Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Nonwoven fabric
Reexamination Certificate
2000-08-31
2003-09-30
Morris, Terrel (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Nonwoven fabric
C428S103000, C428S198000, C442S394000, C264S284000
Reexamination Certificate
active
06627564
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a laminate of thermoplastic fabrics which is permanently conformable to the contour of a wearer by stretching as needed in the cross direction to conform to the contour of the wearer and remaining, essentially, in its extended or stretched state, even after a stretching force is removed, while in the machine direction, stretch and recovery is provided by separated elastic filaments.
BACKGROUND OF THE INVENTION
Laminates, particularly those 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.
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. However, in some instances elasticity, or stretch and recovery, of a fabric may be highly desirable, at least in one axis of the garment.
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 permanently conform to the contours of the wearer's body through a combination of stretching without recovery and stretching with recovery in selected areas of the garment.
SUMMARY OF THE INVENTION
The present invention is directed to a laminate including at least one thermoplastic nonwoven filament web. The web may be laminated to other webs or at least one film, preferably a breathable, substantially liquid-impermeable film. The laminate (which is also preferably breathable) has a machine direction (direction of formation during material production) which corresponds to a primary direction of orientation of the nonwoven filaments, and a cross direction which is perpendicular to the machine direction. The laminate includes elastic filaments bonded to the laminate lengthwise in the machine direction but separated from contacting each other in the cross direction so that they present no significant elastic or retractive force in the cross 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 laminate either does not retract, or retracts by not more than 30% of the difference between the stretched width and the original width.
If a breathable film is not desired, an embodiment may be made wherein the elongated elastic filaments are bonded between two layers of nonwoven webs which are necked and extendible in the cross direction. The laminate may include a breathable, substantially liquid impermeable 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 must retract by more than 30% of the difference between its stretched width and original unstretched width as in the machine direction to provide a better fit for the crotch of a diaper constructed in the machine direction, then the overall laminate is provided with elastic filaments in the machine direction and unconnected in the cross direction to apply retractive force against the wearer's body in only one axis.
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. A series of stretched elastic filaments spaced in the cross direction are bonded in, or to, the web. 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. The laminate is then relaxed and the retraction of the elastic filaments in the machine direction shorten the laminate and create rugae, or wrinkles, in the laminate which extend 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 in the cross direction after being held for one minute in the stretched condition. In this embodiment, the laminate has cross-directional extendibility and machine direction elasticity.
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 retra
Brunner Michael Scott
Datta Paul J.
Gross Jacqueline A.
Morman Michael Tod
Kimberly--Clark Worldwide, Inc.
Morris Terrel
Pauley Petersen Kinne & Erickson
Salvatore Lynda
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