Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Coated or impregnated woven – knit – or nonwoven fabric which... – Coating or impregnation is water absorbency-increasing or...
Reexamination Certificate
1999-08-27
2001-10-09
Morris, Terrel (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Coated or impregnated woven, knit, or nonwoven fabric which...
Coating or impregnation is water absorbency-increasing or...
Reexamination Certificate
active
06300258
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a nonwoven fabric having wettability that is both rapid and durable. More particularly, the invention relates to a nonwoven fabric treated with a hydrophilic surfactant having a broad molecular weight distribution, characterized by a high polydispersity.
BACKGROUND OF THE INVENTION
Nonwoven fabrics and their manufacture have been the subject of extensive development resulting in a wide variety of materials for numerous applications. For example, nonwovens of light basis weight and open structure are used in personal care items such as disposable diapers as liner fabrics that provide dry skin contact but readily transmit fluids to more absorbent materials which may also be nonwovens of a different composition and/or structure. Nonwovens of heavier weights may be designed with pore structures making them suitable for filtration, absorbent and barrier applications such as wrappers for items to be sterilized, wipers or protective garments for medical, veterinary or industrial uses. Even heavier weight nonwovens have been developed for recreational, agricultural and construction uses. These are but a few of the practically limitless examples of types of nonwovens and their uses that will be known to those skilled in the art who will also recognize that new nonwovens and uses are constantly being identified. There have also been developed different ways and equipment to make nonwovens having desired structures and compositions suitable for these uses. Examples of such processes include spunbonding, meltblowing, carding, and others which will be described in greater detail below. The present invention has general applicability to nonwovens as will be apparent to one skilled in the art, and it is not to be limited by reference or examples relating to specific nonwovens which are merely illustrative.
It is not always possible to efficiently produce a nonwoven having all the desired properties as formed, and it is frequently necessary to treat the nonwoven to improve or alter properties such as wettability by one or more fluids, repellency to one or more fluids, electrostatic characteristics, conductivity, and softness, to name just a few examples. Conventional treatments involve steps such as dipping the nonwoven in a treatment bath, coating or spraying the nonwoven with the treatment composition, and printing the nonwoven with the treatment composition. For cost and other reasons it is usually desired to use the minimum amount of treatment composition that will produce the desired effect with an acceptable degree of uniformity.
When a nonwoven web is formed of a hydrophobic material, for example, a polyolefin, it is often desirable to modify the surface of the nonwoven web using a hydrophilic surfactant to increase the wettability of the web. An external hydrophilic surfactant is typically applied to the surface of the nonwoven web. An internal hydrophilic surfactant is typically blended with the polymer used to form the nonwoven web, and later migrates to the surface after the nonwoven web is formed.
External and internal hydrophilic surfactants may be characterized in terms of their durability and wettability. The durability of a surfactant refers generally to its ability to withstand stresses, such as repeated washing cycles of the nonwoven fabric, without being removed from the fabric or otherwise losing its effectiveness. The wettability of a surfactant refers generally to its ability to transform a hydrophobic nonwoven web into a fabric which readily assimilates and distributes aqueous liquids. Surfactants which cause an otherwise hydrophobic nonwoven web to assimilate liquids at a relatively fast pace, with high fluid intake volumes, are referred to as faster wetting surfactants. Surfactants which cause the nonwoven web to assimilate aqueous liquids at a relatively slow pace, with low fluid intake volume, are referred to as slower wetting surfactants. In addition to the surfactant type, other factors affect the ability of the nonwoven web to assimilate liquids, including without limitation the nonwoven web type, nonwoven polymer type, fiber size and density, amount of surfactant, and how it is applied.
Surfactants having high durability are desirable for a variety of reasons.
However, durable surfactants often provide insufficient wetting, and do not lend themselves to optimization of wetting characteristics desired for individual end use applications. There is a need or desire for a surfactant composition having both durability and a faster rate of wetting. There is also a need or desire for a nonwoven fabric having durable wetting whose rate is relatively fast.
SUMMARY OF THE INVENTION
The present invention is directed to a nonwoven web treated with a hydrophilic organosilicone surfactant having a relatively broad molecular weight distribution, characterized by a polydispersity of at least 2.0. The broad molecular weight distribution surfactant imparts both durability and a fast rate of wetting to the nonwoven fabric. The surfactant may be used either internally or externally.
When the nonwoven web is provided with the broad molecular weight hydrophilic surfactant applied internally, it is believed that the smaller surfactant molecules migrate to the nonwoven filament surfaces somewhat rapidly to provide a fast rate of wetting. Over time, the intermediate molecular weight surfactant molecules migrate to the surface. The higher molecular weight surfactant molecules also migrate to the nonwoven filament surfaces, at an even slower rate. This delayed migration of the intermediate and higher molecular weight surfactant molecules causes the nonwoven fabric to have durable wetting properties.
When the nonwoven web is provided with the broad molecular weight hydrophilic surfactant applied externally, the smaller surfactant molecules may provide faster wetting while the larger molecules, which are more difficult to wash away, provide durable wetting. In either case, the nonwoven fabric has fast and durable wetting resulting from the use of a broad molecular weight hydrophilic surfactant.
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Quincy, III Roger Bradshaw
Stano Dana Elizabeth
Kimberly--Clark Worldwide, Inc.
Morris Terrel
Pauley Petersen Kinne & Fejer
Pratt Christopher C.
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