Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
2001-04-30
2002-11-12
Lorengo, J. A. (Department: 1734)
Coating processes
With post-treatment of coating or coating material
Heating or drying
C427S375000, C604S364000, C428S041800, C156S289000
Reexamination Certificate
active
06479105
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 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 modem 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.
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 often have high wet strength and do not disintegrate during flushing. Examples of this type of product include wipes such as baby wipes. This approach to flushability suffers the disadvantage, however, of being restricted to 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, particularly wipes, consists of forming the product from a pH-sensitive gelled polymer, and storing the product in the presence of a separate acidic solution. When the wipe is placed in a large quantity of neutral pH 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 are not well suited for use in, for example, diapers or incontinence pads.
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 disadvantages as those described above for alkaline or acid treatable materials.
UK patent application GB 2 083 762A to Enak Limited discloses an ostomy pouch where a water impermeable layer of polyvinylidene chloride, vinyl chloride-vinylidene chloride-copolymer, atactic polypropylene, nitrocellulose, waxes, greases, silicone, or pressure sensitive adhesives is backed by a layer of polyethylene oxide or polyvinyl alcohol. However, this construction may not be mechanically weak enough in the flow of toilet water to disintegrate sufficiently.
UK patent application GB 2 185 404A to Smiths Industries Public Limited Co. discloses an ostomy bag with an inner layer of polyvinylidene chloride is backed by a layer of polyvinyl alcohol. However, this construction may not be mechanically weak enough in the flow of toilet water to disintegrate sufficiently.
U.S. Pat. No. 4,732,311 to J. E. Potts discloses coating a water soluble polymer, such as polyethylene oxide with a degradable water-insoluble polymer such as a cyclic ester polymer, a poly(beta-hydroxy butyrate), dialkanoyl polymers, such as polyesters and polyurethanes derived from aliphatic polyols, and ethylene polymers.
U.S. Pat. No. 5,283,090 to Y. Umemura discloses a multi-layered urine or ostomy bag, the inner side of which is water-impermeable by means of silicon or fluorine-containing coatings such as polytetrafluoroethylene and methylhydroxypolysiloxane. The sheet may be made of polyvinylpyrrolidine, polyacrylamide, polyvinyl ethers, polyethylene oxide, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, polyacrylic acid and polymethacrylic acid, and isobutene-maleic acid copolymers.
U.S. Pat. No. 5,110,390 to F. Martini, et al., discloses an ostomy bag of a laminate of a water-disintegratable film such as polyvinyl alcohol or polyethylene oxide, and a coextruded film of vinylidene chloride polymer or ethylene copolymer which includes a melt-bondable layer.
U.S. Pat. No. 5,300,358 to G. R. Evers discloses a flushable structure for absorption of body fluids composed of an absorbent degradable fibrous core and a backsheet that is cold-water soluble, but water impermeable.
U.S. Pat. No. 5,468,526 to S. I. Allen, et al., discloses an ostomy bag composed of a homopolymer of vinylidene chloride or methylmethacrylate coated onto a water soluble film layer of a blend of polyvinyl alcohol, polycaprolactone, or polyethyloxazoline and a thermoplastic polyurethane.
U.S. Pat. No. 5,578,344 to N. A. Ahr, et al., discloses a process for impregnating a resin onto a substrate to form a web, where the exposed side of the web is dispersible in water, while the impregnated side is water resistant.
None of the above methods and articles have proven entirely satisfactory. Therefore, there is a need for a flushable product which is not limited in size and which does not require special conditions of disposal.
SUMMARY OF THE INVENTION
The present invention provides a composition comprising a low-molecular weight, amorphous polyalphaolefin layer and a water-sensitive substrate layer. Preferably, the polyalphaolefin is a poly(propylene-ethylene) copolymer or a poly(ethylene-butene) copolymer. When the composition is employed as a diaper outer cover or a pantiliner baffle, for example, the polyalphaolefin layer is exposed to bodily fluids, and inhibits their transport to the water-sensitive layer. When the entire article is disposed of in a toilet, however, the water-sensitive layer is wetted and weakens. Since the low-molecular weight amorphous polyalphaolefin layer is already mechanically weak without the support of the water-sensitive layer, the hydraulic force of the toilet flow causes the composition to disperse into pieces small enough to flow through the toilet and beyond without clogging the water system.
It is, therefore, desirable to provide disposable products that can be flushed in a conventional toilet with subsequent product dispersion into pieces that can be managed by standard sewage treatment or home septic systems. Additionally, it is desired to provide disposable products that can be flushed in a conventional toilet without the addition of a dissolving chemical. Finally, it is d
Campbell Stephen M.
Chang Yihua
Kerins John Edward
Pomplun William Seal
Kilpatrick & Stockton LLP
Kimberly - Clark Worldwide, Inc.
Lorengo J. A.
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