Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
1999-10-27
2002-05-14
Copenheaver, Blaine (Department: 1773)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C428S481000, C428S507000, C428S510000, C428S335000, C428S534000, C264S510000, C427S401000
Reexamination Certificate
active
06387528
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to polymer compositions that are water stable on one surface and water-sensitive on the opposing surface. More particularly, the present invention encompasses flushable, barrier films that retain their integrity in the presence of body waste fluids, but which disintegrate and disperse in the hydraulic flow of a toilet.
BACKGROUND OF THE INVENTION
Disposable products have revolutionized modern lifestyle and are of great convenience to society. Such products generally are relatively inexpensive, sanitary and quick and easy to use. Disposal of such products, however, increasingly is a problem as landfills close and incineration contributes to urban smog and pollution. Consequently there is an urgent need for disposable products that can be disposed of without dumping or incineration. An ideal disposal alternative would be the use of municipal sewage treatment and private residential septic systems. Products suited for disposal in sewage systems that can be flushed down a conventional toilet are termed “flushable.” An essential feature of flushable products is that they must have sufficient strength for their intended use, yet lose structural integrity upon contact with water. Meeting these dual criteria is particularly difficult for products that come in contact with body waste fluids, especially urine.
Numerous attempts have been made to produce flushable fibers, fabrics, films and adhesives that retain their integrity and wet strength in the presence of body waste fluids, yet can be disposed of via flushing in conventional toilets. One approach to producing a flushable product is to limit the size of the product so that it will readily pass through plumbing without causing obstructions or blockages. Such products may have high wet strength and would not disintegrate during flushing. Examples of this type of product might include wipes such as baby wipes. This approach to flushability suffers the disadvantage, however, of being restricted to small sized articles. Many of the current flushable products are limited to such small articles.
Another approach to producing a flushable product is to manufacture a product that is normally insoluble in water, but which disintegrates in the presence of alkaline or acidic aqueous solutions. The end user is provided with an alkaline or acidic material to add to the water in which the product is to be disposed. This approach permits disposal via normal plumbing systems of products substantially larger than wipes, but suffers from the disadvantage of requiring the user to perform the step of adding the dissolving chemical to the water. A further disadvantage is that the inadvertent or intentional disposal of such a product in a conventional toilet without the addition of the dissolving chemical can cause serious obstruction or blockage of the plumbing system. The latter disadvantage can, however, be overcome by incorporating the dissolving acid or alkali into the article but separate from the dissolvable material while in use. The dissolving chemical is only released upon contact with water during flushing.
Similarly, another approach to producing a flushable product consists of forming the product from a pH sensitive polymer and storing the product in the presence of a separate acid pH solution. When the product is placed in a large quantity of normal tap water, it disintegrates as a result of the pH shift. A disadvantage of this pH shift approach to flushability is that some acidic polymers lose wet strength at slightly alkaline pH in the range of 7-8. Because the pH of urine may be as high as 8.5, these flushable materials may not be well suited for use in, for example, diapers or incontinence pads.
Yet another approach to producing a flushable product is to form the product from material that is susceptible to attack by specific enzyme catalysis that breaks down the structural integrity of the material. In such a product the enzymes may be introduced into the disposal water separately. These systems suffer many of the same problems as acid or alkaline treatable materials.
Still others have attempted to make flushable products wherein a non-woven web is bound together with salt-sensitive binders. For example, some acrylic copolymers precipitate in the presence of high concentrations of calcium ions. The problem with calcium-dependent water soluble binders, however, is that across the country the concentration of calcium in normal tap water varies tremendously. Consequently, flushable products made with those binders may not, in fact, be flushable in regions with high calcium containing water.
None of the above approaches have proven completely satisfactory. Therefore, there is a need for a flushable barrier product which is stable in ion-containing bodily fluids, and which does not require special conditions of disposal.
SUMMARY OF THE INVENTION
The present invention provides a composition comprising a an ion-trigger polymer coating joined to a water-sensitive substrate. When the composition is employed as a diaper outercover or a pantiliner baffle, for example, the inner, body-side ion-trigger coating is exposed to bodily fluids, and acts as a barrier coating thereby inhibiting their transport to the lower water-sensitive substrate, maintaining the structural integrity of the composition. When the entire article is disposed of in a large volume of water, such as in the hydraulic flow of a toilet, both the water-sensitive substrate layer and the ion-trigger polymer coating layer mechanically weaken and break apart.
The present invention is, therefore, desirably designed to provide disposable compositions that can be flushed in a conventional toilet. It is also desirable to provide disposable compositions that act as fluid barriers, but are also capable of being flushed in a conventional toilet without the addition of a dissolving chemical. Additionally, it is desirable to provide flushable compositions that are insoluble in the presence of body waste fluids, but which are water dispersible in the presence of normal toilet water. Also, it is desirable to provide flushable compositions that disintegrate and disperse in normal toilet water regardless of geographic variations in toilet water salt concentrations. Additionally, it is desirable to provide flushable compositions that have sufficient strength for their intended use. Finally, it is desirable to provide flushable products, including, but not limited to, feminine care products, diapers and training pants, bandages, packaging, release films, and the like.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a composition comprising an ion-trigger polymer coating joined to a water-sensitive substrate. When the composition is employed as a diaper outercover or a pantiliner baffle, for example, the inner ion-trigger coating is exposed to bodily fluids, and acts as a barrier coating, thereby inhibiting their transport to the lower water-sensitive substrate, maintaining the structural integrity of the composition. When the composition is disposed of in a large volume of water, such as in the hydraulic flow of a toilet, both the water-sensitive substrate layer and the ion-trigger polymer coating layer mechanically weaken and break apart.
Therefore, one embodiment of the present invention provides a composite two-layer article comprising an ion-trigger coating on a water-sensitive substrate. In normal use, it is understood that the inner, ion-trigger coated side of the article will typically be exposed to bodily fluids, such as blood, menstrual fluid, vaginal exudate, urine and perspiration. The term “inner side”, as used herein, means the side of the film closest to the skin of the wearer. Both the inner ion-trigger coating and the outer, water-sensitive substrate will be exposed to toilet water during disposal. The ion-trigger coating on the inner side acts as a barrier coating and inhibits the transport of body fluids from the wearer through the article, effectively providing a barrier between body fluids and the water-se
Kerins John E.
Mumick Pavneet S.
Pomplun William S.
Copenheaver Blaine
Kilpatrick & Stockton LLP
Kimberly--Clark Worldwide, Inc.
Paulraj Christopher
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