CN115003406A

CN115003406A - Water-wettable filter membranes and their preparation

Info

Publication number: CN115003406A
Application number: CN202080067046.9A
Authority: CN
Inventors: W·惠尔赖特
Original assignee: Hydroxsys Holdings Ltd
Current assignee: Hydroxsys Holdings Ltd
Priority date: 2019-08-09
Filing date: 2020-08-10
Publication date: 2022-09-02
Also published as: WO2021028813A1; EP4010108A4; AU2020330484A1; EP4010108A1; GB2600370B; JP2022543874A; GB2600370A; IL290423A; GB202203121D0

Abstract

The present invention describes a filter membrane prepared by adhering a poloxamer to a preformed sheet of microporous polyolefin. In one embodiment, the poloxamer is under the trade name PLURONIC ^TM P-123 and the sheet is microporous poly (ethylene). The membrane provides the advantage of being resistant to cleaning agents used in cleaning-in-place protocols.

Description

Water-wettable filter membranes and their preparation

Technical Field

The present invention relates to durable filter membranes, filter membrane modules comprising the membranes and their use in the recovery of water from a feed stream. In particular, the invention relates to durable filtration membranes and their use in recovering water from feed streams requiring periodic in situ membrane cleaning.

Background

Schmolka's publication (1973) discloses the preparation of polyoxyethylene-polyoxypropylene block polymers represented by the formula:

HO(C ₂ H ₄ O) _b (C ₃ H ₆ O) _a (C ₂ H ₄ O) _b H

wherein a is such that ₃ H ₆ O) has a molecular weight of at least 2,250, and b is an integer of about 8 to 180 or higher. These block polymers are used to prepare solid or semi-solid colloids- "gels" or "hydrosols" (where the liquid is water) containing a large amount of liquid, which are particularly suitable for the formulation of cosmetic and pharmaceutical compositions for topical application. These nonionic triblock copolymers, known as poloxamers, are available under a number of trade names, including ACCLAIM ^TM 、ADEKANOL ^TM 、ANTAROX ^TM 、BASOROL ^TM 、BLAUNON ^TM 、ETHOX ^TM 、KOLLIPHORTM、LUTROL ^TM 、MEROXAPOL ^TM 、PLURIOL ^TM 、PLURONIC ^TM And SYNPERONIC ^TM . The properties of poloxamers are determined by the ratio and size of the integers a and b. Triblock copolymers in which the order of polyoxyethylene and polyoxypropylene blocks is reversed are also supplied under these trade names. These "reverse" triblock copolymers may be identified by the use of the letter "R" and should not be referred to as "poloxamers".

Wang et al publication (2006) discloses forming a film from a blend of polyethersulfone and a different triblock copolymer by a phase inversion method. It was observed that the water flux measured for the membrane was dependent on the triblock copolymer structure rather than the content. For example, it was observed that the composition had PLURONIC ^TM 123 was found to have a water flux (50.161LMH) less than that observed in the polyethersulfone control membrane (109.081 LMH). Observed by having PLURONIC ^TM The blend of F68 formed a membrane with a higher water flux (218.28LMH) than the control membrane.

Liu et al publication (2014) (machine translation) discloses the preparation of microporous membranes with microstructured surfaces for the separation of oils from water-in-oil/water emulsions. In the method of preparing the film, polyoxyethylene-polyoxypropylene-polyoxyethylene (F127) is used as an additive for preparing a homogeneous solution of the polymer in a solvent. The polymer is selected from polyvinylidene fluoride (PVDF) and polysulfone(PSf), Polyethersulfone (PES), Polyacrylonitrile (PAN), Polyvinylchloride (PVC), polylactic acid (PLA), Polyimide (PI), polypropylene (PP) or cellulose acetate, and the solvent is selected from chloroform (CHCl) ₃ ) N, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), triethyl phosphate (TEP), trimethyl phosphate (TMP), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), Tetrahydrofuran (THF), dibutyl phthalate (DBP), dioxane, propiophenone, diphenyl ether and one or more mixtures thereof.

The Yang et al publication (2014) discloses composite polymer electrolytes for lithium-polymer batteries. The composite material consists of mesoporous modified silica filler dispersed in a poly (vinylidene fluoride-hexafluoropropylene) matrix. Triblock copolymer PLURONIC ^TM 123(Aldrich) was used to prepare mesoporous silica fillers.

The Guo et al publication (2015) discloses microporous materials for microfiltration and ultrafiltration membranes. Microporous materials comprise finely divided particles, such as water-insoluble silica fillers, distributed throughout a matrix, such as poly (ethylene). The material further comprises a network of interconnected pores and may be further processed according to the desired application. In such further processing, triblock copolymers based on poly (ethylene oxide) -poly (propylene oxide) -poly (ethylene oxide) may be used as the hydrophilic coating, although polymers containing tertiary amine functional groups are preferred. Without wishing to be bound by theory, it is believed that the components of the coating can interact with the silica particles in the filler of the microporous material and adjust the surface energy, affecting wettability. Covalent bonding of hydrophilic coatings, such as that achievable by grafting, is not disclosed.

The Cheng et al publication (2017) (machine translation) discloses the use of poly (ethylene oxide) -poly (propylene oxide) -poly (ethylene oxide) triblock copolymers as "structure directing agents" in the preparation of mesoporous composite membranes. The structure directing agent is used with one or more of a catalyst and a precursor compound such as tetraethyl orthosilicate, titanium tetrachloride, n-butyl titanoacetate, titanium isopropyl, zinc phthalate diacetate, tin esters, and niobates to provide a mesoporous composite membrane.

Carter et al publicationThe article (2018) discloses a triblock copolymer PLURONIC as a solvent for pore-filling regenerated cellulose membranes during initiator immobilization ^TM Evaluation of L64. In this context, glycerol is identified as a more efficient pore filling solvent.

Fouling by non-specific adsorption or deposition of proteins requires periodic cleaning of the filter membrane. If the filter membrane can be cleaned in situ, the efficiency of the plant operation can be achieved. There is a need for filtration membranes that are resistant to the agents (acids, bases, hypochlorites) used in these cleaning-in-place (CIP) protocols.

It is an object of the present invention to provide a filter membrane suitable for use in, or at least to provide a useful choice in, the selection of filter membranes for use in these and other situations.

Disclosure of Invention

In a first aspect, a water-wettable filter membrane is provided that includes a poloxamer adhered to a substrate comprised of a microporous sheet of polyolefin. The poloxamer is adhered to a preformed microporous sheet of polyolefin. Poloxamers are adhered to the polyolefin matrix of the preformed microporous sheet through the formation of covalent bonds between the two polymers. The covalent bond can be formed directly between the poloxamer and the polyolefin or indirectly through a cross-linking agent.

Preferably, the poloxamer is adhered to the substrate by grafting. Most preferably, the poloxamer adheres to the substrate by photo-initiated grafting. In this context, photo-initiated grafting will be understood to encompass the formation of covalent bonds initiated by irradiation with Ultraviolet (UV) light in the presence of a suitable photoinitiator. Suitable photoinitiators are type II photoinitiators, for example benzophenone (benzophenone; BP). The photoinitiated grafting is advantageously carried out in the presence of a crosslinking agent. Suitable crosslinking agents are low molecular weight divinyl compounds. The low molecular weight divinyl compound is a compound having less than 150g mol ^-1 Such as Divinylbenzene (DVB).

Preferably, the poloxamer is a polymer having the structure:

HO (ethylene oxide) _m - (propylene oxide) _n - (ethylene oxide) _m H

Wherein m is in the range of 15 to 25 and n is in the range of 50 to 90. Most preferably, the poloxamer corresponds to PLURONIC ^TM Triblock copolymer supplied by P-123 (Sigma-Aldrich). It should be understood that for PLURONIC ^TM P-123(Sigma-Aldrich) with m being 20 and n being 70.

Preferably, the polyolefin is poly (ethylene) or poly (propylene). More preferably, the polyolefin is poly (ethylene). Most preferably, the polyolefin is a raw poly (ethylene).

In a first embodiment of the first aspect, there is provided a water-wettable filter membrane consisting of a microporous sheet of grafted poly (ethylene), wherein the graft comprises a poloxamer having the structure:

HO (ethylene oxide) _m - (propylene oxide) _n - (ethylene oxide) _m H

Wherein m is in the range of 15 to 25 and n is in the range of 50 to 90.

In a second embodiment of the first aspect, there is provided a water-wettable filter membrane consisting of a microporous sheet of grafted poly (ethylene), wherein the grafts comprise divinylbenzene and a poloxamer having the structure:

HO (ethylene oxide) _m - (propylene oxide) _n - (ethylene oxide) _m H

Wherein m is in the range of 15 to 25 and n is in the range of 50 to 90.

It is contemplated that in the first or second embodiment of the first aspect, poly (propylene) may be substituted for poly (ethylene).

Preferably, the filter membrane is a semi-permeable membrane.

In a second aspect, there is provided a method of preparing a water-wettable filter membrane, wherein the method comprises:

1. contacting a microporous sheet of polyolefin with a solution of a poloxamer in a solvent to provide a contacted sheet;

2. irradiating the contacted sheet with ultraviolet light in the presence of a photoinitiator to provide an irradiated sheet; then the

3. The irradiated sheet is washed and dried to provide a film.

Preferably, the solution comprises a photoinitiator. More preferably, the solution additionally comprises a cross-linking agent.

Preferably, the poloxamer is a polymer having the structure:

HO (ethylene oxide) _m - (propylene oxide) _n - (ethylene oxide) _m H

Wherein m is in the range of 15 to 25 and n is in the range of 50 to 90. Most preferably, the poloxamer corresponds to PLURONIC ^TM Triblock copolymer supplied by P-123 (Sigma-Aldrich). It should be understood that for PLURONIC ^TM P-123(Sigma-Aldrich), m is 20 and n is 70.

Preferably, the solvent is water-alcohol or water-acetone, wherein the ratio of water to ethanol or acetone (v/v) is in the range of 1:1 to 3: 1. More preferably, the ratio of water to ethanol or acetone (v/v) is in the range of 1:1 to 2: 1. Most preferably, the solvent is water-ethanol.

Preferably, the photoinitiator is a type II photoinitiator. Most preferably, the photoinitiator is benzophenone (benzophenone; BP).

Preferably, the crosslinking agent is a compound having a molecular weight of less than 150g mol ^-1 The divinyl compound of (1). Most preferably, the crosslinking agent is Divinylbenzene (DVB).

Preferably, the wavelength of the ultraviolet light is in the range of 250 to 360 nm. More preferably, the wavelength of the ultraviolet light is in the range of 250 to 280 nm. Most preferably, the wavelength of the ultraviolet light is 250 nm.

Preferably, the duration of irradiation is between 1 and 2 minutes and half minutes. More preferably, the duration of irradiation is 2 minutes plus or minus 10 seconds.

In an embodiment of the second aspect, there is provided a method of preparing a water wettable membrane, the method comprising irradiating a microporous sheet of poly (ethylene) with 3 at a wavelength of 250nmTo 5% (w/v) as PLURONIC ^TM P-123 provides a poloxamer, 0.5 to 1% (w/v) benzophenone, and 0 to 0.5% (w/v) divinylbenzene impregnated in 30 to 50% (v/v) aqueous ethanol.

It is contemplated that poly (propylene) may be substituted for poly (ethylene) in this embodiment of the second aspect.

In a third aspect, there is provided a water-wettable filter membrane prepared according to the second aspect.

In a fourth aspect, there is provided a method of recovering water from a feed stream comprising contacting a first side of the filter membrane of the first or third aspects with the feed stream at a pressure sufficient to provide osmosis.

Preferably, the feed stream is selected from milk and waste water. More preferably, the feed stream is skim milk and waste water containing particulates. Most preferably, the feed stream is selected from waste water containing suspended particulates. The microparticles may be of non-biological or biological origin.

Preferably, the filter membrane is in the form of a filter membrane module or filter element. More preferably, the membrane is in the form of a spirally wound filtration membrane module or filter element.

Preferably, the method comprises at least periodically contacting the filter membrane with an acid, a base or a chlorite.

In a fifth aspect, the present invention provides a spiral wound filter membrane assembly or filter element comprising the filter membrane of the first or third aspects.

In the description and claims of this specification, the following abbreviations, acronyms, phrases and terms have the meanings provided: "Block" refers to a portion of a macromolecule comprising a plurality of structural units, which has at least one structural or conformational feature not present in an adjacent portion; "CAS RN" refers to the Chemical Abstracts Service (CAS, Columbus, Ohio) accession number; "comprising" means "including," "containing," or "characterized by" and does not exclude any additional elements, components, or steps; "consisting essentially of …" means that no element, ingredient, or step is included for material limitations; "consisting of …" means that any unspecified element, ingredient or step is excluded except for impurities and other incidental matters; "crosslinking" refers to a reaction involving sites or groups on or interaction between existing macromolecules that results in the formation of a small region, such as a crosslinking bridge, in the macromolecule from which at least four chains emanate; "crosslinker" refers to a material that is incorporated into the crosslinking bridges of a crosslinked polymer network; "curing" refers to the chemical process of converting a prepolymer or polymer into a higher molecular weight and connectivity polymer and ultimately into a network; "filtration" refers to the removal of particulates from a fluid by passage through a porous substrate, "filtration" having a corresponding meaning; "graft molecule" or "graft polymer molecule" refers to a macromolecule having one or more blocks attached to the backbone as side chains having structural or conformational characteristics that are different from those in the backbone; "grafting" refers to the reaction of one or more blocks attached to the backbone of a macromolecule through side chains having structural configuration characteristics different from those in the backbone, and "grafted" has the corresponding meaning; "LMH" means liters per hour per square meter; "impregnation" means, for example, penetration of the substrate with a solution of the agent in a solvent; "macromolecule" or "polymer" refers to a molecule of high relative molecular mass, the structure of which essentially comprises a plurality of repeating units derived, actually or conceptually, from molecules of low relative molecular mass; "monomeric molecule" refers to a molecule that can undergo a polymerization reaction to provide a structural unit for the basic structure of a macromolecule; "monomeric unit", "monomeric unit" or "unit (mer)" refers to the largest structural unit of a macromolecular structure composed of a single monomer molecule; "permeable" means permitting the passage of a solvent such as water; "permeate" means completely diffuse; "poloxamer" refers to a symmetrical non-ionic triblock copolymer consisting of a central chain of poly (propylene oxide) flanked by two chains of poly (ethylene oxide); "semipermeable" means that some substances are allowed to pass through, but not others, in particular solvents such as water, but not some solutes such as proteins, salts or sugars; "wettable" means becoming saturated with a solvent, such as water, when contacted with the solvent under standard laboratory conditions (i.e., 25 ℃, 100kPa), "water wettable" means being wetted by water.

Synonyms for any defined term have corresponding meanings. When there is uncertainty about the meaning of an undefined abbreviation, acronym, phrase, or term that refers to polymer terms and nomenclature, the meaning provided in the Jones et al publication (2008) controls.

It will be appreciated that the porosity determined for the substrate will depend, at least in part, on the method used to determine the porosity. In the present description, the term "microporous" is used to refer to the porosity of the polyolefin sheet, which corresponds to targaray ^TM Porosity of wet-laid polyethylene separator, cat # SW320H (targaray, Kirkland QC, Canada). As used herein, the term "equivalent" means that the porosity determined for the polyolefin sheet is for TARGRAY by the same method ^TM The wet polyethylene separator, cat # SW320H (targarray, Kirkland QC, Canada) has a porosity of 75 to 125%.

The terms "first", "second", "third", etc. are used with reference to aspects, elements, features or integers of the subject matter described in the specification or defined in the claims or are not intended to imply a preferred order when used with reference to alternative aspects or embodiments of the invention.

When a concentration or ratio of a reagent is defined, the defined concentration or ratio is the initial concentration or ratio of the reagent. When values are expressed as one or more decimal places, then standard rounding applies. For example, 1.7 covers the range of 1.650 cycles to 1.749 cycles.

The invention will now be described with reference to embodiments or examples and figures of the accompanying drawings. In the description of the figures and elsewhere below, the "top" (Ctop, Etop, etc.) of a polyolefin filter membrane or microporous sheet prepared according to a laboratory method refers to the face or side of the membrane or sheet that is in contact with the working solution. "Back" (Cback, Eback, etc.) or "back layer" refers to the opposing face or side. It should be understood that since the membrane or sheet is installed in a filter membrane module, the entire face or side is not exposed to the feed stream. A description of the filter membrane assembly (Sterlitech Corp.) and its use is provided on page 24, line 24 of the specification of the accompanying International application No. PCT/NZ2015/050034[ publication No. WO2015/147657A 1].

Drawings

FIG. 1 is an exploded view of a filter membrane assembly (Sterlitech Corp.) used in the flux testing of sheet samples of filter membranes.

FIG. 2. untreated microporous poly (ethylene) (TARGRAY) ^TM Wet polyethylene separator, cat # SW320H (Targarray, Kirkland QC, Canada) (virgin PE), triblock copolymer (PLURONIC) for the preparation of sample (P123) ^TM P-123; lot # MKCC2305, Sigma-Aldrich) and spectra recorded on the top (Etop) and back (Eback) sides (3800 cm) of each sample designated 040918Wiv, 040918Wv, and 040918Wvi (Eback) ^-1 To 525cm ^-1 ) Comparison of (1).

FIG. 3. untreated microporous poly (ethylene) (TARGRAY) ^TM Wet polyethylene separator, cat # SW320H (Targarray, Kirkland QC, Canada)) (virgin PE), triblock copolymer for sample (P123) Preparation (PLURONIC) ^TM P-123; lot # MKCC2305, Sigma-Aldrich) and spectra recorded on the top (Etop) and back (Eback) sides of each of the samples named 040918Wiv, 040918Wv and 040918Wvi, extended to the "fingerprint region" (1800 cm) ^-1 To 600cm ^-1 ) Comparison of (1).

FIG. 4 comparison of spectra (3800 cm) recorded for a region of the sample designated 040918Wvi with (Ctop and Cback) exposed to the feed stream and without (Etop and Eback) exposure to the feed stream ^-1 To 525cm ^-1 ) Comparison of (1).

FIG. 5 scanning electron micrographs of the top (Etop) side of the sample designated 040918Wiv at magnifications of 250,000x (A), 35,000x (B), and 10,000x (C).

FIG. 6 scanning electron micrographs of two regions on the top (Etop) side of a sample designated 040918Wiv at a magnification of 100,000.

FIG. 7. comparison of the flux (LMH) maintained for filter membrane samples (180419Wi and 230419Wii (■); 180419Wii and 230419Wiii (●)) prepared with (solid line) and without (dashed line) crosslinking agent (DVB).

FIG. 8 is a schematic representation of a prototype production line for making water-wettable filter membranes according to example C.

Detailed Description

Filtration membranes are used in a range of industrial processes including food processing to recover or remove water from feed streams. In one application, the objective may be to separate the water from the contaminating particles. In another application, the objective may be to concentrate high value solutes.

In either application, efficiency is increased by contacting the feed stream with a large surface area of the filter membrane. For this purpose, the filter membranes are usually assembled as spiral wound filter elements, which are then installed in an industrial plant. Such spiral wound membrane modules-or "filter elements" -are supplied by manufacturers such as Synder Filtration (Vacaville, California, USA).

Greater efficiency can be achieved if cleaning can be performed in situ without the need to remove and reinstall the filter element. Clean-in-place solutions use chemically aggressive solutions such as acids, bases, and hypochlorites. Alternatively, the feed stream to which the membrane is exposed may be chemically aggressive, and the durability under these conditions reduces the frequency with which filter elements need to be replaced.

Microporous sheets of polyolefins such as poly (ethylene) are commercially available from suppliers such as Celgard (Charlotte, North Carolina, USA) and Targarray (Kirkland, Quebec, Canada). One obstacle to the use of these substrates as filtration membranes in the above applications is the inherent hydrophobicity. The desired rejection characteristics may also be lacking when the objective is to provide a semi-permeable membrane for concentrating high value solutes.

It has now been determined that grafting of microporous sheets of poly (ethylene) with poloxamer, supplied under the trade name PLURONIC-P123, provides a filter membrane that is easily wetted with water and provides high flux rates at relatively low pressures (5 bar). The filter membranes thus produced have also proven to have the required durability when exposed to chemically aggressive liquids.

The retention of these desirable characteristics-which can be attributed to grafting-is enhanced by the addition of a cross-linking agent to the working solution used in the preparation process. Without wishing to be bound by theory, low molecular weight crosslinkers are advantageous in order not to disrupt the advantageous rejection characteristics that membranes also exhibit.

The method of preparing the filter membrane is readily adaptable to a continuous production process. According to the method, a working solution of the following composition is used to impregnate the microporous substrate prior to irradiation with ultraviolet light having a wavelength in the range of 250nm to 360nm, preferably at or near the lower end of the range (250 nm).

Working solution:

3 to 5% (w/v) poloxamer

0.5 to 1% (w/v) photoinitiator

0 to 0.5% (w/v) crosslinking agent

30 to 50% (v/v) aqueous alcohol or acetone solution

A preferred poloxamer for use in the working solution is supplied under the trade name PLURONICP-123. The preferred photoinitiator for the working solution is benzophenone. The preferred cross-linking agent for the working solution is divinylbenzene.

Example A

Preparation of filters (laboratory methods)

Volume of 5mL of 10% (w/v) triblock copolymer (PLURONIC) ^TM P-123; lot # MKCC2305, Sigma-Aldrich) was mixed with an equal volume of deionized water. The photoinitiator benzophenone (benzophenone; Ph) in an amount of 0.1g was added ₂ O) was dissolved in a separate volume of 5mL ethanol and then added to a dilute solution of the triblock copolymer. The working solution was stored in the dark until use.

From sheets of microporous poly (ethylene) (targaray) ^TM A wet polyethylene separator, cat # SW320H (Targarray, Kirkland QC, Canada)) was cut out of the samples (13.5X 18.5cm) and each sample was coated with a volume of 5mL of the working solution. The coated samples were then irradiated with Ultraviolet (UV) light in the range of 250 to 360nm for 2 minutes, then rinsed with water and air dried on top of a warm oven.

Four replicate samples prepared according to this method were designated 040918Wiv, 040918Wv, 040918Wvi and 151018 Wi. A small piece of sample designated 040918Wiv was cut from the edge of the sample and subjected to Scanning Electron Microscopy (SEM).

Each sample was readily wetted with water and was observed to become uniformly translucent when contacted with the solvent.

Durability, flux and protein entrapment

The flux (LMH) of each sample, designated 040918Wiv, 040918Wv and 040918Wvi, was determined using a filter membrane module (Sterlitech) as shown in figure 1. The samples were mounted individually in a filter membrane module and the flux was measured at 0 and 5 bar. The time to collect a predetermined volume of permeate at a specified pressure and temperature was recorded and the flux (J) was calculated according to the following equation:

where V is the volume of permeate (L), t is the time (h) to collect V, and A is the area of the sample exposed to the feed stream (water or skim milk) (m) ² ). The results are summarized in table 1.

TABLE 1 flux (LMH) measured at the indicated temperature (. degree. C.) with water as feed stream at 0 and 5 bar.

To evaluate durability, flux was also measured after repeated cleaning-in-place (CIP) protocols. The CIP protocol was based on the protocol employed in commercial process operations for Reverse Osmosis (RO) membranes (Anon (2014)) and is summarized in table 2.

TABLE 2 clean-in-place (CIP) protocol was adapted from Anon (2014). The "base" was 2% (w/v) sodium hydroxide (NaOH). The "acid" is 1.9% (w/v) nitric acid (H) ₂ NO ₃ ) And 0.6(w/v) phosphoric acid (H) ₃ PO ₄ )。

For each sample, multiple CIP protocols were repeated alternately using water or skim milk as the feed stream. The flux and percent protein retention (with skim milk as the feed stream) determined for the samples designated 040918Wv and 040918Wvi are provided in table 3. The total protein concentration in the permeate was calculated based on HPLC analysis monitored with UV absorbance.

Table 3 flux (LMH) and protein retention were measured at the indicated temperatures (c) with water or skim milk as feed stream at 0 and 5 bar. The measurements were performed on each sample according to a repeated Clean In Place (CIP) protocol.

The durability of the filters was further evaluated by contacting a sample named 151018Wi with 2% (w/v) sodium hydroxide (NaOH) for 7 days. The flux and percent protein retention (with skim milk as the feed stream) determined for these samples are provided in table 4.

Table 4 flux (LMH) and protein retention were measured at the indicated temperatures (c) with water or skim milk as feed stream at 0 and 5 bar. The samples were tested after 7 days of exposure to 2% (w/v) sodium hydroxide (NaOH).

Fourier Transform Infrared (FTIR) Spectroscopy

Spectra were recorded for each sample designated 040918Wiv, 040918Wv, and 040918Wvi using a Thermo Electron Nicolet 8700 FTIR spectrometer equipped with a single reflectance ATR and diamond crystals. 4cm for each sample ^-1 On average, 32 scans were performed. The recorded spectra (3800 cm) are provided in FIG. 2 ^-1 To 525cm ^-1 ) Comparison of (1): (i) untreated microporous poly (ethylene) (targaray) ^TM Wet-laid polyethylene separator, cat # SW320H (targaray, Kirkland QC, Canada)) ('virgin PE'); (ii) triblock copolymer (PLURONIC) for sample (P123) preparation ^TM P-123; lot # MKCC2305, Sigma-Aldrich); and (iii) the top (Etop) and back (Eback) sides of each sample designated 040918Wiv, 040918Wv, and 040918 Wvi.

Corresponding to the presence of a triblock copolymer (PLURONIC) ^TM P-123) in the spectrumC-O-C fragment of (4) (1108 cm) ^-1 ) Symmetric telescopic mode and CH ₃ (2970cm ^-1 ) The signal of C-H stretch mode of (a) is also present in the spectrum recorded for each sample. Triblock copolymer (PLURONIC) ^TM P-123) is also observed at low intensity in the 'fingerprint' region of the spectrum provided in fig. 3. Triblock copolymer (PLURONIC) ^TM P-123) was retained in the spectrum recorded for the sample region designated 040918Wiv after exposure to the feed stream (water), as shown in fig. 4.

·SEM

Scanning electron micrographs of a small piece cut from the edge of a sample designated 040918Wiv are provided in fig. 5 and 6. The poly (ethylene) fibers of the microporous sheet appear to be coated.

FTIR spectra and SEM observations appear to confirm that the poloxamer is grafted onto the polyolefin matrix of the microporous sheet. The conversion of the inherently hydrophobic microporous sheet of polyolefin to a water wettable permeable membrane is due to this grafting.

Example B

Preparation of filters (laboratory methods)

10% (w/v) triblock copolymer (PLURONIC) in a volume of 10mL ^TM P-123; lot # MKCC2305, Sigma-Aldrich) was mixed with an equal volume of deionized water. The photoinitiator benzophenone (benzophenone; Ph) in an amount of 0.2g ₂ O) and 0 or 0.1g of the crosslinking agent Divinylbenzene (DVB) were dissolved in a separate volume of 10mL of ethanol (methylated spirits) and then added to a volume of 10mL of a diluted solution of the triblock copolymer. These working solutions-without or with the crosslinking agent DVB-were stored in the dark until use.

From sheets of microporous poly (ethylene) (targaray) ^TM Samples (13.5X 18.5cm) were cut from a wet-laid polyethylene separator, cat # SW320H (Targarray, Kirkland QC, Canada) and each sample was coated with a volume of one of the working solutions. The coated samples were then irradiated with Ultraviolet (UV) light in the range of 250 to 360nm for 2 minutes, then rinsed with water and air dried in the open air.

Three replicate samples prepared according to this method using a working solution that did not include DVB were designated 110419Wi, 180419Wi and 180419 Wii. Three replicate samples prepared according to this method with a working solution containing DVB were named 230419Wi, 230419Wii and 230419 Wiii. Each sample was readily wetted with water and was observed to become uniformly translucent when contacted with the solvent.

The water flux of each sample was determined using deionized water as the feed stream (DI 1). The sample was then completely dried before the water flux was again measured using deionized water as the feed stream (DI 2). Each sample was then subjected to a Clean In Place (CIP) protocol, and then the water flux was measured two more times with deionized water as the feed stream (DI3 and DI4) and the samples were dried during this time. Each sample remained readily wettable with water. The results are summarized in tables 5 and 6 and compared in fig. 7.

Table 5 average flux (LMH) (. membrane failure) measured at room temperature (22 to 24 ℃) at 0 and 5bar with water as feed stream.

Table 6 average flux (LMH) determined at room temperature (22 to 24 ℃) at 0 and 5bar with water as feed stream.

Example C

Preparation of filters (prototype method)

10% (w/v) triblock copolymer (PLURONIC) in a volume of 300mL ^TM P-123; lot # MKCC2305, Sigma-Aldrich) was dispensed into a reservoir that prevented exposure to light. An additional 300mL volume of distilled water was then added to provide 5% (w/v) triblock copolymer (PLURONIC) in the reservoir ^TM P-123; lot # MKCC2305, Sigma-Aldrich). Separately, a 1.5% (w/v) solution of benzophenone in ethanol (methylated spirit) was prepared and a volume of the crosslinking agent Divinylbenzene (DVB) was added to provide DVB at a final concentration of 0.75% (v/v). Then the body is putVolume 400mL of the separately prepared solution with a triblock copolymer (PLURONIC) ^TM P-123; lot # MKCC2305, Sigma-Aldrich) in a reservoir to provide a working solution.

Referring to fig. 7 of the drawings, the working solution is delivered from the reservoirs (3, 4) to the two semi-cylindrical tanks (5, 6) of the prototype line using peristaltic pumps (1, 2). During operation of the prototype production line, the reservoirs were periodically replenished with working solution.

Microporous poly (ethylene) of width continuous microporous sheet (7) is fed from a stock dispensing roll to a first impregnation station comprising an idler roll (8) mounted coaxially in the first of two semi-cylindrical tanks (5). The difference between the radii of the roller (8) and the trough (5) is sufficient to allow the sheet (7) to pass freely around the roller and through the trough, but not so large as to promote evaporation of the working solution in the trough. The surface of the roller (8) passing over the sheet (7) may be helically engraved to facilitate the passage of the working solution through the length of the surface.

The sheet (7) leaving the first impregnation station is then fed vertically to a first irradiation station comprising a slotted chamber (9) containing two opposed arrays (10, 11) of ultraviolet light sources. The sheet (7) passes between the opposing arrays (10, 11) such that both sides are illuminated. The feed rate of the sheet (7) is adjusted to provide the desired residence time within the slotted chamber (9).

The irradiated sheet (7) is then passed through a second impregnation station (12) and a second irradiation station (13) having the same configuration as the first impregnation station and the first irradiation station. After these repeated steps, the irradiated sheet (7) is fed around a plurality of idler rollers (14, 15, 16) immersed in water in a washing station (17). The water in the washing station (17) is circulated by an external pump (18) and the depth of the water is controlled by a combination of a level transmitter and a solenoid valve (19). The combination of multiple idler rollers (14, 15, 16) and water depth ensures sufficient residence time before the water-washed sheet (7) is fed into the drying station.

The drying station is a forced air dryer comprising two plenum chambers (20, 21) having opposed perforated panels between which the base sheet passes. Hot air blowers (22, 23) mounted in the walls of each chamber force air through the perforated panels. The dried base sheet (7) is then rewound onto a receiving roll (not shown).

Filter element

The films can be used to make assemblies of various configurations. In one embodiment, the membrane is used to make a spiral wound filter element. The manufacture of such filter elements is well known in the art.

Although the invention has been described with reference to embodiments or examples, it should be understood that variations and modifications of these embodiments or examples may be made without departing from the scope of the invention. Where there are known equivalents to specific elements, features, or integers, such equivalents are incorporated as if specifically referred to in this specification. Variations and modifications of the embodiments or examples, including elements, features or integers disclosed in and selected from the referenced publications, are within the scope of the invention unless otherwise indicated. The advantages provided by the invention and discussed in the description may be provided in these different embodiments of the invention in alternative ways or in combination.

Industrial applicability

Methods of preparing filtration membranes and their use in recovering or removing water from a feed stream are provided. Filtration membranes are advantageously used to recover or remove water from a feed stream where in situ cleaning of the membrane is required to increase the efficiency of plant operations.

Cross-referencing

In the absence of any claim, description or drawing in whole or in part of this specification, the corresponding parts of the specification appended to the recently filed application claiming priority are incorporated by reference for completeness of this specification in accordance with PCT implementation rules items 4.18, 20.5 and 20.6 (effective or subsequently revised as of date 7/1 of 2015).

The disclosures of the following publications (identified more particularly in the "references" section below) are incorporated herein by reference, as specified by U.S. federal regulations 37 c.f.r.1.57: jones et al (2008) and Schmolka (1973).

Reference to the literature

Anon(2014)DOW FILMTEC ^TM Membranes–Cleaning procedures for DOW FILMTEC FT30 elements Tech Fact(Form No.609-23010-0211).

Carter et al (2018) control external vertical internal position modification of ultrafiltration membranes using surface-initiated AGET-ATRP Journal of Membrane Science,554, 109-.

Cheng et al (2017) Method for preparing mesoporous composite film Chinese patent application No. 201611226194[ publication No. CN 106731886A ].

Guo et al (2015) Coated microporosity materials lifting and adsorption properties and the use in fluid purification processes International application No. PCT/US2014/061326[ publication No. WO 2015/073161A 1].

Jones et al (2008) compatibility of polymer determination and nomenclature IUPAC Recommendations, RSC Publishing.

Liu et al (2014) With a multi-scale gradient surface preparation method of a microporous membrane Chinese patent application No. 201310479920[ publication No. CN 103611437A ].

Schmolka (1973) Polyoxylene-polyoxypropylene aquous gels U.S. Pat. No. 3,740,421.

Wang et al (2006) Pluronic polymers and polyvinyl sulfone blends with improved foaming-resistant ability and ultrafiltration performance Journal of Membrane Science,283, 440-.

Yang et al (2014) Preparation and application of PVDF-HFP composite polymer electrolytes in LiNi _0.5 Co _0.2 Mn _0.3 O ₂ lithium-polymer batteries Electrochimica Acta 134,258-265.

Claims

1. A water-wettable filter membrane comprised of a microporous sheet of grafted polyolefin, wherein the graft comprises a poloxamer having the structure:

HO (ethylene oxide) _m - (propylene oxide) _n - (ethylene oxide) _m H

Wherein m is in the range of 15 to 25 and n is in the range of 50 to 90.

2. The film of claim 1, wherein the polyolefin is poly (ethylene).

3. The film of claim 1 or 2, wherein m is 20 and n is 70.

4. The membrane of any one of claims 1 to 3, wherein the grafts comprise a crosslinker.

5. The film of claim 4, wherein the crosslinker has less than 150gmol ^-1 Molecular weight of (2).

6. The film of claim 5, wherein the crosslinking agent is divinylbenzene.

7. A filter assembly comprising a membrane according to any one of claims 1 to 7.

8. The filter element of claim 7, wherein the membrane is spiral wound.

9. A method of making a water-wettable filter membrane comprising:

(a) contacting a microporous sheet of polyolefin with a solution of a poloxamer in a solvent to provide a contacted sheet;

(b) irradiating the contacted sheet with ultraviolet light in the presence of a photoinitiator to provide an irradiated sheet; and

(c) drying and washing the irradiated sheet to provide the film,

wherein the poloxamer is a polymer having the structure

HO (ethylene oxide) _m - (propylene oxide) _n - (ethylene oxide) _m H

Wherein m is in the range of 15 to 25 and n is in the range of 50 to 90.

10. The method of claim 9, wherein the polyolefin is poly (ethylene).

11. The method of claim 9 or 10, wherein m is 20 and n is 70.

12. The method of any one of claims 9 to 11, wherein the solution comprises the photoinitiator.

13. The method of any one of claims 9 to 12, wherein the photoinitiator is a type II photoinitiator.

14. The method of any one of claims 9 to 13, wherein the photoinitiator is benzophenone.

15. The method of any one of claims 9 to 14, wherein the solution comprises a low molecular weight crosslinker.

16. The method of claim 15, wherein the crosslinking agent is divinylbenzene.

17. The method of any one of claims 9 to 16, wherein the solvent is 30 to 50% (v/v) aqueous alcohol or acetone.

18. The method of any one of claims 7 to 14, wherein the solvent is 30 to 50% (v/v) aqueous ethanol.

19. A method of recovering or removing water from a feed stream comprising the step of contacting a first side of the membrane of any one of claims 1 or 8 with the feed stream at a pressure sufficient to provide osmosis.

20. The process of claim 19, wherein the pressure is below 10bar and the flux is greater than 500 LMH.