CA2155516A1 - Inter-penetrating network charge modified microporous membrane - Google Patents
Inter-penetrating network charge modified microporous membraneInfo
- Publication number
- CA2155516A1 CA2155516A1 CA002155516A CA2155516A CA2155516A1 CA 2155516 A1 CA2155516 A1 CA 2155516A1 CA 002155516 A CA002155516 A CA 002155516A CA 2155516 A CA2155516 A CA 2155516A CA 2155516 A1 CA2155516 A1 CA 2155516A1
- Authority
- CA
- Canada
- Prior art keywords
- membrane
- polymer
- network structure
- polyethersulfone
- filtration membrane
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- 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
- B01D71/66—Polymers having sulfur in the main chain, with or without nitrogen, oxygen or carbon only
- B01D71/68—Polysulfones; Polyethersulfones
-
- 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
- B01D67/0002—Organic membrane manufacture
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0011—Casting solutions therefor
-
- 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
- B01D67/0002—Organic membrane manufacture
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0011—Casting solutions therefor
- B01D67/00111—Polymer pretreatment in the casting solutions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/14—Dynamic membranes
- B01D69/141—Heterogeneous membranes, e.g. containing dispersed material; Mixed matrix membranes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/30—Cross-linking
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/14—Membrane materials having negatively charged functional groups
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/36—Hydrophilic membranes
Abstract
Hydrophilic inter-penetrating network charge modified microporous membranes are provided as well as a method of preparing the membranes by casting a membrane matrix blend containing matrix polymer, a solvent system, a wetting polymer compatible with the matrix polymer, and a charge modified system which forms a cross-linked inter-penetrating network structure within the microporous membrane substate during the membrane fabrication process which network structure optionally can be locked in by heat curing. The membranes are useful for filtering ultrapure water with 18 megaohm-cm resistivity for the electronic industry, and they can also be used for the removal of a variety of contaminants from fluid media, such as very fine negatively charged particles, bacteria and endotoxins, with greatly enhanced filtration efficiency.
Description
WO94/17906 215 5 ~1 B PCT~S94/01365 INTER-PENETRATING NETWORK CHARGE
MODIFIED MICROPOROUS MEMBRANE
Fiel~ of the Invent;on This invention relates to novel hydrophilic charge modified microporous membranes useful for filtration of a variety of fluids, such as ultrapure water and biological fluids.
R~ckgrol~n~ of the Invent;on Conventional cationic charge modified microporous membranes for the filtration of ultrapure water typically have a proper charge density, but a slow 18 megaohm-cm water resistivity recovery, a characteristic critical to filtration application in the electronic industry. U.S. Patent 4,702,840 discloses charge modified membranes prepared by casting an acidic polymer solution comprising a matrix polymer and a primary activated polymer having epoxy functional groups on a supportive material to form a thin film, followed by immersing the film in a liquid bath. The resulting nascent membranes are washed in water and finally dried in an oven. During this membrane fabrication process, epoxy functional groups of the primary activated polymer available for the reaction with amino or carboxyl functional groups of the polyamide matrix polymer will be de-activated through an acid-catalyzed ring-opening reaction due to the presence of an acidic solvent.
Therefore, complete grafting of the primary activated polymer on the polyamide membrane surface can be a problem.
Summary of the Invention The invention concerns a hydrophilic charge WO94/17906 PCT~S94/01365 ~ ~ ~3~
modified microporous membrane having a cross-linked structure of an inter-penetrating polymer network. The membrane comprises a homogeneous matrix of polyethersulfone (PES), polyfunctional glycidyl ether, and a polymeric amine such as polyethyleneimine (PEI) and like polyamines, and polyethylene glycol. In a preferred aspect, the matrix comprising PES, the polyfunctional glycidyl ether, and polymeric amine, as described, may optionally contain a homopolymer of vinylpyrrolidone (homopolymer) or a quaternized co-polymer of vinylpyrrolidone and dimethylaminoethyl methacrylate (co-polymer) or a homopolymer and co-polymer mixture. The membrane is unique in that it is cationic charge modified, and possesses low membrane extractables and fast 18 megaohm-cm water resistivity recovery. The invention further concerns a method of making the membrane comprising the step~ of casting a solution in a thin film, precipitating the nascent membrane, and washing and drying it to form a finished dried microporous membrane, thereby achieving the cross-linked structure of the inter-penetrating polymer network. Preferably the membrane is then thermal-baked to stabilize the cross-linked structure of the inter-penetrating polymer network.
Det~iled Description of the Invent;on The invention concerns a hydrophilic, cross-linked inter-penetrating network cationic charge modified, preferably isotropic, microporous filtration membrane that has low membrane extractables and allows fast recovery of ultrapure water resistivity. The membrane is formed by casting in a film a polymer matrix blend solution, preferably homogeneous, comprising polyethersulfone, 094/17906 21~ PCT~S94/0~65 polyfunctional glycidyl ether, a polyamine preferably selected from polyethyleneimine, tetraethylenepentamine, pentaethylenehexamine, and like polyamines (which matrix blend solution in a preferred aspect may optionally Contain a homopolymer or a co-polymer or a mixture thereof), polyethylene glycol, and a suitable solvent or solvent mixture, preCipitating the resulting film as a membrane having said network Structure in air followed by a quench bath, and washing and drying the thuS precipitated membrane. Preferred solvents are N-methylpyrrolidine, dimethyl formamide, or a mixture thereof.
Preferably, the polyethylene glycol has a molecular weight of 400. The solvent preferably iS
dimethyl formamide, but may be any solvent having similar properties.
The preferred membrane matrix solution iS
comprised by weight of the following:
Const;tuentPercent~e R~nge Polyethersulfone 9.4 - 20.7 Polyfunctional glycidylether 0.2 - 0.7 Polymeric amine 0.2 - l.3 PVP and/or quaternized co-polymer 0.0 - 2.7 Polyethyleneglycol56.3 - 63.5 Dimethyl formamide18.3 - 25.2 In a preferred embodiment, the dried membrane is baked sufficiently to stabilize said network struCture. A
preferred PES resin (sold under the trade name Ultrason~
E-6010, BASF Corp.) has the chemical Structure I:
~ ~ ) m where m is an integer in the range from 30 to lO00. PES
WO94/17906 ~ ~ PCT~S94/01365 resin having properties similar to the preferred one can also be used. A preferred PEI resin (sold under the trade name Corcat~ P-600, Hoechst Celanese Corp.) has a molecular weight of 60,000 and the chemical structure II:
--( CH2 CH~ N )n II
R
where n ls an integer in the range of 900-1400, and R is hydrogen or a continuation of the polyamine chain. Other polyfunctional organic amines having chemical properties similar to the preferred one can also be used such as tetraethylenepentamine, pentaethylenehex~m;ne and the like.
A preferred polyfunctional glycidyl ether resin is 1,4-butanediol diglycidyl ether (sold under the trade name Heloxy~ 67, Rhone-Poulenc Corp.), and has the molecular structure III:
CH2--CH--CH2--O~ (CH2)4--O--CH2--CH--CH2 III
`o' ~o/
Other polyfunctional glycidyl ether resins which chemically behave similarly to the above 1,4-butanediol diglycidyl ether can also be used in this invention. This includes polyfunctional aromatic glycidyl ether resins and the like. A preferred membrane is one wherein the matrix comprises by weight about 60-95% of PES resin, about 0.1-20.0% of PEI resin, and about 0.1-20.0% of polyfunctional glycidyl ether resin, and also includes polyethylene glycol. Polymeric amines or polyfunctional organic amines impart not only charge capacity but also hydrophilicity to WO94/17906 PCT~S94/01365 the microporous membrane. The preferred membrane so prepared is hydrophilic and cationically charged. Its hydrophilicity and cationic charge density will stay unchanged even after isopropanol Soxhlet extraction for 24 hours, 120C autoclaving for 40 minutes, or boiling in deionized water for one hour.
The invention contemplates the optional use of a homopolymer and/or a co-polymer. The use of a homopolymer, which is compatible with PES resin, ensures long-term hydrophilicity of the membrane. A preferred homopolymer resin (sold under the trade name Plasdone~ K-90, GAF
Chemical Corp.) has a molecular weight of 700,000. The PVP
resin has the chemical structure IV:
--( CH2--CH--)p N
~ ~eO IV
where p is an integer in the range of 360 to 6300. PVP
resins having properties similar to the preferred one can also be used.
The use of a co-polymer ensures both long-term hydrophilicity and enhanced charge capacity. Preferred co-polymers are sold under the trade name Gafquat~, GAF
Chemicals Corp., as Gafquat 755N (average molecular weight, 1,000,000) and Gafquat 734 (average molecular weight 100,000) and have the molecular structure V:
WO94/17906 PCT~S94101365 ~5~ 6-CH2-CH CH2- l N C=O V
H2C \C =
H2C - CH2 g _ x H2 H5C2~N+ oSo3c2H5 CH3 CH3 y ~ n where n, x and y are integers.
Only very few quaternized polymer resins are compatible with the polyethersulfone membrane mix. Gafquat type charged resins are preferred.
Still another preferred membrane is one wherein the matrix comprises by weight about 60-95~ of PES resin, about 0.1-25% of the homopolymer and/or co-polymer, about 0.1-20% of PEI resin, and about 0.1-20% of polyfunctional glycidyl ether resin based upon the total amount of these resins included in the blend. The preferred membrane has a fast 18 megaohm-cm water resistivity recovery. It is believed that in the process of the present invention, the homopolymer and/or co-polymer is firmly trapped within the inter-penetrating, interlocked cross-linked network due to (1) strong interaction, such as hydrogen bonding or charge-dipole interaction, between the homopolymer and/or co-polymer and the cross-linked network, and ~2) entanglement between polymer chains. The resulting charge modified WO94/17906 ~ PCT~S94/01365 microporous membrane shows a low pH-dependency in its charge capacity because of the presence of the homopolymer and/or co-polymer.
Although the results suggest the advantages of a homopolymer and/or co-polymer in the polymer solution to prepare hydrophilic cationic charge modified membrane, there is no requirement that the present invention be restricted to the use of this material. Very high quality charge modified membranes may be prepared from PES, PEI, polyfunctional glycidyl ether, and polyethylene glycol.
Preferably, the polymer solution is cast as a - liquid film on a suitable support such as a glass plate or a moving stainless-steel belt and subjected to conditions of controlled temperature (practical range between 10C and 35C), and relative humidity (practical range between 50%
and 80%). The liquid film of the polymer imbibes sufficient water to affect partial precipitation of polymer from the solvent. Completion of the precipitation occurs in a quench bath which contains a non-solvent such as water or a non-solvent mixture such as water-alcohol. The membrane is dried in an oven suitably at about 70C, and, optionally, heat-treated or baked sufficiently to stabilize the network structure (preferably carried out at temperature from 90-140C for l to 48 hours, more preferably for at least 3 hours and most preferably for at least 8 hours. A preferred temperature is about 120C).
Another unique aspect of the invention results from the optional heat treatment at elevated temperature.
It was found that the unbaked membrane which did not experience the final thermal baking showed a relatively much slower 18 megaohm-cm water resistivity recovery than did membranes which were baked as deQcribed above.
WO94/17906 ~ PCT~S94/01365 ~P~e~*e~ unheated membranes do generally have a higher cationic charge density (as determined by the anionic dye adsorption) than the membranes heated for the described stabilization of the network structure.
DEFINITIONS
W~ter Ruhhle polnt - This common test for microporous membrane is a measurement of the largest pores in a membrane. It consists of expelling water from a water-wetted membrane by air pressure. Pore size and the pressure necessary to remove water from that pore are related by:
D = B~cos~/P
where P is the pressure, ~is the water-solid contact angle between the membrane material and water, ~ is water-air surface tension, D is pore diameter, and B is a constant.
Isoprop~nol/W~ter Rllhble Po;nt - The water bubble point is not practically suitable for characterizing the pore size of tight microporous membranes due to the safety concern in most laboratories. Therefore, an alcohol mixture, i.e., isopropanol/water (60/40, by volume) is used to characterize the tight membranes in this invention.
W~ter Flow R~te - Water flow rate is the flow rate of water passing through the membrane of given dimension, and commonly expressed in seconds/l00 ml of water at a given pressure.
Dye Adsorpt;on - Membrane surfaces which have a positive zeta potential will adsorb negatively charged organic dyes.
This can be used to semi-quantify the charging efficiency of charged membrane.
WO94/17906 ~1 5 ~ ; PCT~S94/0~65 _g_ Fxtractahles - The amount of extractables is determined by boiling the membrane in water for one hour and measuring the weight loss.
EXAMPLES
(Percentage by Weight) Com~r~t;ve Fx~m~le 1 Prepar~t;on of 0.1 um Unch~r~e~ Polyethersulfone Memhr~ne Polyethersulfone (Ultrason E-6010 available from BASF), dimethyl formamide, polyethylene glycol 400, and polyvinylpyrrolidone were mixed in the ratio of 17.5:20.0:
61.2:1.3. The mixture was stirred to homogeneity and cast at 7-10 mil on glass or stainless steel plate. It was subjected to 60-70% relative humidity ambient air until it became opaque. The film was then immersed in water to leach out excess solvent for 2-12 hours. It was then dried at 70C. The membrane obtained was hydrophilic. The memhrane characteristics were:
Isopropanol/Water Bubble Point: 44 psi Water Flow Rate: 110 seconds/9.62 cm2, 100 ml at 10 psi Com~rat;ve ~x~m~le ?
Pre~r~t;on of 0.1 ~m C~tion;~lly ~h~rge~
Polyetherslllfone M~mhr~ne h~y Po~t-Tre~tm~nt WO94117906 ~ PCT~S94/01365 s~
The membrane made in Comparative Example l was placed in an aqueous solution containing l.0% of polyethyleneimine (Corcat P-600, available from Hoechst Celanese), and 2.35% of l,4-butanediol diglycidyl ether (Heloxy 67, available from Rhone-Poulenc) for a few minutes, and then was removed from the coating solution.
Excess polymer solution was wiped off from the membrane using squeegee bars.
The membrane was then baked in a vented oven at 115C for one hour. After baking, the membrane was washed with deionized water at 90C for 20 minutes and finally dried at 70C for 20 minutes. The membrane performance was:
IsoprQpanol/Water Bubble Point: 45 psi Water Flow Rate: 120 seconds/9.62 cm2, lO0 ml at lO psi The membrane so prepared had cationic charge evidenced by anionic dye adsorption. However, the modified membrane showed a relatively slower 18 megaohm-cm water resistivity recovery than those made according to the present invention.
~x~m~le 3 PreD~r~t;on of O.l ~m Cat;onically Ch~r~e~ Polyethersulfone Memhr~ne A polymer casting solution was prepared according to the invention by mixing polyethersulfone, polyvinylpyrrolidone, polyethylene glycol 400, dimethyl formamide, polyethyleneimine (Corcat P-600, available from Hoechst Celanese), and l,4-butanediol diglycidyl ether wo 94~17906 2 ~ 1 6 PCT~S94/01365 (Heloxy 67 available from Rhone-Poulenc) in the ratio of 16.0:1.2:62.6:19.0:0.8:0.4. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane 50 prepared was hydrophilic and cationically charged, and had the characteristics as follows:
~ .
Isopropanol/Water Bubble Point: 42 psi Water Flow Rate: 123 seconds/9.62 cm2, 100 ml at 10 psi Fx~m~le 4 Prep~r~t;on of 0.1 ~m Cation;c~lly Ch~r~e~ Po~yethersulfone M~mhr~ne A polymer casting solution was prepared according to the invention by mixing polyethersulfone, polyethylene glycol 400, dimethyl formamide, polyethylene imine (Corcat P-600, available from Hoechst Celanese), and 1,4-butanediol diglycidyl ether (Heloxy 67 available from Rhone-Poulenc) in the ratio of 16.0:62.6:20.2:0.8:0.4. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so prepared was hydrophilic and cationically charged, and had characteristics similar to those of the cationically charged membrane prepared as in Example 3.
FxAm~le 5 Prep~r~t;on of 0.1 ~m C~tlon;c~lly r ~ ~,h~rge~ Polyethersulfone Memhr~ne A polymer casting solution was prepared by mixing polyethersulfone, quaternized polymer (Gafquat 755 N, available from GAF Chemical Corp.), polyethylene glycol 400, dimethyl formamide, polyethyleneimine (Corcat P-600, ~ 12- PCT~S94/01365 available from Hoechst Celanese), and 1,4-butanediol diglycidyl ether together in the ratio of 17.0:2.6:60.5:18.6:0.9:0.4. The polymer solution was cast on a glass plate and set as Comparative Example 1. The membrane so prepared was hydrophilic and cationically charged, and had the characteristics as follows:
Isopropanol/Water Bubble Point: 39 psi Water Flow Rate: 102.8 seconds/9.62 cm2, 100 ml at 10 psi Fxam~le 6 Pre~ar~tion of 0.1 ~m Cationically Ch~r~e~ Polyethersulfone M~mhr~ne The preparation procedure for this membrane wa~
the same as that described in Example 3 except that the membrane after drying at 70C was further oven-baked at 120C for one hour. The membrane so prepared was hydrophilic and cationically charged, and had the following characteristics:
Isopropanol/Water Bubble Point: 44 psi Water Flow Rate: 130 seconds/9.62 cm2, 100 ml at 10 psi Fxample 7 Prep~r~tion of 0.1 ~m C~t;on;c~lly ~h~r~e~ Polyethersulfone Me-mhr~ne A casting solution was prepared by mixing polyethersulfone, Gafquat 755N, polyethylene glycol 400, wo g4,l7906 ~ 1 B PCT~S94/01365 dimethyl formamide, tetraethylenepentamine, and 1,4-butanediol diglycidyl ether together in the ratio of 16.4:2.6:62.0:18.6:0.2:0.2. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so obtained was hydrophilic and cationically charged as evidenced by anionic dye adsorption. The membrane performance was as follows:
Isopropanol/Water Bubble Point: 37.4 psi Water Flow Rate: 108.3 seconds/9.62 cm2, 100 ml at 10 psi F.X~ m~le 8 Prep~r~tion of 0.1 ~m C~tionic~lly Ch~r~e~ Polyethersulfone Memhr~ne A casting solution was prepared by mixing polyethersulfone, Gafquat 755N, polyethylene glycol 400, dimethyl formamide, pentaethylenehexamine, and 1,4-butanediol diglycidyl ether together in the ratio of 17.0:2.0:61.4:18.3:0.7:0.6. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so obtained was hydrophilic and cationically charged as evidenced by anionic dye adsorption. The membrane performance was as follows:
Isopropanol/Water Bubble Point: 41.2 psi Water Flow Rate: 80.9 seconds/9.62 cm2, 100 ml at 10 psi WO94tl7906 PCT~S94/01365 ~x~m~le 9 Preparation of 0.03 ~m Cat;o~ic~lly Ch~r~ Polyether~ulfone M~mhr~ne A casting solution was prepared by mixing polyethersulfone, Gafquat 755N, polyethylene glycol 400, dimethyl formamide, polyethyleneimine, and l,4-butanediol diglycidyl ether together in the ratio of 20.5:2.2:56.8:19.2:0.9:0.4. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so obtained was hydrophilic and cationically charged as evidenced by anionic dye adsorption. The membrane performance was as follows:
Isopropanol/Water Bubble Point: 58 psi Water Flow Rate: 186.4 seconds/9.62 cm2, 100 ml at 10 psi Fxample 10 Pr~r~t;on of 0.03 ~m C~tion;c~l]y Ch~rged Polyethersulfone M~mhrane A casting solution was prepared by mixing polyethersulfone, Gafquat 755N, polyethylene glycol 400, dimethyl formamide, pentaethylenehexamine, and 1,4-butanediol diglycidyl ether together in the ratio of 20.6:2.5:56.3:19.1:0.8:0.7. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so obtained was hydrophilic and cationically charged as evidenced by anionic dye adsorption. The membrane performance was as follows:
21~551~
Isopropanol/Water Bubble Point: 62 psi Water Flow Rate: 213.6 seconds/9.62 cm2, 100 ml at 10 psi F~m~le 11 Preparation of 0.03 ~m Cation; CA 1 ly ChArçre~l Polyether.slllfone Memhr~ne A casting solution was prepared by mixing polyethersulfone, polyvinylpyrrolidone, polyethylene glycol 400, dimethyl formamide, polyethyleneimine, and 1,4-butanediol diglycidyl ether together in the ratio of 20.7:1.1:58.0:19.0:0.8:0.4. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so obtained was hydrophilic and cationically charged as evidenced by anionic dye adsorption. The membrane performance was as foliows:
Isopropanol/Water Bubble Point: 66.7 psi Water Flow Rate: 267 seconds/9.62 cm2, 100 ml at 10 psi m~le 12 PreD~rat;on of 0.03 ~lm C~t;on; CA 1 1 y Ch~rçre~l Polyethersulfone Memhr;~ne The membrane was prepared in the same manner as described in Example 11 except that the membrane after drying at 70C was further oven-baked at 120C for 48 hours. The membrane so prepared was hydrophilic and cationically charged, and had the following characteristics:
~ ls~
Isopropanol/Water Bubble Point: 66 psi Water Flow Rate: 260 seconds/9.62 cm2, 100 ml at 10 psi After Soxhlet extraction using isopropanol for 24 hours, the membrane did not lose its hydrophilicity, flow rate, and cationic charge capacity.
~.x~rru;~le 13 Prep~r~t;~n of 0.2 llm C~tion;c~311y Charged Polyethersulfone M~?mhrane A polymer casting solution was prepared by mixing polyethersulfone, polyvinylpyrrolidone, polyethylene glycol 400, dimethyl formamide, polyethyleneimine, 1,4-butanediol diglycidyl ether together in the ratio of 12.9:0.6:61.6:23.7:0.8:0.4. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so prepared was hydrophilic and cationically charged, and had the characteristics as follows:
Water Bubble Point: 62.7 psi Water Flow Rate: 23.2 seconds/9.62 cm2, 100 ml at 10 psi F.x~m,ple 14 Prep~r~t;on of 0.45 llm C;~t;onici?lly Charged Polyethersulfone M~mhr~ne A polymer casting solution was prepared by mixing polyethersulfone, polyvinylpyrrolidone, polyethylene glycol 400, dimethyl formamide, polyethyleneimine, 1,4-WO94/17906 21~ PCT~S94/01365 butanediol diglycidyl ether together in the ratio of 9.4:2.7:63.5:23.2:0.8:0.4. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so prepared was hydrophilic and cationically charged, and had the characteristics as follows:
Water Bubble Point: 41.3 psi Water Flow Rate: 10.1 seconds/9.62 cm2, 100 ml at 10 psi F~m~le 15 Prep~r~t;on of 0.8 ~m C~t;onic~lly Ch~rged Polyethersulfone M~mhr~e A polymer casting solution was prepared by mixing polyethersulfone, polyvinylpyrrolidone, polyethylene glycol 400, dimethyl formamide, polyethyleneimine, 1,4-butanediol diglycidyl ether together in the ratio of 9.4:0.5:63.0:25.2:1.3:0.6. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so prepared was hydrophilic and cationically charged, and had the characteristics as follows:
Water Bubble Point: 22.1 psi Water Flow Rate: 4.3 seconds/9.62 cm2, 100 ml at 10 psi ~x~le 16 An; onic Dye A~orption of the M~mhr~ne The dye adsorption test was done with a dilute WO94/17906 PCT~S94/01365 ~5S~ 18-aqueous solution (10 ppm) of a negatively charged Metanil Yellow. The solution was filtered through the test samples (47 mm in diameter) at 10 psi; the end point of testing was visually determined and expressed in terms of volume of dye solution when the filtrate penetrating through membrane samples became very light yellow. The accuracy of this dye adsorption test was about 5 ml of dye solution. The dye adsorption capacity of membrane samples are set out in Table I below.
TABLE I
DYE ADSORPTION CAPACITY OF VARIOUS MEMBRANES
Membrane Sample Volume of 10 PPM of Metanil of Fx~le # Yellow Dye A~orpt;on (ml) 1 (Comparative) 5 2 (Comparative) 23 ~x~mple 17 Me~surement of 18 me~ohm-cm W~ter Res;st;v;ty Recovery A 293-mm diameter disc of the membrane s,ample was installed in a stainless steel housing which allowed pressurized water to flow through the membrane sample.
Prefiltered and deionized 18 megaohm-cm water was caused to 5 1 ~
MODIFIED MICROPOROUS MEMBRANE
Fiel~ of the Invent;on This invention relates to novel hydrophilic charge modified microporous membranes useful for filtration of a variety of fluids, such as ultrapure water and biological fluids.
R~ckgrol~n~ of the Invent;on Conventional cationic charge modified microporous membranes for the filtration of ultrapure water typically have a proper charge density, but a slow 18 megaohm-cm water resistivity recovery, a characteristic critical to filtration application in the electronic industry. U.S. Patent 4,702,840 discloses charge modified membranes prepared by casting an acidic polymer solution comprising a matrix polymer and a primary activated polymer having epoxy functional groups on a supportive material to form a thin film, followed by immersing the film in a liquid bath. The resulting nascent membranes are washed in water and finally dried in an oven. During this membrane fabrication process, epoxy functional groups of the primary activated polymer available for the reaction with amino or carboxyl functional groups of the polyamide matrix polymer will be de-activated through an acid-catalyzed ring-opening reaction due to the presence of an acidic solvent.
Therefore, complete grafting of the primary activated polymer on the polyamide membrane surface can be a problem.
Summary of the Invention The invention concerns a hydrophilic charge WO94/17906 PCT~S94/01365 ~ ~ ~3~
modified microporous membrane having a cross-linked structure of an inter-penetrating polymer network. The membrane comprises a homogeneous matrix of polyethersulfone (PES), polyfunctional glycidyl ether, and a polymeric amine such as polyethyleneimine (PEI) and like polyamines, and polyethylene glycol. In a preferred aspect, the matrix comprising PES, the polyfunctional glycidyl ether, and polymeric amine, as described, may optionally contain a homopolymer of vinylpyrrolidone (homopolymer) or a quaternized co-polymer of vinylpyrrolidone and dimethylaminoethyl methacrylate (co-polymer) or a homopolymer and co-polymer mixture. The membrane is unique in that it is cationic charge modified, and possesses low membrane extractables and fast 18 megaohm-cm water resistivity recovery. The invention further concerns a method of making the membrane comprising the step~ of casting a solution in a thin film, precipitating the nascent membrane, and washing and drying it to form a finished dried microporous membrane, thereby achieving the cross-linked structure of the inter-penetrating polymer network. Preferably the membrane is then thermal-baked to stabilize the cross-linked structure of the inter-penetrating polymer network.
Det~iled Description of the Invent;on The invention concerns a hydrophilic, cross-linked inter-penetrating network cationic charge modified, preferably isotropic, microporous filtration membrane that has low membrane extractables and allows fast recovery of ultrapure water resistivity. The membrane is formed by casting in a film a polymer matrix blend solution, preferably homogeneous, comprising polyethersulfone, 094/17906 21~ PCT~S94/0~65 polyfunctional glycidyl ether, a polyamine preferably selected from polyethyleneimine, tetraethylenepentamine, pentaethylenehexamine, and like polyamines (which matrix blend solution in a preferred aspect may optionally Contain a homopolymer or a co-polymer or a mixture thereof), polyethylene glycol, and a suitable solvent or solvent mixture, preCipitating the resulting film as a membrane having said network Structure in air followed by a quench bath, and washing and drying the thuS precipitated membrane. Preferred solvents are N-methylpyrrolidine, dimethyl formamide, or a mixture thereof.
Preferably, the polyethylene glycol has a molecular weight of 400. The solvent preferably iS
dimethyl formamide, but may be any solvent having similar properties.
The preferred membrane matrix solution iS
comprised by weight of the following:
Const;tuentPercent~e R~nge Polyethersulfone 9.4 - 20.7 Polyfunctional glycidylether 0.2 - 0.7 Polymeric amine 0.2 - l.3 PVP and/or quaternized co-polymer 0.0 - 2.7 Polyethyleneglycol56.3 - 63.5 Dimethyl formamide18.3 - 25.2 In a preferred embodiment, the dried membrane is baked sufficiently to stabilize said network struCture. A
preferred PES resin (sold under the trade name Ultrason~
E-6010, BASF Corp.) has the chemical Structure I:
~ ~ ) m where m is an integer in the range from 30 to lO00. PES
WO94/17906 ~ ~ PCT~S94/01365 resin having properties similar to the preferred one can also be used. A preferred PEI resin (sold under the trade name Corcat~ P-600, Hoechst Celanese Corp.) has a molecular weight of 60,000 and the chemical structure II:
--( CH2 CH~ N )n II
R
where n ls an integer in the range of 900-1400, and R is hydrogen or a continuation of the polyamine chain. Other polyfunctional organic amines having chemical properties similar to the preferred one can also be used such as tetraethylenepentamine, pentaethylenehex~m;ne and the like.
A preferred polyfunctional glycidyl ether resin is 1,4-butanediol diglycidyl ether (sold under the trade name Heloxy~ 67, Rhone-Poulenc Corp.), and has the molecular structure III:
CH2--CH--CH2--O~ (CH2)4--O--CH2--CH--CH2 III
`o' ~o/
Other polyfunctional glycidyl ether resins which chemically behave similarly to the above 1,4-butanediol diglycidyl ether can also be used in this invention. This includes polyfunctional aromatic glycidyl ether resins and the like. A preferred membrane is one wherein the matrix comprises by weight about 60-95% of PES resin, about 0.1-20.0% of PEI resin, and about 0.1-20.0% of polyfunctional glycidyl ether resin, and also includes polyethylene glycol. Polymeric amines or polyfunctional organic amines impart not only charge capacity but also hydrophilicity to WO94/17906 PCT~S94/01365 the microporous membrane. The preferred membrane so prepared is hydrophilic and cationically charged. Its hydrophilicity and cationic charge density will stay unchanged even after isopropanol Soxhlet extraction for 24 hours, 120C autoclaving for 40 minutes, or boiling in deionized water for one hour.
The invention contemplates the optional use of a homopolymer and/or a co-polymer. The use of a homopolymer, which is compatible with PES resin, ensures long-term hydrophilicity of the membrane. A preferred homopolymer resin (sold under the trade name Plasdone~ K-90, GAF
Chemical Corp.) has a molecular weight of 700,000. The PVP
resin has the chemical structure IV:
--( CH2--CH--)p N
~ ~eO IV
where p is an integer in the range of 360 to 6300. PVP
resins having properties similar to the preferred one can also be used.
The use of a co-polymer ensures both long-term hydrophilicity and enhanced charge capacity. Preferred co-polymers are sold under the trade name Gafquat~, GAF
Chemicals Corp., as Gafquat 755N (average molecular weight, 1,000,000) and Gafquat 734 (average molecular weight 100,000) and have the molecular structure V:
WO94/17906 PCT~S94101365 ~5~ 6-CH2-CH CH2- l N C=O V
H2C \C =
H2C - CH2 g _ x H2 H5C2~N+ oSo3c2H5 CH3 CH3 y ~ n where n, x and y are integers.
Only very few quaternized polymer resins are compatible with the polyethersulfone membrane mix. Gafquat type charged resins are preferred.
Still another preferred membrane is one wherein the matrix comprises by weight about 60-95~ of PES resin, about 0.1-25% of the homopolymer and/or co-polymer, about 0.1-20% of PEI resin, and about 0.1-20% of polyfunctional glycidyl ether resin based upon the total amount of these resins included in the blend. The preferred membrane has a fast 18 megaohm-cm water resistivity recovery. It is believed that in the process of the present invention, the homopolymer and/or co-polymer is firmly trapped within the inter-penetrating, interlocked cross-linked network due to (1) strong interaction, such as hydrogen bonding or charge-dipole interaction, between the homopolymer and/or co-polymer and the cross-linked network, and ~2) entanglement between polymer chains. The resulting charge modified WO94/17906 ~ PCT~S94/01365 microporous membrane shows a low pH-dependency in its charge capacity because of the presence of the homopolymer and/or co-polymer.
Although the results suggest the advantages of a homopolymer and/or co-polymer in the polymer solution to prepare hydrophilic cationic charge modified membrane, there is no requirement that the present invention be restricted to the use of this material. Very high quality charge modified membranes may be prepared from PES, PEI, polyfunctional glycidyl ether, and polyethylene glycol.
Preferably, the polymer solution is cast as a - liquid film on a suitable support such as a glass plate or a moving stainless-steel belt and subjected to conditions of controlled temperature (practical range between 10C and 35C), and relative humidity (practical range between 50%
and 80%). The liquid film of the polymer imbibes sufficient water to affect partial precipitation of polymer from the solvent. Completion of the precipitation occurs in a quench bath which contains a non-solvent such as water or a non-solvent mixture such as water-alcohol. The membrane is dried in an oven suitably at about 70C, and, optionally, heat-treated or baked sufficiently to stabilize the network structure (preferably carried out at temperature from 90-140C for l to 48 hours, more preferably for at least 3 hours and most preferably for at least 8 hours. A preferred temperature is about 120C).
Another unique aspect of the invention results from the optional heat treatment at elevated temperature.
It was found that the unbaked membrane which did not experience the final thermal baking showed a relatively much slower 18 megaohm-cm water resistivity recovery than did membranes which were baked as deQcribed above.
WO94/17906 ~ PCT~S94/01365 ~P~e~*e~ unheated membranes do generally have a higher cationic charge density (as determined by the anionic dye adsorption) than the membranes heated for the described stabilization of the network structure.
DEFINITIONS
W~ter Ruhhle polnt - This common test for microporous membrane is a measurement of the largest pores in a membrane. It consists of expelling water from a water-wetted membrane by air pressure. Pore size and the pressure necessary to remove water from that pore are related by:
D = B~cos~/P
where P is the pressure, ~is the water-solid contact angle between the membrane material and water, ~ is water-air surface tension, D is pore diameter, and B is a constant.
Isoprop~nol/W~ter Rllhble Po;nt - The water bubble point is not practically suitable for characterizing the pore size of tight microporous membranes due to the safety concern in most laboratories. Therefore, an alcohol mixture, i.e., isopropanol/water (60/40, by volume) is used to characterize the tight membranes in this invention.
W~ter Flow R~te - Water flow rate is the flow rate of water passing through the membrane of given dimension, and commonly expressed in seconds/l00 ml of water at a given pressure.
Dye Adsorpt;on - Membrane surfaces which have a positive zeta potential will adsorb negatively charged organic dyes.
This can be used to semi-quantify the charging efficiency of charged membrane.
WO94/17906 ~1 5 ~ ; PCT~S94/0~65 _g_ Fxtractahles - The amount of extractables is determined by boiling the membrane in water for one hour and measuring the weight loss.
EXAMPLES
(Percentage by Weight) Com~r~t;ve Fx~m~le 1 Prepar~t;on of 0.1 um Unch~r~e~ Polyethersulfone Memhr~ne Polyethersulfone (Ultrason E-6010 available from BASF), dimethyl formamide, polyethylene glycol 400, and polyvinylpyrrolidone were mixed in the ratio of 17.5:20.0:
61.2:1.3. The mixture was stirred to homogeneity and cast at 7-10 mil on glass or stainless steel plate. It was subjected to 60-70% relative humidity ambient air until it became opaque. The film was then immersed in water to leach out excess solvent for 2-12 hours. It was then dried at 70C. The membrane obtained was hydrophilic. The memhrane characteristics were:
Isopropanol/Water Bubble Point: 44 psi Water Flow Rate: 110 seconds/9.62 cm2, 100 ml at 10 psi Com~rat;ve ~x~m~le ?
Pre~r~t;on of 0.1 ~m C~tion;~lly ~h~rge~
Polyetherslllfone M~mhr~ne h~y Po~t-Tre~tm~nt WO94117906 ~ PCT~S94/01365 s~
The membrane made in Comparative Example l was placed in an aqueous solution containing l.0% of polyethyleneimine (Corcat P-600, available from Hoechst Celanese), and 2.35% of l,4-butanediol diglycidyl ether (Heloxy 67, available from Rhone-Poulenc) for a few minutes, and then was removed from the coating solution.
Excess polymer solution was wiped off from the membrane using squeegee bars.
The membrane was then baked in a vented oven at 115C for one hour. After baking, the membrane was washed with deionized water at 90C for 20 minutes and finally dried at 70C for 20 minutes. The membrane performance was:
IsoprQpanol/Water Bubble Point: 45 psi Water Flow Rate: 120 seconds/9.62 cm2, lO0 ml at lO psi The membrane so prepared had cationic charge evidenced by anionic dye adsorption. However, the modified membrane showed a relatively slower 18 megaohm-cm water resistivity recovery than those made according to the present invention.
~x~m~le 3 PreD~r~t;on of O.l ~m Cat;onically Ch~r~e~ Polyethersulfone Memhr~ne A polymer casting solution was prepared according to the invention by mixing polyethersulfone, polyvinylpyrrolidone, polyethylene glycol 400, dimethyl formamide, polyethyleneimine (Corcat P-600, available from Hoechst Celanese), and l,4-butanediol diglycidyl ether wo 94~17906 2 ~ 1 6 PCT~S94/01365 (Heloxy 67 available from Rhone-Poulenc) in the ratio of 16.0:1.2:62.6:19.0:0.8:0.4. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane 50 prepared was hydrophilic and cationically charged, and had the characteristics as follows:
~ .
Isopropanol/Water Bubble Point: 42 psi Water Flow Rate: 123 seconds/9.62 cm2, 100 ml at 10 psi Fx~m~le 4 Prep~r~t;on of 0.1 ~m Cation;c~lly Ch~r~e~ Po~yethersulfone M~mhr~ne A polymer casting solution was prepared according to the invention by mixing polyethersulfone, polyethylene glycol 400, dimethyl formamide, polyethylene imine (Corcat P-600, available from Hoechst Celanese), and 1,4-butanediol diglycidyl ether (Heloxy 67 available from Rhone-Poulenc) in the ratio of 16.0:62.6:20.2:0.8:0.4. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so prepared was hydrophilic and cationically charged, and had characteristics similar to those of the cationically charged membrane prepared as in Example 3.
FxAm~le 5 Prep~r~t;on of 0.1 ~m C~tlon;c~lly r ~ ~,h~rge~ Polyethersulfone Memhr~ne A polymer casting solution was prepared by mixing polyethersulfone, quaternized polymer (Gafquat 755 N, available from GAF Chemical Corp.), polyethylene glycol 400, dimethyl formamide, polyethyleneimine (Corcat P-600, ~ 12- PCT~S94/01365 available from Hoechst Celanese), and 1,4-butanediol diglycidyl ether together in the ratio of 17.0:2.6:60.5:18.6:0.9:0.4. The polymer solution was cast on a glass plate and set as Comparative Example 1. The membrane so prepared was hydrophilic and cationically charged, and had the characteristics as follows:
Isopropanol/Water Bubble Point: 39 psi Water Flow Rate: 102.8 seconds/9.62 cm2, 100 ml at 10 psi Fxam~le 6 Pre~ar~tion of 0.1 ~m Cationically Ch~r~e~ Polyethersulfone M~mhr~ne The preparation procedure for this membrane wa~
the same as that described in Example 3 except that the membrane after drying at 70C was further oven-baked at 120C for one hour. The membrane so prepared was hydrophilic and cationically charged, and had the following characteristics:
Isopropanol/Water Bubble Point: 44 psi Water Flow Rate: 130 seconds/9.62 cm2, 100 ml at 10 psi Fxample 7 Prep~r~tion of 0.1 ~m C~t;on;c~lly ~h~r~e~ Polyethersulfone Me-mhr~ne A casting solution was prepared by mixing polyethersulfone, Gafquat 755N, polyethylene glycol 400, wo g4,l7906 ~ 1 B PCT~S94/01365 dimethyl formamide, tetraethylenepentamine, and 1,4-butanediol diglycidyl ether together in the ratio of 16.4:2.6:62.0:18.6:0.2:0.2. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so obtained was hydrophilic and cationically charged as evidenced by anionic dye adsorption. The membrane performance was as follows:
Isopropanol/Water Bubble Point: 37.4 psi Water Flow Rate: 108.3 seconds/9.62 cm2, 100 ml at 10 psi F.X~ m~le 8 Prep~r~tion of 0.1 ~m C~tionic~lly Ch~r~e~ Polyethersulfone Memhr~ne A casting solution was prepared by mixing polyethersulfone, Gafquat 755N, polyethylene glycol 400, dimethyl formamide, pentaethylenehexamine, and 1,4-butanediol diglycidyl ether together in the ratio of 17.0:2.0:61.4:18.3:0.7:0.6. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so obtained was hydrophilic and cationically charged as evidenced by anionic dye adsorption. The membrane performance was as follows:
Isopropanol/Water Bubble Point: 41.2 psi Water Flow Rate: 80.9 seconds/9.62 cm2, 100 ml at 10 psi WO94tl7906 PCT~S94/01365 ~x~m~le 9 Preparation of 0.03 ~m Cat;o~ic~lly Ch~r~ Polyether~ulfone M~mhr~ne A casting solution was prepared by mixing polyethersulfone, Gafquat 755N, polyethylene glycol 400, dimethyl formamide, polyethyleneimine, and l,4-butanediol diglycidyl ether together in the ratio of 20.5:2.2:56.8:19.2:0.9:0.4. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so obtained was hydrophilic and cationically charged as evidenced by anionic dye adsorption. The membrane performance was as follows:
Isopropanol/Water Bubble Point: 58 psi Water Flow Rate: 186.4 seconds/9.62 cm2, 100 ml at 10 psi Fxample 10 Pr~r~t;on of 0.03 ~m C~tion;c~l]y Ch~rged Polyethersulfone M~mhrane A casting solution was prepared by mixing polyethersulfone, Gafquat 755N, polyethylene glycol 400, dimethyl formamide, pentaethylenehexamine, and 1,4-butanediol diglycidyl ether together in the ratio of 20.6:2.5:56.3:19.1:0.8:0.7. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so obtained was hydrophilic and cationically charged as evidenced by anionic dye adsorption. The membrane performance was as follows:
21~551~
Isopropanol/Water Bubble Point: 62 psi Water Flow Rate: 213.6 seconds/9.62 cm2, 100 ml at 10 psi F~m~le 11 Preparation of 0.03 ~m Cation; CA 1 ly ChArçre~l Polyether.slllfone Memhr~ne A casting solution was prepared by mixing polyethersulfone, polyvinylpyrrolidone, polyethylene glycol 400, dimethyl formamide, polyethyleneimine, and 1,4-butanediol diglycidyl ether together in the ratio of 20.7:1.1:58.0:19.0:0.8:0.4. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so obtained was hydrophilic and cationically charged as evidenced by anionic dye adsorption. The membrane performance was as foliows:
Isopropanol/Water Bubble Point: 66.7 psi Water Flow Rate: 267 seconds/9.62 cm2, 100 ml at 10 psi m~le 12 PreD~rat;on of 0.03 ~lm C~t;on; CA 1 1 y Ch~rçre~l Polyethersulfone Memhr;~ne The membrane was prepared in the same manner as described in Example 11 except that the membrane after drying at 70C was further oven-baked at 120C for 48 hours. The membrane so prepared was hydrophilic and cationically charged, and had the following characteristics:
~ ls~
Isopropanol/Water Bubble Point: 66 psi Water Flow Rate: 260 seconds/9.62 cm2, 100 ml at 10 psi After Soxhlet extraction using isopropanol for 24 hours, the membrane did not lose its hydrophilicity, flow rate, and cationic charge capacity.
~.x~rru;~le 13 Prep~r~t;~n of 0.2 llm C~tion;c~311y Charged Polyethersulfone M~?mhrane A polymer casting solution was prepared by mixing polyethersulfone, polyvinylpyrrolidone, polyethylene glycol 400, dimethyl formamide, polyethyleneimine, 1,4-butanediol diglycidyl ether together in the ratio of 12.9:0.6:61.6:23.7:0.8:0.4. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so prepared was hydrophilic and cationically charged, and had the characteristics as follows:
Water Bubble Point: 62.7 psi Water Flow Rate: 23.2 seconds/9.62 cm2, 100 ml at 10 psi F.x~m,ple 14 Prep~r~t;on of 0.45 llm C;~t;onici?lly Charged Polyethersulfone M~mhr~ne A polymer casting solution was prepared by mixing polyethersulfone, polyvinylpyrrolidone, polyethylene glycol 400, dimethyl formamide, polyethyleneimine, 1,4-WO94/17906 21~ PCT~S94/01365 butanediol diglycidyl ether together in the ratio of 9.4:2.7:63.5:23.2:0.8:0.4. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so prepared was hydrophilic and cationically charged, and had the characteristics as follows:
Water Bubble Point: 41.3 psi Water Flow Rate: 10.1 seconds/9.62 cm2, 100 ml at 10 psi F~m~le 15 Prep~r~t;on of 0.8 ~m C~t;onic~lly Ch~rged Polyethersulfone M~mhr~e A polymer casting solution was prepared by mixing polyethersulfone, polyvinylpyrrolidone, polyethylene glycol 400, dimethyl formamide, polyethyleneimine, 1,4-butanediol diglycidyl ether together in the ratio of 9.4:0.5:63.0:25.2:1.3:0.6. The polymer solution was cast on a glass plate and set as in Comparative Example 1. The membrane so prepared was hydrophilic and cationically charged, and had the characteristics as follows:
Water Bubble Point: 22.1 psi Water Flow Rate: 4.3 seconds/9.62 cm2, 100 ml at 10 psi ~x~le 16 An; onic Dye A~orption of the M~mhr~ne The dye adsorption test was done with a dilute WO94/17906 PCT~S94/01365 ~5S~ 18-aqueous solution (10 ppm) of a negatively charged Metanil Yellow. The solution was filtered through the test samples (47 mm in diameter) at 10 psi; the end point of testing was visually determined and expressed in terms of volume of dye solution when the filtrate penetrating through membrane samples became very light yellow. The accuracy of this dye adsorption test was about 5 ml of dye solution. The dye adsorption capacity of membrane samples are set out in Table I below.
TABLE I
DYE ADSORPTION CAPACITY OF VARIOUS MEMBRANES
Membrane Sample Volume of 10 PPM of Metanil of Fx~le # Yellow Dye A~orpt;on (ml) 1 (Comparative) 5 2 (Comparative) 23 ~x~mple 17 Me~surement of 18 me~ohm-cm W~ter Res;st;v;ty Recovery A 293-mm diameter disc of the membrane s,ample was installed in a stainless steel housing which allowed pressurized water to flow through the membrane sample.
Prefiltered and deionized 18 megaohm-cm water was caused to 5 1 ~
6 PCT~S94/01365 19 .
flow through the membrane sample at a constant flow rate of 0.9-l.0 gallons per minute. The effluent resistivity was constantly monitored. The length of time which was required to reach the same resistivity level as upstream was determined and recorded. The test results of memhrane samples are summarized in Table II below.
TABLE II
RESISTIVITY RECOVERY
Membrane SampleFlush Out Time to 18 Megaohm-cm Fx~m~le # (m.nutes) 2 (Comparative) 95.0-l00.0 ll 14.5-35.0 12 2.5-l0.5 Fx~m~Ie l8 Me~sur~ment of Memhr~ne ~xtr~ct~hles The degree of extractables of hydrophilic cationically charged polyethersulfone membranes was determined by pre-weighing the dry membrane samples, then by boiling them in DI water for l hour. After completely drying, the membrane extractables are expressed in terms of percentage weight loss and shown in Table III below.
WO94/17906 PCT~S94/01365 TABLE III
MEMBRANE EXTRACTABLES
Membrane Sample Extractables of Fxample # %
11 0.145 12 0.118 - Fxample 19 Co~r;son of M~mhr~ne Perform~nce Refore ~n~ After ~xtr~ction W;th Ro; 1 ;n~ WAter Cationically charged polyethersulfone membranes prepared from Example 7, all in the form of 47-mm disks, were subjected to extraction with boiling water as in Example 18. The membrane performance before and after extraction with boiling water is shown in Table IV.
TABLE IV
Before After MemhrAne SAm~leF.xtr~ction~xtrAct;on Dye adsorption capacity (10 PPM of Metanil Yellow) 15 ml 13 ml Isopropanol/water bubble point 66.0 psi 65.3 psi Water flow rate (seconds/9.62 cm 100 ml at 10 psi)260.0 255.6 WO94117906 PCT~S94/0~65 ~ -21- 2155~
It will thus be seen that the present invention provides improved, cationically charged porous membranes.
The membranes have a very low level of extractable materials retained therein. They retain a high degree of charge and possess good flow properties. This combination of properties makes them ideally suited for use in preparing high purity water for the semiconductor industry.
In addition, the method by which they are produced, being more reliable than that of the aforementioned U.S. Patent 4,702,840, results in a significant saving of time and money.
flow through the membrane sample at a constant flow rate of 0.9-l.0 gallons per minute. The effluent resistivity was constantly monitored. The length of time which was required to reach the same resistivity level as upstream was determined and recorded. The test results of memhrane samples are summarized in Table II below.
TABLE II
RESISTIVITY RECOVERY
Membrane SampleFlush Out Time to 18 Megaohm-cm Fx~m~le # (m.nutes) 2 (Comparative) 95.0-l00.0 ll 14.5-35.0 12 2.5-l0.5 Fx~m~Ie l8 Me~sur~ment of Memhr~ne ~xtr~ct~hles The degree of extractables of hydrophilic cationically charged polyethersulfone membranes was determined by pre-weighing the dry membrane samples, then by boiling them in DI water for l hour. After completely drying, the membrane extractables are expressed in terms of percentage weight loss and shown in Table III below.
WO94/17906 PCT~S94/01365 TABLE III
MEMBRANE EXTRACTABLES
Membrane Sample Extractables of Fxample # %
11 0.145 12 0.118 - Fxample 19 Co~r;son of M~mhr~ne Perform~nce Refore ~n~ After ~xtr~ction W;th Ro; 1 ;n~ WAter Cationically charged polyethersulfone membranes prepared from Example 7, all in the form of 47-mm disks, were subjected to extraction with boiling water as in Example 18. The membrane performance before and after extraction with boiling water is shown in Table IV.
TABLE IV
Before After MemhrAne SAm~leF.xtr~ction~xtrAct;on Dye adsorption capacity (10 PPM of Metanil Yellow) 15 ml 13 ml Isopropanol/water bubble point 66.0 psi 65.3 psi Water flow rate (seconds/9.62 cm 100 ml at 10 psi)260.0 255.6 WO94117906 PCT~S94/0~65 ~ -21- 2155~
It will thus be seen that the present invention provides improved, cationically charged porous membranes.
The membranes have a very low level of extractable materials retained therein. They retain a high degree of charge and possess good flow properties. This combination of properties makes them ideally suited for use in preparing high purity water for the semiconductor industry.
In addition, the method by which they are produced, being more reliable than that of the aforementioned U.S. Patent 4,702,840, results in a significant saving of time and money.
Claims (13)
1. A hydrophilic inter-penetrating network cationic charge modified microporous filtration membrane having a pore size range between approximately 0.01 µm and 10 µm and further having low membrane extractables and fast recovery of ultrapure water resistivity, comprising:
a microporous membrane matrix, having therewithin a cross-linked inter-penetrating polymer network structure, said matrix being formed by casting in a film a blended polymer membrane solution comprising polyethersulfone, polyfunctional glycidyl ether, polyamine, polyethylene glycol and a solvent, precipitating the resulting film as a membrane having said network structure in a quench bath, and washing and drying the thus precipitated membrane.
a microporous membrane matrix, having therewithin a cross-linked inter-penetrating polymer network structure, said matrix being formed by casting in a film a blended polymer membrane solution comprising polyethersulfone, polyfunctional glycidyl ether, polyamine, polyethylene glycol and a solvent, precipitating the resulting film as a membrane having said network structure in a quench bath, and washing and drying the thus precipitated membrane.
2. A hydrophilic inter-penetrating network cationic charge modified microporous filtration membrane according to claim 1, said matrix being formed by casting in a film a blended polymer membrane solution comprising polyethersulfone, polyfunctional glycidyl ether, polyamine, polyethylene glycol, a solvent and a member selected from a homopolymer of vinylpyrrolidone, a co-polymer of vinylpyrrolidone and dimethylaminoethyl methacrylate, or a mixture of said homopolymer and co-polymer, precipitating the resulting film as a membrane having said network structure in a quench bath, and washing and drying the thus precipitated membrane.
3. A filtration membrane according to claim 1 or claim 2, wherein said polyethersulfone has the chemical structure I:
I
where m is an integer in the range from 30 to 1000.
I
where m is an integer in the range from 30 to 1000.
4. A filtration membrane according to claim 1 or claim 2, wherein said polyamine comprises tetraethylenepentamine, pentaethylenehexamine, or a polyethyleneimine having the chemical structure II:
II
where n is an integer in the range from 900 to 1400 and R
is hydrogen or a continuation of the polymer chain.
II
where n is an integer in the range from 900 to 1400 and R
is hydrogen or a continuation of the polymer chain.
5. A filtration membrane according to claim 1 or claim 2, wherein said polyfunctional glycidyl ether comprises 1,4-butanediol diglycidyl ether having the chemical structure III:
III
III
6. A filtration membrane according to claim 2, wherein said homopolymer of vinylpyrrolidone has the chemical structure IV:
IV
where p is an integer in the range of 360 to 6300.
IV
where p is an integer in the range of 360 to 6300.
7. A filtration membrane according to claim 2, wherein said quaternized co-polymer of vinylpyrrolidone and dimethylaminoethyl methacrylate has the chemical structure V:
V
where n, x and y are integers.
V
where n, x and y are integers.
8. A filtration membrane according to claim 1, wherein said matrix blend comprises by weight about 60-95%
polyethersulfone resin, about 0.1-20% polyethyleneimine resin, and about 0.1-20% polyfunctional glycidyl ether resin.
polyethersulfone resin, about 0.1-20% polyethyleneimine resin, and about 0.1-20% polyfunctional glycidyl ether resin.
9. A filtration membrane according to claim 2, wherein said matrix blend comprises by weight about 60-95%
polyethersulfone resin, about 0.1-20% polyethyleneimine resin, about 0.1-20% polyfunctional glycidyl ether resin, and about 0.1-25% homopolymer of vinylpyrrolidone and/or quaternized co-polymer of vinylpyrrolidone and dimethylaminoethyl methacrylate.
polyethersulfone resin, about 0.1-20% polyethyleneimine resin, about 0.1-20% polyfunctional glycidyl ether resin, and about 0.1-25% homopolymer of vinylpyrrolidone and/or quaternized co-polymer of vinylpyrrolidone and dimethylaminoethyl methacrylate.
10. A method of preparing a hydrophilic charge modified microporous filtration membrane having a network structure according to claim 1, comprising the steps of forming in a solvent a polymer casting solution of a blend of polyethersulfone, polyamine, polyfunctional glycidyl ether, and polyethylene glycol, forming a thin film of said polymer solution, precipitating the resulting film as a membrane having said network structure, and washing and drying the thus precipitated membrane.
11. A method of preparing a hydrophilic charge modified microporous filtration membrane having a network structure according to claim 2, comprising the steps of forming in a solvent a polymer casting solution of a blend of polyethersulfone, polyamine, polyfunctional glycidyl ether, polyethylene glycol, and a homopolymer of vinylpyrrolidone and/or quaternized co-polymer of vinylpyrrolidone and dimethylaminoethyl methacrylate, forming a thin film of said polymer solution, precipitating the resulting film as a membrane having said network structure, and washing and drying the thus precipitated membrane.
12. A method of preparing a hydrophilic charge modified microporous filtration membrane having a network structure according to claim 1, comprising the steps of forming in a solvent a polymer casting solution of a blend of polyethersulfone, polyamine, polyfunctional glycidyl ether, and polyethylene glycol, forming a thin film of said polymer solution, precipitating the resulting film as a membrane having said network structure, washing and drying the thus precipitated membrane, and baking the dried membrane sufficiently to stabilize said network structure.
13. A method of preparing a hydrophilic charge modified microporous filtration membrane having a network structure according to claim 11, comprising baking the thus dried membrane sufficiently to stabilize said network structure.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/017,036 US5277812A (en) | 1993-02-12 | 1993-02-12 | Inter-penetrating network charge modified microporous membrane |
| US08/017,036 | 1993-02-12 | ||
| US08/160,427 US5531893A (en) | 1993-02-12 | 1993-12-01 | Inter-penetrating network charge modified microporous membrane |
| US08/160,427 | 1993-12-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2155516A1 true CA2155516A1 (en) | 1994-08-18 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002155516A Abandoned CA2155516A1 (en) | 1993-02-12 | 1994-02-07 | Inter-penetrating network charge modified microporous membrane |
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| Country | Link |
|---|---|
| US (1) | US5531893A (en) |
| EP (1) | EP0683691A4 (en) |
| JP (1) | JPH08506519A (en) |
| CA (1) | CA2155516A1 (en) |
| WO (1) | WO1994017906A1 (en) |
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| US6039872A (en) * | 1997-10-27 | 2000-03-21 | Pall Corporation | Hydrophilic membrane |
| US6083393A (en) * | 1997-10-27 | 2000-07-04 | Pall Corporation | Hydrophilic membrane |
| DE19810947A1 (en) * | 1998-03-13 | 1999-09-16 | Merck Patent Gmbh | Removal of biological contaminants from biological products using anion-exchange membrane |
| US6264809B1 (en) | 1998-10-30 | 2001-07-24 | Pti Advanced Filtration, Inc. | Enhanced membrane electrode devices useful for electrodeposition coating |
| US6274041B1 (en) | 1998-12-18 | 2001-08-14 | Kimberly-Clark Worldwide, Inc. | Integrated filter combining physical adsorption and electrokinetic adsorption |
| US6537614B1 (en) | 1998-12-18 | 2003-03-25 | Kimberly-Clark Worldwide, Inc. | Cationically charged coating on hydrophobic polymer fibers with poly (vinyl alcohol) assist |
| US6183640B1 (en) | 1999-04-09 | 2001-02-06 | Usf Filtration And Separations Group, Inc. | Highly asymmetric anionic membranes |
| US6849185B1 (en) | 1999-05-14 | 2005-02-01 | Pall Corp | Charged membrane |
| US6645388B2 (en) | 1999-12-22 | 2003-11-11 | Kimberly-Clark Corporation | Leukocyte depletion filter media, filter produced therefrom, method of making same and method of using same |
| ES2220328T3 (en) | 1999-12-23 | 2004-12-16 | Membrana Gmbh | MOLDED BODIES FOR THE RETENTION OF PYROGENS, PROCEDURE FOR PRODUCTION AND USE. |
| DE60011573T2 (en) * | 2000-04-26 | 2004-11-25 | Pall Corp. | Highly asymmetric anionic membranes |
| US6756013B1 (en) * | 2000-08-14 | 2004-06-29 | Cornell Development Corporation, Llc | Compositions of iodonium compounds and methods and uses thereof |
| JP4626301B2 (en) * | 2002-06-14 | 2011-02-09 | 東レ株式会社 | Composite separation membrane and method for producing the same |
| US20050287515A1 (en) * | 2004-06-24 | 2005-12-29 | Reinhold Deppisch | Removal of bacterial DNA from therapeutic fluid formulations |
| EP1710011A1 (en) * | 2005-04-07 | 2006-10-11 | Gambro Lundia AB | Filtration membrane |
| US20110017673A1 (en) * | 2009-07-21 | 2011-01-27 | Ge Healthcare As | Endotoxin removal in contrast media |
| EP2314332A1 (en) | 2009-10-21 | 2011-04-27 | Gambro Lundia AB | Medical fluid delivery system |
| DE102009056884B4 (en) | 2009-12-03 | 2021-03-18 | Novartis Ag | Vaccine Adjuvants and Improved Methods for Making Same |
| DE102009056883B4 (en) | 2009-12-03 | 2012-08-16 | Novartis Ag | Vaccine adjuvants and improved methods of making the same |
| ES2402569T3 (en) | 2009-12-03 | 2013-05-06 | Novartis Ag | Circulation of components during homogenization of emulsions |
| NZ599881A (en) | 2009-12-03 | 2014-01-31 | Novartis Ag | Hydrophilic filtration during manufacture of vaccine adjuvants |
| DE102009056871A1 (en) | 2009-12-03 | 2011-06-22 | Novartis AG, 4056 | Vaccine adjuvants and improved methods of making the same |
| KR101643918B1 (en) | 2009-12-03 | 2016-07-29 | 노파르티스 아게 | Arranging interaction and back pressure chambers for microfluidization |
| WO2011122581A1 (en) * | 2010-03-29 | 2011-10-06 | 富士フイルム株式会社 | Gas separation membrane, manufacturing method for same, separation method for gas mixture using same, gas separation module, and gas separation device |
| CN103055714B (en) * | 2013-01-14 | 2015-05-13 | 北京碧水源膜科技有限公司 | Method for preparing hydrophilic electrical charge separation film by using one-step method as well as product and application thereof |
| CN104289118A (en) * | 2013-07-15 | 2015-01-21 | 华东理工大学 | In situ polymerization method for controlling polyvinylidene fluoride ultrafiltration membrane structure |
| ES2644995T3 (en) | 2014-08-05 | 2017-12-01 | Gambro Lundia Ab | Filter module |
| WO2018034560A1 (en) * | 2016-08-18 | 2018-02-22 | Nx Filtration Holding B.V. | Method for the production of positively charged membranes |
| DE102016224627A1 (en) * | 2016-12-09 | 2018-06-14 | Fresenius Medical Care Deutschland Gmbh | Hollow fiber membrane with improved separation efficiency and production of a hollow fiber membrane with improved separation efficiency |
| CN107474298B (en) * | 2017-07-05 | 2020-04-28 | 常州大学 | Preparation method of silicon dioxide self-assembly adsorption polypropylene microporous membrane |
| US11241657B2 (en) | 2019-11-22 | 2022-02-08 | Pall Corporation | Filter for removing silica from ultra pure water and method of use |
| EP4171514A1 (en) | 2020-06-30 | 2023-05-03 | Seqirus UK Limited | Cold filtration of oil-in-water emulsion adjuvants |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4473475A (en) * | 1981-05-29 | 1984-09-25 | Amf Inc. | Charge modified microporous membrane, process for charge modifying said membrane, and process for filtration of fluids |
| EP0167573A4 (en) * | 1983-12-29 | 1988-05-02 | Amf Inc | Charge modified microporous hollow tubes. |
| US5114585A (en) * | 1988-03-01 | 1992-05-19 | Gelman Sciences, Inc. | Charged porous filter |
| CA2001720C (en) * | 1988-10-31 | 2001-10-02 | Randal A. Goffe | Membrane affinity apparatus and purification methods related thereto |
| US5151189A (en) * | 1990-09-17 | 1992-09-29 | Gelman Sciences, Inc. | Cationic charge modified microporous membrane |
-
1993
- 1993-12-01 US US08/160,427 patent/US5531893A/en not_active Expired - Fee Related
-
1994
- 1994-02-07 JP JP6518288A patent/JPH08506519A/en active Pending
- 1994-02-07 CA CA002155516A patent/CA2155516A1/en not_active Abandoned
- 1994-02-07 WO PCT/US1994/001365 patent/WO1994017906A1/en not_active Application Discontinuation
- 1994-02-07 EP EP94909563A patent/EP0683691A4/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| US5531893A (en) | 1996-07-02 |
| JPH08506519A (en) | 1996-07-16 |
| WO1994017906A1 (en) | 1994-08-18 |
| EP0683691A4 (en) | 1996-02-28 |
| EP0683691A1 (en) | 1995-11-29 |
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Legal Events
| Date | Code | Title | Description |
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| FZDE | Discontinued |