Title of Invention | ''A DEVICE FOR CASTING ION-EXCHANGE MEMBRANES'' |
---|---|
Abstract | This invention provides a device for casting ion-exchange membranes. It has unique features of casting (one surface) as well as deep coating (both surface) of ion-exchange membranes with support base as fabrics. Mono-polar as well as bipolar ion-exchange membranes can be cast on fabrics utilizing this device. With the help of casting blade with micrometer fittings of the device, very thin (of the order of microns) coating of membrane on fabric support can be achieved resulting in low resistance and high mechanical strength. With this device ion-exchange membrane can be cast continuously maintaining uniform coating thickness |
Full Text | The present invention relates to a device for casting ion-exchange membranes. The device of the present invention will be particularly useful for continuous casting of various sizes and lengths of ion-exchange membranes. Using this device, one can cast ion-exchange membranes with fabric support. With the .device of the present invention it is possible to provide ion-exchange membranes on support fabrics having uniform and a very thin coating, of the order of microns. Ion-exchange membranes of low resistance and high mechanical strength can be obtained using this device. The device of the present invention can be used to cast mono-polar as well as bipolar ion-exchange membranes. Reference may be made to "The preparation of ion-exchange membranes by the paste method" by Yokio Mizutani, Reiichi Yamane, Hirofumi Ihara and Hiroji Motomura, Bulletin of the chemical society of Japan, Vol.36, No.4, April, 1963,pp.361-366 wherein a paste containing Mf: a monomer suitable for the introduction of an ion-exchange group; Me: a monomer co-polymerizable with Mf to control the viscosity of the paste, the ontent of resinous components in the base membrane, and the content of ion-exchange groups in the ion-exchange membrane; DVB: divinylebenzene as a cross-linking agent; PVC: the fine powder of polyvinyl chloride which endows the base membrane and the ion-exchange membrane with flexibility and toughness; DOP: dioctyl phthalate as a plasticizer to control the viscosity of the paste; and BPO: benzoyl peroxide as a catalyst were prepared after mixing them thoroughly and de-aerated under pressure. The paste obtained was coated on a reinforcing material and treated in a hot press at 100-120°C for 30 minutes and then 70-80°C for 16 hrs. The coated reinforcing material is called base membrane. The base membranes were sulfonated with 98% sulfuric acid at 55-60°C for several hours to give cation exchange membranes. Similarly anion exchange membranes were prepared by chloromethylation of the base membranes. The drawbacks of the above membrane preparation are: longer duration for membrane preparation, various steps involved and lot of energy consumption. Another reference may be made to" USP 2 388 080 (1963)" by F.de Korozy, A.J.Shorr wherein ion-exchange membranes are prepared by sulfochlorination of polyethylene sheets in a gas mixture of SO2 and C12 by means of a photochemical reaction. The -SO2C1" groups jn sulfochlorinated polyethylene sheets undergo hydrolysis in caustic so'da to become -SOaH and thus build a cation exchange membrane. Anion exchange membranes are made with dimethylaminoprophylmine which replaces the -Cl in the -SO2C1 group to form a weak base tertiaryamine. Quaternization of the amino groups with CH3Br produces a strong base quaternaryamine. Drawbacks of the above membrane preparation are: longer duration for membrane preparation and more energy consumption. Another reference may be made to "Development of new membranes" by H.Strathman, Forschungsinstitute Berghof, Tubingen, Desalination, Vol.35(1980), pp.39-58 wherein ion-exchange membranes are prepared by radiation induced grafting technique to graft acrylic acid onto films of polytetrafluoroethylene(PTFE). By using simultaneous or post-irradiation grafting techniques, PTFE can be grafted by various monomers such as vinylacetate, styrene, acrylic acid, methylmethacrylate etc. Drawbacks of the above membrane preparation are cost intensive and complicated radiation induced grafting technique. In the prior art, the main drawbacks encountered are longer time duration, multiplicity of steps, complicated and hazardous processes such as radiation induced grafting technique, high energy consumption and cost intensive.Prior art literature survey and patent search did not reveal any device for casting ion-exchange membranes. The main object of the present invention is to provide a device for casting ion-exchange membranes which obviates the above noted drawbacks. Another object of the present invention is to provide a device for continuous casting of ion-exchange membranes. Still another object of the present invention is to provide a device which enables use of a fabric as a support base for ion-exchange membranes preparation. Yet another object of the present invention is to provide a device that enables very thin and uniform coating of ion-exchange membranes on support fabric. Still yet another object of the present invention is to provide a device that enables casting of mono-polar and bipolar membranes. A further object of the present invention is to provide a device that will facilitate to cast ion-exchange membranes of low resistance and high mechanical strength. A still further object of the present invention is to provide a device that provides a cost effective and simple technique for membrane preparation. Another object of the present invention is to provide a device capable of casting one surface as well as deep coating, that is both surfaces, of ion-exchange membranes with fabric support base. The device of the present invention for casting ion-exchange membranes consists of: (i) fabric supply roller for continuous supply of fabrics which will work as a support base for ion-exchange membrane; (ii) solution container with casting blade and micrometer fittings for continuous supply of solution and obtaining thin coating on fabrics; (iii) various roller sets which enable drying of the ion-exchange membrane under stretched condition; (iv) hot air chamber for membrane drying under controlled conditions; (v) air blower and heaters with temperature controls for continuous hot air blowing at desired temperature in hot air chamber; (vi) receiving roller coupled with DC geared- motor and speed controls for winding dried ion-exchange membranes and keeping constant speed throughout the casting period for obtaining uniform coating thickness on fabrics. The details of the device of the present invention are shown in figures 1 to 5 of the drawings accompanying this specification. Figure-1 of the drawings represents the plan view of the device. Figure-2 of the drawings represents the side elevation of the device. Figure-3 of the drawings represents air blower and heaters of the device. Figures-4 & 5 of the drawings represents plan and elevation of the solution container with micrometer fittings of the device. In figure-1 of the drawings, the various parts depicted are: (1) represents fabric supply roller. (2) to (6) represent various roller sets which channelise the fabric. (7) represents a membrane-receiving roller which is directly coupled to a DC geared motor. In figure-2 of the drawings, the various parts depicted are: £8) represents header through which hot air enters into the hot air chamber(lO). (9) represents exhaust fan connector. (10) represents hot air chamber. (11) represents solution container with micrometer fittings. In figure-3 of the drawings, the various parts depicted are: (12) represents air blower. (13),(14) and (15) represent electric heaters coupled with temperature controllers. (16) represents connector for header(8) through which hot air enters into the hot air chamber(lO). In figures-4 & 5 of the drawings are shown the plan and elevation of the solution container with micrometer fittings of the device of the present invention. In figure-4 of the drawings, the various parts depicted are: (18) represents plate of stainless steel. (19) represents casting blade attachment for obtaining desired coating thickness. (20) represents a roller. In figure-5 of the drawings the part depicted is: (17) represents micrometer fittings for obtaining very thin coating of membranes. Accordingly the present invention provides a device for casting ion-exchange membranes, which comprises: (i) a main frame having vertical stand mounted support-base fabric supply roller(l) and one or more guide roller(s)(2) capable of channelising the support-base fabric into a coating solution container(l 1) having a fabric-guide roller(20), a flat plate(18) and a casting blade(19) with micrometer fittings(17) capable of adjusting coating thickness; (ii) the said combination of supply roller, guide roller(s) and coating solution container being fixed adjacent to an inlet slit of a hot air chamber(lO) mounted on the said main frame, the hot air chamber(lO) being provided with a plurality of vertical stand(s) mounted guide rollers(3,4,5,6,) capable of guiding the coated support-base fabric through an outlet slit of the hot air chamber(lO) to a membrane receiving roller(7) directly coupled to a prime mover;(iii) the said hot air chamber(lO) being also provided with an exhaust outlet(9) at the top and a plurality of inlet headers(S) at the bottom connected through coupling pipe(16) to a hot air generator consisting of a blower(12) and a plurality of heaters(13,14,15) with temperature controllers. In an embodiment of the present invention the rollers are mounted with conventional bearings. In another embodiment of the present invention the prime mover is such as a conventional DC geared motor with speed controls. In yet another embodiment of the present invention the heaters are such as conventional electric heaters with temperature controllers. In still another embodiment of the present invention the device is capable of casting mono-polar and bipolar ion-exchange membranes. In a further embodiment of the present invention the device is capable of providing ion-exchange membranes of low resistance and high mechanical strength by thin coating technique on support fabric. In a physical embodiment of the device of the present invention the fabric supply roller(l) is of stainless steel material having 55cms.length and 12.5cms.diameter mounted on mild steel stand with bush bearings. Polyester or Nylon fabrics having thickness, mesh opening, open surface in the range of 60-120, 25-60 and 20-40% respectively may be selected as a support base for casting ion-exchange membrane. A stainless steel roller(2) is provided before the solution container so that fabric passing through the solution container is kept stretched. The solution container(l 1) is of stainless steel having rectangular shape of 60cms.X10cms.X10cms dimensions and consists of (i) a guide roller(20) of stainless steel material having 55cms. length and 3.Ocms.diameter; (ii) a plate(18) of stainless steel material having 55cms.length, 20cms.width and 0.3cms; (iii) a casting blade(19) attachment of stainless steel t material having 55cms. length, 1.25cms. thick and 15cms. width for obtaining desired coating thickness; and (iv) micrometer fittings(17) for obtaining very thin coating of membranes. The hot air chamber(lO) is a closed chamber made of glass panes and aluminum channels measuring 4.0X0.80X0.40 meters with slit opening at two sides from which cast membrane enters into the .chamber and comes out after being dried. The hot air chamber is provided with a plurality of roller sets(3,4,5 and 6) which are of stainless steel having 55cms. length and 3.Ocms.diameter. These roller sets allow the membrane to get dried and anchored in stretched condition. The hot air chamber has an exhaust fan connector(9) and headers(S) through which hot air enters into the hot air chamber. The headers(S) with pipe connection(l 6) are provided at the bottom of the hot air chambers for hot air entry and exhaust pipe(9) connection is provided at the top of the hot air chamber for the solvent vapor exit through an exhaust fan. The air blower(12) and electric heaters(l 3,14,15) coupled with temperature controller are connected through connector(l 6) to headers(S) through which hot air enters into the hot air chamber. The air blower and heaters with temperature controls having an air blowing capacity of more than 100CFM(cubic feet per minutes) and air heaters of 4KW capacity connected to a tenrperature controller for heating air at desired temperature. The membrane-receiving roller(7) is of stainless steel having 55cms. length and 7.5cms. diameter. The membrane receiving roller is directly coupled to DC geared motor with speed control. The DC geared motor having 200 watt rating at SOOrpm and 180 volts. Gear ratio of the geared motor is 12:1. Speed of the geared DC motor is controlled by thyrister drives that exhibit fairly constant torque from the minimum to maximum speed. The details of the device of the present invention and its operations for casting ion-exchange membranes are: (i) Fabric supply roller: fabric supply roller of stainless steel material having 55cms.length and 12.5cms.diameter is mounted on mild steel stand with bush bearings. Polyester or Nylon fabrics having thickness, mesh opening, open surface in the range of 60-120, 25-60 and 20-40%, respectively is selected as a support base for casting Ion-exchange membrane. Polyester or Nylon fabric is cut in desired length and width and then rolled on supply roller for continuous supply of fabric. (ii) Solution container with casting blade and micrometer fittings is made of stainless steel material. It is rectangular in shape having 60cms.X10cms.X10cms dimensions. One side of the solution container contains casting blade with micrometers fittings. Thickness of membrane is adjusted with micrometer. Stainless steel roller is provided before solution container so that fabric passing through the solution container is kept stretched. Fabric from supply roller is allowed to pass through the bottom of the solution container by means of a small slit and roller and comes out of solution container via casting blade having very small gap. Solution having mixture of ion-exchange resin, binder such as Polyvinyl chloride (PVC) and solvent such as tetrahydrofuran (THF) is poured in the solution container and a desired thickness of casting on fabric is obtained by adjusting the casting blade height with the help of micrometer. Height of casting blade is adjusted in such a way that very small thickness (in microns) of solution is left on fabric surface. (iii) The roller sets are of stainless steel material having 55cms.length and 3.Ocms.diameters and are mounted on mild steel stand with bush bearings. They are fixed inside the hot air chamber at various distances. Cast membrane on the fabric enters into the hot air chamber and passes through these roller sets. These roller sets allow membrane to get dried and anchored in stretched condition. (iv) Hot air chamber is a closed chamber made of glass panes and aluminum channels measuring 4.0X0.80X0.40 meters with slit opening at two sides from which cast membrane enters into the chamber and comes out after being dried. Headers with pipe connection are provided at the bottom of the hot air chambers for hot air entry. Exhaust pipe connection is provided at the top of the hot air chamber so that solvent vapor can be exhausted into the air through the exhaust fan. (v) Air blower and heaters with temperature controls: air blower having an air blowing capacity of more than 100CFM(cubic feet per minutes) is connected to air heaters of 4KW capacity through l.Sinch diameter pipe line. Outlet from air heaters is connected to the headers through pipeline of l.Sinch diameter. Air from blower enters the air heaters and is heated up to the desired temperature and enters into the hot air chamber through the headers. Heaters are connected to a temperature controller for heating air at desired temperature. (vi) Membrane-receiving roller coupled with DC geared motor and speed controls: membrane-receiving roller of stainless steel material having 55cms.length and 7.5cms.diameter is coupled with DC geared motor having 200 watt rating at SOOrpm and 180 volts. Gear ratio of the geared motor is 12:1. Speed of the geared DC motor is controlled by thyrister drives that exhibit fairly constant torque from the minimum to maximum speed, constant speed of the DC motor is essential to get uniform coating thickness of the membrane and therefore speed control is provided for DC geared motor, membrane after passing through the hot air chamber gets dried and is received at membrane-receiving roller. The novelty of the device of the present invention for casting ion-exchange membranes, comprising in combination (i) fabric supply roller, (ii) solution container with casting blade and micrometer fittings,(iii) external guide roller sets, (iv) hot air chamber with guide roller sets and air blower and heaters with temperature controls and (vi) membrane-receiving roller coupled with DC geared motor and speed controls; is that it provides for casting mono-polar as well as bipolar ion-exchange membranes using fabric as a support base, thus improving mechanical strength. Moreover very thin coating of ion-exchange membrane on fabric support base may be obtained giving low value of membrane resistance and continuous deep coating with uniform membrane thickness for large-scale production. The inventive steps of the device of the present invention which enable the above said novelty of providing improved results are a functioning combination of the sub-systems: 'S 1. Fabric support, through fabric supply roller, has been provided ;.-••• • . ->•' ..•" • * • ? *•>;•?•-•• •' for improving mechanical strength of ion-exchange membranes. 2, Solution container with casting blade and micrometer control provides very thin coating on fabric. 3, Hot air chamber with guide roller sets; air blower and heaters with teffljNtf attire controls. 4. Membrane-receiving roller cdUpled with t)C geared motor having speed controls provides for uniform mono-polar as well as bipolar ion-ex^tiange membrane casting. .The following examples are given for'illustrative purposes and ?provide the functioning 6f the device and steps involved in mono- • polar and bipolar ion-exchange membrane casting using the device of the present invention. These examples being illustrative should not be construed to limit the scope of the present invention. In the following examples polyester or nylon fabric having thickness, mesh opening, open surface in the range of 60-120, 25-60 and 20-40% respectively were selected as a base or support material for casting ion-exchange membranes. Example-1 Mono-polar cation-exchange membrane casting: Fabric of 0.5 meter width was selected as a base or support material for casting ion-exchange membrane. The O.Smeter wide fabric was rolled on the fabric supply roller. One end of the fabric was made to pass through the bottom of the solution container and casting blade and through the hot air chamber having guide rollers and is finally received and rolled on the receiving roller coupled with DC geared motor and speed controls..The solution container was provided with heterogeneous solution consisting of polyvinyl chloride(PVC), tetrahydrofuran (THF) and cation exchange resin. Polyvinyl chloride (PVC) in powder form was used for preparing homogeneous solution using tetrahydrofuran(THF) as solvent. Powder of cation exchange resin (more than 400 mesh particles size) was slowly added to the above solution to form a heterogeneous solution. Cation exchange resin not being soluble in any solvent including THF formed a heterogeneous solution. The micrometer setting was adjusted and the DC geared motor with speed controls was set for a constant speed of 0.5 meter per minute and motor was switched on. The fabric substrate from fabric supply roller entered into the solution container with micrometer fittings and filled with the heterogeneous cation exchange resin solution and passed beneath the casting blade adjusted by micrometer for casting thickness on the fabric. A layer of few micron thickness of cation exchange resin solution was formed on the fabric coming out of the solution container and got dried and anchored after passing through the hot air chamber and roller sets. The fabric with a layer cation exchange resin duly dried and anchored was the required cation exchange membrane. Example-2 Mono-polar anion-exchange membrane casting: Fabric of 0.5 meter width was selected as a base or support material for casting ion-exchange membrane. The O.Smeter wide fabric was rolled on the fabric supply roller. One end of the fabric was made to pass through the bottom of the solution container and casting blade and through the hot air chamber having guide rollers and is finally received and rolled on the receiving roller coupled with DC geared motor and speed controls. The solution container was provided with heterogeneous solution consisting of polyvinyl chloride(PVC), tetrahydrofuran (THF) and anion exchange resin. Polyvinyl chloride (PVC) in powder form was used for preparing homogeneous solution using tetrahydrofuran(THF) as solvent. Powder of anion exchange resin (more than 400 mesh particles size) was slowly added to the above solution to form a heterogeneous solution. Anion exchange resin not Jbeing soluble in any solvent including THF formed a heterogeneous solution. » The micrometer setting was adjusted and the DC geared motor with speed controls was set for a constant speed of 0.5 meter per minute and motor was switched on. The fabric substrate from fabric supply roller entered into the solution container with micrometer fittings and filled with the heterogeneous anion exchange resin solution and passed beneath the casting blade adjusted by micrometer for casting thickness on the fabric. A layer of few micron thickness of anion exchange resin solution was formed on the fabric coming out of the solution container and got dried and anchored after passing through the hot air chamber and roller sets. The fabric with a layer of anion exchange resin duly dried and anchored was the required anion exchange membrane. Example-3 Bipolar ion-exchange membrane casting: The cation exchange membrane as prepared in example-1 was rolled onto the fabric supply roller for casting a bipolar membrane. One end jof the pre-coated fabric (cation exchange membrane) was made to pass through the .bottom of the solution container and casting blade and through the hot air chamber having guide rollers and is finally received and rolled on the receiving roller coupled with DC geared motor and speed controls. The solution container was provided with a pasty solution of anion exchange resin which was prepared by adding more anion resin powder in a heterogeneous solution of polyvinyl chloride(PVC), tetrahydrofuran (THF) and anion exchange resin. The micrometer setting was adjusted and the DC geared motor with speed controls was set for a constant speed of 0.5 meter per minute and motor was switched on. The cation exchange membrane from the fabric supply roller entered into tfhe solution container with micrometer fittings and filled with the. heterogeneous anion exchange resin solution and passed beneath the casting blade adjusted by micrometer for casting thickness on the fabric.A layer of few microns in thickness of anion exchange resin duly formed on the cation exchange membrane and got dried and anchored when it was allowed to pass through the hot air chamber and rolled onto the receiving roller. Thus, one side of the fabric got coated with cation exchange resin and other side of the fabric was coated with anion exchange resin. The membrane thus prepared was a bipolar .membrane which had distinct properties. The main advantages of the present invention are: 1. Continuous casting of ion-exchange membrane is possible for large-scale production. 2. Mechanical strength of the ion-exchange membrane can be increased substantially by casting membrane on the fabric support. 3. Uniform ion-exchange membrane thickness is possible due to the constant speed controls. 4. Very thin coating (in microns) of ion-exchange membrane on fabric reduces electrical resistance and improves performance of ion-exchange membrane. 5. Mono-polar as well as bipolar ion-exchange membrane casting is possible by using this device. 6. Casting as well as deep coating of ion-exchange membrane is possible using this device. We claim: 1. A device for casting ion-exchange membranes, which comprises: (i) a main frame having vertical stand mounted support-base fabric supply roller(l) and one or more guide rollers(2) capable of channelising the support-base fabric into a coating solution container( 11) having a fabric-guide roller(20), a flat plate(18) and a casting blade(19) with micrometer fittings(17) capable of adjusting coating thickness; (ii) the said combination of supply roller, guide rollers and coating solution container being fixed adjacent to an inlet slit of a hot air chamber(lO) mounted on the said main frame, the hot air chamber(lO) being provided with a plurality of vertical stands mounted guide rollers(3,4,5,6,) capable of guiding the coated support-base fabric through an outlet slit of the hot air chamber(lO) to a membrane receiving roller(7) directly coupled to a prime mover; (iii) the said hot air chamber(lO) being also provided with an exhaust outlet(9) at the top and a plurality of inlet headers(S) at the bottom connected through coupling pipe(16) to a hot air generator consisting of a blower(12) and a plurality of heaters( 1 3,1 4,1 5) with temperature controllers. 2. A device as claimed in claim 1, wherein the rollers are mounted with conventional bearings. 3. A device as claimed in claims 1-2, wherein the prime mover is such as a conventional DC geared motor with speed controls. 4. A device as claimed in claims 1-3, wherein the heaters are such as conventional electric heaters with temperature controllers. 5. A device as claimed in claims 1-4, wherein the device is capable of casting mono-polar and bipolar ion-exchange membranes. 6. A device as claimed in claims 1-5, wherein the device is capable of providing ion-exchange membranes of low resistance and high mechanical strength by thin coating technique on support fabric. 7. A device for casting ion-exchange membranes substantially as herein described with reference to the examples and drawings accompanying this specification. |
---|
968-DEL-2002-Abstract (22.OCT.2007).pdf
968-DEL-2002-Abstract-02-05-2008.pdf
968-DEL-2002-Claims (22.OCT.2007).pdf
968-DEL-2002-Claims-02-05-2008.pdf
968-DEL-2002-Correspondence-Others (22.OCT.2007).pdf
968-DEL-2002-Correspondence-Others-02-05-2008.pdf
968-del-2002-correspondence-others.pdf
968-del-2002-correspondence-po.pdf
968-DEL-2002-Description (Complete) (22.OCT.2007).pdf
968-DEL-2002-Description (Complete)-02-05-2008.pdf
968-del-2002-description (complete).pdf
968-DEL-2002-Form-18-02-05-2008.pdf
968-DEL-2002-Form-3 (22.OCT.2007).pdf
968-DEL-2002-Form-3-02-05-2008.pdf
Patent Number | 219641 | ||||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Indian Patent Application Number | 968/DEL/2002 | ||||||||||||||||||||||||||||||
PG Journal Number | 28/2008 | ||||||||||||||||||||||||||||||
Publication Date | 11-Jul-2008 | ||||||||||||||||||||||||||||||
Grant Date | 12-May-2008 | ||||||||||||||||||||||||||||||
Date of Filing | 24-Sep-2002 | ||||||||||||||||||||||||||||||
Name of Patentee | COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH | ||||||||||||||||||||||||||||||
Applicant Address | |||||||||||||||||||||||||||||||
Inventors:
|
|||||||||||||||||||||||||||||||
PCT International Classification Number | C08J 5/22 | ||||||||||||||||||||||||||||||
PCT International Application Number | N/A | ||||||||||||||||||||||||||||||
PCT International Filing date | |||||||||||||||||||||||||||||||
PCT Conventions:
|