IE904677A1 - Composite membrane, process for its production and its use - Google Patents

Composite membrane, process for its production and its use

Info

Publication number
IE904677A1
IE904677A1 IE467790A IE467790A IE904677A1 IE 904677 A1 IE904677 A1 IE 904677A1 IE 467790 A IE467790 A IE 467790A IE 467790 A IE467790 A IE 467790A IE 904677 A1 IE904677 A1 IE 904677A1
Authority
IE
Ireland
Prior art keywords
layer
membrane
gas
permselective
composite membrane
Prior art date
Application number
IE467790A
Original Assignee
Hoechst Ag
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 Hoechst Ag filed Critical Hoechst Ag
Publication of IE904677A1 publication Critical patent/IE904677A1/en

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/02—Physical, chemical or physicochemical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B01D69/1216—Three or more layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B01D69/122—Separate manufacturing of ultra-thin membranes
    • 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
    • B01D71/40—Polymers of unsaturated acids or derivatives thereof, e.g. salts, amides, imides, nitriles, anhydrides, esters
    • B01D71/401—Polymers based on the polymerisation of acrylic acid, e.g. polyacrylate
    • B01D71/4011—Polymethylmethacrylate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
    • B32B27/308—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising acrylic (co)polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
    • C01B13/02—Preparation of oxygen
    • C01B13/0229—Purification or separation processes
    • C01B13/0248—Physical processing only
    • C01B13/0251—Physical processing only by making use of membranes
    • C01B13/0255—Physical processing only by making use of membranes characterised by the type of membrane
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/03—3 layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2305/00—Condition, form or state of the layers or laminate
    • B32B2305/02—Cellular or porous
    • B32B2305/026—Porous
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/724—Permeability to gases, adsorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2323/00—Polyalkenes
    • B32B2323/10—Polypropylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2333/00—Polymers of unsaturated acids or derivatives thereof
    • B32B2333/04—Polymers of esters
    • B32B2333/12—Polymers of methacrylic acid esters, e.g. PMMA, i.e. polymethylmethacrylate
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2210/00—Purification or separation of specific gases
    • C01B2210/0043—Impurity removed
    • C01B2210/0046—Nitrogen

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Analytical Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

A composite diaphragm for gas separation with a three-layer structure, consisting of: A) a supporting diaphragm layer of porous polymer; B) a non-porous, gas-permeable intermediate layer; C) a perm-selective layer of regularly arranged organic molecules with a layer thickness of 3 to 100 nm; where layers (A) and (C) envelop the intermediate layer (B). The perm-selective layer (C) is formed of at least one regularly arranged polymer consisting of at least one of the unsaturated monomers (I) and (II), in which R<1> and R<2> are independently CH3 and C2H5 and X is H, CH3, Cl, F and CN.

Description

Composite membrane, process for its production and its use The present invention relates to a composite membrane constructed from three layers, which is highly suitable for the separation of gas mixtures and which contains a permselective layer of regularly arranged amphiphilic molecules.
In industry, the task is often faced of completely separating gas mixtures or at least concentrating one component of the gas mixture. This task is carried out to an increasing extent with the aid of semipermeable membranes. Depending on solubility and diffusion coeffi15 cients, these membranes allow gases to pass through at a variable rate.
A composite membrane for gas separation having a threelayer structure is already known from DE-OS 3,415,624. It contains a supporting membrane layer made of porous poly20 mer (A), a nonporous, gas-permeable intermediate layer (B) made of polyorganosiloxane and a thin layer of a special polymer (C) which has a favorable O2/N2 permeability coefficient ratio (selectivity). This layer can be obtained by application of a thin film, which can be produced by spreading on a water surface.
For the industrial utility of such gas separation membranes, both their permeability and their selectivity are of particular importance.
The permeability of a membrane for a certain gas depends both on the thickness of the active layer (= permselective layer) and on the permeability »» coefficient for this gas. The gas permeability of the gas-permeable intermediate layer (B) is in general - 2 substantially greater than that of the permselective layer.
The separation selectivity of a membrane is primarily determined by the material of the layer (C). However, experience tells us that materials of high selectivity have a low permeation coefficient.
Therefore all attempts to find polymer materials for C which have both a high selectivity and a high permeability coefficient have hitherto been unsuccessful. The choice is therefore only between highly permeable and slightly selective or selective and slightly permeable membranes. The latter are employed today for industrial applications.
In order to be able to obtain acceptable permeation rates, efforts have been made to make the thickness of the active layer (= permselective layer) as thin as possible. In this case, however, the occurrence of defects, so-called pinholes, sets limits on the efforts towards ever smaller layer thicknesses.
Thus, today it is possible to produce permselective layers having layer thicknesses of about 0.05 to 0.5 μτα (= 50-500 nm) . The use of membranes having such layer thicknesses became possible after it had been learnt virtually to block the pinholes always occurring in such thin (permselective) layers with silicone rubber (Henis, J.M.S.; Tripodi, M.K.; Sep. Sci. Technol. 1980. 15, 1059) .
The silicone layer can thus be applied to the membrane as an outer layer. It can also be enclosed, however, by the supporting membrane layer and the permselective layer (cf. DE-OS 3,415,624).
Nevertheless, even with respect to their permeability, these known membranes are still in need of improvement. - 3 The aim therefore existed of providing a composite membrane suitable for gas separation which has a considerably improved permeability combined with good selectivity.
A composite membrane having the generic features of claim has now been found, wherein the permselective layer (C) is constructed from at least one regularly arranged polymer which is composed of at least one of the unsaturated monomers CH^C-C-O-R1and CH7=CH-O-C-R2 x o S in which R1 and R2 independently of one another are CH3 and C2H5, and X is H, CH3, Cl, F and CN.
The polymers of the permselective layer (C) are preferably constructed from at least 10 monomer units. The layer (A) of the composite membrane is a porous micro- or ultrafilter. The gas-permeable intermediate layer (B) should be composed of an amorphous polymer having a high gas permeability. Suitable polymers are, for example, polymethylpentene, polysiloxane-polycarbonate block copolymers, polytrimethylsilylpropyne, EPDM rubber or chlorinated polyethylene.
The polymers of the permselective layer are insoluble in water but soluble in CH2C12. They form stable monolayers on the water/air interface.
The composite membrane according to the invention can be produced by applying a regularly arranged permselective layer composed of a given polymer to a supporting mem30 brane which is composed of a supporting membrane layer (A) made of porous polymer and a non-porous gas-permeable layer (B) made of an amorphous polymer. In this process, - 4 the polymer is dissolved in an easily volatile organic solvent, the solution is spread on a water surface, and the resulting monomolecular film is compressed by the Langmuir-Blodgett technique and transferred to the immersed supporting membrane. Mixtures of polymers can also be used. Different polymers can be employed in the individual, successively applied monomolecular films.
The supporting membrane employed can be prepared by coating a micro- or ultrafilter composed of polysulfone, polyimide, polyacrylonitrile, polyamide or polyether ketone with the amorphous polymers mentioned. The layer of the amorphous polymer should be nonporous and gaspermeable. The layer thickness is preferably 15 nm to 500 nm, preferably 30 to 250 nm, in particular 50 to 100 nm. Suitable polymers for the gas-permeable intermediate layer (B) are, for example, block copolymers of polysiloxane and polycarbonate or poly-4-methylpentene. The coating process is described in Ward, W.J. Ill, et al: J. Membr. Sci. 1976, 1, 99.
It is an advantage of the process according to the invention that several highly ordered and gas-selective layers can be applied successively to the supporting membrane by the Langmuir-Blodgett technique. The very thin layer can additionally be applied with a homogeneous thickness.
In order to separate or at least to concentrate gases with the aid of the composite membrane according to the invention, the gas to be separated is brought into a container which is closed by the composite membrane. The pressure in the container is higher than that outside the container. The permselective layer of amphiphilic molecules is preferably facing the elevated pressure side. On the outside at the lower pressure, a gas can be withdrawn in which one component of the two-component mixture is concentrated. - 5 By selection of a suitable polymer, the process can be suited to the gas mixture to be separated. The process is even suitable for the separation of 02/N2.
The invention will be explained in more detail by the 5 following examples.
Example 1: Gas-separating membrane of three-layer construction containing poly (methyl methacrylate) as the active separating layer A 70 x 70 mm piece of supporting membrane composed of a porous supporting membrane made of polypropylene (Celgard 2400), which has been coated with a 0.5 pm thick nonporous layer of polydimethylsiloxane-polycarbonate block copolymer, is coated with 12 monolayers of poly(methyl methacrylate) by the method of Langmuir and Blodgett. To do this, a piece of appropriate size is cut out of the supporting membrane and tensioned on a 70 x 90 mm polycarbonate frame. The membrane to be coated is rinsed with water under clean room conditions. Two hundred micro20 liters of a solution of 6 mg of poly (methyl methacrylate) in 5 ml of dichloromethane is poured (spread) onto the water surface of a commercial Langmuir film balance (film balance 2 from MGW Lauda) at a subphase temperature of 30°C. By reducing the size of the monofilm-covered water surface, the force is adjusted to 10 mN/m and kept constant at this value. The frame with the stretched membrane is now immersed perpendicularly through the water surface in the film balance from above (immersion rate: 20 mm/min) and, after a short pause (10 sec.) at the lower turn-around point, taken out again (emersion rate: mm/min). A monolayer is transferred to the support here both in the immersion and in the emersion procedure. After completion of the emersion procedure the residual monofilm is sucked off the water surface and a monofilm is spread again, as described above, and compressed to 10 mN/m, and 10 further monolayers are transferred to the - 6 supporting membrane by immersion and emersion. The transfer ratios are about 40 % on immersion and 90 - 100 % on emersion.
The permeability of the membrane thus prepared is roea5 sured for the gases oxygen, nitrogen, carbon dioxide and helium. The following results are obtained: Gas flow at 25 °C (cm3 (STP)/cm2*sec*cm Hg) N2: 3.3xl05, O2: 8.9xl0’5 CO2: 4.6x10*, He: 4.3x10'* Selectivity: 02/N2: 2.7 CO2/N2: 14 He/N2: 13 Example 2: The membrane of Example 1 has a stream of air applied to the layer (C), while vacuum is applied to the permeate side (layer A). The oxygen content of the gas mixture aspirated by the vacuum pump is examined and the pressure is juxtaposed to the vacuum side. No concentration (20 % 02) is found at 1000 mbar. The 02 content is 28 % at 500 mbar, 33 % at 250 mbar and about 37 volume-% at mbar.

Claims (11)

1. A composite membrane for gas separation having a three-layer structure, constructed from A) a supporting membrane layer made of porous polymer, B) a nonporous, gas-permeable intermediate layer, C) a permselective layer of regularly arranged organic molecules having a layer thickness of 3 to 100 nm, the layers (A) and (C) enclosing the intermediate layer (B), wherein the permselective layer (C) is constructed from at least one regularly arranged polymer which is composed of at least one of the unsaturated monomers ch 7 =c-c- o-r 1 z ι n X 0 and CH->=CH-O-C-R 2 Z H in which R 1 and R 2 independently of one another are CH 3 and C 2 H 5 , and X is H, CH 3 , Cl, F and CN.
2. The composite membrane as claimed in claim 1, wherein the polymers of the permselective layer (C) are constructed from at least 10 monomer units.
3. The composite membrane as claimed in claim 1, wherein the permselective layer (C) is composed of at least two monomolecular layers of polymers arranged one above the other.
4. A process for the production of a composite membrane as claimed in claim 1, in which a permselective layer (C) composed of organic material is applied to a supporting membrane which is composed of a supporting membrane layer (A) made of porous polymer and a nonporous, gas-permeable layer (B) made of amorphous polymer, wherein a waterinsoluble polymer as claimed in claim 1 is dissolved in an easily volatile organic solvent, the solution is spread on a water surface, and the resulting film is
5. The process as claimed in claim 4, wherein the permselective monomolecular layer is applied to the gaspermeable layer (B) of the supporting membrane.
6. A process for separating a gas mixture into concentrated components, in which the gas mixture is brought into a container which is closed by a gas-separating membrane having a permselective outer coating facing the gas mixture, a lower pressure than in the interior of the container is maintained on the other side of the gasseparating membrane and a concentrated component of the gas mixture is withdrawn, wherein the composite membrane as claimed in claim 1 is employed as the gas-separating membrane.
7. The process as claimed in claim 6, wherein a gas mixture composed of nitrogen and oxygen is separated. -98. A composite membrane as claimed in claim 1, substantially as hereinbefore described and exemplified.
8. - 8 compressed by the Langmuir-Blodgett technique and transferred to the immersed supporting membrane as a monomolecular permselective layer.
9. A process as claimed in claim 4, substantially as hereinbefore described and exemplified.
10. A composite membrane as claimed in claim 1, whenever produced by a process claimed in claim 4, 5 or 9.
11. A process as claimed in claim 6, substantially as hereinbefore described and exemplified.
IE467790A 1989-12-23 1990-12-21 Composite membrane, process for its production and its use IE904677A1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE3942868A DE3942868A1 (en) 1989-12-23 1989-12-23 COMPOSITE MEMBRANE, METHOD FOR THEIR PRODUCTION AND THEIR USE

Publications (1)

Publication Number Publication Date
IE904677A1 true IE904677A1 (en) 1991-07-17

Family

ID=6396379

Family Applications (1)

Application Number Title Priority Date Filing Date
IE467790A IE904677A1 (en) 1989-12-23 1990-12-21 Composite membrane, process for its production and its use

Country Status (3)

Country Link
DE (1) DE3942868A1 (en)
IE (1) IE904677A1 (en)
WO (1) WO1991009670A1 (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5160353A (en) * 1990-08-30 1992-11-03 E. I. Du Pont De Nemours & Company Gas separation membrane with ultrathin layer

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3892665A (en) * 1973-10-15 1975-07-01 Standard Oil Co Membrane method and product
US4155793A (en) * 1977-11-21 1979-05-22 General Electric Company Continuous preparation of ultrathin polymeric membrane laminates
JPS58223411A (en) * 1982-06-21 1983-12-26 Matsushita Electric Ind Co Ltd Composite film for selective permeation of gas
JPS59222204A (en) * 1983-04-26 1984-12-13 Asahi Glass Co Ltd Compound membrane for separating gas
KR860001604A (en) * 1984-08-13 1986-03-20 아놀드 하베이롤 Composite Gas Separator
GB8527213D0 (en) * 1985-11-05 1985-12-11 British Petroleum Co Plc Separation process

Also Published As

Publication number Publication date
WO1991009670A1 (en) 1991-07-11
DE3942868A1 (en) 1991-06-27

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