Patent Application
20150131399
Although twin-screw extrusion (TSE) has long been established as one of the most prominent techniques for processing homopolymers, copolymers, and polymer blends from virgin and/or recycled sources as well as polymer composites and/or nanocomposites, the shear mixing in TSE is often not sufficiently rigorous to create a homogenous material in polymer blends or exfoliate (separate) and/or disperse (spread) the fillers in composites and/or nanocomposites. In addition, a long period of exposure to high temperature conditions in TSE can lead to thermal degradation of the materials. These limitations often render TSE ineffective for producing high-performance polymer blends, composites and/or nanocomposites.
Solid-state shear pulverization (SSSP) and solid-state melt-extrusion (SSME) techniques achieve better dispersion of heterogeneous nucleating agents in homopolymers, mixing of immiscible polymer blends, and better exfoliation and/or dispersion in polymer composite and/or nanocomposite systems relative to TSE. The SSSP and SSME production rate can be further improved with modification to the apparatus.
A need exists for modifications to these extrusion approaches that can achieve good mixing, exfoliation and/or dispersion in homopolymers, polymer blends and composites and/or nanocomposites at improved throughput rates.
In an embodiment, an extrusion screw assembly for a solid state screw extruder may include at least one extrusion screw shaft, and at least one extrusion screw element in mechanical communication with the at least one extrusion screw shaft, in which the at least one extrusion screw shaft is composed of at least one extrusion shaft channel along at least a portion of a length of the at least one extrusion screw shaft, and in which the at least one extrusion shaft channel is configured to transfer a heat transfer medium.
In an embodiment, a method of controlling a temperature of a solid state screw extruder may include providing a screw extruder, causing a heat transfer medium to flow from a source of the heat transfer medium through an at least one extrusion shaft channel, causing an at least one extrusion screw element to form a thermal contact with the heat transfer medium flowing through the at least one extrusion shaft channel, and controlling, by a temperature controller, a temperature of one or more of the at least one extrusion shaft and the at least one extrusion screw element. The screw extruder may include an extrusion screw assembly, the source of the heat transfer medium, and the temperature controller configured to control the temperature of the heat transfer medium. The extrusion screw assembly may further include the at least one extrusion screw shaft and the at least one extrusion screw element in mechanical communication with the at least one extrusion screw shaft, in which the at least one extrusion screw shaft includes the at least one extrusion shaft channel along at least a portion of a length of the at least one extrusion screw shaft, and in which the at least one extrusion shaft channel is configured to transfer the heat transfer medium.
In an embodiment, a method of dispersing materials in a polymer composition may include providing a screw extruder, causing a heat transfer medium to flow from a source of the heat transfer medium through an at least one extrusion shaft channel, causing an at least one extrusion screw element to form a thermal contact with the heat transfer medium flowing through the at least one extrusion shaft channel, controlling, by a temperature controller, a temperature of one or more of the at least one extrusion shaft and the at least one extrusion screw element via the heat transfer medium, introducing a polymeric mixture into the screw extruder, solid-state shearing the polymeric mixture in an initial zone of the screw extruder to yield a dispersal material in which the temperature of one or more of the at least one extrusion shaft and the at least one extrusion screw element within the initial zone has a temperature less than or equal to a liquefication temperature of the polymeric mixture, and dispensing the dispersal material from the screw extruder. The screw extruder may include an extrusion screw assembly, the source of the heat transfer medium, and the temperature controller configured to control the temperature of the heat transfer medium. The extrusion screw assembly may further include the at least one extrusion screw shaft and the at least one extrusion screw element in mechanical communication with the at least one extrusion screw shaft, in which the at least one extrusion screw shaft includes the at least one extrusion shaft channel along at least a portion of a length of the at least one extrusion screw shaft, and in which the at least one extrusion shaft channel is configured to transfer the heat transfer medium.
As used herein, the term “screw element” refers to an article in any form, shape, or combination thereof. Non-limiting examples of shapes include monolobe, bilobe, trilobe, quadralobe, pentalobe, etc. Furthermore, any of the above screw elements can function as forward, neutral, or reverse and be used for kneading, mixing, pulverization, or conveying polymers and compounds. The screw elements can comprise metals in whole or part. In addition, the screw element may be clad, layered or solid.
As used herein, the term “screw shaft” refers to an article in any form, shape or combination thereof. Non-limiting examples of cross-sectional shapes of a screw shaft may include hexagonal, rectangular, triangular, pentagonal, octagonal, spline, and round cross-sections. The shaft can also be threaded or unthreaded, bored to any length or unbored, and of any overall length. The screw shaft can comprise metals in whole or part. In addition the screw shaft may be clad, layered or solid.
The term “metal” as used herein, refers to the material that makes up the screw shaft and/or screw element. Non-limiting examples of metals include iron, copper, nickel, niobium, molybdenum, vanadium, chromium, titanium, calcium, rare earth elements, zirconium, stainless steel, a corrosion resistant high performance alloy, Cr Steel, Nitriding steel, carbon steel, spring steel, alloy steel, maraging steel, weathering steel, tool steel, and a high isotactic pressing (HIP) treated material. The term metal also refers to alloys comprising any combination of metals previously described.
As used herein, the term “thermal grease” refers to heat transfer media that increases heat transfer between screw shaft and screw elements. Non-limiting examples of thermal grease include electrically non-conductive, silicone and zinc thermal greases, and electrically conductive, silver, copper, and aluminum-based greases.
As used herein, the term “heat transfer media” refers to materials that are useful for transferring heat to or from the extruder apparatus. Non-limiting examples of heat transfer media include water, glycol, alcohols, carbon dioxide, nitrogen and mixtures thereof. Noting that their state is dependent upon the operating temperature, it is understood that the materials may be a gas, liquid, solid or combinations thereof.
As used herein, the term “gasket” refers to an object that creates a seal between the screw elements, the screw shafts, the extruder apparatus or any combination of objects that must control the movement of heat transfer media and or thermal grease. A gasket is an article in any form, shape or combination thereof commonly known to those of ordinary skill in the art. Non-limiting examples of gasket materials include silicone rubber, nitrile rubber, butyl rubber, fluoropolymer, chlorosulfonated polyethylene, ethylene propylene, fluorosilicone, hydrogenated nitrile, natural rubber, perfluoroelastomer, polychloroprene, polyurethane, and styrene butadiene.
As used herein, the term “welding,” refers to any method of operably connecting the screw element onto the screw shaft as to prevent the screw element from moving with respect to the screw shaft and reduce the contact resistance between screw shaft and screw element. Non-limiting examples of welding include shielded metal arc welding, gas metal arc welding, flux-cored arc welding, and resistive welding.
As used herein, the term “liquefication” may be defined as a phase transition of a polymer material from a solid state to a softened, liquid, or near-liquid state. A “liquefication temperature” may be defined as a temperature at which the polymer material transitions from a solid state to a softened, liquid, or near-liquid state. For a semi-crystalline polymer, a “liquefication temperature” may correspond to a melting point temperature. For an amorphous polymer, a “liquefication temperature” may correspond to a glass transition temperature. Some polymers may exist as combinations or admixtures of semi-crystalline and amorphous phases, and therefore the “liquefication temperature” may refer to either a melting point temperature or a glass transition temperature depending on the material composition.
Twin-screw extrusion (hereafter, “TSE”) has been established as a prominent technique for processing homo-polymers, copolymers, and polymer blends from virgin and/or recycled sources. TSE has also been applied in the production of polymer composites and nano-composites. However, the shear mixing in TSE is often insufficiently rigorous to create a homogenous material in polymer blends. Additionally, TSE may not be effective for exfoliating (separating) or dispersing (spreading) fillers within a polymer matrix to form composites or nano-composites. Further, long TSE processing times may expose the extrusion materials to high temperature conditions that may result in thermal degradation of the initial materials. Such limitations may render TSE ineffective for producing high-performance polymer blends, composites, and nanocomposites.
Solid-state shear pulverization (hereafter, “SSSP”) and solid-state melt-extrusion (hereafter, “SSME”) techniques have been proven to achieve better dispersion of heterogeneous nucleating agents in homo-polymers compared to TSE processes. In addition, such techniques may improve the mixing of immiscible polymer blends, as well as exfoliating or dispersing fillers in polymer composites or nano-fillers in nanocomposites.
The ability to combine different polymer types into a hetero-polymeric composition may be limited by the physical-chemical properties of the individual polymers. As non-limiting examples, polymers that differ in one or more of their liquefication temperature, viscosity, and density may not readily combine in a homogeneous manner when in a liquid or softened state. It is understood that micro phase separation between polymers may occur for suspensions of liquid polymers that differ in their viscosity. Similarly, the combination of recycled polymers having added colorants may result in inhomogeneously colored products due to micro phase separation of the colorant materials. It is therefore apparent that combining polymers into hetero-polymeric compositions by liquefying the initial components may not result in favorable component mixing.
SSSP and SSME techniques may suffer from low production rates of hetero-polymeric materials because the initial materials must be processed below the liquefication temperature. During the pulverization process, the mechanical action of the pulverizing and mixing elements may lead to frictional heating of the initial polymeric material to temperatures above the liquefication temperatures of the polymers. Therefore, the production rate of SSSP and SSME techniques may be reduced to maintain the frictional heating of the polymers to temperatures below their liquefication temperature. Thus, a need exists for modifications to SSSP and SSME techniques to achieve good hetero-polymeric mixing while improving the throughput rates of these processes.
Non-limiting examples of the active elements of the extrusion screw 120 may include one or more shearing elements, transport elements 122, mixing elements 124, and pulverizing elements 126, 128. The order, number, or type of the active elements along the extrusion screw 120 may not be limited to the configuration as depicted in
Although
The enclosure 100 may be divided into effective work zones, as depicted in
Work zones Zone 1-Zone 6 may be defined functionally in terms of their operating temperatures or the mechanical processes occurring therein. Non-limiting examples of such work zones may have physical embodiments as barrel sections (for example, 115). Barrel sections 115 may be composed of segments of metal or other materials that physically surround one or more sections of the extruder screw 120 and one or more active elements such as mixing elements 124. In one non-limiting example, the enclosure 100 may be composed of one or more barrel sections 115 linked together. In another non-limiting example, the one or more barrel sections 115 may be separate structural elements contained within the enclosure 100. The one or more barrel sections 115 may be composed of any suitable material including, without limitation, stainless steel, aluminum, iron, high carbon steel, tempered steel, and surface-hardened metals.
It may be understood that the configuration of the extruder screw 120 and the active elements as disclosed in
As disclosed above, frictional heating of the composition during processing may lead to the mixture being heated to or above a liquefication temperature of at least some component of the mixture, such as a polymeric matrix material. Such frictional heating and liquefication may result in inhomogeneous mixing of the polymeric matrix material and the biologically active agent. Thus, in one embodiment, the temperature of the at least one extrusion screw 120 of the extruder may be controlled to remove at least some of the friction-induced heat from the composition. In one non-limiting embodiment, the temperature of the at least one extrusion screw 120 may be maintained at a temperature less than or equal to the liquefication temperature of the polymeric matrix material. Table I presents illustrative polymeric matrix materials and their liquefication temperatures.
In some non-limiting examples, the temperature of at least one portion of the at least one extrusion screw 120 may be maintained at a temperature of about 35° F. to about 45° F. (about 1.7° C. to about 7.2° C.). Some non-limiting examples of temperatures at which the at least one portion of the at least one extrusion screw 120 may be maintained may include a temperature of about 35° F. (about 1.7° C.), about 37° F. (about 2.8° C.), about 39° F. (about 3.9° C.), about 40° F. (about 4.4° C.), about 42° F. (about 5.6° C.), about 44° F. (about 6.7° C.), about 45° F. (about 7.2° C.), or ranges between any two of these values including endpoints. As one example, the one or more extrusion screw 120 may be maintained at a temperature of about 40° F. (about 4.4° C.). Because the polymeric matrix materials may not have high thermal conductivity, the extrusion screw 120 may be maintained at temperatures significantly lower than the liquefication temperature of the biocompatible matrix material in order to maintain the matrix material in a solid state. For example, it may be necessary to maintain the extrusion screw 120 temperature at about 12° F. (about −11° C.) in order to maintain the temperature of the polymeric materials at about 38° F. (about 3.3° C.) during the manipulation steps of the extruder.
It may be understood that the material in any of the one or more work zones or barrel sections 115 in an SSSP device as illustrated in
Non-limiting examples of the active elements of the extrusion screw 220 may include one or more shearing elements, transport elements 222, pulverizing elements 224, kneading elements 226, and mixing elements 228. The order, number, or type of the active elements along the extrusion screw 220 may not be limited to the configuration as depicted in
Although
The enclosure 200 in which the one or more extrusion screws 220 are housed may be divided into effective work zones, as depicted in
While the SSSP process produces particulate material, the SSME process incorporates an additional melt extrusion step. Consequently, the SSME extruder depicted in
Work zones Zone 1-Zone 6 may be defined functionally in terms of their operating temperatures or the mechanical processes occurring therein. Non-limiting examples of such work zones may have physical embodiments such as barrel sections (for example, 215). Barrel sections 215 may be composed of segments of metal or other materials that may physically surround one or more sections of the extruder screw 220 and one or more active elements such as pulverizing elements 224. In one non-limiting example, the enclosure 200 may be composed of one or more barrel sections 215 linked together. In another non-limiting example, the one or more barrel sections 215 may be separate structural elements contained within the enclosure 200. The one or more barrel sections 215 may be composed of any suitable material including, without limitation, stainless steel, aluminum, iron, high carbon steel, tempered steel, and surface-hardened metals.
It may be understood that the configuration of the extruder screw 220 and the active elements as disclosed in
As disclosed above, frictional heating of the polymeric mixture during processing may lead to the mixture being heated to or above a liquefication temperature of at least some component of the mixture. Such frictional heating and liquefication may result in inhomogeneous mixing of the polymeric material during pulverization. In one non-limiting embodiment, the temperature of one or more portions of the at least one extrusion screw 220 having active elements that may pulverize the polymer mixture (for example, in one or more initial zones such as Zone 2 and Zone 3) may be maintained at a temperature less than or equal to the liquefication temperature of the polymeric mixture. In some non-limiting examples, the temperature of the one or more portions of the at least one extrusion screw 220 having active elements to pulverize the polymer mixture may be maintained at a temperature of about 35° F. to about 45° F. (about 1.7° C. to about 7.2° C.). Some non-limiting examples of temperatures at which at least one portion of the at least one extrusion screw 220 may be maintained may include a temperature of about 35° F. (about 1.7° C.), about 37° F. (about 2.8° C.), about 39° F. (about 3.9° C.), about 40° F. (about 4.4° C.), about 42° F. (about 5.6° C.), about 44° F. (about 6.7° C.), about 45° F. (about 7.2° C.), or ranges between any two of these values including endpoints.
Similarly, the temperature of one or more portions of the at least one extrusion screw 220 having active elements to mix or knead the melted sheared polymer mixture (for example, in one or more heating zones such as Zone 5 and Zone 6) may be maintained at a temperature greater than or equal to the liquefication temperature of the polymeric mixture. In some non-limiting examples, the temperature of one or more portions of the at least one extrusion screw 220 having active elements to mix or knead the melted polymer mixture may be maintained at a temperature of about 90° F. to about 500° F. (about 32° C. to about 260° C.). Some non-limiting examples of temperatures at which the at least one extrusion screw 220 may be maintained to mix or knead the melted polymer mixture may include a temperature of about 90° F. (about 32° C.), about 199° F. (about 93° C.), about 250° F. (about 121° C.), about 300° F. (about 149° C.), about 351° F. (about 177° C.), about 399° F. (about 204° C.), about 450° F. (about 232° C.), about 500° F. (about 260° C.), or ranges between any two of these values including endpoints.
It may be understood that temperature control, such as cooling, of the polymeric matrix materials and filler materials, either separately or in any combination throughout the manipulations by the screw extrusion device may be accomplished by any appropriate means.
Cooling may be accomplished by cooling one or more portions of the extrusion screw according to the type of manipulation of the material contacting the extrusion screw (for example, in one or more initial zones such as Zone 2 and Zone 3 in
It may be understood that the one or more portions of the enclosure 100, 200, extrusion screw 120, 220, barrel sections 115, 215, and active elements 124, 126, 128, 224, 226, and 228, may be controlled to have any appropriate temperature such as a temperature at or below a liquefication temperature of one or more components of the polymer matrix materials. It may further be understood that each of the one or more portions of the enclosure 100, 200, extrusion screw 120, 220, barrel sections 115, 215, and active elements 124, 126, 128, 224, 226, and 228, may be controlled to have about the same temperature or a different temperature. In some non-limiting examples, the one or more portions of the enclosure 100, 200, extrusion screw 120, 220, barrel sections 115, 215, and active elements 124, 126, 128, 224, 226, and 228, may be controlled to have a temperature less than or equal to about 40° C. In some other non-limiting examples, the one or more portions of the enclosure 100, 200, extrusion screw 120, 220, barrel sections 115, 215, and active elements 124, 126, 128, 224, 226, and 228, may be controlled to have a temperature of about 35° C. to about 45° C.
With respect to SSME processing, heating of the particulate form of the biologically active agent delivery composition may be accomplished by heating one or more portions of the extrusion screw according to the type of manipulation of the polymeric material contacting the extrusion screw (for example, in one or more heating zones such as Zone 5 and Zone 6 in
It may be understood that the mechanical communication between the extrusion screw shaft 320 and the one or more extrusion screw elements 330 may include direct physical contact between an outer surface of the extrusion screw shaft and an inner surface of the one or more extrusion screw elements. Alternatively, some amount of space may be left between outer surface of the extrusion screw shaft 320 and an inner surface of the one or more extrusion screw elements 330. In some embodiments, an amount of a heat conducting medium 340 may be placed within a space between the outer surface of the extrusion screw shaft 320 and an inner surface of the one or more extrusion screw elements 330.
In some embodiments, the heat conducting medium 340 may include a viscous non-flowing material such as a thermal grease. Non-limiting examples of a thermal grease may include non-electrically conductive, silicone and zinc thermal greases, and electrically conductive, silver, copper, and aluminum-based greases. In other embodiments, the heat conducting medium 340 may include less viscous material capable of flowing within a space between an outer surface of the extrusion screw shaft 320 and an inner surface of the one or more extrusion screw elements 330. Non-limiting examples of such less viscous heat transfer media may include water, glycol, alcohols, carbon dioxide, nitrogen and mixtures thereof. Noting that its state may be dependent upon an operating temperature, a heat transfer medium may be a gas, a liquid, a solid, or any combination thereof.
In one non-limiting example, as depicted in
In yet another embodiment, gaskets 350 may be placed around the extrusion screw shaft 320 to form fluid seals between adjoining extrusion screw elements 330. Non-limiting examples of gasket materials may include one or more of a silicone rubber, a nitrile rubber, a butyl rubber, a fluoropolymer, a chlorosulfonated polyethylene, an ethylene propylene, a fluorosilicone, a hydrogenated nitrile, a natural rubber, a perfluoroelastomer, a polychloroprene, a polyurethane, and a styrene butadiene. The gaskets 350 may be placed with respect to the extrusion screw elements 330 to allow the heat conducting medium 340 to flow along a length of the extrusion screw shaft 320. In one non-limiting example, the gaskets 350 may be placed between facing surfaces of successive extrusion screw elements 330. In this manner, the heat conducting medium 340 may flow along a length of the extrusion screw shaft 320 and absorb heat from a number of extrusion screw elements 330 without leaking between the elements.
In one embodiment, the extrusion screw shaft 320 may include one or more extrusion shaft channels 360 fabricated on an exterior surface of the extrusion screw shaft. In one non-limiting example, the one or more extrusion shaft channels 360 may be linear channels, fabricated on an exterior surface of the extrusion screw shaft, which extend effectively parallel to a longitudinal axis of the extrusion screw shaft 320. In another non-limiting example, the one or more extrusion shaft channels 360 may be helical channels fabricated on an exterior surface of the extrusion screw shaft, each helical channel having a helical axis that runs effectively parallel to the longitudinal axis of the extrusion screw shaft 320. It may be understood that the number of such extrusion shaft channels 360 on the extrusion screw shaft 320 is not limited. It may also be understood that the orientations of such extrusion shaft channels 360 with respect to either each other or with respect to any geometric parameter that may characterize the extrusion screw shaft 320 are also not limited.
Additionally, as depicted in
In one embodiment, each of the one or more extrusion screw elements 330 may include one or more extrusion element channels 370 fabricated on an interior surface of each of the one or more extrusion screw elements. In one non-limiting example, the one or more extrusion element channels 370 may be linear channels, fabricated on an interior surface of an extrusion screw element, which extend effectively parallel to a longitudinal axis of the extrusion screw shaft 320 on which the extrusion screw element may be mounted. In another non-limiting example, the one or more extrusion element channels 370 may be helical channels, fabricated on an interior surface of an extrusion screw element, each helical channel having a helical axis that runs effectively parallel to the longitudinal axis of the extrusion screw shaft 320. It may be understood that the number of such extrusion element channels 370 on any one or more extrusion screw elements 330 is not limited. It may also be understood that the orientations of such extrusion element channels 370 with respect to either each other or with respect to any geometric parameter that may characterize the extrusion screw shaft 320 are also not limited.
It may be understood that an extrusion screw assembly may include one or more extrusion shaft channels 360, one or more extrusion element channels 370, or any combination thereof. In one non-limiting example, an extrusion screw assembly may include one or more extrusion shaft channels 360 and one or more extrusion element channels 370, in which the one or more extrusion shaft channels may be aligned with the one or more extrusion element channels to provide paths for a heat conducting medium 340 to flow through both sets of channels.
Heat transfer media may be caused to flow through an extrusion shaft channel 360 and/or one or more extrusion element channels 370 according to any method as known to those skilled in the art. In one non-limiting embodiment, a rotary union may be used as depicted in
It may be understood that a rotary union 380 may be used to receive heat transfer media that may flow along one or more extrusion shaft channels 360. In such a case, heat transfer media that may flow along one or more extrusion shaft channels 360 may be received in a reservoir 390 within a rotary union 380 and may exit the reservoir by means of one or more access ports 385.
In some non-limiting examples, the extrusion screw shaft 420 may have a non-circular cross-section, for example a square cross-section or a splined cross-section. The one or more extrusion screw elements 430 may have an interior surface having a cross-section configured to match the geometry of the exterior of the extrusion screw shaft 420. An extrusion screw shaft 420 having a non-circular cross-section may be able to drive one or more extrusion screw elements 430 having a mating non-circular cross-section interior cut-out portion due to mechanical interactions therebetween. Such mechanical interactions may not be adversely affected by an intervening layer of a thermal grease 425.
A heat transfer medium may be introduced into an extrusion shaft channel 660 from a source of the heat transfer medium external to the extrusion screw shaft 620. The heat transfer medium may be introduced into an extrusion shaft channel 660 using one or more rotary unions 680. Such rotary unions 680 permit the extrusion screw shaft 620 to rotate within the one or more rotary unions while the rotary unions remain stationary with respect to the source of the heat transfer medium. Each rotary union 680 may include an access port 685a,b. An access port (for example 685a) may serve as an inlet for the heat transfer medium, permitting the heat transfer medium to enter an extrusion shaft channel 660 through one or more extensions of the channel to the surface of the extrusion screw shaft 620. Alternatively, an access port (for example 685b) may serve as an outlet for the heat transfer medium, permitting the heat transfer medium to exit an extrusion shaft channel 660 through one or more extensions of the channel to the surface of the extrusion screw shaft 620.
In one non-limiting example, a heat transfer medium circulating system may transfer the heat transfer medium from its source, through an access port 685a in a rotary union 680, and into an extrusion shaft channel 660. The circulating system may then receive the heat transfer medium from the extrusion shaft channel 660 via a second access port 685b in a rotary union 680. In one non-limiting application, the heat transfer medium circulating system may transfer a cold medium through the extrusion shaft channel 660 where the medium may absorb heat from the extrusion screw shaft 620 due to the mechanical actions of the extrusion screw elements on a polymer mixture. The heated medium may be transferred by the circulating system to a heat transfer medium source in which the heated medium is cooled to an appropriate temperature. In another non-limiting application, the heat transfer medium circulating system may transfer a heated medium through the extrusion shaft channel 660 to heat the extrusion screw shaft 620 and the extrusion screw elements (as well as polymer mixture). The heat transfer medium may then be recovered from the extrusion shaft channel 660 and reheated in the heat transfer medium source.
In an alternative embodiment, a single rotary union 680 may include a first access port 685a to allow a heat transfer medium to enter the extrusion shaft channel 660, and a second access port 685b to allow a heat transfer medium to exit the extrusion shaft channel. The two access ports 685a,b may be oriented so that a first end of the extrusion shaft channel 660 can align only with a first access port (for example 685a) while a second end of the extrusion shaft channel can align only with a second access port (for example 685b). In this manner a unidirectional flow of the heat transfer medium may be maintained through the extrusion shaft channel 660.
As disclosed above with respect to
A method of placing the extrusion screw elements 630 in physical communication with an extrusion screw shaft 620, as depicted in
In a removable placement method, the extrusion screw elements 630 may be slid onto the extrusion screw shaft 620 without otherwise fixing them onto the shaft. Because the extrusion screw elements 630 may not be welded onto the extrusion screw shaft 620, gaskets 650 may be placed between surfaces of adjacent extrusion screw elements to prevent loss of the heat transfer medium. Such gaskets 650 may contact only the surfaces of adjacent extrusion screw elements 630 or they may also contact one or more exterior surfaces of the extrusion screw shaft 620.
It may be understood, in light of the disclosure regarding
The source of a heat transfer material may also include a pump or other mechanism configured to cause 720 the heat transfer medium to flow from the source of the heat transfer medium through the at least one extrusion shaft channel. The at least one extrusion screw element may be placed in thermal communication with the extrusion screw shaft causing 730 the at least one extrusion screw element to form a thermal contact with the heat transfer medium flowing through the at least one extrusion shaft channel. A temperature of one or more of the at least one extrusion screw shaft and the at least one extrusion screw element may be controlled 740 by the temperature controller via the heat transfer medium flowing from the source of the heat transfer medium.
The source of a heat transfer material may also include a pump or other mechanism configured to cause 820 the heat transfer medium to flow from the source of the heat transfer medium through the at least one extrusion shaft channel. The at least one extrusion screw element may be placed in thermal communication with the extrusion screw shaft causing 830 the at least one extrusion screw element to form a thermal contact with the heat transfer medium flowing through the at least one extrusion shaft channel. A temperature of one or more of the at least one extrusion screw shaft and the at least one extrusion screw element may be controlled 840 by the temperature controller via the heat transfer medium flowing from the source of the heat transfer medium.
One or more polymer matrix materials may be introduced 850 into the screw extruder, for example through an extruder feed chute. A sheared mixture starting material may be produced in at least an initial zone of the extruder by means of solid-state shearing 860 of the polymer matrix materials. Such a sheared mixture may be fabricated by any combination of mixing, pulverizing, or kneading the polymer matrix materials by one or more active elements of the extruder. The sheared mixture may be dispensed 870 from the extruder at a dispensing end as a particulate composition. In one non-limiting example, a dispensed composition may be fabricated as a fine particulate material having an average particle diameter of about 1 μm to about 10 μm. Some non-limiting examples an average particle diameter may include a diameter of about 1 μm, about 2 μm, about 3 μm, about 4 μm, about 5 μm, about 6 μm, about 7 μm, about 8 μm, about 9 μm, about 10 μm, or ranges between any two of these values including endpoints.
Table I presents non-limiting examples of compositions of materials prepared using SSSP or SSME using the methods and systems disclosed herein (values presented as weight percent of a total combination).
Solid-State Shear Pulverization (SSSP) and Solid-state/melt extrusion (SSME) was performed using an intermeshing, co-rotating twin screw extruder with a diameter (D) of 25 mm and a length to diameter ratio (L/D) of 34. The barrel temperature setting was customized to create three distinct zones along the length of the barrel. The screws are modular in nature and designed as a combination of spiral conveying and bilobe kneading/pulverization elements. For the SSSP apparatus, all of the barrels are continuously cooled by recirculating ethylene glycol/water (60/40 vol/vol) mixture maintained at −2° C. by a chiller. The barrel section with several kneading elements in the upstream portion of the screws is termed the mixing zone. A conveying zone follows the mixing zone to cool the deformed material before intense pulverization takes place downstream in the pulverization zone.
For the SSME apparatus, the barrel temperature setting was customized to create three distinct zones along the length of the barrel. Zone 1, spanning the beginning length of L/D=16, was designed for solid-state pulverization; this portion of the barrel was continuously cooled at −12° C. by circulating ethylene glycol/water mixture from a chiller. Subsequent Zone 2 (L/D=6) is an intermediate barrel section set at 21° C., where the materials transition from the solid-state to the melt-state. Finally, Zone 3 (L/D=12) is the melt extrusion zone in which the barrel was heated to 204° C. by standard cartridge-type electrical heaters. The screw setting designed for this study contained spiral conveying (for L/D=8.5) and bilobe kneading (for L/D=7.5) elements in Zone 1, all spiral conveying in Zone 2, and spiral conveying (for L/D=8.3) and bilobe shearing and mixing (for L/D=3.7) elements in Zone 3. The screw rotation speed was maintained constant at 200 rpm for set ups.
The present disclosure is not to be limited in terms of the particular embodiments described in this application, which are intended as illustrations of various aspects. Many modifications and variations can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and apparatuses within the scope of the disclosure, in addition to those enumerated in this disclosure, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is to be understood that this disclosure is not limited to particular methods, reagents, compounds, or compositions, which can, of course, vary. It is also to be understood that the terminology used in this disclosure is for the purpose of describing particular embodiments only, and is not intended to be limiting.
With respect to the use of substantially any plural and/or singular terms in this disclosure, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth in this disclosure for sake of clarity.
It will be understood by those within the art that, in general, terms used in this disclosure, and especially in the appended claims (for example, bodies of the appended claims) are generally intended as “open” terms (for example, the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). While various compositions, methods, and devices are described in terms of “comprising” various components or steps (interpreted as meaning “including, but not limited to”), the compositions, methods, and devices can also “consist essentially of” or “consist of” the various components and steps, and such terminology should be interpreted as defining essentially closed-member groups.
It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (for example, “a” and/or “an” should be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (for example, the bare recitation of “two recitations,” without other modifiers, means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (for example, “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”
As will be understood by one skilled in the art, for any and all purposes, such as in terms of providing a written description, all ranges disclosed in this disclosure also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed in this disclosure can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as “up to,” “at least,” and the like include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member. From the foregoing, it will be appreciated that various embodiments of the present disclosure have been described for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
This application claims benefit of and priority to U.S. Provisional Application No. 61/903,389 entitled “Screw Design for Solid-State Shear Pulverization or Solid-State Melt Extrusion” filed Nov. 12, 2013, the disclosure of which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61903389 | Nov 2013 | US |
