EP0000687B1 - Verfahren zur Herstellung einer mikroporösen Membran für Filtrationsanlagen - Google Patents

Verfahren zur Herstellung einer mikroporösen Membran für Filtrationsanlagen Download PDF

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Publication number
EP0000687B1
EP0000687B1 EP78810003A EP78810003A EP0000687B1 EP 0000687 B1 EP0000687 B1 EP 0000687B1 EP 78810003 A EP78810003 A EP 78810003A EP 78810003 A EP78810003 A EP 78810003A EP 0000687 B1 EP0000687 B1 EP 0000687B1
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EP
European Patent Office
Prior art keywords
particles
layer
membrane
plastics material
mixed
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.)
Expired
Application number
EP78810003A
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German (de)
English (en)
French (fr)
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EP0000687A1 (de
Inventor
Ludwig Proelss
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Kilcher-Chemie AG
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Kilcher-Chemie AG
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Publication date
Application filed by Kilcher-Chemie AG filed Critical Kilcher-Chemie AG
Publication of EP0000687A1 publication Critical patent/EP0000687A1/de
Application granted granted Critical
Publication of EP0000687B1 publication Critical patent/EP0000687B1/de
Expired legal-status Critical Current

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    • 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
    • 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
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/26—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a solid phase from a macromolecular composition or article, e.g. leaching out

Definitions

  • the invention relates to a method for producing a microporous membrane for filtration systems, in which fine-particle, insoluble particles are mixed into a plastic or plastic pre-product and aligned perpendicular to the surface and released after reaching the final position, forming a flow structure with channel-shaped cavities.
  • a microporous membrane for filtration systems in which fine-particle, insoluble particles are mixed into a plastic or plastic pre-product and aligned perpendicular to the surface and released after reaching the final position, forming a flow structure with channel-shaped cavities.
  • hollow fibers as particles, there is no need to separate them out.
  • Such membranes can be used for ultrafiltration of aqueous media, for reverse osmosis and for dialysis.
  • Ultrafiltration is generally understood to mean the removal of colloidal particles under moderate excess pressure, while reverse osmosis is understood to mean the task of separating or concentrating significantly smaller, namely really dissolved, particles from the solvent under high pressure.
  • Previously known high-performance membranes consist predominantly of an asymmetrically constructed, porous layer of plastic such as cellulose acetate, polyamide, polyacrylonitrile, etc. They are produced by pouring complex composite solutions into one layer, achieving a smooth, narrow-pore "active" top side by evaporation or precipitation forms the layer immediately below it by coagulation with suitable media to form a relatively coarse-pored support layer.
  • plastic such as cellulose acetate, polyamide, polyacrylonitrile, etc.
  • Such membranes currently have a high level of development.
  • the number of polymers that are suitable for producing asymmetric membranes is limited. The manufacturer is therefore not necessarily able to provide a membrane substance that can be the desired chemical resistance, wettability and mechanical properties would best suit the intended purpose.
  • filter layers are known which are produced by limited sintering (firing) of metal-ceramic, carbon or plastic powders. Often, the side facing the filter material is still provided with a fine-pored sintered or precoat layer (so-called composite membranes). These membranes also do not optimally meet the aforementioned requirements.
  • the flow line of an imaginary liquid particle through the separation layer is highly branched, which creates a high volume resistance.
  • DE - OS 2 133 848 discloses a process for producing a porous polytetrafluoroethylene tape, in which metal or glass fibers are mixed with a plastic and formed into an ingot by pressure, as a result of which the fibers are preferably oriented perpendicular to the direction of pressure, that is to say radially. Peeling produces a thin film, in which fibers are also oriented essentially perpendicular to the film surface and are then partially rinsed out.
  • the peeling phase in particular is quite difficult to carry out and is too expensive for industrial production of the microporous membrane mentioned at the beginning.
  • the process that solves this task is characterized in that the mixture used to produce the membrane is formed into a thin layer in the flowable state and the particles are oriented essentially perpendicular to the surface of the layer and that after the layer has solidified the particles are detached to form a flow structure with channel-shaped cavities. If hollow fibers are used as particles, there is no need to separate them.
  • FIG. 6 shows a section of a membrane produced by a further method according to the invention.
  • the intended plastic is added dry, by extruder, mixing roller mill, or wet, by stirring in plastic solutions or in low-molecular plastic intermediate products, fine powdery solid particles in high concentration.
  • a layer is then formed from this material and the particles are aligned as long as the plastic part is plastic or flowable.
  • the layer is then hardened and further treated in order to obtain a flow structure.
  • cavities filled with air or water remain at the original location of the particles, which are connected to each other by spherical caps and, due to the orientation process, pass through the membrane in a channel-like manner. They are more or less perpendicular to the surface of the membrane.
  • a film remains after extraction with a structure that resembles a hexagonally closest spherical packing and resembles an open-cell rigid foam film under the microscope.
  • This film can be called a reverse sintered layer because the structure corresponds to that of a sintered plate, with the difference that instead of the solid particles present there are uniform cavities, as can be seen from FIGS. 1 and 2.
  • the filter performance of the so-called reverse sinter layer leaves something to be desired. Because their structure is more like a microfoam than a capillary layer, their flow rate - in relation to the pore size - can be described as average. In order to increase the output, it is necessary to orient the particles in the substrate before solidification so that they form capillary or flow structures perpendicular to the membrane surface and finally expose them by etching.
  • the structure formation is possible in different ways, for example:
  • the particles can be finely ground, water-soluble salts.
  • these are usually too soft and therefore have too wide a grain size and thus pore width spectrum.
  • the resulting membranes are insufficient for the aforementioned applications.
  • These substances are finely dispersed with approximately spherical particles, narrow grain size distribution, available in defined grain sizes and extractable by hydrofluoric acid.
  • other particles (fillers) produced by precipitation or grinding can also be used.
  • ferromagnetic fillers such as iron II / III oxide, iron powder, nickel powder, chromium II / II / oxide.
  • This PVC paste is applied to a commercially available polyethylene sintered plate with a pore size of 0.04 mm and completely scraped off with a metal doctor. The cavities adjacent to the surface are completely filled with the paste.
  • the carrier plate is then dried and the doctoring process repeated three times. As described above, the particles are aligned as a result of laminar flow processes and capillary structures are formed in the pores in the flowing plastic.
  • the carrier plate is checked with methylene blue solution in the filtering device before etching. In order to be able to check the depth of penetration of the paste better, it is advisable to rub it beforehand with a little pigment (e.g. copper phthalocyanine blue).
  • the capillaries are then exposed by etching for two hours with 40% hydrofluoric acid.
  • the ready-to-use membrane now consists of, for example, a 2 mm thick carrier layer made of porous polyethylene and a one-sided, firmly anchored fine filtration layer of 0.04-0.07 mm thick.
  • the surface of the fine filtration layer consists of 50-60% of dense polyethylene particles and 50-40% of the actual filter mass. Their filtration capacity compared to distilled water is 6.3-6.7 cm 3 fcm at 2 hours bar at 20 ° C.
  • Example 1 The membrane produced according to Example 1 is rinsed for one hour at 20 ° with 10% aqueous chromic acid. It is then washed with distilled water and the filtration performance is determined. This is now much higher. The behavior towards red gold sol remains unchanged compared to example 1.
  • the layer is allowed to dry for 5 hours at 50 °, it is removed from the base and the nickel particles are removed from the membrane by etching for 4 hours with 20% hydrofluoric acid, which contains about 10% concentrated hydrogen peroxide.
  • a 0.08 mm thick milky-cloudy white film is obtained. This reveals channels opening out under the microscope in the glassy matrix perpendicular to the surface.
  • the filtration capacity of this membrane is 60-70 cm 3 / cm 2 hours. Goldsol passes this membrane completely. 1% polyvinyl Acetate dispersion with a particle size of 0.5-2 ⁇ m is completely retained, so-called "bare" filtrate.
  • Nickel wire with a thickness of 40 ⁇ m is processed into a fibrous powder with an average length of 0.3 mm.
  • the layer is placed on the face of the above-mentioned bar magnet (with the particles standing upright) and allowed to dry at 50 ° C for several hours.
  • the velvet-like film obtained in this way is removed from the base and first freed from the outer solid polymer layer by pickling with 20% chromic acid.
  • the particle fraction is then removed, as described above, with hydrofluoric acid and hydrogen peroxide.
  • the throughput was approximately 50,000 cm 3 water / cm 2 hours bar.
  • quartz fibers of 5 IL m in thickness are converted into a fibrous form with a staple length of about 0.5 mm.
  • a 20% solution of polyphenylsulfone in N, N'-dimethylformamide is applied in a 0.4 mm thick layer to a hard-chromed metal disc 50 mm in diameter.
  • the particles are introduced into the polymer solution on the hard chrome disc at a potential difference of 30,000 volts.
  • the velvety layer can be easily separated from the metal plate by placing it in water containing wetting agent. After two hours of exposure to 40% hydrofluoric acid, the pores are completely exposed. Under the microscope, the membrane shows completely uniform, equally large pores with a meniscus-shaped collar. A flow rate of approximately 1,200 cm 3 / cm 2. Hours bar was obtained.
  • the starting material for the hollow fibers is a borosilicate glass tube of 7 mm outside and 0.4 mm inside diameter used for the manufacture of so-called full glass thermometers. It is inserted vertically hanging into a ceramic tube heated to 1400 ° C with an inner diameter of 20 mm and a length of 150 mm and drawn down as an endless hollow fiber over rubber squeeze rollers. It is relatively easy to achieve fibers with a constant cross section of 25 ⁇ m and a light width of approx. 1.5 1L m. They are transferred into hollow fiber meal of about 0.5 mm stack length. This flour is stored in a thin layer isothermally in a desiccator at 80 ° above a high-boiling kerosene fraction. In this way, the capillaries are filled with kerosene and are not blocked by the polymer solution during the subsequent flocking process.
  • the hollow fiber flour is introduced as described in Example 5 in 25% phenoxy resin solution in dimethylformamide (0.4 mm thick layer), dried, annealed at 90 ° C for several hours and then the capillary orifices are exposed by pickling with 20% chromic acid.
  • a velvety glossy film of approximately 0.15 mm thick and with approximately 0.5 mm long capillaries embedded upright is obtained.
  • the flow rate is about 350 cm3 / cm2 hours. bar.
  • the membrane can be hot sterilized at 150 ° without changing its flow behavior.
  • Suitable particles are pyrogenic silicon dioxide as well as aluminum oxide, titanium dioxide, zinc oxide and water-precipitated particles of aluminum hydroxide, beryllium hydroxide and zirconium hydroxide with a grain size maximum of 7 nm-50 nm.
  • Usable magnetizable particles can be made of magnetite, iron sulfide, iron oxide, chromite and iron-nickel-cobalt metal or from Heusler's alloys.
  • Precursors of epoxy resins, acrylic resins, phenol formaldehyde resins, silicone resins, polyester resins and the polymers PVC, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), PAN mixed polymers, polyamides, phenoxy resins and polyphenyl sulfone can be used as binders.
  • the membrane produced by the above method can have any shape, that is to say it can be in the form of a flat layer or tubular or pot-shaped.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
EP78810003A 1977-07-15 1978-06-20 Verfahren zur Herstellung einer mikroporösen Membran für Filtrationsanlagen Expired EP0000687B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH8765/77 1977-07-15
CH876577A CH625966A5 (nl) 1977-07-15 1977-07-15

Publications (2)

Publication Number Publication Date
EP0000687A1 EP0000687A1 (de) 1979-02-07
EP0000687B1 true EP0000687B1 (de) 1981-09-16

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EP78810003A Expired EP0000687B1 (de) 1977-07-15 1978-06-20 Verfahren zur Herstellung einer mikroporösen Membran für Filtrationsanlagen

Country Status (16)

Country Link
US (1) US4177228A (nl)
EP (1) EP0000687B1 (nl)
JP (1) JPS5420970A (nl)
AU (1) AU3754678A (nl)
CA (1) CA1107922A (nl)
CH (1) CH625966A5 (nl)
DE (1) DE2861072D1 (nl)
DK (1) DK293578A (nl)
ES (1) ES471714A1 (nl)
FI (1) FI782208A (nl)
GR (1) GR64587B (nl)
IL (1) IL55011A (nl)
IT (1) IT1097184B (nl)
NO (1) NO782448L (nl)
PT (1) PT68212A (nl)
ZA (1) ZA783619B (nl)

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Also Published As

Publication number Publication date
FI782208A (fi) 1979-01-16
GR64587B (en) 1980-04-18
IL55011A0 (en) 1978-08-31
JPS5420970A (en) 1979-02-16
US4177228A (en) 1979-12-04
IL55011A (en) 1981-05-20
IT1097184B (it) 1985-08-26
IT7825737A0 (it) 1978-07-14
ES471714A1 (es) 1979-02-01
CA1107922A (en) 1981-09-01
EP0000687A1 (de) 1979-02-07
DK293578A (da) 1979-01-16
DE2861072D1 (en) 1981-12-03
AU3754678A (en) 1980-01-03
PT68212A (de) 1978-07-01
CH625966A5 (nl) 1981-10-30
ZA783619B (en) 1979-06-27
NO782448L (no) 1979-01-16

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