WO1995003949A1 - Dispositif de fermeture a membrane - Google Patents

Dispositif de fermeture a membrane Download PDF

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Publication number
WO1995003949A1
WO1995003949A1 PCT/US1994/008368 US9408368W WO9503949A1 WO 1995003949 A1 WO1995003949 A1 WO 1995003949A1 US 9408368 W US9408368 W US 9408368W WO 9503949 A1 WO9503949 A1 WO 9503949A1
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WO
WIPO (PCT)
Prior art keywords
membrane
perfluoro
dioxole
dimethyl
polymer
Prior art date
Application number
PCT/US1994/008368
Other languages
English (en)
Inventor
Stuart Marshall Nemser
Original Assignee
E.I. Du Pont De Nemours And Company
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 E.I. Du Pont De Nemours And Company filed Critical E.I. Du Pont De Nemours And Company
Publication of WO1995003949A1 publication Critical patent/WO1995003949A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
    • B01D53/228—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion characterised by specific membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
    • B01D63/02—Hollow fibre modules
    • B01D63/031—Two or more types of hollow fibres within one bundle or within one potting or tube-sheet
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K15/00—Arrangement in connection with fuel supply of combustion engines or other fuel consuming energy converters, e.g. fuel cells; Mounting or construction of fuel tanks
    • B60K15/03—Fuel tanks
    • B60K15/035—Fuel tanks characterised by venting means
    • B60K15/03504—Fuel tanks characterised by venting means adapted to avoid loss of fuel or fuel vapour, e.g. with vapour recovery systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K15/00—Arrangement in connection with fuel supply of combustion engines or other fuel consuming energy converters, e.g. fuel cells; Mounting or construction of fuel tanks
    • B60K15/03—Fuel tanks
    • B60K15/04—Tank inlets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2317/00—Membrane module arrangements within a plant or an apparatus
    • B01D2317/02—Elements in series
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2317/00—Membrane module arrangements within a plant or an apparatus
    • B01D2317/04—Elements in parallel

Definitions

  • the present invention relates to closure devices such as a check valve or rehef valve which incorporate selectively permeable membranes formed from a polymer.
  • closure devices such as a check valve or rehef valve which incorporate selectively permeable membranes formed from a polymer.
  • Such valves may be advantageously used with underground storage tanks, above-ground storage tanks, automotive fuel tanks, automotive filler necks, ventilating devices and the like.
  • BACKGROUND OF THE INVENTION This invention relates generally to means for closing the filler tube or vent line of containers such as fuel tanks, underground storage tanks and above-ground storage tanks and the like, and more particularly to a safety-type closure assembly which prevents fuel vapors from escaping from the tank at the time of refueling a vehicle or pumping fuel into a tank or container.
  • Check valves and rehef valves are well known. They may also be referred to as pressure relief valves, expiration valves or controllable expiration valves. Such valves are useful to trap or seal-in vapors or gaseous emissions from a tank or vessel storing a gas or liquid. However, such valves disadvantageously permit the release of noxious fumes.
  • a vented type of filler cap is screwed on or otherwise secured to the outer end of a filler tube to prevent fuel loss from the fuel tank.
  • the filler caps take many forms and some even include filter elements which operate to filter incoming air and/or prevent dirt from entering rehef valve assemblies while in position on the filler tube.
  • the closure was designed to prevent the outflow of organic vapors from a tank during filling.
  • the closure comprises a housing which is essentially cylindrical with a central axial opening.
  • the axial opening permits the passage of the fuel delivery nozzle therethrough.
  • the cyhndrical housing contains an elastically resilient fuel vapor absorbent filter element having a central circular opening which is selected to be slightly less than the delivery of the fuel delivery nozzle.
  • the filter element may become saturated which impairs its effectiveness and, therefore, must be periodically replaced.
  • conventional filter elements may not readily permit the expiration of air during the filling operation, thereby prolonging the filling operation and increasing the risk of explosion. For the same reason, the use of such filter elements may not be satisfactory in conjunction with check valves, pressure relief valves, expiration valves or the like.
  • a closure assembly for fuel tanks and the like is therefore needed which is of simple construction, permits outflow of air but prevents outflow of organic vapors, functions for long periods of time so that it does not require periodic replacements and retains the advantages of prior art devices.
  • the present invention is a closure assembly which may be engageable with the filler tube of a tank such as a fuel tank or the vent line of a storage tank for preventing the outflow of organic vapors from the tank during a filling procedure or venting of the tank.
  • the closure assembly comprises a gas separation membrane which selectively permits the permeation of nitrogen and/or oxygen but not organic vapors.
  • the gas separation membranes are preferably a bundle of hollow-fiber membranes. The bundle may have a central axial opening therein for permitting the passage of a fuel dehvery nozzle therethrough.
  • the gas separation membranes may be formed from polymers which preferentially permit the permeation of nitrogen and/or oxygen in favor of organic vapors.
  • the preferred membrane of the present invention is formed from an amorphous polymer of perfluoro-2,2-dimethyl-l,3-dioxole.
  • the membrane is preferably a supported membrane, in the form of a film or coating on a porous support, or preferably in the form of a hollow fiber.
  • the selective permeation of nitrogen over organic compounds, such as hydrocarbons is at least 10:1.
  • the present invention provides a method for selectively closing or sealing a tank storing a gas or liquid, especially hydrocarbons in a fuel tank, said method comprising:
  • the polymer is a copolymer of perfluoro-2,2-dimethyl-l,3-dioxole, especially a copolymer having a complementary amount of at least one monomer selected from the group consisting of tetrafluoroethylene, perfluoromethyl vinyl ether, vinylidene fluoride and chlorotrifluoroethylene.
  • the polymer is a homopolymer of perfluoro-2,2-dimethyl-l,3-dioxole.
  • Figure 1 is a schematic representation of a process for the separation of gaseous mixtures using a selectively permeable membrane.
  • Figure 2 is a schematic representation of a fuel tank filler tube closure assembly.
  • FIG 3 is a schematic representation of the membrane separation cell used in the filler tube closure assembly shown in Figure 2.
  • Figure 4 is a schematic representation of a membrane expiration valve for a fuel storage tank.
  • FIG. 5 is a schematic representation of the membrane separation cell used in the expiration valve shown in Figure 4. DESCRIPTION OF THE INVENTION
  • the closure assembly may use a polymer membrane which is in the form of a film or coating on a porous support or preferably a hollow fiber.
  • An apparatus for a hollow-fiber membrane separation process is schematically illustrated in Figure 1.
  • membrane separation cell A has a feed or upstream section B and a permeate section C that are separated by selectively permeable membrane D.
  • Feed section B has connected thereto an inlet pipe E.
  • inlet section B has connected thereto an outlet pipe F.
  • Permeate section C is connected to outlet transfer line G.
  • a gaseous admixture containing organic vapors is fed through inlet pipe E to feed section B of membrane separation cell A.
  • the gaseous admixture may be at any temperature, preferably a temperature below the glass transition temperature of the polymer used to form the membrane.
  • a hold-up time which will depend primarily on the flow rate of the gaseous admixture and the volume of the feed section, the portion of the gaseous admixture, primarily organic vapors, that has not passed through the selectively permeable membrane D will pass from the feed section B by means of outlet pipe F.
  • outlet transfer line G might be vented directly or indirectly to the atmosphere; as described herein, the gaseous admixture in outlet transfer line G will have substantially less of the gaseous organic compound than the inlet feed stream, and it might be environmentally acceptable to vent outlet transfer line G to the atmosphere.
  • the feed section of the membrane cell may be pressurized; eg., be at a pressure above atmospheric pressure as a result of periodic filling of the tank or pressure increases resulting from heating or reacting of the contents of the tank.
  • FIG. 2 depicts a membrane closure assembly for the filler neck of a fuel tank in accordance with a preferred embodiment of the invention.
  • the filler tube 2 for the fuel tank 6 is customarily covered by a conventional gas cap, for example a threaded cap (not shown).
  • the filler tube 2 having an opening 4 is shown including a well known spring-loaded flap valve 12.
  • the spring-loaded flap valve 12 may be located in front of or behind the membrane separation cell 8.
  • the spring-loaded valve may have one or more vent openings for equalizing pressure in the fuel tank 6.
  • the membrane separation cell 8, shown in greater detail in Figure 3, has a central opening 9, preferably a circular opening, and a plurality of hollow fiber membranes 7.
  • the circular opening 9 is of a predetermined size to receive a fuel delivery nozzle.
  • the circular opening 9 is defined by cyhndrical structure 13 which is made from a material which is impermeable to the gaseous admixture in the tank 6.
  • the circular opening 9 of the membrane separation cell may also comprise an elastically resilient material or the like which forms a secure seal around the fuel delivery nozzle when it is inserted into the filler tube 2.
  • the membrane separation cell may be held in place within the filler tube 2 by any suitable means, for example by a retaining ring.
  • the membrane separation cell 8 is characterized by having at least one end of each of the hollow fiber membranes 7 embedded in a solid material in a fluid-tight manner to form tubesheets 14 and 15.
  • These tubesheets 14 and 15 are typically composed of a potting material, typically a crosslinkable epoxy resin, which provides support for the hollow fibers 7, mechanical integrity to withstand operating pressure and temperature conditions, chemical resistance, and imparts a tight seal to prevent fluid communication between the exterior side and the bore side of each of the hollow-fiber membranes except through the walls of the hollow-fiber membranes.
  • the potting material and the embedded hollow-fiber membranes are referred to as a tubesheet.
  • the hollow fibers may be placed in communication with the outside by slicing the tubesheet so as to cut off the loops of fiber projecting therefrom.
  • a tubesheet is usually formed near at least one end of the hollow-fiber membrane bundle.
  • the tubesheets are preferably sealingly engaged with the inside of the filler tube 2 by, for example, O-rings 18.
  • the tubesheet, the filler tube 2 and the hollow-fiber membranes together define a space external, typically an annular space, to membranes.
  • the gaseous admixture containing organic vapors flows into the open bores of the hollow-fiber membranes in tubesheet 14.
  • the nonorganic components of the gaseous admixture will readily permeate through the selectively permeable membrane.
  • Such gas will accumulate in annular space 17, which is in fluid communication with permeate discharge port 11.
  • permeate discharge port 11 is vented to the atmosphere. Very httle organic vapors are discharged to the atmosphere.
  • the organic components of the gaseous admixture do not readily permeate through the membranes.
  • the gas enriched in organic components is collected in a manifold area 16 which is in fluid communication with the bores of the hollow fibers 7. Such gas is discharged via discharge port 10, which is preferably in fluid communication with the tank 6, so as to permit recycle of the organic enriched gas.
  • the organic vapors may also be disposed of or filtered by other means weU known in the art.
  • Figure 4 depicts a membrane closure assembly for the vent line
  • the vent pipe 22 for the storage tank 26 comprises a membrane separation cell 28.
  • the membrane separation cell 28 shown in greater detail in Figure 5, has a plurality of hollow fiber membranes 27.
  • the membrane separation cell may be held in place within the vent pipe by any suitable means, for example by a retaining ring.
  • the membrane separation cell 28 is characterized by having at least one end of each of the hollow fiber membranes 27 embedded in a solid material in a fluid-tight manner to form tubesheets 34 and 35.
  • the tubesheets 34 and 35 are sealingly engaged with the inside of the vent pipe 22.
  • the tubesheets, 34 and 35, the vent pipe 22 and the hollow-fiber membranes 27 together define a space external, typically an annular space 38, to membranes.
  • the gaseous admixture from the storage tank containing organic vapors flows into the open bores of the hollow-fiber membranes in tubesheet 34.
  • the nonorganic components of the gaseous admixture will readily permeate through the selectively permeable membrane.
  • Such gas will accumulate in annular space 38, which is in fluid communication with permeate discharge port 31.
  • permeate discharge port 31 is vented to the atmosphere. Very little organic vapors are discharged to the atmosphere.
  • the organic components of the gaseous admixture do not readily permeate through the membranes.
  • the gas enriched in organic components is collected in a manifold area 36 which is in fluid communication with the bores of the hollow fibers 27. Such gas is discharged via discharge port 30, which is preferably in fluid communication with the tank 26 (not shown in Figure 5), so as to permit recycle of the organic enriched gas back to the storage tank.
  • the membrane separation cell may also be placed within an independent shell or housing which may be then readily placed or inserted within the filler tube or vent line.
  • the shell or housing may be fabricated from metal, ceramics, plastic, elastomers, or other materials known in the art.
  • the membrane separation cell may also be used in conjunction with conventional valves such as a check valve or pressure rehef valve.
  • the membrane separation cell is not limited to any particular configuration of a hollow-fiber membrane separation device. However, a cylindrical configuration is preferred. The shell side of the permeator generally operates at atmospheric pressure.
  • hollow fibers may be arranged such that both ends of the fiber protrude through a single tubesheet or a single central tubesheet may also be used.
  • the bundle of membranes may have a noncircular cross-section with nonuniform packing density of membranes. It should be noted that a number of separation devices can be stacked or connected in parallel or series to increase capacity and/or to improve separation. The skilled artisan can readily adapt the teachings herein to such configurations.
  • the potting material used to form the tubesheet may be comprised of any suitable material.
  • this invention enables a wide range of materials to be employed as the potting material.
  • the potting material can be in an essentially liquid form when preparing the tubesheet and can thereafter be solidified; e.g., by cooling, curing, or the like.
  • the solidified potting material should be relatively inert to moieties to which it will be exposed during fluid separation operation.
  • the selectively permeable membrane may be formed from a wide variety of polymeric materials.
  • the membranes for gas separation, according to the invention can be films or hollow filaments, or fibers, having a porous separation membrane, or substrate, and a coating in contact with the porous separation membrane.
  • the permeability constants of the materials of the coating and porous separation membranes are the permeability constants of the materials of the coating and porous separation membranes, the total cross-sectional area of the holes (i.e., pores or flow channels) relative to the total surface area of the porous separation membrane, the relative thickness of each of the coating and the porous separation membrane of the membrane, the morphology of the porous separation membrane, and most importantly the relative resistance to permeate flow of each of the coating and the porous separation membrane in a multicomponent membrane.
  • the degree of separation of the gas separation membrane is influenced by the relative resistance to gas flow for each gas in the gas mixture of the coating and the porous separation membrane, which can be specifically chosen for their gas flow resistance properties.
  • the material used for the porous separation membrane may be a solid natural or synthetic substance having useful gas separation properties.
  • both addition and condensation polymers which can be cast, extruded or otherwise fabricated to provide porous separation membranes are included.
  • the porous separation membranes can be prepared in porous form, for example, by casting from a solution comprised of a good solvent for the polymeric material into a poor or nonsolvent for the material. The spinning and/or casting conditions and/or treatments subsequent to the initial formation, and the like, can influence the porosity and resistance to gas flow of the porous separation membrane.
  • Typical polymers suitable for the porous separation membrane according to the invention can be substituted or unsubstituted polymers and may be selected from polysulfones; poly(styrenes), including styrene-containing copolymers such as acrylonitrilestyrene copolymers, styrene-butadiene copolymers and styrene-vinylbenzylhalide copolymers; polycarbonates; cellulosic polymers, such as cellulose acetate-butyrate, cellulose propionate, ethyl cellulose, methyl cellulose, nitrocellulose, etc.; polyamides and polyimides, including aryl polyamides and aryl polyimides; polyethers; poly(arylene oxides) such as poly(phenylene oxide) and poly(xylene oxide); poly(esteramide-diisocyanate); polyurethane
  • porous separation membrane for the membrane for gas separations may be made on the basis of the heat resistance, solvent resistance, and mechanical strength of the porous separation membrane, as well as other factors dictated by the operating conditions for selective permeation, as long as the coating and porous separation membrane have the prerequisite relative separation factors in accordance with the invention for at least one pair of gases.
  • the porous separation membrane is preferably at least partially self-supporting, and in some instances may be essentially self-supporting.
  • the porous separation membrane may provide essentially all of the structural support for the membrane. It is emphasized that the inventive apparatus is not restricted to these particular membranes.
  • Particularly useful membranes are formed from a polymer having an ahphatic ring structure containing fluorine, for example, a perfluoro-2,2-dimethyl-l,3-dioxole, preferably an amorphous polymer of perfluoro-2,2-dimethyl-l,3-dioxole.
  • the polymer is a homopolymer of perfluoro-2,2-dimethyl-l,3-dioxole.
  • the polymer is a copolymer of perfluoro-2,2-dimethyl-l,3-dioxole, including copolymers having a complementary amount of at least one monomer selected from the group consisting of tetrafluoroethylene, perfluoromethyl vinyl ether, vinyhdene fluoride and chlorotrifluoroethylene.
  • the polymer is a dipolymer of perfluoro-2,2-dimethyl-l,3-dioxole and a complementary amount of tetrafluoroethylene, especially such a polymer containing 65-99 mole % of perfluoro-2,2-dimethyl-l,3-dioxole.
  • the amorphous polymer preferably has a glass transition temperature of at least 140°C, and more preferably at least 180°C.
  • Glass transition temperature (Tg) is known in the art and is the temperature at which the polymer changes from a brittle, vitreous or glassy state to a rubbery or plastic state. Examples of dipolymers are described in further detail in U.S. Patent Nos. 4,754,009 and 4,935,477 both of E. N. Squire.
  • the polymer may also be an amorphous copolymer of perfluoro(2,2-dimethyl-l,3-dioxole) with a complementary amount of at least one other comonomer, said copolymer being selected from dipolymers with perfluoro(butenyl vinyl ether) and terpolymers with perfluoro(butenyl vinyl ether) and with a third comonomer, wherein the third comonomer can be (a) a perhaloolefin in which halogen is fluorine or chlorine, or (b) a perfluoro(alkyl vinyl ether); the amount of the third comonomer, when present, preferably being at most 40 mole % of the total composition.
  • Tg of such dipolymers range from about 260°C for dipolymers with tetrafluoroethylene having low amounts of tetrafluoroethylene comonomer down to less than 100°C for the dipolymers containing at least 60 mole % of tetrafluoroethylene.
  • suitable polymers having an aliphatic ring structure containing fluorine are described un U.S. Patent No. 4,897,457 of Nakamura et al. and Japanese Published Patent Application Kokai 4-198918 of Nakayamura et al.; e.g., a fluorine-containing thermoplastic resinous polymer containing a group of repeating units to be represented by the following general formula:
  • perfluorodioxole membranes are particularly suited to the inventive membrane closure assembly because the polymer may be readily processed into a thin membrane.
  • the membrane preferably is thin, in order to maximize the rate of gas transmission through the membrane, preferably less than 0.01 mm and especially less than 0.001 mm in thickness; in the case of composite membranes, such thickness refers to the thickness of the layer or coating of the polymer.
  • Perfluorodioxole membranes exhibit extremely high gas transmission compared to other membranes, while also exhibiting very good selectivity. In addition, perfluorodioxole membranes exhibit essentially constant performance over a wide range of temperatures.
  • Perfluorodioxole materials have relatively high permeability constants for fluids such that it does not unduly reduce the permeation rate of the membrane for desired components. Moreover, organic compounds such as toluene do not adversely interact with the membrane so as to impair permeation rates. In addition, perfluorodioxole membranes are long lasting and inert to most organic compounds. It is also beheved that perfluorodioxole membranes are resistant to the effects of impurities such as dirt or water vapor.
  • Perfluorodioxole membranes may be manufactured by a variety of methods known to those skilled in the art, particularly in the light of the versatile processability of the perfluorodioxole polymers. These methods include solvent and melt film-casting and fibre-casting methods, as weU as coating techniques; other fluoropolymers tend to be either melt processible but not solvent processible or not processible by either method.
  • the gaseous admixture fed to the membrane separation cell may be an admixture of nitrogen, usually containing oxygen and especially in the form of air, and a gaseous organic compound(s).
  • the gaseous organic compound may be a compound that is a gas at atmospheric temperature and pressure, but will more commonly be the vapor of an organic compound that is in hquid form at atmospheric pressure and temperature.
  • the gaseous admixture will usually be at about ambient temperature but may be at higher temperatures; the membranes used in the method of the present invention are capable of being used at elevated temperature, including in some embodiments at temperatures about 100°C.
  • perfluorodioxole membranes preferably should be used at a temperature below the glass transition temperature, and especially at least 30°C below the glass transition temperature, of the amorphous polymer used to form the membrane.
  • the glass transition temperature of the perfluorodioxole membrane is at least 140°C, preferably at least 180°C and most preferably about 240°C.
  • the method of the present invention may be operated at relatively low temperatures; e.g., as low as about -50°C, and especially about 15°C.
  • the gaseous admixture may be vapors from a fuel tank or storage vessel for gasoline, heating oil, jet fuel or the like.
  • the admixture may be from a process for the manufacture of foamed materials, in which event the organic compound may be a fluorocarbon or hydrocarbon of the type used in such processes.
  • the admixture may be from a dry-cleaning process in which event the organic compound may be a hydrocarbon or chlorinated hydrocarbon, or from a coating process in which event the organic compound may be mixtures of aromatic and aliphatic hydrocarbons and derivatives thereof; e.g., ethers, alcohols and the like.
  • the gaseous admixtures may contain a wide range of amounts of organic compounds.
  • the permeate should normally not contain an amount of organic compounds that preferably should not or cannot be discharged to the atmosphere because of regulatory or other reasons.
  • organic compounds may advantageously be used with the apparatus of the present invention.
  • examples of such compounds include butane, pentane, hexane, septane, octane, and fluorocarbons; e.g., trichloromonofluoromethane, dichlorodifluoromethane, monochlorotrifluoromethane, trichlorotrifluoroethane, dichlorotetrafluoroethane, monochloropentafluoroethane, CF3CH2F, toluene, xylene, naphtha and other mixed hydrocarbon fractions, chlorinated hydrocarbon solvents, polar organic compounds; e.g., methyl ethyl ketone, and the like.
  • oxygen and nitrogen are preferentially passed through the membrane, especially at relatively low concentrations of the organic compound.
  • the feed stream is enriched in the organic compound.
  • oxygen and nitrogen pass through the membrane at a high rate; i.e., there is high flux rate, which is necessary in order that use of the present membrane closure assembly be of commercial interest.
  • cm ⁇ (STP)/sec is the flux (flow rate) in units volume per seconds of permeated gas at standard temperatures and pressure
  • cm ⁇ is the area of film
  • cm Hg is the pressure (or driving force).
  • the selectivity of a membrane in separating a 50/50 mixture of a two-component fluid is defined as the ratio of the rate of passage of the more readily passed component to the rate of passage of the less readily passed component.
  • Selectivity may be obtained directly by contacting a membrane with a known mixture of fluids and analyzing the permeate. Alternatively, a first approximation of the selectivity is obtained by calculating the ratio of the rates of passage of the two components determined separately on the same membrane under equivalent driving pressure differences. Rates of passage may be expressed GPU units.
  • Example I The present invention is illustrated by the following examples.
  • Example I The present invention is illustrated by the following examples.
  • Example I is illustrated by the following examples.
  • Membranes with a thickness of 0.25 mm were melt-pressed from three dipolymers of perfluoro-2,2-dimethyl-l,3-dioxole and tetrafluoroethylene of different dioxode contents and glass transition temperatures (Tg).
  • Tg glass transition temperatures
  • Single-gas permeation tests were conducted using a membrane prepared from a membrane of this high-Tg dipolymer. A number of different gases were tested. As a comparison, tests were also conducted on a membrane formed from polytetrafluoroethylene (PTFE).
  • PTFE polytetrafluoroethylene
  • Permeation measurements were conducted using a permeation cell that was immersed in water in a temperature-controlled water bath.
  • the permeate from the permeation ceU was passed through a sampler bulb of a gas chromatograph, to measure the composition of the permeate, and then to a soap film capillary to measure the permeate flow rate.
  • Concentrations in gas mixtures were measured with a HP Gas Chromatograph Model 5700A foUowed by a Spectra Physics Integrator type Model SP4400. Pressure and pressure drop could be measured in the ceU.
  • the membrane was placed on a porous sinter (pore size 15-20 microns) and held in place using two TEFLON ® rings.
  • the effective membrane area for mass transfer was 9.62 cm ⁇ (3.5 cm diameter).
  • melt pressed membranes were prepared by placing polymer in a mold and heating to a temperature of about 20°C above the glass transition temperature (Tg). When that temperature was reached, the polymer was treated by applying pressure and releasing it, using pressures of up to 50 tonnes/ 12.5 cm diameter of the membrane, for 5 minutes. The mold was then slowly cooled under a pressure of 40 tonnes/ 12.5 cm diameter, to room temperature.
  • the resultant thick powder was transferred to the center of a flat plate covered by aluminum fott.
  • Another aluminum foil-covered flat plate was mounted on it, without any spacer.
  • the two plates were heated in a melt press, at minimal pressure, to a temperature of 100°C above Tg, after which the pressure was raised to 40 tonne/12.5 cm diameter, and the sample was pressed for 10 minutes. The sample was then cooled slowly to room temperature under pressure, and the aluminum foil was peeled off carefully.
  • Cast membranes were prepared from solutions of the polymers in FC-75 solvent. The solution was warmed to 50-60°C, and filtered through a 3 micron filter. The filtered solution was cast onto clean glass, and dried at ambient temperature in a dust-free environment. The membrane was further dried in an oven at 80°C for at least 2 hours, and then in an oven at 110°C overnight.
  • Membranes were formed from a dipolymer of perfluoro-2,2-dimethyl-l,3-dioxole and tetrafluoroethylene having a glass transition temperature of 240°C, by solvent casting from a 2.5% solution in FC-75 solvent using the procedure described above, with the heating at 110°C being for 12 hours. The resultant membrane was 20 micron thick.
  • the mixed gas fed to the permeation ceU had the following composition: N2, 78.25%; O2, 260.67%; and CFC-12, 1.0%. Further experimental details and the results obtained are given in Table II. Measurements were made at 20°C under steady-state conditions in this and the following examples, unless stated to the contrary.
  • Membranes were prepared from a number of different polymers of perfluoro-2,2-demethyl 1,3-dioxole, using the solvent casting method described in Example II. The membranes were tested for permeability using the gaseous mixture of Example ⁇ .
  • B Copolymer of chlorotrifluoroethylene and perfluoro-2,2-dimethyl-l,3-dioxole, with a Tg of 157°C; membrane thickness was 13 microns.
  • C Homopolymer of perfluoro-2,2-dimethyl 1,3-dioxole, with a Tg of 330°C; membrane thickness was 17 microns.
  • a copolymer of perfluoro(methyl vinyl ether) and perfluoro-2,2-dimethyl-l,3-dioxole having a Tg of 139°C was solvent cast into membranes from a 10% solution of the polymer in FC-75 solvent and dried as described in Example II.
  • a second membrane was prepared in the same manner, except that the membrane was heated to a temperature above the Tg, to a temperature of 150°C for an additional hour. Both membranes were tested with single gases.
  • Permeability measurements were conducted on a variety of membranes, formed by melt pressing or by solvent casting.
  • the method of measurement of permeability was that described in Example ⁇ .
  • the gases used were nitrogen and CFC-12, the permeabihties for which were measured separately.
  • Example VO The membranes of Example VO were tested using single gases viz. nitrogen, toluene vapor, water vapor and butane gas, and in one instance using nitrogen saturated with toluene; the latter was achieved by passing nitrogen over the surface of liquid toluene and feeding the resultant stream to the membrane.
  • a membrane made by solvent casting the homopolymer of perfluoro-2,2-dimethyl-l,3-dioxole was tested using butane and nitrogen.
  • the nitrogen permeabilities were measured at 790 kPa, it is known from results given above that the permeabUity for that gas is independent of pressure; comparison may therefore be made with the results obtained with the other gases and vapors.
  • a membrane of the homopolymer of perfluoro-2,2-dimethyl-l,3-dioxole was prepared using the solvent casting technique described in Example II; the membrane thickness 33 microns. It was tested for permeabUity using synthetic air and several single gases with a feed pressure of 790 kPa.

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Abstract

L'invention concerne un appareil de fermeture à membrane constitué d'une membrane de séparation des gaz sélectivement perméable (8) présentant un côté d'alimentation communiquant avec un gaz organique dans un réservoir de carburant ou de stockage (6). Ledit appareil est particulièrement utile en tant que moyen de fermeture du tube de remplissage (2) ou de la ligne de mise à l'air libre d'un réservoir de carburant de stockage. Les membranes de séparation des gaz pouvant être utilisées avec ledit appareil sont multiples. Il est toutefois préférable d'utiliser une membrane à base de polymères amorphes de perfluoro-2,2-diméthyl-1,3-dioxole, en particulier des copolymères contenant une dose complémentaire d'au moins un tétrafluoro-éthylène, un éther vinylique de perfluoro-méthyle, un fluorure de vinylidène et de chlorotrifluoroéthylène. Le polymère est, de préférence, un dipolymère contenant 65 à 99 % en moles de perfluoro-2,2-diméthyl-1,3-dioxole et présentant une température de transition vitreuse d'au moins 140 °C.
PCT/US1994/008368 1993-07-27 1994-07-25 Dispositif de fermeture a membrane WO1995003949A1 (fr)

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US08/098,493 1993-07-27

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10020296A1 (de) * 2000-04-26 2001-10-31 Mannesmann Vdo Ag Entlüftungseinrichtung für einen Kraftstoffbehälter
EP1810863A1 (fr) * 2006-01-20 2007-07-25 Bemis Manufacturing Company Orifice comprenant un séparateur de membrane
US7491258B2 (en) * 2004-11-05 2009-02-17 Ti Automotive Fuel Systems Sas Fuel tank ventilation device
EP2063098A1 (fr) * 2005-11-18 2009-05-27 Basf Catalysts Llc Procédé d'adsorption d'hydrocarbures et dispositif de contrôle des émissions d'évaporation issues du système de stockage de combustible de véhicules à moteur
WO2011098896A1 (fr) * 2010-02-11 2011-08-18 Eaton Corporation Ensemble tête de remplissage à membrane de protection de conduite de recirculation
US8051998B1 (en) * 2005-06-28 2011-11-08 Csp Technologies, Inc. Product container with integral selective membrane
CN104448097A (zh) * 2014-11-19 2015-03-25 中昊晨光化工研究院有限公司 一种全氟间二氧杂环戊烯改性的含氟聚合物
EP2883734A1 (fr) * 2013-12-11 2015-06-17 CNH Industrial Belgium nv Ensemble de reniflard de réservoir de fluide d'échappement diesel
US9381449B2 (en) 2013-06-06 2016-07-05 Idex Health & Science Llc Carbon nanotube composite membrane
US9403121B2 (en) 2013-06-06 2016-08-02 Idex Health & Science, Llc Carbon nanotube composite membrane
EP3434347A1 (fr) * 2017-07-24 2019-01-30 Hamilton Sundstrand Corporation Système de désoxygénation de réservoir de carburant
DE102018206970A1 (de) * 2018-05-04 2019-11-07 Mahle International Gmbh Treibstoffversorgungssystem für eine Brennkraftmaschine

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WO1990015662A1 (fr) * 1989-06-15 1990-12-27 Du Pont Canada Inc. Membranes de perfluorodioxole
JPH0356114A (ja) * 1989-07-25 1991-03-11 Nitto Denko Corp 有機溶剤貯蔵容器の排ガス処理方法
US5042678A (en) * 1990-07-20 1991-08-27 Munguia Preston T Fuel tank filler tube closure assembly
DE4006465A1 (de) * 1990-03-01 1991-09-05 Fraunhofer Ges Forschung Vorrichtung zur ent- und belueftung eines treibstofftankes
EP0461852A2 (fr) * 1990-06-13 1991-12-18 Du Pont Canada Inc. Moteurs mobiles, système d'entrée d'air pour cela et méthode pour opérer ce système
DE9205925U1 (de) * 1992-04-27 1992-12-03 GKSS-Forschungszentrum Geesthacht GmbH, 2054 Geesthacht Vorrichtung zur Trennung von über Flüssigkeiten entstehenden Gasgemischen

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Publication number Priority date Publication date Assignee Title
WO1990015662A1 (fr) * 1989-06-15 1990-12-27 Du Pont Canada Inc. Membranes de perfluorodioxole
JPH0356114A (ja) * 1989-07-25 1991-03-11 Nitto Denko Corp 有機溶剤貯蔵容器の排ガス処理方法
DE4006465A1 (de) * 1990-03-01 1991-09-05 Fraunhofer Ges Forschung Vorrichtung zur ent- und belueftung eines treibstofftankes
EP0461852A2 (fr) * 1990-06-13 1991-12-18 Du Pont Canada Inc. Moteurs mobiles, système d'entrée d'air pour cela et méthode pour opérer ce système
US5042678A (en) * 1990-07-20 1991-08-27 Munguia Preston T Fuel tank filler tube closure assembly
DE9205925U1 (de) * 1992-04-27 1992-12-03 GKSS-Forschungszentrum Geesthacht GmbH, 2054 Geesthacht Vorrichtung zur Trennung von über Flüssigkeiten entstehenden Gasgemischen

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DATABASE WPI Section Ch Week 9116, Derwent World Patents Index; Class J01, AN 91-114325 *
PATENT ABSTRACTS OF JAPAN vol. 15, no. 202 (C - 0834) 23 May 1991 (1991-05-23) *

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10020296A1 (de) * 2000-04-26 2001-10-31 Mannesmann Vdo Ag Entlüftungseinrichtung für einen Kraftstoffbehälter
US6783022B2 (en) 2000-04-26 2004-08-31 Mannesmann Vdo Ag Ventilation device for a fuel tank
US7491258B2 (en) * 2004-11-05 2009-02-17 Ti Automotive Fuel Systems Sas Fuel tank ventilation device
US8051998B1 (en) * 2005-06-28 2011-11-08 Csp Technologies, Inc. Product container with integral selective membrane
EP2063098A1 (fr) * 2005-11-18 2009-05-27 Basf Catalysts Llc Procédé d'adsorption d'hydrocarbures et dispositif de contrôle des émissions d'évaporation issues du système de stockage de combustible de véhicules à moteur
EP1810863A1 (fr) * 2006-01-20 2007-07-25 Bemis Manufacturing Company Orifice comprenant un séparateur de membrane
WO2011098896A1 (fr) * 2010-02-11 2011-08-18 Eaton Corporation Ensemble tête de remplissage à membrane de protection de conduite de recirculation
US8459237B2 (en) 2010-02-11 2013-06-11 Eaton Corporation Fill head assembly having membrane for protecting recirculation line
US9403121B2 (en) 2013-06-06 2016-08-02 Idex Health & Science, Llc Carbon nanotube composite membrane
US9381449B2 (en) 2013-06-06 2016-07-05 Idex Health & Science Llc Carbon nanotube composite membrane
US9962661B2 (en) 2013-06-06 2018-05-08 Idex Health & Science Llc Composite membrane
EP2883734A1 (fr) * 2013-12-11 2015-06-17 CNH Industrial Belgium nv Ensemble de reniflard de réservoir de fluide d'échappement diesel
US9186632B2 (en) 2013-12-11 2015-11-17 Cnh Industrial America Llc Diesel exhaust fluid tank breather assembly
CN104448097A (zh) * 2014-11-19 2015-03-25 中昊晨光化工研究院有限公司 一种全氟间二氧杂环戊烯改性的含氟聚合物
EP3434347A1 (fr) * 2017-07-24 2019-01-30 Hamilton Sundstrand Corporation Système de désoxygénation de réservoir de carburant
DE102018206970A1 (de) * 2018-05-04 2019-11-07 Mahle International Gmbh Treibstoffversorgungssystem für eine Brennkraftmaschine

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