Title of Invention

A PROCESS FOR PREPARATION OF A TRANSPARENT AMORPHOUS AIO(OH) 0.2H2O GLASS

Abstract

A transparent amorphous AlO(OH).(H2Oglass having transparency from 75 to 95% , preferably 85 to 95 % with or without doping with rare-earth or other metal cations and a process of preparing the same. The transparent amorphous AlO(OH). (H2Oglass having purity of 99.5 to 99.9%, preferably 99.9%. The process involves providing surface treated Al-metal having highly reactive nascent Al; hydrolysis of the surface treated Al-metal to provide AlO(OH). (H2O in gel form; heating in the temperature range of 75 to 95°C, preferably 80 to 90°C to a homogenous viscous mass followed by quenching .

Full Text

1A- The field of the invention : The present invention relates to the transparent AlO(OH)-0.2 H2O glass in monolithic and /SM. doped forms with transition or rare-earth metal cations and a process of preparing the same. The said glass has transparency of 75 to 95%, preferably from 85 to 95%:The said glass has purity of 99.5 to 99.9%, preferably 99.9%. Such glass with or without doping and their derivatives are useful for inkjet labeling, surface coating, medicines, biomaterials, catalysts, and structural, optical and electronic devices. Background and Prior Art: AlO(OH)0.2 H2O is an important precursor for preparation of alumina and alumina /SM. ceramics for advanced catalysts, coatings, and structural or electronic devices. As such it is used in medicines, biomaterials, inkjet labeling {Japanese patent, Hei 08-230342 (1996)} and coated paper for photography {US Patent 5,472,773 (1995)}. It transforms to Al2O3 on heating at temperature as low as 500 K. Several Al2O3 polymorphs occur on heating at higher temperatures as per the initial rnicrostructure. The metastable polymorphs of a controlled microstructure with a controlled porosity in a mesoporous structure obtained at low temperatures offer new applications of surface catalysts, coatings, gas sensor and optical sensors (especially after doping of Cr3+ and other transition or rare-earth metal cations). A significant strength useful for structural applications develops in corundum structure on heating at high temperature ~ 1500 K. ]n the inkjet recording system, an inkjet labeling is used which can be obtained if a transparent plastic film is utilized as the tape substrate material and a highly transparent material is used as the ink-receptive layer. Due to its good inkjet ink absorption and superior color retention nature, this glass can be used as ink-receptive layer in the inkjet recording system. 0 •> AlO(OH)0.2 H2O has a layered structure with adjacent layers being bound by hydrogen /SM. bonds. Derivative of Al2O3 occurs on heating it at temperature as low as 250°C in air. It lies in several polymorphs depending on the final temperature. The Al2O3 polymorphs derived with a controlled porosity in a mesoporous structure at low temperatures offer new applications of surface catalysts, catalyst carriers, filters, acoustic materials, insulators, 2 thin coatings, high -temperature gas-separation and reactors, gas or optical sensors (especially after doping of Cr +, Eu3+ or other transition or rare-earth metal cations R3+). A significant mechanical strength useful for structural applications develops in corundum structure on heating at high temperature - 1250°C or above. The nature, purity, particle size, and calcination history of A1O(OH) 0.2 H2O precursor determine the characteristics and / sinterability in the final derivatives. Sol gel and several other methods are used to synthesize AlO(OH).0.2 H2O and derivatives.. / SM. The sol-gel method uses an aluminum alkoxide to perform the gelation in an amorphous structure. In this method, the reaction is performed with nonaqueous solution(s). Obviously, this is too expensive for mass scale production of A1O(OH)-0.2 H2O and /8M * derivatives in industries. Both the alkoxide as well as the solvents involved are toxic. Moreover, it never gives a stable transparent bulk amorphous glass. None of these methods gives a transparent bulk amorphous gel or glass with a pure AlO(OH).0.2 H2O. A doping of / SM. transition or rare-earth metal cations is used to improve the properties of microhardness, chemical inertness, and others. A chemical process that initiates with a solution leads to formation of a high-energy amorphous structure of precursor with a greater molecular mixing of ingredients. It prevents the elements from phase separation before the decomposition into a metastable product. Hence, a need remains for a low cost manufacturing of a transparent AlO (OH)0.2 H2O glass, which is stable up to temperature of 100oC. It can be resolved with a small doping of Cr3+, Eu3+ or other similar additives with a simple hydrolysis reaction in water at room temperature. Objects of the Invention: The basic object of the present invention is to provide a transparent amorphous AlO(OH)0.2 H2O glass with a transparency of 75 to 95 % and preferably 85 to 95 %. /SM 3 Another object is to provide a transparent amorphous A1O(OH)0.2H2O glass which is /SM highly pure, with purity from 99.5 to 99.9 %, preferably 99.9% useful for optical sensors, catalysts, surface coating, phosphors and other applications. A further object of the present invention is to provide a transparent amorphous A1O(OH)0.2H2O glass doped with additives which is stable up to a temperature of 100°C. /SM. Another object of the present invention is to provide a simple and cost effective process for synthesizing modified organic polymers or composites with metal cations and derivatives more particularly preparation of transparent amorphous AlO(OH)0.2H2O glass / SM, with or without doping with additives. A further object of the present invention is to provide a process for preparation of a transparent amorphous AlO(OH)0.2H2O glass with or without doping which is a very /8a' convenient, simple and economic when compared with the conventional sol-gel or other methods used to synthesize AlO(OH)0.2 H2O and derivatives and the final product is ' obtained in a fewer steps as shown in the Schematic representation. Another object of the present invention is to provide a process for preparation of a transparent amorphous A1O(OH)0.2 H2O glass with or without doping which deals with /sm reaction in water, which is one of the cheapest solvents and is easily available in plenty of amounts, environmental friendly and overall it is nontoxic in nature no additional reagent is used during the reaction. A further object of the present invention is to provide a process for preparation of a transparent amorphous AlO(OH)0.2H2O glass with or without doping which is a very /sm convenient and simple method and needs a very small amount of dopants to induce optical and other useful properties in doped AlO(OH)0.2H2O or derivatives in a /SM. homogeneous structure. ummary of the Invention : Thus according to one aspect of the present invention there is provided a transparent amorphous AlO(OH)0.2 H2O glass having transparency from 75 to 95%, preferably, 85 to /SM. 95%. According to a further aspect there is provided a transparent amorphous AIO(OH)0.2 H2O /SM glass having a purity of 99.5 to 99.9%, preferably 99.9%. According to another aspect of the present invention there is provided a transparent amorphous AlO(OH).jA;H2O glass doped with transition and rare earth metal additives. H** D a According to a further aspect of the present invention there is provided a process for preparation of transparent amorphous AlO(OH).dx,H2Oglass having a transparency from 75 to 95%, preferably 85 to 95% comprising the steps of: (i) providing surface treated Al-metal having highly reactive nascent Al; (ii) hydrolysis of the surface treated Al-metal to provide AJO(OH).ytH2O in gel form; (iii) heating in the temperature range of 75 to 95°C, preferably 80 to 90°C to a homogenous viscous mass followed by quenching . According to a further aspect of the present invention there is provided a process for preparation of transparent amorphous AlO(OH).^tH2Oglass additionally comprising / ' doping with additives during the step of hydrolysis. Detailed Description of the Invention 5 The said transparent amorphous AlO(OH)0.2 H2Oglass with or without doping provides a /SM high degree of transparency and stability. The process of preparation the said glass is by simple reaction of hydrolysis of Al-metal in an acidic water at low temperature which is cost effective. The small doping of Cr3+ or rare-earth cations R3+ is used during the reaction to add optical properties in the final glass and also promotes formation and stability of the glass. The additives for doping the transparent amorphous AlO(OH)0.2H2Oglass are selected from Cr+3, Eu+3, Tb+3,La+3 and other transition and rare earth metal cations in amount of 0.01-5 mol %, preferably 1 to 2 mol % and in the concentration of 0.01 to 0.5, preferably, 0.1 to 0.4M. The said transparent amorphous AlO(OH).AH2Oglass with or without doping have a /SM. stability up to a temperature of 80 to 100°C, preferably 100°C. It decomposes to Al2O3 on heating to temperature of 250 to 350°C , preferably 250-300°C. The surface treated Al-metal having highly reactive nascent Al used in the said process of preparation of the transparent amorphous AIO(OH)0.2H2Oglass with or without doping is provided by (i) treating the surface of Al-metal with dilute Hydrochloric acid of concentration 0.02 to 1.0, preferably 0.05-0.1 M in water (ii) treating of the Al -metal from step (i) with Hg+2 ions preferably obtained fromHgCl2 in aqueous solution of concentration 0.05 to 0.5M , preferably 0.1-0.3M Hydrolysis of the surface treated Al-metal is carried out with Hydrochloric acid in water at a concentration of 0.5 to 2.0, preferably 1.0 to 2.0 N at a temperature of 0 to 10, preferably 1-5 °C for 1-2 hours when polycondensation in a polymer structure of desired glass takes place. 6 The doping is carried out during hydrolysis with additives selected from Cr+3, Eu+3, Tb+3,La+3 and other transition and rare earth metal cations. The additives used are in amount of 0.01 to 5.0 mol %, preferably 1.0 to 2.0 mol%. The concentration of the additives used is from 0.01 to 0.5, preferably 0.1 to 0.4M The polymer structure obtained after polycondensation is heated to 75 to 95 , preferably 80 to 90°C to form a viscous mass. It is then quenched at room temperature. Scheme of preparation of the transparent AlO(OH)0.2 H2O glass with doping /SH As shown schematically below, the method of the present invention includes the steps of (a) taking an Al-metal and refreshing its surface by reaction with 0.05 to 0.10 N dilute HC1 acid in water and surface treatment of the refreshed Al-metal surface with an aqueous HgCl2 solution of 0.1 to 0.3 M concentration, and then (b) immersing the specimen of the Al-metal after step (a) in an acid water to perform the hydrolysis reaction. The doping of Cr3+ or R3+ cations is made through the aqueous salt solutions during the hydrolysis of the Al-metal in step (b). The reaction in cold water or solution at 1 to 5°C promotes the A1-hydrolysis into a hydrolyzed product of A1O(OH)0.2H2O followed by polycondensation in a polymer structure of desired glass. Finally (c ) heating and quenching of the glass. 7 AIO(OH)0.2H2O glass (Transparent) Schematic representation of the formation of a transparent bulk AlO(OH)0.2H2O glass with doping 8 The as-received Al-metal, as usual, has a spontaneous surface oxide layer. That prevents reaction of the Al-metal surface covered in it if put in H2O at an elevated temperature. In order to remove it, the sample of a thin Al-metal foil is thoroughly washed in distilled water and then treated with 0.05 to 0.1 M HCl in water for 10 to 20 min followed by washing repeatedly in water. It yields cleaned surfaces, which still have part of oxide surface layers sufficient to prevent the reaction. A further refined metal surface to allow the reaction is obtained by treating with Hg -cations. In this process, the specimen with refreshed surfaces is dipped in an aqueous Hg2+ solution (0.1 to 0.3 M) for 1 to 2 min and then rinsed in distilled water followed by in oxalic acid to remove excess Hg cations. This yields highly reactive nascent Al-metal surfaces. A self-induced hydrolysis reaction occurs of Al-metal when put in water. The reaction is done with occasional stirring at 1 to 5°C temperatures. Addition of drops of HC1 acid promotes the reaction in acidic water. The reaction occurs the best at 1 to 2 N HC1 in water. An exothermic reaction occurs with formation of the product of AlO(OH)0.2H2O in form of a gel, which is dispersed in the water. After the reaction, the specimen is heated at 80-90°C (by stirring with a magnetic stirrer) to a homogeneous viscous mass, which then poured and quenched in form of a transparent glass in a plastic mold at room temperature in air. As mentioned above, the use of foreign additives (through aqueous solution) during the hydrolysis uniformly distribute in the final structure in a doped glass in a similar method of the reaction followed by quenching by a viscous state. X-ray diffraction confirms amorphous structure in the virgin and doped A1O(OH)-&H2O glasses with different additives. /f H'- 0% The invention will now be described with reference to following illustrative non limiting examples.. 9 Example-1 : The hydrolysis reaction of Al-metal was carried out by reaction with H2O molecules in an acidic water at 1 to 5°C temperature. The acidic water had an average concentration of 1 to 2 N HC1 in a batch of 250 ml water. Al-metal foils of 0.3 to 1.0 mm of thickness (30 mm width and 40 to 50 mm lengths) are used. These were added in a total of 5 to 10 g of mass in the 250 ml batch of water. The A1O(OH)0.2H2O product, obtained after 1 to 2 h of the reaction, is heated at 80-90°C to a viscous mass and then poured and quenched at room temperature. The obtained specimen is a transparent AlO(OH)0.2H2O glass. It is stable in /8M this form unless heating above 100°C in air. Thermal decomposition and transformation to Al2O3 occurs on heating at 250°C or above. The data regarding transparency , stability, purity are provided in Table 1. Example-2 : The reaction in example-1 was repealed with an additive of 0.01 to 5.0 mol % of Cr6+ cations in the acidic water at 1 to 5°C temperature. An aqueous (NH4)2Cr2O7 solution, 0.2 to 1.0 M concentration, was used to provide Cr6+ cations in predetermined amounts during the hydrolysis of Al-metal foils by reaction with H2O molecules. As analyzed with optical absorption studies, the reaction occurred with a change of the oxidation state of Cr6+ ® Cr3+ cations. Product of AlO(OH)0.2H2O doped with Cr3+ cations formed in 1 to 2 h of /SM. reaction at this temperature. In subsequent step, the product with the water is heated at 80-90°C to form a transparent viscous Cr3+: A1O(OH)0.2H2O glass, which is then poured and / quenched at room temperature. This yielded a transparent Cr3+:AlO(OH)0.2H2O glass of /SM characteristic light yellowish-green colour depending on the Cr3+ content. Bulk glasses of different compositions of 0.01 to 5.0 mol % Cr3+were prepared in shape of plates or discs in thickness of 2 to 50 mm. All glasses formed with different amount of Cr additives in had a high quality of 90 to 95% transparency in amorphous structure unless heating above 100°C in air. The data regarding transparency , stability, purity are provided in Table 1. 10 Example-3 : In this example the Al-hydrolysis reaction in example-1 was carried out with addition of EuCl3-6H2O to the acidic water. An aqueous EuCl3-6H2O solution of 0.1 to 0.4 M initial concentration was used. During the reaction process, the dispersed Eu3+ cations in the solution arrange in a polymer network structure with Al3+ cations, resulting in a transparent glass of Eu :AlO(OH)0.2H2O after heating and casting from an adequately /SM viscous state as in the above examples. Several batches of the reactions were carried out by varying the initial concentration of EuCl3-6H2O solution according to the predetermined level of Eu3+ doping in the final product of the glass. A high quality of 90 to 95% transparency occurs in amorphous structure unless heating above 100°C in air. The data regarding transparency , stability, purity are provided in Table 1. Example-4 : Several batches of the reactions were carried out of Al-hydrolysis by varying the additives of the rare-earth cations of La3+, Dy, or Tb3+ in aqueous RCI36H2O solution (of 0.1 to 0.4 M initial concentration) at 1 to 5°C temperatures. The content of the additives was varied in the 0.01 to 5 mol % range. This had been adjusted with the RCl3-6H2O concentration in the final precursor solution. It is found that the additives La+3,Dy,Tb+support formation of R3+:A1O(OH)^H2O in a transparent colourless bulk amorphous glass . The data regarding transparency , stability, purity are provided in Table 1. Table 1 Example Transparency Purity Stability Decomposition to A12O3 1.A1O(OH)0.2H2O 85 to95% 99.5 to 99.9 % 100°C ~250°C 2. AlO(OH)0.2H2O with 0.01 to 5 mol % Cr3+ 75 to85% 99.5 to 99.9 % 100°C ~ 300°C 3. AlO(OH)0.2 H2O with 0.01 to 5 mol % Eu3+ 85 to95% 99.5 to 99.9 % 100°C ~ 300°C SM 11 4. A1O(OH)0.2H2O with 0.01 to 5 mol % Tb3+ 85 to95% 99.5 to 99.9 % 100°C - 300°C A1O(OH)0.2H2O with 0.01 to 5 mol % La3+ 85 to95% 99.5 to 99.9 % 100°C ~ 300°C The final temperature of stability or decomposition depends on the content of the additives. Thus the AIO(OH)0.2H2O glass as produced in the present invention is highly pure, with / purity in the range of 99.5 to 99.9 %, preferably 99.9% useful for optical sensors, catalysts, surface coating, phosphors and other applications. It maintains the transparency of 75 to 95% preferably 85 to 95% up to temperature of 100°C.The process of the present invention is a very convenient, simple and economic when compared with the conventional sol-gel or other methods used to synthesize A1O(OH)0.2H2O and derivatives and the final product is obtained in a fewer steps. The /SM process deals with reaction in water, which is one of the cheapest solvents and is easily available in plenty of amounts, and overall it is nontoxic in nature. The present process may have other applications of synthesizing modified organic polymers or composites with metal cations and derivatives. This is the subject of immense interest to develop new hybrid materials for structural, optical and electronic applications. The process is environmentally friendly and no additional reagent is used during the reaction. It is a very convenient and simple method and needs a very small amount of dopants to induce optical and other useful properties in doped AlO(OH)0.2H2O or derivatives in a /SM homogeneous structure. WE CLAIM 3. A process for preparation of transparent amorphous A1O(OH)0.2H2Oglass having a transparency from 75 to 95%, preferably 85 to 95% comprising the steps of: (i) providing surface treated A1-metal having highly reactive nascent Al; (ii) hydrolysis of the surface treated Al-metal to provide A1O(OH)(.aH2O in gel form (iii) heating in the temperature range of 75 to 95oC, preferably 80 to 90oC to a homogenous viscous mass followed by quenching . A process as claimed in claim 1 additionally comprising doping with additives during hydrolysis. A process as claimed in any one of claims 1 to 2 wherein providing surface treated Al-metal having highly reactive nascent Al is carried out following the steps of: (i) treating the surface of Al-metal with dilute Hydrochloric acid of concentration 0,02 to 1.0, preferably 0.05-0.1 M in water (ii) treating of the Al -metal from step (i) with Hg+2 ions preferably obtained fromHgCl2 in aqueous solution of eoncentration 0.05 to 0.5M, preferably 0.1-0.3M 4. A process as claimed in any one of claims 1 to 3 wherein hydrolysis is carried out with Hydrochloric acid in water 5. A process as claimed in claim 4 wherein the concentration of hydrochloric acid in water is 0.5 to 10, preferably 1.0 to 2.0 N 13 6. A process as claimed in any one of claims 1 to 5 wherein the hydrolysis is carried on at a temperature of 0 to 10°C, preferably 1-5 °C. 7. A process as claimed in claims 1 to 6 wherein hydrolysis is carried on for 1-2 hours when polycondensation in a polymer structure of desired glass takes place. 8 A process as claimed in claims 1 to 7 wherein doping is carried out with additives selected from Cr+3, Eu+3, Tb+3,La+3 and other transition and rare earth metal cations. 9 A process as claimed in claims 1 to 8 wherein doping is carried out with additives in amount of 0.01 to 5.0 mol %, preferably 1.0 to 2.0 mol%. 10 A process as claimed in claims 1 to 8 wherein doping is carried out with additives in concentration of 0.01 to 0.5 M, preferably 0.1 to 0.4M 11 A process as claimed in claims 1 to 10 wherein quenching is carried out at 1 room temperature. 12 A process for preparation of transparent amorphous AlO(OH)0.2H2O glass having a transparency from 75 to 95%, preferably 85 to 95% with or without doping substantially as herein described and illustrated with reference to the Examples 1-4 Dated this 19th day of May, 2003 A transparent amorphous AlO(OH).(H2Oglass having transparency from 75 to 95% , preferably 85 to 95 % with or without doping with rare-earth or other metal cations and a process of preparing the same. The transparent amorphous AlO(OH). (H2Oglass having purity of 99.5 to 99.9%, preferably 99.9%. The process involves providing surface treated Al-metal having highly reactive nascent Al; hydrolysis of the surface treated Al-metal to provide AlO(OH). (H2O in gel form; heating in the temperature range of 75 to 95°C, preferably 80 to 90°C to a homogenous viscous mass followed by quenching .

Documents:

00269-kol-2003-abstract.pdf

00269-kol-2003-claims.pdf

00269-kol-2003-correspondence.pdf

00269-kol-2003-description(complete).pdf

00269-kol-2003-form-1.pdf

00269-kol-2003-form-18.pdf

00269-kol-2003-form-2.pdf

00269-kol-2003-form-3.pdf

00269-kol-2003-pa.pdf

269-KOL-2003-FORM-27.pdf

269-kol-2003-granted-abstract.pdf

269-kol-2003-granted-claims.pdf

269-kol-2003-granted-correspondence.pdf

269-kol-2003-granted-description (complete).pdf

269-kol-2003-granted-examination report.pdf

269-kol-2003-granted-form 1.pdf

269-kol-2003-granted-form 18.pdf

269-kol-2003-granted-form 2.pdf

269-kol-2003-granted-form 3.pdf

269-kol-2003-granted-letter patent.pdf

269-kol-2003-granted-pa.pdf

269-kol-2003-granted-reply to examination report.pdf

269-kol-2003-granted-specification.pdf