Stock material or miscellaneous articles – Structurally defined web or sheet – Including aperture
Utility Patent
1997-11-14
2001-01-02
Raimund, Christopher (Department: 1771)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including aperture
C428S138000, C428S218000, C428S212000, C428S913000, C442S383000, C604S378000, C604S383000, C156S148000, C156S168000, C156S176000
Utility Patent
active
06168849
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a cover material or topsheet for personal care absorbent articles such as diapers, training pants, adult incontinence garments, feminine care products such as sanitary napkins, and the like. The cover material of this invention provides for faster fluid intake rates, lower rewet, less fluid retention, and smaller stain sizes compared to conventional cover materials.
2. Description of Prior Art
Almost all personal care absorbent articles include a cover material, sometimes hereinafter referred to as a liner, topsheet layer, body-side liner, or cover sheet, an absorbent core, and some type of backing material which is generally liquid impervious to help prevent leakage. The types of cover materials generally fall into two main groups based, at least in part, upon performance and aesthetic preferences. In the area of feminine care and sanitary napkins, the market is polarized into two segments, women who prefer clean and dry film covers and women who prefer soft, cloth-like nonwoven covers. The advantage of film covers for sanitary napkins is that they provide a relatively clean and dry surface as menses tends to pass through the film layer and into the interior of the absorbent product. A drawback, however, is that such film layers do not provide the degree of softness and comfort that a nonwoven cover material can provide. An additional drawback is the smooth, slick, non-clothlike feel that is characteristic of many films due. Nonwoven-based cover materials, on the other hand, are very soft and cloth-like in feel, but tend to retain more of the menses at or just below the surface of the cover material which, in turn, makes the product suffer from the standpoint of properties such as cleanliness and dryness. The difference in functionality is a direct result of the structure of nonwoven including small average pore size and nonuniform pore size distribution.
Absorbent articles have typically employed various types of absorbent pads composed of cellulose fibers. Particular absorbent garments have been configured to control the distribution of absorbed liquid. For example, an absorbent article can have a liquid permeable transport layer which is located between a topsheet layer and an absorbent body. In other configurations, a conventional absorbent member can have fluid storage and acquisition zones composed of cellulosic fluff mixed with absorbent gelling particles, and may include a dual-layer absorbent core arrangement comprising a bottom fluff pad containing hydrogel particles, and a top fluff pad with little or no hydrogel particles.
In addition, the absorbent core may consist of synthetic fibers in combination with natural fibers. These types of structures tend to be more resilient and possess a more uniform pore structure under load or when in contact with fluid than traditional absorbents.
Conventional hydrophilic cover materials or topsheets in contact with the skin effectively transport body fluids into the absorbent core, but they cause a wet feel against the skin of the user and may adversely affect skin health. In addition, they may wick liquid in the plane of the layer, allowing liquid to approach the edges of the absorbent article and possibly leak or seep out.
To achieve the goal of softness and a dry feel in topsheets of absorbent articles, many manufacturers have turned to nonwoven fabrics made of hydrophobic fibers for the body-contacting topsheet. While the use of hydrophobic nonwoven fabrics results in improved dry feel, the hydrophobic material hinders wicking into the absorbent core causing fluid to pool on the surface until enough pressure is applied to permeate the structure under conditions of low pressure and flow. As a result, the fluid may run off the pad and leak.
To improve the poor wicking and absorbent properties of hydrophobic materials, it is known to apply a finish comprising surfactants on the surface of the hydrophobic fibers, rendering them wettable or introducing fibers which are intrinsically wettable. Intrinsically wettable fibers may be natural, such as cellulose, or synthetic, such as rayon, polyester, or polyamides. Although providing good intake properties, wettable fibers introduce higher fluid retention and more fluid staining.
In the case of absorbent pads for feminine care, two distinct approaches involving topsheets or covers are commonly employed. One approach is to use a soft, clothlike nonwoven hydrophilic material which increases comfort but has the drawback of fluid retention and staining. A second approach is to use an apertured plastic film of hydrophobic polymer or other materials. The hydrophobic cover material repels many body fluids while the apertures allow wicking away from the cover into the absorbent material below.
Theoretically, the hydrophobic apertured material should allow the user's skin to remain relatively dry while allowing wicking in the z-direction (normal to the plane of the cover) into the underlying absorbent core. However, in practice, hydrophobic apertured films possess a number of problems. Apertured films have the drawback of being disliked by some users for their plastic and hot feel. Likewise, pockets or pools of liquid may form between the film and the user's skin. In the absence of hydraulic pressure or physical compression, menses in particular may pool on the hydrophobic surface rather than penetrate into the apertures, especially if there is a significant interfacial gap between the cover and the underlying absorbent material.
Accordingly, there is a need for an improved cover material which can provide the clean and dry feel characteristic of hydrophobic film cover materials while also delivering the softness of nonwoven cover materials.
SUMMARY OF THE INVENTION
Accordingly, it is one object of this invention to provide a material structure for use as a topsheet or cover in a personal care absorbent article such as a sanitary napkin, catamenial pad, pantiliner, incontinence guard, diapers or training pants for infant care, adult care or child care, bandages, or wound dressings capable of handling viscous or viscoelastic fluids, as well as elastic fluids.
It is another object of this invention to provide a topsheet or cover layer for personal care absorbent articles which is soft and comfortable, absorbent, clean and dry.
These and other objects of this invention are achieved by a multilayer cover system for personal care absorbent articles in accordance with this invention comprising a top layer and a bottom layer, the top layer forming a plurality of top layer apertures which can extend down into and/or through the bottom layer and having land areas between the apertures, the top layer contacting the bottom layer in the land areas, and the bottom layer having a permeability substantially equal to or higher than the top layer. The top layer and the bottom layer comprise at least one material selected from the group consisting of nonwovens, wovens, foams, fibrous structures, and mixtures and combinations thereof and composites of film and nonwovens, wovens, foams and/or fibrous structures. Thus, the approach of this invention is to accept the attributes of softness and comfort that nonwoven covers typically offer and address the issue of poor fluid functionality typical of conventional nonwoven covers. To satisfy these requirements, it is important to understand why these systems have poor fluid functionality and identify opportunities to address these issues.
It is well known in the art that nonwoven webs contain a random arrangement of fibers joined by bonding points that provide the mechanical integrity for these materials. These characteristics have an important influence on fluid management. Due to the random arrangement of fibers, a non-uniform pore size is present through the width and length of a specific web. As a result of this non-uniformity, fluid is retained in the small pores, creating a material which lacks a clean and dry appearance. In addition, the bonding points provide a barrier fo
Braverman Jaime
Daley Michael Allen
Garavaglia Arthur Edward
Griffin Rebecca
Mace Tamara Lee
Kimberly--Clark Worldwide, Inc.
Pauley Peterson Kinne & Fejer
Raimund Christopher
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