Plastic and nonmetallic article shaping or treating: processes – Forming articles by uniting randomly associated particles – Projecting particles in a moving gas stream
Reexamination Certificate
2003-03-11
2004-11-09
Lechert, Jr., Stephen J. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Forming articles by uniting randomly associated particles
Projecting particles in a moving gas stream
C264S109000, C264S126000
Reexamination Certificate
active
06814911
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to the production of fibrous products, and relates more particularly to methods and apparatus for the application of additives to fibrous elements during the production thereof, and to the products so-produced.
2. Discussion of the Prior Art
Various prior art techniques are known for the production of products from polymeric fibers. The polymeric fibers themselves may be produced by a number of common techniques, oftentimes dictated by the nature of the polymer and/or the desired properties and applications for the resultant fibers. Among such techniques are conventional melt spinning processes wherein molten polymer is pumped under pressure to a spinning head and extruded from spinerette orifices into a multiplicity of continuous fibers. Melt spinning is only available for polymers having a melting point temperature less than its decomposition temperature, such as nylon, polypropylene and the like, whereby the polymer material can be melted and extruded to fiber form without decomposing. Other polymers, such as the acrylics, cannot be melted without blackening and decomposing. Such polymers can be dissolved in a suitable solvent (e.g., acetate in acetone) of typically 20% polymer and 80% solvent. In a wet spinning process, the solution is pumped at room temperature through the spinerette which is submerged in a bath of liquid (e.g., water) in which the solvent is soluble to solidify the polymeric fibers. It is also possible to dry spin the fibers into hot air, rather than a liquid bath, to evaporate the solvent and form a skin that coagulates. Other common spinning techniques are well known and do not form a critical part of the instant inventive concepts.
After spinning, the fibers are commonly attenuated by withdrawing them from the spinning device at a speed faster than the extrusion speed, thereby producing fibers which are finer. The fibers may be attenuated by taking them up on nip rolls rotating at a speed faster than the rate of extrusion or between nip rolls operating at different speeds. Depending on the nature of the polymer, drawing the fibers in this manner can make them more crystalline and, thereby, stronger.
Attenuation can also be effected by contacting the fibers as they emanate from the spinerette orifices with a fluid such as high velocity air to draw the same into fine fibers, commonly collected as an entangled web of fibers on a continuously moving surface such as a conveyor belt or a drum surface, for subsequent processing. This process, known as “melt blowing”, is of particular commercial importance in the production of many products because of its ability to attenuate the fibers while they are still molten.
Polymeric fibers can be formed of a single polymer or of multiple 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 coating of a more expensive or less robust sheath material may provide the fiber with unique properties.
Mono- or multi-component fibers may also be extruded in various shapes, such as circular, multi-lobal or the like. Moreover, a web of fibers having mixed characteristics can be simultaneously extruded from the same apparatus as seen, for example, in commonly assigned U.S. Pat. No. 6,103,181 (the '181 patent), the subject matter of which is incorporated herein in its entirety by reference.
Regardless of the manner of forming the fibers, they may be gathered into a sheet form which can be pleated to increase the surface area, particularly for certain filtering applications. Alternatively, a web of fibers may be gathered together and passed through a series of forming stations, such as steam-treating and cooling stations, which may bond the fibers at their points of contact to form a continuous rod-like porous element defining a tortuous path for passage of a fluid material therethrough.
The products produced from fibrous materials have many applications, for example as filter elements for use in various commercial and industrial environments, such as tobacco smoke filter elements, coalescing filters, and even high efficiency particulate air (HEPA) filters which may also function as heat and moisture exchangers for use in an artificial airway of a breathing apparatus as described in commonly assigned U.S. Pat. No. 6,330,833 (the '833 patent), the subject matter of which is also incorporated herein in its entirety by reference. Because of their high capillarity, porous fibrous products also function effectively in the production of simple wicks for transferring liquid from one place to another, as in the production of fibrous nibs found in certain marking and writing instruments. Additionally, such elements find use in diverse medical applications, for example, to transport a bodily fluid by capillary action to a test site in a diagnostic device. Other applications of fibrous products are as absorption reservoirs, products adapted to take up and simply hold the liquid as in a diaper or an incontinence pad. Absorption reservoirs are also useful in medical applications. For example, a layer or pad of such material may be used in an enzyme immunoassay test device where they will draw a bodily fluid through the fine pores of a thin membrane coated, for example, with monoclonal antibodies that interact with antigens in the bodily fluid pulled through the membrane and then held in the absorption reservoir.
Among the diverse products produced from fibrous materials, of particular commercial importance are highly porous ink reservoir elements used in marking and writing instruments where the reservoirs are designed to take up ink of various formulations and controllably release the same. Such elements have, for example, been formed of a fibrous bundle compacted together into a rod-like shaped unit having longitudinal capillary passageways which extend therethrough between the fibers and which serve to hold the ink and release it at the required rate. For many years, the material generally employed for the production of such ink reservoirs was plasticized cellulose acetate fibers which, historically, was also the material of choice for tobacco smoke filters and other such products, and which could readily be heat-bonded into a unitary body compatible with many ink formulations in use at one time.
Over the years, ink formulations have been developed that are not compatible with, and tend to degrade, cellulose acetate. Thus, various thermoplastic fibers, in particular, fine denier polyester fibers, such as polyethylene terephthalate fibers, replaced cellulose acetate as the polymer of choice in the production of ink reservoir elements for disposable writing and marking instruments. Efforts to heat-bond polyester fibers to each other in the absence of additive adhesives have not met with much success. Because of the narrow softening point of crystalline polyester polymers, it has not been feasible to commercially bond drawn polyester fibers, such as tow, with heat. Undrawn or amorphous polyester fibers are heat-bondable, but produce an unusable product which shrinks excessively during processing. Moreover, such materials lack stability in the presence of commercial inks at the temperature required for storage of writing instruments. Consequently, for some time, polyester fiber ink reservoir elements were commercially produced in the form of an unbonded bundle of fibers, compacted and held together in a rod-shaped unit by means of a film over-wrap. Depending upon the design of the writing instrument in which such reservoirs were incorporated, they could be provided with a small diameter plastic “breather” tube disposed between the fibrous bundle and the over-wrap to serve as an air release passage, if necessary.
Such film over-wrapped polyester fiber ink reservoir elements, when made with parallel continuous-filament fi
Nelson Raymond J.
Nutter Brian V.
Payne, Jr. Jackie F.
Pugh Roy B.
Spencer Michael W.
Filtrona Richmond, Inc.
Hunton & Williams
Lechert Jr. Stephen J.
LandOfFree
Method and apparatus for applying additive to fibrous... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for applying additive to fibrous..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for applying additive to fibrous... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3345839