Title of Invention

"A PROCESS FOR PRODUCING POLYAMIDE COMPOSITE MEMBRANE FOR REVERSE OSMOSIS"

Abstract This invention deals with a process of producing polyamide composite membranes for reverse osmosis. The polyamide composite membrane is made by coating a micro porous polysulfone support for about one minute with an aqueous solution containing 2-wt % m-phenylenediamine (MPD).The excess MPD solution is drained off, and coated support is dipped into a solution of 0.1 wt% trimesoyl chloride (TMC) in hexane for a minute. After draining the TMC solution, the resulting polyamide composite membrane is cured in an air-circulating oven at 40 to 90 C for 2-10 minute. The membrane is given post treatment with acid solution and dried in presence of surface- active agent and disinfectant. The resultant membrane exhibits a product flux of 30.5 gfd and a salt rejection of 95.5 % when tested at 2 to 5 psi pressure for an aqueous solution containing 0.2 % sodium chloride. This membrane can be operated in the pressure range of 200 to 400 psi and the salinity range of 2000 to 10000ppm
Full Text The present invention relates to a process for producing polyamide composite membranes for reverse osmosis In particular, the present invention relates to an aromatic polyamide membrane containing more hydrophilicity therein, which is highly permeable and useful for desalination of an aqueous solution. The present invention relates to process for preparing the membrane.
It is known that the semi permeable membrane can be used for separating dissolved salts from the solvents. For example, of great practical interest is the removal of salts from the saline water by reverse osmosis. The efficiency and economy of such removal is of great significance in order to provide potable water from brackish and seawater for household purposes. A critical factor in desalination is the performance of the membrane in terms of salt rejection or salt removal and flux, i.e., the flow rate across the membrane. For practical applications, the flow should be of the order of greater than about 10-gallons/ft square of membrane area day (gfd) at a pressure of 55 atmospheres (atm) for seawater and 15 gfd at a pressure of 15 atm. for brackish water. The continuing goal of improvement in this area is to develop membranes having increased flux and/or salt rejection, which are useful in desalination.
Among the known membranes used in desalination are included a large number of various types of polyamides which are prepared by a variety of methods. Of particular interest within this broad group of polyamide membranes are cross-linked aromatic polyamide membranes. The cross linked polyamide thin film composite membrane is formed in situ on to the top surface of a porous support are disclosed in the following U.S. patents in the prior art below.
Reference may be made to U.S. Pat. No. 4,277,344,( 1981) to Cadotte J E et al., and U.S.Pat No 4,761,234 (1988) to Uemura et al who discloses the preparation of composite membrane wherein an ultra thin aromatic polyamide film which is formed by interfacial reaction of an aromatic polyamine with an aromatic acyl halide having at least three acyl halide constituents. A porous polysulfone support membrane is coated with p-phenylenediamine solution; the coated support is covered with a solution of trimesoyl chloride dissolved in "FREON" TF solvent (trichloro tri fluoro ethane). The contact time for the interfacial reaction is 10 seconds, and the reaction is substantially complete in 1 second. The draw back of the process is that it uses solvents of very low boiling point and thereby has to maintain at very low temperature (below 20 C) to avoid the loss on evaporation. Moreover maintaining the temperature below 20°C is difficult. The membrane also gives low flux, which makes the process uneconomical.
U.S. Pat. No.4,872,984 (1989) and No.4,948,507, (1990) to Tomaschke et al.discloses the preparation of polyamide composite membrane wherein the polysulfone film is immersed in a solution containing triethylamine salt which is obtained by reacting triethylamine with a sulphonic acid, and polyfunctional amines in a ratio of 0.1 to 4.0. The film is immersed in a solution of 0.2% of acyl halide. Then it is heated at higher temperature to form a thin film. Drawback of this method is that it requires very high concentration of diamine and high temperature like 120°C to form the ultra thin film. US Pat No 4,983,291,(1991) to Chau et al discloses the preparation of polyamide composite membrane wherein the polar aprotic solvent, a polyhydnc compound and an acid acceptor are added in diamine solution to increase the hydrophihcity in the membrane and is reacted with polyacyl halide The so formed membrane is treated with hydroxy polycarboxylic acid, sulphonic acid, inorganic acid etc and washed with water before the membrane is dried Drawback of the method is that it requires elaborate wash treatment to remove the sticky ingredients incorporated into amine solution
U S Pat No 5,658,460, (1997) to Cadotte discloses the method of treating thin film with unsubstituted inorganic ammonium cation salts of an acid before or after its formation to maintain the flux and salt rejection characteristics of reverse osmosis membrane during drying The drawback of the method is the high curing temperature to form the membrane The membrane is cation selective, the anions are passing through the membrane However the permeability of this membrane is low
U S Pat No 5, 336,409, (1994) to Hachisuka et al describes a polyamide composite reverse osmosis membrane prepared by immersing micro porous polysulfone m a
diamine solution containing tertiary amine, and camphorsulfonic acid to increase the hydrophihcity in the membrane It is then reacted with bicyclo (2,2,2, loct-7ene-2, 3,5,6)-tetra carbonyl chloride containing various isomers dissolved in hexane After the film formation, it is heated at 120°C for 5 minutes The drawback comprises the complicated syntheses of acyl halides, low yields, and difficulty m procuring starting materials
U S Pat No 5,733,602, (1998) to Hirose et al discloses the preparation of improved polyamide composite membrane by adding 0 15% sodium lauryl sulfate,2% tnethylamme and 4% camphorsulphonic acid into 2% m-phenylene diamine solution After draining off the excess solution it is immersed in a 0 2% trimesoyl chloride solution in hexane for 1 to 10 minutes Optionally 0 5% alcohol or ether was added in either amine or acyl hahde solution The coated membrane was then heated at 120°C for 3 minutes to form thin film Heating was also carried out in presence of gaseous atmosphere of alcohol or ether Though the resulting membrane gave high salt rejection, permeability is low as it is heated at very high temperature to form the thin film The ingredients added into diamine solution require to be removed completely from the membrane surface, as they are toxic
US Pat No 5,843,351, Hirose et al, (1998), discloses polyamide composite membrane formed by immersing porous polysulfone support m a solution containing 2% m-phenylene diamine and then immersing in the trimesoyl chloride solution in hexane and drying the film in air at 120 C for 3 minutes The film so prepared is negatively charged which preferably rejects anions from the salt water This membrane is further treated with quaternary ammonium salt and coated with a cross-linked layer of an organic polymer having positively charged groups Being a positively charged this membrane rejects cations from the saline water also However, due to the second coating of the positively charged compounds water permeability decreases considerably as compared to the conventional composite membrane
U S Pat No 5,922,203, (1999) to Tomaschke et al discloses the invention related to polyamide composite membrane by incorporating monomenc amine salt, in diamines
solution which increases the permeability of the resulting membrane However the salt rejection of this membrane is poor
U S Pat No 6,026,968, (2000) to Hachisuka et al discloses a composite membrane prepared by immersing polysulfone support into a solution containing 3% of m-phenylene diamine, 0 15% of sodium lauryl sulfate, 3% of tnethyl amine, 6% of camphor sulfonic acid and 5% of isopropyl alcohol for several seconds After drain off the excess solution, it was immersed into a solution containing 0 2% tnmesoyl chloride and 0 05% isopropyl alcohol dissolved m isoparaffine hydrocarbon oil for 3 minutes The film was then heated at 120°C for 3 minutes in hot air The film thus formed was again coated with the solution of 0 25 % sulfonated polysulfone dissolved in ethyleneglycol monomethyl ether and was dried at 60°C for 3 minutes to form a second thin layer. The resulting membrane is anionic and rejects preferably anions from the salt water The membrane permeability reduces due to presence of two layers and extra wash treatments are needed to remove too many ingredients added
US Pat No6,063,278, (2000) to Koo et al discloses a composite polyamide membrane prepared by immersing polysulfone support membrane into a solution containing 2% m-phenylene diamine, 1% of 1,4-diazbicyclo (2,2,2) octane and 0 85% of methane sulfonic acid for 40 seconds , and then the film was immersed in a 0 1% solution of polyfunctional acyl hahde, sulphonyl halide and isocyanate The membrane is heated at 90 C for 30 minutes to form the film It is then treated with 0 2% sodium carbonate solution at 40 to 60°C for 2 to 30 minutes the resultant membrane has improved permeability over the U S Pat NO 6,028,968 but salt rejection has been reduced in the process Treatment of waste disposal of such system is complicated The components used in the polymerization are uncommon, thus not generally in the practice
The polyamide composite reverse osmosis membranes described above have a high desalting performance and water permeability, however, in recent water treatment systems, higher membrane performance is required according to their applications For example in desalination of brackish water, higher rejections are required for each type of mixed ions It has further been the need for these polyamide composite
membranes to improve the water permeability while keeping the salt rejecting performance high For these requirements, various kinds of additives and cross-linking agents have been added in either diamine or in acylhalide solutions However, the improvement of the water permeability is insufficient and a composite reverse osmosis membrane having higher water permeability is the need of the day
The mam object of the present invention is to provide a polyamide composite membrane for reverse osmosis and method of producing the same, which obviates the drawbacks as detailed above Another object of the present invention is to provide a simple method of preparation of polyamide thin film composite membrane for reverse osmosis process.
Still another object of the present invention is to dispense the use of aprotic solvents, alcohols, ketones, quaternary amines, salts of sulfonic acids, surfactants etc. in diamine solutions which interfere in the formation of thin film, and which are difficult to wash out from the surface and which add further disposal problem of used stream. Hence making the process simple and cost effective.
Still another object of present invention is to prepare a stabilized thin film membrane by giving heat treatment
Still another object of the present invention is to treat the ultra thin film with the hydrophilic compounds, which imparts increased hydrophilicity, removes excess diamine, imparts increased hydrophilicity, and increases the water permeability.
Still another object of the present invention is to coat the membrane with polyhydric alcohols and the disinfectants to keep the membrane in dry conditions and stable against bacterial attack.
Still another object of the present invention is to provide a method of producing a composite polyamide reverse osmosis membrane, suitable for use in separation processes like desalination of brackish water, waste water treatments and the like which cause environmental pollution problems. Statement of invention
Accordingly, the present invention provides a process for producing polyamide composite membranes for reverse osmosis
(i) coating the polysulfone porous support with diamine in the concentration range of 0.1 to 10% by weight in the temperature range of 10 to 25°C, relative humidity in the range of 60 to 90% and for an immersion period in the range of 1 to 5 minutes;
(ii)treating the diamine coated support of step i) with the hexane solution containing acyl halide, in the concentration range of 0.01% to 2% by weight, while maintaining the conditions as in (i) for a contact time in the range of 10 to 120 seconds;
(iii) curing the support as obtained in step (ii) in the temperature range of 40 to 90°C for a period in the range of 1 to 10 minutes;
(iv) treating the cured membrane with hydroxy carboxylic acids for a period in the range of 1 to 10 minutes, in the concentration range of 1 to 10% by weight at ambient temperature in the range of 20 to 40°C;
(v) washing the membrane as obtained in step (v) with deionized water to remove the residual acid;

(vi) immersing the washed membrane in a mixture of glycerol and sodium bisulfite in the concentration of 0.5 to 15% by weight; and maintaining the immersion period in the range of 5 to 10 minutes;
(vii) drying the membrane in air in the temperature range of 20 to 50°C; and (viii) preserving the membrane so formed in absence of sunlight.
In an embodiment of the present invention, the polysulfone membrane used as a porous support substrate having pore size in the range of 100 to 300 nanometer, thickness in the range 100 to 150 microns and water permeability in the range of 300 to 400 gfd at 50 psi operating pressure.
In another embodiment of the present invention, porous supports useful in the present invention may be selected from a group of polymers consisting of a sulfonated polysulfone, a polyethersulfone, and a polycarbonate.
In yet another embodiment of the present invention, the diamine may be selected from the group consisting of aromatic primary diamines viz metaphenylene diamine, p-phenylene diamine and secondary diamines viz piperazine and substituted diamines there from.
In yet another embodiment of the present invention, the acyl halide may be selected from the group consisting of aromatic acylhalides viz trimesoyl chloride, isophthaloyl chloride, terephthaloyl chloride and mixture thereof.
In still another embodiment of the present invention, the acyl halide treated support may be cured in the temperature range of 40 to 90 C for a period in the range of 1 to 10 minutes.
In still another embodiment of the present invention, the cured membrane may be treated with hydroxy carboxylic acids viz. citric acid and tartaric acid and inorganic acids viz hydrochloric acid.
In still another embodiment of the present invention, the membrane may be washed with distilled water, deionized water and the like.
In still another embodiment of the present invention, the membrane may be immersed in the solution of polyhydric alcohols viz. glycerol, polyethylene glycol and the like and bio-disinfectants viz. sodium bisulfite, potassium bisulfite and the like.
In still another embodiment of the present invention, the said polyamide composite membrane may be tested in a reverse osmosis test kit using the 0.2% to 1% sodium chloride solution at pressure of 225 psi and at 25 C for water desalination. The present invention utilizes the porous support made from the polysulfone, is a polymeric material containing pore sizes which are of sufficient size to permit the passage of permeate, but not large enough so as to interfere with the bridging over of the ultra thm membrane formed thereon The pore size of the support will generally range from 100 to 300 nanometers, the larger pore size than 300 nanometers will
permit the ultra thin film to sage into the pores, thus disrupting the flat sheet configuration so desired The porous supports used in the present invention include a polysulfone, (Udel P-3500 Amoco Performance Products, Rosewell, Ga), a sulfonated polysulfone, (ICI England), and a polyether sulfone,(Gafone-3200, Gharda Chemicals, India) The thickness of the micro porous support is not critical in the present invention
Freshly prepared polysulfone is first immersed in the aqueous solution of a diamine which is a monomenc amine having at least two amine functional groups The amine functional group is typically a primary or secondary, preferably a primary amine functional group The particular polyamine employed m the present invention is not critical thereto and may be a single polyamine or a combination thereof The polyammes used.include aromatic primary diamines, such as m-phenylenediamine and p-phenylenediamme and substituted derivatives thereof, wherein the substituent includes, e g, an alkyl group, such as a methyl group or an ethyl group, an alkoxy group, such as a methoxy group or an ethoxy group, a hydroxy alkyl group, a hydroxy group Other suitable polyammes include cycloaliphatic secondary diamines, such as pipenzine and its alkyl derivatives, aromatic secondary amines, such as Benzedrine The principal solvent for the aromatic polyamine used in the present method is water, it is particularly desirable to avoid excessive aromatic or hydrocarbon character in the polyammes The polyamine is present in the aqueous solution in an amount in the range of from about 0 1 to 10%, preferably 0 5 to 8%, by weight, most preferably in the range of 2% to 5% of the aqueous solution
The amine coated polysulfone support is next immersed in a solution of a polyfunctional acyl hahde, which is essentially a monomenc, aromatic, polyfunctional acyl hahde, some of which used are, di-or tricarboxylic acid hahdes, such as trimesoyl chloride (TMC), isophthaloyl chloride (IPC), terephthaloyl chloride (TPC) and mixtures thereof Since the interfacial condensation of aromatic polyamide has been carried out on the micro porous polysulfone film, so long as the pores on polysulfone support have less than 300 nanometer diameter, the ultra thin layer bridges over the pores and forming a relatively uniform and defect-free cross linking structure Alternatively, by mixing the diacyl hahde with tnacyl hahde benefits substantially in increasing the network polymer structure The acyl hahde being present in the organic
solvent is in the range of 0 01 to 2%, preferably 0 01 to 0 5%, by weight, of the solution The organic solvent, which is used for dissolving the polyacylhalide, comprises any organic solvent immiscible with water such as hexane, cyclohexane, heptane, octane, benzene, toluene, alkanes, and halogenated hydrocarbons, such as the FREON Among these the lower boiling hydrocarbon, such as hexane, is adequate with respect to its inertness, volatility, and non-toxicity Higher boiling solvent requires higher curing temperature and curing time to effectively remove these solvents from the membrane The concentration of the polyacyl hahde is extremely significant m the formation of polyamide thin film The higher concentration of acyl hahde than 2% increases the thickness of polyamide ultra thin layer, which results in low flux and the concentration lower than 0 01% results in a extremely thin layer of polyamide which may rupture the thin film During this step formation of nascent ultra thin film takes place on to the surface of porous support Subsequently, nascent ultra thin film is heat cured to stabilize on to the porous polysulfone support, which is in the range from 40 to 90°C in an air-circulating oven The curing temperature is m the range of 50 to 90°C, more preferably in the range from 60 to 75 °C for about 5 minutes, thereby the thin film is fixed on to the surface of polysulfone membrane
Subsequently the thin film is treated with hydrophihc hydroxycarboxyhc acids selected from the group consisting of glycohc acid, lactic acid, malic acid, tartaric acid, and citric acid, including inorganic acids comprising hydrochloric acid, and phosphoric acid This step is effective in increasing the hydrophilicity and permeability of composite membrane The immersion time in this treatment can be from 5 minutes to 15 minutes, but it should be preferably 5 to 10 minutes The concentration of these compounds should not exceed 10% of the total aqueous solution, more preferably it should be 1 to 5% by weight of aqueous solution The treatment can also comprises of hot water rinse at 80°C The membrane post-treatment is followed by the simple water wash of the aforementioned polyamide membrane The stabilized and partially heated polyamide ultra thin layer comes into the contact with hydroxycarboxyhcacid, neutralizes the unreacted and excess diamine which is entrapped into the pores of the membranes, thereby removing diamine from the surface The polyamide composite membrane of this invention exhibited increased hydrophilicity after this treatment Accordingly, after the thin layer has been formed
this treatment is essential which eliminate the pore plugging of surface layer generated by diamine components The diamine components sometime fuse into the pores and remain adhering to the pore walls When these polyamide membranes expose to the sunlight and atmosphere they darken due to the oxidation of diamine This oxidized product is insoluble in water and causes dark black and impervious patches on the membrane surface Thus this treatment therefore, is essential in one aspect to increase the hydrophihcity of the polyamide membrane and in another aspect to eliminate pore-plugging components from the surface Although this invention is not bound by any theorized that the acid treatment step extracts unreacted diamine from the ultra thin polyamide composite and stabilizes the polyamide against further oxidation
In the present invention the polysulfone support is coated with the solution of m-phenylene diamine and was immersed with trimesoyl chloride solution, The ultra thin film thus formed is cured in an air circulating oven and post treated with the solution of hydroxy carboxyhc acid and then it was water washed The membrane was then immersed in the mixture of surface-active agent and bio-disinfectant Then it was dried and preserved in absence of sunlight The hydrophihc nature of the polyamide composite membrane induced by the treatment of hydroxy carboxyhc acid is being reported for the first time Beside, the polyamide composite membrane is made resistant to bacterial attack by the treatment of bio-disinfectant The inventive steps adopted in the present invention are (1) coating of polysulfone support with m-phenylene diamine solution and it dispenses the use of tnchloro tnfluoro ethane, which is hazardous and corrosive, (u) the solvent used in the membrane preparation are stable to temperature up to 40°C and therefore it obviate the need to maintain temperature below 20°C, (111) the polysulfone support is coated first with m-phenylenediamine solution obviates the need of adding aprotic solvents, quaternary amine salts and camphorsulfonic acid, (IV) the treatment of membrane with simple organic and inorganic acids enhances the hydrophihcity and dispenses the use of costly triethyl amine and camphorsulfonic acid,(v) the polyamide composite membrane is cured below 70°C and does not require high temperature (100°C) curing, (vi) the treatment of washed membrane with glycerol solution containing sodium
bisulfite reduces the fouling of membrane via bacterial attack, (vn)the membrane is prepared at ambient temperature (20 to 40°C) and need not be below 20°C
The following examples are provided by way of illustration and therefore should not be construed to limit the scope of the present invention
EXAMPLE 1
A casting solution containing 15 wt % of polysulfone in dimethylformamide was caste on a polyester non-woven fabric, and was immersed in water at ambient temperature to solidify the caste film of the polysulfone The polysulfone support film was removed from the gelation bath, and washed thoroughly with water This polysulfone suppqrt film had pores in the range 100 to 300 nm in diameter
The freshly cast porous support was then immersed in a solution of 2 weight-% m-phenylenediamine m water for a period of 2 minutes Excess m-phenylenediamine solution was drained, and was immersed in a solution of 0 1% by weight of tnmesoyl chloride (TMC) dissolved in hexane, the contact time for the interfacial reaction was 60 seconds The polyamide thin film so formed was cured in an oven at 60°C for 5 minutes to stabilize the ultra thin film on porous support It was then further treated with 1 wt % hydrochloric acid in water for 5 minutes and further treated in the mixture of 10 weight percent glycerol and 2-wt percent sodium bisulfite in water for 5 minutes This treated membrane was dried in air and finally preserved in absence of sunlight The membrane so prepared was tested for salt rejection and flux In a standard test procedure, at 225 psi operating pressure and using 0 2% sodium chloride solution at 25°C feed temperature, the membrane gave 95 5 %salt rejection and 30 5 gfd flux
EXAMPLE 2
The porous polysulfone membrane was immersed in an aqueous solution containing 5% by weight of m-phenylenediamme for a period of 2 minutes Excess solution is then allowed to drain off from the surface and the membrane is immersed in a hexane
solution containing 0 1% by weight of tnmesoyl chloride for a period of 2 minutes This membrane is cured in an oven maintained at 60°C for a period of 5 minutes This cured membrane is treated with 1% of hydrochloric acid for 5 minutes, washed for excess of acid and again treating it with the mixture of 10 % glycerol and 2% sodium bisulfite in water for 5 minutes The membrane is at ambient temperature and preserved m absence of sunlight The membrane so prepared was tested for salt rejection and flux In a standard test procedure, at 225-psi operating pressure and using 0 2% sodium chloride solution at 25°C feed temperature, the membrane gave 95 5 %salt rejection and 30 5 gfd flux
EXAMPLE 3
The porous polysulfone membrane was immersed m an aqueous solution containing 5% by weight of m-phenylenediamme for a period of 2 minutes Excess solution is then allowed to drain off from the surface and the membrane is immersed in a hexane solution containing 0 1% by weight of tnmesoyl chloride for a period of 2 minutes This membrane is cured in an oven maintained at 60 C for a period of 5 minutes This cured membrane is treated with 1% of hydrochloric acid for 5 minutes, washed for excess of acid and again treating it with the mixture of 10 % glycerol and 2% sodium bisulfite in water for 5 minutes The membrane is at ambient temperature and preserved in absence of sunlight The membrane so prepared was tested for salt rejection and flux In a standard test procedure, at 225-psi operating pressure and using 0 2% sodium chloride solution at 25°C feed temperature, the membrane gave 95 5 %salt rejection and 30 5 gfd flux
EXAMPLE 4
The porous polysulfone membrane was immersed in an aqueous solution containing 1% by weight of metaphenylene diamine and 1% piperazme for a period of 2 minutes Excess solution is then allowed to drain off from the surface and the membrane is immersed in a hexane solution containing 0 1% by weight of tnmesoyl chloride for a period of 2 minutes This membrane is cured in an oven maintained at 60C for a period of 5 minutes This cured membrane is treated with 1% of hydrochloric acid for
5 minutes, washed for excess of acid and again treating it with the mixture of 10 % glycerol and 2% sodium bisulfite in water for 5 minutes The membrane is at ambient temperature and preserved in absence of sunlight The membrane so prepared was tested for salt rejection and flux In a standard test procedure at 225-psi operating pressure and using 0 2% sodium chloride solution at 25°C feed temperature, the membrane gave 84 %salt rejection and 43 gfd flux
EXAMPLE 5
The porous polysulfone membrane was immersed in an aqueous solution containing 2% of 3,5-diaminobenzoic acids for a period of 2 minutes Excess solution is then drained off from the surface and next the membrane is immersed in a hexane solution containing 0 1% by weight of tnmesoyl chloride for a period of 2 minutes Next the membrane is cured at the temperature of 68 C for a period of 5 minutes It was further treated with 1% by weight of hydrochloric acid in water for 5 minutes After washing this membrane with water it is again treated in the mixture of 10 % by weight glycerol and 2-% by weight sodium bisulfite in water for 5 minutes and dried in air, at ambient temperature and preserved in absence of sunlight The membrane was tested using 0 2% sodium chloride solution at 225-psi pressure and 25°C feed temperature The salt rejection was 55% and flux was 67 5 gfd
EXAMPLE 6
The porous polysulfone membrane was immersed in an aqueous solution containing 2% of m-phenylenediamine for a period of 2 minutes Excess solution is then drained off from the surface and next the membrane is immersed m a hexane solution containing mixture of 0 05% tnmesoyl chloride and 0 05% of isophthaloyi chloride for a period of 2 minutes Next the membrane is cured at the temperature of 60°C for a period of 5 minutes It was further treated with 1% by weight of hydrochloric acid in water for 5 minutes After washing this membrane with water it is again treated in the mixture of 10 % by weight glycerol and 2-% by weight sodium bisulfite in water for 5 minutes and dried m air, at ambient temperature and preserved m absence of sunlight The membrane was tested using 0 2% sodium chloride solution at 225-psi pressure and 25°C feed temperature The salt rejection was 95% and flux was 30 5 gfd
EXAMPLE 7
The freshly cast and gelled support film was immersed in a solution of 2-weight % m-phenylenediamme in water for a period of 2 minutes After removal of excess m-phenylenediamine solution from the surface of the polysulfone support film, the wet film was then immediately immersed in a solution of 0 1% by weight of tnmesoyl chloride (TMC) dissolved in hexane The contact time for the interfacial reaction was 60 seconds The polyamide thin film so formed was cut in to two pieces One membrane piece was cured in an oven at 80°C for 5 minutes and second piece of membrane was cured at 90°C for 5 minutes, both the membrane pieces were further treated with 1 weight percent hydrochloric acid in water for 5 minutes followed by water wash It was treated in the mixture of 10 weight percent glycerol and 2%by weight sodium bisulfite in water for 5 minutes The membrane was dried in air, and preserved in absence of sunlight The membrane was tested using 0 2% sodium chloride solution at 225-psi pressure and 25°C feed temperature The membrane cured at 80°C and 90°C depicted 95 % salt rejection and flux 27 2 gfd and 97 8% and 12 gfd respectively
EXAMPLE 8
The porous polysulfone membrane was immersed in an aqueous solution containing 5% by weight of m-phenylenediamine for a period of 2 minutes Excess solution is then allowed to drain off from the surface and the membrane is immersed in a hexane solution containing 0 1% by weight of tnmesoyl chloride for a period of 2 minutes This membrane is cured in an oven maintained at 60°C for a period of 5 minutes This cured membrane is treated with 2% of citric acid for 5 minutes, washed for excess of acid and again treating it with the mixture of 10 % glycerol and 2% sodium bisulfite in water for 5 minutes The membrane is at ambient temperature and preserved in absence of sunlight The membrane so prepared was tested for salt rejection and flux In a standard test procedure, at 225 psi operating pressure and using 0 2% sodium chloride solution at 25°C feed temperature, the membrane gave 95 5 % salt rejection and 33 5 gfd flux
EXAMPLE 9
The porous polysulfone membrane was immersed in an aqueous solution containing 2% of m-phenylenediamme for a period of 2 minutes Excess solution is then drained off from the surface and next the membrane is immersed in a hexane solution containing 0 1 % tnmesoyl chloride for a period of 2 minutes Next the membrane is cured at the temperature of 62°C for a period of 5 minutes It was further treated with 2% by weight of tartaric acid in water for 5 minutes After water wash membrane is again treated in the solution containing mixture of 10 % glycerol and 2-% by weight sodium bisulfite in water for 5 minutes and dried in air, at ambient temperature and preserved in absence of sunlight The membrane was tested using 0 2% sodium chloride solution at 225-psi pressure and 25°C feed temperature The salt rejection was 95 8% and flux was 34 5 gfd
EXAMPLE 10
The porous polysulfone membrane was immersed in an aqueous solution containing 2% of m-phenylenediamine for a period of 2 minutes Excess solution is then drained off from the surface and next the membrane is immersed in a hexane solution containing 0 1 % tnmesoyl chloride for a period of 2 minutes Next the membrane is cured at the temperature of 62°C for a period of 5 minutes It was further treated with 2% by weight of tartaric acid in water for 5 minutes After water wash membrane is again treated in the solution containing mixture of 15 % glycerol and 1% by weight sodium meta-bisulfite in water for 5 minutes and dried in air, at ambient temperature and preserved in absence of sunlight The membrane was tested using 0 2% sodium chloride solution at 225-psi pressure and 25°C feed temperature The salt rejection was 95% and flux was 36 gfd
EXAMPLE 11
The porous polysulfone membrane was immersed in an aqueous solution containing 2% of m-phenylenediamine for a period of 2 minutes Excess solution is then drained
off from the surface, next the membrane is immersed in a hexane solution containing 0 1 % tnmesoyl chloride for a period of 2 minutes Next the membrane is cured at the temperature of 62°C for a period of 5 minutes It was further treated with 2% by weight of tartaric acid in water for 5 minutes After water wash membrane is again treated in the solution containing mixture of 5 % glycerol and 0 1 % by weight sodium metabisulfite in water for 5 minutes and dried in air, at ambient temperature and preserved in absence of sunlight The membrane was tested using 0 2% sodium chloride solution at 225psi pressure and 25°C feed temperature The salt rejection was 94 5% and flux was 28 5 gfd
EXAMPLE 12
The porous polysulfone membrane was immersed in an aqueous solution containing 2% of m-phenylenediamine for a period of 2 minutes Excess solution is then drained off from the surface and next the membrane is immersed in a hexane solution containing 0 1 % tnmesoyl chloride for a period of 2 minutes Next the membrane is cured at the temperature of 62°C for a period of 5 minutes It was further treated with 2% by weight of tartaric acid in water for 5 minutes After water wash membrane is again treated in the solution containing mixture of 4% polyethylene glycol (400 MW) and 1% sodium bisulfite in water for 5 minutes and dried in air, at ambient temperature and preserved in absence of sunlight The membrane was tested using 0 2% sodium chloride solution at 225-psi pressure and 25 C feed temperature The salt rejection was 94 8% and flux was 29 5 gfd
The main advantages of the present invention are
1 The process of making polyamide composite membrane is simplified, efficient and cost effective by way of elimination of tedious compositions The ingredients used are inexpensive, easy to handle and can be dispose off with minor treatments
2 Increased hydrophilicity of the thin film composite membrane ensure improved permeability and good selectivity for a large number of solutes
3 This membrane can be operated in the pressure range of 200 to 400 psi and the salinity range of 2000 to l0000ppm
4 This polyamide thin film composite membranes has applications in purifying highly saline waters, polluted waters, industrial waters and domestic waters







WE CLAIM:
1. A polyamide composite membranes for reverse osmosis, and method of
producing the same, the said method comprising of
(i) coating the support with diamine in the concentration range of 0.1 to 10% by weight in the temperature range of 10 to 25°C, relative humidity in the range of 60 to 90% and for an immersion period in the range of 1 to 5 minutes;
(ii)treating the diamine coated support with the hexane solution containing acyl helide, in the concentration range of 0.01% to 2% by weight, while maintaining the conditions as in (i) for a contact time in the range of 10 to 120 seconds;
(iii) curing the support as obtained in (ii) in the temperature range of 40 to 90°C for a period in the range of 1 to 10 minutes;
(iv) treating the cured membrane with hydroxy carboxylic acids for a period in the range of 1 to 10 minutes, in the concentration range of 1 to 10% by weight at ambient temperature in the range of 20 to 40°C;
(v) washing the membrane as obtained in (v) with deionized water to remove the residual acid;
(vi) immersing the washed membrane in a mixture of glycerol and sodium bisulfite in the concentration of 0.5 to 15% by weight; and maintaining the immersion period in the range of 5 to 10 minutes;
(vii) drying the membrane in air in the temperature range 20 to 50°C; and (viii) preserving the membrane so formed in absence of sunlight.
2. A process as claimed in claim 1, wherein porous supports useful in the present invention is selected from a sulfonated polysuifone, a polyether sulfone, and a polycarbonate.
3. A process as claimed in claim 1 to 2 , wherein the support membrane used in polysuifone membrane a porous support substrate have pore size in the range of 100 to 300nm, thickness in the range 100 to 150 microns and water permeability in the range of 300 to 400 gallons per feet square of membrane area per day (gfd).
4. A process as claimed in claimslto3, wherein the diamine is selected from the group consisting of aromatic primary diamines viz metaphenylene diamine, p-phenylenediamine and secondary diamines viz piperazine and substituted diamines and mixture thereof.
5. A process as claimed in claims lto 4, wherein acyl halide is selected from trimesoyl chloride, isophthaloyl chloride, terephthaloyl chloride and mixture thereof.
6. A process as claimed in claims 1 to 5, wherein the acyl halide treated support is cured in the temperature maintained range of 40 to 90C for a period maintained the range of 1 to 10 minutes.
7. A process as claimed in claims 1 to 6, wherein the cured membrane is treated with hydroxy carboxylic acids, viz-citric acid, tartaric acid and inorganic acids, viz hydrochloric acid and phosphoric acid.
8. A process as claimed in claims 1 to 7, wherein the membrane is immersed in the mixture of glycerol and sodium bisulfite having (i) glycerol concentration in the range of 0.5 to 15 %and (ii) sodium bisulfite in the range of 1 to 5 % and the immersion period is maintained in the range of 5 to 10 minutes.
9. A process as- claimed in claims 1 to 8, wherein the polyamide composite
membrane is dried in the temperature range of 20 to 40°C and preserved for a longer
period in absence of sunlight.
10. A process as claimed in claims 1 to 9 wherein polyamide composite membrane for
reverse osmosis and method of producing the same substantially as herein described
with references to the examples accompanying this specification.

Documents:

1216-DEL-2004-Abstract-(05-10-2010).pdf

1216-del-2004-abstract.pdf

1216-DEL-2004-Claims-(05-10-2010).pdf

1216-del-2004-claims.pdf

1216-DEL-2004-Correspondence-Others-(05-10-2010).pdf

1216-del-2004-correspondence-others.pdf

1216-DEL-2004-Description (Complete)-(05-10-2010).pdf

1216-del-2004-description (complete).pdf

1216-del-2004-form-1.pdf

1216-del-2004-form-18.pdf

1216-DEL-2004-Form-2-(05-10-2010).pdf

1216-del-2004-form-2.pdf

1216-DEL-2004-Form-3-(05-10-2010).pdf

1216-del-2004-form-3.pdf

1216-del-2004-form-5.pdf


Patent Number 244150
Indian Patent Application Number 1216/DEL/2004
PG Journal Number 48/2010
Publication Date 26-Nov-2010
Grant Date 19-Nov-2010
Date of Filing 30-Jun-2004
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 POPATBHAI DANSANG PARMAR CENTRAL SALT & MARINE CHEMICALS RESEARCH INSTITUTE, GIJUBHAI BADHEKA MARG, BHAVNAGAR- 3640 002, GUJARAT INDIA.
2 PUSHIPITO KUMAR GHOSH CENTRAL SALT & MARINE CHEMICALS RESEARCH INSTITUTE, GIJUBHAI BADHEKA MARG, BHAVNAGAR- 3640 002, GUJARAT INDIA.
3 SHARDA VITHALDAS JOSHI CENTRAL SALT & MARINE CHEMICALS RESEARCH INSTITUTE, GIJUBHAI BADHEKA MARG, BHAVNAGAR- 3640 002, GUJARAT INDIA.
4 JITENDRA JAYDEVPRASAD TRIVEDI CENTRAL SALT & MARINE CHEMICALS RESEARCH INSTITUTE, GIJUBHAI BADHEKA MARG, BHAVNAGAR- 3640 002, GUJARAT INDIA.
5 CHHAGANLAL VITHALDAS DEVMURARI CENTRAL SALT & MARINE CHEMICALS RESEARCH INSTITUTE, GIJUBHAI BADHEKA MARG, BHAVNAGAR- 3640 002, GUJARAT INDIA.
6 AYYANASOMAYAJULA PRAKASH RAO CENTRAL SALT & MARINE CHEMICALS RESEARCH INSTITUTE, GIJUBHAI BADHEKA MARG, BHAVNAGAR- 3640 002, GUJARAT INDIA.
7 KOOVAPADY SIVARAMAN BALARAMAN CHENNAI PETROLEUM CORPORATION LIMITED, CHENNAI, INDIA.
8 MRUTHINTI SEETHARAMA SWAMI CHENNAI PETROLEUM CORPORATION LIMITED, CHENNAI, INDIA.
9 VIRENDRAKUMAR JAYANTILAL SHAH CENTRAL SALT & MARINE CHEMICALS RESEARCH INSTITUTE, GIJUBHAI BADHEKA MARG, BHAVNAGAR- 3640 002, GUJARAT INDIA.
10 NAGJIBHAI KHODABHAI VAGHANI CENTRAL SALT & MARINE CHEMICALS RESEARCH INSTITUTE, GIJUBHAI BADHEKA MARG, BHAVNAGAR- 3640 002, GUJARAT INDIA.
11 TEMUBHA BHUPATSINGH GOHIL CENTRAL SALT & MARINE CHEMICALS RESEARCH INSTITUTE, GIJUBHAI BADHEKA MARG, BHAVNAGAR- 3640 002, GUJARAT INDIA.
PCT International Classification Number B01D 67/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA