Flat membrane with an integral column

Abstract

A membrane, such as a flat sheet membrane, has columns extending from a separation layer. The columns extend through one or more support structures such as, for example, a base layer and / or a porous carrier, or the columns extend between two separation layers, or both. The columns can help connect the separation layer to the support structure, connect two support structures together, reinforce the support structure, and / or connect two separation layers together. In some examples, one or more support structures that can be temporary or remain in the membrane are made to have openings for the columns. A liquid containing separation layer material is poured onto one or more support structures, and some of the liquid flows at least partially through the openings before the liquid solidifies. The temporary support structure can be removed, for example, dissolved. In other examples, while the columns are being formed, two support structures are kept separate in a casting die.

Description

[0001] Related Applications

[0002] This application claims the benefit and priority of U.S. Provisional Patent Application No. 62 / 811,689, filed on February 28, 2019, for a flat sheet membrane with integral pillars, which is incorporated herein by reference. Technical Field

[0003] This specification relates to filtration membranes, such as microfiltration, ultrafiltration, nanofiltration, or reverse osmosis membranes, optionally in flat sheet form. Background Art

[0004] Flat sheet filtration membranes can be prepared by casting a liquid (which can be a mixture of liquids) onto a substrate and then curing the liquid to form a separation layer. The liquid can be a polymer solution (commonly referred to as a coating) or a two-part polymer forming solution. The substrate can be, for example, a woven fabric, a knitted fabric, or a non-woven fabric. The substrate is formed tightly relative to the viscosity of the liquid such that the liquid does not flow through the entire thickness of the substrate. The curing mechanism can be, for example, interfacial polymerization, non-solvent induced phase separation, or temperature induced phase separation. After casting, the coating cures in a bath to form a porous membrane. The resulting separation layer can have pores ranging from nanofiltration to microfiltration, typically ultrafiltration or microfiltration. Interfacial polymerization can be used to form a dense (i.e., substantially pore-free) separation layer in the reverse osmosis or nanofiltration range. In some cases, particularly for reverse osmosis membranes, there can be two liquid application steps, first forming a porous membrane on the substrate and then forming a dense membrane on the porous membrane.

[0005] Flat sheet membranes can be used, for example, in spiral wound, flat sheet and frame, or immersed flat sheet modules. In a typical spiral wound membrane, the membrane is formed with a separation layer on a non-woven substrate. The membrane is folded and / or sealed around its edges to form an envelope around the permeate carrier. The permeate carrier is a structure that can resist compression but has a void arrangement, such as raised stripes in a woven fabric, which allows the permeate to flow into and through the permeate carrier. One or more envelopes are wrapped around a central tube, and multiple layers of feed conveyors are provided between adjacent membrane layers. When in use, the entire structure is compressed and the membrane is further compressed against the permeate carrier by the applied feed liquid. Traditional flat sheet and frame modules have a similar membrane envelope around the permeate carrier, but the envelopes are assembled in a stack of parallel planar forms, usually (although not always) with feed conveyors sandwiched in between. Immersed flat sheet membrane modules also have a membrane material envelope around a planar form of permeate carrier, but without an intermediate feed conveyor layer. Spiral wound membranes and flat sheet and frame membranes include a housing that restricts the feed water from flowing through the membrane, while immersed membranes are submerged in a relatively large water tank, having a free surface and a less defined flow pattern. Immersed membranes tend to be assembled into large structural modules, such as having an area of 2 - 5 m in at least one perspective view 2, while single spiral and flat and frame modules tend to be more compact structures. The term "flat membrane" can refer to a single layer or envelope with a separation layer or other structures with two layers (each with a separation layer, surrounding the permeate collection space).

[0006] The permeate carrier keeps the two sides of the membrane envelope spaced apart from each other while providing a channel for the permeate flow to at least one collection point. Due to the transmembrane pressure applied during the filtration process, the permeate carrier resists the compression of the envelope. In some cases, especially for immersed membranes, the membrane is backwashed regularly. In these cases, the membrane is usually attached to the permeate carrier at least at some positions within its edges, and if there is no sufficiently close feed conveyor, the permeate carrier, any other substrate, adhesive, or other intermediate material must also resist the expansion of the membrane envelope. Various materials must also resist delamination (or other separation) within them or between them.

[0007] In one example of a backwashable immersed membrane sold by Microdyn-Nadir, the separation layer is cast onto a nonwoven substrate. The substrate is adhered to a permeate carrier in the form of a 3D spacer fabric by discontinuous adhesive sheets. This material has been rather successful in being used as an immersed membrane, but may become unstable during the filtration process under large transmembrane pressures or delaminate under frequent or high-pressure backwashing. In another example of a backwashable immersed membrane sold by Bluefoot, the membrane is cast directly onto a 3D spacer woven fabric with many filaments such that the outer layer of the 3D spacer fabric itself can act as the substrate. This material is not commonly used in the industry, but may have sufficient strength for filtration and backwashing. However, this material requires a thick separation layer because the outer layer of the 3D spacer fabric is not as smooth and dense as the nonwoven. The thick 3D spacer fabric also consumes a large amount of material. SUMMARY OF THE INVENTION

[0008] This specification describes one or more membranes that have integral columns extending from at least one separation layer of the membrane material. (a) The columns extend from the separation layer through one or more support structures such as, for example, a base layer and / or a permeate carrier, (b) the columns extend between two separation layers, or (c) both (a) and (b). The columns extending from the separation layer to or through one or more support structures help connect the separation layer to the support structure and / or connect two support structures together. The columns extending between two separation layers help connect the two separation layers to each other. During the filtration and / or backwashing process, the columns can respectively help resist the compression and / or expansion of the membrane. A membrane with two separation layers can have a continuous space (i.e., a space without a permeate carrier) or a discontinuous space (i.e., a space without a permeate carrier) between the two separation layers. The membrane can have a separation layer supported on a base layer or can have no separation layer (which is not supported on a base layer).

[0009] This specification describes one or more methods of manufacturing a membrane. In some examples, one or more support structures retained in the membrane are made to have openings for pillars. In some examples, temporary (i.e., soluble) support structures are made to have openings for pillars. For example, the support structure can optionally be pierced by a roller or a flat plate with protrusions, whether cold or hot, to create openings. A liquid containing a separation layer material, e.g., in the form of a coating or other mixture or solution, is poured onto one or more support structures, and before the liquid cures, some of the liquid at least partially flows through the openings. The temporary support structure can be removed during or after the step of curing the liquid. For example, the temporary structure can be dissolved. In other examples, two base layers or other support structures are made to have openings for pillars and are held apart, e.g., by a central plate or other component of a pouring assembly, while a liquid containing a separation layer material is poured onto one or more support structures. Some of the liquid flows through the openings and cures to form pillars extending between two separation layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic cross-section of a non-supported 3D membrane made of a soluble support structure.

[0011] Figure 2 is a schematic cross-section of a supported 3D membrane made of a soluble support structure.

[0012] Figure 3A is a schematic cross-section of another 3D membrane with a permanent support structure.

[0013] Figure 3B is a schematic cross-section of another supported 3D membrane with a permanent support structure.

[0014] Figure 4 is during the pouring step according to Figure 1 , Figure 2 , Figure 3A or Figure 3B is a schematic cross-section of a 3D membrane according to any one of.

[0015] Figure 5 is a schematic cross-section of a flat membrane with a separation layer and a base layer.

[0016] Figure 6 is a schematic cross-section of another membrane having two separation layers, two base layers, and a permeate carrier layer, which in this embodiment is a 3D spacer fabric bonded to the base layer by pillars or columns or by a separate adhesive (not shown) or both.

[0017] Figure 7Schematic cross-section of a 3D membrane made in the absence of a temporary support structure but with a permeation carrier that is intermittently or periodically compressed in this example.

[0018] Figure 8 Schematic cross-section of a supportable 3D membrane made in the absence of a temporary support structure or a permeation carrier.

[0019] Figure 9 Is of the manufacturing in use Figure 8 Cross-sectional side view of a casting assembly for a supportable 3D membrane.

[0020] Figure 10 Is Figure 9 Front view of the central plate of the casting assembly.

[0021] Figure 11 Is Figure 9 Top view of the casting assembly.

[0022] Figure 12 Schematic cross-section of a supportable 3D membrane made in the absence of a temporary support structure or a permeation carrier but with a wavy base layer. Detailed Description

[0023] This specification describes various membranes, such as flat membranes. The membrane can have a separation layer in the range of reverse osmosis, nanofiltration, ultrafiltration, or microfiltration, preferably ultrafiltration or microfiltration. For example, the membrane can be used in a housing (forming or not forming a traditional flat and frame type envelope) or as an immersed membrane module. In at least some examples, the membrane can be backwashed.

[0024] The term pillar refers to a structure extending from the separation layer of the membrane. The pillar can be integral with the separation layer, but it extends from the separation layer in terms of the typical thickness where the pillar deviates from the majority (i.e., at least 50% of the surface area) of the separation layer. In some cases, the pillar extends from one separation layer to the separation layer or the base layer on the other side of the membrane. A membrane having a pillar extending between two separation layers or otherwise from one side of the membrane to the other side of the membrane can be referred to as a 3D membrane.

[0025] Reference Figure 1 , shows a precursor of a first 3D membrane 10. The completed first 3D membrane 10 without a soluble substrate 14 is as Figure 2As shown. The first 3D film 10 has two separate layers 12 that are separated and connected together by columns 16. The columns 16 are made of the same material as the separation layers 12, which can be a porous membrane-forming coating (i.e., a liquid containing a polymer in a solvent), and may have other components that will form the separation layers. In this example, the columns 16 are formed before the liquid cures and become integral with the separation layers 12. The coating can include, for example, one or more polymers such as PVDF, PS, PES, PPEK, PPS, PVC, or CA and at least one organic solvent. When the soluble substrate 14 is removed, a permeate collection space for the non-permeable carrier is formed.

[0026] The separation layers 12 are formed directly on the soluble substrate 14. The soluble substrate 14 has a plurality of openings 18 that form the columns 16. The openings 18 can be formed, for example, by passing a roller with protrusions through the sheet of the soluble substrate 14, optionally by passing the sheet of the soluble substrate 14 through a pair of rollers, or by pressing a flat plate with protrusions (which can be cold or hot) against the soluble substrate 14. Alternatively, laser cutting or other suitable methods for making the openings 18 can be used, or the soluble substrate 14 (or any other material with the openings 18) can be made by a method that creates the openings 18 when forming the sheet of the soluble substrate 14. The openings 18 can be an orthogonal or staggered grid or other arrangement so that they are dispersed, preferably substantially uniformly dispersed over the area of the soluble substrate 14.

[0027] The soluble substrate 14 can be, for example, an open-cell or closed-cell foam sheet or a fabric sheet (e.g., a non-woven sheet) made of a soluble polymer such as hemicellulose or PVA. In some examples, a foam hemicellulose sheet with a porosity in the range of 60 - 90% can be used. The soluble substrate 14 can be in the range of 1 to 8 mm thick. The openings 18 can be cylindrical with a diameter in the range of 0.1 to 1.5 mm or other shapes with a similar cross-section. For example, the openings 18 can be arranged in an orthogonal or offset (i.e., staggered) grid with a spacing between the openings 18 in the range of 1 - 15 mm.

[0028] In one example, the release layer 12 is made of a coating that is cured by passing a precursor of the liquid coating through a cold dip bath. The soluble substrate 14 can be water-soluble and the cold dip bath can contain water. The soluble substrate 14 can dissolve in the cold dip bath, or in a subsequent bath (i.e., a downstream bath or at a later time), or partially dissolve in both. The soluble substrate 14 can dissolve at least partially when the coating is cured or not cured. If desired, the soluble substrate 14 can be allowed to dissolve at least partially before the coating is fully cured to provide a slightly uneven or wavy surface to the cured release layer 12. Alternatively, a flatter release layer 12 can be provided by restricting the amount (if any) of the soluble substrate 14 that dissolves before the coating is cured. The dissolution rate of the soluble substrate 14 can be changed, for example, by changing the density (i.e., porosity) of the soluble substrate 14 or the temperature of the bath. Optionally, the dissolution of the soluble substrate 14 in the first bath can be substantially prevented by flowing the coating around and over the edges of the soluble substrate 14. In this way, the soluble substrate 14 is substantially encapsulated in the coating and the release layer 12 after the coating is cured. In this case, at least a portion of the soluble substrate 14 can be delayed in dissolution until a later bath after the coating is fully cured to form the release layer 12. The first membrane 10 is cut to expose one or more edges of the soluble substrate 14 before the membrane is placed in a subsequent bath to dissolve the soluble substrate 14.

[0029] Figure 2 A precursor of the second 3D membrane 10 is shown. The completed second 3D membrane 10 is as Figure 2 shown but without the soluble substrate 14. The second 3D membrane 10 has two release layers 12 that are separated and connected by columns 16. The material of the columns 16 is the same as that of the release layer 12 and can be a porous membrane-forming coating. In this embodiment, the columns 16 are formed before the liquid cures and are formed integrally with the release layer 12. When the soluble substrate 14 is removed, a permeate collection space without a permeate carrier is formed.

[0030] The second 3D membrane 10 also includes a base layer 20 that is adjacent to the interior of each release layer 12. Each base layer 20 can be, for example, a woven, knitted, or non-woven sheet. In the completed second 3D membrane 10, the release layer 12 can adhere to the base layer 20 by chemical and / or physical forces.

[0031] A separation layer 12 is formed on a base layer 20 supported on a soluble substrate 14. The soluble substrate 14 and the base layer 20 have a plurality of corresponding openings 18 that form columns 16. The openings 18 can be formed, for example, by passing a roller with protrusions through the assembly of the soluble substrate 14 and the base layer 20, or by pressing a flat plate with protrusions against the assembly of the soluble substrate 14 and the base layer 20, or by any other method described for the soluble substrate 14. Alternatively, the openings 18 can be formed separately in the soluble substrate 14 and the base layer 20. The openings 18 can be in an orthogonal grid or other arrangement such that they are preferably evenly dispersed over the area of the soluble substrate 14 and the base layer 20.

[0032] In one example, the separation layer 12 is formed by curing a coating by passing a precursor through a cold dip bath. The soluble substrate 14 can be water-soluble and the cold dip bath can contain water. The soluble substrate 14 can be dissolved in the cold dip bath, dissolved in a subsequent bath, or partially dissolved in both. The soluble substrate 14 can be at least partially dissolved when the coating is cured or uncured. The dissolution rate of the soluble substrate 14 can be changed, for example, by changing the density of the soluble substrate 14 or the temperature of the bath. Optionally, dissolution of the soluble substrate 14 in the first bath can be substantially prevented by allowing the coating to flow around and cover the edges of the soluble substrate 14. In this case, dissolution of at least a portion of the soluble substrate 14 can be postponed to a subsequent bath after the coating has completely solidified. Before placing the membrane 10 in a subsequent bath, the second 3D membrane 10 is cut to expose one or more edges of the soluble substrate 14.

[0033] Figure 3A A third 3D membrane 10 is shown. Both the precursor and the completed third 3D membrane 10 can be as Figure 3A shown. The third 3D membrane 10 has two separation layers 12 that are separated and connected by columns 16. The columns 16 are made of the same material as the separation layer 12, which can be a porous membrane-forming coating. In this example, the columns 16 are formed before the liquid cures and become integral with the separation layer 12.

[0034] The third 3D membrane 10 also includes a permeation isolation zone 22 adjacent to the inside of each separation layer 12. The permeation isolation zone 22 can be, for example, a 3D spacer fabric, a mesh, a fabric such as a warp knitted fabric, or an extruded or rolled form such as an extruded sheet with internal channels. Optionally, the voids of the permeation isolation zone 22 can be temporarily filled with a soluble or otherwise removable material when the separation layer 12 is formed thereon. In the completed third 3D membrane 10, the separation layer 12 can be adhered to the permeation isolation zone 22 by chemical forces and / or physical forces. In Figure 3A the example, the permeation isolation zone 22 also serves as a substrate directly supporting at least one of the separation layers 12. Alternatively, in as Figure 3BThe fourth 3D film 10 shown in the figure can have a base layer 20 as shown between the permeation isolation zone 22 and the separation layer 12. Figure 2 The base layer 20, if any, can be combined or not combined with the permeation isolation zone 22. The base layer 20 can be, for example, a woven, knitted or non-woven sheet.

[0035] The separation layer 12 can be formed directly or indirectly on the permeation isolation zone 22. The permeation isolation zone 22 has a plurality of openings 18 that form columns 16. The openings 18 can be formed, for example, by passing a roller with protrusions through the permeation isolation zone 22, or by pressing a flat plate with protrusions against the permeation isolation zone 22, or by any other method described for the soluble substrate 14. The openings 18 are formed in any base layer 20 as Figure 2 described. In one example, the openings 18 are optionally formed, for example, during the 3D weaving process during the formation of the permeation isolation zone 22. The openings 18 can be in an orthogonal grid or other arrangement such that they are preferably evenly dispersed over the area of the permeation isolation zone 22.

[0036] In one example, the precursor is passed through a cold dip bath to cure the coating. The permeation isolation zone 22 remains as part of the completed third film 10 and is not dissolved in the bath or otherwise removed.

[0037] In Figure 1 、 Figure 2 、 Figure 3A and Figure 3B , the 3D film 10 is made of an outer separation layer 12 connected to each other by polymer columns 16. The polymer columns 16 are made of the same material as the separation layer 12 and are formed when the separation layer 12 is cast. The columns 16 are integral with the separation layer 12. The columns 16 pass through the gaps between the separation layers 12. The gap can contain or not contain one or more support structures such as, for example, the base layer 20 and / or the permeation isolation zone 22. In Figure 1 、 Figure 2 、 Figure 3A and Figure 3BIn the examples, the gap has a uniform thickness. However, in other examples, the gap may have a non-uniform thickness or may not exist over the entire region of the membrane 10. For example, in a corrugated membrane, the two base layers 20 may be joined to each other along multiple lines or other contact regions and may result in a self-supporting structure without a soluble or permanent support or permeation carrier. In such a case, the pillars 16 may be positioned along the contact regions and extend from one separation layer 12 through the two base layers 20 to the other separation layer. In all of these examples, the three-dimensional membrane is formed with one or more void spaces between the separation layers 12 (which may be void spaces that contain or do not contain a permeation carrier 22), and the separation layers 12 have or do not have support in addition to the pillars 16 for the separation layers 12. In various examples, the membrane 10 may have or may not have a base layer 20.

[0038] Figure 4 FIG. shows a schematic cross-sectional side view of the 3D membrane 10 during the casting step. A support structure that may include one or more of the soluble substrate 14, the base layer 20, and / or the permeation carrier 22 is pulled down by a casting knife 30 or what is referred to as a casting head or casting assembly. The casting knife 30 has a lower casting nozzle 32 and an upper casting nozzle 34. The opening 18 is mainly filled with a coating provided from the lower casting nozzle 32, which is optionally operated at a higher pressure than the upper casting nozzle 34. To improve coating flow and remove air from the opening 18, suction may be applied through a nozzle opposite the upper casting nozzle 34. Offsetting the nozzles 32, 34 and having different pressures for the nozzles 32, 34 helps to avoid trapping air in the opening 18.

[0039] Figure 5 FIG. is a schematic cross-section of a flat membrane 10 having a single separation layer 12 and a single base layer 20. The membrane 10 is made by casting a coating on a base layer 20 provided with an opening 18, as described in other parts of this specification. The resulting pillars 16 may help to adhere the separation layer 12 to the base layer 20 and / or may help to avoid separation or delamination of the base layer 20 itself. Optionally, envelopes or other structures may also be made using the flat membrane 10. For example, the flat membrane 10 may be assembled into a spiral membrane module, a flat and frame membrane module, or an immersed flat membrane module in the same manner as a conventional flat membrane, where the separation layer is simply coated on the base layer.

[0040] Figure 6 FIG. is a schematic cross-section of a membrane 10 having two separation layers 12, two base layers 20, and a permeation carrier 22. The permeation carrier 22 may be bonded to the base layer 20, for example, with or without a separate adhesive (not shown). For example, the flat membrane 10 may be as Figure 5fabricated as described in , and then joined (i.e., glued, welded, or solvent joined) to the permeation carrier 22. Alternatively, the separation layer 12 can be formed after the base layer 20 is placed (and optionally joined) on the permeation carrier 22. In this case, the pillars 16 can be joined to the permeation carrier 22. In another alternative, the permeation carrier 22 can have openings that partially extend into the permeation carrier but do not completely pass through the permeation carrier 22. In this option, the pillars 16 are anchored within the thickness of the permeation carrier 22 rather than being primarily joined to the surface of the permeation carrier.

[0041] In the example shown, although another permeation isolation zone can be used, the permeation isolation zone 22 is a 3D spacer fabric. A portion of the pillars 16 can be embedded in a portion of the outer layer of the 3D spacer fabric. However, relative to the forces applied during casting and the viscosity of the coating (or other separation layer forming liquid), the outer layer of the 3D spacer fabric is sufficiently filled with filaments such that the liquid does not completely pass through the outer layer of the 3D spacer fabric. The pillars 16 can be embedded in filaments that are only located in the outer layer of the 3D spacer fabric, or can also be embedded in filaments that pass through between the outer layers of the 3D spacer fabric.

[0042] The 3D spacer fabric can also be referred to as a double-sided fabric or a double-layered fabric, or, for brevity, as a 3D spacer or spacer fabric. The 3D spacer fabric is made, for example, by knitting or weaving such that it has an internal space between two outer layers. One or more threads that are also woven or knitted into the outer layers extend through the internal space to join the outer layers together and optionally also to space the outer layers apart. In some examples, the internal space between the two outer layers is further partially filled, for example, with another fabric layer. In use, the permeate flows through and exits from a drainage layer that has openings retained within the internal space of the spacer fabric. Examples of suitable spacer fabrics are described in: U.S. Patent No. US8,393,477B2, filtration media; International Publication No. WO2011 / 026879A1, a frame for supporting a filtration membrane; International Publication No. WO2008 / 141935A1, a membrane bag having a seamless membrane material, its use, and its filtration device; International Publication No. WO2012 / 098130A1, a three-dimensional fabric, an integrated permeation channel membrane comprising the fabric, and its use; U.S. Patent No. US7,862,718B2, an integrated permeation channel membrane; U.S. Patent Application Publication No. US2013 / 0186827A1, a forward osmosis membrane based on an IPC spacer fabric; U.S. Patent No. US6,634,190B2, a double-sided thick knitted fabric having a flexible structure; and German Utility Model 8902259U1. All of these publications are incorporated herein by reference. Warp-knitted spacer fabrics made for other applications, such as in the automotive interior or clothing fields, can also be used, such as products sold by Eastex Products, Apex Mills, or Jason Mills.

[0043] Figure 7 is a schematic cross-section of another 3D film made of an optional discontinuous or compressible permeation carrier 22. Two layers of substrate material 20 are in contact with each other, for example, in parallel lines or a grid or other layout of contact areas. The layers of substrate material 20 can be held together at the contact points, for example, by adhesives, heat welding, or laser welding, optionally having a compressed and optionally melted portion of the permeation carrier 22 therebetween. Openings 18 are formed as described in other parts of this specification. The columns 16 passing through between the separation layers 12 strengthen the bond between the substrate materials 20 in the contact area. Additional columns 16 outside the contact area are optional. The layers of substrate material 20 can be brought into contact with each other before, during, or after the application of the separation layer 12. In some examples, Figure 7 represents a modified example of a conventional immersion flat film, for example, manufactured by Kubota.

[0044] Figure 8 Shows a fifth 3D film 10. The fifth 3D film 10 is made without a permeation carrier and a soluble substrate. The fifth 3D film 10 has two separation layers 12 separated and connected by columns 16. The columns 16 are made of the same material as the separation layers 12, which can be a porous membrane-forming coating. In this example, the columns 16 are formed before the liquid cures and are formed integrally with the separation layers 12.

[0045] The fifth 3D film 10 also includes a base layer 20 adjacent to the inside of each separation layer 12. Each base layer 20 can be, for example, a woven, knitted, or non-woven sheet. In the completed fifth 3D film 10, the separation layers 12 can adhere to the base layer 20 by chemical forces and / or physical forces.

[0046] Referring to Figures 9 to 11 , the base layers 20 are unrolled from the reel 46 and pulled through the casting knife 30. The base layers 20 are supported on the center plate 36 of the casting knife 30 as they pass through the casting knife 30. For example, the base layers 20 can pass through the gaps 39 (as shown in Figure 11 ) inside the casting knife 30 on both sides of the center plate 36. The center plate 36 has a series of grooves 38 (see Figure 10 ). A hole cutter 42, such as a laser cutter, a knife, or a roller with protrusions radiating outward therefrom, cuts a series of openings 18 in the base layer 20 as the base layer passes through the hole cutter 42. The hole cutter 42 can act on the solid surface of the center plate 36 or through the grooves 38 of the center plate 36. The coating 40 is injected into the casting knife 30 and flows over the base layer 20 as they pass through the casting knife 30 to form the separation layers 12. Some of the coating passes through the openings 18 and the grooves 38 to form the columns 16.

[0047] In one embodiment, the coated base layer 20 is passed through a cold dip bath 42 to cure the coating 40 to form the separation layer 12. The column 16 is also cured in the cold dip bath 42. The resulting membrane 10 can be wound around a roller 44 and withdrawn from the cold dip bath 42. Optionally, the center plate 36 can extend into the cold dip bath 42.

[0048] Figure 12 The sixth 3D membrane 10 is shown. The sixth 3D membrane 10 is similar to Figure 8 the fifth 3D membrane 10, and the description of the fifth 3D membrane 10 and how it is manufactured applies to the sixth 3D membrane 10, unless inconsistent. In addition to what is described herein, the sixth 3D membrane 10 is manufactured by the method as described for the fifth 3D membrane 10 and using equipment generally as Figure 9 , Figure 10 and Figure 11 shown. The base layers 20 of the sixth 3D membrane 10 are close to each other along some lines and optionally in contact with each other. In the example shown, there are some columns 16 at positions where the base layers 20 are spaced apart from each other, and there are some columns 16 at positions where the base layers 20 are closer to each other or in contact with each other. In this case, some columns 16 are shorter than other columns 16. In other examples, the base layers 20 can be close to each other or in contact with each other along each line of the columns 16. The wavy shape of the base layer 20 is maintained by the corresponding shape of the casting knife 30 and / or by the tension between the upper and lower rollers 44 in the regions where the base layers 20 are close to each other or in contact with each other, which can have a wavy shape corresponding to the wavy shape of the base layer 20. The center plate 36 can have a large gap 38 or be made into a plurality of spaced segments to provide regions where the base layers 20 can be close to each other or in contact with each other. Optionally, the base layers 20 can also be connected together, for example, by an adhesive or sonic welding or thermal welding, where the base layers 20 are in contact with each other. Optionally, the base layers 20 can be connected together during the casting process, for example, by a heating element or an ultrasonic welding tip in the upstream part of the casting head 30 or in a separate unit upstream of the casting head 30. Alternatively, the base layers 20 can be connected together only by curing the columns 16.

[0049] As discussed and illustrated by examples above, in some examples, the three-dimensional membrane has two outer separation layers that are interconnected by polymer columns made of the same material as the separation layer and formed during the casting process of the separation layer. In some examples, the three-dimensional membrane has a continuous or discontinuous permeation collection space between two separation layers interconnected by polymer columns, which has or does not have a substrate supporting the separation layer and has or does not have a permeation carrier. In some examples, the flat membrane has a separation layer, a base layer, and columns extending from the separation layer to openings in the base layer.

[0050] Although the above examples are all flat membranes, the present invention can be applied to other forms of membranes. For example, some hollow fiber or tubular membranes are cast on a support structure such as a knitted or woven tube or a spirally wound fabric tape. These membranes can additionally or alternatively have a soluble core. The core and the support structure (if any) can pass through the chord or diameter of the core. When the coating is cast on the core, some of the coating will flow through the pierced cord and / or diameter and form columns passing through the membrane when cured.

Claims

1. A membrane, the membrane comprising: a first separation layer; a second separation layer; and a plurality of columns, each of the columns extending between the first separation layer and the second separation layer, wherein each of the plurality of columns is integrally formed with the first separation layer and the second separation layer and the plurality of columns are made of the same material as the first separation layer and the second separation layer, wherein the membrane is a 3D membrane, and the first separation layer and the second separation layer are separated and connected by the columns, wherein the columns and the first separation layer and the second separation layer are made of a porous membrane forming coating.

2. The membrane according to claim 1, wherein the membrane comprises one or more support structures, and wherein the columns extend through the one or more support structures.

3. The membrane according to claim 2, wherein the one or more support structures comprise a base layer.

4. The membrane according to claim 2, wherein the one or more support structures comprise a permeation carrier.

5. The membrane according to claim 1, wherein the first separation layer and the second separation layer are directly supported on a 3D spacer fabric.

6. The membrane according to claim 1, the membrane having two base layers, wherein each of the separation layers is supported on one of the base layers.

7. The membrane according to claim 6, the membrane further comprising a permeation carrier between the two base layers.

8. The membrane according to claim 6, the membrane having no permeation carrier.

9. A method of manufacturing the membrane according to claim 1, comprising the steps of: creating openings in one or more support structures; pouring separation layer forming liquid on two opposite surfaces of the one or more support structures such that at least some of the liquid flows into the openings; and curing the liquid to form a first separation layer and a second separation layer and columns within the openings.

10. The method according to claim 9, wherein the one or more support structures are selected from the group consisting of: a base layer, a permeation carrier, and a soluble substrate, the base layer being a woven, knitted or non-woven sheet.

11. The method according to claim 10, wherein the permeation carrier comprises a 3D spacer fabric.

12. The method according to claim 9, wherein the one or more support structures comprise a 3D spacer fabric.

13. The method according to claim 9, wherein the one or more support structures comprise two base layers spaced apart from each other without an intervening permeation carrier when passing through a pouring knife.

14. The method according to claim 13, wherein the two base layers are spaced apart from each other by a central plate of the pouring knife.

15. The method according to claim 9, wherein the one or more support structures comprise a soluble substrate.

16. The method according to claim 15, the method comprising dissolving the soluble substrate.

17. The method according to claim 9, wherein the openings are formed using a roller or a flat plate having protrusions corresponding to the openings or using a laser cutter.

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