Surgery – Means and methods for collecting body fluids or waste material – Absorbent pad for external or internal application and...
Reexamination Certificate
1997-09-12
2002-07-16
Weiss, John G. (Department: 3761)
Surgery
Means and methods for collecting body fluids or waste material
Absorbent pad for external or internal application and...
C604S383000, C428S138000
Reexamination Certificate
active
06420625
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to materials useful in forming barriers that are impervious to liquids. Such materials are often used as outer covers or baffles for disposable diapers, sanitary napkins, incontinent pads, and other products where a liquid-impervious barrier may be desired. More specifically, the present invention relates to a composite material formed from a breathable film, an apertured film, and a non-woven substrate, as well as the process for making such composite material.
BACKGROUND OF THE INVENTION
Absorbent articles and products such as disposable diapers, sanitary napkins, bedpads, pantiliners, training pants, incontinent pads and garments, and the like, are items designed to be worn or placed adjacent to the body to absorb discharged bodily fluids. Bodily fluids absorbed by such products include urine, blood, menses and other excrements discharged by the body at various times.
Typically, such products are multilayered in construction and have a liquid-permeable cover, a liquid-impermeable baffle, and an absorbent material positioned in between the liquid-permeable cover and liquid-impermeable baffle. The liquid-permeable cover is designed to allow rapid transfer of bodily fluids into the absorbent layer(s) where the fluids can be retained. The baffle, which is usually an outer cover but may in some cases be positioned internally in the product, prevents leakage of the liquid retained within the absorbent area of the product. If the baffle were absent, leakage of the absorbed liquid could result in soiling of clothing, bedding, furniture, and other items positioned close to the absorbent article.
For many years, liquid-impermeable plastic films, such as polyethylene and polypropylene films, have been used to form the outer covers and baffles. Generally, such plastic films are impermeable to gases and water vapor, as well as liquids. The films prevent, or at least minimize, leakage by establishing a barrier to the passage of liquid from the absorbent article in situations where either the capacity of the absorbent article has been exceeded or the loading of the target zone has exceeded the capacity of the absorbent article to wick liquid from that target zone to liquid storage areas.
While completely liquid-impermeable films are well-suited to prevent the migration of liquid waste from the absorbent materials to the outer clothing of persons wearing such absorbent articles, the use of such liquid- and vapor-impermeable covers can result in a relatively high degree of humidity being maintained in the article when liquid has been absorbed. Oftentimes, a clammy feeling may result from this retained humidity. Such resulting clamminess also may contribute to skin irritations such as rashes if the article is left on a wearer for an extended period of time. In addition, due to the complete impermeability of such covers, the absorbent articles often feel hot to the user before being insulted with fluids.
Such completely impermeable films have been replaced in certain products with breathable, liquid-impermeable barriers. As used herein, the term “breathable” means that the barrier or film is pervious to water vapor and gases. In other words, “breathable barriers” and “breathable films” allow water vapor and gases to pass therethrough, but not necessarily liquids.
In some cases, breathable, liquid-impermeable barriers are made from various nonporous breathable films which, because of their molecular structures, are impervious to liquid but not impervious to vapors. These types of breathable barriers are generally composed of sufficient amounts of polymers such as poly(vinyl alcohol) (“PVOH”), polyvinyl acetate (“PVA”), ethylene vinyl alcohol (“EVA”), polyurethane, ethylene methyl acrylate (“EMA”), and ethylene methyl acrylic acid (“EMM”) to make them breathable.
One such breathable, liquid-impermeable barrier is disclosed in U.S. Pat. No. 4,828,556 to Braun et al. Braun et al. is commonly owned by the assignee of the present invention and is incorporated herein in its entirety by reference. The breathable barrier of Braun et al. is a multilayered, clothlike barrier comprised of at least three layers. The first layer is a porous nonwoven web; the second layer, which is joined to one side of the first layer, comprises a continuous film of PVOH; and the third layer, which is joined to either the second layer or the other side of the first layer not joined with the second layer, comprises another porous nonwoven web. The second layer continuous film of PVOH is not microporous, i.e., nonporous, meaning that it is substantially free of voids which connect the upper and lower surfaces of the film.
In other cases, breathable films are constructed with micropores therein to provide desired levels of liquid impermeability and vapor permeability. The micropores form what is often referred to as tortuous pathways through the film. Liquid contacting one side of the film does not have a direct passage through the film. Instead, a network of microporous channels in the film prevents liquids from passing, but allows gases and water vapor to pass. Due to their structure, such films are termed for purposes of the present application as “porous”.
In some of such products, the breathable, liquid-impermeable barriers are made from polymer films that are highly filled with a substance such as calcium carbonate. The films are made breathable by stretching the filled films to create the microporous passageways as the polymer breaks away from the calcium carbonate during stretching.
Such porous breathable films are obviously more expensive to construct. In addition, porous breathable films are more susceptible to possible liquid penetrations than are nonporous breathable films.
An example of a breathable, yet fluid penetration-resistant material is described in U.S. Pat. No. 5,591,510 to Junker et al. The fabric material described in Junker et al. comprises a breathable outer layer of paper stock and a layer of breathable, fluid-resistant nonwoven material. The fabric also includes a thermoplastic film having a plurality of perforations which allow the film to be breathable while resisting direct flow of liquid therethrough.
Another breathable film barrier is disclosed in U.S. patent application Ser. No. 08/169,826 to McCormack. McCormack is also commonly owned by the assignee of the present invention and is incorporated herein in its entirety by reference. (The published PCT application that corresponds to this United States patent application is WO 95/16562, published on Jun. 22, 1995.) As disclosed therein, a breathable film is adhered to a fibrous polyolefin nonwoven web to form a breathable, cloth-like film
onwoven composite. In particular, McCormack discloses a bonding agent incorporated into one or more layers of the composite which makes the layers easier to thermally bond into a composite.
Another film
onwoven laminate is disclosed in U.S. patent application Ser. No. 08/359,987 to McCormack et al. This application is also commonly owned by the assignee of the present invention and is incorporated herein in its entirety by reference. (The PCT application corresponding to this United States patent application was published on Jun. 27, 1996, under WO 96/19346.) McCormack et al. discloses a low gauge, multilayer film, which may be laminated to other materials such as, for example, fibrous nonwoven webs. In particular, the films have a core layer made from an extrudable thermoplastic polymer and then has one or more skin layers attached to the exterior surfaces of the core layer. In some instances, the multilayer films are made breathable either through the use of specialized polymers which permit diffusion of gases through the layer and/or through the use of particulate fillers.
Other designs of breathable absorbent articles include diapers that are arranged to provide some level of breathability at the leg cuff regions of the diaper, articles that have humidity transfer regions in the form of breathable panels in otherwise vapor-impermeable outer
Jones Billy R.
Majors Mark B.
Shaffer Robert L.
Kimberly--Clark Worldwide, Inc.
Nelson Mullins Riley & Scarborough
Webb Jamisue
Weiss John G.
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