Stock material or miscellaneous articles – Layer or component removable to expose adhesive – Release layer
Reexamination Certificate
1999-12-29
2001-07-10
Lam, Cathy (Department: 1775)
Stock material or miscellaneous articles
Layer or component removable to expose adhesive
Release layer
C428S040100, C428S195100, C428S335000, C428S352000, C604S358000
Reexamination Certificate
active
06258427
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a flushable double-sided release liner. The flushable double-sided release liner is a three-layer laminate of a water-sensitive film sandwiched between two layers of a release coating. The double-sided flushable release liner is formed by applying a release coating onto both surfaces of a water-sensitive film. The flushable double-sided 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 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, is a concern 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 plants 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 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 affect 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 pressure-sensitive, 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 silicone-containing 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 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 or household sewer line.
What is needed in the art is a flushable double-sided release sheet, which can be discarded and then flushed in a conventional toilet. Such a double-sided 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 comprises a flushable laminate having release characteristics, said laminate comprising a water-sensitive film and a release coating of polymeric material on both surfaces of the water-sensitive film, wherein the coating adheres to the water-sensitive film and provides release characteristics to both sides of the water-sensitive film. The present invention is also a method of making a flushable three-layer laminate having release characteristics, said method comprising applying a release coating of a polymeric material onto the surface of a water-sensitive film, wherein the release coating adheres to the water-sensitive film and provides release characteristics to both sides of the water-sensitive film.
The present invention is a double-sided flushable release liner based on a three-layer laminate comprising a water-sensitive film sandwiched between two layers of a release coating and to methods of making the double-sided flushable release liner. The release coating may be either a continuous coating or a coating in a discontinuous pattern. The advantages of this double-sided release liner are two-fold. The first is the cost savings of using half the number of release liners. For example, a feminine care panty liner pad is attached to each side of the flushable release strip by the garment adhesive. In service, the first of the pads is peeled for use, leaving the peel strip attached to the second; the garment adhesive on the second pad is still protected by the release liner until removed for use of that pad. Current practice places a release liner on each individual pad. With the present invention, two pads are placed on each liner. The second advantage of the double-sided release liner is the option of disposal through flushing the release liner after the second pad has been used. When discarded in the toilet, water rapidly reaches the water-sensitive film which loses strength and cohesive integrity. After the loss of strength due to contact with water, the force created from flushing is sufficient to break the release liner into pieces.
The present invention is also directed to a method of preparing a double-sided flushable release liner. The method comprises coating a thin layer of polymer having release characteristics onto both surfaces of a base film, wherein the base film comprises a water-sensitive polymer. When dry, the three-layer laminate displays mechanical features comparable to a conventional coated paper liner. The core base film itself may be manufactured, taking into consideration variables such as film thickness, molecular weight, and blending additives, to control the functionality of the plastic film The polymeric coating controls the release characteristics of the plastic film. The 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 three-layer polymer film peels at the surface of the release coating, not at the interface between the coating and the water-sensitive base film. It is further contemplated that the three-layer laminate comprising a water-sensitive film sandwiched between two layers of a release coating can be manufactured by coextrusion processes that are well known to those of ordinary skill in the art.
The present invention is also directed to articles containing the two layer 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 double-sided sanitary napkins, panty liners, diapers, wound dressings, bandages, an incontinence garment, sterile wraps, surgical drapes, and the like. Although the double-sided release liner of the present invention finds particular use in the above-mentioned products, the concept of a flushable two sided 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.
Genke Nathan A.
Kerins John E.
Kilpatrick & Stockton LLP
Kimberly--Clark Worldwide, Inc.
Lam Cathy
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