WO1991004785A1 - Membranes poreuses utilisables dans des dispositifs de separation et dans d'autres applications - Google Patents

Membranes poreuses utilisables dans des dispositifs de separation et dans d'autres applications Download PDF

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Publication number
WO1991004785A1
WO1991004785A1 PCT/CA1990/000329 CA9000329W WO9104785A1 WO 1991004785 A1 WO1991004785 A1 WO 1991004785A1 CA 9000329 W CA9000329 W CA 9000329W WO 9104785 A1 WO9104785 A1 WO 9104785A1
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WO
WIPO (PCT)
Prior art keywords
film
support
porous
process according
anodizing
Prior art date
Application number
PCT/CA1990/000329
Other languages
English (en)
Inventor
Aron Marcus Rosenfeld
Mark Adrian Jozefowicz
Robin Christopher Furneaux
Michael Patrick Thomas
Original Assignee
Alcan International Limited
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
Priority claimed from GB898922069A external-priority patent/GB8922069D0/en
Application filed by Alcan International Limited filed Critical Alcan International Limited
Priority to EP90914039A priority Critical patent/EP0494187B1/fr
Priority to CA002057930A priority patent/CA2057930C/fr
Priority to DE69010915T priority patent/DE69010915T2/de
Publication of WO1991004785A1 publication Critical patent/WO1991004785A1/fr

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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
    • B01D67/0039—Inorganic membrane manufacture
    • B01D67/0053—Inorganic membrane manufacture by inducing porosity into non porous precursor membranes
    • B01D67/006—Inorganic membrane manufacture by inducing porosity into non porous precursor membranes by elimination of segments of the precursor, e.g. nucleation-track membranes, lithography or laser methods
    • B01D67/0065—Inorganic membrane manufacture by inducing porosity into non porous precursor membranes by elimination of segments of the precursor, e.g. nucleation-track membranes, lithography or laser methods by anodic oxidation
    • 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
    • B01D67/0039—Inorganic membrane manufacture
    • B01D67/0046—Inorganic membrane manufacture by slurry techniques, e.g. die or slip-casting
    • 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
    • B01D71/02—Inorganic material
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/04—Characteristic thickness

Definitions

  • This invention relates to porous membranes suitable for separation devices, e.g. those used to separate constituent elements of a mixture of materials of different particle or molecule size, and for other uses.
  • porous oxide films can be grown on certain metals, most notably aluminum and anodizable aluminum alloys, by anodizing such metals in electrolytes containing strong acids, such as sulfuric acid and phosphoric acid and films of this type have been suggested for use in filter devices (see U.S. patent 3,850,762 issued on November 26, 1974 to A. W. Smith).
  • Anodic films can be made very thin (e.g. in the order of nanometers) and can be grown to any desired larger thicknesses by continuing the anodization process for a suitable length of time.
  • anodic films adhere tenaciously to the underlying metal on which they are formed and cannot easily be removed without resorting to dissolving away the metal substrate (a slow and expensive procedure) .
  • anodic films produced by porous anodization have imperforate barrier layers at the bases of the pores, immediately adjacent to the metal substrate, so this layer has to be removed if the film is to be used in a device which requires complete penetration of the film, but its removal is very difficult without damaging the remaining porous structure.
  • An object of the present invention is to provide a process for producing a very thin porous membrane suitable for separation devices and other purposes.
  • Another object of the invention is to provide separation devices incorporating very thin porous membranes having very narrow pores.
  • a process for producing a porous membrane characterized by porous anodizing a suitable metal substrate to form a porous anodic film on said metal, said film having an outer surface, creating a weakened stratum in said porous anodic film without causing said film to separate at said weakened stratum, attaching a support to said outer surface of said porous anodic film, and separating at least an outer part of said film from said metal substrate to form a porous membrane supported on said support.
  • the porous membrane attached to the support can be transferred to a different support, e.g. a perforated support, suitable as part of a separation device or other device.
  • a process for producing a separation device which comprises porous anodizing a suitable metal substrate to form a porous anodic film on said metal, said film having an outer surface, creating a weakened stratum in said porous anodic film without causing said film to separate at said weakened stratum, attaching a support to said outer surface of said porous anodic film, separating at least an outer part of said film attached to said support from said metal substrate at said weakened stratum and, if said support is insufficiently perforated for the laminate of the support and the outer film part to act as a suitable separation device, carrying out a further step selected from the group consisting of perforating said support and replacing said support with a perforated supporting structure.
  • the invention also relates to supported porous membranes and separation devices.
  • perforated 11 support or supporting structure we mean to include a continuous layer or body having penetrating holes, a mesh or web made up of fibres or filaments having gaps between the fibres or filaments, or any kind of reinforcements which leave clear access to at least some of the pores of the membrane.
  • the present invention enables the thin porous membrane to be supported during detachment of the anodic film from the metal substrate on which it is formed and during subsequent handling. This means that the membrane can be made very thin (less than 50 microns, for example, and even less than 0.5 microns) and that membranes of large area (e.g. greater than 50 square centimetres) can be formed and incorporated into final products.
  • the anodizing process time can be considerably reduced (e.g. by a factor of 20-30 if supported membranes only a few microns in thickness are adequate and 100 or more if membranes of submicronic thickness are desired) . Not only does this save energy and result in thinner membranes which are more flexible and have lower flow resistance, but it also means that closer control of pore size may be more readily accomplished. If processing times are long, considerable dissolution occurs along the length of the pore due to the dwell time in the acidic electrolyte and asymmetric pores may be produced. In the present invention, the pores may be made more symmetrical throughout the thickness of the membrane.
  • porous membrane is securely supported also has the advantage that any resulting separation device can be cut by mechanical means or by laser into suitable shapes with reduced risk of splitting or cracking as can be the case with unsupported films.
  • Fig. 1 is a cross-section of a porous anodic film produced by a conventional porous anodization technique
  • Fig. 2 is a cross-section of a porous anodic film having a weakened stratum at the oxide/metal interface
  • Fig. 3 is a cross-section of a film similar to that of Fig. 2 having an attached perforated support;
  • Fig. 4 is a cross-section ' of an apparatus used for the process.
  • Fig. 1 is a cross-section through a porous anodic film produced in the conventional manner.
  • the film 10 is grown on a substrate 11, which is generally made of aluminum or an anodizable aluminum alloy, by anodizing the substrate at a voltage of 1-1000 volts, more usually 3-200 volts and more preferably 5-80 volts, in an electrolyte containing an acid such as phosphoric acid, sulfuric acid or oxalic acid.
  • the film contains pores 12 which extend inwardly from the outer surface 14 of the film towards the metal substrate 11. However, the pores are separated from the metal by an imperforate barrier layer 10a which adheres tenaciously at the metal/oxide interface.
  • Fig. 2 shows a similar cross-section of a porous anodic film 10 formed by a similar porous anodization technique.
  • the final stage of the anodization is modified to produce a region of branched pores 15 at the base of each pore 12 by a voltage- reduction procedure as disclosed in our published European patent application referred to above.
  • a voltage- reduction procedure as disclosed in our published European patent application referred to above.
  • this involves varying the voltage in a continuous or stepwise manner.
  • the anodization voltage may be reduced from the original anodization voltage about 25 V to 0 V in 0.5 V increments.
  • the voltage reduction has the effect of causing single pores to branch into numerous small pores that weaken the film.
  • the branched pore regions 15 introduce a weakened stratum into the anodic film 10 adjacent to the metal/oxide interface and the film can be separated fairly easily along this stratum.
  • the barrier layer 10a of Fig. 1 is extremely thin at the end of the pore branching step and is either destroyed or left behind when the film is separated along the weakened stratum, so that the pores 12 in the detached part of the film (the porous membrane) are open at both opposed surfaces of the detached film and completely penetrate the film.
  • the pore branching step should be kept reasonably short in terms of time to prevent premature separation of the film.
  • porous anodization can be carried out after the pore branching step. This prolongs the pores beneath the weakened zone without causing the upper film part to spall off and without compromising the release capability.
  • the weakened stratum can thus be removed from the metal/oxide interface which may give a cleaner separation (fewer defects) if there are localized effects caused by the substrate.
  • a supporting layer 20 (which in this embodiment is itself perforate but need not be) is attached to the outer surface of the film 10 as shown in Fig. 3.
  • the layer 20 preferably has perforations 21 which are quite large compared to the width of the pores 12 in the anodic membrane and can be made, for example, by punching holes in an originally impermeable layer.
  • the layer 20 in this embodiment is a plastic film adhered or heat sealed to the anodic film.
  • the ratio of the size of the perforations to the thickness of the detached film can be important in some cases when the resulting device is to be used as a separation device.
  • the detached film is essentially unsupported in the areas that lie within the perforations 21. Thinner anodic films require more support than thicker films because of their resulting fragility and so it may be necessary to reduce the width of the perforations 21 as the thickness of the membrane 10 decreases. As a rule of thumb, the diameter of the perforations should be less than the membrane thickness for very thin films. Normally, the perforations range in size from 0.1 micron for very thin membranes (e.g. 0.1 micron) to 500 microns for thicker membranes.
  • the layer 20 can be used to assist the detachment of the anodic film from the metal substrate.
  • a part of the layer may extend beyond the anodic film 10 at an edge in order to form a graspable tab and the tab may be used to peel the layer and attached upper anodic film part (porous membrane) from the underlying structure.
  • the membrane 10 is quite thin (e.g. less than 30 microns and preferably less than 5 microns) , it is quite flexible and the bending of the membrane caused when the layer 20 is peeled from the metal substrate does not usually result in damage to the membrane.
  • a stratum of weakness can be introduced into the anodic film by means other than the voltage reducing step mentioned above.
  • a similar effect can be obtained by a voltage increase, a change of current wave form (e.g. from a.c. to d.c), or a change of anodizing acid, individually or in combination.
  • the support 20 there can be considerable variation associated with the support 20. Not only can the nature of the support be varied widely, but the support may also be subsequently removed and replaced by another support or supporting structure. If the membrane is to be used to form a separation device, the final support should itself be perforate.
  • the original support is to be replaced, it need not be perforated because it can be replaced by a perforated member, but even if the support is to remain, it need not be perforated initially since it can be perforated after the detachment of the membrane from the substrate, e.g. by the use of a laser to burn holes in the support or by dissolution or degradation (e.g. by exposing the film to degrading UV radiation from a flash lamp or the-like through the anodic film which acts as a mask except in the area of the pores, or by using the anodic film as a resist for a dissolution process) .
  • Replacement of the support can be carried out by sandwiching the laminate of the porous membrane and the support between a pair of fine mesh grids (made for example of TEFLON or stainless steel) and dissolving or burning away the original substrate in situ .
  • the mesh grids can then form the supporting structure for subsequent handling even though they may not be bonded to the anodic film.
  • selected pores in the membrane may be filled with a material (e.g. a settable liquid such as a lacquer or a polymer solution) that itself reinforces the film.
  • a material e.g. a settable liquid such as a lacquer or a polymer solution
  • a suitable pattern of application such as a dot or grid pattern, good support may be provided while maximizing the areas of unfilled pores.
  • the material penetrating the pores in this way can act alone as a supporting structure after the original support has been removed or it can provide additional support in combination with a porous layer or other support structure.
  • the support is a porous layer of the type shown in Fig. 3, it may be organic, such as the polymeric film already mentioned, or inorganic, such as a ceramic.
  • the porous membrane may be incorporated into a porous composite structure of the type disclosed in our co-pending British patent application serial number 8912425.9 filed on May 31, 1989, the disclosure of which is incorporated herein by reference.
  • the porous membrane is integrally bonded to an overlying layer of partly sintered inorganic particles by one of two methods. In the first method, a slurry of inorganic particles is "tape cast" onto the membrane surface and then heated to partly sinter the particles together.
  • a slurry of inorganic particles is tape cast onto the surface, a preformed layer of sintered particles is then applied on top and finally the coatings are heated.
  • the average pore size of the ceramic layer is larger than the average minimum pore size of the porous membrane.
  • Hot melt interfacing materials can be applied in preprogrammed patterns or designs. This provides a meltable layer between the anodic membrane and the support.
  • iron-on interfacing normally used for stiffening fabrics, can be used to attach a supporting layer, such as a porous nylon mesh, to the anodic film. If the support is to be adhered to the anodic film, this may be done by the spot application of adhesive or polymer solution, e.g. using ink jet printing techniques, to prevent complete blocking of the pores.
  • Yet another attachment technique involves so-called heat staking a porous polymeric membrane of polypropylene, if necessary facilitated by the use of a laser.
  • the above description has been concerned mainly with the attachment of the porous anodic membrane to a porous support in order to form a separation device.
  • the membrane may be attached to an imperforate support in order to form other types of devices, such as catalyst supports and the like.
  • the layers used to support the porous membrane are preferably polymeric and are advantageously heat sealed to the membrane.
  • the substrate can be a thin gauge foil, rather than a thick layer or plate, without the risk of "burning" .during anodizing. .
  • foil substrates make it possible to operate the process on a continuous or semi-continuous basis.
  • An example of the process and suitable apparatus therefor is shown in Fig. 4.
  • Aluminum foil 30 is withdrawn from a roll 31 and passed over a roller 32 which acts as a positive electrode. The foil then passes through a bath 33 holding an acidic electrolyte (H 3 P0 4 ) . The walls of the bath form the cathode and porous anodization of the film takes place.
  • the foil Upon emerging from the bath 33, the foil is then passed through a further bath 35 also containing an acidic electrolyte 36 for the introduction of the weakened stratum.
  • the bath has electrically separate vertically disposed side wall sections which act as cathodes 37, 38, 39, 40 each of which exerts a reduced potential.
  • the resulting anodized foil bearing an anodic film containing a weakened stratum is fed past a roll 41 which applies a porous polymer support.
  • the laminate of the foil, film and support then passes roll 42 which detaches the foil and re-rolls it for further use.
  • the remaining support and film combination 43 is then fed to suitable rolling or cutting equipment (not shown) .

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

L'invention se rapporte à des membranes poreuses dans lesquelles sont incorporés des films anodiques poreux. On produit ces membranes, qui peuvent être utilisées comme filtres, comme moyen de diffusion gazeuse, comme membranes de dialyse, etc., en effectuant une opération d'anodisation poreuse d'un aluminium ou d'un autre métal anodisable poreux, en créant une couche affaiblie dans le film anodique poreux qui en résulte (par exemple par un procédé de réduction de la tension pendant l'étape d'anodisation), en fixant un support au film anodique poreux et en séparant le film le long de la couche affaiblie. Si le support est perforé, la structure qui en résulte est utilisable comme dispositif de séparation. S'il n'est pas perforé le support peut, si nécessaire être perforé par la suite ou être remplacé par un support ou une structure de support perforé. La structure qui est utilisable comporte une couche de support perforé ou non perforé non métallique (par exemple en plastique ou en céramique), ou une autre structure de support, renforçant un film anodique poreux dont les pores pénètrent complètement dans le film.
PCT/CA1990/000329 1989-09-29 1990-09-28 Membranes poreuses utilisables dans des dispositifs de separation et dans d'autres applications WO1991004785A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP90914039A EP0494187B1 (fr) 1989-09-29 1990-09-28 Membranes poreuses utilisables dans des dispositifs de separation et dans d'autres applications
CA002057930A CA2057930C (fr) 1989-09-29 1990-09-28 Membranes poreuses adaptables sur des dispositifs de separation et a d'autres usages
DE69010915T DE69010915T2 (de) 1989-09-29 1990-09-28 Poröse membran für trennungsvorrichtungen und andere anwendungen.

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB898922069A GB8922069D0 (en) 1989-09-29 1989-09-29 Separation devices incorporating porous anodic films
GB8922069.3 1989-09-29
US49755490A 1990-03-22 1990-03-22

Publications (1)

Publication Number Publication Date
WO1991004785A1 true WO1991004785A1 (fr) 1991-04-18

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5582884A (en) * 1991-10-04 1996-12-10 Alcan International Limited Peelable laminated structures and process for production thereof
WO1998002737A1 (fr) * 1996-07-11 1998-01-22 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Element de detection et/ou separation, son procede de production et son utilisation
US6811037B2 (en) 1996-07-11 2004-11-02 Fraunhofer-Fesellschaft Zur Forderung Derangewandten Forschung E.V. Sensor and/or separating element and process for the production and use thereof
US7547393B2 (en) 2005-12-07 2009-06-16 General Electric Company Membrane structure and method of making
US8047382B2 (en) 2005-12-07 2011-11-01 General Electric Company Membrane structure and method of making
WO2014187049A1 (fr) * 2013-05-21 2014-11-27 东莞劲胜精密组件股份有限公司 Procede de micro-nano-traitement pour surface en aluminium ou en alliage d'aluminium et structure en aluminium ou en alliage d'aluminium

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0178831A1 (fr) * 1984-10-17 1986-04-23 Alcan International Limited Films poreux et leur procédé de fabrication
EP0242204A1 (fr) * 1986-04-16 1987-10-21 Alcan International Limited Membranes en oxyde d'aluminium formé par anodisation

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0178831A1 (fr) * 1984-10-17 1986-04-23 Alcan International Limited Films poreux et leur procédé de fabrication
EP0242204A1 (fr) * 1986-04-16 1987-10-21 Alcan International Limited Membranes en oxyde d'aluminium formé par anodisation

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
CHEMICAL ABSTRACTS, volume 80, no. 26, 1 July 1974, (Columbus, Ohio, US), see page 428, abstract no. 152076u & JP - A - 72 044 418 (Sumito Electric Industries, Ltd) 9 November 1972 *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5582884A (en) * 1991-10-04 1996-12-10 Alcan International Limited Peelable laminated structures and process for production thereof
WO1998002737A1 (fr) * 1996-07-11 1998-01-22 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Element de detection et/ou separation, son procede de production et son utilisation
US6811037B2 (en) 1996-07-11 2004-11-02 Fraunhofer-Fesellschaft Zur Forderung Derangewandten Forschung E.V. Sensor and/or separating element and process for the production and use thereof
US7547393B2 (en) 2005-12-07 2009-06-16 General Electric Company Membrane structure and method of making
US8047382B2 (en) 2005-12-07 2011-11-01 General Electric Company Membrane structure and method of making
US8056731B2 (en) 2005-12-07 2011-11-15 General Electric Company Membrane structure and method of making
WO2014187049A1 (fr) * 2013-05-21 2014-11-27 东莞劲胜精密组件股份有限公司 Procede de micro-nano-traitement pour surface en aluminium ou en alliage d'aluminium et structure en aluminium ou en alliage d'aluminium

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