Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1997-08-15
2003-10-28
Dixon, Merrick (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S352000, C428S351000
Reexamination Certificate
active
06638603
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a novel process of making water-dispersible products. In addition, the present invention is directed to water-dispersible products, which maintain their integrity and strength when in use, but dissolve or disperse when placed in contact with water, such as in a conventional toilet. Moreover, the present invention is directed to water-dispersible products, including flushable products such as release liners, product packaging, etc., which possess a tailored degree of water protection due to strategically placed hydrophobic coating material along one or more exterior surfaces of the product.
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 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 wet 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 during use, 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 have high wet strength, yet do not disintegrate during flushing. Examples of this type of product include 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 insensitive to solutions having a neutral pH such as water, but which disintegrates in the presence of alkaline 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 forcing the user to perform the step of adding the dissolving chemical to the water. A further disadvantage is that the inadvertent or unintentional disposal of such a product in a conventional toilet without the addition of the dissolving chemical can cause serious obstruction of 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.
Another approach to producing a flushable product is to prepare products such as fibers, fabrics and films from water soluble materials. Upon contact with water, the water soluble material dissolves, reducing the structural integrity of the product, and causing its disintegration, such that it will easily pass through the plumbing system. Although the products prepared by this approach are suitable for applications wherein the product does not come in contact with water, these products are not suited for applications wherein the product may come into contact with even a relatively small amount of water. In applications where a water-sensitive product is most likely to contact water during normal use, the product must possess a degree of water protection. However, too much water protection negatively impairs the flushability of water-sensitive products.
One approach to protecting a water-soluble film from the contact of water is described in U.S. Pat. No. 5,300,358, issued to Evers. Evers discloses degradable absorbent structures comprising a water-impervious backsheet, which rapidly dissolves in cold water. The backsheet comprises a water-soluble polymeric material, usually in the form of a film, coated with a hydrophobic material. The hydrophobic material forms a coating which provides “permanent” water protection, at least until the coating is made discontinuous, for example by tearing the coating with a drawstring, to expose the surface of the water-soluble film. Evers does not disclose or provide guidance regarding the relationship between degree of water protection and coating parameters such as coating pattern, coating thickness, and pore geometry.
What is needed in the art is a method of temporarily protecting a water-sensitive film from water contact so that the film can have optimum utility and yet still readily disperse when placed in a conventional toilet. Also, what is needed in the art is a method of determining optimum coating parameters (i.e., degree of coating, coating thickness, pore geometry, etc.) to maximize the water protection of the film without a continuous or permanent coating. Moreover, a method of producing water resistant, water-sensitive, coated films having tailored degrees of water resistance is also needed.
SUMMARY OF THE INVENTION
The present invention is directed to a novel process of making coated water-sensitive films. Hydrophobic polymers are coated in a discrete pattern of dots on a water-sensitive film using a hot-melt screen printing technique. The coating provides the film with protection from damage by water when the film is brought into contact with water on the coated side. The degree of protection can be controlled by varying the distance between dots. Maximum protection is achieved when the dots touch each other; however, in some applications such as flushable articles, care must be taken to insure that the coating disperses sufficiently so as to not cause clogging during the flushing process of a conventional toilet.
In addition, the present invention is directed to the coated water-sensitive films and articles containing the coated water-sensitive films. Specifically, the coated films of the present invention are useful in connection with a variety of water-dispersible products, and especially absorbent products such as sanitary napkins, diapers, dressings and the like. The articles of the present invention exhibit adequate tensile strength and retain their structural integrity when in contact with body fluids, yet are readily dispersible in water so that the absorbent product may be flushed away after use.
Films are widely used as components of such disposable goods as sanitary napkins, diapers, bandages, and the like. Such films, if they are to function effectively, must maintain their structural integrity, as well as exhibit satisfactory tensile strength, when they are wet or damp with various body fluids such as blood, menstrual fluid and urine, with which they come into contact during use. It has been recognized that if such films, while retaining their strength in body fluids, were to lose substantially all their tensile strength when exposed to water and become readily dispersible therein, disposal problems would be substantially eliminated since the films could be easily and conveniently disposed of by contacting the film with water. The present invention provides a mechanism for eliminating disposal problems associated with various consumer products.
In a further embodiment of the present invention, the coated film may serve as a primer layer for additional coatings on the water-sensitive film, such as latex coatings. The primer layer provides enough water protection so that a water-base solution coating may be applied to the coated water-sensitive film, the water being subsequently removed prior to any
Chang Yihua
Kerins John E.
Pomplun William S.
Dixon Merrick
Kilpatrick & Stockton LLP
Kimberly--Clark Worldwide, Inc.
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