosphogypsum with chemical additives namely alkyl, alkenyl and alkanol used singularly or by taking a mixture of these substituted derivatives of ammonia before it is used in industrial applications, including Cement Manufacture or the phosphogypsum is inertised during the process of manufacture, in the interblending or intergrinding of cement and cementitious Materials. The afore mentioned chemical additives may be used individually or in combination with one another. The substituted derivatives of ammonia react with the phosphate ions in phosphogypsum to form a stable ionic phosphate salt. Similarly they react with the fluoride impurities in phosphogypsum to form stable ionic fluorides salt. Thus the soluble impurities of phosphogypsum, which form undesirable phosphates and fluorides of calcium on the hydrating grains in the industrial application are inertised. In another embodiment of this invention the alkyl, alkenyl and alkanol substituted derivatives of ammonia either individually or in combination are added in the proportion of 0.08% to 5% by weight of phosphogypsum. The percentage of the additive used depends on the relative purity of the phosphogypsum and that of the chemical additive. When the additives used are in the form of industrial wastes the proportion of the additives would depend on the concentration of these derivatives of ammonia in the wastes. The alkyl, alkenyl and / or alkanol substituted derivatives of ammonia used are all covered under the following molecular formula : C2H7NO, C4H11N02, C6H15N03, C2H8N2, C4H13N5 C6H15NO, C4H11NO, C5H13NO2, C4N11O, C5Hi3N02,C3H9NO, C9H21N03.
The alkyl, alkenyl and / or alkanol substituted derivatives of ammonia used may be among one or more substituted amines containing primary , secondary and tertiary amines and mixture there of and include Monoethanolamine (C2H7NO), Di-ethanolamine (C4HHNO2 ) , Tri-ethanolamine (C6H15NO3 ) ethylenediamine (C2HgN2), diethylene -tri amine (C4H13N3) , tri-ethylene terta - amine (C6HIgN4 ) ,
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tetra-ethylene penta-amine (C8H23N5 ),N,N-diethyl-ethanolamine(C6Hi5NO),N,N-dimethylethanolamine (C4H11NO), N-methyl di-ethanolamine [C5H13NO2], N-methylethanolamine [C3H9NO], tri - isopropyl amine (C9H21NO3) ..
Substituted Phosphoric acid alkyl, alkenyl/alkanol ammonium
derivatives of Ammonia hydrogen phosphate salt

The formation of these stable salts is of particular relevance in the cement industry. Unlike the water soluble phosphates and fluorides, these stable ionic substituted ammonium phosphate salts and the substituted ammonium fluoride salts, do not interfere with the cement hydration reactions at early stages of cement setting. The reaction of water soluble phosphates (i.e free phosphoric acid) and fluorides (i.e free hydrofluoric acid) in phosphogypsum and primary, secondary and tertiary alkyl, alkenyl and alkanol derivatives and their mixtures there of during hydration process is exemplified below by a typical example, The reaction produces an alkyl, alkenyl alkanol substituted ammonium salts of the acids viz: phosphoric acids and hydrofluoric acid.

Substituted Hydrofluoric acid alkyl, alkenyl/alkanol ammonium fluoride salt
derivatives of Ammonia
Wherein R is a Alkyl or Alkenyl or Alkanol or substituted derivatives of ammonia
These salts formed in the presence of water, further undergo reaction with calcium hydroxide released during the hydration process [2C3S +6H —► C3S2H3 +3Ca(OH)2 ] and forms insoluble calcium phosphate and calcium fluoride which does not take part in the hydration reaction and in turn does not affect the setting time of cement as shown below. The substituted alkyl, alkenyl alkanol substituted ammonium salts forming the corresponding hydroxide salt.
2(R3NH)+H2P04' +3Ca(OH)2 ► Ca3(P04)2 + 2(R3NH)+(OH) + 2H20
alkyl, .alkenyl/alkanol Calcium hydroxide Calcium phosphate Hydroxide salt
ammonium hydrogen
phosphate

alkyl, alkenyl/alkanol Calcium hydroxide Calcium fluoride Hydroxide salt ammonium fluoride
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The characteristics of cement depend on the setting time and the relative compressive strength. Chemically pretreated or in - process treated phosphogypsum, by the method of disclosed herein, significantly enhances compressive strength and reduces initial and final setting time.
The following examples gives the comparative values of setting time as well as compressive strengths of OPC, PPC, PSC with chemically treated phosphogypsum The Example 1,2,3 gives the comparative levels of soluble and insoluble phosphates and fluoride impurities in phosphogypsum and the chemically treated phosphogypsum of different sources with different levels of impurities with use of alkyl, alkenyl, alkanol substituted derivatives of ammonia The phosphogypsum from different sources at different levels of the fluoride and phosphate impurities, designated as Phosphogypsum- A, B, C.
While the subsequent Examples 4,5,6 illustrates the comparative properties of the Cements viz Ordinary Portland Cement (OPC) , Portland Pozzolana Cement (PPC) and Portland Slag Cement (PSC) produced with & without the chemically treated Phophogypsum.
EXAMPLE -1: Characteristics of Chemically treated phosphogypsum - A ( with
Raw material %by weight Initial content After Treatment
Total Water soluble Total Water soluble
p2o5 F p2o5 F P2O5 F P2Os F
Phospho Gypsum -A 95-99.95% 0.50 0.29 0.16 0.13 0.50 0.29 0.07 0.07
Alkyl,alkenyI,alkanol substituted ammonia 0.08-5.0%

EXAMPLE-2: Characteristics of Chemically treated phosphogypsum (with 0.8 - 1.3 % phosphate and fluoride impurities) -B
Raw material %by weight Initial content After Treatment
Total Water soluble Total Water soluble
P2Os F P2O5 F P2O5 F P2Os F
Phospho Gypsum -B 95-99.95% 0.81 0.24 0.24 0.13 0.81 0.24 0.08 0.08
Alkyl,aIkenyl,alkanol substituted ammonia 0.08-5.0%
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EXAMPLE-3: Characteristics of Chemically treated phosphogypsum ( with >1.3% phosphate and fluoride impurities) - C
Raw material %by weight Initial content After Treatment
Total Water soluble Total Water soluble
P2Os F P2Os F P2Os F P2O5 F
Phospbo Gypsum -C 95-99.95% 0.72 1.47 0.30 0.24 0.72 1.47 0.09 0.10
Alkyl,alkenyl,alkanol substituted ammonia 0.08 -5.0%

Example - 4 : Improvement in setting time and strength of OPC with use of Chemically Treated Phophogypsum
OPC With Phosphogypsum OPC With Chemically Treated Phosphogypsum
Setting Time (Mins.)
Initial 350 70-150
Final >420 160 - 240
Compressive Strength 1Day 15.5 17-20
3 Days 48.7 50-53
7 Days 59.0 58-61
28 days 69.3 72-74

Example - 5 : Improvement in setting time and strength of PPC with use of Chemically Treated Phophogypsum
PPC with Phosphogypsum PPC with Chemically Treated Phosphogypsum
Setting Time (Mins.)
Initial 340 1 70-170
Final >420 1 140-250
Compressive Strength (MPa)
1Day 11.8 12-15
3 Days 40.1 40-42
7 Days 51.4 51-53
28 days 64.3 63-65
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Example - 6 : Improvement in setting time and strength of PSC with use of Chemically Treated Phophogypsum
PSC with Phosphogypsum PSC with Chemically Treated Phosphosypsum
Setting Time (Mins.)
Initial 250 70 - 140
Final >340 180-250
Compressive Strength (MPa)
1Day 7.7 7 -9
3 Days 25.6 23-26
7 Days 40.9 39-42
28 days 56.1 53-57
Soluble phosphates and fluoride impurities in the treated phosphogypsum are at the level of
Example 7 Example 8 Example 9
OPC with PG-C OPCwith PG-C +0.08 - 5.0 %C8H23N+C5H13N02 PPC with PG-C PPCwith PG-C +0.08 - 5.0 %C4H10NO2+ PSC with PG-C PSCwith PG-C +0.08 - 5.0 %C3H9NO+C9Hi5N03
Setting Time (Minutes )
Initial 340 70-150 340 70-150 340 70-150
Final >420 150-250 >420 150-250 >420 150-250
Compressive strengths (MPa)
1Day 15.0 17-20 11.0 12-15 7.5 7-9
3 Days 47.0 48-51 39.0 38-41 25.0 24-26
7 Days 58.0 58-61 48.0 47-50 40.0 39-41
28 days 67.0 68-70 60.0 59-61 55.0 54-56
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The above examples illustrates the efficacy of the additive to substantially enhance the setting characteristics and compressive strengths of the different Cements manufactured with Phosphogypsum.
The setting of cement involves the reaction of clinker minerals with water to form a system of interlocking crystals, which lock the material together. The setting of cement is primarily due to the reaction of tri-calcium aluminate (Ca3A1O4), which is the most reactive of the clinker minerals present in cement.
The set regulating action of gypsum is primarily due to its reaction with tri-calcium aluminate. Calcium sulphate is soluble in water and aides in the setting process when it reacts with tri-calcium aluminate as given by the following reaction:

The stable intermediary ionic salts formed by the derivatives of ammonia temporarily
locks the soluble fluoride and phosphate ions, so that the initial setting reaction is
complete.
The ettringite is usually formed as a very fine grained crystal, which forms a coating
on the surface of tricalcium aluminate particles. These crystals are too small to bridge
the gaps between the particles of cement. The cement mix therefore remains plastic.
After the initial hydration reaction of cement, a dormant period occurs during which
the rate of hydration of cement is usually reduced. During this dormant period,
ettringite crystals continue to grow and eventually are large enough to impede the
mobility of cement particles. At this stage setting occurs. The ettringite crystal
formation is not impeded by the insoluble phosphates and fluorides of calcium which
are subsequently formed.
Thus treated phosphogypsum without the free impurities of phosphates and fluorides
is made a cost effective equivalent to mineral or marine gypsum, for use in industrial
application.
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WE CLAIM:
1. A method of inertising the free soluble impurities of phosphates and / or fluoride ions in phosphogypsum , to make it a suitable substitute for gypsum in industrial applications , by pre-treatment of phosphogypsum individually or in process treatment of phosphogypsum together with standard constituents for the industrial application , with alkyl, alkenyl and / or alkanol derivatives of ammonia , either individually or in combination with one another , to form stable intermediary phosphate and / or fluoride salts of the compounds of alkyl, alkenyl and / or alkanol derivatives of ammonia..
2. A method as claimed in claim 1, where in the alkyl, alkenyl and alkanol derivatives of ammonia are added in the proportion of 0.08% to 5% by weight of phosphogypsum.
3. A method as claimed in claim 2, where in the alkyl, alkenyl and/or alkanol derivatives of ammonia are among C2H7NO, C4H11NO2, C6H15NO3, C2H8N2, C4H13N3, C6Hi8N4, C8H23N5, C6H15NO, C4HnNO, C5H13NO2, C3H9NO, C9H21NO3.
4. A method as claimed in claim 3, where in industrial waste, containing alkyl, alkenyl and / or alkanol derivatives of ammonia is used.
5. A method as claimed in claim 3 and 4, where the industrial application for which phosphogypsum is to be used is manufacture of multigrade cement, including Ordinary Portland Cement, Portland Pozzolana Cement and Portland Slag Cement.
6. A method as claimed in claim 5, where the in process treatment of phosphogypsum consists of addition of the alkyl, alkenyl and / or alkanol derivatives of ammonia while intergrinding/interblending phosphogypsum with standard constituents during the process of cement manufacture , to form the stable intermediary phosphates and fluorides salts of alkyl, alkenyl and / or alkanol derivatives of ammonia
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7. A method as claimed in claim 6, where in the standard constituents are among the group of Cement, clinker and cementitious mineral constituents like fly ash, slag, Metakaolin, silica fume, calcined clays and volcanic ash.
8. A method as claimed in claim 7, where in the cement manufactured has compressive strengths of 15 to 75 MPa at hydration ages of 1 to 28 - days.
9. A method as claimed in claim 8, where in the cement manufactured has an initial setting time of 70 to 150 minutes ... and a final setting time of 150 to 250 minutes.
10. Phosphogypsum treated by the method described in claim 1 to 9.
Dated this 23rd day of August 2006 at Mumbai
For ACC limited
Usha Chandrashekhar Patent Attorney.
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ABSTRACT:
The invention pertains to a method of inertising free soluble impurities of phosphates and / or fluoride ions, in phosphogypsum, to make it a suitable substitute for gypsum in commercial and industrial applications. The Phosphogypsum is pre-treated individually or treated along with standard constituents during the process of manufacture , with alkyl, alkenyl and/or alkanol derivatives of ammonia , either individually or in combination with one another , to form stable intermediary phosphates and / or fluoride salts of alkyl, alkenyl and/or alkanol derivatives of ammonia
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Documents:

1342-MUM-2006-ABSTRACT(GRANTED)-(1-9-2011).pdf

1342-mum-2006-abstract.doc

1342-mum-2006-abstract.pdf

1342-MUM-2006-CANCELLED PAGES(12-7-2011).pdf

1342-MUM-2006-CLAIMS(AMENDED)- (12-7-2011).pdf

1342-MUM-2006-CLAIMS(AMENDED)-(15-4-2010).pdf

1342-MUM-2006-CLAIMS(CANCELLED)-(15-4-2010).pdf

1342-MUM-2006-CLAIMS(GRANTED)-(1-9-2011).pdf

1342-MUM-2006-CLAIMS(MARKED COPY)- (12-7-2011).pdf

1342-MUM-2006-CLAIMS(MARKED COPY)-(15-4-2010).pdf

1342-mum-2006-claims.doc

1342-mum-2006-claims.pdf

1342-mum-2006-correspondance-received.pdf

1342-MUM-2006-CORRESPONDENCE (12-7-2011).pdf

1342-MUM-2006-CORRESPONDENCE(17-3-2008).pdf

1342-MUM-2006-CORRESPONDENCE(22-10-2010).pdf

1342-MUM-2006-CORRESPONDENCE(4-6-2009).pdf

1342-MUM-2006-CORRESPONDENCE(7-2-2011).pdf

1342-MUM-2006-CORRESPONDENCE(IPO)-(5-9-2011).pdf

1342-mum-2006-description (complete).pdf

1342-MUM-2006-DESCRIPTION(GRANTED)-(1-9-2011).pdf

1342-MUM-2006-FORM 18(17-3-2008).pdf

1342-MUM-2006-FORM 18(COPY)-(15-4-2010).pdf

1342-MUM-2006-FORM 2(GRANTED)-(1-9-2011).pdf

1342-MUM-2006-FORM 2(TITLE PAGE)-(25-8-2006).pdf

1342-MUM-2006-FORM 2(TITLE PAGE)-(GRANTED)-(1-9-2011).pdf

1342-MUM-2006-FORM 3(4-6-2009).pdf

1342-MUM-2006-FORM 3(4-9-2006).pdf

1342-MUM-2006-FORM 5(4-9-2006).pdf

1342-mum-2006-form-1.pdf

1342-mum-2006-form-2.doc

1342-mum-2006-form-2.pdf

1342-mum-2006-form-26.pdf

1342-MUM-2006-REPLY TO EXAMINATION REPORT(15-4-2010).pdf


Patent Number 248860
Indian Patent Application Number 1342/MUM/2006
PG Journal Number 36/2011
Publication Date 09-Sep-2011
Grant Date 01-Sep-2011
Date of Filing 25-Aug-2006
Name of Patentee ASSOCIATED CEMENT COMPANY LIMITED
Applicant Address CEMENT HOUSE, 121 MAHARSHI KARVE ROAD, MUMBAI 400 020,
Inventors:
# Inventor's Name Inventor's Address
1 SHREESH ANANT KHADILKAR RESEARCH & CONSULTANCY DIRECTORATE THE ACC LIMITED CRS COMPLEX, LAL BAHADUR SHASTRI MARG, THANE - 400 604,
2 MANISH VASANT KARANDIKAR Research & Consultancy Directorate The ACC Limited CRS Complex, Lal Bahadur Shastri Marg, Thane-400 604,Maharashtra,India
3 ANIKODE PADMANABHAN RAMALINGAM Research & Consultancy Directorate The ACC Limited CRS Complex, Lal Bahadur Shastri Marg, Thane-400 604,Maharashtra,India
4 PRADIP GOPAL LELE Research & Consultancy Directorate The ACC Limited CRS Complex, Lal Bahadur Shastri Marg, Thane-400 604,Maharashtra,India
5 RINA SURESH VAITY Research & Consultancy Directorate The ACC Limited CRS Complex, Lal Bahadur Shastri Marg, Thane-400 604,Maharashtra,India
6 ABHAY KANT PATHAK Research & Consultancy Directorate The ACC Limited CRS Complex, Lal Bahadur Shastri Marg, Thane-400 604,Maharashtra,India
PCT International Classification Number C04B22/16,C04B9/04
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA