Title of Invention	A PROCESS OF MANUFACTURING INORGANIC-ORGANIC HYDRID SOL AND USEFUL AS SCRATCH RESISTANT POLYCARBONATE SHEETS AND LENSES AND OTHER RELATED PLASTICS
Abstract	In the present invention a process for the manufacture of inorganic-organic hybrid sols suitable for scratch resistant coating deposition up to SO days on polycarbonate sheets and lenses have been disclosed. The sol is prepared from tetraethylorthosilicate (TEOS), 3-glycidoxypropyltrimethoxysilane (GLYMO), 3-methacryloxypropyltrimethoxysilane (MEMO) and p-tolune sulphonic acid (PTSA) modified boemite nanoparticles dispersed in butanol-methanol mixture. Hydrolysis and condensation reactions form inorganic polymeric networks like Si-0-Si and Al-O-Si. Epoxy groups of GLYMO is polymerised in the sol stage in presence of an initiator 1-methyl imidazole. One UV photo initiator (Benzoyl peroxide or 1-hydroxy-cyclohexyl-phenyl-ketone) is mixed with the sol to help the methacrylate polymerization during UV curing of the coating. The concentrated so! (viscosity in the range 18 to 32 cps) is used for coating deposition. Scratch resistant coatings of thickness 5 to 8 µm thick can be deposited on polycarbonate sheets and lenses by dip-coating techniqque. The sol after 90 days of ageing (viscous sol having viscosity in the range of 32 cps <viscosity<65 cps) can be reused for coating deposition after dilution with mother solvent.

Title of Invention

A PROCESS OF MANUFACTURING INORGANIC-ORGANIC HYDRID SOL AND USEFUL AS SCRATCH RESISTANT POLYCARBONATE SHEETS AND LENSES AND OTHER RELATED PLASTICS

Abstract

In the present invention a process for the manufacture of inorganic-organic hybrid sols suitable for scratch resistant coating deposition up to SO days on polycarbonate sheets and lenses have been disclosed. The sol is prepared from tetraethylorthosilicate (TEOS), 3-glycidoxypropyltrimethoxysilane (GLYMO), 3-methacryloxypropyltrimethoxysilane (MEMO) and p-tolune sulphonic acid (PTSA) modified boemite nanoparticles dispersed in butanol-methanol mixture. Hydrolysis and condensation reactions form inorganic polymeric networks like Si-0-Si and Al-O-Si. Epoxy groups of GLYMO is polymerised in the sol stage in presence of an initiator 1-methyl imidazole. One UV photo initiator (Benzoyl peroxide or 1-hydroxy-cyclohexyl-phenyl-ketone) is mixed with the sol to help the methacrylate polymerization during UV curing of the coating. The concentrated so! (viscosity in the range 18 to 32 cps) is used for coating deposition. Scratch resistant coatings of thickness 5 to 8 µm thick can be deposited on polycarbonate sheets and lenses by dip-coating techniqque. The sol after 90 days of ageing (viscous sol having viscosity in the range of 32 cps <viscosity<65 cps) can be reused for coating deposition after dilution with mother solvent.

Full Text	The present invention relates to a process of manufacturing inorganic-organic hybrid sol and sol coated scratch resistant polycarbonate sheets and lenses and other related plastics. The present invention particularly relates to a method of manufacturing inorganic-organic hybrid sols useful for providing scratch resistant hard coatings on plastics such as over the surfaces of polycarbonate sheets and ophthalmic lenses and other related plastic materials to improve the durability and optical properties. Transparent polycarbonate organic glasses and other related plastic materials are promising materials for optical applications. Some important properties are: (i) excellent clarity; (ii) complete ultra violet (UV) cut off; and (iii) can withstand much greater impact than glass, that is virtually unbreakable. Such qualities offer a lot of industrial applications of polycarbonates and presently glasses, including ophthalmic glasses, are being replaced by transparent plastics, such as polycarbonates, polyallyl bicarbonate. One of the main disadvantages of these plastics is that they are not scratch resistant to the requisite degree, as a result the optical properties deteriorate very quickly due to surface damage. In particular, in Indian atmosphere this problem seems to be severe due to dust and smoke pollution. Scratch-resistant coating of these plastics with hard materials seems to be a means to overcome this hurdle. The scratch-resistant film coated plastics can be utilized as substitute of glass windows for domestic, railway compartments and other related applications. Present literature shows that some sol-gel hybrid materials exhibit abrasion resistance in addition to optical clarity. Schmidt and co-workers have reported thick films of organically modified silica (ORMOSILS) on polycarbonate substrates as a abrasion resistant coatings. Reference may be made to the work of: (i) H. Schmidt, B. Seiferling, G. Philipp, K. Deichmann, in Ultrastructure Processing of Advanced Ceramics, III, eds. J. D. Mackenzie, D. R. Ulrich, Wiley, New York, 1988, p 651. (ii) H. Schmidt, G. Rinn, R. Mass and D. Sporn, in Better Ceramics Through Chemistry III, eds. C. J. Brinker and D. R. Ulrich Mat. Res. Soc., Pittsburgh, Pa, 1988, p 743. (iii) R. Mass, E. Arpac, W. Glaubitt, H. Schmidt, J. Non-Cryst. Solids 1990, 727, 370; H. Schmidt, J. Non-Cryst. Solids, 1994, 778, 302). These films were prepared by a combination of silicon alkoxide like tetraethyl orthosilicate (TEOS) and epoxy functional group containing organic chain bonded with silicon alkoxides like 3-glycidoxypropyl-trimethoxysilane (GLYMO). They cured the coatings at temperatures in the range of 120° and 130°C for 3 hours, which are not suitable for PC because softening temperature of PC is close to 120°C and yellowing of PC also results. Etiente et al also reported preparation of coatings from similar systems and also containing colloidal silica. They also used relatively high temperature (100°C) and time (3h) to cure the coatings. They mainly reported the tribological properties after deposition of coatings. In the above articles nothing related to the stability of the sol is discussed which is essential for commercial exploitation. Wang and Wilkes reported the preparation method of high abrasion resistant coatings using inorganic-organic hybrids comprising trialkoxysilane containing organic component and Ti- or Zr-alkoxides. Reference may be made to B. Wang and G.L. Wilkes, 'high abrasion resistant coating materials from organic/inorganic hybrid materials by the sol-gel method' US patent no. 5,316,855 May 31, 1994. The curing temperature (150°C) used in this process is rather high. Abrasion resistant coatings derived from UV-curable organic monomer group such as acrylic, methacrylic, bonded with alkoxy silane, such as 3-methacryloxypropyl-trimethoxysilane also known as MEMO, 3-acryloxypropyltrimethoxysilane, and colloidal silica have been disclosed by R.H. Chung in US patent no. 4,348,462, September 1982, titled 'Abrasion resistant ultraviolet light curable hard coating compositions'. In US patent no. 5,086,087, February 4, 1992, A. Tosko Misev, have dicclosed 'a composition containing UV curable unsaturated monomers and/or oligomers, a photoinitiator and colloidal silica with an oragnosilane compound, and the application of this composition in coatings'. The main disadvantage of these works is poor adhesibility of the coatings with polycarbonate substrates and a primer coat prior to this coating is necessary. Furthermore no data regarding the stability of these sols with respect to time is reported. Schmidt and co-workers have developed boehmite nanoparticle incorporated inorganic-organic hybrids, such as epoxy-silica-boehmite or methacrylate-silica-boehmite, to enhance the scratch resistant property of the coatings. Reference may be made to: (a) H.K. Schmidt, J. Sol-Gel Sci. and Tech. 1997, 8, 557; S. Sepeur, N. Kunze, B. Werner, H. Schmidt, In Coatings on Glass 1998. (b) Pulkar, H.; Schmidt, H.; Aegerter, M. A. Eds. Proc. 2nd International Conference on Coatings on Glass, 1998 (Saarbruecken, Germany) pp 319-322. (c) H. K. Schmidt, E. Geiter, M. Mennig, H. Krug, C. Becker R.-P. Winkler, J. Sol-Gel Sci. and Technol., 1998, 13, 397. (d) M. Mennig, P. W. Oliveira H. Schmidt, In Coatings on Glass 1998. (e) Pulkar, H.; Schmidt, H.; Aegerter, M. A. Eds. Proc. 2nd International Conference on Coatings on Glass, 1998 (Saarbruecken, Germany) pp 328-332. (f) Schmidt, H. K.; Geiter, E.; Mennig, M.; Krug, H.; Becker C.; Winkler, R.-P. J. Sol-Gel Sci. and Technol., 1998, 13, 397. (g) Mennig, M., Oliveira P. W.; Schmidt, H. In Coatings on Glass 1998. Pulkar, H.; Schmidt, H.; Aegerter, M. A. Eds. Proc. 2nd International Conference on Coatings on Glass, 1998 pp 328-332. In these works also no data regarding the stability of the sols with respect to time is reported. They have introduced boehmite nanoparticles stabilised with acetic acid and these are easily dispersable in acid-water but not in organic solvents. So there is every possibility of enhancment of the viscosity of the sol with time and sol will become unusable in a shorter period of time. In one of the references the authors pointed out formation of pasty solids during incorporation of large amount boehmite nanoparticles. In another work Schmidt pointed out that a curing temperature in the range 130-150°C is necessary for obtaining ultra hard coatings, which is not at all suitable for PC substrates. Therefore, the main drawbacks of the hitherto known prior art processes are: (i) The curing temperature is on the higher side. (ii) The 'epoxy-silica1, 'epoxy-silica-boehmite1 or 'methacrylate-silica-boehmite1 systems used by different workers could not control the polymerization reactions and as a result the viscosity of the sol will increase with time and the sol will become unusable in a shorter period of time. (iii) The boehmite particles stabilised with acetic acid are easily dispersible in acid-water but not in organic solvents. This leads to increase the viscosity of the sol due to presence of more water. (iv) There is virtually no data available in the literature about the stability of the sol with respect to time and the range of viscosity usable for depositing transparent and good quality optical coatings on PC. This is absolutely necessary for commercial purpose. (v) Whether the sol is suitable for optical grade coating preparation on large substrates. (vi) Whether the viscous sol (after attaining viscosity beyond the limit of coating preparation) can be reused after any treatment. From the above referred prior art, it is clear that there is a definite need for providing a process of making scratch resistant coating on polycarbonate sheets and lenses and other related plastics. The main object of the present invention is to provide a process of manufacturing inorganic-organic hybrid sol and sol coated scratch resistant polycarbonate sheets and lenses and other related plastics, which obviates the drawbacks of the hitherto known prior art as referred and described herein above. Another object of the present invention is to provide a process of manufacturing inorganic-organic hybrid sols having long shelf life of the order of 90 days and good quality scratch resistant coatings on polycarbonate sheets and lenses and other related plastics. Yet another object of the present invention is to provide a process wherein the viscous sol (unusable for coating) can be made reusable after proper dilution with suitable organic solvents. Still another object of the present invention is to improve the composite structure of the coating by using dual organic functionalities epoxy and methacrylate. Still yet another object of the present invention is to use modified boehmite particles, which is easily dispersible in organic solvents. A further object of the present invention is to prepare hard scratch resistant coating on polycarbonate sheets and lenses. A still further object of the present invention is to control the yellowing effect of the cured coating to a minimum level. A yet further object of the present invention is to increase the optical transmission of the coated polycarbonate. In the present invention there is provided a process of manufacturing inorganic-organic hybrid coating sol having longer shelf life, suitable for deposition of scratch resistant coatings on polycarbonate (PC) sheets and lenses. Polycarbonate lenses and large sized sheets can be coated with these sols by dip-coating technique. Scratch resistant protective coatings with an improvement of surface quality and increase of optical transmission can be obtained after oven drying and UV curing of the above coated polycarbonate substrates. In the present invention a process for the manufacture of inorganic-organic hybrid sols suitable for scratch resistant coating deposition up to 90 days on polycarbonate sheets and lenses have been disclosed. The sol is prepared in the present invention from tetraethylorthosilicate (TEOS), 3-glycidoxypropyltrimethoxysilane (GLYMO), 3-methacryloxypropyltrimethoxysilane (MEMO) and p-tolune sulphonic acid (PTSA) modified boemite nanoparticles dispersed in butanol-methanol mixture. Hydrolysis and condensation reactions form inorganic polymeric networks like Si-O-Si and Al-O-Si. Epoxy groups of GLYMO is polymerised in the sol stage in presence of an initiator 1-methyl imidazole. One UV photo initiator (Benzoyl peroxide or 1-hydroxy-cyclohexyl-phenyl-ketone) is mixed with the sol to help the methacrylate polymerization during UV curing of the coating. The concentrated sol (viscosity in the range 18 to 32 cps) is used for coating deposition. Scratch resistant coatings of thickness 5 to 8 (im thick can be deposited on polycarbonate sheets and lenses by dip-coating techniqque. The sol after 90 days of ageing (viscous sol having viscosity in the range of 32 cps Accordingly the present invention provides a process of manufacturing inorganic-organic hybrid sol useful as scratch resistant coating on polycarbonate sheets and lenses and other related plastics, which comprises: (a) mixing 15 to 20 wt% boehmite powder in organic solvent by known methods to obtain a boehmite-dispersion; (b) heating the dispersion at a temperature in the range of 55 to 65°C in closed condition for 10 to 15 hours; (c) mixing 50 to 75% of total boehmite dispersion so obtained with 2.3 to 2.4 mol 3-(glycidoxypropyl)trimethoxysilane (GLYMO) and 1 mol tetraethyl orthosilicate (TEOS), adding 3.5 to 4 mol water mixed with catalytic amount of HCI of the order of 3.2 to 3.5 x 10"4 mol HCI per alkoxy group, under stirring to obtain a hydrolyzed product; (d) mixing 0.7 to 0.8 mol 3-(methacryloxy-propyl)trimethoxy silane (MEMO) and the balance, 50 to 25%, of the said total boehmite dispersion to obtain a sol; (e) mixing the sol obtained in step (c) to the said hydrolyzed product obtained in step (b) to obtain a resultant sol; (f) adding to the resultant sol 4 to 3.5 mol water mixed with catalytic amount of HCI of the order of 5.0 to 6.0 x 10"4 mol HCI per alkoxy group with respect to MEMO, under stirring to obtain further hydrolyzed product; (g) adding methyl imidazole of the order of 0.05 to 0.1 mol per mol of GLYMO, followed by adding a ultra-violet (UV) photo polymerizing initiator, (h) heating the mixture at a temperature in the range of 50 to 70°C to obtain epoxy polymerized sol; (i) subjecting the said polymerized sol to 15 to 23 wt% evaporation of the total amount of sol to obtain concentrated sol having coating viscosity. In an embodiment of the present invention, the boehmite powder used is p-toluene sulphonic acid stabilised boehmite nanoparticles. In another embodiment of the present invention, the organic solvent used is such as methanol, n-butanol, mixture of methanol-butanol. In still another embodiment of the present invention, the boehmite-dispersion is made by known methods such as mechanical stirring with ultrasonication. In yet another embodiment of the present invention, the total boehmite concentration in the sol is maintained in the range of 1.78 to 6.45 mol. In still yet another embodiment of the present invention, the ultra-violet (UV) photo polymerizing initiator used is such as benzoyl peroxide, 0.0015 to 0.0025 mol per mole of MEMO or 1-hydroxy-cyclohexyl-phenyl-ketone, 0.05 to 0.15 wt% of the final sol. In another embodiment of the present invention, the coating sol contains 7 to 15 wt% boehmite nanoparticles. In a further embodiment of the present invention, 16 to 40 wt% boehmite nanoparticles is incorporated in the hybrid coating matrix. In a still further embodiment of the present invention, the coating contains 23 to 32 wt% silica, incorporated in the hybrid coating matrix by using inorganic-organic hybrid precursors and TEOS. In a yet further embodiment of the present invention, the coating contains 37 to 52 wt% organics such as polyethylene oxide and methacrylates, incorporated in the hybrid coating matrix by using inorganic-organic hybrid precursors. In another embodiment of the present invention, the viscosity of the sol remains within working condition, 18 to 32 cps, up to about 90 days. Accordingly the present invention provides a process of manufacturing inorganic-organic hybrid sol coated scratch resistant polycarbonate sheets and lenses and other related plastics, which comprises diluting with mother solvent, if required, the sol obtained by the process as herein above described, coating the sol onto polycarbonate sheets and lenses and other plastic substrates by known methods such as dipping, subjecting the coated substrates to oven drying at a temperature in the range of 50 to 70°C followed by ultra-violet (UV) curing of both sides and thermal curing at a temperature in the range of 80 to 90°C. In an embodiment of the present invention, the high viscosity, of the order of 32 cps In still another embodiment of the present invention, the sol coating is provided by dip-coating technique with a lifting speed of 4 to 20 cm/min. In yet another embodiment of the present invention, both surfaces of the oven dried sol coated polycarbonate is ultra-violet (UV) cured in a conveyorized UV curing machine of 5000 W, 200 to 400 nm at a conveyor speed of 0.8 to 1.5 m/min. In the process of the present invention for manufacturing inorganic-organic hybrid sol and sol coated scratch resistant polycarbonate sheets and lenses and other related plastics, the 'inorganic-organic sol-gel method1 is found to be very appropriate for providing hard coatings. The molecular level inorganic-organic hybrids from organic and inorganic polymer materials show promising applications as hard and abrasion resistant coatings on polycarbonates. 3- (glycidoxypropyl)tri-methoxysilane (GLYMO) and 3- (methacryloxypropyl)trimethoxy silane (MEMO) have been largely used as precursors for inorganic-organic hybrid sol-gel materials. Both GLYMO and MEMO have the ability to form simultaneously an inorganic network, =Si-O-Sh through hydrolysis and condensation reactions of alkoxy groups and organic network, polyethylene oxide and polymethacrylate through the polymerization of epoxy and methacrylate groups, respectively. The abrasive resistance is attributed to the Si-O-Si inorganic backbone structure of the hybrids along with the high level of organic polymer cross-linking. Incorporating boehmite nanoparticles and making chemical bonds (Al-O-Si) with silica network formed as mentioned above could increase further abrasion resistance. The inorganic-organic hybrid precursors are depicted below: (Formula Removed) The novelty of the present invention resides in providing a sol which is stable, can provide better scratch resistant coating on polycarbonate sheets and lenses with an increase of 2-3 % optical transmission. In this process two organic polymerizable groups (i.e. dual organic functionality, epoxy and methacrylate) are taken and polymerization is done in two steps for fabricating better nanocomposite with silica network and boehmite nanoparticles. First epoxy groups are polymerized in presence of methyl imidazole and boehmite at the sol stage and UV light in presence of benzoyl peroxide or irgacure-184 does methacrylate polymerization at the coating stage. Initial polymerization of epoxy groups (at the sol stage) changing the system from its original liquid state into a more viscous liquid. The methacrylate and its initiator become entrapped in the silica, boehmite and heat-polymerized polyethylene oxide network at this stage. Subsequent UV exposure of the film causes cure of the methacrylate as well as silica network leading to a final interpenetrating polymer network structure. As a result these coating materials exhibit excellent abrasion resistance and is highly promising for polycarbonates sheets and lenses. A novel feature of this process is the use of p-toluene sulphonic acid stabilised boehmite nanoparticles (Condea, Germany) which can be dispersed in large quantities in organic solvents (average particle size measured after dispersion is 51 nm) and incorporation into the sol (average particle size measured in the sol is Another novel feature of this process is that the sol viscosity can be kept in the workable region (18 to 32 cps) for 90 days while storing at ambient in closed condition because of the presence of monomeric methacrylate groups in the sol. Yet another novel feature of this process is that the sol can be reprocessed easily after storing even more than 3 months. Still another novel feature of this process is that the high viscosity (32 cps Yet another novel feature of this process is that large substrates such as sheets up to 600 mm x 600 mm and lenses can be coated easily with this boehmite nanoparticle incorporated inorganic-organic hybrid sol. Still yet another novel feature of the process is that the surface quality of the uncoated PC (if any scratch mark is already present prior to coating deposition) can be improved after deposition of coating with this sol. The non-obvious inventive steps of the present invention lie in using MEMO, along with GLYMO and boehmite nanoparticles for making the hybrid sol, the organic part of which remains monomeric form and inhibits polymerization and agglomaration of nanoparticles at an early stage thus making the sol stable. In addition to above inventive step further includes the use of dual organic functionality (epoxy and methacrylate) which causes interpenetrating polymeric network. In addition to above inventive step further includes that the use of p-toluene sulphonic acid modified boehmite nanoparticles, which causes better dispersion in organic solvents and sols. A further inventive step is the use of mother solvent mixture to dilute the aged sol (32 cps The complete description of all the process steps are given below: 1. Boehmite dispersion (15 to 20 wt%) in organic solvent, such as methanol, butanol, methanol-butanol mixture, is prepared. The dispersion was heated at a temperature in the range of 55 to 65°C in closed condition for 10 to 15 hours and used for sol preparation as described below. 2. A mixture of 3-(glycidoxypropyl)trimethoxysilane (GLYMO), tetraethyl orthosilicate (TEOS) and Boehmite (50 to 75% of the total amount) is prepared. 3. Hydrolysis and polymerization of the alkoxy groups of GLYMO and TEOS by adding HCI (catalytic amount)-H2O mixture under stirring. 4. 3-(methacryloxy-propyl)trimethoxy silane (MEMO) (full amount) and rest boehmite (50 to 25 % of the total amount) mixture is prepared and added to the above sol (3). 5. HaO-HCI (catalytic amount) mixture is added into the sol obtained to facilitate further hydrolysis reactions of MEMO originated alkoxy groups and condensation. 6. Epoxy polymerization initiator, 1-methyl imidazole is added into (5). 7. Methacrylate polymerization initiator, benzoyl peroxide or 1-hydroxy- cyclohexyl-phenyl-ketone is added to (6). 8. The above sol is kept at 50 to 70°C for epoxy polymerization. 9. The sol is concentrated by evaporating the solvents, 15 to 23% of the total amount of the sol. 10.The coating is prepared from the above sol on cleaned polycarbonate sheets by dip-coating technique (lifting speed 4 to 20 cm/min). .* 11. The coated polycarbonate is dried in the temperature range of 50 to 70°C. 12. The above coated polycarbonate (dried) is then UV cured (both surface) in a conveyorized UV curing machine (5000 W, 200-400 nm; conveyor speed: 0.8 to 1.5 m/min. 13.The UV cured-coated polycarbonate is finally cured in the temperature range of 80 to 90°C. The following examples are given as illustrations of the process of the present invention in actual practice, which should not be construed to limit the scope of the present invention. EXAMPLE -1 Boehmite nanoparticles (OS1) were dispersed in butanol-methanol (4:1 by weight) mixture under mechanical stirring and ultrasonication. 15 wt% boehmite. These dispersions were heated at 60°C in closed condition for 10 hrs and used for sol preparation as described below. 120 gm GLYMO and 45.5 gm TEOS and 240 gm of above boehmite dispersion (15 wt%) were mixed and stirred for 15 min. To this, water (10.5 gm), HCI (N/10, 8.7 gm) and methanol (12 gm) mixture was added with stirring and the stirring was continued for 2 hrs at room temperature (25±2°C). MEMO (40.8 gm) and rest amount of boehmite dispersion (79.5 gm) was mixed separately and added to the above mixture with stirring followed by water (14.5 gm)-HCI (N/10, 2.4 gm) mixture was added. Stirring was continued further for another 2 hrs. To this, methanolic solution of 1-methyl imidazole (6 gm in 12 gm methanol) was added with stirring and the mixture was stirred for 15 min. 1-hydroxy-cyclohexyl-phenyl-ketone (irgacure-184 / Ciba) (0.5 gm) dissolved in methanol (8.4 gm) was then added and stirred for another 20 min. This sol was kept at ambient in closed condition for 2 days followed by at 60°C for another 8 hrs. This as-prepared sol was then subjected to evaporation at 60°C in an air oven by making pin holes on the polyethylene sheet used as cover. In this way about 22% solvent was evaporated out and 468 gm of the required sol of viscosity about 20 cps was obtained. EXAMPLE - 2 Boehmite nanoparticles was dispersed in butanol-methanol (3.5:1 by weight) mixture under mechanical stirring and ultrasonication. 15 wt% boehmite dispersions were prepared in this way. These dispersions were heated at 65°C in closed condition for 15 hrs and used for sol preparation. 278.1 gm GLYMO (99%) and 105.2 gm TEOS (99%) and 178 gm boehmite dispersion (15 wt%) were mixed and stirred for 15 min. To this, 26.97 gm water and 4.5 gm N/10 HCI dissolved in 15 gm methanol was added with stirring and the stirring was continued for 2 hrs at room temperature (25±2°C). MEMO (96.85 gm) and rest amount of boehmite dispersion (178 gm) was mixed separately and added to the above mixture with stirring followed by a mixture of 19.77 gm water, 16.19 gm N/10 HCI and 15 gm methanol was added. Stirring was continued further for another 2 hrs. To this, methanolic solution of 1-methyl imidazole (13.65 gm in 13.2 gm methanol) was added with stirring and the mixture was stirred for 15 min. 1-hydroxy-cyclohexyl-phenyl-ketone (irgacure-184 / Ciba) (1.19 gm) dissolved in methanol (10 gm) was then added and stirred for another 20 min. This sol was kept at ambient in closed condition for 2 days followed by at 60°C for another 8 hrs. This as-prepared sol was then subjected to evaporation at 60°C in an air oven by making pin holes on the polyethylene sheet used as cover. This sol can be used for coating preparation after evaporation of solvent 16-20% by weight. The corresponding viscosity will be in the range of 20-32 cps. EXAMPLE - 3 Boehmite nanoparticles was dispersed in butanol-methanol (4:1 by weight) mixture under mechanical stirring and ultrasonication. 18 wt% boehmite dispersions was prepared in this way. The dispersions were heated at 55°C in closed condition for 15 hrs and used for sol preparation. 567.6 gm GLYMO (97%) and 212.6 gm TEOS (98%) and 840 gm boehmite dispersion (18 wt%) were mixed and stirred for 15 min. To this, 45 gm water, 34.9 gm N/10 HCI and 40 gm methanol mixture was added with stirring and the stirring was continued for 3 hrs at room temperature (25±2°C). MEMO (193.7 gm) and rest amount of boehmite dispersion (280 gm) was mixed separately and added to the above mixture with stirring followed by a mixture containing 59.9 gm water and 10 gm N/10 HCI was added. Stirring was continued further for another 3 hrs. To this, methanolic solution of 1-methyl imidazole (27.3 gm in 40 gm methanol) was added with stirring and the mixture was stirred for 30 min. 1-hydroxy-cyclohexyl-phenyl-ketone (irgacure-184 / Ciba) (2.38 gm) dissolved in methanol (26.2 gm) was then added and stirred for another 30 min. This sol was kept at ambient in closed condition for 2 days followed by at 60°C for another 10 hrs. This as-prepared sol was then subjected to evaporation at 60°C in an air oven by making pin holes on the polyethylene sheet used as cover. This sol can be used for coating preparation after subsequent evaporation of solvent (mainly methanol) for attaining the required viscosity suitable for coating. EXAMPLE - 4 Boehmite nanoparticles (OS1) was dispersed in butanol-methanol (4:1 by weight) mixture under mechanical stirring and ultrasonication. 20 wt% boehmite dispersions was prepared in this way. These dispersions were heated at 60°C in closed condition for 12 hrs and used for sol preparation. 70.85 gm TEOS (99%), 184.57 gm GLYMO (97%) and 293.3 gm boehmite dispersion (20 wt%) were mixed and stirred for 15 min. To this, a mixture of 16.06 gm water, 13.14 gm N/10 HCI and 13 gm methanol was added with stirring and the stirring was continued for 2 hrs at room temperature (25±2°C). MEMO (62.1 gm) and rest amount of boehmite dispersion (125.7 gm) was mixed separately and added to the above mixture with stirring followed by a mixture of 21.91 gm water and 3.66 gm N/10 HCI was added. Stirring was continued further for another 2 hrs. To this, methanolic solution of 1-methyl imidazole (9.07 gm in 9.5 gm methanol) was added with stirring and the mixture was stirred for 30 min. Benzoyl peroxide (0.15 gm) dissolved in minimum amount of methanol was then added and stirred for another 30 min. This sol was kept at ambient in closed condition for 2 days followed by at 60°C for another 8 hrs. This as-prepared sol was then subjected to evaporation at 50°C in a rotary evaporator. This sol was used for coating preparation after evaporation of solvent (mainly methanol) for attaining the required viscosity suitable for coating. EXAMPLE - 5 Boehmite nanoparticles (OS1) was dispersed in butanol-methanol (3.5:1 by weight) mixture under mechanical stirring and ultrasonication. 15 wt% boehmite dispersions were prepared in this way. These dispersions were heated at 60°C in closed condition for 15 hrs and used for sol preparation. 212.6 gm TEOS (98%), 565.1 gm GLYMO (97%) and 1248 gm of above boehmite dispersion (15 wt%) were mixed and stirred for 15 min. To this, 48 gm water, 38.5 gm N/10 HCI and 25 gm methanol mixture was added with stirring and the stirring was continued for 3 hrs at room temperature (25±2°C). MEMO (186.3 gm) and rest amount of boehmite dispersion (672 gm) was mixed separately and added to the above mixture with stirring followed by a mixture containing 65.7 gm water, 11 gm N/10 HCI and 25 gm methanol was added. Stirring was continued further for another 3 hrs. To this, methanolic solution of 1-methyl imidazole (27.2 gm in 25 gm methanol) was added with stirring and the mixture was stirred for 30 min. 1-hydroxy-cyclohexyl-phenyl-ketone (irgacure-184 / Ciba) (2.3 gm) dissolved in methanol (20 gm) was then added and stirred for another 30 min. This sol was kept at ambient in closed condition for 2 days followed by at 60°C for another 10 hrs. This as-prepared sol was then subjected to evaporation at a temperature 50°C to 55°C in a rotary evaporator. This sol after evaporation (18 % of total weight before evaporation) of solvent was used for coating by dipping technique. The dip-coated PC sheets and lenses can be cured by UV light and heat (90°C). EXAMPLE - 6 Boehmite nanoparticles (OS1) wes dispersed in butanol-methanol (4:1 by weight) mixture under mechanical stirring and ultrasonication. 20 wt% boehmite dispersions were prepared in this way. These dispersions were heated at 60°C in closed condition for 12 hrs and used for sol preparation. 452.12 gm GLYMO (97%), 170.1 gm TEOS (98%) and 1004 gm of above boehmite dispersion (20 wt%) were mixed and stirred for 15 min. To this, 35.05 gm water and 28.69 gm N/10 HCI dissolved in 25 gm methanol was added with stirring and the stirring was continued for 3 hrs at room temperature (25±2°C). MEMO (149.04 gm) and rest amount of boehmite dispersion (430.4 gm) was mixed separately and added to the above mixture with stirring followed by a mixture of 47.91 gm wate.r 7.99 gm N/10 HCI and 22 gm methanol was added. Stirring was continued further for another 3 hrs. To this, methanolic solution of 1-methyl imidazole (21.76 gm in 22 gm methanol) was added with stirring and the mixture was stirred for 30 min. 1-hydroxy-cyclohexyl-phenyl-ketone (irgacure-184 / Ciba) (1.84 gm) dissolved in methanol (15 gm) was then added and stirred for another 30 min. This sol was kept at ambient in closed condition for 2 days followed by at 60°C for another 10 hrs. This as-prepared sol was then subjected to evaporation at a temperature 50°C to 55°C in a rotary evaporator. This sol after evaporation of solvent (16% of the total) was used for coating by dipping technique. The dip-coated PC sheets and lenses can be cured by UV light and heat (90°C). EXAMPLE - 7 Boehmite nanoparticles was dispersed in butanol-methanol (3.5:1 by weight) mixture under mechanical stirring and ultrasonication. 20 wt% boehmite dispersions were prepared in this way. These dispersions were heated at 55°C in closed condition for 12 hrs and used for sol preparation. 136.2 gm TEOS (98%), 370.4 gm GLYMO (97%) and 539 gm of above boehmite dispersion (20 wt%) were mixed and stirred for 15 min. To this, 58.75 gm water containing catalytic amount of HCI and methanol (25 gm) mixture was added with stirring and the stirring was continued for 2 hrs at room temperature (25±2°C). MEMO (122.1 gm) and rest amount of boehmite dispersion (179.6 gm) was mixed separately and added to the above mixture with stirring followed by water (49.1 gm) containing catalytic amount of HCI, mixed with methanol (25 gm) was added. Stirring was continued further for another 3 hrs. To this, methanolic solution of 1-methyl imidazole (17.9 gm in 25 gm methanol) was added with stirring and the mixture was stirred for 30 min. 1-hydroxy-cyclohexyl-phenyl-ketone (irgacure-184 / Ciba) (1.5 gm) dissolved in methanol (25 gm) was then added and stirred for another 30 min. This sol was kept at ambient in closed condition for 2 days followed by at 60°C for another 10 hrs. This as-prepared sol was then subjected to evaporation at 60°C in an air oven by making pin holes on the polyethylene sheet used as cover. This sol can be used for coating preparation after subsequent evaporation of solvent (mainly methanol) for attaining the required viscosity suitable for coating. EXAMPLE - 8 An aged 100 gm sol (more than 3 months old) of viscosity 39 cps was diluted with 7.5 gm butanol-methanol (1.2:1 by weight) solvent (7.5% dilution). The viscosity of the diluted sol became 23 cps and found to be useful for coating preparation for more than 60 days. This sol was used to prepare coatings on polycarbonate sheets using dip-coating technique. The coatings so obtained were dried at 60°C for 30 minutes and both side of the coatings were UV cured (5000 W mercury vapour lamp; 200W/sq. inch) with a conveyor speed of 0.8 to 1.5 m/min and finally cured at 90°C for 60 min. EXAMPLE - 9 An aged 1 00 gm sol (more than 5 months old) of viscosity about 65 cps was diluted with 10 gm butanol-methanol (1.2:1 by weight) solvent (10% dilution). The viscosity of the diluted sol became 29 cps. This sol was found to be suitable for coating preparation. This sol was used to prepare coatings on polycarbonate sheets using dip-coating technique. The coatings so obtained were dried at 60°C for 30 minutes and both side of the coatings were UV cured (5000 W mercury vapour lamp; 200W/sq. inch) with a conveyor speed of 0.8 to 1.5 m/min and finally cured at 90°C for 60 min. EXAMPLE -10 A 7.5% diluted aged 100 gm sol of viscosity 39 cps was further diluted with 7 gm butanol-methanol (1.2:1 by weight) solvent (7% dilution). This sol (viscosity 22-24 cps) was then used to prepare coatings on polycarbonate sheets using dip-coating technique. The coatings so obtained were dried at 60°C for 30 min and both side of the coatings were UV cured (5000 W mercury vapour lamp; 200W/sq. inch) with a conveyor speed of 0.8 to 1.5 m/min and finally cured at 90°C for 60 min. The resultant coatings 5 to 8 ^m in thickness were optically transparent having refractive index of 1.50 to 1.52 and showed good abrasion property. The optical transmission of the coated polycarbonate increased by 2 to 3 % compared to the uncoated substrate. The scotch tape test (following DIN 53151 specification) shows no damage of the coatings when examined under optical microscope using 100X magnification. The abrasion test of the coating was performed using US federal specification lens coating hardness tester kit in accordance with MIL-E-12397B. The abrasion test was done by rubbing the abrading head (with 2V2 Ibs of pressure) across the coated and uncoated surfaces of polycarbonate. After rubbing, the surface was examined with the profilometer. It has been observed that the uncoated polycarbonate is suffering from damage even after 1-5 times of abrasion. Whereas 20 abrasion cycles is the specification of this test. On the contrary, the coated polycarbonate showed resistance towards damage even after more than 100 times of abrasion confirming the coatings are highly abrasion resistant. The main advantages of the process of the present invention are: (i) The shelf life of sol is about 3 months (viscosity remains within 32 cps). (ii) The high viscosity (32 cps (iii) Larger substrates (e.g. sheets up to 600 mm x 600 mm) and lenses can be coated easily with this boehmite nanoparticle incorporated inorganic-organic hybrid sol. (v) The surface quality of the uncoated PC (if any scratch mark is already present prior to coating deposition) can be improved after deposition of coating with this sol. (vi) The optical transmision of the coated polycarbonate can be increased by 2 to 3%. We claim: 1. A process of manufacturing inorganic-organic hybrid sol useful as scratch resistant coating on polycarbonate sheets and lenses and other related plastics, which comprises: (a) mixing 15 to 20 wt% boehmite powder in organic solvent by known methods to obtain a boehmite-dispersion; (b) heating the dispersion at a temperature in the range of 55 to 65°C in closed condition for 10 to 15 hours; (c) mixing 50 to 75% of total boehmite dispersion so obtained with 2.3 to 2.4 mol 3-(glycidoxypropyl)trimethoxysilane (GLYMO) and 1 mol tetraethyl orthosilicate (TEOS), adding 3.5 to 4 mol water mixed with catalytic amount of HCI of the order of 3.2 to 3.5 x 10-4 mol HCI per alkoxy group, under stirring to obtain a hydrolyzed product; (d) mixing 0.7 to 0.8 mol 3-(methacryloxy-propyl)trimethoxy silane (MEMO) and the balance, 50 to 25%, of the said total boehmite dispersion to obtain a sol; (e) mixing the sol obtained in step (d) to the said hydrolyzed product obtained in step (c) to obtain a resultant sol; (f) adding to the resultant sol 4 to 3.5 mol water mixed with catalytic amount of HCI of the order of 5.0 to 6.0 x 10-4 mol HCI per alkoxy group with respect to MEMO, under stirring to obtain further hydrolyzed product; (g) adding methyl imidazole of the order of 0.05 to 0.1 mol per mol of GLYMO, followed by adding a ultra-violet (UV) photo polymerizing initiator, (h) heating the mixture at a temperature in the range of 50 to 70°C to obtain epoxy polymerized sol; (i) subjecting the said polymerized sol obtained in step (h) to 15 to 23 wt% evaporation of the total amount of sol to obtain concentrated sol; 2. A process as claimed in claim 1, wherein the boehmite powder used is p- toluene sulphonic acid stabilised boehmite nanoparticles. 3. A process as claimed in claim 1-2, wherein the organic solvent used is such as methanol, n-butanol, mixture of methanol-butanol. 4. A process as claimed in claim 1-3, wherein the boehmite-dispersion is made by known methods such as mechanical stirring with ultrasonication. 5. A process as claimed in claim 1-4, the total boehmite concentration in the sol is maintained in the range of 1.78 to 6.45 mol. 6. A process as claimed in claim 1-5, wherein the ultra-violet (UV) photo polymerizing initiator used is such as benzoyi peroxide, 0.0015 to 0.0025 mol per mole of MEMO or 1-hydroxy-cyclohexyl-phenyl-ketone, 0.05 to 0.15 wt% of the final sol. 7. A process as claimed in claims 1 to 6, wherein the high viscosity, of the order of 32 cps range of 18 to 32 cps by dilution of the order of 1 to 10% by weight with 1.2:1 by weight butanol-methanol solvent mixture. 8. A process of manufacturing inorganic-organic hybrid sol useful as scratch resistant coating on polycarbonate sheets and lenses and other related plastics, substantially as herein described with reference to the examples.

Full Text

The present invention relates to a process of manufacturing inorganic-organic hybrid sol and sol coated scratch resistant polycarbonate sheets and lenses and other related plastics.
The present invention particularly relates to a method of manufacturing inorganic-organic hybrid sols useful for providing scratch resistant hard coatings on plastics such as over the surfaces of polycarbonate sheets and ophthalmic lenses and other related plastic materials to improve the durability and optical properties.
Transparent polycarbonate organic glasses and other related plastic materials are promising materials for optical applications. Some important properties are: (i) excellent clarity; (ii) complete ultra violet (UV) cut off; and (iii) can withstand much greater impact than glass, that is virtually unbreakable. Such qualities offer a lot of industrial applications of polycarbonates and presently glasses, including ophthalmic glasses, are being replaced by transparent plastics, such as polycarbonates, polyallyl bicarbonate.
One of the main disadvantages of these plastics is that they are not scratch resistant to the requisite degree, as a result the optical properties deteriorate very quickly due to surface damage. In particular, in Indian atmosphere this problem seems to be severe due to dust and smoke pollution. Scratch-resistant coating of these plastics with hard materials seems to be a means to overcome this hurdle. The scratch-resistant film coated plastics can be utilized as substitute of glass windows for domestic, railway compartments and other related applications.
Present literature shows that some sol-gel hybrid materials exhibit abrasion resistance in addition to optical clarity. Schmidt and co-workers have reported thick films of organically modified silica (ORMOSILS) on polycarbonate substrates as a abrasion resistant coatings. Reference may be made to the work of:
(i) H. Schmidt, B. Seiferling, G. Philipp, K. Deichmann, in Ultrastructure Processing of Advanced Ceramics, III, eds. J. D. Mackenzie, D. R. Ulrich, Wiley, New York, 1988, p 651.
(ii) H. Schmidt, G. Rinn, R. Mass and D. Sporn, in Better Ceramics Through Chemistry III, eds. C. J. Brinker and D. R. Ulrich Mat. Res. Soc., Pittsburgh, Pa, 1988, p 743.
(iii) R. Mass, E. Arpac, W. Glaubitt, H. Schmidt, J. Non-Cryst. Solids 1990, 727, 370; H. Schmidt, J. Non-Cryst. Solids, 1994, 778, 302).
These films were prepared by a combination of silicon alkoxide like tetraethyl orthosilicate (TEOS) and epoxy functional group containing organic chain bonded with silicon alkoxides like 3-glycidoxypropyl-trimethoxysilane (GLYMO). They cured the coatings at temperatures in the range of 120° and 130°C for 3 hours, which are not suitable for PC because softening temperature of PC is close to 120°C and yellowing of PC also results.
Etiente et al also reported preparation of coatings from similar systems and also containing colloidal silica. They also used relatively high temperature (100°C) and time (3h) to cure the coatings. They mainly reported the tribological properties after deposition of coatings.
In the above articles nothing related to the stability of the sol is discussed which is essential for commercial exploitation.
Wang and Wilkes reported the preparation method of high abrasion resistant coatings using inorganic-organic hybrids comprising trialkoxysilane containing organic component and Ti- or Zr-alkoxides. Reference may be made to B. Wang and G.L. Wilkes, 'high abrasion resistant coating materials from organic/inorganic
hybrid materials by the sol-gel method' US patent no. 5,316,855 May 31, 1994. The curing temperature (150°C) used in this process is rather high.
Abrasion resistant coatings derived from UV-curable organic monomer group such as acrylic, methacrylic, bonded with alkoxy silane, such as 3-methacryloxypropyl-trimethoxysilane also known as MEMO, 3-acryloxypropyltrimethoxysilane, and colloidal silica have been disclosed by R.H. Chung in US patent no. 4,348,462, September 1982, titled 'Abrasion resistant ultraviolet light curable hard coating compositions'.
In US patent no. 5,086,087, February 4, 1992, A. Tosko Misev, have dicclosed 'a composition containing UV curable unsaturated monomers and/or oligomers, a photoinitiator and colloidal silica with an oragnosilane compound, and the application of this composition in coatings'.
The main disadvantage of these works is poor adhesibility of the coatings with polycarbonate substrates and a primer coat prior to this coating is necessary. Furthermore no data regarding the stability of these sols with respect to time is reported.
Schmidt and co-workers have developed boehmite nanoparticle incorporated inorganic-organic hybrids, such as epoxy-silica-boehmite or methacrylate-silica-boehmite, to enhance the scratch resistant property of the coatings. Reference may be made to:
(a) H.K. Schmidt, J. Sol-Gel Sci. and Tech. 1997, 8, 557; S. Sepeur, N.
Kunze, B. Werner, H. Schmidt, In Coatings on Glass 1998.
(b) Pulkar, H.; Schmidt, H.; Aegerter, M. A. Eds. Proc. 2nd International
Conference on Coatings on Glass, 1998 (Saarbruecken, Germany) pp
319-322.
(c) H. K. Schmidt, E. Geiter, M. Mennig, H. Krug, C. Becker R.-P. Winkler,
J. Sol-Gel Sci. and Technol., 1998, 13, 397.
(d) M. Mennig, P. W. Oliveira H. Schmidt, In Coatings on Glass 1998.
(e) Pulkar, H.; Schmidt, H.; Aegerter, M. A. Eds. Proc. 2nd International
Conference on Coatings on Glass, 1998 (Saarbruecken, Germany) pp
328-332.
(f) Schmidt, H. K.; Geiter, E.; Mennig, M.; Krug, H.; Becker C.; Winkler,
R.-P. J. Sol-Gel Sci. and Technol., 1998, 13, 397.
(g) Mennig, M., Oliveira P. W.; Schmidt, H. In Coatings on Glass 1998.
Pulkar, H.; Schmidt, H.; Aegerter, M. A. Eds. Proc. 2nd International
Conference on Coatings on Glass, 1998 pp 328-332.
In these works also no data regarding the stability of the sols with respect to time is reported. They have introduced boehmite nanoparticles stabilised with acetic acid and these are easily dispersable in acid-water but not in organic solvents. So there is every possibility of enhancment of the viscosity of the sol with time and sol will become unusable in a shorter period of time. In one of the references the authors pointed out formation of pasty solids during incorporation of large amount boehmite nanoparticles. In another work Schmidt pointed out that a curing temperature in the range 130-150°C is necessary for obtaining ultra hard coatings, which is not at all suitable for PC substrates.
Therefore, the main drawbacks of the hitherto known prior art processes are: (i) The curing temperature is on the higher side.
(ii) The 'epoxy-silica1, 'epoxy-silica-boehmite1 or 'methacrylate-silica-boehmite1 systems used by different workers could not control the polymerization reactions and as a result the viscosity of the sol will increase with time and the sol will become unusable in a shorter period of time.
(iii) The boehmite particles stabilised with acetic acid are easily dispersible in acid-water but not in organic solvents. This leads to increase the viscosity of the sol due to presence of more water.
(iv) There is virtually no data available in the literature about the stability of the sol with respect to time and the range of viscosity usable for depositing transparent and good quality optical coatings on PC. This is absolutely necessary for commercial purpose.
(v) Whether the sol is suitable for optical grade coating preparation on large substrates.
(vi) Whether the viscous sol (after attaining viscosity beyond the limit of coating preparation) can be reused after any treatment.
From the above referred prior art, it is clear that there is a definite need for providing a process of making scratch resistant coating on polycarbonate sheets and lenses and other related plastics.
The main object of the present invention is to provide a process of manufacturing inorganic-organic hybrid sol and sol coated scratch resistant polycarbonate sheets and lenses and other related plastics, which obviates the drawbacks of the hitherto known prior art as referred and described herein above.
Another object of the present invention is to provide a process of manufacturing inorganic-organic hybrid sols having long shelf life of the order of 90 days and good quality scratch resistant coatings on polycarbonate sheets and lenses and other related plastics.
Yet another object of the present invention is to provide a process wherein the viscous sol (unusable for coating) can be made reusable after proper dilution with suitable organic solvents.
Still another object of the present invention is to improve the composite structure of the coating by using dual organic functionalities epoxy and methacrylate.
Still yet another object of the present invention is to use modified boehmite particles, which is easily dispersible in organic solvents.
A further object of the present invention is to prepare hard scratch resistant coating on polycarbonate sheets and lenses.
A still further object of the present invention is to control the yellowing effect of the cured coating to a minimum level.
A yet further object of the present invention is to increase the optical transmission of the coated polycarbonate.
In the present invention there is provided a process of manufacturing inorganic-organic hybrid coating sol having longer shelf life, suitable for deposition of scratch resistant coatings on polycarbonate (PC) sheets and lenses. Polycarbonate lenses and large sized sheets can be coated with these sols by dip-coating technique. Scratch resistant protective coatings with an improvement of surface quality and increase of optical transmission can be obtained after oven drying and UV curing of the above coated polycarbonate substrates.
In the present invention a process for the manufacture of inorganic-organic hybrid sols suitable for scratch resistant coating deposition up to 90 days on polycarbonate sheets and lenses have been disclosed. The sol is prepared in the present invention from tetraethylorthosilicate (TEOS), 3-glycidoxypropyltrimethoxysilane (GLYMO), 3-methacryloxypropyltrimethoxysilane (MEMO) and p-tolune sulphonic acid (PTSA) modified boemite nanoparticles dispersed in butanol-methanol mixture. Hydrolysis and condensation reactions form inorganic polymeric networks like Si-O-Si and Al-O-Si. Epoxy groups of GLYMO is polymerised in the sol stage in presence of an initiator 1-methyl imidazole. One UV photo initiator (Benzoyl peroxide or 1-hydroxy-cyclohexyl-phenyl-ketone) is mixed with the sol to help the methacrylate polymerization during UV curing of the coating. The concentrated sol (viscosity in the range 18 to 32 cps) is used for coating deposition. Scratch resistant coatings of thickness 5 to 8 (im thick can be deposited on polycarbonate sheets and lenses by dip-coating techniqque. The sol after 90 days of ageing (viscous sol having viscosity in the range of 32 cps Accordingly the present invention provides a process of manufacturing inorganic-organic hybrid sol useful as scratch resistant coating on polycarbonate sheets and lenses and other related plastics, which comprises:
(a) mixing 15 to 20 wt% boehmite powder in organic solvent by known
methods to obtain a boehmite-dispersion;
(b) heating the dispersion at a temperature in the range of 55 to 65°C in
closed condition for 10 to 15 hours;
(c) mixing 50 to 75% of total boehmite dispersion so obtained with 2.3 to
2.4 mol 3-(glycidoxypropyl)trimethoxysilane (GLYMO) and 1 mol
tetraethyl orthosilicate (TEOS), adding 3.5 to 4 mol water mixed with
catalytic amount of HCI of the order of 3.2 to 3.5 x 10"4 mol HCI per
alkoxy group, under stirring to obtain a hydrolyzed product;
(d) mixing 0.7 to 0.8 mol 3-(methacryloxy-propyl)trimethoxy silane
(MEMO) and the balance, 50 to 25%, of the said total boehmite
dispersion to obtain a sol;
(e) mixing the sol obtained in step (c) to the said hydrolyzed product
obtained in step (b) to obtain a resultant sol;
(f) adding to the resultant sol 4 to 3.5 mol water mixed with catalytic
amount of HCI of the order of 5.0 to 6.0 x 10"4 mol HCI per alkoxy
group with respect to MEMO, under stirring to obtain further hydrolyzed
product;
(g) adding methyl imidazole of the order of 0.05 to 0.1 mol per mol of
GLYMO, followed by adding a ultra-violet (UV) photo polymerizing
initiator,
(h) heating the mixture at a temperature in the range of 50 to 70°C to obtain epoxy polymerized sol;
(i) subjecting the said polymerized sol to 15 to 23 wt% evaporation of the total amount of sol to obtain concentrated sol having coating viscosity.
In an embodiment of the present invention, the boehmite powder used is p-toluene sulphonic acid stabilised boehmite nanoparticles.
In another embodiment of the present invention, the organic solvent used is such as methanol, n-butanol, mixture of methanol-butanol.
In still another embodiment of the present invention, the boehmite-dispersion is made by known methods such as mechanical stirring with ultrasonication.
In yet another embodiment of the present invention, the total boehmite concentration in the sol is maintained in the range of 1.78 to 6.45 mol.
In still yet another embodiment of the present invention, the ultra-violet (UV) photo polymerizing initiator used is such as benzoyl peroxide, 0.0015 to 0.0025 mol per mole of MEMO or 1-hydroxy-cyclohexyl-phenyl-ketone, 0.05 to 0.15 wt% of the final sol.
In another embodiment of the present invention, the coating sol contains 7 to 15 wt% boehmite nanoparticles.
In a further embodiment of the present invention, 16 to 40 wt% boehmite nanoparticles is incorporated in the hybrid coating matrix.
In a still further embodiment of the present invention, the coating contains 23 to 32 wt% silica, incorporated in the hybrid coating matrix by using inorganic-organic hybrid precursors and TEOS.
In a yet further embodiment of the present invention, the coating contains 37 to 52 wt% organics such as polyethylene oxide and methacrylates, incorporated in the hybrid coating matrix by using inorganic-organic hybrid precursors.
In another embodiment of the present invention, the viscosity of the sol remains within working condition, 18 to 32 cps, up to about 90 days.
Accordingly the present invention provides a process of manufacturing inorganic-organic hybrid sol coated scratch resistant polycarbonate sheets and lenses and other related plastics, which comprises diluting with mother solvent, if required, the sol obtained by the process as herein above described, coating the sol onto polycarbonate sheets and lenses and other plastic substrates by known methods such as dipping, subjecting the coated substrates to oven drying at a temperature in the range of 50 to 70°C followed by ultra-violet (UV) curing of both sides and thermal curing at a temperature in the range of 80 to 90°C.
In an embodiment of the present invention, the high viscosity, of the order of 32 cps In still another embodiment of the present invention, the sol coating is provided by dip-coating technique with a lifting speed of 4 to 20 cm/min.
In yet another embodiment of the present invention, both surfaces of the oven dried sol coated polycarbonate is ultra-violet (UV) cured in a conveyorized UV
curing machine of 5000 W, 200 to 400 nm at a conveyor speed of 0.8 to 1.5 m/min.
In the process of the present invention for manufacturing inorganic-organic hybrid
sol and sol coated scratch resistant polycarbonate sheets and lenses and other
related plastics, the 'inorganic-organic sol-gel method1 is found to be very
appropriate for providing hard coatings. The molecular level inorganic-organic
hybrids from organic and inorganic polymer materials show promising
applications as hard and abrasion resistant coatings on polycarbonates. 3-
(glycidoxypropyl)tri-methoxysilane (GLYMO) and 3-
(methacryloxypropyl)trimethoxy silane (MEMO) have been largely used as precursors for inorganic-organic hybrid sol-gel materials. Both GLYMO and MEMO have the ability to form simultaneously an inorganic network, =Si-O-Sh through hydrolysis and condensation reactions of alkoxy groups and organic network, polyethylene oxide and polymethacrylate through the polymerization of epoxy and methacrylate groups, respectively. The abrasive resistance is attributed to the Si-O-Si inorganic backbone structure of the hybrids along with the high level of organic polymer cross-linking. Incorporating boehmite nanoparticles and making chemical bonds (Al-O-Si) with silica network formed as mentioned above could increase further abrasion resistance.
The inorganic-organic hybrid precursors are depicted below:
(Formula Removed)
The novelty of the present invention resides in providing a sol which is stable, can provide better scratch resistant coating on polycarbonate sheets and lenses with an increase of 2-3 % optical transmission.
In this process two organic polymerizable groups (i.e. dual organic functionality, epoxy and methacrylate) are taken and polymerization is done in two steps for fabricating better nanocomposite with silica network and boehmite nanoparticles. First epoxy groups are polymerized in presence of methyl imidazole and boehmite at the sol stage and UV light in presence of benzoyl peroxide or irgacure-184 does methacrylate polymerization at the coating stage. Initial polymerization of epoxy groups (at the sol stage) changing the system from its original liquid state into a more viscous liquid. The methacrylate and its initiator become entrapped in the silica, boehmite and heat-polymerized polyethylene oxide network at this stage. Subsequent UV exposure of the film causes cure of the methacrylate as well as silica network leading to a final interpenetrating polymer network structure. As a result these coating materials exhibit excellent abrasion resistance and is highly promising for polycarbonates sheets and lenses.
A novel feature of this process is the use of p-toluene sulphonic acid stabilised boehmite nanoparticles (Condea, Germany) which can be dispersed in large quantities in organic solvents (average particle size measured after dispersion is 51 nm) and incorporation into the sol (average particle size measured in the sol is Another novel feature of this process is that the sol viscosity can be kept in the
workable region (18 to 32 cps) for 90 days while storing at ambient in closed condition because of the presence of monomeric methacrylate groups in the sol.
Yet another novel feature of this process is that the sol can be reprocessed easily after storing even more than 3 months.
Still another novel feature of this process is that the high viscosity (32 cps Yet another novel feature of this process is that large substrates such as sheets up to 600 mm x 600 mm and lenses can be coated easily with this boehmite nanoparticle incorporated inorganic-organic hybrid sol.
Still yet another novel feature of the process is that the surface quality of the uncoated PC (if any scratch mark is already present prior to coating deposition) can be improved after deposition of coating with this sol.
The non-obvious inventive steps of the present invention lie in using MEMO, along with GLYMO and boehmite nanoparticles for making the hybrid sol, the organic part of which remains monomeric form and inhibits polymerization and agglomaration of nanoparticles at an early stage thus making the sol stable. In addition to above inventive step further includes the use of dual organic functionality (epoxy and methacrylate) which causes interpenetrating polymeric network. In addition to above inventive step further includes that the use of p-toluene sulphonic acid modified boehmite nanoparticles, which causes better dispersion in organic solvents and sols. A further inventive step is the use of mother solvent mixture to dilute the aged sol (32 cps The complete description of all the process steps are given below:
1. Boehmite dispersion (15 to 20 wt%) in organic solvent, such as
methanol, butanol, methanol-butanol mixture, is prepared. The
dispersion was heated at a temperature in the range of 55 to 65°C in
closed condition for 10 to 15 hours and used for sol preparation as
described below.
2. A mixture of 3-(glycidoxypropyl)trimethoxysilane (GLYMO), tetraethyl
orthosilicate (TEOS) and Boehmite (50 to 75% of the total amount) is
prepared.
3. Hydrolysis and polymerization of the alkoxy groups of GLYMO and
TEOS by adding HCI (catalytic amount)-H2O mixture under stirring.
4. 3-(methacryloxy-propyl)trimethoxy silane (MEMO) (full amount) and
rest boehmite (50 to 25 % of the total amount) mixture is prepared and
added to the above sol (3).
5. HaO-HCI (catalytic amount) mixture is added into the sol obtained to
facilitate further hydrolysis reactions of MEMO originated alkoxy
groups and condensation.
6. Epoxy polymerization initiator, 1-methyl imidazole is added into (5).
7. Methacrylate polymerization initiator, benzoyl peroxide or 1-hydroxy-
cyclohexyl-phenyl-ketone is added to (6).
8. The above sol is kept at 50 to 70°C for epoxy polymerization.
9. The sol is concentrated by evaporating the solvents, 15 to 23% of the total amount of the sol.
10.The coating is prepared from the above sol on cleaned polycarbonate
sheets by dip-coating technique (lifting speed 4 to 20 cm/min).
.*
11. The coated polycarbonate is dried in the temperature range of 50 to
70°C.
12. The above coated polycarbonate (dried) is then UV cured (both
surface) in a conveyorized UV curing machine (5000 W, 200-400 nm;
conveyor speed: 0.8 to 1.5 m/min.
13.The UV cured-coated polycarbonate is finally cured in the temperature range of 80 to 90°C.
The following examples are given as illustrations of the process of the present invention in actual practice, which should not be construed to limit the scope of the present invention.
EXAMPLE -1
Boehmite nanoparticles (OS1) were dispersed in butanol-methanol (4:1 by weight) mixture under mechanical stirring and ultrasonication. 15 wt% boehmite. These dispersions were heated at 60°C in closed condition for 10 hrs and used for sol preparation as described below. 120 gm GLYMO and 45.5 gm TEOS and 240 gm of above boehmite dispersion (15 wt%) were mixed and stirred for 15 min. To this, water (10.5 gm), HCI (N/10, 8.7 gm) and methanol (12 gm) mixture was added with stirring and the stirring was continued for 2 hrs at room temperature (25±2°C). MEMO (40.8 gm) and rest amount of boehmite dispersion (79.5 gm) was mixed separately and added to the above mixture with stirring
followed by water (14.5 gm)-HCI (N/10, 2.4 gm) mixture was added. Stirring was continued further for another 2 hrs. To this, methanolic solution of 1-methyl imidazole (6 gm in 12 gm methanol) was added with stirring and the mixture was stirred for 15 min. 1-hydroxy-cyclohexyl-phenyl-ketone (irgacure-184 / Ciba) (0.5 gm) dissolved in methanol (8.4 gm) was then added and stirred for another 20 min. This sol was kept at ambient in closed condition for 2 days followed by at 60°C for another 8 hrs. This as-prepared sol was then subjected to evaporation at 60°C in an air oven by making pin holes on the polyethylene sheet used as cover. In this way about 22% solvent was evaporated out and 468 gm of the required sol of viscosity about 20 cps was obtained.
EXAMPLE - 2
Boehmite nanoparticles was dispersed in butanol-methanol (3.5:1 by weight) mixture under mechanical stirring and ultrasonication. 15 wt% boehmite dispersions were prepared in this way. These dispersions were heated at 65°C in closed condition for 15 hrs and used for sol preparation. 278.1 gm GLYMO (99%) and 105.2 gm TEOS (99%) and 178 gm boehmite dispersion (15 wt%) were mixed and stirred for 15 min. To this, 26.97 gm water and 4.5 gm N/10 HCI dissolved in 15 gm methanol was added with stirring and the stirring was continued for 2 hrs at room temperature (25±2°C). MEMO (96.85 gm) and rest amount of boehmite dispersion (178 gm) was mixed separately and added to the above mixture with stirring followed by a mixture of 19.77 gm water, 16.19 gm N/10 HCI and 15 gm methanol was added. Stirring was continued further for another 2 hrs. To this, methanolic solution of 1-methyl imidazole (13.65 gm in 13.2 gm methanol) was added with stirring and the mixture was stirred for 15 min. 1-hydroxy-cyclohexyl-phenyl-ketone (irgacure-184 / Ciba) (1.19 gm) dissolved in methanol (10 gm) was then added and stirred for another 20 min. This sol was kept at ambient in closed condition for 2 days followed by at 60°C for another 8 hrs. This as-prepared sol was then subjected to evaporation at 60°C in an air oven by making pin holes on the polyethylene sheet used as
cover. This sol can be used for coating preparation after evaporation of solvent 16-20% by weight. The corresponding viscosity will be in the range of 20-32 cps.
EXAMPLE - 3
Boehmite nanoparticles was dispersed in butanol-methanol (4:1 by weight) mixture under mechanical stirring and ultrasonication. 18 wt% boehmite dispersions was prepared in this way. The dispersions were heated at 55°C in closed condition for 15 hrs and used for sol preparation. 567.6 gm GLYMO (97%) and 212.6 gm TEOS (98%) and 840 gm boehmite dispersion (18 wt%) were mixed and stirred for 15 min. To this, 45 gm water, 34.9 gm N/10 HCI and 40 gm methanol mixture was added with stirring and the stirring was continued for 3 hrs at room temperature (25±2°C). MEMO (193.7 gm) and rest amount of boehmite dispersion (280 gm) was mixed separately and added to the above mixture with stirring followed by a mixture containing 59.9 gm water and 10 gm N/10 HCI was added. Stirring was continued further for another 3 hrs. To this, methanolic solution of 1-methyl imidazole (27.3 gm in 40 gm methanol) was added with stirring and the mixture was stirred for 30 min. 1-hydroxy-cyclohexyl-phenyl-ketone (irgacure-184 / Ciba) (2.38 gm) dissolved in methanol (26.2 gm) was then added and stirred for another 30 min. This sol was kept at ambient in closed condition for 2 days followed by at 60°C for another 10 hrs. This as-prepared sol was then subjected to evaporation at 60°C in an air oven by making pin holes on the polyethylene sheet used as cover. This sol can be used for coating preparation after subsequent evaporation of solvent (mainly methanol) for attaining the required viscosity suitable for coating.
EXAMPLE - 4
Boehmite nanoparticles (OS1) was dispersed in butanol-methanol (4:1 by weight) mixture under mechanical stirring and ultrasonication. 20 wt% boehmite dispersions was prepared in this way. These dispersions were heated at 60°C in
closed condition for 12 hrs and used for sol preparation. 70.85 gm TEOS (99%), 184.57 gm GLYMO (97%) and 293.3 gm boehmite dispersion (20 wt%) were mixed and stirred for 15 min. To this, a mixture of 16.06 gm water, 13.14 gm N/10 HCI and 13 gm methanol was added with stirring and the stirring was continued for 2 hrs at room temperature (25±2°C). MEMO (62.1 gm) and rest amount of boehmite dispersion (125.7 gm) was mixed separately and added to the above mixture with stirring followed by a mixture of 21.91 gm water and 3.66 gm N/10 HCI was added. Stirring was continued further for another 2 hrs. To this, methanolic solution of 1-methyl imidazole (9.07 gm in 9.5 gm methanol) was added with stirring and the mixture was stirred for 30 min. Benzoyl peroxide (0.15 gm) dissolved in minimum amount of methanol was then added and stirred for another 30 min. This sol was kept at ambient in closed condition for 2 days followed by at 60°C for another 8 hrs. This as-prepared sol was then subjected to evaporation at 50°C in a rotary evaporator. This sol was used for coating preparation after evaporation of solvent (mainly methanol) for attaining the required viscosity suitable for coating.
EXAMPLE - 5
Boehmite nanoparticles (OS1) was dispersed in butanol-methanol (3.5:1 by weight) mixture under mechanical stirring and ultrasonication. 15 wt% boehmite dispersions were prepared in this way. These dispersions were heated at 60°C in closed condition for 15 hrs and used for sol preparation. 212.6 gm TEOS (98%), 565.1 gm GLYMO (97%) and 1248 gm of above boehmite dispersion (15 wt%) were mixed and stirred for 15 min. To this, 48 gm water, 38.5 gm N/10 HCI and 25 gm methanol mixture was added with stirring and the stirring was continued for 3 hrs at room temperature (25±2°C). MEMO (186.3 gm) and rest amount of boehmite dispersion (672 gm) was mixed separately and added to the above mixture with stirring followed by a mixture containing 65.7 gm water, 11 gm N/10 HCI and 25 gm methanol was added. Stirring was continued further for another 3 hrs. To this, methanolic solution of 1-methyl imidazole (27.2 gm in 25 gm

methanol) was added with stirring and the mixture was stirred for 30 min. 1-hydroxy-cyclohexyl-phenyl-ketone (irgacure-184 / Ciba) (2.3 gm) dissolved in methanol (20 gm) was then added and stirred for another 30 min. This sol was kept at ambient in closed condition for 2 days followed by at 60°C for another 10 hrs. This as-prepared sol was then subjected to evaporation at a temperature 50°C to 55°C in a rotary evaporator. This sol after evaporation (18 % of total weight before evaporation) of solvent was used for coating by dipping technique. The dip-coated PC sheets and lenses can be cured by UV light and heat (90°C).
EXAMPLE - 6
Boehmite nanoparticles (OS1) wes dispersed in butanol-methanol (4:1 by weight) mixture under mechanical stirring and ultrasonication. 20 wt% boehmite dispersions were prepared in this way. These dispersions were heated at 60°C in closed condition for 12 hrs and used for sol preparation. 452.12 gm GLYMO (97%), 170.1 gm TEOS (98%) and 1004 gm of above boehmite dispersion (20 wt%) were mixed and stirred for 15 min. To this, 35.05 gm water and 28.69 gm N/10 HCI dissolved in 25 gm methanol was added with stirring and the stirring was continued for 3 hrs at room temperature (25±2°C). MEMO (149.04 gm) and rest amount of boehmite dispersion (430.4 gm) was mixed separately and added to the above mixture with stirring followed by a mixture of 47.91 gm wate.r 7.99 gm N/10 HCI and 22 gm methanol was added. Stirring was continued further for another 3 hrs. To this, methanolic solution of 1-methyl imidazole (21.76 gm in 22 gm methanol) was added with stirring and the mixture was stirred for 30 min. 1-hydroxy-cyclohexyl-phenyl-ketone (irgacure-184 / Ciba) (1.84 gm) dissolved in methanol (15 gm) was then added and stirred for another 30 min. This sol was kept at ambient in closed condition for 2 days followed by at 60°C for another 10 hrs. This as-prepared sol was then subjected to evaporation at a temperature 50°C to 55°C in a rotary evaporator. This sol after evaporation of solvent (16% of the total) was used for coating by dipping technique. The dip-coated PC sheets and lenses can be cured by UV light and heat (90°C).
EXAMPLE - 7
Boehmite nanoparticles was dispersed in butanol-methanol (3.5:1 by weight) mixture under mechanical stirring and ultrasonication. 20 wt% boehmite dispersions were prepared in this way. These dispersions were heated at 55°C in closed condition for 12 hrs and used for sol preparation. 136.2 gm TEOS (98%), 370.4 gm GLYMO (97%) and 539 gm of above boehmite dispersion (20 wt%) were mixed and stirred for 15 min. To this, 58.75 gm water containing catalytic amount of HCI and methanol (25 gm) mixture was added with stirring and the stirring was continued for 2 hrs at room temperature (25±2°C). MEMO (122.1 gm) and rest amount of boehmite dispersion (179.6 gm) was mixed separately and added to the above mixture with stirring followed by water (49.1 gm) containing catalytic amount of HCI, mixed with methanol (25 gm) was added. Stirring was continued further for another 3 hrs. To this, methanolic solution of 1-methyl imidazole (17.9 gm in 25 gm methanol) was added with stirring and the mixture was stirred for 30 min. 1-hydroxy-cyclohexyl-phenyl-ketone (irgacure-184 / Ciba) (1.5 gm) dissolved in methanol (25 gm) was then added and stirred for another 30 min. This sol was kept at ambient in closed condition for 2 days followed by at 60°C for another 10 hrs. This as-prepared sol was then subjected to evaporation at 60°C in an air oven by making pin holes on the polyethylene sheet used as cover. This sol can be used for coating preparation after subsequent evaporation of solvent (mainly methanol) for attaining the required viscosity suitable for coating.
EXAMPLE - 8
An aged 100 gm sol (more than 3 months old) of viscosity 39 cps was diluted with 7.5 gm butanol-methanol (1.2:1 by weight) solvent (7.5% dilution). The viscosity of the diluted sol became 23 cps and found to be useful for coating preparation for more than 60 days. This sol was used to prepare coatings on polycarbonate sheets using dip-coating technique. The coatings so obtained
were dried at 60°C for 30 minutes and both side of the coatings were UV cured (5000 W mercury vapour lamp; 200W/sq. inch) with a conveyor speed of 0.8 to 1.5 m/min and finally cured at 90°C for 60 min.
EXAMPLE - 9
An aged 1 00 gm sol (more than 5 months old) of viscosity about 65 cps was diluted with 10 gm butanol-methanol (1.2:1 by weight) solvent (10% dilution). The viscosity of the diluted sol became 29 cps. This sol was found to be suitable for coating preparation. This sol was used to prepare coatings on polycarbonate sheets using dip-coating technique. The coatings so obtained were dried at 60°C for 30 minutes and both side of the coatings were UV cured (5000 W mercury vapour lamp; 200W/sq. inch) with a conveyor speed of 0.8 to 1.5 m/min and finally cured at 90°C for 60 min.
EXAMPLE -10
A 7.5% diluted aged 100 gm sol of viscosity 39 cps was further diluted with 7 gm butanol-methanol (1.2:1 by weight) solvent (7% dilution). This sol (viscosity 22-24 cps) was then used to prepare coatings on polycarbonate sheets using dip-coating technique. The coatings so obtained were dried at 60°C for 30 min and both side of the coatings were UV cured (5000 W mercury vapour lamp; 200W/sq. inch) with a conveyor speed of 0.8 to 1.5 m/min and finally cured at 90°C for 60 min.
The resultant coatings 5 to 8 ^m in thickness were optically transparent having refractive index of 1.50 to 1.52 and showed good abrasion property. The optical transmission of the coated polycarbonate increased by 2 to 3 % compared to the uncoated substrate. The scotch tape test (following DIN 53151 specification) shows no damage of the coatings when examined under optical microscope using 100X magnification. The abrasion test of the coating was performed using
US federal specification lens coating hardness tester kit in accordance with MIL-E-12397B. The abrasion test was done by rubbing the abrading head (with 2V2 Ibs of pressure) across the coated and uncoated surfaces of polycarbonate. After rubbing, the surface was examined with the profilometer. It has been observed that the uncoated polycarbonate is suffering from damage even after 1-5 times of abrasion. Whereas 20 abrasion cycles is the specification of this test. On the contrary, the coated polycarbonate showed resistance towards damage even after more than 100 times of abrasion confirming the coatings are highly abrasion resistant.
The main advantages of the process of the present invention are:
(i) The shelf life of sol is about 3 months (viscosity remains within 32 cps).
(ii) The high viscosity (32 cps (iii) Larger substrates (e.g. sheets up to 600 mm x 600 mm) and lenses can be coated easily with this boehmite nanoparticle incorporated inorganic-organic hybrid sol.
(v) The surface quality of the uncoated PC (if any scratch mark is already present prior to coating deposition) can be improved after deposition of coating with this sol.
(vi) The optical transmision of the coated polycarbonate can be increased by 2 to 3%.

We claim:
1. A process of manufacturing inorganic-organic hybrid sol useful as scratch resistant coating on polycarbonate sheets and lenses and other related plastics, which comprises:
(a) mixing 15 to 20 wt% boehmite powder in organic solvent by known
methods to obtain a boehmite-dispersion;
(b) heating the dispersion at a temperature in the range of 55 to 65°C in
closed condition for 10 to 15 hours;
(c) mixing 50 to 75% of total boehmite dispersion so obtained with 2.3 to
2.4 mol 3-(glycidoxypropyl)trimethoxysilane (GLYMO) and 1 mol
tetraethyl orthosilicate (TEOS), adding 3.5 to 4 mol water mixed with
catalytic amount of HCI of the order of 3.2 to 3.5 x 10-4 mol HCI per
alkoxy group, under stirring to obtain a hydrolyzed product;
(d) mixing 0.7 to 0.8 mol 3-(methacryloxy-propyl)trimethoxy silane
(MEMO) and the balance, 50 to 25%, of the said total boehmite
dispersion to obtain a sol;
(e) mixing the sol obtained in step (d) to the said hydrolyzed product
obtained in step (c) to obtain a resultant sol;
(f) adding to the resultant sol 4 to 3.5 mol water mixed with catalytic
amount of HCI of the order of 5.0 to 6.0 x 10-4 mol HCI per alkoxy
group with respect to MEMO, under stirring to obtain further hydrolyzed
product;
(g) adding methyl imidazole of the order of 0.05 to 0.1 mol per mol of GLYMO, followed by adding a ultra-violet (UV) photo polymerizing initiator,
(h) heating the mixture at a temperature in the range of 50 to 70°C to obtain epoxy polymerized sol;
(i) subjecting the said polymerized sol obtained in step (h) to 15 to 23 wt% evaporation of the total amount of sol to obtain concentrated sol;
2. A process as claimed in claim 1, wherein the boehmite powder used is p-
toluene sulphonic acid stabilised boehmite nanoparticles.
3. A process as claimed in claim 1-2, wherein the organic solvent used is such as
methanol, n-butanol, mixture of methanol-butanol.
4. A process as claimed in claim 1-3, wherein the boehmite-dispersion is made
by known methods such as mechanical stirring with ultrasonication.
5. A process as claimed in claim 1-4, the total boehmite concentration in the sol
is maintained in the range of 1.78 to 6.45 mol.

6. A process as claimed in claim 1-5, wherein the ultra-violet (UV) photo
polymerizing initiator used is such as benzoyi peroxide, 0.0015 to 0.0025 mol per
mole of MEMO or 1-hydroxy-cyclohexyl-phenyl-ketone, 0.05 to 0.15 wt% of the
final sol.
7. A process as claimed in claims 1 to 6, wherein the high viscosity, of the order
of 32 cps range of 18 to 32 cps by dilution of the order of 1 to 10% by weight with 1.2:1 by
weight butanol-methanol solvent mixture.
8. A process of manufacturing inorganic-organic hybrid sol useful as scratch resistant coating on polycarbonate sheets and lenses and other related plastics, substantially as herein described with reference to the examples.

Documents:

744-del-2003-abstract.pdf

744-del-2003-claims.pdf

744-del-2003-correspondence-others.pdf

744-del-2003-correspondence-po.pdf

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

744-del-2003-form-1.pdf

744-del-2003-form-19.pdf

744-del-2003-form-2.pdf

744-del-2003-form-3.pdf

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Patent Number

228274

Indian Patent Application Number

744/DEL/2003

PG Journal Number

40/2007

Publication Date

05-Oct-2007

Grant Date

09-Mar-2007

Date of Filing

29-May-2003

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	GOUTAM DE	CENTRAL GLASS & CERAMIC RESEARCH INSFTITUTE, KOLKATA-700032, INDIA.
2	DEBTOSH KUNDU	CENTRAL GLASS & CERAMIC RESEARCH INSFTITUTE, KOLKATA-700032, INDIA.
3	SAMAR KUMAR MEDDA	CENTRAL GLASS & CERAMIC RESEARCH INSFTITUTE, KOLKATA-700032, INDIA.

PCT International Classification Number

B32B 09/04

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA