Surgery – Means and methods for collecting body fluids or waste material – Absorbent pad for external or internal application and...
Reexamination Certificate
1998-12-15
2001-06-05
Weiss, John G. (Department: 3761)
Surgery
Means and methods for collecting body fluids or waste material
Absorbent pad for external or internal application and...
C604S367000
Reexamination Certificate
active
06241713
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process of making a superabsorbent roll good suitable for fabrication into thin disposable absorbent hygiene articles such as for example pantyliners and sanitary napkins and to the products prepared according to the process of the invention. According to the invention, an aqueous solution of a hydrogel-forming polymer having superabsorbent properties upon drying and curing is foamed to several times its original volume and applied to a sheeted fibrous absorbent material to form a distinct, porous layer of a superabsorbent material on the surface of the sheeted fibrous absorbent material.
BACKGROUND OF THE INVENTION
Conventional absorbent articles such as baby diapers, adult incontinence devices, and feminine napkins are typically made with a cellulose fiber fluff-based absorbent core sandwiched between a liquid pervious top sheet, which allows the unobstructed passage of fluid to the absorbent core, and a liquid impervious backing sheet usually of plastic material, which contains the absorbed fluid and prevents it from passing through the absorbent core and soiling the undergarments of the wearer of the absorbent article.
The absorbent core of these absorbent articles is typically constructed of defiberized wood pulp with or without superabsorbent polymer granules. The absorbent core is typically formed on a pad-forming unit of a converting machine on a carrier tissue to facilitate processing. Some absorbent core forming units are equipped with layering capability in which a second discrete fluff layer may be laid over a primary fluff-based absorbent layer to form a multi-layer absorbent structure. In these absorbent structures, the primary layer may include superabsorbent polymer granules. With regard to conventionally produced absorbent structures, reference is made to U.S. Pat. Nos. 5,009,650, 5,378,528, 5,128,082, 5,607,414, 5,147,343, 5,149,335, 5,522,810, 5,041,104, 5,176,668, 5,389,181, and 4,596,567, the disclosures of which are hereby incorporated herein by reference.
In recent years, market demand for thinner and more comfortable absorbent articles has increased. Ultra-thin feminine napkins are no longer constructed from loose wood pulp, which tends to give a bulky product, but with roll good-based air-laid absorbent cores in which a roll of preformed absorbent core material is unwound directly onto the absorbent pad-making machine without the defiberization step required for fluff-based products. The roll good-based approach results in a product thinness, which can not be achieved by loose fluff-based technology.
It is known in the art, as described in U.S. Pat. Nos. 3,669,103 and 3,670,731 for example, that carboxylic polyelectrolytes may be cross-linked to create hydrogel-forming materials, now commonly referred to as superabsorbents. These materials are used to enhance the absorbency of disposable absorbent articles. The use of continuous and discontinuous coatings of superabsorbent polymers on various materials is described, for example, in U.S. Pat. Nos. 4,076,673, and 5,071,681 discloses preparation of an air-laid fibrous web and application of a water-insoluble binder to one surface of the web and a water-soluble polymer capable of forming a superabsorbent to the other surface of the web. U.S. Pat. No. 4,444,830 discloses a liquid superabsorbent precursor solution, which is chemically foamed and applied to a base fluffing material, which coated fluffing material is then dried, disintegrated and mechanically worked into a fibrous fluff matrix containing absorbent polymer platelets distributed throughout the matrix.
The above-mentioned approaches for coating fibrous and non-woven materials with superabsorbent-forming compositions cause stiffness of the coated materials due to the inherent brittleness of polyelectrolytes. Humectants such as glycerol may be used to overcome this problem, however, humectants can only plasticize polyelectrolytes in the presence of a substantial amount of water. Maintaining the necessary moisture content is difficult in dry climates. Furthermore, spraying a dilute liquid superabsorbent precursor solution onto an air-laid web may cause deep polymer penetration into the web so that the superabsorbent polymer is not a discrete layer on the surface of the web but a diffuse coating on the fibers of the web.
It has now been surprisingly discovered that it is not necessary nor even desirable to have the superabsorbent polymer material dispersed throughout the absorbent composite for the superabsorbent to work in its intended fashion. Indeed, having the superabsorbent concentrated in a distinct layer, which may be placed (in a disposable absorbent product) away from the source of the liquid insult, provides more efficient utilization of the fibrous material in the absorbent product for initially imbibing and then transporting the fluid. This result is accomplished by foaming a composition containing a water soluble polymer capable of forming a superabsorbent polymer upon drying and curing and applying the foam onto the absorbent web.
SUMMARY OF THE INVENTION
The present invention relates to an absorbent sheeted material containing a layer of a foamed hydrogel-forming polymer having superabsorbent properties coated on the surface of a sheeted fibrous absorbent material suitable for use in disposable absorbent products and to methods of making thereof.
Accordingly, in one aspect of the invention, an absorbent sheeted material containing a layer of a foamed hydrogel-forming polymer coated on the surface of a sheeted fibrous absorbent material is provided.
In another aspect of the invention, a disposable absorbent product prepared by using the absorbent sheeted material of the invention is provided.
In yet another aspect of the invention, a method for making the absorbent sheeted product of the invention is provided.
DETAILED DESCRIPTION OF THE INVENTION
All patents, patent applications and references cited herein are incorporated hereby by reference. In case of inconsistencies, the present disclosure governs.
The present invention relates to an absorbent sheeted material, and a method of preparing the absorbent sheeted material, suitable for fabrication into thin disposable absorbent hygiene articles such as, for example, pantyliners and sanitary napkins.
The absorbent sheeted material of the invention comprises (i) a sheeted fibrous absorbent material and (ii) a foamed hydrogel-forming polymeric material coated on the surface of the sheeted fibrous absorbent material.
The “sheeted fibrous absorbent material” is any absorbent fibrous matrix in the form of a sheet and is referred to hereinafter as “fibrous structure.” Such fibrous structures may be prepared by methods well known in the art such as for example by using air-laying or wet laying processes. Representative examples of such fibrous structures are: air-laid non-wovens prepared from individualized wood fibers alone or in admixture with synthetic fibers and bonded using adhesives or thermal bonding fibers or powders. The fibrous structure could also be a composite of several layers of fibers. The fibrous structure may contain any natural fiber, including wood fibers such as for example, air laid-fluff cellulose, chemically modified cellulose fibers, cross-linked cellulose fibers, or cotton linter fibers. Synthetic fibers, such as polyester fibers, such as polyethyleneterephthalate (“PET”), polypropylene, nylon and acrylic, may also be used.
The fibers in the fibrous structure may be latex-bonded and/or thermally-bonded. Other methods known in the art for creating physical entanglements, such as needle punching and hydroentangling, may also be used.
A latex-bonded fibrous structure contains latex, such as for example polymers and copolymers of alkylacrylate, vinyl acetate and styrene-butadiene. A thermally-bonded fibrous structure may contain thermoplastic fibers or powder, which are well known in the art, and which are known to provide bonding upon heating to the melting point of the thermoplastic fiber or powder. In one embodiment of
Baer Samuel C.
Erspamer John P.
Gross James R.
Leptick Steve
Buckeye Technologies Inc.
Darby & Darby
Shanoski Paul A
Weiss John G.
LandOfFree
Absorbent structures coated with foamed superabsorbent polymer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Absorbent structures coated with foamed superabsorbent polymer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Absorbent structures coated with foamed superabsorbent polymer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2545134