Title of Invention

A COMPOSITION FOR MAKING PROCELAIN CERAMICS AND A PROCESS OF MAKING PORCELAIN THEREFROM

Abstract A composition for making porcelain ceramics and a process of making porcelain therefrom The present invention relates to a composition for making porcelain ceramics and a process of making porcelain therefrom. The present invention is useful for the production of porcelain ceramics of better properties by utilizing pyrophyllite as a replacement of china clay, quartz and like other substances. The present invention relates to a composition for making porcelain ceramics and a process of making porcelain therefrom. The present invention is useful for the production of porcelain ceramics of better properties by utilizing pyrophyllite as a replacement of china clay, quartz and like other substances. Addition of pyrophyllite effected in improving the mechanical properties of the fired specimen, while decreasing the thermal expansion. Elimination of stress in the structure and presence of felt like interlocking mullite needles improved ceramic properties. The composition consists of Pyrophyllite powder in the range of 37.5 to 5%, China clay in the range of 12.5 to 25%, Plastic clay in the range of 15 to 35%, Feldspar in the range of 35 to 15% and Quartz in the range of 0 to 20%
Full Text The present invention relates to a composition for making porcelain ceramics and a process of making porcelain therefrom. The present invention particularly relates to the production of porcelain ceramics of better properties by utilizing pyrophyllite, a low cost alumino-silicate material which is abundantly available in India but finds very little use in ceramic industry, as a replacement of china clay, quartz and other like substances.
Porcelain finds very wide usage in industry and is extensively used for manufacturing high tension and low tension insulator, crockery, sanitary wares, art and novelty wares, wall and floor tiles.
Two kinds of feldspathic porcelain are used in producing high-voltage insulators; namely, common porcelain and alumina-containing porcelain. The common porcelain consists essentially of quartz-type mineral, feldspathic mineral, and clay mineral, while the alumina-containing porcelain consists essentially of a composition where quartz has been replaced partially or completely by alumina.
Tri-axial porcelain body essentially consists of kaolinite clay of the order of 50%, quartz of the order of 25% and feldspar of the order of 25%. Although the quartz plays a significant role in the development of ultimate properties of the product as well as appropriate microstructure, only a small portion of it gets dissolved in the melt during firing while a significant amount remains unreacted. The unreacted quartz phase undergoes transformations during cooling and the resultant volume change leads to the development of stresses in the structure which adversely affects the mechanical strength as well as thermal shock resistance. Reference in this regard may be made to H. Moertel, "Influence of the batch composition on the reaction behavior and properties of fast fired (2h) porcelain" in Science of ceramics 9 (1977), 84-91 (1). The thermal shock resistance of hard porcelain deteriorated with the increasing amount of quartz and glassy matrix while the same improved with increasing mullite content for which reference may be made to S.P.
Chaudhuri, "Ceramic properties of hard porcelain in relation to mineralogical composition and microstructure (VI) - Thermal shock resistance and thermal expansion" in Trans. Ind. Ceram. Soc. 34 (1975) (1) 30-34. The temperature at which quartz begins to dissolve and interact with surrounding materials are strongly affected by composition as well as particle size of quartz for which reference may be made to ST. Lundin, "Microstructure of porcelain" in Microstructure of ceramic material in the Proceedings of the American Ceram. Soc. Symposium, Chapter 6 (pp 93 to 106), National Bureau of standards Miscellaneous Publications 257 (1964), Gaithersburg. Cracks commonly observed in and around quartz grains with sizes > 20 urn resulting from large thermal expansion mismatch between crystalline quartz (a=23 X 10"6 K"1) and the glassy phase (a = 3X10"6 K'1) in the temperature range 20° - 750° C reference for which may be made to Mattyasovszky - Zsolnay, "Mechanical strength of porcelain" in J. Am. Ceram. Soc. 40 (1957) [9] 299-306. The stress in the glassy phase creates tensile force perpendicular and compressive force parallel to the grain boundaries and highest dissolution of quartz in the melt will reduce the tensile force between residual quartz and surrounding glassy phase reference for which may be made to M.F. Tomizaki and T. Sugiyama, "Study on high silica porcelain bodies: effect of siliceous stone grain size" in Interceram 44 (1995) [4] 223-228.
Mullite is the only stable phase in the AI2O3, SiO2 system at atmospheric pressure. Mullite phase is believed to play a significant role in the development of traditional and advanced ceramics and replacement of quartz by aluminium oxide in an electrical porcelain composition resulted in 100 % increase in flexural strength references for which may be made to S.P. Chaudhuri, "Influence of mineralizers on the constitution of hard porcelain : II Microstructures" in Am. Ceram. Soc. Bull 53 (1974) [3] 251-54, J. Liebermann, "Reliability of materials for high voltage insulators" in Am. Ceram. Soc. Bull (2000) [5] 55-58, S.K. Khandelwal and R.L. Cook, "Effect of alumina additions on crystalline constituents and fired properties of electrical porcelains" in Am. Ceram. Soc. Bull. 49 (1970) [5] 522-26. Khandelwal and
Cook correlated the increase in strength with the amount of mullite and corundum as well as decrease in the number of micro craks. Khandelwall and Cook achieved 200 % increase in transverse strength by adding 40% Alumina to a vitreous china body. Increasing alumina and decreasing feldspar content increased the total crystalline content of the fired body. Analysis of microstructures revealed a higher mullite content. Increased interlocking of the mullite crystals is thought to increase thermal shock resistance. On the other hand the same author compared the strength of two quartz bodies with different mullite contents and opined that it was not the mullite content but the microstructure ( the quantity, size, size distribution and shape of various constituent phases) contributed significantly in the development of porcelain properties. Tkalcec and Falz et. al. observed that addition of talc upto 4 % increased the quantity of mullite but reduced the MOR due to increase in the quantity and size of pores in the fired bodies reference for which may be made to E. Tkalcec & D. Prodanovic and W. Falz. & H.W. Hennicke, "Microstructure and properties of aluminous electrical porcelain doped with talc" in Brit. Ceram. Trans & Jour. 83 (1984) [3] 76-80. Maiti and Kumar in the reference "Effect of substitution of quartz by beach sand sillimanite on the properties of conventional porcelain" in Br. Ceram. Trans. J. 89 (1990) 24-27, observed that progressive replacement of quartz by sillimanite sand in a porcelain composition resulted in increased flexural strength and fracture toughness.
In the U.S. Patent nos.: 3860432, 3846098, 3674519, 3431126 and 3097101 are mentioned that it is empirically known in the art of porcelain production that the finer the particle size of the starting material, the more likely the occurrence of cracks is in the drying and firing processes. In general, when the content of particles with effective diameters of not greater than 10 µm surpasses 85% by weight, the crack tends to occur in the above processes. Accordingly, the particle size of porcelain material has been controlled so that the content of particles with effective diameters of not greater than 10 µm is
less than 85%in both common porcelain and alumina-containing porcelain.
The above "cracks" occurring in the drying or firing process refers to those cracks which can be caused at strained portions of the porcelain by the difference of expansion and shrinkage between the inside and the surface thereof due to temperature differences there between during the drying and firing processes. The strained portions include both inside strains caused during kneading and extrusion as a result of difference of particle orientation and density between the inside and the surface of body material and the surface strains caused during cutting the working of the body. Thus, the cracks discussed in the description of the invention refers to cracks formed in the inside and on the surface of the porcelain during the drying and firing processes.
In short, the feldspathic porcelain of the prior art has a shortcoming in that, when the particle size of the starting material is very fine, the risk of crack occurrence becomes high, and such risk is further increased when such porcelain is used in making large high-voltage insulators or the like in which the temperature difference between the insideandthe surface of the porcelain is large.
Accordingly, the particle size of the starting material is restricted to be larger than a certain value, which restriction is reflected in a limitation of the homogeneity of the porcelain microstructure and a comparatively low mechanical strength of porcelain. For instance, the three-point bending strength of an unglazed test piece with a 12 mm diameter for insulator porcelain is about 1,000 kg/cm2 in case of common porcelain and about 1,400 kg/cm2 in case of alumina-containing porcelain containing 20% of corundum. If the particle size of the starting material is made very fine, cracks occur in the drying process and/or firing process of porcelain production as pointed out above. Thus, for products which require a high mechanical strength, such as
large high-voltage insulators, special measures have been taken, for example adding a large amount of corundum or by applying static hydraulic pressure onto the body for densification followed by carving an insulator out of the densified body. Such special measures result in an increase in the production cost or a complication of the production process.
In U.S. Patent No 4717695, wherein Isas Oda discloses that high strength feldspathic porcelain having bending strength of greater than 1,400 kg/cm2 and consisting essentially of 22-85% by weight of Si02, 10-73% by weight of Al203 and 1.5-6.5% by weight of K20 and/or Na20. The porcelain has a total degree of crystallinity of more than 40% by weight, and a crystalline grain size of not greater than 20 µm, and it is free from defects of larger than 40 µm. The procelain is produced by pulverizing a starting material mixture of quartz-feldspar-alumina system so that 85-95% by weight of particles thereof have a grain size of not greater than 10 µm, calcining the mixture, adding clay-mineral material therein, pulverizing so that the clay-mineral-added mixture contains less than 85% by weight of particles with a grain size of not greater than 10 (j.m, forming, drying, and firing at 1100-1400°C.
Reference may also be made to C. S. Prasad, K. N. Maiti, R. Venugopal in Interceram, 40(2), 1991. 94 - 98, "Replacement of wuartz and potash feldspar with sericitic pyrophyllite in whiteware compositions" wherein quartz and potash feldspar were replaced by sericitic pyrophyllite of comparatively higher alkali content for the manufacture of whiteware bodies. The main drawback of the referred process is incorporation of alkali metal oxides in the composition that forms higher amount of liquid with lower viscosity rendering the resultant material more brittle. It may be mentioned that replacement of feldspar may not be a good suggestion unless it is done by a material which produces liquid of comparable viscosity at vitrification temperature without increasing total alkali content of the sintered body.
The general disadvantages of the above noted hitherto known prior art are:
Presence of unconverted quartz as well as large volume of glassy phase results in higher thermal expansion and poor thermal shock resistance of the specimen.
Vitrification temperature is rather high and use of flux in large proportion shorten the vitrification range.
Improving mechanical strength by incorporating alumina in the composition which increases product cost.
The main object of the present invention is to provide a composition for making porcelain ceramics, which obviates the drawbacks of the above noted hitherto known prior art.
Another object of the present invention is to provide a process of making porcelain from the said composition which obviates the drawbacks of the above noted hitherto known prior art.
Yet another object of the present invention is to provide a composition useful for the production of porcelain ceramics of better properties by utilizing pyrophyllite, a low cost alumino-silicate material which is abundantly available in India but finds very little use in ceramic industry, as a replacement of china clay, quartz and like other substances.
Still another object of the present invention is to provide a process for the production of porcelain ceramics of better properties, wherein pyrophyllite is used as one of the major raw materials which is abundantly available but has limited use.
Still yet another object of the present invention is to provide replacement of quartz and like substances by low cost material such as pyrophyllite to reduce cost of the product.
A further object of the present invention is to provide a broadened vitrification range.
In the hitherto known prior art tri-axial porcelain body essentially consists of kaolinite clay of the order of 50%, quartz of the order of 25% and feldspar of the order of 25%. Presence of unconverted quartz as well as large volume of glassy phase in the tri-axial composition results in poor thermal shock resistance. In addition to that good quality kaolinitic clay for producing porcelain is rapidly depleting. To overcome these problems, a low cost alumino-silicate material, pyrophyllite, which is abundantly available in India but finds very little use in ceramic industry, has been introduced in the porcelain composition as a partial replacement of kaolinitic clay and quartz. Addition of pyrophyllite effected in improving the mechanical properties of the fired specimen, while decreasing the thermal expansion. Elimination of stress in the structure and presence of felt like interlocking mullite needles improved ceramic properties. Judicious selection of composition results in wider vitrification range. Improved ceramic properties are realized due to control of microstructures, glass and crystal ratio, shape, size and quantity of pores.
Addition of pyrophyllite effected in the reduction of fired shrinkage by around 6% while improving the flexural strength by around 29% in comparision to that of standard body. This was primarily due to elimination of stress in the structure with decreasing quartz and like substances content as well as due to presence of felt-like interlocking of fine mullite needless in higher proportions. Mullite was found even at 1150°C and its amount increased to a maximum at 1250°C to 1300°C and decreasing at higher temperature. The gradual decrease in the quantity of quartz and like substances showed the partial dissolution of this phase with increasing temperature. Beyond some optimum proportion of pyrophyllite, there was large volume of glass formation and large elongated pores were found non-uniformly distributed in the microstructure which resulted in deterioration of mechanical properties. The amount of closed pores in the specimens with pyrophyllite content beyond
15% to 22.5% and fired at 1250°C to 1300°C was found to increase very abruptly which in turn is expected to increase the mean free fracture path per unit volume thereby resulting in decrease in strength.
Pyrophyllite is an inert hydrous alumino-silicate mineral having the general formulae A12O3. 4SiO2. H2O with 67% A12O3, 28% Si02 and 5% H20. The term is well known in the prior art.
The novelty of the composition for making porcelain ceramics and a process of making porcelain therefrom of the present invention lies in providing a porcelain ceramic having superior mechanical strength with substantially lower firing shrinkage.
The novelty of the composition for making porcelain ceramics and a process of making porcelain therefrom of the present invention has been realized by the non-obvious inventive step of formulating a composition in which quartz, china clay and like substances were replaced partially by pyrophyllite a low cost alumino-silicate material which is abundantly available in India but finds very little use in the ceramic industry, alumino-silicate material,
Accordingly the present invention provides a composition for making porcelain ceramics, which comprises pyrophyllite (inert hydrous alumino-silicate mineral) powder in the range of 5 to 37.5 wt.%, China clay in the range of 12.5 to 25 wt.%, plastic clay in the range of 15 to 35 wt.%, feldspar in the range of 35 to 15 wt.%, and quartz in the range of 0 to 20 wt.%.
In an embodiment of the present invention the pyrophyllite powder is of 100 mesh
B.S.
In another embodiment of the present invention the mass percent of pyrophyllite used
is in the range of Si02 58 to 60 wt.%, A1203 29 to 31 wt.%, Ti02 below 0.5 wt.%,
Fe203 below 1.0 wt.%, MgO below wt.1.0 %, K20 1.0 to 2.0 wt.% and Na20 below
1.0 wt.%.


Accordingly the present invention provides a process of making porcelain ceramics from the above composition by mixing pyrophyllite powder in the range of 5 to 37.5 wt.%, China clay in the range of 12.5 to 25 wt.%, plastic clay in the range of 15 to 35 wt.%, feldspar in the range of 35 to 15 wt.%, and quartz in the range of 0 to 20 wt.%, to obtain a mixed material; adding 300 to 500 ml of water per kilogram of mixed material; wet milling the mixed material for a period in the range of 10 to 20 hours to obtain an intimately mixed material; sieving the intimately mixed material; demagnetizing the sieved slurry; dewatering the demagnetized slurry; forming green shapes from demagnetized slurry; firing the green shapes so obtained at a temperature in the range of 1150 to 1300°C for a soaking time period in the range of 1 to 4 hours.
In an embodiment of the present invention the wet milling of the mixed material is carried out by known methods such as pot milling, ball milling. In another embodiment of the present invention the sieving of the intimately mixed material is done by known methods such as vibrating screen. In yet another embodiment of the present invention the demagnetizing of the sieved slurry is effected by known methods such as permanent magnet. In still another embodiment of the present invention the dewatering of the demagnetized slurry is done by known methods such as filter press. In a further embodiment of the present invention the forming of green shapes from demagnetized slurry is effected by the known processes such as extrusion, pressing. The detailed steps of the present invention are given below :
a) Pyrophyllite is first crushed and ground by conventional methods such as ball milling, vibro milling and passed through 100 mesh B.S.
b) A batch is formulated by using sieved pyrophyllite of step 'a' in the range of 5 to 37.5 wt.%, China clay in the range of 12.5 to 25 wt.%, plastic clay in the range of 15 to 35 wt.%, feldspar in the range of 35 to 15 wt.% and quartz in the range of 0 to 20 wt.%.
The batch of step 'b' is mixed to obtain a mixed material.
Water is added to the mixed material batch obtained in step "c" in the range of 300 ml to 500 ml water per kg of mixed material.
The mixed material of step 'd' is subjected to wet grinding for a period in the range of 10 to 20 hours to obtain an intimately mixed material.
The intimately mixed material of step 'e' was then sieved by conventional processes such as vibrating screens.
The sieved slurry of step f was then demagnetized by conventional processes such as using permanent magnet.
h) The demagnetized slurry of step 'g' was then dewatered by conventional processes such as filter press.
i) The green shapes were formed from the dewatered slurry of step 'h' by conventional processes such as extrusion, pressing.
j) The green shapes obtained in step 'i' were fired at a temperature in the range of 1150 to 1300°C with soaking time period in the range of 1 to 4 hours.
The following examples are given by way of illustration of the present invention in actual practice and should not be construed to limit the scope of the present invention in any way.
Example 1
15 wt.% pyrophyllite powder, 25 wt.% china clay, 25 wt.% plastic clay, 25 wt.% feldspar and 10 wt.% quartz were mixed and wet ground for 15 hours. The ground slurry was sieved and passed through permanent magnet, dewatered and green specimen were fabricated. The green specimen were fired at 1250 °C with 2 hours soaking at the peak temperatures. MOR, bulk
density, water absorption of the fired specimen were measured and the results were 83.3 mPa, 2.4 gm/cc, 0.06% respectively. The coefficient of thermal expansion of the matured specimen (x10"6/°C) was measured in the temperature range 30°C to 1200°C. The result were reported as α3o300, α30600, α3o900, α3o120055.8, 61.5, 59.0, 54.0 respectively.
Example 2
22.5 wt.% pyrophyllite powder, 17.5 wt.% china clay, 20 wt.% plastic clay, 30 wt.% feldspar and 10 wt.% quartz were mixed and wet ground for 20 hours. The ground slurry was sieved and passed through permanent magnet, dewatered and test specimen were fabricated. The test specimen were fired at 1200 °C with 3 hours soaking at the peak temperatures. MOR, bulk density, water absorption of the fired specimen were measured and the results were 75.9 mPa, 2.4 gm/cc, 0.08% respectively. The coefficient of thermal expansion of the matured specimen (x10"6/°C) was measured in the temperature range 30 °C to 1200 °C. The result were reported as α3o300, α30600, α30900, α301200 55.8, 66.7, 59.3, 57.3 respectively.
Example 3
30 wt.% pyrophyllite powder, 20 wt.% china clay, 20 wt.% plastic clay and 30 wt.% feldspar were mixed and wet ground for 10 hours. The ground slurry was sieved and passed through permanent magnet, dewatered and test specimen were fabricated. The test specimen were fired at 1150 °C with 1 hours soaking at the peak temperatures. MOR, bulk density, water absorption of the fired specimen were measured and the results were 65.0 mPa, 2.3 gm/cc, 0.25% respectively. The coefficient of thermal expansion of the matured specimen (x10"6/°C) was measured in the temperature range 30 °C to 1200 °C. The result were reported as α30300, α30600, α30900, α301200 57.8, 62.8, 60.3, 56.5 respectively.
Example 4
5 wt.% pyrophyllite powder, 25 wt.% china clay, 25 wt.% plastic clay, 25 wt.% feldspar and 20 wt.% quartz were mixed and wet ground for 20 hours. The ground slurry was sieved and passed through permanent magnet, dewatered and test specimen were fabricated. The test specimen were fired at 1200 °C with 2 hours soaking at the peak temperatures. MOR, bulk density, water absorption of the fired specimen was measured and the results were 60.8 mPa, 2.2 gm/cc, 6.54%. The coefficient of thermal expansion of the matured specimen (x10"6/°C) was measured in the temperature range 30°C to 1200°C. The result were reported as α30300, α30600, α30900, α30120058.6, 72.3, 60.1, 59.1 respectively.
Example 5
22.5 wt.% pyrophyllite powder, 17.5 wt.% china clay, 25 wt.% plastic clay, 25 wt.% feldspar and 10 wt.% quartz were mixed and wet ground for 20 hours. The ground slurry was sieved and passed through permanent magnet, dewatered and test specimen were fabricated. The test specimen were fired at 1300°C with 3 hours soaking at the peak temperatures. MOR, bulk density, water absorption of the fired specimen were measured and the results were 75.9 mPa, 2.4 gm/cc, 0.08% respectively. The coefficient of thermal expansion of the matured specimen (x10"6/°C) was measured in the temperature range 30 °C to 1200 °C. The result were reported as α30300, aso600, α30900, α30120055.8, 66.7, 59.3, 57.3 respectively.
Example 6
37.5 wt.% pyrophyllite powder, 12.5 wt.% china clay, 35 wt.% plastic clay and 15 wt.% feldspar were mixed and wet ground for 10 hours. The ground slurry was sieved and passed through permanent magnet, dewatered and test specimen were fabricated. The test specimen were fired at 1300 °C with 4 hours soaking at the peak temperatures. MOR, bulk density, water absorption
of the fired specimen were measured and the results were 75.0 mPa, 2.4 gm/cc, 0.18% respectively. The coefficient of thermal expansion of the matured specimen (x10"6/°C) was measured in the temperature range 30°C to 1200°C. The result were reported as α3o300, α3o600, α30900, a3o1200 55.8, 61.5, 59.0, 54.0 respectively.
The composition for making porcelain ceramics and a process of making porcelain therefrom of the present invention provides porcelain ceramic having superior mechanical strength with substantially lower firing shrinkage. The novel features have been realized by the non-obvious inventive step of formulating a composition in which quartz, china clay and like substances are replaced partially by pyrophyllite a low cost alumino-silicate material which is abundantly available in India but finds very little use in the ceramic industry. This effectively obviates the drawbacks of the hitherto known prior art wherein tri-axial porcelain body essentially consists of kaolinite clay of the order of 50%, quartz of the order of 25% and feldsper of the order of 25%. Presence of unconverted quartz as well as large volume of glassy phase in the tri-axial composition results in poor thermal shock resistance. In addition to that good quality kaolinitic clay for producing porcelain is rapidly depleting. To overcome these problems, pyrophyllite, a low cost alumino-silicate material which is abundantly available in India but finds very little use in ceramic industry, has been introduced in the porcelain composition as a partial replacement of kaolinitic clay and quartz. Addition of pyrophyllite effected in improving the mechanical properties of the fired specimen, while decreasing the thermal expansion. Elimination of stress in the structure and presence of felt like interlocking mullite needles improved ceramic properties. Judicious selection of composition results in wider vitrification range. Improved ceramic properties are realized due to control of microstructures, glass and crystal ratio, shape, size and quantity of pores.

The main advantage of the present invention are :
Is economical due to incorporation of pyrophyllite a low cost material which is abundantly available in India but finds very little use in the ceramic industry.
Replacement of costlier ingredient like China clay reduces the cost of production without impairing the ultimate properties of the product.
Reduces losses due to cracking, chipping and deformation in comparison to conventional porcelain.
Reduction in thermal expansion provides better resistance to denting and thermal shock.
5. Conserves energy by lowering of the vitrification temperature while improving the vitrification range.






WE CLAIM:
1. A composition for making porcelain ceramics which comprises; pyrophyllite (inert hydrous alumino-silicate mineral) powder in the range of 5 to 37.5 wt.%, China clay in the range of 12.5 to 25 wt.%, plastic clay in the range of 15 to 35 wt.%, feldspar in the range of 35 to 15 wt.%, and quartz in the range of 0 to 20 wt.%.
2. A composition as claimed in claim 1, wherein the mass percent of pyrophyllite used is in the range of SiO2 58 to 60 wt.%, Al2O3 29 to 31 wt.%, TiO2 below 0.5 wt.%, Fe2O3 below 1.0 wt.%, MgO below 1.0 wt.%, K2O 1.0 to 2.0 wt.% and Na2O below 1.0 wt.%.
3. A process of making porcelain ceramics from the composition as claimed in claims 1 - 2, which comprises; mixing pyrophyllite powder in the range of 5 to 37.5 wt.%, China clay in the range of 12.5 to 25 wt.%, plastic clay in the range of 15 to 35 wt.%, feldspar in the range of 35 to 15 wt.%, and quartz in the range of 0 to 20 wt.% to obtain a mixed material; adding 300 to 500 ml of water per kilogram of mixed material; wet milling the said mixed material for a period in the range of 10 to 20 hours to obtain an intimately mixed material; sieving the intimately mixed material; demagnetizing the sieved slurry; dewatering the said demagnetized slurry; forming green shapes from the demagnetized slurry; firing the green shapes so obtained at a temperature in the range of 1150 to 1300 °C for a soaking time period in the range of 1 to 4 hours.
4. A process as claimed in claim 3, wherein the wet milling of the mixed material is carried out by known methods, pot milling, ball milling.
5. A process as claimed in claim 3-4, wherein the sieving of the intimately mixed material is done by known method, vibrating screen.
6. A process as claimed in claims 3-5, wherein the demagnetizing of the sieved slurry is effected by known method permanent magnet.
7. A process as claimed in claims 3-6, wherein the dewatering of the
demagnetized slurry is done by known method, filter press.
8. A process as claimed in claims 3-7, wherein the forming of green shapes from demagnetized slurry is effected by the known process, extrusion, pressing.

Documents:

473-del-2005-Abstract-(21-04-2011).pdf

473-del-2005-abstract.pdf

473-del-2005-Claims-(21-04-2011).pdf

473-DEL-2005-Claims-(29-06-2011).pdf

473-del-2005-claims.pdf

473-DEL-2005-Correspondence Others-(29-06-2011).pdf

473-del-2005-Correspondence-Others-(21-04-2011).pdf

473-del-2005-correspondence-others.pdf

473-del-2005-Description (Complete)-(21-04-2011).pdf

473-del-2005-description (complete).pdf

473-del-2005-form-1.pdf

473-del-2005-form-18.pdf

473-del-2005-form-2.pdf

473-del-2005-Form-3-(21-04-2011).pdf

473-del-2005-form-3.pdf

473-del-2005-form-5.pdf


Patent Number 249263
Indian Patent Application Number 473/DEL/2005
PG Journal Number 42/2011
Publication Date 21-Oct-2011
Grant Date 13-Oct-2011
Date of Filing 04-Mar-2005
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address ANUSANDHAN BHAWAN, RAFI MARG, NEW DELHI-110 001, INDIA
Inventors:
# Inventor's Name Inventor's Address
1 MUKHOPADHYAY TAPAS KUMAR GENERAL GLASS & CERAMIC RESEARCH INSTITUTE, P.O JADAVPUR UNIVERSITY, KOLKATA 700 032
2 GHOSH SYAMAL GENERAL GLASS & CERAMIC RESEARCH INSTITUTE, P.O JADAVPUR UNIVERSITY, KOLKATA 700 032
3 DAS SWAPAN KUMAR GENERAL GLASS & CERAMIC RESEARCH INSTITUTE, P.O JADAVPUR UNIVERSITY, KOLKATA 700 032
4 GHATAK SANKAR GENERAL GLASS & CERAMIC RESEARCH INSTITUTE, P.O JADAVPUR UNIVERSITY, KOLKATA 700 032
5 MAITI HIMADRI SEKHAR GENERAL GLASS & CERAMIC RESEARCH INSTITUTE, P.O JADAVPUR UNIVERSITY, KOLKATA 700 032
PCT International Classification Number A47G19/02; C04B41/91
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA