Classifications

• • 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
  • B01D63/06—Tubular membrane modules
  • B01D63/061—Manufacturing thereof
• • 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
  • B01D69/04—Tubular membranes
• • 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
  • B01D69/10—Supported membranes; Membrane supports
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04B—KNITTING
  • D04B31/00—Crocheting processes for the production of fabrics or articles
• • D—TEXTILES; PAPER
  • D10—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
  • D10B—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
  • D10B2505/00—Industrial
  • D10B2505/04—Filters

Definitions

• the invention relates to a method for producing tubular membranes.
• EP 0 349 914 B1 discloses a method for producing tubular nonwoven bodies from a strip of a thermoplastic carrier nonwoven, which is wound up to form a nonwoven tube in the form of a spiral in such a way that the longitudinal edges of the strip along at least one in the wound area of the nonwoven tube Overlap the connecting seam, the longitudinal edges being thermally welded to one another to form this connecting seam.
• a hollow rod is formed which has an outlet opening at its free end through which a coating solution can be applied to the inner wall of the wound nonwoven tube, a tubular membrane being formed by the subsequent contact with a coagulation solution.
• tubular membranes are particularly suitable for ultrafiltration and nanofiltration, the membranes in question form microporous filter media, the passage pores of which are so small that they not only form a barrier for particles of all types and shapes, such as impurities, heavy metals etc. but also for all microorganisms, for example in the form of bacteria, parasites and viruses.
• the active layer of the membranes is also referred to in technical terminology as a semipermeable layer.
• a disadvantage of the tubular membranes produced in this way is that they often tear open under the pressure load of the fluid to be filtered in the area of the thermal connecting seams and accordingly fail.
• German Offenlegungsschrift 2 255 989 to surround the otherwise thin and fragile, semi-permeable membrane tubes on the outer circumference with a reinforcement in the form of a fiber braid structure in order to counteract the high hydraulic internal pressure Act; only the known method is complex and therefore expensive to manufacture, and the reinforcing fiber braiding structure lying directly against the semipermeable membrane adversely affects the flow and filtration behavior of the tubular membrane. bran.
• DE 199 09 930 A1 proposes a tubular composite made of a braid of thread bundles and / or wires, preferably in the form of an electron-conducting material and a layer of an ion-conducting material arranged above, as a fuel cell element.
• a so-called PEM fuel cell it is proposed, among other things, for producing a so-called PEM fuel cell, to produce the tubular inner electrode consisting of carbon fibers and / or metal wires by means of a braiding machine.
• This tubular braid runs for centering on a mandrel up to an application nozzle for the catalyst coating, the nozzle diameter determining the thickness of the catalyst layer.
• a short drying section through e.g. B. ceramic the coated braid passes through an annular gap nozzle through which the ion-conductive membrane is applied in the form of a polymer solution. This step is followed by a longer drying section to drive off the solvent.
• a second catalyst layer is applied with an application nozzle and then the outer electrode is braided around the still pasty catalyst layer.
• the paste-like consistency of the catalyst layer allows the braided strands to penetrate and thus an intimate bond between the catalyst and the electrode.
• this tubular composite consisting at least partially of a flat thread mesh is exposed to correspondingly high fluid pressures, it cannot be ruled out that the longitudinal and transverse tensile stresses in the thread mesh cause the threads to shift relative to one another, and this can lead to undesirable stretching effects, in particular also in the manufacture of the braid before the actual coating with the membrane material, which has the consequence that the known tubular membrane takes on a shape, in particular changes in the diameter range in such a way that it can become unsuitable for later use.
• the object of the invention is to further improve the known technical process solutions for the production of tubular membranes in such a way that functionally reliable tubular membranes can be obtained at high production speed and at low cost, neither during their manufacture nor during later operation exhibit undesirable stretching effects with changes in the membrane geometry.
• a related problem is solved by a method with the features of claim 1 in its entirety.
• a tubular body is constructed from several threads in such a way that along web-like connecting lines there is an essentially firm connection of at least some of the threads, that between the web-like connecting lines at least some of the threads make the cross-connection between the adjacent connecting lines, and that a specifiable membrane material is applied to the tubular body, this results in a great deal Cost-effective manufacturing process with which very high ejection rates on tubular membranes can be obtained.
• tubular bodies can be obtained prior to the application of the membrane material, in the manner of a knitted conductor or circular conductor knitting and with the mentioned knitted conductor pattern, any longitudinal tensile stresses that occur can be reliably absorbed by means of continuous longitudinal threads along the web-like connecting lines.
• the looping at the crossing points of the conductor knitting pattern that is to say at the points of the essentially fixed connection between the connecting lines and the above-mentioned cross-connections, prevents the thread systems from shifting against one another and the undesired stretching effect described during the coating is minimized, with the fabric-reinforced in this way Filtration capillary withstands very high internal pressures and mechanically applied longitudinal tensile forces.
• the wrapping at the points of the fixed link between connecting lines and cross connections means that there can be no displacements, so that any longitudinal or transverse movements of the thread system are determined solely by the inherent elasticity of the thread material used.
• using the method according to the invention results in tubular bodies that are very stable in shape and pressure, both in the manufacture of the membrane tubes and in their later ones Use in the ultra or nanofiltration range of fluids of any kind, including in the areas of water and beverage treatment.
• the tubular body designed as a knitted conductor is created by means of a mechanical crochet device, with each thread used being assigned its own hook or crochet needle.
• crocheting is a process of hanging, whereby with the help of the hook or crochet needle the thread is formed into loops "in the air", ie without a base, whereby the intertwined loops can be combined into patterns.
• the crochet device it is possible to insert supporting or holding threads continuously along the web-like connecting lines in order to create a kind of basic structure in order to then use the further threads for the looping at the crossing points along the connecting lines and to produce the cross thread connection between the mentioned connecting lines.
• the tubular body is preferably created by crocheting in such a way that fluid passage points with a high flow rate are formed between the individual cross connections, the web-like connecting lines being essentially fluid-tight or with a lower flow rate.
• the threads mentioned are selected from the group
• plastic materials such as polyester, polyaramides, other polymers, carbon, Kevlar etc. or
• the metal materials such as nickel, platinum, palladium, gold, silver, stainless steels etc. or -
• the catalytically active materials such as ruthenium, rhodium, iridium, nickel etc. or
• the other materials such as cellulose acetate, glass fibers, graphite powder, activated carbon etc. or
• thread is to be drawn broadly and, in addition to the usual monofilament and multifilament threads, also includes other linear elements such as yarns, wires or rod-like components, also made from powders.
• the adjacent cross connections that are arranged in this way between two connecting lines delimit an angle between them of 10 ° to 70 °, preferably of approximately 25 ° to 45 °, particularly preferably of approximately 30 °.
• the tubular body is coated with a membrane-activatable substance which is passed through a precipitation bath, the substance being converted into a microporous membrane layer.
• Particularly suitable membrane materials are those from the group of plastic materials, such as polyether sulfone (PES), polysulfone (PSU), polyacrylonitrile (PAN) or polyvinylidene fluoride (PVDF).
• PES polyether sulfone
• PSU polysulfone
• PAN polyacrylonitrile
• PVDF polyvinylidene fluoride
• the method according to the invention for producing tubular membranes provides that a tubular body, designated as a whole by 10, is constructed from a plurality of threads 12 in such a way that an essentially firm connection of at least part of the threads 12 takes place along web-like connecting lines 14, between the web-like connecting lines 14 at least some of the threads 12 make the cross connection 16 between the adjacent connecting lines 14, and a predeterminable membrane material 18 is applied to the tubular body 10.
• the web-like connecting lines 14 form a type of longitudinal thread system that forms a type of knitted conductor, in particular circular knitted fabric, via the transverse threads 12 of the respective transverse connection 16.
• the tubular body 10 is produced by means of an industrial crochet device, with each thread used being assigned its own hook or crochet needle. Since mechanical crochet devices are state of the art, no further reference is made to the crochet production of the tubular body 10. In any case, the tubular body 10 is created by the aforementioned crochet in such a way that fluid passage points 20 with a high flow rate are formed between the individual cross connections 16 in the form of the transverse threads 12 in question, the web-like connecting lines 14 as longitudinal thread system being designed to be essentially fluid-tight or with a correspondingly lower flow rate.
• the threads 12 used for the cross-connections 16 and for their connection to one another along the points 22 in the transition region to the web-like connecting lines 14 consist of multifilament plastic threads, for example of polyester or polyaramides, whereby other polymers can also be used here.
• the longitudinal threads along the web-like connecting lines 14 are made of carbon fiber materials. If, for example, one wants to use the tubular membrane in question as a fuel cell element or the like, it is possible to construct part of the threads from an electron-conducting material and another part of the threads from an ion-conducting material.
• the thread system which acts as an ion conductor can be provided with a catalyst layer which can additionally be provided with hydrophobicizing agents and / or proton conductor material. It is also possible in this way to use the tubular membrane described as a bipolar ion exchange membrane in order to obtain lactic acid or the like in this way.
• the electrical charge potential of the tubular membrane can also be specified.
• the tubular body 10 consists of eight connecting lines 14 and eight cross-connecting surfaces 16.
• tubular bodies 10 which are constructed from six connecting lines 14 and six cross-connections 16, have proven to be particularly advantageous. The minimum requirement for building a tubular body 10 with a triangular cross section (not shown) is to build it from three connecting lines 14 with three cross connections 16.
• the tubular body 10 produced in this way is passed through a precipitation bath, the substance being converted into a microporous membrane layer.
• a precipitation bath Such a method is disclosed by way of example in WO 03/076055 A1, so that it will not be discussed in detail here.
• the known solution according to the WO publication relates to a process for the production of fabric-reinforced capillary membranes, in particular for ultrafiltration, in which a fabric tube is coated with a polymer solution and passed through a precipitation bath, the conversion of the polymer solution into a microporous layer in the precipitation bath he follows. In this way, a membrane reinforced by the fabric tube is formed.
• the fabric hose coated with the polymer solution passes through the precipitation bath without mechanical contact from top to bottom and exits through a nozzle on the underside. Liquid flows out through the nozzle and exerts a tensile force which stabilizes the running of the coated fabric tube on the capillary membrane leaving the precipitation bath.
• the relevant coating process is only selected as an example and there are a large number of other coating processes including immersion bath processes which can be used here.
• the membrane material is one from the group of plastic materials. selects like polyether sulfone (PES), polysulfone (PSU), polyacrylonitrile (PAN) or polyvinylidene fluoride (PVDF).
• the tubular membrane according to the invention can be produced continuously and therefore inexpensively, ie. H. the tubular body 10 is permanently provided via the crochet process for the subsequent coating process with the membrane material 18.
• the filter material in the form of a knitted conductor or circular conductor knit using conventional crochet technology, a filter pipe is formed in which the longitudinal tensile stresses occurring during the filtration are created are taken up by the continuous longitudinal threads along the web-like connecting lines 14, the tensions on the circumference being reliably absorbed by the transverse threads 12 of the fabric layer composite by means of the flat cross connections 16.
• the looping at the crossing points (balls 22) reduces the displacement of the threads 12 against one another, so that undesirable stretching effects in the longitudinal direction as well as in the transverse direction of the tubular body 10 are significantly minimized during the coating with the membrane material and the filtration capillary, which is reinforced in this way, withstands very high internal pressures and Longitudinal lines in the filtration.
• threads 12 with a diameter of 20 to 200 ⁇ m can be used as thread thickness and the number of threads along lines 14 is preferably three to six pieces.
• the technical solution selected as a circular conductor knit tensile strengths of 100 N / mm 2 can be achieved with an elongation at break of 1 to 5% and in the dynamic pressure test such pipes hold a burst pressure of approx without further ado, with a shortening of the tube of only 1% being observed, so that the membrane tube according to the invention, which is designed as a circular conductor knit, is securely fixed in a holding device, in particular in the form of at least one module (not shown) of an overall filtration system.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Textile Engineering (AREA)
• Separation Using Semi-Permeable Membranes (AREA)
• Shaping Of Tube Ends By Bending Or Straightening (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

Family

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Family Applications (1)

Country Status (8)

Cited By (7)

Families Citing this family (16)

Citations (4)

Family Cites Families (14)

• 2003
  • 2003-12-11 DE DE10358477A patent/DE10358477B3/de not_active Expired - Fee Related
• 2004
  • 2004-09-17 ES ES04765330T patent/ES2293325T3/es not_active Expired - Lifetime
  • 2004-09-17 EP EP04765330A patent/EP1689517B1/de not_active Expired - Lifetime
  • 2004-09-17 CA CA002548409A patent/CA2548409A1/en not_active Abandoned
  • 2004-09-17 AT AT04765330T patent/ATE376874T1/de not_active IP Right Cessation
  • 2004-09-17 DE DE502004005399T patent/DE502004005399D1/de not_active Expired - Lifetime
  • 2004-09-17 JP JP2006543375A patent/JP4718481B2/ja not_active Expired - Fee Related
  • 2004-09-17 US US10/582,349 patent/US8393479B2/en not_active Expired - Fee Related
  • 2004-09-17 WO PCT/EP2004/010434 patent/WO2005061081A1/de not_active Ceased

Patent Citations (4)

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