# US 5,348,569 A · Modified poly(phenylene oxide) based membranes for enhanced fluid separation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,348,569 A - Document ID: US5348569A - Status: Granted - Kind: A - Application number: 08/083,594 - Filed: 1993-06-30 - Granted: 1994-09-20 - Earliest claimed: 1993-06-30 - Assignees: Praxair Technology, Inc. - Inventors: Benjamin Bikson; Gertrud Gotz; Yurdagul Ozcayir; Joyce K. Nelson - Web page: https://patentgrep.com/patent/US5348569A ## CPC - B01D 71/5223: {Polyphenylene oxide, phenyl ether polymers or polyphenylethers} - B01D 53/228: {characterised by specific membranes} - Y02C 20/40: of CO2 - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - Y02C: CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG] ## Abstract The present invention relates to composite membranes and membranes which are formed from modified poly(phenylene oxide) polymers having improved film forming properties and separation characteristics. The present invention further relates to poly(phenylene oxide) polymer and modified poly(phenylene oxide) polymer, having improved membrane forming characteristics and processes for producing the same. ## Claims ### Claim 1 A process for separating at least one gas component from a gas mixture, said process comprising bringing said gas mixture into contact with a composite membrane at a pressure sufficient to permeate said at least one gas component from said gas mixture, said composite membrane comprising a porous substrate coated with modified poly(phenylene oxide) polymer, said modified poly(phenylene oxide) polymer being prepared with poly(phenylene oxide) precursor having a number average molecular weight above 25,000, said modified poly(phenylene oxide) polymer defined by having a chemical structure with at least 10% of the polymer backbone comprised of the following recurring unit: ##STR3## wherein R.sub.1 and R.sub.2 are selected from the group consisting of H, SO.sub.3 H, SO.sub.3 M, sulfonyl SO.sub.2 R.sub.3, sulfonamide SO.sub.2 N(R.sub.3).sub.2, carbonyl COR.sub.3 and amide COHNR.sub.3, with R.sub.3 being a C.sub.1 to C.sub.4 aliphatic radical or aryl radical, and M being alkali metal, alkaline earth metal, transition metal, NH.sup.+.sub.4 or organic base, provided that at least one of R.sub.1 and R.sub.2 is not H. ### Claim 2 A process for separating at least one fluid component from a fluid mixture, said process comprising: bringing said fluid mixture into contact with a membrane at a pressure sufficient to separate at least one fluid component from said fluid mixture, said membrane comprised of sulfonated poly(phenylene oxide) polymer which is prepared via a process comprising: (a) dissolving poly(phenylene oxide) polymer in an inert solvent to form a solution; (b) adding a sulfonation agent to said solution at a temperature sufficiently low to avoid any significant sulfonation reaction to form a substantially homogeneous reaction mixture; (c) raising the temperature of said substantially homogeneous reaction mixture to effect sulfonation of the dissolved poly(phenylene oxide) polymer and; (d) recovering the resulting sulfonated poly(phenylene oxide) polymer. ### Claim 3 A composite membrane comprising at least one separation layer of modified poly(phenylene oxide) polymer on a porous substrate, said modified poly(phenylene oxide) polymer being prepared with poly(phenylene oxide) precursor having a number average molecular weight above 25,000, said modified poly(phenylene oxide) polymer defined by having a chemical structure with at least 10% of the polymer backbone comprised of the following recurring unit: ##STR4## wherein: R.sub.1 and R.sub.2 are selected from the group consisting of H, SO.sub.3 H, SO.sub.3 M, sulfonyl SO.sub.2 R.sub.3, sulfonamide SO.sub.2 N(R.sub.3).sub.2, carbonyl COR.sub.3 and amide CONHR.sub.3, with R.sub.3 being a C.sub.1 to C.sub.4 aliphatic radical or aryl radical, and M being alkaline metal, alkaline earth metal, transition metal, NH.sup.+.sub.4 or organic base, provided that at least one of R.sub.1 and R.sub.2 is not H. ### Claim 4 (depends on 3) The composite membrane according to claim 3, wherein said modified poly(phenylene oxide) polymer is prepared from poly(phenylene oxide) precursor having a number average molecular weight above 35,000. ### Claim 5 (depends on 3) The composite membrane according to claim 3, wherein the ratio of weight average molecular weight to number average molecular weight of poly(phenylene oxide) precursor is kept below 2. ### Claim 6 (depends on 3) The composite membrane according to claim 3, wherein said modified poly(phenylene oxide) polymer has an intrinsic viscosity above 0.52 dl/g. ### Claim 7 (depends on 3) The composite membrane according to claim 3, wherein said modified poly(phenylene oxide) polymer is selected from the group consisting of substituted poly(phenylene oxide) polymer and sulfonated poly(phenylene oxide) polymer. ### Claim 8 (depends on 7) The composite membrane according to claim 7, wherein said sulfonated poly(phenylene oxide) polymer has an ion exchange capacity of about 1.9 to 3.2 meq/g. ### Claim 9 (depends on 7) The composite membrane according to claim 7, wherein said sulfonated poly(phenylene oxide) polymer is at least partially neutralized or salified with at least one neutralizing or salifying means which is selected from the group consisting of Li.sup.+, Na.sup.+, Ag.sup.+, NH.sub.4.sup.+ and an organofunctional amine. ### Claim 10 (depends on 3) The composite membrane according to claim 3, wherein said membrane is a composite hollow fiber membrane. ### Claim 11 A membrane capable of separating at least one fluid component from a fluid mixture, said membrane comprising sulfonated poly(phenylene oxide) polymer which is prepared via a process comprising: (a) dissolving poly(phenylene oxide) polymer in an inert solvent to form a solution; (b) adding a sulfonation agent to said solution at a temperature sufficiently low to avoid any significant sulfonation reaction to form a substantially homogeneous reaction mixture; (c) raising the temperature of said substantially homogeneous reaction mixture to effect sulfonation of poly(phenylene oxide) polymer; and (d) recovering the resulting sulfonated poly(phenylene oxide) polymer. ### Claim 12 (depends on 11) The membrane according to claim 11, wherein said poly(phenylene oxide) polymer has a number average molecular weight above 25,000. ### Claim 13 (depends on 12) The membrane according to claim 12, wherein said poly(phenylene oxide) polymer having a number average molecular weight above 25,000 is prepared by a process comprising: (i) bringing poly(phenylene oxide) polymer containing low molecular weight fractions and/or polymerization catalyst in contact with solvent having a solubility parameter value of about 9.1 to about 9.7 [cal/cm.sup.3 ].sup.1/2 to form a slurry; (ii) filtering said slurry to recover purified poly(phenylene oxide) polymer in solid form to remove low molecular weight fractions; and (iii) washing said purified poly(phenylene oxide) polymer in solid form with an inert solvent to remove additional low molecular weight fractions. ### Claim 14 (depends on 11) The membrane according to claim 11, wherein said sulfonated poly(phenylene oxide) is partially or completely neutralized with at least one neutralizing means selected from the group consisting of Li.sup.+, Na.sup.+, Ag.sup.+, NH.sub.4.sup.+ and an organofunctional amine. ### Claim 15 (depends on 11) The membrane according to claim 11, wherein said sulfonated poly(phenylene oxide) polymer is further purified by ultrafiltration, dialysis, or diafiltration to remove impurities and low molecular weight fractions. ### Claim 16 (depends on 15) The membrane according to claim 15, wherein the sulfonated poly(phenylene oxide) polymer is dialyzed or diafiltered in a membrane device with a molecular weight cutoff of 10,000. ### Claim 17 (depends on 11) The membrane according to claim 11, wherein said membrane is a composite hollow fiber membrane capable of separating at least one gas component from a gas mixture. ### Claim 18 (depends on 11) The membrane according to claim 11, wherein the sulfonation agent is chlorosulfonic acid. ### Claim 19 (depends on 18) The membrane according to claim 18, wherein said sulfonating agent is added at a temperature of about -20.degree. C. or below to form said substantially homogeneous reaction mixture. ### Claim 20 (depends on 19) The membrane according to claim 19, wherein the sulfonation is carried out at a temperature of about 20.degree. C. to about 25.degree. C. ### Claim 21 A process for making composite membranes comprising at least one Separation layer of modified poly(phenylene oxide) polymer on a porous substrate, with such polymer defined as having chemical structure with at least 10% of the polymer backbone comprised of the following recurring unit: ##STR5## wherein R.sub.1 and RR.sub.2 are selected from the group consisting of H, SO.sub.3 H, SO.sub.3 M, sulfonyl SO.sub.2 R.sub.3, sulfonamide SO.sub.2 N(R.sub.3).sub.2, carbonyl COR.sub.3 and amide COHNR.sub.3, with R.sub.3 being a C.sub.1 to C.sub.4 aliphatic radical or aryl radical, and M being alkali metal, alkaline earth metal, transition metal NH.sup.+.sub.4 or organic base, provided that at least one of R.sub.1 and R.sub.2 is not H, said process comprising: (a) purifying poly(phenylene oxide) polymer to remove low molecular weight fractions; (b) chemically modifying the purified poly(phenylene oxide) polymer to form said modified poly (phenylene oxide ) polymer; (c) dissolving said modified poly(phenylene oxide) polymer in a solvent to form a solution; and (d) coating said porous substrate with said solution. ### Claim 22 (depends on 21) The process according to claim 21, wherein said substrate is polysulfone hollow fibers. ### Claim 23 The process according to claim wherein said purification of poly(phenylene oxide) in step (a) is carried out by: (i) bringing poly(phenylene oxide) polymer containing low molecular weight fractions and/or polymerization catalyst in contact with solvent having a solubility parameter value of about 9.1 to about 9.7 [cal/cm.sup.3 ].sup.1/2 to form a slurry; (ii) filtering said slurry to recover purified poly(phenylene oxide) polymer in solid form and to remove low molecular weight fractions as the filtrate; and (iii) washing said purified poly(phenylene oxide) polymer in solid form with an inert solvent to remove additional low molecular weight fractions. ### Claim 24 A process for making composite membrane, said process comprising: (a) dissolving modified poly(phenylene oxide) polymer in an inert solvent, said modified poly(phenylene oxide) polymer being defined as having a chemical structure with at least 10% of the polymer backbone comprised of the following recurring unit: ##STR6## wherein: R.sub.1 and R.sub.2 are selected from the group consisting of H, SO.sub.3 H, SO.sub.3 M, sulfonyl SO.sub.2 R.sub.3, sulfonamide SO.sub.2 N(R.sub.3).sub.2, carbonyl COR.sub.3 and amide CONHR.sub.3, with R.sub.3 being a C.sub.1 to C.sub.4 aliphatic radical or aryl radical, and M being alkali metal, alkaline earth metal, transition metal, NH.sup.+.sub.4 or organic base, provided that at least one of R.sub.1 and R.sub.2 is not H; (b) subjecting the dissolved modified poly(phenylene oxide) polymer to ultrafiltration, diafiltration and/or dialysis to obtain purified modified poly(phenylene oxide)polymer; (c) dissolving the purified modified poly(phenylene oxide) polymer in a solvent to form a coating solution; and (d) coating a porous substrate with said coating solution. ### Claim 25 A process for producing poly(phenylene oxide) polymer having a number average molecular weight above 25,000, said process comprising: (i) bringing poly(phenylene oxide) polymer containing low molecular weight fractions and/or polymerization catalyst in contact with solvent having a solubility parameter value of about 9.1 to about 9.7 [cal/cm.sup.3 ].sup.1/2 to form a slurry; (ii) filtering said slurry to recover purified poly(phenylene oxide) polymer in solid form and to remove said low molecular weight fractions as the filtrate; and (iii) washing said purified poly(phenylene oxide) polymer in solid form with an inert solvent to remove additional low molecular weight fractions. ### Claim 26 (depends on 25) The process according to claim 25, wherein said solvent is aliphatic ketone or ether. ### Claim 27 (depends on 26) The process according to claim 26, wherein the temperature of said aliphatic ketone or said ether is at about 70.degree. C. or higher. ### Claim 28 (depends on 27) The process according to claim 27, wherein said aliphatic ketone is methyethyl ketone. ### Claim 29 A process for preparing a membrane forming material capable of forming a membrane useful for separating at least one fluid component from a fluid mixture, said process comprising: (a) dissolving poly(phenylene oxide) polymer in an inert solvent to form a solution; (b) adding a sulfonation agent to said solution at a temperature sufficiently low to avoid any significant sulfonation reaction to form a substantially homogeneous reaction mixture; (c) raising the temperature of said substantially homogeneous reaction mixture to effect sulfonation of the dissolved poly(phenylene oxide) polymer and; (d) recovering the resulting sulfonated poly(phenylene oxide) polymer. ### Claim 30 (depends on 29) The process according to claim 29, further comprising purifying said poly(phenylene oxide) polymer before being dissolved in said inert solvent, said purifying comprising: (i) bringing poly(phenylene oxide) polymer containing low molecular weight fractions and/or polymerization catalyst in contact with solvent having a solubility parameter value of about 9.1 to about 9.7 [cal/cm.sup.3 ].sup.1/2 to form a slurry; (ii) filtering said slurry to recover purified poly(phenylene oxide) polymer in solid form to remove low molecular weight fractions; and (iii) washing said purified poly(phenylene oxide) polymer in solid form with an inert solvent to remove additional low molecular weight fractions.