FORM2
THE PATENTS ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
"A WATER RESISTANT PHOSPHOGYPSUM COMPOSITION"
2. APPLICANTS
NAME :SARODE DILIP DHONDU
NATIONALITY : INDIAN
ADDRESS : DEPARTMENT OF GENERAL ENGINEERING,
INSTITUTE OF CHEMICAL TECHNOLOGY, NATHALAL PAREKH MARG, MATUNGA (EAST), MUMBAI 400 019, INDIA.
NAME : NEMADE PARAG RAMESH
NATIONALITY : INDIAN
ADDRESS : DEPARTMENT OF CHEMICAL ENGINEERING
AND DEPARTMENT OF OILS,
OLEOCHEMICALS, AND SURFACTANTS
TECHNOLOGY,
INSTITUTE OF CHEMICAL TECHNOLOGY, NATHALAL PAREKH MARG, MATUNGA (EAST), MUMBAI 400 019, INDIA.
The following specification particularly describes the invention and manner in which it is to be performed.

FIELD OF THE INVENTION
The present invention relates to phosphogypsum based composition having high
resistance capacity for ingress of water or humidity and method for production thereof. Phosphogypsum based composition as disclosed in present invention can be used in production of plaster, plaster boards, gypsum fiber boards, and gypsum blocks. Tn present invention, phosphogypsum based composition utilizes phosphogypsum generated from the phosphoric acid plants in fertilizer industries. Thus by utilizing by-product generated in Fertilizer industries, effective waste management of phosphogypsum can be carried out.
BACKGROUND OF INVENTION
At present, in production of plaster, plaster boards, gypsum fiber boards, gypsum
blocks and similar construction field utilizes cement and river sand. Therefore, the dependence on cement and river sand for constructional and building purposes is very high, resulting in huge demand. This has also necessitated increased production of cement and mining of river sand causing great environmental hazards to the fluvial ecology, besides the fact that traders hold consumers and public to ransom by demanding arbitrary prices.
Gypsum is one of such alternative material which offers various advantages for its use as a building material. Gypsum is a common ingredient in many consumer products which includes drywall, chalk, alabaster, wall plaster, etc. It is chemically inert, cost-effective and is readily available. The another form of Gypsum is phosphogypsum, which is obtained as a byproduct in the preparation

of phosphoric acid by contacting sulphuric acid with rock phosphate in fertilizer
industries. Gypsum is generated in large quantities and presents a disposal
problem.
It is, therefore, of great interest to convert the waste gypsum into a value-added
saleable consumer product, both commercially and ecologically. Gypsum plaster
products are already commercially available and widely used for interior walls;
however, they are commonly made from mineral gypsum.
Phosphogypsum generated from phosphoric acid plants is presently stacked and some quantity of the same is sold to the industries for beneficial use especially as a raw material in cement manufacturing as substitute for mineral gypsum as well as for alkali soil amendment or re-conditioning. The handling of phosphogypsum through trucks or railways involves loading, unloading and temporary storage at yards/depots is likely to cause environmental impacts, especially during rainy season. In order to have minimal impacts on environment, there is a need for eco-friendly green technologies and product thereof evolved out of safe handling, utilization and disposal of phosphogypsum. In view of the above, the over all aspects of phosphogypsum handling storage and disposal including its utilization need to be addressed.
Phosphogypsum is generated from filtration process in phosphoric acid plants where insoluble gypsum (and other material) are separated from the product i.e. phosphoric acid as efficiently as possible. The quality & quantum of

phosphogypsum generation depends upon the quality of the phosphate rock, process route used to produce phosphoric acid, calcium sulphate generated either as di-hydrate (CaSO4.2H20) or as hemi-hydrate (CaSO4.l/2 H2O) form. Phosphogypsum generation in the Country is about 11 Million Tonnes per annum (based on the assumption that 5 Tonnes of phosphogypsum generated per ton of phosphoric acid production).
On other hand, India is the second largest cement producer in the world. With increasing population and urbanization there is an increased demand for low budget housing and shelter, which indeed has led to increase in demand for the construction materials. This excess demand is causing scarcity of cement and other construction materials such as sand leading to increasing construction costs. Moreover, optimization in the use of cement is beneficial to the environment as manufacturing of cement involves liberation of huge amount of CO2 as 0.93 kg of CO2 is released per kg of cement.
US patent no. US 4151000, disclosing an anhydrite binder and to the method of making the same from the gypsum by-product (phosphogypsum) resulting from the production of phosphoric acid by the wet method, said binder comprising particulate anhydrous CaS04 with an of at least 93% of insoluble CaS04.
The inventors have developed the Phosphogypsum based composition having high resistance capacity for water or humidity and Phosphogypsum based composition of invention can be used in production of plaster, plaster boards, gypsum fiber

boards, and gypsum blocks having high water resistance capacity, to protect the construction and internal walls from rain water. The composition of disclosed invention consumes large quantities of phosphogypsum which will help in abating pollution and disposal problems associated with phosphogypsum.
OBJECTIVE OF INVENTION
• The main objective of the present inventionis to disclose Phosphogypsum based composition having high resistance capacity for water or humidity.
• Phosphogypsum based composition of invention can be used in production of plaster, plaster boards, gypsum fiber boards, and gypsum blocks having high water or humidity resistance capacity.
• Another objective of the invention is to develop water resistant exterior wall plaster.
• Another objective of the present invention is to develop an exterior wall plaster which is prepared from fertilizer by-product.
• Another objective of the present invention is to develop an exterior wall plaster which consumes large quantities of industrial by-product i.e phosphogypsum and help in abating pollution and disposal problems associated with phosphogypsum.
• One more objective of present invention is to develop cost saving and value added product which involve ecofriendly methods of manufacture of gypsum plaster.

• It is another objective, of the invention to prevent misuse of natural resources viz., river sand and address the problem of scarcity of river sand by providing viable substitute for cement plaster manufactured from river sand for sustainable development
SUMMARY OF INVENTION
The present invention is relates to a development of phosphogypsum based composition with high resistance capacity for water or humidity. The said composition has application in production/ manufacture of plaster, plaster boards, gypsum fiber boards, and gypsum blocks. More particularly, the present invention provides a phosphogypsum based external plaster composition comprising of phosphogypsum 90 to 95 weight percent, with 5 to 80 % of binder, 0 to 10.0 % of retarder, 0 to 10.0 % hydrophobicizer, 0 to 10.0 % plasticizer can be used as such as plaster composition. The said phosphogypsum is in the form of hemihydrates form with particle size below 150 microns and free moisture content is below 1 %.
STATEMENT OF INVENTION
The present invention relates to phosphogypsum based composition having high resistance capacity for water or humidity comprising of 90 to 95 weight percent of phosphogypsum and 5 to 80 weight percent of binders, wherein said phosphogypsum is in the form of hemihydrates form with particle size below 150 microns and free moisture content is below 1 %. The 70% particles of phosphogypsum is below 60 micron and 30 % articles are above 60 micron.

The said composition further comprises of retarder, hydrophobisizer, plastisizer and mixture thereof, wherein concentration of retarder is in the range of 0 to 10 weight percent, concentration of hydrophobisizer is in the range of 0 to 10 weight percent and concentration of plastisizer is in the range of 0 to 10 weight percent of phosphogypsum.
The binder is selected from group of Ordinary Portland Cement, Lime and
mixture thereof.
The retarder is selected from group of Borax, Citric acid,
Ethylenediaminetetraacetic acid, Disodium salt of ethylenediaminetetraacetic acid,
Diethylenetriaminepentaacetic acid, Disodium salt of ethylenetriaminepentaacetic
acid and mixture thereof.
The hydrophobisizer is selected from Methyl cellulose, Carboxy methyl cellulose,
Hydroxyethyl methyl cellulose, Hydroxyl propyl methyl cellulose, Calcium salt of
stearic acid and Magnesium salt of stearic acid and mixture thereof.
The plastisizer is selected from group of Naphthalene sulfonate formaldehyde,
Lignosulfonate, Poly-carboxylate ether and Polyacrylates and mixture thereof.
A method of manufacture of said phosphogypsum based composition comprising steps of;
a) Mixing phosphogypsum thoroughly with 5 to 80 %of binder, 0 to 10.0 %
of retarder, 0 to 10.0 % hydrophobicizer, 0 to 10.0 % plasticizer,
b) Adding sufficient amount of water for adjusting the consistency of the
mixture.

DESCRIPTION OF INVENTION
While making and using of the various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.
To facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as "a", "an" and "the" are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims.
In present invention, phosphogypsum based composition having high resistance capacity for water or humidity has been developed. Phosphogypsum based composition can be used in production/ manufacture of plaster, plaster boards, gypsum fiber boards, and gypsum blocks having resistance capacity for water or humidity.

The present invention is development of phosphogypsum based composition with high resistance capacity for water or humidity application, wherein phosphogypsum is obtained as a byproduct in the preparation of phosphoric acid by contacting sulphuric acid with rock phosphate in fertilizer industries. The production of this Phosphogypsum based composition will consume large quantities of phosphogypsum and help in abating pollution and disposal problems associated therewith.
Phosphogypsum based composition comprising of phosphogypsum, with binder, retarder, hydrophobicizer, and plasticizer can be used in production/ manufacture of plaster, plaster boards, gypsum fiber boards, and gypsum blocks having resistance capacity for water or humidity.
The additives and supplementary components can be added as per requirement of end use as in production/ manufacture of plaster, plaster boards, gypsum fiber boards, and gypsum blocks.
Gypsum plaster currently used for interior walls although is aesthetically pleasing, but it suffers from high water permeability. If this plaster, in its current form, is applied externally over brick, the resulting wall will be susceptible to water seepage - especially during the monsoons.
The present invention relates to an innovative and economical composition for application on exterior walls of the construction buildings.

One of the embodiments of the present invention is that, phosphogypsum based composition can be used as plaster composition which incorporates use of fertilizer by-product, Gypsum, which will result into a very high water resisting plaster composition. Performance of gypsum has proved satisfactory as a plaster for interior work, but is inadequate for exterior application, as it is susceptible to moisture transmission and becomes soft when exposed to water. The vast majority of the effort is geared towards development of better gypsum boards and very little attention has been paid towards developing a more water resistant gypsum plaster mix for external plaster applications.
So in accordance to present invention, it provides the phosphogypsum based external plaster composition with high resistance capacity for water or humidity.
In accordance to one of the important embodiment, the present invention provides the phosphogypsum based external plaster composition comprising of phosphogypsum based composition comprising of phosphogypsum 90 to 95 weight percent, with 5 to 80 % of binder, 0 to 10.0 % of retarder, 0 to 10.0 % hydrophobicizer, 0 to 10.0 % plasticizer can be used as such as plaster composition.
The said phosphogypsum is in the form of hemihydrates form with particle size below 150 microns and free moisture content is below 1 %. The 70% particles of hemihydrates phosphogypsum is below 60 micron and 30 % articles are above 60 micron.

Accordingly second embodiment of present invention, it provides the plaster composition consisting water resistant wall plaster for exterior application, includes conserving nature entirely.
Another embodiment of invention consists of a manufacture of wall plaster for exterior purpose, and method thereof from phosphogypsum obtained during the course of manufacture of phosphoric acid by the wet process, by contacting rock phosphate by sulphuric acid, and subsequent filtration and washing, is discharged from the filter. This gypsum may contain some impurities like water soluble phosphate, fluorides, silica, high acidity. The phosphogypsum aforesaid is calcined at aboutlOO to 180 °C to get hemihydrate gypsum from dihydrate form. This phosphogypsum thoroughly mixing with 5 to 80 % of binder, 0 to 10.0 % of retarder, 0 to 10.0 % hydrophobicizer, 0 to 10.0 % plasticizer, and sufficient amount of water adjusting the consistency of the mix, applying the mix on wet brick wall and allowing to set in atmospheric condition to obtain the finished wall plaster which is more water resistant than the internal gypsum wall plaster.
The additives of the present invention may be added to mixtures of phosphogypsum and water without adversely affecting properties of the mixture which are necessary to the manufacture of gypsum wall plaster. Such properties include compressive strength, fluidity, knife set time, hydrophobicity, and shrinkage of plaster. The binders include Ordinary Portland Cement, or lime; hydrophobicizers include Methyl cellulose, Carboxy methyl cellulose,

Hydroxyethyl methyl cellulose, Hydroxy! propyl methyl cellulose, Calcium salt of stearic acid, Magnesium salt of stearic acid; retarders include Borax, Citric acid, Ethylenediaminetetraacetic acid, Disodium salt of ethylenediaminetetraaceticacid, Diethylenetriaminepentaacetic acid, Disodium salt of ethylenetriaminepentaacetic acid; and plasticizer includes Naphthalene sulfonate formaldehyde, Lignosulfonate, Poly-carboxylate ether, and Polyacrylates.
According to the method proposed herein, the phosphogypsum obtained from the phosphoric acid plant can be utilized directly for the manufacture of gypsum plaster without any intermediate processing or purification operation and the resultant plaster do not shrink on drying. This apart, the resultant gypsum plaster has water absorbing characteristics and compressive strength comparable with the conventional cement plaster.

Table No. 1: List of chemical additives for phosphogypsum formulation
The present invention is further described with the help of the following example which are given by way of illustration and therefore should not be construed to limit the scope of the invention in any manner.
Content Additive name Generic name
Binder Ordinary Portland Cement Lime
Retarder Borax Chelating
Citric acid agents,
Ethylenediaminetetraacetic acid electrolytes
Disodium salt of and salts of
ethylenediaminetetraacetic acid Diethylenetriaminepentaacetic acid Disodium salt of ethylenetriaminepentaacetic acid acids
Hydrophobicizer Methyl cellulose Hydroxyalkyl
Carboxy methyl cellulose derivatives of
Hydroxyethyl methyl cellulose Hydroxy 1 propyl methyl cellulose Calcium salt of stearic acid Magnesium salt of stearic acid cellulose
Plasticizer Naphthalene sulfonate formaldehyde Viscosity
Lignosulfonate Poly-carboxylate ether Polyacrylates modifiers

EXAMPLES:
Example 1: Examples for composition:The phosphogypsum thoroughly mixing with about 15 % of binder, 0.5 % of retarder, 1.0% hydrophobicizer, 0.1 % plasticizer and 55 % of water adjusting the consistency of the mixture.
Example 2: Example for method for production of Composition: The
phosphogypsum thoroughly mixing with about 15 % of binder, 0.5 % of retarder, 1.0 % hydrophobicizer, 0.1 % plasticizer and 55 % of water adjusting the consistency of the mixture, applying the mixture on wet brick wall and allowing to set in atmospheric condition to obtain the finished wall plaster which is more water resistant than the internal gypsum wall plaster.
The below tables shows the several compositions for water resistant phosphogypsum plasters prepared as explained in example 1 and 2 with the test results.

Ingredients ExampI es
Blank 1 2 3 4 5 6
Phosphogypsum (g) 100 100 100 100 100 100 100
Water (g) 55 55 55 55 55 55 55
Cement (g) - 15 15 15 10 20 10
Diethylenetriaminepentaacetic acid - 0.5 0.5 0.5 0.5 0.5 0.5
(g)
Hydroxyethyl methyl cellulose (g) - 1.0 0.5 1.0 0.75 0.75 0.75
Poly-carboxylate ether (g) - 0.1 0.5 0.5 0.1 0.1 0.5
Table No. 2: Formulations

Test performed Blank 1 2 3 4 5 6
3 days dry compressive strength (N/mm2) 14.21 5.5 6.01 5.4 6.51 6.08 5.95
Setting time (min) 1.20 46 80.5 63 50.5 59.5 61.5
Water absorption (%) 22.62 20.78 21 30.29 19.39 25.69 19.62
Table No. 3: Test results for Formulations mentioned in table no. 2.

Ingredients Examples
Blank 7 8 9 10 11 12
Phosphogypsum (g) 100 100 100 100 100 100 100
Water (g) 65 65 65 65 65 65 65
Cement (g) - 15 15 15 15 15 15
Diethylenetriaminepentaacetic - 0.75 0.25 0.75 0.5 0.5 0.5
acid (g)
Hydroxyethy] methyl cellulose (g) - 0.75 0.75 0.75 0.75 0.75 0.75
Poly-carboxylate ether (g) - 0.1 0.5 0.5 0.3 0.3 0.3
Table No. 4: Formulations

Test performed Blank 1 2 3 4 5 6
3 days dry compressive strength (N/mm2) 9.97 5.53 4.75 4.55 4.66 4.66 4.6
Setting time (min) 1.13 177 137 179 139.5 147 144
Water absorption (%) 30.9 28.11 27.17 24.83 19.7 17.57 21.4
Table No. 5: Test results for Formulations mentioned in table no. 4.

Material Mean particle size (jim)
Phosphogypsum 12.50
Sundried gypsum 44.16
Gypsum plaster 19.45
Table No. 6: Particle size.

Ingredients Examples
13 14 15 16 17 18 19 20
Phosphogypsum (g) 80 80 100 100 100 100 100 100
Water (g) 65 65 65 65 65 65 65 65
Cement (g) 20 - - - - - -
Lime (g) - 20 - - - - -
Diethylenetriaminepentaacetic acid - - 0.5 - - - -
(g)
Borax (g) - - - 0.5 - - -
Citric acid (g) - - - - 0.5 - -
Ethylenediaminetetraacetic acid (g) - - - - - ■ 0.5 -
Disodium salt of - . - - . - 0.5 -
ethylenediarninetetraacetic acid (g)
Disodium salt of - - - - - - 0.5
ethylenetriaminepentaacetic acid (g)
Table No. 7: Formulations

Ingredients Examples
21 22 23 24 25 26 27 28 29 30
Phosphogypsum (g) 100 100 100 100 100 100 100 100 100 100
Water (g) 65 65 65 65 65 65 65 65 65 65
Hydroxyethyl methyl 1
cellulose (g)
Hydroxyl propyl - 1 - - - - - - -
methyl cellulose (g)
Carboxy methyl - - 1 - - - - - -
cellulose (g)
Methyl cellulose (g) - - - 1
Calcium salt of stearic - - - - 1 - - - -
acid (g)
Magnesium salt of - - - - 1 - - - -
stearic acid (g)
Poly-carboxylate ether - - - - - 0.2 - - -
(g)
Naphthalene sulfonate - - - - - - 0.2 - -
formaldehyde (g)
Lignosulfonate (g) - - - - - - - 0.2 -
Polyacrylates (g) 0.2
Table No. 8: Formulations

Ingredients
Examples

31 31 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49
Phosphogypsu m(g) 100 100 50 49 90 80 70 60 50 90 80 70 60 50 90 80 70 60 50
Waterg) 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65 65
Lime (g) - - - - 10 20 30 40 50 - - - - - - - - - -
Cement (g) - - 50 50 - - - - - 10 20 30 40 50 - - - - -
Fly ash (g) - - - - - - - - - - - - - 10 20 30 40 50
Hydroxyl propyl methyl cellulose (g) 1 1
Setting time (min) 1.13 1.30 4.55 4.8 1.30 1.85 2.95 4.18 5.70 1.7 2.1 2.5 2.9 3.3 1.3 1.48 2.13 2.30 2.55
3 days wet compressive strength (N/mm2) 3.7 4.08 3.68 2.56 2.32 1.73 0.92 3.5 4.4 4.5 4.7 5.2 3.06 1.95 1.42 1.04 0.67
3 days dry compressive strength (N/mm2) 9.97 7.71 i 11.2 10.4 9.6 8.7 8.4
Water absorption (%) 30,9 0.59 24.86 4.28 - - - - - - - - - - - - - - -
ime taken to absorb 100 uL water (sec.) 21.2 33.99 39.9 30.6
Tab e No. 9: Formulations and test results

Phosphogypsum
Wall Water 3 days Settin % Water Time
(g) plaster (g) dry g time absorption taken to
(g) compres sive
strength (N/mm2) (min) absorb 100 μL water
(sec.)
100 - 55 14.21 1.20 22.62 -
100 65 9.92 1.33 30.9 21.2
- 100 55 5.11 15.23 33.24 -
- 100 65 4.02 19.67 39.62 7.03
Table No. 10: Comparative studies

CLAIMS
We claim,
1) A phosphogypsum based composition having high resistance capacity for water or humidity comprising of phosphogypsum and binders, wherein said phosphogypsum is in the form of hemihydrates form with particle size below 150 microns and free moisture content is below 1 %.
2) The phosphogypsum based composition as claimed in claim 1,wherein phosphogypsum is in concentration range of 90 to 95 weight percent.
3) The phosphogypsum based composition as claimed in claim 1, wherein binder is in concentration range of 5 to 80 weight percent of phosphogypsum.
4) The phosphogypsum based composition as claimed in claim 1, wherein binder is selected from group of Ordinary Portland Cement, Lime and mixture thereof.
5) The phosphogypsum based composition as claimed in claim 1, wherein composition further comprises of retarder, hydrophobisizer ,plastisizer and mixture thereof.
6) The phosphogypsum based composition as claimed in claim 1 and 5, wherein concentration of retarder is in the range of 0 to 10 weight percent, concentration of

hydrophobisizer is in the range of 0 to 10 weight percent and concentration of plastisizer is in the range of 0 to 10 weight percent of phosphogypsum.
7) The phosphogypsum based composition as claimed in claim 5, wherein retarder is selected from group of Borax, Citric acid, Ethylenediaminetetraacetic acid, Disodium salt of ethylenediaminetetraacetic acid, Diethylenetriaminepentaacetic acid, Disodium salt of ethylenetriaminepentaacetic acid and mixture thereof.
8) The phosphogypsum based composition as claimed in claim 5, wherein hydrophobisizer is selected from Methyl cellulose, Carboxy methyl cellulose, Hydroxyethyl methyl cellulose, Hydroxyl propyl methyl cellulose, Calcium salt of stearic acid and Magnesium salt of stearic acid and mixture thereof.
9) The phosphogypsum based composition as claimed in claim 5, wherein plastisizer is selected from group of Naphthalene sulfonate formaldehyde, Lignosulfonate, Poly-carboxylate ether and Polyacrylates and mixture thereof.
10) The phosphogypsum based composition as claimed in claim 1 and 5, wherein the particle size of 70% particles are below 60 micron and 30 % articles are above 60 micron.

11) A method of manufacture of phosphogypsum based composition of claims 1 to 10 comprising steps of;
c) Mixing phosphogypsum thoroughly with 5 to 80 %of binder, 0 to 10.0 %
of retarder, 0 to 10.0 % hydrophobicizer, 0 to 10.0 % plasticizer,
d) Adding sufficient amount of water for adjusting the consistency of the
mixture.