Spiral filtration device and manufacturing method

Abstract

To improve performance of a filtration module which is wound in a spiral shape.SOLUTION: A method for forming a filter module includes: providing at least one membrane sheet, at least one supply screen, and at least one permeable sheet; folding at least the one membrane sheet along its length, and forming a leaf in which two halves are integrally formed; arranging at least the one supply screen between the two halves, and forming a membrane packet having a membrane packet fold; arranging an impermeable support at a position of the membrane packet fold, and forming a tip of the membrane packet; and winding the membrane packet and at least the one permeable sheet in a spiral shape around a core, wherein the position of the impermeable support avoids formation of a gap region in front of the tip of the membrane packet.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This application claims priority to U.S. Provisional Patent Application No. 62 / 779,860, filed December 14, 2018, U.S. Provisional Patent Application No. 62 / 779,867, filed December 14, 2018, U.S. Provisional Patent Application No. 62 / 780,634, filed December 17, 2018, and U.S. Provisional Patent Application No. 62 / 780,689, filed December 17, 2018, the disclosures of which are incorporated herein by reference in their entireties.

[0002] FIELD OF THE DISCLOSURE The present disclosure relates generally to spiral wound membrane filter elements or modules and methods for making the same. More specifically, spiral wound filter modules are disclosed, wherein the modules include one or more features to provide adhesive migration control, prevent feed path geometry changes, and minimize or eliminate voids, thereby resulting in a more consistent manufacturing process and consistent repeatability of the spiral wound filters. Also disclosed is a manufacturing method based on a novel assembly process in which the membrane and screen are first wound around a permeate drainage core to form a spiral, and then an adhesive is applied to form the permeate envelope, securing the spiral to the core, sealing the periphery, and filling the annulus into a housing or providing a pressure-containing circumferential shell. [Background technology]

[0003] Spiral wound filter modules are commonly used in filtration, including ultrafiltration and reverse osmosis. Typically, such modules are manufactured by spirally winding multiple membrane sheets, spacer materials, and permeate sheets around a perforated hollow core or mandrel, which may then be centrally placed in a housing or cartridge.

[0004] More specifically, spiral-wound filtration modules are multilayer devices that may include one or more permeate spacers, which may be porous fabrics, one or more membrane sheets, and one or more feed screens or spacers. The module may be constructed by spirally winding one or more membranes, feed spacers, and permeate screens around a permeate core, tube, or mandrel, which has multiple openings, such as slots or holes, that communicate with a central bore for collecting permeate. Adhesives may be used to secure the resulting assembly in place around the mandrel. The resulting module may be placed in a housing capable of withstanding typical operating pressures.

[0005] Some spiral wound filtration modules may contain multiple leaves, each with a layer of permeate sheet or screen, which may be a porous fabric material sandwiched between two membrane sheets. The membrane sheet may be folded in half with a feed screen placed between the two halves to form a membrane packet. The membrane packet and permeate sheet are wound around a mandrel or core with openings for collecting permeate. Modules with one and four leaves are common, but any number of leaves may be configured. For example, a 0.1 m 2 The module has a single leaf and is 0.5m 2 The module has four leaves and a membrane area of ​​1 m 2 exceeding (e.g. 2.0m 2 etc.) Larger spiral apparatus may have up to 16 lobes. Summary of the Invention [Problem to be solved by the invention]

[0006] However, the spiral wrapping of the membrane packet results in a wedge-shaped void in front of the leading edge of the packet (see Figure 1). Additionally, the membrane can pull back away from the feed screen, also resulting in a gap or void in front of the feed screen (Figure 1), which creates bypass flow around the screen. This bypass flow reduces performance.

[0007] Additionally, adhesive is manually introduced into the assembly to bond the layers together and to the perforated core, a process that often results in irregular adhesive edges that can lead to high risk of human error caused by integrity failures and membrane area variations.

[0008] It would therefore be desirable to reduce or eliminate these problems and improve the performance of spiral wound filtration modules. [Means for solving the problem]

[0009] Problems of the prior art have been overcome by the embodiments disclosed herein, which relate to spiral wound filtration modules and methods for manufacturing same. In certain embodiments, the filtration module includes a support, such as a wedge-shaped support, that functions to eliminate one or more voids that would otherwise form as a result of the winding operation during assembly, and to eliminate one or more voids as the membrane separates from the feed screen. In certain embodiments, the support is positioned to occupy some or all of the area where such voids would normally form, and supports the membrane and screen wound radially outward from the core. This prevents the feed channel geometry of all layers above from changing at high pressure, an added benefit of this is that the feed channel geometry remains consistent throughout the device, improving performance and reducing pressure drop variations. Furthermore, creases, cracks, and folding failures at the tip of the membrane packet are well-known forms of loss of spiral integrity, and supports attached to the tip of the membrane packet can reduce the likelihood of tip failure during operation.

[0010] An additional benefit of the support is realized when adhesive is pulled or forced into the device during the potting process. The support prevents detrimental migration of potting adhesive through the wedge gap into the device, especially when biplane spiral-wound modules are involved. The presence of the support also reduces the amount of adhesive required.

[0011] In a particular embodiment, a filter module is disclosed that is formed by spirally winding multiple layers of material around a core to form a generally cylindrical structure having two opposing spiral end faces. Because of the layers bonded along the longitudinal and transverse edges, in use, unfiltered fluid fed into the unit from one spiral end face must pass through or tangentially cross one or more membrane layers before exiting the unit through the opposite spiral end face. Sealing arrangements are provided on each spiral face of the wound filter to ensure that the incoming fluid passes through a membrane surface before exiting the unit. In certain embodiments, the multilayer material includes one or more membrane sheets, one or more feed screens, and one or more permeate sheets or screens. One or more membrane sheets may be folded once along their length to form a leaf with two halves joined together, with the feed screen positioned or sandwiched between the two halves to form the membrane packet. The assembly forms spirally wound permeate and concentrate fluid flow paths. Supports are placed at the membrane packet folds during winding to eliminate void areas that would otherwise form when the packet and permeate sheets are wound around the core.

[0012] To filter a product, the product is introduced under pressure into one end of a spiral-wound membrane module and flows axially through a feed screen. The product then flows tangentially across the membranes, with a portion flowing through the membranes. The product reaches the permeate channels defined between each membrane and the adjacent permeate sheet. The permeate then flows into the perforated core and is finally removed from the module.

[0013] In certain embodiments, a spiral wound membrane module is disclosed that includes a perforated core having an axially extending internal bore, at least one membrane packet including a folded membrane sheet defining a first outer surface, a first inner surface, a second outer surface, and a second inner surface, where a fold in the folded membrane sheet is a leading edge of the membrane packet, a feed sheet disposed between the first and second inner surfaces so as to be sandwiched by the folded membrane sheet, a first permeate screen adjacent the first outer surface of the membrane sheet that defines a first permeate passage, a second permeate screen adjacent the second outer surface of the membrane sheet that defines a second permeate passage, and a fluid-impermeable support coupled to the leading edge of the membrane packet.

[0014] In some embodiments, there are a plurality of membrane packets, each having a distal end and a fluid-impermeable support coupled to each distal end.

[0015] In some embodiments, the impermeable support is wedge-shaped.

[0016] In some embodiments, the impermeable support is non-uniformly deformable to fill non-uniform voids.

[0017] In some embodiments, the module is cylindrical in cross section and has an outer surface of cured adhesive.

[0018] In certain embodiments, a method for potting a spiral wound membrane is disclosed that includes placing the spiral wound membrane in sealing relationship with a mold cavity, introducing an adhesive into the mold cavity, applying a vacuum to a permeate core, tube, or mandrel such that the vacuum forces the adhesive around the permeate channels and the periphery of the core, and allowing the adhesive to cure. When a wrap of permeable screen is placed around the core, adhesive is also forced into the permeable screen, securing the spiral to the core. The spirals in this method are equipped only with edged feed screens designed to prevent adhesive from entering the feed channels during the potting process. They contain impermeable edges on all three sides corresponding to the three sides of the permeable envelope. The side edges are narrower than the side seams of the permeation envelope, so that when the spiral adhesives are removed (e.g., cut) after they have cured, the permeation envelope remains sealed, while the feed passage is open to tangential flow. The feed screen may also have four edges, the fourth edge being at the leading edge of the feed screen (near the fold of the membrane packet) to prevent damage to the leading edge membrane from the feed screen. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a photograph showing the wedge-shaped gap formed between the membrane and feed screen of a prior art spiral-wound filter. [Figure 2] FIG. 2 is a photograph showing supports inserted into the gaps formed between the membrane and the permeate screen and between the membrane and the feed screen of a spiral wound filtration device according to certain embodiments. [Figure 3] FIG. 3 is a cross-sectional view of a support according to a particular embodiment. [Figure 4] FIG. 4 is a schematic diagram of the support and membrane packet during the wrapping operation. [Figure 5]FIG. 5 is a cross-sectional view of a potting mold according to certain embodiments. [Figure 6] FIG. 6 is a photograph of a top view of a spiral wound membrane module according to certain embodiments. [Figure 7] FIG. 7 is a photograph of a module with a feed screen having edges according to certain embodiments. [Figure 8] FIG. 8 is a photograph of a four-edge feed screen according to certain embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0020] A more complete understanding of the components, processes, and apparatus disclosed herein can be obtained by reference to the accompanying drawings, which are merely schematic illustrations based on ease and convenience of illustrating the present disclosure, and are therefore not intended to define or limit the scope of the example embodiments.

[0021] Although the following description uses specific terminology for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings and are not intended to define or limit the scope of the disclosure. In the drawings and description that follow, it should be understood that like numerical designations refer to components of similar function.

[0022] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0023] As used herein, various devices and components may be described as "comprising" other elements. As used herein, the terms "comprise(s)," "include(s)," "having," "has," "can," "contain(s)," and variations thereof, are intended to be open-ended transitional phrases, terms, or words that do not exclude the possibility of additional elements.

[0024] In certain embodiments, the filtration device is a filtration module having a fluid inlet, a fluid outlet spaced from the fluid inlet, a permeate outlet, a central core having a plurality of openings and a bore extending axially along its entire length, and one or more membrane packets. Each membrane packet is sandwiched between a feed sheet or screen, which may be a polyolefin sheet such as polypropylene, and one or more permeate sheets, such as one or more polyester screens, which may be epoxy-impregnated to provide sufficient strength to withstand typical operating pressures encountered during use. The feed screen provides a space for the feed flow between the opposing membranes that sandwich it. The permeable sheet provides a fluid path for the permeate flow to the perforated core. One or more membrane packets and one or more permeable sheets are wound in a spiral configuration around the core. The membranes within each membrane packet may be single or multi-layer membranes and may be used to filter unwanted substances, including contaminants such as infectious organisms and viruses, and environmental toxins and pollutants that can be removed by chemical or physical adsorption, size exclusion, or a combination thereof. The membrane may be constructed of any suitable material, including, but not limited to, polyethersulfone, polyamides such as nylon, cellulose, polytetrafluoroethylene, polysulfone, polyester, polyvinylidene fluoride, polypropylene, fluorocarbons such as poly(tetrafluoroethylene-coperfluoro(alkyl vinyl ether)), polycarbonate, polyethylene, fiberglass, polycarbonate, ceramic, and metal. It may be a microfiltration, ultrafiltration, or reverse osmosis membrane. Ultrafiltration membranes are particularly preferred.

[0025] One suitable spiral wound filtration device (spiral filtration device) is the Pellicon® capsule, available from MilliporeSigma. The Pellicon® capsule is a single-use, single-pass tangential flow filtration device that uses a solvent-resistant membrane of Ultracel® composite material and is suitable for the bioprocessing of antibody-drug conjugates and monoclonal antibodies. Those skilled in the art will appreciate that other spiral wound devices, including reusable and / or multi-pass tangential flow devices, are also suitable.

[0026] Typically, spiral wound devices are manufactured by winding one or more packets of folded membrane and feed clean sandwiched between the folded membrane, and one or more permeable sheets into a device around a perforated core or mandrel. In some embodiments, one complete circumferential wrap of permeable sheet may be first wrapped around the core to provide an appropriate fluid path for permeate migration to the openings in the core. Because membrane packets are generally thicker than other materials, the wrapping operation of the membrane packet creates a wedge-shaped void area in front of the leading edge 5 of the membrane packet as it wraps around itself, as seen in FIG.

[0027] More specifically, Figure 1 shows a folded tip 5 of membrane 10 with a feed screen 12 sandwiched by the folded membrane 10. The folded membrane 10, with the feed screen sandwiched within the folds, contains a membrane packet 14. As the membrane packet 14 is wrapped onto itself, a void area 15 is formed, as can be seen just to the left of the membrane packet tip 5. Typically, this void area 15 is generally wedge-shaped. To eliminate this void area 15, conventional methods involve filling the void area 15 with excess adhesive to seal it. This is a laborious manual process that is not always successful. For example, the compression and nip forces of the subsequent winding tension can force the adhesive out of the space, again creating a void area and deforming the surrounding area. This creates a bypass area for fluid flow, reducing product yield and overall equipment performance.

[0028] According to certain embodiments, supports 20 are attached to the leading edge 5 of the membrane packet so that when the packet is rolled, the supports 20 occupy the space that would otherwise form void areas 15, as shown in Figures 2 and 4. The size and shape of the support 20 may be determined based on previous experience with the size and shape of the void areas 15 formed during a typical winding operation of a filter module of a given size. The support 20 may be attached to the tip 5 using adhesive means, ultrasonic welding means, heat welding means, UV adhesive means or any other suitable means.

[0029] 3 shows a preferred embodiment of the support 20. It shows a wedge-shaped support 20. When the membrane packet 14 is rolled, the support 20 occupies areas where void areas 15 would normally form, forcing the membranes 10 to remain in contact with the feed screen 12, thereby minimizing or avoiding fluid bypass areas.

[0030] Also, according to certain embodiments described below, during the potting process, the device is submerged in adhesive and a vacuum is pulled on the permeate fluid paths. If voids 15 are present, adhesive will migrate into the permeate fluid paths, causing blockage of the paths. Thus, the support 20 also functions to reduce or eliminate such adhesive migration, reducing the amount of adhesive required to seal the area. This also results in more uniform permeate path seams near the core or mandrel 12 and ultimately more uniform membrane area within each spiral-wound filtration module.

[0031] In certain embodiments, the supports 20 are attached to the leading edges 5 of the membrane packets 14, such as at seam locations, using a suitable adhesive (e.g., epoxy or polyurethane). When multiple membrane packets 14 are wound on a single core, e.g., in a bi-leaf assembly, each membrane packet 14 may have a support 20 attached to its leading edge 5. For example, FIG. 6 shows a four-leaf assembly, such that there are four supports 20 visible radially outward from the central perforated core 12.

[0032] In some embodiments, the support 20 is wedge-shaped to conform to the expected void that would form in the absence of the support 20 . In some embodiments, the thicker end 21 of the support 20 is 0.031 inches thick and tapers to the thin end 22 of the support 20 which is 0.003 inches thick, although one skilled in the art will appreciate that size is not critical as the support 20 is compressible and will conform to the shape of the gap. The thin end 22 may be radiused or have rounded corners to eliminate sharp edges that may tear the material it contacts. The thicker end 21 of the support 20 may be secured to the leading edge 5 of the membrane packet with a suitable adhesive. In certain embodiments, the support 20 is elongated and extends the entire length of the membrane packet 14, as best seen in FIG. In other embodiments, the individual supports 20 may be located only on opposite sides of the membrane packet 14 to block the ingress of adhesive into the permeate channels, and do not extend the entire length of the membrane packet 14. In certain embodiments, the support 20 is made of a solid, fluid-impermeable material that is not detrimental to the filtration operations performed with the module and that can provide a suitable seal for vacuum sealing on a mold used to introduce adhesive, as described in more detail below. Suitable materials include thermoplastic elastomers such as Pebax 5533 SA01 Med Pantone 298C. Preferably, the material is flexible enough to conform to the shape of the core 12.

[0033] Once the support 20 is secured to the leading edge 5 of the membrane packet 15, the membrane packet 15, together with the permeable screen 16 (FIG. 4) and adhesive, can be tightly wrapped under tension around the core 12 to form a spirally wound assembly. As the support 20 is rolled in, it becomes sandwiched on both sides by the transmission screen 14. This holds the support 20 in place until adhesive is applied to secure the support 20 in place. Because the leading edge 5 of the membrane packet 14 is supported by the support 20, the membrane 10 remains in contact with the feed screen 12, preventing collapse during the nip roller step which would remove adhesive from the area and lead to detrimental fluid bypass.

[0034] However, bonding the assembly with adhesive during wrapping is somewhat variable and prone to gaps forming which can lead to device failure.

[0035] Thus, according to certain embodiments, the assembly can be glued together using a driving force such as a vacuum or some pressure differential to evenly distribute the generally low viscosity adhesive onto the permeable sheet 14 to create a robust, uniform seam without the variations that occur with hand-made seams. To prevent the potting adhesive foam from entering the feed lines during the potting process, a fluid-impermeable feed screen edge may be used, as shown in Figure 7. The feed screen edge also prevents the feed flow from reaching the membrane outside of its edge. This action defines the effective membrane area and greatly reduces membrane area variation. Applying feed screen edges to the leading and trailing ends restricts flow to the membrane area only within these ends, thereby defining the effective membrane length of each membrane packet and improving feed and permeate channel geometry. In certain embodiments, at least three of the sides of the feed screen include fluid impermeable edges to prevent adhesive from entering the feed lines during potting. In some embodiments, one fluid-impermeable edge is on the feed face, one on the retentate face, and one on the open end of the membrane packet (which is part of the periphery). To activate the spiral of the feed flow, the feed edge and the retentate edge are removed. The feed end edge may be left in place. In some embodiments, all four sides of the feed screen include fluid-impermeable edges during potting (FIG. 8), and the feed and retention edges are also removed to activate the feed flow spiral. Adhesives in the feed lines can lead to loss of operational integrity or catastrophic loss of flow in the feed lines due to membrane delamination, for example, due to membrane separation under feed pressure.

[0036] Once the potting adhesive has been applied and cured, the edges on the spiral inlet and outlet faces can be removed, such as by cutting, to reopen the feed paths. A viscous polyurethane adhesive (or thermoplastic, silicone, or thermoplastic elastomer) is suitable for forming a solid, impermeable feed screen edge. In certain embodiments, a film, such as a polyethylene film, may be used as a backing layer for the feed screen while dispensing an edge adhesive onto the feed screen to form a fluid impermeable edge. In some embodiments, after all the adhesive has been deposited around the perimeter, a second layer of film, such as a polyethylene film, is also applied to the top of the feed screen, and the resulting feed screen sandwich is compressed to distribute the adhesive to the shape of the edge.

[0037] FIG. 5 shows a mold body 30 suitable for potting spiral wound assemblies using vacuum as the driving force to distribute the adhesive. In certain embodiments, the dry wound spiral assembly 25 is disposed within a mold body 30. The mold body 30 has an adhesive injection port 31 in fluid communication with an interior mold body cavity 32 in which the dry wound spiral assembly 25 is disposed. Preferably, adhesive injection port 31 is located at or near the bottom of mold body 30 so that upon application of a driving force, the adhesive flows upward and trapped air is removed during filling. In some embodiments, the perforated core 12 of the dry wound spiral assembly 25 is disposed in sealing relationship with a tapered or O-ring interface 33 of the mold body 30 . An O-ring seal 36 or the like may be provided at the opposite end of the mold body 30 to ensure that the dry wound spiral assembly 25 is in a sealed relationship with the mold body 30 so that no leakage occurs when a vacuum is applied.

[0038] In some embodiments, a suitable potting adhesive, such as epoxy or polyurethane, is introduced into injection port 31 and a vacuum is applied to vacuum inlet 40 to force the adhesive into the permeable screen, creating all necessary device seams and completely encasing assembly 25 around spiral assembly 25. Suitable vacuum levels range from 1 to 15 inches of mercury for 1 to 300 seconds. Once the adhesive cures, the device is covered with an annular hard shell reinforced with a permeable screen 35 (FIG. 6), which resists expansion under pressure drops, e.g., up to 100 psig, which could open the feed channel geometry and degrade device performance.

[0039] In some embodiments, the mold body 30 can be configured so that certain features, such as an annular ring for receiving an O-ring when the formed spiral assembly is used as a stand-alone module (i.e., a module without an external housing or pressure vessel), are formed in the outer surface of the cured adhesive. These features can also be machined.

[0040] In some embodiments, the mold can be a housing that forms part of the final product, for example a plastic housing into which the spiral wound filter is placed.

[0041] The device can be sterilizable by steam, ethylene oxide gas, or radiation, such as beta or gamma radiation.

[0042] While various aspects and embodiments have been disclosed herein, other aspects, embodiments, modifications, and alterations will be apparent to those skilled in the art upon reading and understanding the foregoing detailed description. The various aspects and embodiments disclosed herein are for purposes of illustration and not limitation. It is intended that the present disclosure be construed as including all such aspects, embodiments, modifications, and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

1. A spirally wound membrane module, a perforated core having an axially extending internal bore; at least one membrane packet including a folded membrane sheet defining a first outer surface, a first inner surface, a second outer surface, and a second inner surface, wherein a fold in the folded membrane sheet is a leading edge of the membrane packet; a feed sheet disposed between the first inner surface and the second inner surface so as to be sandwiched by the folded membrane sheet; a first permeate sheet adjacent the first outer surface of the membrane sheet, the first permeate sheet defining a first permeate passage; a second permeate sheet adjacent the second outer surface of the membrane sheet, the second permeate sheet defining a second permeate passage; a fluid-impermeable support coupled to the leading edge of the membrane packet and occupying a space between the leading edge and the first and second permeable sheets; Equipped with the impermeable support is wedge-shaped; the membrane module is cylindrical in cross section and has an outer surface of cured adhesive; A spirally wound membrane module.

2. A plurality of membrane packets are provided, each of the plurality of membrane packets having a leading end and a fluid-impermeable support disposed at each leading end.

10. The spiral wound membrane module of claim 1.

3. 1. A method of potting a spiral wound membrane, comprising: placing the spiral wound membrane module of claim 1 in sealing relationship with a mold cavity; introducing an adhesive into the mold cavity; applying a vacuum to the mold cavity, whereby the vacuum forces the adhesive into the first and second permeate channels; and allowing the adhesive to cure. Including, method.

4. the feed sheet has four edges and has a solid, liquid-impermeable edge on at least three edges during the potting operation; The method of claim 3.

5. the spirally wound membrane further comprises liquid-impermeable edges on the supply surface and the support surface, the edges on the supply surface and the support surface being removed after the adhesive is cured; The method of claim 3.

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