Compressed absorbent composites

Details Compressed absorbent composites Compressed absorbent composites

1998-11-16

2002-05-14

Morris, Terrel (Department: 1771)

Fabric (woven, knitted, or nonwoven textile or cloth, etc.)

Nonwoven fabric

Including strand or fiber material which is stated to have...

C442S153000, C442S329000, C442S416000

Reexamination Certificate

active

06387831

ABSTRACT:

FIELD OF THE INVENTION
present invention relates to absorbent articles, particularly absorbent structures which are useful in personal care products such as disposable sanitary napkins, diapers, or incontinence guards. More particularly, the invention relates to absorbent articles which have a portion designed for rapid uptake, temporary liquid control, and subsequent release of repeated liquid surges to the remainder of the article.
BACKGROUND OF THE INVENTION
The desired performance objectives of personal care absorbent products include low or no leakage from the product, a dry feel to the wearer, and thinness as a means to provide comfort to the wearer. Current absorbent products, however, often fail to meet these objectives for a variety of reasons.
Leakage can occur, for example, due to insufficient uptake rate by layers intended to provide retention or distribution capability in the intake or target zone. Attempts to alleviate leakage occurring by this mechanism include absorbent articles that incorporate surge material structures located above (i.e., toward the wearer) the retention or distribution materials. U.S. Pat. No. 5,364,382 to Latimer discloses nonwoven materials such as meltblowns, bonded carded webs, and pulp conforms that receive and subsequently release liquid to the retention means. The material structures of Latimer utilize large denier resilient fibers blended with small denier wettable fibers to achieve rapid liquid uptake and rapid liquid release to the underlying retention storage material. Additionally, U.S. Pat. No. 5,490,846 to Ellis discloses layered structures to improve intake rates of surge materials.
Despite the development of surge materials that attempt to achieve rapid uptake and rapid release to the retention material, the objective of thinness remains to be satisfactorily reached. The cited surges are quite thick and when placed into the intake zone of the absorbent article can cause poor fit in the crotch region of the absorbent product upon initial wearing and can lead to several performance problems. Firstly, the product can leak due to gapping that is created by the bulky surge material. Secondly, the product is not comfortable to the wearer when a bulky material is utilized to provide the necessary void volume for uptake. There remains a need, therefore, for a surge material which will rapidly uptake an insult to the target area and release it for subsequent storage and which also remains relatively thin prior to insult.
It is an object of this invention to provide a surge material for personal care products which rapidly uptakes an insult and transfers it to an adjacent material for distribution or storage, and which remains relatively thin prior to initial insult. It is another object of this invention to provide a personal care product which, prior to insult, is thin and comfortable for a wearer.
SUMMARY OF THE INVENTION
The objectives of the invention are achieved by materials and products which have been designed to be very thin prior to insult and expand rapidly when insulted. In its broadest definition the invention is a fibrous web which includes a binder and which is compressed to a density of up to about 0.3 g/cc. The web may preferably be formed by the bonded carded web process, conform process or air lay process. The binder may depend on hydrogen bonding using moisture or may be a non-aqueous solution, a powder, a fibrous binder or a conjugate fiber binder including a moisture triggerable component. Conjugate fibers may be crimped. When wetted the web of this invention should expand rapidly to greater than 80% of its uncompressed thickness and greater than 90% of its thickness when saturated if starting from the uncompressed state.
DEFINITIONS
“Hydrophilic” describes fibers or the surfaces of fibers which are wetted by the aqueous liquids in contact with the fibers. The degree of wetting of the materials can, in turn, be described in terms of the contact angles and the surface tensions of the liquids and materials involved. Equipment and techniques suitable for measuring the wettability of particular fiber materials or blends of fiber materials can be provided by a Cahn SFA-222 Surface Force Analyzer System, or a substantially equivalent system. When measured with this system, fibers having contact angles less than 90° are designated “wettable” or hydrophilic, while fibers having contact angles equal to or greater than 90° are designated “nonwettable” or hydrophobic.
“Layer” when used in the singular can have the dual meaning of a single element or a plurality of elements.
“Liquid” means a nongaseous, non-particulate substance and/or material that flows and can assume the interior shape of a container into which it is poured or placed.
As used herein the term “nonwoven fabric or web” means a web having a structure of individual fibers or threads which are interlaid, but not in an identifiable manner as in a knitted fabric. Nonwoven fabrics or webs have been formed from many processes such as for example, meltblowing processes, spunbonding processes, and bonded carded web processes. The basis weight of nonwoven fabrics is usually expressed in ounces of material per square yard (osy) or grams per square meter (gsm) and the fiber diameters useful are usually expressed in microns. (Note that to convert from osy to gsm, multiply osy by 33.91).
As used herein the term “microfibers” means small diameter fibers having an average diameter not greater than about 75 microns, for example, having an average diameter of from about 0.5 microns to about 50 microns, or more particularly, microfibers may have an average diameter of from about 2 microns to about 40 microns. Another frequently used expression of fiber diameter is denier, which is defined as grams per 9000 meters of a fiber and may be calculated as fiber diameter in microns squared, multiplied by the density in grams/cc, multiplied by 0.00707. A lower denier indicates a finer fiber and a higher denier indicates a thicker or heavier fiber. For example, the diameter of a polypropylene fiber given as 15 microns may be converted to denier by squaring, multiplying the result by 0.89 g/cc and multiplying by 0.00707. Thus, a 15 micron polypropylene fiber has a denier of about 1.42(15
2
×0.89×0.00707=1.415). Outside the United States the unit of measurement is more commonly the “tex”, which is defined as the grams per kilometer of fiber. Tex may be calculated as denier/9.
“Spunbonded fibers” refers to small diameter fibers which are formed by extruding molten thermoplastic material as filaments from a plurality of fine, usually circular capillaries of a spinneret with the diameter of the extruded filaments then being rapidly reduced as by, for example, in U.S. Pat. No. 4,340,563 to Appel et al., and U.S. Pat. No. 3,692,618 to Dorschner et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S. Pat. No. 3,338,992 and 3,341,394 to Kinney, U.S. Pat. No. 3,502,763 to Hartman, and U.S. Pat. No. 3,542,615 to Dobo et al. Spunbond fibers are generally not tacky when they are deposited onto a collecting surface. Spunbond fibers are generally continuous and have average diameters (from a sample of at least 10) larger than 7 microns, more particularly, between about 10 and 20 microns.
“Meltblown fibers” means fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging high velocity, usually hot, gas (e.g. air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly disbursed meltblown fibers. Such a process is disclosed, for example, in U.S. Pat. No.3,849,241. Meltblown fibers are microfibers which may be continuous or discontinuous, are generally smaller than 10 microns in average diameter, and are generally tacky when deposited onto a collecting surf

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