Patent Application
20070144716
Hollow fibers and thin walled hollow tubes have been used in mass transfer, heat exchange, and cross flow particle filtration devices. In these applications the hollow tubes or porous fibers provide a high surface to volume ratio which permits a greater transfer of heat and mass in a smaller volume than a device made with flat sheet materials of similar composition.
A hollow fiber or a hollow tube includes an outer diameter and surface, an inner diameter and surface, and a porous or non-porous material between the first and second surfaces or sides of the tube or fiber. The inner diameter defines the hollow portion of the fiber or tube and is used to carry one of the fluids. For what is termed tube side contacting, a first fluid phase flows through the hollow portion, sometimes called the lumen, and is maintained separate from a second fluid phase, which surrounds the tube or fiber. In shell side contacting, the first fluid phase surrounds the outer diameter and surface of the tube or fibers and the second fluid phase flows through the lumen. In an exchange apparatus, packing density relates to the number of useful hollow fiber or hollow tubes that are available in the apparatus.
Examples of applications in semiconductor manufacturing where heating or cooling of a liquid is used include sulfuric acid and hydrogen peroxide photoresist strip solutions, hot phosphoric acid for silicon nitride and aluminum metal etching solutions, ammonium hydroxide and hydrogen peroxide SC1 cleaning solutions, hydrochloric acid and hydrogen peroxide SC2 cleaning solutions, hot deionized water rinses, and heated organic amine based photoresist strippers. Mass exchange with a fluid is important where for example particles are removed from a fluid during filtration, where gases like ozone or hydrogen are added to water, or where dissolved gases like oxygen are removed from fluids such as copper electroplating solutions.
Exchange devices have been potted by preparing a shell or housing with a thin layer of a potting material sintered to the inside diameter surface of the shell. The device assembly, including hollow fiber media, is then potted by surrounding the assembly with a thermoplastic resin, and raising the temperature in a controlled environment to melt the resin, thus filling the space around the media at one end of the device. The resin would flow sufficiently into the shell to encapsulate the media and adhere to the sidewall of the shell that had been sintered with the potting material in an earlier step. Other potting methods previously used include: potting the device with hollow tubes outside of the shell and machining the potted area to create a bonding surface and thermally bonding the potted material to a housing; potting the device with tubes outside of the shell, machining the potted area to create a mating flange and sealing surface which could be mechanically joined to the shell using an o-ring or other contact sealing method—these parts could be held together by a snap ring, threaded fasteners and or a secondary bonding operation. Additional methods include inserting pins in each fiber, potting the assembly and removing the pins after potting. Some exchange devices are made by filling the lumen inside diameter with a binder and extracting out the binder after potting and machining.
Embodiments of the present invention are exchange devices that include a housing, shell, or sleeve bonded to one or more thermoplastic potted hollow conduits, the housing, shell or sleeve can includes structures such as grooves or channels on a surface of the housing. Where grooves are present, the thermoplastic potting material fills at least a portion of the grooves in the housing surface and bonds to a portion of them to form a unitary end structure with the potted hollow conduits. The unitary end structure may then be cut open to expose the hollows of the conduits at each potted end of the device. The structures permit potted devices to be used at higher temperatures and pressures while maintaining the fluid integrity of the potted device. Exchange devices of the present invention and methods for making them include any device that requires potting the working media into a housing meant for containment of the process fluid including but not limited to fully bonded membrane contactors, gas contactors, ozone contactors, degassers, heat exchangers, heaters, gas scrubbers, hollow fiber filters, and combinations of these. The device can be made using thermoplastic materials, including perfluorinated thermoplastics. Preferably the exchange device is made from one or more perfluorinated thermoplastics.
The present invention improves the strength of such potted devices by creating a mechanical interlock and or a fused bond between the potting material and structures such as channels or grooves in the housing shell. The interlock and or bond serves as a molded in sealing surface, that has mechanical strength, preventing separation of the mating parts. The grooves, and their additional surface area, some of which may not be parallel to the housing walls, result in fusion and adhesion of the potting resin to at least a portion of the surfaces of the groove. Without wishing to be bound by theory, it is believed that this bond can add a shear component to the radial force created by thermal or pressure expansion of the housing shell. This shear component is believed to improve the strength of the device.
One embodiment of the present invention is an exchange device that includes a thermoplastic housing having one or more thermoplastic hollow conduits that can include hollow tubes, porous hollow fibers, or a combination of these fluidly sealed to at least one end of a housing or sleeve by a thermoplastic resin. The thermoplastic resin is fluidly sealed, by fusion and or mechanical bonds, to an end portion of the housing to one or more structures such as protrusions, grooves, or a combination of these in the housing. The housing structures and resin form a unitary end structure where the resin, conduits, and housing fuse at a portion of the housing. The unitary end structure may be machined or cut to open the hollows of the conduits. The exchange device may have a sintered thermoplastic coating on the inside of the housing including the surfaces of the grooves. The exchange device housing may include fluid fittings in fluid communication with the shell side and fluid fittings in fluid communication with the lumen or bore side of the device. The exchange device is made from various thermoplastic materials, preferably the thermoplastics are perfluoropolymers such as but not limited to FEP, PFA, MFA or a combination of these. The exchange device may include but is not limited to potted conduits that can be hollow tubes, porous hollow fibers, skinned hollow fibers, thermoplastic tubes, co-extruded hollow tubes or a combinations of these. Preferably the ends of the potted hollow conduits are open by cutting following the potting process. The mechanical interlock and or fusion of the potting resin with the housing grooves serves to entrain the shell and potted area together, particularly when stressed due to temperature or pressure. Expansion or contraction of the housing more than the potted material is reduced, keeping the assembly (housing, potting, and hollow conduits) integral.
Another embodiment of the present invention is an exchange device that includes a thermoplastic housing having one or more fluidly sealed hollow conduits potted in a thermoplastic resin where the thermoplastic resin occupies a volume of one or more grooves on an interior surface of the housing. During potting, the grooves and resin with hollow conduits form a unitary end structure where the thermoplastic resin and housing fuse at a portion of the groove and the resin and hollow conduits fuse to form a unitary end structure. The housing inner surface and grooves may be coated with a sintered thermoplastic material to which the potting resin may fuse. The potted hollow conduits may be opened by cutting or machining a portion of the unitary end structure to expose the conduit lumens. Preferably the exchange device is constructed so that fluid contacting surfaces are perfluorinated, more preferably the exchange device is constructed of all perfluorinated thermoplastics.
Another embodiment of the present invention is an apparatus for exchanging energy or mass with a process fluid used to clean or coat substrates. The apparatus can include an exchange device having one or more thermoplastic hollow conduits fused at a first end portion of the conduits to a thermoplastic resin. The thermoplastic resin can be fused to an interior surface of a first sleeve or first end of a thermoplastic housing or fused to one or more structures on an interior surface of a first sleeve or to a first end of thermoplastic housing. A second end portion of the thermoplastic hollow conduits are fused with a thermoplastic resin. The thermoplastic resin can be fused to an interior surface of a second sleeve or second end of the thermoplastic housing or the resin can be fused to one or more structures on an interior surface of a second sleeve or to structures on a second end of the thermoplastic housing. A source of working or exchange fluid is connected to a first fluid inlet of the exchange apparatus and a source of process fluid connected to a second fluid inlet of the exchange apparatus. The first and second fluid inlets are separated by the hollow tubing wall and by the potting material bonded to the housing or sleeves. A fluid controller in fluid communication with the second fluid inlet of the exchange device can be used to provide controlled amounts of conditioned fluid to one or more substrates to be treated by the apparatus. The fluid controller may provide conditioned fluid to a tank or weir containing one or more substrates or it may provide conditioned fluid directly to a stationary, rotating, or translating substrate. The fluid controller can be but is not limited to a fluid pump, a dispense pump, or a liquid flow controller. Preferably the exchange fluid is a source of temperature controlled fluid. Preferably the substrate to be treated includes silicon.
Another embodiment of the present invention is an exchange device that includes a thermoplastic housing having one or more fluidly sealed hollow conduits potted in a thermoplastic resin. The exchange apparatus may include one or more co-extruded thermoplastic hollow conduits preferably has a housing or one or more sleeve where the hollow conduits are bonded to a portion of the housing by one or more structures such as protrusions, grooves, or a combination of these in the housing. The resin can occupy a volume of one or more grooves on an interior surface of the housing and bonds to the surface. The structures, which can be grooves, and resin form a unitary end structure with the hollow conduits where the resin and housing fuse at a portion of the grooves or a coating on the housing to form the unitary end seal with one or more hollow conduits. The device may be used to treat a fluid while maintaining the fluid integrity of the device, for example the bond between the housing and the potting resin or hollow conduits and resin, at temperatures below the melting point or the continuous use temperature of the thermoplastic. This temperature may depend upon the pressure of fluids on either side of the hollow conduit walls. The device may be used to treat a fluid while maintaining the fluid integrity of the device, for example the bond between the housing and the potting resin or hollow conduits and resin at a temperatures of at least 50° C., preferably at least 140° C., more preferably to 200° C., and most preferably 200° C. or more but below the melting or continuous use temperature of the thermoplastic materials. Preferably the exchange device maintains its fluid integrity at these temperatures when the pressure of the fluid is at least 10 psig, preferably at least 50 psig, and more preferably 70 psig or greater. The integrity of the device can be maintained for an exchange apparatus having a packing density of hollow conduits from 3-99 percent by volume, preferably 20-70 percent by volume and is more preferably from 40-60 percent by volume.
Another embodiment of the present invention is a method of making an exchange device that includes flowing a thermoplastic material into an end portion of a housing or sleeve, the housing or sleeve optionally having structures such as protrusions, grooves, or a combination of these on an inner surface of the housing or sleeve; the thermoplastic material flows between one or more hollow conduits positioned within the housing or sleeve. Grooves in the housing can be interconnected by other grooves or vent channels along a surface or axis of the housing or sleeve. The method further includes forming a fluid tight seal between the thermoplastic material and the hollow conduits and a fluid tight seal between the thermoplastic potting resin and the housing to form a unitary end structure. Where grooves are used, preferably the thermoplastic potting resin occupies at least a portion of the grooves in the housing or sleeve and even more preferably the resin fuses with a portion of the groove or a sintered thermoplastic material coating the housing and groove surfaces. The hollow portions of the conduits can be cut opened or machined to permit fluid flow through the hollow conduits. Preferably the housing has a coating of a thermoplastic material capable of fusing with the potting resin on one or more of the housing surfaces.
Another embodiment of the present invention is a method of treating a fluid that includes flowing a process fluid to be treated on a first side of at least one hollow conduit having two sides and a thermoplastic wall interposed between them, the hollow conduit potted in a fluid tight manner within a thermoplastic material. The thermoplastic potting material is bonded to housing for the device, the housing has a thermoplastic sintered, co-extruded, or molded to at least a portion of the inner surface, to a portion of one or more structures, or a combination of these on the inside surface of the housing that can fuse with the potting resin. Where grooves are present on the housing, at least a portion of the housing grooves are bonded to the thermoplastic material to form a fluid tight seal between the thermoplastic material, the hollow conduit and the housing. The method includes exchanging energy, mass, or a combination of these with the process fluid to be treated by flowing an exchange or working fluid on a second side of the hollow conduits. The energy, mass, or a combination of these is transferred to or from the process fluid to the exchange fluid through the hollow conduit wall. The hollow conduits may be one or more non-porous hollow tubes, skinned or unskinned porous hollow fibers, co-extruded non-porous hollow tubes, co-extruded porous hollow tubes, or a combination of these.
Exchange devices in embodiments of the present invention are advantageous in that the structures such as grooves permit bonding of the hollow conduits to the housing or sleeve and permit venting of gases, generated or dissolved, that coalesce to form bubbles in the thermoplastic resin melt. The thermoplastic resin, preferably a perfluorinated thermoplastic resin melts at a temperature of greater than about 100° C. The thermoplastics used in the present exchange devices fuse to a portion of the hollow conduits and to the housing or grooves during the potting process. The exchange devices of the present invention can be made from all perfluorinated materials bonded together eliminating the need for mechanical locking pins, silicon resins, and other non-perflorinated polymeric bonding resins. Further, the exchangers of the present invention eliminate the need for a reinforcing rib bonded to the housing. Eliminating the reinforcing rib decreases the costs of manufacture and also permits a greater number of hollow conduits to be used in the device resulting in higher contact surface area and packing density that improves transfer performance and efficiency. By providing structures such as grooves in the housing, endcap, or sleeve that the hollow conduits are bonded with in the exchange devices of the present invention, a wide variety of devices including immersion exchangers, weldable zero clearance exchangers, and exchangers with one or more different end caps can be made using readily available or readily machined parts. Advantageously, for high purity applications, stress relief channels in the potting resin, which can trap fluids and contaminants are not required in exchange devices of the present invention. This greatly simplifies the manufacturing process and permits a greater numbers of thin walled hollow conduits to be used in exchange devices.
In part, other aspects, features, benefits and advantages of the embodiments of the present invention will be apparent with regard to the following description, appended claims and accompanying drawings where:
Before the present compositions and methods are described, it is to be understood that this invention is not limited to the particular molecules, compositions, methodologies or protocols described, as these may vary. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present invention which will be limited only by the appended claims.
It must also be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural reference unless the context clearly dictates otherwise. Thus, for example, reference to a “hollow tube” is a reference to one or more hollow tubes and equivalents thereof known to those skilled in the art, and so forth. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, the preferred methods, devices, and materials are now described. All publications mentioned herein are incorporated by reference. Nothing herein is to be construed as an admission that the invention is not entitled to antedate such disclosure by virtue of prior invention.
Versions of exchange devices of the present invention can include one or more thermoplastic hollow conduits fused or bonded in a potting process at a first end portion of the conduits to a thermoplastic resin. The thermoplastic resin bonded to the conduits can be fused or bonded to the interior surface and or one or more structures by potting on an interior surface of a first sleeve or to structures on the first end of a thermoplastic housing. The second end portion of the thermoplastic hollow conduits are fused or bonded with a thermoplastic resin; the thermoplastic resin fused to the interior surface or to one or more structures on an interior surface of a second sleeve or to structures on a second end of the thermoplastic housing. The hollows of the fused conduits may be opened by cutting the resin and opening the conduit ends. The surface on the housing or sleeves that the thermoplastic resin bonds to can also include structures such protrusions, grooves, or a combination of these; preferably the structures are grooves in the surface of the housing or sleeves. The exchange device hollow conduits can be hollow tubes, porous hollow fibers, skinned hollow fibers, thermoplastic tubes, co-extruded hollow tubes, or combinations of these.
Exchange devices of the present invention and methods for making them include potting a working media, for example thin walled hollow tubing or porous hollow fibers, into a housing or one or more sleeves with a thermoplastic resin. The hollow tubes or fibers potted in the housing separate through their walls a process fluid to be conditioned from an exchange or working fluid that can transfer mass, energy, or a combination of these with the process fluid. Such exchange devices can include but are not limited to fully bonded membrane contactors, gas contactors, ozone contactors, degassers, heat exchangers, gas scrubbers, heaters, hollow fiber filters, or combinations of these. These devices may be used to exchange or transfer heat, mass, or a combination of these between fluids separated by hollow thermoplastic tubes. The devices may be immersion style or include a housing for separately containing the process and exchange fluids.
One version of an exchange device includes one or more co-extruded thermoplastic hollow conduits fused at a first end portion of the conduits to a thermoplastic resin; the thermoplastic resin fused to an interior surface of a first sleeve or to a first end of thermoplastic housing. A second end portion of the thermoplastic hollow conduits are fused with a thermoplastic resin, the thermoplastic resin fused to an interior surface of a second sleeve or to a second end of the thermoplastic housing. The ends of the hollow conduits from the potted unitary end structure may be opened to fluid flow by cutting or milling a portion of the thermoplastic resin and conduits. Optionally the exchange device housing or sleeve includes one or more fluid fittings. The co-extruded hollow conduits may include a thermally conductive material mixed or combined with one or more of the layers that make up the hollow conduit. The thermoplastic housing or sleeve for the exchange device is chosen to have a composition that permits it to fuse with the potting resin during the potting process. It may include housings or sleeves that are made from a thermoplastic, thermoplastics with a sintered material on its interior surface, co-extruded thermoplastics with one or more thermoplastic layers, molded thermoplastics with one or more thermoplastic portions. Preferably the housings have a thermoplastic on a portion of the wall of the housing or sleeve in contact with the potting material that is capable of fusing with the potting material during a bonding process. The housing or sleeve may have a smooth surface or it may have one or more structures formed on its inner surface to bond with the potting resin.
A fluid-fluid phase contactor or exchange device of the present invention may be made from thermoplastic polymeric materials and preferably perfluorinated thermoplastic polymers. The device can be used for contacting a fluid to be conditioned with a working or exchange fluid. The contactor or exchange device includes a bundle of a plurality of perfluorinated thermoplastic hollow fiber membranes or hollow tubes 130 as for example shown in
A method of making a fluid-fluid phase contactor substantially made from thermoplastic polymers and preferably perfluorinated thermoplastic polymers for contacting a first fluid with a second fluid may include forming a bundle of a plurality of perfluorinated thermoplastic hollow conduits such as hollow fiber membranes, hollow tubes, or a combination of these having a first end and a second end. The hollow conduits have an outer surface and an inner surface, the inner membrane surface comprising a lumen or bore. The hollow fiber membranes that can be used in the device and the method of making it may be selected from the group consisting of hollow fiber membranes having a porous skinned inner surface, a porous outer surface, and a porous support structure between them; hollow fiber membranes having a non-porous skinned inner surface, a porous outer surface, and a porous support structure between them; hollow fiber membranes having a porous skinned outer surface, a porous inner surface, and a porous support structure between them; and hollow fiber membranes having a non-porous skinned outer surface, a porous inner surface, and a porous support structure between. As illustrated in
Potting and bonding of hollow conduit cords, hollow fibers or hollow tubes, into the housing can be done in a single step using for example a thermoplastic resin potting material such as but not limited to Hyflon® MFA 940 AX resin, available from Ausimont USA Inc. Thorofare, N.J. The devices can be made by vertically placing a portion of a bundle hollow tube and or hollow fiber cord lengths with at least one closed end, prepared for example by wrapping the hollow tube or hollow fiber on a frame and annealing, into a pot lifted off the bottom surface of the pot by approximately ⅛-¼ inch (0.318 to 0.635 cm). Thermoplastic resin in pellet form can be placed around the outside of the shell of the device, and the pot can be heated to melt the resin. The temperature can be from about 270-285° C. for hollow fibers, and about 280-305° C. for thin wall hollow tubes and co-extruded hollow tubes. The resin melts and flows into the shell and between the lumens by head pressure and capillary action. An alternative method is to make a temporary recess made in a pool of molten thermoplastic polymer held in a container. The hollow conduits are held in a defined vertical position, maintaining the thermoplastic polymer in a molten state so that it flows into the temporary recess, around the hollow conduits and vertically up the hollow conduits, filling the interstitial spaces between the hollow conduits and one or more structures like grooves in the housing or sleeve walls. A temporary recess is a recess that remains as a recess in the molten potting material for a time sufficient to position and fix the bundle of hollow conduits in place and then will be filled by the molten thermoplastic The temporary nature of the recess can be controlled by the temperature at which the potting material is held, the temperature at which the potting material is held during hollow conduit bundle placement, and the physical properties of the potting material. The end of the hollow conduits can be closed by sealing, plugging, or in a preferred embodiment, by being formed in a loop.
While co-extruded hollow conduits, hollow tubes, and hollow fiber having one or more layers of thermoplastic as illustrated in
Another method for potting hollow tubes includes fusing a portion of a plurality of thermoplastic hollow tubes or fibers in a housing end or sleeve into a thermoplastic potting resin to form a unitary end structure of the potting resin, hollow tubes, and housing. The interior of the housing or sleeve can have one or more fusible protrusions, one or more channels or grooves in its surface. Alternatively, an inner layer of a co-extruded housing can have a layer of thermoplastic that can fuse to the potting resin. The process may involve, as illustrated in
The exchange device may have a process fluid inlet and outlet connected to the housing for receiving and delivering a process fluid into a re-circulation loop or to a dispense tool. The exchange device can have an exchange fluid or working fluid inlet and outlet fittings for flow of an exchange fluid; the exchange fluid separated from the treated fluid or process fluid by the material in the walls of the hollow tubes and the potting bonding the housing to the tubes. The exchange fluid exchanges or transfers mass and or energy to or from the process fluid through the hollow tube walls. The exchange device of the present invention may be used in an apparatus that optionally includes a re-circulating pump in fluid communication with the process fluid inlet on the exchange device and optionally a tank for holding an article to be treated by the process fluid. The exchange device may be used as part of a dispense system or a re-circulating fluid flow circuit. The apparatus may also further include a particle filter. The apparatus may exchange mass and or energy with gases, organic containing fluids, or aqueous fluids including ultra high purity water. Preferably the substrate or article to be treated by the process fluid includes but is not limited to metals such as copper and aluminum, semiconductors including arsenic or silicon, or ceramics including aluminum, barium, and strontium.
An apparatus or system for treating substrates may utilize one or more exchange devices as illustrated in
The exchange devices can also be used in a method and apparatus for the purification of gases which may be used in chemical processes or which may be removed from an effluent stream. In particular, the present invention provides a device which maintains the integrity of the potting resin and housing seal during exothermic scrubbing reactions where for example an exhaust fluid is purified by reacting a component of the exhaust fluid with a reactive liquid, gel, or slurry contained on one side of a porous hollow fiber membrane potted into a housing having grooves, the potting and hollow conduits forming a unitary end structure with the housing that can be cut open for fluid flow through the potted hollow conduits.
An exchange device of the present invention may be used for cleaning or coating of moving substrates. For example,
An example of a housing, sleeve, or portion of an endcap with one or more channels in the inner or outer wall of the housing is illustrated in
A test apparatus for measuring the integrity or performance of an exchange device may include an exchange device, sensors, one or more test fluids, and fluid handling devices such as pumps, conduits, and valves.
The wall of a sleeve or housing with grooves and vent slots from
The wall of a sleeve or housing with grooves and vent slots similar to
The potting of one or more hollow conduits 1106 into a housing having one or more grooves 1112 and 1116 and grooves or vent slots 1132 fluidly interconnecting the adjacent grooves is illustrated in
The exchange device may include but is not limited to one or more potted hollow conduits that can be porous hollow fibers, skinned hollow fibers, thermoplastic tubes, or combinations of these bonded to a thermoplastic housing or sleeve. The exchange device of the present invention can be made with a variety of hollow conduits having variously shaped inner and outer surfaces including but not limited hollow tubes, rectangular conduits, triangular conduits. The hollow conduits generally have an outer surface and can have one more channels along the inside of conduit. The porosity of the hollow conduits walls can vary from non-porous to those having a porosity suitable for filtration, liquid-liquid contacting, and liquid-gas contacting. A fluid phase that flows through the hollow portion of a potted hollow conduit, called the lumen or bore for hollow tubes and hollow fibers, can transfer mass or energy to a fluid which surrounds the outer surface of the hollow conduit. A hollow conduit that is a porous membrane can be described by an outer shape or dimension and an inner shape or dimension with a porous wall thickness between them. A hollow non-porous conduit is a conduit that can be described by an outer shape or dimension, an inner shape or dimension, with a non-porous wall thickness between them. For hollow tubular filaments, having porous or non-porous walls, inner diameter defines the hollow portion or lumen of the tube and can used to carry one of the fluids or exchange medium.
The hollow membranes or hollow conduits may be braided or twisted and optionally thermally annealed in a first step and then the individual tubes separated from each other after cooling to form self supporting helical shaped or non-circumferential shaped single tubes. Thermal annealing sets the crests and bends of the hollow tube so that the individual hollow tubes or cords can be separated and handled without straightening. These shaped hollow tube may be potted in the thermoplastic resin as described.
The outer or inner surface of a hollow fiber membrane can be skinned or unskinned. A skin is a thin dense surface layer integral with the substructure of the membrane. In skinned membranes, the major portion of resistance to flow through the membrane resides in the thin skin. The surface skin may contain pores leading to the continuous porous structure of the substructure, or may be a non-porous integral film-like surface. In porous skinned membranes, permeation occurs primarily by connective flow through the pores. Asymmetric refers to the uniformity of the pore size across the thickness of the membrane; for hollow fiber conduits, this is the porous wall of the fiber. Asymmetric membranes have a structure in which the pore size is a function of location through the cross-section, section, typically, gradually increasing in size in traversing from one surface to the opposing surface. Another manner of defining asymmetry is the ratio of pore sizes on one surface to those on the opposite surface.
Manufacturers produce conduits such as pipe and thick walled channels useful for housings, sleeves, and endcaps; hollow porous membrane conduits; and non-porous hollow conduits from a variety of materials, the most general class being synthetic thermoplastic polymers. These can be flowed and molded when heated and recover their original solid properties when cooled. As the conditions of the application to which the hollow conduit is being used become more severe, the materials that can be used becomes limited. For example, the organic solvent-based solutions used for wafer coating in the microelectronics industry will dissolve or swell and weaken most common polymeric hollow fiber membranes or thin walled hollow tubes. The high temperature stripping baths in the same industry consist of highly corrosive liquids that can destroy membranes and thin walled hollow tubes made of common polymers. High temperatures and pressures will deform and weaken may polymeric hollow membranes and thin walled hollow tubes. Perfluorinated thermoplastic polymers useful for housings, sleeves, and hollow conduits may include but not limited to perfluoroalkoxy (Teflon® PFA from Dupont, Neoflon® PFA from Daikin, Teflon® PFA Plus from Dupont), perfluoromethylalkoxy (Hyflon® MFA from Ausimont), fluorinated ethylene propylene (Teflon® FEP from Dupont) and co-polymers of these. These perfluorinated thermoplastics are chemically resistant and thermally stable, so that hollow membranes and hollow tubes made from these polymers, co-polymers, and co-extruded versions of them can have a decided advantage over less chemically and thermally stable polymers. Other useful thermoplastic fluoropolymers that can be used may include homopolymers and copolymers comprising monomeric units derived from fluorinated monomers such as vinylidene fluoride (VF2), hexafluoropropene (HFP), chlorotrifluoroethylene (CTFE), vinyl fluoride (VF), trifluoroethylene (TrFE), and tetrafluoroethylene (TFE), among others, optionally in combination with one or more other non-fluorinated monomer. A modified PTFE, PTFM is suitable as a shell material or containment material for the lumens as this material is capable of bonding and adhearing to the potted material, but is still not melt processable. For less severe conditions of use, other thermoplastics or their blends may be used in the practice of this invention and can include but not limited to, polyether sulfone (PES), ultra high molecular weight polyethylene (UHMWPE), high density polyethylene (HDPE), and other polyolefins The invention can also be used for similar but non identical materials such as polyethylene potting material in a polypropylene shell or NFA potting material in a PFA shell. Protrusions, grooves, or channels can be made in housings or sleeves made from these materials.
The exchange device may be made from a housing, hollow conduits, and potting resin that includes several thermally stable, chemically compatible, and mechanically strong fluoropolymers. The fluoropolymers may include, for example, a homopolymer or a copolymer formed from monomer units containing fluorine. The housing and hollow conduits may be co-extruded and include one or more layers of fluoropolymer, or different layers of fluoropolymer on the inner and outer surfaces.
PFA and FEP are examples of fluoropolymers that can be made into hollow porous membranes using the Thermally Induced Phase Separation (TIPS) process. In one example of the TIPS process a polymer and organic liquid are mixed and heated in an extruder to a temperature at which the polymer dissolves. A membrane is shaped by extrusion through an extrusion die, and the extruded membrane is cooled to form a gel. During cooling the polymer solution temperature is reduced to below the upper critical solution temperature. This is the temperature at or below which two phases form from the homogeneous heated solution, one phase primarily polymer, the other primarily solvent. If done properly, the solvent rich phase forms a continuous interconnecting porosity. The solvent rich phase is then extracted and the membrane dried.
The housing, endcaps, or sleeves used in exchange devices may be but are not limited to thick walled conduits that are cylindrical tubes, conduits having any number of sides including hexagonal, rectangular or triangular conduits. The housing, endcaps, or sleeves have an inner dimension capable of containing one or more hollow thin walled conduits bonded to the interior of the housing, endcap, or sleeve. The housing or sleeve may be a thermoplastic, preferably a perfluorinated thermoplastic, but can also be a thermoplastic coated metal, composite thermoplastic, or thermoplastic coated ceramic material with grooves that exhibits chemical compatibility for the bonding process and the intended use of the device. The housing or sleeves may be formed from co-extruded thermoplastics with the thermally bonded inner layer capable of bonding to the potting resin or hollow conduits and the outer layer providing mechanical support for the housing. Preferably the inner layer of a co-extruded thermoplastic housing will have a lower melting temperature than the outer layer. Alternatively, the housing or sleeves can be molded to have one or more thermoplastic portions or layers in the bonding region. The structures such as protrusions, grooves, a combination of these, or the interior surface of the housing or sleeve may be coated or molded with a thermoplastic inner layer, for example MFA, to provide an adhesion layer to the housing or sleeve material. One skilled in the art would know to look to ASTM tables to find the permitted housing or sleeve conduit wall thickness for the housing, endcap, or sleeves for a particular use of the exchange device. Where a housing, endcap or sleeve includes one or more structures that are grooves, preferably the depth of the grooves or channels are in the conduit wall are less than about one half the thickness of the wall.
The housing, sleeve, or endcap used to form a single entity consisting solely of thermoplastic materials, and preferably perfluorinated thermoplastic materials, can be prepared by first pretreating the surfaces of both ends of the housing or one or more sleeve before the potting and bonding step. This can be accomplished by melt-bonding or sintering a powdered form of the thermoplastic potting material to the housing, one or more sleeves, and groove or protrusions on their inner surfaces. The internal surfaces on both ends of the housing may be heated close to their melting point or just at the melting point and immediately immersed into a cup containing powdered [Polytetrafluoroethylene-co-perfluoromethylvinylether], MFA, thermoplastic potting resin available from Ausimont USA Inc. Thorofare, N.J. Since the surface temperature of the heated surface of the housing is higher than the melting point of the potting resins, the potting resin is then fused or sintered to the thermoplastic housing, any channels, grooves, or raised features or a combination of these for bonding the potting resin, the hollow conduits, or a combination of these to the housing. A non-limiting example of raised features or protrusion on the housing or sleeve surface is the sintered thermoplastic coating 936 illustrated in
Hollow conduit exchange devices of the present invention, especially those including one or more porous and or non-porous hollow tubes or other shaped conduits, are advantageous because they can be made with high fluid contact surface areas. The high contact surface area is due to the ability to obtain a very high packing densities of the hollow conduits in these devices. Packing density relates to the amount of useful membrane surface per volume of the device. It is related to the number of tubes, conduits, fibers, or combinations of these that can be potted in a finished contactor. The packing density of the hollow conduits such as hollow fibers, hollow tubes, cords of these and combinations of these within the shell tube, housing, or sleeve can be in the range of from 3-99 percent by volume, preferably 20-70 percent by volume, and more preferably 40-60 percent by volume.
Hollow fiber microporous membranes can be used for mass exchange operations such as filtration, gas contacting, and degassing. Hydrophobic microporous hollow fibers membranes are commonly used for degasser or contactor applications, with a liquid to be treated that does not wet the membrane. For gas contacting, the liquid flows on one side of the membrane and a gas mixture preferably at a lower pressure than the solution flows on the other. Pressures on each side of the membrane are maintained so that the liquid pressure does not overcome the critical pressure of the membrane, and so that the gas does not bubble into the liquid. Critical pressure, the pressure at which the liquid will intrude into the pores, depends directly on the material used to make the membrane, inversely on the pore size of the membrane, and directly on the surface tension of the liquid in contact with the gas phase. Typical applications for contacting membrane exchangers are to remove dissolved gases from liquids, “degassing”; or to add a gaseous substance to a liquid. For example, ozone can be added to very pure water to wash semiconductor wafers.
Exchange devices of the present invention may be operated with the process fluid contacting the inside or the outside surface of the potted hollow tubes or conduits, depending on which is more advantageous in the particular application. Baffles and other inserts may be mounted on the inside of the housing or fluid flow fittings to effect fluid distribution on the shell side of the hollow conduits and housing.
Potting is a process of forming a liquid tight seals around each hollow conduit, for example hollow tube or hollow fiber, within the housing. The tube sheet or pot separates the interior of the housing for the exchanger or contactor from the environment. The potting material is bonded to the housing including surface structures such as protrusions, channels, or grooves. This bonding may include physical mixing of melted materials as during welding or fusion of thermoplastics, mechanical interlocking of material, as well as chemical bonding of the materials. Preferably the bond between the housing and its grooves provides a fluid tight seal. The bond to form the unitary end structure may be formed between the potting material and the housing surfaces and housing groove surfaces. The bond may be the result of a union of the potting and housing materials by fusion, melting, or welding. Preferably the potting and housing, including any of the housing's coated surfaces, are thermoplastics that can be fused or welded together by various heating methods such as but not limited to welding, induction heating, ultrasonic bonding, infrared heating, and potting. The housing and potting material may be the same or different materials, for example the housing may be PFA and the potting MFA. The potting material can be thermally bonded to the housing vessel and channels, grooves, or raised structures on the inside of the housing in the present invention to produce a unitary end structure. The inside of the housing and channels may be coated with a layer of the potting resin sintered, molded or co-extruded to the one or more inner housing surfaces to facilitate the bonding between the potting and housing.
Fluidly sealed refers to potting resin, thermoplastic housing, hollow conduits and combinations of these that have either welded or fused together or formed a mechanical bond together that is characterized in that fluid does not flow past the bonded areas. For hollow conduits like fibers or tubes in the potted area, fluid flows through inside of the tubes and is physically separated from fluid on the outside of the hollow tubing or fiber by the conduit walls and potting.
The term unified terminal end block or unitary end structure describes a mass or well of a thermoplastic resin bonded to one or more hollow conduits such as hollow tubes, hollow fibers, or cords of these and a housing or sleeve. Bonding of the resin with the housing and conduits can include mechanical bonds between the resin and structures of the housing and conduits, chemically bonding, welding, or fusion bonding, or any combination of these.
The unitary end structure(s) may be cut or machined and the lumen of the hollow conduits exposed. The potting resin and hollow tube ends may be opened so that the resin and tube ends are even with the housing or sleeve end as illustrated for a single end portion of an exchange device shown in
Porous or skinned hollow fiber diameters can range from 100-1000 um in diameter. Wall thickness should be minimized and preferred thickness is 25-350 um. Hollow fiber beds can consist of mats of fibers with thickness ranging from 1-25 cm in depth and length and width of 10-100 cm. The beds can be circular with diameters of 1-25 cm and lengths of 20-300 cm and contain multiple baffles to distribute gas throughout the bed of fibers. Hollow fibers in the contactor may be straight or can be loosely packed. The hollow fibers may be extremely long and wrapped to a length nearly equivalent to the length of the device, effectively closing off the ends of the fiber to melt resin flow during the potting process.
Hollow conduits that are non-porous hollow tubes made from thermoplastics with outside diameters ranging from 0.007 to 0.5 inches (0.017 to 1.27 cm), and more preferably 0.025 to 0.1 inches (0.063 to 0.25 cm) may be used in the exchange devices of the present invention. For heat exchanger or mass exchange through non-porous hollow tube, preferably the hollow tubes may have a wall thickness ranging from 0.001 to 0.1 inches (0.0025 to 0.25 cm), preferably 0.003 to 0.05 inches (0.0075 to 0.0125 cm) in thickness. For mass exchange through non-porous hollow tubes—gas separations—the thickness of the hollow tube wall can be made thinner. The hollow tubes can be used individually, or the tubes can be combined by braiding, plaiting, or twisting them to form cords comprised of multiple hollow tubes. The hollow tubes may be extremely long and wrapped to a length nearly equivalent to the length of the device, effectively closing off the ends of the hollow tube to melt resin flow during the potting process.
Thermoplastic hollow conduits may include co-extruded thermoplastic tubes and porous hollow fibers that can be potted into sleeves or housings to form exchange devices. The co-extruded tubing or porous hollow fibers can, for example, have one or more outer layers or portions that include a thermoplastic with a lower melting point or melt flow index that the inner most portion or layer of the co-extruded tubing. The layers of the co-extruded tubing are thermally bonded or fused to one another. One non-limiting example of this type of co-extruded tubing has an MFA outer layer and a PFA inner layer. Another example is a hollow tube having an FEP outer layer and a PFA inner portion. One or more of the layers of the co-extruded hollow conduit may include a thermally conductive material, preferably one or more of the outer layers of the hollow conduit includes a thermally conductive material. For example the MFA outer portion of a co-extruded tube may include a conductive carbon particles. During potting, the conductive particles in the MFA of the tubes will mix or combine with NWA from adjacent hollow tubes or with the thermoplastic potting resin. Unpotted regions of the co-extruded tube will retain the MFA layer with the thermally conductive particles as illustrated in
The one or more thermoplastic materials for the co-extruded tubing can be selected for their chemical and or physical properties, for example thermal conductivity, as well as properties that make the tube suitable for bonding with each other, bonding to a resin, or a combination of these used in the potting process. For example, during potting, the outer MFA layer of the tubing will melt and fuse with the MFA from adjacent hollow tubes, fuse with resin in the pot, or a combination of these while the inner PFA layer of the tube keeps the lumen opened. Potting temperature or fusion temperature can be chosen so that the one or more outer layers of the co-extruded tubing melt and fuse or combine with adjacent tubes or a thermoplastic potting resin but the inner layer remains open. For tubing having an outer MFA layer and an inner PFA layer, the preferred potting temperature is between about 290-305° C.; potting temperatures for other co-extruded thermoplastic hollow tubes may be determined by routine experimentation and use of the testing manifold of
As illustrated in
Hollow thermoplastic conduits and co-extruded hollow thermoplastic conduits used in the invention can be impregnated with thermally conductive powders or fibers to increase their thermal conductance. Examples of useful thermally conductive materials include but are not limited to glass fibers, metal nitride fibers, silicon and metal carbide fibers, or graphite. The thermal conductivity of the hollow thermoplastic tubes or impregnated thermoplastic hollow tubes useful in this invention for energy exchange is preferably greater than about 0.05 watts per meter per degree Kelvin. The co-extruded hollow tubes may includes a thermal heat conductor material mixed or combined with any of the layers of the hollow tube, preferably the outer layer. The thermoplastic of the outer layer can include, for example, carbon nanotubes, graphite fibers made from petroleum pitch that can have thermal conductivity values of about 500-1000 W/mK, carbon fibers based on polyacrylonitrile (PAN) that can have thermal conductivities of about 10 W/mK, electrically insulative ceramic fillers like boron nitride that can have a thermal conductivity of about 60-80 W/mK, aluminum nitride with a thermal conductivity of about 300 W/mK, or mixtures of these.
In the practice of various embodiments of the present invention, combinations of porous and non-porous hollow tubes may be potted together. Such devices may be used to limit the amount of mass transferred while maximizing the amount of energy transferred between a process and an exchange fluid. For example temperature conditioned aqueous sulfuric acid may be re-circulated on the shell side of an exchange device to condition the temperature of air in a cleanroom and remove trace amounts of organic amines from the air. Temperature conditioning of the air may be changed by the number of non-porous potted hollow tubes while the amount of air in contact with the aqueous sulfuric acid scrubbing solution for mass exchange is controlled by the number and type of porous potted fibers present in the device.
Baffles may be useful in the practice of the present invention to enhance the mixing and distribution of fluids on either side of the hollow tube contactor or exchange device (not shown in
As shown in
Groove, channel, or slot refer to narrow openings or depressions in the housing, endcap, or sleeve wall and may be used interchangeably. In a preferred embodiment the grooves are interconnected with each other as illustrated for one end portion of a housing in
The groove and vent edges as well as the bottoms of the grooves may have but are not limited to square, beveled, or a radius finish; the edge of the top and bottom most groove in the housing may be slotted or vented with the slots tapering to the inner wall (not shown). One or more of the grooves in the end portion of the exchange device are preferably interconnected by slots or channels and the exchange device may have one or more end portions.
The grooves or channels may have a shape that maximizes surface area of contact and bonding between the potting material and the housing grooves. The depth and angles of the sidewalls of the grooves may be made to vary the amount of bonding surface between the potting material and the grooves. Where an increase in the amount of shear component for the bond between the channel and potting is desired, deep thin channels are preferred. The additional surface area of the channels, some of which may not be parallel to the housing walls, result in fusion and adhesion of the potting resin to all faces or surfaces of the groove. The radial force created by thermal or pressure expansion of the device during use may have a portion of this force transferred to a shear component through bonding of the potting resin with the surfaces of the grooves which greatly improves the strength of the device.
While grooves and channels are preferred for bonding the thermoplastic resin to the housing of the present invention, it is also contemplated that raised structures permanently bonded or fused onto the inner surface of the housing tube could be made and used with the same effect as channels or grooves for purposes of bonding the thermoplastic potting resin to the housing. Such raised structures may be considered as an equivalent to grooves or channels for purposes of the present invention. A sintered thermoplastic bonded to the inner housing wall is a non-limiting example of raised surface structures or protrusions on the housing. Preferably the structures result in bonding or fusion between the raised structures and the potting resin. Preferably the bonding transfers a portion of the radial force into a shear component of force between the potting resin and the raised structure.
Channels or grooves may be formed in a housing which can include, endcaps, sleeves, or any of these bonded to a housing wall. The depth and area of the grooves or height of protrusions on the inner wall of the housing that are used to bond with a thermoplastic resin and bond to one or move hollow tubes are chosen to bond with the resin and form a fluid tight seal that maintains separation between fluids on the inside and outside of the hollow tubes. The depth and area of the grooves, vent channels, or height and area of protrusions on the inner wall of the housing for a particular use of the exchange device may be determined using the test manifold of
It is also contemplated that additional means for reducing stress between the housing and the potting material may be used in addition to channels or grooves in the housing. For example a housing with channels in the inside of the housing may have the outer wall of the housing thinned by machining to relieve pressure on the interface between the potting material and the shell. The thinned material will yield to material movement more readily, allowing temperature and pressure effects to be self compensating by flexible components to maintain the integrity of the bond between the potting resin fused to the housing.
The exchange device may include one or more hollow conduits potted at each end into to a thermoplastic housing. Integral exchange devices made with hollow tubes potted into a thermoplastic housing, a packing density of about 40-50%, but without one or more grooves in the housing were made and used as heat exchangers as summarized by the data in Table 1. It would be reasonable to expect that exchange devices of the present invention, with for example co-extruded tubes or grooves in the housing, having similar numbers of hollow conduits would have exchange performance similar to those shown in Table 1.
Heat transfer between water on the lumen side of the hollow tubes and water on the shell side of the hollow tubes fluids at the inlet temperatures given in Table 1 were approximately the same (within experimental error of less than about 10%) through the hollow tube walls potted in the device. Calculated heat, Q, transferred by the shell fluid ranged from about 8,000 watts to 10,000 watts at different tube flow rates for the exchange device in Table 1 with 2.25 inch diameter and 18 inch length; Q ranged from about 13,900 watts to 15,000 watts at different tube flow rates for the 2.75 inch diameter housing with 8 inch length, and Q for the 2.25 inch inside diameter device with 27 inch length was about 14,700 watts.
One advantage of the present invention is the large surface area of hollow conduit that can be potted in a device in a small volume device. For example, the devices of Table 1 with packing densities of from about 40 to 50%, have approximately 11 cm2 of transfer surface area per cubic centimeter of housing volume. Higher packing densities would give a higher value, and lower packing densities would give smaller value.
One embodiment of the present invention is an exchange device including one or more potted hollow conduits capable of transferring heat from a first fluid to a second fluid through the walls of the hollow conduits, the exchange device integral at a temperature of at least 100° C. and a pressure of at least 50 psig, the temperature below the continuous use temperature or melting temperature of the hollow conduit material; preferably the exchange device remains integral at a temperature of at least 160° C. and a pressure of at least 70 psig, the temperature below the continuous use temperature or melting temperature of the hollow conduit material. Preferably the exchanger has a packing density by volume of hollow conduits between 20 and 70%; more preferably 40-60% by volume. A device configured with potted hollow conduits to have about 9 ft2 (0.85 m2) of exchange surface area is capable of exchanging at least about 13,000 watts of energy between a fluid flowing on a first side of the hollow conduit with a second fluid flowing on a second side of the hollow conduits; preferably the first fluid flows at 9.5 lpm or less on a first side of the hollow conduits and the second fluid flows at 5.8 lpm or less on the second side of the hollow conduits. The exchanger is capable of maintaining its fluid integrity under a variety of test conditions of temperature, pressure, and duration as shown by the results listed in Tables 2-5 with packing densities in the range of 20 to 70 percent. Where the hollow conduits of the devices are similar to those used for the exchangers of Table 1, it would be reasonable to expect that exchange devices of the present invention could be made and have similar exchange capabilities.
For devices prepared using porous hollow fibers, devices having a similar packing density as shown in Table 1 may be made and similar transfer surface areas obtained (not including the internal membrane area).
Various aspects of the present invention will be illustrated with reference to the following non-limiting examples.
This example compares the ability of various potted exchange devices to withstand stress testing.
Table 2 shows the advantage of adding the grooved interface. The original PFA design showed loss of housing to potting material integrity at 120° C. The temperature/Pressure test is a method of accelerating long term ambient conditions for the device. The MFA only device showed loss of bond integrity at 150° C. All tests on MFA devices with the improved interface are integral up to 200° C. and beyond, the PFA device with the improved groove or channel interface is also integral at temperatures up to 160° C. This device was destructively tested after the 160° C. to determine the strength of the bond. The strength of the bond is determined by cutting off thinning the outside of the device leaving approximately 0.080-0.100″ wall thickness. Axial and circumferential cuts are made into the shell approximately 0.25″ above the potted area, leaving a tab approximately 0.5″ wide by 0.25 long. The tab can then be used to pull up on the material in an attempt to pull apart the shell material from the potted material. In this manner the strength of the bond can be tested qualitatively by force, or quantitatively by an instrument such as an Instron.
The process of this example improves the overall strength of the device by eliminating stress at this interface, and transferring the stress to the potted material entrapped in the grooves. Without wishing to be bound by theory, the grooves, and their additional surface area, some of which is not parallel to the housing walls, also add adhesion of the potting resin to at least a portion, and preferably all surfaces or faces of the groove, adding a shear component to a radial force created by thermal or pressure expansion of the housing shell. This shear component greatly improves the strength of the device.
This prophetic example illustrates that the potted devices of the present invention may be used for heat and or mass exchange including but not limited to filtration, gas contacting, heat exchange, gas scrubbing and combinations of these.
The potted devices may be placed in an apparatus for cleaning or chemical modification of substrate surfaces including but not limited to single wafer cleaning tools, re-circulating cleaning baths. The device can also be used for temperature conditioning of fluids prior to disposal (such as hot sulfuric acid used to remove polymer coatings from optical fibers and photoresists from coated silicon wafers). As illustrated in
This example illustrates a potted membrane device and method of making it suitable for use at high temperature.
A potted filtration device having a 2.25″ ID and 12.65″ in length MFA housing, and contained about 3000 MFA porous hollow fibers. The device contained 4 grooves each having a depth of 0.25 cm and height 0.15 cm. Vent channels were formed between the grooves. There were about 6 vent channels per groove and the depth of the vent channels was about 0.15 cm. The potting melt was NFA heated to 278° C. for 3 days.
The device was tested for fluid integrity under the following conditions. Hot fluid at the temperature of 100° C. to 210° C. under pressure was fed into the shell side of the device at a very slow flow rate and no fluid flow on the tube side. Both end-caps were capped. Visaully inspect the device daily. Any accumulation of oil on the lumen side indicate device failure. The result from this experiment is listed in Table 3.
A test setup which can be used to test these devices is shown in
This example illustrates co-extruded hollow tubing potted into a thermoplastic resin to form hollow tubes bonded into a thermoplastic sleeve.
In the preparation of potted devices, the process window can vary and is dependent on the MFA tubing material properties (melting point, melt flow index, tubing dimension and geometry). These properties can vary from batch to batch and can be accommodated by varying and adjusting process variables like temperature and potting time. Overheating during potting can result in the collapsed of the tubing and under heating can cause some tubing not to bond during the potting. Various techniques may be used to prevent tubing collapse, for example putting a metal wire into the fiber or tube lumen or filling the lumen with an inorganic salt. These methods however are labor intensive, costly and may add contaminants to the device.
Co-extruded tubing can be potted to sleeves or housings to form exchange devices. One embodiment of the invention is perfluorinated co-extruded tubing or articles such as exchange devices made from it. The co-extruded perfluorinated tubing can have one or more outer layers or portions that include a perfluorinated thermoplastic with a lower melting point or melt flow index than the inner most portion or layer of the co-extruded tubing. The different perfluorinated layers of the co-extruded tubing are thermally bonded to one another. One non-limiting example of such co-extruded tubing has an MFA outer layer and PFA on the inside layer as illustrtated in
An exchanger sample was made using five 3 inch (7.6 cm) long MFA outer layer/PFA inner layer co-extruded tubes thermoplastic hollow conduits inserted into a ⅜ inch (0.95 cm)×3 inch (7.6 cm) PFA shell. This assemble was placed in a pool of molten MFA at 300° C. for 16 hours. The sample was removed, cool down and cut opened to exposed the lumen. The sample was analyzed under the light microscope as shown in
This example illustrates the fabrication and integrity of an exchange device made with one or more co-extruded hollow conduits potted in a housing.
A bundle of 650 twisted and looped co-extruded tubing, about 13 twists per foot was made. The tubing were 8.7″ long, with 0.0042″ internal diameter and a wall thickness of 0.006″. The tubing were made from two materials, MFA and PFA (Dupont 450 HP) thermally bondede to each other. The outer wall was MFA and the inner wall was PFA. Both the MEA and PFA layers had a thickness of about 0.003 inches, total wall thickness of about 0.006 inches. The bundle was placed in a shell made from MEFA, having a 2.25″ ID, 2.88″ OD and 8.7″ long. The shell contained 3 internal grooves on both ends. Each groove was 0.25 cm in depth and 0.15 cm in width. The inside shell or housing wall on each end was sintered with a layer of powdered MFA.
The packing density was approximately 40%. The shell was placed in a heater block with a 4″ ID by 4″ deep cavity. The cavity was lined with a layer of aluminum foil. The shell was held vertically in the cavity with clamp. 310 grams of Ausimont's MFA 940AX resin was poured into the space between the shell and the cavity wall. The heater block was then heated to 297° C. and held at the temperature for 2 days. After 2 days the heater block was cooled slowly to 150° C. and then to room temperature. The shell with tubing was removed. The opposing end of the tubing was sealed to the opposite end of the housing using a similar potting method described. A cut was made across the diameter of the shell through the pots, at a position above the looped ends in the bundle to expose the hollow of the hollow conduits. Excess potting material was removed. Two ¾″ PFA fluid fittings were thermally bonded to the shell.
The device was tested for fluid integrity under the following conditions, hot fluid at a temperature of 140° C. to 200° C. under pressure. The heated fluid was fed to the shell side of the device at 6 liters per minute with no flow on the tube side. Both end of the device were uncapped and expose to air. Visual inspected the device daily. Any accumulation of oil on the tube side indicated device failure. The result from the test is listed in the Table 4. The test set up is generally shown in
The results of the tests show that a perfluorinated exchange device with one or more hollow conduits bonded to the housing, the housing prepared with one or more grooves, remains integral under these test conditions.
This example illustrates potting a mixture of co-extruded thermoplastic hollow tubing (MFA outer wall and PFA inner wall) and hollow tubing made from MFA to make an exchange device.
Co-extruded tubing device example. A bundle of 650 twisted (13 twists per foot) and looped co-extruded tubing was made. Approximately ⅔ of the 650 tube bundle were hollow tubes made from MWA only, approximately ⅓ of the 650 tubes were made from co-extruded MFA/PFA hollow tubes. The tubing was about 8.7″ long, with 0.0042″ internal diameter and a wall thickness of about 0.006″. The two tubing materials were: hollow tubes of MFA only, and co-extruded hollow tubes with an MFA outer layer and a PFA (Dupont 450 BP) inner layer. For the co-extruded tubes, both the WA and PFA layers had a thickness of about 0.003 inches, total wall thickness of about 0.006 inches. The bundle was placed in a shell made from MFA, having a 2.25″ ID, 2.88″ OD and 8.7″ long. The shell contained 3 internal grooves on both ends. Each groove was 0.25 cm in depth and 0.15 cm in width. The inside shell wall on each end was sintered with a layer of powdered MFA.
The packing density was approximately 40%. The shell was placed in a heater block with a 4″ ID by 4″ deep cavity. The cavity was lined with a layer of aluminum foil. The shell was held vertically in the cavity with clamp. About 310 grams of Ausimont's MFA 940AX resin was poured into the space between the shell and the cavity wall. The heater block was then heated to 295° C. and held at that temperature for 48 hours. After 2 days the heater block was cooled slowly to 150° C. and then to room temperature. The shell with tubing was removed. The opposing end of the tubing was sealed to the opposite end of the housing using a similar potting procedure. A cut was made across the diameter of the shell through the pots, at a position above the looped ends in the bundle. Excess potting material was removed. Two ¾″ PFA fluid fittings were thermally bonded to the shell.
The device was tested for fluid integrity under the following conditions, hot oil fluid heated at a temperature of fro 100 to 140° C. under pressure was fed into the shell side of the device at 6 liters per minute with no fluid flow on the tube side. Both end of the device were uncapped and expose to air. The device was visually inspected daily. Any accumulation of oil on the tube side indicated device failure. The conditions and result from the test is listed in the Table 5. The test set up is shown in
The results of the tests show that an exchange device of the present invention having a mixture of hollow thermoplastic conduits and hollow co-extruded thermoplastic conduits and one or more grooves in the housing can remain integral up to a temperature of 140° C. and pressures of 50 psig for at least 24 hours.
Although the present invention has been described in considerable detail with reference to certain preferred embodiments thereof, other versions are possible. Therefore the spirit and scope of the appended claims should not be limited to the description and the preferred versions contain within this specification.
This application claims the benefit of and priority to U.S. Provisional Application Ser. No. 60/531,666 filed Dec. 22, 2003 and U.S. Provisional Application Ser. No. 60/586,363 filed Jul. 7, 2004 the contents of each incorporated herein by reference in their entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US04/42941 | 12/21/2004 | WO | 1/16/2007 |
| Number | Date | Country | |
|---|---|---|---|
| 60531666 | Dec 2003 | US | |
| 60586363 | Jul 2004 | US |
