Title of Invention

A PROCESS FOR MANUFACTURE OF SYMMETRIC MICRO-FILTRATION (MF) ALUMINA TUBULAR MEMBRANES

Abstract

The present invention relates to a method for manufacture of alumina ceramic tubular symmetric micro-filtration (MF) single or multi-channeled membranes with versatility in geometry / profile i.e., single or multi-channeled hollow or any other profile and variable physical dimensions e.g., length, internal diameter (ID), outer diameter (OD), channeled-diameter (CD) etc., with consistent pore size, porosity, mechanical strength and chemical stability. The derived membranes possess superior mechanical strength (minimum value of modulus of rupture, MOR 60 MPa), high chemical stability (pH resistance 0 - 14) and good thermal stability as well. The MF membranes according to the invention is applied in filtration / separation process covering the entire micro-filtration (MF) range and more specifically, in the range of 1 -2 micrometer (micron) with counter porosity, more specifically in the range of 30 - 50 volume % could be made. Properties of the derived membranes are characterized, tested and validated by standard laboratory techniques. The derived symmetric membranes are perm-selective with respect to the size of the species to be filtered and can be used for the selective separation / filtration of a desired substance from a raw.

Full Text

-2- FIELD OF THE INVENTION Tha present invention is related to the fabrication of single / multi-channeled micro-filtration (MF) ceramic tubular membranes, which can be adapted for variety of purposes / applications, in particular to the fluid / suspension filtration / separation technologies. More particularly, the present invention is related to manufacture of a ceramic-based membrane formed by methodology for fabricating tubular-type alumina symmetric membranes with pore size covering the entire micro-filtration (MF) rartge and more specifically, in the range of 1-2 micrometer (micron) with counter superior mechanical strength and high chemical stability. Precisely, the concept of the disclosed alumina Ceramic-based membrane system provides, a guideline to fabricate tubular symmetric membranes in a large spectrum of micro-filtration (MF) range, besides the defined pore size range of 1-2 micron, by various modified combinations of the chemical constituents and also by altering / substituting the chemical constituents by similar materials/s or group of materials therein. -3- BACKGROUND OF THE INVENTION WITH PRIOR STATE OF ART DIFFICULTIES Membrane-based processes are known for numerous applications, each with its own driving force and separation characteristics. Pressure-driven filtration processes, e.g. micro-, ultra- and nano-filtration, reverse osmosis; concentration driven processes, e.g. gas separation, pervaporation, dialysis; temperature driven processes, e.g. membrane distillation; electrically driven processes, e.g. electrodialysis. The key property that is exploited in membrane filtration / separation process is the ability of the membrane to permeate selectively. Indeed, approximately 60 - 75 % of synthetic polymer membranes are today employed as semi-permeable barrier layers. Organic / Polymeric membranes have numerous advantages like flexibility to fabricate in the form of fibers, tubes and sheets. However they have great limitations like, they are susceptible to biodegradation (organic ones), have relatively short shelf and operating life, less resistant to organic solvents, chlorines, and extreme pH conditions and poor .4- mechanical strength. In order to overcome the above-mentioned disadvantages, there was long-felt need of industry need to develop new membrane materials, which can overcome the disadvantages of the polymeric / organic membranes, and at the same time, it should provide similar advantages to that of the polymer / organic membranes. During the past few decades, ceramic membranes have been receiving greater attention to the manufacturers because of their advantages over polymeric / organic and metallic membranes. Compared to polymer-based membranes, ceramic membranes exhibit unquestionable advantages, essentially due to their inherit properties. They can withstand high temperatures, high pressure (>100 bar), abrasion, and chemical attack, which makes them a very good materials for applications in harsh and extreme environments. Besides, disposal of ceramic membranes do not pose any threat to environment. Recent studies have showed that ceramic membranes exhibit high stability against microbiological attack. Generally, they are stable up to 1000° C, which enable them for high- temperature applications and thereby permitting sterilization operation in biochemical applications. Ceramic membranes can weH tolerate chemical / mechanical cleaning, can readily accommodate the abrasion -5- encountered in slurries, and resist the build up at high pressure operations (up to 30 atm) when cleaned by using back-flushing techniques. Ceramic membranes have excellent reliability and long operating life. There is no structural deformation even under a wide range of operating conditions at high pressures. Moreover, a well-developed production technology could provide membranes with high permeability and desired pore size. Due to the stringent operating conditions (wide pH range, repeated vapor sterilization, organic solvents, and temperatures up to 500°C) several industries have thought to immensely benefit from ceramic membranes in the field of wastewater treatment, effluent treatment, water for power plants, pre-filtration for reverse osmosis (RO) systems, agro-foodstuffs industries, biotechnology, biomedicine, paper industries, textile, and petroleum industries. Some membranes, which have been commercialized recently, have, unequivocally, longer life under harsh industrial conditions and their industrial use have shown a good degree of reliability in several applications. In some cases, the lifespan of membranes is greater than five years and have also significantly decreased the cost of maintenance in industrial facilities. -6- However, even though the basic principles and methodology of ceramic membrane processing have already been understood, tailoring / monitoring pore size and pore connectivity, uniformity in physical dimensions (variations in diameter across the length) of the tubular membranes are still a major task to accomplish. Besides, the improvement in mechanical strength and good surface finish despite allowing the MF membrane to possess a high porosity level is also a major task. In this context, the present invention proposes to provide a manufacturing method to produce micro-filtration (MF) single / multi-channeled alumina ceramic membranes with defined pore size and superior mechanical strength. Many investigators have been previously pursued the preparation of ceramic membranes. Hay et al. in U.S. Patent No. 4,968,426 describes the procedure of preparation of strong and durable alpha phase alumina ultrafiltration membranes by seeding boehmite sols, and further coating on the support with a thin layer of gel to obtain a final pore size of less than about 500 nm. The preparation of membranes by sol gel technology as disclosed by Mori et al. in U.S. Patent No. 4,770,908 describes a procedure of membrane preparation by disposing a layer -7- of alumina sol on a porous membrane formed by hydrolyzing an alcoholate or a chelate of alumina followed by drying and burning thereof. Anderson, Marc A et al. conducted significant work on preparation of membrane by various procedures EP No. 0537944B1, U.S. Patent No. 5,006,248, U.S. Patent No. 5,096,745, U.S. Patent No. 5,104,539, U.S. Patent No. 5,169,576, US. Patent No. 5,194,200, U.S. Patent No. 5,208,190, U.S. Patent No. 5,215,943, U.S. Patent No. 5,610,109, U.S. Patent No. 5,712,037, and was able to create a stable, transparent metal oxide ceramic membrane, particularly alumina, titanium, and silica based with a narrow pore size distribution and with pore diameter manipulable in the range of 5-100 A. All those inventions were based on preparation of membranes using sol-gel or improved sol-gel techniques using different precursors. The same group also invented the procedure (U.S. Pat. No. 5,268,101) of preparing combine alumina and silica membranes having high surface area, small pore size with high temperature stability. Various other investigators like, Van T Veen et al U.S. Patent No. 5,089,299, Maier U.S. Patent No. 5,250,184, Nishio et al. U.S. Patent No. 5,250,242, de Jong et al. U.S. Patent No. 5,407,703, Chen et al. U.S. Patent No. 6, 165, 553, describes the method of creating membranes suing sol-gel techniques. -8- Liu et al. in U.S. Patent No. 5,645/891, describes the method of preparation of mesoporous ceramic membranes by inserting a substrate into the reaction chamber at pressure and thereby allowing the deposition of nucleates on the substrate leading to the formation of a membrane layer therein. Yet in the same patent, the group discloses one more method of preparation of ceramic membranes by placing a substrate between two solutions permitting the formation of membrane on the surface by or within the pores of the porous substrate. Webster et al. in U.S. Patent No. 5,269,926 has disclosed the creation of supported microporous membranes by placing a porous support on one side in a colloidal suspension and drying the other side by exposing it to the drying stream of air or a reactive gas stream so that the particle are deposited on the drying side as membrane. Shimai et al. in U.S. Patent No. 5,405,529 describes yet another method of preparing ceramic filter consisting of bone like structure using ceramic-slurring foaming techniques. -9- Bartton et al. in U.S. Patent No. 5,935,440 discloses process for treating membrane comprising a film of crystalline ceramic zeo-type material which process comprises treating the membrane with a silicic acid and or a polysilicic acid or a mixture of both. Takahashi et al. in U.S. Patent No. 6,007,800 investigated on preparation of ceramic porous membrane and ceramic filter by the deposition of titania form titania slurry (1-70 % by weight) on the surface on the porous substrate followed by thermally treating the membrane at 100-300° C in an aqueous vapor phase environment. Herrmann et al. in U.S. Patent No. 6,309, 546 discloses various examples of preparing the micro and ultra pore membrane with controlled pore size like, single membrane layer by immersing the substrate in a solution of desired metal (dip coating) followed by sintering to remove organic binder (double dip coating), two layer graded membrane by dip coating, tape casting, screen printing, and finally two layer hybrid membrane on a metallic substrate via spin coating. -10- Fain, Sr, et al, in U.S. Patent No. 6,649, 255 reports the unexpected invention, a process for controlling the ultimate pore size of a fine-pored inorganic membrane, particularly chosen from the group of alumina, zirconia, titania, silica alumina / silica mixtures, can be achieved by depositing one monolayer at a time of an inorganic compound where the layer thickness approximately equals to the size of the molecule, such as metal oxide, metal nitride or the pore walls of the inorganic membrane followed subsequently by drying the membrane. Pliner et al in U.S. Patent No. 6,528,214 presented yet another method of preparing inorganic membranes by suspending the mixture of fine and coarse particles in a liquid to form a slurring followed by poring the prepared slurry into a mould such as one made up of "Plaster of Paris" thereby obtaining green intermediate product and finally baking, firing or sintering the green intermediate so as to obtain a finished membranes having a density distribution of fine particles that increases in one direction (surface in use) across the finished membrane and a density distribution of the coarse particles that decreases in the same direction across the finished membrane. -11- The method of preparation of ceramic filters or membranes by sol-gel, tape casting methods is believed to suffer from the disadvantage like higher chances for cracks formation on the membrane surface during the binder burn-off and sintering due to large shrinkage ratio between the film and the substrate. Presence of even small cracks, crevices can have a remarkable deleterious effect on the performance of membranes and can render them substantially little value in many operations. This is because in many separation operations the effect of defects is essentially to provide a channel where the un-separated products can pass through. S. Roy et al in Indian Patent Application No. 169/KOL/06 dated 24.2.2006 has disclosed the fabrication method of high-alumina disc MF membranes covering the pore size broadly in the range of 0.3 - 2.0 micron by using bi-modal alumina powders with magnesium / calcium alumino-silicate glass along with graphite powder (spherical morphology) as pore formers in the composition. The above invention primarily addresses disc-based alumina ceramic membranes, which is fabricated using uni-axial pressing technique and no attempts were made to fabricate tubular membranes. -12- Though there are different methods reported to produce tubular-type ceramic membranes, e.g. slurry slip casting, gel casting, extrusion etc, the methodology along with the chemical composition / formulations used in each case vary largely from case to case. In this context, the present invention discloses a ceramic-based membrane system with novel fabrication technique for the manufacturing of defect-free alumina ceramic (in particular alpha phase of alumina) tubular symmetric membranes with versatility in geometry / shape / profile (19-channeled, 7- channeled and single-channeled / hollow or any other kind) and physical dimensions (variable Internal Diameter (ID), Outer Diameter (OD), Channel Diameter (CD) length) having uniform pore size in the micrometer (micron) with superior mechanical strength (minimum) valve of modulus of rupture MOR 60 (Mpa), thermal (≤ 700° C) and chemical stability (chemically stable in the pH range of 0-14) by combinations of the supplied raw material constituents / formulations or by altering / substituting the raw materials by similar group of materials. -13- DESCRIPTION OF THE INVENTION One objective of the present invention is to develop a ceramic-based membrane system comprising of particular combination of various ceramic raw materials and its additives by a manufacturing process for producing micro-filtration (MF) alumina ceramic symmetric tubular membranes at different levels of pore size in the entire MF range and more specifically, in the range of 1-2 micron with a counter porosity, more specifically, in the range of 30-50 volume % by extrusion technique and by adjusting the same base composition. Another objective of the present invention is to fabricate tubular alumina MF symmetric membranes with a variety of i) geometry / profile (19-channeled, 7- channelled and single-channeled or hollow, or any other kind) and ii) physical dimensions like OD, ID, CD length with uniform pore size, more specifically in the range of 1-2 micron, iii) superior mechanical strength (minimum MOR 60 Mpa), iv) high chemical stability (pH resistance in the range of 0-14) and good thermal stability of the derived membranes. -14- Yet another objective of the invention is to propose the methodologies adopted in the course of manufacturing process and thereby employing all optimized steps to fabricate single / multi-channeled tubular alumina MF symmetric membranes in an efficient and predictable manner. A still another objective of the present invention is to define various process parameters critically in each step for producing the above alumina MF membranes and thereafter characterizing and validating them, which are very significant for the continuous and beneficial production of the process. A further objective of the invention is to provide a fabrication method for generating reproducible and reliable alumina-based tubular symmetric membranes for its applications in various filtration / separation processes. A still further objective of the present invention is to provide single / multi- channeled alumina MF symmetric membrane tubular base supports for generating ultra-filtration (UF), nano-filtration (NF), reverse osmosis (RO) membranes by applying additional ceramic / polymer layer/s on the MF tubes thereby generating the said UF, NF and RO membranes, which has great applications in different areas of separation/ purification technologies. -15- A still further yet another objective of the invention is to provide novel features, advantages and applications of the present invention as set forth in the description and Tables enumerating these according to the proposed invention on utilizing appropriate instrumentations. SUMMARY OF THE INVENTION The present invention provides a ceramic-based membrane system comprising particular combination of various ceramic raw materials and its additives by a manufacturing process to produce micro-filtration (MF) aluminium oxide (alumina) ceramic tubular symmetric membranes at different levels of pore size in the entire MF range and more specifically, in the range of 1-2 micron with a counter porosity, more specifically, in the range of 30 - 50 volume % with versatility in profile / geometry and physical dimensions, superior mechanical strengrth (minimum MOR value 60 Mpa), excellent chemical (pH resistance in the range of 0-14) and thermal stability as well ( ≥ 700° C ), by tailoring the same base composition or by altering / substituting the raw materials in the base composition by similar group of material/s. -16- According to the invention there is provided a process for manufacture of symmetric micro-filtratfon (MF) alumina tubular membranes comprising the steps of: mixing / milling a batch composition in a ball mill with alumina or other balls for a period of 30 to 60 hours the batch composition in % weight consisting of: raw materials e.g., alumina powder 1 of 47.7 ± 5 % with chemical purity: > 99 %, mean particle size - D 50: 3.5 ± 0.5 micron, specific surface area - 0.85 + 0.2 m2 / g; alumina powder 2 of 25.7 + 3 % with chemical purity: > 99 %, mean particle size - D50: 0.4 + 0.1 micron, specific surface area: 8.6 ± 2.0 m2 / g; pore former, graphite powder of 24.3 ± 3 % with chemical purity : > 99 %, mean particle size, D50: 10 + 3 micron, specific surface area : 7.0 ± 3 m2 / g, particle si2e, morphology: spherical; inorganic additives magnesium / calcium alumino silicate glass of 1.50 ±1.0 %; magnesium oxide of 0.4 + 0.2 %; organic additives sodium stearate of 0.3 ± 0.2 %; sieving the milled raw materials through a 100 - 200 mesh nylon / sieve, after segregating the alumina balls to form a homogenous batch; preparing a dough / paste by mixing in a zigma blade mixture or zigma kneader or similar machine the homogenous batch with an aqueous binder carboxy methyl cellulose (CMC) - 1250 ± 50 ml or any other binder and a plastlcizer polyethylene glycol (PEG) or any other kind -70+10 -17- ml; degassing / deairing the dough; extruding the degassed dough in a preformed multichanneled die fitted with hydraulic extruder to form green tubes; drying the green tubes in two consecutive steps of natural drying in ambient conditions at 15-45° C to result semi dried green tubes and then oven drying at 65 - 120° C; firing / sintering the dried green tubes at 1530 - 1600° C in air / oxygen, furnace cooling to 100 - 200° C and further cooling down the sintered tubes in ambient condition and; characterization and validation of the sintered tubes to ensure the properties and quality of the produced membrane tubes in respect of bulk density, volume porosity, minimum modulus of rupture and pore size, chemical (pH resistance), thermal stability, microstructure, surface texture, dear water (distilled water) flux and 100 % yeast rejection tests using yeast- Contaminated feeds at various trans-membrane pressures. The present invention discloses a ceramic-based membrane system comprising particular combination of various ceramic raw materials and its additives and further describes the entire manufacturing process for fabrication of single / multi-channeled tubular-type ceramic symmetric membranes with versatility in i) profile / geometry (19-channeled, 7-channeled and single-channeled or hollow or -18- any other kind) and ii) physical dimensions (variable length, CD, OD, ID etc) using alpha phase of alumina material and its additives that generates defined pore diameter covering micro-filtration (MF) range and in particular to the range of 1 - 2 micron with porosity, more specifically, in the range of 30 - 45 volume % in the derived membranes. The geometry / profile of the membranes could further be versatile and this invention does not restrict to fabricate any kind of geometry / profile or shapes in the membranes by using the same base composition. The proposed invention will be better understood from the following description with reference to the accompanying drawings in which: Figure 1 represents pore size profile of 19-channeled alumina symmetric MF membranes mean pore diameter. figure 2 represents typical clean water (distilled water) flux of the 19-channeled alumina tubular symmetric membranes with pore size of 1.14 micron, porosity ~ 35 volume % at different levels of trans-membrane pressure (TMP). -19- Figure 3 represents pore size profile of 19-channeled alumina symmetric membranes mean pore diameter 1.27 micrometer. Figure 4 represents typical clean water (distilled water) flux of the 7-channeled alumina tubular symmetric membranes with pore size of 1.27 micron, porosity ~ 37 volume % at different levels of trans-membrane pressure (TMP). Figure 5 represents pore size profile of 19-channeled tubular alumina symmetric membranes mean pore diamter 1.5 micron. Figure 6 represents typical clean water flux for 19-channeled alumina symmetric membranes with a pore size in the range of 1.5 micron with porosity of in the range of ~ 41 volume % at different trans-membrane pressure (TMP). -20- Figure 7 represents process flow chart for manufacturing of MF tubular symmetric alumina membranes. Figure 8 represents schematic diagram for loading pattern of green tubes during drying / firing steps (one example). Alumina powders with different particle size distribution but with similar physical and chemical properties along with other additive materials those used as binders, plasticizers, sintering agent, grain growth inhibitor, pore former etc as used in the prior art, were used as the starting raw materials. The typical constituents of the raw materials and its proportion thereby constitute the membrane system in which by altering the chemical constituents in the disclosed membrane system, different ceramic membrane with different levels of pore size, porosity and mechanical strength could be fabricated (Table 3). In general, the fabrication process starts with homogenization / milling operation for a mixing period about 30 - 60 hours using predetermined quantities of the said raw materials and alumina balls as homogenizing / milling media in nylon / metallic / ceramic pots or similar kind of containers using a pot mill or ball mill machine. -21- The time for homogenizing / milling operation would depend on the quantity of the balls used as media as well as the efficiency of the ball mill machine. Alumina balls are used in order to avoid contamination in the batch composition and materials those come out of friction / wear of the media would only be alumina which would not effect in a alumina-base composition. However, any type of balls belonging to different material/s other than alumina could also be used, provided the media does not give rise any contamination to the batch composition. Due to similar reasons, nylon pots are used, however other inert material like Teflon pots or even pots with any base material lined with alumina could also be used. By keeping the batch size fixed, higher quantity of balls and higher RPM of the ball mill machine reduces the homogenizing / milling time drastically to reach similar level of homogeneity in the batch. After the homogenizing / milling operation is over, the alumina balls from the pot are segregated and the resultant homogenized powder is collected and sieved using 100 - 200 mesh nylon / stainless steel sieves. -22- The said homogenized powder is then mixed with an organic binder and plasticizer using a zigma blade mixer/zigma kneader or similar machine, wherein an extrudable dough is prepared. For this purpose, the homogenized powder is first mixed thoroughly with an aqueous solution of carboxy methyl cellulose (CMC) binder inside the cavity of the zigma blade kneader and the plasticizer(Polyethelene glycol, PEG) in prescribed quantity is to be added about 10-20 minutes before the mixing process is ended. Other than the CMC, any kind of binder could also be used to prepare an extrudable dough, since the binder takes the advantage of the ceramic composition plastic. Another organic additive, so-called the plasticizer, PEG, makes the dough soft and improves its flow properties under pressure and hence other kind of plasticizers could also be used. At the end of the dough preparation step, the moisture level of the dough is to be brought in the range of 20.0 ± 3 wt.%. As the dough may contain certain volume of entrapped gases/air during the dough preparation step, the entrapped gases are to be removed prior extrusion, which is carried out by a so-called de-gassing/de-airing step. Hence, degassing/de-airing of the dough is carried out by keeping the dough inside the -23- cavity of the extruder under pressure and then holding the RAM for some time (2 -3 mins, the time may vary from cases to case) and then extruding the dough into the form of tubes using a suitable die, depending on the requirements in physical dimension (length, outer diameter, internal diameter, channel diameter) and versatility in geometry ( 19-channeled, 7-channeled, single-channeled, hollow or any other type) of the membrane tubes. Such an extrusion operation is done either in horizontal or vertical mode of extrusion depending on the conveniences in the extrusion set-up. The process of manufacture of MF tubular symmetric Alumina membranes can be understood from the flow chart as outlined in Figure 7. During the extrusion, the extruded tubes are to be launched / received into some objects. Normally, semi-circled pipes or V-shaped channels made out of plastic or metals (SS, brush) are used as launching / receiving channels / pads for the green tubes. It is obvious that diameter of the semi-circled pipes need to be kept slightly more than the diameter of the green tubes to be extruded so that self-guiding of the green tubes takes place during extrusion process. In case of V-shaped channels, an appropriate internal angle of the V-shaped channels is to -24- be made in a way that self-guidance of the green tubes during the extrusion takes place. The surface finish of the launching / receiving pads / channels is extremely important, as bad surface finish can retard the smooth flow of the green tubes into the pads besides damaging the straightness and the surface finish of the green tubes. Application of any oil-based lubricant on the surface of the semi-circles launching pipes further guides the extruded green tubes to move forward smoothly during the extrusion process. An alcoholic / acetone solution of stearic acid could be used as a lubricant for this purpose as well, besides usage of numerous other lubricants for this purpose as well. During extrusion, compaction of the dough occurs by redistribution of the de-gassed dough into a closed packed array. The internal mechanical pressure usually aids in this redistribution and the binder / plasticisers in the dough provides cohesion and flow of the dough. The green tubes are to be dried, which is carried out in two consecutive steps. The first step here is called 'Natural Drying', by which the green tubes are exposed under ambient conditions (humidity: 60 - 90 % Temperature 15 - 45° C) for a period in the range of 6 -12 hours resulting semi-dried green tubes. -25- The second step of drying here is so-called 'Oven Drying', by which the semi- dried tubes are kept in electrical / gas fired or microwave or similar oven/s at a temperature in the range of 65 - 120° C for a period of 10 - 24 hours and at the end of this step, the moisture level of the tubes comes down to a level in the range of 1.0 ±_0.5 %. The atmospheric condition during the natural drying process and also the temperature or humidity level even during the oven drying process could vary largely from case to case. Loading pattern (style of laying out) of the green tubes during the drying process is important. For natural drying, the green tubes are laid horizontally on a flat glass surface (or similar) using metallic / polymeric / glass support tubes / rods (straight) aside each tube across-the length of the tube and thereby allowed to leave the tubes as it is, under open atmosphere for natural drying (See Figure 8). The metallic / polymeric / glass supports are inserted in between the tubes to maintain the straightness of the green tubes and to prevent any possible warpage / bending during the natural drying process. Hence, the straightness of the support metallic / polymeric / glass tubes / rods is also very important. The outer diameter of the support tubes / rods needs to be slightly bigger to that of -26- the OD of the membrane tubes, so that the membrane tubes are supported completely across the diameter. As the moisture escapes from the surface of the green tube, stress may generate in any portion of the tubes - the green tubes are thus vulnerable to bending. Hence, insertion of metallic / polymeric / glass rods / tubes in between the green tubes helps to maintain the straightness of he green tubes. Any other type of support rods / tubes could be used for this purpose or even different types of loading pattern could be adopted. After the above natural drying step, the resultant green tubes, by then, have acquired some strength and called semi-dried green tubes. For further drying, the semi-dried green tubes to be placed horizontally on a glass surface along with the said supports in the same fashion to that of the natural drying in an oven (electrical, gas-fired or microwave) maintaining a set temperature in the range of 65 - 120° C for a period in the range of 10 - 24 hours in air. Apart form the insertion of support tubes across the length, additional supports on the top of the surface across the diameter are also to be inserted in every three to six inches of the length. The weight of such supports should be such that a proper contact between the surfaces of both the support and the membrane -27- tubes has been taken place and at the same time, there is no damage in the physical structure of the tubes. Here also, the loading pattern of the semi-dried green tubes could vary from case to case. The next step in the manufacturing process is firing / sintering in which the dried green tubes are to be fired in order to get sintered membrane tubes with desired properties. The sintering/firing of the dried tubes is to be carried out at a set temperature in the range of 1530 - 1600° C with a soaking of about two hours at the firing temperature in air/oxygen using a suitable refractory-lined kiln/furnace maintaining typical firing schedule in each case. The firing temperature, firing schedule, atmosphere and furnaces/kilns could vary largely from case to case. Lower firing temperature would yield larger pores with higher porosity and lower mechanical strength and vice versa. Loading style/pattern of the tubes during the sintering process in the kiln is important, as the straightness of the articles during the firing process may effect largely depending on the loading style adopted thereby. Prior loading the articles, the tubes need to be cleaned with compressed air, in order to remove any loosely-held dust particles those might have been accumulated during handling stage. In the present invention, the -28- tubes have been loaded both in horizontal and vertical fashion/mode. After the firing cycle is completed, the fired tubes are off-loaded from the furnace, after the temperature of the furnace is cooled down to 200° C or below. The next step is characterization and testing of the tubes, which are carried out to ensure the properties and quality of the derived membrane tubes. The sintered tubes showed a bulk density in the range of 1.90 - 2.40 ± 0.2 g / cc, porosity - 30 - 50 volume %, modulus of rupture minimum of 60 MPa and a pore size of in the range of 1 - 2 micron, depending on the batch composition and other processing parameters followed in the manufacturing process. All the tubes showed excellent stability towards pH ranges 0-14 and also good thermal stability up to ≥ 700° C. The machine, processing equipment and characterization techniques employed in this invention may vary from case to case. The process flow diagram of the manufacturing process is furnished in the Figure 7. -29- The final step is to measure the flux of the derived membranes at different trans- membrane pressures (TMP) in cross flow mode using clean water (distilled water) and further to carry out experiments to validate the membranes by carrying out rejection studies using species of larger particles than the pore size of the membranes. The membranes were validated by using Baker's yeast solution as feed, in which the permeate showed absence of yeast and hence 100 % rejection of yeast in the yeast contaminated feeds. The scope of performance of the invention as narrated herein above will be best understood from the following illustrative examples with practical test results achieved covering all the aspects of the steps of manufacture of the tubular filtration membranes. Example 1: 19-channeled tubular alumina (AI2O3) symmetric membranes with physical dimensions of (outer diameter: 26.2 ± 0.2 mm, channel diameter: 3.4 ±0.1 mm) with a length of 500 mm was fabricated in accordance with the method described in the above and are mentioned in the below. All the dimensions mentioned in the above are after firing. -30- Alumina (AI2O3) and particular combination of other raw materials (inorganic type) were used as per furnished in Table 1 whereas Table 2 shows the technical specifications of the other additives (organic type) those used along with the said alumina for a batch preparation. A typical batch composition as per Table 3 was prepared using the above raw materials. Accurately weighed raw materials as per the batch composition (Table 3) are placed in a nylon pot mill together with alumina balls having variable diameters (3 mm, 6 mm and 9 mm) as grinding media and the lid of the pot is to closed tightly before placing it on the ball / pot mill operation for homogenization / milling of the batch composition. In this homogenization / milling operation, the weight ratio of the batch composition and alumina balls was kept approximately 1:2, although the ratio may vary from case to case. The size of the batch depends on the scale of manufacturing. The homogenization / milling operation is carried out for a period of ~ 60 hours using 75 RPM of the ball / pot mill machine. -31- After the homogenizing / milling of the raw materials is over, a homogenized batch is formed which are discharged from the pot and sieved using a 200 mesh nylon sieve, after segregating alumina balls from the batch. Now, the resultant sieved batch is called 'Homogenous batch'. A dough / paste is then prepared using this homogenous batch and a machine, zigma blade mixer. For this purpose, the sieved homogenous batch is placed inside the cavity of the zigma blade mixer and prescribed quantity (Table 3) of freshly prepared 2.5 ± 0.5 wt % of aqueous carboxy methyl cellulose (CMC) solution is added slowly and mixed thoroughly at least for a period of one hour, so as to get the dough / paste. Polyethelene glycol (PEG) in prescribed quantity (Table 3) is to be added 10 - 30 minutes before the mixing process is ended. A the end of the dough preparation step, the moisture level of the dough is found to be in the range of 21.5± 2 wt %. The degassing of the dough / paste was carried out by keeping the dough / paste inside the cavity of another machine, hydraulic extruder for ~ 3 - 5 minutes of minutes under pressure. By using an appropriate die (19-channeled, -32- OD 32 mm, pin dia 3.9 mm) that is fitted with the extruder, the de-gassed mass was then extruded into 19-channeled green tubes' in a horizontal mode with a length of ~ 650 mm. Plastic pipes (half-circled) with good surface finish was used as launching / receiving channels in a way that self-guiding takes place during extrusion besides maintenance of stiaightness and good surface finish of the green tubes. A mixture of coconut oil and kerosene was used as a lubricant. The drying of the green tubes was carried out in two consecutive steps. The first step called 'Natural Drying', which is completed within a period of ~ 10 hours and starts with the freshly-fabricated green tubes in which the green tubes were allowed to remain under atmospheric conditions (Temperature: 25 ± 5° C, relative humidity: 65 - 75 %) and at the end of the step, the moisture level of the green tubes comes down to a level of 15 ± 2 % from the original moisture level of 21.5 ±2 % of the dough resulting semi-dried green tubes. The second step of drying here is so-called 'Oven Drying' in which the 'semi-dried' green tubes were kept in an electrically-heated oven at a set temperature of 90 ± 5° C for a period of ~ 10 hours and at the end of this step, the moisture level of the tubes came down to 1. 0 + 0.5 % from the previous level of moisture of 15 ± 2 %. The green density of the dried tubes is observed to be in the range of 2.05 ± 0.05 g / cc. -33- For natural drying, the green tubes are laid horizontally on a flat glass surface using stainless steel (SS) supports (straight and OD of 35 mm) aside each tube across the length of the tube and thereby allowed to leave the tubes as it is under open atmosphere. The SS supports are inserted in between the tubes to maintain the straightness of the green tubes and to prevent any possible warpage / bending during the natural drying process. Alternatively, V-shaped channels could also be used for the purpose of drying the green tubes. In case of V-shaped channels, no supporting rods are required. The loading pattern in case of the former method is furnished in Figure 8, as an example. Also, in order to prevent any dust falling on the surface of the tubes, cellulose papers is covered on the top of the tubes in this step. After the above natural drying step, the green tubes are called semi-dried green tubes, which are again placed horizontally on a glass surface along with the SS supports in between (in the same fashion to that of the natural drying) in an electrically-heated oven maintaining a set temperature of 90 ± 5° C for a period in the range of ~ 10 hours. Apart from the insertion of support tubes across the length, additional supports on the top of the surface across the diameter are also -34- to be inserted in every six inches of the iength in order to maintain the straightness of the tubes. At the end of this stage, the moisture content of the green tubes are reduced to a level of 1.0 ± 0.5 %, which shows a green density corresponding to 2.05 ± 0.05 g / cc. The derived dried tubes with moisture content firing or densification (sintering) operation in a refractory-lined high-temperature furnace (furnace procured from commercial sources) at a temperature of 1540° C in presence in air. The heating rate was maintained constant at 1.0° C / mm till 600° C and the heating rate was increased to 1.5° C / min until the furnace temperature reaches 1000° C where it was soaked for 60 min. Further sintering operation was continued by increasing the temperature of the furnace at 1540° C with a heating rate of 2° C / min and was soaked at 1540° C for a period of 120 min in air. The heating of the furnace was stopped after the soaking and the furnace was then allowed to cool down to 100° C naturally after which the further cooling to room temperature was carried by exposing the tubular membranes in ambient condition. Once the said process of sintering was completed, the so-derived tubes (19-channeled tubular alumina MF membranes) were characterized for various physical properties. -35- The fired tubes showed an OD in the range of 26.2 ± 0.2 mm and a channel diameter in the range of 3.4 ± 0.1 mm. The tubes also showed a bulk density in the range of 2.3 ± 0.1 g / cc, volume porosity in the range of 35.0 ± 2 %, shrinkage across the length of 12.0 ± 1 %, shrinkage (diameter) 1.5.0 ± 1 %, modules of rupture in the range of 90 ± 10 MPa and a pore size of 1.14 micron in the course of pore size analysis by Hg-porosimetry technique. The pore size profile of this membrane is furnished in the Figure 1. Scanning electron microscopy (SEM) investigations of the surface texture and fracture surface of this membrane sample corroborates the pore size profile. Figure 2 presents average clean water (distilled water) flux for this membrane at different trans- membrane pressure (TMP). The membranes were validated by conducting permeability studies using different concentrations (3 - 10 g / liter) of Baker's yeast at different trans-membrane pressure (TMP) that showed 100 % rejection of the yeast in the permeate. The membranes showed excellent stability in liquid chemical environments having pH in the entire range of 0 - 14 at ambient and above ambient temperatures. -36- Example 2: 7-channeled tubular type alumina symmetric membranes (OD: 27.0 MM ± 0.2 mm, channel diameter: 5.4 ± 0.1 mm, length: 700 mm) were fabricated in the same manner as explained in Example 1, except the firing process, by using the same composition to that of the example 1. The firing process in this case was carried out at 1600° C in air with a uniform rate of heating from ambient until 1600° C in a way that the ambient to ambient temperature of the kiln (35° C) was completed within 24 hours. Also, an appropriate extrusion die was used to fabricate a 7-channeled profile with targeted internal and external diameter in the present membrane tubes. The fired tubes showed an OD in the range of 27.0 ± 0.2 mm and a channel diameter in the range of 5.4 ± 0.1 mm. The tubes also showed a bulk density in the range of 2.2 ± 0.1 g / cc, volume porosity in the range of 38.0 ± 2 %, shrinkage across the length of 11.0 ± 1 %, shrinkage (diameter) 14.0 ± 1 %, modulus of rupture in the range of 85 ± 10 MPa and a pore size of 1.27 micron (Figure 3). The clean water flux of this membrane is presented in the Figure 4. The membranes were validated by conducting permeability studies using -37- different concentrations of Baker's yeast at different trans-membrane pressure (TMP) that showed 100 % rejection of the yeast in the permeate. The membranes are stable in chemical environments having pH in the range of 0-14. Example 3: 19-channeled tubular alumina symmetric membranes (OD: 25.4 mm ± 0.2 mm, channel diameter; 3.4 ± 0.1, length: 600 mm) were fabricated in the same manner as explained in Example 1, except the composition in which the constituent, Mg / Ca alumino-silicate glass was reduced to 0.75 weight % instead of 1.5 weight % in reference to the example 1. An appropriate extrusion die was used to maintain the diameter variation in the present membrane tubes. The fired tubes showed an OD in the range of 25.4 ± 0.2 mm and an internal diameter (ID) in the range of 3.4 ±0.1 mm. The tubes also showed a bulk density in the range of 2.2 ± 0.1 g / cc, volume porosity in the range of 40.0 ± 2 %, shrinkage across the length of 12.0 ± 1 %, shrinkage (diameter) 15.0 + 1 %, modulus of rupture in the range of 80 ± 10 MPa and a pore size of 1.6 micron -38- (Figure 5). The clean water flux of this membrane is furnished in the Figure 6. The membranes were validated by conducting permeability studies using different concentrations of Baker's yeast at different trans-membrane pressure (TMP) that showed 100 % rejection of the yeast in the permeate. The membranes are stable in chemical environments having pH in the range of 0 - 14. Example 4: Single-channeled (hollow) tubular type alumina symmetric membranes (OD: 26.2 mm ± 0.2 mm, internal diameter: 18.3 ± 0.2, length: 800 mm) were fabricated in the same manner as explained in Example 1. The fired tubes showed an OD in the range of 26.2 ± 0.2 mm and an internal diameter (ID) in the range of 18.3 ±_0.2 mm. The tubes also showed a bulk density in the range of 2.3 ± 0.1 g / cc, volume porosity in the range of 35.0 ± 2 %, shrinkage across the length of 12.0 ± 1 %, shrinkage (diameter) 15.0 ± 1 %, modulus of rupture in the range of 90 ± 10 MPa and a pore size of 1.2 micron in -39- the course of characterization and testing. The pore size profile of this membrane is similar to that of the Figure 1. The membranes were validated by conducting permeability studies using different concentrations of Baker's yeast at different trans-membrane pressure (TMP) that showed 100 % rejection of the yeast in the permeate. The membranes are stable in chemical environments having pH in the range of 0 -14. Example 5: Single-channeled (hollow) tubular type alumina symmetric membranes (OD: 26.2 MM ± 0.2. mm, internal diameter: 16.8 ± 0.2 mm, length: 1000 mm) were fabricated in the same manner as explained in Example 1, by using the same composition to that of the example 1. The fired tubes showed an OD in the range of 26.2 + 0.2 mm and an internal diameter (ID) in the range of 16.8 ± 0.2 mm. The tubes also showed a bulk density in the range of 2.3 ± 0.1 g / cc, volume porosity in the range of 35.0 ± 2 %, shrinkage across the length of 12.0 ± 1 %, shrinkage (diameter) 15.0 ± 1 %, -40- modulus of rupture in the range of 90 ± 10 N / mm2 and a pore size of 1.2 micron in the course of charactrization and testing. The pore size profile of this membrane is similar to that of the Figure 1. The membranes were validated by conducting permeability studies using different concentrations of Baker's yeast at different trans-membrane pressure (TMP) that showed 100 % rejection of the yeast in the permeate. The membranes are stable in chemical environments having pH in the range of 0 - 14. Characterization, testing and validation of the derived alumina symmetric membranes: Sufficient number of alumina symmetric tubular membranes were prepared in accordance with examples 1-5 and were subjected to characterization, testing and validation for their effectiveness in maintaining consistent and reproducible physical properties. The tubular membranes those derived from a particular batch trial exhibited similar values (within the limit described in the above examples) of physical properties like, bulk density, volume porosity, pore size, mechanical strength (MOR), chemical (pH resistance) and thermal stability, microstructure, surface texture, clear water (distilled water) flux. -41- Membranes fabricated in accordance to examples 1-5 were also tested for their effectiveness in filtering different feeds and effluents. For this purpose, a concentration in the range of 3 - 10 g / liter synthetic Baker's yeast suspension was prepared and filtered through the membranes in a cross filtration fashion. The trans-membrane pressure (TMP) across the membrane was varied from ambient until 125 kPa and subsequent flux and quality of permeate was determined as a function of time. The concentration of the Baker's yeast in the permeate was sampled using standardized methods. All the membrane tubes showed 100 % rejection of Baker's yeast in the above range of TMP. -42- Table 1: Technical Specifications of the Raw Materials (Inorganic type) Raw material Crystallinephase ChemicalPurity, (%) Particle Sizeµm)D50 Specific surfaceArea (m2/gm) Particlemorphology Alumina Powder 1 Alpha 99.70 3.5 +0.5 0.85 + 0.2 Irregular Alumina Powder 2 Alpha 99.80 0.4 + 0.1 8.6 + 2.0 Irregular Graphite Powder Amorphous 99.94 10 + 3.0 7.0 + 3.0 Spherical Magnesium Oxide,(MgO) Crystalline Min. 99.00 - - Irregular Magnesium/calciumaluminosilicateglass A homogeneous mixture of heat-treated (600°C/2 hours) Talc (magnesium/calcium silicate)powder and Clay (alumino silicate) powder in 1: 1 ratio by weight Table 2: Technical specifications of the other additives (Organic type) Raw material Chemical purity(%) ApproximateMolecular Weight(Range) Physical State Sodium stearate Min 99 - Solid Polyethylene glycol (PEG) Min 99 400-1000 Liquid Carboxy methyl cellulose (CMC) Min 99 - Solid Table 3: The Ceramic-based Membrane System with chemical composition for the fabrication of tubular alumina symmetric membranes having porosity of ~ 35 volume % with a pore size of 1.14 urn SI. No. Raw Materials /Chemical Constituent's Amount (% Weight) 1 Alumina Powder I 47.75 + 5.0 2 Alumina Powder 2 25.70 + 3.0 3 Graphite powder 24.27 4 Magnesium/calcium alumino silicate Glass 1.50+1.0 5 Magnesium oxide (MgO) 0.40 + 0.2 6 Sodium Sterate 0.30 + 0.2 Total 100.00%Binders and Plasticizers (ml): 7 CMC (2.5 wt%) Aq Solution (ml) 1250+ 100 8 Polyethylene glycol (PEG) (ml) 70. + 10 -43- The proposed invention as narrated hereinabove and illustrated with examples as exemplary embodiments, should not be read and construed in a restrictive manner as various modifications, alterations and adaptations are possible in respect of maintaining end product profiles and micro porosity, process parameters and formers during fabrication and combination and substitution of staring materials are possible within the scope and limit of the invention as defined in the encompassed appended claims. -44- WE CLAIM 1. A process for manufacture of symmetric micro-filtration (MF) alumina tubular membranes comprising the steps of: - mixing / milling a batch composition in a ball mill with alumina or other balls for a period of 30 to 60 hours the batch composition in weight % consisting of: raw materials e.g., alumina powder 1 of 47.7 ± 5 % with chemical purity: > 99 %, mean particle size - D 50: 3.5 ± 0.5 micron, specific surface area - 0.85 ± 0.2 m2 / g; alumina powder 2 of 25.7 ± 3 % with chemical purity: > 99 %, mean particle size - D50: 0.4 ± 0.1 micron, specific surface area: 8.6 ± 2.0 m2 / g; pore former, graphite powder of 24.3 ± 3 % with chemical purity : > 99 %, mean particle size, D50: 10 ± 3 micron, specific surface area : 7.0 ± 3 m2 / g, particle size, morphology: spherical; inorganic additives magnesium / calcium alumino silicate glass of 1.50 ±1.0 %; magnesium oxide of 0.4 ± 0.2 %; organic additives sodium stearate of 0.3 ± 0.2 %; -45- sieving the milled batch composition through a 100 - 200 mesh nylon / sieve, after segregating the alumina balls to form a homogenous batch; preparing a dough / paste by mixing the homogenous batch with 1250 ± 100 ml of an aqueous solution of binder, carboxymethyl cellulose (CMC) or any other binder and 70 ± 10 ml of a plasticizer i.e, polyethylene glycol with molecular weight in the range of 400 - 800 (PEG) or any other kind, in a zigma blade mixture or zigma kneader or similar machine; degassing / de-airing the resultant dough to remove the trapped air / gases; extruding the degassed dough in a preformed die fitted with the extruder to form green tubes; drying the green tubes in two consecutive steps of natural drying under ambient conditions at 15-45° C to result semi dried green tubes and then oven drying at 65 - 120° C to result dried green tubes; -46- - firing / sintering the dried green tubes at 1530 - 1600° C in air / oxygen in a refractory-lined furnace and cooled down to ambient temperature to obtain sintered membrane tubes; - characterization and validation of the sintered membrane tubes to ensure the properties and quality of the membrane tubes with respect to bulk density, volume porosity, pore size, mechanical strength (modulus of rupture), straightness / wrapage, uniformity in physical dimensions, chemical stability (pH resistance), thermal stability, surface finish, clean water (distilled water) flux and yeast rejection characteristics at various trans-membrane pressures. 2. The process of manufacture of MF alumina tubular membranes as claimed in claim 1, wherein the said ball mill is pot mill with pot / containers made of nylon / teflon / ceramic or alumina-lined metallic or any similar group of material/s. -47- 3. A process as claimed in claim 1, wherein the homogenized batch mixed with the aqueous solution of CMC (2.5 ±1.0 wt%)For 1-2 hours and the plasticizer is added 10 - 30 minutes before the mixing operation is ended and at the end, moisture level of the dough is maintained in the range of 20.0 ± 3 wt %. 4. The process as claimed in the preceding claims, wherein the said extrusion process is carried out either in horizontal or vertical mode and the MF membrane tubes are extruded using preformed dies according to requirement of physical dimensions, e.g., length (L), outer diameter (OD), internal diameter (ID), channeled diameter (CD) and various geometrical profiles (19-channeled, 7-channeled, single-channeled, hollow or any other type). 5. The process as claimed in the preceding claims, wherein during the extrusion of the dough, the semicircle pipes, or V-shaped channels made out of plastic or metals (SS, brush etc.) are employed as launching / receiving channels / pads for the green tubes in which the diameter of the semi-circled pipes being kept slightly more than the diameter of the green tubes and V-shaped channels being maintained with an appropriate angle so that self guiding of the green tubes takes place during extrusion. -48- 6. The process as claimed in claim 5, wherein to ensure straightness and surface finish of the green tubes, any oil-based lubricants alcohol / acetone solution of stearic acid are used on the surface of the launching pipes to further guide the extruded green tubes to move forward smoothly during extrusion of degassed dough to form a close packed array of membranes. 7. The process as claimed in claim 1, wherein natural drying at ambient temperature is carried out at humidity range of 60 - 90 % for a period of 6-12 hours to maintain moisture level at 15 ± 2 % and oven drying is carried out in electrical / gas fired or microwave or similar oven/s for a period of 10 - 24 hours to reduce the moisture level of the semi-dried green tubes in the range of 1.00 ± 0.5 %. 8. The process as claimed in claims 6 and 7, wherein for natural drying the green tubes are laid horizontally on a flat glass surface using SS or plastic or similar supports aside each tube across the length of the tube and thereby allowed to leave the tubes as it is under open atmosphere to -49- maintain straightness of the green tubes and to prevent any possible wrappage / bending during natural drying to form semi-dried green tubes and the said tubes during oven drying are again placed horizontally on a glass surface along with SS supports in between in the same manner as carried out during natural drying and further supporting additionally on the top of the surface across the diameter inserted in every six inches of the length in order to maintain the straightness of the tube during oven drying. 9. A process as claimed in claim 1, in which sintering / firing is carried out in a refractory-lined high temperature furnace on heating the furnace at heating rate not greater than 1.0° C / min till 600° C, soaking at this temperature for a minimum period of 60 minutes, then continuing the heating of the furnace until sintering temperature in the range of 1530 - 1600° C with a heating rate not greater than 3° C / min and soaking at the sintering temperature for a minimum period of 60 minutes, but grater than 180 minutes in air and then cooling the furnace at ambient temperature and collecting the so-derived fired MF symmetric membrane tubes. -50- 10. The MF symmetric membrane tubes manufactured according to the preceding claims, wherein the MF membranes tubes are characterize and tested to maintain bulk density in the range of 1.90 - 2.40 ± 0.2 g / cc, porosity, 30 - 50 volume %, minimum modulus of rupture of 60 MPa, pore size 1-2 micron, chemical stability towards pH range 0 -14 minimum thermal stability up to 700° C, and confirming 100 % rejection of Baker's yeast at variable TMP of the Membrane tubes. 11. The symmetric product according to claim 10, wherein the derived symmetric membranes are perm-selective with respect to the size of the species to be filtered and can be used for the selective separation / filtration of a desired substance from a raw fluid or suspension by physical or mechanical means and can be used as a porous-support base for the fabrication of ultra-filtration (UF), nano-filtration (NF), and reverse osmosis (RO) membranes for various filtration applications using different polymer / ceramic materials or the derived membranes can further be used as a support for heterogeneous catalysis reactions and photo- catalysis reactions and processing involving adsorption or absorption reactions. -51- 12. A process for manufacture of symmetric micro filtration (MF) alumina tubular membranes as herein described and illustrated. Dated this 29th day of March 2007. The present invention relates to a method for manufacture of alumina ceramic tubular symmetric micro-filtration (MF) single or multi-channeled membranes with versatility in geometry / profile i.e., single or multi-channeled hollow or any other profile and variable physical dimensions e.g., length, internal diameter (ID), outer diameter (OD), channeled-diameter (CD) etc., with consistent pore size, porosity, mechanical strength and chemical stability. The derived membranes possess superior mechanical strength (minimum value of modulus of rupture, MOR 60 MPa), high chemical stability (pH resistance 0 - 14) and good thermal stability as well. The MF membranes according to the invention is applied in filtration / separation process covering the entire micro-filtration (MF) range and more specifically, in the range of 1 -2 micrometer (micron) with counter porosity, more specifically in the range of 30 - 50 volume % could be made. Properties of the derived membranes are characterized, tested and validated by standard laboratory techniques. The derived symmetric membranes are perm-selective with respect to the size of the species to be filtered and can be used for the selective separation / filtration of a desired substance from a raw.

Documents:

00505-kol-2007-abstract.pdf

00505-kol-2007-claims.pdf

00505-kol-2007-correspondence others 1.1.pdf

00505-kol-2007-correspondence others.pdf

00505-kol-2007-description complete.pdf

00505-kol-2007-drawings.pdf

00505-kol-2007-form 1.pdf

00505-kol-2007-form 18.pdf

00505-kol-2007-form 2.pdf

00505-kol-2007-form 3.pdf

00505-kol-2007-gpa.pdf

505-KOL-2007-ABSTRACT 1.1.pdf

505-KOL-2007-AMANDED CLAIMS.pdf

505-KOL-2007-AMANDED PAGES OF SPECIFICATION.pdf

505-KOL-2007-CORRESPONDENCE.1.3.pdf

505-KOL-2007-DESCRIPTION (COMPLETE) 1.1.pdf

505-KOL-2007-DRAWINGS 1.1.pdf

505-KOL-2007-EXAMINATION REPORT REPLY RECIEVED.pdf

505-KOL-2007-EXAMINATION REPORT.1.3.pdf

505-KOL-2007-FORM 1-1.1.pdf

505-KOL-2007-FORM 18.1.3.pdf

505-KOL-2007-FORM 2-1.1.pdf

505-KOL-2007-FORM 3.1.3.pdf

505-KOL-2007-FORM-27.pdf

505-KOL-2007-GPA.1.3.pdf

505-KOL-2007-GRANTED-ABSTRACT.pdf

505-KOL-2007-GRANTED-CLAIMS.pdf

505-KOL-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

505-KOL-2007-GRANTED-DRAWINGS.pdf

505-KOL-2007-GRANTED-FORM 1.pdf

505-KOL-2007-GRANTED-FORM 2.pdf

505-KOL-2007-GRANTED-LETTER PATENT.pdf

505-KOL-2007-GRANTED-SPECIFICATION.pdf

505-KOL-2007-OTHERS 1.1.pdf

505-KOL-2007-PA.pdf

505-KOL-2007-REPLY TO EXAMINATION REPORT.1.3.pdf