Composite film

Abstract

Embodiments of the present invention provide for the integration of the functions of a feed spacer, a permeate carrier, or both, as part of the membrane sheet of a spiral-wound membrane element.

Description

[Technical field]

[0001] FIELD OF THEINVENTION The present invention relates to a permeable membrane system, particularly a spiral-wound membrane element, used to separate fluid components, as described in U.S. Provisional Patent Application No. 61 / 771,041, filed February 28, 2013, and U.S. Provisional Patent Application No. 62 / 797,357, filed January 27, 2019, each of which is incorporated herein by reference. [Background technology]

[0002] 2. Description of Related Art Spiral-wound membrane filtration elements known in the art comprise a laminated structure with membrane sheets sealed to or around a porous permeate spacer that creates a path for fluid passing through the membrane to travel to a central tube, while the laminated structure is spirally wound around the central tube and is itself spaced apart by a porous feed spacer to allow fluid to flow axially through the element. The feed spacer is necessary to maintain free and uniform axial flow within the laminated structure, but it also causes flow restriction and pressure drop in the axial flow path and creates areas of flow restriction and contact with the membrane, which are major contributors to membrane fouling through biological growth, scale formation, and particle entrapment. In pressure retarded osmosis (PRO), forward osmosis (FO), and reverse osmosis (RO) applications, the flow paths of the feed spacer and permeate spacer can be advantageous for optimal system operation.

[0003] Improvements to the spiral wound element design have been disclosed by Barger et al. and Bradford et al., in which the feed spacers are replaced by islands or protrusions that are deposited or embossed directly onto the outer, working surface of the membrane. This configuration can be advantageous in that it minimizes obstructions in the flow path while preserving space for axial flow through the element. It also simplifies the manufacture of the element by eliminating the need for a porous feed spacer as a separate component. U.S. Patent Application Publication No. 2016-0008763-A1, entitled "Improved Spiral Wound Element Construction," incorporated herein by reference, teaches the application of a printed pattern on the backside of the working surface of the membrane sheet or directly on the surface of the permeate spacer.

[0004] The membrane sheet itself is usually made of three layers. A first porous layer can be composed of, for example, polyester, followed by a porous support layer of polysulfone, and finally a membrane polymer layer deposited on the polysulfone substrate. The polymer coating has usually been applied by a casting method. Three-dimensional (3D) printing technology has now advanced to the point where the membrane polymer material can be printed directly onto the polysulfone substrate. Printing of polymer coatings onto polysulfone substrates is described by Chris Arnush of the Zukerberg Institute of Water Technology at Ben Gurion University in a paper entitled "2-D and 3-D Printing Assisted Fabrication and Modification of UF / NF / RO Membranes for Water Treatment". Polyamide coatings applied by electrospray are also described by Jeffery McCutcheon of the University of Connecticut. The following references, each of which is incorporated herein by reference, may facilitate an understanding of the present invention: No. 3,962,096, U.S. Patent No. 4,476,022, U.S. Patent No. 4,756,835, U.S. Patent No. 4,834,881, U.S. Patent No. 4,855,058, U.S. Patent No. 4,902,417, U.S. Patent No. 4,861,487, U.S. Patent No. 6,632,357, and U.S. Patent Application Publication No. 2016-0008763-A1. Summary of the Invention [Problem to be solved by the invention]

[0005] Description of the Invention A conventional spiral-wound membrane element typically comprises three components: a membrane sheet, a feed spacer, and a permeate carrier. The membrane sheet typically comprises a porous polyethylene layer, e.g., a polysulfone layer, and a polymer layer, e.g., cast on the polysulfone layer. The present invention provides a system with a three-layer membrane sheet that can integrate all of the features of the membrane element, polymer membrane, permeate carrier, and feed spacer into one composite assembly. The polysulfone layer can incorporate a feed spacer pattern. The porous, typically non-woven, polyethylene layer can be thicker than a conventional polyethylene layer and can incorporate the features of the permeate carrier as an integral part rather than a separate permeate carrier sheet. The permeate carrier can also integrate channels that are printed or machined into the permeate carrier to direct flow through the permeate carrier in specific flow paths, which can be useful, for example, in pressure retarded osmosis and forward osmosis applications. In one exemplary embodiment, the membrane layer, permeate carrier, and feed spacer are integrated onto one composite sheet. Casting has been the industry standard method for applying polymer film coatings over the past 50 years. [Means for solving the problem]

[0006] In some spiral membrane separation applications involving serial flow through a continuous element permeate spacer layer, such as those described in the PRO patents mentioned above, it can be advantageous to have a smaller flow resistance than that exhibited by conventional woven permeate spacer fabrics, while maintaining other properties, including resistance to deformation under high external pressure. Furthermore, the ability to accommodate any shape of flow path in the permeate spacer can allow for a controllable distribution of flow through the permeate spacer layer. An embodiment of the present invention provides for a channel to be printed, deposited, or integrated into the porous permeate spacer to create a positive feed channel in the permeate spacer. In other embodiments, the material that creates the channel can be a photosensitive resin, a hot melt polyolefin, a curable polymer or adhesive, or other material. [Brief description of the drawings]

[0007] BRIEF DESCRIPTION OF THE DRAWINGS [Figure 1] FIG. 1 shows a cross-sectional view with a conventional three-layer membrane sheet, a feed water spacer sheet, and a permeate carrier sheet. [Diagram 2] FIG. 2 is a cross-sectional view of a composite membrane sheet comprising a porous polyethylene layer, a polysulfone layer having features integral thereto, and a porous polyamide filtration layer. [Diagram 3] A cross-sectional view of 3D printed material protruding above the permeate spacer of a composite membrane sheet assembly in the intermediate space, with integrated feed spacer features and thick permeate carrier required for the membrane sheet, with integrated flow paths in the permeate carrier. [Figure 4] FIG. 13 is a cross-sectional view of a composite membrane sheet with a feedwater spacer feature added on 1 / 2 the length of the membrane sheet assembly. [Diagram 5] FIG. 1 is a cross-sectional view of a composite membrane sheet incorporating a polymeric membrane layer, feed spacer features integrated into the support layer, and an integral permeate carrier, folded at the centerline and attached to the central tube of a spiral-wound membrane element. [Figure 6] FIG. 1 is a cross-sectional view of a composite membrane sheet incorporating a polymer membrane layer, feed spacer features integrated into the support layer, and an integral permeate carrier, folded at the centerline and attached to the central tube of a spiral-wound membrane element, including fold protection and bridge support features. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] MODE FOR CARRYING OUT THE PRESENTINVENTION AND INDUSTRIAL APPLICABILITY Embodiments of the invention provide a membrane element comprising: (a) a porous polysulfone layer having a plurality of spacing features integrated on a first surface of the polysulfone layer; (b) a porous polymeric filtration layer disposed on the first surface of the polysulfone layer; and (c) a porous support layer attached in contact with a second surface of the polysulfone layer, the second surface of the polysulfone layer being opposite the first surface of the polysulfone layer. In some embodiments, the support layer comprises polyethylene. In some embodiments, the support layer comprises a mesh material. In some embodiments, the support layer has a greater permeability at a portion of the support layer proximal to the polysulfone layer than at a portion of the support layer distal from the polysulfone layer.

[0009] Some embodiments further comprise one or more substantially impermeable barrier features disposed within the support layer, the barrier features defining fluid flow paths within the support layer, hi some embodiments, the barrier features disposed within the support layer do not extend to the polysulfone layer, and the support layer comprises nonwoven polyester.

[0010] Some embodiments further comprise a permeate carrier layer having one or more substantially impermeable barrier features disposed therein, the permeate carrier layer being bonded to the porous support layer on a surface of the porous support layer opposite the surface of the porous support layer in contact with the polysulfone layer. In some embodiments, the spacing features are disposed on only 1 / 2 of the first face of the polysulfone layer. In some embodiments, a first subset of the spacing features are disposed near the inlet edge, the outlet edge, or near both edges of the polysulfone membrane, the spacing features of the first subset having a first height, and a second subset of the spacing features are disposed on only no more than 1 / 2 of the first face of the polysulfone membrane, the spacing features of the second subset having a second height, the second height being twice the first height.

[0011] Some embodiments provide a filtration element comprising a membrane element as described above, folded near the middle of the length of the membrane element such that the porous filtration layer is inside the folded membrane element. Some embodiments further comprise a collection tube, the folded membrane element being placed with its support layer in contact with the collection tube, and the folded membrane element being spirally wound around the collection tube. Some embodiments further comprise one or more additional membrane elements as described in claim 1, each additional membrane element being placed with its support layer in contact with the collection tube, and each additional membrane element being spirally wound around the collection tube. Some embodiments further comprise a crease protection element disposed on the porous filtration layer near the fold line. Some embodiments further comprise a bridge support pattern of spacers disposed on the membrane sheet at the end distal to the fold line.

[0012] An embodiment of the invention provides a method of making a membrane element comprising: (a) providing a plurality of spacing features on a first side of a polysulfone layer; (b) bonding a porous polymeric filtration layer to the first side of the polysulfone layer; and (c) bonding a porous support layer to a second side of the polysulfone layer, the second side of the polysulfone layer being opposite the first side of the polysulfone layer. In some embodiments, the support layer comprises polyethylene. In some embodiments, the support layer comprises a mesh material. In some embodiments, the support layer has a greater permeability at a portion of the support layer proximal to the polysulfone layer than at a portion of the support layer distal from the polysulfone layer.

[0013] Some embodiments further include forming one or more substantially impermeable barrier features in the support layer, where prior to step (c), the barrier features define fluid flow paths in the support layer. Some embodiments further include forming one or more substantially impermeable barrier features in the permeate carrier and bonding the permeate carrier to the porous support layer on a surface of the porous support layer opposite the surface of the porous support layer in contact with the polysulfone layer. In some embodiments, the spacing features are disposed on only 1 / 2 of the first face of the polysulfone layer. In some embodiments, a first subset of the spacing features are disposed near the inlet edge, near the outlet edge, or near both edges of the polysulfone membrane, the spacing features of the first subset having a first height, and a second subset of the spacing features are disposed on only no more than 1 / 2 of the first face of the polysulfone membrane, the spacing features of the second subset having a second height, the second height being twice the first height.

[0014] Some embodiments provide a method of making a filtration element, comprising: (a) providing a membrane element according to the method described above; and (b) folding the membrane element near the middle of the length of the membrane element such that the porous filtration layer is inside the folded membrane element. Some embodiments further comprise placing the folded membrane element such that its support layer is in contact with a collection tube, and spirally winding the folded membrane element around the collection tube. Some embodiments further comprise providing one or more additional membrane elements according to the method described above; folding each of the additional membrane elements near the middle of the length of such membrane element such that its porous filtration layer is inside the folded membrane element, placing each additional membrane element such that its support layer is in contact with a collection tube, and spirally winding the additional membrane element around the collection tube. Some embodiments further comprise placing a fold protection element on the porous filtration layer near the fold line. Some embodiments further comprise placing a bridge support pattern of spacers on the membrane sheet at an end distal to the fold line.

[0015] In a representative embodiment of an existing reverse osmosis spiral-wound membrane element shown in FIG. 1, the spiral-wound element composite layer 10 comprises a membrane sheet assembly 18, for example, comprising a porous polyethylene layer 16 bonded to a porous polysulfone layer 14, and coated with a polymer membrane layer 12, for example, cast in place. To distribute the feed water evenly across the polymer membrane layer 12, a feed spacer mesh 22 is placed, for example, against the surface of the polymer membrane layer 12. As the feed fluid 24 moves through the polymer membrane layer 12 and impurities are rejected by the polymer membrane layer 12, the filtrate fluid 26 is transferred to a separate permeate carrier 20. In practice, the membrane assembly is sealed with adhesive around the permeate carrier 20 to avoid loss of clean solution, and then a flat envelope is wrapped around the central tube, where the clean product water enters and is collected in the membrane element housing.

[0016] In an exemplary embodiment of the invention shown in FIG. 2, the composite membrane sheet 30 includes spacer features 38 integrated into the layer 32 made, for example, from porous polysulfone. The polymer layer 36 can be applied by processes such as spraying, electrospraying, or printing directly onto the support layer 32. The polymer layer 36 can be printed with features as taught by Arnush et al. that provide the polymer layer 36 with antifouling properties. The polymer layer 36 can also include an antifouling biocide as taught by Bradford et al. In one exemplary embodiment, the composite membrane sheet 30 can also include a support layer 34 made, for example, from polyethylene that is thick and porous enough to also act as an integral permeate carrier layer. The support layer 34 can also have a graded density profile that becomes more porous or more permeable (less dense) as the support layer material is disposed more distally perpendicular to the polymer layer 34. The more porous or more permeable portions of the support layer 34 can be treated, for example, with a hardener such as an epoxy coating, to make them more solid and capable of supporting higher pressures without losing porosity or permeability. In another exemplary embodiment, the composite membrane sheet 30 can include a permeate carrier layer, made, for example, from another woven polyester or other material, that is laminated to the support layer during fabrication. If the permeate carrier layer is integrated or laminated to the composite membrane sheet, the effective thickness of the permeate carrier layer must be only half the thickness of a conventional permeate carrier layer to provide the same flow, because the folded and rolled composite membrane places two such permeate carrier layers in contact with each other to create a permeate flow space.

[0017] 3, the composite membrane sheet 30 may include a barrier pattern 52 in the support layer 34 that directs fluid flow to specific flow paths within the support layer 34 to facilitate improved efficiency, for example, for pressure retarded osmosis (PRO) or forward osmosis (FO) applications. In another exemplary embodiment of the invention, the support layer 34 with integral channels 52 may be fabricated separately and then the porous polysulfone layer 32 may be later bonded to the support layer 34.

[0018] In an exemplary embodiment of the present invention shown in FIG. 4, the membrane sheet assembly 70 can have feed spacer features 74 added only to half the length of the composite membrane 72. In the assembly of the spiral-wound element, each leaf is folded in half. By adding the feed spacer features 74 only to half of the composite membrane 72, interference of the spacer features 74 is avoided when the folded leaf is wrapped around the central tube of the spiral-wound element. On the inlet and outlet edges of the composite membrane 72, special spacer features 74 including lines, dots, or other patterns can be fabricated only half-height along the entire length of the composite membrane 72, and the patterns of the inlet and outlet areas of the membrane feed space are established to properly interfere to provide support for the adhesive layer sealing the permeate carrier envelope. In the open area of ​​the membrane sheet 70 between the inlet and outlet areas of the membrane sheet, the spacer features 74 can be full height and printed only half-length of the composite membrane sheet 72.

[0019] In an exemplary embodiment of the invention shown in FIG. 5, a composite membrane sheet 92 is folded in half and wrapped around a central tube 94. Permeate 100 flow passage holes 96 in the central tube 94 facilitate passage of the permeate 100 to the center of the central tube 94 for exiting the permeate 100 from the spiral-wound element assembly. Adhesive 98 can be applied to the edges of the permeate envelope so that it permeates the permeate carrier and bonds to the polymer coating to provide a closed permeate carrier envelope, and further provides a seal of the permeate carrier envelope to the central tube 94. It is known to those skilled in the art of making membrane elements that multiple sheets can be wrapped from the central tube 94 to make membrane elements having much larger membrane sheet surface areas for much larger operating capabilities, for example, 2-1 / 2, 4, or 8 inch diameter elements, or any other diameter.

[0020] In an exemplary embodiment of the invention shown in FIG. 6, the folded composite membrane sheet 92 can include a crease protection material 120 at the centerline of the composite membrane sheet 92. The crease protection material 120 can include a tape or other material printed or otherwise applied to the center area of ​​the composite membrane sheet 92 prior to folding. Alternatively, the composite membrane sheet can include a crease protection integrated into a porous layer made from polysulfone, for example, by placing a non-porous layer before the polyamide layer is applied. The composite membrane sheet 92 can also include solid or segmented bridge supports 122 printed or otherwise applied to the distal ends of the folded composite membrane sheet 92. Alternatively, the composite membrane sheet can include a bridge support end pattern integrated into a porous layer made from polysulfone, for example.

[0021] The present invention has been described in connection with various exemplary embodiments. It is to be understood that the above description is merely illustrative of the application of the principles of the invention, the scope of the invention being to be determined from the claims read in light of the specification. Other variations and modifications of the present invention will be apparent to those skilled in the art.

Claims

1. (a) a porous polysulfone layer having a plurality of spacing features integrated on a first surface of said polysulfone layer; (b) a porous polymeric filtration layer disposed on the first surface of the polysulfone layer so as to cover both the spacing features and the polysulfone layer; (c) a porous support layer attached in contact with the second surface of the polysulfone layer; and Equipped with the second side of the polysulfone layer is opposite the first side of the polysulfone layer; the support layer has a greater permeability at a portion of the support layer proximal to the polysulfone layer than at a portion of the support layer distal from the polysulfone layer; Membrane element.

2. the support layer comprises polyethylene; The membrane element according to claim 1 .

3. the support layer comprises a mesh material; The membrane element according to claim 1 .

4. further comprising one or more substantially impermeable barrier features disposed within the support layer; the barrier features define fluid flow paths within the support layer; The membrane element according to claim 1 .

5. the barrier features disposed within the support layer do not extend into the polysulfone layer; the support layer comprises nonwoven polyester; The membrane element according to claim 4.

6. a water permeable carrier layer having one or more impermeable barrier features disposed therein; the permeate carrier layer is bonded to the support layer on a surface of the support layer opposite the surface of the support layer in contact with the polysulfone layer; The membrane element according to claim 1 .

7. the spacing features are disposed on only one-half of the first surface of the polysulfone layer; The membrane element according to claim 1 .

8. a first subset of the spacing features are disposed near an inlet edge, near an outlet edge, or near both edges of the polysulfone layer; the first subset of spacing features having a first height; a second subset of the spacing features disposed on no more than one-half of the first surface of the polysulfone layer; the second subset of spacing features having a second height; the second height is twice the first height; The membrane element according to claim 1 .

9. 2. The membrane element of claim 1, wherein the porous polymer filtration layer is folded along a fold line near the center of the length of the membrane element such that the porous polymer filtration layer is on the inside of the folded membrane element. Filtration element.

10. a collection tube, the folded membrane element being placed such that the support layer is in contact with the collection tube, and the folded membrane element is spirally wound around the collection tube.

10. The filtration element of claim 9.

11. 2. The method of claim 1, further comprising: providing one or more additional membrane elements, the additional membrane elements being positioned such that the support layer is in contact with the collection tube, the additional membrane elements being spirally wound around the collection tube. The filtration element of claim 10.

12. further comprising a crease protection element disposed on the porous polymeric filtration layer proximate the fold line.

10. The filtration element of claim 9.

13. a bridge support pattern of spacers disposed on the membrane elements at ends distal to the fold lines.

10. The filtration element of claim 9.

14. (a) a porous polysulfone layer having a plurality of spacing features integrated on a first surface of said polysulfone layer; (b) a porous polymeric filtration layer disposed on the first surface of the polysulfone layer so as to cover both the spacing features and the polysulfone layer; (c) a porous support layer attached in contact with the second surface of the polysulfone layer; and Equipped with the second side of the polysulfone layer is opposite the first side of the polysulfone layer; the support layer has a greater permeability at a portion of the support layer distal to the polysulfone layer than at a portion of the support layer proximal to the polysulfone layer; Membrane element.

15. (a) providing a plurality of spacing features on a first surface of a polysulfone layer; (b) after step (a), bonding a porous polymeric filtration layer to the first surface of the polysulfone layer such that the porous polymeric filtration layer covers both the spacing features and the polysulfone layer; (c) bonding a porous support layer to the second surface of the polysulfone layer; and Including, the second side of the polysulfone layer is opposite the first side of the polysulfone layer; the support layer has a greater permeability at a portion of the support layer proximal to the polysulfone layer than at a portion of the support layer distal from the polysulfone layer; Method for making membrane elements.

16. the support layer comprises polyethylene; The method of claim 15.

17. the support layer comprises a mesh material; The method of claim 15.

18. forming one or more substantially impermeable barrier features in the support layer, the barrier features defining fluid flow paths in the support layer prior to step (c); The method of claim 15.

19. forming one or more substantially impermeable barrier features in a permeate carrier; bonding said permeate carrier to said support layer on a surface of said support layer opposite a surface of said support layer in contact with said polysulfone layer; Further comprising: The method of claim 15.

20. the spacing features are disposed on only one-half of the first surface of the polysulfone layer; The method of claim 15.

21. a first subset of the spacing features are disposed near an inlet edge, an outlet edge, or near both edges of the polysulfone layer, the spacing features of the first subset having a first height, a second subset of the spacing features are disposed on no more than one-half of the first surface of the polysulfone layer, the spacing features of the second subset having a second height, the second height being twice the first height; The method of claim 15.

22. (a) providing a membrane element according to the method of claim 15; (b) folding the membrane element along a fold line near the center of the length of the membrane element such that the porous polymer filtration layer is inside the folded membrane element; Including, How to make a filter element.

23. placing the folded membrane element so that the support layer contacts a collection tube; winding the folded membrane element in a spiral shape around the collection tube; Further comprising:

23. The method of claim 22.

24. providing one or more additional membrane elements according to the method of claim 15 and folding each of the additional membrane elements near the center of the length of such membrane element such that the porous polymer filtration layer is inside the folded membrane element; placing the additional membrane element such that the support layer contacts the collection tube; spirally winding the additional membrane element around the collection tube; Further comprising:

24. The method of claim 23.

25. further comprising placing a crease protection element on the porous polymeric filtration layer proximate the fold line.

24. The method of claim 23.

26. and placing a bridge support pattern of spacers on the membrane element at an end distal to the fold line.

23. The method of claim 22.

27. (a) providing a plurality of spacing features on a first surface of a polysulfone layer; (b) after step (a), bonding a porous polymeric filtration layer to the first surface of the polysulfone layer such that the porous polymeric filtration layer covers both the spacing features and the polysulfone layer; (c) bonding a porous support layer to the second surface of the polysulfone layer; and Including, the second side of the polysulfone layer is opposite the first side of the polysulfone layer; the support layer has a greater permeability at a portion of the support layer distal to the polysulfone layer than at a portion of the support layer proximal to the polysulfone layer; Method for making membrane elements.

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