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WO1999010089A1 - Procede de remise en etat d'une membrane presentant des imperfections - Google Patents

Procede de remise en etat d'une membrane presentant des imperfections Download PDF

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Publication number
WO1999010089A1
WO1999010089A1 PCT/IL1998/000409 IL9800409W WO9910089A1 WO 1999010089 A1 WO1999010089 A1 WO 1999010089A1 IL 9800409 W IL9800409 W IL 9800409W WO 9910089 A1 WO9910089 A1 WO 9910089A1
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WIPO (PCT)
Prior art keywords
imperfection
membrane
plugging
process according
particles
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PCT/IL1998/000409
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English (en)
Inventor
Mordechai Perry
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BPT - BIOPURE TECHNOLOGIES Ltd
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BPT - BIOPURE TECHNOLOGIES Ltd
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Priority to EP98940534A priority Critical patent/EP1017484A1/fr
Priority to AU88837/98A priority patent/AU8883798A/en
Priority to JP2000507465A priority patent/JP2001513436A/ja
Publication of WO1999010089A1 publication Critical patent/WO1999010089A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0081—After-treatment of organic or inorganic membranes
    • B01D67/0088—Physical treatment with compounds, e.g. swelling, coating or impregnation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
    • B01D65/10—Testing of membranes or membrane apparatus; Detecting or repairing leaks
    • B01D65/106—Repairing membrane apparatus or modules
    • B01D65/108—Repairing membranes

Definitions

  • the present invention relates to a process for blocking and/or plugging imperfections found in membranes in order to improve their solute rejection and or reduce the passage of microorganisms (bacteria and viruses, for example) therethrough.
  • the present invention also provides a process for blocking and/or plugging imperfections found in partially or completely torn or split capillaries, hollow fibers and tubelets.
  • the size of the imperfection may vary from nano-meters to millimeters, centimeters and greater.
  • membrane In water or solvent applications for RO, MF, UF and NF, membrane there is also a need to improve performance by blocking imperfections because the resultant increase in selectivity improves the economics of many applications, for example sea and brackish water desalination, the growing areas of MF, UF and NF in water, waste water treatment or pretreatment prior to RO.
  • the RO membranes are primarily asymmetric structures based on cellulosics, polyamides and composites.
  • the coating may be formed from polymers, oligomers and particles (ex. latex or colloids). Examples of these approaches may be found in the following US patents 3,373,056; 3,877,978; 4,634,531 ; 2,886,066; 4,828,700; 4,812,238; 4,239,714; and 4,704,325.
  • These state of art methods have the following shortcomings. They are general coating methods which do not discriminate between coating the entire external membrane surface uniformly and the plugging or filling primarily the imperfections in a selective manner. In addition while some of these methods will fill imperfections to different degrees the plugging is of a relatively low density material. If the plugging was of high density it would necessarily biock the intact surface and significantly reduce flux of the entire membrane.
  • pore modification is a general method for modifying all membrane pores and not selectively filling the imperfections (Koros - Desalination, US 4704 324).
  • the state of art does not teach how to plug a range of imperfections (from the microscopic to the macroscopic ) without coating the intact membrane area.
  • a process for plugging at least one imperfection found in a membrane comprising applying a solution containing a reactive component in dilute concentration to the surface of said membrane under pressure, said components having low reaction rates at said dilute concentration, wherein at least one reactive component is at least partially entrapped within said imperfection for sufficient time so that a reaction with an other reactive component is induced as a result of a higher level of local accumulation and concentration of said components within said imperfection, whereby there are formed covalently linked reaction products within said imperfection thus permanently plugging the same
  • capillaries hollow fibers and tubelets
  • reactants only into such damaged areas and/or fibers so that after completing the reaction the above damaged fibers and/or areas are blocked.
  • the selective mechanisms for introducing reactants only into the damaged fibers and not into the intact fibers can be achieved, according to the present invention, by introducing reactive particles (optionally expandable) and other non particulate reactants from the external walls of the fiber only into the broken ends of the fiber under the effect of pressure or vacuum in such a way that the interior of the fiber becomes blocked.
  • reactive particles are chosen to be of an appropriate size so that they will not permeate across the intact membrane and they will not block the pores or lumens of the intact membrane.
  • the present invention provides a process for plugging at least one imperfection found in a membrane comprising applying a solution containing different reactive components or identical, self condensing or self polymerizing components of the same chemical structure in dilute concentration to the surface of said membrane under pressure, said components having low reaction rates at said dilute concentration, wherein at least one of said components is at least partially entrapped within said imperfection for sufficient time so that a reaction with said other component is induced as a result of a higher level of local accumulation and concentration of said mixture of components within said imperfection, whereby there are formed covalently linked reaction products within said imperfection thus permanently plugging the same.
  • a process for plugging the lumen of a broken or damaged hollow fiber, capillary or tubelet comprising first applying pressure or vacuum that causes the dispersion of solid or liquid particles to flow into the lumen of the capillary and reacted therein to form a stable plug.
  • Such dispersions are chosen so that they will neither permeate across the membrane nor will they plug the pores of the intact membrane and will selectively pass into the lumen only through the damaged parts of the membrane.
  • reactive reagents may be used in many cases at very low concentration in the solution, without a significant reaction taking place in the bulk of a solution facing the membrane being repaired and on the surface of this membrane.
  • the reaction between the reactive components of the plugging solution/preparate will significantly occur only after they have been accumulated and concentrated within the imperfection. After reacting the plugging material inside the imperfection, the permeability of the solutes and/or of the microorganisms/viruses will be reduced and the rejection of the membrane towards these species will be improved.
  • the material deposited and reacted or precipitated within the imperfection or within the lumen of the capillary may be further densified and stabilized by additional precipitation and/or further chemical reactions such as crosslinking or by modifying the dimensions of the plug by agglomeration and/or expansion through a subsequent chemical reactions or thermal treatments. It has also been found that in many cases the reactants in solution begin to react slowly with each other if left for sufficiently long periods of reaction time so that they can interact and form larger molecules, oligomers, macromolecules, colloids, particles or precipitates which can plug progressively larger imperfections. Furthermore individual particles can grow in size with time by expansion due to evolution of gas inside the particle. Thus in the initial stages of the repairing process, small imperfections are filled and plugged efficiently.
  • the materials that may be used in the present invention are low molecular weight multi-functional reagents for precipitation, complexation and crosslinking, monomers and initiators for polymerization, oligomers, particles (latex, colloids, emulsions, etc.) and liquids which do not dissolve but may form emulsions or liquid suspensions which react with other components to form a solid plug.
  • dilute solutions at low pressures are applied for short periods of time. If the solution concentration is increased, than either the pressure and/or the time of application should be adjusted.
  • the solution may contain one or more of the following components depending on the type of membrane for repair (RO, NF, UF or MF):
  • Reactive particles or colloids of the same type containing the same functional groups which can self condense and/or react within the membrane imperfections and fuse together.
  • Reactive particles or colloids in a solution of reactive polymers, oligomers or low molecular weight reagents containing more than one reactive group where the particles, oligomers and low molecular reagent contain more than one reactive group which may react to form a crosslinked structure.
  • a mixture of polyamines and polyacid under base or acid condition which precipitate at neutral conditions.
  • Reactive particles liquid or solid
  • blowing agents and conditions that can increase their size either in solution and/or inside the imperfection and/or inside the lumen of the damaged hollow fiber, capillary or tubelet membrane.
  • a plugging solution containing a liquid emulsion or suspension which can condense, fuse, expand or polymerize by itself or in combination with other components described in 1 to 8 above , in a relatively rapid rate within the imperfection, to form a plug and in a relatively slow rate in the solution or on the surface of the intact membrane so that no significant flux decline is caused to the membrane.
  • All the above solutions may be applied and subsequently may be subjected to additional steps such as curing, fixation, precipitation, temperature change; and, further crosslinking by immersion for example in solution of additional crosslinkers.
  • additional steps such as curing, fixation, precipitation, temperature change; and, further crosslinking by immersion for example in solution of additional crosslinkers.
  • chemical crosslinking may be applied in a second step.
  • the correct combination of solution concentration and the time of pressure application is easily determined by trial and error.
  • the objective being to increase rejection to the desirable level, without a large decrease in flux; and, further to decrease the passage of microorganisms and viruses.
  • the application of pressure is the preferred driving force which concentrates the reactants and fillers within the imperfection.
  • Other driving forces may also be used as for example an electric field, diffusion via a concentration gradient, centrifugal force, gravity, capillary forces, vacuum etc.
  • spiral wound RO membrane elements that exhibits only 99.0% salt rejection show that in a smaller isolated membrane samples taken from the same element, 99.5% to 99.9% rejection can be found.
  • the rejection of the entire spiral wound element can be increased to around 99.5% rejection or more with less than a 10% loss of flux.
  • tublets of Ultra-filtration membranes in a modular membrane element have a retention to viruses of three orders of magnitudes (3 logs).
  • the retention of viruses is improved to 4,5 or even 6 logs. This is also true for bacteria.
  • the present invention also provides, in a preferred embodiment thereof, a process for plugging an imperfection in a membrane selected from the group consisting of hollow fiber membranes, capillary membranes and tubelet membranes and for plugging the whole lumen such damaged membranes wherein the flux of the plugging substances is directed into the lumen of said membranes by a pressure or vacuum and wherein the reaction between the different components of the plugging solution occurs inside the lumen thus permanently plugging the same.
  • a polymeric or oligomeric material is dissolved in a solvent, preferably water (for polymeric membranes) and a soluble crosslinker, containing at least two reactive groups, which may react with the polymer or oligomer.
  • a solvent preferably water (for polymeric membranes) and a soluble crosslinker, containing at least two reactive groups, which may react with the polymer or oligomer.
  • This mixture is applied under pressure to the membrane.
  • concentrations of reactive components and/or pH and/or temperature is in range so the reaction is sufficiently slow that at least in the initial stages mostly uncrosslinked and unreacted polymer or oligomer and crosslinker are pressed into the imperfection and undergo a more rapid reaction within the imperfections because of their higher concentration inside these imperfections.
  • the polymer or oligomer may react with the crosslinker at a lower rate and a population of larger molecules builds up in the bulk solution and these larger molecules are also pressed into the imperfection. These larger molecules can more efficiently fill the larger imperfections where they are also crosslinked. Therefore as a result of this procedure, a large portion of the molecules are crosslinked and bound inside the imperfection during the stage of the application of pressure. This step may be repeated if needed. Optionally if needed additional crosslinking and additional curing may take place, by application of more or different crosslinkers, with or without pressure, change of pH, heating ,or drying.
  • a polymer, copolymer, tripolymer or mixture thereof, and a crosslinker under conditions where the materials are all initially dissolved or suspended at a given pH. As the reaction is allowed to continue within the imperfection pores and solution, the pH may then be changed to precipitate the materials within the pores. Additional crosslinking may occur in this condensed state at the same pH-Temperature or a different pH- Temperature combinations. In some cases the crosslinker may be left out until the material is pressed into the imperfection and precipitated. In another variation of this embodiment the polymers are applied with a crosslinker and the reaction occurs during application and then further precipitation can be carried out in an additional stage.
  • the solutions mentioned above under numbers in 1 and 2 contain particles, colloids emulsions and/or latex particles; these particles may or may not be reactive with each other or with other components in the solution. These particles enhance the efficiency of plugging large imperfections. Any component which becomes entrapped within the plug without reacting is a filler.
  • colloids or latex may be used alone for certain applications where only large imperfections are expected (ex. in UF or MF membranes) the material will condense or react preferably within the imperfection as it is being concentrated.
  • monomers and initiators are dissolved in the solution in relatively dilute form, and when pressed into the membrane are concentrated and react within the imperfections at a greater rate than in the solution.
  • the polymer or oligomer may also form in solution and these will also be pressed into the membrane.
  • a preferred monomer initiator combination is a water soluble monomer (ex acrylic acid) and free radical initiators (azo initiators, peroxides, hydro peroxides, and redox salt combination which form radical initiators) which undergo addition polymerization. Multi functional vinyl compounds which form crosslinked networks are also preferably included.
  • Another preferred embodiment is a combination of water soluble monomers (ex. methyimethacrylate), which become insoluble upon polymerization. When further polymerization occurs, within the imperfection a water insoluble plug will form in the aqueous phase of the imperfection. Cationic and anionic polymerization and condensation polymerization may also be used.
  • a liquid monomer suspension will interact with the initiator which will polymerize within the imperfection.
  • a preferred case is the use of a multi-functional vinyl compound within the solution.
  • Another case further provides the addition of a is liquid epoxy containing molecules, silicones, adhesives and curing agents in the liquid form.
  • a selective plugging of torn or damaged hollow fibers, capillaries or tubelets is achieved with the use of reactive particles alone or in combination with polymers and low molecular weight reactants which form an insoluble lumen plugs.
  • the imperfections may vary in size from angstroms to microns to a fraction of a millimeters. If the imperfection are a crack or slit the length may be from 1 nano-meter to 10 centimeters, or even larger. In case of damaged hollow fibers, capillaries or tubelets the lumen which have to be plugged may have inner diameter of 20 microns and up to 5 millimeters.
  • the object of the present invention is the use of reactive particles or polymers and/or oligomers with multi functional reagents which form crosslinked or condensed particles or plugs, in situ, within the imperfection, or low molecular weight monomers or multi functional compounds which can condense to form polymers or crosslinked materials inside such imperfections.
  • the particles may be 1 nano-meter to 50 microns and up to few millimeters, depending on the size of the imperfection to be and the type of membrane being repaired .
  • At least the surface of the particles contains reactive groups (the interior of the particles may or may not contain reactive groups). These reactive groups may self condense with groups on other particles (with or without the same groups) or monomers, or oligomers or polymers present in a solution when pressed into an imperfection. Once within the imperfection, the particles fuse and cure to one another or to the membrane walls and or some or all of the additional components of the plugging solution. Alternatively the particles do not react, but become embedded in a crosslinked matrix formed from the polymer, oligomer, additional crosslinking agents, a polymerization process.
  • a polymer or oligomer or monomer soluble in a solution and pressed into the imperfection, precipitates by for example by the change of concentration or pH or increase in concentration of crosslinkers or increase of molecular weight, which causes the polymer or oligomer to become insoluble.
  • This precipitate may, if necessary, be further cured to form a stable plug within the pore.
  • the curing may occur via a crosslinking or self condensation between the mixed components during the time they are being concentrated within the imperfection, or may be added at a latter stage of the process after the imperfection has been filled.
  • the invention includes forcing under pressure (hydrostatic, capillary, vacuum or osmotic) reactive particles, polymers or monomers which then cure within the imperfection.
  • the reactive polymers, particles or monomers pass preferentially into the imperfection and do not accumulate substantially on and inside of the intact membrane pores, because of the higher flow rate of liquid into the damaged areas versus the flow on the intact membrane areas.
  • the imperfections are filled, with only a thin coating covering the area of the intact membrane.
  • the reaction rates are higher in the imperfections because of the higher concentration. It is of importance that at least one component of the plugging solution is sufficiently retained such that it and other components (of smaller size) are also retained, because of the first components' retention, and concentration.
  • Reactive epoxy particles which may be either latex, colloidal particles and may also extent to the micron range of 10 nm up to 100 microns and up to millimeter size. These epoxy particles may be made solely of one or more epoxy materials or epoxy particles with a surface coating of another material or a particle of another material coated with epoxy, wherein the epoxy is either chemically bonded or physically absorbed. The particles can self cure with heat, a catalyst, or by compression into the imperfection with low molecular weight reactive compounds (e. g.
  • amines oligomers and polymers containing active hydrogen atoms on 1st, 2nd, tertiary aliphatic and/or aromatic amines, hydroxyl, aliphatic or aromatic groups, carboxyl and sulfide groups, with catalysts or without catalysts.
  • the particles may be pressed into the imperfections and then cured with the application of an external crosslinker.
  • the crosslinker or hardener may be included in the same solution containing the reactive epoxy particles
  • Other particles may contain reactive triazines and diazines and alkyl/halogens or benzyl halogen groups.
  • the triazine and diazine are preferably (but not exclusively) reactive because of the presence of reactive halogen groups. These particles may be applied in the same way as epoxy particles.
  • Another preferred process is the utilization of a solution containing a polymer or a mixture of different polymers or a mixture of a polymer and low molecular weight, multi-functional reactive compounds or polymers and oligomers. These mixtures are applied in a clear solution or in a mixture of a solution where some of the components have precipitated to form a colloidal, latex or particle suspension that may still contain soluble material which can be further precipitated.
  • the above solution or suspension is applied under pressure to the membrane. After having been forced into the imperfection it is further precipitated and cured within the imperfection.
  • This precipitation may occur due to the increased concentration within the imperfection, changing pH, adding salt, or by a crosslinking agent already in solution which through crosslinking, precipitates densities the polymers or polymers and particles together.
  • solutions of polymers or polymers and a suspension of these particles may contain reactive particles described in the approach above which contain, epoxy, triazine, diazines and alkyl or benzyl halogen compounds.
  • the two previous approaches may contain non reactive colloids, latex, particles, polymers or oligomers which act as fillers in the cured plug.
  • the curing of the precipitated plugs or coalescing particles within the imperfections may be carried out by a reaction between the groups already on the molecules within the precipitate or mixture, otherwise the reaction may occur between the groups and molecules applied to the plugs or precipitate after the latter has formed.
  • Any of the above reactions may occur, for example, between low molecular weight species, oligomers, polymers or particles (including colloidal and latex particles) containing an active hydrogen on a primary, secondary, aliphatic and aromatic amines (including tertiary amines without hydrogens but with reactive electron pair), hydroxyl, sulfide, carboxyl, multi-functional low molecular weight molecules, oligomers, polymers or particles (including colloidal particles) containing epoxy, or halo triazine and aliphatic and benzylic halogen containing compounds.
  • Examples of the above and other crosslinkers are disclosed in US 4,767,645; US 4,778,596; and, US 4,659,474.
  • the epoxy particles may be made in numerous ways. Some of the procedures are covered in the following patents and are included in the present invention. These patents are, US 5176959 German Offenlegungsshrift 3,644,37 and 3,726,497.
  • Epoxy particles may also be made by dissolving a multi functional epoxy compound (examples of such compounds are given in US 4,265,745) in a water miscible solvent and adding water to the solution with stirring. Either or both solutions way contain surfactants, emulsifiers and stabilizers to achieve a predetermined particle size or particle size range, and to stabilize the particles from aggregating or coalescing.
  • particles may be made to contain halogen groups on triazine and diazines and alkyl compounds.
  • the materials for making the particles should contain reactive groups for curing or crosslinking reactions or binding reactions between particles or polymers and particles.
  • Particles on the nano, sub-micron or micron level may be polymers with reactive pendants.
  • Such polymers are readily available with the following reactive pendants - amino groups with primary, secondary or tertiary aliphatic or aromatic amines, hydroxy groups and sulfides. These groups are readily used to add molecules which contain epoxy, alkyl halides, benzyl halides and halides bound to diazines and triazines.
  • By reacting an excess of molecules containing two or more epoxy, or reactive halogens with the polymers containing amino, OH or SH groups polymers and particles can be created with reactive epoxy and halogen groups. The excess should be sufficient so that the polymers do not crosslink or form a precipitating mass.
  • the new epoxy or halogen containing materials will now be able to condense with one of their free epoxy or halide groups.
  • homogeneous polymer solutions are pressed into the imperfections and then precipitated and cured to a crosslinked mass within these imperfections.
  • the precipitation may be carried out by a change in pH or by a crosslinking reagent which crosslink the polymers at a very low rate, so that a homogeneous solution will be maintained above the membrane, but once pressurized into the imperfections these substances will concentrate and undergo fast crosslinking and precipitation reactions will occur within the imperfections.
  • a mechanism which allows the mixing of polymers solutions with crosslinkers without precipitation or gel formation in the bulk solution is based on:
  • the crosslinker may be multifunctional epoxy, alkyl halides, benzyl halides triazine and diazine derivatives, aldehydes, activated double bonds. If the precipitates contain epoxy alkyl halides, benzyl halides triazine, diazine aldehydes and activated double bonds then the crosslinking molecules may contain amine, alkyl halides, benzyl halides, diazines and triazines.
  • a preferred embodiment of the present invention is the utilization of a mixture of polyamine and a polyacid. Normally upon mixing solutions of such polymers a precipitate forms. Outside this range, in the basic or acidic pH extremes the solutions are soluble. A mixture of these polymers is applied in the soluble state to fill the imperfections of a membrane, then the pH is a adjusted to precipitate the polymer mixture.
  • the precipitated polymer may then be crosslinked by applying a multi-functional epoxy, multi halo alkyl, benzyl halogens, aldehyde compounds, reactive triazine or diazine derivatives.
  • these crosslinkers may be added to the polyamine/poly acid solutions. This can be done if the pH of the solutions does not hydrolyze the functional groups of the crosslinker. In this way the polymers are crosslinked as they concentrate within the imperfection and/or after they precipitate.
  • the respective ratio of the two may be adjusted so that a pH can be found where the solution is clear and does not hydrolyze (to a large extent) any reactive component.
  • the relatively low concentration of polyamine, polyacid and a crosslinker, for example are such that the reaction does not occur rapidly and the solution may be applied without precipitation or gel formation occurring in the solution.
  • the polymers will concentrate in the imperfection, thus, the reaction rates will increase and the reaction will happen selectively inside the imperfection.
  • the increased concentration within the imperfection may cause a precipitation of the components.
  • a polyamine may be applied to the imperfections and then a polyacid may be applied to precipitate as an acid base complex.
  • the polyacid may be citric and/or polyacrylic acid (molecular weights from 500 to 5x10 6 Daltons).
  • the acid-base precipitate may be further crosslinked by chemically crosslinking either the polyamine, polyacid or both, as follows:
  • the polyamine in all the embodiments may be taken from the category of polyvinylamines and their co and tri polymers, poiyaromatic compounds such as polyamino-styrene, amine containing engineering plastics of the aromatic polysulfones (ex polysulfone, polyether sulfone, polyphenylene sulfones, PEK, PEEK) polyethyleneimines and derivatives of polyethyleneimine.
  • the different types of polyamines and amines which may be used may be chosen from the lists found in US 4,265,745; US 4,659,474 and US 4,039,440.
  • the polyacids may be low molecular weight polyacids of 2 or more carboxylic, sulfonic groups or phosphonic (such is citric and malic acid), succinic acid, polyacrylic acid (in molecular weight ranges of from 200 to 5 million), polyvinyl sulfonic acid and polystyrene sulfonic acid.
  • the polyacids may be from naturally occurring polymers such as alginic acid homopolymers, random co, tri and ternary polymers or block and graft polymers may be used.
  • the functional groups on all the polymers other than the homogeneous polymers may contain both basic amines and anionic functions (carboxylic acids). These polymers may also be chosen from the sulfonic, carboxylic, phosphonic derivatives of polysulfone, polyether sulfones, polyether ketones and other engineering plastics.
  • a crosslinker and particles may be used.
  • the polymer should be able to wet the surface of the particles, with or without additional agents such as surfactants.
  • the particles may or may not be reactive arid may be chosen from a wide range of candidates.
  • the solvent of the plugging solutions may be primary water.
  • Organic solvents and/or salts may be added to the water to change the flow and plugging rates by changing for example surface tension, solution viscosity, and/or permeability.
  • crosslinking may occur by an in situ crosslinker or by the application of an outside crosslinker while, the above process is used to modify the entire membrane surface; the present invention is concerned with selectively fixing or plugging holes and imperfections.
  • crosslinkers may be applied in a second stage to the precipitated plug, otherwise the crosslinkers are present within the solution of monomers, polymer, or polymers and particles, used to plug the imperfection and are thus intimately mixed.
  • tannins are used to improve RO salt rejection of asymmetric or composite membranes. There is no chemical crosslinking, and the process is for improvement and not fixing imperfections.
  • the Tannins adhere to the selective layer.
  • the tannins change the surface properties of the contacted membranes. Since they are not covalently crosslinked, and/or bound to the membrane, the Tannins can be washed off and must be reapplied.
  • the process is for coating the entire surface of the exterior or filling all pores of the hollow fiber without sticking of the hollow fibers to each other, utilizing the application of pressure without flow.
  • This invention is for uniform coating and not the filling of imperfection.
  • the use of the term pores does not describe imperfections and the coating materials are sufficiently large molecular weight molecules or sufficiently large particles (for example colloidal dispersions) that the deposited material does not readily pass through the walls of the hollow fibers. Small molecules may be used penetrating into the pores when the objective is for the material of the hollow fiber to substantially effect the fluid separation.
  • After depositing the coating material the deposit may be further crosslinked. All the examples are for gas separation using silicone coatings, and fluid separation within the context of the patent is gas separation. The above patent only applies to a bundle of hollow fibers.
  • a water soluble polymer containing amines and carboxylic acids can be crosslinked and insolubilized with nitrous acid when a concentrated NaNO 2 salt solution is used.
  • This crosslinked layer can be a discriminating layer in a composite membrane.
  • This formulation and process cannot be used to give a selective filling and forming of dense plugs within imperfections, as it is claimed to form uniform selective barriers, on the surface.
  • the crosslinking requires a diazonium step after coating. The diazonium reaction is hard to control and in the examples is carried out on the dry film.
  • selective RO membranes are improved by forming an additional selective layer comprising an ionic complex of one compound containing quaternary ammonium, imidazolium or py ⁇ dinium groups and a second compound bearing at least one carboxylate, phosphonate or sulfonate groups where at least one of the first and second compounds is a polymer or prepolymer bearing more than one ionic group per polymer.
  • the objective of the above is a selective homogenous layer and not selective blockage of membrane imperfections
  • the layers may be crosslinked by crosslinking agents, or groups on one of the above compounds.
  • the formation of the ionic crosslinking results from a sequential coating of the cationic compound and anionic compound accomplished by the following options, by application of the solutions from opposite sides of the membrane, or by application of a solution of one of the components to a membrane containing functional groups of the opposite charge.
  • EP 0,631 ,806 a coating is used as an external defect sealing layer. There is no disclosure of pore plugging rather a coating for covering a defect. This approach cannot seal large defects and results in a significant reduction in flux.
  • Pre-made colloidal particles mixed with reactive polymers, and/or multi functional reagent may be forced together into the imperfection to form a dense plug.
  • Particles, dispersions, latexs, colloids for example synthetic latex particles
  • material examples include anionic acrylic, anionic nitrite - styrene-butadiene, styrene- butadiene-vinyl pyridine, terpolymer, vinyl and vinylidene chloride copolymer, resorcinol-formaldehyde, polyvinyl chloride-acrylic copolymer, and vinyl fluoride latexs.
  • Commercially available latex particles may be purchased from Dow Chemical Co., B.F. Goodrich Co. And many others. • Multiple layer latexs or core shell latexs or particles produced by sequential emulsion polymerization of the same or different polymers.
  • Particles produced by suspension polymerization such as that from polystyrene and polymethylmethacrylate.
  • Aqueous dispersions of epoxy containing compounds which are stabilized against flocculation by external stabilizers (US 4,122,067 and EP-OS 81 ,163 and others) or by internal emulsifiers (German offenkgungsschrift 3,643,751 and 3,820,301 and in EP-OS 51 ,483).
  • blowing agents such as: volatile liquids, chemical blowing agents (sodium bicarbonate, sulfonyl hydrazides, dinitrozopentamethylenetetraamine, azidocarbonamides.
  • the solutions containing the particles, dispersions, latexs, colloids may contain additional agents that act to stabilize the solutions against precipitation and flocculation while in solution.
  • agents may be surfactants, emulsifiers, protective polymeric or particles which act to prevent aggregation.
  • Example 1 A sea water RO membrane area 20 cm 2 is placed in a 10 cm long and 2cm wide flow cell and tested at 55 bars 20 ° C, flow rate 5 liters/min over the surface, and gave a rejection of 97.5% to 3.2% solution of NaCI with a flux of 650 liters/m 2 day. The cell is opened and a 10 cm crack is made on the membranes length by bending it back and forth for several times. Reinserting the membrane under the above conditions gives a rejection of only 90% to 3.2% solution of NaCI with a flux of 720 liters/m 2 day.
  • the membrane is then processed as follows.
  • Example 2 Example 1 is repeated using a 0.1 % solution of polyethyleneimine and 0.05% solution of polyacrylic acid.
  • the initial rejection and flux before making a crack was 98.2% and 620 liters/m 2 day at 55 bar. After making the crack the salt rejection drops to 89% and the flux increases to 740 liters/m 2 day. After the repairing sequence of steps the salt rejection increases to 99.0% and the flux is 610 liters/m 2 day.
  • Example 3 Example 2 was repeated using a brackish water membrane instead of a sea water membrane. The membranes was tested at 15 atm. and gave 96.5% rejection and 1030 liters/m 2 day using a 1500 ppm solution of NaCI. After making a crack the rejection dropped to 93.0% and the flux increased to 1500 liters/m 2 day. After repairing as in example 2 the salt rejection increased to 98% and the flux was 965 liters/m 2 day at @15 atm.
  • Example 4 Example 1 is repeated without the first epoxy step and gave similar results.
  • Example 5 Example 4 is repeated without the first epoxy step and a polyethyleneimine and polyacrylic acid concentration of 0.1 and 0.35% respectively.
  • the membrane performance starting, after crack, and after the repair is 98.2%/720 liters/m 2 day, 91 %/816 and 98.7%/690 liters/m 2 day respectively.
  • Example 6 A brackish water membrane as used in example 3 had a starting rejection of 97.2% 1420 liters/m 2 day. After making 10 pin holes down to the non woven (but not through the non woven), the membrane was pressurized at 10 atm. for 40 minutes with a pH 9.5 solution containing 500 ppm solution of water insoluble epoxy particles (1 micron average diameter), 1000 ppm polyethyleneimine and 1000 ppm of the ethyleneglycol diglycidyl ether. The membrane after the pin holes, and then after repairing had rejection & fluxes of 57% & 1720 liters/m 2 day and 98.1% & 1400 liters/m 2 day to 1500 ppm NaCI solution.
  • the particles were made by taking 2 grams of a novolak epoxy dissolving in 100 ml/acetone and adding this rapidly with stirring to 900 ml H 2 O containing 50 mg of SDS. This solution was diluted by four folds before application in the plugging experiment.
  • Example 7 Example 5 is repeated with the difference of adjusting the pH of mixed solution containing 0.1 % polyethyleneimine and 0.35% polyacrylic acid from pH 10.5 to pH 9.2 and adding enough water soluble epoxy (ethylene glycol diglycidyl ether) to make a 0.1% solution. This solution was pressed through the membrane for 40 minutes at a pressure of 10 atm. The solution was discarded after this step and the membrane left to stand in. citric acid buffer at pH 6.5 for 20 minutes. The epoxy crosslinked and precipitated the polymer inside the crack. The starting membrane had a salt rejection of 95% and a flux of 700 liters/m 2 day. The rejection after the crack was 29% and a flux of 20,000 liters/m 2 day, after plugging the rejection was 96% and the flux 620 liters/m 2 day.
  • water soluble epoxy ethylene glycol diglycidyl ether
  • Example 8 Example 7 is repeated with the difference that only polyethyleneimine without the polyacrylic acid is used. The rejections in 1500 ppm NaCI solution at 15 bars drops from 98.1 % in the original membrane to 85% after the crack formation and is repaired after the plugging experiment to 98.5%.
  • Example 8 is repeated by damaging the top selective layer over a 0.5 cm 2 area and exposing the underlying supporting UF membrane. Following the procedure of the example 8 the membrane was repaired and brought back to its original rejection of 98.5% plus an addition 0.6% to 99.1 %. The rejection of the damaged membrane before the repair is only 82%.
  • Example 10 Example 6 is repeated with a membrane having a 3.5 mm diameter hole protruding through the RO selective layer and through the supporting UF layer down to the non-woven.
  • the rejection and flux is 0% and 25,000 liters/m 2 day to 1500 ppm NaCI at 12 atm. After repairing according to the procedure in example 6, the rejection was 95% and the flux was 650 iiters/m 2 day respectively.
  • Example 11 A brackish water membrane as in example 8 was scratched with a sharp needle to make thin long lines down to the non-woven. The membrane was repaired according to example 8. The rejection/flux originally, after the crack, and after the repair are 97% & 826 liters/m 2 day, 35% & 1020 liters/m 2 day and 98% & 750 liters/m 2 day respectively.
  • Example 12 An RO membrane as in example 8 is scratched with a sharp needle to make a 8 cm long scratch which penetrates to the non-woven.
  • the rejection/flux at 15 atm., 1500 ppm NaCI goes from 97.8% & 650 liters/m 2 day to 75% & 1120 liters/m 2 day.
  • a solution 0.3 millimoles/liter of cyanuric chloride is added to the polyethyleneimine solution at 10°C at pH 9.5 and pressed at 15 atm. through the membrane.
  • the resultant membrane had a rejection of 98.2% & 616 liters/m 2 day.
  • Example 13 Example 11 is repeated but instead of cyanuric chloride, a 0.2% solution of glutaraldehyde was added to the solution and the membrane's salt rejection is brought back to its original value with only a 10% loss of flux.
  • Example 14 Example 11 is repeated but instead of cyanuric chloride, using this time a solution of 0.15% of reactive Blue 4 (Aldrich catalog 24,481-3) dye with similar results as an example 11 with only a 5% loss in flux.
  • Example 15 Example 11 is repeated but instead of polyethyleneimine, polyvinyl alcohol having a molecular weight of 90,000 is used. The results are similar as in example 11.
  • Example 15 is repeated with a copolymer of polyvinyl/vinyiacrylic acid. The results are similar as in example 15.
  • Example 17 Example 8 is repeated using a copolymer of polyvinyl aniiine/styrene sulfonate. The results are similar as in example 8.
  • Example 8 is repeated using a nano-filtration membrane from DDS. A crack is made in the membrane by multiple bends to reduce the rejection of glucose from 96% to 86%. After correcting the membrane according to the procedure of example 8 the rejection was 98% to glucose.
  • Example 19 A UF membrane from Kalle has a 95% rejection to a 1 % BSA solution.
  • a 7 mm diameter hole is made, by removing the polysulfone membrane and exposing the non-woven.
  • a solution containing 500 ppm of polystyrene colloidal particle (0.5 micron diameter) with carboxylic surface groups, 200 ppm polyethyleneimine and 200 ppm of the water soluble epoxy at pH 9.5 flowed along the membrane surface at 2 atm. for 30 minutes. After this treatment the rejection to BSA was 96% and the flux decreased by only 5%.
  • Example 20 A supported microporous membrane, Gelman AP-200W (acrylic copolymer on polyester support) with a nominal Cutoff of 0.2 microns is used. A 50 micron sized needle is used to make 50 micron sized holes. The intact membrane shows a clear permeate with a feed of 5 micron diameter polystyrene particles under pressure of 1 atm. The membrane with 50 micron sized holes gives a cloudy permeate under the same conditions.
  • Gelman AP-200W acrylic copolymer on polyester support

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

L'invention porte sur un procédé visant à colmater au moins une imperfection trouvée dans une membrane, ce procédé consistant à appliquer sur la surface de la membrane sous pression une solution contenant un composant réactif dans une concentration diluée. Les composants ayant de faibles vitesses de réaction au niveau de la concentration diluée, au moins l'un d'eux est partiellement piégé dans l'imperfection sur une durée suffisante, ce qui induit une réaction avec un autre composant réactif du fait d'un niveau très élevé de l'accumulation et de la concentration locales des composants dans l'imperfection. On obtient ainsi des produits de réaction liés de manière covalente dans l'imperfection et colmatant définitivement celle-ci.
PCT/IL1998/000409 1997-08-26 1998-08-25 Procede de remise en etat d'une membrane presentant des imperfections Ceased WO1999010089A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP98940534A EP1017484A1 (fr) 1997-08-26 1998-08-25 Procede de remise en etat d'une membrane presentant des imperfections
AU88837/98A AU8883798A (en) 1997-08-26 1998-08-25 A process for repairing membrane imperfections
JP2000507465A JP2001513436A (ja) 1997-08-26 1998-08-25 膜欠陥の修復方法

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IL121632 1997-08-26
IL12163297A IL121632A (en) 1997-08-26 1997-08-26 Process for repairing membrane imperfections

Publications (1)

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WO1999010089A1 true WO1999010089A1 (fr) 1999-03-04

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Cited By (8)

* Cited by examiner, † Cited by third party
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WO2002040140A1 (fr) * 2000-11-20 2002-05-23 Aquasource Perfectionnements apportes aux procedes de reparation par obturation des fibres creuses des membranes, notamment d'ultra-, nano-, et hyper-filtration
WO2007148147A1 (fr) 2006-06-22 2007-12-27 Gambro Lundia Ab Utilisation d'une suspension colloïdale d'un polymère cationique pour traiter un support à usage médical
EP1808221A4 (fr) * 2004-10-18 2008-06-18 Kurita Water Ind Ltd Agent renforçateur de rapport de blocage pour membrane perméable, procédé d augmentation du rapport de blocage, membrane perméable et procédé de traitement d eau
EP2119675A4 (fr) * 2007-01-24 2012-05-23 Kurita Water Ind Ltd Procédé de traitement par une membrane d'osmose inverse
CN106102878A (zh) * 2013-11-21 2016-11-09 Oasys水有限公司 用于修复膜以及改进渗透驱动膜系统的性能的系统和方法
WO2019132051A1 (fr) * 2017-12-26 2019-07-04 예일 유니버시티 Procédé de restauration de membrane de séparation de traitement d'eau endommagée à l'aide de microparticules de silice fonctionnalisées en surface
US10384167B2 (en) 2013-11-21 2019-08-20 Oasys Water LLC Systems and methods for improving performance of osmotically driven membrane systems
CN111389233A (zh) * 2020-03-20 2020-07-10 北京碧水源膜科技有限公司 针对功能层损伤的微滤膜修复液的制备方法及微滤膜修复方法

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KR102209493B1 (ko) * 2013-12-31 2021-01-28 도레이첨단소재 주식회사 물리적 결함이 제거된 역삼투막, 그 제조방법 및 이를 포함하는 역삼투 모듈

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Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2816851A1 (fr) * 2000-11-20 2002-05-24 Aquasource Perfectionnements apportes au procedes de reparation par obturation des fibres creuses des membranes, notamment d'ultra-, nano- et hyper-filtration
WO2002040140A1 (fr) * 2000-11-20 2002-05-23 Aquasource Perfectionnements apportes aux procedes de reparation par obturation des fibres creuses des membranes, notamment d'ultra-, nano-, et hyper-filtration
US8025159B2 (en) 2004-10-18 2011-09-27 Kurita Water Industries Ltd. Agent for increasing rejection with a permeable membrane, process for increasing the rejection, permeable membrane and process for water treatment
TWI396584B (zh) * 2004-10-18 2013-05-21 Kurita Water Ind Ltd 穿透膜之阻止率提昇劑、阻止率提昇方法、穿透膜及水處理方法
EP1808221A4 (fr) * 2004-10-18 2008-06-18 Kurita Water Ind Ltd Agent renforçateur de rapport de blocage pour membrane perméable, procédé d augmentation du rapport de blocage, membrane perméable et procédé de traitement d eau
CN101505858B (zh) * 2006-06-22 2012-11-21 甘布罗伦迪亚股份公司 阴离子聚合物的胶体悬浮液用于处理医疗用支持物的用途
US8137562B2 (en) 2006-06-22 2012-03-20 Gambro Lundia Ab Use of a colloidal suspension of a cationic polymer to treat a support for medical use
FR2902670A1 (fr) * 2006-06-22 2007-12-28 Gambro Lundia Ab Utilisation d'une suspension pour traiter un support a usage medical, support a usage medical, echangeur et dispositif d'adsorption comprenant le support
WO2007148147A1 (fr) 2006-06-22 2007-12-27 Gambro Lundia Ab Utilisation d'une suspension colloïdale d'un polymère cationique pour traiter un support à usage médical
EP2119675A4 (fr) * 2007-01-24 2012-05-23 Kurita Water Ind Ltd Procédé de traitement par une membrane d'osmose inverse
CN106102878A (zh) * 2013-11-21 2016-11-09 Oasys水有限公司 用于修复膜以及改进渗透驱动膜系统的性能的系统和方法
EP3071319A4 (fr) * 2013-11-21 2017-10-18 Oasys Water, Inc. Systèmes et procédés pour réparer les membranes et améliorer la performance des systèmes de membranes à entraînement osmotique
US10384167B2 (en) 2013-11-21 2019-08-20 Oasys Water LLC Systems and methods for improving performance of osmotically driven membrane systems
CN106102878B (zh) * 2013-11-21 2019-11-08 欧赛斯水务有限公司 用于修复膜以及改进渗透驱动膜系统的性能的系统和方法
WO2019132051A1 (fr) * 2017-12-26 2019-07-04 예일 유니버시티 Procédé de restauration de membrane de séparation de traitement d'eau endommagée à l'aide de microparticules de silice fonctionnalisées en surface
CN111389233A (zh) * 2020-03-20 2020-07-10 北京碧水源膜科技有限公司 针对功能层损伤的微滤膜修复液的制备方法及微滤膜修复方法

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AU8883798A (en) 1999-03-16
JP2001513436A (ja) 2001-09-04
IL121632A0 (en) 1998-02-08
IL121632A (en) 2000-08-13
EP1017484A1 (fr) 2000-07-12

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