Special receptacle or package – For a tool – Body treatment
Reexamination Certificate
2000-05-30
2002-02-26
Lewis, Kim M. (Department: 3761)
Special receptacle or package
For a tool
Body treatment
C602S041000, C428S198000, C428S537500, C162S146000
Reexamination Certificate
active
06349826
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to fabrics useful in forming packages for the medical field, including packaging for medical instruments that require a sterilization process. More specifically, the present invention relates to an improved medical packaging substrate produced by combining wood pulp, synthetic fibers, latex, and various optional physical property-enhancing add-ons. The latex is applied to the fibers by a latex deposition process.
BACKGROUND OF THE INVENTION
Surgical instruments and devices and appliances must be sterilized prior to use. Such instruments and devices are often wrapped in a hospital surgical supply or central supply room prior to being sterilized. Typically, the packages, in which the instruments and devices are placed are made of a textile or nonwoven fabric which serves to protect the instruments during sterilization and to preserve their sterility upon subsequent storage until the packages are opened and the instruments used. Fabrics typically used in this area are either tightly woven textiles or nonwovens which possess a closed structure with certain porosity characteristics. (As used herein, the term “fabric” is intended to encompass any sheet-like or web material which is formed, in whole or in part, from a plurality of fibers.) The resulting packages usually take the form of bags, pouches, or the like.
The normal sterilization procedure used by hospitals and surgical supply rooms today involves using sterilizing materials, such which the surgical instruments or medical devices are maintained. The gas flows through the pores in the packaging material and sterilizes the instruments contained therein. Over time, the gas will diffuse out of the package. Other sterilization processes well known in the art have also been used to sterilize surgical instruments and medical devices.
Thus, a suitable fabric for packaging surgical instruments and medical devices must exhibit the combined effects of good permeability to steam, ethylene oxide, or Freon sterilizing gases while offering adequate bacterial filtration efficiency in order to prevent the entry of bacteria into the package. In addition to being permeable, the fabric should be strong and exhibit relatively high internal bonding, or delamination and tear resistances. The product should also possess a certain degree of fluid repellency to prevent further transmission of the bacteria. Other properties necessary for such packaging is that it be non-toxic in accordance with industry and federal guidelines, substantially lint-free, odor-free, and drapable.
In terms of permeability, a fabric's suitability as a bacteria barrier may be partially predicted by a cumulative pore number of at least 3 million pores per square centimeter. The cumulative pore number reflects the creation of surfaces that prohibit the passage of bacteria by enabling the bacteria to lodge on a surface and, thus, be trapped by the barrier. The greater the cumulative pore numbers, the greater possibility of bacteria lodging in a pore and not passing through the substrate.
Other desirable properties for suitable bacteria barrier fabrics include those normally desired in other fabrics for use in forming packages and coverings, including strength, particularly in terms of delamination and tear resistance, suppleness, drapability, smoothness, etc. Obviously, the inclusion of such characteristics will depend on the particular product for which the bacteria barrier fabric is to be used.
One example of these gas-pervious, bacteria-impervious materials which has certain of these properties is a spunbonded polyolefin material sold under the trademark TYVEK® by E.I. DuPont De Nemours & Co. TYVEK® is a lightly consolidated or unconsolidated fabric made from spun bonded sheets of flash-spun polyolefin (usually polyethylene or polypropylene) plexifilamentary film-fibril strands. The general procedure for manufacturing TYVEK® is disclosed in U.S. Pat. No. 3,169,898 to Steuber.
TYVEK® fabric exhibits high strength, as well as providing the necessary pore distribution to allow for sterilization processes to act on instruments contained within packaging made from the material. TYVEK® material acts as a barrier to particulate matter that is sub-micron in size. TYVEK®, however, is a purely synthetic material and lacks the qualities inherent in material made with cellulosic webs. Such characteristics include suppleness, softness, drapability, and ease of printing.
To form sterile packaging trays from bacteria barrier fabrics, a surgical device or medical appliance is placed in an impervious tray or tub and a layer of the gas-pervious, bacterial-impervious paper or plastic is sealed to flanged edges of the tray. The sealed package is then exposed to ethylene oxide which permeates the paper or plastic and sterilizes the contents of the package. Since the paper or plastic is designed to prevent the passage of bacteria, the contents of the package will remain sterile until the seal is broken. One such example of a needle/suture package is disclosed in U.S. Pat. No. 4,183,431 to Schmidt et al. Another package for housing a medical instrument is shown in U.S. Pat. No. 5,031,775 to Kane.
A high-strength porous material, such as TYVEK®, may also be used as the backing material for a medical packaging breather pouch. Such pouches generally have an outer layer of plastic film material heat sealed to the edges of a TYVEK® sheet to secure the medical instrument within the package. One such breather pouch is described in U.S. Pat. No. 5,217,772 to Brown et al.
U.S. Pat. No. 5,418,022 to Anderson et al, relates to a method of forming a pocket from a spunbonded olefin sheet and a microbial resistant package produced thereby. The package disclosed therein comprises a spunbonded olefin sheet material, such as TYVEK®, at least a portion of which has been stretched or thermally deformed.
Alternatives to DuPont's TYVEK® product have also been developed. In particular, medical packaging substrates consisting of paper-based webs that have been saturated with binders such as latex have also been used for packaging surgical instruments and medical devices. In some of these substrates, a synthetic staple fiber, such as polyester or nylon, is incorporated directly into the wood pulp furnish for forming the composite web. Latex, usually at a high add-on, is necessary in order to bind the synthetic fibers to the cellulose-based web because, otherwise, the fibers would tend to pick or pull out of the sheet with relative ease.
The synthetic fiber that is incorporated into the product increases the tear resistance of the medical packaging substrate but generally reduces delamination resistance and tensile strength. The add-on latex builds up the necessary delamination resistance to prevent the substrate from splitting during its end use.
The latex in these bacteria barrier products is normally applied by a saturation process which typically involves dipping the formed fabric web into a bath of latex or subjecting the fabric web to latex-saturated rollers. Alternatively, the webs are subjected to latex application while still on the forming web through the use of various emulsion processes and the like. In each of these previously known processes for forming bacteria barrier fabrics, the latex is applied to the fabric after the web has been formed and dried or after the web has been formed on the wire. Such processes where latex is applied to a formed web are generally referred to herein as “latex saturation” processes. The application of latex in this manner fills in many of the smaller (less than 1 micron) pores in the fabric, often reducing the permeability of the fabric.
Examples of such products include products designated as BP 388 and BP 321 which are available from Kimberly-Clark Corporation. These products are base papers that are typically used as medical packaging substrates and comprise various amounts of cellulosic pulps and synthetic latex. Although such products function well as medical packaging substrates, their permeabilit
Deka Ganesh C.
Kapik Rene
Kimberly--Clark Worldwide, Inc.
Lewis Kim M.
Nelson Mullins Riley & Scarborough
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