Gas separation – Specific media material – Fibrous or strand form
Reexamination Certificate
1999-11-16
2003-07-22
Simmons, David A. (Department: 1724)
Gas separation
Specific media material
Fibrous or strand form
C055S522000, C055S524000, C055S527000, C055SDIG003, C425S072200, C425S131500, C425S377000, C425S382200, C425S463000, C425S464000, C264S555000, C264S172140, C264S172150, C264S176100, C264S177130, C264S210800, C264S211120
Reexamination Certificate
active
06596049
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to a method and apparatus for extruding or spinning synthetic fibers and relates more particularly to the production of a homogeneous web of polymeric fibers wherein at least some of the fibers in the web have different characteristics from other fibers in the web, and to unique products that can be produced from such fibers. Of particular importance is the production of a homogeneously mixed fibrous web of the type described wherein at least certain of the fibers are multi-component polymeric fibers, such as sheath/core bicomponent fibers and wherein, if desired, more than one multiple-component fiber may be uniformly dispersed throughout a web of fibers, with at least the sheath of such multiple-component fibers being formed of different polymeric materials.
This invention is also concerned with unique fibrous products having diverse applications, and particularly to such products when made using the advanced homogeneous mixed fiber technology referred to above.
This invention also relates to a heat and moisture exchanger and more particularly to a gas-permeable element, preferably comprising a fibrous media which may be made by the improved mixed fiber technology discussed above and which is adapted to be warmed and to trap moisture from a patient's breath during exhalation and to be cooled and to release the trapped moisture for return to the patient during inspiration, to thereby conserve the humidity and body heat of the patient's respiratory tract during treatment of the patient requiring communication of the patient with an extracorporeal source of a gas through an artificial airway. The heat and moisture exchanger of this invention is also effective for the removal of particulate contaminants contained in the gas to protect the patient from inhaling such contaminants, and to protect the atmosphere from contaminants in the patient's exhalation.
Artificial airways are used in diverse medical procedures and take a variety of forms. The insertion of an endotracheal tube to permit a choking patient access to air provides a simple illustration. Short- and long-term connection to a mechanical ventilator when a patient requires breathing assistance is another example of a situation requiring the use of an artificial airway. Artificial airways are also necessary when infusing a patient with oxygen as is common in the intensive care unit, or an anesthetic in the surgical theater.
Regardless of the particular circumstances, the use of an artificial airway creates a common set of problems. When a person exhales normally, the mouth, nose, and pharynx retain heat and moisture and tend to warm and humidify incoming air during the next breath, to thereby substantially saturate the air at body temperatures. The artificial airways in a breathing circuit of the type discussed above, bypass the natural humidification systems allowing relatively cool and dry gases, such as oxygen or an anesthetic, access to the trachea and lungs without modification impairing the ability of the respiratory tract to properly function. Dry anesthetic gases can damage cellular morphology, ciliary function and increase patient susceptibility to infection. The lack of humidity causes water to vaporize from the tracheal mucosa. Additionally, heat is lost when a cool gas is inspired, causing the mucosa to dry and secretions to thicken. The resultant difficulty in clearing the respiratory tract can produce an obstruction of the natural airway.
Thus, the inhalation of poorly humidified gases can not only cause a patient discomfort, but it can increase the risks of pulmonary damage. Moreover, the resultant heat loss through the respiratory tract may cause post-operate patient shivering and require unnecessary patient reheating during recovery.
Another complication resulting from the need to connect a patient to an extracorporeal source of gas through an artificial airway is the possibility of infecting the patient with bacterial, viral or other contaminants present in the inspired gas. Similarly, contaminants passing to the environment through the artificial airway can pollute the atmosphere. These problems are particularly important when treating infected or immno-compromised patients, or in the intensive care unit where both the patient being treated and other patients in the area are likely to be especially sensitive to the airborne transmission of pathogenic organisms.
2. Discussion of the Prior Art
Various prior art techniques are known for the production of polymeric fibers, including monocomponent fibers and multiple-component fibers of various configurations. Among such multiple-component fibers, bicomponent fibers comprising a core of one polymer and a coating or sheath of a different polymer are particularly desirable for many applications.
For example, in my prior U.S. Pat. No. 5,509,430 issued Apr. 23, 1996, the subject matter of which is incorporated herein in its entirety by reference, unique polymeric bicomponent fibers comprising a core of a low cost, high strength, thermoplastic polymer, preferably polypropylene, and a bondable sheath of a material which may be cellulose acetate, ethylene-vinyl acetate copolymer, polyvinyl alcohol, or ethylene-vinyl alcohol copolymer are disclosed for use particularly in the production of tobacco smoke filters. The bicomponent fibers produced according to the techniques of the '430 patent may be melt blown to produce very fine fibers, on the order of about 10 microns or less in diameter, in order to obtain enhanced filtration. Such products are shown to have improved tobacco smoke filtration efficiency, acceptable taste, and can be produced at a substantial lower cost than conventional tobacco smoke filters formed from fibers consisting entirely of cellulose acetate.
In my subsequent U.S. Pat. Nos. 5,607,766 issued Mar. 4, 1997, 5,620,641 issued Apr. 15, 1997, and 5,633,082 issued May 27, 1997, the subject matters of which are also incorporated herein in their entireties by reference, unique melt blown bicomponent fibers comprising a core of a thermoplastic material covered by a sheath of polyethylene terephthalate and methods of making same are disclosed as particularly useful in the production of elongated, highly porous elements having numerous applications. For example, such products are useful as wick reservoir elements for marking and wring instruments, that is, materials designed to take up a liquid and later controllably release the same as in an ink reservoir. Additionally, because of their high capillarity, such materials function effectively in the production of simple wicks for transferring liquid from one place to another, such as in the production of the fibrous nibs found in certain marking and writing instruments. Wicks of this sort are also useful in diverse medical applications, for example, the transport of bodily fluid by capillary action to a test site in a diagnostic device.
Products made from the bicomponent fibers of the '766, '641 and '082 patents are also shown to be useful as absorption reservoirs, i.e., as a membrane 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 which is pulled through the membrane and then held in the absorption reservoir. Such materials are also suggested, with the possible addition of a smoke-modifying or taste-modifying material, for use in tobacco smoke filters.
Polymeric fibers, in general, may be produced by a number of common techniques, oftentimes dictated by the polymer itself or the desired properties and applications for the resultant fibers. Among such techniques, are conventional melt spinning processes wherein molten polymer is pumped under pressu
Filtrona Richmond, Inc.
Jacobson & Holman PLLC
Pham Minh-Chau T.
Simmons David A.
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