Patent Application
20060216506
The invention relates generally to the field of multicomponent fibers and bonded fiber structures. More particularly, the invention is directed to multicomponent fibers wherein at least one fiber component is elastomeric and to three dimensional self-sustaining bonded fiber structures comprised of such elastomeric fibers.
There are many forms of and uses for multicomponent fibers, as well as methods of manufacture. Bicomponent fibers are typically manufactured by melt spinning techniques (including conventional melt spinning, melt blowing, spun bond, and other melt spun methods). Bicomponent fibers may be manufactured in a side-to-side structure, a centric sheath-core structure, or an acentric (e.g. self-crimping) sheath-core structure. They can be used in continuous filament or staple form and/or collected into webs or tows. They may be produced alone or as part of a mixed fiber system.
Multicomponent fibers can be used for a variety of purposes, including but not limited to woven and non-woven fabrics or structures and bonded or non-bonded structures. Porous, bonded structures formed from such fibers have demonstrated distinct advantages for fluid storage and fluid manipulation applications, since such bonded fiber structures have been shown to take up liquids of various formulations and controllably release them. A typical use for these structures may include use as nibs for writing instruments, ink reservoirs for writing instruments and/or ink jet printer cartridges, wicks for a wide variety of devices and applications, depth filters, and other applications where the characteristics of such structures are advantageous.
Additionally, bonded fiber structures may find use in diverse medical and/or diagnostic applications, for example, to transport a bodily fluid by capillary action to a test site or diagnostic device. Other applications of fibrous products are as absorption reservoirs, products adapted to take up and simply hold liquid as in a diaper or incontinence pad. Still other applications of bonded fiber structures may involve their use as filtration elements. Characteristics beneficial to the application as a filtration element include the ability to provide a tortuous interstitial path effective for capturing of fine particulate matter when a gas or liquid is passed through the fiber filter.
As described in U.S. Pat. Nos. 5,607,766, 5,620,641, 5,633,082, 6,103,181, 6,330,883, and 6,840,692, each of which is incorporated herein by reference in its entirety, there are many forms of and uses for bonded fiber structures, as well as many methods of manufacture. In general, such bonded fiber structures are formed from webs of thermoplastic fibrous material comprising an interconnecting network of highly dispersed fibers bonded to each other at points of contact. These webs are formed into substantially self-sustaining, three-dimensional porous components and structures, which may be produced in a variety of sizes and shapes.
Many of the advantageous characteristics of bonded fiber structures stem from the materials used in the fibers from which these structures are formed. The above-referenced patents describe a wide variety of polymer materials that may be used to form fibers for use in three dimensional bonded structures. These structures, however, are often unsuitable for certain applications where resiliency or penetrability is required. There has accordingly been a need for fibers that can be used to produce resilient bonded fiber structures.
Aspects of the invention include multicomponent fibers having one or more elastomeric components and bonded fiber structures formed from such fibers. A particular aspect of the invention provides a sheath-core multicomponent fiber comprising a thermoplastic polymer core material and an elastomeric polymer sheath material surrounding the core material. Another aspect of the invention provides a melt-blown multicomponent fiber comprising a first component comprising a thermoplastic polymer material and a second component comprising an elastomeric polymer material. Yet another aspect of the invention provides a bonded fiber structure comprising a plurality of fibers bonded to each other at spaced apart points of contact, at least a portion of the fibers being multicomponent fibers having at least one elastomeric fiber component.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. The accompanying drawings constitute a part of the specification, illustrate certain embodiments of the invention and, together with the detailed description, serve to explain the principles of the invention.
In order to assist in the understanding of the invention, reference will now be made to the appended drawings, in which like reference characters refer to like elements. The drawings are exemplary only, and should not be construed as limiting the invention.
Reference will now be made in detail to embodiments of the invention, examples of which are illustrated in the accompanying drawings.
Embodiments of the present invention provide multicomponent fibers having one or more elastomeric components that can be used to form resilient bonded fiber structures. As used herein, the term “multicomponent fiber” refers to a fiber having two or more distinct components formed from polymer materials having different characteristics and/or different chemical nature. Bicomponent fibers are a particular type of multicomponent fiber. As used herein, the term “bicomponent fiber” refers to a fiber having two or more distinct components integrally formed from polymer materials having different characteristics and/or different chemical nature. While other forms of bicomponent fiber are possible, the most common types are integrally formed with “side-by-side” or “sheath-core” relationships between the two polymer components. For example, bicomponent fibers comprising a core of one polymer and a coating or sheath of a different polymer are particularly desirable for many applications since the core material may be relatively inexpensive, providing the fiber with bulk and strength, while a relatively thin layer of a more expensive but unique sheath material may provide the fiber with unique properties, particularly with respect to bonding.
As used herein, the term “elastomeric component multicomponent fiber” or “ECM fiber” means a multicomponent fiber having at least one component comprising an elastomeric material. The term “elastomeric component bicomponent fiber” or “ECB fiber” means a bicomponent fiber having at least one component comprising an elastomeric material. As used herein the term “elastomeric material” refers to a macromolecular material that returns rapidly to its initial dimensions and shape after substantial deformation and release of stress.
As used herein, the term “fluid” means a substance whose molecules move freely past one another, including but not limited to a liquid or gas. The term “fluid” as used herein may also be multi-phase, and may include particulate matter suspended in a liquid or gas.
In seeking to devise structures for certain applications, the inventors have developed methods for producing ECM fibers whose resilient characteristics can be used to great advantage in bonded fiber structures. It has been found, for example, that bonded fiber structures may be formed from fibers having a first component that is elastomeric and a second component that is either non-elastomeric or that is elastomeric but with different physical and/or thermal characteristics than the first component. These fibers are of particular value when their elastomeric components are bondable to one another and to other fiber materials to form a resilient, porous structure.
Embodiments of the present invention provide ECM fibers in various forms. In some embodiments, the elastomeric first component has an exposed surface and doubles as a bonding material, either as one component in a side-by-side fiber configuration or as the sheath component in a sheath/core fiber configuration. As will be discussed in more detail, ECM fibers according to embodiments of the invention include (i) sheath-core multicomponent fibers where the sheath is comprised of an elastomeric material and the core is comprised of a non-elastic material; (ii) sheath-core multicomponent fiber where the sheath and the core are both comprised of elastomeric materials with the core material different physical and/or thermal characteristics from the sheath material; (iii) melt blown side-by-side bicomponent fibers, where one component is comprised of an elastomeric material; and (iv) melt blown side-by-side bicomponent fibers, where both components are comprised of elastomeric materials, and one component has different physical and/or thermal characteristics from the other.
It will be understood that certain ECM fibers have been produced in the past. These, however, were limited to (a) sheath-core bicomponent fibers in which the core material was elastomeric and the sheath material was substantially inelastic and (b) conventionally spun side-by-side bicomponent fibers. Significantly, none of these fibers have been used to produce a bonded fiber structure.
In contrast, many of the ECM fibers of the invention are particularly suited to use in bonded fiber structures. With reference to
The use of an elastomer as the sheath component is particularly advantageous in elastomeric materials that bond to one another and to other fiber materials. When bonded, the core component of a sheath-core ECB fiber of the invention provides strength and stability to the fiber, while the elastomeric sheath component allows the fiber to stretch relative to other fibers to which it is bonded. This stretchable bond provides a resiliency to the bonded structure that is not attainable using conventional sheath-core fibers.
The sheath-to-core ratio of ECB fibers of the invention may be tailored depending on the particular materials, the application of the fibers and the method of manufacture. Typical sheath-to-core volume ratios may be in a range from 10:90 to 90:10. In particular embodiments, the sheath-to-core volume ratio may be in a range from 25:75 to 40:60.
ECB fiber 100 is a concentric sheath-core fiber; that is, the sheath and core have substantially concentric circular cross-sections. Other ECB fibers according to the invention may be formed as acentric sheath core fibers as exemplified by the ECB fiber 200 shown in
Melt-blown ECB fibers according to the invention may be formed in a side-by-side configuration as exemplified by the ECB fiber 300 shown in
It will be understood that the ECM fibers of the invention are not limited to bicomponent fibers. For example,
ECM sheath-core fibers may also be produced with more than two components. With reference to
The core components 120, 220, 530 of sheath-core ECM fibers 100, 200, 500, the second component 320 of the side-by-side ECM fiber 300, and the second and third components 420, 430 of the side-by-side ECM fiber 400 may be non-elastomeric or may comprise elastomeric materials having different material and/or thermal characteristics from the elastomeric materials of the first fiber components 110, 210, 310, 410, 510. In some embodiments, core components 120, 220, 530 and side-by-side components 320, 420, 430 may comprise a crystalline or semi-crystalline polymer. Such polymers may include but are not limited to polypropylene, polybutylene terephthalate, polyethylene terephthalate, high density polyethylene and polyamides such as nylon 6 and nylon 66.
The various elastomeric components of the ECM fibers of the invention may comprise any suitable elastomeric material. Suitable thermoplastic elastomers may include but are not limited to polyurethanes, polyester copolymers, styrene copolymers, olefin copolymers, or any combination of these materials. More particularly, thermoplastic polyurethanes, thermoplastic ureas, elastomeric or plastomeric polypropylene, styrene—butadiene copolymers, polyisoprene, polyisobutylene, polychloroprene, butadiene-acrylonitrile, elastomeric block olefinic copolymers (such as styrene—isoprene—styrene), elastomeric block co-polyether polyamides, elastomeric block copolyesters, and elastomeric silicones may be used.
Thermoplastic polyurethanes have been shown to be particularly suitable for producing ECM fibers for use in bonded fiber structures. As used herein, the term “thermoplastic polyurethane” or “TPU” encompasses a linear segmented block polymer composed of soft and hard segments, wherein the hard segments are either aromatic or aliphatic and the soft segments are either linear polyethers or polyesters. The defining chemicals of TPUs are diisocyanates, which react with short chain diols to form a linear hard polymer block. Aromatic hard segment blocks are usually based in aromatic diisocyanates, most commonly MDI (4,4′-Diphenylmethane diisocyanate). Aliphatic hard segment blocks are usually based in aliphatic diisocyanates, most commonly hydrogenated MDI (H12MDI). Linear polyethers soft segment blocks commonly used include poly (butylene oxide) diols, poly (ethylene oxide) diols and poly (propylene oxide) diols or products of reactions of different glycols. Linear polyester soft segment bocks commonly used include the polycondensation product of adipic acid and short carbon chain glycols. Polycaprolactones may also be used. In general, ether-based TPUs are more resistant to hot, humid, acidic, or basic environments, while ester-based TPUs are generally more oil-resistant and typically have a greater mechanical strength.
Thermoplastic polyurethanes are commercially available from suppliers such as DuPont®, Bayer®, Dow®, Noveon®, and BASF®.
The particular elastomeric material selected for use in an ECM fiber may depend on a variety of factors including its spinning ability, bondability, the degree of resiliency required of the bonded fiber structure formed from the fiber, and other characteristics related to the use of the bonded fiber structure. A particular elastomeric material may be selected, for example, based on its relative hydrophobicity or hydrophilicity or based on its compatibility with fluids or other materials expected to interact with the bonded fiber structure.
As a general matter, ECM fiber component materials may be selected at least in part based on their ability to adhere to one another throughout the manufacturing process and, later, upon formation into a bonded fiber structure. Illustrative examples of ECM fiber component combinations that have been produced include TPU/polypropylene, TPU/nylon, TPU/polyester, TPU/polybutylene terephthalate, and TPU/polyethylene terephthalate. ECM fiber component combinations that have also been produced include ethylene polypropylene copolymer elastomer/polypropylene, ethylene polypropylene copolymer elastomer/polybutylene terephthalate, and ethylene polypropylene copolymer elastomer/nylon 6.
With any of the above-described ECM fiber embodiments, care must be taken to assure that fiber integrity is maintained throughout the manufacturing process. As discussed below, the fibers of the invention may be produced using any of several methods. Regardless of the method of manufacture, however, the specific processing parameters must be tailored to the particular materials used in order to assure that viable fibers are produced. In sheath-core ECM fibers, for example, processing parameters must be tailored to assure complete coverage of the core and to assure that the sheath will remain adhered to the core.
ECM fibers according to the invention may be produced using any manufacturing techniques typically used for producing multicomponent fibers including without limitation conventional melt spinning, melt blowing and spun bond processes. The particular methodology used is often dictated by the nature of the polymer and/or the desired properties and applications for the resultant fibers.
While other processes may be used to produce ECM fibers, melt spinning techniques in general, and melt blowing techniques in particular, have been found to be highly successful in producing the ECM fibers of the invention. In a melt spinning process, molten polymers are pumped under pressure to a spinning head and extruded from spinneret orifices into a multiplicity of continuous fibers. Melt spinning techniques are commonly employed to make both mono-component and side-by-side or sheath-core multicomponent fibers. Sheath-core multicomponent fibers may be manufactured through centric or acentric melt spinning processes.
After extrusion, the fibers may be attenuated to reduce their diameter. Attenuation can be accomplished by drawing the fibers from the spinning device at a speed faster than their extrusion speed. In some processes, this may be done by taking the fibers up on rolls rotating at a speed faster than the rate of extrusion. In other processes, the fibers may simply be post drawn through draw rolls operating at different speeds. Depending on the nature of the polymer materials, drawing the fibers in this manner may orient the polymer chains, thus tailoring the physical properties of the fiber.
In a particular form of melt-spinning process, attenuation is accomplished by hitting the fiber with a blast of hot air upon extrusion. This process is typically referred to as melt blowing and the fibers produced are referred to as melt blown fibers. In melt-blowing, a high speed, typically high temperature, gas stream is applied at the exit of a fiber extrusion die to attenuate or draw out the fibers while the fibers are in their molten state. Melt blowing processes are described in detail in U.S. Pat. Nos. 3,595,245, 3,615,995 and 3,972,759, which are incorporated herein by reference in their entirety.
Through the use of melt blowing, ECM fibers according to the invention may be produced with diameters approximately in the range of about 1 micron to about 50 microns. By comparison, conventional melt-spinning can be used to produce ECM fibers in a range of about 15 microns to about 200 microns, or even larger. Melt-blowing also provides the ability to effect process-related characteristics to the fiber and/or to webs formed therefrom. For example, a chilled air stream or water spray may be directed transversely to the direction of extrusion and attenuation of the melt blown bicomponent fibers. The chilled air or water spray cools the fibers to enhance entanglement while minimizing bonding of the fibers to each other at this point in the processing, thereby retaining the fluffy character of the fibrous mass and increasing productivity. In some bicomponent fibers, cooling of the fiber immediately after extrusion may prevent one or more of the component materials from crystallizing. Depending on the relative characteristics of the component materials, this may produce a fiber having one or more crystalline components and one or more amorphous components. In sheath-core fibers, the cooling of the sheath material may produce a fiber having a crystalline core and an amorphous sheath as described, for example, in U.S. Pat. No. 5,607,766. Retaining its non-crystalline character may enhance the bondability of the sheath material.
As noted above, specific processing parameters such as melt temperature, melt viscosity, melt flow, and melt pressure may be tailored to the specific materials used in the ECM fibers. These parameters may be different for different fiber components. As is described in the Berger '766 patent, however, it may be desirable when selecting fiber components to choose materials with similar melt indexes. As also described in the Berger '766 patent, the viscosity of one or more of the fiber component materials may be tailored to insure compatibility in the melt extrusion process. Other parameters may also be tailored to produce fibers with consistent integrity.
After extrusion and attenuation, the ECM fibers of the invention may be gathered or further processed in a variety of ways. In some processes, continuous fibers may be drawn and taken up on a bobbin or package in the case of filament yarns, or combined into a tow and cut into staple fibers. Continuous tows of ECM fibers may be also subsequently processed into bonded fiber structures. Staple ECM fibers may be formed into non-woven fabrics or webs. These too may be subsequently processed into bonded fiber structures.
In other processes, the ECM fibers are deposited on one another, and may or may not be immediately formed into a loosely bonded fiber web. This is accomplished by depositing the extruded fibers in a randomly dispersed entangled web on a moving surface such as a conveyer belt. The web may be collected for later use or may be drawn directly into an in-line processing system for forming a bonded fiber structure.
In some processes, staple fibers may be carded in order to achieve a web having fibers lying generally in the same orientation.
As described in U.S. Pat. No. 6,814,911, which is incorporated herein by reference in its entirety, fiber webs and products formed therefrom sometimes require, or are enhanced by, the incorporation of an additive in the fibrous web during manufacture. Accordingly, surfactants or other chemical agents in a particular concentration may be added ECM fiber webs to be used, for example, in the formation of an ink reservoir for marking or writing instruments or ink jet printer reservoirs. These additives may modify the surface characteristics of the fibers to enhance absorptiveness and/or compatibility with particular ink formulations. Wicking materials used in various medical applications may also be treated with solutions of active ingredients, such as monoclonal antibodies, to interact with materials passed there-through. Similarly, particulate matter may be adhered to the fibrous webs, in order to produce certain characteristics (e.g., increase absorptiveness) in the web.
Webs comprising ECM fibers according to the invention may be formed from a single fiber type; that is, all of the fibers comprise substantially the same component geometry and materials. Alternatively, bimodal webs comprising ECM fibers may be formed using the methods described in U.S. Pat. No. 6,103,181. Bimodal webs are webs formed from a combination of fibers of different types, materials and/or configurations. For example, a first fiber type may be a bicomponent fiber in which the sheath material is an elastomer and the core is a non-elastomer, and a second fiber type is an elastomeric or non-elastomeric monocomponent fiber. In some embodiments, a web may comprise a first fiber type that is an elastomeric sheath core bicomponent fiber in which the core material is an elastomer and the sheath is a non-elastomer and a second fiber type that is a monocomponent fiber formed from the same elastomer as the core of the bicomponent fiber. In other embodiments, the web may be formed from alternating ECM and multicomponent fibers with no elastomeric component. In any of these embodiments, the bimodal fiber collection can be used to form a bonded web in which fibers of one type serve to bond to each other and to fibers of the other type.
It can be seen from the above that that ECM fibers according to the invention may be gathered in the form of bundled individual filaments, continuous filaments, tows, roving or lightly bonded non-woven webs or sheets. Fibers collected in any of these forms may be further processed into bonded fiber articles such as sheets or porous three dimensional structures. The process used to form these bonded fiber articles may depend on the form in which the ECM fibers were collected, the desired geometry and/or physical characteristics of the bonded structure, and the constituent materials in the fibers.
A bondable web of collected ECM fibers according to the invention may be used to form an essentially two dimensional non-woven fabric having recoverable elasticity properties. As will be discussed in more detail below, these webs may be used to produce bonded two dimensional three dimensional structures. Alternatively, the fibers may be subjected to needle-punching, where multiple needles push through the fibers, causing the fibers to be tangled in such a manner as to cause a sustainable web. The fibers may also be hydro-entangled. The sustainable webs may then be rolled up or otherwise gathered and prepared for further processing.
In some processing embodiments, ECM fibers in the form of a web, bundled fibers or tows may be fed to a continuous processing line for producing bonded fiber articles. There, the fibers are heated to establish bonds between the fibers and formed into a desired cross-section. If desired and depending on the form in which they are provided, the fibers may be mechanically crimped or self-crimping may be induced (e.g., by stretching and then relaxing the fibers) during the continuous forming process. Additionally, in some embodiments, self-sustaining webs formed from ECM fibers may be post-drawn to create more elastic crimps along the machine direction. The additional crimps may help to generate a loftier, bulkier and more elastic substrate.
The processing line 600 of
The bonding/forming portion 650 of the processing line 600 may comprise nip rolls 620 or other mechanism for drawing the web 632 from the belt 640. The bonding/forming portion 650 may include a heating zone 660 through which the fiber material 632 is passed. The heating zone 660 may include any of various mechanisms for heating the fiber material to a desired temperature, typically a temperature in excess of the melt or softening temperature of at least one fiber component to facilitate bonding of the fibers in the web at their points of contact with one another. In particular embodiments, the heating zone 660 is configured to heat the fibers to a temperature in excess of the melt or softening temperature of an elastomeric fiber component such as, for example, an elastomeric sheath material in a sheath-core ECB fiber. The heating mechanism of the heating zone 660 may include but is not limited to sources of radiant heat, hot air or steam. The heating mechanism may include an oven or, in some embodiments, a heated die that not only serves as a heating mechanism, but also forces the web to adopt a predetermined cross-section.
Once the fiber material has been heated to a temperature sufficient to melt or soften one or more of the fiber components, it may be passed through a cooling zone 670 configured for cooling the fiber material and set the bonds established in the heating zone, thereby producing a self-sustaining bonded fiber structure 634. The cooling zone 670 may comprise any of various mechanisms for cooling the now-bonded fiber material including the application of relatively cool air or water. In some embodiments, the cooling zone may simply be configured to allow passage of the bonded fiber material through ambient air. In some embodiments, the cooling zone 670 may also comprise a chilled die through which the fiber material is forced, thereby causing the bonded material to permanently adopt a particular cross-section. In some embodiments, the bonding/forming portion 650 may be configured to pass the fiber material through multiple dies, one or more of which may be in the heating zone 660 and one or more of which may be in the cooling zone 670.
The processing line may also include a cutting station (not shown) where the bonded fiber structure 634 may be cut to desired lengths.
At S130, ECM fibers are spun by the fiber spinning machine 620 and deposited onto the moving surface 610 where they form a loosely bonded web. This action may include attenuation of the extruded fibers. The action may be carried out using the melt blowing technique discussed above if the fiber spinning machine 620 is so configured. The action may include quenching the fiber upon extrusion. As previously discussed, additional fibers may be simultaneously extruded if a bimodal fiber distribution is desired.
At S140, the fibers are lifted or removed from the moving surface 610. At this stage, the fiber surface may optionally be chemically modified through the application of finishes or surfactants at S141. Fibrous products often require, or are enhanced by, the incorporation of an additive (or “finish”) in the fibrous web during or after fiber manufacture. Melt additives may be added to the polymer in the spinning machine 620 before fiber spinning. Topical additives may be added immediately following fiber extrusion, before the fibers are deposited on the conveyor belt 640 or other moving surface. The addition of selected surfactants or other chemical agents in a particular concentration to a fibrous media may modify and enhance certain characteristics of the fibers. For example, in a fibrous structure used as an ink reservoir, additives may enhance absorptiveness and/or compatibility with a particular ink formulation. Similarly, wicking materials used in various medical applications may be treated with solutions of active ingredients, such as monoclonal antibodies, to interact with materials passed there-through. If desired, a reactive finish may be incorporated into the water spray to make fiber surface more hydrophilic or hydrophobic.
At S142, particulate matter may optionally be adhered to the fibers. Such particulate matter may improve particular characteristics of the fibers and any resultant fiber structure, making for example, the fibers more absorptive of liquids or odors.
At S150 the collected web, which may or may not be loosely bonded, may be drawn through the heating zone 660, where the fibers are heated to the melt or softening temperature of one of the exterior components (e.g., the sheath component of a sheath-core ECM fiber). The temperature may be selected so that it will melt or soften the sheath component, but will not melt or soften the core component. This causes the ECM fibers to bond to one another at their points of contact. As discussed above, this action may include drawing the web through a heated die, thereby causing the bonded fibers to adopt the cross-section of the die.
At S160, the bonded fiber material may be passed through a cooling zone wherein the melted or softened fiber material may harden to produce a self sustaining bonded fiber structure. In certain instances, cooling of the fiber structure may be accomplished merely by introduction into the ambient environment.
At S170, the self sustaining bonded fiber structure may be cut to its desired size. The size of the final product may be determined based upon the bonded fiber structure's application. The method ends at S180.
It will be understood that integrally formed three bonded fiber structures comprising ECM fibers may be made by other manufacturing processes. For example, a pneumatic forming process such as that disclosed in U.S. Pat. Nos. 3,533,416, 3,599,646 3,637,447 and 3,703,429, each of which is incorporated herein by reference in its entirety may be used. These processes utilize tows of fibers that may be impinged in a forming die with air pressure and then treated with steam to form a porous, three dimensional, self sustaining, bonded fiber structure.
The fibers used to form bonded ECM fiber structures may be in the form of bundled individual filaments, continuous filaments, filament tows, lightly bonded (or mechanically entangled) webs or sheets of filament fibers, staple fibers, staple fiber tows, rovings of staple fibers or lightly bonded (or mechanically entangled) webs or sheets of non-woven staple fibers The fibers may be mechanically crimped or may be structured so that self-crimping may be induced (e.g., by stretching and then relaxing the fibers) during the continuous forming process. Additionally, in some embodiments substantially self-sustaining webs formed from ECB fibers may be post-drawn to create more elastic crimps along the machine direction. The additional crimps help to generate a loftier, bulkier and more elastic substrate.
The structures produced by the methods described above are each a self-sustaining network of bonded ECM fibers. This network defines a tortuous flow path for passage of fluids through the structure. Depending on the characteristics of the fibers (e.g., surface energy) and such over all structure characteristics as density and porosity, bonded fiber structures of this type may be used for wicking applications, diagnostic devices or filtration devices. The bonded fiber structures of the invention may be formed as substantially planar sheets or as three dimensional structures. In either case, the bonded fiber structures may typically have porosities in a range of about 20% to 95%.
The properties of the bonded ECM fiber structures provide advantages in a wide range of applications. They provide a unique set of properties as a result of the combination of stretchability and resiliency provided by their more elastic constituents and the strength and stability provided by their less elastic (or non-elastic) constituents. A high degree of structural resiliency may be achieved based on the bonding of the elastomeric components of the fibers. Particularly valuable applications include filtration applications where elasticity or partial elasticity is required or use as a reservoir in an ink jet cartridge. As will be discussed, one particular advantage is the ability of these structures to return to their original state after having been deformed, such as by penetration by a needle or other device. Bonded ECM fiber structures may also provide for a high coefficient of friction, abrasion resistance, biocompatibility, insulation and sound absorption. In addition, the stretchable bonds of these structures allow them to be elongated by 200% to 700% while retaining their structural integrity.
These characteristics make bonded ECM fiber structures ideal for widely disparate applications, including without limitation use in a white board eraser, a sponge contraceptive, a wound care dressing, ear plugs, disposable wipes/cleaners, nibs for writing instruments, face masks, automobile fluid filters, squeegees, cosmetic pads, sound deadening materials, non-skid pads, and stamp pads.
It is also contemplated that bonded ECM fiber structures may be used in such widely varying products as penetrable wine corks, diaper liners, scouring pads, blood separation devices, lateral flow wicks, saliva wicks, drug delivery devices, chamois, seals, pump gaskets, aircraft condensation pads, pipette filters, mattress pads/table cloths, and non-slip gloves.
Sheath-core ECB fibers were formed by the previously described melt blown process using Noveon® Estane® X4280 polyester-based TPU and Atofina® PP3960 polypropylene as sheath and core materials, respectively. The ratio of dried TPU sheath material to the polypropylene core material was approximately 35:65 by volume. The TPU sheath material, which has a melt temperature of 151° C. was heated to and extruded at temperatures in a range of 218° C. to 241° C. The PP core resin, which has a melt temperature of 165° C., was heated to and extruded at temperatures in a range of 177° C. to 200° C. The fiber forming die tip was at 168° C. Fibers were produced with an average diameter of about 10 microns and demonstrated complete coverage of the core by the sheath and good integrity.
Fibers having the same material components but formed by free-fall without quench were also produced. A photograph of these fibers, which have diameters ranging from 40 to 50 microns, is shown in
Sheath-core ECB fibers were formed by the previously-described melt blown process using Noveon® Estane® 58245 polyether-based TPU and Atofinae PP3960 polypropylene as sheath and core materials, respectively. The ratio of dried TPU sheath material to the polypropylene core material was approximately 35:65 by volume. The TPU sheath material, which has a melt temperature of 150° C. was heated to and extruded at temperatures in a range of 193° C. to 210° C. The PP core resin, which has a melt temperature of 165° C., was heated to and extruded at temperatures in a range of 177° C. to 199° C. The fiber forming die tip was at 168° C. Fibers were produced with an average diameter of about 11 microns and demonstrated complete coverage of the core by the sheath and good integrity.
Self-sustaining, bonded fiber structures were formed from melt blown sheath-core ECB fibers. In an illustrative example, the ECB fibers were formed using a Noveon® Estanee X4280 TPU and an Atofina® PP3960 PP as sheath and core materials, respectively. The TPU was initially dried for 4 hours at 60° C. The ratio of dried TPU sheath material to PP core material was about 30:70 by volume. The TPU sheath material was extruded in a temperature range of 218° C. to 240° C., and the core resins were extruded in a temperature range of 177° C. to 199° C., with the fiber forming die tip at 168° C. The resulting web displayed good bulk and softness. Steam bonding was used to form a self-sustaining rod, which was cut to length. Bonded fiber structures were produced with a diameter of 7.5 mm and a length of 3 mm and densities in a range of 0.2 to 0.7 g/cc using fiber sizes in a range of 5 to 15 microns. These structures exhibited effective porosities in a range of 42% to 87% and exhibited the capability of returning to these porosity levels after penetration by and withdrawal of a 0.9 mm diameter needle.
The mechanical properties of the bonded ECB units with various densities were measured by an Instron 3365 with a 1 kN load cell using Instron Series IX/S Automated Materials Test, Version 8.27.00 software. Samples were placed in the hydraulic clamps, with an initial 50.0 mm gap between upper and lower clamps. Testing began by stretching the sample at speed of 10 mm/min until break. Stress, strain, modulus and energy to break were collected and recorded at the end of each specimen. These values are illustrated in table 1.
Self-sustaining bonded fiber structures were formed from melt blown sheath-core ECB fibers. In an another illustrative example, the ECB fibers were formed using a ExxonMobil® Vistamaxx 2330 ethylene polypropylene copolymer elastomer and an Atofina® 3860 PP as sheath and core materials, respectively. The ratio of Vistamaxx sheath material and PP core material was about 30:70 by volume. The Vistamaxx sheath material was extruded in a temperature range of 204° C. and 238° C., with the fiber forming die tip at 277° C. The resulting web displayed good loftiness and bulk. Steam bonding was used to form a self-sustaining rectangular rod with width of 3 mm and length of 13 mm, resulting a cross-section area of 39 mm2. The bonded fiber unit was produced in a density range of 0.15-0.75 g/cc using fiber sizes in a range of 6-20 microns.
The mechanical properties of the bonded ECB units using Vistamaxx/PP sheath-core materials with various densities were measured by an Instron 3365 with a 1 kN load cell using Instron Series IX/S Automated Materials Test, Version 8.27.00 software. Samples were placed in the hydraulic clamps, with an initial 50.0 mm gap between upper and lower clamps. Testing began by stretching the sample at speed of 10 mm/min until break. Stress, strain, modulus and energy to break were collected and recorded at the end of each specimen. These values are illustrated in Table 2.
It will be apparent to those skilled in the art that various modifications and variations can be made in the method, manufacture, configuration, and/or use of the present invention without departing from the scope or spirit of the invention.
This application claims priority to U.S. Provisional Application Ser. No. 60/664,032, titled “Elastomeric Bicomponent Fibers and Bonded Structures Formed Therefrom,” filed on Mar. 22, 2005, and U.S. Provisional Application Ser. No. 60/737,342, titled “Ink Reservoirs Formed From Elastomeric Bicomponent Fibers,” filed on Nov. 16, 2005, both of which are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60664032 | Mar 2005 | US | |
| 60737342 | Nov 2005 | US |
