Surgery – Means and methods for collecting body fluids or waste material – Absorbent pad for external or internal application and...
Reexamination Certificate
2000-08-31
2003-06-17
Ruhl, Dennis (Department: 3761)
Surgery
Means and methods for collecting body fluids or waste material
Absorbent pad for external or internal application and...
C604S385160
Reexamination Certificate
active
06579274
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a breathable laminate (i.e., breathable to water vapor but substantially liquid-impermeable) which is permanently conformable to the contour of a wearer. The laminate stretches as needed to conform to the contour of the wearer and remains, essentially, in its extended or stretched state, even after a stretching force is removed.
BACKGROUND OF THE INVENTION
Laminates which are breathable to water vapor but substantially impermeable to liquid water are known in the art, and are commonly used in diaper backings, other personal care absorbent garments, medical garments and the like. These laminates may be composed of a breathable, stretch-thinned filled film and a spunbond web. The breathable film can be formed by blending one or more polyolefins with an inorganic particulate filler, forming a film from the mixture, and stretching the film to cause void formation around the filler particles. The resulting film may have thin polymer membranes around the filler particles which permit molecular diffusion of water vapor, while the overall film substantially blocks transmission of liquid water, or may have micropores going through the film. The breathable film can be laminated to a nonwoven web, for instance, a spunbond web, by thermal or adhesive bonding. The spunbond web adds strength and integrity to the breathable laminate, and provides a soft, cloth-like feel.
One trend affecting the personal care absorbent garment industry, and the medical garment industry, involves the demand and need for products with higher breathability to water vapor, which retain or increase the barrier to water, blood and other liquid substances. This trend reflects the demand for increased wearer comfort without loss of barrier performance. Another trend affecting these industries involves the demand and need for products having better fit, which conform to the contours of the wearer's body. To date, much of the investigation in this area has involved use of elastic materials.
One challenge involving the use of elastic materials is that many of the products, including absorbent garments, have a complex layer structure. Absorbent garments typically include at least a liquid-permeable top layer, an absorbent core layer, and a breathable, substantially liquid-impermeable outer cover laminate. If one of these materials is made elastic, the absorbent garment will not necessarily be elastic. In order for the absorbent garment to have elastic properties, each layer must either a) exhibit a desired minimum level of stretching and retraction or b) be “free floating” and not attached to the elastic or extendible layers.
Another challenge of using elastic materials to promote conformability is the conversion of kinetic energy to potential energy during stretching. The stored potential energy in the stretched regions of the garment creates a retractive force which acts against the wearer's body, causing compression of the skin and discomfort. Wherever an elastic garment is stretched in selected regions to conform to a wearer's body, the garment will exhibit a tighter fit in the stretched regions. Skin ripples, red marks or even rashes may form where the elastic material exhibits the greatest retractive force against the wearer's skin. These problems become more acute when the garment contains more than one elastic layer.
There is a need or desire in the industries of personal care absorbent garments and medical garments, for less expensive materials which stretch in order to conform to the contours of a wearer's body. There is also a need or desire for materials which do not store significant amounts of potential energy when stretched, and which do not exhibit excessive retractive force against the wearer's body. In short, there is a need or desire for materials and garments which remain stretched, i.e., which permanently conform to the contours of the wearer's body.
SUMMARY OF THE INVENTION
The present invention is directed to a substantially liquid-impermeable laminate including at least one thermoplastic nonwoven filament web and at least one film, preferably a breathable, substantially liquid-impermeable film laminated to it. The laminate (which is preferably breathable) has a machine direction (direction of formation) which corresponds to a primary direction of orientation of the nonwoven filaments, and a cross direction which is perpendicular to the machine direction. The breathable laminate is extendible in the cross direction to a stretched width that is at least 25% greater than an original, unstretched width upon application of a stretching force. When the stretching force is removed, the breathable laminate either does not retract, or retracts by not more than 30% of the difference between the stretched width and the original width.
The breathable, substantially liquid impermeable laminate preferably includes a breathable, microporous film having cross-directional extendibility at least as great as the laminate, and a fibrous nonwoven web, bonded to the film, which also has cross-directional extendibility at least as great as the laminate. The film may alternatively be made of an inherently breathable polymer. The component which has the least cross-directional extendibility (whether the film or the web) will limit the useful cross-directional extendibility of the entire laminate. In other words, the laminate will extend to the same or a lesser extent than the least extendible layer. Similarly, neither the film nor the web should exhibit significantly more retractive force than is desired for the laminate in general. If either the film or the web has a tendency to retract by more than 30% of the difference between its stretched width and original unstretched width, then the overall laminate may retract too much or apply excessive retractive force against the wearer's body.
In one embodiment, the thermoplastic nonwoven filament web is a neck-stretched nonwoven web, for example, a neck-stretched spunbond web. The nonwoven web, which is made of a relatively inelastic polymer material, is extended in the machine direction to cause narrowing or neck-in of the web in the cross direction. The web is laminated and bonded to a breathable microporous film while the web is in the necked condition. The film includes at least one thermoplastic polymer which renders the film stretchable (but not elastic, or highly retractable) in the cross direction. Thus, when the laminate is stretched in the cross direction, the film is stretched, and the nonwoven web returns toward its original, un-necked state. The stretched laminate exhibits little or no retractive force after being held for one minute in the stretched condition. In this embodiment, the laminate has cross-directional extendibility but may not have machine direction extendibility if the nonwoven web is made from a non-extendible polymer composition.
In another embodiment, the thermoplastic nonwoven web is not necessarily neck-stretched, but is made using an extendible (but not elastic, or highly retractable) polymer material. The film also includes at least one thermoplastic polymer which renders the film extendible (but not elastic, or highly retractable) in the cross direction. When the laminate is stretched in the cross direction, the film is stretched, and the fibers in the nonwoven web are also stretched. The stretched laminate exhibits little or no retractive force. In this embodiment, the laminate may have extendibility in the machine direction as well as the cross direction, since both the film and web are made from extendible polymers.
In another embodiment, the thermoplastic web is not necessarily neck-stretched or made using a stretchable polymer. Instead, the nonwoven web is rendered stretchable by crimping of the filaments. Crimped filaments have undulations and/or spirals along their length which tend to straighten out when a stretching force is applied, thus rendering the filaments elongatable. Again, the film includes at least one thermoplastic polymer which ren
Conyer Sjon-Paul Lee
Hwang Patricia Hsiaoyin
Morell Charles John
Morman Michael Tod
Ono Audrie Tomoko
Bogart Michael G.
Kimberly--Clark Worldwide, Inc.
Pauley Petersen Kinne & Erickson
Ruhl Dennis
LandOfFree
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