Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
2001-10-12
2004-06-01
Nutter, Nathan M. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C525S507000, C525S509000, C525S511000, C525S512000, C525S513000, C525S514000, C525S515000
Reexamination Certificate
active
06743522
ABSTRACT:
TECHNICAL FIELD
The present invention is directed to saturants for fibrous webs. The present invention is further directed to saturated fibrous webs and methods for saturating such webs. The invention is further directed to packages or containers comprising the saturated webs and methods of manufacturing such packages. Such packages have particular utility for the medical field, including packaging for medical instruments and other devices that require sterilization. The invention is further directed to coatings used with the saturated webs, a method for applying the coatings. The invention is further directed to fibrous webs coated with such coatings and articles comprising such webs.
BACKGROUND OF THE INVENTION
Many products, especially devices and supplies used in surgical and other medical applications, must be sterilized prior to use. Examples of such products in the medical context include but are not limited to surgical devices, implants, tubing, valves, gauzing, syringes, and protective clothing such as surgical gowns and gloves. Such products and supplies are often packaged prior to being sterilized. One sterilization procedure for such products involves using sterilizing gases that will penetrate pores in the packaging. Steam and ethylene oxide are examples of such sterilizing gases. The gas flows through the pores in the packaging material and sterilizes the instruments contained therein. Over time, the gas will then diffuse out of the package. The packaging serves to protect the instruments during sterilization and to preserve their sterility upon subsequent storage until the packages are opened for use of the product. To allow proper sterilization, packaging for medical products should be sufficiently permeable to sterilization gases to allow the gases to sterilize the product within. To avoid contamination after sterilization, the packaging should also prevent the entry of bacteria and pathogens into the package.
Packaging for many medical and sterile supplies includes two components, referred to herein as the base component and the breathable cover. The two components are attached to one another to form such structures as a pouch, which combines two flexible layers, or a rigid container, which uses a rigid base component often in the form of a tub or tray with the breathable cover acting as a lid. The sterile devices are stored between the two layers in a pouch or within the tub, tray, or other space within the rigid base component in a rigid container. The package is completed by sealing the two layers together, often by heating the materials so that a seal is formed using a temperature sensitive adhesive. When the device contained in the package is needed, the package is opened. Such packages are opened commonly and desirably by pulling the two components apart along the seal. Examples of such packages are widely known and include: U.S. Pat. No. 3,991,881 to Augurt, U.S. Pat. No. 4,183,431 to Schmidt et al.; U.S. Pat. No. 5,217,772 to Brown et al.; and U.S. Pat. No. 5,418,022 to Anderson et al.
Seals between components of a package must have sufficient strength to assure that stresses resulting from package handling after assembly will not cause the seal to open before the desired time and will remain impervious to pathogens. Seal strength is commonly expressed as the force required to separate the two sealed layers when holding the layers at facing edges and pulling the layers in opposite directions, commonly referred to as a “T-peel” because peeling results in the two separated portions of the layers forming the arms of the letter “T” with the base of the letter “T” being the portion of the two layers that remain attached until pulled apart. One method used to evaluate seal strength using a “T-peel” is found in American Society of Testing and Materials (ASTM) method F904-98. Other methods for testing seal strength exist, some of which are based on this ASTM method. Many users of such packages specify that the seal have a minimum strength of 0.70 pounds per inch in a T-peel test. Accordingly, seal strengths that are at least about 0.70 pounds per inch are especially desirable. In some applications, the seal strength desirably is not so great that one or more of the package components will tear before the seal opens. A desirable seal strength in such applications is thus greater than 0.70 pounds per inch but lower than a value that would result in tearing of one or more of the package components upon opening.
The base component in this type of package should be impervious to bacteria and other pathogens. Typical materials used in making base components include, but are not limited to, such polymers as nylon, polyester, polypropylene, polyethylene and polystyrene. Of these materials, nylon, polyester, polyethylene (including but not limited to low density, linear low density, ultra low density and high density polyethylene), and polypropylene are particularly useful for flexible base components. Polyester, polyethylene (including but not limited to high density polyethylene), polypropylene, and polystyrene are examples of polymers that are particularly useful for rigid containers such as tubs or trays. Those skilled in the art will recognize that the preceding lists of base components and materials used in making base components are for illustration purposes only and are not meant to be exclusive.
The breathable cover is typically a nonwoven web, which is a sheet comprised of cellulose fibers, synthetic fibers, or a combination thereof. Different materials, including some fabrics, have been used to form breathable covers for use in medical supply packaging. (As used herein, the term “fabric” is intended to encompass any sheet-like or web material that is formed in whole or in part from a plurality of fibers). One such material comprises webs of polyolefin fibers such as the spunbonded polyolefin material sold under the trademark TYVEK® by E.I. Du Pont De Nemours & Co. Others are webs comprising cellulose fibers or papers that have been saturated with one or more polymers such as acrylates to impart certain qualities to the paper. Such polymer reinforcement improves one or more of dimensional stability, resistance to chemical and environmental degradation, resistance to tearing, embossability, resiliency, conformability, moisture vapor transmission, and abrasion resistance, among others. In addition, saturation of paper-based webs by such emulsions ties down the cellulose fibers so that particulate generation is reduced when the fabric is torn or peeled. Polymer saturated papers provide certain advantages over polyolefin webs. Webs made from polyolefins often lack the suppleness, softness, and drapability that polymer saturated papers may possess. Use of cellulose webs is also a less expensive alternative to the polyolefin webs.
The polymer is normally applied by a saturation process, which involves dipping the formed fabric web into a bath of emulsion or subjecting the fabric web to an emulsion-flooded nip. Alternatively, the webs may be subjected to polymer impregnation while still on the forming wire through the use of various emulsion processes and the like. Polymer impregnation may also occur prior to forming the web as described in International Publication Number WO 99/00549 to Deka, et. al. Processes in which polymer is applied to a formed web are generally referred to herein as “latex saturation” processes. The term “latex” as used herein refers to a synthetic polymer emulsion. Processes in which polymer is applied to the fibers before the web is formed are generally referred to herein as “wet end deposition,” the term “wet end” referring to the section of the paper machine.
Examples of latex-saturated substrates include products designated as BP 336 and BP 321 that are available from Kimberly-Clark Corporation. These products are base papers that may be used as medical packaging substrates and comprise various amounts of cellulosic pulps and synthetic latex.
In addition to being permeable to sterilizing gases and relatively impermeable to bacteria, th
Bean Karen H.
Stokes Bruce G.
Dority & Manning P.A.
Nutter Nathan M.
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