EP0606198A4 - Membrane microporeuse sous forme de fibre creuse ou de film, a base de sulfure de polyphenylene. - Google Patents

Membrane microporeuse sous forme de fibre creuse ou de film, a base de sulfure de polyphenylene.

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Publication number
EP0606198A4
EP0606198A4 EP91916695A EP91916695A EP0606198A4 EP 0606198 A4 EP0606198 A4 EP 0606198A4 EP 91916695 A EP91916695 A EP 91916695A EP 91916695 A EP91916695 A EP 91916695A EP 0606198 A4 EP0606198 A4 EP 0606198A4
Authority
EP
European Patent Office
Prior art keywords
membrane
diphenyl
solvent
pps
phenyl
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.)
Withdrawn
Application number
EP91916695A
Other languages
German (de)
English (en)
Other versions
EP0606198A1 (fr
Inventor
Henry N Beck
Robert D Mahoney
Hawk S Wan
Chieh-Chun Chau
Timothy M Finney
Ritchie A Wessling
Jiro Kawamoto
Mark F Sonnenschein
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dow Chemical Co
Original Assignee
Dow Chemical Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Dow Chemical Co filed Critical Dow Chemical Co
Priority claimed from PCT/US1991/005862 external-priority patent/WO1993004223A1/fr
Publication of EP0606198A1 publication Critical patent/EP0606198A1/fr
Publication of EP0606198A4 publication Critical patent/EP0606198A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • B01D67/0018—Thermally induced processes [TIPS]
    • 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
    • B01D67/0023—Organic membrane manufacture by inducing porosity into non porous precursor membranes
    • B01D67/0025—Organic membrane manufacture by inducing porosity into non porous precursor membranes by mechanical treatment, e.g. pore-stretching
    • B01D67/0027—Organic membrane manufacture by inducing porosity into non porous precursor membranes by mechanical treatment, e.g. pore-stretching by stretching
    • 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
    • B01D67/0023—Organic membrane manufacture by inducing porosity into non porous precursor membranes
    • B01D67/003—Organic membrane manufacture by inducing porosity into non porous precursor membranes by selective elimination of components, e.g. by leaching
    • 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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/24—Formation of filaments, threads, or the like with a hollow structure; Spinnerette packs therefor
    • D01D5/247—Discontinuous hollow structure or microporous structure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/219—Specific solvent system
    • B01D2323/22—Specific non-solvents or non-solvent system
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/20—Specific permeability or cut-off range
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2381/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing sulfur with or without nitrogen, oxygen, or carbon only; Polysulfones; Derivatives of such polymers
    • C08J2381/02—Polythioethers; Polythioether-ethers

Definitions

  • the present invention relates to the solubilization of solvent resistant polymers to form an article. More specifically, the present invention relates to a process to solubilize poly (phenylene sulfide) (PPS) at elevated temperatures using high boiling organic solvents, and to form a useful permselective fiber or film to separate liquids and/or gases.
  • PPS poly (phenylene sulfide)
  • Crystalline poly(phenylene sulfide) is a very useful high temperature polymeric material.
  • the properties of commercially available PPS include:
  • Poly(phenylene sulfide) is generally regarded as being insoluble in most common solvents.
  • a number of hot aprotic polar organic compounds, peralkylated cyclic ureas, or N- alkyllactams such as N-methyl-2-pyrrolidinone, or N,N- diethylbenzamide, N,N-diethyl-toluamide, N,N-dimethyl- ethylene urea, dimethylacetamide, hexamethylphosphoramide or N-methylcaprolactam as described as "solvents" in the synthesis of PPS. It appears that these organic compounds are really solvents (or dispersants and/or heat transfer agents) for the reactants and from which the PPS precipitates after formation. H.A.
  • Hill in U.S. Patent No. 4,118,363 discloses that PPS is a difficult polymer to solubilize, and that diphenyl oxide has been used as a high boiling solvent at elevated temperatures. Further, Hill discloses that alkyl substituted and halogen substituted diphenyl oxides have also been used to solubilize PPS.
  • Strongly acidic hot materials such as concentrated sulfuric acid, chlorosulfonic acid, and trifluoromethylsulfonic acid, are suggested as solvents for PPS.
  • these materials may react with aromatic portion of the polymer forming an acid derivative which as properties completely different than PPS, and the derivative then "dissolves" in the hot solvent.
  • J. Kawabata, et al., in Japanese Kokai patent application No. 59-120779 (June 14, 1984) (Kokai No. 01- 432) disclose the use of poly (phenylene sulfide) as a composite film for use in gas separation.
  • Japanese patent disclosures No. 62-15323 (January 23, 1987), No. 59-59917 (April 5, 1984) and No. 58-67733 (assigned to Dainippon Ink and Chemicals) describe a production process for a porous or microporous hollow fibers. The process uses a melt spinning of PPS followed by stretching to create "porosity.” There is no solvent or gas or liquid permeability described.
  • Japanese patent disclosure No. 61-000432 (January 6, 1986) assigned to Dainippon Ink and Chemicals, describes a "porous" film of PPS.
  • Japanese patent disclosure No. 60-248202 (December 7, 1985) assigned to Dainippon Ink and Chemicals, describes a hollow fiber membrane of PPS by dissolving in a solvent extruding a hollow fiber while coagulating it with a core liquid that is a mixture of solvent and a non-solvent. No drawing step is disclosed.
  • the present invention relates to a process for preparing a permselective microporous membrane comprising poly (phenylene sulfide), which process comprises the steps of:
  • the process includes step
  • the present invention relates to a process for preparing a permselective microporous membrane comprising poly (phenylene sulfide), which process comprises the steps of:
  • the process includes step (e'), drawing the membrane before, during and/or after the leaching of step (e) at a temperture at or above the ambient temperature and below the melting point of the polyphenylene sulfide or the depressed melting point of the mixture to elongate the membrane and to induce orientation of the polyphenylene sulfide in the membrane, and also to control micropore size.
  • the process includes at least one of the solvents and at least one of the non- solvents listed hereinbelow.
  • the solvent is independently selected from the organic compounds listed below as solvents or mixtures of these compounds.
  • the present invention relates to a process for the production of a fiber or film which is permselective comprising a polymer itself comprising (poly) phenylene sulfide), which process comprises:
  • the present invention relates to the article of manufacture of PPS obtained from the process described herein, particularly where the article is porous, permeable, semi-permeable or selectively permeable.
  • the present invention relates to a process for the production of an article comprising polymer itself comprising poly(phenylene sulfide), which process comprises: (A) contacting poly (phenylene sulfide) with:
  • a solvent organic compound consisting essentially of carbon and hydrogen and optionally oxygen, nitrogen, sulfur, halogen, or mixtures of these atoms, said at least one organic compound having a molecular weight of between 160 and 450 daltons and having at least one six membered aromatic ring structure, which compound is a stable liquid at a temperature of between about 240 and 400 degrees C at ambient pressure for a time effective to dissolve greater than about 10% by weight of the poly(phenylene sulfide) present, with the proviso for each organic compound that when oxygen is present the organic compound is not diphenyl oxide or a substituted diphenyl oxide; and, optionally,
  • the present invention relates to the article of manufacture of PPS obtained from the process described herein, particularly where the article is porous, permeable, semi-permeable or selectively permeable.
  • the present invention uses at least one organic compound, which is a solid at ambient temperature but which melt when heated above ambient temperature to produce a stable organic liquid or mixture of organic liquids.
  • organic compound melts at temperature above 80°C.
  • the solid organic compound may be heated and melted separately, and the solid PPS then added and dissolved at temperatures between 160 and 400°C.
  • the nonsolvent compounds optionally are selected in the same manner as above.
  • the solid organic compound and the solid PPS are combined and then heated together as solid until the solid organic compound melts to form a stable liquid.
  • the liquid/solid mixture then is heated between about 160 and 400°C to solubilize up to about 50% or greater by weight of the PPS.
  • Figure 1(B) is a schematic representation of double drum membrane casting process using nip rolls.
  • Figure 2 (A) is a schematic representation of a single drum liquid (water) quench membrane casting process.
  • Figure 2(B) is a schematic representation of a double drum liquid (water) quench membrane casting process.
  • Figure 3 is a graph of the effect of cooling condition on the nitrogen permeability of a 30% PPS/CLTA membrane cast on an aluminum plate.
  • Figure 4 is a scanning electron micrograph (5000x) of a 30% PPS/e-CLTA membrane showing liquid-solid phase separation and resultant nodular bulk porosity structure.
  • Figure 5 is a scanning electron micrograph (5000x) of a 30/70 PPS/diphenylsulfone (DPS) membrane showing liquid- liquid phase separation and resultant cellular bulk porosity structure.
  • Figure 6 is an illustration of qualitative test to evaluate the ability of the membrane to undergo stress.
  • Figure 7 is a graphic representation of the nitrogen gas permeability of PPS/DPS extruded film membrane as a function of the quench temperature.
  • Figure 8 is a graphic representation of the nitrogen gas permeability of PPS/DPS as a film membrane as a function of the quench temperature.
  • Figure 9 is a graphic representation of the water flux permeability of PPS/DPS binary blend as a film membrane as a function of the quench temperature.
  • Figure 10 is a graphic representation of the water permeability of PPS membranes from PPS/DPIP as a function of the quench temperature.
  • Figure 11 is graphic representaiton of water permeability of PPS/DPIP as a function of the quench temperature.
  • Figure 12 is a scanning electron micrograph of a PPS membrane as produced in Example 14. The scale is that of
  • Article refers to any type of article of manufacture which can be formed from a polymeric material.
  • the article is a sheet, film membrane, hollow tube, hollow or solid fiber.
  • These articles when permeable, semi- permeable, permselective or selectively permeable, can be used in the separation of various materials.
  • the potential utility of such a membrane article depends upon the membrane material, its structure (which depends upon its mode of preparation), and the mode in which it is operated.
  • such articles can be used to permeate gasses, e.g. oxygen or nitrogen, to separate solutes of suspended matter from solutions, e.g.
  • Forming the article refers to the shaping of the hot pliable poly (phenylene sulfide) /solvent (organic compound) mixture or the hot pliable PPS/solvent/nonsolvent (organic compound) mixture or the hot pliable PPS/solvent/nonsolvent mixture into a desired article configuration.
  • the forming may be accomplished by extruding, pressure molding, solvent casting blow molding, or any of the convention methods used in the art to shape a flexible polymer.
  • Halogen refers to fluorine, chlorine, bromine, iodine or mixtures of these atoms, generally as is found in a substitute in an organic molecule. Generally, bromine and/or fluorine as atoms are preferred.
  • Nonsolvent refers to an organic compound as described in Table 1 which dissolves less than about 5 percent by weight of the polymer PPS at a specific temperature about 100° C.
  • Non-solvent organic compounds for PPS include, for example, those compounds independently selected from the group consisting of 1,3,5- triphenylbenzene, tetra-phenylsilane, diphenyl sulfoxide, diphenic acid, 4-acetylbiphenyl, bibenzyl, diphenyl methyl phosphate, triphenyl phosphate, cyclohexyl phenyl ketone, mineral oil, butyl stearate, phenyl benzoate, 1-phenyl- decane, 1,3-diphenoxybenzene, 1,8-dichloroanthraquinone, polyphos-phoric acid, dioctyl phthalate, 5-chlorobenzoxazolone, bis-(4-chlorophenyl sulfone), di
  • optically refers to a step in a process which may or may not be performed, or to a component which may or may not be present.
  • Organic compound refers to those organic materials consisting of carbon and hydrogen having a molecular weight of between about 160 and 450 daltons and usually having at least one six membered aromatic ring structure. This includes organic compounds such as triphenylmethane, fluoranthene, pyrene and tt ⁇ e like. It also includes those compounds which further include oxygen, nitrogen, sulfur, halogen or mixtures of these atoms. Heteroaromatic compounds having molecular weights of between about 160 and 450 daltons are included.
  • An organic compound which is useful in the present invention as a solvent will dissolve greater than about 10% by weight of the PPS-type polymer.
  • a poor solvent is an organic compound as described herein in Table 1 below which dissolves between 5 and 10 percent by weight of the PPS polymer at a specific temperature above 100 degrees C.
  • the instant invention includes solvents for PPS that may be readily removed from such mixtures by treatment with other more conventional organic solvents that dissolve the solvent for PPS, but do not dissolve the PPS.
  • the instant invention also discloses solvents for PPS that may be removed from such mixtures by water or by aqueous alkali; such water or aqueous alkali-soluble solvents are desired in processing, because they allow the use of less flammable, more inexpensive, and less potentially hazardous or toxic leach processes.
  • R a , R b , R c , R d , R e , and R 1 to R 8 are each independently selected from hydrogen, methyl, ethyl, propyl, butyl, fluorine, chlorine or bromine.
  • Organic compound refers to those high boiling organic compounds as solvents for PPS (preferably which are solids at ambient temperature and pressure and usually do not melt lower than about 50°C).
  • the solvents include, for example, those independently selected from the group consisting of 4,4'-dibromobiphenyl; 1-phenyl-naphthalene; phenothiazine; 2,5-diphenyl-1,3,4-oxadiazole; 2,5-diphenyloxazole; triphenyl-methanol; N,N-diphenylformamide; m-terphenyl; benzil; anthracene; 4-benzoylbiphenyl; dibenzoylmethane; 2-biphenyl-carboxylic acid; dibenzothiophene; pentachlorophenol; benzophenone; 1-benzyl-2-pyrrolidione; 9-fluorenone; 2-benzoyl-naphthalene; 1-bromonaphthalene; diphenyl s
  • a poly(phenylene sulfide)-type structure may have as a structure poly(2-chlorophenylene sulfide) or poly (2- methylphenylene sulfide).
  • the p-phenylene is preferred wherein at least two groups of R 1 to R 4 are hydrogen and the other two groups are each independently selected from methyl, ethyl, propyl, butyl, fluorine, chlorine or bromine.
  • p-phenylene where three of the groups R 1 to R 4 are hydrogen and the remaining group is independently selected from methyl, ethyl, propyl, butyl, fluorine, chlorine or bromine.
  • the method of combining the crystalline polymer with the organic compound (s) as a solvent (solubilizing agent) medium this includes solvent/nonsolvent mixtures, it is not critical to the process of the present invention.
  • the combination may be conveniently prepared by mixing, stirring, extrusion, gear pumps, rotary mixers, static mixers, or other means well known in polymer, membrane, and mixing technologies.
  • the pressure and composition of the atmosphere above and on the polymer (PPS) and organic compound in the practice of this invention is not critical. Generally ambient pressure is used. In some cases, above atmospheric pressure is possible, particularly if higher temperatures than the boiling point of the organic compound is desired. Preferably, the atmosphere above the polymer and organic compound is essentially inserted to prevent undesirable side reactions of any of the components. Nitrogen is suitable inert atmosphere.
  • the dissolution of PPS in a given solvent is a function of the polymer concentration and the temperature. Solubility curves for thirteen typical solvents for PPS have been performed: m-terphenyl, 4-phenylphenol, and diphenylsulfone; anthracene, benzopheneone, and 2- phenylphenol; 1-cyclohexyl-2-pyrrolidonone, o,o'-biphenol, and epsilon-caprolactam (e-caprolactam); benzil and 9- fluorenone; and pyrene and fluoranthene, respectively.
  • any temperature-concentration combination above each curve represents a homogenous one phase composition; any combination below each curve, a multiphase mixture in which the polymer is not completely soluble.
  • a mixture of 50% PPS in 4-phenylphenol requires a temperature in excess of about 257 degrees C for complete dissolution to be achieved.
  • 40% PPS in anthracene requires a temperature in excess of about 243 degrees C for complete solubility to occur.
  • a solvent and a nonsolvent are combined at an elevated temperature and are soluble in each other, when the PPS is added, the PPS may be dissolved.
  • the ⁇ olvent/non-solvent combination is extremely useful in the production of porous permselective membranes of PPS.
  • a solution for preparing hollow fiber membranes might consist of about 50 weight percent PPS with the remainder consisting of the solvent, solvent/nonsolvent, or solvent/poor solvent mixture.
  • the ratio of solvent to nonsolvent, or solvent to poor solvent typically might vary from about 1.5/1 to about 20/1 depending upon the relative solvent power of the solvent and the nonsolvent or poor solvent.
  • the organic compounds or mixtures thereof are essentially inert to the PPS at elevated temperatures.
  • the article, e.g. film or fiber, of PPS obtained should be essentially the same composition as the starting PPS.
  • the article of PPS will contain trace quantities of the organic compound(s) used as solvents (and nonsolvents). These traces will prove useful in determining whether or not the solvents of this present invention have been used for the PPS article of manufacture.
  • the polymer/solvent mixture is shaped into a hollow fiber by techniques well known in the art. Such techniques are described by Israel Cabasso in "Hollow Fiber Membranes” in Kirk-Othmer “Encyclopedia of Chemical Technology," Volume 12, pages 492-517, John Wiley and Sons, New York, 3rd edition, (1980), M.Grayson and D. Eckroth, editors.
  • the solvent/polymer mixture may also be solvent cast on a flat surface, the solvent is removed by evaporation and/or reduced pressure or by using a liquid which dissolves the solvents but not the polymer.
  • the membrane which typically has a thickness of between about 0.2 and 50.0 mils is porous and is useful in separation devises, such as for ultrafiltration, microfiltration, and as microporous supports in composite membranes for gas or liquid separation.
  • phase separation of the polymer-solvent mixture is important in determining the final bulk structure of the hollow fiber or film membrane.
  • the type of phase separation can be either liquid-solid (L-S) leading to a nodular (N) structure, or a liquid-liquid (L-L) phase separation leading to a finer cellular (C) bulk structure (see Figures 4 and 5).
  • the type of phase separation obtained is dependent upon the polymer concentration, solvent character, and rate of cooling. Neither a nodular (N) or cellular (C) structure is in all cases preferable, but the preference is determined by the end use of the membrane.
  • SEM scanning electron micrographs
  • Figure 1(B) is shown a process to produce an air melt cast and quenched membrane.
  • the polymer/solvent 11 is melt cast through a die 12 onto drum 15 and drum 16.
  • the rotating drums can be each at the same predetermined temperature or more likely are at different temperatures.
  • the formed polymer membrane (17) is taken from the circular surface of drum 15.
  • the process of Figure 1(B) results in a polymer membrane that is similar in properties to one cast in air between two heated metal plates.
  • Figure 2(A) is similar to Figure 1(A) except that the polymer is quenched in a liquid and optionally the solvent is leached into the liquid. Alternatively, the leach liquid can be in another container.
  • the molten polymer/solvent/optional nonsolvent 21 is extruded through die 22 to shape the hot polymer/solvent 23.
  • Drum 24 is rotating and the formed membrane is quenched (and optionally concurrently drawn) between rotating drum 24 and drums 25 and 26.
  • Figure 2(B) is similar to Figure 1(B) except that the polymer is quenched in a liquid and (optionally leached at the same time).
  • the molten polymer/solvent and/or non- solvent 21 is extruded through a die 22 to produce a shaped membrane film.
  • the hot film passes between rotating drums 27 and 28 which further shapes the membrane to desired dimension.
  • the membrane is then quenched in liquid 29 (e.g. water) and optionally can be drawn (elongated) at the same
  • PEEK poly(etheretherketone)
  • the PEEK is replaced by about an equivalent weight of PPS.
  • the selection of the components for the extrusion blend is dependent upon whether a non-interconnecting or interconnecting porous structure or permselective is desired.
  • the fibers or films may possess either a non-interconnecting or an interconnecting porous structure.
  • the pores within the membrane are not completely interconnected so that the pores do not directly connect one side of the membrane with the other side of the membrane, although fluid flow through the membrane may still be accomplished by solution- diffusion transport of the fluid through the dense polymer regions of the membrane.
  • the pores are completely interconnected so that the pores directly connect one side of the membrane with the other side of the membrane so that fluid flow through the membrane may be accomplished primarily by transport through the membrane's pores.
  • the factors which determine the formation of interconnecting versus non-interconnecting pores include the polymer concentration in the extrusion blend, volatility of the solvent, cooling rate of the nascent fiber or film, and composition of non-solvent in the extrusion blend.
  • the formation of fibers with non-interconnecting pores preferably uses an extrusion blend containing polymer and solvent.
  • the formation of fibers with interconnecting pores preferably uses an extrusion blend containing polymer, solvent and non-splvent.
  • the concentration of the components in the extrusion mixture may vary and are dependent upon the desired type of pore structure (interconnecting versus non-interconnecting pores), porosity, and pore size of the fibers.
  • concentration of poly(phenylsulfide) polymer-type in the extrusion mixture is that which results in a mixture with a suitable viscosity for extrusion at the extrusion temperature.
  • the viscosity of the mixture must not be so high that the fluid is too viscous to extrude or cast; the viscosity must not be too low such that the fluid cannot maintain its desired shape upon exiting the extrusion die.
  • Extrusion blends of PPS polymers generally possess non- Newtonian viscosity behavior; therefore, such blends exhibit a shear rate dependence upon viscosity.
  • the mixture preferably has a viscosity at extrusion temperatures of between about 100 and 10,000 poise at a shear rate from about 10 to 10,000 sec -1 , more preferably between about 300 and 1,000 poise at a shear rate of from about 50 to 1,000 sec -1 .
  • the concentration of PPS polymer is preferably from about 10 to about 90 wt %, more preferably from about 20 to 80 wt %.
  • the concentration of poly(phenylene sulfide)- type polymer is preferably from about 20 to about 70 wt %, more preferably from about 30 to 65 wt %.
  • the concentration of the solvent is preferably from about 1 to about 90 wt %, more preferably from about 2 to about 80 wt %.
  • the concentration of the optional nonsolvent is preferably from about 0 to about 90 wt %, more preferably from about 0 to about 80 wt %.
  • the solvent/non-solvent ratio is preferably from about 0.05 to 24, more preferably from about 0.1 to 12.
  • the fibers or films are extruded or cast from the poly (phenylene sulfide) polymer compositions hereinbefore described.
  • the components of the extrusion mixture may be combined prior to extrusion by mixing in any convenient manner with conventional mixing equipment, as for example, in a Hobart mixer.
  • the extrusion blend may also be combined and mixed under heating in a resin kettle.
  • the extrusion composition may be homogenized by extruding the mixture through a twin screw extruder, cooling the extrudate, and grinding or pelletizing the extrudate to a particle size readily fed to a single or twin screw extruder.
  • the components of the extrusion composition may be combined directly in a melt- pot or twin screw extruder and extruded into fibers in a single step.
  • the use of static mixers helps to ensure blend homogeneity.
  • the mixture is heated to a temperature which results in a homogeneous fluid possessing a viscosity suitable for extrusion.
  • the temperature should not be so high or the exposure time so long as to cause significant degradation of the PPS polymer, solvents and optional non-solvents.
  • the temperature should not be so low as to render the fluid too viscous to extrude.
  • the extrusion temperature is preferably between about 170 and 400°C, more preferably between about 275 and 350°C.
  • the mixture of polymer, solvent, and optional non- solvent is extruded through a solid fiber or hollow fiber die (spinneret).
  • Solid fibers refer to fibers which are non-hollow. Such, solid fiber dies or hollow fiber spinnerets typically are multi-holed and thus produce a tow of multiple fibers.
  • the hollow fiber spinnerets include a means for supplying fluid to the core of the extrudate. The core fluid is used to prevent the collapsing of the hollow fibers as they exit the spinneret.
  • the core fluid may be a gas such as nitrogen, air, carbon dioxide, or other inert gas or a liquid which is non-solvent for the PPS polymer such as dioctyl phthalate, methyl stearate, polyglycol, mineral oil, paraffin oil, petroleum oil, for example, Mobiltherm R 600, 603, and 605 heat transfer oils (TMtrademarks of Mobil Oil Corporation), and silicone oil, for example, DC-704 R and DC-710 R silicone oil (TMtrademarks of Dow-Corning Corporation of Midland, Michigan).
  • a liquid non-solvent as the core fluid may result in a microporous membrane with an inside skin.
  • a solvent and non-solvent core fluid mixture may be used to control the inside skin morphology.
  • the extrudate exiting the die enters one or more quench zones.
  • the environment of the quench zone may be gaseous or liquid.
  • the extrudate is subjected to cooling to cause solidification of the fibers with the optional simultaneous removal of a portion of the solvent and optional non-solvent.
  • the fibers are initially quenched in a gaseous environment such as air, nitrogen, or other inert gas.
  • the temperature of the gaseous quench zone is preferably in the range from about 0 to about 100°C, more preferably in the range from about 10 to about 40°C.
  • the residence time in the gaseous quench zone is preferably less than about 120 sec, more preferably less than about 30 sec. Shrouds may. be used to help control gaseous flow rates and temperature and profiles in the gaseous quench zone.
  • the least one organic compound is removed by evaporation, heating, subliming, reduced pressure, use of solvents which dissolve the organic compound (and/or the non-solvent), but do not dissolve PPS, or combinations of these techniques.
  • the formed organic compound PPS article is cooled somewhat, preferably to between about ambient temperature and 100°C, and contacted with one or more removal solvents to remove the organic compound (and/or the non-solvent present) but retain the form of the article of PPS, e.g. fiber, tube or film.
  • Removal solvents include, for example, one or more organic compounds, such as acetone, methylene chloride, dimethyl- sulfoxide, methanol, ethanol or mixtures thereof, and also water, and aqueous base (5 to 10% NaOH or KOH).
  • Aqueous base is particularly useful to dissolve and remove phenolic organic compounds.
  • the organic compound/PPS article is cooled to about 150°C and reduced pressure (about 1 mm and 0.001 microns) is applied to remove the organic compound.
  • the fibers or films may optionally be quenched in a liquid environment which is substantially a non-solvent for the PPS polymer such as water or ethylene glycol and which optionally contains an effective amount of a swelling agent.
  • the maximum temperature of the given liquid is that temperature at which the fiber is not adversely affected.
  • the temperature is preferably between about 0 and about 200°C, more preferably between about 0 and 100°C.
  • the residence time in the liquid quench zone is preferably less than about 120 sec, more preferably less than 30 sec.
  • the fibers may be passed through one or more leach baths to remove at least a portion of the solvent and/or optional non-solvent.
  • the leach bath need not remove all of the solvent and/or non-solvent from the fibers.
  • the leach bath removes the solvent and/or non-solvent to a level of less than about 2.0 wt % in the leached fiber.
  • the leach bath is comprised of a solution which is a non-solvent for the PPS polymer but which is a solvent for the extrusion solvent and/or non- solvent.
  • Preferred leach liquids include toluene, xylene, acetone, chlorinated hydrocarbons such as methylene chloride, carbon tetrachloride, trichloroethylene, and 1,1,1-trichloro-ethane.
  • the maximum temperature is that temperature at which solvent and/or non-solvent removal from the fibers occurs at a reasonable rate.
  • the temperature of the leach bath is preferably between about 0 and about 200°C, more preferably between about 0 and 80°C.
  • the residence time in the leach bath is preferably less than about 14 hr, more preferably less than about 1 hr.
  • the fibers may drawn down using conventional godet equipment to the appropriate size. Drawing may occur before, during or after leaching. Line speeds are not critical and may vary significantly. Typical line speeds range from about 30 ft/min to about 300 ft/min. In the case of hollow fibers used in membrane applications, the fibers preferably possess an outside diameter of from about 50 to about 3,000 microns, more preferably of from about 80 to about 2,000 microns with a wall thickness of preferably from about 10 to about 400 microns, more preferably from about 20 to about 400 microns.
  • the fibers preferably possess an outer diameter of from about 5 to 100 microns, more preferably from about 5 to about 50 microns; optionally the fibers may be hollow with a wall thickness preferably of from about 2 to about 45 microns, more preferably from about 2 to 20 microns.
  • the fibers are dried.
  • the leach liquid remaining in the fibers may optionally be exchanged with more volatile, non-polar drying agent which possesses a low surface tension and is a solvent for the leach liquid, but a non-solvent for the polymer, in order to reduce the possibility of pore collapse during drying.
  • Preferred drying agents include Freon 113 R chlorofluorocarbon (TMtrademark of E.I. duPont de Nemours).
  • the exchange may be carried out at temperatures which do not adversely affect the membrane, preferably from between about 0 to about 45°C.
  • the fibers may be dried in air or an inert gas such as nitrogen. Drying may also be done under reduced pressures.
  • the fibers may be dried at temperatures at which drying takes place at a reasonable rate and which do not adversely affect the membrane.
  • the drying temperature is preferably between about 0 and about 140°C, more preferably between about 10 and 80°C.
  • the drying time is preferably less than about 24 hr, more preferably less than about 6 hr.
  • the microporous fibers or films of this invention may be characterized by their porosity and pore size. Porosity refers to the volumetric void volume of the fibers. Porosity is defined as 100 x [1-(d f /d pps )] where d f is the density of the final leached fiber or film and d is the density of the PPS polymer.
  • the fibers or films of this invention which possess non-interconnecting pores preferably have a porosity of between about 10 and 90 percent, more preferably between about 20 and about 80%. Fibers of this invention which possess interconnecting pores preferably have a porosity of between about 20 and about 70%, more preferably between about 30 and about 65%. Pore size may be estimated by several techniques, including be scanning electron microscopy and/or measurement of bubble point, solvent flux, and molecular weight cutoff. Such techniques are known in the art for characterizing the pore size of microporous membranes, see, for example, Robert Resting, Synthetic Polymeric Membranes, 2nd edition, John Wiley & Sons, New York, 1985, pp. 46-56; Channing R.
  • the pore size is preferably between about 1 x 10 -3 microns to about 3.0 microns, more preferably between about 3 x 10 -3 microns to about 1.0 micron.
  • the process produces microporous hollow fiber or film membranes having interconnecting pores.
  • Such membranes are useful in the treatment of liquids by the membrane separation processes of microfiltration, ultrafiltration, reverse osmosis, pervaporation, and membrane distillation.
  • Such hollow fibers may also be used as porous supports for composite gas or liquid separation membranes.
  • the process produces microporous hollow fiber membranes useful for ultrafiltration or microfiltration.
  • Ultrafiltration and microfiltration are pressure driven filtration processes using microporous membranes in which particles or solutes are separated from solutions. Separation is achieved on the basis of differences in particle size or molecular weight.
  • Membranes of this invention useful in ultrafiltration and microfiltration preferably possess a molecular weight cut off for ultrafiltration of about 10 to 500 Angstroms and a molecular weight cut off for microfiltration of about 0.05 to 7.0 microns.
  • Microfiltration and ultrafiltration may be carried out at temperatures which do not adversely affect the membranes. Operating temperatures preferably range from about 0 to about 130°C.
  • Operating pressures are dependent upon the pore size of the membrane and the particles or solutes being separated from solution. Preferred operating pressures range from about 5 to about 150 psi.
  • the membrane is heated to a temperature between the glass transition temperature of PPS and the melting point of PPS, with preferred lower temperatures being at least about 90°C, more preferably at least about 100°C, and with preferred upper temperatures being less than about 280°C, more preferably less than about 270°C.
  • the membrane is heated to a temperature between ambient temperature and the melting point of PPS or the depressed melting point of PPS/solvent/optional non-solvent mixture, with preferred lower temperatures being at least about 10 °C below the depressed melting point.
  • the membrane is drawn by stretching the membrane under tension. Flat sheet membranes may be uniaxially or biaxially drawn.
  • Uniaxial drawing or orientation is generally performed by running the membranes over a pair of godets in which the latter godets are moving at a faster rate than the former godets.
  • the draw down elongation ratio is the ratio of the beginning length of the membrane of the final length of the membrane.
  • the lower limit on the draw dow or elongation ratio is about 1.05, more preferably 1.1.
  • the upper limit on the draw down or elongation ratio is about 1.05, more preferably 1.1.
  • the upper limit on the draw down or elongation ratio is about 10.
  • the membrane may be drawn in one or more stage with the options of using different temperatures, draw rates, and draw ratios in each stage. Line speeds are generally not critical and may vary significantly. Practical minimum preferred line speeds are at least about 10 ft/min, a e preferably at least about 30 ft/min. Practical maximum preferred line speeds are less than about 2000 ft/min, more preferably less than about 1000 ft/min.
  • Biaxial orientation or drawing may be accomplished by techniques known in art such as the tenter frame process, the double bubble method, or the blown film process (see Encyclopedia of Polymer Seance and Engineering, John Wiley & Sons, New York, Vol. 7, pages 98-102 (1987)).
  • the biaxial orientation of drawing may be carried out sequentially or simultaneously.
  • drawing via a tentering operation may be sequential (e.g. transverse orientation may be carried out followed by longitudinal orientation or vice-versa) or both transverse or longitudinal orientation may both be accomplished at the same time (i.e. simultaneously).
  • Orientation by the blown film method would be a simultaneous transverse and longitudinal operation.
  • asymmetric membranes are usually accomplished by having the rate of phase change different on the two sides of the membrane.
  • This phase change may be coagulation, phase inversion, liquid-liquid phase separation, or liquid-solid phase separation.
  • One of the methods to control this rate of phase change, and therefore control the morphology, pore size, and asymmetry is to contact one side of the hollow fiber and flat membrane with a second liquid.
  • This second liquid may or may not be a solvent for the solvent used to initially dissolve the polymer.
  • An asymmetric flat membrane may be easily visually identified by an examination of the surfaces. The side with smaller pores and less porosity appears shiny compared to a more porous, higher pore size surface. This latter surface appears dull compared to the shiny surface. Therefore, a membrane with one "shiny" (smooth) side, and a "dull" side is by definition asymmetric.
  • Examples 12 and 13 The experimental section has a detailed description of these permselective membranes.
  • the PPS/solvent/optional nonsolvent are heated 0.5 to 2 hr, preferably about one hr, until the reaction mixture turns dark (but clear). Further heating of 0.2 to 1 hr usually does not result in any further darkening of the reaction mixture.
  • the membranes show good permselective and tensile properties.
  • the microporous fiber or membrane described have hydaulic permeability of at least 500 ml/HR- M 2 •cm Hg or greater.
  • the microporous fiber or membrane described have a gas flux through the membrane of at least 1 x 10 -5 cm 3 /cm 2 • sec•cm Hg or greater. In one aspect, the microporous PPS fiber or membrane described have hydaulic permeability of at least 2000 ml/HR-M 2 •cmg Hg. In one aspect, the microporous PPS fiber or membrane described have a gas flux through the membrane of at least 1 x 10 -4 cm 3 /cm 2 • sec•cm Hg.
  • the PPS membrane produced for microfiltration using a drawing step has an average effective pore size of 0.05 microns or larger.
  • the PPS produced for ultrafiltration by the process having a drawing step wherein the effective pore size is less than 0.05 microns.
  • Poly(phenylene sulfide,” or “PPS” refers to a polymeric material which comprises poly(phenylene sulfide).
  • this polymer is prepared from p-dichlorobenzene and sodium sulfide or obtained from Phillips Petroleum Co.
  • the PPS designated lot #1726CJ from Aldrich Chemical Company was used as received for solubility determinations. Most of the organic compounds examined as high temperature solvents are obtained from Aldrich Chemical Company and are used as received. Other organic chemicals are obtained from suppliers as listed in Chemical Sources U.S.A., published annually by Directories Publishing Co., Inc., of Boca Ratan, Florida.
  • Solubility is determined usually at about 10 weight percent polymer, followed by additional determinations at about 25 and 50 weight percent if necessary.
  • Table 2 below illustrates those organic compounds which dissolve at least 50 weight percent PPS.
  • "g” represents “greater than” (>).
  • EXAMPLE BB SOLUTION PPS IN A SOLVENT/NONSOLVENT MIXTURE (a) Simil rly as is described above in Example 1 for the solution of PPS is repeated, except that the solvent is replaced by a solvent/nonsolvent mixture.
  • solutions consisting of (a) PPS (50%), anthracene solvent (32%), and 1,3,5-triphenylbenzene nonsolvent (18%) or (b) PPS (40%), 4-phenylphenol solvent (35%), and sulfolane nonsolvent (15%) may be cast at elevated temperatures on a flat surface.
  • the solvent/nonsolvent mixtures may be removed with solvents such as toluene, methylene chloride, and, in the case of (b) with aqueous potassium hydroxide to produce a porous membrane having a thickness of about 20 mils.
  • the polyphenylene sulfide (PPS) used in the following Examples was obtained from the HOECHST Celanese Corporation of Chatham, New Jersey, and was FORTRON R grade 300.
  • the viscosity of this polymer is approximately 7,000 poise at 300°C.
  • the melting point of the polymer, as measured by differential scanning calorimetry (DSC) was found to be 281°C.
  • Example 1 (A) and heating to 270°C the concentration of PPS in the mixutre was 50%. The blend exhibited a depressed melting point of approximately 264°C.
  • a mixture of 30% PPS and diphenylsulfone was prepared in a 2 oz. bottle, and the bottle placed in an air oven at 290°C for approximately 40 minutes.
  • Max pore size 0.298 micron.
  • Figure 4 shows the type of nodular bulk structure from liquid solid phase separation.
  • Figure 5 shows the type of cellular bulk structure from liquid-liquid phase separation.
  • Figure 4 or a cellular structure in Figure 5 depends upon the desired application of the final membrane. It is possible using the present process to tailor these membranes accordingly.
  • a membrane was prepared by casting 30% solution of PPS in e-caprolactam onto metal plates in a manner similar to that described in Example 2.
  • the e-caprolactam was extracted from the membrane by soaking in water at 40°C for 2 hours.
  • the final thickness of the membrane was approximately 10 mil.
  • a membrane was cast from a 30% solution of PPS and onto metal plates as in Example 2. The cast membrane was allowed to air cool to room temperature. The phenylphenol was extracted by soaking in a 3% NaOH solution at 40°C for 1-1/2 to 2 hours. The dried membrane was then evaluated for permeability and pore size. The final thickness of the membrane was approximately 6 mils.
  • the side (surface) which was brought in contact with the glycerol was "shiny", while the surface against the glass was quite dull in comparison.
  • the schematic diagram indicates the steps odf drawing the membrane at various stages in the process. This step may be done to modify the pore size, pore size distribution, permeability, or tensile properties of the membrane.
  • the membranes may be drawn before the leach step, during the leach step, or after the leach step.
  • a solution of 60% PPS in DPS was prepared.
  • the membranes were prepared by casting on a glass plate at various thickenss by use of a casting bar:
  • Membranes were prepared from a 60% PPS in DPS solution as described in Example 6A.
  • the membranes for this experiment were cast at 5 mil thickness and immediately quenched in 40°C water.
  • the membranes were leached in acetone and then dried.
  • the leached membrane were immersed in a glycerine bath at the temperature of draw, and then drawn to maximum strain until break occurred.
  • the membrane strips were intially 4.0 cm long, and drawn at a rate of 15 cm/min. The maximum draw was obtained was:
  • the membranes subjected to the draw step had greatly improved tensile properties over those of the undrawn samples.
  • the drawn samples were flexible, and could be handled and bent without breakage when compared to undrawn samples.
  • Membranes were prepared and leached as in Example 6B. Although the Tg of the PPS in 88°C, the microporous leached membranes can be drawn even at room temperature if the correct liquid is chosen. The maximum draw obtained in chloroform at room temperature was determined as a function of the residence time in chloroform before the draw was attempted.
  • Examples 6A and 6B above illustrate the improvement in tensile properties of a membrane with the draw (elongation) step.
  • the permeability of a membrane was examined without and with a pre-leach draw step.
  • Membranes were prepared from a 60% solution of PPS in diphenylsulfone (DPS).
  • the membranes were cast at 5 mil. thickness, and then quenched in water at 40°C. The membranes were leached and dried as described in Example 6.
  • a beneficial effect of the pre-leach draw step that is of importance is that the membrane (hollow fiber or film) preferably is continuously handled prior to the leaching step.
  • Two membrane samples were prepared, and both had been prepared by quenching of the PPS/DPS in water at 40°C.
  • One of the membranes was placed in a glycerine both at
  • the drawn film could be handled and processed much more easily than the undrawn sample.
  • the sample in a glass bottle was placed in a forced air oven at 275°C.
  • the PPS dissolved in about 30 to 45 min.
  • the solution was mixed well by rotating the bottle.
  • a pair of aluminum substrates were kept at room temperature, 100°C, 200°C or at 275°C.
  • the 30% PPS solution at 275°C was poured onto one of the substrates. Immediately after being poured, the blend solution was covered by the other substrate and pressed to yield a 0.5 to 1 mm thick sheet.
  • this binary blend sheet After being cooled down to room temperature, this binary blend sheet was immersed in a water bath for twelve hours to leach out e-CLTA and then vacuum dried for six hours. This cast procedure is comparable to a film extrusion where two rolls are utilized (see Process of Figure 1B).
  • the samples prepared by the pour-pressing method had two distinct regions on their air side surfaces (Region I and Region II), which were originating from the solvent flash off occurred during the pour-pressing method.
  • the melt blend took a hemispherical shape after being poured onto the bottom substrate, and the solvent continued to flash off from its surface until the top substrate was pressed on. Pressing the top substrate caused the melt blend to flow outward, and previously unexposed part of the melt blend came in contact with the substrates. Once covered, solidification of the PPS binary blend occurred without further loss of solvent. This solidification resulted in the creation of two distinct regions in the pour-pressed samples.
  • Region I was located in the center of tho sample, where solvent flash off from the air side surface occurred prior to solidification.
  • the membranes prepared from this region had dense skin on the air side surface.
  • Region II, surrounding Region I where solidification of newly exposed (squeezed) melt blend occurred without solvent loss.
  • the membranes prepared from Region II did not have skin on the air side surface.
  • PPS Membrane Evaluation The PPS membranes thus prepared were tested for nitrogen permeability and water permeability. Pore size distributions were determined by the bubble point measurement method (ASTM F316-86). The results were summarized below in Table 3 and in Table 4.
  • Region I the membrane had surface skin (one side) due to solvent flash off.
  • Region II the membrane did not have surface skin because solvent flash off was suppressed.
  • cc/sec*cm 2 *cmHg c) cc/hr*m 2 *cmHg d)
  • Blends A homogeneous mixture of the polymer and solvent were prepared by heating a mixture of the polymer and solvent to a temperature sufficient to cause melting and mixing of both components. This was accomplished utilizing a heated 2 L nitrogen blanketed resin kettle and a motor driven propeller for mixing. The minimum temperature for the blend preparation is the depressed melting poing ofthe polymer solvent mixture. To ensure a quick mixing, the temperature can be raised to one above the melting point of the pure polymer.
  • Hot-Cast Film Procedure B' Procedure B' is similar to procedure A' except that electric heating plates, and support aluminum plates are not used.
  • the glass plates are heated to different temperatures in a furnace or oven.
  • the first and second plates (at different temperatures) are removed and placed on non-heated ceramic tiles.
  • the films are cast as in procedure AA, see Table t below).
  • the sample in a glass bottle was placed in a forced air oven at 310°C. It took about 30 to 45 min to dissolve PPS.
  • the solution was mixed well by rotating the bottle.
  • a pair of substrates (aluminum, TEFLON R , or glass) were kept at ambient temperature, 100 or 200°C, and the 30% PPS solution at 310°C was poured onto one of the substrates at the indicated temperature.
  • the blend solution was covered by the other substrate at the same temperature and pressed to yield at 0.5 to 1 mm thick sheet. After being cooled down to ambient temperature, this blend sheet was immersed in an acetone bath for two hr to leach out DPS and then vacuum dried for two hr.
  • PPS Membrane Evaluation The PPS membranes thus prepared were tested for nitrogen permeability. Their pore size distributions were determined by the bubble point measurement method (ASTM F316-86). The results were summarized below, see Table 6 below. Figure 7 shows the effect of temperature of the top and bottom substrate between which a molten PPS/solvent mixture is quenched. The nitrogen permeability of the final leached membrane is changed. Generally, the higher the quench temperature, the higher the nitrogen permeability (and is comparable to the process of Figure 1(A), 1(B) or 2(B).
  • the permselective membranes were prepared by adaption were prepared by adaption of the procedures described in Example 8 (B) above.
  • Figure 8 shows the effect on nitrogen permeability of the final leached PPS membrane by the varying effective quench temperature.
  • PPD/DPS membranes are prepared by adaption of the processes of Examples 8 (A) or 8 (B).
  • the higher the quench temperature the higher the nitrogen permeability using the processes illustrated in Figures 1(A), 1(B), 2(A) and 2(B).
  • Figure 9 is a graph showing water permeability of the
  • Figure 9 shows the effect of the temperature of the liquid .solution quench upon the final water permeability of a leached membrane, similar to the processes of Figure 2 (A) or 2 (B). The higher temperature of the quench liquid, the higher water permeability of the final leached membrane.
  • EXAMPLE 10 (A) MEMBRANES OF PPS AND DIPHENYLPHTHALATE BLENDS DPTP, DPIP and the commercially obtained blend of DPIP, DPTP (75%/25%) were mixed 50/50 (w/w) with PPS and heated to 315°C for 20 min and allowed to passively mix and then stirred by a gentle mixing motion of the glass jar holding the blend. All samples had an identical translucent amber color. Translucence is a good visual indication of miscibility. Upon solidification, the blends all possessed the same gray/light brown color.
  • a differential scanning calorimeter (DSC) thermograph obtained from the DPIP/DPTP blend indicated from a 24°C melting point depression that PPS was indeed solvated by the DPIP/DPTP blend.
  • the observed melting point depression, and recrystallization temperature is nearly the same as that found for diphenylsulphone, a material known to be a good solvent of PPS.
  • Figure 10 is a graph of the nitrogen permeability of PPS membrane of PPS/DPIP binary blend as a function of quench temperature.
  • Figure 10 shows the effect of the quenching plate temperature upon the nitrogen permeability of the final leached membrane as performed by process of Figures 1(A) or 1(B). Generally, the higher the quench temperature the higher the nitrogen permeability.
  • Figure 11 is a graph of the water permeability of PPS membranes for PPS/DPIP binary blend as a function of quench temperature.
  • Figure 11 shows the effect of the quenching plate temperature upon the water permeability of the final leached membrane as found in Figures 1(A) or 1(B). Generally, the higher the quench temperature the higher the water permeability.
  • EXAMPLE 10 B) PPS AND DIPHENYLISOPHTHALATE (DPIP)
  • Membranes were prepared by the procedures described in 8 (B), e.g. see Table 5 for conditions.
  • Table 8 shows some blends of PPS/DPIP.
  • Microporous PPS membranes were fabricated by extruding the binary blends of PPS/diphenylsulfone followed by acetone leach. The results were summarized below:
  • PPS powder (30 wt% or 40 wt%) and diphenylsulfone (70 wt% or 40 wt%) were free mixed in a vinyl bag.
  • This powder blend was extruded by a twin screw with a KOCH R static mixer with four 1/2 in mixing units and a 2 and 1/4 in wide slit die.
  • the temperature profile and the other operating conditions are listed below in Table 9.
  • the extruded blend was cooled on the surface of the aluminum roller operated at the speed to make the draw down ratio of the melt close to one. It was difficult to extrude the 30/70 PPS/DPS blend due to its low viscosity, and the gap of the die had to be adjusted from time to time to obtain the best possible result.
  • PPS MEMBRANE EVALUATION The PPS membranes prepared in Example 11 were tested for nitrogen permeability. Their pore size distributions were determined by the bubble point measurement method (ASTM F316-86). The results were summarized below. (Also see Figure 7.
  • PPS secured from Philips Petroleum under the trademark Ryton P-6 in the form of a powder is mixed with solvents identified.
  • the solvents and PPS are heated on a Sybron Nuova-II hot plate at the highest setting (producing a surface temperature of about 290°C) to dissolve the PPS. Heating is continued until the solution is clear and dark brown in color.
  • the solution is heated for 1 hour. At the conclusion of the heating period the solution is observed to be clear and brownish. Heating for additional time (20-30 min) does not result in any further color change.
  • a heated glass plate was preheated on the hot plate.
  • the PPS solution was cast on the heated glass plate in the shape of a flat sheet membrane then cooled to room temperature.
  • FIG. 12 is an electron scanning micrograph of the air contacting surface of the membrane thus formed.
  • the SEM scale is 1 cm represents 0.89 micron.
  • the interconnecting pore structure is apparent from the micrograph.
  • the pore size visible in the micrograph ranges from 0.2 to 0.8 ⁇ m. The membrane is useful for microfiltration.
  • Green strength means the pliability of the unleached membrane right after casting process (polymer is warm and cooling). When the green strength is high, it is easier for handling during subsequent handling or processing.
  • Table 11 the first six experiments are run at 280°C for 1 hr. The last six experiments were run at 260°C for 1 hr. The footnotes for Table 11 are the same as found in Table 10. The results are self evident under the specific reaction conditions used. Poor results may be improved when additional experiments are performed.

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Abstract

Procédé de préparation d'une membrane microporeuse à perméabilité sélective à partir d'un polymère de sulfure de polyphénylène et d'un composé organique qui solubilise pratiquement le PPS au-dessus de son point de fusion pour former un mélange homogène, qui consiste à chauffer le mélange obtenu, à extruder ou à couler ledit mélange en une membrane (fibre ou film), à refroidir ou à coaguler la membrane et à lessiver la membrane, tout en tirant éventuellement la membrane avant, pendant, après le lessivage ou en adoptant une combinaison de ces trois solutions. Dans un mode de réalisation, le solvant comprend éventuellement un non-solvant organique destiné à aider à obtenir la microporosité désirée. Lesdits polymères à perméabilité sélective sont utiles pour séparer des constituants gazeux ou liquides d'un mélange de constituants.
EP91916695A 1991-08-17 1991-08-17 Membrane microporeuse sous forme de fibre creuse ou de film, a base de sulfure de polyphenylene. Withdrawn EP0606198A4 (fr)

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CA002115826A CA2115826A1 (fr) 1991-08-17 1991-08-17 Fibre creuse ou membrane microporeuse de poly(sulfure de phenylene)

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