Patent Description:
Spirally wound filter modules are commonly used in filtration, including ultrafiltration and reverse osmosis. Typically, such modules are manufactured by spirally winding a plurality of membrane sheets, spacer materials and permeate sheets around a perforated hollow core or mandrel, which may then be centrally located in a housing or cartridge.

More specifically, spiral wound filtration modules are multi-layered devices that may include one or more permeate spacers, which may be a porous fabric, one or more membrane sheets, and one or more feed screens or spacers. The module may be constructed by spirally winding the one or more membranes, feed spacers and permeate screens around a permeate core, tube or mandrel which has a plurality of openings such as slots or holes therein communicating with a central bore to collect the permeate. An adhesive may be used to fix the resulting assembly in place around the mandrel. The resulting module may be positioned in a housing capable of withstanding typical operating pressures.

Some spiral wound filtration modules may include a plurality of leaves, each having a layer of a permeate sheet or screen, which may be a porous fabric material, sandwiched between two membrane sheets. The membrane sheets may be folded in half with a feed screen positioned between the two halves to form a membrane packet. The membrane packets and permeate sheet are wound around a mandrel or core which has openings in it to collect permeate. Modules with one and four leaves are typical but can consist of any number of leaves. For example, a <NUM><NUM> module may have a single leaf; a <NUM><NUM> module may have four leaves and larger spiral devices with membrane areas greater than <NUM><NUM> (e.g., <NUM><NUM>) may have up to <NUM> leaves.

<CIT> discloses a reverse osmosis separator assembly useful in the purification of fluids. A central core element thereof comprises an outer exhaust conduit defining an inner volume and a gap starting at a first end thereof the outer exhaust conduit and extending towards a second end of the outer exhaust conduit, and an inner porous exhaust conduit comprising a first section disposed within the inner volume defined by outer exhaust conduit and a second section configured to abut and seal the first end of the outer exhaust conduit.

However, spiral wrapping of the membrane packet results in a wedge-shaped void in front of the leading edge of the packet (see <FIG>). In addition, the membrane can back away from the feed screen, also resulting in a gap or void in front of the feed screen (<FIG>) that causes bypass flow to occur around the screen. This bypass flow reduces performance.

In addition, adhesive is manually introduced into the assembly to bind the layers together and to the perforated core, and this process often results in an irregular adhesive border, which in turn can cause variability in membrane area as well as a higher risk of human error caused integrity failures.

It therefore would be desirable to mitigate or eliminate these issues and improve the performance of the spiral wound filtration modules.

The problems of the prior art have been overcome by embodiments disclosed herein, which relate to spiral wound membrane modules according to claim <NUM> and methods of potting a spiral wound membrane the same according to claim <NUM>. Preferred embodiments are described in the subclaims.

The filtration module includes a wedge-shaped support that functions to eliminate the void or voids that otherwise forms as a result of the winding operation during assembly, and functions to eliminate the void or voids as the membrane moves away from the feed screen. The support is positioned to occupy all of the region where such a void would normally form, and supports the membrane and screen that is radially wound outwardly from the core. This prevents the feed channel of every layer above from changing geometry at higher pressures. This added benefit keeps the feed channel geometry consistent throughout the device, increasing performance and reducing pressure drop variability. Furthermore, crease, cracks and fold failures of the leading edge of the membrane packet are a well-known mode of loss of retention in spirals, and a support coupled to the leading edge of the membrane packet can reduce chance of failure of the lead edge in operation.

A further advantage of the support is realized when adhesive is drawn or driven into the device during a potting process. The support prevents deleterious potting adhesive migration into the device through the wedge gaps, particularly where multi-leaf spiral modules are involved. The presence of the support also reduces the amount of adhesive required.

In certain embodiments, disclosed is a filter module formed by spirally winding multiple layers of materials around a core to form a generally cylindrical construction having two opposing spiral end surfaces. The layers are adhered along the lengthwise and widthwise edges so that, in use, unfiltered fluid supplied to the unit through one spiral end surface must pass through, or tangentially across a membrane layer or layers before it passes out of the unit through the opposing spiral end surface. Sealing arrangements are provided at each spiral surface of the wound filter to assure that incoming fluid passes through a membrane surface before leaving 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. The one or more membrane sheets may be folded once along its length to form a leaf with two halves integrally joined together, and a feed screen positioned or sandwiched between the two halves to form a membrane packet. The assembly forms spirally wound permeate and concentrate flow channels. A support is positioned at the location of the membrane packet fold, which is its leading edge during winding, to eliminate the void region that otherwise forms upon winding the packet and permeate sheet about the core.

To filter product, the product may be introduced at one end face of the spiral wound membrane module under pressure, and flows axially through the feed screens, where it then flows tangentially across the membrane and a portion of it flows through the membranes where it reaches the permeate channels defined between each membrane and an adjacent permeate sheet. The permeate then flows to the perforated core and is ultimately removed from the module.

Disclosed is a spiral wound membrane module, comprising a perforated core having an axially extending internal 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 said folded membrane sheet being a leading end of the membrane packet; a feed sheet positioned between said first and second inner faces so as to be sandwiched by the folded membrane sheet; a first permeate screen adjacent said first outer face of said membrane sheet defining a first permeate channel; a second permeate screen adjacent said second outer face of said membrane sheet defining a second permeate channel; and a fluid impermeable support coupled to said leading edge of said membrane packet.

In some aspects, there are a plurality of membrane packets, each having a leading edge and a fluid impermeable support coupled to each respective leading edge.

According to the invention, the impermeable support is wedge-shaped.

The impermeable support is non-uniformly deformable in such a manner as to fill a non-uniform void space.

In some aspects, the module is cylindrical in cross-section and has an outer surface of cured adhesive.

In certain embodiments, a method of potting a spiral wound membrane is disclosed, the method comprising positioning the spiral wound membrane into sealing relation with a mold cavity; introducing an adhesive into the mold cavity; applying a vacuum to the permeate core, tube or mandrel, whereby the vacuum drives the adhesive into the permeate channels and around the outer perimeter of the core; and allowing the adhesive to cure. Where a wrap of permeate screen is placed around the core, the adhesive is also driven into that permeate screen to anchor the spiral to the core. The spiral in this method comprises only bordered feed screens, designed to prevent intrusion of adhesive into the feed channel during the potting process; they contain impermeable borders on all sides corresponding to the three sides of the permeate envelope. The side borders are made narrower than the permeate envelope side seams; thus, when they are removed (e.g., cut off) after the spiral adhesive is cured, the feed channel is opened for tangential flow, while the permeate envelope remains sealed. The feed screen may also have four borders, wherein the fourth border is on the lead edge of the feed screen (near fold in the membrane packet); it may prevent damage of the lead edge membrane from the feed screen.

A more complete understanding of the components, processes and devices disclosed herein can be obtained by reference to the accompanying drawings. The figures are merely schematic representations based on convenience and the ease of demonstrating the present disclosure, and is, therefore, not intended to define or limit the scope of the exemplary embodiments.

Although specific terms are used in the following description 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 the following description below, it is to be understood that like numeric designations refer to components of like function.

As used in the specification, various devices and parts may be described as "comprising" other components. The terms "comprise(s)," "include(s)," "having," "has," "can," "contain(s)," and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional components.

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 an axially extending bore along its entire length, one or more membrane packets, in each of which is sandwiched 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 that may be epoxy impregnated to provide it with sufficient strength to withstand the typical operating pressures encountered during use. The feed screen provides space for the flow of feed between the opposing membranes that sandwich it. The permeate sheets provide fluid pathways for permeate flow to the perforated core. The membrane packet or packets and permeate sheet or sheets are wound in a spiral configuration about the core. The membrane within each membrane packet may be a single layered or multilayered membrane, and may be used for filtration of unwanted materials including contaminants such as infectious organisms and viruses, as well as environmental toxins and pollutants that could be removed by size exclusion and chemical or physical adsorption of the combination thereof. The membrane may be comprised of any suitable material, including, but not limited to polyether sulfone, polyamide, e.g., Nylon, cellulose, polytetrafluoroethylene, polysulfone, polyester, polyvinylidene fluoride, polypropylene, a fluorocarbon, e.g. poly (tetrafluoroethylene-co-perfluoro(alkyl vinyl ether)), poly carbonate, polyethylene, glass fiber, polycarbonate, ceramic, and metals. It may be a microfiltration, ultrafiltration or reverse osmosis membrane. Ultrafiltration membranes are particularly preferred.

One suitable spiral wound filtration device is the Pellicon® capsule commercially available from MilliporeSigma. The Pellicon® capsule is a single use, single pass tangential flow filtration device that uses Ultracel® composite, solvent-resistant membranes and is suitable for bioprocessing of antibody-drug conjugates and monoclonal antibodies. Those skilled in the art will appreciate that other spiral wound devices are also suitable, including re-usable and/or multiple pass tangential flow devices.

Typically, a spiral wound device is manufactured by winding one or more packets made up of a folded membrane and feed screen sandwiched by the folded membrane, and one or more permeate sheets, into the device around a perforated core or mandrel. In some embodiments, one full circumferential wrap of a permeate sheet may be first wound around the core to provide an adequate fluid pathway for permeate fluid to travel to the openings in the core. Since the membrane packet is generally thicker than the other materials, the winding operation of the membrane packet creates a wedge-shaped void region in front of the leading edge <NUM> of the membrane packet as it winds over itself, as can be seen in <FIG>.

More specifically, <FIG> illustrates the folded over leading edge <NUM> of a membrane <NUM> with a feed screen <NUM> sandwiched by the folded over membrane <NUM>. The folded over membrane <NUM> with a feed screen sandwiched within the fold comprises a membrane packet <NUM>. As the membrane packet <NUM> is wound over itself, void region <NUM> forms as seen just to the left of the membrane packet leading edge <NUM>, and this void region <NUM> is typically generally wedge-shaped. To eliminate this void region <NUM>, it has been conventionally filled with excess adhesive to seal it, which is a tedious manual process and not always successful. For example, the subsequent compression of the winding tension, and nip forces, can cause the adhesive to be squeezed out of the space, again creating a void region and possibly deforming the areas around it. This creates a bypass region for fluid flow and reduces product yield and overall performance of the device.

According to the invention, a support <NUM> is coupled to the leading edge <NUM> of the membrane packet so that upon winding of the packet, the support <NUM> occupies the space where the void region <NUM> would otherwise form, as shown in <FIG> and <FIG>. The size and shape of the support <NUM> can be determined based on prior experience of the size and shape of the void region <NUM> formed during a typical winding operation for a given size filter module. Support <NUM> is coupled to the leading edge <NUM> using adhesive means, ultrasonic welding means, heat welding means, or ultra-violet glue.

<FIG> illustrates a wedge-shaped support <NUM>. Upon winding of the membrane packet <NUM>, the support <NUM> will occupy the region where a void region <NUM> would normally form, and a fluid bypass region is minimized or avoided, as the membrane <NUM> is forced to remain in contact with the feed screen <NUM>.

In addition, in accordance with certain embodiments as set forth below, during the potting process the device is submerged in adhesive, and a vacuum is pulled on the permeate fluid flow channel. If the void <NUM> is present, adhesive migrates into the permeate fluid flow channel, causing blockage of the channel. The support <NUM> thus also functions to mitigate or eliminate such adhesive migration, and reduces the amount of adhesive necessary to seal the area. This also results in a more uniform permeate channel seam near the core or mandrel <NUM> and ultimately a more uniform membrane area within each spiral wound filtration module.

In certain embodiments, the support <NUM> is attached to the leading edge <NUM> of the membrane packet <NUM>, such as at seam locations, with a suitable adhesive (e.g., an epoxy or polyurethane). Where multiple membrane packets <NUM> are wound on a single core, e.g., in a multi-leaf assembly, each membrane packet <NUM> may have a support <NUM> attached to its leading edge <NUM>. For example, <FIG> illustrates a four-leaf assembly, and consequently there are four supports <NUM> visible radially outwardly from the central perforated core <NUM>.

According to the invention, the support <NUM> is wedge-shaped to match the anticipated void that forms in the absence of the support <NUM>. In some embodiments, the thicker end <NUM> of the support <NUM> is <NUM> inches thick (<NUM> inch= <NUM>) and tapers to the thin edge <NUM> of the support <NUM> which is <NUM> inches thick, although those skilled in the art will appreciate that the size is not critical, since the support <NUM> is compressible and will conform to the shape of the void. The thin edge <NUM> may have corners that are radiused or rounded to eliminate sharp edges that could tear the materials that it comes into contact with. The thicker end <NUM> of the support <NUM> is fixed to the leading end <NUM> of the membrane packet with a suitable adhesive. In certain embodiments, the support <NUM> is elongated and extends the entire length of the membrane packet <NUM>, as best seen in <FIG>. In other embodiments, individual supports <NUM> may be positioned at only the opposite faces of the membrane packet <NUM> to block adhesive intrusion into the permeate channel, and not extend the entire length of the membrane packet <NUM>. The support <NUM> is made of a solid, fluid impervious material not deleterious to the filtration operation to be carried out with the module, and capable of providing an adequate seal for vacuum seals on the mold used to introduce adhesive, as discussed in greater detail below. Suitable materials include thermoplastic elastomers, such as Pebax <NUM> SA01 Med Pantone 298C. Preferably the material has sufficient flexibility to conform to the shape of the core <NUM>.

Once the support <NUM> is fixed to the leading edge <NUM> of the membrane packet <NUM>, the membrane packet <NUM> may be tightly wound under tension about the core <NUM> together with the permeate screen <NUM> (<FIG>) and adhesive to form a spirally wound assembly. As the support <NUM> is wound in, it becomes sandwiched on either side by the permeate screen <NUM>, which holds the support <NUM> in place until adhesive is applied to fix it in position. Because the leading edge <NUM> of the membrane packet <NUM> is supported by the support <NUM>, the membrane <NUM> stays in contact with the feed screen <NUM> and is prevented from collapsing during a nip roller step, which removes the adhesive from the area and leads to a deleterious fluid bypass.

However, binding the assembly with adhesive during winding is somewhat variable, and is prone to gap formation which can lead to device failure.

Accordingly, in accordance with certain embodiments, the assembly can be bonded together with the use of a driving force such as a vacuum, or some pressure differential, to distribute the generally low-viscosity adhesive into the permeate sheet <NUM> uniformly to create a robust and uniform seam without the variability that results with manually made seams. In order to prevent potting adhesive form entering the feed channel during the potting process, a fluid impermeable feed screen border may be used as shown in <FIG>. The feed screen border also prevents any feed flow from reaching any membrane outside of the border. This effect defines the effective membrane area, greatly reducing membrane area variability. Applying a feed screen border on the leading and trailing edge restricts the flow to membrane area only inside these edges, and thus defines the active membrane length for each membrane packet, which also improves feed channel geometry and permeate channel geometry. In certain embodiments, at least three of the feed screen sides include fluid impermeable borders to prevent adhesive from entering feed channels during potting. In some embodiments, one of the fluid impermeable borders is on the feed face, one is on the retentate face, and one is one the open tail end of the membrane packet (which is part of the circumference). The feed and retentate borders are removed to activate the spiral for feed flow. The feed tail border may remain. In some embodiments all four of the sides of the feed screen include fluid impermeable borders (<FIG>) during potting, and again the feed and retentate borders are removed to activate the spiral for feed flow. Adhesive in the feed channel could lead to catastrophic loss of feed channel flow, or loss of integrity in operation by delaminating the membrane e.g. as the membrane moves apart under feed pressurization.

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

<FIG> shows a suitable mold body <NUM> for potting a spirally wound assembly using vacuum as a driving force for distributing the adhesive. In certain embodiments, a dry would spiral assembly <NUM> is placed in the mold body <NUM> having an adhesive injection port <NUM> in fluid communication with an interior mold body cavity <NUM> in which the dry wound spiral assembly <NUM> is positioned. Preferably the adhesive injection port <NUM> is located at or near the bottom of the mold body <NUM>, so that the adhesive flows upwardly upon the application of a driving force so that any entrapped air is removed during filling. In some embodiments, the perforated core <NUM> of the dry wound spiral assembly <NUM> is placed in sealing relation with a tapered, or O-ring interface <NUM> of the mold body <NUM>. O-ring seals <NUM> or the like may be provided at the opposite end of the mold body <NUM> to ensure that the dry wound spiral assembly <NUM> is in sealing relation with the mold body <NUM>, so that upon the application of vacuum, there are no leaks.

In some embodiments, a suitable potting adhesive, such as an epoxy or a polyurethane, is introduced into the injection port <NUM>, and a vacuum is applied at the vacuum inlet <NUM> to drive the adhesive into the permeate screen creating all necessary device seams, and around the spiral assembly <NUM> to completely envelope the assembly <NUM>. Suitable vacuum levels range from <NUM>-<NUM> in Hg from <NUM>-<NUM> seconds. Once the adhesive cures, the device is covered in an annular hard shell reinforced with permeate screen <NUM> (<FIG>), which resists expansion under high pressure drop situations, for example up to <NUM> psig. Such expansion can open the feed channel geometry and lead to a reduction in device performance.

In some embodiments, the mold body <NUM> can be configured so that certain features are formed on the outer surface of the cured adhesive, such as an annular ring for receiving an O-ring in the event the formed spiral assembly is used as a stand-alone module, i.e., without any outer housing or pressure vessel. These features may also be machined.

In some embodiments, the mold can be a housing that forms part of the final product, such as a plastic housing inside of which the spiral wound filter is positioned.

The device is sterilizable such as by steam, ethylene oxide gas or radiation such as beta or gamma radiation.

Claim 1:
A spiral wound membrane module, comprising
a perforated core (<NUM>) having an axially extending internal bore;
at least one membrane packet (<NUM>) 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 said folded membrane sheet being a leading edge (<NUM>) of said membrane packet (<NUM>);
a feed screen positioned between said first and second inner faces so as to be sandwiched by the folded membrane sheet;
a first permeate screen (<NUM>) adjacent said first outer face of said membrane sheet defining a first permeate channel;
a second permeate screen (<NUM>) adjacent said second outer face of said membrane sheet defining a second permeate channel; and
a wedge-shaped, fluid-impermeable support (<NUM>) coupled to said leading edge of said membrane packet prior to winding so that upon winding of the packet (<NUM>), the support occupies all of the region where a void would otherwise form,
wherein the wedge-shaped support (<NUM>) is made of a compressible material such that it will conform to the shape of the void, and
wherein a thicker end (<NUM>) of the wedge-shaped support (<NUM>) is coupled to the leading edge (<NUM>) of the membrane packet (<NUM>) prior to winding using adhesive means, ultrasonic welding means, heat welding means, or ultra-violet glue.