Title of Invention

A NOVEL HIGH STRENGTH ANHYDRITE PLASTER COMPOSITION FOR MAKING FLOOR TILES

Abstract

The present invention is directed towards a novel high strength anhydrite plaster composition consisting of waste by-product phospho and fluorogypsum and flooring tiles made therefrom. The production of these tiles will consume large quantities of phospho and fluorogypsum and may help in abating pollution and disposal problems associated therewith. Further, the anhydrite tiles are more durable than the gypsum tiles made from hemihydrite plaster.

Full Text

The present invention relates to a novel high strength anhydrite plaster composition for making floor tiles. The present invention particularly relates to a novel high strength anhydrite plaster composition consisting waste by-product phospho and fluorogypsum and flooring tiles made therefrom. The composition can be used for casting flooring tiles based on waste by-product materials such as phosphogypsum anhydrite or fluorogypsum, pigments, polymers, glass fibre, fly ash or red mud. The production of these tiles will consume large quantities of phosphor and fluorogypsum and may help in abating pollution and disposal problems generated by them. Flooring tiles are essential part of architecture since the dawn of civilization. Flooring tiles are used in large numbers in domestic and in industrial buildings in different colours, styles, sizes, textures and configurations. Tiles are laid over a strong base of concrete or wood forming wearing and decorative surfaces. Flooring tiles of various thicknesses with variable strength properties are produced. Tiles provide ecstasy, life and colour to official and residential buildings including showrooms and involves meagre maintenance cost to the reception rooms, lobbies and heavy duty places. Variety of materials comprising natural and synthetic are used for moulding flooring tiles. Choice of tiles depends on the usage to which the floor will be subjected. The other factors which govern the use of flooring tiles are their sound absorption, colour, finish, chemical and abrasion resistance and maintenance in addition to visual and asthetic values. Materials like plastic, rubber, cork, asphalt and vinyl and wood veneer form thin floor coverings and tiles. Refeience may fo made to C.Hornbostal and W.J.Horning, " Material and Methods for Contemporary Construction ", Prentice - Hall Inc. New Jersy ( USA ), 1975; H.J.Elderidge, "Properties of Building Materials, ", Medical and Technical Publishing Company Ltd., Lancaster ( U.K.) 1974; IS :809-1970, Rubber Flooring Materials for General Purpose; IS : 3461-1980. PVC Asbestos Floor Tiles; IS : 3462-1986, Unbacked Flexible PVC Flooring ; IS : 5389-1969, Code of Practice for Laying of Hardwood Paraquet and Wood Block Floors. The inorganic tiles are mostly cast from cement, either in plain, plain coloured or terrazzo tiles. Terrazzo tiles consist of marble or stone chippings embeded in the binder matrix generally coloured cementitious materials (IS : 1237-1980, Specification for Cement and Concrete Flooring Tiles ). Sometimes oxychloride cement and sand admixed with colouring agents are employed to mould flooring tiles as reported by Mohan Rai and M.P.Jaisingh, Advances in Building Materials and Construction, C.B.R.I., Roorkee, 1985, pp 80-84. These tiles are produced by pressing the mixture of cement and aggregate into moulds into two layers-backing layer and top layer. Inorganic tiles have also been produced by sintering ceramic materials such as clay and fly ash. Reference may be made to R.B.Hajela, J.M.Bhatnagar and R.G.Gupta , Clay Flooring and Terracing Tiles from Alluvial Soils, Indian Standard Institution Bulletin, vol.33, No.l, 1981, pp 12-71; J.M.Bhatnagar, R.K.Goyal, E.S.Hiralal and R.B.Hajela, Utilization of fly ash in the Manufacture of Clay Flooring / Terracing Tiles from Alluvial Soils, Proc. of National Workshop on Utilization of Fly ash , Roorkee, May 19-20, 1988, pp 55-58. Internationally, Italy held the number one spot in ceramic tile production producing 16.6 million square feet per day in 1989 according to a report prepared by E.de.Miguel and JJ.Dalmau of Valencia Polytechnic (Valencia ,Spain). The combination of Italian technology and design makes the Italian tiles a king throughout the world. U.S.A. is the largest consumer of Italian tiles (G.Geiger, Development in Tile Industry, Ceramic Bulletin, Vol.70, No. 12, 1991, pp. 1879-1885). The trend is towards tiles that duplicate marble, granite and other natural stones. Parquet flooring is another variety which is very popular in U.S.A. The use of vinyl tiles, vitrified porcelain tiles and luminous jevel - like tiles is well known in U.S.A. and other countries. In several countries terrazzo cement tiles are most common flooring material. In India terrazzo cement tiles are widely used in residential and commercial housing. These tiles are bulky in nature and thus pose handling and transportation problems. Large amount of valuable matrix is lost during casting of these tiles and grinding process. These tiles also require prolonged setting and curing period so heavy capital investments are held up. In India there is great demand of cost effective and long lasting flooring tiles. Majority of tiles are currently made with conventional raw materials which are expensive and scarcely available. In view of strain on the conventional materials, there is Products, Canadian Institute of Mining and Metallurgical Bulletin, Vol.65, Sept.1972, pp.41-51; Manjit Singh, Physico - Chemical Studies on Phosphogypsum for Use in Building Materials, Ph.D Thesis, University of Roorkee, Roorkee, India 1980. Whereas fluorogypsum is available as by-product of the hydrofluoric acid industry and collected as anhydrite. Several building materials namely, building boards, blocks, tiles, water resistant binders have been produced from phosphogypsum. Reference may be made to Manjit Singh, Utilization of Phosphogypsum for Use in Uuilding Materials, Building Research Note 9, CBRI Publication, Roorkee, 1989; K.Gustaw, J.Dziedzie and J.Pietron, Durability of Anhydrite Binder Activated by Portland Cement and Potassium Sulphate, Cement - Wapno - Gips, Vol.45, 1992, pp.158-161; Manjit Singh and Mridul Garg, Investigation of a Durable Gypsum Binder for Building Material, Construction and Building Materials, Vol.6, No.l, March 1992, pp. 52-55; Manjit Singh and Mridul Garg, Glass Fibre Reinforced Water Resistant Gypsum Based Composite, Cement and Concrete Composite, Vol.14, No.l, 1992, pp.23-32. The industrial waste may be gainfully utilized for the manufacture of flooring tiles. Little work has been reported in the literature about the production of flooring tiles from gypsum. The flooring tiles are generally produced by pressing or by vibration techniques. A composition has been developed for producing flooring tiles from waste by-product phospho and fluorogypsum in variable colours by activating moist phosphoanhydrite (produced at 900 - 1000°C) or fluorogypsum with different chemicals duly blended with pigments, polymer, glass fibre and materials like fly ash or red mud in their optimum quantities by vibration moulding. The flooring tiles conform to the requirements laid down in IS: 1237 - 1980, Specification for Cement Concrete Flooring Tiles. The quantity of polymer, pigments and glass fibre does not exceed 3.0% each. Further addition of red mud or fly ash industrial solid waste (up to!5 %) can be beneficial as they may eliminate the use of costly metallic oxide pigments in addition to accruing economy. The development of high strength anhydrite plaster from phosphogypsum and fluorogypsum wastes and its use in making flooring tiles are the novel features which are not possible with the medium strength hemihydrate plaster. The flooring tiles from the anhydrite plaster have been produced for the first time. The main object of the present invention is to provide a novel high strength anhydrite plaster composition consisting of waste by-product phospho and fluorogypsum which obviates the use of high purity natural gypsum which is costly as well as scarcely available in India. Another object is to provide flooring tiles made from the novel composition consisting of industrial waste material. Accordingly, the present invention provides a novel high strength anhydrite plaster composition for making floor tiles which comprises: (i) neutral gypsum anhydrite (450 to 500 m2/ kg) : 100 (ii) chemical activators : 2 to 3 wt.%; (iii) catalysed methacrylate polymer : 2 to 3 wt.%; (iv) metallic oxide pigment(s) : 2 to 3 wt.%; (v) fly ash, red mud or mixture thereof : 10 to 15 wt.%; (vi) chopped glass fibres : 1 to 2 wt.%; (vii) quartz sand ( In an embodiment of the present invention the neutral gypsum anhydrite used may be such as obtained from waste by-products phospho and fluorogypsum. In another embodiment of the present invention the phosphoanhydrite used may be obtained by calcining phosphogypsum at a temperature in the range of 900 to 1000°C for a period of 3 to 5 hours. In yet another embodiment of the present invention the phosphogypsum used may have impurities such as P2O5 in the range of 0.42 to 0.92 wt.%, F in the range of 0.44 to 0.86 wt.%, organic matter in the range of 0.11 to 0.65 wt.% and alkalies in the range of 0.27 to 0.46 wt.%. In still another embodiment of the present invention the flouroanhydrite used may be obtained by blending fluorogypsum with 0.5 to 1.0 wt.% hydrated lime to neutralize the free acidity in the gypsum. In another embodiment of the present invention the fluorogypsum used may have impurities such as F in the range of 1.0 to 2.0 wt.%. In yet another embodiment of the present invention, the phosphoanhydrite / fluoroanhydrite may be ground to a fineness of 450 to 500 m2/kg (Blaine) in a ball mill or a pulverizer. In still another embodiment of the present invention, a mixture of commercial grade chemical activators such as sodium sulphate (Na2SO4.10H2O) and ferrous sulphate (FeSO., .7H2 O) may be used. In another embodiment of the present invention, methyl methacrylate polymer may be duly catalysed with 0.1-0.3 % benzoyl peroxide. All these ingredients are mixed by wt. % of anhydrite. Accordingly the present invention provides floor tiles made from the anhydrite mix as prepared above by mixing with 20-25 wt.% water and casting tiles by known methods such as putting the mix thus prepared into brass moulds (size 300 mm x 300 mm x 20 mm) ensuring top surface is covered with the embeded coloured stone chips (2-3 mm), (not more than 10 % by the wt. of anhydrite) and then vibrating for 5-10 minutes to remove any trapped air / voids from the matrix followed by flushing top of the tiles to form smooth surface followed by curing and drying. The composition of theijztggent invention Js not a mere admixture but a synergistic mixture having properties which are distinct from the mere aggregated properties' of the individual ingredients. The process for making high strength anhydrite plaster from by-product phospho and fluorogypsum and its use in producing flooring tiles consists of converting phosphogypsum into anhydrite by heating phosphogypsum at elevated temperature (900 - 1000°C) whereby insoluble property of CaHPO4 is transformed into inert calcium pyrophosphate. The anhydrite after fine grinding is blended with chemical activators (2 to 3 % by mass of anhydrite) and small quantity of polymer, pigments including cut glass fibres. The anhydrite mixture thus prepared, is wetted with water to form paste suitable for moulding tiles (size 300 mm x 300 mm x 20 mm) by vibration. The tiles after curing in high relative humidity (>90%) are dried at 42 +, 2° C followed by cooling to ambient temperature. The flooring tiles have been found to comply with the requirements of relevant Indian standards. In making of these tiles, fluorogypsum, a by-product of hydrofluoric acid industry may be used as an alternative to calcined phosphogypsum. The use of fly ash or red mud wastes in making these tiles would be advantageous being filler as well as colouring agent. The phosphogypsum and fluorogypsum samples are analysed for their chemical constituents and subjected to DTA and XRD to find out the nature and quantity of impurities present in them. Phosphogypsum samples is then calcined at 900-1000" C for a period of 3-5 hours in an electric furnace to form anhydrite (ft- CaSO4) where by the impurity of P2O5 is transformed into inert and insoluble3- Ca2P2O7 (3- Calcium pyrophosphate). During heating, the impurities of F" and organic matter get volatilized. In case of fluorogypsum, the impurity of free acidity is neutralized with 0.5 tol.O wt.% calcium hydroxide (Ca(OH)2) and no further processing of material is required as fluorogypsum is produced as anhydrite. The phosphoanhydrite or fluorogypsum are then ground to a fine powder of fineness 450-500 mVkg (Blaine) and mixed with a mixture of chemical activators i.e. Na2SO4.10H20 (1.5 wt.%) + FeSO4.7H2O (0.5 wt.%) by the weight of anhydrite in a ball mill to form anhydrite plaster. The anhydrite plaster is then uniformally mixed with 2.0 to 3.0 % methyl methacrylate polymer duly catalysed with 0.1-0.3 % benzoyl peroxide, 2-3 % metallic oxide pigments, 10-15 % fly ash / red mud, 1.0 -1.5 % chopped glass fibres (E-type 12mm long) and 1-2 % fine quartz sand (passing 150 micron IS seive) at normal consistency to form uniform moist mix. The kneeded wet mass thus produced is then filled in the metallic moulds of size 300 mm x 300 mm x 20 mm already placed on the vibrating table. The moulds are vibrated for 5-10 minutes. During vibration, the coloured stone chips about 8-10 % by weight are embedded in the top surface of moist anhydrite mass and ensured that air is eliminated. The top surface of tiles is then flushed with a metallic straight to get a uniform smooth surface. The tiles are demoulded after 1.0-1.5 hours of their casting and then cured for a period of 28 days in a humidity chamber (over 90% relative humidity) at 27 +2°C followed by drying at 42 ± 2° C. The tiles are finally ground so that coloured stone chips are distinctly exposed and then polished with Mansion polish. In anhydrite, the Caf+ and SO4" ions are closly packed and a dense structure in produced which shows low reactivity towards water. To augment interaction of anhydrite with water, the chemical activators are required. These materials react with CaSO4 ions and form transient double salts which arises through process of reconstruction of displacement on a crystalloid scale. The colloidal particles of Na2SO4.10H2O and FeSO4.7H2O activators concentrate on the surface of cacium sulphate molecule and establish potential centers around which crystallization sets in when solution becomes supersaturated. The possible interaction of activators with the anhydrite to form gypsum may be summarised as follows: H2O H2O CaSO4(S) ^ Ca++ + SO4" > CaSO4.2H20(S) Na+, SO4", Fe"++ It has been confirmed by X-ray diffraction that the hydration of anhydrite with Na2SO4.10H2O + FeSO4.7H2O activators proceeds through formation of glauborite (NajSO,,), ferrinatrite (Na3Fe(SO4)3.3H2O) compounds along with gypsum matrix. During, hydration of anhydrite, uniformally stacked euhedral prismatic crystals along with needles having radiating habit are formed. Due to interlocking nature of these crystals, high strength is developed in the anhydrite. Further, the addition of the methyl methacrylate polymer to anhydrite gets polymerised through catalytical action of benzoyl peroxide as per following mechanism. On initiation (Formula Removed) Polymerized Acrylate Molecule Where M = Monomer, . = Free electron, Ar = C6H5 The polymerised product fills up voids and pores in the gypsum matrix during hydration process and thus improves density, strength and durability of the anhydrite towards water. The strength development in anhydrite takes place just like hydration of cement. It continuously increases with the increase in curing period and reaches maximum at 28 days. The mixing of fly ash or red mud with the anhydrite works not only as filler but add colour to the anhydrite matrix or tile. The addition of small quantity of glass fibre improves strength of the tiles. The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of the present invention. Example 1 The samples of phosphogypsum, fly ash and red mud were procured from M/S Rashtriya Chemicals and Fertilizers Ltd., M/S Tata Thermal Power Plant, Mumbai and M/S Bharat Aluminium Company Ltd., Korba, Madhya Pradesh respectively and chemically analysed in Table 1. Table 1 Chemical Composition of Phosphogypsum, Fly ash and Red mud (Table Removed)The phosphogypsum sample was calcined at 1000" C for 4.0 hours in a furnace, cooled to room temperature to form anhydrite and ground in a ball mill to a fineness of 450 m2/kg (Elaine). The residual impurities in the anhydrite were determined as per standard test procedures. The results are reported in Table 2. Table 2 Impurity Contents in Phosphoanhydrite(Table Removed) Data show there is no loss of phosphate on heating but fluorides volatilized to some extent whereas organic matter is totally eliminated on heating. The anhydrite thus produced is ground in a ball mill with a mixture of chemical activators i.e. Na2SO4.10H2O(1.5%) + FeSO4.7H2O(0.5%) by wt. The physical properties of phosphoanhydrite are reported in Table 3. Table 3 Physical Properties of Phosphoanhydrite (Table Removed) The results show that anhydrite develops quite high compressive strength than the minimum specified value of 17.0 MPa at 28 days. The other properties also comply with the requirements of ASTM and Indian Standards. The development of high strength is useful for making good quality products such as flooring tiles. The properties of flooring tiles (size 300 mm x 300 mm x 20 mm) moulded from the polymerised and activated phosphoanhydrite are listed in Table 4. Table 4 Properties of Phosphoanhydrite Tiles (Table Removed) Data show that phosphoanhydrite tiles complied with the requirements of flexural strength, water absorption and wear resistance as reported in IS : 1237 - 1980, Indian Standard Specification for Cement Concrete Flooring Tiles. The tiles produced using fly ash or red mud as filler / pigments have also complied with the standard requirements. These tiles are suitable for use in flooring for general purpose such as office buildings, schools, colleges, hospitals and residential buildings. Example 2 The sample of flourogypsum / flouroanhydrite was collected from M/S Navin Fluorine Industry, Gujarat and chemically analysed inTable 5. Table 5 Chemical Composition of Fluorogypsum (Table Removed) It can be seen that fluorogypsum contains main impurity of fluoride which is normally present as CaF2 which is more or less inert and the free acidity as denoted by low pH value. The acidity in fluorogypsum makes it hygroscopic and attack lining of the grinding media i.e. ball mill / pulverizers. Due to this problem, the material requires neutralization of the acidity with suitable dose of lime. Normally, 0.5 - 1.0 % (by wt. %) of lime is sufficient to offset the bad effect of the acidity. After mixing lime with the fluorogypsum (dried at 45° C), the material is ground in a ball mill to a fineness of 450 mVkg (Blaine) and blended with the chemical activators i.e. NajSCvlOHp (1.5%) + FeSO<.7h2o by weight> The physical properties of fluorogypsum in presence of chemical activators are depicted in Table 6. Table 6 Physical Properties of Fluoroanhydrite plaster (Table Removed) The results show that flooring tiles conformed to the properties laid down in IS : 1237-1980. The use of fluorogypsum is thus found suitable in making flooring tiles. From the two examples cited above it can be concluded that high strength anhydrite plaster can be produced by calcining phosphogypsum at elevated temperature (or fluorogypsum) followed by fine grinding and blending with suitable activators. During heating, the impurity of CaHPO4.2H2O is transformed into inert and inactive - Ca2P2O7 (pyrophosphate) and the organic matter and fluoride get volatilized. The properties of flooring tiles made from the activated and polymerized anhydrite plaster develop higher strength values and low water absorption than the specified values in IS : 1237-1980. The main advantages of the present invention are : 1. The composition is suitable for making high strength anhydrite plaster. 2. The phosphogypsum and fluorogypsum, used as raw material are industrial waste by products. 3. The production of anhydrite flooring tiles will consume sizeable quantities of phosphogypsum and fluorogypsum industrial solid wastes which will help in abatement of pollution and health hazards. 4. The anhydrite tije_s are more durable than the gypsum tiles made from hemihydrate plaster. We Claim: 1. A novel high strength anhydrite plaster composition for making floor tiles which comprises: 2/ [i] neutral gypsum anhydrite (450 to 500 m /kg) [ii] chemical activators [iii] catalyzed methacrylate [iv] metallic oxide pigment(s) [v] fly ash, red mud or mixture thereof [vi] chopped glass fibres [vii] quartz sand ( 100 2 to 3 wt% 2 to 3 wt% 2 to 3 wt% 10tol5wt% 1 to 2 wt% 1 to 2 wt%. 2. A novel composition as claimed in claim 1, wherein the neutral gypsum anhydrite used is selected from waste by-product phosphor and fluoro gypsum. 3. A novel composition as claimed in claim 1, wherein the neutral gypsum anhydrite is phosphoanhydrite obtained by calcining phosphogypsum at a temperature in the range of 900 to 1000°C for a period of 3 to 5 hours. 4. A novel composition as claimed in claim 1, wherein the phosphogypsum used has impurities preferably P2Os in the range of 0.42 to 0.92 wt%, F in the range of 0.44 to 0.86 wt%, organic matter in the range of 0.11 to 0.65 wt% and alkalies in the range of 0.27 to 0.46 wt%. 5. A novel composition as claimed in claim 1, wherein the neutral gypsum anhydrite is fluoroanhydrite obtained by blending fluorogypsum with 0.5 to 1.0 wt% hydrated lime. 6. A novel composition as claimed in claim 1, wherein the fluorogypsum used has impurities preferably F in the range of 1.0 to 2.0 wt%. 7. A novel composition as claimed in claim 1, wherein the phosphoanhydrite/fluoroanhydrite is ground to a fineness of 450 to 500 m2/kg [Blaine] in a ball mill or pulverizer. 8. A composition as claimed in claim 1, wherein a mixture of chemical activators selected from sodium sulphate [NaaSCU.lOFkO] and ferrous sulphate [Fe2SO4.7H2O] is used. 9. A composition as claimed in claim 1, wherein the methyl methacrylate polymer is duly catalyzed with 0.1 to 0.3% benzoyl peroxide. 10. A novel high strength anhydrite plaster composition for making floor tiles substantially as herein described with reference to the foregoing examples.

Documents:

696-del-2000-abstract.pdf

696-del-2000-claims.pdf

696-del-2000-correspondence-others.pdf

696-del-2000-correspondence-po.pdf

696-del-2000-description (complete).pdf

696-del-2000-form-1.pdf

696-del-2000-form-19.pdf

696-del-2000-form-2.pdf