Title of Invention

"A SYNERGISTIC COMPOSITION AND PROCESS FOR THE PRODUCTION OF TRANSPARENT FRIT "

Abstract

The present invention provides a synergistic composition and a process for the production of transparent frit. This composition is and a process is useful in manufacturing rapid once fired ceramic wall tile glossy glaze. The synergistic frit composition of the present invention essentially consists of quartz, clay, k-felspar, colemenite, wallastonite, soda ash, calcite and zinc oxide. The synergistic frit composition of the present invention allows the production of transparent frit which is free from unmelted inclusions and trapped carbonaceous material and suitable for manufacturing defect free glossy glaze surfaces. Use of alkaline earth oxides and calcium borate as powerful fluxes plays a key role in order to achieve the desired fusion, flow values and thermal expansion characteristics. 90 wt% of the presently developed frit can be used with 10 wt% white burning clay to prepare glossy glaze material for rapid once fired ceramic wall tile.

Full Text

The present invention relates to a synergistic composition and a process for the production of transparent frit. The present invention particularly relates to a synergistic frit composition and a process for the production of transparent frit, useful for manufacturing rapid once fired wall tile glossy glaze, which allows the unavoidable gases produced by maturing of both the glaze and the body to escape at an appropriate time and temperature and finally results in a defect free glossy glazed wall tile. With the advent of faster firing schedule in manufacturing glazed ceramic wall tile, the use of greater proportion of frit in glazes is a technological requirement to eliminate the unnecessary reactions involved. Such fully fritted glaze compositions should have desired fusion and flow characteristics at the peak firing temperature. Selection of appropriate raw materials for this type of special frit is very essential factor due to several reasons, the most important being melting or dissolution rate. Each of the raw materials containing inorganic oxides has some limitations due to the inherent characteristics that are allowed and balanced in a given composition. While the very purpose of fritting is to convert the water soluble substances into wholly insoluble, another prime requisite is to eliminate the volatile constituents which produces bubbles and results in defective surfaces when used in rapid once fired wall tile glaze. The most commonly used present day method for the production of transparent frit comprises of thorough blending and mixing of a large number of raw materials, melting the blended mass at high temperature in a glass melting furnace followed by water quenching. Most of the presently available commercial frits are suitable only for long double fired wall tile glaze and produces defective surfaces if they are used in rapid once fired wall tile glaze. The most commonly used present day method for the production of transparent frit comprises of thorough blending and mixing of a large number of raw materials, melting the blended mass at high temperature in a glass melting furnace followed by water quenching. Most of the presently available commercial frits are suitable only for long double fired wall tile glaze and produces defective surfaces if they are used in rapid once fired wall tile glaze. Reference may be drawn to the work of Bertochchi, Paolo, Crichton Steven and CAO Yuan, US patent no. 6,132,837 wherein frit having oxide composition of 25-60 wt% Si02, 10-40 wt% AI203, 0-10 wt% CaO, 0-15 wt% BaO, 0-20 wt% MgO, 0-30 wt% ZnO, 0-15 wt% K2O, 0-15 wt% Na2O, 0-10 wt% Li2O has been used as major component in the production of a glossy glaze. Another reference may be drawn to Japanese patent nos. JP-1042340, JP-1042342, JP-1133960 of Hatanaka Kimki, wherein a frit having oxide composition of 55-65 wt% SiO2, 10-18 wt% AI2O3, 18-25 wt% CaO, 0.5 - 4 wt% Li2O, 0-10 wt% ZrO2, 0-2 wt% B2O3, 0-10 wt% MgO, BaO, SrO, ZnO has been used as major component to produce glaze for tile. Reference may be made to Taniguchi Kenji, patent no. WO 8600611, wherein low alkali, low boron containing frit composition is used to produce milky white TiO2 based glaze for porcelain tile. Reference may also be drawn to the work of Ishikawa Takahisa, patent no. JP-8165141, wherein 2-20 wt% zeolite has been used along with frit to produce glaze. Reference may further be made to Taylor, J.R. and Bull A.C., Ceramics glaze technology, Pergamon Press, N.Y., 1986 and Eppler, R.A., Ceramic Engg. Sci. Proc. 19,2,9 (1998), wherein various kinds of raw materials used for frit compositions have been described. In all the present day methods, a large number of raw materials are commonly used for the production of frit, most of which are naturally occurring minerals such as quartz (SiO2), Kaolinite clay (AI2O3 2SiO2 2H2O), different kinds of felspar (K20. AI2O3. 6SiO2 or Na20. AI2O3 6 SiO2), Soda ash (Na2CO3), Borax (Na2B4O7 10 H2O)), limestone (CaCO3) Zinc oxide (ZnO) dolomite (CaCO3. v1gCO3), lithium oxide (Li2O), Barium Carbonate, (BaCO3), titanium di-oxide ;TiO2, Zircosil (ZrSiO4). The major drawbacks of all the presently manufactured commercial frit compositions used for the production of wall tile glossy glaze are : 1. Use of a large number of natural raw materials containing significant amount of organic impurities. 2. Presence of unmelted inclusions and trapped carbonaceous materials. 3. Require longer holding time during melting, hence more energy intensive process. 4. Non uniform and inadequate fusion and flow characteristics 5. Produce defective (mainly pinholes) glazed surfaces. 6. Suitable mostly for long double fired wall tile glaze. 7. Tailor made properties are not achieved for using in rapid once fired wall tile glaze. In the double firing process of producing glossy glazed wall tiles, the conventional frits used in glazed composition is not suitable for method of single fast firing schedule. It is necessary to develop special frit composition for rapid once fired wall tile glaze which allow the unavoidable gases produced by maturing of both the glaze and the body to escape at an appropriate time and temperature and finally results in a defect free glossy glazed wall tile. Hence, it is clear that there is a definite need to provide an improved frit composition useful for the production of wall tile glossy glaze. The main object of the present invention is to provide a synergistic composition for the production of transparent frit useful for providing rapid once fired wall tile glossy glaze, which obviates all the above noted drawbacks. Another object of the present invention is to provide a process for the production of transparent frit from the synergistic frit composition, useful for providing rapid once fired wall tile glossy glaze, which obviates all the above noted drawbacks. Yet another object of the present invention is to provide a synergistic composition and a process for the production of transparent frit useful for manufacturing rapid once fired wall tile glaze which allows the unavoidable gases produced by maturing of both the glaze and the body to escape at an appropriate time and temperature and finally results in a defect free glossy glazed wall tile. Still another object of the present invention is to provide a synergistic composition and a process for the production of transparent frit utilizing less number of raw materials which is turn reduces the chances of pinhole formation caused by organic impurities. Still yet another object of the present invention is to provide a synergistic composition and a process for the production of transparent frit having adequate fusion and flow characteristics. A further object of the present invention is to provide a synergistic composition and a process for the production of transparent frit free from unmelted inclusions and trapped carbonaceous material. A still further object of the present invention is to provide a synergistic composition and a process for the production of transparent frit, which will require less holding time during melting, hence save energy. In the present invention there is provided a synergistic composition and a process for the production of transparent frit useful in manufacturing rapid once fired ceramic wall tile glossy glaze. The synergistic frit composition of the present invention essentially consists of quartz, clay, K-felspar, colemenite, wollastonite, soda ash, calcite and zinc oxide. The synergistic frit composition of the present invention allows the production of transparent frit which is free from unmelted inclusions and trapped carbonaceous materials and suitable for manufacturing defect free glossy glaze surfaces. Use of alkaline earth oxide and calcium borate as powerful fluxes plays a key role in order to achieve the desired fusion, flow values and thermal expansion characteristics. 90 wt% of the presently developed frit can be used with 10 wt% white burning clay to prepare glossy glaze material for rapid once fired ceramic wall tile. Accordingly ,the present invention provides a synergistic composition for the production of transparent frit, which comprises: Quartz 15 to 18wt%; Clay 0 to 5wt%; K-felspar 30 to 38wt%; Colemenite 4 to 13wt%; Wollastonite 19 to 25wt%; Soda Ash 0 to 1 wt%; Calcite 0 to 10wt%; Zinc Oxide 9 to 12wt%. In an embodiment of the present invention, the quartz has SiO2 content in the range of 99.0 to 99.8 wt% with less than 0.5 wt% Fe2O3. In another embodiment of the present invention, the clay consists of major chemical constituents such as SiO2 in the range of 55 to 57 wt%, AI203 in the range of 25 to 27 wt%, Fe2O3 less than 1.5 wt%. In still another embodiment of the present invention, the K-felspar consists of major chemical constituents such as Si02 in the range of 65 to 67 wt%, AI203 in the range of 18 to 20 wt%, K2O in the range of 10 to 11 wt%, Fe2O3 less than 0.5 wt%. In yet another embodiment of the present invention, the colemenite is hydrated calcium borate having major chemical constituents such as CaO in the range of 27 to 28 wt%, B2O3 in the range of 42 to 43 wt%, SiO2 in the range of 5 to 6 wt%. In still yet another embodiment of the present invention, the wollastonite consists of major chemical constituents such as Si02 in the range of 50 to 51 wt%, CaO in the range of 45 to 47 wt%, Fe203 less than 0.5 wt%. In a further embodiment of the present invention, the soda ash has Na20 content in the range of 58 to 60 wt%. In a yet further embodiment of the present invention, the calcite has CaO content in the range of 52 to 55wt%. In a still further embodiment of the present invention, the zinc oxide has ZnO content in the range of 90 to 93 wt%. The composition of the present invention for the production of transparent frit is not a mere admixture but a synergistic mixture having properties which are distinct and different than the mere aggregation of the properties of the individual ingredients. There is no chemical reaction in the synergistic composition. Accordingly, the present invention provides a process for the production of transparent frit which comprises: blending and mixing uniformly 15 to 18 wt% clay, 30 to 38 wt% k-f!espar, 4 to 13 wt% colemenite, 19 to 25 wt% wollastonite, 0 to 1 wt% soda ash, 0 to 10 wt% calcite, 10 to 12 wt% zinc oxide to obtain blended mass, subjecting the said blended mass to complete melting at a temperature in the range of 1400 -1500°C for aperiod in the range of 3 to 6 hours to obtain homogenous melt, quenching the said homogenous melt with water to obtain the transparent frit. In an embodiment of the present invention, the homogeneity of the melt is checked by drawing a thread till the melt is free from any unmelted inclusions. In another embodiment of the present invention, the frit has flow values of 70 to 77 mm. In yet another embodiment of the present invention, the frit has thermal expansion characteristics of 66.0 to 76.6 x 10-7 / °C in the temperature range of RT to 600°C. In the present invention, during the process for the production of transparent frit various changes occur during heating, such as chemical decomposition, diffusion of elements, one with another, and solution till a homogeneous mass is obtained which is free from unmelted inclusions and trapped carbonaceous materials. Higher RO/SiO2 ratio (RO group consisting of alkali, alkaline earth oxide and ZnO) and calcium borate content plays an important role in the presently developed frit composition in order to achieve desired fusion and flow characterisation without producing any surface defects. Another interesting finding in the presently developed frit composition is the effective fluxing action of alkaline earth oxides than total alkalies towards achievement of proper flow values. Hence, the combined powerful fluxing action of alkaline earth oxide and calcium borate is the prime factor in developing frit for rapid once fired wall tile glaze that has been achieved in the present invention. The novelty of the present invention resides in providing a synergistic composition for the production of transparent frit useful for rapid once fired glossy wall tile glaze materials. The frit composition developed in the present invention allows the unavoidable gases produced by maturing of glaze and body to escape during rapid once firing schedule, which does not happen in case of commercially available frit. The inventive steps of the present invention resides in providing higher RO/SiO2 ratio (RO group consisting of alkali, alkaline earth oxide and ZnO) and calcium borate content to achieve desired fusion and flow characteristics during rapid once firing schedule. Another inventive step lies in combined powerful fluxing action of alkaline earth oxide and calcium borate content. The detailed process steps of the present invention are : 1. Blending and mixing uniformly 15 to 18 wt% quartz, 0 to 5 wt% clay, 30 to 38 wt% K-felspar, 4 to 13 wt% colemenite, 19 to 25 wt% wollastonite, 0 to 1 wt% soda ash, 0 to 10 wt% calcite, 10 to 12 wt% zinc oxide, to obtain a blended mass. 2. Complete melting of the blended mass at a temperature in the range of 1400 to 1500°C for a period of 3 to 6 hours, to obtain a homogenous melt. 3. Checking for homogeneity of the melt by drawing thread till the melt is free from any unmelted inclusions. 4. Subjecting the homogenous melt to water quenching. The following examples are given by way of illustration of the process of the present invention in actual practice. However, the examples, should not be construed to limit the scope of the present invention. Example -1 180 gms of quartz, 380 gms of Potash (K-) felspar, 130 gms of Colemenite, 190 gms of wollastonite and 120 gms of zinc oxide were thoroughly blended and uniformly mixed. The blended mixer of the above 1000 gms batch was taken in a refractory crucible and melted in laboratory furnace at 1400°C for a period of 6 hours. The homogeneity of the melt was occasionally checked by drawing a thread till it was free from any unmelted inclusions. Finally, the melt was poured in water for quenching. The quenched frit was tested which had the following characteristics. Flow value (mm): 75 Coefficient of thermal Expansion (RT-600°C): 67.6 X10-7/°C 90 wt% of the frit obtained as above was used with 10 wt% of white burning clay to produce glaze materials and the performances was studied by applying on green tile body during rapid once firing schedule programme at 1100°C. A white color, superior glossiness and defect free surface was observed. Example - 2 164 gms of quartz, 375 gms of K-felspar, 125 gms of Colemenite, 236 gms of wollastonite, 3 gms of soda ash, 97 gms of zinc oxide were thoroughly blended and uniformly mixed. The blended mixer of the above 1000 gms batch was taken in a refractory crucible and melted in laboratory furnace at 1450°C for a period of 5 hours. The homogeneity of the melt was occasionally checked by drawing a thread till it was free from any unmelted inclusions. Finally, the melt was poured in water for quenching. The quenched frit was tested which had the following characteristics. Flow value (mm) : 77 Coefficient of thermal Expansion (RT-600°C): 67.4 X1Q-7/°C 90 wt% of the frit obtained as above was used with 10 wt% of white burning clay to produce glaze materials and the performances was studied by applying on green tile body during rapid once firing schedule programme at 1100°C. A white color, superior glossiness and defect free surface was observed. Example - 3 150 gms of quartz, 50 gms of clay, 300 gms of K-felspar, 40 gms of Colemenite, 250 gms of Wollastonite, 10 gms of soda ash, 100 gms of Calcite, 100 gms of Zinc oxide were thoroughly blended and uniformly mixed. The blended mixer of the above 1000 gms batch was taken in a refractory crucible and melted in laboratory furnace at 1500°C for a period of 3 hours. The homogeneity of the melt was occasionally checked by drawing a thread till it was free from any unmelted inclusions. Finally, the melt was poured in water for quenching. The quenched frit was tested which had the following characteristics. Flow value (mm): 70 Coefficient of thermal Expansion (RT-600°C): 66.0 X10'7/°C 90 wt% of the frit obtained as above was used with 10 wt% of white burning clay to produce glaze materials and the performances was studied by applying on green tile body during rapid once firing schedule programme at 1100°C. A white color, superior glossiness and defect free surface was observed. In the present invention, a synergistic composition has been developed for the production of transparent frit useful in manufacturing rapid once fired ceramic wall tile glossy glaze. The frit developed in the present invention is free from unmelted inclusions and tapped carbonaceous materials and suitable for defect free glossy gloze surfaces. Use of alkaline earth oxide and calcium borate as powerful fluxes played a key role in order to achieve desired fusion, flow values of 70 to 77 rnm and thermal expansion characteristics of 66.0 to 76.6 x 10~7 / °C in the temperature range of RT to 600°C. 90 wt% of the presently developed frit when used with 10 wt% white burning clay to prepare glossy glaze material for rapid once fired ceramic wall tile provided a white color, superior glossiness and defect free tile surface. The main advantages of the present invention are : 1. The present invention uses less number of natural minerals and resulted minimum quantity of organic impurities. 2. The present invention produces transparent frit which is free from unmelted inclusions and tapped carbonaceous materials, hence suitable for defect free glaze surfaces. 3. The present invention requires less holding time during melting, hence save energy. 4. The present invention produces transparent frit useful for rapid once fired wall tile glaze. 5. Tailor made properties are achieved. We claim : 1 A synergistic composition for the production of transparent frit , which comprises: Quartz 15 to 18wt% Clay 0 to 5wt% K-felspar 30 to 38wt% Colemenite 4 to 13wt% Wollastonite 19 to 25wt% Soda Ash 0 to 1wt% Calcite 0 to 10wt% Zinc Oxide 9 to 12 wt% 2 A synergistic composition claimed in claim 1, is useful for manufacturing rapid once fired wall tile glossy glaze. 3 A process for the production of transparent frit from the synergistic composition as claimed in claim 1,which comprises: (i) blending and mixing uniformly 15 to 18 wt% clay, 30 to 38 wt% k-felspar, 4 to 13 wt% colemenite, 19 to 25 wt% wollastonite, 0 to 1 wt% soda ash , 0 to 10 wt% calcite, 10 to 12 wt% zinc oxide to obtain a blended mass, (ii) subjecting the above said blended mass obtain from step (i), to complete melting at a temperature in the range of 1400 -1500°C, for a period in the range of 3 to 6 hours, to obtain homogenous melt, (iii) quenching the above said homogenous melt obtain from step (ii) with water to obtain the transparent frit. 4 A synergistic composition and a process for the production of transparent frit substantially as herein described with reference to the examples.

Documents:

636-DEL-2003-Abstract-(17-09-2008).pdf

636-del-2003-abstract.pdf

636-DEL-2003-Claims-(17-09-2008).pdf

636-del-2003-claims.pdf

636-DEL-2003-Correspondence-Others-(17-09-2008).pdf

636-del-2003-correspondence-others.pdf

636-del-2003-correspondence-po.pdf

636-del-2003-description (complete)-17-09-2008.pdf

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

636-DEL-2003-Form-1-(17-09-2008).pdf

636-del-2003-form-1.pdf

636-DEL-2003-Form-18-(17-09-2008).pdf

636-del-2003-form-18.pdf

636-DEL-2003-Form-2-(17-09-2008).pdf

636-del-2003-form-2.pdf

636-DEL-2003-Form-3-(17-09-2008).pdf

636-del-2003-form-3.pdf