Abstract
The present invention is related to a method for fabricating multilayer singlebore membranes (10) or multilayer multibore membranes (20) for ultrafiltration applications including the following method steps: (a) feeding at least a material of a substrate (12), at least one material of a functional layer (14, 15) and a bore fluid (36) to a spinneret (30) simultaneously; (b) forming said membranes (10, 20) as a tube-like string (54) in a one-step process in said spinneret (30); (c) thereby assigning a functionality to said functional layer (14, 15) applied on at least one surface (13, 17) of said substrate (12). The invention is also related to a spinneret (30) for fabricating multilayer singlebore membranes (10) or multilayer multibore membranes (20), using the inventive method, and to a system comprising such a spinneret (30).
Claims
1. A method for fabricating multilayer multibore membranes, the method comprising the following: (a) feeding at least a material of a substrate, a material of a first functional layer, a material of a second functional layer which is different from the material of the first functional layer and a bore fluid to a spinneret simultaneously; (b) forming said multilayer multibore membranes as a tube-like string in a one-step process in said spinneret; and (c) thereby assigning functionality to said first and second functional layers, wherein said first functional layer is applied to an inner surface of said substrate, and said second functional layer is applied to an outer surface of said substrate, whereat said first functional layer surrounds several bores; and wherein said material of said substrate comprises a first polymer, said material of said first functional layer comprises a second polymer, and said material of said second functional layer comprises a third polymer; said first, second and third polymers being different with respect to each other.
2. The method of claim 1, wherein said tube-like string is guided through a precipitation bath and/or a coagulation bath.
3. The method of claim 2, wherein said tube-like string is fed to a water spray arranged downstream with respect to said precipitation bath and/or said coagulation bath.
4. The method of claim 1, wherein said functionality of said first functional layer and said second functional layer is an anti-fouling function and/or an isoporous function.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The subject-matter of the present invention is disclosed in more detail in connection with the accompanying drawings showing:
(2) FIG. 1: A multilayer singlebore membrane,
(3) FIG. 2: multilayer multibore membranes,
(4) FIG. 3: a rough process of fabricating a multilayer singlebore membrane,
(5) FIG. 4: the components of a system for fabricating multilayer singlebore or multilayer multi-bore membranes,
(6) FIG. 5: a cross-sectional view of a spinneret according to the present invention,
(7) FIG. 6: a side view of said spinneret according to FIG. 5,
(8) FIG. 7: a view at the lower side of the spinneret according to FIG. 5,
(9) FIG. 8: a detail of the outlet opening of the lower side of the spinneret according to FIG. 7,
(10) FIG. 9: a sectional view of said spinneret showing the inner and outer funnel sections in greater detail,
(11) FIG. 10: an exploded view of the components of the spinneret when separated from one another.
PREFERRED EMBODIMENTS OF THE PRESENT INVENTION
(12) FIG. 1 shows a multilayer singlebore membrane 10.
(13) The multilayer singlebore membrane 10 according to FIG. 1 includes a substrate 12 of annular shape having an inner surface 13 and an outer surface 17. Here, the inner surface 13 is directed towards the center of the annular shape of the substrate 12 and the outer surface 17 is directed to the outside of the annular shape of the substrate 12. Onto the inner surface 13 a material of a functional layer 14 is applied. The functional layer 14 surrounds a bore 16 for a liquid to be treated or filtered.
(14) The singlebore membrane 10 given here contains exactly two layers, namely the substrate 12 and the functional layer 14. But, another functional layer 14 could be applied to the outer surface 17 of the substrate 12. Furthermore, one or more functional layers 14 could be applied to a functional layer 14 that is applied directly to the inner surface 13 or to the outer surface 17 of the substrate 12. Hence, the singlebore membrane 10 could contain for example three, four or more layers.
(15) The material of the substrate 12 is a first polymer such as PESU material providing a mechanical support and being the bulk material. The material of the functional layer 14 adopts an anti-fouling function and/or an isoporous function. According to the present invention, the material of the functional layer 14 is concentrated in a relatively thin layer thickness, so that high efficiency on the one hand and on the other hand lower material costs can be achieved. The material to be chosen to apply a functionality according to the properties of the functional layer gives a high flexibility to tailor the material of the functional layer 14 according to the applications envisaged, for instance ultrafiltration applications. Since the material having the functional properties, i.e. functional layer 14, can be chosen independently from the material for the substrate 12, no change of the bulk material property, i.e. no change of the material for the substrate 12, is necessary.
(16) In FIG. 2, two kinds of multilayer multibore membranes 20 are shown.
(17) According to FIG. 2a, the multilayer multibore membrane 20 comprises the substrate 12, i.e. a first polymer, with a circular cross-section having several, presently seven, holes arranged therein. The inner surface 13 of the substrate 12 is the amount of area at the sides of said holes directed towards the centers of said holes. The outer surface 17 of the substrate 12 is directed to the outside of the substrate 12. The multilayer multibore membrane 20 also comprises the material forming the functional layer 14 on the respective inner surface 13 of the material of the substrate 12. The functional layer 14 surrounds several bores 16 for the liquid to be treated or filtered.
(18) The multibore membrane 20 given in FIG. 2a contains exactly two layers, namely the substrate 12 and the functional layer 14. Furthermore, one or more functional layers 14 could be applied to the functional layer 14 that is applied directly to the inner surface 13 of the substrate 12. Hence, the multibore membrane 20 according to FIG. 2a could contain for example three, four, five or more layers.
(19) According to FIG. 2b, the multilayer multibore membrane 20 also comprises the substrate 12, i.e. a first polymer, with a circular cross-section having several, presently seven, holes arranged therein. The inner surface 13 of the substrate 12 is the amount of area at the sides of said holes directed towards the centers of said holes. The outer surface 17 of the substrate 12 is directed to the outside of the substrate 12. The multilayer multibore membrane 20 also comprises the material forming the functional layer 14 on the respective inner surface 13 of the material of the substrate 12. The functional layer 14 surrounds several bores 16 for the liquid to be treated or filtered. An additional functional layer 15 is applied to the outer surface 17 of the substrate 12.
(20) The multibore membrane 20 given in FIG. 2b contains exactly three layers, namely the substrate 12, the functional layer 14 and the additional functional layer 15. Furthermore, one or more functional layers 14, 15 could be applied to the functional layer 14 that is applied directly to the inner surface 13 of the substrate 12 or to the additional functional layer 15 that is applied directly to the outer surface 17 of the substrate 12. Hence, the multibore membrane 20 according to FIG. 2b could contain for example three, four, five or more layers.
(21) In FIG. 2b, the multibore membrane 20 is shown immediately after fabricating in a spinneret 30 when emerging the spinneret 30.
(22) In FIGS. 2a and 2b, reference numeral 18 depicts the flow direction of said liquid to be treated; a liquid to be treated may be either sea water or waste water, to give examples.
(23) While the material for substrate 12 is considered to be the bulk material, it usually is a first polymer which offers mechanical support such as for example PESU material.
(24) The material forming the functional layer 14 is a second polymer that may implement an anti-fouling function or an isoporous function or both of them. The material forming the additional functional layer 15 is another polymer that also may implement an anti-fouling function or an isoporous function or both of them. The polymer of the additional functional layer 15 can of the same material as the second polymer of the functional layer 14.
(25) One embodiment of the anti-fouling functionality is given by PESU-b-PEGMA:
(26) Another embodiment may be given by sPPSU:
(27) A still further embodiment of an anti-fouling functionality is given by PS-b-PEGMA:
(28) On the other hand, the functionality coming along with an isoporous function is embodied by S/DPE-b-4-Vpy:
(29) According to FIG. 3, a multilayer singlebore membrane 10 as shown in FIG. 1 is fabricated in a spinneret 30 which is shown here schematically only. According to the schematic view in FIG. 3, said spinneret 30 includes a flow 32 of a first polymer, a flow 34 of a second polymer and a flow 36 of a bore fluid. Said first polymer, said second polymer and said bore fluid are fed to the spinneret 30 substantially simultaneously. At the lower hand of the outlet side of the spinneret 30, a tube-shaped string of a multilayer singlebore membrane 10 is formed. Said tube-shaped string is fed to a precipitation bath 38. In the area of the precipitation bath 38, it can be derived from FIG. 3 that said material of the functional layer 14 has a relatively thin thickness as compared to the thickness of the material of the substrate 12. A bore 16 within the hollow multilayer singlebore membrane 10 is maintained by said bore fluid 36, which is fed to the center portion of the spinneret 30 according to the schematically given view in FIG. 3.
(30) FIG. 3 still further shows a top view of a multilayer singlebore membrane 10. It can be derived from FIG. 3 that the relatively thin material of the functional layer 14 is arranged on the surface 13 of the tube-like shaped material for forming the substrate 12, i.e. the first polymer. The bore 16 allows a flow of liquid to be treated by means of the multilayer singlebore membrane 10 according to the present invention.
(31) FIG. 4 shows a system for a larger scale fabrication of either multilayer singlebore membranes 10 or multilayer multibore membranes 20 according to the present invention.
(32) According to FIG. 4, said system comprises a number of components. To start with, said system comprises a first material dispensing station 42 for the material of a substrate 12. The material 12 of a substrate is fed as a flow 32 of the first polymer towards the spinneret 30, particularly a dual-layer forming spinneret 30, as schematically shown in conjunction with FIG. 3.
(33) Said system according to FIG. 4 still further comprises a second material-dispensing station 44 storing the material for forming the functional layer 14. The flow 34 of the second polymer is established from the second material dispensing station 44 to the spinneret 30, i.e. particularly a dual-layer spinneret 30, which is likewise included in the system according to FIG. 4.
(34) Still further, the system according to FIG. 4 comprises a third material dispensing station 46 for the bore fluid.
(35) The flow of the bore fluid 36 is identified in the schematic view of the system according to the present invention in FIG. 4 by reference number 36. All three materials are simultaneously fed to the spinneret 30 arranged in the center of the system according to FIG. 4.
(36) As can be derived from FIG. 4, in the path of flow 32 of the first polymer, a first dosing valve 48 and a second dosing valve 50 are arranged.
(37) At the outlet portion of the spinneret 30 of the system shown in FIG. 4, a tube-like string 54 of a multilayer singlebore membrane 10 is formed. Within a further path of transportation thereof, in transport direction 58, a number of deviation elements 56 are arranged. Said deviation elements 56 are arranged within a coagulation bath 52. By means of the deviation elements 56, the path of the tube-like shaped string 54 of the multilayer singlebore membrane 10 through the coagulation bath 52 is elongated.
(38) Downstream of said coagulation bath 52, seen in transport direction 58 of said tube-shaped string 54 of the multilayer singlebore membrane 10, a water spray 64 is arranged. Said water spray 64 includes a roller 60. On said roller's surface 62 the water spray 64 is applied, for instance in vertical direction as shown in FIG. 4.
(39) Downstream of said water spray 64 a flushing bath 66 is arranged within which the endless tube-like shaped string, i.e. the generated multilayer singlebore membrane 10, is collected.
(40) FIGS. 5, 6, 7 and 8, respectively, show details of a spinneret 30 for fabricating a multilayer multibore membrane 20 as schematically shown in FIG. 2.
(41) FIG. 5 discloses a spinneret 30, particularly a dual-layer spinneret 30. Said spinneret 30 according to the cross-sectional view given in FIG. 5 comprises a center part 70, a cone-shaped part 72 and a lower part 74, respectively. FIG. 5 shows said parts 70, 72, 74 in an assembled state of the spinneret 30. The center part 70 includes a central feed 80 for the bore fluid 36. At the lower end of the central feed 70, a tip-like nozzle arrangement is provided. Said center part 70 of the spinneret 30 is mounted within the cone-shaped part 72 of the spinneret 70. Said cone-shaped part 72 of the spinneret 30 comprises a laterally arranged second feed 78 for the second polymer. As can be derived from the assembly given in FIG. 5, opposite with respect to the second feed 78 for the second polymer, on the corresponding section of the center part 70, a second annular channel 90 is arranged, allowing for transportation of the second polymer to an inner funnel section 82 of said spinneret 30.
(42) Further, according to FIG. 5, said cone-shaped part 72 of the spinneret 30 is mounted within the lower part 74 of the spinneret 30. The lower part 74 comprises a first feed 76, likewise extending in lateral direction with respect to the center axis of the spinneret 30 shown in the cross-sectional view according to FIG. 5. Opposite with respect to the first feed 76 for the first polymer, said cone-shaped part 72 of the spinneret 30 comprises a first annular channel 88, allowing for transportation of the first polymer to an outer funnel section 84 of said spinneret 30.
(43) The spinneret 30 shown here allows fabricating membranes 10, 20 with two layers, namely with a substrate 12 and with a functional layer 14. A spinneret 30 for fabricating membranes 10, 20 with more than two layers is also feasible. Such a spinneret 30 for fabricating membranes 10, 20 with more than two layers has individual feeds for every layer of the multilayer membrane to be formed.
(44) According to the cross-sectional view according to FIG. 5, the inner funnel section 82 is defined between the outer contour of the center part 70 of the spinneret 30 on the one hand and on the other hand by the inner contour of said cone-shaped part 72 of the spinneret 30. The inner funnel section 82 is fed from the second annular channel 90, which in turn is in connection with the second feed 78 for the second polymer. Thus, a flow of the second polymer from the second feed 78 to the inner funnel section 82 within the spinneret 30 is established.
(45) Between the outer contour of the cone-shaped part 72 and the inner contour of the lower part 74 of the spinneret 30, the outer funnel section 84 is defined. Said outer funnel section 84 is fed from the first annular channel 88, which is in connection with the first feed 76 for the first polymer. Thus, the outer funnel section 84 is fed with the first polymer, i.e. the material of a substrate 12.
(46) As can be derived from FIG. 5, however better shown in an enlarged view according to FIG. 9, said spinneret 30 given in FIG. 5 comprises a tube section 86. Said tube section 86 includes a number of single tubes 87 as best shown in an enlarged view according to FIG. 9. Said single tubes 87 form the bores 16, i.e. hollow spaces, within which the liquid to be treated, for instance sea water or waste water, flows through the multilayer multibore membrane 20, see FIG. 2, as fabricated with the spinneret 30, the cross-sectional view of which is given in FIG. 5.
(47) FIG. 6 shows the spinneret 30 in a side view.
(48) According to the side view given in FIG. 6, the spinneret 30 comprises the center part 70, mounted in the cone-shaped part 72, having the second feed 78 for the second polymer, being the material forming the functional layer 14 and the lower part 74. The cross-sectional view shown in FIG. 5 is indicated in the side view according to FIG. 6 by intersection line V-V.
(49) FIG. 7 shows the lower end of the spinneret 30 according to FIG. 5.
(50) In the center portion of the lower part 74, the pattern of the multibore arrangement of the multi-layer multibore membrane 20 according to FIG. 2 can be seen. This detail is shown in an enlarged view according to FIG. 8, which shows the tube section 86 having a number of single tubes 87 ending at the lower side of the lower part 74 of the spinneret 30.
(51) FIG. 9 shows the lower section of the spinneret 30, the cross-sectional view of which is given in FIG. 5, in a greater scale.
(52) According to the cross-sectional view given in FIG. 9, it is disclosed that the inner funnel section 82 is fed with the second polymer, induced by the second feed 78.
(53) The single tubes 87 forming the tube section 86 extend to the inner funnel section 82, defined between the center part 70 and the cone-shaped part 72 of the spinneret 30.
(54) The outer funnel section 84 established between the cone-shaped part 72 of the spinneret 30 and the inner contour of the lower part 74 of the spinneret 30 is fed through a gap vertically extending from the first feed 76 as best shown in the cross-sectional view according to FIG. 5 of the spinneret 30. Likewise, said single tubes 87 of the tube section 86 extend to the outer funnel section 84 as well.
(55) Thus, downstream of the outer funnel section 84 the tube-like string 54 of the multilayer multi-bore membrane 20 is formed in an endless manner by continuously feeding the first polymer to the first feed 76, the second polymer to the second feed 78 and the bore fluid 36 to the central feed 80 arranged in the center part 70 of the spinneret 30.
(56) As can be derived from the enlarged view in FIG. 8, this pattern of tubes 87 corresponds to the pattern of bores 16 given in FIG. 2, showing the multilayer multibore membrane 20, fabricated by the dual-layer multibore spinneret 30 schematically shown in the cross-sectional view according to FIG. 5 and in larger detail in the cross-sectional view according to FIG. 9.
(57) As can be derived from FIG. 9, the tube-shaped string 54 fabricated within the dual-layer multibore spinneret 30 comprises a number of bores 16, encapsulated by the material of the functional layer 14 which in turn is surrounded by the material of the substrate 12.
(58) FIG. 10 shows an exploded view of the components of the spinneret, in this case a dual-layer spinneret.
(59) As best shown in the exploded view according to FIG. 10, the spinneret 30 comprises the lower part 74, the cone-shaped part 72 as well as the center part 70. Between the cone-shaped part 72 and the lower part 74, a ring-shaped sealing element 92 is arranged. A further sealing element 92 is arranged between the cone-shaped part 72 and the center part 70 of the spinneret 30 according to the exploded view in FIG. 10. The parts 70, 72, 74 are centered with respect to each other by at least one centering rod 94. Fastening elements 96 extend through openings 98 of the center part 70 and the cone-shaped part 72, respectively, cooperating with corresponding threads in lower part 74, although not shown here.
(60) It can be derived from FIG. 10 that the cone-shaped part 72 comprises the second annular channel 90 cooperating with the second feed 78 according to the cross-sectional view given in FIG. 5, whereas the first annular channel 88 of the lower part 74 corresponds with the first feed 76 for the first polymer.
REFERENCE NUMERAL LIST
(61) 10 multilayer singlebore membrane 82 inner funnel section (for 14)
(62) 12 substrate (support) (polymer 1) 84 outer funnel section (for 12)
(63) 13 inner surface (of 12) 86 tube section (for 36)
(64) 14 functional layer (polymer 2) 87 single tube
(65) 15 additional functional layer 88 first annular channel (of 72)
(66) 16 bore (free cross-section) 90 second annular channel (of 70)
(67) 17 outer surface (of 12) 92 sealing element
(68) 18 flow direction 94 centering rod
(69) 20 multilayer multibore membrane 96 fastening elements
(70) 30 spinneret (dual-layer) 98 through-openings
(71) 32 flow of polymer 1 V intersection line
(72) 34 flow of polymer 2
(73) 36 bore fluid (third material)
(74) 38 precipitation bath
(75) 40 functional material (hydrophilic, isoporous properties)
(76) 42 first material dispensing station (substrate 12)
(77) 44 second material dispensing station (functional layer 14)
(78) 46 third material dispensing station (bore fluid 36)
(79) 48 first dosing valve
(80) 50 second dosing valve
(81) 52 coagulation bath
(82) 54 tube-like string
(83) 56 deviation elements
(84) 58 transport direction
(85) 60 roller
(86) 62 roller surface
(87) 64 water spray
(88) 66 flushing bath
(89) 70 center part (of spinneret)
(90) 72 cone-shaped part (of spinneret)
(91) 74 lower part (of spinneret)
(92) 76 first feed (of 74 for 12/polymer 1)
(93) 78 second feed (of 72 for 14/polymer 2)
(94) 80 central feed (of 70 for third material bore fluid 36)
