Surgery – Means and methods for collecting body fluids or waste material – Absorbent pad for external or internal application and...
Reexamination Certificate
2000-09-13
2003-05-27
Lo, Weilun (Department: 3761)
Surgery
Means and methods for collecting body fluids or waste material
Absorbent pad for external or internal application and...
Reexamination Certificate
active
06570057
ABSTRACT:
GENERAL FIELD OF THE INVENTION
The present invention relates to hygienic absorbent articles, such as disposable baby diapers, training pants, adult incontinence articles, feminine hygiene articles and the like, which comprise fluid distribution members exhibiting an improved performance for distributing liquid within such articles.
BACKGROUND/PRIOR ART
In the general field of disposable absorbent articles and structures, materials exhibiting specific fluid distribution properties are well known. Such materials became more and more relevant with the introduction of highly absorbent materials, also called Absorbent Gelling Materials or superabsorbent materials or shortly superabsorber, which do provide a good means for storing aqueous fluids such as urine, but do not enhance fluid transport, and even reduction of fluid transport can occur, when, sub-optimal designs and/or suboptimal materials are employed, and phenomena often referred to as “gel-blocking” take place. For example, in structures where the superabsorbent is homogeneously mixed with cellulose fibers, a certain critical concentration, which is strongly depending on the choice of the superabsorbent material, should not be exceeded in order to not deteriorate efficacy of the absorbent core.
As a consequence, a vast number of absorbent core designs have appeared with a separated functionality, such as by comprising not only liquid storage regions or materials, but also regions with specialized properties for enhanced acquisition and/or distribution of the fluid. Often, one region aimed at enhancing acquisition and distribution at the same time.
Initially, the requirements for a distribution material were not very high, and standard paper tissue materials such as used as wrapsheets in the cores and described for example in U.S. Pat. No. 3,952,745 (Duncan), were applied to also enhance the fluid distribution, as described in EP-0 343 941 (Reising) or U.S. Pat. No. 4,578,068 (Kramer).
Further developments can be exemplified by EP-A-0,397,110 (Latimer) disclosing an absorbent article comprising a surge management portion for improved fluid handling, having specific basis weights, acquisition times and residual wetness; U.S. Pat. No. 4,898,642 (Moore et al.) discloses specially twisted, chemically stiffened cellulosic fibers and absorbent structures made therefrom; EP-A-0,640,330 (Bewick-Sonntag et al.) discloses the use of such fibers in a specific arrangement with specific superabsorbent materials.
Further approaches aimed at improving the wicking properties of cellulose fiber based materials, such as U.S. Pat. Nos. 3,575,174 or 4,781,710, whereby parts of the structure are compressed to a higher density, thus creating smaller pores for increased wicking height for example along “wicking lines” or in closed mesh patterns.
As some of these materials did exhibit an undesired hard feel, methods for post formation treatments were well known to improve softness. “Post formation treatment” refers to the fact that—instead of or in addition to increasing softness during the making or formation of the tissue—the tissue is treated mechanically in a separate process step after forming and drying of the tissue, often just prior to further processing such as combining the tissue with other materials to form an absorbent core or article. Examples for such treatments are U.S. Pat. No. 5,117,540 (Walton) or U.S. Pat. No. 4,440,597 (Wells).
Other attempts to impact on the pore size of distribution materials is described in U.S. Pat. No. 5,244,482 (Hassenboehler), aiming at reducing maximum pore size by stretching a fibrous structure comprising meltable fibers in one direction and “freezing” the deformation by heat curing.
Also, special material composites were developed, aiming at a allowing to tailor the pore size and pore size distribution. Examples for such improvements are described in greater detail in U.S. Pat. No. 5,549,589 (Homey et al.) or in PCT application WO 97/38654 (Seger et al.). Both aim essentially at providing a resilient structure by using specially stiffened cellulosic fibers such as crosslinked cellulose soft-wood fibers, and by filling the large pores with small and thin cellulosic fibers such as eucalyptus fibers. Both applications further add means for providing sufficient integrity and strength to the structure, the first one (U.S. Pat. No. 5,549,589) by adding thermoplastic fibers and partially melt these, the second (WO 97/38654) by adding a chemical binder.
A further approach as disclosed in EP Application EP-A-0,810,078 (d'Acchioli et al.) uses a special post-formation mechanical treatment of webs, thereby imparting improved fluid handling properties such as described by higher liquid flux rates at certain wicking heights.
With the wish to improve the functionality of the absorbent articles, more specific requirements for distribution materials developed, such that porous materials were investigated in more depth. In order to improve the longitudinal fluid distribution, high surface area synthetic fibers were applied in absorbent structures, such as described in US Statuary Invention Registration H1511. Another class of materials are foamed structures, such as cellulosic foams such as commercially available by Spontex SA, France.
Other polymeric foams for being used in absorbent articles were disclosed in U.S. Pat. No. 5,268,224 (DesMarais), namely High Internal Phase polymerized materials, which can be used for storing liquids, and have at the same time the ability to avoid localized saturation, by spreading the stored fluid throughout the material.
However, all these investigations so far aimed at improving the wicking properties of the distribution materials such as flux, wicking height and wicking times, but failed to recognize the importance of the dewatering mechanism of the distribution materials by the liquid storage materials, especially when such materials are not fully saturated, such as can be relevant in absorbent articles between multiple loadings.
OBJECTS OF THE INVENTION
Henceforth, it is an object of the present invention to provide improved absorbent articles having an improved dewatering functionality of distribution members, especially under low saturation conditions.
It is another object of the present invention, to provide improved absorbent articles comprising materials which allow liquid to be transported throughout an absorbent article even being saturated to a low or moderate degree of saturation.
It is a further object of the present invention to provide such articles further comprising liquid storage materials having a good capillary sorption absorption performance.
SUMMARY
The present invention is an absorbent article containing a fluid distribution member, which has a relatively high permeability even at subsaturation conditions, and which has a lower Capillary Sorption Absorption Height at 50% of its capacity at 0 cm, which is higher than the Capillary Soprtion Desorption Height at 50% of its capacity at 0 cm of a fluid storage member in liquid communication with this distribution member in this article.
Thus, the distribution member has a permeability at 50% of its saturation, which is at least more than about 14%, preferably more than 18%, even more preferably more than 25% or even more than 35% of the permeability at 100% saturation.
Thus, the first fluid storage member has as CSAH 50 of more than about 15 cm, preferably of more than about 23 cm, even more preferably of more than about 27 cm, or even more than about 30 cm, and most preferably more than about 47 cm.
In a further preferred executions, the absorbent article comprises a fluid distribution member which has a permeability at 30% of its saturation k(30) which is more than about 3% of k(100), preferably more than about 5%, more preferably even more than about 10% of k(100).
In further preferred embodiments, the fluid distribution member has a CSDH 50 value of less than about 150 cm, more preferably less than about 100 cm, even more preferably less than about 75 cm, and most preferably less than about 50 cm.
In a
Desai Fred
Ehrnsperger Bruno Johannes
Schmidt Mattias
Bogart Michael
Hughett Eileen L.
Lo Weilun
Milbrada Edward J.
Patel Ken K.
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