Independent spacer and method

Abstract

A method of making a membrane element for fluid or gas filtration comprising applying feed or reject spacers, or intermediate spacers, or fold protection strips, or edge support strips directly to the membrane sheet or to a substrate material that is subsequently applied to the membrane sheet, thereby avoiding contamination from directly printed adhesives, inks, or polymers, or damage from heat or radiation damage to the membrane sheet when applying the spacers or patterns directly to the surface of the membrane sheet, thereby avoiding the use of conventional feed spacer mesh materials.Membrane sheets and spiral wound filtration elements with spacers applied to defined areas of the sheet, in some embodiments, have spacers mounted on a substrate having different material properties, e.g., stiffness, than the underlying membrane.

Description

[Technical Field]

[0001] The subject invention relates to membrane systems, particularly spiral wound membrane elements, utilized for the separation of fluid components. [Background technology]

[0002] Spiral wound membrane filtration elements are well known in the art and typically comprise a laminated structure comprising a membrane sheet sealed to or around a porous permeate carrier that forms a path for removal of fluid passing through the membrane to a central tube, longitudinally relative to the axis of the central tube; the laminated structure is spirally wrapped around the central tube and spaced from itself by a porous feed spacer to allow axial flow of fluid through the element. Conventionally, a mesh feed spacer is used to allow feed flow, a portion of which passes through the membrane and into the spiral wound element, and reject water to exit the element in a direction parallel to the central tube and the axis of the element construction.

[0003] Improvements to spiral wound element design are disclosed in U.S. Patent No. 6,632,357 to Barger et al., U.S. Patent No. 7,311,831 to Bradford et al., and in patents in Australia (2014223490) and Japan (6499089) to Herrington et al. entitled "Improved Spiral Wound Element Construction," which replace traditional feed spacers with islands or protrusions deposited or embossed directly onto the inner or outer surface of the membrane. U.S. Provisional Application No. 62797357 to Herrington et al. entitled "Integral Spacers" describes a method for integrating feed spacer components into the actual membrane sheet beneath a polymer layer, creating a membrane sheet that can also incorporate a thick nonwoven polyester support, thick enough to also function as a permeate carrier. U.S. Provisional Application No. 62,849,952 to Beckman et al., entitled "Entrance Features," describes features that minimize fluid resistance by reducing stagnation points in the feed and rejection regions of a spiral wound element. U.S. Provisional Application No. 62,855,166 to Herrington et al., entitled "Variable Velocity Patterns," describes features in the feed space that maintain constant fluid velocity along the flow path from the feed end to the rejection end of a spiral wound element. U.S. Provisional Application No. 62,885,453 to Herrington et al., entitled "UV Enhanced," describes a method for modifying the flux and rejection characteristics of polyamide membranes in spiral wound elements. PCT Application No. US2018 / 55671 to Herrington et al., entitled "Bridge Support and Reduced Feed Spacers," describes spacer features that support the edges of the membrane envelope during rolling and reduce feed spacer feature patterns in spiral wound elements. PCT Application No. US2018 / 016318 to Roderick et al., entitled "Graded Spacers," describes feed spacer features that decrease in height as they approach the central tube of a longitudinal flow convolution to maintain a constant velocity and reduce flow resistance in a feed flow path.PCT Application No. US2017 / 52116 to Roderick et al., entitled "Permeate Flow Patterns," describes flow paths in the permeate space of a spiral wound element, including printing feed spacer patterns on a permeate carrier that serve as embossing points for the membrane sheet when the spiral wound element is compressed during initial startup. Korean Patent No. 10-2033982 to Roderick et al., entitled "Interference Patterns," describes feed spacer features that eliminate nesting of feed spacer features when rolling a spiral wound element during construction. PCT Application No. US2018 / 27367 to Roderick et al., entitled "Non-Nesting Patterns," describes printed spacer patterns that avoid nesting of feed spacer patterns during spiral wound element rolling and operation. PCT Application No. US2018 / 28453 to Herrington et al., entitled "Mixing Promoting Spacers," describes feed spacer features in the feed space channels of spiral wound elements to reduce concentration polarization and other deleterious effects. PCT Application No. US2019 / 45222 to Weingardt et al., entitled "Preferred Flow Paths," describes flow paths in the feed space of spiral wound elements. PCT Application No. US2019 / 58652 to Roderick et al., entitled "Flow Separators for RO Elements," describes various flow path schemes in the feed space of spiral wound membrane elements. Each of the references cited in this paragraph is incorporated herein by reference.

[0004] Typically, the fluid feed flow is perpendicular to the central tube of the spiral-wound element. During manufacturing, after the element is wound into a spiral configuration, the membrane sheet envelope is glued and then cut, so that the feed edge of the membrane envelope presents a flat surface to the flow of the feed solution. PCT Application No. US 17 / 62425 to Herrington et al., entitled "Flow Directing Devices for Spiral Sound Elements," describes a stretch prevention device incorporating a rotating vane that sweeps the feed end of the spiral-wound element into the fluid flow to help prevent particle interference in the feed stream from impinging on the edge of the membrane envelope. PCT Application No. US 63 / 006638 to Herrington et al., entitled "Independent Spacers," describes spacing features that are separately manufactured and applied to the surface of a membrane sheet. Each of the references cited in this paragraph is incorporated herein by reference. Summary of the Invention

[0005] An understanding of the present invention can be readily understood in the context of U.S. Patent No. 6,632,357 to Barger et al., U.S. Patent No. 7,311,831 to Bradford et al., and patents by Herrington et al. entitled "Improved Spiral Wound Element Construction" in Australia (2014223490) and Japan (6499089), each of which is incorporated herein by reference.

[0006] Embodiments of the present invention provide feed inlet spacers, reject outlet support spacers, and in some embodiments, internal support spacers that are not printed or embossed directly on the membrane surface and are not integral with the permeate carrier. The support spacers are attached to the membrane surface before rolling into a spiral element, or applied in a flat configuration for applications in electrodialysis or related types of plate and frame systems. The spacers can be applied to the top surface of the leaf, the bottom leaf surface of the leaf, or both surfaces. Attachment can be achieved by applying an adhesive to the support spacers or portions of the support spacers, or all or part of the support spacers can be glued to the membrane surface using an adhesive similar to that used to seal the permeate carrier envelope, or can be glued with other adhesives such as epoxy, urethane adhesives, or other adhesives similar or identical to those used to seal the permeate carrier envelope. The spacer strips can be embossed, injection molded, stencil cut, and cut into short or long segments before assembly. The support spacers can be dots, lines, line segments, curves, or other features that provide support to the bond lines in the permeate carrier during rolling of the spiral element, and optionally support the center of the spiral element to keep the membrane sheets separated, provide turbulence in the flow paths, or a combination thereof, optionally located inside the spiral wound membrane element.

[0007] In one method of manufacturing membrane sheets currently practiced in the art, a complete sheet of membrane is printed, embossed, or otherwise applied with a pattern, typically applied to a complete membrane sheet, e.g., 1 meter wide by 2 meters long, or other suitable dimensions, etc. This process leaves a significant open space in the center of the membrane sheet that is not printed, but takes up space in the printing system and utilizes the time to process the membrane sheet without applying significant material to the membrane surface in the open areas, e.g., areas of the membrane sheet that are not near the feed or reject ends of the membrane.

[0008] Embodiments of the present invention allow inlet and outlet supply and reject spacers to be printed on strips in a dense pattern on a large-format photopolymer, offset, or screen printer, or other such system for applying material to flat or curved substrates. To maximize the use of printers, screen, offset, gravure, or other devices or methods for applying spacers to substrates, strips with applied supply, reject, or intermediate spacers can be aligned closely together during the deposition process. The spacers on the substrate can then be cut into strips. The spacer strips can then be applied to the surface of the membrane by an adhesive or bonding process, without the need to print the entire membrane sheet surface. By applying adhesive to the spacer strips during rolling, the adhesive can remain viscous, allowing the spacer strip to slide against the surface of the membrane sheet during rolling so that the spacer strip does not cause the membrane sheet to bond during rolling. Alternatively, the spacer strip can be applied and dried with adhesive to the bottom of the spacer substrate before application and rolling of the spiral element module, or application in a plate and frame configuration. Furthermore, the substrate on which the spacers are printed can be cut into short segments with single or multiple spacer features on each substrate segment. A significant advantage of printing spacer features only on separate strips having a pattern of spacer features is that the membrane sheet is not contacted in any way by the printing process, which could adversely affect the performance of the membrane sheet. Embodiments of the present invention avoid the addition of heat or wavelength energy to the membrane or volatile materials on the membrane sheet by utilizing spacing features formed on a separate substrate material that facilitates attachment of the spacer features to the membrane sheet by some of the many conventional attachment methods that do not have such adverse effects on the performance of the membrane sheet.

[0009] The present invention contemplates various methods for creating freestanding spacers. For example, a material such as a vinyl sheet can be obtained already attached to a first substrate via an adhesive bonded to the vinyl. When the first substrate is removed from the vinyl material, the adhesive does not remain on the substrate but remains on the vinyl. The vinyl material can then be applied to a surface, adhering the vinyl to the surface. These techniques are widely used to adhere advertisements to the sides of vehicles. Furthermore, vinyl cutting machines can be used to cut shapes, such as letters or logos, from the vinyl without damaging the first substrate, but without a cutting depth deep enough to cut through the first substrate. Unwanted vinyl material, e.g., the unwanted vinyl between the letters and logo, is removed from the pattern, leaving only the letters or logo on the first substrate. A second substrate with adhesive, i.e., the second substrate, can then be applied on top of the vinyl. This second substrate can have an adhesive on its surface that adheres more strongly to the top of the vinyl. The first substrate can then be removed from the vinyl, leaving the vinyl attached to the second substrate. The vinyl with the second substrate can then be applied to a surface, such as the side of a vehicle or window. The adhesive on the bottom of the vinyl provides stronger adhesion to the desired surface than the second substrate. The second substrate can then be removed from the vinyl, leaving the vinyl attached to the desired surface, such as a vehicle or glass surface. Similarly, a vinyl pattern of a specific shape can be applied to the surface of a membrane, such as a membrane used in fluid separation, where the vinyl pattern is used as a feed spacer material or a spacer material for spiral wound elements in a plate and frame configuration. Note that materials other than vinyl can also be used, including PCV, CPVC, acrylic, ABS, polyethylene, polypropylene, polysulfone, polyester, metal materials, and other materials used in the fields of spiral wound or plate and frame technology.

[0010] In another exemplary embodiment, a first substrate with a thin adhesive coating can be used as a substrate, with vinyl, photopolymer coating, urethane coating, hot melt, or other materials printed or applied directly to the adhesive-coated surface of the first substrate. A spacer material can also be applied to the adhesive-coated surface of the first substrate using screen printing, gravure printing, inkjet printing, laser jet printing, and other techniques. A second adhesive material can then be applied on top of the material applied to the surface of the first substrate. The first substrate with the spacer material and adhesive applied on top of the spacer material can then be applied to another surface, such as a membrane sheet. The first substrate with the adhesive coating can then be removed, leaving the spacer material bonded to the membrane surface. Here, the spacer material can be adhesively applied to the membrane surface, with the top of the spacer material being adhesive-free. The membrane sheet with the spacer applied can be wound into a spiral membrane element or used in plate-and-frame membrane applications or other types of membrane separation processes where membrane sheets are spaced apart, allowing liquid or gas to reach the membrane surface.

[0011] To support high-speed automation and speed up the weeding process of unwanted vinyl, patterns can be designed so that all of the "negative" space can be removed as a single piece. To do this, the pattern can be designed so that the spacer pieces left after weeding are individual elements, with the removed pieces fully interconnected.

[0012] During development and testing related to the present invention, it was found that a spacer sticker can be weeded much more easily if there is a larger section of spacer at the head of the portion that remains after weeding. This larger section increases the bond strength between the spacer and the backing, making it less likely that the spacer will be removed with the negative space as it is removed.

[0013] In addition to making the spacer feature heads larger to increase adhesive strength to the backing paper, the heads can also have rounded edges or a double-headed arrow-like shape that tapers to an end point and to the width of the spacer bar on the other side of the head. This tapered shape reduces the area over which pulling force is applied during weeding, making it easier to remove the negative space without removing the spacer feature from the backing.

[0014] When designing large heads to increase weeding capacity, it is desirable to make the heads as large as possible, but it has also been found that the space between the heads must be wide enough to prevent the material from breaking when pulled during the weeding process. The width of the negative space between the spacer heads can be at least 0.015 inches, and the space can be increased as the material thickness increases.

[0015] To reduce the number of times spacers need to be weeded and increase productivity, the spacers can be made two to three times the length of a standard spacer and then cut to the width of the strip after weeding. This reduces labor, as the most time-consuming part of weeding is starting the process. Reducing the number of times weeding needs to be started reduces the overall labor time per spacer strip, increasing productivity.

[0016] When removing undesired material, it may be advantageous to remove perpendicular to the direction of the spacer features. To facilitate weeding at 90 degrees from the normal orientation of the spacer segment direction, for example, weeding at 90 degrees from the direction of feed flow to the spiral element, or weeding in the fluid path of a plate and frame application, it may be advantageous to orient the spacer at an angle other than perpendicular to the flow, i.e., other than perpendicular to the centerline of the central tube of the spiral element. In this way, the lead portion of the undesired material is first removed from the spacer, followed by removal of undesired material along the length of the spacer element.

[0017] If the weeding process is automated, a spool or take-up reel can be used to accumulate waste material from the weeding process. This take-up reel can be oriented at an angle offset from the line of the spacer strip, allowing the weeding material to be brought off the spacer strip at an angle that facilitates removal of the weeding material from the spacer strip, rather than attempting to remove the weeding material perpendicular or parallel to the spacer strip. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram of a conventional spiral wound membrane element before rolling. [Figure 2] FIG. 1 is an end view of a spiral membrane element. [Figure 3] FIG. 1 is a cross-sectional view of a conventional mesh-type membrane element. [Figure 4] 1A-1C are three views of the entrance or rejection end of a spiral membrane element with feed spacers. [Figure 5] FIG. 1 is a diagram of a spacer on a substrate having features that facilitate removal of unwanted interstitial material. [Figure 6] FIG. 10 is a diagram of a spacer on a substrate oriented at an angle relative to the direction of the substrate, with features that facilitate removal of unwanted interstitial material. [Figure 7]10A-10C are diagrams of spacers on a substrate oriented at an angle other than 90 degrees relative to the direction of the substrate, with features to facilitate removal of unwanted interstitial material. [Figure 8] FIG. 1 is a diagram of a substrate sheet having individual spacer features deposited thereon. [Figure 9] FIG. 1 is an illustration of a substrate sheet having continuous spacer features deposited thereon. [Figure 10] FIG. 1 is a diagram of a substrate sheet having continuous spacer features deposited on the substrate and cut into spacer segments of various lengths. [Figure 11] FIG. 10 is a diagram of spacer features applied to the inlet and outlet feed portions of the membrane sheet. [Figure 12] FIG. 10 is a diagram of spacer features applied to the inlet and outlet feed ports of a membrane sheet, as well as spacer features applied to non-edge regions of the membrane sheet. [Figure 13] FIG. 1 is a cross-sectional view of a membrane sheet with feed spacers attached to strips at the feed and entrance ends of the membrane sheet. [Figure 14] FIG. 1 is a cross-sectional view of a membrane sheet with feed spacers attached to strips at the feed and entrance ends of the membrane sheet and at the interior region of the membrane sheet. [Figure 15] FIG. 10 is a diagram of a spacer strip having a continuous bottom surface and features on top of the strip. [Figure 16] FIG. 10 is a diagram of a spacer strip having features integrated into the strip without a continuous bottom surface. [Figure 17] FIG. 10 is a diagram of a spacer strip made of multiple segments. [Figure 18] 1A-1C are diagrams of a procedure for stencil cutting features on a substrate. [Figure 19] 1A-1C are diagrams of an apparatus and method for stencil cutting and applying spacer features to a membrane. [Figure 20] FIG. 10 is an illustration of a method of printing or depositing spacer features onto a substrate, applying adhesive to the spacer features, and applying the spacer features to a membrane. [Figure 21] 1 is a diagram of an apparatus and method for screen printing or gravure printing spacer features onto a substrate, applying adhesive to the spacer features, and applying the spacer features to a membrane.

[0019] MODES FOR CARRYING OUT THE INVENTION AND INDUSTRIAL APPLICABILITY FIG. 1 illustrates the key elements of a conventional spiral-wound membrane element 100. The permeate collection tube 12 has holes 14 therein through which permeate fluid is collected from the permeate feed spacer 22. In manufacture, the membrane sheets 24 and 28 comprise a single sheet folded about a centerline 30. The membrane sheets 24 and 28 are typically constructed of a porous support layer, such as a porous nonwoven polyester layer, e.g., polysulfone, and an active polymer membrane layer bonded or cast onto the support layer. The active polymer membrane surface 24 is adjacent to the feed spacer mesh 26, and the non-active support layer 28 is adjacent to the permeate carrier 22. The feed solution 16 enters between the active polymer membrane surfaces 24 and flows through the open spaces in the feed spacer mesh 26. As the feed solution 16 flows through the feed spacer mesh 26, total dissolved solids (TDS) ions are rejected at the active polymer membrane surface 24, and permeate fluid molecules, e.g., water molecules, pass through the active polymer membrane surface 24 and into the porous permeate carrier 22. As the feed solution 16 passes along the activated polymer membrane surface 24, the concentration of TDS ions increases due to the loss of permeate in the bulk feed solution 16, causing the feed solution to exit the rejection end of the activated polymer membrane sheet 24 as rejection solution 18. The permeate in the permeate carrier 22 flows from the distal end 34 of the permeate carrier 22 toward the central tube 12, where it enters the central tube 12 through the central tube entrance holes 14 and exits the central tube 12 as permeate solution 20. To avoid contamination of the permeate by the feed solution 16, the activated polymer membrane surface 24 is adhesively sealed along adhesive lines 32 through the permeate carrier 22, thereby creating a sealed membrane envelope in which the only exit path for the permeate solution 20 is through the central tube 12.

[0020] 2, the spiral wound membrane element 200 comprises a membrane envelope 102 of membrane sheets folded at one end with a permeate carrier disposed between the membrane sheets and sealed along the edges with a suitable adhesive. In conventional designs of membrane element 200, a feed spacer mesh 26 is positioned adjacent to the envelope 102 to allow the flow of feed fluid 16 to flow within the feed space of the membrane envelope 102, exposing all of the active polymer surfaces of the membrane sheets to the feed fluid 16. The permeate or product fluid is collected in the permeate carrier inside the membrane envelope 102 and spirals further down to the central tube 12 where the product or permeate fluid is collected.

[0021] Referring to Figure 3, which is a cross-sectional view of a portion of such an element, the membrane envelope is produced by sealing together the edges of a first membrane sheet 24, a layer of permeate carrier 22, and a second membrane sheet 28 with adhesive 104. In the spiral-wound element manufacturing process, individual membrane leaves 24 and 28 are folded in half, a permeate carrier 22 is placed between each folded sheet, adhesive is applied on top of the permeate carrier, and the element is rolled to produce a layered spiral configuration. During the rolling process, the adhesive 104 must penetrate the permeate carrier 22 to properly seal the membrane sheets 24 and 28 together to create the membrane envelope 102, as shown in Figure 2. Referring again to Figure 3, the edges are trimmed through the adhesive material 104 along cut lines 44 to complete the final structure of the membrane element 200 (Figure 2). In many fluid feed applications, the feed fluid 16 contains particles or impurities that can impinge on the flat end edge 134 of the envelope 102, allowing particles to collect on the end face of the envelope 102 and potentially restricting fluid flow into the feed space between the leaves of the envelope 102. Furthermore, the feed spacer mesh 26 typically comprises a plastic webbing-type mesh, the cut edges of which also function to accumulate particles in the entrance area of ​​the feed space between the envelopes 102. The feed spacer mesh 26 comprises upper and lower strands 136 and 138 joined together at contact points 140. Another undesirable feature of existing mesh-type spacer membrane elements is that the feed fluid 16 must flow over and under the strands 136 and 138, creating pressure losses across the mesh spacer. These pressure losses increase the energy costs of operating the membrane system. If the pressure losses could be reduced, the overall energy requirements of the system could be reduced. In a typical construction of a conventional membrane element 200, membrane sheets 24 and 28 surround a permeate carrier 22 that extends to the edges of the membrane sheets to allow permeate flow to a central collection tube 12 (FIG. 2).

[0022] From a fluid dynamics perspective, the feed fluid 16 impinging on the flat end surface 134 of the membrane envelope 102 is suboptimal and creates additional resistance to fluid flow as the fluid transitions from bulk flow into the feed channel. In an alternative embodiment of a spiral wound membrane system, the feed spacer mesh 26 can be replaced with individual spacer features applied directly to the membrane sheet 24, thereby eliminating the need for the feed spacer mesh 26. These individual spacer elements can be applied directly to the membrane sheet 24 or can be applied directly to a substrate material that can then be transferred to the membrane sheet 24.

[0023] Alternative embodiments of spacing features attached to a substrate are referenced in US Provisional Patent Application No. 63,006,638 to Herrington et al., entitled "Independent Spacers," which is incorporated herein by reference.

[0024] 4A , the spacing features 206 are attached to the membrane envelope 102 individually or are attached prior to fabrication of the membrane envelope 102 by applying the spacing features 206 directly to membrane surface 24, or alternatively by applying them alternately to membrane surface 28, or by applying them to both membrane surfaces 24 and 28. In this embodiment, the spacing features 206 are attached to the membrane surfaces by any suitable adhesive 230, which can be applied to the attachment surface of the spacing features 206, or directly to membrane surface 24 or 28, or alternatively to the membrane envelope 102.

[0025] Referring to FIG. 4B, membrane envelope 102 is created by adding adhesive 104 to seal permeate carrier 22 to membrane surfaces 24 and 28, creating membrane envelope 102. In some instances using printed spacers 206, membrane surfaces 24 and 28 may be insufficiently supported, causing adhesive 104 to bulge during the spiral-wound element rolling process. This partially blocks feed solution 16 (FIG. 2) from entering feed space 232. Referring to FIG. 4C, to help alleviate this problem, adhesive backing or printed spacers 206 applied to substrate 204 can be made from a material that is more rigid than membrane sheets 24 or 28, thus providing support for adhesive 104 bulging or blocking inlet feed space 232. This reduces fluid pressure loss across the feed and outlet regions of the spiral-wound element feed space, thus reducing overall operating energy costs.

[0026] FIG. 5 illustrates an assembly 500 including spacer features 46 applied to a substrate 40. The spacer features 46 need not, but can, incorporate weeding heads 48 to facilitate removal of unwanted spacer material from the substrate 40. In one exemplary embodiment, a vinyl or other material covers the entire surface of the substrate 40, and a cutting machine is programmed to cut through the vinyl material to cut the outlines of the spacers 46, but not into the substrate 40. Note that the spacers 46 are comprised of vinyl material. In an exemplary embodiment, unwanted material 47 is removed from the substrate 40, leaving only the spacers 46. Special features, such as weeding heads 48, can be incorporated into the cut pattern of the spacer features 46 to facilitate removal of the unwanted material 47 from the substrate 40 without disturbing the individual spacers 46. In some exemplary embodiments, the material overlying the substrate 40 can be any type of suitable material, including PVC, CPVC, polyester, polycarbonate, ABS, or any number of other plastics, polymers, or even metals or alloys.

[0027] Referring to FIG. 6, the alignment of the spacer 46 can be oriented at a non-zero angle "V" relative to the normal to the orientation of the substrate 40. The angle V can be positive or negative, as shown in FIGS. 6 and 7. FIG. 7 also illustrates an embodiment in which the weeding head 48 is oriented at the opposite end of the spacer 46 from that shown in FIG. 6. During assembly of the spiral wound element 200 (FIG. 2), the weeding head 48 can be trimmed at the cut lines 44 (FIG. 3) on both the feed and removal ends of the envelope 102 (FIG. 2) after the initial winding of the element 200. This process leaves only the spacer 46 on the active surface of the membrane surface 24, or alternatively, on the active surface of the membrane 28 (FIG. 1). Removing the weeding head 48 during the assembly process reduces resistance to the feed fluid 16 entering the feed space of the spiral wound element.

[0028] In the prior art, spacers are otherwise printed or applied directly to the surface of the film sheet 24. To optimally design spacers 46 on a film sheet for a spiral element configuration, the spacers 46 are placed on the film sheet at various locations to support the adhesive lines or ensure proper spacing of the film sheet 24 after it has been rolled in a spiral configuration. Direct printing or application on the film sheet necessarily requires creating significant open space on the film sheet 24. As shown in FIG. 8 , printing or depositing the spacers 46 can be accomplished in a high-density pattern that maximizes utilization of the spacers 46 on the film 70. This process ensures maximum utilization of the available space on the film 70 and also maximizes the rate of material deposition onto the film 70, thereby increasing the production rate of the spacers 46. The spacers 46 can be manufactured to any length X on the film 70, or the value of X can be varied from one spacer length to another on the same sheet of film 70. The spacers 46 optionally incorporate a weeding head 48 into their design. Weeding head 48 is particularly suited to applications where a spacer pattern is cut into a substrate as shown in FIG.

[0029] As shown in FIG. 9, spacers 46 can be fabricated across the entire length / width of film 70. A weeding head 48 can optionally be utilized. As previously indicated, weeding head 48 is particularly suited for cutting a spacer pattern into a substrate, as shown in FIG. 9. Fabricating spacers 46 across the entire length of film 70 maximizes material utilization in the manufacturing process. Subsequently, as shown in FIG. 10, spacers 46 can be cut to any number of lengths Y and Z, or random lengths, as desired, to optimize the design of the pattern utilized for spacers 46 on film sheet 24 prior to rolling the film sheet into a spiral element configuration.

[0030] FIG. 11 shows spacers 46 applied to membrane sheet 24. The prior art discusses processes that utilize spacers in appropriate locations on the membrane sheet. A complete membrane sheet can be, for example, 1 meter wide and 2 meters long. Half of the membrane sheet may not have spacers applied, such as membrane sheet area 28. Spacers 46 may be applied only to membrane sheet area 24. By applying spacers 46 to only half of the membrane sheet and folding the membrane sheet at fold line 208, interference of the spacers 46 when the membrane sheet is rolled into spiral configuration 102 (FIG. 2) can be avoided. In an alternative embodiment discussed in the prior art, feed and outlet end spacers may be applied along the entire length of the membrane sheet.

[0031] 12 shows a membrane sheet 24 with spacers 206 applied to the feed and reject ends of the membrane sheet 24, and intermediate spacers 210 applied to the intermediate spaces of the membrane sheet 24 to provide spacing support to the intermediate region of the membrane sheet 24. Any number of rows of spacers 210 can be applied to the membrane sheet 24.

[0032] Referring to FIG. 13 , spacers 206 attached to substrate 204 can be attached to film surface 24, or in some configurations, film surface 28, or both film surfaces 24 and 28, using a suitable adhesive 234 ( FIG. 4C ). Substrate-independent spacers can be stencil cut or otherwise formed using any number of methods or manufacturing techniques known in the art. Adhesive 234 can be applied to the bottom surface of substrate 204 so that substrate 204 self-adheres to film surface 24 or 28. Prior to the rolling process, film sheets 24 and 28 can be folded over one another at fold line 208. During the rolling of spiral element 200, mechanical interference between film surface 24 or 28 and substrate 204 can occur due to differences in the winding radii of film surface 24 or 28 relative to substrate 204. This creates a gap between membrane surface 24 and membrane surface 28 relative to substrate 204, which creates stresses and discontinuities between the two surfaces, creating stresses on membrane surface 24, 28, or both, damaging the membrane surfaces and reducing ion rejection from the membrane surfaces. Another option for bonding substrate 204 is the application of a thixotropic adhesive, such as a urethane adhesive, which does not dry quickly but allows substrate 204 to slide against membrane surface 24 or 28 during the rolling process. This is the same process used to bond membrane sheets 24 and 28 together with permeate carrier 22 during the spiral wound element rolling process.

[0033] Referring to FIG. 14, longer spiral wound elements, e.g., 12 inches or longer, may require additional support between the feed and reject ends of the spiral wound element to maintain a clear feed space between the feed and reject ends of the spiral wound element. To achieve this additional support and mitigate the need to treat membrane sheets 24, 28 with thermal or radiation processes that could damage the properties of membrane sheets 24, 28, spacer strips 210 (FIG. 12) can be attached to membrane sheets 24, 28, or both, and placed at one or more locations across the membrane surface to provide intermediate support. The pattern on spacer strips 210 can comprise dots, dashed lines, straight lines, curved lines, or other special shapes that help maintain local vorticity and minimize concentration polarization, which is the accumulation of ions at the membrane surface that locally increases osmotic pressure at the membrane surface.

[0034] The supply or removal support substrate 204 can be manufactured by any number of methods, as shown in Figure 15. This includes injection molded substrates with integral solid spacers 206, compression molded substrates, or any other method used to manufacture three-dimensional materials. Figure 16 shows a spacer 206 integrated into the substrate 204 with open channels 220 that can aid in fluid flow through the supply spacer 206 in some applications. These substrates 204 can be manufactured by any of the known methods for manufacturing materials of this nature, including injection molding, casting, compression molding, embossing, or other such techniques.

[0035] 17 further illustrates a spacer 206 substrate 204 divided into segments, for example, from 0.25 inches long to 40 inches long. The segments are separated by break lines 222, which can be any width from a line cut up to a width of 0.25 inches or greater. Incorporating break lines 222 in substrate 204 can reduce stress buildup in substrate 204 between membrane sheets 24, 28 during the spiral element rolling process, thereby limiting damage to the membrane sheets in terms of flux or rejection properties.

[0036] FIG. 18 shows the steps involved in an example embodiment in which vinyl (or other material) is cut from a substrate to create spacer material that can be applied to a film surface. In the first step, a cutting machine is used to precisely cut a pattern into the overlying material, but not into the underlying substrate, creating spacers in the material. The overlying material incorporates an adhesive that holds the overlying material on the substrate, but when the substrate is removed from the overlying material, the adhesive on the overlying substrate is not transferred to the substrate. In the second step of FIG. 18, the unwanted overlying material is removed or removed from the overlying material, leaving only the desired spacers attached to the underlying substrate. In the third step, an adhesive-backed film is attached to the top of the spacers. The adhesive on the film is attached to the film so that it does not transfer to the spacers when the film is finally removed from the spacers. In step 4 of FIG. 18, the underlying substrate is removed from the bottom of the spacers, leaving the adhesive bonded to the bottom of the spacers. In step 5, the spacers with the adhesive film attached thereto are applied to the appropriate locations on the film surface. Spacers incorporating adhesive on their bottoms can adhere the spacers to the film surface. In the sixth and final step of Figure 18, the film and adhesive attached to it are removed from the top of the spacer, thereby leaving the spacer bonded to the membrane surface.

[0037] In an exemplary embodiment of the invention shown in FIG. 19, spacers 46 are applied to membrane 24 in an automated or semi-automated process. The process begins with a roll 78 of material 80 attached to substrate 40 and a light adhesive peeled from the reel. The material enters between roller 84 and die cutter 74, which includes cutting die 76. The die-cut material continues around roller 84. Film 70 unwinds from film reel 72. An embossing roller 86 selectively presses film 70, which incorporates a medium-strength adhesive, against spacers 46 of die-cut material 80. The strong adhesive on film 70 separates spacers 46 from die-cut material 80. Attached to film 70, spacers 46 advance around roller 90, which bonds spacers 46 to membrane 24. The adhesive on spacers 46 is stronger than the adhesive on film 70, thereby bonding the spacers to membrane 24. The membrane 24 is mounted on a vacuum table 96, which moves laterally to match the rotational speed of roller 90. The vacuum table 96 can also incorporate top and bottom features that allow for the release of the membrane 24 with the attached spacers 46 to begin the next cycle. At the beginning and end of each cycle, the membrane 24 can be placed / removed onto the vacuum table 96 by a pick-and-place or robotic device, or other means, to begin the next cycle. The substrate 40, with material 47 removed, proceeds to a waste bin 94. The film 70 proceeds over rollers 88 to a waste bin 95. A film separator 92 is utilized to ensure the separation of the film 70 from the rollers 88.

[0038] FIG. 20 illustrates an exemplary embodiment of the present invention in which spacers 46 are applied to film 70 using photopolymer, hot melt, or other techniques prior to application of spacers 46 to membrane 24. Film 70, optionally including an adhesive coating, is dispensed from a roll 72 of film 70 and advanced to support platform 98, where material 122 is deposited onto film 70 via dispensing mechanism 120. Material 122 may include, for example, a liquid photopolymer material that is subsequently irradiated and cured by an energy source. The energy source may include any wavelength spectrum of energy, including visible light, ultraviolet light (UV), or other energy frequencies, appropriate for the material. In an exemplary embodiment of the present invention, material 122 may include a hot melt material that is deposited onto film 70. Support platform 98 may incorporate cooling features to appropriately cool the hot melt material so that it exhibits the correct dimensional characteristics, such as the desired thickness. Once material 122 is cured by an energy source, cooled from support platform 98, or hardened by conventional drying or curing methods to form the desired shape, the shape is configured to form spacers 46. The film 70 with the attached spacers 46 now proceeds to have adhesive 126 applied to the surface of the spacers 46. The adhesive 126 is dispensed from an adhesive dispenser 124. The spacers 46 attached to the film 70 then proceed through one or more rollers 90 to be attached to the membrane sheet 24. The adhesive 126 has a higher bond strength than the adhesive contact between the film 70 and the spacers 46. Therefore, the film 70 is removed from the backside of the spacers 46 with the rollers 90 once the spacers 46 are bonded to the membrane sheet 24. The membrane 24 can be mounted on a vacuum table 96 that moves laterally to match the rotational speed of the rollers 90. The vacuum table 96 can also incorporate an upper / lower feature that allows the membrane 24 with the attached spacers 46 to be released to begin the next cycle. At the beginning and end of each cycle, the membrane 24 is placed on / removed from the vacuum table 96 by a pick-and-place or robotic device, or other means, to begin the next cycle.The film 70 travels over rollers 88 to a waste bin 94. A film separator 92 is utilized to ensure separation of the film 70 from the rollers 88. The film 70 can be recycled or disposed of as desired.

[0039] In the exemplary embodiment of the invention shown in FIG. 21 , the spacers 46 are applied to the film 70 using a screen printing or stencil printing process. A screen 152 is placed on the film 70, and adhesive is spread onto the screen 152 via a screed 154 to fill the spaces within the screen 152, forming the desired shape of the spacers 46. Energy sources 158 and / or 156 are used to cure the adhesive to a desired hardness before removing the screen 152 from the surface of the film 70. A support table 150 is used to support the film 70 during the screening process. The support table 70 can be transparent to allow energy from the energy source 158 to reach the adhesive within the spaces within the screen 152. The energy source 158 can be used to pre-cure the adhesive within the spaces within the screen 152 to allow removal of the screen 152 from the surface of the film 70. A post-cure process utilizing the energy source 156 can then be used to fully cure the adhesive to an appropriate strength to avoid tackiness. The film 70 with the attached spacers 46 advances over a roller 90. In a simultaneous or subsequent process, adhesive is applied to the surface of the spacers 46 via an adhesive application device / roller 160. The film 70, with the spacers 46 attached and adhesive applied to its surface, advances via roller 90 and is applied to the surface of the membrane sheet 24. The membrane 24 may be mounted on a vacuum table 96 that moves laterally to match the rotational speed of the roller 90. The vacuum table 96 may also incorporate an upper / lower feature that allows the membrane 24, with the spacers 46 attached, to be released to begin the next cycle. At the beginning and end of each cycle, the membrane 24 is placed / removed onto the vacuum table 96 by a pick-and-place or robotic device, or other means, to begin the next cycle. The film 70 advances over roller 88 to a waste bin 94. A film separator 92 is utilized to ensure the film 70 is separated from the roller 88.

[0040] The present invention has been described in connection with various exemplary embodiments. It is to be understood that the foregoing description is merely illustrative of the application of the principles of the invention, the scope of which is to be determined by the claims viewed in light of the specification. Other variations and modifications of the present invention will be apparent to those skilled in the art.

Claims

1. 1. A method for manufacturing a membrane element for fluid treatment, comprising: (a) forming a spacer sheet comprising a first substrate sheet having a plurality of spacing features disposed thereon; (b) adhering the spacer sheet to a membrane sheet, the spacer sheet being adhered to the membrane sheet such that the spacing features are adhered to the membrane sheet; and (c) separating the first substrate sheet from the spacing features after the spacing features are adhered to the film sheet, leaving the spacing features but not the first substrate sheet adhered to the film sheet; A method comprising:

2. The method of claim 1 further comprising spirally winding the membrane element to form a spiral wound membrane element.

3. The method of claim 1 further comprising placing the membrane element in a plate and frame type membrane system.

4. 1. A method for manufacturing a membrane element for fluid treatment, comprising: (a) forming a spacer sheet comprising a first substrate sheet having a plurality of spacing features disposed thereon; (a1) joining a second substrate sheet to a first feature sheet at a first surface thereof; (a2) cutting a pattern into the first feature sheet from a second surface of the first feature sheet, the second surface being opposite the first surface, and the cuts not passing completely through the first feature sheet; (a3) bonding the first substrate to the first feature sheet such that a first surface of the first substrate sheet is adjacent to the second surface of the first feature sheet; (a4) separating the first substrate sheet and the cut pattern portion of the first feature sheet from the second substrate sheet such that the first feature sheet and the cut pattern portion of the first substrate sheet form the spacer sheet; forming a spacer sheet comprising a first substrate sheet having a plurality of spacing features disposed thereon; (b) adhering the spacer sheet to the membrane sheet; A method comprising:

5. The method of claim 4 , wherein the spacing features are shaped to have features on one or more ends that facilitate removal of unwanted interstitial material.

6. The method of claim 4 , wherein the spacing features are shaped to have portions that are substantially straight line segments at angles greater than zero degrees and less than 90 degrees relative to an edge of the first substrate sheet.

7. The method of claim 4 further comprising spirally winding the membrane element to form a spiral wound membrane element.

8. The method of claim 4 further comprising placing the membrane element in a plate and frame type membrane system.

9. 1. A method for manufacturing a membrane sheet for fluid treatment, comprising: forming a spacer sheet comprising a first substrate sheet having a plurality of spacing features disposed thereon; depositing spacing features directly onto a surface of a second substrate sheet; adhering the first substrate sheet to the spacing feature with a bond stronger than a bond of the spacing feature to the second substrate sheet; separating the second substrate sheet from the spacing features; adhering the spacing feature to a film sheet with a bond stronger than the bond of the spacing feature to the first substrate sheet; Separating the first substrate sheet from the spacing features; forming a spacer sheet comprising a first substrate sheet having a plurality of spacing features disposed thereon; A method comprising:

10. The method of claim 7 further comprising spirally winding the membrane sheet to form a spiral wound membrane element.

11. The method of claim 7 further comprising placing the membrane sheet in a plate and frame type membrane system.

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