Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Coated or impregnated woven – knit – or nonwoven fabric which... – Coating or impregnation increases electrical conductivity or...
Reexamination Certificate
1998-10-08
2003-03-25
Juska, Cheryl A. (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Coated or impregnated woven, knit, or nonwoven fabric which...
Coating or impregnation increases electrical conductivity or...
C442S110000, C427S538000, C427S393100, C427S002310, C206S363000, C206S439000, C422S294000
Reexamination Certificate
active
06537932
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a nonwoven web which may be sterilized. More specifically, the present invention relates to a sterilization wrap.
Sterilization wrap is a barrier material which is impermeable to liquids and microorganisms, while being permeable to gases. Sterilization wrap typically is manufactured in roll form and subsequently converted to cut sheets of various sizes as required by such end users as hospitals, clinics, and other health care providers. In order to minimize or prevent static buildup during the manufacturing and/or converting processes, an antistatic agent typically is applied to the wrap early in the manufacturing process. In general, the antistatic agent is dissolved or dispersed in water and the resulting aqueous medium is applied to the web by any suitable procedure. For example, the aqueous medium may be applied by spraying, brushing, or dipping and nipping.
The presence of an antistatic agent on the sterilization wrap also is of benefit during the wrapping process. Items to be sterilized, such as surgical instruments, typically are placed in a suitable instrument transport tray and the combination of instruments and tray is wrapped with, for example, two layers of sterilization wrap and the top layer is taped to provide a sealing relationship. Thus, the first wrapping is closed before the second wrapping is applied. This procedure is referred to in the art as sequential wrapping. The presence of a static charge on the sheets may result in more than one sheet being picked up at a time, leading to inefficiency and sometimes increased cost in the wrapping process. However, simultaneous wrapping may be employed and involves wrapping with two sheets of wrap at the same time. In either case, the wrap is designed to permit the entrance of sterilants such as steam or ethylene oxide to sterilize the contents while presenting a barrier to the entrance of contaminants such as bacteria once the sterilization process is complete.
Antistatic agents are, of course, well known in the art. One commercially available antistatic agent which has been used extensively in the past is a mixture of dipotassium butyl phosphate and potassium dibutyl phosphate salts. The material is available from DuPont Chemicals, Wilmington, Delaware, and is described in U.S. Pat. No. 3,821,021 to McMillin as part of a class of antistatic agents. Such class is defined by the formula M
n
R
3-n
PO
4
, where M is selected from the group consisting of lithium, sodium, potassium, and ammonium ions, R represents an alkyl group containing 3 to 5 carbon atoms, and n is selected from the integers 1 and 2. According to the patent, the preferred agents are those where M represents the potassium ion, and the most highly preferred finish is a mixture of approximately equimolar quantities of potassium dibutyl phosphate and dipotassium butyl phosphate in which the butyl moieties are straight-chain hydrocarbon groups, i.e., n-butyl groups.
When the most highly preferred finish of the above patent is added to a sterilization wrap and treated by one of the more recently developed sterilization processes which utilize an oxidizing gas plasma, the wrap may exhibit one or more of several undesirable characteristics. First, a sharp, acidic odor (referred to hereinafter as a malodor) often is present in the wrap. The term “malodor” is used herein to mean any odor deemed by those using the wrap to be unpleasant or objectionable. Second, the barrier property of the wrap, as measured by hydrohead values, typically is reduced. Third, the antistatic property of the wrap, as measured by surface resistivity, also is reduced; that is, the surface resistivity of the wrap after sterilization is higher than the surface resistivity before sterilization. Accordingly, there is a need for an improved antistatic agent for a sterilization wrap which is to be exposed to an oxidizing gas plasma.
SUMMARY OF THE INVENTION
The present invention is grounded in the discovery that replacing a mixture of approximately equimolar quantities of potassium dibutyl phosphate and dipotassium butyl phosphate with an antistatic agent adapted to be free of a malodor after exposure to an oxidizing gas plasma of a nonwoven web or sterilization wrap coated with the antistatic agent successfully reduces or eliminates malodor. For example, the use of an antistatic agent which involves one or more salts of mono- and di-C
3
-alkyl phosphates and/or one or more salts of &bgr;-carbon substituted mono- and dialkyl phosphates, both defined hereinafter, reduces or eliminates the above-noted undesirable characteristics when the sterilization process involves exposing a sterilization wrap to an oxidizing gas plasma.
Thus, the present invention addresses some of the difficulties and problems discussed above by providing a method of preparing a sterilized nonwoven web. The method includes providing a nonwoven web; coating the nonwoven web with from about 0.005 to about 3 percent by weight, based on the weight of the web, of an antistatic agent; and exposing the coated nonwoven web to an oxidizing gas plasma. The antistatic agent is adapted to be free of malodors after exposure of the coated nonwoven web. The antistatic agent may be further adapted to provide a sterilized nonwoven web having a hydrohead value as measured by Method 5514 of Federal Test Method Standard No. 191A which is at least 50 percent of the hydrohead value of the coated nonwoven web before exposure to the oxidizing gas plasma. The antistatic agent also may be adapted to provide a sterilized nonwoven web having a surface resistivity in ohms which is lower than the surface resistivity in ohms of the coated nonwoven web before exposure of the coated nonwoven web to the oxidizing gas plasma.
By way of example, the antistatic agent may be an alkali metal or ammonium salt of a mono- or di-C
3
-alkyl phosphate in which the C
3
-alkyl moiety is an alkyl group containing three carbon atoms optionally substituted with hydroxy groups. Desirable members of this group are the alkali metal and ammonium salts of propyl phosphate, dipropyl phosphate, isopropyl phosphate, and diisopropyl phosphate, or mixtures of two or more of the foregoing. For example, such salt may be a potassium salt.
As another example, the antistatic agent may be an alkali metal or ammonium salt of a &bgr;-carbon substituted alkyl phosphate, a di(&bgr;carbon substituted alkyl) phosphate, or a mixture of two or more of the foregoing. The &bgr;-carbon substituted alkyl group in general may contain from four to about seven carbon atoms. Desirable members of this group are the alkali metal and ammonium salts of isobutyl phosphate, diisobutyl phosphate, and mixtures of the foregoing. For example, such salt may be a potassium salt.
Also by way of example, the nonwoven web may be a meltblown web. As another example, the meltblown web may be a component of a laminate. For example, the meltblown web may be between and bonded to two spunbond webs.
The present invention further provides a sterilization wrap which includes a gas-permeable, water-impermeable nonwoven web coated with from about 0.005 to about 3 percent by weight, based on the weight of the web, of an antistatic agent. The antistatic agent is adapted, after exposure of the coated water-impermeable nonwoven web to an oxidizing gas plasma, to be free of malodors and to have a hydrohead value as measured by Method 5514 of Federal Test Method Standard No. 191A which is at least 50 percent of the hydrohead value of the coated water-impermeable nonwoven web before exposure to the oxidizing gas plasma. The antistatic agent in general may be that described hereinbefore.
By way of example, the nonwoven web may be a meltblown web. As another example, the meltblown web may be a component of a laminate. As still another example, the meltblown web may be between and bonded to two spunbond webs.
The present invention additionally provides a barrier fabric, a sterilization wrap, and a surgical garment, each composed of the fibrous sheet-like material described h
Fitting Steven Wayne
Powers Michael David
Quincy, III Roger Bradshaw
Dority & Manning PA
Juska Cheryl A.
Kimberly--Clark Worldwide, Inc.
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