WO2009067087A1 - Hydrophilisation de membranes polymères hydrophobes perméables - Google Patents

Hydrophilisation de membranes polymères hydrophobes perméables Download PDF

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Publication number
WO2009067087A1
WO2009067087A1 PCT/SG2008/000440 SG2008000440W WO2009067087A1 WO 2009067087 A1 WO2009067087 A1 WO 2009067087A1 SG 2008000440 W SG2008000440 W SG 2008000440W WO 2009067087 A1 WO2009067087 A1 WO 2009067087A1
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membrane
hydrophilic
permeable
polymer
groups
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PCT/SG2008/000440
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English (en)
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Yali Li
Jyh-Jeng Shieh
Olivia Lum
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Hyflux Membrane Manufacturing (S) Pte Ltd
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Publication of WO2009067087A1 publication Critical patent/WO2009067087A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/26—Polyalkenes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/26—Polyalkenes
    • B01D71/261—Polyethylene
    • 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
    • B01D67/0093—Chemical modification
    • 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
    • B01D67/0093—Chemical modification
    • B01D67/00931—Chemical modification by introduction of specific groups after membrane formation, e.g. by grafting
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F8/00—Chemical modification by after-treatment
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
    • D06M10/00—Physical treatment of fibres, threads, yarns, fabrics, or fibrous goods made from such materials, e.g. ultrasonic, corona discharge, irradiation, electric currents, or magnetic fields; Physical treatment combined with treatment with chemical compounds or elements
    • D06M10/04—Physical treatment combined with treatment with chemical compounds or elements
    • D06M10/06—Inorganic compounds or elements
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
    • D06M11/00—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising
    • D06M11/32—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising with oxygen, ozone, ozonides, oxides, hydroxides or percompounds; Salts derived from anions with an amphoteric element-oxygen bond
    • D06M11/34—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising with oxygen, ozone, ozonides, oxides, hydroxides or percompounds; Salts derived from anions with an amphoteric element-oxygen bond with oxygen, ozone or ozonides
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
    • D06M14/00—Graft polymerisation of monomers containing carbon-to-carbon unsaturated bonds on to fibres, threads, yarns, fabrics, or fibrous goods made from such materials
    • D06M14/18—Graft polymerisation of monomers containing carbon-to-carbon unsaturated bonds on to fibres, threads, yarns, fabrics, or fibrous goods made from such materials using wave energy or particle radiation
    • D06M14/26—Graft polymerisation of monomers containing carbon-to-carbon unsaturated bonds on to fibres, threads, yarns, fabrics, or fibrous goods made from such materials using wave energy or particle radiation on to materials of synthetic origin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/02—Hydrophilization
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/38—Graft polymerization
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2810/00—Chemical modification of a polymer
    • C08F2810/20—Chemical modification of a polymer leading to a crosslinking, either explicitly or inherently
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
    • D06M14/00—Graft polymerisation of monomers containing carbon-to-carbon unsaturated bonds on to fibres, threads, yarns, fabrics, or fibrous goods made from such materials
    • D06M14/18—Graft polymerisation of monomers containing carbon-to-carbon unsaturated bonds on to fibres, threads, yarns, fabrics, or fibrous goods made from such materials using wave energy or particle radiation
    • D06M14/26—Graft polymerisation of monomers containing carbon-to-carbon unsaturated bonds on to fibres, threads, yarns, fabrics, or fibrous goods made from such materials using wave energy or particle radiation on to materials of synthetic origin
    • D06M14/28—Graft polymerisation of monomers containing carbon-to-carbon unsaturated bonds on to fibres, threads, yarns, fabrics, or fibrous goods made from such materials using wave energy or particle radiation on to materials of synthetic origin of macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
    • D06M2101/00—Chemical constitution of the fibres, threads, yarns, fabrics or fibrous goods made from such materials, to be treated
    • D06M2101/16—Synthetic fibres, other than mineral fibres
    • D06M2101/18—Synthetic fibres consisting of macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D06M2101/20—Polyalkenes, polymers or copolymers of compounds with alkenyl groups bonded to aromatic groups

Definitions

  • the present invention generally relates to processes for hydrophilizing ' hydrophobic permeable polymer membranes, such as polyolefins membranes, and the hydrophilized permeable polymer membranes thereof.
  • Polymer membranes such as polyolefin membranes, are used extensively in membrane separation processes in numerous industries, for example in the analytical, pharmaceutical, chemical and food industries.
  • the extensive usage of polyolefin membranes is due to their numerous advantages, in particular their high chemical resistance, high mechanical strength, and low cost.
  • polyolefin membranes are, however, limited by their hydrophobic nature which renders the membranes non-wettable and reduces water permeability of the membranes.
  • polyolefin membranes have limited use in applications which require wettable or water- permeable membranes. Accordingly, polyolefin membranes, and membranes made from other hydrophobic polymers, tend to be not suitable for water treatment applications.
  • polyolefin membranes are characterized by a flux decline that is caused by membrane fouling as a result of solute adsorption and pore blocking.
  • fouling of hydrophilic membranes occurs to a lesser extent than fouling of hydrophobic membranes, like polyolefin membranes, various ⁇ methods have been developed to hydrophilize permeable polyolefin membranes to reduce fouling.
  • hydrophilization methods for film-like materials having smooth surfaces cannot simply be applied to the hydrophilization of permeable polyolefin membranes which have more complex surface configurations.
  • a known method for hydrophilization of permeable ' polyolefin membranes involves organic solvent wetting and water substituting. In this method, the membrane have to be immersed in water throughout the process, which renders the process cumbersome.
  • the wetting agents or surfactants may migrate to and • contaminate the permeate stream. Of course, this leads to contamination of the permeate stream.
  • the membranes are hydrophilized by blending polypropylene with hydrophilized polypropylene. After extraction, most of the hydrophilic functional groups such as -OH, -NH 2 , and -COOH in the hydrophilized polypropylene are located on the surface of the membrane including the pore surfaces.
  • the porous membrane • produced thereof generally have a low porosity.
  • Graft polymerization processes have also been used to modify and introduce desirable properties, such as . hydrophilicity, to permeable hydrophobic membrane surfaces by attaching various functional hydrophilic monomers onto the surface of the permeable hydrophobic membranes.
  • the permeable hydrophobic membrane is brought in contact with a solution of the functional hydrophilic monomer (s) in the presence of an initiator.
  • the free-radical polymerization is initiated by irradiation with UV light or plasma treatment.
  • the disadvantage of this process is that it is difficult to achieve uniform hydrophilization of the membrane throughout the depth of the membrane, particularly if the membrane has a . large thickness or is in the form of a hollow fibre, without damaging the membrane or reducing its mechanical strength.
  • graft polymerization processes which involve reacting a hydrophobic polymer surface with monomeric solutions comprising hydrophilic functional groups.
  • a problem with some of these known processes is that they are not suitable for being applied to a permeable membrane. This is because the grafting processes involves • the functional hydrophilic groups applied in such an amount that they completely cover the polymer substrate.
  • such methods are unsuitable for application to permeable polymer membranes because they block the pores and render the membrane impermeable, or at least reduce their permeability to such an extent that they are no longer functional.
  • a process of at least partially hydrophilizing a hydrophobic polymer comprising the step of graft polymerizing a hydrophilic monomer solution while in contact with the permeable polymer membrane having peroxide groups along the polymer chains thereof, under conditions that prevent substantial reduction of the pore diameter of said permeable polymer membrane.
  • the peroxide groups include hydroperoxide groups .
  • thermal decomposition of the peroxide groups initiates the graft polymerization of the hydrophilic monomers, thus allow chemical bonding of the hydrophilic functional groups onto the permeable polymer membrane .
  • the pore diameter of the pores of the permeable polymer membrane are not substantially blocked during the polymerizing " step.
  • a process of at least partially hydrophilizing a hydrophobic polymer comprising the step of graft polymerizing a hydrophilic monomer solution while in contact with the permeable polymer membrane having peroxide groups, including hydroperoxide groups, along the polymer chains thereof, wherein the concentration of hydrophilic monomer in said hydrophilic monomer solution is selected to substantially prevent reduction of the pore diameter of said permeable polymer membrane during said graft polymerizing.
  • the pore diameter of the pores of the permeable polymer membrane are not substantially blocked during the polymerizing step because the concentration of hydrophilic monomer in said hydrophilic monomer solution does not exceed a predetermined amount.
  • the concentration of hydrophilic monomer in said hydrophilic monomer solution does not exceed a predetermined amount.
  • the pores will become blocked and the permeable membrane will not be able to function because it will no longer be permeable, or its permeability will be significantly impaired.
  • the degree of graft hydrophilic polymerisation may be controlled to produce a thin layer
  • the .amount of hydrophilic polymer held on the permeable polymer membrane is preferably in the range of about 1% to about 30% by weight based on the weight of the permeable polymer membrane) of hydrophilic polymer and thereby minimize the pore blocking.
  • the degree of graft polymerisation can mainly be carried out in three aspects: grafting time, grafting temperature, monomer concentration.
  • the permeable polymer membrane has hydrophilic groups chemically coupled to the hydrophobic membrane via the peroxide moiety that has initiated the graft polymerization of hydrophilic monomers with hydrophilic functional groups.
  • the permeable membrane made from hydrophobic materials is able to be used in applications involving hydrophilic fluids.
  • the permeable membranes disclosed herein can therefore be used for water treatment applications.
  • hydrophilized permeable polymer membrane comprising: a permeable polymer substrate made of hydrophobic polymer; and hydrophilic groups that have been chemically bonded to said hydrophobic polymer having peroxide groups along the polymer chains thereof.
  • the amount of hydrophilic groups at least partially hydrophilizes the polymer substrate without substantial reduction of the pore diameter of said permeable polymer membrane.
  • water treatment process comprising the hydrophilized permeable polymer membrane of the second aspect to treat said water.
  • a hydrophilizing hydrophobic polymer made in the process of the first aspect.
  • peroxide and grammatical variations thereof are interpreted to mean, in the context of this specification, peroxides and hydroperoxides.
  • a peroxide means an compound containing an oxygen-oxygen bond capable of cleaving and forming oxygen free-radicals.
  • the peroxides may include hydrogen peroxide and peroxidized precursors thereof r peroxyacids of carboxylic acids, peroxyesters of carboxylic acids and the dimeric product of carboxylic peroxyacids.
  • hydroperoxide refers to peroxide compounds having at least one HOO- group, or a compound which upon reaction, produces the peroxide group.
  • Hydroperoxides as used herein are intended to include both organic and inorganic hydroperoxides and cover all hydroperoxides including hydrogen peroxide.
  • exemplary organic hydroperoxides may include alkyl hydroperoxides such as methyl hydroperoxide, ethyl .
  • hydroperoxide isopropyl hydroperoxide, n-butyl hydroperoxide, t-butyl hydroperoxide, t-amyl hydroperoxide, 2, 5-dimethylhexane- 2, 5-dihydroperoxide sec-butyl hydroperoxide, tert-butyl hydroperoxide, cyclo-alkyl hydroperoxide such as cyclohexyl hydroperoxide cyclopentyl hydroperoxide, cyclobutyl hydroperoxide, cyclopropyl hydroperoxide and epoxy hydroperoxides such as 2-methoxy-2-propyl hydroperoxide.
  • Exemplary inorganic hydroperoxides may include hydrogen peroxide, peroxonitrous acid, peroxophosphoric acid, and peroxosulfuric acid.
  • graft-polymerization refers to polymerizing the hydrophilic monomers in the hydrophilic monomer solution to express hydrophilic polymer chains onto polymer chains of the hydrophobic polymer membrane. Accordingly, at least one part or a total part of the hydrophobic polymer membrane ⁇ is chemically bonded with hydrophilic polymer chains.
  • such graft polymerization can be initiated by irradiating the hydrophilic monomer solution with various actinic rays such as election-rays, X-rays, UV-rays, low temperature plasma or by thermal decomposition of the peroxide groups in the presence of hydrophilic monomer solutions using a polymerization initiator and by using a polymerization initiator well known in this art in a solution system or an emulsion system, whereby radicals for initiation of the polymerization are formed on the surface or in the internal space of the polymer membrane and the graft polymerization takes place according to the free-radical polymerization mode.
  • actinic rays such as election-rays, X-rays, UV-rays, low temperature plasma or by thermal decomposition of the peroxide groups in the presence of hydrophilic monomer solutions using a polymerization initiator and by using a polymerization initiator well known in this art in a solution system or an emulsion system, whereby radicals for initiation of
  • hydrophobic polymer as used herein is to- be interpreted to mean any polymer resistant to wetting, or not readily wet, by water. That is, a polymer material that has .a lack of affinity for water.- A hydrophobic polymer typically will have a water contact angle approximately equal to or greater than 90 degree..
  • Exemplary hydrophobic polymers include, but are not limited to, polyolefins, such as polyethylene, poly (isobutene) , poly (isoprene) , poly (4-methyl-l-pentene) , polypropylene, ethylene-propylene copolymers, ethylene- propylene-hexadiene copolymers, and ethylene-vinyl acetate copolymers; styrene polymers, such as poly (styrene) , poly(2-methylstyrene) , ; vinyl polymers, such as poly (vinyl butyrate) , poly (vinyl decanoate) , poly (vinyl dodecanoate) , poly (vinyl hexadecanoate) , poly (vinyl hexanoate) , poly(vinyl propionate), poly(vinyl octanoate) ; acrylic polymers, such as poly (n ⁇ butyl a
  • polyolefin is used herein to mean a polymer prepared by the addition polymerization of one or more unsaturated monomers which contain only carbon and hydrogen atoms.
  • examples of such polyolefins include polyethylene, polypropylene, poly (1-butene) , poly (2-butene) , poly (1-pentene) , poly (2-pentene) , poly (3-methyl-
  • 1-pentene poly (4-methyl-1-pentene) , and the like.
  • the terms is also meant to include blends of two or more polyolefins and random and block copolymers prepared from two or more different unsaturated monomers. Because of their commercial importance, the most desired polyolefins are polyethylene and polypropylene.
  • thermoplastic polymer as used herein is to be intepreted to mean any of the hydrophobic polymers have thermoplastic properties, including thermoplastic elastomers, as well as
  • hydrophilized and grammatical variations thereof, when used to refer to a hydrophobic polymer, refers to a permeable polymer membrane made predominantly of hydrophobic polymers that has undergone graft polymerization and which has a higher affinity for water relative to a hydrophobic polymer that has not undergone graft polymerization as described herein. That is, the hydrophilized hydrophobic polymer membranes as described
  • .herein are capable of taking up a larger volume of water relative to hydrophobic polymer membranes that have not undergone graft polymerization.
  • hydrophilic polymer refers to a polymer that is synthesized from the hydrophilic monomer solution during the graft polymerizing step, which are characterized in that they have a high affinity for water. Hence, the hydrophilic polymers are capable of taking up a large volume of water in aqueous solutions, but which are insoluble therein. Most hydrophilic polymers have a sufficient number of oxygen atoms incorporated therein to form hydrogen bonds in water or said aqueous solution.
  • Exemplary hydrophilic polymers may include, but are not limited to alkyl glycols such as methyl glycols, ethyl glycols, propyl glycols, and alkenyl-glycols such as poly-ethylene glycol, propylene glycol, butylene glycol, and also polyoxyethylene, polytriethylene glycols and copolymers thereof.
  • alkyl glycols such as methyl glycols, ethyl glycols, propyl glycols, and alkenyl-glycols such as poly-ethylene glycol, propylene glycol, butylene glycol, and also polyoxyethylene, polytriethylene glycols and copolymers thereof.
  • hydrophilic monomer solution refers to hydrophilic monomers that are dissolved in a solvent and which are capable of being polymerized.
  • hydrophilic monomer as used here denotes a monomer whose homopolymers have the ability to absorb water.
  • hydrophilic monomers include, but are not limited to, 2- acrylamido-glycolic acid, 2-hydroxyethyl methacrylate, 1- vinyl-2-pyrrolididone, acrylamide, meth ' acrylamide,- N- methylacrylamide, N-alkyl acrylamide, diacetoneacrylamide, hydroxypropyl methacrylate, hydroxypropyl acrylate, various methoxypolyethyleneglycol acrylates, .alkyl vinyl ether, vinyl alcohol, methacrylic acid, acrylic acid, hydroxypropylmethacrylamide, vinyl acetate, 2-sulfoethyl methacrylate, 3-sulfopropyl acrylate, 3-sulfopropyl methacrylate, and PEG-methacrylate.
  • aqueous medium as used herein is to be interpreted to mean any liquid medium of which- water is a major component. Thus, the term includes water per se and aqueous solutions.
  • the aqueous medium also may contain organic solvents which are soluble in water such as "polar organic solvents"
  • polar organic solvent and grammatical variations thereof, means any organic solvent that is miscible with water, such as lower alcohols, polyhydric alcohols, and ketones.
  • lower alcohols are methanol, ethanol, propanol, butanol, pentanol, heptanol, ethanediol, propanediol, butanediol, pentanediol, heptanediol and the like, or the mixtures thereof.
  • admixture refers to physical contact of components added ⁇ to a medium including solution, emulsion, suspension; to alter their properties.
  • ⁇ permeable polymer membrane' is to be interpreted broadly to a membrane having a series of pores extending therethrough which substantially allow fluids to pass therethrough.
  • the word “substantially” does not exclude “completely” e.g. a composition which is “substantially free” from Y may be completely free from Y. Where necessary, the word “substantially” may be omitted from the definition of the invention.
  • non-polar and hydrophobic are to be used interchangably and are to be understood to mean a polymer, or part of a polymer, or a mixture of polymers, that exhibit a low intermolecular attraction for aqueous solvents such as water.
  • polar and hydrophyllic are to be used interchangably and are to be understood to mean a polymer, or part of a polymer, or a mixture of polymers, that exhibit a high intermolecular attraction for aqueous solvents such as water.
  • the terms “comprising” and “comprise”, and grammatical variants thereof, are intended to represent “open” or “inclusive” language such that they include recited elements but also . permit inclusion of additional, unrecited elements.
  • the term “about”, in the context of concentrations of components of the formulations typically means +/- 5% of the stated value,, more typically +/- 4% of the stated value, more typically +/- 3% of the stated value, more typically, +/- 2% of the stated value, even more typically +/- 1% of the stated value, and even more typically • +/- 0.5% of the stated value.
  • range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosed ranges. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.
  • a process of at least partially hydrophilizing a hydrophobic polymer and a hydrophilized permeable polymer membrane prepared by the process, thereof will now be disclosed.
  • a process of at least partially hydrophilizing a hydrophobic polymer comprising the step of graft polymerizing a hydrophilic monomer solution while in contact with the permeable polymer membrane having peroxide groups, including hydroperoxide groups, along the polymer chains thereof, under conditions that prevent substantial reduction of the pore diameter of said permeable polymer membrane.
  • the conditions include selecting the concentration of said hydrophilic monomer in said hydrophilic monomer solution that is less than about 10% by volume.
  • concentration of hydrophilic monomer in said hydrophilic monomer solution disclosed herein substantially prevents reduction of the pore diameter of said permeable polymer membrane during the polymerizing step. Furthermore, because the polymerization conditions are controlled, the amount of hydrophilic polymer is minimized so that said hydrophilic polymer is evenly distributed over the pore surfaces of said permeable polymer membrane.
  • the conditions contributing to uniform distribution of grafted polymer may, in one embodiment, include the time and amount of ozone gas treatment of the membrane which introduces peroxide groups evenly in the direction of membrane thickness; the presence of organic solvent in the monomer solution may facilitate the penetration of the monomer solution into the membrane.
  • thermal polymerization may allow the monomers to be uniformly polymerized on the entire pore surface since thermal energy permits the pore portions of the porous hollow fibers to be heated evenly.
  • the hydrophilic monomer concentration in said hydrophilic monomer solution is in the range selected from the group consisting of about 0.1% to about 10% by volume; about 0.1% to about 8% by volume; about 0.1% to about 6% by volume; about 0.1% to about 4% by volume; about 0.5% to about 10% by volume; about 1% to about 10% by volume; about 2% to about 10% by volume; and about 4% to about 10% by volume.
  • the permeable polymer membrane may be a thermoplastic polymer such as polyolefin.
  • the polyolefin may comprise polyethylene, polypropylene, polymethyl pentene and copolymers thereof. Any polyolefin capable of being fabricated into an article may be suitable for use in said process.
  • the polyolefin articles may include but are not limited to fibers, films, tubes, microporous films or microporous hollow fibres.
  • said microporous articles refer to an article having a plurality of pores with diameters of 10 micron or less.
  • the microporous articles may have a plurality of pores with diameters in the range of 10 microns to 0.01 microns.
  • the step of providing peroxide groups on the surface of said permeable polymer membrane there is provided the step of providing peroxide groups on the surface of said permeable polymer membrane.
  • the peroxide groups may include hydroperoxide groups
  • the step of providing peroxide groups on the surface of said permeable polymer membrane comprises exposing said permeable polymer membrane to ozone.
  • the permeable polymer membrane is exposed to said ozone in an aqueous medium.
  • the aqueous medium may comprise water.
  • the peroxides may be made by exposing an oxygen-contai ⁇ ing gas, such as air or substantially pure oxygen, to ultraviolet radiation to produce ozone, which can then be exposed to said aqueous medium.
  • ozone was separately produced from oxygen-containing gas, such as air, using an ozonator via corona discharge or UV-irradiation. Then the produced ozone gas was passed through the permeable membrane in aqueous medium.
  • the peroxide groups that are provided on the surface of said . permeable membrane upon exposure to ozone may be degraded by thermal energy in the presence of ⁇ the redox initiator to initiate graft polymerization. .
  • the step of providing peroxide groups as disclosed herein is undertaken at a temperature between about 25°C to about 100°C for less than one hour to allow sufficient peroxide groups, including hydroperoxide groups, to be introduced onto the surface of the. permeable polymer membrane while minimizing the formation of higher oxidation products of the polymer and reducing molecular weight degradation.
  • the step of providing said peroxides groups on the . surface of said permeable polymer membrane is undertaken at a temperature in the range selected from the group consisting of about 25°C to about 100 0 C; about 25°C to about 85°C; about 25°C to about 70 0 C; about 25°C to about 55°C; about 30 0 C to about 100 0 C; about 30 0 C to about 85°C; about .30 0 C to about 60 0 C; about 40 0 C to about 100 0 C; about 40 0 C to about 85°C; about 40 0 C to about 60 0 C; and about 40 0 C to about 100 0 C.
  • the step of providing said peroxides groups on the surface of said permeable polymer membrane is carried out for a time period of less than one hour. In another embodiment, the step of providing said peroxides groups on the surface of said permeable polymer membrane is carried out for a time period in the range selected from the group consisting of about 5 min to about 60 min; about 5 broadlyn to about 45 min; about 5 n ⁇ in to about 30 min; about 5 min to about 15 min; about 5 min to about 10 min; about 10 min to about 60 min; about 10 min to about 45 min; and about 10 min to about 20 min.
  • a process of at least partially hydrophilizing a hydrophobic polymer further comprising, before the step of providing peroxide groups on the surface of said permeable polymer membrane, the step of applying an organic solvent to said permeable polymer membrane.
  • the method may comprise the step of applying said permeable polymer membrane with water.
  • a process wherein the step of graft polymerizing is carried out in- an inert gas atmosphere.
  • the inert gas may be selected from the group consisting of nitrogen, argon, helium, neon, krypton, xenon and radon.
  • the permeable polymer membranes are washed with water and exposed to nitrogen to remove unreacted ozone before said membranes are subjected to graft polymerization in said inert gas atmosphere.
  • the presence of the inert gas removes any residual ozone and oxygen so that the step of graft polymerization is carried out in an oxygen free environment.
  • the residual ozone and oxygen is removed, otherwise graft polymerization may be significantly inhibited.
  • the step of graft polymerizing is undertaken at a temperature in the range selected from the group consisting of about ⁇ 25°C to about 100 0 C; about 25°C to about 85°C; about 25°C to about 70 0 C; about 25°C to about 55°C; about 30 0 C to about 100 0 C; about 30 0 C to about 85 0 C; about 30 0 C to about 60 0 C; about 40 0 C to about 100 0 C; about 40 0 C to about 85°C; about 40 0 C to about 60 0 C; and about 40 0 C to about 100 0 C.
  • the step of graft polymerizing is undertaken at a temperature in the range of 30 0 C to about 100 0 C. Accordingly, higher temperatures are preferred because they facilitate the degradation of said peroxide .groups to radicals and facilitate the graft polymerization of said hydrophilic monomers onto said permeable polymer membrane.
  • the step of graft polymerizing is undertaken for a time in the range of about 2 min to about 180 min.
  • the thermal energy during the step of graft polymerization allows the pores on the surfaces of the permeable polymer membrane to be substantially uniformly heated.
  • the hydrophilic monomers in said hydrophilic monomer solution can be uniformly polymerized ⁇ on the pore surface of said permeable polymer membrane, wherein the hydrophilic groups of said hydrophilic monomers are chemically coupled to said permeable polymer membrane via the peroxide moiety of the peroxide groups during graft polymerization.
  • the hydrophilic polymer can be evenly distributed on the pore surfaces of the permeable polymer membrane without substantial damage to said membrane.
  • the hydrophilic polymer imparts good hydrophilicity thereto, without impairing- the physical properties of pore diameter, high porosity and sufficiently high mechanical strength.
  • the hydrophilic monomer in said hydrophilic monomer solution is dissolved in an aqueous solvent.
  • the aqueous solvent may be in admixture with an organic solvent such as alcohol.
  • the aqueous solvent may comprise water.
  • the alcohol is selected from the group consisting of methanol, ethanol, n- propanol, butanol, pentanol, isopropanol, n-butanol, sec- ' butanol, isobutanol, tert-butanol, n-pentanol, 3-methly-l- butanol, 2-methly-l-butanol, 2, 2-dimethyl-l-propanol, 3- pentanol, 2-pentanol, 3-methyl-2-butanol and 2 methyl ⁇ 2- butanol as well as derivatives thereof.
  • the alcohol is ethanol.
  • Ethanol is a preferred organic solvent because of its low toxicity and high polarity.
  • it has good dissolving power for hydrophilic monomers in said hydrophilic monomer solution.
  • the use of the organic solvent in said hydrophilic monomer solution during the step of graft polymerizing allows said solution to penetrate into the pores of said permeable polymer membrane in a relatively short period of time.
  • the presence of the organic solvent in said hydrophilic monomer solution can reduce the ' time required for the graft polymerization to complete.
  • the organic solvent which is in admixture with said aqueous solvent is in the range selected from the group consisting of about 5% to about 60% of the total volume; about 5% to about 45% of the total volume; about 5% to about 30% of the total volume; about 5% to about 15% of the total volume; about 10% to about 60% of the total volume; about 10% to about 45% of the total volume; about 10% to about 30% of the total volume; and about 10% to about 15% of the total volume.
  • the hydrophilic monomer in said hydrophilic monomer solution is a monomer having at least one polar group.
  • exemplary polar groups that may be provided on said hydrophilic monomer may include a hydroxyl group, a carboxyl group, an ester group, an ethoxy groupa sulfonic acid group, a sulfinic acid group, an amino group, an amide group, .
  • at least one polar group in said hydrophilic monomer is a hydroxyl group.
  • the hydrophilic monomer in said hydrophilic monomer solution is a monomer having at least one non-polar group-
  • non-polar groups include, an alkyl group, preferably a lower alkyl group, an alkylene group, preferably a lower alkylene group, and an alkenyl group, preferably a lower alkenyl group.
  • at least one non-polar group in said hydrophilic monomer is an ethylene group.
  • At least one of said polar group in said hydrophilic monomer is selected to enable said monomer to be miscible with said organic solvent.
  • at least one of said non-polar group in said hydrophilic monomer is selected to enable said monomer to not be repelled by said permeable polymer membrane.
  • the hydrophilic monomer is dissolved in a polar solvent system when in admixture with said organic solvent, the non-polar groups can be selected and localized on the surface of said non-polar permeable polymer membrane, during the step of graft polymerizing. Accordingly, the polar units in said hydrophilic monomer are localized away from said permeable polymer membrane because the polar groups in said hydrophilic monomer are selected to enable said monomer to be miscible with said organic solvent which is in admixture with said aqueous solvent.
  • the mechanism of graft polymerization can be generally be described as follows:
  • Initiation step The formed radicals react with monomers of the monomeric solution to produce a chain radical.
  • Propagation step The chain radical reacts with another monomer to produce a chain radical and so on.
  • Termination step two polymer chain radicals react resulting chain termination.
  • the hydrophilic monomer solution may comprise an amount of redox initiator to initiate the graft polymerizing step.
  • concentration of redox initiator within the hydrophilic monomer solution may be
  • the amount of redox initiator within the hydrophilic monomer solution is about 10 ⁇ 3 M.
  • the redox initiator may be selected from the group consisting of bisulfites, sulfites, thiosulfates, dithionites,
  • the ferrous salts may be iron (II) sulfate or a ferrous halide such as iron
  • the hydrophilic monomer solution may further comprise at least one accelerator and homopolymerization inhibitor.
  • the activator in solution form ensures the uniformity in the thickness direction.
  • the activation solution can penetrate into the membrane and hence allow complete contact of the membrane surface including the pore surface with the activator to thereby promote uniform activation on the membrane surface.
  • the activation solution is capable of oxidizing the surface of said permeable polymer membrane to introduce oxygen-containing functional groups onto the membrane, which has much lower activation energy than the carbon-hydrogen (C-H) bond. Hence, later treatment with ozone to introduce peroxide groups is more efficient.
  • the activation solution may be an inorganic acid.
  • the inorganic acid may be selected from the group consisting of chromic acid, sulfuric acid, nitric acid, fuming sulfuric acid, hydrochloric acid, phosphoric acid, and combinations thereof.
  • the activation solution may comprise chromic acid.
  • the activating solution may comprise potassium dichromate.
  • the concentration of potassium dichromate may be in the range selected from the group consisting of about 2% to about 38% by weight; about 2% to about 30% by weight; about 2% to about 22% by weight; about 2% to about 14% by weight; about 2% to about 8% by weight; about 4% to about 38% by weight; about 4% to about 38% by weight; about 4% to about 30% by weight; about 4% to about 22% by weight; about 4% to about 14% by weight; and about 4% to about 8% by weight of the total ⁇ solution.
  • the concentration of sulfuric acid is selected from the group of inorganic acids is in the range selected from the group consisting of about 20% to about 60% by weight; about 20% to about 55% by weight; about 20% to about 50% by weight; about 20% to about 45% by weight; about 40% to about 60% by weight; about 40% to about 55% by weight; and about 40% to about 50% by weight of the total solution.
  • the activation solution may comprise hydrogen peroxide together with a redox agent such as for example Fe 2+ .
  • a hydrophilized permeable polymer membrane prepared by a process comprising the step of graft polymerizing a hydrophilic monomer solution while in contact with the permeable polymer membrane having peroxide groups, including hydroperoxide groups, along the polymer chains thereof, wherein the concentration of hydrophilic monomer in said hydrophilic monomer solution is selected to substantially prevent reduction of the pore diameter of said permeable polymer membrane during said graft polymerizing.
  • the permeable polymer membrane has at least one hydrophilic group chemically coupled to the hydrophobic permeable polymer membrane via the peroxide moiety that has reacted with the alkenyl groups during graft polymerization.
  • the hydrophilic polymer prepared during the step of graft polymerization is a hydrophilic crosslinked polymer.
  • the hydrophilic polymer undergoes only a slight degree of swelling without the risk of blocking the pores on the surface of permeable polymer membrane. More advantageously, the hydrophilized permeable polymer has excellent hydrophilicity, exhibits good water permeability without being subjected to a hydrophilizing pretreatment with an alcohol, and shows no substantial reduction in filtration performance.
  • the hydrophilic polymer comprises at least one of polymerizing monomer and a crosslinkable monomer.
  • Exemplary crosslinkable monomers may be selected from the group consisting of ethylene glycol diacrylate, ethylene glycol dimethyacrylate, 1, 2-propylene glycol diacrylate, 1, 2-propylene glycol dimethacrylate, 1,4- butanediol diacrylate, 1, 4-butanediol ' dimethacrylate, hexanaediol diacrylate, hexandiol dimethacrylate, neopentylglycol diacrylate, neopentylglycol dimethacrylate, 3-methylpentanediol diacrylate and 3- methylpentanediol dimethacrylate.
  • the crosslinkable monomer is ethylene glycol dimethyacrylate.
  • exemplary polymerizing monomers may be selected from the group consisting of alkyl methacrylate; alkyl acrylate, 2-hydroxyethyl methacrylate, vinyl acetate, vinyl propionate, mixtures of styrene and acrylonitrile, and mixtures of styrene and various maleates.
  • the polymerizing- monomer is 2-hydroxyethyl methacrylate.
  • the proportion of said crosslinkable monomer relative to the hydrophilic polymer is in an amount of about 0.3 to about 100 parts by volume, more preferably about 0.5 to 80 parts by volume, per 100 parts by volume of said polymerizing monomer.
  • a copolymerizable monomer may be added into the hydrophilic monomer solution.
  • the amount of copolymerizable monomer is preferably in an amount of 0.3 to 110 parts by weight, more preferably 0.5 to 100 parts by weight, per 100 parts by weight of said polymerizing monomer, in said hydrophilic monomer solution.
  • the graft polymerizing step is interrupted by providing the hydrophilized permeable polymer membrane in an aqueous medium to remove any unreacted monomers or free polymers remaining on the surface of said permeable polymer membrane.
  • the hydrophilized permeable polymer membrane is dried in air.
  • the hydrophilized permeable polymer membrane prepared by the process as defined above can be used in a water treatment process.
  • said hydrophilized permeable polymer membrane can be used in filtration systems for purification of water.
  • said hydrophobic polymers are produced by a melt spinning process without any solvent, hence they reduce the risk of contaminating hydrophilic fluids during filtration processes.
  • the hydrophilized permeable polymer membranes exhibit good water permeability because the pore diameter of the pores of the permeable polymer membrane are not substantially blocked during the polymerizing step due to the concentration of hydrophilic monomer in said hydrophilic monomer solution which does not exceed a predetermined amount. Accordingly, said hydrophilized permeable polymer membranes can be wetted repeatedly without showing . any substantial reduction in the filtration performance. Hence, the hydrophilized permeable polymer membranes are useful in various fields of water treatment.
  • Fig. 1 is a scanning electron microscopy (SEM) micrograph of a hydrophilized porous membrane in accordance with a disclosed embodiment
  • Fig. 2 is a SEM micrograph of a hydrophilized porous membrane, in accordance with a disclosed embodiment, showing the inner surface of a spinning hollow fiber membrane that has been melt spun.
  • Non-limiting examples of the invention, including the best mode, and a comparative example will be further described in greater detail by reference to specific
  • the tensile strength of the membranes was determined according to ASTM 638-91 using an Instron model 5542.
  • Water permeability (liter/m 2 .hr . atm) determines the volume of permeate through the membrane per unit area and time under pressure.
  • a hydrophilic monomer solution was prepared by adding 1 ml of 2-hydroxyethyl methacrylate (Sigma-Aldrich Corporation) to 200 ml water. The solution was heated to 35°C while it was being purged with dry nitrogen for 20 minutes .
  • Example 2
  • polypropylene hollow fiber membranes obtained from Hyflux Ltd, Singapore, were bundled together and one open-end portion was fastened with a urethane resin to fabricate a module.
  • the effective length of the hollow fibers was 25 cm.
  • the module was wetted using ethanol, which was subsequently substituted with water. The wetted module was then dipped into water. A mixture of ozone and oxygen gas was then passed through the lumen side of the fibers for 20 min.
  • the scanning electron microscopy (SEM) micrograph of the resulting hydrophilized porous hollow- fiber membrane is shown in Figure 1.
  • SEM scanning electron microscopy
  • the porous hollow fiber membranes were bundled into a module with both open-ends fastened with resin.
  • the water permeability of the hollow fiber membranes was found to be 57 Iiter/m 2 .hr. atm. while the tensile strength and tensile strain of the fiber were found to be 83 MPa and about 50%, respectively.
  • the flux decreased as the temperature of the hydrophilic monomer solution used was increased.
  • the higher temperature facilitated the degradation of peroxide groups to radicals and also facilitated the permeation of monomer solutions into the membrane and thereby facilitated graft polymerization.
  • too high temperature may result in extensive grafting and pore-- blocking.
  • a hydrophilic monomer solution was prepared by adding 1 ml 2-hydroxyethyl methacrylate and 0.2 ml ethylene glycol dimethacrylate to a solution of 160:40 water/ethanol (i.e. 160 ml water, 40 ml ethanol) .
  • the pH of the solution was set to 3.
  • the solution was heated to 35 0 C while being purged with dry nitrogen.
  • the solution was applied to polypropylene hollow fiber membranes PPlOOO under the same conditions as employed in Example 2.
  • the water permeability of the hydrophilized membrane was 79 liter/m 2 . hr. atm. Accordingly, there was a significant increase in flux rate when ethylene glycol dimethacrylate which is a crosslinkable monomer was added into the hydrophilic monomer solution, compared to the hydrophilized membrane of Example 2 in which the flux rate of the hydrophilized membrane was 57 liter/m 2 .hr. atm, when only the polymerizing monomers (i.e. 2-hydroxyethyl methacrylate ⁇ were present in the hydrophilic monomer solution
  • Example 7 A chromic acid solution was prepared from 80 ml water, 20 ml sulfuric acid obtained from Skychem Pte Ltd of Singapore and 20 g potassium dichr ⁇ mate obtained from Sigma-Aldrich Corporation. The solution was heated to 75°C.
  • Polyethylene hollow fiber membrane PE3000 from Hyflux Ltd of Singapore was hydrophilized under the same conditions as employed . in Example 6 with the exception that, prior to ozone treatment, the membrane was dipped into the chromic acid solution (of Example ⁇ 7) and was allowed to stand for 15 minutes, and was washed thoroughly with water.
  • the SEM micrograph of the resulting hydrophilized membrane is shown in Figure 2. It will be seen from the SEM that the pores of the membrane are clearly not blocked.
  • Examples 9-13 A series of polyethylene hollow fiber membranes from Hyflux Ltd of Singapore, (PE3000) were hydrophilized under the same conditions as employed in Example 8, except that 2-hydroxyethyl methacrylate was used in the respective amounts shown in Table 4. The results of filtration using these membranes are also summarized in Table 4.
  • the hydrophilized permeable polymer membrane made of hydrophobic materials shows permanent hydrophilicity while maintaining the properties of the membrane such as pore size, porosity and mechanical strength.
  • the hydrophilized permeable polymer membrane can be used in a water treatment process.
  • the hydrophilized permeable polymer membrane can be used in filtration systems for purification of water.
  • the hydrophilic groups are grafted on the hydrophobic polymer, the hydrophilic groups do not degrade and therefore the process reduces the risk of contaminating hydrophilic fluids during filtration processes.
  • the hydrophilized permeable polymer membranes exhibit good water permeability because the pore diameter of the pores of the permeable polymer membrane are not substantially blocked during the polymerizing step because the polymerization conditions are controlled.
  • the concentration of hydrophilic monomer in said hydrophilic monomer solution may be selected such that it does not exceed a predetermined amount that would result in the pores of the membrane becoming blocked. Accordingly, said hydrophilized permeable polymer membranes can be wetted repeatedly without showing any substantial reduction in the filtration performance. Hence, the hydrophilized permeable polymer membranes are useful . in various field of water treatment.
  • the process for hydrophilization of permeably polymer membranes is relatively simple and hence provides a more efficient process than that of the- known methods .
  • ethanol is a preferred organic solvent because of its low toxicity and high polarity hence it provides good dissolving power for hydrophilic monomers in said hydrophilic monomer solution.
  • the hydrophilized polymer membrane exhibits permanent hydrophilicity due to the presence of the peroxide groups which allow chemical bonding of the hydrophilic polymer to the permeable polymer membrane.

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Abstract

L'invention porte sur un procédé d'hydrophilisation d'un polymère hydrophobe. Le procédé comprend l'étape de polymérisation par greffage d'une solution de monomère hydrophile alors qu'elle est en contact avec la membrane polymère perméable. La membrane polymère perméable a des groupes peroxyde le long de ses chaînes polymères. La polymérisation par greffage est menée dans des conditions qui empêchent une réduction substantielle du diamètre des pores de la membrane pour s'assurer que celle-ci demeure perméable.
PCT/SG2008/000440 2007-11-23 2008-11-20 Hydrophilisation de membranes polymères hydrophobes perméables WO2009067087A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11925569B1 (en) * 2018-10-26 2024-03-12 Arrowhead Center, Inc. Porous prosthetic sleeve liner material

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3008920A (en) * 1959-04-27 1961-11-14 Dow Chemical Co Method of inhibiting homopolymerization in graft copolymers with copper salts
US4845132A (en) * 1986-05-07 1989-07-04 Agency Of Industrial Science And Technology Hydrophilic porous membrane, method for production thereof, and plasma separator using said membrane
US4968532A (en) * 1989-01-13 1990-11-06 Ciba-Geigy Corporation Process for graft copolymerization on surfaces of preformed substrates to modify surface properties
EP0574352A1 (fr) * 1992-06-09 1993-12-15 Ciba-Geigy Ag Procédé de polymérisation par greffage sur les surfaces de substrats préformés afin de modifier leurs propriétés de surface
US5805264A (en) * 1992-06-09 1998-09-08 Ciba Vision Corporation Process for graft polymerization on surfaces of preformed substates to modify surface properties

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3008920A (en) * 1959-04-27 1961-11-14 Dow Chemical Co Method of inhibiting homopolymerization in graft copolymers with copper salts
US4845132A (en) * 1986-05-07 1989-07-04 Agency Of Industrial Science And Technology Hydrophilic porous membrane, method for production thereof, and plasma separator using said membrane
US4968532A (en) * 1989-01-13 1990-11-06 Ciba-Geigy Corporation Process for graft copolymerization on surfaces of preformed substrates to modify surface properties
EP0574352A1 (fr) * 1992-06-09 1993-12-15 Ciba-Geigy Ag Procédé de polymérisation par greffage sur les surfaces de substrats préformés afin de modifier leurs propriétés de surface
US5805264A (en) * 1992-06-09 1998-09-08 Ciba Vision Corporation Process for graft polymerization on surfaces of preformed substates to modify surface properties

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11925569B1 (en) * 2018-10-26 2024-03-12 Arrowhead Center, Inc. Porous prosthetic sleeve liner material

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