Search

EP-3319713-B1 - MEMBRANE SEPARATION MODULE COMPRISING POTTING WITH POLAR THERMOPLAST

EP3319713B1EP 3319713 B1EP3319713 B1EP 3319713B1EP-3319713-B1

Inventors

  • IYER, GANAPATHYSUBRAMANIAN
  • DOH, Cha

Dates

Publication Date
20260506
Application Date
20160630

Claims (9)

  1. A membrane separation module, comprising: at least one membrane (112) constructed of a first material, the at least one membrane having a first potted end region (108a), a second potted end region (108b), and an open middle region (107), wherein the first potted region and the second potted region are encapsulated in a thermoplastic blended potting resin; and a housing (110) constructed of a second material that is different from the first material, wherein the housing is heat bonded to the membrane by the thermoplastic blended potting resin; wherein the two potted end regions are encapsulated with the thermoplastic blended potting resin to form a fluid-tight seal between the two potted end regions and the open middle region; and wherein the thermoplastic blended potting resin comprises either: (1) a non-polar thermoplastic polymer and a polar thermoplastic polymer, wherein the polar thermoplastic polymer is greater than 1% by weight of the total weight percent of the thermoplastic blended potting resin, and wherein the polar thermoplastic polymer is high density polyethylene maleic anhydride, ethylene vinyl alcohol, ethylene vinyl acetate, ethylene acrylic acid or polybutadiene maleic anhydride; or (2) a modified thermoplastic polymer comprising polar groups, wherein the polar groups are 0.1% or greater by weight of the total weight of the modified thermoplastic polymer, and wherein the polar groups are amides, alcohols, acid anhydrides, cyanides, sulfates, sulfonates, carboxylic acids, aldehydes, amines or ammonium groups.
  2. The membrane separation module of claim 1, wherein the modified thermoplastic polymer comprises polar groups from about 0.1% to 75% by weight of the total weight of the modified thermoplastic polymer.
  3. The membrane separation module of claim 1, wherein the polar thermoplastic polymer is 5% to 50% by weight of the total weight percent of the thermoplastic blended potting resin.
  4. The membrane separation module of claim 1 or claim 3, wherein the non-polar thermoplastic polymer is polyethylene, high density polyethylene, polypropylene, polystyrene, polybutadiene, poly(tetrafluoroethylene-co-perfluoro(alkyviny1ether)), perfluoroalkoxyalkane or perfluoromethylalkoxy.
  5. The membrane separation module of any preceding claim, wherein the at least one membrane is (i) a hollow fiber, a flat sheet, or a pleated sheet, or (ii) a plurality of membranes.
  6. The membrane separation module of any preceding claim, wherein the at least one membrane is a polyamide, a polyimideamide, a polyimide, a polysulfone, a cellulose acetate, a polyvinyl alcohol or a polyacrylate.
  7. The membrane separation module of any preceding claim, wherein: (1) the first material is a polar material and the second material is a non-polar material; or (2) the first material is a non-polar material and the second material is a polar material.
  8. A fluid separation device, comprising: a housing having: a first end and a second end; a separation element contained within the housing to divide the interior of the housing into first and second volumes, the separation element comprising the membrane separation module of any preceding claim and a series of flow passages upstream and downstream of said membrane separation module; a first connector at the first end for introducing a fluid feed to the interior of the housing; a second connector for removing a permeate from the interior of the housing; and a central conduit attached to the first connector and extending longitudinally within the housing to the second end so as to direct all of the flow between the first connector and the second end; wherein the second end is in fluid communication with the first volume, wherein the second volume is in fluid communication with the second connector, and wherein a fluid fed into the first connector is processed by the separation element to form the permeate collected and removed by the second connector.
  9. A method of making a fluid separation device, the method comprising: • providing at least one polar membrane having a first end region, a second end region, and a middle region; • contacting at least one of the two end regions of the at least one polar membrane with an extrusion of molten thermoplastic blended resin comprising a non-polar thermoplastic polymer and a polar thermoplastic polymer, wherein the polar thermoplastic polymer is high density polyethylene maleic anhydride, ethylene vinyl alcohol, ethylene vinyl acetate, ethylene acrylic acid or polybutadiene maleic anhydride, wherein the molten thermoplastic blended resin is heated sufficiently above its melting point such that the molten thermoplastic blended resin flows around the at least one polar membrane, and wherein the polar thermoplastic polymer is 1% or greater by weight of the molten thermoplastic blended resin; • cooling the molten thermoplastic blended resin to form a blended resin potted membrane comprising two potted ends; • inserting the blended resin potted membrane comprising two potted ends into a housing; and • applying heat to the housing sufficient to bond the two potted ends to the housing, and wherein the bond between the blended potted membrane and the housing is also a fluid-tight seal between the two end regions and the middle region of the blended resin potted membrane.

Description

RELATED APPLICATION BACKGROUND OF THE INVENTION Membranes used for most common applications are potted using thermosetting adhesives or sealants which are in a liquid state (low viscosity state) when applied to the fibers and then solidify around the fiber after curing. Some examples are, epoxy and acrylics (see e.g. JPH09206563). These work because they are initially in the form of a low viscosity liquid which can percolate in between the fibers and into the surface pores of the fiber to form a strong bond once they solidify. Some of the sealants also form a chemical bond with the fiber material. But sealant or adhesive based potting tends to be very dirty and frequently shed particles or leach impurities in application solvents. So these are not preferred for "clean" applications (applications which require high levels of purity in the manufacturing environment) such as for fluids used in semiconductor industry. Thermoplastics have been used for potting hollow fibers to overcome the drawbacks of thermosetting adhesives and sealants (see e.g. US4269712, US2014263061) Membranes used in clean applications, such as semiconductors are potted using thermoplastic polymers, otherwise referred to as potting resins. The thermoplastics resins are applied to the membranes in a molten liquid state using special techniques like spiral lamination or centrifugal potting, and subsequently solidified around the membrane upon cooling creating a fluid-tight seal. Generally, the thermoplastic resin is physically and/or chemically compatible with the membrane material to promote bonding of the potting resin to the membrane and to ensure integrity of the bond. Once the membranes are potted together, they are bonded into a housing which becomes part of the filter device. The potting material must also be physically and/or chemically compatible to the housing material in order to create a sufficiently strong bond. When the housing, potting resin and membranes are physically and/or chemically incompatible with each other, structural defects in the filter device and sealing failures between the membrane and the potting can occur. Thus, there is a need to develop potting materials that can be used in applications when it is desirable to join together housings and membranes that are physically and/or chemically incompatible with each other. SUMMARY OF THE INVENTION The present invention is directed to the discovery that a membrane and a housing constructed from materials that do not share similar physical and/or chemical properties (e.g., one is polar and the other non-polar) can be fluidly sealed and bonded through the use of a blended potting resin. Specifically, the present invention is directed to blended thermoplastic resins, potted membranes, membrane separation modules, methods of making membrane separation modules, and methods of using membrane separation modules, all of which use the blended thermoplastic potting resins described herein. The blended potting resins allow for greater flexibility in designing membrane separation modules having membranes and housings constructed from different materials (e.g., one polar and the other non-polar), while maintaining high structural integrity demands of the filtration industry. BRIEF DESCRIPTION OF THE DRAWINGS The foregoing will be apparent from the following more particular description of example embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention. FIGs. 1A-B illustrate example embodiments of a housing holding a polar membrane and potting resin useful in the present invention.FIG. 2A is a perspective diagram of the apparatus used in the process of making an array of hollow fiber membranes in accordance with a preferred embodiment of the present invention.FIG. 2B illustrates a top view of a finished array of hollow fiber membranes used in carrying out the process of FIG. 2A.FIG. 3 is a schematic representation of the apparatus used in the process of making hollow fiber membrane modules in accordance with an example embodiment of the present invention.FIG. 4 is a detailed view, in perspective, showing the spiral winding sealing aspect of the hollow fiber membranes by the application of molten thermoplastic in accordance with an example embodiment of the present invention.FIG. 5 illustrates an example housing for centrifugal sealing which is useful in an example embodiment of the present invention.FIG. 6 is a photograph of a hollow fiber membrane pulled from a potting resin.FIG. 7 is a photograph illustrating the results of the tensile testing in Table 4. DETAILED DESCRIPTION OF THE INVENTION While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the