Stock material or miscellaneous articles – Structurally defined web or sheet – Including aperture
Reexamination Certificate
1998-05-15
2001-05-08
Watkins, III, William P. (Department: 1772)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including aperture
C428S131000, C428S137000, C428S138000, C428S516000, C428S913000, C604S378000, C604S383000
Reexamination Certificate
active
06228462
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to macroscopically expanded, three dimensional apertured polymeric webs. More particularly, the present invention relates to such webs being microapertured, and having improved compression resistance.
BACKGROUND
It has long been known in the disposable articles art that it is extremely desirable to construct absorptive devices such as disposable diapers, catamenials, sanitary napkins, incontinent articles, and the like, presenting a dry surface feel to the user. Such absorptive articles generally have a fluid pervious topsheet with a first wearer-contacting (or body-facing) surface and a second absorbent pad-contacting (or garment-facing) surface. By presenting a dry surface feel to the user, the topsheet gives improved wearing comfort, and minirnizes the development of undesirable skin conditions due to prolonged exposure to moisture absorbed within the absorptive device.
A dry surface is achieved by designing the topsheet to have both fluid transport and fluid retaining characteristics. Desirable fluid transport characteristics allow the topsheet to acquire fluids, such as urine or menses, and pass the fluid into the absorptive article. Once absorbed into the absorptive article, the fluid retaining feature of the topsheet preferably prevents rewet, i.e., the movement of fluid back through the topsheet. Rewet can be a result of at least two causes: (1) squeezing out of the absorbed fluid due to pressure on the absorptive article; and/or (2) wetness entrapped within or on the topsheet. Preferably, both properties, fluid acquisition and fluid retention, are maximized. Said differently, preferably a topsheet will exhibit high rates of fluid acquisition, and low levels of rewet.
While woven and nonwoven fibrous webs are often employed as topsheets on disposable absorbent garments because of their pleasant surface feel, polymeric formed film webs have been shown to exhibit more desirable fluid transport and fluid retention characteristics in many circumstances. For example, one viable prior art solution is disclosed in commonly assigned U.S. Pat. No. 4,342,314 issued to Radel et al. on Aug. 3, 1982 and hereby incorporated herein by reference. Radel et al. discloses an absorbent article with a wearer-contacting topsheet comprising a resilient macroscopically expanded, three-dimensional, plastic web exhibiting a combination of fiber-like and plastic properties. The web's fiber-like appearance is due to a continuum of fiber-like elements, wherein the opposed ends of each of the fiber-like elements are interconnected to at least one other of the fiber-like elements.
A topsheet of the type generally disclosed by Radel et al. is highly effective in promoting rapid fluid transfer from the wearer-contacting surface to the second absorbent pad-contacting surface of the topsheet. Accordingly, topsheets of this type have enjoyed widespread commercial success on catamenial pads due to their clean and dry appearance in use when contrasted to conventional nonwoven fibrous topsheets. While the Radel et al. topsheet is highly effective in promoting rapid transfer of bodily fluids from the first wear-contacting surface to the second absorbent pad-contacting surface, there remains some negative consumer reaction to placing polymeric webs comprised of plastic in contact with the user's skin.
Because of the superior fluid handling characteristics that can be provided in polymeric webs of the aforementioned type and their inherent cost advantages when contrasted to woven and non-woven fibrous webs, considerable effort has been expended to improve the consumer's reaction to the use of polymeric webs in contact with the skin. For example, an improved macroscopically expanded three-dimensional polymeric web exhibiting a substantially non-glossy visible surface and cloth-like tactile impression is disclosed in commonly assigned U.S. Pat. No. 4,463,045 issued to Ahr et al. on Jul. 31, 1984. The visible surface of the macroscopically expanded three-dimensional polymeric web of Ahr et al. is preferably provided with a regularly spaced, microscopic pattern of surface aberrations, the pattern being too fine to be discernible by the normal naked eye when the perpendicular distance between the viewer's eye and the plane of the web is about 12 inches. The pattern, however, is highly effective in substantially eliminating specular reflection of incident light.
U.S. Pat. No. 4,629,643, issued to Curro et al. on Dec. 16, 1986 discloses a particularly effective solution to providing a polymeric web exhibiting a soft and silky tactile impression. Curro et al. discloses a microapertured polymeric web having a fine scale pattern of discrete surface aberrations. Unlike prior art webs such as those disclosed in the aforementioned patent to Ahr et al., at least one tiny aperture, i.e., a microaperture, is provided substantially coincidental with the maximum amplitude of each surface aberration. The discontinuity created by the aperture at the peak of each surface aberration substantially reduces its resistance to compression and shear and significantly alters the tactile response of the web. The microapertured web of Curro et al. not only appears substantially non-glossy, but, in addition, exhibits a soft and silky tactile impression which appears to be preferred by many consumers. The aforementioned Curro '643 patent is hereby incorporated herein by reference.
While the Curro '643 microapertured web exhibits superior softness and tactile impression, as well as superior fluid acquisition rates, experience has shown that topsheets made with such webs can have relatively poor rewet properties as compared to other formed-film apertured webs, such as those disclosed generally in the aforementioned Radel patent. Without being bound by theory, it appears the limited compression resistance of the Curro '643 web tends to make it more susceptible to rewet under pressure. Because rewet properties contribute to overall dryness and cleanliness to the consumer, this drawback could limit consumer acceptance of apertured or microapertured webs.
Accordingly, it would be desirable to provide a soft, porous web having improved compression resistance.
Additionally, it would be desirable to provide a soft, porous web having superior fluid transport and fluid restraining characteristics.
Further, it would be desirable to provide an absorbent article having a soft, porous topsheet having superior improved resistance to compression under pressure.
SUMMARY OF THE INVENTION
An apertured, compression-resistant web is disclosed, the web comprising a first surface having a plurality of microapertures forming volcano-shaped surface aberrations, a second surface generally parallel to and spaced apart from the first surface. A plurality of fluid passageways extend between the first surface and the second surface to place the first surface and the second surface in fluid communication with one another. The web is formed of a multilayer polymeric film comprising at least one rigid layer and at least one substantially less rigid layer joined to the rigid layer.
In a preferred embodiment, a rigid layer has an elastic modulus of at least 120 kpsi, and a substantially less rigid layer has an elastic modulus of not greater than 75 kpsi. The multilayer film is preferably formed by coextuding a rigid layer comprising a blend of polystyrene and polypropylene, and a substantially less rigid layer comprising a blend of LDPE and LLDPE.
REFERENCES:
patent: 3929135 (1975-12-01), Thompson
patent: 4041951 (1977-08-01), Sanford
patent: 4152387 (1979-05-01), Cloeren
patent: 4197069 (1980-04-01), Cloeren
patent: 4324246 (1982-04-01), Mullane et al.
patent: 4342314 (1982-08-01), Radel et al.
patent: 4395215 (1983-07-01), Bishop
patent: 4463045 (1984-07-01), Ahr et al.
patent: 4533308 (1985-08-01), Cloeren
patent: 4629643 (1986-12-01), Curro et al.
patent: 4637819 (1987-01-01), Ouellette et al.
patent: 4747991 (1988-05-01), Bishop
patent: 5006394 (1991-04-01), Baird
patent: 5261899 (19
Lee Yann-Per
O'Donnell Hugh Joseph
Bullock Roddy M.
Hughett Eileen L.
Miller Steven W.
The Procter & Gamble & Company
Watkins III William P.
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