Stock material or miscellaneous articles – Layer or component removable to expose adhesive – Release layer
Reexamination Certificate
1999-09-15
2001-10-02
Wu, David W. (Department: 1713)
Stock material or miscellaneous articles
Layer or component removable to expose adhesive
Release layer
C428S040100, C428S335000, C428S422000, C428S352000, C428S447000, C428S500000, C428S516000, C604S364000
Reexamination Certificate
active
06296914
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a flushable release liner. The flushable release liner is formed by applying a release coating onto at least one surface of a water-sensitive film. The flushable release liner maintains its structural integrity and strength when in use, but disperses when placed in contact with water, such as in a conventional sink or toilet. Moreover, the present invention is directed to products, including flushable and non-flushable products, which contain the flushable release liner.
BACKGROUND OF THE INVENTION
Disposable products have dramatically altered modern lifestyle, adding great convenience to everyday living for 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 materials that retain their integrity and strength for their intended purpose 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 sized articles. Many current flushable products are limited to such small articles.
Numerous consumer products, which were formerly unable to be disposed of in a conventional toilet, are made flushable today. Such products include water-soluble films, wipes, tampon applicators, etc. However, many consumer products have remained unflushable.
One such product that has remained unflushable to date is release liners. Release liners are used to temporarily cover an adhesive layer before use in many personal care products. The release liner provides protection for the adhesive layer against exposure to materials, which might negatively effect the ability of the adhesive strip to adhere to a desired substrate and provides protection against undesired, premature adhesion to a substrate. Conventional release liners comprise a paper substrate coated with a release coating. The release coating is formulated to provide very little adhesion of the coated paper to any other substrate, particularly pressuresensitive, hot-melt adhesives, so the release liner may be easily removed from the adhesive strip without disturbing the adhesive strip. Typically, release coatings comprise a siliconecontaining polymeric material.
Release liners are used in many personal care products. For example, many sanitary napkins have an adhesive strip on the backside of the napkin (the napkin surface opposite to the body-contacting surface) to fix the napkin to an undergarment and hold the napkin in place against the body. Before use, the adhesive strip is protected with a peelable release liner. Once removed, the peelable release liner must be discarded. Since peelable release liners are typically silicone-coated paper, the release liners do not readily disperse in water; consequently, disposal options are limited to depositing the release liner in a trash receptacle. Although disposing of conventional release liners in a toilet would be convenient to the consumer, such disposal potentially creates blockages in the toilet.
What is needed in the art is a flushable release sheet, which can be discarded and then flushed in a conventional toilet. Such a flushable release liner would offer convenience to the consumer, and not cause problems such as blockages in the sewage transport process
SUMMARY OF THE INVENTION
The present invention is directed to a flushable release liner comprising a thin discontinuous release coating on at least one surface of a water-sensitive film. The coated water-sensitive film functions like conventional release papers currently used. Conventional release papers comprise a peelable coated paper, which covers the adhesive strip on, for example, a feminine sanitary napkin. Unlike conventional release papers, the coated water-sensitive film of the present invention rapidly loses integrity and strength when discarded in a conventional toilet or sink. Without the support of the water-sensitive film, the thin discontinuous release coating readily breaks up under the force of flushing water in a toilet or water flow in a sink. The two-layer structure of the flushable release liner offers the performance of a paper-based release liner with the additional option of disposal in a toilet or sink and of potentially lower cost.
The present invention is also directed to a method of preparing a flushable release sheet. The method comprises coating a thin discontinuous layer of polymer having release characteristics onto a base film, wherein the base film comprises a water-sensitive polymer. When dry, the coated water-sensitive film displays mechanical features comparable to a conventional coated paper liner. The base film itself may be manufactured, taking into consideration variables such as film thickness, molecular weight, and blending additives, to control the functional similarity of the plastic film to a coated paper liner. Desirably, the discontinuous coating is present on the film surface in the form of a discrete pattern of dots, wherein the dots are coated onto the film by a hot melt screen printing process. The discontinuous polymeric coating controls the release characteristics of the plastic film. The discontinuous coating is formulated to provide very little adhesion to many substrates, particularly pressure-sensitive, hot-melt adhesives, so that the coating may be easily removed from an adhesive strip without disturbing the adhesive strip, while having high adhesion to the water-sensitive substrate. The coating formulation ensures that the coated water-sensitive film peels at the surface of the release coating, not at the interface between the coating and the water-sensitive base film.
The present invention is also directed to articles containing the flushable release liner. Specifically, the flushable release liners of the present invention are useful in connection with a variety of products, and especially absorbent products such as sanitary napkins, panty liners, diapers, dressings and the like. Although the release liner of the present invention finds particular use in the above-mentioned products, the concept of a flushable release liner has potential for any other application requiring a release material.
The present invention provides a mechanism for eliminating disposal problems associated with various consumer products. A nonlimiting detailed description of the invention and examples of specific embodiments are provided below.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a flushable release liner comprising a thin discontinuous release coating on at least one surface of a water-sensitive film. As used herein, a “release liner” refers to a layer which adheres to and protects an adhesive on a product, until the product is to used, at which time the layer is removed to expose the adhesive. The coated water-sensitive film of the present invention functions like conventional release papers currently used. However, unlike conventional release papers, the coated water-sensitive film of the present invention is “flushable.” As used herein, the term “flushable
Chang Yihua
Kerins John E.
Pomplun William S.
Kilpatrick & Stockton LLP
Kimberly-Clark Corporation
Lu Caixia
Wu David W.
LandOfFree
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