Spiral wound filter device and method of manufacturing the same

Abstract

A spiral wound membrane module comprising: a perforated core having an axially extending internal bore; at least one membrane pack comprising a folded membrane sheet defining a first outer face, a first inner face, a second outer face and a second inner face, the fold of the folded membrane sheet being the leading end of the membrane pack; a feed sheet positioned between the first and second inner faces so as to be sandwiched between the folded membrane sheet; a first permeate screen adjacent the first outer face of the membrane sheet so as to define a first permeate channel; a second permeate screen adjacent the second outer face of the membrane sheet so as to define a second permeate channel; and a fluid impermeable support coupled to the leading edge of the membrane pack. Also disclosed is a method of manufacturing a spiral wound membrane module.

Description

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 62 / 779,860, filed December 14, 2018; U.S. Provisional Patent Application Serial No. 62 / 779,867, filed December 14, 2018; U.S. Provisional Patent Application Serial No. 62 / 780,634, filed December 17, 2018; and U.S. Provisional Patent Application Serial No. 62 / 780,689, filed December 17, 2018, the disclosures of all of the above U.S. Provisional Patent Applications of which are hereby incorporated by reference.

[0002] This application is a divisional application of Chinese Patent Application 201980082409.3 (Application date: December 5, 2019; Title: Spiral-wound Filter Device and Method for Manufacturing the Same). Technical Field

[0003] This disclosure generally relates to helical wound membrane filter elements or modules and methods of manufacturing the same. More specifically, a helical wound filter module is disclosed, wherein the module includes one or more features to provide binder migration control, prevent feed channel geometry changes, and minimize or eliminate voids, thereby resulting in a more consistent manufacturing process and consistent reproducibility for the helical wound filter. A manufacturing method is also disclosed, based on a novel assembly process in which the membrane and screen are first wound around a permeate discharge core to form a helix, followed by the application of an binder to form a permeate envelope, attaching the helix to the core, sealing the circumference, and filling the toroidal surface into a housing or providing a pressure-bearing circumferential housing. Background Technology

[0004] Spiral-wound filter modules are commonly used for filtration, including ultrafiltration and reverse osmosis. Such modules are typically manufactured by spirally winding multiple membrane sheets, spacer materials, and permeate sheets around a perforated hollow core or mandrel, and can then be centrally positioned within a housing or cylinder.

[0005] More specifically, the spirally wound filter module is a multi-layer device that may include one or more permeation spacers (which may be porous fabrics), one or more membrane sheets, and one or more feed screens or spacers. The module can be constructed by spirally winding the one or more membranes, feed spacers, and permeation screens around a permeation core, tube, or mandrel, which has multiple openings such as slots or holes communicating with a central orifice to collect permeate. An adhesive can be used to secure the resulting assembly in place around the mandrel. The resulting module can be positioned within a housing capable of withstanding typical operating pressures.

[0006] Some spirally wound filter modules may include multiple blades, each blade having a layer of permeate material, which may be a porous fabric material, sandwiched between two membranes. The membranes may be folded in half, and a feed screen is positioned between the two halves to form a membrane pack. The membrane pack and permeate sheet are wound around a mandrel or core having openings within it to collect permeate. Modules with one or four blades are typical, however, they can be constructed from any number of blades. For example, 0.1m 2 The module can have a single blade; 0.5m 2 The module can have four blades and a length greater than 1m. 2 (For example, 2.0m) 2 A spiral device with a larger membrane area can have up to 16 blades.

[0007] However, the spiral winding of the membrane pack results in a wedge-shaped gap in front of the pack's leading edge (see Figure 1). Furthermore, the membrane's ability to exit the feed screen rearward also creates a gap or void in front of the feed screen (Figure 1), leading to a bypass flow around the screen. This bypass flow degrades performance.

[0008] Furthermore, the adhesive is manually introduced into the component to bond the layers together and to the perforated core, and this process often results in irregular adhesive boundaries, which in turn can lead to variability in membrane area and a higher risk of integrity failure due to human error.

[0009] Therefore, it is desirable to mitigate or eliminate these problems and improve the performance of spiral-wound filter modules. Summary of the Invention

[0010] The problems of the prior art have been overcome by the embodiments disclosed herein, which relate to a helically wound filter module and a method of manufacturing the same. In some embodiments, the filter module includes supports, such as wedge supports, for eliminating one or more voids that would otherwise be formed during assembly due to the winding operation, and for eliminating one or more voids when the membrane moves away from the feed screen. In some embodiments, the supports are positioned to occupy some or all of the areas where such voids would normally form, and support the membrane and screen wound radially outward from the core. This prevents the feed channels of each layer above from changing geometry under higher pressure. This additional advantage maintains a constant feed channel geometry throughout the device, thereby increasing performance and reducing pressure drop variability. Furthermore, creases, cracks, and folds at the leading edge of the membrane pack are known modes of retention loss in the helix, and supports coupled to the leading edge of the membrane pack can reduce the likelihood of leading edge failure during operation.

[0011] Another advantage of the support is realized when the adhesive is drawn into or driven into the device during the potting process. The support prevents harmful potting adhesive from migrating into the device through the wedge-shaped gap, especially in cases involving multi-bladed helical modules. The presence of the support also reduces the amount of adhesive required.

[0012] In some embodiments, a filter module is disclosed, formed by spirally winding a multilayer material around a core to form a generally cylindrical structure with two opposing spiral end surfaces. The layers are adhered along their longitudinal and transverse edges such that unfiltered fluid supplied to the unit through one spiral end surface during use must pass through or tangentially cross one or more membrane layers before leaving the unit through the opposing spiral end surfaces. A sealing arrangement is provided at each spiral surface of the wound filter to ensure that the influent fluid passes through the membrane surface before leaving the unit. In some embodiments, the multilayer material includes one or more membrane sheets, one or more feed screens, and one or more permeate sheets or screens. The one or more membrane sheets may be folded once along their length to form blades with two halves integrally connected together, and the feed screen is positioned or sandwiched between the two halves to form a membrane package. The assembly forms spirally wound permeate and concentrate flow channels. A support is positioned at the location where the membrane package is folded, which is its leading edge during winding to eliminate void areas that would otherwise be formed when winding the package and permeate sheets around the core.

[0013] To filter the product, it can be introduced under pressure at one end of a spirally wound membrane module and flows axially through a feed screen, where it then flows tangentially through the membrane, and a portion of it flows through the membrane to reach the permeate channels defined between each membrane and the adjacent permeate sheet. The permeate then flows to the perforated core and is eventually removed from the module.

[0014] In some embodiments, a helically wound membrane module is disclosed, comprising: a perforated core having an axially extending internal aperture; at least one membrane pack including a folded membrane sheet defining a first outer surface, a first inner surface, a second outer surface, and a second inner surface, the fold of the folded membrane sheet being a front end of the membrane pack; a feed sheet positioned between the first and second inner surfaces to be sandwiched between the folded membrane sheet; a first permeate screen adjacent to the first outer surface of the membrane sheet to define a first permeate channel; a second permeate screen adjacent to the second outer surface of the membrane sheet to define a second permeate channel; and a support for an impermeable fluid coupled to the leading edge of the membrane pack.

[0015] In some aspects, there are multiple membrane packs, each having a leading edge and a support for an impermeable fluid connected to each respective leading edge.

[0016] In some aspects, impermeable supports are wedge-shaped.

[0017] In some respects, impermeable supports are non-uniformly deformable in order to fill non-uniform voids.

[0018] In some aspects, the module has a cylindrical cross-section and an outer surface with cured adhesive.

[0019] In some embodiments, a method for potting a spirally wound membrane is disclosed, the method comprising: positioning the spirally wound membrane in a sealed relationship with a mold cavity; introducing an adhesive into the mold cavity; applying a vacuum to a permeation core, tube, or mandrel, thereby driving the adhesive into the permeation channels and around the outer periphery of the core; and allowing the adhesive to cure. In the case where a permeation screen is placed around the core, the adhesive is also driven into the permeation screen to anchor the spiral to the core. The spiral in this method comprises only boundary feed screens designed to prevent adhesive intrusion into the feed channels during the potting process; they include impermeable boundaries on all three sides corresponding to the three sides of the permeation envelope. The side boundaries are made narrower than the side seams of the permeation envelope; therefore, when they are removed (e.g., cut off) after the spiral adhesive has cured, the feed channels open for tangential flow while the permeation envelope remains sealed. The feed screen can also have four boundaries, with the fourth boundary on the leading edge of the feed screen (near the fold in the membrane pack); this prevents the feed screen from damaging the leading edge membrane. Attached Figure Description

[0020] Figure 1 is a photograph showing a wedge-shaped gap formed between the membrane and the feed screen of a spirally wound filter device, according to the prior art;

[0021] Figure 2 The photographs, according to certain embodiments, show supports inserted into wedge-shaped gaps formed between the membrane and the permeate screen of a spirally wound filtration device and between the membrane and the feed screen.

[0022] Figure 3 This is a cross-sectional view of the support member according to certain embodiments;

[0023] Figure 4 This is a schematic diagram of the support and membrane pack during the winding operation;

[0024] Figure 5 This is a cross-sectional view of a potting mold according to certain embodiments;

[0025] Figure 6 This is a photograph of a top view of a spirally wound membrane module according to certain embodiments;

[0026] Figure 7 These are photographs of a module having a bordered feed screen according to certain embodiments;

[0027] Figure 8 This is a photograph of a feed screen with four borders according to certain embodiments. Detailed Implementation

[0028] A more complete understanding of the components, processes, and apparatus disclosed herein can be obtained by referring to the accompanying drawings. The drawings are merely illustrative representations for convenience and ease of demonstrating this disclosure, and are therefore not intended to limit or restrict the scope of exemplary embodiments.

[0029] Although specific terms are used in the following description for clarity, these terms are intended only to refer to the specific structures in the drawings for illustrating selected embodiments and are not intended to limit or restrict the scope of this disclosure. In the drawings and the following description, it should be understood that similar reference numerals refer to components having similar functions.

[0030] The singular forms “a”, “an”, and “the” include plural referents unless the context clearly indicates otherwise.

[0031] As used in the specification, various devices and parts may be described as "including" other components. As used herein, the terms "including," "comprising," "having," "having," "may," "accommodating," and variations thereof are intended as open-ended transitional phrases, terms, or words that do not exclude the possibility of additional components.

[0032] In some embodiments, the filtration device is a filtration module having a fluid inlet, a fluid outlet spaced apart from the fluid inlet, a permeate outlet, a central core having multiple openings and pores extending axially along its entire length, one or more membrane packs, and one or more permeate sheets. Each membrane pack is sandwiched between feed sheets or screens, which may be polyolefin sheets such as polypropylene, and may also be one or more permeate sheets such as one or more polyester screens, which may be impregnated with epoxy resin to provide them with sufficient strength to withstand the typical operating pressures encountered during use. The feed screen provides space for the feed flow between the opposing membranes sandwiched therebetween. The permeate sheets provide a fluid path for the permeate flow to the perforated core. One or more membrane packs and one or more permeate sheets are wound into a helical configuration around the core. The membrane within each membrane pack may be a single-layer or multi-layer membrane and can be used to filter unwanted materials, including contaminants such as infectious organisms and viruses, as well as environmental toxins and pollutants, which can be removed by size exclusion and a combination of chemical or physical adsorption. The membrane can be composed of any suitable material, including but not limited to polyethersulfone, polyamides such as nylon, cellulose, polytetrafluoroethylene, polysulfone, polyester, polyvinylidene fluoride, polypropylene, fluorocarbons (e.g., poly(tetrafluoroethylene-co-perfluoro(alkyl vinyl ether))), polycarbonate, polyethylene, glass fiber, ceramics, and metals. It can be a microfiltration, ultrafiltration, or reverse osmosis membrane. Ultrafiltration membranes are particularly preferred.

[0033] A suitable spiral-wound filter device is commercially available from MilliporeSigma. capsule. The capsule is a single-use, single-pass tangential flow filter. The composite solvent-resistant membrane is suitable for the bioprocessing of antibody-drug conjugates and monoclonal antibodies. Those skilled in the art will recognize that other helical winding devices are also suitable, including reusable and / or multiple-pass tangential flow devices.

[0034] Typically, a spiral-wound device is manufactured by winding a package consisting of one or more pleated membranes and feed screens sandwiched between the pleated membranes, along with one or more permeate sheets, around a perforated core or mandrel. In some embodiments, a complete circumferential winding of the permeate sheet may first be wound around the core to provide a suitable fluid path for the permeate fluid to travel into the openings in the core. Because the membrane package is typically thicker than other materials, the winding operation of the membrane package creates a wedge-shaped void region in front of the leading edge 5 of the membrane package as it is wound around itself, as can be seen in Figure 1.

[0035] More specifically, Figure 1 illustrates the folded leading edge 5 of the membrane 10, with the feed screen 12 sandwiched between the folded membranes 10. The folded membrane 10 with the feed screen sandwiched within the fold includes a membrane bundle 14. As the membrane bundle 14 winds itself, a void region 15 is formed, as seen, on the left side of the membrane bundle leading edge 5, and this void region 15 is typically wedge-shaped. To eliminate this void region 15, it is conventionally filled with excess adhesive to seal it, a cumbersome manual process that is not always successful. For example, subsequent compression and clamping forces from the winding tension can cause the adhesive to be squeezed out of the space, thus recreating the void region and potentially deforming the surrounding area. This creates a bypass area for fluid flow and reduces the product yield and overall performance of the apparatus.

[0036] According to some embodiments, the support 20 is attached to the leading edge 5 of the film pack such that once the pack is wound, the support 20 occupies the space that would otherwise form the void region 15, such as... Figure 2 and Figure 4 As shown in the diagram. The size and shape of the support 20 can be determined based on prior experience with the size and shape of the void region 15 formed during typical winding operations of a filter module of a given size. The support 20 can be attached to the leading edge 5 using adhesive means, ultrasonic welding means, thermal welding means, UV adhesive means, or any other suitable means.

[0037] Figure 3 A preferred embodiment of the support 20 is illustrated, showing a wedge-shaped support 20. Once the membrane pack 14 is wound up, the support 20 will occupy the area that would normally form the void region 15 and minimize or avoid the fluid bypass region because the membrane 10 is forced to remain in contact with the feed screen 12.

[0038] Furthermore, according to some embodiments described below, during the potting process, the device is immersed in adhesive and a vacuum is applied to the permeate fluid flow channels. If voids 15 are present, adhesive migrates into the permeate fluid flow channels, causing blockage. Therefore, the support 20 also serves to mitigate or eliminate such adhesive migration and reduce the amount of adhesive required for the sealing area. This also results in a more uniform permeate channel seam near the core or mandrel 12 and ultimately a more uniform membrane area within each spirally wound filter module.

[0039] In some embodiments, the support 20 is attached to the leading edge 5 of the membrane pack 14 using a suitable adhesive (e.g., epoxy or polyurethane), such as at seam locations. In cases where multiple membrane packs 14 are wound around a single core (e.g., in a multi-leaf assembly), each membrane pack 14 may have a support 20 attached to its leading edge 5. For example, Figure 6The illustration shows a four-blade assembly, and therefore there are four support members 20 that are visible radially outward from the central perforated core 12.

[0040] In some embodiments, the support 20 is wedge-shaped to match the expected gap that would form without the support 20. In some embodiments, the thicker end 21 of the support 20 is 0.031 inches thick and tapers towards the thinner edge 22 of the support 20, which is 0.003 inches thick; however, those skilled in the art will recognize that this size is not critical, as the support 20 is compressible and will conform to the shape of the gap. The thin edge 22 may have rounded or rounded corners to eliminate sharp edges that could tear the material it contacts. The thicker end 21 of the support 20 can be secured to the front end 5 of the membrane pack using a suitable adhesive. In some embodiments, the support 20 is elongated and extends the entire length of the membrane pack 14, such as... Figure 8 The best view is as shown. In other embodiments, the individual support 20 may be positioned only on the opposite side of the membrane pack 14 to prevent adhesive from entering the permeation channels and not extend the entire length of the membrane pack 14. In some embodiments, the support 20 is made of a solid, fluid-impermeable material that is harmless to the filtration operation of the module to be performed and provides sufficient sealing for vacuum sealing on the mold used to introduce the adhesive, as discussed in more detail below. Suitable materials include thermoplastic elastomers such as Pebax 5533SA01 Med Pantone 298C. Preferably, the material is flexible enough to conform to the shape of the core 12.

[0041] Once the support 20 is secured to the leading edge 5 of the membrane pack 15, the membrane pack 15 can be held under tension with the permeate screen 16 ( Figure 4 The membrane 10 is tightly wound around the core 12 along with the adhesive to form a wound spiral assembly. As the support 20 is wound inside, it becomes sandwiched between the permeate screen 14 on either side, which holds the support 20 in place until the adhesive is applied to secure it in place. Because the leading edge 5 of the membrane pack 14 is supported by the support 20, the membrane 10 remains in contact with the feed screen 12 and is prevented from collapsing during the pinch roll step, which would remove the adhesive from that area and cause harmful fluid bypass.

[0042] However, there are some variations in bonding components with adhesives during winding, and gaps can easily form that can lead to device malfunction.

[0043] Therefore, according to some embodiments, the components can be joined together using a driving force (such as a vacuum) or some pressure difference to uniformly distribute a generally low-viscosity adhesive into the permeation sheet 14, producing a robust and uniform seam without the variability caused by manually manufactured seams. To prevent the potting adhesive from entering the feed channel during the potting process, the feed screen boundary, which is impermeable to fluids, can be as follows: Figure 7 The feed screen boundary is used as shown. The feed screen boundary also prevents any feed flow from reaching any membrane outside the boundary. This effect defines the effective membrane area, thus significantly reducing membrane area variability. Applying the feed screen boundary at the leading and trailing edges restricts the flow to the membrane region only within these edges, and thus defines the effective membrane length for each membrane pack, which also improves the feed channel geometry and permeate channel geometry. In some embodiments, at least three feed screen sides include an impermeable fluid boundary to prevent binder from entering the feed channel during filling. In some embodiments, one of the impermeable fluid boundaries is on the feed face, one on the retentate face, and one at the open tail end of the membrane pack (which is part of the circumference). The feed and retentate boundaries are removed to activate the helical nature of the feed flow. The feed tail boundary may be retained. In some embodiments, all four sides of the feed screen include an impermeable fluid boundary during filling. Figure 8 Similarly, the feed and sludge boundaries are removed to activate the feed flow spiral. Adhesive in the feed channel can cause catastrophic loss of the feed channel flow or loss of operational integrity due to membrane delamination (e.g., when the membrane separates under feed pressure).

[0044] Once the potting adhesive is applied and cured, the boundaries on the helical inlet and outlet faces can be removed, such as by cutting them off to reopen the feed channel. Adhesive polyurethane adhesives (or thermoplastics, silicones, or thermoplastic elastomers) are suitable for forming impermeable solid boundaries on the feed screen. In some embodiments, a membrane, such as a polyethylene film, can be used as a backing layer for the feed screen during the application of boundary adhesive to the feed screen to form impermeable fluid boundaries. In some embodiments, after all the adhesive has been deposited around the perimeter, a second layer of film (e.g., a polyethylene film) is also applied to the top of the feed screen, and the resulting feed screen interlayer is compressed such that the adhesive is distributed in the shape of the boundaries.

[0045] Figure 5A suitable mold body 30 is shown for filling a wound helical assembly using a vacuum as the driving force for distributing the adhesive. In some embodiments, a dry wound helical assembly 25 is placed in the mold body 30, which has an adhesive injection port 31 in fluid communication with an internal mold body cavity 32 in which the dry wound helical assembly 25 is positioned. Preferably, the adhesive injection port 31 is located at or near the bottom of the mold body 30 such that the adhesive flows upward when the driving force is applied, thereby removing any trapped air during filling. In some embodiments, the perforated core 12 of the dry wound helical assembly 25 is positioned in a sealing relationship with the tapered or O-ring interface 33 of the mold body 30. An O-ring seal 36 or similar element may be provided at the opposite end of the mold body 30 to ensure that the dry wound helical assembly 25 is sealed to the mold body 30 so that there is no leakage when a vacuum is applied.

[0046] In some embodiments, a suitable potting adhesive (such as epoxy or polyurethane) is introduced into the injection port 31, and a vacuum is applied at the vacuum inlet 40 to drive the adhesive into the permeation screen, thereby creating all necessary device seams and completely encapsulating the spiral assembly 25. Suitable vacuum levels range from 1 to 15 mercury for 1-300 seconds. Once the adhesive has cured, the device is encased in an annular rigid shell reinforced by the permeation screen 35. Figure 6 This will resist expansion under high pressure drops (e.g., up to 100 psig). Such expansion can open up the feed channel geometry and lead to a decrease in device performance.

[0047] In some embodiments, the mold body 30 can be configured such that certain features, such as annular rings, are formed on the outer surface of the cured adhesive to receive O-rings when the formed spiral assembly is used as a stand-alone module (i.e., without any external housing or pressure vessel). These features can also be machined.

[0048] In some embodiments, the mold can be a housing that forms part of the final product, such as a plastic housing in which a spirally wound filter is positioned.

[0049] The device can be sterilized by means of steam, ethylene oxide gas, or radiation such as beta or gamma radiation.

[0050] While various aspects and embodiments have been disclosed herein, other aspects, embodiments, modifications, and variations 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 illustrative purposes and are not intended to be limiting. This disclosure is intended to be construed as including all such aspects, embodiments, modifications, and variations, provided they fall within the scope of the appended claims and their equivalents.

Claims

1. A method of forming a filter module comprising providing at least one membrane sheet, at least one feed screen, and at least one permeate sheet; folding the at least one membrane sheet along its length to form a leaflet having two halves integrally joined together; positioning the at least one feed screen between the two halves to form a packet with a membrane packet fold; positioning an impermeable support at the location of the membrane packet fold to form a leading edge of the membrane packet; and spirally winding the membrane packet and the at least one permeate sheet around a core, the location of the impermeable support avoiding the formation of a void area in front of the leading edge of the membrane packet.

2. The method of claim 1, wherein, The impermeable support is wedge shaped.

3. The method of claim 1, wherein, The module is cylindrical in cross section and has an outer surface of cured binder.

4. The method of claim 1 comprising providing a plurality of membrane packets, each having a leading edge and an impermeable fluid support coupled to each respective leading edge.

5. The method of claim 1 wherein there are at least a first permeate sheet and a second permeate sheet, and the method further comprises potting the filter module by positioning the spirally wound membrane module in sealing relationship with a mold cavity; introducing a binder into the mold cavity; applying a vacuum to the mold cavity; whereby the vacuum drives the binder into first and second permeate channels, the first permeate channel formed between the first permeate sheet and a first outer face of the membrane sheet, the second permeate channel formed between the second permeate sheet and a second outer face of the membrane sheet; and allowing the binder to cure.

6. A method of filtering a product through a spiral wound membrane module having an end face, the module comprising: a perforated core having an axially extending interior bore; at least one membrane packet comprising a folded membrane sheet defining a first outer face, a first inner face, a second outer face, and a second inner face, the fold of the folded membrane sheet being a leading edge of the membrane packet; a feed sheet positioned between the first and second inner faces so as to be sandwiched between the folded membrane sheet; a first permeate sheet adjacent the first outer face of the membrane sheet defining a first permeate channel; a second permeate sheet adjacent the second outer face of the membrane sheet defining a second permeate channel; and an impermeable fluid support coupled to the leading edge of the membrane packet and occupying a void between the leading edge and the first and second permeate sheets; the method comprising: introducing the product under pressure at the end face, causing the product to flow axially through the feed sheet, and then tangentially through the membrane sheet, a portion of which flows through the membrane sheet where it reaches a permeate channel defined between each membrane sheet and an adjacent permeate sheet.

7. The method of claim 6 further comprising removing permeate flowing to the perforated core from the module.

8. The method of claim 6, wherein, The impermeable support is wedge shaped.

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